Nd evolution in the deep Pacific provides information on the deepwater transit time. Seven new foraminiferal εNd records are presented to systematically constrain glacial to interglacial changes in deep Pacific overturning and two different εNd evolution regimes occur spatially in the Pacific with reduced meridional εNd gradients in glacials, suggesting a faster deep Pacific overturning circulation. This implies that greater glacial carbon storage due to sluggish circulation, that is believed to have occurred in the deep Atlantic, did not operate in a similar manner in the Pacific Ocean. Other mechanisms such as increased biological pump efficiency and poor high latitude air-sea exchange could be responsible for increased carbon storage in the glacial Pacific.There is evidence for greater carbon storage in the glacial deep Pacific, but it is uncertain whether it was caused by changes in ventilation, circulation, and biological productivity. The spatial ε The response of deep Pacific overturning to glacial-interglacial climate change is still debated. Here the authors show a generally faster deep Pacific overturning operated in recent glacial periods based on a novel application of Nd isotopes recorded in foraminifera. One of the central questions is how the Pacific Ocean circulation linked to atmospheric CO2 concentration over glacial–interglacial (G–I) cycles. Previous studies in the Atlantic Ocean have attributed the enhanced respired carbon storage at the Last Glacial Maximum (LGM) to an increase in the residence time of deep Atlantic waters5, but few studies have focused on the past variability of Pacific deep ocean circulation and the results are still controversial11. One of the reasons is that foraminifera tests, a primary archive of past ocean chemistry, are poorly preserved in the deep Pacific due to the presence of more corrosive deep waters. The partial dissolution of foraminifera calcite might complicate the reliable reconstruction of foraminifera-based geochemical proxies , which otherwise would provide valuable information about the past nutrient and ventilation states of the deep oceans. These proxies are also controlled by a combination of high latitude air-sea exchange, biological production, and ocean circulation, and thus have difficulty in distinguishing whether the increased CO2 storage in the glacial deep Pacific was the result of reduced air-sea exchange in the Southern Ocean or sluggish deepwater circulation.Being volumetrically the largest ocean basin and most enriched in nutrients, Pacific deep water stores the largest amount of dissolved inorganic carbon in the Earth’s ocean-atmosphere system today and may have been an even larger carbon reservoir during the glacial periods14. However, unlike north–south convection structure in the Atlantic, there is no deepwater formation in the North Pacific today, and the deep Pacific basin is exclusively ventilated by northward-flowing Lower Circumpolar Deep Water (LCDW). The strong linear relationships between seawater Nd isotope compositions and oxygen/phosphate concentrations in the deep Pacific15 support the dominant role of LCDW advection and the presence of an external (i.e. not from a particular water mass) radiogenic Nd source which is added to the deep ocean in a nearly spatially homogenous way similar to nutrients, but not a link with the biological processes per se15. In this regard, the accumulation of external Nd input to the deep water might be time-dependant and the large-scale spatial Nd isotope gradients are likely to be associated with the deep Pacific circulation rate.Neodymium isotope has been demonstrated to be an effective proxy to trace the mixing in the global deep oceanNd records throughout the deep Pacific  and eastern/western equatorial Pacific (EEP/WEP) over the last and penultimate glacial maximum 30 and 160 ka) are presented in this study and compared with another 10 ε60 ka areNd record shows a continually increasing trend from glacial values −1.6 ± 0.2 at 24.8 ka to +0.1 ± 0.2 at 6.4 ka, and then the Nd isotope values start to stabilize at ~−1 to ~0 in the late Holocene. However, the detrital Nd isotope compositions are much more radiogenic (~0 to + 4.5) and evolved differently from the foraminiferal record. The largest radiogenic shift (+2.7 εNd units) in detrital Nd isotopes occurred from 12.4 ka to 10.9 ka, followed by a steadily εNd decreasing trend during the Holocene, when the foraminiferal εNd was in a continuous increasing evolution. Another discrepancy in these two records can be seen during the last glacial period when there was a rapid detrital εNd elevation from +0.6 ± 0.2 at 28.2 ka to + 1.8 ± 0.2 at 27.2 ka, followed by a sharp decline to +0.2 ± 0.2 at 26.7 ka, while the foraminiferal Nd isotope compositions showed a negative shift from −0.9 ± 0.2 to −1.4 ± 0.2. On the other hand, the foraminiferal Nd isotope compositions of the western equatorial core V28-239 are less radiogenic and showed little variability  across the last 30 kyr  and ~−5.5 during glacial periods (MIS 2 and 6). To the north of Chatham Rise, the intermediate-depth core CHAT16K had much more radiogenic εNd values (average = −3.6 ± 0.3) and less variability than SO136-38. The εNd values of ODP846 in the deep EEP also did not vary much over the past 160 ka and were generally about 1 εNd unit higher than CHAT16K, with an average εNd value of −2.6 ± 0.4. Although there are only eight εNd data points for RC13-114 over the past 160 ka, these εNd data (average = −2.6 ± 0.4) match well with the nearby record of ODP846, confirming that they are recording the εNd signals of the same water mass. The most northern site ODP1241 in the EEP showed the most radiogenic foraminiferal εNd values in this study, ranging between −1.5 and +1, with less radiogenic εNd signatures during glacial periods (MIS 2 and 6). Unlike the foraminiferal Nd isotope record, the Nd isotopes of the detrital fractions did not change following G–I cycles. Instead, the least radiogenic detrital Nd isotope composition (−2.1 ± 0.2) occurred at 135 ka, whereas the most radiogenic signal appeared at late Holocene (+4.4 ± 0.2) and MIS 4 (+3.3 ± 0.1).Four foraminiferal Nd isotopic records over the last 160 ka are measured on two intermediate SWP sites (SO136-38 and CHAT16K) and two deep EEP sites (ODP1241 and ODP846), along with eight εNd values of V21-30 varied between 0 and +5 22 and the other from old continental particles with unradiogenic εNd signatures (average εNd = −10)23. The variation in detrital εNd records of V21-30 and ODP1241 can be regarded as reflecting changing proportions of inputs from these two endmembers.The detrital ε +5 Fig.  and thos +5 Fig.  during t24, while those of V21-30 (−0.6 ± 0.3) and ODP1241 (+0.4 ± 0.2) are slightly more radiogenic than ambient seawater signatures  is beneficial for reliable interpretation of the variation in foraminiferal εNd records.The foraminiferal Nd isotopic composition of the youngest material of V28-239 (−3.3 ± 0.1) matches well with that of nearby seawater value (−3.4 ± 0.4)Nd-pw G–I change from detrital contribution can explain only one third of the actual measured foraminiferal εNd G–I change in our parameter setting  in the South Pacific implying a breakdown of ocean stratification7 and a larger contribution of shoaled glacial NACW29 or Ross Sea bottom water (RSBW)7 to the upper Pacific ocean. Since the glacial LCDW and SO AAIW inflow have higher εNd values than interglacials, a more radiogenic εNd signature during glacial periods would be expected for the North Pacific if the glacial ocean had a circulation regime similar to the modern one11. However, unlike Y9 and SO136-38, the intermediate-depth core CHAT16K situated on the northern Chatham Rise saw a relatively smooth εNd pattern over the past 160 ka, likely reflecting the εNd signatures of Tasman AAIW which circulates around the South Pacific gyre and mixes its εNd signatures with recirculating southward NPDW and possible Indonesian inputs, although a modification due to local exchange with materials from North Islands could not be excluded30. Similarly, the deeper sediment core CHAT10K located close to the North Island and outside the main flow path of the deep western boundary current probably reflects modification by local exchanges30. Therefore, it seems the cores located on the main south-to-north flowpath , show similar or even less radiogenic glacial εNd signatures  are prone to local modification resulting in more radiogenic εNd compositions in the porewater than ambient seawater, while εNd of slowly circulated deepwater is dominantly modified by the accumulation of external Nd input along the flowpath. The spatial εNd gradients below 3 km can therefore be linked with deep water transit time in the Pacific.In contrast, the higher than modern glacial εres Fig. , 6a. ThiNd gradients between South and North deep Pacific (ODP1123 and ODP846) decreased from ~4–5 εNd units in MIS 1, 3 and 5 to ~2–3 εNd units during MIS 2, 4 and 6  would be expected to be slightly decreased (~4–15%)35, while this could be partly balanced by small increase in cation weathering flux by enhanced exposure of island area available for weathering36. The counteracting effect thus likely results in negligible G–I variation in continental chemical weathering rates37. Rather, our data are more consistent with faster Pacific overturning circulation reducing the spatial εNd gradients during the glacial periods.The spatial εd 6 Fig. , indicat39. The deep Pacific transit time in glacial times  was systematically shorter compared to interglacials , with fastest circulation during peak glacial periods. Deep water δ13C has been traditionally regarded as a ventilation tracer, and the spatial gradients have shed light on water mass ageing. When LCDW travels across the Pacific, it progressively accumulates nutrients and depleted δ13C through the remineralization of sinking organic matter, as well as mixing with the overlying waters. The similarity between the Δδ13C846–1123 and our ΔεNd846–1123 records . Our study provides a first crude estimation for the deep Pacific transit time, which varied between 350 and 1200 years over the last 160 ka Fig. . The averds Fig.  lends sues MIS 2, and 6 wa41 and/or a northward expansion of RSBW7 into the Pacific due to increased sea-ice production and brine rejection43. The Nd isotopes from S-Pac regimes also support a reduced water mass mixing between LCDW and AAIW during glacials29, likely associated with reduced diapycnal mixing in a more stratified ocean44. The shoaling of NADW in the North Atlantic would lead to more NACW restricted to the upper cell which made their way to the Pacific basin via the eastward flowing ACC. Based on benthic carbon isotopes and radiocarbon evidence, the water mass geometry in the glacial South Pacific was not greatly different to the modern state9. The water mass boundary between the LCDW and UCDW/NPDW remained at ~3.5 km, while the lower boundary of AAIW may have been slightly shoaled to 1.2 km45. The potential increased carbon stock in the deep Pacific inferred from low oxygenated deep water46 would probably not be related to reduced circulation strength, but rather indicating lower oxygen concentration in the Southern Ocean47, in accordance with depleted radiocarbon observations48. We conclude that a faster but less ventilated overturning circulation might have operated in the glacial Pacific Ocean, and mechanisms such as increased biological pump efficiency and poor high latitude air-sea exchange49 may be responsible for atmospheric CO2 drawdown in the deep Pacific Ocean during glacial periods. Our results here thus put constraints on ocean circulation models to better simulate the atmospheric CO2 change through past G–I cycles.The hypothetical Pacific overturning circulation states during the interglacial and glacial stages are synthesized in Fig. Foraminiferal Nd isotopes are measured on seven new cores in this study, including two from the SWP, one from the WEP and four from the EEP.N and AAIWs9), respectively  are located to the north and south of the Chatham Rise, recording the signatures of two different AAIW types, i.e. Tasman AAIW and SO AAIW  for the upper 60 cm of Hole B . The shallowest core V21-30 is situated in the modern oxygen minimum zone, with an average sedimentation rate of 13 cm kaNd isotopes are measured on both foraminifera  and detrital fraction of the bulk sediments (for EEP cores V21-30 and ODP 1241). The former is used to trace the porewater Nd isotope changes, whereas the latter is used to identify changes in provenance and inputs of lithogenic materials.13. In brief, 30–100 mg planktonic foraminifera of each sample were handpicked from >63 μm fraction. All clays were removed by ultrasonication after the foraminiferal tests were broken open. The physically cleaned foraminifera were then dissolved in 1 M acetic acid.Foraminifera for each sample were prepared following a routine protocol2 production indicating no carbonate remained. Then the decarbonated samples were MilliQ water rinsed and leached twice with a 0.02 M solution of hydroxylamine hydrochloride in 25% (v/v) acetic acid. The residues were then MilliQ rinsed, dried and soaked in 10% peroxide to remove organic matter. After drying down again, the detrital samples were sequentially digested by the mixture of concentrated HNO3 and HF for at least 48 h at 110 °C and by aqua regia for another 24 h at 80 °C.For detrital analysis, 3–5 g sediment was repeatedly decarbonated overnight using a buffered acetic acid solution until the lack of CO146Nd/144Nd of 0.7219 and each sample was bracketed with the concentration-matched reference standard JNdi-1, the measured composition of which was corrected to the accepted value of 143Nd/144Nd = 0.512115. The external reproducibilities (2σ) of Nd isotope measurement during each analytical session are given by repeated measurements on concentration-matched JNdi-1 standards. The average 2σ external reproducibility for 20 ng of Nd is ~0.2 (on Neptune Plus) and ~0.5 (on Nu Plasma) εNd units, while larger errors for some samples reflect low Nd abundance due to small sample sizes.After dissolution, all samples underwent a two-step ion chromatographic separation (Eichrom TRUspec and Eichrom LNspec resin) to isolate and purify Nd. The isotopic ratios of Nd were analysed on a Nu Plasma or Thermo Neptune Plus multi-collector inductively-coupled plasma mass spectrometer (MC-ICP-MS) in the Department of Earth Sciences at the University of Cambridge. Procedural blanks for foraminiferal and detrital samples were negligible  and were therefore not corrected for. Instrumental mass bias was corrected by applying an exponential mass fractionation law using Nd for V21-30 and ODP1241 over the studied periods is estimated via a binary mixing model: the εNd of the sedimentary porewater (εNd-pw) is determined by a mixing of seawater derived Nd (authigenic) and lithogenic particulate Nd . The relationship is expressed as follows:The influence of detrital dissolution to porewater ε56, which allows us to estimate the authigenic Nd flux (Fau) to the sea floor. A mean authigenic Nd flux in the Pacific Ocean (Fmean) is calculated based on Nd residence time (τ = ~500 yr)25 as follows:All the parameters and their values used in this model are shown in Supplementary Table Fmean) in the Pacific of ~2.76 × 10−5 g m−2 yr−1. This number is in agreement with previous INDOPAC box estimation using 10-box model25. Settling particles are considered to be the main flux of particulate material to the seafloor. The authigenic Nd flux thus varies with different particle fluxes, resulting in higher flux in the marginal region and much lower flux in the pelagic central Pacific region56. The adopted Fmean should be taken as the lower limit of authigenic flux for our EEP cores and thus is a conservative estimation.Using the parameters in Supplementary Table 57, the lithogenic Nd flux (Flitho) composed is taken as the non-carbonate sedimentary flux when a detrital Nd concentration (Cp) is applied:Given a rich carbonate (~60–80%) and low diatom contents (<10%) of V21-30 and ODP1241 in our studied intervals−3), low-resolution CaCO3% data points of ODP1241 are from the initial IODP report (~60–70%)17, and the rest CaCO3% are extrapolated based on exponential relationship with measured coarse fraction%55. The shallower core V21-30 has high CaCO3%, and the contents of MIS 1 and MIS 2 are represented by the measurements of core-top = 70%58 and LGM = 77%59, respectively. The core-top and LGM Nd concentrations for the detritus of ODP1241 (Cp) we measured are very similar , and thus a constant value of 15 ppm is taken for both cores for simplicity.Linear sediment rate (LSR) is calculated based on the age model. Constant dry bulk density (DBD = 0.63 g cmFcont) and volcanic flux (Fvol):The lithogenic detrital Nd flux is composed of continental flux (Xcont) and volcanic (1-Xcont) components over time can be further calculated based on a two-endmember mixing model: the detrital εNd is determined by a mixing of Nd from old continental particles (average εNd-cont = −10)23 and Central America/Galapagos volcanic arcs (average εNd-vol = + 7)22 as follows:The proportions of old continental particles (α) of the corresponding components are assumed to be constant with respect to time25. The proportion of soluble Nd in marine particles is thought to be highly variable63, but literature suggests that the basaltic material is usually more reactive compared to continental/granitic material64 and has been replicated in closed-system experiments65. αcont = 2% derived from laboratory experiment60 is commonly used in Nd budget calculations66, while there is no common αvol so far in the literature, ranged from < 0.4%67 to ~1.5–8.5%68 based on batch reactor experiments.The Nd dissolution factors , we obtain αarc = 3% for V21-30 and αarc = 9% for ODP1241, both of which are within the range of reported marine particle dissolution factors. This means the discrepancy between the seawater and core-top foraminiferal εNd for our EEP cores could be explained by detrital contamination of 2% continental particle dissolution and 3–9% volcanic material dissolution during diagenesis after burial. The parameters are then applied back in time to derive the εNd-pw records of both cores in Figs. We have taken approach that first making the core-top εd in Eq. . AssuminFau) and the wide range of dissolution factors of volcanic and continental materials (αvol and αcont), a sensitivity test is performed by creating the same G–I change in porewater εNd records artificially to see how the εNd-pw calculated compared to our measured foraminiferal εNd through time  equals to the sum of Nd brought by the LCDW inflow  and the accumulation of external input over transit time (t). The reference flux of external input (fEI = 3.24 × 109 g yr−1) is averaged from previous model estimations for the Pacific Ocean66, and the reference εNd value of external input (εNd-EI = +1) is adopted from earlier model of oceanic Nd budget25. The εNd of the deep water along the pathway over time can thus be calculated by the mass and isotope balance as follows:In this model, the deep Pacific Ocean is treated as a box with LCDW exclusively ventilated from the Southern Ocean, and the water mass εNd distribution12.All the parameters and their values used in this model are shown in Supplementary Table Nd-EI = 0, + 0.5, + 1, + 1.5, + 2 and fEI = 2.84, 3, 3.24, 3.4, 3.63 × 109 g yr−1, respectively, for reconstructing the deep Pacific transit time during the last 160 ka (Supplementary Fig. Considering the uncertainties and the potential variability of the external Nd input into the deep ocean over time, sensitivity tests have been performed varying εPeer Review FileSupplementary Information


Little is known about the formation pathway of colloidal semiconductor magic‐size clusters (MSCs). Here, the synthesis of the first single‐ensemble ZnSe MSCs, which exhibit a sharp optical absorption singlet peaking at 299 nm, is reported; their formation is independent of Zn and Se precursors used. It is proposed that the formation of MSCs starts with precursor self‐assembly followed by Zn and Se covalent bond formation to result in immediate precursors (IPs) which can transform into the MSCs. It is demonstrated that the IPs in cyclohexane appear transparent in optical absorption, and become visible as MSCs exhibiting one sharp optical absorption peak when a primary amine is added at room temperature. It is shown that when the preparation of the IP is controlled to be within the induction period, which occurs prior to nucleation and growth of conventional quantum dots (QDs), the resulting MSCs can be produced without the complication of the simultaneous coproduction of conventional QDs. The present study reveals the existence of precursor self‐assembly which leads to the formation of colloidal semiconductor MSCs and provides insights into a multistep nucleation process in cluster science. Semiconductor QDs have emerged as a special class of functional nanomaterials and have attracted a great deal of attention for more than two decades.We report in the present work an elaboration regarding the precursor self‐assembly that drives the formation of MSCs. Based on the concept that the development of MSCs can occur preferentially through a structural transformation from their immediate precursors (IPs) following first‐order unimolecular reaction kinetics,2, Zn(OOCC17H33)2) was used as a Zn precursor, the first step was performed in 1‐octadecene (ODE). For Reactions 2, Zn(OOCCH3)2) was used in oleylamine  to prepare Zn(OAc)2/OLA as a Zn precursor,n‐octylphosphine (TOP) and/or a secondary phosphine diphenylphosphine (HPPh2), or ODE to promote its reactivity. The two‐step approach, different from hot‐injection and heating‐up approaches,For Reactions ZnOOCC17H32) was ue OLA, C1H35NH2 to2For our investigation on the formation pathway of MSCs, we used ZnSe as a model system, exploring the above reactions with experimental conditions optimized for the first step of a two‐step approach to MSC‐299. The optimum method to effectively synthesize ZnSe MSCs as a single product, exhibiting a single and sharp absorption peak, in one step on a routine basis is yet to be determined. For the optical spectra reported,FigureFigureFigure2 + SeTOP + HPPh2 was identified to be the most efficient for synthesizing ZnSe MSC‐299 in a single‐ensemble form, with the optimized experimental window demonstrated in Figure1H NMR, 31P—1H heteronuclear multiple bond correlation (HMBC) NMR, and 1H NMR with diffusion ordered spectroscopy (DOSY), as shown in FigureSchemeOptical absorption spectroscopy was used to explore the induction period of each of the reactions, for the presence of IP‐299 which led to the formation of ZnSe MSC‐299. 2.12 + SeTOP. The two precursors have been used previously to synthesize ZnSe RQDs,Figure For the cyclohexane dispersions  but the same Zn precursor Zn(OA)2 For Reactions −1. In Figure S1‐4 (Supporting Information) which deals with Reaction −1, we noticed again that MSC‐299 was detected. It is reasonable that the actual CMC value is related to the precursor reactivity in a reaction, as demonstrated by our exploration for Reactions To further explore the concept of the self‐assembly process which takes place prior to the formation of the Zn—Se covalent bond, we used lower Se feed concentrations for Reactions 2.22 + SePPh2H, focusing also on the induction period prior to the nucleation/growth of ZnSe RQDs.To further explore another Se precursor , we investigated Reaction For the cyclohexane dispersions, ZnSe RQDs were detected even in the 120 °C sample, for which a bandgap absorption peak appeared at ≈325 nm. When the temperature was increased to 200 °C, the RQDs grew in size with the bandgap absorption peak redshifting to ≈360 nm. Thus, the nucleation/growth of RQDs took place at temperatures slightly above 100 °C. For the CH–OTA mixture dispersions, MSC‐299 was detected even in the 40 °C sample. Accordingly, the formation of IP‐299 must have occurred at a similarly low temperature. A decrease in the population of IP‐299 started from 160 °C due to the growth of RQDs.2.32 to Reaction For Reactions 2 has been used to improve the synthetic reproducibility and particle yield of small‐size E‐based colloidal RQDs.2 was first introduced for PbSe,2 to SeTOP feed molar ratios.2, as described by Equation [25] and supported by 31P NMR,HPPh2H is much more reactive than SeTOP.2.This equilibrium is heavily weighted toward the left,2 + SeTOP + HPPh2. Each of the samples (15 µL) was dispersed in 3.0 mL of cyclohexane (blue traces) and in 3.0 mL of the 2CH–1OTA mixture (red traces). For the investigation of the induction period, Figure S3‐1 (Supporting Information) illustrates the evolution with temperature of the absorption of the nine samples (from 80 to 240 °C) in the two dispersions. Figure S3‐2 (Supporting Information) shows the comparison of the absorption spectra collected from each of the nine samples dispersed in the two solvents. Optical absorption spectroscopy demonstrates that the use of HPPh2 increased the difference between the temperatures at which IP‐299 formed and RQDs nucleated and grew.Figure 2 + SeTOP without the use of the secondary phosphine HPPh2.For the cyclohexane dispersions, ZnSe RQDs were observed only for the 220 and 240 °C samples, which exhibited bandgap absorption peaks at ≈375 and ≈385 nm, respectively. For the other seven samples from 80 to 200 °C, there were no significant absorption peaks above 290 nm. It thus appears that the induction period prior to the nucleation/growth of RQDs must have occurred below 220 °C, which seems to be similar to the behavior in the reaction of Zn(OA)For the CH–OTA mixture dispersions, the results were radically different, as MSC‐299 was detected in all the seven samples taken from 100 to 220 °C, with a continuous increase in the MSC population from the 100 °C sample to the 200 °C sample. Above this temperature range, the MSC‐299 population decreased for the 220 °C sample and disappeared entirely for the 240 °C sample. Thus, there was apparently little formation of IP‐299 at 80 °C  as well as the reaction period at a constant temperature  shows the evolution with temperature of the UV–vis absorption of the samples extracted at different reaction temperatures and growth periods and then dispersed in 3.0 mL of CH and the 2CH–1OTA mixture. Figure S5‐1b (Supporting Information) shows the ESI‐MS study results for six samples taken at 40, 120, and 160 °C, with Figure S5‐1c (Supporting Information) containing the MS isotopic patterns simulated for Zn, Se, and Zn1Se1. It has been reported that the II–VI clusters detected by MS are free of surface ligands, which have low‐dissociation energy from the surface atoms and could be detached readily.As shown in Figure m/z range of 300–1600 Da. In the m/z range of 300–800 Da, the small cluster fragments detected have been assigned to Zn3Se3, Zn4Se5, Zn6Se4, Zn4Se6, and Zn6Se5. Figure S5‐1d (Supporting Information) contains a detailed assignment of these various peaks which are isotopic‐weighted. In the m/z range of 1000–1600 Da, two cluster peaks were detected with significant strength at 1027 and 1280 Da, which were assigned to Zn6Se8 and Zn10Se8, respectively. These two peaks were also detected in the 120 and 160 °C samples . Clearly, the formation of Zn—Se covalent bonds took place at 40 °C; interestingly, no MSC‐299 was detected in the 40 °C sample as shown in Figure S5‐1a (Supporting Information).For the 40 °C/5 min sample with ESI‐MS, cluster fragments (rather than the starting compound and/or cluster due to the high energy of the electrospray ionization) were detected consisting of Zn and Se isotopic peaks in the xSey cluster fragments in the m/z range of 800–1600 Da. In the m/z range of 880–1400 Da, Zn8Se4 seemed to have a strong strength, with the formula of ZnxSe8 (x = 4–11) being indicative of the other dominant cluster. The peaks with less intensity were attributed to ZnxSe9 (x = 4–9) and ZnxSe6 (x = 6–12), in addition to Zn7Se5 and Zn8Se5, as shown in Figure S5‐1e (Supporting Information). In the m/z range of 1400–1600 Da, clusters described by the general formula ZnxSe12 (x = 7–9) were detected. Figure S5‐1e (Supporting Information) shows the detailed assignment of these isotopic peaks. These peaks detected in the 160 °C samples were also present in the 120 °C sample , for which a small amount of MSC‐299 was apparent, but only when dispersed in the CH–OTA mixture . For the 160 °C samples taken from the reaction between 5 and 45 min, the MSC‐299 population increased considerably up to 15 min and then became stable.For the 160 °C/15 min sample, ESI‐MS indicated that there were 12 to 21‐atom ZnOn the whole, the formation of Zn—Se covalent bonds took place in the 40 °C sample; however, IP‐299 was not produced. For the 120 °C sample, there was much less IP‐299 formed than that in the four 160 °C samples. Such an observation is in agreement with the results shown by Figure D, diffusion coefficient) and size  follows the Stokes–Einstein equationkB the Boltzmann constant and η the dynamic viscosity of the liquid. For the two toluene solutions from left to right, the toluene (7.1 ppm) diffusion coefficient obtained was 10−8.640 and 10−8.719 m2 s−1, respectively. The decreased diffusion coefficient of the toluene signal in Zn(OA)2 + SeTOP + HPPh2 (right) suggests a probable increase in viscosity, which is in agreement with the precursor self‐assembly process proposed and with the formation of Zn—Se covalent bonds at 40 °C detected.Figure 1H NMR (left) and 31P—1H heteronuclear multiple bond correlation (HMBC) NMR (right) spectra shown in Figure S5‐2 (Supporting Information). Based on this 1.6 ppm proton, the averaged diffusion coefficient for SeTOP of the right solution was about 10−9.349 m2 s−1, which is smaller than that of the left solution (10−9.106 m2 s−1). Upon the approximation of viscosity with the toluene signal, the 1.6 ppm proton in Zn(OA)2 + SeTOP + HPPh2 (right) is estimated to be associated with species about (10−9.106 × 10−8.719)/(10−9.349 × 10−8.640) = 1.5 times in size, as compared to that in SeTOP (left). Thus, the DOSY measurements seem to be qualitatively consistent with the hypothesis of precursor self‐assembly proposed.For the peaks at about 1.6 ppm in the Figure 2.52/OLA as a Zn precursor. With Reaction Scheme [39a–c]), the noncovalent interaction between them resulted in the formation of “micellar‐like” aggregates prior to the formation of Cd—E covalent bonds. As the reaction progressed, Cd—E covalent bonds started to form inside the self‐assembled aggregates, leading eventually to the formation of the IPs. It was demonstrated that the whole process of the IP formation could be controlled to take place only in the induction period . By the same token,To obtain a product with high purity, yield, and reproducibility from a crystallization process, a fundamental understanding of the processes is of help. To comprehend more fully the two‐step approach employed to achieve ZnSe MSC‐299, we will briefly review the formation of IPs and RQDs reported for the two other relevant systems using a two‐step approach.a–c), theWe anticipate that the present understanding of the formation of ZnSe IP‐299 via the self‐assembly of the various Zn and Se precursors will help comprehend molecular association,32En MSCs that have evolved in a single‐ensemble form without the coproduction of RQDs. The hypothesis that the formation of MSCs begins with general self‐assembly of M and E precursors enriches the Yu pathway that has been proposed for the induction period of colloidal semiconductor compound NCs .We have demonstrated that precursor self‐assembly can be a general pathway for the formation of colloidal semiconductor MSCs, based on a study of the ZnSe model system (Scheme The authors declare no conflict of interest.SupplementaryClick here for additional data file.


Separation of a homogeneous mixture of different components to reach an ordered out-of-equilibrium state in solution has attracted continuous attention. While this can be achieved using external chemical fuels or photo energy, an alternative energy source is heat. Here we realize a temperature-controlled cycle of transitions between ordered and disordered states based on a mixture of two kinds of building blocks that self-assemble into cubic structures (nanocubes). An almost statistical mixture of nanocubes (disordered state) is thermodynamically most stable at lower temperature (25 °C), while homoleptic assemblies composed of single components are preferentially produced at higher temperature (100 °C) followed by rapid cooling. The scrambling of the building blocks between the nanocubes takes place through the exchange of free building blocks dissociated from the nanocubes. Based on this mechanism, it is possible to accelerate, retard, and perfectly block the scrambling by the guest molecules encapsulated in the nanocubes. In this paper, the authors study the temperature-controlled dynamic behavior of a system of nanocubes self-assembled from two different building blocks. Non-intuitively, the disordered, equilibrium state (a mixture of heteroleptic cubes) and the ordered, out-of-equilibrium state (a mixture of homoleptic cubes) are cycled by heating and subsequent rapid cooling. The homogeneity of a mixture of gases in equilibrium derives from their negligibly weak interactions. Contrary to mixing of gases, molecular self-assembly of multiple components can spontaneously form homoleptic self-assemblies composed of single components through self-sorting under thermodynamic control with the aid of intermolecular interactions between well-designed molecular building blocks that discriminate between oneself and others19. Furthermore, in the case where a statistical mixture of components in molecular assemblies is thermodynamically preferred, recent progress on adaptive chemistry has realized the transition of such disordered states into an ordered out-of-equilibrium state by external photo or chemical energy34.Two kinds of different gases put into a box spontaneously mix together to reach a homogeneous fluid in equilibrium. Such a disordered state is thermodynamically favored and entropy is the quantity that determines which direction a reaction spontaneously proceeds to. Thus, the separation of each component from a homogeneous mixture (towards ordered state) needs external energy or help of Maxwell’s demon if we want to realize the separation without any energy except for information6 and B6) spontaneously takes place at 25 °C to reach an almost statistical mixture of nanocubes composed of two kinds of building blocks, AnBn6– (n = 0–6), a disordered state. Then, a metastable ordered state  is spontaneously recovered by heating at 100 °C and subsequent rapid cooling. The reversible transition between the two states is realized by the change in the energy landscape of the system consisting of two kinds of building blocks in response to the temperature. It is also found that the scrambling is accelerated, retarded, or blocked by guest molecules encapsulated in the nanocubes, which enables us to lock and unlock a metastable state by the encapsulation and release of hydrophobic molecules in the nanocubes.Here we present a simple example of a temperature-controlled reversible transition between ordered and disordered states consisting of a mixture of two kinds of molecular building blocks that self-assemble into hexameric cubic structures, i.e. nanocubes, with different thermal stabilities. Because of a structural similarity between the two components (A and B for example), scrambling of the building blocks between the nanocubes (A1·Cl2 and 2·Cl2), which are C2v-symmetric hexaphenylbenzene (HPB) derivatives possessing three kinds of substituents on the periphery of HPB, self-assemble into a cube-shaped structure  in water driven by the hydrophobic effect and van der Waals (vdW) and cation–π interactions between GSA molecules  of 16 is 130 °C, while that of 26 is 65 °C). To investigate the relation between the thermal and kinetic stabilities of the nanocubes, scrambling of GSAs between nanocubes assembled from non-deuterated GSAs (16 or 26) and from partially deuterated GSAs ((1D)6 or (2D)6) was monitored by electrospray ionization-time-of flight (ESI-TOF) mass spectrometry. When aqueous solutions of 16 and (1D)6 were mixed at room temperature ([1] = [1D] = 0.025 mM), the scrambling was clearly monitored by change in the distribution of mass signals for [1x(1D)x6–(SO4)6]2– (x = 0–6), which captured two electrons during the ionization (an aqueous H2SO4 solution was added just before the mass measurement in order to detect the nanocubes as negative ion species), and an almost statistical signal pattern was observed in 2 days 6, finished just after the mixing of the two solutions  was monitored by ESI-TOF mass spectrometry  were mixed at 25 °C, the signal for 26 decreased faster than that for 16 and finally reached an almost statistical compositional mixture of the nanocubes in 2 days. The scrambling in the same concentration of the nanocubes ([1] = [2] = 0.4 mM) was monitored by 1H NMR spectroscopy , tend to preferentially exchange GSAs with 26 because the scrambling between less stable nanocubes takes place faster, which supports the idea that the scrambling takes place through the exchange of monomer GSAs dissociated from the nanocubes. The scrambling was accelerated by heating and reached convergence in 8 h at 50 °C.Next, the scrambling between the two different nanocubes  is thermally more stable than 26 (Td = 65 °C) due to the vdW interactions around p-tolyl methyl groups in 1, nanocubes composed of more 2 would be less stable than those composed of more 1. Hence, at higher temperature than Td of 26, the nanocubes composed of more 2 should be disassembled to lead to a mixture of monomer 2 and the nanocubes composed of more 1. Then rapid cooling of the mixture of the nanocubes (mainly 16) and free 2 thus obtained leads to a mixture mainly containing homoleptic nanocubes (16 and 26) through faster self-assembly of monomer 2 into 26 than the scrambling  (disordered state), which is thermodynamically most stable at 50 °C. The interconversion between the ordered and disordered states is repeatable simply by changing the temperature of the solution without any degradation because the GSAs are completely stable even at 100 °C , TBM2@16 (Td > 150 °C), and of 26 (Td = 65 °C) were mixed, nothing happened for 6 months  and 16 (Td = 130 °C) were mixed   dissociated GSAs of 1 should promote the scrambling. On the other hand, no scrambling took place when insoluble TBM was present in a solution of TBM2@16 and 26, though gradual encapsulation of TBM in 26 was observed , so the scrambling did not take place. These results indicate that whether the scrambling takes place or not is determined by the existence of monomer GSAs (1 and 2) and that in the case where the thermal stabilities of the two nanocubes are significantly different the rate-determining step of the scrambling is the dissociation of monomer GSAs from a thermally more stable nanocube.As the nanocubes can encapsulate neutral and anionic species in their about-1-nm-sized hydrophobic inner space to lead to thermally more stable nanocubes2@16 and 26 were mixed together, the scrambling was significantly retarded (65% of PCCP2@16 and 20% of 26 existed in the solution after 1 month) )  .Quite different results were observed when anionic species (NaPCCP: sodium pentacyanocyclopentadienide) was used as a guest molecule Fig. . When PCn-hexane) was added in the mixture to form the nanocubes that encapsulate the guest molecules, Hex3@16 and Hex2@26. The scrambling of the GSAs between the two nanocubes was blocked for 7 days, indicating that the metastable ordered state was kinetically locked. The removal of the guest molecules by heating at 100 °C is the trigger to unlock the ordered state to lead to a mixture of guest-free homoleptic nanocubes, 16 and 26, which then was converted into the disordered state again.Because of the lower stability of the ordered state at 25 °C, spontaneous scrambling takes place to reach the disordered state. To control the timing of the scrambling, a guest-encapsulation-release system was coupled with the cycle of transitions Fig. . After t16 and 26) and the thermodynamically most stable disordered states ) was realized simply by changing the temperature. The result that the induced-sorted state was preferred by heating at 100 °C and subsequent rapid cooling was realized because only the nanocubes composed of more 1 can survive at this temperature. The rate of the scrambling can be controlled by anionic guest species. The blocking of the scrambling by the encapsulation of guest molecules would enable to kinetically capture a certain metastable species that is selected from a dynamic combinatorial library of compositional and positional isomers of nanocubes consisting of several kinds of GSAs in response to external stimuli.In conclusion, a temperature-controlled cycle of transitions that is fabricated from two kinds of building blocks that self-assemble into homoleptic and heteroleptic cubic assemblies (nanocubes) with different thermal stability was realized. The scrambling experiments (intermolecular exchange) of the building blocks (GSAs) between the nanocubes indicate that the kinetic stability of the nanocube is closely related to the thermal stability of the nanocubes; a thermally more stable nanocube is kinetically more inert. The concentration effect on the rate of the scrambling and the results obtained from the scrambling experiments in the presence of guest molecules indicate that the scrambling takes place through the exchange of free GSAs dissociated from the nanocubes and that the rate of the scrambling is determined by the dissociation of free GSAs provided from a thermally more stable nanocube. The interconversion between the metastable ordered (a mixture of 1H and 13C NMR spectra were recorded using a Bruker AV-500 (500 MHz) spectrometer. High-resolution mass spectra (HRMS) were obtained using a Waters Xevo G2-S QTOF mass spectrometer. All reagents were obtained from commercial suppliers  and were used as received. GSAs 1·Cl2 and 2·Cl2 and compounds 3 and 4 were synthesized according to previously reported procedures35. See supplementary information for synthetic procedures, including Supplementary Figs. 2@16, TBM2@26 , PCCP2@16 (PCCP indicates pentacyanocyclopentadienide) and Hex3@16 (Hex indicates n-hexane) were prepared according to the literatures37. Hex (1 μL) was added by a syringe to a D2O solution of 26  in an NMR tube. The suspension was mixed by inverting the NMR tube four times and sonicated for 5 min to afford Hex2@26  in negative ionization mode at 0.88 kV with a 0 V sampling cone voltage and source offset voltage, 4 V trap and 2 V transfer collision energy, and 1.5 mL/min trap gas flow. The scrambling experiment between 16 and 1D6 was presented as an example. Solutions of 16 and of 1D6 ([GSA] = 0.8 mM) in H2O were prepared separately. The solutions of 16 (150 μL) and of 1D6 (150 μL) were added to an Eppendorf microcentrifuge tube. Then, the concentration of GSAs was adjusted to be 0.4, 0.1, and 0.025 mM by addition of Milli-Q water. The scrambling of the GSAs was monitored by mass spectrometry. A portion of the mixture was taken. After addition of 1 mM H2SO4 aq., this solution was immediately injected into gold-coated glass capillaries made in house  and the mass spectrum was recorded. The spectra were calibrated using 1 mg/mL CsI and analyzed using MassLynx software (Waters).ESI-TOF mass spectra of the scrambling of the nanocubes in water were recorded on a SYNAPT G2-S16 and of 26 ([GSA] = 2 mM) in D2O were prepared separately. A solution of TMACl  in D2O (15 μL), which was used as an internal standard, was added to an Eppendorf microcentrifuge tube. Then the solutions of 16 (120 μL) and of 26 (120 μL) in D2O and D2O (345 μL) were added to the Eppendorf microcentrifuge tube to adjust the concentration of GSAs to 0.4 mM or the solutions of 16 (150 μL) and of 26 (150 μL) in D2O and D2O (285 μL) were added to the Eppendorf microcentrifuge tube to adjust the concentration of GSAs to 0.5 mM. The scrambling of the GSAs was monitored at 25 °C by 1H NMR spectroscopy. The existence ratios of 16 and 26 were determined by their integrated values against that of the signal of TMA+. Three p-tolyl methyl signals observed at 0.5–2 ppm were used to determine the existence ratio of 16. As 26 lacks p-tolyl methyl groups, N-methyl signals at 3–4 ppm were used to determine the existence ratio of 26. In order to confirm the reproducibility of the measurements, the same experiments were carried out three times. Similar procedures were conducted for the scrambling of the nanocubes with guest molecules. See supplementary information for more details  was produced from a mixture of 16 and 26 ([1] = [2] = 0.5 mM) at 25 °C for 3 days or at 50 °C for 8 h. A mixture of 16 and 26 was preferentially produced by heating at 100 °C for 20 min followed by rapid cooling at 0 °C for 20 s. The induced-sorting of 16 and 26 was monitored by variable temperature 1H NMR measurements  (1 μL) was added via a syringe to a D2O solution of 16 and 26 ([1] = [2] = 0.5 mM) in an NMR tube. The suspension was mixed by shaking the NMR tube for 30 s to afford a D2O solution of Hex3@16 and Hex2@26. The encapsulated n-hexane was removed upon heating at 100 °C for 60 min and then a mixture of 16 and 26 was obtained by rapid cooling at 0 °C for 20 s (Supplementary Fig. Supplementary InformationPeer Review File


The technique was validated against conventional methods in phantom and 9 healthy subjects.The free‐running sequence is inversion recovery (IR)‐prepared followed by continuous 3D golden angle radial data acquisition. 1D respiratory motion signal is extracted from the k‐space center of all spokes and used to bin the k‐space data into different respiratory states, enabling estimation and correction of 3D translational respiratory motion, whereas cardiac motion is recorded using electrocardiography and synchronized with data acquisition. 3D translational respiratory motion compensated T2 = 0.99) of T1 estimation with reference method. Homogeneous systolic and diastolic 3D T1 maps were reconstructed from the proposed technique. Diastolic septal T1 estimated with the proposed method (1140 ± 36 ms) was comparable to the saturation recovery single‐shot acquisition (SASHA) sequence (1153 ± 49 ms), but was higher than the modified Look‐Locker inversion recovery (MOLLI) sequence (1037 ± 33 ms). Precision of the proposed method (42 ± 8 ms) was comparable to MOLLI (41 ± 7 ms) and improved with respect to SASHA (87 ± 19 ms).Phantom results demonstrated good agreement (R1 mapping method allows for reconstruction of isotropic resolution 3D T1 maps at different cardiac phases, serving as a promising tool for whole heart myocardial tissue characterization.The proposed free‐running whole heart T They acquire multiple images with different T1 contrasts and estimate pixel‐wise T1 by fitting the acquired signal to an exponential recovery model. Respiratory and cardiac motion may result in blurring artefacts in each T1‐weighted image and can cause misalignment between different images, influencing the T1 mapping accuracy.1 estimation.The modified Look‐Locker inversion recovery (MOLLI)1 and T2 imaging without breath‐holding or ECG triggering.1 mapping is technically challenging, because respiratory gating and ECG‐triggering together with the requirement of whole heart coverage, may lead to very long scan time. To cover the whole heart in an acceptable scan duration, current 3D T1 mapping techniquesRecently, the magnetic resonance multitasking technique using 2D radial acquisition has been proposed for motion‐resolved quantitative myocardial T1 mapping, we propose a free‐running  3D whole heart T1 mapping technique with high isotropic spatial resolution (1.5 mm3), which is able to provide images in any desired orientation. The proposed sequence consists of an inversion recovery (IR)‐prepulse, followed by an efficient 3D golden angle radial acquisition1 relaxation curve. The k‐space center is repeatedly sampled within each spoke and used to estimate 1D respiratory motion. ECG signal is recorded and synchronized with data acquisition. Respiratory binning is performed based on the estimated 1D respiratory signal, enabling estimation and correction of 3D translational respiratory motion. For the reconstruction, a recently proposed algorithm that combines dictionary‐based low‐rank inversion1 mapping at different cardiac phases. The feasibility, accuracy and precision of the proposed technique was validated against conventional T1 mapping methods in a standardized T1 phantom and 9 healthy subjects.To address the current technical challenges of myocardial T22.11 contrast, after which a spoiled gradient‐echo (SPGR) readout is performed with small flip angle (θ). Spatial‐spectral pulse for selective water excitation is adopted for fat suppression. To achieve pseudo‐uniform distribution of radial spokes for retrospective cardiac and respiratory binning, the continuously acquired radial spokes conform to the 3D golden angle distribution.ϕ1 = 0.4656, ϕ2 = 0.6823 are the 2D golden angle means.The proposed IR‐prepared 3D radial sequence is shown in Figure 2.21 mapping of a given cardiac phase is shown in Figure The flowchart of retrospective processing, including motion extraction, respiratory motion correction and data sorting for T1 mapping at a given cardiac phase.After retrospective respiratory binning and cardiac gating, 3D translational respiratory motion is estimated via registration from the intermediate reconstruction of low‐resolution respiratory bin images at diastolic cardiac phase by using central part of selected k‐space data. Representative diastolic bin images of 5 respiratory motion states and the difference images with the end‐expiratory bin are shown in Figure 2.32.3.11 mapping at a given cardiac phase, spokes for the corresponding cardiac delay and acquisition window are selected, which are then sorted into a time series of T1 contrasts according to TI and a given temporal window for each T1 frame. After data selection, the highly undersampled 3D radial data is reconstructed over multiple T1 contrasts by combining a dictionary‐based low‐rank inversion1 contrasts to be reconstructed with a recently proposed high‐dimensionality 3D patch‐based undersampled reconstruction (HD‐PROST), exploiting local (within a patch), non‐local (between similar patches), and contrast redundancies.F and ||·||* denote the Frobenius norm and nuclear norm respectively; I is the compressed T1 image series to be reconstructed; E=DAUrFS is the encoding operator, with S being sensitivity maps, F being Fourier transform, rU being the low‐rank operator obtained by truncating the singular value decomposition (SVD) of a dictionary generated by Bloch simulation,A being the convolutional gridding operator, transforming Cartesian data back to 3D radial, and D being the non‐Cartesian density compensation function; K is the undersampled data; pP(·) is the patch selection operator at pixel p of a 3D multi‐contrast image set. This operator selects patches on local (patch for a given pixel location and contrast), non‐local (similar patches within a neighborhood for a given contrast) and contrast  scales and Tp is a 3D tensor built by the selected patches centered at pixel p; T represents the denoised multi‐contrast images constructed by folding and aggregating the tensors Tp for each pixel p (see the step 2 below); Y is the Augmented Lagrangian multiplier; λ is the sparsity‐promoting regularization parameter and µ is the penalty parameter. Equation For 3D Tndancies.LI,T,Y=EIStep 1: joint reconstruction updateI by incorporating the denoised multi‐contrast images T obtained at the end of step 2 as prior informationThe first step is a joint reconstruction of the compressed TI image series  Step 2: high‐order singular value decomposition based denoisingThe above equation can be efficiently solved using the conjugate gradient (CG) algorithm.I and Y from step 1 and step 3 separately, the second step is to minimize the following equation regarding to the high order tensor TpWith obtained Tp is obtained by thresholding the singular values obtained via high‐order singular value decomposition of the 3D tensor built by the patches selected from the multi‐contrast images. The thresholding parameter is defined by λμ. The denoised Tp is then rearranged to form the denoised image patches. This process is repeated for all the pixels in the singular images, and aggregation is then performed to generate the final denoised singular images T.Step 3: Lagrangian multiplier updateThe details to solve the above equation can be found in Bustin et al.I and T from step 1 and step 2, the Lagrangian multiplier is updated by Y = Y + I − T. The above 3 steps are iteratively interleaved in the reconstruction process to improve the reconstructed image quality.Finally, with the optimized 2.3.23, spatial resolution = 1.5 × 1.5 × 1.5 mm3, TR/TE = 11.6 ms/5.1 ms, flip angle = 6°, IRTR = 2200 ms, number of readouts after IR = 175, gapT = 9.5 ms , exT = 160.5 ms, scan duration = 9.5 min.The sequence was implemented on a 1.5 T MRI scanner  for cardiac imaging. The following scan parameters were used for both phantom and in vivo experiments: FOV = 200 × 200 × 200 mm1 frame was also set to 186 ms, resulting in 10 T1 frames to be reconstructed. A dictionary‐based low‐rank compression1 contrast dimension to further reduce the number of T1 frames to be reconstructed  was set to 15, and the regularization parameter µ, balancing the contribution of the prior term, was empirically set to 0.01. Coil sensitivity maps were estimated by using spokes of TI larger than 1000 ms and reconstructed in low resolution by using only the central half of k‐space to reduce noise. The regularization parameter λ of HD‐PROST was optimized by visual inspection of the reconstruction quality on 1 subject and used for all other data set. For the patch‐based denoising step in HD‐PROST,2.41 mapping accuracy of the 3D T1 mapping sequence, a standardized T1 phantom1 values ranging from ~250–1600 ms was imaged using a 28‐channel cardiac coil. To obtain reference T1 values of the phantom for validation, a 2D inversion recovery spin echo (IR‐SE) sequence was performed with the following imaging parameters: FOV = 140 × 140 mm2, in‐plane spatial resolution = 1.5 × 1.5 mm2, slice thickness = 8 mm, TR/TE = 10,000/5.8 ms, 13 TIs = 50, 100, 200, 300, 400, 500, 700, 900, 1200, 1500, 2000, 2500, and 3000 ms. Standard T1 values were determined by a 3‐parameter non‐linear least square fitting algorithm.To test the T1 mapping sequence, the ECG signal used for the retrospective binning was generated by physiological simulation with heart rate varying between 50 bpm and 70 bpm during the acquisition. The acquired 3D radial data was retrospectively binned into 10 T1 contrasts for a simulated diastolic phase with cardiac delay of 650 ms. The phantom T1 map acquired with the 3D imaging sequence was generated using the HD‐PROST reconstruction as explained above.For the proposed 3D radial T2.51 mapping reference consisted of the clinically adopted breath‐hold 2D MOLLI (3‐3‐5)2, in‐plane resolution = 2 × 2 mm2, and slice thickness = 8.0 mm. The SASHA sequence was performed with TR/TE = 2.6/1.3 ms, flip angle = 70°, and the same FOV and spatial resolution as used for MOLLI. Parallel imaging with SENSE acceleration factor of 2 in the phase‐encoding direction was used in the 2D MOLLI and SASHA mapping acquisitions, resulting in a mid‐diastolic acquisition window of ~187 ms. MOLLI and SASHA images were acquired in the same short‐axis location as the cine scan and reconstructed to an in‐plane resolution of 1.5 × 1.5 mm2. The 2D T1 maps for MOLLI and SASHA were obtained by fitting the corresponding standard 3‐parameter models.The study was approved by the local institutional review board and 9 healthy subjects  were imaged using a 28‐channel cardiac coil. All volunteers provided written informed consent before inclusion into this study. First, standard breath‐hold 2D cine images were acquired in the mid ventricular short‐axis view with retrospective gating to 16 cardiac phases, based on which the cardiac delays for systole and diastole were determined. The T1 mapping sequence was also acquired in short‐axis orientation covering the entire heart and centered around the slice location of the 2D MOLLI and SASHA scans. Besides diastole, T1 mapping was also reconstructed for systole using the proposed framework, considering that systolic T1 maps may find applications in patients with thin myocardium or arrhythmias.The proposed free‐running 3D T2.61 values were calculated for each vial. The accuracy of the proposed 3D T1 mapping technique was evaluated by comparing the estimated T1 values to the 2D IR‐SE method using Pearson's linear correlation and Bland‐Altman analyses.For phantom data, circular region‐of‐interests (ROIs) were drawn for each vial and the mean and SD of T1 map in the mid short‐axis view that was most similar to the MOLLI and SASHA geometry was selected from the 3D T1 maps of the proposed approach for each subject. Septal ROIs with the same size were drawn for the 3 T1 mapping methods. The mean and SD of T1 values in the septum were measured and compared between the proposed 3D method and 2D MOLLI and SASHA separately using the Wilcoxon rank‐sum test with Bonferroni correction to evaluate the in vivo accuracy and precision.For the analysis of in vivo images, the diastolic T1 maps, 3 slices from base, mid to apex were selected from the diastolic and systolic T1 maps. T1 values of the myocardium were measured according to the myocardial segments model defined by the American Heart Association (AHA),1 values were calculated for all segments to evaluate the spatial T1 distribution of the proposed method. The T1 value in each segment was compared between diastole and systole using the paired t‐test. Then the diastolic and systolic T1 values for each segment were determined by averaging across all the volunteers and visualized with bull's‐eye plots.For the analysis of 3D in vivo TP‐value of <0.05 was considered statistically significant.All image reconstruction and analysis were performed using MATLAB  on a server with a dual 16‐core CPU and 256 GB RAM. Statistical analysis was carried out in GraphPad Prism 7 . A 33.11 maps with the proposed approach and 2D IR‐SE are shown in Figure 1 values of all vials are shown in Figure 1 estimations between the proposed 3D technique and the 2D IR‐SE reference (R = 0.99). Bland‐Altman plot demonstrates no correlation between the difference and average of T1 measurements of the 2 methods  (P = 0.68), but is higher than that of MOLLI (1037 ± 33 ms) ( P < 0.01). The SD, indicating the precision of septal T1 measurements, was 42 ± 8 ms with the proposed approach, which is much lower than the SD of SASHA (87 ± 19 ms) (P < 0.01) and similar to that of MOLLI (41 ± 7 ms) (P = 0.79).Diastolic T1 maps from 2 subjects are shown in Figure 1 maps also demonstrated a uniform T1 distribution with thicker myocardium compared with diastole. The diastolic and systolic T1 values of each AHA segment are shown in the bull's‐eye and box plots in Figure 1 values in diastole and systole for all myocardium segments are summarized in Table 1 values estimated with the proposed technique in most of the AHA segments, except for the inferior segments in the apical and mid ventricular slices, and the inferoseptal segment in the basal slice, with significantly longer T1 values in diastole than in systole.Representative systolic and diastolic T41 mapping with 1.5 mm3 isotropic spatial resolution has been successfully achieved with predictable 9.5 min scan time. The proposed sequence features free‐breathing, retrospective cardiac gating and continuous data acquisition, so T1 maps can be compensated for 3D translational respiratory motion and reconstructed at different cardiac phases by retrospective data binning. Using combined dictionary‐based low‐rank inversion1 mapping was demonstrated in vivo. Myocardial T1 measurements with the proposed 3D technique were comparable to conventional breath‐hold, cardiac‐gated 2D MOLLI and SASHA.In this study, free‐running 3D whole heart myocardial T1 values estimated with the proposed technique showed good accuracy for T1 ranging from 250–1600 ms as compared with the reference 2D IR‐SE. Septal T1 values at diastole with the proposed technique were comparable to SASHA and were significantly larger than those for MOLLI, which has been reported to underestimate T1.1 increment of 1%, resulting in 10–12 ms increments in the myocardial T1 range of 1000–1200 ms, which are small compared with the measured septal T1 SD (42 ± 8 ms). The precision of septal T1 was similar to MOLLI and significantly higher than SASHA. The results indicate that the proposed 3D T1 mapping technique improves accuracy compared to MOLLI and precision compared to SASHA. Therefore, the proposed technique may be a promising tool for myocardial T1 mapping with the advantages of both high accuracy and precision. In addition, with the proposed 3D high resolution T1 mapping technique, visualization of the right ventricle was improved, which may facilitate fibrosis quantification in the thin wall of the right ventricle. Nevertheless, T1 values of the thin right ventricle should be interpreted carefully, considering that there may be partial volume effects resulting from residual fat caused by the imperfection of the water selective excitation pulse.In the phantom study, T1 mapping.In this study, respiratory motion was addressed by correcting the phase of k‐space data using motion parameters estimated from 3D translational image registration of images acquired at different respiratory states. More sophisticated registration methods, such as affine and non‐linear transforms could be considered in future work to account for more complex respiratory‐induced cardiac movement. To extract reliable cardiac trigger signal to account for cardiac motion, ECG signal was logged and synchronized with data acquisition for retrospective data selection. Previous studies have proposed several approaches for cardiac self‐navigation using radial or spiral trajectories.1 mapping at systole has special diagnostic value when the diastolic T1 map cannot be reliably obtained, such as in patients with thin myocardium, where partial volume effects may corrupt myocardial T1 estimation, and in patients suffering from frequent arrhythmias, where the diastolic onset and duration are changing.1 maps were reconstructed along with diastolic T1 maps for each subject. The AHA segment analysis showed good spatial uniformity of the myocardial T1 values measured across the left ventricle in both diastole and systole. In general, the systolic myocardium T1 was comparable to the diastolic myocardium T1. The shorter T1 in the inferoseptal segment of the basal slice and inferior segments of the mid and apical slices may be explained by increased myocardial thickness and therefore reduced partial volume effects from blood during systole compared to diastole.1 mapping was set to ~186 ms, which was adequate for diastole, but may not be optimal for systole. In spite of this, radial data acquisition is less sensitive to motion than Cartesian sampling, and no obvious motion artefacts were observed in the systolic T1 maps.T1 maps were reconstructed for each subject separately in our experiments. Instead of separate reconstruction for each cardiac phase, cardiac‐resolved T1 maps can be reconstructed simultaneously, by which additional redundancy along cardiac phases can be exploited and improved reconstruction performance can be expected at the expenses of memory requirement and computational times. Furthermore, 3D cardiac cine reconstruction from the free‐running sequence should be also possible. This could be done by sorting the respiration motion compensated k‐space data with a small temporal window along the cardiac phase  and a large temporal window along contrast. After binning, the undersampled k‐space data of different cardiac phases could be reconstructed simultaneously, e.g., by adding a total variation constraint along the cardiac phase directionSystolic and diastolic T1 and B0 field inhomogeneities that will influence T1 estimation and may cause banding artefacts in the image. The proposed technique was investigated at 1.5 T in this study, but has potential to be extended to 3 T. Furthermore, benefits of higher SNR, and therefore shortened scan time or improved spatial resolution can be expected at 3 T.SPGR readout with low flip angle instead of balanced steady‐state free precession (bSSFP) readout was used in the proposed sequence. Although bSSFP readout may have SNR benefits, the low flip angle SPGR readout is less sensitive to B1 mapping technique cannot estimate T1 of flowing blood accurately. This is because the signal model used for T1 mapping assumes that the tissue of interest is static and experiences all the inversion and excitation pulses in the sequence, which may not be true for flowing blood. When measurement of myocardial extracellular volume is needed, estimation of blood T1 could be performed using a free‐breathing rapid low spatial resolution (enough to only define a region of interest within the blood pool) T1 mapping sequence acquired in a mid‐ventricular slice. Second, in this study the proposed technique was only tested for native myocardial T1 mapping. However, post‐contrast myocardial T1 mapping using this technique should be also feasible. Furthermore, considering the reduced T1 after contrast injection, shorter IRTR could be adopted and shorter scan duration can be expected. Third, in the free‐running sequence with retrospective binning, although inter‐bin respiratory and cardiac motion has been carefully addressed, compared with breath‐hold images, there may still be some remaining intra‐bin respiratory motion and cardiac motion that result in some blurring of the reconstructed images. Future studies will investigate the performance of the proposed sequence in a cohort of patients with cardiovascular disease. Last, the current implementation of HD‐PROST reconstruction is suboptimal and it takes ~3 h to reconstruct a whole heart 3D T1 map. GPU implementation will be investigated in the future for the non‐uniform Fourier TransformSeveral limitations of the proposed technique need to be mentioned. First, the proposed T51 mapping technique with whole heart coverage and high isotropic spatial resolution is proposed. 3D T1 mapping was shown to have good accuracy and precision in comparison to reference sequence in phantom and conventional T1 mapping methods in in vivo experiments. Based on retrospective data selection and combined dictionary‐based low‐rank inversion and patch‐based reconstruction, high resolution 3D T1 maps could be obtained for different cardiac phases. Future studies will investigate the clinical value of the proposed technique.In this study, a free‐running 3D myocardial T Click here for additional data file.


Comparing the irradiation effects induced by both the beams, the stopping processes of C60 ions in SiO2 are discussed in this paper. Despite of having almost the same elongation efficiency, the C60+ irradiation induced ~10 times more efficient sputtering due to the clustering enhancement and/or the synergy effect. Ion tracks of ~10.4 nm in diameter and 60–80 nm in length were observed in crystalline SiO2 under 4 MeV C60 irradiation. While the track diameter was comparable to those by SHIs of the same electronic stopping, much shorter track lengths than those predicted by a rigid C60 molecule model indicates that the fragmentation occurred due to nuclear collisions. The elongation of the metal NPs was induced only down to the depth where the tracks were observed but not beyond.This study reports that high fluence fullerene ion (C The examples include the anisotropic deformation of amorphous metals/glasses3, shape elongation of metal nanoparticles (NPs) embedded in materials15, and etched ion-track engineering16. When NPs embedded in SiO2 are irradiated with SHIs, the NPs are elongated toward the direction parallel to the SHI beam. Many impacts of SHIs gradually transform originally-spherical NPs to nano-rods. This paper describes that the same deformation is also induced by 1–6 MeV fullerene (C60) ions, while such C60 ions are not classified in SHIs because of their slow velocities. The energy per nucleon of several MeV C60 ion, which is an index of ion velocity, is on the order of 10−3 MeV/u, while that of SHI is ~1 MeV/u or higher. However, C60 ions provide high electronic energy deposition comparable to SHIs due to the coincident impacts of 60 carbon atoms within a limited area of the C60 molecule size of ~0.7 nm in diameter. The stopping powers of the C60 ion is approximated as the sum of sixty independent carbon monomer ions with the energy of each one (E/60) expressed as,i = n (nuclear) or e (electronic)17. The monomer stopping power Si  is derived from SRIM 2013 code18. A 6 MeV C60 ion provides ~15.5 keV/nm of electronic stopping power Se in amorphous SiO2, which is as high as Se of 200 MeV Xe ion (15.0 keV/nm), as shown in Table 60 ions of 1–6 MeV were applied, which correspond to Se of 6.3–15.5 keV/nm. Using the same Se range of SHIs, we have already succeeded in the elongation of NPs as shown in Table 14.Modification of materials using swift heavy ions (SHIs), i.e., high energy ions with stopping power in materials that are primarily dominated by electronic forces, has recently received an increasing amount of attention60 ions of up to 40 MeV have been available at the Orsay facility, France21. However, the available fluences have been limited because of the extremely low fluxes on the order of 106 C60/cm2s21. Conversely, obvious NP elongation was thought to require high fluences as 1013 C60+/cm2 or more, i.e., irradiation time of ~4 months. The elongation experiments have only recently become possible because the Takasaki group, a part of the research team that conducted this study, has developed an electron-attachment-type C60 ion source which generates enormous fluxes of ~1010 C60/cm2s and consequently attains the high fluences22.Since 1990s, C60 ion source, we have firstly succeeded in elongating the shape of NPs by the cluster ion irradiation. Simultaneously we observed different phenomena which have not been observed under SHI irradiation, i.e., the formation of short ion tracks, and significantly enhanced sputtering, and unexpectedly weak velocity effect. In this paper, the interplay between these phenomena and NP elongation are also discussed.Using the high-flux C2, (a)(c) before and (b)(d) after the irradiation with 4 MeV C60+ ions to a fluence of 5 × 1013 C60+/cm2. The incident angle of the C60+ beam was set to 45°, as shown by the arrows in Figs. oblate spheroidal shape with principle axis pointing to the surface normal . The Pt marker was observed on the top of a 100 nm thick SiO2 layer over the Au NP layer as shown in Fig. 13 C60+/cm2  mapping made it possible to clearly distinguish the Pt marker and Au NPs, as shown in Figs. Figures cm2 Fig. , the thiprolate spheroids with the principle axes pointing in the direction of the 45° beam angle. These observations have clearly indicated that the shape elongation of NPs was induced by the slow and low energy 4 MeV C60+ ions.The widely distributed markers in Fig. 24 irradiated with C60 ions to various fluences were detected under linearly polarized light illumination. The polarization angle is 0° when the polarization plane includes the major axes of the elongated NPs. As reported in ref.11, the difference in the optical absorption at 0° polarization and 90° polarization is, in certain conditions, proportional to the aspect ratio (AR) of the elongated NPs. The absorption spectra at 0° (solid curves) and 90° (broken curves) polarization at various fluences are presented in Fig. Se = 15.5 keV/nm) and 2 MeV (9.3 keV/nm) C60 ions, respectively. At both the ion energies, the Se was high enough to induce NP elongation if it was supplied from SHIs as shown in Table Optical absorption spectra of Zn NP samples13 C60+/cm2. Simultaneously, the absorption peak intensity at ~4.8 eV decreased with increased fluence, which can be attributed to sputtering loss of Zn atoms from the samples. The absorption mostly disappeared at 5 × 1013 C60+/cm2 for 6 MeV but a half of the peak remained for 2 MeV. According to Rutherford backscattering spectrometry (RBS) measurements combined with Rump code analysis25, more than 90% and 40% of Zn atoms were lost from the samples at the fluence of 5 × 1013 C60/cm2 with 6 MeV and 2 MeV C60 ions, respectively  and 6 MeV (15.5 keV/nm) C60 irradiation induced shape elongation comparable to or slightly higher than 200 MeV Xe irradiation (15.0 keV/nm), while irradiation at 1 and 2 MeV induced less elongation. However, it should be noted that the elongation is induced with even 1 MeV C60ions (Se = 6.3 keV/nm). It is not surprising because the 1st threshold of the shape elongation by SHIs is ~3 keV/nm4. The 1 MeV C60 ions have higher Se than the threshold. It is noted that the elongation is induced by SHIs with much lower efficiency even below the 1st threshold4. The slightly higher efficiency of 4 and 6 MeV C60 ions compared to 200 MeV Xe ions could be attributed to two: (i) The much slower velocity of the cluster ions compared to SHIs, which reduces the energy of δ-rays and excitation volume, resulting in a higher excitation density26. (ii) The synergy effect between Sn and Se. While Sn is much lower than Se for SHIs, this is not the case for MeV C60 ions, as shown in Table The fluence dependence of NP elongation was determined from optical spectra using the method described in12 C60+/cm2. However, the slope was reduced to less than unity above 1 × 1012 C60+/cm2, and finally turned to a negative slope around 1 × 1013 C60+/cm2. The sublinear increase in intermediate fluences and the decrease in high fluences can be attributed to the destruction of the elongated NPs caused by the enhanced sputtering of the cluster ions. In fact, the quantities of Zn atoms in the samples decreased with the fluence as evidenced by RBS, as shown in Fig. From the slope of unity in the log-log plot in Fig. 4. To compare the elongation efficiency between the different beams, the efficiency was defined as the inverse of the fluence, where the optical elongation reaches to the value of 0.02, and shown in Table 60 ion irradiation. However, both the data by SHIs (closed circles) and by C60 ions (open circles) fall on almost the same dependence, indicating that large difference due to the velocity effect was not observed.As shown in Fig. Se and the fluence Φ. Therefore the elongation is determined only by the electroni deposited energy density4. Of course, this kind of simple relation is not applied to sputtering induced by SHIs27. To check whether this simple relation is hold in this case or not, the optically detected elongation was plotted with the product of Se and the fluence Φ. In contrast to SHIs, the data points do not fall on the same curve. A simple relationship like the elongation induced by SHI irradiation was not observed, probably this process included the strong electronic sputtering.In the previous literature, the elongation induced by SHI irradiations is normalized when the abscissa is plotted with the product of 15. However, the tracks cannot be directly observed by TEM in amorphous matrices28, except in a very thin self-standing film29. For reference, a piece of crystalline SiO2 (c-SiO2) without NPs was irradiated with the C60 ions and observed by XTEM. Figure 60 ions at a fluence of 5 × 1011 C60+/cm2. The incident angle of the C60 beam was set to 7° from the surface normal to avoid channeling. The irradiated surface was coated by a thin Pt layer as a surface marker for XTEM analysis. It should be noted that the surface was much flatter than that in Fig. Although the mechanism of NP shape elongation induced by SHIs is yet to be identified, a majority of researchers agree with the importance of the ion-track formation in matrix materials60 ion at depth x in SiO2 was calculated based on the rigid C60 molecule model, i.e., the fragmentation of C60 molecule is excluded,Eo is the incident energy of the C60 ion. The results for 4 and 6 MeV ions are shown in Fig. Se(E) + Sn(E) and Se(E) are provided in Fig. 2 is known to be ~2 keV/nm30, tracks by 4 MeV C60 ions would be formed down to a depth of 270 nm, where Se > 2 keV/nm. It should be noted again that the experimentally observed track lengths were 60–80 nm, much shorter than the rigid model predicted.Many cylindrical structures of 10.4 ± 3.0 nm in diameter and 60–80 nm in length were observed below the black surface marker layer in Fig. 2 underneath. The hillocks are indirectly observed in this case. In fact, it is clearly observed that the lateral dimensions of the dots are larger the diameters of the tracks inside of c-SiO2, because of the thickness of the deposited Pt marker. The hillocks are most likely formed when the tracks met the surface31.As more clearly shown in the inset of Fig. 2 was deposited on a Zn NP sample, irradiated with 6 MeV C60 ions, and compared with samples without the deposited layer. As shown in Fig. The next question is whether NP elongation was only induced within the track depth or also beyond. A 200 nm thick layer of amorphous SiO60 ions. In this configuration, Zn NPs did not interact with the ion tracks unless the deposited layer was severely sputtered. According to Fig. 60 ions was reduced from 6 MeV to ~2.5 MeV after passing through the 200 nm thick SiO2 layer. The energy of ~2.5 MeV was still high enough to induce NP elongation since the anisotropic absorption, i.e., elongation was observed even under 2 MeV C60 irradiation, as shown by curve (ii) in Fig. 60 ions induced higher elongation than indirect irradiation with ~2.5 MeV C60 ions through the 200 nm-thick deposited layer, although the latter had higher energy. This observation can be interpreted that the 6 MeV C60 ion lost the energy going through the deposited layer of 200 nm thick and was fragmented. The fragmented carbon ions which totally have ~2.5 MeV no longer to form ion tracks nor elongation of NPs. Probably the distances between the fragments become too long to induce the cooperative effect between them. However, since the track length of ~120 nm was determined from quartz but not from amorphous SiO2, further confirmation is necessary.The 200 nm thickness was wider than the typical track length of ~120 nm for 6 MeV C32. Since the present case is in an intermediate energy region, we evaluated which mechanism, i.e., Sn or Se was dominant for the observed enhanced sputtering under C60 irradiation.It is well known that there are two types of sputtering mechanisms: nuclear and electronic sputtering. Furthermore, the synergy effect between both types could be possibleSe and Sn, of C60 ions are plotted in Fig. Se was higher than Sn when E > 1 MeV. However, Sn was not negligible, which is different from SHIs. An important observation was revealed in this energy region, namely Seincreased but Sndecreased with ion energy. Figure 60 ion irradiation at three different energies, 2, 4, and 6 MeV. The Zn loss was more efficient at higher energies. The energy dependence of the sputtering efficiency and that of Se and Sn are presented in Table Se and the observed sputtering yield increased with increasing the energy, while the nuclear stopping power Sn decreased. This difference in energy dependence indicated that sputtering can be attributed to an Se-related mechanism, not an Sn-related one.Energy dependences of stopping powers, 2 from C60 ion irradiation was estimated using both the models. In the nuclear sputtering model, the nuclear sputtering yield Yn by a C60 ion with energy E is given by a sum of those independent sixty C monomer ions with E/60,2 by the C monomer ion, Yn , was determined by SRIM 2013 code. The yield was 16.3 atoms/C60-ion for 6 MeV C60 ions.A further quantitative evaluation is presented in Table 60 ion, which is characterized as Se, is treated as a swift heavy ion. Applying an experimental cubic formula for SiO2,B1 = 0.20 atoms/ion (nm/keV)3 27, the yield of 745 atoms/C60-ion was estimated for 6 MeV C60 ion. As shown in Fig. 2 top-layer decreased from 100 to 30 nm under 4 MeV C60 irradiation at a fluence of 5 × 1013 C60+/cm2. Also as shown in Fig. 60 irradiation, below 5 × 1013 C60+/cm2. The observed sputtering yields were 3.2 × 103 and >3.2 × 103 atoms/C60 for 4 MeV and 6 MeV irradiation, respectively, both of which were much higher than the calculated values. The sputtering yield was greatly enhanced probably due to cluster enhancement or the synergy effect34.In the electronic sputtering model, a Cmentclass2pt{minim2 under 4 MeV C60+ irradiation (Se = 12.7 keV/nm). Afra et al. summarized various experimental data of Se dependence of the track sizes of crystalline SiO2 with the i-TS calculations of the velocities of 0.5 MeV/u and 7.0 MeV/u30. The calculated track diameters for 15.3 keV/nm (4 MeV C60+ in c-SiO2) were ~11 nm and ~9 nm for the low and high velocities, respectively. The track radius of the 4 MeV C60+ ion in c-SiO2 was not so large compared to SHIs. Kluth et al. evaluated amorphous SiO2 by small angle X-ray scattering (SAXS) and reported the total track diameters of ~10 nm for low velocity and ~8 nm for high velocity, respectively28. It should be noted that tracks in amorphous SiO2 have core/shell structures15, which is different from the hard-cylinder-type of crystalline SiO230.As shown in Fig. et al. have studied the Se dependence of track diameter in C60 films using TEM observation under various ions (Se = 0.04–40.8 keV/nm) irradiations. They observed the largest ion track of ~20 nm in diameter under 30 MeV C60 irradiation. Furthermore, they observed that the diameter increased in proportional to Se, which was different from the conventional one that the square of the diameter is proportional to the Se. To explain the dependence, Kumar et al., proposed the Coulomb explosion model for the track formation in C60 films35. Kitayama et al. studied the core/shell ion tracks in amorphous SiN film by C60 ion irradiation. The total and core diameters did not depend on Se and were almost constant of 11.2 nm and 4.3 nm between Se = 3 and 22 keV/nm36. Relatively large but unusual energy dependent track formations were reported, which could be related to the synergy effect between Se and Sn.P. Kumar 60 ions. Acceleration of SHIs requires the world-class big accelerator facilities. The number of the facilities available for materials science applications is quite limited, e.g., a few facilities in Japan. Since a few to several MeV C60 ions provide high electronic energy deposition comparable to SHIs, they could be used as substitution of SHIs. The acceleration energy of a few MeV is not practically high. It is easily attainable in quite common accelerator facilities with the terminal voltage of ~1–2 MV, which are found at many places. If the newly-developed high flux C60 ion sources can be combined with the commonly-used ~1 MV accelerator facilities, the high-density electronic excitation which are comparable to SHIs would be easily accessible in quite many facilities, i.e., more than 20 facilities in Japan.Another concern, i.e., rather pragmatic motivation, of this study is possible substitutability of swift heavy ions (SHIs) by MeV C60 ions are different from those of SHIs. Ion ranges of SHIs are e.g., ~10 μm, much longer than those of MeV C60 ions, even assuming the ion range of C60 ion as that of constitute C monomer ion, e.g., ~a few hundred nm. As shown in this paper, the depths where the high Se is available are further limited, by the fragmentation of C60 ions. The cluster enhanced sputtering cannot be neglected. The perfect substitution of SHIs by MeV C60 ions is difficult. However, substitution of certain aspects could be possible. To understand the substitutability, we are studying the interaction between MeV C60 ions and materials, in this case, NPs.However, some irradiation effects of MeV C2 comparable to swift heavy ions of 200 MeV Xe14+. Shape elongation of Au and Zn NPs was confirmed in amorphous SiO2 under the C60+ ion irradiation. According to the optical dichroism spectroscopy, 4 MeV and 6 MeV C60 ion irradiation induced Zn NP shape elongation with a high efficiency at low fluences, which was comparable to or slightly higher than 200 MeV Xe ions. While the Se of 6 MeV C60 ions and that of 200 MeV Xe ions were virtually the same, the slower velocity of the former reduced the δ-ray energy, which resulted in the enhancement of the excitation density26. While the NP elongation linearly increased with the fluence up to 1 × 1013 Xe14+/cm2 for 200 MeV Xe ions, the elongation by C60 ions sublinearly increased exceeding 1 × 1012 C60+/cm2 and decreased above 1 × 1013 C60+/cm2 due to the highly efficient sputtering. It should be noted that the elongation is induced even with 1 MeV C60 ions.Fullerene ions of 1–6 MeV induce dense electronic excitation in SiO2 layer. The significant loss was also confirmed by RBS and even the naked eye as loss of the NP layer’s color. Since Se increased and Sn decreased in the energy region between 1 and 6 MeV, the observed sputtering that increased with increasing energy was ascribed to the electronic origin. However, the observed magnitude was higher by more than one order than the empirical cubic law27, Y = B1Se3 for electronic sputtering by monomer SHIs, indicating the cluster enhancement and/or the synergy effect34.XTEM observations clearly showed not only the elongation of NPs but also a significant loss of the SiO60 ion irradiation were observed in crystalline SiO2 by XTEM observations. The tracks of 10.4 ± 3.0 nm in diameter and 60–80 nm in length were formed under 4 MeV C60 ion irradiation. The track length was much shorter than those associated with SHIs having the same Se. To understand whether the elongation of NPs was induced in a layer deeper than the ion tracks, a SiO2 layer of 200 nm was deposited on the NP layer and irradiated with 6 MeV C60 ions. The NPs were rarely elongated in this configuration where the NPs were not touched by any ion tracks but impacted with C60 ions at ~2.5 MeV if they could not be fragmented. This observation confirmed that most of the C60 ions were fragmented beyond the track length. Since the fragments were too small and too separated in the region deeper than the track lengths, cooperative excitation between the fragments were no longer expected.Ion tracks and possible hillocks caused by C2 by sequential vacuum depositions and annealing: At first, 3 nm thick of Au film was deposited on SiO2 substrate by electron beam vaporization. Rapid thermal annealing at 300 °C for 10 minutes transformed the continuous Au film to isolated NPs. Then the NPs were covered with SiO2 film of 100 nm thick by sputtering deposition. See supplementary materials. (ii) Zn NPs were formed by implantation of 60 keV Zn ions to SiO2 to a fluence of 1 × 1017 Zn+/cm2. Even without post thermal annealing, Zn NPs of 10.3 ± 2.3 nm in diameter were formed in the depth region between 20 and 70 nm.Two types of NP samples were prepared: (i) Au NPs were formed in amorphous SiO60+ ions was carried out at Takasaki Advanced Radiation Research Institute (TARRI), National Institutes for Quantum and Radiological Science and Technology (QST), using a 3 MV tandem accelerator and a newly developed high-flux C60 negative ion source. While the samples were irradiated with C60 positive ion beams of four different energies, 1, 2, 4, and 6 MeV, the beam current was utilized at ~50 pA for 6 MeV and ~100 pA for other energies through an aperture of 3 mm in diameter. Some samples were irradiated with an incident angle of 45°, to detect the shape elongation of NPs by the optical linear dichroism (OLD) spectroscopy. Crystalline SiO2 samples were irradiated with 0 or 7° from the surface normal for ion-track observation by cross-sectional transmission electron microscopy (XTEM).The irradiation of C−5 each) were used. A sample was set between the two polarizers, P and A, and illuminated by linearly polarized monochromatic light from the spectrophotometer through the first polarizer P. Light transmitted through the sample was detected through the second polarizer A, whose polarization plane was set to the same angle as that of polarizer P. The role of the second polarizer is to remove the birefringence signal. The optical transmittance was plotted in the form of optical density (OD = −log10T) without correction of reflection, where T denotes the transmittance. An area of approximately 1 mm in diameter of the sample was illuminated through an aperture.A standard dual-beam spectrophotometer was used for the OLD spectroscopy in the wavelength region of 215–800 nm with a resolution of 1 nm; a pair of optical polarizers  and JEM-2100F, JEOL (for scanning TEM and X-ray energy dispersive spectrometry mapping) under an acceleration voltage of 200 kV. The XTEM samples were fabricated with 30 keV Ga focused ion beam (FIB) milling. To identify the surface position in the cross-sectional configuration, thin layer of Pt was deposited on the sample surface before the FIB milling. Rutherford backscattering spectrometry (RBS) was carried out in TARRI to determine the content of Zn atoms in the sample using a 2 MeV HeSupplementary Information