The performance of this precursor in FEBID is poor, resulting in maximum metal content of 26 atom % under optimized conditions. Furthermore, the Ru/Fe ratio in the FEBID deposit (≈3.5) is higher than the 3:1 ratio predicted. This is somewhat surprising as in recent FEBID studies on a structurally similar bimetallic precursor, HFeCo3(CO)12, metal contents of about 80 atom % is achievable on a routine basis and the deposits are found to maintain the initial Co/Fe ratio. Low temperature (≈213 K) surface science studies on thin films of H2FeRu3(CO)13 demonstrate that electron stimulated decomposition leads to significant CO desorption (average of 8–9 CO groups per molecule) to form partially decarbonylated intermediates. However, once formed these intermediates are largely unaffected by either further electron irradiation or annealing to room temperature, with a predicted metal content similar to what is observed in FEBID. Furthermore, gas phase experiments indicate formation of Fe(CO)4 from H2FeRu3(CO)13 upon low energy electron interaction. This fragment could desorb at room temperature under high vacuum conditions, which may explain the slight increase in the Ru/Fe ratio of deposits in FEBID. With the combination of gas phase experiments, surface science studies and actual FEBID experiments, we can offer new insights into the low energy electron induced decomposition of this precursor and how this is reflected in the relatively poor performance of H2FeRu3(CO)13 as compared to the structurally similar HFeCo3(CO)12.In the current contribution we present a comprehensive study on the heteronuclear carbonyl complex H Direct-write technologies using electron beams for nanostructure deposition can surpass the limitations of standard lithography techniques, such as the growth of three-dimensional nanostructures with complex geometries –2. FocusIn FEBID precursor decomposition is primarily induced by secondary electrons produced as the high-energy primary beam impinges on the substrate's surface –18. Thes3NO − with n = 4–7 is also observed. The apex loss appears predominantly with charge retention on the iron containing moiety through the formation of [Fe(CO)4]− and to a much lesser extent through the formation of [Fe(CO)3]− and [Fe(CO)2]−, as is shown in 4]−, [M − Fe(CO)3]− and [M − Fe(CO)2]− with appreciable intensity on the [M − Fe(CO)3]− fragment. Charge retention on the remaining Ru3(CO)n base plane moiety is also observed along with further CO loss, up to 11 CO in total, as shown in 4 and additional loss of up to 7 CO from the charge retaining moiety.4]− with significant intensity and the formation of [Ru(CO)3]− and [Ru(CO)2]− with considerably less intensity, as shown in 4]− and [M − Ru(CO)3]− and further, sequential CO loss from the charge retaining, FeRu2 containing moiety up to a total loss of 11 CO units. Similar to the apex loss we attribute these fragments to an initial loss of a neutral Ru(CO)4 unit and an additional loss of up to 7 CO units from the charge-retaining moiety. The ion yield curves for these channels are shown in Similar to the apex loss, we also observe the formation of [Ru(CO)n]− apex loss and the [Ru(CO)n]− loss from H2FeRu3(CO)13, shown in 3(CO)12 and reported earlier. We have discussed these in detail elsewhere − anion is markedly larger than that on the cobalt atoms forming the base plane.The respective ion yield curves for the − anion, strained within the neutral geometry, is very similar on all metal atoms. Relaxation to the ground state anionic geometry (2FeRu3(CO)13 and HFeCo3(CO)12, the spin density of their anions and the geometrical changes between the respective neutral and anionic ground states, does not offer a quantitative explanation of their different behavior with regards to DEA. However, the difference is significant, especially with regards to the relaxation of the metal–metal bonds between the base plane and the apex as well as within the base plane. While the relaxation of the ground state anion of HFeCo3(CO)12 leads to a spontaneous and significant weakening of the metal bonds from the base plane to the apex, the bond weakening within H2FeRu3(CO)13 is much less significant and is similar within the Ru3 base plane and between the base plane and the apex. Furthermore, the relative spin density on the apex iron is much more significant for the anionic ground state of HFeCo3(CO)12 than for H2FeRu3(CO)13. This is in line with the observation of the apex loss from HFeCo3(CO)12 being restricted to charge retention on the Fe containing moiety while that from H2FeRu3(CO)13 also leads to a considerable fraction with charge retention on the base plane fragment. Tentatively we offer the explanation that the apex loss from HFeCo3(CO)12 is a spontaneous process proceeding directly along a repulsive path on the respective potential energy surface of the ground state anion. For H2FeRu3(CO)13, on the other hand, energy dissipation is more effective leading to more apparent competition between the apex loss and base plane fragmentation of the ground state [H2FeRu3(CO)13]− anion.The situation is different for Hgeometry , however2(CO)n]− with n = 4–7, though with comparatively low intensity. The m/z ratios for the isotope distributions for these fragments overlap considerably with those for [M − Ru(CO)4 − nCO]− with n = 7–4, respectively. These fragments, thus appear in the same ion yield curves displayed in panels (f)–(i) in 2(CO)n]−n = 4–7 thresholds are lower, these could in principle contribute to the corresponding higher energy yields assigned to [M − Ru(CO)4 − nCO]− with n = 7–4, respectively. We do, however, consider this unlikely as the threshold values for the respective fragments correspond very well with the respective onsets. These are distinct progressions of sequential CO loss and as is discussed here below we attribute these to metastable decay. As typical for such processes the onset of a proceeding channel (n + 1 CO) coincides with the maximum probability for the preceding one (n CO), and correspondingly the onset should coincide with the thermochemical threshold.Furthermore, fragmentation of the base plane is also observed through the formation of [Ru2FeRu3(CO)13 with the remaining metal core intact is not observed. This is distinctly different from the fragmentation pattern observed for HFeCo3(CO)12 through DEA [4]−, [Fe(CO)3]− and [Fe(CO)2]− formation is also observed from HFeCo3(CO)12 with similar relative cross sections as for H2FeRu3(CO)13, charge retention on the Co3 base plane is not observed in HFeCo3(CO)12, neither is the formation of [Co(CO)4]− or [Co(CO)3]−. However, similar to H2FeRu3(CO)13 the loss of a single Co and 4–10 CO is observed from HFeCo3(CO)12, though with very low intensity 12, while, as stated above, this channel is not observed from H2FeRu3(CO)13.Based on our analysis, sequential loss of CO from Hough DEA –40. Whil2]−, [M − Fe(CO)3]−, [M − Fe(CO)4]− and [M − Fe(CO)4 − nCO]− with n = 1–7, i.e., the apex loss with charge retention on the Ru3 base plane and additional CO loss. The threshold for the corresponding channels are denoted in the respective panels, assuming neutral Fe(CO)n loss up to n = 4 and further sequential CO loss after that. In these calculations the hydrogens are retained on the respective ruthenium base plane fragments. We note in this context, that from the respective m/z ratios, these fragments could principally also be assigned as [M – (n + 2)CO]−, however, the threshold for such sequential CO loss from the molecular anion are generally about 3–9 eV above the observed ones. These are listed in comparison with the thresholds for the corresponding [M – Fe(CO)4 – nCO] fragments in Table S3, 2FeRu3(CO)13 the loss of the neutral Fe(CO)2 unit, i.e., the rupture of both Fe–CO bonds to the bridging CO ligands is observed with low intensity through a narrow contribution at around 0 eV 4]− are found to be exothermic by 0.14 and 0.75 eV, respectively, while the thresholds for the complementary channels leading to the formation of [Fe(CO)3]− and [Fe(CO)4]− 3]− is observed with moderate intensity and an appearance energy of about 0.5 eV. Conversely, [M − Fe(CO)4]− is only observed with moderate intensity and an appearance energy of about 0.5 eV, while the complementary fragment [Fe(CO)4]− is the highest intensity fragment observed from this compound, with the main contribution peaking at about 0 eV. In principle all exothermic channels are competing paths at 0 eV incident electron energy, however, the paired energy dependence of the [M − Fe(CO)3]− and [Fe(CO)3]− fragments as well as that of the [M − Fe(CO)4]− and [Fe(CO)4]− fragments implies that the rate determining step is strongly coupled to the charge retention. Tentatively we attribute this to two competing initial steps on the respective reaction paths, i.e., the initial rupture of a) a Fe−CO or b) a Ru−CO bond to one of the two Fe−CO−Ru bridging carbonyls. In this picture, the initial rupture of a Fe−CO bond to one of the two Fe−CO−Ru bridging carbonyls leads predominantly to charge retention on the iron containing moiety while a Ru−CO bond rupture leads predominantly to charge retention at the Ru3 base plane moiety.With regards to the charge retention, this is the complementary channel to the formation of [Fe(CO)out 3 eV  and for e(CO)4]−  are founIn this context, and to aid the proceeding discussion, we note that the observation window of our experimental setup is about 10 μs, which is the extraction time from the electron–molecule interaction region. Fragments that dissociate further after extraction do not maintain stable trajectories within the quadrupole mass filter and are thus not detected. This is about 50 μs, which is the approximate lifetime required for a fragment to be observed.4 − nCO]− and [M − Ru(CO)4 − nCO]− fragments from H2FeRu3(CO)13 with n = 1–7 (3(CO)12 leading to the fragments [M – nCO]− with n = 3–12. These regressions are remarkable for three different reasons, as is discussed in detail for HFeCo3(CO)12 elsewhere − from HFeCo3(CO)12 and [M – Fe(CO)4 – nCO]− and [M – Ru(CO)4 – nCO]− from H2FeRu3(CO)13 coincide with the succeeding [M − (n + 1)CO]−, [M – Fe(CO)4 – (n + 1)CO]− and [M – Ru(CO)4 – (n + 1)CO]− fragments, respectively. This behavior is typical for sequential metastable ligand loss, where [M − nCO]− is the precursor of [M − (n + 1)CO]− and the extent of the fragmentation is determined by the available excess energy. This, however, would require a quasi-continuous electron attachment over the energy range from around few eV up to above 20 eV for both compounds. For HFeCo3(CO)12 we postulated − but also [Fe(CO)3]− and (ii) sequential CO loss from the molecular anion leading to the fragments [M – nCO]− with n = 1–12. Hence, there are two parallel paths where the initial CO loss competes with the apex loss in the low energy range:The main difference between these compounds, with regards to DEA, lies in the fragmentation process of the molecular anions formed, rather than the initial electron attachment process. For HFeCoand2FeRu3(CO)13, on the other hand, the apex loss (mainly as Fe(CO)4) or the loss of a single ruthenium from the base plane (mainly as Ru(CO)4) precedes all further fragmentation. Where the charge retention is on the metal tetracarbonyl (M(CO)4) fragment, further fragmentation of the neutral fragment is not expected, as this channel proceeds predominantly at or close to 0 eV. However, when the charge retention is on the respective Ru3 or FeRu2 containing fragments further loss of up to 7 CO units is observed. This situation is shown in 4 and further CO loss from the Ru3 base plane fragment:For Hand3(CO)12, base plain fragmentation of H2FeRu3(CO)13 is observed through [Ru(CO)n]− and [M – Ru(CO)n]− formation with n = 2–4, [M – Ru(CO)4 – nCO]− with n = 1–7 and [Ru2(CO)n]− with n = 4–7.Furthermore, while insignificant base plane fragmentation is observed for HFeCoDissociative ionization, different from DEA, is a non-resonant process with an onset at or slightly above the ionization limit of the respective compounds. At threshold, DI is generally characterized by single bond ruptures, i.e., the lowest energy channels. With increasing electron impact energy further channels open up and the DI cross sections for individual channels increases until the total cross section reaches a maximum in the range between 70 and 100 eV. At higher electron impact energies the energy transfer efficiency diminishes, reflected in a gradual decrease in the total cross section as the impact energy increases further. At about 70 eV all DI channels are generally close to their maxima and DI spectra at this energy normally give a good picture of the integral efficiency of the individual channels, though they do not accurately reflect the onset region where different channels are opening up and the branching ratios are markedly different.2FeRu3(CO)13 recorded at an impact energy of 70 eV. Panel (a) shows the m/z range from about 50 to 315 while panel (b) shows the m/z range from about 280 to 670. The fragmentation of H2FeRu3(CO)13 at 70 eV impact energy is very rich and characterized by broad contributions and significant overlap resulting from the wide isotope distribution of ruthenium. The accurate interpretation of the spectra is further complicated due to the fact that the mass of the principal iron isotope (56 amu) is two times that of CO, not allowing for differentiation between Fe loss and the loss of two CO from the m/z ratios alone. Furthermore, in the lower m/z range we observe contributions from doubly charged fragment ions, though with comparably low intensity. For the low m/z range up to about 300, the dominating regression can be unambiguously assigned to [Fe(CO)n]+ with n = 0–5. The higher m/z range, on the other hand, is characterized by two main regressions which cannot be unambiguously assigned to defined molecular composition from the m/z ratios alone. The first regression may be assigned as [M – nCO]+ with n = 3–13, but may also be attributed to [M – Fe – (n − 2)CO]+. The second regression is [M – Ru – nCO]+ with n = 6–11 which similarly may also be attributed to [M – Ru – Fe – (n − 2)CO]+. Further significant contributions are observed from [M – 2Ru – 6CO]+ and [M – 2Ru – 7CO]+ in this m/z range. Again, these m/z fragments may also be assigned to the respective [M – 2Ru – Fe – 4CO]+ and [M – 2Ru – Fe – 5CO]+ ions.2FeRu3(CO)13 physisorbed on a substrates surface, we have estimated the average CO loss per incident electron for both the DI and DEA process. For DEA this is estimated by multiplying the integrated intensity of the individual channels with the number of CO lost in the process, summing this up for all channels and dividing the derived total CO loss with the total DEA intensity. For DI the same procedure is used, however, the respective integral intensities are estimated from the peak intensities at the m/z ratios for the respective principal isotopes. The measured intensities are then divided by the fractional contribution of the principal isotope to the total isotope distribution. For simplification only the isotope distribution of the metal content of the respective fragments is considered.To enable better comparison with the surface experiments discussed in the next section and specifically to try to identify whether DEA or DI is likely to play the dominating role in the decomposition of HThe main problem with these estimations is that we do not have any information on the fragmentation of the neutral counterparts; this is especially true for DI where we have no information on the available excess energy.2FeRu3(CO)13 per incident, both for the DI and the DEA process. For the lower limit in DI we presume the high m/z regressions to be associated with neutral iron loss as neutral Fe(CO)4, i.e., loss of the apex iron with both the bridging carbonyls and both terminal carbonyls. For the [Fe(CO)n]+ regression we presume that the neutral counterpart stays intact. For the higher limit we presume that the high m/z ratios are not associated with iron loss and that the neutral counterparts to the [Fe(CO)n]+ regression fragment through complete CO loss. Similarly, for DEA we estimate the upper limit by assuming additional CO loss from the neutral counterparts formed in the individual processes. However, here we have a fair estimation of the excess energy available as we have calculated the thermochemical thresholds for the individual processes. For the neutral Fe(CO)4 and Ru(CO)4 loss and additional CO loss the onset of the individual contributions is mostly close to the calculated thermochemical threshold of the individual processes, but the respective contributions generally stretch over a range of about 4–5 eV. On the high energy side of the respective contribution, further loss of 2–3 CO from the respective metal neutral tetracarbonyl is thus in principle possible. Accordingly, we calculate the lower limit for CO loss through DEA by presuming the intact neutral Fe and Ru carbonyls (mainly tetracarbonyls). For the higher limit we simply presume additional loss of two CO from these.To account for this, we have calculated a lower limit and a higher limit for the CO loss from H2FeRu3(CO)13 per incident through DEA and 3–9 for DI. In this context we note that all DEA channels are associated with metal–metal bond ruptures, while in DI this number is somewhere between 50–100% depending on how large a fraction of the m/z ratios matching the [M – nCO]+ regression are actually due to the formation of [M – Fe – (n − 2)CO]+. For HFeCo3(CO)12 the same estimations give the bracketing numbers 4–9 for CO loss per incident through DI and 2–3 for DEA, while metal–metal bond rupture constitutes 50% of the DI intensity and about 30% of the DEA intensity.From these estimations we derive the bracketing numbers 0.5–3 for CO loss from H3)4, it has been shown that the cross sections for electronic excitations are very significant  is formed by reduction of Fe(CO)5 in THF using a sodium/benzophenone mixture as described in literature [3(CO)12 in 70 mL THF was added dropwise to a refluxing solution of 140 mg Na2[Fe(CO)4] in 80 mL THF. The colorless solution turned red upon the first addition of Ru3(CO)12 and was refluxed for additional 75 min after complete mixing of the compounds. The solvent was subsequently removed from the solution under reduced pressure. Hexane was added to the residue and further addition of 30 mL 20% H3PO4 led to a coloration of the hexane phase due to phase transfer. The organic phase was pipetted in another flask containing anhydrous MgSO4, filtered and concentrated under reduced pressure. The concentrate was chromatographically purified under argon atmosphere using silica gel  and hexane as eluent with the column length being sufficient to clearly separate the different fractions containing other metal carbonyls. Three fractions of distinct color  were eluted with hexane and discarded. The red product was finally stripped from the column using benzene and the solvent was removed. The crude product was crystallized from hexane to obtain sheet-like crystals of H2FeRu3(CO)13, which were dried under reduced pressure. 1H NMR identified a small concentration of impurity hexanes with very low concentration in a saturated solution. These are however removed under reduced pressure. Crystals were checked by single crystal XRD (with R = 2.8%) without any solvent molecules incorporated in the crystals. Unit cell parameters were determined for different crystals and gave the same results. IR spectra are recorded, and were found to be in accordance with literature data. The thermal stability of H2FeRu3(CO)13 was investigated by thermogravimety with a heating rate of 5 K·min−1. The onset of thermal decomposition for the precursor is at ≈390 K. Since the stability at elevated temperatures is important for the evaporation of the precursor, isotherms at different temperatures under nitrogen were recorded. The most important one for the evaporation procedure showed a mass loss of <1.5% during heating for 4 h at 343 K.All handling and synthesis procedures were carried out under inert atmosphere using Schlenk and glove box techniques to prevent oxidation. Fe(CO)terature . The solGas phase experiments were conducted in a crossed electron/molecular beam instrument under single collision condition. A full description of the experimental setup can be found in [2FeRu3(CO)13 produced by subliming the precursor molecule into the collision chamber through a capillary tube. The flow of the molecular beam can be precisely controlled with a leak valve. Prior to the measurement, the background pressure of the collision chamber was ≈6 × 10−8 mbar. With heating of the inlet system to 338–343 K, the precursor pressure increased to 2–4 × 10−7 mbar. In order to avoid charging of the electrical lense components of the monochromator due to condensation on its surfaces, the monochromator was maintained at a temperature of about 393 K. The electron energy scale was calibrated based on the SF6−/SF6 formation at 0 eV and the energy resolution of the electron beam was estimated from the FWHM of the SF6−/SF6 signal at 0 eV. Both positive and negative ions formed by the interaction of electrons with H2FeRu3(CO)13 were analyzed and detected using a quadrupole mass spectrometer (Hiden EPIC1000).found in  and thus3(CO)12 the handling of H2FeRu3(CO)13 was more demanding. Maintaining sufficient pressure for acceptable signal to noise ratios and acquisition times required temperatures above 338 K, preferably higher, while heating above 348–353 K caused decomposition of H2FeRu3(CO)13 . For HFeCo3(CO)12, on the other hand, it was easy to maintain sufficient working pressure and no change in the behavior of this compound was observed, even at temperatures as high as 358 K.Compared to HFeCoThe quantum chemical calculations of the thermochemical thresholds for the negative ion fragment formation were performed using the ORCA computational chemistry software [2FeRu3(CO)13 precursor molecule was heated during the experiments, we included the thermal energy of the neutral molecule in the calculations 13 is 1.16 eV). We note, that this is the most probable internal energy and does not account for the actual Maxwell–Boltzmann distribution of internal energies at the current temperature. The molecular orbitals and spin density of H2FeRu3(CO)13 were plotted using VMD [software . In mostsoftware –100 /defsoftware  level ofsoftware –76 and tsoftware . The enesing VMD .The surface science experiments were performed in a UHV-chamber equipped with XPS and MS (more details can be found in [+ ions. To create H2FeRu3(CO)13 films, H2FeRu3(CO)13 was sublimed into the UHV-chamber from a glass finger through heating to 338–343 K. The heating increased the chamber pressure from ≈9 × 10−9 mbar to ≈4 × 10−7 mbar. H2FeRu3(CO)13 was deposited onto a cooled (153 K) Au substrate. To get sufficiently thick films, it was necessary to dose the precursor continuously for 4 h. The thickness of the film was determined from the attenuation of the Au 4f XPS signal, using an inelastic mean free path of 2 nm for the Au 4f photoelectrons [2FeRu3(CO)13 film thickness ranged from 1.1 to 1.4 nm. Based on the effective size of the H2FeRu3(CO)13 molecule (estimated from the computed structure of H2FeRu3(CO)13) this film thickness corresponds to 1 to 2 monolayers. The composition of the film was determined from analysis of the Ru 3d/C 1s, Fe 2p and O 1s XPS transitions.found in ,102). A lectrons . Typical2FeRu3(CO)13. For all surface science experiments, we used an electron energy of 500 eV. This value corresponds to the sum of the flood gun's electron energy and a positive bias of +20 eV applied to prevent the escape of secondary electrons generated in the surface by the impact of primary electrons. Electron flux was measured based on the target current, which was held constant during a particular experiment by adjusting the electron current as needed. Changes in the film’s composition and bonding as a result of electron irradiation were determined by measuring the Ru 3d/C 1s, Fe 2p and O 1s transitions in terms of electron dose (electron dose = target current × exposure time).Following deposition, the substrate temperature was increased from 153 K to 213 K to ensure that any co-adsorbed water had desorbed prior to electron irradiation. A commercial flood gun (Spec FG 15/40) was used to irradiate the adsorbed film of Hhν = 1253.6 eV). The measured spectra were de-convoluted using commercial software CASA XPS. The Ru 3d/C 1s, Fe 2p and O 1s regions were calibrated by aligning the measured Au 4f7/2 substrate XPS peak to 84 eV. Gas phase species which desorbed from the surface as a result of electron irradiation were monitored using a quadrupole mass spectrometer .All XPS data were recorded with a PHI 5400 XPS using Mg Kα X-rays  equipped with a Schottky electron emitter. The base pressure of the system was 4 × 10−6 mbar. An Omniprobe gas injector with inner diameter of the capillary of 0.5 mm was used. The distances of the capillary to the substrate surface and the center of the field of view was 100 µm  and 90 to 100 µm , respectively. The precursor HFeCo3(CO)12 was heated to 337 K leading to an increase of the chamber pressure by about 1 × 10−7 mbar. The precursor H2FeRu3(CO)13 was heated in several steps up to 338 K leading to a hardly detectable increase of the chamber pressure. The deposition experiments were done on p-doped Si(100) substrates with native oxide, thermally grown SiO2 (200 nm) or Si3N4 (100 nm). We did not observe an appreciable influence of the different substrate materials on the results of the deposition experiments. The substrate temperature was 296 K for all deposition experiments. After some preliminary experiments we set the beam energy to 5 keV for the deposition experiments with H2FeRu3(CO)13, as we observed a strong reduction in both deposition yield and metal content at higher beam energies. For HFeCo3(CO)12 we have shown in previous work that high metal contents can be obtained for a wide range of beam energies and currents [currents .Energy-dispersive X-ray analysis (EDX) experiments were performed in situ directly after growth at 5 keV beam energy and 1 nA beam current.Transport measurements were performed in the temperature range from 2 to 300 K under fixed bias voltage conditions in two- or four-probe configuration, employing Cr/Au electrode structures prepared by dc magnetron sputtering and standard UV lithography.Atomic force microscopy (Nanosurf EasyScan 2) in dynamic, non-contact mode was done on selected samples.File 1Additional data.


Tight regulation of the eukaryotic cell cycle is paramount to ensure genomic integrity throughout life. Cell cycle checkpoints are present in each phase of the cell cycle and prevent cell cycle progression when genomic integrity is compromised. The G2 checkpoint is an intricate signaling network that regulates the progression of G2 to mitosis (M). We propose here a node‐based model of G2 checkpoint regulation, in which the action of the central CDK1–cyclin B1 node is determined by the concerted but opposing activities of the Wee1 and cell division control protein 25C (CDC25C) nodes. Phosphorylation of both Wee1 and CDC25C at specific sites determines their subcellular localization, driving them either toward activity within the nucleus or to the cytoplasm and subsequent ubiquitin‐mediated proteasomal degradation. In turn, this subcellular balance of the Wee1 and CDC25C nodes is directed by the action of the PLK1 and CHK1 nodes via what we have termed the ‘nuclear and cytoplasmic decision states’ of Wee1 and CDC25C. The proposed node‐based model provides an intelligible structure of the complex interactions that govern the decision to delay or continue G2/M progression. The model may also aid in predicting the effects of agents that target these G2 checkpoint nodes. PLK1 paves the way for degradation of Wee1 by phosphorylating its Ser53 residue As a result of various replication events, even in the absence of genotoxic stress, healthy eukaryotic cells acquire basal levels of DNA damage during S phase that may not be resolved until late G2 phase et al. PLK1 has been described as harboring a nuclear translocation signal that allows for tight regulation of its subcellular localization during the cell cycle Detection of DNA damage during S and G2 phase, causes induction of a G2 checkpoint arrest that allows for proper DNA repair and prevention of mitotic catastrophe CHK1 controls both CDK1 regulatory nodes by managing the subcellular localization balance of Wee1 as well as CDC25C. CHK1 phosphorylates Wee1 on Ser642, preventing it from being targeted for extranuclear translocation and activating its CDK1‐directed kinase activity S268/S301/S345 is competed for by the E3 ubiquitin ligase Skp1‐Cul1‐Fbox F‐box only protein 6 (SCFFBX6) on one hand and phosphatases on the other hand, designating this form as the CDS. FBX6 targets CHK1 for ubiquitin‐mediated proteasomal degradation by phosphodegron recognition of the Ser345 residue Following dephosphorylation by PP2A, CHK1 can be targeted by the CDK1‐Cyclin B1 complex, reinforcing nuclear CDK1 activity. This interaction has been shown to promote Crm‐1 (exportin‐1)‐mediated translocation of CHK1 to the cytoplasm by phosphorylation of the Ser286 and Ser301 residues Wee1 kinase is the primary negative regulator of the CDK1 node through phosphorylation of active CDK1 on the Tyr15 residue Fig.  68, 69. Once transported into the nucleus, Wee1 needs to be released from Hsp90α to carry out its downstream function, which occurs by a mechanism that is not yet elucidated but might involve dephosphorylation of Hsp90α by any tyrosine phosphatase. This unbound form of Wee1 can best be designated as the Wee1 NDS since two kinases compete for this unphosphorylated Wee1. On one hand CHK1 targets the Ser642 residue of Wee1, favoring the Wee1 decision toward phosphorylation of CDK1 S642Phosphorylation of the Ser642 residue by CHK1 creates a binding site for the cup‐shaped phosphorylation stabilization family of 14‐3‐3 proteins, which shelters the phosphorylated residue and stabilizes phosphorylated Wee1S123 can be designated as the Wee1 CDS since, again, two proteins compete for this form. At one end, cell division control protein 14A (CDC14A) dephosphorylates Ser123, undoing the action of CDK1, preventing Wee1 degradation, and completing the Wee1 cycle by again enabling complex formation with Hsp90α Y210 in a complex with phosphorylated casein kinase 2 (CK2) competes with CDC14A for the Wee1 CDS. Phosphorylation of the Ser53 residue by PLK1 and the Ser121 residue by CK2 creates two additional phosphodegrons β‐TrCP), preparing Wee1 for proteasome‐mediated degradation The resulting cytoplasmic phosphorylated Wee1In human cells, three isoforms of CDC25 have been identified that can in part not only compensate for each other's role upon perturbation of the cell cycle machinery but also perform distinct functions throughout the cycle under physiological conditions PP1 remains associated with CDC25C during its nuclear translocation, facilitating its own nuclear shuttling T130/S198/T236 that is weakly associated with PP1 can be designated as the NDS of CDC25C, since both CDK1 and CHK1 compete for phosphorylation to determine its fate. Favoring entry into mitosis, CDK1 can phosphorylate the Ser214 residue as part of a positive feedback loop, enabling CDC25C to carry out its phosphatase function on CDK1 Nuclear triple phosphorylated CDC25COpposite to the action of CDK1, CHK1 can phosphorylate the NDS of CDC25C on the Ser216 residue, favoring nuclear exclusion and causing dissociation of PP1 S216 is recognized by components of the degradation pathways, promoting G2 arrest and implicating the phosphorylated S216 residue as a phosphodegron β‐TrCPCytoplasmically located phosphorylated CDC25CEven though CDK1 can form a complex with other cyclins earlier in the cell cycle, the Cyclin B1‐CDK1 complex is responsible for triggering mitotic onset. The Cyclin B1‐CDK1 complex is localized cytoplasmically during interphase but is rapidly translocated to the nucleus to instigate G2/M transition during prophase In the nucleus, the active Cyclin B1‐CDK1 can be designated as the NDS of Cyclin B1‐CDK1, since Wee1 competes for this state with the mitosis‐promoting activity of CDK1. Moreover, the active Cyclin B1‐CDK1 complex directly counteracts the effects of CHK1 in the nucleus by competing for the NDS of Wee1 and CDC25C and priming CHK1 for nuclear export Fig. . Wee1 phY15. MYT1 further consolidates the inactivation of CDK1 by phosphorylating the Thr14 residue of CDK1, sequestering it from the nuclear cytoplasmic cycle In the cytoplasm, MYT1 competes with a yet unidentified phosphatase for the phosphorylated CDS of Cyclin B1‐CDK1T14/Y15 might be reintroduced into the nuclear cytoplasmic cycle and subsequently further dephosphorylated by a yet unidentified phosphatase, allowing reactivation by CDK1 by CAK Indeed, it was shown that overproduction of MYT1 sequesters CDK1 in the cytoplasm by preventing nuclear import The node‐based model of the G2 checkpoint represents a tightly controlled biomolecular switch. The Wee1 and CDC25C nodes are two arms of a scale that is influenced by the CHK1 and PLK1 nodes (depicted as weights and hydraulic arms) to tip to either the active or inactive form of CDK1 Fig. . Even unAlthough not yet all details of the G2 checkpoint have been resolved, the model of the G2 checkpoint as proposed here already offers support in explaining some of the thus far poorly understood observations in studies using inhibitors interfering in the checkpoint. The interplay between the different G2 checkpoint nodes is predominantly determined by influencing the decision states of Wee1, CDC25C, and CDK1 Fig. . ConsequFor instance, as has been reported, inhibition of CHK1 would result in enhanced nuclear‐to‐cytoplasmic export and subsequent degradation of Wee1 since its competition with CDK1 is compromised. On the other hand, however, inhibition of the KD of Wee1 by a small molecule would not affect the decision states and therefore does not change cellular Wee1 levels Although the last two decades have generated a framework of the biomolecular network of the G2 checkpoint, many interesting questions remain. Several steps of the G2 network remain to be elucidated in full detail, among which the factor responsible for the cytoplasmic phosphatase activity on Cyclin B1‐CDK1, the signal priming Cyclin B1‐CDK1 for extranuclear transport, the E3‐ligase responsible for CDC25C degradation, and the specific PP2A regulatory subunit determining CHK1 substrate recognition. Moreover, the cytoplasmic activation of the Cyclin B1‐CDK1 complex has interesting implications for the regulatory effect of CDK1 on the Wee1 and CDC25C nodes, although the extent to which these implied mode of actions truly influence the nodal balance of the G2 checkpoint has yet to be determined. On the one hand, cytoplasmically active CDK1 might already activate CDC25C for CDK1‐targeted activity prior to nuclear entry, possibly preventing nuclear phosphorylation by CHK1 and thereby loosening the control of CHK1 on the NDS of CDC25C. On the other hand, it might directly counteract the effect of the phosphatase CDC14A on cytoplasmic Wee1, promoting Wee1 to re‐enter the NDS of Wee1 by phosphorylating it and subsequently promoting degradation of Wee1. Together, this would allow CDK1 to simultaneously promote G2/M progression in the nucleus and the cytoplasm, adding to the strength of the G2 molecular switch.Although beyond the scope of this review, it is intriguing to note that, many reports suggest a role for several G2 checkpoint players or homologs thereof in the regulation of the G1 or intra‐S checkpoints. Among these are Cyclin A, CDK2, CDC25A, CAK, PP2A, PP1, CHK1/2, PLK2/3, and Wee1 In summary, the G2 checkpoint is an ingenious node‐based molecular switch which outcome is determined by the interplay of the PLK1, CHK1, Wee1, CDC25C and CDK1 nodes that are influenced by DNA damage and repair signaling. Together, this system allows the cell to intricately relay DNA status information to the cell cycle machinery, making it a pivotal process in maintaining cellular integrity.MG, AT, and IB searched the literature; MG, AT, IB, and OT designed the model; MG, OT, JB, and TW wrote the manuscript.Fig. S1. Complete overview of the G2 checkpoint network.Click here for additional data file.Video S1. The G2 checkpoint ‐ a node‐based molecular switch.Click here for additional data file. Click here for additional data file.


Amorphous‐like Ni–Fe–S ultrathin nanosheets by oxygen incorporation and electrochemical tuning show excellent OER activity at high current densities. Such excellent performance could be attributed to the unique 3D porous configuration composed of amorphous‐like ultrathin nanosheets with much more active sites and improved conductivity, as well as the proper electronic structure benefiting from the oxygen incorporation and electrochemical tuning. TheThe NFS ultrathin nanosheets are synthesized via an electrodeposition method from aqueous solution containing nickel salt, iron salt, and thiourea . The as‐prepared samples are first characterized by scanning electron microscopy (SEM). As shown in Figure S1a,b in the Supporting Information, the nanosheet arrays are grown tightly on Ti plate on a large scale. The interconnected nanosheets construct a 3D open structure, facilitating effectively the electrolyte penetration and charge transport.Figure−1, marked with blue dotted box) as well as the vibrational modes of NFS in O‐NFS ultrathin nanosheets, revealing the incorporation of oxygen into NFS ultrathin nanosheets. Moreover, the oxygen atom bonded to metal in O‐NFS can also be testified by the comparison of O 1s XPS in O‐NFS and NFS, as well as the Ni 2p, Fe 2p, and S 2p regions of O‐NFS ultrathin nanosheets . All the linear sweep voltammetry (LSV) curves are 95% I−R corrected. In addition, the OER activities of Ni–S and Fe–S samples are also tested to compare with NFS ultrathin nanosheets . The NFS ultrathin nanosheets catalyst shows smaller overpotentials under the same current densities than that of Ni–S and Fe–S counterparts, indicating the better OER activity of NFS. As shown in Figure−2 under overpotentials of 312 and 334 mV, respectively. In brief, the O‐NFS ultrathin nanosheets catalyst shows smaller overpotentials under the same current densities than that of NFS counterpart, indicating the better OER activity of O‐NFS. When the oxygen‐incorporation amount is further increased to 5.5% by annealing the NFS ultrathin nanosheets in air for 5 h (denoted as O‐NFS‐con), the current densities of O‐NFS‐con toward OER decrease compared with that of O‐NFS, indicating the proper oxygen‐incorporation amount is important for the OER activity . From Nyquist plots of O‐NFS and NFS in Figure To get insight into the influence of oxygen‐incorporation on the electrochemical performance toward OER, NFS, and O‐NFS ultrathin nanosheets are directly served as working electrodes to be tested in 1 −1 in 1 m KOH solution. Only 120 s is needed to complete the entire ECT process. Then, LSV curve of O‐NFS after ECT (denoted as O‐NFS‐ECT) is recorded . It is found that the OER activity can be enhanced with the treatment time increased in the range of 0–120 s, however, it does not change when the treatment time is extended to much longer (280 s). Since the electrochemical activities are sensitive to the surface electronic states and active areas, it is necessary to measure XPS and electrochemical double‐layer capacitance (Cdl) in proportion to the electrochemically active surface area (ECSA)p XPS spectra of O‐NFS and O‐NFS‐ECT. The Ni2+ peak shows a negative shift (≈0.2 eV) compared to that of O‐NFS, when O‐NFS are electrochemically reduced by ECT. The electronic structure changes happen to Ni in O‐NFS‐ECT may weaken Ni—O bond from Ni‐OO species in the last step of OER process and thus accelerate the release of O2.Cdl of O‐NFS and O‐NFS‐ECT ultrathin nanosheets can be determined from the cyclic voltammetry (CV) curves, which were tested at different scan rates from 20 to 120 mV s−1  and O‐NFS‐ECT (1.1 mF cm−2) ultrathin nanosheets  for three times at a scan rate of 10 mV sed Figure4a. The2 with the same mass loading of 0.17 mg cm−2 deposited on Ti plate, and bare Ti plate are also measured . Note that, the O‐NFS‐ECT achieves a large current density up to 500 mA cm−2 under an extremely low overpotential of 300 mV, which can meet the demand for industrial applications.[[qv: 2a]] The corresponding Tafel slopes for O‐NFS‐ECT and RuO2 are calculated as 39 and 71 mV dec−1, respectively  as an efficient OER catalyst, especially at large current densities. The strategy combining the oxygen incorporation with ECT successfully realizes the synergistic regulations of electronic and structural (active sites) properties. The influence of oxygen‐incorporation and ECT on the OER activity is also investigated. The O‐NFS‐ECT catalyst offers new possibilities to meet the industrial demand of highly efficient catalysts. It shows large current densities of 500 and 3000 mA cmPreparation of Ni–Fe–S Ultrathin Nanosheets: NFS ultrathin nanosheets were prepared by an electrodeposition method in a standard three‐electrode electrochemical cell with Ti plate, Pt plate, and saturated calomel reference electrode (SCE) as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte bath contained 4 × 10−3m Ni(NO3)2·6H2O, 1.2 × 10−3m Fe(NO3)3·9H2O and 0.5 m thiourea. The constant potential electrodeposition was carried out at −1.044 V (vs SCE) for 11 min. The electrodeposited Ti plate was cleaned by rinsing with water and ethanol, followed by drying in air at room temperature. The mass loading of NFS ultrathin nanosheets on Ti plate was determined by the mass differences before and after the electrodeposition using a microbalance (Mettler Toledo XS205). The typical mass loading is about 0.17 mg cm−2.Preparation of Ni–S or Fe–S Ultrathin Nanosheets: The preparation procedures of Ni–S or Fe–S ultrathin nanosheets were similar to the preparation of NFS ultrathin nanosheets, except that 4 × 10−3m Ni(NO3)2·6H2O and 1.2 × 10−3m Fe(NO3)3·9H2O were replaced with 5.2 × 10−3m Ni(NO3)2·6H2O or 5.2 × 10−3m Fe(NO3)3·9H2O.Preparation of Oxygen‐Incorporated Ni–Fe–S Ultrathin Nanosheets: The oxygen‐incorporated ultrathin nanosheets were obtained by annealing the electrodeposited NFS ultrathin nanosheets at 200 °C for 1 and 5 h in air .Electrochemical Tuning of Oxygen‐Incorporated Ni–Fe–S (O‐NFS‐ECT) Ultrathin Nanosheets: The electrochemical tuning of O‐NFS was conducted in 1 m KOH electrolyte by in situ negative linear sweeps from 0.126 to −0.274 V (vs RHE) for three times at a scan rate of 10 mV s−1. Only 120 s is needed to complete the entire ECT process. Then, the O‐NFS‐ECT ultrathin nanosheets were obtained.Structural Characterization: The SEM images were taken with a Hitachi S‐4800 scanning electron microscope. TEM and HRTEM images were obtained with FEI Tecnai G2 F20 system equipped with GIF 863 Tridiem (Gatan), and EDS elemental distribution images were determined by JEM 2100F transmission electron microscope. The XRD was recorded with a Bruker D8 Focus Diffraction System using a Cu Kα source (λ = 0.154178 nm). Raman spectra were recorded on a RENISHAW inVia reflex Raman Microscope at excitation laser wavelength of 532 nm. XPS analysis was performed on a PHI 5000 Versaprobe system using monochromatic Al Kα radiation. All binding energies were referenced to the C 1s peak at 284.8 eV.Electrochemical Measurements: Electrochemical measurements were carried out in a typical three‐electrode cell consisting of a working electrode, a glassy carbon counter electrode, and a Hg/HgO (1 m KOH) reference electrode using an electrochemical workstation . The Ni–Fe–S catalyst samples on Ti plate were directly used as the working electrode. The RuO2 sample as control catalyst was dispersed in water/isopropanol with Nafion solution and drop‐cast into the Ti plate. All the loading mass of the catalysts on the Ti plate was about 0.17 mg cm−2. All the potentials in the text, if not specified, were recorded relative to the reversible hydrogen electrode (vs RHE) and the current density was normalized to the effective geometrical surface area. OER measurements were carried out in the presence of Ar‐saturated 1 m KOH (pH = 14.00) as electrolyte. The electrochemical impedance spectroscopy measurements were carried out in the same configuration at 1.576 V (vs RHE) from 1000 KHz to 1 Hz. The Faradaic efficiency was calculated by comparing the amount of gas theoretically calculated and experimentally measured. The gas experimentally generated from the water splitting was collected by water–gas displacing method. The theoretical amount of O2 was calculated by applying the Faraday law.TOF Calculation: TOF was calculated according to the following Equation j is the measured geometrical current density at a given overpotential of 300 mV, A is the surface area of the electrode, the number 4 represents four electron transfer for per mole of O2, F is the Faraday constant, and n is the number of moles of the Ni atom on the electrode. The Ni content was calculated from the total charge by integration of the Ni2+/Ni3+ redox peak area in the cyclic voltammogram.As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.SupplementaryClick here for additional data file.


RNA regulons consisting of mRNAs whose protein products act cooperatively allows RNA binding proteins to exert their effects at multiple points in a pathway. Here, we review recent evidence demonstrating the importance of RNA binding proteins that control the cell cycle in lymphocyte development and discuss the implications for tumorigenesis. WIREs RNA 2017, 8:e1419. doi: 10.1002/wrna.1419Lymphocytes undergo dynamic changes in gene expression as they develop from progenitor cells lacking antigen receptors, to mature cells that are prepared to mount immune responses. While transcription factors have established roles in lymphocyte development, they act in concert with post‐transcriptional and post‐translational regulators to determine the proteome. Furthermore, the post‐transcriptional regulation of WIREs website.For further resources related to this article, please visit the  Lymphocytes are the cells responsible for adaptive immunity in vertebrates. B cells are the subset of lymphocytes uniquely producing antibodies (secreted immunoglobulins) and recognize antigens through their B cell receptors . In mammals B cells continuously develop from haematopoietic stem cells in the bone marrow throughout adulthood to sustain the mature pool of antigen inexperienced (naïve) B cells. T cells are lymphocytes that recognize antigenic determinants that have been processed and presented by antigen presenting cells through their T cell receptors (TCRs). T cells provide cell‐mediated immunity and help B cells produce antibodies. T cells develop from progenitor cells that have migrated from the bone marrow to the thymus.Developing B and T cells must execute V(D)J recombination of the DNA encoding immunoglobulin heavy and light chain or of the TCRα and TCRβ loci respectively to produce diverse receptor specificities while avoiding inappropriate DNA damage and maintaining genome integrity. Lymphocytes that produce functional antigen receptors with nonself‐specificities must be positively selected while those producing non‐functional proteins or self‐reactive specificities must be removed. Furthermore, lymphocytes must adapt to a number of distinct niches as they migrate within the bone marrow, blood, spleen, lymph nodes, and other tissues in a developmental stage appropriate manner. To mediate these processes, developing lymphocytes are known to respond to environmental and developmental cues through signal transduction pathways activated by cytokine/chemokine, adhesion receptors and the antigen receptor or its precursor (the pre‐BCR or the pre‐TCR). These regulate gene expression through the expression and activation of developmental stage‐specific transcription factors.Zfp36, Zfp36l1, Zfp36l2, Elavl1, and Cnot3 are broadly expressed throughout the early stages of lymphocyte development and may exert their effects at many distinct stages.Post‐transcriptional control of gene expression is mediated by RNA binding proteins (RBPs) and non‐coding RNAs. Although microRNAs have important roles in lymphocyte development, this review will focus on the role of RBP in early lymphoid development as this topic has received less attention. Regulation through RBP allows signaling events to rapidly influence the fate of existing coding and non‐coding RNAs, thus avoiding the lag time associated with transcriptional changes, and allowing a more diverse and dynamic range of molecular outcomes. Co‐regulated RNAs may comprise sets of transcripts mediating a common function and have been termed RNA regulons.Amongst sequence elements recognized by specific RBPs, the AU‐rich element (ARE), which has the consensus sequence WWAUUUAWW, where W may be U or A, is one of the best studied. AREs are present in as many as 10% of human mRNAsCdkn1b) transcription and enhances the transcription of Cyclin D3, which activates CDK‐4 and ‐6 to drive cell cycle progression in early pre‐B cells.V(D)J recombination is a process of somatic gene rearrangement unique to lymphocytes where variable (V), diversity (D), and joining (J) gene segments, encoding the complementarity determining regions of the antigen receptors, are recombined by the activity of the recombination activating genes (RAG) to form different coding sequences resulting in a large number of receptor specificities. This allows generation of a diverse repertoire of B and T cells each able to recognize a unique antigen. In B cell development, V(D)J recombination generally occurs first at the immunoglobulin heavy chain (IgH) locus with D to J recombination which is complete at the pre‐pro‐B cell stage of development Figure . Next, VThe deliberate introduction of DNA strand breaks (DSBs) and the joining of the resected DNA carries the risk that the DNA will not be repaired correctly and it is known that chromosomal translocations and other aberrations do occur in some cells at this stage of development.Recent evidence suggests that the transcriptional and signaling pathways regulating processes that co‐ordinate the dynamic proliferation of developing B and T cells are integrated with post‐transcriptional mechanisms mediated by the ZFP36 family RBP. The ZFP36 family bind to AREs in the 3′UTR of their target mRNAs through a conserved CCCH‐zinc finger structure and recruit deadenylases and decapping enzymes to destabilize their targets.The mechanistic insight into this process was revealed by the application of individual nucleotide crosslinking and immunoprecipitation (iCLIP) for ZFP36L1. These experiments performed on mitogen activated mature B cells (which bear overlap in their transcriptomes with proliferating pro‐B cells) demonstrated ZFP36L1 bound to AREs in the 3′UTRs of a group of mRNAs encoding proteins involved in the G1‐S transition.Zfp36l1 Zfp36l2 KO pro‐ and pre‐B cells was rescued by administration of the CDK4/6 inhibitor palbociclib. Conditional overexpression of a GFPZFP36L1 fusion protein inhibited the proliferation of pre‐B cells. Thus Zfp36l1 and Zfp36l2 are necessary to establish a quiescent state permissive for V(D)J recombination in pro‐B and pre‐B cells. Furthermore, the increased proliferation of Igμ‐negative pro‐B cells led to defective selection as loss of Zfp36l1 and Zfp36l2 allowed some Igμ‐negative cells to express the pre‐B cell marker CD25 indicating that they had bypassed the pre‐BCR checkpoint. However, these cells were apoptotic indicating they had not received the survival signals provided by the pre‐BCR.Overexpression of the RNA regulon repressed by ZFP36L1 and ZFP36L2 amplifies the sensitivity of the E2F pathway thus tipping the balance towards S phase entry and leading to activation of the mechanisms which prevent V(D)J recombination from occurring. The V(D)J recombination defect in Zfp36 and Zfp36l1 are transcriptionally repressed by c‐Myc, which is transcribed following IL7R or pre‐BCR signaling providing a further mechanism for regulation of these RBP during early B cell development.The regulation of cell cycle mRNAs by ZFP36 family proteins provides a mechanism by which developing B cells may rapidly change their behavior according to signals from the pre‐BCR and IL7R. Phosphorylation of ZFP36L1 by protein kinase B (PKB) downstream of PI3kinase signaling and through the P38 MAPKAPK2 kinase pathway could repress its ability to promote RNA decay.Zfp36l1 and Zfp36l2 in the T cell lineage leads to the development of T cell acute lymphoblastic leukemia.Zfp36l1 and Zfp36l2 play roles in early T cell development that are very similar to those in B cell development. Thus, in the T cell lineage, Zfp36l1 and Zfp36l2 limit proliferation to those cells that have productively rearranged the TCRβ and thus enforce the β‐selection checkpoint.Zfp36l1 Zfp36l2 double conditional KOs resembled post β‐selection cells (termed DN3b) more than the quiescent pre‐selection DN3a cells despite not expressing the TCRβ protein. Since DN3b cells are proliferating, the DN3b transcriptional profile includes expression of cell cycle regulators involved in the G1‐S transition, providing further evidence of the control of this RNA regulon by ZFP36L1 and ZFP36L2. NOTCH1 is an important target of ZFP36L1 and ZFP36L2 which is required for driving leukaemogenesis in their absence.Zfp36l1 and Zfp36l2 cannot provide all the signals required for β‐selection. Pre‐TCR signaling increases expression of the IL7R, rendering the cells more responsive to IL‐7,Zfp36l1 Zfp36l2 double conditional KO DN3 cells do not upregulate the IL7R pathway and are more apoptotic than controls.T cells develop in the thymus in an analogous manner to B cell development Figure . The TCRZfp36l1 Zfp36l2 DCKO DN3 cells was linked to an increased rate of differentiation consistent with findings that differentiation is linked to the numbers of cell divisions during T cell development.Zfp36l1 Zfp36l2 cKO DN3 thymocytes were also found to have increased γH2AX, which marks double strand breaks, and increased phosphorylation of substrates of the ATM/ATR kinases that initiate the DNA damage checkpoint. Despite this, it remains unclear whether the DCKO cells actually have increased DNA damage or whether the DNA damage response is more activated per se and it is possible that the phosphatases that regulate γH2AX may be less active in the DCKO cells. If DNA damage itself is increased, this may contribute to the oncogenic transformation of Zfp36l1 Zfp36l2 cKO thymocytes into T‐ALL.The increased proliferation of Zfp36l1 and Zfp36l2. Mdm2 transcript was increased in these cells, as well as late pre‐B cells from the B cell DCKO and Mdm2 mRNA was bound by ZFP36L1 in both thymocytes and B cells. Thus, Mdm2 is likely a direct target of ZFP36l1 and ZFP36L2. MDM2 is a negative regulator of P53 so ZFP36L1 and ZFP36L2 may enhance P53 responses in B and T cell progenitors during the periods in which cell cycle progression is being inhibited and V(D)J recombination is occurring. The DSBs caused by V(D)J recombination induce p38 signalingUnlike the situation in developing B cells, the DNA damage response is able to promote the developmental progression of DN3 thymocytes, and irradiation can do so in the absence of TCRβ, the obligate progression factor.Zfp36l1 and Zfp36l2, there was no evidence of a P53 transcriptional response in DN3 thymocytes or late pre‐B cells lacking Zfp36l1 and Zfp36l2. P21 (Cdkn1a) mRNA, a well‐known p53 target, was elevated in DN3 thymocytes and late pre‐B cells lacking Zfp36l1 and Zfp36l2, however, this does not imply activation of the p53 pathway in this context as the p21 mRNA is also an ARE‐containing target of ZFP36L1.Although there was evidence of increased DNA damage checkpoint signaling in thymocytes lacking Cnot3 in pro‐B cells (Cnot3 cKOs) leads to impaired B cell development.Zfp36l1 and Zfp36l2; in the Inoue study CNOT3 was found to destabilize TP53 mRNA and in Cnot3 cKOs P53 was overexpressed leading to the induction of apoptosis. P53 mRNA abundance was not affected in pre‐B cells lacking Zfp36l1 and Zfp36l2 and there was no induction of P53 transcriptional targets  suggesting an alternative RBP is recruiting CNOT3 to the P53 mRNA in these cells. Additionally, no transcript signature relating to cell cycle progression was enriched in Cnot3 cKO pro‐B cells suggesting that either the CCR4‐NOT complex can destabilize mRNAs independently of the CNOT3 subunit or the ZFP36 family RBPs can interact with other mRNA‐repressive complexes in pro‐B cells. As the Galloway et al. study did not characterize the transcriptome of Zfp36l1 Zfp36l2 DCKO pro‐B cells comparison between the RNA data in these two studies should be made with the appreciation that each study analyzed a different population of developing B cells.ZFP36 family proteins exert their mRNA‐destabilizing effects in part by recruiting the CCR4‐CNOT deadenylase complex, which interacts with a C‐terminal domain that is conserved among ZFP36 family members through the scaffolding component CNOT1.P53 rescued the apoptotic phenotype of the Cnot3 cKO pro‐B cells observed by Inoue et al., however, there was still a strong defect in V(D)J recombination and development. This defect was linked to decreased transcription of the IgH V genes and decreased IgH locus contraction in Cnot3 cKOs. These processes bring together the IgH‐V gene segments and D‐J gene segments making them amenable for recombination.Cnot3 deficient pro‐B cells. They noted that CCR4‐NOT complex has additional roles in transcription and in nonsense‐mediated decay (NMD) which is required to degrade non‐coding IgH mRNAs which impede further attempts at V(D)J recombination, this could be a mechanism through which CNOT3 might potentiate V(D)J recombination. In contrast, the study by Yang et al. demonstrated reduced expression of PAX5, a transcription factor required for IgH locus contraction, in Cnot3 cKO pro‐B cells.Cnot3 RERTcre cKOs and suggested that the P53 induction observed by Inoue et al. could be dependent on the genotoxic stress induced by Mb1cre interacting with loss of Cnot3. Yang et al. demonstrated that CNOT3 interacts with the transcription factor EBF1 and that this interaction is required for the expression of several EBF1 target genes that are essential for B lineage specification and B cell development. A mutant EBF1 that could not interact with CNOT3 bound less efficiently to approximately half of EBF1 target genes. However, neither Pax5 nor Ebf1 itself appeared to be sensitive to loss of the EBF1‐CNOT3 interaction. The discrepancy in these results could be due to the difference in developmental stage at which Cnot3 expression is lost since the transcriptomics was performed on pro‐B cells isolated from RERT2cre‐expressing mice following tamoxifen treatment. CNOT3 could have slightly different roles in the initial induction of Ebf1 and Pax5 expression in earlier B cell progenitors. Notably some EBF1 target genes had higher mRNA expression in the absence of the EBF1–CNOT3 interaction, and this was associated with increased transcript stability indicating the role of CNOT3 in gene expression in pro‐B cells is complex and can be repressive or activating depending on the context.Knockout of Elavl1), is a RNA recognition motif (RRM) domain containing, ARE‐binding protein that is proposed to antagonize the destabilizing effects of the ZFP36 family.The dynamic control of RNA regulons is, in principle, facilitated by the potential for RBP with the same binding specificities to mediate distinct outcomes for the fate of the RNA. The ARE, with its ability to bind multiple different RBP, may be an exemplar of this form of regulation. HuR, encoded by a paralog of the drosophila embryonic lethal abnormal vision gene  into short dominant negative forms that promote cell cycle progression and lymphomagenesis,Here, we have discussed examples of RNA regulons that coordinate important processes in lymphocyte development. Several challenges must be faced to advance our understanding of RNA regulons in lymphocyte development and other biological contexts. Many RBPs share sequence specificity for simple motifs such as the ARE and this can make studying their functions challenging, for example, all three ZFP36 family members are expressed in developing T and B cells and KO of two family members is required to have dramatic effects on early lymphocyte cell development. This ‘redundancy’ was also observed in lymphomagenesis: T cell acute lymphoblastic leukemia develops in There may also be context‐dependent differences in transcript structure caused by alternative splicing and alternative polyadenylation as well as enzymatic modification that allow transcripts to include or exclude certain regulatory elements.


The differences in emission intensities of 4I13/2 → 4I15/2 transition in NIR region when excited with Ar+ and 980 nm lasers were explained in terms of energy transfer mechanisms. Temperature and power dependence of upconversion bands in the visible region centered at 528, 548 and 660 nm pertaining to 2H11/2, 4S3/2 and 4F9/2 → 4I15/2 transitions were investigated. Fluorescence intensity ratio (FIR) technique was used to explore temperature sensing behaviour of the thermally coupled levels 2H11/2/4S3/2 of Er3+ ions in the phosphors within the temperature range 14–300 K and the results were extrapolated up to 600 K. Anomalous intensity trend observed in Er3+ doped SLA phosphor was discussed using energy level structure. Cytotoxicity of phosphors has been evaluated using 3--2,5-diphenyltetrazolium bromide (MTT) assay in Bluegill sunfish cells (BF-2). The non-cytotoxic nature and high sensitivity of the present phosphors pay a way for their use in vitro studies and provide potential interest as a thermo graphic phosphor at the contact of biological products.Er Fluorescence intensity ratio (FIR) technique is widely used for the temperature sensors based on glasses/glass-ceramics doped with RE3+, providing high detection spatial resolution, precision and excellent sensitivity7. As for concerned with low temperature sensors, CdSe, CdTe semiconductor quantum dots were used as optical temperature nanoprobes as their peak emission wavelength changes with the temperature8, but are of limited application due to low intensity along with difficult preparation procedures. RE3+ doped glasses and glass-ceramics also suffer from low intensity and poor performance. One of the important conditions a material should satisfy in order to be used as temperature sensor is that the radiative transitions from a fluorescent level should dominate its non-radiative transitions. This could be achieved only when the host has considerably low maximum phonon energy. This condition is also relevant to achieve UC, since a material which has low maximum phonon energy can be effectively used for RE3+ UC.Recent interest on rare earth  and visible (Vis) region18. Hence UC materials with near infrared (NIR) excitation would be the best suitable materials for the temperature sensing at the contact of biological product.In order to use an UC phosphor for bio-imaging, it is mandatory to have low cytotoxicity with low phonon energy. Though fluoride based phosphor materials are found to have low maximum phonon energy, their reported dubious nature concerned to cytotoxicity make the usage of these materials for biological applications suspicious3+, Tm3+, Ho3+, Nd3+, Dy3+ and Eu3+ have been used as PL centres of optical thermometry. But the Er3+ ion has proved itself to be an efficient UC centre among RE3+ ions and tremendous increase of its efficiency when combined with Yb3+ ions, acting as sensitizer, makes it the ultimate choice among UC ions. The UC PL intensity ratio between 2H11/2 and 4S3/2 levels has been proved to be very efficient as the bands are due to two photon excitation and the ratio is very sensitive to the temperature7.Many of the trivalent lanthanides such as Er3O7 (SLA) is a complex compound that crystallizes in the tetragonal melilite-like structure with a space group P421m with a general chemical formula ABC3O7 20. The crystal structure of SLA is composed of five membered rings of AlO4 tetrahedra linked at each corner, with the Sr2+ and La3+ ions situated at the centres of these tetrahedra20. It is reported to have good mechanoluminescence properties and can be prepared with RE3+ ions as dopants in several methods24.Strontium lanthanum aluminate, SrLaAl26. The release of these particles into the aquatic environment as ‘an ultimate sink’ cannot be denied and can pose serious risk to the inhabiting organism27. Cytotoxicity evaluation is an important tool to understand the particles impact on the aquatic environment. The BF-2 cells derived from the caudal fin tissue of the bluegill sunfish (Lepomis macrochirus), is extensively used in both in vivo and in vitro toxicity evaluation29. Moreover, recent investigations show that the MTT -2,5-diphenyltetrazolium bromide) assay has been widely used and remains the most popular assays to be relied in academic and research works to know the material’s cytotoxic nature31.To use any of the phosphor particles in industrial production, the impacts of these particles are to be monitored scientifically for its safer development as technology-based product. The particles during their production, transport, use and disposal are seen entering into the environment32. This requirement is the base of our investigation in which non-cytotoxic oxide based material with low phonon energy has been investigated for its application in temperature sensing applications in biological materials. We describe the experiments done to evaluate the application of SLA doped with Er3+ ion or with the Er3+-Yb3+ ion pair, synthesized by Penchini process, to monitor the temperature by FIR method. The UC PL of SLA:Er and SLA:Er/Yb phosphor were studied at various laser pump powers and temperatures. The temperature dependent behavior of the PL intensity and the ratio of PL bands were studied, and the thermometry characteristics were evaluated. In vitro cytotoxicity of SLA phosphor particles has also been evaluated using BF-2 fish cell line and MTT assay28.As a variety of cellular events are effectively marked by temperature changes, a way to monitor the temperature of biological materials by a non-contact method is very essential3O7 (SLA) was identified using XRD. The pattern contains pure tetragonal phase of SLA matrix with space group P421m as shown in Fig. 33, D = kλ / (B cos θ), where D is the average grain size, k (0.9) is the shape factor of the average crystallite, λ represents the Kα1 radiation wavelength of copper, B is the full width at half maximum (FWHM) of the diffraction peak, and θ represents the angle of diffraction, i.e., half of the diffraction angle 2θ. The estimated crystallite size is found to be 65 nm and the unit cell parameters for tetragonal phase is calculated with Unit Cell software are a = b = 7.895 Å and c = 5.217 Å with V = 325.21 Å3.The phase purity and crystal structure of the host SrLaAl−1. Studies on Strontium lanthanum aluminate compounds suggest that the band falling in the 585–595 cm−1 region seems to be originated as a consequence of local distortion of AlO6 octahedron and / or other defects in the matrix36. In low wavenumber region below 400 cm−1, the spectrum possess several overlapped modes at 146, 219, 275 and 306 cm−1 that are attributed to vibrational modes of La/Sr–O and the bridge Sr/La - O - Sr/Al oxygen atoms, respectively37. The SEM image of SLA host is shown in Fig. Figure 4I13/2 → 4I15/2 transition of Er3+ ions as shown in Fig. Under 514.5 and 980 nm excitation the NIR emission spectra for SLA:Er and SLA:Er/Yb0.1 samples exhibits a broad emission band attributed to + laser radiation (514.5 nm) excites Er3+ ion to 2H11/2 state, from where it readily de-excite radiatively or non-radiatively (NR) reaching 4I13/2 level. The final radiative transition to the ground state generates the broad NIR peak , 548 (4S3/2 → 4I15/2) and 660 nm (4F9/2 → 4I15/2), which are labeled by G1, G2 and R respectively and are schematically represented in Fig. 3+ ions in SLA phosphor would be excited to 4I11/2 level through GSA, since the level possess longer lifetime, the same Er3+ ion excites to 4F7/2 level through ESA. The green and red emissions are the outcome of this ESA followed by phonon decay to the 2H11/2 or 4S3/2 level for G1 or G2 and further to 4F9/2 level for R emission. At all powers the G2 emission transition (4S3/2 → 4I15/2) is stronger than that of G1 emission transition (2H11/2 → 4I15/2). As shown in Fig. 3+:2H11/2, 4S3/2 and 4F9/2 levels39. For all laser powers the emission spectra of SLA:Er exhibited same features except increment in their intensities.Figure 3+) ions is low, the trend of increment follows linear. At high concentration and high powers UC emission follows saturation phenomena due to depletion of pump power. It is well known that the intensity ‘I’ of UC emission is proportional to some power ‘n’ of excitation power ‘p’. The number n indicates the number of IR photons required to excite the luminescent ions to get the UC emission. The slope of line plotted with integrated emission intensity of the UC PL as a function of the pump power in logarithmic scale, gives the number of photons required for UC process. In Fig. 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions respectively, which proves that two photon process predominant in present SLA:Er phosphorThe UC emission and pump power dependence emissions are sensitive to dopant concentration. As the concentration of dopant  process dominates in Er3+/Yb3+ codoped sample compared to ESA in singly Er3+ doped sample. The population accumulation in 2H11/2 and 4S3/2 states occur by successive ET process from the excited 2F5/2 state of Yb3+ ions to the Er3+ ions exciting them first to the 4I11/2 state and in a second step to the 4F7/2 excited state. Followed by a non-radiative (NR) relaxation process as shown in Fig. 3+ ions de-excite to 2H11/2 and due to a small energy gap between 2H11/2 and 4S3/2 states, the Er3+ ions can relax fast to the 4S3/2 state resulting in the observed two green emission bands G1 and G2. Alternatively, the ions can relax non-radiatively to the 4F9/2 level leading to red emission of R band. Figure 3+ concentration until 0.1 mol after which the intensities decrease with increase of Yb3+ concentration. This may be due to probable energy migration among Yb´3+ ions due to higher/saturated concentrations. To compare the changes in relative intensities of all the three bands with increase of Yb3+ concentration, the spectra were normalized with respect to G2 band and are presented in Fig. 3+ ions in to SLA:Er sample, the intensity of G1 band decreased initially and then increased till 0.1 mol of Yb3+ ions. For the 0.2 mol of Yb3+ ions G1 band intensity stays same as of 0.1 mol with respect to G2 band. It is also noticed that the band widths of all the UC emission bands increased with the addition as well as increase of Yb3+ ions’ concentration. The case of R band intensity is different than those of G1 and G2. The increase of R band with Yb3+ concentration is more pronounced. This may be due to the cross-relaxation (CR) process 4F7/2 + 4I11/2 → 4F9/2 + 4F9/2 between nearby Er3+ ions due to availability of high number of excited Er3+ ions with effective energy transfer from Yb3+ in their own vicinities as shown in Fig. 41. The CR channel promotes accumulation of more number of Er3+ ions at 4F9/2 adding more intensity to R emission compared to G1 and G2. Further increase of Yb3+ concentration, beyond 0.2 mol may eventually quench the overall UC emission from SLA sample with the CR channel and energy migration phenomenon. From all the different UC of SLA:Er and SLA:Er/Yb samples, it is found that SLA:Er/Yb0.1 has intense emission property among all the prepared phosphors.UC emission in singly ErUC has also been recorded for SLA:Er/Yb0.1 sample by varying 980 nm laser power and is presented in Fig. 2H11/2 level raises exponentially with increase of temperature compared to 4S3/2 level as the energy difference between these two levels is very small based on the formulanA, nB are populations of considered energy levels, C is a constant which depends on the radiative transition rates and the degeneration of these levels and ΔE is the energy gap between the two energy levels. However, G2 and R transitions show a different behaviour. Their intensities first increase up to 90 K and then decrease with increase of temperatures. In comparison, the decrease of G2 is larger than R transition as shown in Fig. 4S3/2 and 4F9/2 levels which is quite common and known as thermal quenching. But the increase of G2 and R UC band intensities from lowest temperature to 90 K is due to the depopulation of higher sublevels of the 4I11/2 manifold which have a resonant match with the 4F7/2 level. Similar results were observed by I.R. Martin et al. and Van Der Ziel et al.43. According to Van Der Ziel et al., at low temperatures, after initial excitation of Er3+ ion from 4I15/2 to 4I11/2 level with 980 nm radiation, the excited ions occupy the lowest crystal field level of 4I11/2. Further, there would be a large mismatch of the energy to excite the ion at lowest crystal field level of 4I11/2 to 4F7/2 level. This mismatch leads to low intensity of UC bands at low temperatures. As the temperature increases, due to thermal agitation, occupancy of other crystal field levels pertaining to 4I11/2 increases that in fact decreases the mismatch to resonant transfer, leading to the increase in UC emission. However, the non-radiative rate increases rapidly at high temperatures and cause the radiative probability to decrease significantly. Therefore, the emission intensity decreases as temperature is increased beyond 90 K. Moreover, it is also observed that the intensity beyond 90 K decreased exponentially and hence the effect of energy mismatch was negligible as shown in Fig. Temperature dependent UC emission spectra of SLA:Er phosphor is shown in Fig. −1. The other is the radiative transition of upper level should dominate over its non-radiative component6. There are two TCL in Er3+ ions, which can be used for FIR technique. One set is 2H11/2/4S3/2 and the other is 4D7/2/4G9/2. As the second set of Er3+ falls in UV region, its determination using UC is hindered with low signals. Hence the first set of TCL is the appropriate set to be used for FIR technique. FIR is defined as the ratio of the PL from each thermally coupled levels of active ions and can be expressed as45A is a fitting constant, B is the overlapping of fluorescence peaks, ΔEf is the fitting energy difference between the two thermally couples levels, K is Boltzmann’s constant and T is absolute temperature.FIR is one of the best techniques to determine the temperature sensitivity of a material to be used as thermographic phosphor. For this technique to be used for sensitivity, any active ion should have two adjacent energy levels which are thermally coupled. Any two adjacent energy levels will be called as thermally coupled levels (TCL) if they follow certain criteria. One of the important criteria which affect the efficiency of the ion for its sensitivity is the separation between these two TCL to be between 200 and 2000 cmFIR in response to the temperature variation. Hence the absolute sensitivity (SA) of the TCL can be expressed as47.The absolute sensitivity of optical thermometry is the rate of change in the To allow the comparison of different sensitivities of the materials, relative sensitivity has been derived by the following relationEf is the fitting energy difference between the thermally coupled levels and the error with respect to experimental energy difference (ΔEm) gives an in site of its agreement with the experimental values. The error δ, can be expressed as49.ΔFigure 3+ ions which could not compensate the large energy mismatch during effective UC process. For peak intensities of SLA:Er and SLA:Er/Yb0.02 samples, the fitting has been performed from 90 K as the typical intensity trends follow beyond that temperature. Whereas, for peak intensities of the remaining SLA:Er/Yb samples, the fitting has been performed from the lowest temperatures. In all the Figs Ef, the fitting energy difference of the two peaks G1 and G2 for all the samples are presented in Table Ef and the fitting parameters of Eq. SA) and relative sensitivity (SR) have been calculated according to Eqs Ef of Eq. SA, SR at room temperature (297 K) and error between ΔEf and ΔEmExcept in case of SLA:Er/Yb0.02 sample, the UC emission spectra of all SLA:Er/Yb phosphors with respect to temperature show similar trend. As the temperature increases, the intensity of G1 bands increase exponentially, whereas with the increase of temperature, intensities of G2 and R decrease exponentially contrary to the trend observed for SLA:Er phosphor. This is explained based on the increase of phonon vibrations with the increase of temperature at high concentrations, eventually leading to decrease in UC intensities of G2 and R. In case of SLA:Er/Yb0.02 phosphor, the intensities of G2 and R  show similar trend as of SLA:Er sample and this phenomenon may have occured because of low concentration of YbSA is maximum at 440, 280, 310, 320 and 300 K for SLA:Er, SLA:Er/Yb0.02, SLA:Er/Yb0.04, SLA:Er/Yb0.1 and SLA:Er/Yb0.2, respectively. Maximum SAvalue temperature determines the temperature at which a material works with sensitively. The temperatures at which SA values are maximum for the present UC phosphors show that they can be used at room temperature as well as at low temperatures effectively. The reliability of the temperature sensing can be made by the error, δ According to Eq. δ is found to be 0.15, 0.44, 0.38, 0.36 and 0.40 for SLA:Er, SLA:Er/Yb0.02, SLA:Er/Yb0.04, SLA:Er/Yb0.1 and SLA:Er/Yb0.2, respectively. Larger the value of δ for SLA:Er/Yb mean that the energy transfer between thermally coupled levels and other levels is not neglected and the population of thermally coupled levels at high temperature is induced by the routes of Boltzmann distribution which is essential for temperature sensing6. Hence, relatively larger values of δ values for SLA:Er/Yb phosphors over SLA:Er phosphor shows that the temperature sensing behaviour of SLA:Er/Yb phosphors can be relied more. In case of relative sensitivity, the SR value is greater in SLA:Er samples than that of SLA:Er/Yb counterparts due to the greater value of ΔEf for SLA:Er as shown in Table 3+ concentrations, SR increased with Yb3+ concentration until 0.1 mol and then decreased with further increase in Yb3+ concentration. SLA:Er/Yb0.1 has greater SR value, higher temperature for maximum SA value. Same phenomenon has been explored in relative intensities of UC with 980 nm at same excitation power as shown in Fig. 3+ ions would yield maximum SR value at different temperatures. Moreover, the UC intensity of SLA:Er is too low to be used practically in comparision to the SLA:Er/Yb samples. From literature it is also evident that the sensitivity of SLA:Er and SLA:Er/Yb phosphors are also in accordance to the low phonon hosts such as fluorides, rare earth oxides etc that are highly used in bio-imaging due to their high UC efficiencies in spite of their toxic nature54.It has been found that vitro studies were conducted on BF-2 cell line. There was no significant cytotoxicity induced by SLA in BF-2 cells as evaluated using MTT assay. It is evident from the Fig. −1. Moreover, most of the researches have used BF-2 and other fish cells for toxicological evaluations of a number of contaminants. However, TiO2 and Ag particles were found to non-cytotoxic on BF-2 cells when exposed to simulated solar light and dark conditions28.To evaluate the cytotoxicity induced by SLA powders on aquatic biota, in −1 of SLA particles for a time interval of 48 h and later observed under optical microscope. The SLA particles even at a concentration of 200 µg ml−1 did not induce any morphological changes in the exposed BF-2 cells until 48 h  phosphors doped with Er3+ and Er3+/Yb3+ were prepared by one step Pechini method. The structural and morphological properties of the products were analyzed by X-ray diffraction, Raman spectroscopy and Scanning electron microscopy show that the materials prepared are structurally pure. NIR emission has been recorded with 980 nm and 514.5 nm laser radiation and show similar peak structure. The upconversion in SLA:Er and SLA:Er/Yb phosphors was found to be due to two-photon using power dependent upconversion spectra. Saturation of upconversion luminescence has been noticed at high powers in SLA:Er/Yb0.1 phosphor. Temperature dependent upconversion for SLA:Er and SLA:Er/Yb0.0.02 phosphors show exponential increase for G1 band whereas steady increase till 90 K and then decrease for the bands at G2 and R were observed. In other SLA:Er/Yb phosphors, G1 band increased exponentially whereas G2 and R quenched exponentially as usual. The maximum absolute sensitivity of SLA:Er was at 440 K and between 280–320 K for various SLA:Er/Yb variable concentrations. Among SLA:Er/Yb phosphors, the phosphor with highest intensity of UC emission exhibited higher relative sensitivity. Overall, SLA:Er/Yb0.1 phosphor exhibited better sensing qualities either in terms of ability to upconvert the radiation or sensing the temperature. The cytotoxicity evaluated for SLA particles on BF-2 fish cell found to be non-cytotoxic even at a concentration of 200 µg ml−1 and did not induce any morphological changes in the exposed cells until 48 h.In conclusion, strontium lanthanum aluminate (SrLaAl3)3), Lanthanum (La(NO3)3), Aluminium (Al(NO3)3), Erbium (Er(NO3)3) and Ytterbium (Yb(NO3)3) nitrates were used as starting materials, citric acid as complexant agent and ethylene glycol used as chelating agent. The dopant ions, Er3+ and Yb3+, were expected to replace the La3+ ions with identical valence and similar ionic radius SLA matrix. The doping was done by fixing Er3+ concentration and varying Yb3+ concentration viz. SrLa1−(x+y)Al3O7:ErxYby  referred as SLA:Er, SLA:Er/Yb0.02, SLA:Er/Yb0.04, SLA:Er/Yb0.1 and SLA:Er/Yb0.2, respectively. The molar ratio of metal ions to citric acid was maintained as 1:1. A homogeneous solution was obtained by dissolving starting nitrates into distilled water, and the pH of the solution was adjusted to 1.5, 3 or 6.5 using ammonium hydroxide. The solution was dried at 100 °C for 12 h under continuous stirring. After complete evaporation of water, the gel was dried in oven at 250 °C for 3 h followed by heat treatment at 800 °C for 6 h to promote crystallinity. Finally, the collected powders were re-milled thoroughly by mixing acetone and pressed into pellets using a uniaxial pressure system.The SLA, SLA:Er and SLA:Er/Yb phosphors were synthesized by Pechini route. In a typical procedure, stoichiometric amounts of Strontium  using Philips PANalytical Xpert Pro analyser with Cu-Kα radiation. Raman spectra were measured by Jobin Yvon HR800 spectrometer with a 442 nm laser excitation source in reflection mode. The morphology of prepared phosphor powders was investigated by scanning electron microscopy (SEM) using TESCAN VEGA3 instrument.+ ion laser (514.5 nm) as well as 980 nm laser diode.Steady state UC spectra were recorded by a Spex 1704 monochromator equipped with a cooled Hamamatsu R928 photomultiplier. The samples were mounted in the cold finger of an optical cryostat, and the temperature was maintained in the range 14 to 300 K. A power-controllable 980 nm laser diode was used to exciting the samples. NIR PL was measured in FTIR Bruker IFS66V instrument with Arin vitro cytotoxicity has been performed on BF-2 fish cell obtained from the caudal fin of L. macrochirus. The cell line was maintained in Eagles minimum essential medium (EMEM) with non-essential amino acids supplemented with 10% fetal bovine serum, 100 U ml−1 pencillin, 100 µg ml−1 streptomycin, 1.25 µg ml−1 fungizone and 2 mM glutamine. Cultures were grown in 75 cm2 culture flask (Corning). The cultures were maintained at 23 ± 2 °C in an incubator supplied with 5% CO2. After the cell reaching 90% confluence, cells were harvested using 0.25% trypsin-EDTA and were sub-cultured in 96 well plates (5 × 103 cells well−1) and were cultured over night at 23 °C under 5% CO2. Cells were allowed to attach to the surface for 24 h prior to treatment. After 24 h the cell culture medium was replaced with SLA particles at a concentration range of (50–200 µg ml−1) for 48 h. After 48 h the 96 well plates were subjected to centrifugation (100 xg for 5 min) using the swing bucket rotor  such that all the cells get deposited in the bottom of the plate and the supernatant is free from cells. After 48 h the entire medium was replaced with new medium containing MTT (5 mg ml−1) and incubated for 4 h at 21 °C in dark until a purple colour formazan product is formed. This product was dissolved in isopropanol and the absorbance was measured at 570 nm using a UV-Vis spectrophotometer . Effects of SLA particles on cell viability were calculated using control cells (without particles).BF-2 cells were obtained from American Type Culture Collection (ATCC # CCL91). The 4 cells. After overnight incubation, the old medium is replaced with fresh medium containing 200 µg ml−1 of SLA particles for 48 h and the cells without any treatment served as control cells. After 48 h the cells were recovered and washed thoroughly with phosphate buffer saline and the morphological changes were observed using Polyvar, Reichert-Jung light microscope attached to a CCD camera  at 10x magnification.Cells were plated in six well culture plates at a density of 2 × 10