To verify results, all‐inorganic 2D layered CsPb2Br5 is synthesized and used in memory devices. The memory devices that use CsPb2Br5 show much better stability and lower operating voltages than devices that use CsPbBr3. These findings are expected to provide new opportunity to design materials for reliable device applications based on calculation, screening, and experimental verification.Memory devices have been advanced so much, but still it is highly required to find stable and reliable materials with low‐power consumption. Halide perovskites (HPs) have been recently adopted for memory application since they have advantages of fast switching based on ionic motion in crystal structure. However, HPs also suffer from poor stability, so it is necessary to improve the stability of HPs. In this regard, combined first‐principles screening and experimental verification are performed to design HPs that have high environmental stability and low‐operating voltage for memory devices. First‐principles screening identifies 2D layered AB 2X5) as the best candidate for RSM. To verify the calculation results, 2D‐layered CsPb2Br5 is synthesized and applied to RSM. The CsPb2Br5‐based RSM shows stable operation with low operating voltages.A design of halide perovskites (HP) for use in resistive switching memory (RSM) by combining first‐principles screening and experimental verification is conducted. First‐principles calculations identify 2D HP structure (AB DFT calculations have enabled identification of candidate materials by so‐called “high‐throughput screening.” For example, DFT calculations have been employed to search for a lead‐free halide perovskites (HPs) photo‐absorber to overcome the presence of toxic lead and thermal instability. In the field of halide HP‐based resistive switching memory (RSM), the use of first‐principles DFT calculations has mainly limited to identifying the origin of electrical characteristics such as low operating voltage, resistive switching failure, and forming‐free behavior. HP‐based RSM has limited stability, so progress in this field requires new materials to improve the stability of HP‐based RSM using first‐principles calculations.First‐principles density functional theory (DFT) calculations have been used in various fields to determine the physical origin of phenomena, and to predict the electrical properties of materials.18 DFT However, this method induces the problems such as the device complexity and cost of fabrication. Other strategy is to use a low‐dimensional‐layered HP. 2D HP is more stable than a 3D ABX3 HP, thus use of 2D HP may yield stable RSM devices. However, the experimental approach to find appropriate HPs for use in RSM requires enormous time and effort. Instead, a combination of candidate screening by first‐principles calculation with experimental validation may be an effective method to find candidate HPs for use in RSM. In this study, we combined first‐principles screening and experimental verification to design HPs for use in RSM. We focused on inorganic 2D HPs, which showed better thermal stability than 3D HP structures. By comparing formation energy of several 2D perovskite structures, we selected AB2X5 structure, which has the lowest formation energy, as a candidate structure for use in RSM. To estimate the potential of HP as an RSM material, we used two descriptors: formation energy (Eform) and defect formation energy (DFE). Our DFT calculations predicted that CsPb2Br5 is a good candidate material for RSM because this HP is expected to show better stability with low operating voltage than other inorganic HPs. To verify our calculation results, we fabricated RSM that used CsPb2Br5 (CsPb2Br5‐RSM) and compared its resistive switching behavior with RSM that used CsPbBr3 (CsPbBr3‐RSM). The DFT calculation results matched experimental observations that the CsPb2Br5‐RSM tended to have lower set electric field than the CsPbBr3‐RSM. Also, the CsPb2Br5‐RSM exhibited resistive switching behavior at 140 °C. Therefore, this combination of first‐principles calculations and experiments identified that CsPb2Br5 is an appropriate material for use in RSM.Two strategies have been reported to increase the stability of HP‐based RSM. One strategy is the introduction of a passivation layer such as zinc oxide or polymethyl methacrylate. The passivation layers isolate the HPs from ambient humidity.31 Howα‐CsPbI3 perovskite at room temperature (RT) is a well‐known problem. Also, it is reported that resistive switching property of α‐CsPbI3‐based RSM was degraded within a short period of time. To overcome this problem, we focused on the 2D‐layered HP materials, which are generally known to be more stable than 3D perovskite. We considered three 2D‐layered perovskite structures  to compare their energetic stability with 3D cubic perovskite structure (ABX3). We calculated Eform of four corresponding Cs‐Pb‐I compounds to find most energetically stable structure for inorganic HP  as descriptors for screening. First, Eform  was chosen because it can determine the stability of a material.Eform of a AB2X5 compound can be calculated asEtotbulk is the total energy of the AB2X5 compound, and EtotAX and EtotBX2 are the total energies of the precursors. AX and BX2 were chosen as the precursors, because they are widely used precursors in synthesis of layered HP. The stoichiometry of the AB2X5 compound was maintained by choosing a and b  appropriately.To find an appropriate composition of ABDFE of halide vacancy (VX•) was chosen since the Pearson correlation analysis predicts that it is the most correlated materials property with the operating (set) voltage (VOP) of an RSM device. In this study, candidate materials that can minimize the energy consumption of RSM by reducing VOP are investigated. To identify material characteristics that are most correlated with VOP, we calculated Pearson correlation coefficients with various materials properties such as DFE of VX•, tolerance factor, electronegativity of X‐site halide ion, average bonding length between B‐site cation and X‐site anion, migration barrier of a halide ion, in‐plane bonding angle between two B—X bonds, and band gap  of VX• (DFE[VX•]) can be calculated as Etot[VX•] is the total energy of the defective system with VX•,Etotbulk is the total energy of a perfect system, μx is the chemical potential of an X anion, q is the charge of a vacancy, and μe is the chemical potential of an electron; here, the valence‐band maximum of the perfect system is used for μe. First‐principles DFT calculations were employed to calculate Eform and DFE of VX• to find candidate materials that have AB2X5 structure for use in RSM. The A‐site was fixed as Cs+, the B‐site was a divalent cation , and the X‐site was a halide anion . To compare the properties of AB2X5 structure, the properties of ABX3 structure were also calculated. Our DFT calculations predicted that Eform of AB2X5 structure is lower than that of ABX3 structure when Pb2+ and Sn2+ sit on B‐site  and CsPb2Cl5 (−0.83 eV f.u.−1) are the two lowest Eform compounds. The results on the DFE of VX• show that halide vacancies can be preferentially formed in the order of I, Br, and Cl , CsPb2I5 (0.53 eV), CsGe2Br5 (0.61 eV), and CsPb2Br5 (0.61 eV) show relatively low DFE of VX•. Thus, they are expected to show high VX• concentration and therefore a low set electric field for resistive switching.Second, p Figure . Detail voltage VOP of an voltage VOP of an voltage VOP of an voltage VOP of an voltage VOP of an voltage VOP of an l Figure . Since tEform and DFE of various compounds. The Eform and DFE seem to be inversely proportional to each other, but the DPE defines how much the defective system can be stabilized compared to the perfect system. Therefore, the system can have low DFE even if Eform is low from our calculation results. As can be seen from Figure 3 compounds are not suitable materials for RSM due to their high Eform and DFE of VX•. On the other hand, many AB2X5 compounds show relative lower Eform and DFE of VX•. Especially, CsPb2Br5 had the lowest Eform and quite low DFE of VX•. Although CsGe2I5 and CsGe2Br5 had relatively low DFE of VX•, they had high Eform, so they were not suitable materials for RSM. In contrast, CsPb2Cl5 had low Eform, but high DFE of VX•, so it was not suitable as well. In this study, thus CsPb2Br5 was selected as the active layer of RSM to ensure the maximum stability and low VOP.The most suitable candidate for use in RSM is chosen by comparing 3 has already been reported as an RSM active material and known to be stable phase in CsPbBr3 composition at RT. The screening calculations in the previous section considered cubic‐ABX3 structure, so we further calculated the Eform and the DFE of VBr• of orthorhombic‐CsPbBr3 and compared them with those of CsPb2Br5 to verify its feasibility as an RSM active material. Our DFT calculations predicted that Eform of CsPb2Br5 (−0.88 eV f.u.−1) is much lower than that of orthorhombic‐CsPbBr3 (−0.45 eV f.u.−1), thus CsPb2Br5 is more stable than orthorhombic‐CsPbBr3. Also, the calculated DFE of VBr• for CsPb2Br5 (0.61 eV) is lower than that for orthorhombic‐CsPbBr3 (1.24 eV). So, we confirm that CsPb2Br5 can have better stability and lower set electric field than orthorhombic‐CsPbBr3. To conclude, our DFT study predicts that CsPb2Br5 has superior characteristics for use in RSM.Among various Cs‐Pb‐Br compounds, the orthorhombic‐CsPbBr material48 and2Br5 and CsPbBr3 as resistive switching layers to confirm the calculation results and to compare the device performance such as set electric field and ON/OFF ratio. Water vapor–induced transformation was used to transform CsPbBr3 to CsPb2Br5. A CsPbBr3 precursor was spin‐coated on the indium tin oxide (ITO)–coated glass substrate , RT). CsPb2Br5 has a 2D structure, which is composed of Cs+ cations sandwiched between [Pb2Br5]− layers 3 reacts with water molecules during water treatment, Cs+ and Br− are extracted from the CsPbBr3, so it decomposes to PbBr2, Cs+(aq), and Br−(aq). This change occurs because CsPbBr3 has ionic nature, and the cesium bromide (CsBr) has high solubility in water. If lead bromide (PbBr2) is abundant, it crystalizes with CsBr to form tetragonal CsPb2Br5, which is thermodynamically stable in humid air.When the CsPbBrumid air.503 and transformed CsPb2Br5 films were investigated at incidence angles 10° ≤ 2θ ≤ 50°. The XRD patterns , (121), (004), (202), and (242) planes, respectively. The XRD patterns of CsPb2Br5 .The X‐ray diffraction (XRD) patterns of CsPbBrCsPb2Br5.42 TheI–V) characteristics of Au/CsPbBr3/ITO and Au/CsPb2Br5/ITO devices were measured under ambient air. During these electrical characterizations, DC bias voltages (V) were applied to the Au top electrodes in the sequence of 0  → 1.5  → 0  → −1.5  → 0 V, while the ITO (bottom electrode) was grounded. These devices showed bipolar resistive switching behavior under a compliance current (CC) = 10−4 A  instead V to compensate for the difference in tP of the CsPbBr3 and CsPb2Br5 films. The set process occurred at 13.7 kV cm−1 for CsPbBr3, and 10.4 kV cm−1 for CsPb2Br5; each was the average taken from 10 individual devices . The set electric field (ESET) of CsPb2Br5‐RSM was 1.32 times lower than the CsPbBr3‐RSM  and high‐resistance state (HRS) for at least 103 s, and the electrical properties of the devices showed almost no change for 40 cycles. Also, we confirmed the endurance properties using pulse measurement. Set voltage pulses  and reset voltage pulses  were applied to induce LRS and HRS, respectively. Each resistance state was measured at read voltage  under CC = 10−4 A. The device showed distinguishable LRS and HRS over 500 cycles without degradation . The ON/OFF ratio of the CsPb2Br5‐RSM was higher than that of the CsPbBr3‐RSM. The difference was a result of a decreased HRS current in CsPb2Br5. The reduced dimensionality of CsPb2Br5 increases the Schottky barrier height between the electrode and CsPb2Br5, and this can lead to high ON/OFF ratio of 2D perovskite‐based RSM. A comparison between previous HP‐based RSM and our devices was made . CsPb2Br5‐RSM in this study showed memory characteristics comparable to previously reported HP‐based RSM devices.Data retention and endurance were measured to confirm the reliability of the memory device with a reading voltage of 0.1 V Figure ,d. The Cased RSM.44 A cI–V curves of CsPbBr3‐ and CsPb2Br5‐RSM on a full‐logarithmic scale . In the LRS state, the fitted curves showed slopes near 1 , which indicated that both devices showed Ohmic conduction behavior. This result showed that the conductive filaments might be formed between the top electrode (Au) and the bottom electrode (ITO). In the HRS state, the conduction mechanism consisted of two parts. At low voltage, the curves showed Ohmic conduction behavior  as in the LRS state. However, at high voltage region, the fitted curves almost conformed to Child's law , which indicated that the mechanism had changed to trap‐filled space‐charge‐limited conduction.To understand the conduction mechanism, we replotted the 2Br5 has low Eform (−0.88 eV f.u.−1), so it is expected to be more thermodynamically stable than CsPbBr3. To evaluate the thermal stability of CsPb2Br5‐ and CsPbBr3‐RSM, the I–V characteristics and XRD patterns of CsPb2Br5 and CsPbBr3 were measured at elevated temperatures . Also, we confirmed the thermal stability of the states for 104 s at 60 °C . However, the electrical properties of CsPbBr3‐RSM were degraded with a rapid drop in ON/OFF ratio at 140 °C . In the annealed CsPbBr3 thin film, the additional phases were observed, such as CsPb2Br5, CsBr, and PbBr2. The phase evolution from CsPbBr3 to CsPb2Br5 during annealing in ambient air might be caused by the moisture and the difference in Gibbs free energy of the reaction. Also, due to high ionic character of the CsPbBr3, the decomposition of CsPbBr3 might occur by the moisture and heat. This degradation in the annealed CsPbBr3 thin film can cause malfunction of CsPbBr3‐RSM at 140 °C. These results suggest that the CsPb2Br5‐RSM is thermally stable in the air.The poor stability of HPs impedes its use in practical memory devices. DFT calculations suggested that CsPbC Figure . We measC Figure ,c. To che Figure , but CsPEform and DFE of VX•) were chosen to screen candidate materials for RSM because they were closely related to stability and operating voltage. Our DFT calculation predicted that 2D HP structure (AB2X5) would be more stable and have lower set electric field than 3D HP structure (ABX3) due to the low Eform and DFE of VBr•. Among the various composition of AB2X5 HPs, DFT calculations predicted that CsPb2Br5 would be the best candidate for use in RSM. To confirm the prediction, we fabricated Au/CsPbBr3/ITO and Au/CsPb2Br5/ITO devices to compare their resistive switching behaviors. The CsPb2Br5‐RSM had lower set electric field and higher ON/OFF ratio than the CsPbBr3‐RSM. CsPb2Br5‐RSM retained resistive switching behavior even at 140 °C. Therefore, we confirmed that the CsPb2Br5‐RSM showed a superior resistive switching behavior and thermodynamic stability than CsPbBr3‐RSM. These results provide a promising route to design HPs that are suitable for use in RSM.In conclusion, first‐principles screening was combined with experimental verification to design new HPs for use in RSM. Two descriptors , dimethyl sulfoxide , dimethylformamide , and ITO‐coated glass substrates were purchased from Sigma‐Aldrich. All materials were used without further purification.Cesium acetate , lead bromide  for 20 min. The solution was spin‐coated at 900 rpm for 10 s, then annealed at 100 °C for 10 min to form the CsPbBr3 perovskite film. To form CsPb2Br5 film, the CsPbBr3 perovskite film was held in a home‐made humidity chamber with 85% RH until the CsPbBr3 had completely converted to CsPb2Br5. Au electrodes were deposited on the HP films by thermal evaporation through a shadow mask.First, 1 3 and CsPb2Br5 was measured using XRD (Rigaku D/MAX‐2500 Diffractometer) with Cu Kα radiation. Current‐voltage characteristics were measured using a semiconductor parameter analyzer  in the probe station in ambient condition. The microstructure as observed using high‐resolution field‐emission SEM .The crystal structure of CsPbBr2Br5. The DFT calculations were conducted using the projector augmented wave  method with the Perdew–Burke–Ernzerhof functional for exchange and correlation potentials, as implemented in the Vienna Ab‐initio Simulation Package code. For calculations of various AB2X5 and ABX3 compounds, structures with 8 formula unit (8 f.u.) were constructed and Monkhorst‐Pack k‐point[2Br5 and orthorhombic‐CsPbBr3, 16 f.u. structures with a 2 × 2 × 2 k‐point grid were used. To consider the interlayer interactions the van der Waals correction by using DFT‐D3 method was used. The total energy was converged to within 1 meV with a kinetic energy cut‐off of 500 eV for all calculations.First‐principles DFT calculations were used to identify candidate perovskites for use as an active material for RSM and, to understand the physical origin of resistive switching in RSM based on CsPbted wave 56 metThe authors declare no conflict of interest.J.‐S.L. conceived and directed the research. D.L. directed the calculation part. J.H.J. and Y.P. performed the experiment and acquired the data. S.H.K. and D.L. performed the first‐principle calculations. Y.P., S.H.K., D.L., and J.‐S.L. revised the manuscript. J.H.J., S.H.K. and Y.P. contributed equally to this work.Supporting InformationClick here for additional data file.


In this study, we investigated to what degree the apparent myelin water fraction (MWF) depends on the angle between white matter fibers and the main magnetic field.The multi‐exponential TMaps of the apparent MWF were acquired using multi‐echo Carr‐Purcell‐Meiboom‐Gill and gradient‐echo spin‐echo sequences. The Carr‐Purcell‐Meiboom‐Gill sequence was acquired with a TR of 1073 ms, 1500 ms, and 2000 ms. The fiber orientation was mapped with DTI. By angle‐wise pooling the voxels across the brain’s white matter, orientation‐dependent apparent MWF curves were generated.We found that the apparent MWF varied between 25% and 35% across different fiber orientations. Furthermore, the selection of the TR influences the apparent MWF.White matter fiber orientation induces a strong systematic bias on the estimation of the apparent MWF. This finding has implications for future research and the interpretation of MWI results in previously published studies. In contrast, the T2 relaxation time of the intracellular and extracellular water is in the range of 30 ms to 60 ms, and the CSF has a T2 relaxation time of more than 1 second.2 signal decay of a white matter voxel can be measured using a multi‐echo spin‐echo scan and be decomposed into its individual components, resulting in a T2 spectrum.2 spectrum spanning the short T2 components, referred to as the myelin water peak, divided by the area of the total T2 spectrum, is defined as the myelin water fraction (MWF). A strong correlation between the MWF and independent measures of myelin has been demonstrated in various postmortem studies.Myelin is a lipid bilayer membrane wrapped around the axon, protecting it from mechanical and chemical damage0 also affects the magnitude and phase of the complex MRI signal and a wide range of quantitative MRI parameters. Strong orientation effects have been reported for R2∗ relaxation,1 relaxation.2 signal of white matter shows an anisotropic behavior0. In the present study, we acquired MWI using a gradient and spin‐echo (GRASE) sequence,The human brain’s white matter is highly anisotropic. This circumstance is widely exploited in DTI, which allows us to map the brain’s complex fiber architecture.2Eight healthy volunteers  with a mean age of 26 years (age range = 21‐33 years) and without any history of neurological disorder participated in this study, which was approved by the University of British Columbia Clinical Research Ethics Board. All volunteers gave written, informed consent. The MRI was performed on a 3T MR system  using a 32‐channel SENSE head coil.2.11‐weighted sequence with TE = 4.9 ms, TR = 9.8 ms, flip angle = 8°, resolution = 0.8 × 0.8 × 0.8 mm3, FOV = 256 × 256 × 180 mm, compressed SENSE factor = 3.6, and acquisition time = 5:50 minutes was acquired for anatomical overview. Compressed SENSE is a combination of compressed sensing2, 60 diffusion directions, resolution = 2.3 × 2.3 × 2.4 mm3, FOV = 224 × 168 × 224 mm, multiband factor = 2,3, and FOV = 230 × 120 × 180 mm. The DTI and MWI sequences were acquired in axial orientation without angulation. Due to the long data‐acquisition times, not all sequences were acquired in all volunteers. A summary of all acquired sequences for each volunteer, including their acquisition times, is provided in Supporting Information Table A 3D T2.2The DTI data were analyzed with the FMRIB Software Library (FSL v5.0.9).2 distributions were computed using a regularized nonnegative least‐squares algorithm with stimulated‐echo correction and a T2 range of 8 ms to 2.0 seconds.2 distribution, in which the myelin water T2 is defined as the T2 times of the distribution between 8 ms and 25 ms. The intracellular and extracellular water T2 is defined as the T2 times above 25 ms. The cutoff between the two water pools was set to 25 ms, which was based on the measured T2 distributions. The apparent MWF was calculated as the ratio of the myelin water T2 to the entire T2 components.For MWI analysis, the T1 and DTI was linearly registered to the MWI using FLIRT. FSL’s vecreg was used to register the first eigenvector to the MWI space. The fiber orientation was calculated from the angle between the first eigenvector and the direction of the main magnetic field B0.2, and intracellular and extracellular water T2 were computed as a function of local fiber orientation θ. The fiber orientations were divided into 18 intervals of 5° between 0°  and 90° (perpendicular to B0). To compute apparent MWF (θ), voxels from across the entire white matter were pooled for each angle interval, to reduce the influence of tract‐specific differences in apparent MWF.The T2.32, an analysis of variance was used. All statistical analyses were performed using R .All parameters were tested for normal distribution using the Shapiro‐Wilk test. A t‐test was used to determine the significance of differences between GRASE and CPMG. To test whether the fiber angle and TR had a significant effect on apparent MWF and T32 distributions plotted for different fiber angles of a representative subject are shown for CPMG in Figure 2 relaxation times, and a small peak from CSF at very long T2 relaxation times. The plotted T2 distribution highlights the intracellular and extracellular water peak, whereas the myelin water peak and CSF peak are represented by increased signal intensity at the left and right border of the plot, respectively. The zoomed inserts display the systematic angle dependency of the distribution. Figure 2,min = 8 ms to T2 = T2,max, computed as the integral of the area under the T2 distribution from T2,min to the respective T2 time normalized by the total area of the T2 distribution. The zoomed insert shows how the integral differs between fiber angles and between the CPMG and GRASE sequence.The T0 and the corresponding apparent MWF maps are shown in Figure Representative maps of the angle between white matter fibers and B2, intracellular and extracellular water T2, and the white matter fiber orientation is shown in Figure 2  and the myelin water T2 (P < .001). The orientation dependency of the intracellular and extracellular water T2 (P = .79) showed no significant difference between the two scan types.The relationship among the apparent MWF, myelin water T2 Figure  and intr2 Figure  increase3.1P < .001), myelin water T2 (P < .001), and intracellular and extracellular water T2 (P < .001), as shown in Figure 2, and intracellular and extracellular water T2 was similar but shifted with increasing TR. The effect of TR is further evident by plotting the global white matter mean of the apparent MWF , as shown in Figure By increasing TR from 1073 ms to 1500 ms and 2000 ms, the orientation‐dependent apparent MWF decreased across all regions, as shown in Figure F Figure , myelin 2 Figure , and int2 Figure . For exa42 relaxation times of both myelin water and intracellular and extracellular water, and therefore the measurement of the apparent MWF, are considerably influenced by the angle between the white matter fiber tracts and the main magnetic field. Furthermore, the TR of the sequence also has an impact on estimating the apparent MWF. Orientation effects of the transverse relaxation signal have been ascribed primarily to dipole–dipole interaction and to magnetic susceptibility effects. In the following, we first discuss both mechanisms qualitatively in the context of previous literature. Then, we apply previously presented models to our experimental data to investigate the possible origins of the orientation dependency.We demonstrated that the T2 distribution depends on the fiber angle. As the estimation of the apparent MWF relies on the separation of the myelin water pool from the intracellular and extracellular water pool in the T2 spectrum, an alteration of the T2 spectrum will affect the estimation of the apparent MWF. This is further evident as the myelin water pool and the intracellular and extracellular water pool show a different sensitivity to changes in fiber orientation. Furthermore, as the T2 spectrum is based on the T2 relaxation properties per se, the orientation‐dependent behavior of the apparent MWF can be related through the orientation dependency of the T2 spectrum to T2 anisotropy effects in general.The observed orientation dependency of the apparent MWF is based on the fact that the underlying T2 has been observed in highly ordered tissues, such as cartilage and tendons.2 signal when they are oriented near the magic angles, where the term 3 cos2θ − 1 describing the z‐component of the dipole field approaches zero. When water is bound to highly ordered tissue, the dipolar interactions depend on the orientation of the tissue with respect to the main magnetic field. These dipolar interactions result in a rapid signal dephasing, unless the tissue is oriented at or near the magic angle. In experimental work on tendons,2θ − 1)2.Orientation dependency of TR2∗ has been studied extensively,2 in the brain has been considered weak for a long time.2 in ex vivo formalin‐fixed white matter that is best described by dipole–dipole interaction according to k·(3 cos2θ − 1)2.2 data were small, which could be a consequence of fixation‐induced cross‐linking, which reduces tissue anisotropy at length scales that are relevant to T2 relaxation. Furthermore, with the decreased T2 relaxation times due to tissue fixationR2∗ in fixed tissue.Another cause of orientation effects is the magnetic susceptibility of tissue, which has a strong influence on phase and magnitude of the gradient‐echo signal. Although the orientation dependency of white matter  k·3 cos2θ − 12.22 and results in an additional reduction of the spin‐echo signal. For anisotropic perturbers, such as cylindrical structures, the spin‐echo signal becomes orientation‐dependent. The theory predicts two possible sources of T2 anisotropy, which are referred to as (1) a sin4 (θ)‐related orientation dependency caused by diffusion‐mediated loss of coherence due to susceptibility differences and (2) a sin2 (θ) orientation dependency related to interactions between susceptibility differences and applied field gradients.2 times for white matter fibers parallel to the B0, and the shortest T2 times for white matter fibers perpendicular to B0, which is in good agreement with their theoretical framework. These results are also in agreement with our present study, in which we observed the longest T2 times of both myelin water T2 and intracellular extracellular water T2 at low angles, and the shortest T2 times in tissue perpendicular to the main magnetic field. Note, however, that in our data both the myelin water T2 and the intracellular and extracellular water T2 exhibit a small increase between 0° and about 20°, which is not explained by the model by Knight et al.Knight et al presented a model for the orientation dependency of the spin‐echo signal based on the loss of spin coherence due to diffusion through field inhomogeneities.2 and intracellular and extracellular water R2 data  resulted in a poor fit of the R2 signal  was based on the theory that Knight et al2 signal according toThe third model Sb3·sin2 (θ), and orientation effects due to diffusion‐mediated loss of coherence contribute to c3·sin4 (θ). This model allowed us to properly fit the myelin water R2 and intracellular and extracellular water R2  and contributions related to sin2 (θ), we see that this allows us to fit the myelin water R2 and intracellular and extracellular water R2  = a1 + b1 (3 cos2 (θ) − 1) can be rewritten as R2,1 (θ) = a1 + 2b1 − 3b1 sin2 (θ), which is also evident as the curves of both model fits superimpose, as shown in Figure R2,2 (θ)  = a2 + 4b2 − 12b2 sin2θ + 9b2 sin4θ, which is in line with model R2,3 (θ), where a3 = a2 + 4b2, b3 = −12b2 and c3 = 9b2. This supposes that model R2,3 (θ) also incorporates orientation effects due to dipole–dipole interaction, along with orientation effects due to magnetic susceptibility effects. The fitting parameters of all different models are summarized in Supporting Information Table R2, and in Supporting Information Table 2.In addition, if we independently investigate the orientation effects relating to sin2 Figure . It shou1 relaxation and magnetization transfer, will affect the different T2 components, and therefore the estimation of the apparent MWF. The dependency of apparent MWF and T2 on TR could be additionally affected by the different T1 relaxation times of myelin water and the intracellular and extracellular water. The overall T1 of white matter at 3 T is about 1100 ms,1 of myelin water is about 200 ms.1 and water content measurements, of 2.5% and 0.8%, respectively.1 of about 0.4 · 10−4 Hz between parallel fibers and fibers at the magic angle.1 of white matter weakly depends on the fiber angle with the highest T1 near the magic angle of 54.7°.Other contributions, such as T2 components through the fiber orientation dependency of the RF absorption lineshape. In their experiments, they observed a fiber orientation–dependent T2 of the bound water pool , with a similar orientation dependency compared to our observed myelin water T2. The orientation dependency in T2,b was attributed to chemical exchange and cross‐relaxation effects.Finally, magnetization‐transfer effects may influence the estimation of the apparent MWF. Pampel et al showed that magnetization‐transfer experiments in white matter are sensitive to fiber‐orientation effects, and therefore affect the estimation of short T1 of the long T1 component. The shortest TR of 1073 ms, on the contrary, was defined by the specific absorption rate of the scan. With the required anatomical T1 and DTI scans and the comparison with the GRASE approach at 1073 ms, the total scan protocol took approximately 75 minutes. Therefore, the present study is not able answer the question of how apparent MWF behaves in the absence of T1 weighting. A comprehensive study that explores the effects of TR would require several long scans with TRs of up to 5000 ms, in which T1 weighting of the intracellular and extracellular water is reduced to less than 2%. Such study may be feasible by not scanning every TR in every participant and with reduced brain coverage and lower spatial resolution, which both make image registration more challenging.One limitation of the study is that we only investigated TR up to 2000 ms, which is approximately two times the TR2∗ weighting of the GRASE sequence, leading to a reduction of the signal due to field inhomogeneities created by the myelinated axons at larger angles. Future MWI studies will increasingly use the CPMG sequence with compressed sensing, as it allows for shorter echo spacing and for shorter scan times compared with the GRASE‐based approach.Furthermore, the orientation dependency of GRASE and CPMG were different, particularly at larger angles. The increase in apparent MWF at angles above 54.7° was stronger for CPMG compared with GRASE, which may be due to some θ) of all subjects followed a similar pattern, independently of individual differences in head orientation or white matter anatomy. According to Knight et al, crossing fibers led to a decrease in T2 compared with voxels containing only a single fiber orientation, which will affect the observed orientation‐dependent T2, and therefore the estimated apparent MWF.The approach of using DTI to determine the fiber orientation and pooling voxels according to their local fiber orientation was previously applied in several studies.R2∗, where only an orientation‐dependent analysis was able to reveal group differences.R2∗ relaxation as a function of white matter orientation, myelin, and iron content, and were able to compute whole white matter myelin and iron content.R2∗. Because variations in iron concentration explain approximately 25% of the measured variance in the apparent MWF,Our findings have consequences for the interpretation of past results and for future research. The orientation dependency of the apparent MWF might mask longitudinal changes in MWF or changes between cohorts, if whole white matter averages are investigated. A corresponding effect was observed in white matter Our findings suggest that comparison of apparent MWF of individual subjects may exhibit paradoxical results if their head orientation differs. A difference in angle by 10°, for example, would result in a relative difference in apparent MWF by 5% to 7%, which is similar to the reduction in apparent MWF in the normal‐appearing white matter in multiple sclerosis over 5 years.2 distribution, myelin water T2, and the intracellular and extracellular water T2, as well as the apparent MWF, depend on white matter fiber orientation. Furthermore, with increasing TR, the overall apparent MWF decreases, while the orientation dependency persists.In conclusion, our study shows that the TTABLE S1 Summary of all volunteers, the corresponding acquired sequences, and the acquisition time of each sequenceTABLE S2 Fitting parameters of the different models to the measured myelin water R2 dataTABLE S3 Fitting parameters of the different models to the measured intracellular and extracellular water R2Click here for additional data file.


Here, we construct a Cu2O-Pt/SiC/IrOx composite by a controlled photodeposition and then an artificial photosynthetic system with Nafion membrane as diaphragm separating reduction and oxidation half-reactions. The artificial system exhibits excellent photocatalytic performance for CO2 reduction to HCOOH and H2O oxidation to O2 under visible light irradiation. The yields of HCOOH and O2 meet almost stoichiometric ratio and are as high as 896.7 and 440.7 μmol g−1 h−1, respectively. The high efficiencies of CO2 reduction and H2O oxidation in the artificial system are attributed to both the direct Z-scheme electronic structure of Cu2O-Pt/SiC/IrOx and the indirect Z-scheme spatially separated reduction and oxidation units, which greatly prolong lifetime of photogenerated electrons and holes and prevent the backward reaction of products. This work provides an effective and feasible strategy to increase the efficiency of artificial photosynthesis.The stoichiometric photocatalytic reaction of CO 2 with H2O is one of the big challenges in photocatalysis. An artificial photosynthetic system based on a direct and indirect Z-scheme heterostructure is synthesised, enabling simultaneous CO2 reduction to HCOOH and H2O oxidation to O2.The stoichiometric photoreaction of CO Reduction of CO2 under visible light accounting for 45% sunlight energy by water rather than organic compound as an electron donor is the ultimate goal of photocatalysis. Enormous efforts have been devoted to developing a highly efficient photocatalyst for this prospect7. However, so far none of photocatalyst systems is satisfactory. Development of novel photocatalyst or system to realize highly efficient conversion of CO2 remains the focus of future research.Solar-driven photocatalytic conversion of carbon dioxide , trimethylamine (TEA), or ethylenediaminetetraacetic acid (EDTA))16. Such photocatalytic CO2 reduction at the cost of sacrificial electron donors is not sustainable and likely economically unsound. Even using hole scavenger, the photocatalysts only exhibit a formation rate of HCOOH with tens of micromoles, typically such as some metal-organic framework (MOF) materials (NH2-MIL-125(Ti), MIL-101(Fe))18, inorganic–organic hybrid materials (a binuclear ruthenium(II) complex coupled with Ag/C3N4 (ref. 20), Cu(I) complex photosensitized Mn(I) complex catalysts21), and metal sulfide semiconductors ((Mo−Bi)Sx/CdS)22. The C and Fe co-doped LaCoO3 was reported to display an HCOOH yield up to 128 μmol g−1 h−1 without sacrificial reagent, but the oxidation product O2 was not analysed23. Such photocatalytic CO2 reduction without accompanying oxidation half-reaction is inexplicable. The photosynthesis essentially requires the stoichiometric photocatalytic CO2 reduction and H2O oxidation which remains a great challenge in photocatalysis24.In various reduction products of CO2 reduction with H2O into carbon fuel and oxygen by solar energy26. So it has been considered as a promising photocatalyst for CO2 conversion since the early research work27. However, the expected photocatalytic efficiency has not been achieved so far. This is due to very large difference between electron and hole migration rates in SiC , which leads to the accumulation of photogenerated holes in the bulk and in turn suppresses the further generation of electrons under light irradiation. This makes the photogenerated carriers to be short-lived, especially the oxidation ability to be poor29. Moreover, the pristine SiC is lack of active sites for CO2 adsorption and activation. Therefore, it is desirable to find the suitable cocatalysts to modify SiC. Additionally, the thermodynamically favourable backward reaction of the produced organics with oxygen on the photocatalyst surface is detrimental to decrease efficiency of CO2 with pure H2O in the conversional one-pot reaction. These problems can be concurrently solved by constructing the multi-photocatalyst integration systems in which the oxidation and reduction reactions are independent in space but coupled in the transfer of photogenerated charges.Silicon carbide (SiC), a metal-free semiconductor material, possesses a moderate wide band gap (2.4 eV) with an enough negative CB (ca. −1.1 V) to satisfy multielectron reactions of CO2O–Pt/SiC/IrOx hybrid photocatalyst, which is prepared by loading the photo-oxidation unit (IrOx) and the photoreduction unit (Cu2O–Pt) on SiC surface. This configuration can enhance the lifetime of photogenerated charges and the CO2 adsorption, and thus the photocatalytic efficiency. Furthermore, we construct a spatially separated reaction system consisting of two reaction chambers analogous to the natural photosynthetic systems. One chamber is loaded with the Cu2O–Pt/SiC/IrOx photocatalyst and Fe2+ for CO2 reduction, while the other chamber with the known Pt/WO3 and Fe3+ for H2O oxidation, and the two chambers are divided by a Nafion membrane that allows Fe2+ and Fe3+ ions to permeate through. This design facilitates H2O oxidation half-reaction and suppresses the backward reaction of the products. For the photocatalytic reaction of CO2 with H2O to HCOOH and O2, the system shows very high photocatalytic efficiency under visible light irradiation. The HCOOH yield is as high as 896.7 μmol g−1 h−1 for the long-term reaction, 527 times higher than that of the pristine SiC (1.7 μmol g−1 h−1) in the conversional one-pot reaction. Most importantly, O2 with a stoichiometric ratio is evolved concurrently. To the best of our knowledge, such high activity for reaction of CO2 with pure H2O to HCOOH and O2 is rarely reported before.Here, we report a Cu2O–Pt/SiC/IrOx through the step-by-step photodeposition of Pt, Cu2O and IrOx on 3C-SiC (face centre cubic phase of SiC) surface. First, Pt nanoparticles were loaded onto SiC by a simple photodeposition to obtain Pt/SiC sample. Then the resulting Pt/SiC samples were dispersed in aqueous solution containing both Cu2+ and IrCl63− ions with UV light illumination, which led Cu2+ to reduction into Cu2O species and IrCl63− to oxidation into IrOx. Due to higher work function (5.6 eV) of Pt, the photogenerated electrons on SiC migrated to Pt and the photogenerated holes remained on SiC31. Thus the reduction reaction occurred on the Pt particle, while the oxidation reaction did on SiC. We thus concluded that the Cu2O was deposited on the Pt, while the IrOx on SiC. The resulting Cu2O–Pt and IrOx were located at different region of SiC surface. For comparison, the two reference samples, Cu2O–Pt/SiC and Pt/SiC/IrOx, were prepared also in the similar conditions with Cu2+-contained solution and IrCl63−-contained solution, respectively. The loading amounts of cocatalysts on SiC samples were controlled by the photodeposition time (0.5–15 h) and then were quantified by a quadrupole inductively coupled plasma mass spectrometry (ICP-MS), as summarized in Supplementary Table 2O and IrOx on the samples were controlled in the range of 0.83–2.6, 0.52–2.7 and 0.87–3.2 wt%, respectively. Based on the photocatalytic CO2 reduction results, the optimal amount of Pt, Cu2O and IrOx is ascertained to be 1.3%, 1.8% and 2.2 wt% for Cu2O–Pt/SiC/IrOx photocatalyst, respectively. For the sake of brevity, hereafter the optimal photocatalyst with 1.3 wt% Pt, 1.8 wt% Cu2O and 2.2 wt% IrOx is referred simply to Cu2O–Pt/SiC/IrOx, unless specifically noted otherwise.Figure 2O and IrOx) are observed due to their low contents and high dispersion on SiC surface. The BET specific surface area of SiC has a slight reduction from ~18 m2 g−1 for bare SiC to ~14 m2 g−1 for Cu2O–Pt/SiC/IrOx  and HRTEM images  facet of IrO2 (refs. 35), respectively. The Cu2O–Pt intimate contact structure is further testified by STEM-EDS mapping   studies. 3 keV tra Fig.  give thef XPS peaks can be assigned to metallic Pt0 and partially oxidized Pt2+ and Pt4+ species36. The ratio of Pt0 is calculated to be accounting for 70 ± 4% of the sum Pt species for the all Pt-contained samples , respectively38. Nevertheless, the binding energies (BE) of Pt, Cu or Ir have obvious differences among samples. For Pt/SiC, the BE of Pt 4f7/2 and Pt 4f5/2 are respectively 70.8 and 74.1 eV, which are lower than that of the pure metallic Pt (Pt 4f7/2 = 71.2 eV)39. This is because the electron transfer occurs from the SiC substrate to Pt particles with higher work function41. When Cu2O is subsequently deposited on Pt/SiC to form Cu2O–Pt/SiC, the BE of Pt 4f7/2 shifts towards higher energy (71.1 eV), but is still slight lower than that of metallic Pt, indicating the electron transfer still from SiC to Cu2O under mediation of Pt nanoparticles. On the contrary, when IrOx is deposited onto Pt/SiC to form Pt/SiC/IrOx, the BE of Pt 4f shifts to lower position. This indicates that IrOx deposition induces the electron transfer from IrOx to the SiC surface and thus enhances the electron transfer to Pt particles. In the case of the co-deposition of IrOx and Cu2O on Pt/SiC, the BE of Pt 4f in Cu2O–Pt/SiC/IrOx is comparable with Cu2O–Pt/SiC. This demonstrates that the electrons are finally transferred from both SiC and IrOx into Cu2O. As a result, the BE of Cu 2p for Cu2O–Pt/SiC/IrOx is also lower than that of Cu2O–Pt/SiC. In reverse, the BE of Ir 4f for Cu2O–Pt/SiC/IrOx is slightly positively shifted as compared with Pt/SiC/IrOx. The above results show the existence of the strong interfacial interaction between co-catalyst and SiC, which would be favourable for the electron migration and transfer in Cu2O–Pt/SiC/IrOx.The chemical states of the Pt, Cu and Ir elements in samples were analysed by XPS Fig. . Three s2 reduction was performed in the spatially separated reaction system. Fe2+ and Fe3+ were added respectively in the CO2-reduction compartment and the H2O-oxidation compartment in the beginning of the reaction  occurs at 1.3 wt% Pt content  at 1.8 wt% content of Cu2O , the optimal loading content of IrOx is 2.2 wt% at which the HCOOH yield is ca. 472.0 μmol g−1 h−1  in the whole process. Influence of the Pt amount of Pt/WO3 on the photocatalytic O2 and HCOOH evolutions in the separated reaction system was also investigated 3, as confirmed by the Fe 2p XPS spectrum of the sample after the reaction  and 71.5 eV (Pt 4f 7/2) are attributed to Pt(0). The shoulder peaks are belonged to Pt2+ and Pt4+ species. It can be seen that a part of high valence Pt species were translated also into Pt (0) after longtime reaction, which could be beneficial to the photocatalysis. (ii) For IrOx, the Ir 4f peaks not only become narrow but also shift towards lower energy after the photocatalytic reaction. The wide Ir 4f peaks of both the fresh and the used samples cover Ir0, Ir3+ and Ir4+ species, indicating the mix valence state feature of IrOx. Accordingly, the Ir 4f7/2 peak can be deconvoluted into a contribution of Ir0 (61.3 eV), Ir4+ (62.4 eV) and Ir3+ (63.5 eV) species46. The phenomena are universal for Ir-loaded catalysts, which is also the reason why iridium oxide is usually be expressed as IrOx rather than IrO247. It is estimated from the peak intensities that the contents of Ir4+ are increased, while Ir3+ contents are decreased in the used sample as compared with the fresh sample  to the d(eg) band (1.5–2.75 eV) under visible light irradiation based on the literature50. It is possible that the change in Ir valence state or crystallinity do not affect the photoinduced d–d transition and thus photocatalytic performance. (iii) As for Cu2O, the Cu 2p XPS spectrum shows a minor change. The BEs of the main peaks of Cu 2p remain almost the same before and after the reaction, only a minuscule shift towards lower energy. We could not exclude the possibility that a small amount of Cu(I) was translated into Cu(0) after the photocatalytic reaction. Because some Cu2O is deposited synchronously on the SiC surface, the small change of Cu valence state can occur partly for these Cu2O species, which could have no remarkable influence on the photocatalytic performance.The Cu13CO2 instead of CO2 was used as a reactant, 13C NMR analysis for the reaction solution verifies that only a strong peak at 171.5 ppm attributed to the 13C in H13COOH was observed  to pure H2O is determined firstly. Only very limited amount of HCOOH (<5%) is diffused to the pure water across the Nafion membrane within 8 h  and Fe2+/Fe3+ (2 mmol L−1) under visible light illumination. The concentration of HCOOH remains almost unchanged . As introduction of CO2, Cu2O–Pt/SiC/IrOx shows very weak several absorption peaks before visible light irradiation. However, three strong absorption bands appear upon visible light irradiation. Both the wide absorption band at 1394 cm−1 and the weak band at 1503 cm−1 are ascribed to bidentate carbonate species bonded to the Cu2O surface, while the absorption band at 1262 cm−1 is assigned to a monodentate carbonate to the Cu2O surface54. This demonstrates that CO2 molecules are activated at room temperature by the Cu2O co-catalyst on Cu2O–Pt/SiC/IrOx surface under light irradiation. Moreover, the acidic aqueous solution (pH = 2.3) is helpful for formation of the carboxyl radical intermediate (·COOH) or the formate anion (HCOO−) that is further easily converted into HCOOH55. This could be the second possible reason for the high efficiency of the spatially separated system. High selectivity of product HCOOH may be related to the different reaction mechanism dependent on the reaction conditions, such as the photocatalyst states , reaction conditions , co-catalyst and so on. In the gas –solid  mode, it has been found that the SiC-based composite (MoS2/SiC) photocatalyzed the CO2 reduction into CH4 undergoing HCOOH, HCHO and CH3OH intermediates on SiC surface by the hydrogenation pathways26. In the present work, the reaction is conducted in gas (CO2)–liquid (H2O)–solid mode and the acidic aqueous solution. In addition, the reduction of CO2 occurs on the Cu2O sites rather than SiC, which is helpful for formation of the carboxyl (hydroxyformyl) radical intermediate ·COOH and HCOOH56.The photocatalytic activity of Cu2O–Pt/SiC, Pt/SiC, Pt/SiC/IrOx and Cu2O–Pt/SiC/IrOx, and the AC impedance values decrease in the same order. Obviously, Cu2O–Pt/SiC/IrOx shows the biggest photocurrent and the smallest AC impedance, indicating the highest electron transfer rate and separation efficiency. However, the sample Cu2O–Pt/SiC and Pt/SiC show a slight abnormality, i.e. both the photocurrent increase order and the AC impedance decrease order are inconsistent with the increase order of photocatalytic activity. This can be explained by the dependence of photocatalytic activity on not only the transfer rate and separation efficiency of photogenerated charges but also the surface chemistry characteristics of photocatalyst. Figure 2O–Pt/SiC, Pt/SiC/IrOx and Cu2O–Pt/SiC/IrOx, which agree with the change in the photocatalytic activity. Since low PL intensity corresponds to low recombination rate of photogenerated charges, the lowest PL intensity indicates the smallest recombination rate of photogenerated charge for Cu2O–Pt/SiC/IrOx. Figure τ) of charge carriers (the inset table). The τ value of nude SiC is about 1.2 ns, consistent with the reported literature57. Loading Pt, Cu2O and IrOx nanoparticles lead to an increase in the lifetime τ. In these samples, Cu2O–Pt/SiC/IrOx has the highest τ value. The increase in the lifetime τ of the charge carriers could increase the probability of their involvement in photocatalytic reactions before recombination60. So, increases in the transfer rate, separation efficiency and lifetime of photogenerated charges could be the third reason for high efficiency of the spatially separated system.The photoelectrochemical responses and the photoluminescence spectra of these photocatalysts were measured. Figure 2O–Pt/SiC/IrOx and the photocatalytic mechanism of the spatially separated system. The electron structure parameters of SiC and Cu2O were reckoned by combination of the UV–Vis diffuse reflection spectra with the Mott-Schottky analysis  to the d(eg) band (1.5–2.75 eV) by visible irradiation and from the O-p band to the d(eg) (>3.0 eV) band by ultraviolet irradiation, and its CB is +0.35 V50. For the Cu2O–Pt/SiC/IrOx photocatalyst, Cu2O–Pt and IrOx cocatalysts are separated each other on SiC surface, and Pt is sandwiched between Cu2O and SiC. Thus, Cu2O–Pt/SiC/IrOx is suggested to have the energy band alignment in Fig. The next issue is the electron structure of Cu2O co-catalyst directly contacts with SiC without Pt, the photoelectron transfers on the resulting Cu2O/SiC composite is speculated to follow the Z-scheme transfer from SiC to Cu2O, which has been reported in many literatures63. Such Z-scheme photoelectron transfer was verified by a photocatalytic probe reaction. When the water solution containing the Cu2O/SiC sample and H2PtCl6 was illuminated by UV light, the reduction reaction (PtCl62− + 4e− → Pt + 6Cl−) would occur on the Cu2O/SiC surface. The TEM image clearly indicates preponderant photodeposition of Pt particles over Cu2O particle rather than over SiC surface  of Cu2O would be accelerated by the Pt nanoparticles located between Cu2O and SiC, due to the excellent conductivity and high work function of Pt. The controlled experiment shows that the Cu2O/SiC displays the HCOOH evolution of about 40.5 μmol g−1 h−1, which is little higher than that of the pristine SiC but much lower than that of Cu2O–Pt/SiC samples  would transfer towards the VB of SiC (+1.40 V). Synchronously, the photogenerated electrons from the CB of SiC (−1.08 V) would transfer towards Pt nanoparticles, and then towards the VB of Cu2O (+0.70 V) where they combine with the photogenerated holes at Cu2O. On the whole, the coupled direct Z-scheme processes result in the photogenerated electrons accumulating in the CB of Cu2O (−1.28 V) where the adsorbed CO2 is reduced into HCOOH [E(CO2/HCOOH) = −0.61 V], while the photogenerated holes on the VB of IrOx (t2g = +1.85 V) to oxidize Fe2+ into Fe3+ [E(Fe2+/Fe3+)  = +0.77 V]65. Meanwhile, in the H2O oxidation chamber, Pt/WO3 is excited also by visible irradiation. The photogenerated electrons would transfer from the CB of WO3 (+0.74 V) towards Pt and then reduce Fe3+ into Fe2+ [E(Fe2+/Fe3+) = +0.77 V], while the photogenerated holes of WO3 (+2.06 V) would oxidize H2O to O2 (E = +1.23 V). As shown in Fig. 2 reduction half-reaction and the photocatalytic H2O oxidation half-reaction take place at two separated reactors by the relaying role of Fe3+/Fe2+ redox couple. To prove that the total reaction is a combination of the spatially separated reduction and oxidation, two controlled experiments were done. When the water solution containing photocatalyst Pt/WO3 and Fe3+ is illuminated with visible light, O2 is generated also as a main product .If the Cu2 E = +1. V. As sh2 and H2PtCl6·6H2O were acquired from Aladdin, and the Na3IrCl6 was supplied from Alfa Aesar. Other reagents used in this work, including glucose, methanol, WO3, NaOH, CuSO4·5H2O and NaIO3 were of analytical reagent grade and obtained from Sinopharm Chemical Reagent Co., Ltd. All of the above chemicals were used without further purification.SiO2 and glucose were mixed in the molar ratio of Si:C = 1:6 and pulverized in a mortar to well disperse the mixed powders. The well-mixed powder was calcined under Ar atmosphere at 1450 °C for 5 h at a rate of 2 °C min−1 in a tubular furnace. The calcined powder was then cooled to room temperature and further purified to remove unreacted raw materials based on our previous report26. Briefly, the sample was calcined under O2 atmosphere at 873 K for 5 h and steeped with 10 wt% sodium hydroxide solution in order to remove free carbon and unreacted SiO2.The SiC nanoparticles were prepared by the carbothermic reduction method. Powders of SiO2PtCl6 solution with a concentration of 1 mmol L−1 was mixed with SiC powder in a quartz cell. In the process of stirring, 2 mL of methanol was added into the mixture. After evacuation, the suspension was irradiated with a 125 W Hg lamp to load Pt nanoparticles onto the SiC. After a certain irradiation time, the obtained sample was washed thoroughly with deionized water and dried in vacuum for 1 h. The irradiation time was changed from 0.5 to 2 h to tune the content of Pt in sample, which was denoted as Pt−xh/SiC .Platinum (Pt) was loaded on SiC by the photodeposition method as described in the following steps. The H2O–Pt/SiC and Pt/SiC/IrOx photocatalysts were also prepared by the similar procedure by using Pt/SiC (Pt-1h/SiC) instead of pure SiC. In the preparation of Cu2O–Pt/SiC, CuSO4·5H2O aqueous solution in the concentration of 0.6 mmol L−1 and 2 mL of methanol were introduced to the quartz cell together with Pt/SiC. The content of Cu species in the final sample was controlled by changing the irradiation time from 1 to 10 h, the resulting sample was denoted as Cu2O–Pt−yh/SiC . For the synthesis of Pt/SiC/IrOx, Na3IrCl6 and NaIO3 aqueous solution with the respective concentration of 0.6 and 0.01 mol L−1 were added into the reactor to mix with Pt/SiC. The content of Ir species in the final sample was adjusted also by the irradiation time from 1 to 10 h, the resulting sample was denoted as Pt/SiC/IrOx − yh . After IrOx photodeposition, the samples were washed by deionized water and ethanol for several times to remove residual iodine species. The final sample was obtained after drying in vacuum for 1 h. In order to detect the residual iodine ions, the samples were immersed in the AgNO3 solution. However, we did not find any precipitates AgIO3 or AgI in solution, indicating iodine ion can be completely washed away in the synthesis process.Cu4·5H2O (0.6 mmol L−1) and Na3IrCl6 (0.6 mmol L−1) followed by evacuation and irradiating with a 125 W Hg lamp. The content of Cu and Ir species in the final sample was controlled by the irradiation time from 3 to 15 h. The obtained sample was washed thoroughly with deionized water and dried in vacuum for 1 h, which was denoted as Cu2O–Pt-zh/SiC/IrOx .Pt/SiC was added to the aqueous solution with CuSO3 photocatalyst was also prepared by the photoreduction method similar to that in preparation of Pt/SiC photocatalyst with the irradiation time of 0.5 h.Pt/WO4 was used as a reflectance standard. Brunauer–Emmett–Teller (BET) surface area was measured with an ASAP2020M apparatus . Nitrogen adsorption and desorption isotherms were measured at 77 K. Contents of Pt, Cu and Ir in the samples were measured using an inductively coupled plasma optical emission spectrometer . HS-LEIS measurements were carried out on an IonTOF Qtac100 low-energy ion scattering analyser. 4He+ ions with a kinetic energy of 3 keV were applied at a low ion flux equal to 1325 pA cm−2, which was necessary to avoid the sputtering of surfaces. 20Ne+ ions with a kinetic energy of 5 keV were applied at a low ion flux equal to 445 pA cm−2. The scattering angle was 145°. XPS measurements were performed on a Quantum 2000 Scanning ESCA Microprobe  using Al Kα radiation (1846.6 eV) as the X-ray source. 13C NMR spectra were recorded on AVANCE III 400 MHz spectrometer using TMS as the internal standard. 13CO2 and H218O were employed as the reactants in the isotope labelling comparison reaction instead of CO2 and H2O, respectively. After irradiation, the reaction solution was characterized with 13C NMR directly. FT-IR experiments were carried out on a Nicolet 670 FT-IR spectrometer at a resolution of 4 cm−1 and 64 scans. FT-IR experiments were performed in a home-made IR cell in conjunction with a vacuum system. The catalyst powders were first pressed into a self-supporting disk , and then the disk was placed in the sample cell, which allowed the disk to move vertically along the cell tube. Prior to the FT-IR measurements, the disk was treated under a dynamic vacuum (10−4 Torr) at 473 K for 2 h. After cooling the disk to room temperature, CO2 was introduced into the cell via the septum with a syringe. Photoluminescence excitation spectra was recorded on a FL/FS920 spectrofluorimeter (Edinburgh Instruments) fluorescence spectrometer at room temperature; the excitation wavelength is 375 nm.XRD patterns were recorded with Ni filtered Cu Kα radiation at 40 kV and 40 mA on a Bruker D8 Advance X-ray diffractometer. Morphology of sample was characterized by a field emission scanning electron microscopy (JSM-6700F) and TEM. TEM images were obtained at an accelerating voltage of 200 kV using a JEOL model JEM 2010 EX instrument. UV–Vis diffuse reflectance (UV–Vis DRS) spectra were obtained on a UV–Vis spectrophotometer (Cary 500) with a self-supporting sample cell, and the pure BaSO2-reduction chamber and an O2-generation chamber that are divided by a Nafion membrane (The circular Nafion membrane was Fe-ion exchanged before used in the reactor.)  and 2 mM FeCl2 and another aqueous solution containing 100 mg Pt/WO3 and 2 mM FeCl3 were added to the two reaction chambers, respectively. The pH of solutions was adjusted to 2.3 by adding hydrochloric acid to prevent hydrolysis of the iron ions. Prior to irradiation, ultra-pure Ar (99.9995 v%) gas was bubbled through the solution to purge any dissolved air in the O2-generation compartment and filled to atmospheric pressure, while ultra-pure CO2 gas was bubbled through the solution in the CO2-reduction chamber and filled to atmospheric pressure. During the photoreaction, the solution in each chamber was stirred and irradiated with a 300 W xenon (Xe) lamp. The lamp with an optical filter (λ ≥ 420 nm) was vertically placed at equal distance from each chamber, which makes both solutions to receive the same amount of visible light intensity. The solution in the CO2-reduction chamber was sampled every 2 h and analysed by ion chromatography  after filtering catalyst. The gaseous products in O2 evolution chamber were sampled every 2 h by an off-line sampling syringe (0.5 mL) and then analysed by the gas chromatography  using ultra-pure Ar as the carrier gas.The spatially separated Z-scheme system includes a COλ = 320–780 nm) as the light source. The working electrode was prepared by FTO glass pieces, which was cleaned by sonication in cleanout fluid, acetone and ethanol in sequence prior to use. The photocatalyst was dispersed in ethanol under sonication to form a suspension. A photocatalyst film was fabricated by spreading the suspension onto the conductive surface of the FTO glass.Photoelectrochemical measurements were carried out with a BAS Epsilon workstation using a standard three-electrode electrochemical cell with a working electrode, a platinum foil as the counter electrode, and a saturated Ag/AgCl electrode as the reference. A sodium sulfate solution (0.2 M) was used as the electrolyte, and a 300 W Xe lamp (Supplementary InformationPeer Review File


According to the velocity equation, the increase of Δεα will increase the molecular chain displacement, resulting in a larger free volume, which will provide electrons with larger free path λ to form hot electrons. A positive correlation exists between the activation energy of the dielectric relaxation process δ and trap density, and the increase of δ dielectric relaxation strength (Δεδ) will adversely affect the breakdown strength of the specimen. HDPE/LDPE blends with 15 wt% HDPE content have lower Δεα and lowest Δεδ, which decreases the mean free path λ of molecular chain and thermal ion polarization. At the same time, it has the highest deep trap density, thus increasing the probability of hot electrons being captured and improving the DC breakdown strength. It is concluded the breakdown of the dielectric is synergistically affected by the molecular chain displacement and carrier trap. This work focuses on the coupling effect of molecular chain displacement and trap characteristics on direct current (DC) breakdown properties of high density/low density polyethylene (HDPE/LDPE) blend insulation. Frequency domain spectroscopy (FDS) and isothermal discharge current (IDC) are used to characterize the dielectric relaxation and trap characteristics of HDPE/LDPE blends. A DC breakdown model is proposed to reveal the mechanisms of the molecular chain displacement and carrier trap on the DC breakdown strength. The dielectric relaxation α and δ present segmental motions and thermal ion polarization behaviours of HDPE/LDPE blends, respectively. α dielectric relaxation strength (Δ Cross-linked polyethylene (XLPE) insulation cables are widely used and developed in high-voltage power transmission projects due to their advantages such as light weight, high operating temperature, and high transmission power ,2. HowevAs an environmentally friendly material, polyethylene is widely used as the insulation of power cables, which are considered to have excellent prospects ,7. Chen Deep traps are known to play a crucial role in the breakdown performance of polymer ,12. DeepIn this study, the DC breakdown, dielectric relaxation, and carrier trap characteristics of HDPE/LDPE blend insulation are investigated. A relationship between the dielectric relaxation and molecular chain displacement is investigated, and a DC breakdown model is proposed to reveal the coupling effect of the molecular chain displacement and carrier trap on the DC breakdown strength.HDPE / LDPE blends samples were prepared by melt blending, using LD100BW low density polyethylene from Beijing Yanshan Petrochemical Company  and L501 high density polyethylene from Beijing Yanshan Petrochemical Company . The specimen preparation method used in this article is shown below. The melt blending was conducted in a twin-screw continuous mixer rotation  and the test specimens were prepared by hot press forming machine . First, HDPE and LDPE should be dried at 50 °C for 6 h before the experiment. Second, HDPE and LDPE should be blended into a 175 °C blender for 20 min in a certain proportion, and the ratio of HDPE / LDPE is 0 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, respectively. Third, the above blended materials are put into a stainless-steel mold and pressed at a pressure of 10 MPa for 10 min under a 175 °C environment. Finally, samples with thicknesses of 85 µm and 300 µm were obtained, which were used to test the DC breakdown strength and dielectric properties, respectively. The hot-press forming process can effectively control the thickness difference of the samples to not exceed 5 µm, and the temperature and time during hot pressing are strictly controlled to ensure that the morphology are basically the same. The same PET film is used as the gasket on the sample film to ensure the same surface morphology.−2 to 104 Hz.The real and imaginary parts of the permittivities of the samples at 40, 60 and 80 °C are measured using the frequency domain spectroscopy (FDS) method . Aluminum foil is affixed to both sides of the sample, and the sample was is placed between the electrodes, and the measurement voltage is 1 kV. The test frequency varied from 10The DC breakdown field strength of samples in this article is tested by the ball electrode method. The schematic diagram of DC breakdown test is shown in In this paper, the trap level distribution of the five HDPE/LDPE blends is calculated by isothermal discharge current (IDC) method , as is stN(E)) and the traps energy (tE) can be derived from the following equations: [l is the depth of charge injection and d is the thickness of samples in this paper. q represents the standard charge amount and k is the Boltzmann’s constant, k = 1.38 × 10−23 J/K. T is the absolute temperature, where T is 323.15 K. v is the escape frequency of trapped charges, and its value is ~1012 s−1. In order to improve the fitting of discharge current data for short times, two exponential decay function has been used for a better approximation of the experimental results.IDC is a method proposed by Simmons in 1973 to study the density distribution of trap energy level in materials, and the density of traps (uations: :(1)Nt(E)ε′) and dielectric loss (ε″) test results of five samples at 40, 60, and 80 °C are shown in −2 to 104 Hz, where α and δ relaxation processes occur at high and low frequencies, respectively. Frist, both the ε′ and ε″ results show a remarkable relaxation peak above 10 Hz, which is α relaxation process, and the α relaxation is closely relevant to the displacement of molecular segments in the polymer [ε′ and ε″ spectrum have an upward process when the frequency continues to decline. This process is the δ relaxation process, which is related to the localized states hopping behavior of the carrier in the polymer [ε′ and ε″ spectrum of the same sample, the spectral peaks will move towards a higher frequency and the ε″ spectrum shows a distinct upswing process during the temperature rise process. Hence, this process mainly causes dielectric loss [Dielectric constant  function equation, the ~10−13 s . ω repreThe isothermal discharge current and the trap levels distributions of HDPE/LDPE blends are obtained and illustrated in Eb is the breakdown strength at a breakdown possibility of 63.2%. Eb is 263.2, 254.7, 276.6, 293.8 and 276.1 kV/mm for HDPE/LDPE blends with HDPE content from 0 to 20 wt%, respectively. The addition of HDPE first reduce and then induce the DC breakdown performance of HDPE/LDPE blends, Eb reaches the highest value at 15 wt% then declines when the HDPE content increases to 20 wt%. The distribution parameter of the Weibull plots is 10.1, 10.1, 10.9, 11.8 and 10.4 for HDPE/LDPE blends with HDPE content from 0 to 20 wt%, respectively.τα, τδ, Δεα, Δεδ and σDC are obtained from Equation (3). α relaxation strength (Δεα) and δ relaxation strength (Δεδ) of five samples at 40, 60, and 80 °C.The calculated results for α relaxation is relevant to the movement of molecular segments in amorphous phase [α relaxation is caused by the orientation of the dipoles in the molecular chain under the action of microscopic Brownian motion [εα declines with temperature as shown in εδ keeps an upward tendency with the temperature, because carriers get more energy and the motion of carriers is easier in HDPE/LDPE blends.The us phase . α relaxn motion . The incα relaxation process is closely related with the dipoles in polymer, which is coincident with the crystallinity of samples. In addition, Δεα also depend on the number of dipoles in the amorphous area [εα. Δεα increases as the amount of HDPE increases from 0 to 5 wt%, and then decreases when the HDPE content increases to 20 wt%. Thus, it is inferred that the sample with 5 wt% content HDPE has the highest molecular chain alignment disorder, looseness, and flexibility, so that molecular chains can easily be rearranged under the action of an electric field to form a void segment.The ous area . Polymerδ involves hopping polarization [The dielectric relaxation process rization . Localizrization .τδ and absolute temperature is fitted by the following equation, and the required energy for hopping polarization is calculated [τ0 is a constant, Eτ represents the activation energy of hopping polarization, and k represents the Boltzmann’s constant. The δ relaxation time constant and Arrhenius plot is illustrated in δ is in the range of 10−1~102 s, so this process refers to hopping polarization [Eτ of HDPE/LDPE blends with HDPE content from 0 to 20 wt% are 0.61, 0.71, 0.72, 0.76, and 0.53 eV, respectively.The relationship between lculated .(4)τδ(Trization . The fitΦeff) in polymer is positively correlated to the trap level of the localized states (Φt) [Eext represents the external field, and λ represents the mean free path of charges. Φeff represents the potential barrier for trapped electrons to overcome for hopping from localized states. Equation (5) implies that a deeper trap level has a higher potential barrier in hopping polarization behavior. Moreover, increasing the density of deep traps increases the possibility of trapping during carrier migration, enhances trap trapping effects and reduces the mean free path of carriers [The trap level is potential barriers that carriers need to overcome to jump between localized states. With the increase of trap density in HDPE/LDPE blends, the activation energy in δ relaxation process also increase, since the increase of trap density will also cause more homopolar charges to be confined on the surface of the dielectric, and the electric field generated by these homopolar charges  will reduce the carrier injection equivalent electric field , eventuates (Φt) .(5)ϕeffcarriers . Thus, mεδ has an upward tendency with the content of HDPE from 0 to 5 wt%, then declines when HDPE content increases to 15 wt%, but when the HDPE content reaches 20 wt%, Δεδ attains the highest value. δ relaxation and trap density of HDPE/LDPE blends, and both the activation energy and trap density show the opposite trend from Δδε in δε and the highest deep trap density and activation energy of the δ relaxation.In addition, ΔPrevious works  showed tIt is assumed that free volumes exist in HDPE/LDPE blends, and electrons can accumulate energy under the electric field and not dissipate. The breakdown mechanism can be demonstrated as follows .(6)Ecriλe) and deep potential barriers (Et) cooperate to affect the dielectric critical breakdown field strength , and the deep trap level represents Et [Ecritical, since higher barriers limit the transport and migration of free carriers. All samples in this paper have similar deep trap energy levels as shown in As a consequence, the mean free path of electrons Pteλ is about 3.1~3.5 nm when the breakdown occurs, which is obviously not equal to the mean free path inherent in polyethylene (<1 nm). Moreover, HDPE/LDPE blends with 0 wt% and 5 wt% HDPE mass fraction samples have almost similar deep trap levels and densities, but the sample with HDPE content of 5 wt% has a lower breakdown strength. Therefore, the investigation of the breakdown mechanism needs to consider the free path of the charge generated by the displacement of the molecular segment.Nevertheless, according to Equation (6), the longest electron mean free path τtrap) of traps of different energy levels might be several orders of magnitude, which can be expressed as [Hence, a molecular chain displacement model was established, as shown in essed as (8)τtrap−13 s when trap level is 0.1 eV, and trap residence time is about 500 s for 1.0 eV traps [Hence, the trap residence time constant is approximately 10eV traps ,41.λ is the molecular chain displacement in m, Eappl is applied field in V/m.Hence, deep traps play a major role in the molecular chain displacement process. This phenomenon of molecular chain displacement process can be further investigated by the following velocity equation .(9)dλdtC stands for a constant. Here the carrier mobility μ0 is assumed to be in the range from 1 × 10−15 to 5 × 10−15 m2V−1s−1 [τα at 40 °C calculated by Equation (3) are shown in Therefore,m2V−1s−1 . The valεα will increase the displacement of the molecular chain, thereby forming many larger free volumes. The larger free volume will make the electrons accelerate to get more energy under the action of the electric field, which may then become hot electrons. In the Kao’s model [In this case, it can be considered that charged molecular chain is formed, which will be displaced by the electric field, the increase of Δ’s model , the chaHence, a breakdown model combining the molecular chain displacement and carrier trap was established as shown in Wappl are smaller than the deep potential barrier Et, these electrons will be captured by deep traps. On the other hand, these hot electrons with energy as Wappl are larger than the potential barrier Et, they can directly cross over deep traps and constantly hit the molecular chain. Moreover, the growth of deep trap density Nt will enhance the possibility of hot electrons being captured [If the hot electrons with an energy of captured , preventHDPE/LDPE blends are prepared to study the coupling effect of molecular chain displacement and carrier trap characteristics on their DC breakdown strength, and the following conclusions have been drawn.α and δ relaxation in HDPE/LDPE blends turn out to contain the molecular segments displacement and carrier’s hopping, respectively. Δεα declines with the increase of temperature, because of random thermal motion of dipoles caused by Brownian motion. Δεδ increases with the temperature, since higher temperatures provide more energy for the carriers to hop polarization. The activation energy of the dielectric relaxation process δ is positive related to the trap density obtained by IDC test.The εα increases as the amount of HDPE increases from 0 to 5 wt%, then declines with a further increase of HDPE content to 20 wt%. The increase of Δεα will increase the displacement of the molecular chain inside the sample, resulting in a larger free volume, which will provide electrons with larger mean free path to obtain energy, and eventually continue to hit the molecular chain to cause breakdown.Δεα and deep trap density Nt synergistically influence the average free path of the carrier and ultimately affect the breakdown performance of the dielectric. Moreover, the growth of deep traps density decreases the mean free path of electrons and prevents hot electrons from hitting the molecular chain directly, leading to an improvement in the DC breakdown field.Δ


Bacillus thuringiensis (Bt) insecticidal toxins have been globally utilized for control of agricultural insects through spraying or transgenic crops. Binding of Bt toxins to special receptors on midgut epithelial cells of target insects is a key step in the mode of action. Previous studies suggested aminopeptidase N1 (APN1) as a receptor or putative receptor in several lepidopteran insects including Helicoverpa armigera through evidence from RNA interefence‐based gene silencing approaches. In the current study we tested the role of APNs in the mode of action of Bt toxins using clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR‐associated protein 9‐mediated gene knockout. Three APN genes  were individually knocked out in a susceptible strain (SCD) of H. armigera to establish three homozygous knockout strains. Qualitative in vitro binding studies indicated binding of Cry1Ac or Cry2Ab to midgut brush border membrane vesicles was not obviously affected by APN knockout. Bioassay results showed that none of the three knockouts had significant changes in susceptibility to Cry1A or Cry2A toxins when compared with the SCD strain. This suggests that the three HaAPN genes we tested may not be critical in the mode of action of Cry1A or Cry2A toxins in H. armigera. Bacillus thuringiensis (Bt) is a Gram‐positive bacterium that produces insecticidal crystal (Cry) proteins during sporulation  transporters, alkaline phosphatases (ALPs), and aminopeptidase Ns (APNs). A large amount of evidence from both forward and reverse genetics have confirmed that cadherins and ABC transporters are functional receptors for Cry1A or Cry2A toxins in some lepidopteran insects  and the ABC transporter C2 gene (HaABCC2) are genetically linked to Cry1Ac resistance  are genetically linked with resistance to Cry2Ab  as receptors for Bt Cry toxins, current evidence is still suggestive. Silencing of HaAPN1 with RNAi caused reduced transcript levels and a corresponding decrease in the susceptibility of H. armigera larvae to Cry1Ac  were individually knocked out from the susceptible strain SCD. Three homozygous knockout strains were established and named as SCD‐APN1, SCD‐APN2 and SCD‐APN5.The background strain SCD, originally started from the Côte D'Ivoire (Ivory Coast), Africa has been maintained in the laboratory without exposure to insecticides or Bt toxins for over 30 years . Cry2Ab protoxin was provided by the Institute of Plant Protection, Chinese Academy of Agricultural Sciences (CAAS), China. Cry1A and Cry2A toxins were produced according to Monnerat et al. .μL) was dispensed into each well (surface area = 2 cm2) of a 24‐well plate. After the diet cooled and solidified, 100 μL of Bt toxin solution was applied evenly to the diet surface in each well. A single unfed neonate (24 h old) was put in each well after the toxin solution was dried at room temperature. Forty‐eight larvae were tested at each concentration of Bt toxins and PBS control. Mortality was recorded after 7 days, and larvae were considered as dead if they had died or weighed less than 5 mg.Toxicological responses of each strain to Bt toxins were determined with diet overlay bioassays. Gradient concentrations of Bt toxin solution were prepared by diluting the toxin stock suspensions with a 0.01 mol/L, pH 7.4, phosphate‐buffered solution (PBS). Liquid artificial diet  and the 95% fiducial limits of the LC50 for each strain were calculated using the PoloPlus program , HaAPN2 (GenBank accession no. EU325551.1) and HaAPN5 (GenBank accession no. AY038608.1) according to the target sequence principle: 5′‐GGN18NGG‐3′. HaAPN1, HaAPN2 and HaAPN5 were named according to the phylogenetic tree analysis based on lepidopteran APN protein sequences . In vitro transcription of each sgRNA was performed with MEGAshortscriptTM T7 High Yield Transcription Kit  according to the optimized manufacturer's instructions.The sgRNA was produced according to the method reported by Bassett et al. . The speet al.  were indet al.  in a polμL) and Cas9 messenger RNA (mRNA) (500 ng/μL) was injected into lined eggs according to the method reported by Wang et al.  with BBMVs were carried out as previously reported by Wang et al. . Brieflyμg BBMVs with 0.28 nmol/L Cry2Ab toxin were incubated in 100 μL binding buffer  for 1 h at 37 °C. After incubation, BBMVs were pelleted by centrifugation at 16 000 × g and 4 °C for 10 min, and washed three times with 0.5 mL ice‐cold binding buffer to remove unbound toxins. The final pellet was resuspended in sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS‐PAGE) sample buffer and boiled for 10 min. Denatured proteins were resolved on a 10% SDS‐PAGE gel and transferred to polyvinylidene difluoride (PVDF) filter. Filters were blocked with 5% BSA in PBST  for 1 h. Toxin binding was revealed by Western blot using rabbit polyclonal antibodies of Cry1Ac or Cry2Ab (1 : 2000)  followed by horseradish peroxidase (HRP)‐conjugated goat anti‐rabbit immunoglobulin G  (1 : 5000) in PBST at room temperature for 1 h. Cry1Ac or Cry2Ab in the filter was visualized using SuperSignal® West Pico Chemiluminescent Substrate  according to the manufacturer's instructions.Twenty micrograms BBMVs with 0.04 nmol/L Cry1Ac toxin, or 5 HaAPN1 and HaAPN5, and exon 3 of HaAPN2 respectively  and Cas9 mRNA (500 ng/μL) was injected into individual eggs from the SCD strain. The hatched larvae were reared to adults (G0) and mass crossed to produce the next generation (G1). Data of the number of eggs injected, hatching rate and HaAPN genotyping are detailed in Table 0 adults was prepared after oviposition, and sequencing results showed that 62.0% to 96.6% of the G0 individuals were edited for HaAPN1, HaAPN2 and HaAPN5. The indel mutation types for each HaAPN gene are summarized in Figure 1 were reared to pupae and genotyped using the exuviates of the final instar larvae. To create the homozygous HaAPN1 knockout strain, four heterozygotes (2♀ and 2♂) with a 5‐bp deletion allele (the major mutation type) and a wild type allele of HaAPN1 were mass crossed to produce G2. In a similar way, 10 heterozygotes (5♀ and 5♂) with 1‐bp insertion in HaAPN2 were mass crossed, and 14 heterozygotes (5♀ and 9♂) with 1‐bp deletion in HaAPN5 were mass crossed to produce G2. Seventy to 96 individuals of G2 from the three populations were genotyped using exuviates of the final instar larvae, and only the individuals with homozygous indel mutations were pooled to generate homozygous knockout strains, named as SCD‐APN1, SCD‐APN2 and SCD‐APN5, respectively.About 1 nL of mixed sgRNA  was first shown to bind to Cry toxins  was genetically linked with Cry1Ac resistance, suggesting TnAPN1 as a functional receptor of Cry1Ac (Tiewsiri & Wang, APN1 of Ostrinia nubilalis was genetically associated with Cry1Ab resistance, also suggesting OnAPN1 is a critical receptor in the Cry1Ab mode of action (Coates et al., Down‐regulation of