Modulation of Disordered Coordination Degree Based on Surface Defective Metal-Organic Framework Derivatives toward Boosting Oxygen Evolution Electrocatalysis.

Seeking potential electrocatalysts with both large-scale application and robust activity for the oxygen evolution reaction allows for no delay. Herein, a squarate-based metal-organic framework (MOF) ([Co3 (C4 O4 )2 (OH)2 ]⋅3H2 O) is reported for electrocatalytic water oxidation. A facile, green, and low-cost strategy is proposed to introduce defects by not only rationally breaking CoO bonds to form defective coordination environment and electronic reconfiguration, but also systematically modulates defect concentration to optimize electrochemical performance. As a result, the post-treated surface defective MOF derivative (Co-MOF-3h) achieves a current density of 50 mA cm-2 at an overpotential of 380 mV, owing to larger active surface area, more opened active sites, and favorable conducting channels. Finally, density functional theory calculations have further validated the effect of defective coordination in regard to electronic structure for electrocatalysts. This study delivers inspirations in defect engineering and is in favor of developing high-efficiency electrocatalysts.

Facilitating Phase Evolution for a High-Energy-Efficiency, Low-Cost O3-Type NaxCu0.18Fe0.3Mn0.52O2 Sodium Ion Battery Cathode.

The phase transition and lattice parameter evolution of O3 structure commonly occurs in O3-type sodium ion battery (SIB) cathodes, which might enlarge the voltage hysteresis and lower the energy efficiency. Given that the cost is one of the issues discouraging the application of SIBs in large-scale energy storage, here we focus on Co/Ni-free NaxCu0.18Fe0.3Mn0.52O2 (x = 0.8, 0.85, 0.9) and propose a convenient strategy to reduce the voltage hysteresis. It is found that when the Na content is 0.8, the highest energy efficiency of 95.4% after activation is achieved (2.5-4.0 V, 50 mA g-1, the 50th cycle), in addition to a satisfactory capacity retention (about 0.056% decay per cycle). The further characterizations reveal that Na0.8Cu0.18Fe0.3Mn0.52O2 owns a gentle O3-P3 phase transition process and does not undergo O3 phase lattice parameter evolution. The key point lies in the attainability of the O3/P3 composite of the material. This work will provide a simple strategy for the rational design of O3-type cathodes with a high energy efficiency and might offer inspiration to search for layered oxides with a higher O3/P3 critical Na content through element adjustments.

Interfacial Engineering of Hierarchical Transition Metal Oxide Heterostructures for Highly Sensitive Sensing of Hydrogen Peroxide.

Hydrogen peroxide (H2 O2 ) is a major messenger molecule in cellular signal transduction. Direct detection of H2 O2 in complex environments provides the capability to illuminate its various biological functions. With this in mind, a novel electrochemical approach is here proposed by integrating a series of CoO nanostructures on CuO backbone at electrode interfaces. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction, and X-ray photoelectron spectroscopy demonstrate successful formation of core-shell CuO-CoO hetero-nanostructures. Theoretical calculations further confirm energy-favorable adsorption of H2 O2 on surface sites of CuO-CoO heterostructures. Contributing to the efficient electron transfer path and enhanced capture of H2 O2 in the unique leaf-like CuO-CoO hierarchical 3D interface, an optimal biosensor-based CuO-CoO-2.5 h electrode exhibits an ultrahigh sensitivity (6349 µA m m-1 cm-2 ), excellent selectivity, and a wide detection range for H2 O2 , and is capable of monitoring endogenous H2 O2 derived from human lung carcinoma cells A549. The synergistic effects for enhanced H2 O2 adsorption in integrated CuO-CoO nanostructures and performance of the sensor suggest a potential for exploring pathological and physiological roles of reactive oxygen species like H2 O2 in biological systems.

Three-Dimensional Hierarchical Architectures Derived from Surface-Mounted Metal-Organic Framework Membranes for Enhanced Electrocatalysis.

Inspired by the rapid development of metal-organic-framework-derived materials in various applications, a facile synthetic strategy was developed for fabrication of 3D hierarchical nanoarchitectures. A surface-mounted metal-organic framework membrane was pyrolyzed at a range of temperatures to produce catalysts with excellent trifunctional electrocatalytic efficiencies for the oxygen reduction, hydrogen evolution, and oxygen evolution reactions.

Machine Learning Enhanced DFTB Method for Periodic Systems: Learning from Electronic Density of States.

Density functional tight binding (DFTB) is an approximate density functional based quantum chemical simulation method with low computational cost. In order to increase its accuracy, we have introduced a machine learning algorithm to optimize several parameters of the DFTB method, concentrating on solids with defects. The backpropagation algorithm was used to reduce the error between DFTB and DFT results with respect to the training data set and to obtain adjusted DFTB Hamiltonian and overlap matrix elements. Afterward, the generalization capability of the trained model was tested for geometries not being part of the training set. In the current work, we have focused on defective periodic silicon and silicon carbide systems as target materials and the density of states (DOS) as target property to demonstrate the feasibility of our approach. The trained model was able to reduce the differences between the DFTB and DFT DOS significantly, while other derived properties (for example, Mulliken population distribution, projected DOS) remained physically sound. Also, the transferability of the obtained model could be verified. Our method allows to carry out relatively fast simulations with high accuracy and only moderate training efforts, and represents a good compromise for cases, where long-range effects make direct machine learning predictions difficult.

Obtaining Electronic Properties of Molecules through Combining Density Functional Tight Binding with Machine Learning.

We have introduced a machine learning workflow that allows for optimizing electronic properties in the density functional tight binding method (DFTB). The workflow allows for the optimization of electronic properties by generating two-center integrals, either by training basis function parameters directly or by training a spline model for the diatomic integrals, which are then used to build the Hamiltonian and the overlap matrices. Using our workflow, we have managed to obtain improved electronic properties, such as charge distributions, dipole moments, and approximated polarizabilities. While both machine learning approaches enabled us to improve on the electronic properties of the molecules as compared with existing DFTB parametrizations, only by training on the basis function parameters we were able to obtain consistent Hamiltonians and overlap matrices in the physically reasonable ranges or to improve on multiple electronic properties simultaneously.

Synergetic stability enhancement with magnesium and calcium ion substitution for Ni/Mn-based P2-type sodium-ion battery cathodes.

The conventional P2-type cathode material Na0.67Ni0.33Mn0.67O2 suffers from an irreversible P2-O2 phase transition and serious capacity fading during cycling. Here, we successfully carry out magnesium and calcium ion doping into the transition-metal layers (TM layers) and the alkali-metal layers (AM layers), respectively, of Na0.67Ni0.33Mn0.67O2. Both Mg and Ca doping can reduce O-type stacking in the high-voltage region, leading to enhanced cycling endurance, however, this is associated with a decrease in capacity. The results of density functional theory (DFT) studies reveal that the introduction of Mg2+ and Ca2+ make high-voltage reactions (oxygen redox and Ni4+/Ni3+ redox reactions) less accessible. Thanks to the synergetic effect of co-doping with Mg2+ and Ca2+ ions, the adverse effects on high-voltage reactions involving Ni-O bonding are limited, and the structural stability is further enhanced. The finally obtained P2-type Na0.62Ca0.025Ni0.28Mg0.05Mn0.67O2 exhibits a satisfactory initial energy density of 468.2 W h kg-1 and good capacity retention of 83% after 100 cycles at 50 mA g-1 within the voltage range of 2.2-4.35 V. This work deepens our understanding of the specific effects of Mg2+ and Ca2+ dopants and provides a stability-enhancing strategy utilizing abundant alkaline earth elements.

Interfacial Effects on the Band Edges of Ta3N5 Photoanodes in an Aqueous Environment: A Theoretical View.

Ta3N5, as a fascinating photoanode for solar hydrogen production, is expected to split water without any bias, because its band edge potentials straddle H2O redox potentials. Unfortunately, Ta3N5 photoanodes can split water only when a bias of at least 0.6-0.9 V is applied. It means that they exhibit an onset potential as high as 0.6-0.9 VRHE (reversible hydrogen electrode). In this study, density functional theory calculations show that the band edge potentials of Ta3N5 have a shift of approximately -0.42 eV relative to vacuum level when exposed to water. The increased ratio of dissociated water at Ta3N5-water interface will further make the band edge potentials shift -0.85 eV relative to vacuum level, implying the anodic shifts of the onset potential for water oxidation. The findings may reveal the mystery of the unexpectedly high onset potential of Ta3N5, as high as 0.6-0.9 VRHE.

[Association study on microsatellite polymorphisms of MSX1 gene and nonsyndromic cleft lip and palate].

OBJECTIVE: To investigate muscle segment homeobox 1 (MSX1) microsatellite marker distribution and the relationship between MSX1 gene and the genetic susceptibility of nonsyndromic cleft lip and palate (NSCLP) in Hunan Hans. METHODS: One microsatellite DNA marker CA repeat in MSX1 intron region was used as genetic markers. The genotypes of 129 patients with NSCLP and 108 controls were analyzed by the techniques of polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis (PAGE). Then case-control study was used to conduct association analysis. RESULTS: The allele frequencies of the CA repeat microsatellite DNA in Hunan Han normal population were in good agreement with Hardy-Weinberg equilibrium. The polymorphism information content and heterozygosity of CA repeat microsatellite DNA were 0.50 and 0.50 respectively. The allele CA4 frequency in CL/P and CPO group was significantly higher than that of normal controls (P<0.05). The genotype CA4,4 frequency was significantly higher in CL/P and CPO group than that in normal controls (P<0.05). CONCLUSION: The microsatellite DNA marker CA repeat in MSX1 is a good genetic marker. MSX1 gene is significantly associated with NSCLP in Hunan Hans.

[Association between retinoic acid receptor alpha gene polymorphisms and nonsyndromic cleft lip with or without cleft palate susceptibility].

OBJECTIVE: To investigate the relationship between D17S579 microsatellite marker allelic polymorphisms in retinoic acid receptor-alpha (RARA) gene and the genetic susceptibility to nonsyndromic cleft lip with or without cleft palate (NSCL/P) in Hunan Hans. METHODS: PCR and denaturing polyacrylamide gel electrophoresis (PAGE) were used to detect the polymorphism of RARA gene marked by D17S579 among 140 patients with NSCL/P, 82 males and 58 females, aged 3 months-14 years, and 132 healthy persons, 68 males and 64 females, aged 6 months-14 years, who underwent physical examination. RESULTS: The A6 allele frequency of the NSCL/P patients was 8.93%, significantly higher than that of the healthy persons (4.17%, P = 0.026). The A9 allele frequency the NSCL/P patients was 13.21%, significantly higher than that of the healthy persons (5.68%, P = 0.003). There were not significant differences in the frequencies of different alleles between the patients with family history and the patients without family history (chi2 = 2.710, P = 0.978). CONCLUSION: The A6 and A9 alleles in D17S579 microsatellite marker of RARA gene may be correlated with the development of NSCL/P in Hunan Hans. There is no association between the family history and RARA polymorphism in the NSCL/P patients.

[Transmission disequilibrium test for nonsyndromic cleft lip and palate and segment homeobox gene-1 gene].

OBJECTIVE: To investigate the relationship between muscle segment homeobox gene-1 (MSX1) and the genetic susceptibility of nonsyndromic cleft lip and palate (NSCLP) in Hunan Hans. METHODS: One microsatellite DNA marker CA repeat in MSX1 intron region was used as genetic marker. The genotypes of 387 members in 129 NSCLP nuclear family trios were analyzed by polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis. Then transmission disequilibrium test (TDT) and Logistic regression analysis were used to conduct association analysis. RESULTS: TDT analysis confirmed that CA4 allele in CL/P and CPO groups preferentially transmitted to the affected offspring (P = 0.018, P = 0.041). Logistic regression analysis indicated that the recessive model of inheritance was supported, and CA4 itself or CA4 acting as a marker for a disease allele or haplotype was inherited in a recessive fashion (P = 0.009). CONCLUSIONS: MSX1 gene is associated with NSCLP, and MSX1 gene may be directly involved either in the etiology of NSCLP or in linkage disequilibrium with disease-predisposing sites.