A High-Efficiency Bioorthogonal Tumor-Membrane Reactor for In Situ Selective and Sustained Prodrug Activation.

The site-specific activation of bioorthogonal prodrugs has provided great opportunities for reducing the severe side effects of chemotherapy. However, the precise control of activation location, sustained drug production at the target site, and high bioorthogonal reaction efficiency in vivo remain great challenges. Here, we propose the construction of tumor cell membrane reactors in vivo to solve the above problems. Specifically, tumor-targeted liposomes with efficient membrane fusion capabilities are generated to install the bioorthogonal trigger, the amphiphilic tetrazine derivative, on the surface of tumor cells. These predecorated tumor cells act as many living reactors, transforming the tumor into a "drug factory" that in situ activates an externally delivered bioorthogonal prodrug, for example intratumorally injected transcyclooctene-caged doxorubicin. In contrast to the rapid elimination of cargo that is encapsulated and delivered by liposomes, these reactors permit stable retention of bioorthogonal triggers in tumor for 96 h after a single dose of liposomes via intravenous injection, allowing sustained generation of doxorubicin. Interestingly, an additional supplement of liposomes will compensate for the trigger consumed by the reaction and significantly improve the efficiency of the local reaction. This strategy provides a solution to the efficacy versus safety dilemma of tumor chemotherapy.

Electrocatalytic activity of MoSi2N4monolayers decorated with single transition metal atoms: a computational study.

Two-dimensional (2D) MoSi2N4is a newly created material that has superstability and ultrahigh carrier mobility. Besides, the hydrogen evolution reaction activity was proved excellent by doping transition metal (TM) atoms and introducing N vacancies. But, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of 2D MoSi2N4is unclear even. We have explored the electrocatalytic properties (OER/ORR) of MoSi2N4by introducing Si vacancies and attaching various TM atoms. The structure and optoelectronic characteristics of MoSi2N4have been researched in detail using density functional theory calculations. By analyzing the density of states, the free energy change diagram and contour maps of TM@VSi-MoSiN, the results show that Co@VSi-MoSiN has the lowest OER overpotential (0.53 V) among all samples. Additionally, the d-band center is used to explain the electrocatalytic origin of the OER and ORR of TM@VSi-MoSiN. Our discoveries expand the 2D TM@VSi-MoSiN applicability in the realm of catalysis.

Core-Shell Reactor Partitioning Enzyme and Prodrug by ZIF-8 for NADPH-Sensitive In Situ Prodrug Activation.

Enzyme-prodrug therapies have shown unique advantages in efficiency, selectivity, and specificity of in vivo prodrug activation. However, precise spatiotemporal control of both the enzyme and its substrate at the target site, preservation of enzyme activity, and in situ substrate depletion due to low prodrug delivery efficiency continue to be great challenges. Here, we propose a novel core-shell reactor partitioning enzyme and prodrug by ZIF-8, which integrates an enzyme with its substrate and increases the drug loading capacity (DLC) using a prodrug as the building ligand to form a Zn-prodrug shell. Cytochrome P450 (CYP450) is immobilized in ZIF-8, and the antitumor drug dacarbazine (DTIC) is coordinated and deposited in its outer layer with a high DLC of 43.6±0.8 %. With this configuration, a much higher prodrug conversion efficiency of CYP450 (36.5±1.5 %) and lower IC50 value (26.3±2.6 µg/mL) are measured for B16-F10 cells with a higher NADPH concentration than those of L02 cells and HUVECs. With the tumor targeting ability of hyaluronic acid, this core-shell enzyme reactor shows a high tumor suppression rate of 96.6±1.9 % and provides a simple and versatile strategy for enabling in vivo biocatalysis to be more efficient, selective, and safer.

Thermal transport properties of novel two-dimensional CSe.

Recently, as a novel member of the IV-VI group compounds, two-dimensional (2D) buckled monolayer CSe has been discovered for use in high-performance light-emitting devices (Q. Zhang, Y. Feng, X. Chen, W. Zhang, L. Wu and Y. Wang, Nanomaterials, 2019, 9, 598). However, to date, the heat transport properties of this novel CSe is still lacking, which would hinder its potential application in electronic devices and thermoelectric materials that can generate electricity from waste heat. Here we systematically study the heat transport properties of monolayer CSe based on ab initio calculations and phonon Boltzmann transport theory. We find that the lattice thermal conductivity κlat of monolayer CSe is around 42 W m-1 K-1 at room temperature, which is much lower than those of black phosphorene, buckled phosphorene, MoS2, and buckled arsenene. Moreover, the longitudinal acoustic phonon mode contributes the most to the κlat, which is much larger than those of the out-of-plane phonon mode and transverse acoustic branches. The calculated size-dependent κlat shows that the sample size can significantly reduce the κlat of monolayer CSe and can persist up to 10 µm. These discoveries provide new insight into the size-dependent thermal transport in nanomaterials and guide the design of CSe-based low-dimensional quantum devices, such as thermoelectric devices.

A diagonal masking self-attention-based multi-scale network for motor imagery classification.

Objective. Electroencephalography (EEG)-based motor imagery (MI) is a promising paradigm for brain-computer interface (BCI), but the non-stationarity and low signal-to-noise ratio of EEG signals make it a challenging task.Approach. To achieve high-precision MI classification, we propose a Diagonal Masking Self-Attention-based Multi-Scale Network (DMSA-MSNet) to fully develop, extract, and emphasize features from different scales. First, for local features, a multi-scale temporal-spatial block is proposed to extract features from different receptive fields. Second, an adaptive branch fusion block is specifically designed to bridge the semantic gap between these coded features from different scales. Finally, in order to analyze global information over long ranges, a diagonal masking self-attention block is introduced, which highlights the most valuable features in the data.Main results. The proposed DMSA-MSNet outperforms state-of-the-art models on the BCI Competition IV 2a and the BCI Competition IV 2b datasets.Significance. Our study achieves rich information extraction from EEG signals and provides an effective solution for MI classification.

Transition metal doped WSi2N4monolayer for water splitting electrocatalysts: a first-principles study.

High-performance water splitting electrocatalysts are urgently needed in the face of the environmental degradation and energy crisis. The first principles method was used in this study to systematically examine the electronic characteristics of transition metal (Sc, Ti, V, Cr, Mn, Fe, and Ru) doped WSi2N4(TM@WSi2N4) and its potential as oxygen evolution reaction (OER) catalysts. Our study shows that the doping of TM atoms significantly improves the catalytic performance of TM@WSi2N4, especially Fe@WSi2N4shows a low overpotential (ηOER= 470 mV). Interestingly, we found that integrated-crystal orbital Hamilton population and d-band center can be used as descriptors to explain the high catalytic activity of Fe@WSi2N4. Subsequently, Fe@WSi2N4exhibits the best hydrogen evolution reaction (HER) activity with a universal overpotential of 47 mV on N1sites. According to our research, Fe@WSi2N4offers a promising substitute for precious metals as a catalyst for overall water splitting with low OER and HER overpotentials.

Transition Metal and N Doping on AlP Monolayers for Bifunctional Oxygen Electrocatalysts: Density Functional Theory Study Assisted by Machine Learning Description.

It is vital to search for highly efficient bifunctional oxygen evolution/reduction reaction (OER/ORR) electrocatalysts for sustainable and renewable clean energy. Herein, we propose a single transition-metal (TM)-based defective AlP system to validate bifunctional oxygen electrocatalysis by using the density functional theory (DFT) method. We found that the catalytic activity is enhanced by substituting two P atoms with two N atoms in the Al vacancy of the TM-anchored AlP monolayer. Specifically, the overpotential of OER(ORR) in Co- and Ni-based defective AlP systems is found to be 0.38 (0.25 V) and 0.23 V (0.39 V), respectively, showing excellent bifunctional catalytic performance. The results are further presented by establishing the volcano plots and contour maps according to the scaling relation of the Gibbs free-energy change of *OH, *O, and *OOH intermediates. The d-band center and the product of the number of d-orbital electrons and electronegativity of the TM atom are the ideal descriptors for this system. To investigate the activity origin of the OER/ORR process, we performed the machine learning (ML) algorithm. The result indicates that the number of TM-d electrons (Ne), the radius of TM atoms (rd), and the charge transfer of TM atoms (Qe) are the three primary descriptors characterizing the adsorption behavior. Our results can provide a theoretical guidance for designing highly efficient bifunctional electrocatalysts and pave a way for the DFT-ML hybrid method in catalysis research.

Tunable Schottky Barrier and Interfacial Electronic Properties in Graphene/ZnSe Heterostructures.

With a direct bandgap, two-dimensional (2D) ZnSe is a promising semiconductor material in photoelectric device fields. In this work, based on first-principles methods, we theoretically studied the modulation of the Schottky barrier height (SBH) by applying horizontal and vertical strains on graphene/ZnSe heterojunction. The results show that the inherent electronic properties of graphene and ZnSe monolayers are both well-conserved because of the weak van der Waals (vdW) forces between two sublayers. Under horizontal strain condition, the n(p)-type SBH decreases from 0.56 (1.62) eV to 0.21 (0.78) eV. By changing the interlayer distance in the range of 2.8 Å to 4.4 Å, the n(p)-type SBH decreases (increases) from 0.88 (0.98) eV to 0.21 (1.76) eV. These findings prove the SBH of the heterojunction to be tuned effectively, which is of great significance to optoelectronic devices, especially in graphene/ZnSe-based nano-electronic and optoelectronic devices.

The External Electric Field-Induced Tunability of the Schottky Barrier Height in Graphene/AlN Interface: A Study by First-Principles.

Graphene-based van der Waals (vdW) heterojunction plays an important role in next-generation optoelectronics, nanoelectronics, and spintronics devices. The tunability of the Schottky barrier height (SBH) is beneficial for improving device performance, especially for the contact resistance. Herein, we investigated the electronic structure and interfacial characteristics of the graphene/AlN interface based on density functional theory. The results show that the intrinsic electronic properties of graphene changed slightly after contact. In contrast, the valence band maximum of AlN changed significantly due to the hybridization of Cp and Np orbital electrons. The Bader charge analysis showed that the electrons would transfer from AlN to graphene, implying that graphene would induce acceptor states. Additionally, the Schottky contact nature can be effectively tuned by the external electric field, and it will be tuned from the p-type into n-type once the electric field is larger than about 0.5 V/Å. Furthermore, the optical absorption of graphene/AlN is enhanced after contact. Our findings imply that the SBH is controllable, which is highly desirable in nano-electronic devices.

Extrapolated Defect Transition Level in Two-Dimensional Materials: The Case of Charged Native Point Defects in Monolayer Hexagonal Boron Nitride.

Defect formation energy as well as the charge transition level (CTL) plays a vital role in understanding the underlying mechanism of the effect of defects on material properties. However, the accurate calculation of charged defects, especially for two-dimensional materials, is still a challenging topic. In this paper, we proposed a simplified scheme to rescale the CTLs from the semilocal to the hybrid functional level, which is time-saving during the charged defect calculations. Based on this method, we systematically calculated the formation energy of four kinds of intrinsic point defects in two-dimensional hexagonal boron nitride (2D h-BN) by uniformly scaling the supercells by which we found a time-saving method to obtain the "special vacuum size" (Komsa, H.-P.; Berseneva, N.; Krasheninnikov, A. V.; Nieminen, R. M. Phys. Rev. X, 2014, 4, 031044). Native defects including nitrogen vacancy (VN), boron vacancy (VB), nitrogen atom anti-sited on boron position (NB), and boron atom anti-sited on nitrogen position (BN) were calculated. The reliability of our scheme was verified by taking VN as a probe to conduct the hybrid functional calculation, and the rescaled CTL is within the acceptable error range with the pure HSE results. Based on the results of CTLs, all the native point defects in the h-BN monolayer act as hole or electron trap centers under certain conditions and would suppress the p- or n-type electrical conduction of h-BN-based devices. Our rescale method is also suitable for other materials for defect charge transition level calculations.

Tunable Electronic Properties of Graphene/g-AlN Heterostructure: The Effect of Vacancy and Strain Engineering.

The structural and electronic properties of graphene/graphene-like Aluminum Nitrides monolayer (Gr/g-AlN) heterojunction with and without vacancies are systematically investigated by first-principles calculation. The results prove that Gr/g-AlN with nitrogen-vacancy (Gr/g-AlN-VN) is energy favorable with the smallest sublayer distance and binding energy. Gr/g-AlN-VN is nonmagnetic, like that in the pristine Gr/g-AlN structure, but it is different from the situation of g-AlN-VN, where a magnetic moment of 1 µB is observed. The metallic graphene acts as an electron acceptor in the Gr/g-AlN-VN and donor in Gr/g-AlN and Gr/g-AlN-VAl contacts. Schottky barrier height Φ B , n by traditional (hybrid) functional of Gr/g-AlN, Gr/g-AlN-VAl, and Gr/g-AlN-VN are calculated as 2.35 (3.69), 2.77 (3.23), and 1.10 (0.98) eV, respectively, showing that vacancies can effectively modulate the Schottky barrier height. Additionally, the biaxial strain engineering is conducted to modulate the heterojunction contact properties. The pristine Gr/g-AlN, which is a p-type Schottky contact under strain-free condition, would transform to an n-type contact when 10% compressive strain is applied. Ohmic contact is formed under a larger tensile strain. Furthermore, 7.5% tensile strain would tune the Gr/g-AlN-VN from n-type to p-type contact. These plentiful tunable natures would provide valuable guidance in fabricating nanoelectronics devices based on Gr/g-AlN heterojunctions.