Neural network kinetics for exploring diffusion multiplicity and chemical ordering in compositionally complex materials.

Diffusion involving atom transport from one location to another governs many important processes and behaviors such as precipitation and phase nucleation. The inherent chemical complexity in compositionally complex materials poses challenges for modeling atomic diffusion and the resulting formation of chemically ordered structures. Here, we introduce a neural network kinetics (NNK) scheme that predicts and simulates diffusion-induced chemical and structural evolution in complex concentrated chemical environments. The framework is grounded on efficient on-lattice structure and chemistry representation combined with artificial neural networks, enabling precise prediction of all path-dependent migration barriers and individual atom jumps. To demonstrate the method, we study the temperature-dependent local chemical ordering in a refractory NbMoTa alloy and reveal a critical temperature at which the B2 order reaches a maximum. The atomic jump randomness map exhibits the highest diffusion heterogeneity (multiplicity) in the vicinity of this characteristic temperature, which is closely related to chemical ordering and B2 structure formation. The scalable NNK framework provides a promising new avenue to exploring diffusion-related properties in the vast compositional space within which extraordinary properties are hidden.

Exceptional electronic transport and quantum oscillations in thin bismuth crystals grown inside van der Waals materials.

Confining materials to two-dimensional forms changes the behaviour of the electrons and enables the creation of new devices. However, most materials are challenging to produce as uniform, thin crystals. Here we present a synthesis approach where thin crystals are grown in a nanoscale mould defined by atomically flat van der Waals (vdW) materials. By heating and compressing bismuth in a vdW mould made of hexagonal boron nitride, we grow ultraflat bismuth crystals less than 10 nm thick. Due to quantum confinement, the bismuth bulk states are gapped, isolating intrinsic Rashba surface states for transport studies. The vdW-moulded bismuth shows exceptional electronic transport, enabling the observation of Shubnikov-de Haas quantum oscillations originating from the (111) surface state Landau levels. By measuring the gate-dependent magnetoresistance, we observe multi-carrier quantum oscillations and Landau level splitting, with features originating from both the top and bottom surfaces. Our vdW mould growth technique establishes a platform for electronic studies and control of bismuth's Rashba surface states and topological boundary modes1-3. Beyond bismuth, the vdW-moulding approach provides a low-cost way to synthesize ultrathin crystals and directly integrate them into a vdW heterostructure.

Synergizing Fe2O3 Nanoparticles on Single Atom Fe-N-C for Nitrate Reduction to Ammonia at Industrial Current Densities.

The electrochemical reduction of nitrates (NO3 -) enables a pathway for the carbon neutral synthesis of ammonia (NH3), via the nitrate reduction reaction (NO3RR), which has been demonstrated at high selectivity. However, to make NH3 synthesis cost-competitive with current technologies, high NH3 partial current densities (jNH3) must be achieved to reduce the levelized cost of NH3. Here, the high NO3RR activity of Fe-based materials is leveraged to synthesize a novel active particle-active support system with Fe2O3 nanoparticles supported on atomically dispersed Fe-N-C. The optimized 3×Fe2O3/Fe-N-C catalyst demonstrates an ultrahigh NO3RR activity, reaching a maximum jNH3 of 1.95 A cm-2 at a Faradaic efficiency (FE) for NH3 of 100% and an NH3 yield rate over 9 mmol hr-1 cm-2. Operando XANES and post-mortem XPS reveal the importance of a pre-reduction activation step, reducing the surface Fe2O3 (Fe3+) to highly active Fe0 sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe2O3 particles and Fe-Nx sites at highly cathodic potentials, maintaining a current of -1.3 A cm-2 over 24 hours. This work exhibits an effective and durable active particle-active support system enhancing the performance of the NO3RR, enabling industrially relevant current densities and near 100% selectivity.

Cu Promoted the Dynamic Evolution of Ni-Based Catalysts for Polyethylene Terephthalate Plastic Upcycling.

Upcycling plastic wastes into value-added chemicals is a promising approach to put end-of-life plastic wastes back into their ecocycle. As one of the polyesters that is used daily, polyethylene terephthalate (PET) plastic waste is employed here as the model substrate. Herein, a nickel (Ni)-based catalyst was prepared via electrochemically depositing copper (Cu) species on Ni foam (NiCu/NF). The NiCu/NF formed Cu/CuO and Ni/NiO/Ni(OH)2 core-shell structures before electrolysis and reconstructed into NiOOH and CuOOH/Cu(OH)2 active species during the ethylene glycol (EG) oxidation. After oxidation, the Cu and Ni species evolved into more reduced species. An indirect mechanism was identified as the main EG oxidation (EGOR) mechanism. In EGOR, NiCu60s/NF catalyst exhibited an optimal Faradaic efficiency (FE, 95.8%) and yield rate (0.70 mmol cm-2 h-1) for formate production. Also, over 80% FE of formate was achieved when a commercial PET plastic powder hydrolysate was applied. Furthermore, commercial PET plastic water bottle waste was employed as a substrate for electrocatalytic upcycling, and pure terephthalic acid (TPA) was recovered only after 1 h electrolysis. Lastly, density functional theory (DFT) calculation revealed that the key role of Cu was significantly reducing the Gibbs free-energy barrier (ΔG) of EGOR's rate-determining step (RDS), promoting catalysts' dynamic evolution, and facilitating the C-C bond cleavage.

Wemics: A Single-Base Resolution Methylation Quantification Method for Enhanced Prediction of Epigenetic Regulation.

DNA methylation, an epigenetic mechanism that alters gene expression without changing DNA sequence, is essential for organism development and key biological processes like genomic imprinting and X-chromosome inactivation. Despite tremendous efforts in DNA methylation research, accurate quantification of cytosine methylation remains a challenge. Here, a single-base methylation quantification approach is introduced by weighting methylation of consecutive CpG sites (Wemics) in genomic regions. Wemics quantification of DNA methylation better predicts its regulatory impact on gene transcription and identifies differentially methylated regions (DMRs) with more biological relevance. Most Wemics-quantified DMRs in lung cancer are epigenetically conserved and recurrently occurred in other primary cancers from The Cancer Genome Atlas (TCGA), and their aberrant alterations can serve as promising pan-cancer diagnostic markers. It is further revealed that these detected DMRs are enriched in transcription factor (TF) binding motifs, and methylation of these TF binding motifs and TF expression synergistically regulate target gene expression. Using Wemics on epigenomic-transcriptomic data from the large lung cancer cohort, a dozen novel genes with oncogenic potential are discovered that are upregulated by hypomethylation but overlooked by other quantification methods. These findings increase the understanding of the epigenetic mechanism by which DNA methylation regulates gene expression.

Virus detection light diffraction fingerprints for biological applications.

The transmission of viral diseases is highly unstable and highly contagious. As the carrier of virus transmission, cell is an important factor to explore the mechanism of virus transmission and disease. However, there is still a lack of effective means to continuously monitor the process of viral infection in cells, and there is no rapid, high-throughput method to assess the status of viral infection. On the basis of the virus light diffraction fingerprint of cells, we applied the gray co-occurrence matrix, set the two parameters effectively to distinguish the virus status and infection time of cells, and visualized the virus infection process of cells in high throughput. We provide an efficient and nondestructive testing method for the selection of excellent livestock and poultry breeds at the cellular level. Meanwhile, our work provides detection methods for the recessive transmission of human-to-human, animal-to-animal, and zoonotic diseases and to inhibit and block their further development.

Dynamic Behavior of Platinum Atoms and Clusters in the Native Oxide Layer of Aluminum Nanocrystals.

Strong metal-support interactions (SMSIs) are well-known in the field of heterogeneous catalysis to induce the encapsulation of platinum (Pt) group metals by oxide supports through high temperature H2 reduction. However, demonstrations of SMSI overlayers have largely been limited to reducible oxides, such as TiO2 and Nb2O5. Here, we show that the amorphous native surface oxide of plasmonic aluminum nanocrystals (AlNCs) exhibits SMSI-induced encapsulation of Pt following reduction in H2 in a Pt structure dependent manner. Reductive treatment in H2 at 300 °C induces the formation of an AlOx SMSI overlayer on Pt clusters, leaving Pt single-atom sites (Ptiso) exposed available for catalysis. The remaining exposed Ptiso species possess a more uniform local coordination environment than has been observed on other forms of Al2O3, suggesting that the AlOx native oxide of AlNCs presents well-defined anchoring sites for individual Pt atoms. This observation extends our understanding of SMSIs by providing evidence that H2-induced encapsulation can occur for a wider variety of materials and should stimulate expanded studies of this effect to include nonreducible oxides with oxygen defects and the presence of disorder. It also suggests that the single-atom sites created in this manner, when combined with the plasmonic properties of the Al nanocrystal core, may allow for site-specific single-atom plasmonic photocatalysis, providing dynamic control over the light-driven reactivity in these systems.

Distribution of Pt single atom coordination environments on anatase TiO2 supports controls reactivity.

Single-atom catalysts (SACs) offer efficient metal utilization and distinct reactivity compared to supported metal nanoparticles. Structure-function relationships for SACs often assume that active sites have uniform coordination environments at particular binding sites on support surfaces. Here, we investigate the distribution of coordination environments of Pt SAs dispersed on shape-controlled anatase TiO2 supports specifically exposing (001) and (101) surfaces. Pt SAs on (101) are found on the surface, consistent with existing structural models, whereas those on (001) are beneath the surface after calcination. Pt SAs under (001) surfaces exhibit lower reactivity for CO oxidation than those on (101) surfaces due to their limited accessibility to gas phase species. Pt SAs deposited on commercial-TiO2 are found both at the surface and in the bulk, posing challenges to structure-function relationship development. This study highlights heterogeneity in SA coordination environments on oxide supports, emphasizing a previously overlooked consideration in the design of SACs.

Effect of Phosphorus Modulation in Iron Single-Atom Catalysts for Peroxidase Mimicking.

Fe-N-C single-atom catalysts (SACs) exhibit excellent peroxidase (POD)-like catalytic activity, owing to their well-defined isolated iron active sites on the carbon substrate, which effectively mimic the structure of natural peroxidase's active center. To further meet the requirements of diverse biosensing applications, SAC POD-like activity still needs to be continuously enhanced. Herein, a phosphorus (P) heteroatom is introduced to boost the POD-like activity of Fe-N-C SACs. A 1D carbon nanowire (FeNCP/NW) catalyst with enriched Fe-N4 active sites is designed and synthesized, and P atoms are doped in the carbon matrix to affect the Fe center through long-range interaction. The experimental results show that the P-doping process can boost the POD-like activity more than the non-P-doped one, with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can greatly enhance POD-like activity initially, but its effect becomes insignificant with increasing amount of P. As a proof of concept, FeNCP/NW is employed in an enzyme cascade platform for highly sensitive colorimetric detection of the neurotransmitter acetylcholine.

NiFe Nanoparticle Nest Supported on Graphene as Electrocatalyst for Highly Efficient Oxygen Evolution Reaction.

Designing cost-efffective electrocatalysts for the oxygen evolution reaction (OER) holds significant importance in the progression of clean energy generation and efficient energy storage technologies, such as water splitting and rechargeable metal-air batteries. In this work, an OER electrocatalyst is developed using Ni and Fe precursors in combination with different proportions of graphene oxide. The catalyst synthesis involved a rapid reduction process, facilitated by adding sodium borohydride, which successfully formed NiFe nanoparticle nests on graphene support (NiFe NNG). The incorporation of graphene support enhances the catalytic activity, electron transferability, and electrical conductivity of the NiFe-based catalyst. The NiFe NNG catalyst exhibits outstanding performance, characterized by a low overpotential of 292.3 mV and a Tafel slope of 48 mV dec-1, achieved at a current density of 10 mA cm- 2. Moreover, the catalyst exhibits remarkable stability over extended durations. The OER performance of NiFe NNG is on par with that of commercial IrO2 in alkaline media. Such superb OER catalytic performance can be attributed to the synergistic effect between the NiFe nanoparticle nests and graphene, which arises from their large surface area and outstanding intrinsic catalytic activity. The excellent electrochemical properties of NiFe NNG hold great promise for further applications in energy storage and conversion devices.

Concentration-Dependent Photocatalytic Upcycling of Poly(ethylene terephthalate) Plastic Waste.

Photocatalytic plastic waste upcycling into value-added feedstock is a promising way to mitigate the environmental issues caused by the nondegradable nature of plastic waste. Here, we developed a MoS2/g-C3N4 photocatalyst that can efficiently upcycle poly(ethylene terephthalate) (PET) into valuable organic chemicals. Interestingly, the conversion mechanism is concentration-dependent. For instance, at a low ethylene glycol (EG) concentration (7.96 mM), acetate is the main product. Unexpectedly, the conversion of PET water bottle hydrolysate with only 7.96 mM ethylene glycol (EG) can produce a 4 times higher amount of acetate (704.59 nmol) than the conversion of 300 mM EG (174.50 nmol), while at a higher EG concentration (300 mM), formate is the dominant product. Herein, a 40 times higher EG concentration (300 mM compared to 7.96 mM) would produce only ∼3 times more formate (179 nmol compared to 51.86 nmol). In addition, under natural sunlight conditions, comparable amounts of liquid and gaseous products are produced when commercial PET plastics are employed. Overall, the photocatalytic PET conversion process is quite efficient under a low concentration of EG in PET hydrolysate, indicating the enormous potential of this photocatalysis strategy for real plastics upcycling.

Deep-Learning Terahertz Single-Cell Metabolic Viability Study.

Cell viability assessment is critical, yet existing assessments are not accurate enough. We report a cell viability evaluation method based on the metabolic ability of a single cell. Without culture medium, we measured the absorption of cells to terahertz laser beams, which could target a single cell. The cell viability was assessed with a convolution neural classification network based on cell morphology. We established a cell viability assessment model based on the THz-AS (terahertz-absorption spectrum) results as y = a = (x - b)c, where x is the terahertz absorbance and y is the cell viability, and a, b, and c are the fitting parameters of the model. Under water stress the changes in terahertz absorbance of cells corresponded one-to-one with the apoptosis process, and we propose a cell 0 viability definition as terahertz absorbance remains unchanged based on the cell metabolic mechanism. Compared with typical methods, our method is accurate, label-free, contact-free, and almost interference-free and could help visualize the cell apoptosis process for broad applications including drug screening.

How Pt Influences H2 Reactions on High Surface-Area Pt/CeO2 Powder Catalyst Surfaces.

The addition of platinum-group metals (PGMs, e.g., Pt) to CeO2 is used in heterogeneous catalysis to promote the rate of redox surface reactions. Well-defined model system studies have shown that PGMs facilitate H2 dissociation, H-spillover onto CeO2 surfaces, and CeO2 surface reduction. However, it remains unclear how the heterogeneous structures and interfaces that exist on powder catalysts influence the mechanistic picture of PGM-promoted H2 reactions on CeO2 surfaces developed from model system studies. Here, controlled catalyst synthesis, temperature-programmed reduction (TPR), in situ infrared spectroscopy (IR), and in situ electron energy loss spectroscopy (EELS) were used to interrogate the mechanisms of how Pt nanoclusters and single atoms influence H2 reactions on high-surface area Pt/CeO2 powder catalysts. TPR showed that Pt promotes H2 consumption rates on Pt/CeO2 even when Pt exists on a small fraction of CeO2 particles, suggesting that H-spillover proceeds far from Pt-CeO2 interfaces and across CeO2-CeO2 particle interfaces. IR and EELS measurements provided evidence that Pt changes the mechanism of H2 activation and the rate limiting step for Ce3+, oxygen vacancy, and water formation as compared to pure CeO2. As a result, higher-saturation surface hydroxyl coverages can be achieved on Pt/CeO2 compared to pure CeO2. Further, Ce3+ formed by spillover-H from Pt is heterogeneously distributed and localized at and around interparticle CeO2-CeO2 boundaries, while activated H2 on pure CeO2 results in homogeneously distributed Ce3+. Ce3+ localization at and around CeO2-CeO2 boundaries for Pt/CeO2 is accompanied by surface reconstruction that enables faster rates of H2 consumption. This study reconciles the materials gap between model structures and powder catalysts for H2 reactions with Pt/CeO2 and highlights how the spatial heterogeneity of powder catalysts dictates the influence of Pt on H2 reactions at CeO2 surfaces.