材料科学最新文献

In the quest to enhance Zn-air batteries (ZABs) for operating across a wide spectrum of temperatures, synthesizing robust oxygen electrocatalysts is paramount. Conventional strategies focusing on orbital hybridization of d-d and p-d aim to moderate the excessive interaction between the d-band of the transition metal active site and oxygen intermediate, yet often yield suboptimal performance. Herein, an innovative s-block metal modulation is reported to refine the electronic structure and catalytic behavior of Co─NC catalysts. Employing density functional theory (DFT) calculations, it is revealed that incorporating Mg markedly depresses the d-band center of Co sites, thereby fine-tuning the adsorption energy of the oxygen reduction reaction (ORR) intermediate. Consequently, the Mg-modified Co─NC catalyst (MgCo─NC) unveils remarkable intrinsic ORR activity with a significantly reduced activation energy (Ea) of 10.0 kJ mol^-1, outstripping the performance of both Co─NC (17.6 kJ mol^-1), benchmark Pt/C (15.9 kJ mol^-1), and many recent reports. Moreover, ZABs outfitted with the finely tuned Mg_0.1Co_0.9─NC realize a formidable power density of 157.0 mW cm^-2, paired with an extremely long cycle life of 1700 h, and an exceptionally minimal voltage gap decay rate of 0.006 mV h^-1. Further, the Mg_0.1Co_0.9─NC-based flexible ZAB presents a mere 2% specific capacity degradation when the temperature fluctuates from 25 to -20 °C, underscoring its robustness and suitability for practical deployment in diverse environmental conditions.

In polymer electrolyte fuel cells (PEFCs), the gas diffusion layer (GDL) is crucial for managing the flooding tolerance, which is the ability to remove the water produced during power generation from the assembled cell. However, an improved understanding of the properties of GDLs is required to develop effective waterproofing strategies. This study investigated the influence of the polytetrafluoroethylene (PTFE) content on the pore diameter, porosity, wettability, water saturation, and flooding tolerance of waterproofed carbon papers as cathode GDLs in PEFCs. The addition of minimal PTFE (∼6 wt %) to carbon paper provided external waterproofing, whereas internal waterproofing was achieved at a higher PTFE content (∼13 wt %). However, excessive PTFE (∼37 wt %) led to macropore collapse within the carbon paper, reducing fuel cell performance. Although PTFE addition was expected to improve the flooding tolerance, operando synchrotron X-ray radiography revealed that the water saturation level in carbon paper increased with increasing PTFE content. These findings provide a benchmark for assessing whether GDLs meet the flooding tolerance requirements of PEFCs and may be applicable to waterproofed GDLs in electrochemical devices for water and CO₂ electrolysis.

A high-performance large-scale-integrated organic phototransistor needs a semiconductor layer that maintains its photoelectric conversion ability well during high-resolution pixelization. However, lacking a precise design for the nanoscale structure, a trade-off between photoelectric performance and device miniaturization greatly limits the success in commercial application. Here we demonstrate a photovoltaic-nanocell enhancement strategy, which overcomes the trade-off and enables high-performance organic phototransistors at a level beyond large-scale integration. Embedding a core-shell photovoltaic nanocell based on perovskite quantum dots in a photocrosslinkable organic semiconductor, ultralarge-scale-integrated (>2²¹ units) imaging chips are manufactured using photolithography. 27 million pixels are interconnected and the pixel density is 3.1 × 10⁶ units cm^-2, at least two orders of magnitude higher than in existing organic imaging chips and equivalent to the latest commercial full-frame complementary metal-oxide-semiconductor camera chips. The embedded photovoltaic nanocells induce an in situ photogating modulation and enable photoresponsivity and detectivity of 6.8 × 10⁶ A W^-1 and 1.1 × 10¹³ Jones (at 1 Hz), respectively, achieving the highest values of organic imaging chips at large-scale or higher integration. In addition, a very-large-scale-integrated (>2¹⁶ units) stretchable biomimetic retina based on photovoltaic nanocells is manufactured for neuromorphic imaging recognition with not only resolution but also photoresponsivity and power consumption approaching those of the biological counterpart.

In this study, the synthesis of a MXene (Ti₃C₂T_x)-derived TiO₂/starbon (M-TiO₂/Starbon-800 °C) nanocomposite using a facile calcination method is explored. High-temperature exposure transforms layered Ti₃C₂T_x into rod-like TiO₂ and starbon into amorphous carbon. The resulting M-TiO₂/Starbon-800 °C nanocomposite exhibits a significantly larger surface area and pore volume compared to its individual components, leading to superior electrochemical performance. In a three-electrode configuration, the nanocomposite achieved a specific capacitance (C_sp) of 1352 Fg⁻¹ at 1 Ag⁻¹, while retaining more than 99% of its C_sp after 50 000 charge/discharge cycles. Furthermore, when incorporated into a two-electrode symmetric coin cell, it demonstrates a C_sp of 115 Fg⁻¹ along with exceptional long cycle life. Moreover, the device shows an energy density (ED) of 51 Whkg^-1 and a power density (PD) of 7912 Wkg^-1 at 5 Ag^-1. The enhanced charge storage is attributed to the formation of a porous structure with a high specific surface area resulting from the interaction between M-TiO₂ nanorods and starbon, which facilitates efficient ion penetration.

In this study, a novel synthesis of ultrathin, highly uniform colloidal bismuth sulfohalide (BiSX where X = Cl, Br, I) nanowires (NWs) and NW bundles (NBs) for room-temperature and solution-processed flexible photodetectors are presented. High-aspect-ratio bismuth sulfobromide (BiSBr) NWs are synthesized via a heat-up method using bismuth bromide and elemental S as precursors and 1-dodecanethiol as a solvent. Bundling of the BiSBr NWs occurs upon the addition of 1-octadecene as a co-solvent. The morphologies of the BiSBr NBs are easily tailored from sheaf-like structures to spherulite nanostructures by changing the solvent ratio. The optical bandgaps are modulated from 1.91 (BiSCl) and 1.88 eV (BiSBr) to 1.53 eV (BiSI) by changing the halide compositions. The optical bandgap of the ultrathin BiSBr NWs and NBs exhibits blueshift, whose origin is investigated through density functional theory-based first-principles calculations. Visible-light photodetectors are fabricated using BiSBr NWs and NBs via solution-based deposition followed by solid-state ligand exchanges. High photo-responsivities and external quantum efficiencies (EQE) are obtained for BiSBr NW and NB films even under strain, which offer a unique opportunity for the application of the novel BiSX NWs and NBs in flexible and environmentally friendly optoelectronic devices.

Developing multifunctional, stimuli-responsive nanomedicine is intriguing because it has the potential to effectively treat cancer. Yet, poor tumor penetration of nanodrugs results in limited antitumor efficacy. Herein, an oxygen-driven silicon-based nanomotor (Si-motor) loaded with MnO and CaO₂ nanoparticles is developed, which can move in tumor microenvironment (TME) by the cascade reaction of CaO₂ and MnO. Under acidic TME, CaO₂ reacts with acid to release Ca²⁺ to induce mitochondrial damage and simultaneously produces O₂ and H₂O₂, when the loaded MnO exerts Fenton-like activity to produce ·OH and O₂ based on the produced H₂O₂. The generated O₂ drives Si-motor forward, thus endowing active delivery capability of the formed motors in TME. Meanwhile, MnO with glutathione (GSH) depletion ability further prevents reactive oxygen species (ROS) from being destroyed. Such TME actuated Si-motor with enhanced cellular uptake and deep penetration provides amplification of synergistic oxidative stresscaused by intracellular Ca^2 + overloading, GSH depletion induced by Mn²⁺, and Mn²⁺ mediated chemodynamic treatment (CDT), leading to excellent tumor cell death. The created nanomotor may offer an effective platform for active synergistic cancer treatment.

Covalent organic framework (COF) aerogels with functional groups offer exceptional processability and functionality for various applications. These hierarchical porous materials combine the advantages of COFs with the benefits of aerogels, overcoming the limitations of conventional insoluble and nonfusible COF powders. However, achieving both high crystallinity and shape retention remains a challenge for functionalized COF aerogels. In this work, we develop a novel and general solvent substitution method for the one-step synthesis of formyl-functionalized COF aerogels without harsh vacuum conditions. These aerogels exhibit excellent processing capabilities, superior mechanical strength, and enhanced functionality. As a proof-of-concept, they were used in adsorption and lithium metal battery applications, significantly maximizing the structural advantages of COFs, e.g.: (i) the hierarchical porous structure is fully wetted by the electrolyte to form continuous transport channels; (ii) the polar groups, which are easier to be acquired, help in desolvation and transfer of Li⁺; (iii) the regular pore structures stabilize deposition of Li⁺ and inhibit the growth of lithium dendrites. These combined benefits contribute to a lighter battery with improved energy density and enhanced safety.

Helicobacter pylori (HP), a common microanaerobic bacteria that lives in the human mouth and stomach, is reported to infect ≈50% of the global population. The current diagnostic methods for HP are either invasive, time-consuming, or harmful. Therefore, a noninvasive and label-free HP diagnostic method needs to be developed urgently. Herein, reduced graphene oxide (rGO) is composited with different metal-based materials to construct a graphene-based electronic nose (e-nose), which exhibits excellent sensitivity and cross-reactive response to several gases in exhaled breath (EB). Principal component analysis (PCA) shows that four typical types of gases in EB can be well discriminated. Additionally, the potential of the e-nose in label-free detection of HP infection is demonstrated through the measurement and analysis of EB samples. Furthermore, a prototype of an e-nose device is designed and constructed for automatic EB detection and HP diagnosis. The accuracy of the prototype machine integrated with the graphene-based e-nose can reach 92% and 91% in the training and validation sets, respectively. These results demonstrate that the highly sensitive graphene-based e-nose has great potential for the label-free diagnosis of HP and may become a novel tool for non-invasive disease screening and diagnosis.

It is imperative to develop affordable multi-functional catalysts based on transition metals for various applications, such as dye degradation or the production of green energy. For the first time, we propose a simple chemical bath method to create a SnO₂-BiOBr-rGO heterojunction with remarkable photocatalytic and electrocatalytic activities. After introducing graphene oxide (GO) into the SnO₂-BiOBr nanocomposite, the charge separation, electron mobility, surface area, and electrochemical properties were significantly improved. The X-ray diffraction results show the successful integration of GO into the SnO₂-BiOBr nanocomposite. Systematic material characterization by scanning and transmission electron microscopy showed that the photocatalysts are composed of uniformly distributed SnO₂ nanoparticles (∼11 nm) on the regular nanosheets of BiOBr (∼94 nm) and rGO. The SnO₂-BiOBr-rGO photocatalyst has outstanding photocatalytic activity when it comes to reducing a variety of organic dyes like rhodamine B (RhB) and methylene blue (MB). Within 90 minutes of visible light illumination, degradation of a maximum of 99% for MB and 99.8% for RhB was noted. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance was also tested for the ternary nanocomposite, and significantly lower overpotential values of 0.34 and -0.11 V (vs. RHE) at 10 mA cm^-2 were observed for the OER and HER, respectively. Furthermore, the Tafel slope values are 34 and 39 mV dec^-1 for the OER and HER, respectively. The catalytic degradation of dyes with visible light and efficient OER and HER performance offer this work a broad spectrum of potential applications.