ACS Applied Nano Materials最新文献

Designing clean, stable, and efficient electrocatalysts is the key to achieving overall water splitting. The introduction of active metals or metal nanoparticles into metal–organic frameworks (MOFs) is a research strategy. In this work, silver nanoparticles (Ag NPs) loaded on NiFe-MOF can increase the surface area, active sites, and conductivity of the catalyst. Therefore, the electrocatalytic performances of Ag/NiFe-MOF exhibit higher activity for HER and OER in an alkaline medium, and the overpotential is also significantly lower than that when NiFe-MOF is used alone. When the current density is 10 mA cm^–2, the overpotential of the optimized Ag/NiFe-MOF-30 catalyst is 138 mV for HER and 173 mV for OER. In addition, when Ag/NiFe-MOF-30 is used as a bifunctional electrocatalyst, the overall water splitting can be achieved with 1.61 V at 10 mA cm^–2, and it demonstrates excellent stability of over 100 h at 100 mA cm^–2. This work provides an efficient approach for developing highly active MOF-based catalysts by loading coin metal nanoparticles for overall water splitting.

Perovskite CsPbBr₃/Rb₄PbBr₆ yolk–shell structure was synthesized by using the hot injection method. X-ray diffraction confirms that the crystal structure of CsPbBr₃ NCs remains unaffected after being encapsulated with Rb₄PbBr₆ coating. The photoluminescence (PL) intensity of the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure is 1.5 times greater than that of CsPbBr₃ NCs. The PL lifetime of the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure increases by 2 orders of magnitude compared to that of CsPbBr₃ NCs. This indicates that the surface defects of CsPbBr₃ NCs have been successfully passivated by Rb₄PbBr₆ coating, thereby suppressing nonradiative recombination. Importantly, the water stability and thermal stability of the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure have been significantly enhanced. Subsequently, the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure was dispersed in methyl methacrylate to prepare CsPbBr₃/Rb₄PbBr₆/PMMA organic glasses (OGs). The air stability of the CsPbBr₃/Rb₄PbBr₆/PMMA OGs has been improved. The temperature-dependent PL spectra of CsPbBr₃ NCs and the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure were studied. The high PL intensity and long lifetime of the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure are attributed to the enhanced electron–hole interactions. Additionally, green light-emitting diodes fabricated with the CsPbBr₃/Rb₄PbBr₆ yolk–shell structure and CsPbBr₃/Rb₄PbBr₆/PMMA OGs have stable light conversion and maintain high color output quality. This research offers an effective method for the fabrication of perovskite-based optoelectronic devices.

The development of highly sensitive and ultralow-power NO₂ sensors is crucial for real-time NO₂ monitoring. This study synthesizes tiny SnO₂ nanoparticles with enriched oxygen vacancies for use in microelectromechanical system (MEMS) gas sensors, enabling ppb-level NO₂ detection at reduced operating temperatures. PVP was used to adjust the particle size and surface oxygen vacancies in the hydrothermal method. The gas sensing performance shows that the 0.75 g PVP-SnO₂ exhibited the highest response of 14.7 to 500 ppb NO₂ at a low operating temperature of 102 °C, which is 3.2 times higher than that of the 0.00 g PVP-SnO₂ sensor under the same conditions. Compared to similar studies, this sensor achieved a high response value and ultralow power consumption of 8.4 mW. The improvement in performance is mainly attributed to N doping and the abundance of oxygen vacancies. This research presents a promising strategy for the development of high-performance, low-energy, real-time NO₂ gas sensors.

Designing a structurally unique and highly active transition metal-based bifunctional electrocatalyst for alkaline water splitting remains challenging. Herein, a bifunctional electrocatalyst consisting of Co/VN nano-heterojunction anchored on nitrogen-doped carbon (NC) with three-dimensional porous carbon structures was successfully synthesized. Vanadium nitride (VN) can act as an intermediate “bridge” for electron transfer, receiving or supplying electrons; optimizing the charge transfer path on the surface of Co-NC materials; enhancing the electronic synergy between Co, VN, and NC; making the catalytic sites on NC more active; and achieving faster hydrogen evolution reaction (HER) kinetics. The conversion of the active site Co to cobalt oxides and hydroxides in the oxygen evolution reaction (OER) process has also been rapidly optimized under the action of the “sacrificial promoter” VN, providing more prosperous active sites at the heterojunction as VN dissolves. In an alkaline solution, the optimized Co/VN/NC-8 catalyst only requires 116 and 311 mV to provide a current density of 10 mA/cm² for HER and OER, respectively. Moreover, a low battery voltage of 1.74 V is required for overall water splitting to reach the current density of 10 mA/cm². This work provides a strong basis for interface engineering to regulate transition metals supported by carbon materials.

The types of nitrogen atoms in single-atom nanozymes are of paramount importance to their enzyme-like catalytic activity. Herein, we report that single-atom iron nanozymes anchored on graphitic nitrogen-doped porous carbon (g-FeN₄) could serve as efficient oxidase mimics. The g-FeN₄ was found to display 1.6 times higher catalytic activity than pyridinic nitrogen-dominated single-atom iron nanozymes (FeN₄). Combined with experiments and theoretical simulations, it is shown that graphitic nitrogen could effectively regulate the charge distribution at the Fe active site, thereby accelerating O₂ activation and thus enhancing its oxidase-like activity. As a concept verification application, we constructed an ultrasensitive alkaline phosphatase activity assay method, integrating a smartphone as a colorimetric reader, based on the superior oxidase activity of g-FeN₄. This study not only unravels the significant effect of nitrogen types on the activity of single-atom nanozymes but also provides important guidance for designing highly efficient single-atom nanozymes.

Nanozymes exploit the acidic pH and abundant biomarkers in the tumor microenvironment (TME) to selectively target tumors and enhance chemodynamic therapy (CDT) via a cascade of enzymatic reactions that generate cytotoxic free radicals, thereby improving the therapeutic efficacy. In this study, we engineered a MOF-supported gold nanozyme (Au@ABI-ZIF-8). By depleting the abundant glutathione (GSH) in TME, the resulting Au@ABI-ZIF-8_G exhibited outstanding superoxide dismutase-like and glucose oxidase-like activities, capable of continuously converting endogenous superoxide anion (^•O₂^–) and oxygen into H₂O₂. Meanwhile, in the acidic TME, the peroxide-like activity of Au@ABI-ZIF-8_G converted H₂O₂ into more toxic ^•OH, demonstrating a stronger killing effect on cancer cells, as comprehensively validated using HeLa and SiHA cell lines. Therefore, the cascade enzymatic reaction of Au@ABI-ZIF-8 depleted GSH and glucose, achieved more toxic ^•OH, amplified oxidative stress in the TME, and ultimately improved the CDT efficacy against cancer cells. This approach could potentially be extended to design other MOF-supported AuNCs with coligands and multienzymes, offering a promising direction for the development of novel nanozymes and expanding their applications in the field of nanobiomedicine.

Chameleons rapidly and intricately alter their color in response to environmental changes through the interaction of light with their two-layer structural skin. Inspired by chameleons, we propose a strategy to address the limitations of conventional infrared (IR) stealth materials, which often struggle to conceal objects in fluctuating ambient temperatures or thermally inhomogeneous backgrounds. Herein, we present a dynamically tunable IR camouflage (DTIC) device that combines a vanadium dioxide (VO₂) IR digital camouflage layer with an indium tin oxide (ITO) temperature-regulating layer. The upper laser-patterned VO₂ layer generates inhomogeneous IR speckle patterns and transitions from an initial emissivity of 0.83 to final values of 0.48, 0.38, and 0.28 through the metal–insulator transition (MIT) of VO₂, controlled by the lower ITO layer. Alternatively, the device can sustain a uniform IR appearance when the MIT is inactive, accompanied by temperature regulation. By adapting its IR appearances to backgrounds, the DTIC device ensures a minimal radiant temperature difference of 0.8–2.2 °C between the simulated target and its surroundings over 24-h cycles across typical environments, including grassland, road, and sand. The DTIC device significantly outperforms conventional low-emissivity materials, static solutions, and individual phase-change materials, offering a versatile and effective approach to real-world IR camouflage.

Gold nanoclusters (AuNCs) with surface ligand modifications have been developed as antibacterial agents. While understanding the mechanisms and efficacy of bacterial killing is crucial for determining the clinical applications of AuNCs, the effects of different surface charges on their antibacterial mechanisms are still not well understood. Herein, the AuNCs were synthesized with a negatively charged ligand, 6-mercaptohexanoic acid (AuNCs-MHA), and with a positively charged ligand, 4,6-diamino-2-mercaptopyrimidine (AuNCs-DAMP), via a simple one-pot method. The successful preparations of both AuNCs were confirmed by their optical and structural characterizations. Antibacterial activities of the positive and negative surface charges of AuNCs against Gram-negative bacterium Escherichia coli and Gram-positive bacterium Staphylococcus aureus were observed by analyzing bacterial growth curves and reactive oxygen species (ROS) generation. The bacterial growth curves revealed that the antibacterial activity of AuNCs increased in direct proportion to their weight concentration, and the generation of ROS confirmed this finding. In agar plate assays, the antibacterial activity of positively charged AuNCs-DAMP was more potent than that of negatively charged AuNCs-MHA. Based on the Scanning Electron Microscopy (SEM) observation, the positively charged AuNCs-DAMP had a better antibacterial effect compared to the negative surface charge of AuNCs-MHA, showing that the clusters had electrostatic interactions and van der Waals forces between the negatively charged bacterial membrane and cationic AuNCs.

N-aryl amides are essential in pharmaceuticals and fine chemicals, with one-pot reductive amidation of nitroarenes providing a straightforward synthesis approach. To enhance the catalyst stability under reducing conditions, four single-Pd-site catalysts with N, O, P, and I heteroatoms were developed. Among them, the Pd₁/NC catalyst achieved excellent ∼100% conversion of nitrobenzene, 90% selectivity for acetanilide, and a turnover frequency (TOF) of 681 h^–1, with no obvious decay after six cycles in an autoclave reactor and over 220 h in a fixed-bed durability test. Various substrates further showed the universality for the reductive amidation of nitroaromatics on robust single-Pd-site catalysts. The Pd–N coordination facilitated H₂ activation and stabilized the single Pd^δ+ ions. In situ DRIFTS and control experiments confirmed a mechanism involving PhNO and PhNH₂ intermediates. This work provides valuable insights into the design of highly stable single-Pd-site catalysts for reductive amidation.

Ammonia (NH₃) production by the Haber-Bosch method is one of the foremost commercial technologies; however, it suffers serious problems, such as high energy consumption and emission of greenhouse gas. Electrocatalytic nitrate reduction to NH₃ (NO₃RR) provides a more prospective pathway for NH₃ production in terms of environmental problems and energy conversion. In this work, a nanobiohybrid composed by ionic liquid-modified chloroperoxidase (CPO-IL_EMB) immobilized on bimetallic Pd₂Ag nanodendrites (Pd₂Ag-BNs) was proposed for NO₃RR through a novel electroenzyme cascade catalytic reaction. The electrocatalytic reduction of nitrate (NO₃^–) to nitrite (NO₂^–) was achieved using Pd₂Ag-BNs, followed by CPO-IL_EMB’s enzymatic transformation of NO₂^– to NH₃. Herein, Pd₂Ag-BNs not only promoted the electrocatalytic conversion of NO₃^– to NO₂^– but also immobilized CPO-IL_EMB via electrostatic interaction. In an electroenzymatic cascade catalysis system, Pd₂Ag-BNs boosted the reduction efficiency of NO₃^– to NO₂^–, and CPO-IL_EMB subsequently transformed NO₂^– to NH₃. This electroenzymatic cascade catalysis system could achieve a high Faraday efficiency of 97.1% and a high NH₄⁺ yield of 109.91 mg·h^–1·mg_cat^–1 for NO₃RR in a neutral solution.