Nano Materials Science最新文献

Surface-enhanced Raman Spectroscopy (SERS) is a nondestructive technique for rapid detection of analytes even at the single-molecule level. However, highly sensitive and reliable SERS substrates are mostly fabricated with complex nanofabrication techniques, greatly restricting their practical applications. A convenient electrochemical method for transforming the surface of commercial gold wires/foils into silver-alloyed nanostructures is demonstrated in this report. Au substrates are treated with repetitive anodic and cathodic bias in an electrolyte of thiourea, in a one-pot one-step manner. X-rays absorption fine structure (XAFS) spectroscopy confirms that the AuAg alloy is induced at the surface. The unique AuAg alloyed surface nanostructures are particularly advantageous when served as SERS substrates, enabling a remarkably sensitive detection of Rhodamine B (a detection limit of 10⁻¹⁴ ​M, and uniform strong response throughout the substrates at 10⁻¹² ​M).

The hydrothermal synthesis of In₂O₃ and CeO₂–In₂O₃ is investigated as well as the properties of sensor layers based on these compounds. During the synthesis of In₂O₃, intermediate products In(OH)₃ and InOOH are formed, which are the precursors of stable cubic (c-In₂O₃) and metastable rhombohedral (rh-In₂O₃) phases, respectively. A transition from c-In₂O₃ to rh-In₂O₃ is observed with the addition of CeO₂. The introduction of cerium into rh-In₂O₃ results in a decrease in the sensor response to hydrogen, while it increases in composites based on c-In₂O₃. The data on the sensor activity of the composites correlate with XPS results in which CeO₂ causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In₂O₃. The reverse situation is observed in composites based on c-In₂O₃. Compared to In₂O₃ and CeO₂–In₂O₃ obtained by other methods, the synthesized composites demonstrate maximum response to H₂ at low temperatures by 70–100 ​°C, and have short response time (0.2–0.5 ​s), short recovery time (6–7 ​s), and long-term stability. A model is proposed for the dependence of sensitivity on the direction of electron transfer between In₂O₃ and CeO₂.

Electrochemical water splitting has long been considered an effective energy conversion technology for transferring intermittent renewable electricity into hydrogen fuel, and the exploration of cost-effective and high-performance electrocatalysts is crucial in making electrolyzed water technology commercially viable. Cobalt phosphide (Co-P) has emerged as a catalyst of high potential owing to its high catalytic activity and durability in water splitting. This paper systematically reviews the latest advances in the development of Co-P-based materials for use in water splitting. The essential effects of P in enhancing the catalytic performance of the hydrogen evolution reaction and oxygen evolution reaction are first outlined. Then, versatile synthesis techniques for Co-P electrocatalysts are summarized, followed by advanced strategies to enhance the electrocatalytic performance of Co-P materials, including heteroatom doping, composite construction, integration with well-conductive substrates, and structure control from the viewpoint of experiment. Along with these optimization strategies, the understanding of the inherent mechanism of enhanced catalytic performance is also discussed. Finally, some existing challenges in the development of highly active and stable Co-P-based materials are clarified, and prospective directions for prompting the wide commercialization of water electrolysis technology are proposed.

Photocatalytic CO₂ reduction to produce high value-added carbon-based fuel has been proposed as a promising approach to mitigate global warming issues. However, the conversion efficiency and product selectivity are still low due to the sluggish dynamics of transfer processes involved in proton-assisted multi-electron reactions. Lowering the formation energy barriers of intermediate products is an effective method to enhance the selectivity and productivity of final products. In this study, we aim to regulate the surface electronic structure of Bi₂WO₆ by doping surface chlorine atoms to achieve effective photocatalytic CO₂ reduction. Surface Cl atoms can enhance the absorption ability of light, affect its energy band structure and promote charge separation. Combined with DFT calculations, it is revealed that surface Cl atoms can not only change the surface charge distribution which affects the competitive adsorption of H₂O and CO₂, but also lower the formation energy barrier of intermediate products to generate more intermediate ∗COOH, thus facilitating CO production. Overall, this study demonstrates a promising surface halogenation strategy to enhance the photocatalytic CO₂ reduction activity of a layered structure Bi-based catalyst.

High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and ferromagnetic cobalt ferrite (CoFe₂O₄) (0.00 ​wt% to 0.2 ​wt%) are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling. The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments. For pure PVDF-HFP films, when the maximum electric field E_max is 120 ​MV/m, the calibrated open circuit voltage reaches 2.93 ​V, which is much higher than those poled at lower electric fields (70 ​MV/m: 1.41 ​V; 90 ​MV/m: 2.11 ​V). Furthermore, the addition of CoFe₂O₄ also influences the piezoelectricity dramatically. In the samples containing 0.15 ​wt% CoFe₂O₄, the calibrated open circuit voltage increases to the maximum value of 3.57 ​V. Meanwhile, the relative fraction of the β-phase and the crystallinity degree are 99% and 48%, respectively. The effects of CoFe₂O₄ nanoparticles on initial crystallization, uniaxial stretching and high electric field poling are investigated by XRD, FTIR and DSC.

Energy storage and conservation are receiving increased attention due to rising global energy demands. Therefore, the development of energy storage materials is crucial. Thermal energy storage (TES) systems based on phase change materials (PCMs) have increased in prominence over the past two decades, not only because of their outstanding heat storage capacities but also their superior thermal energy regulation capability. However, issues such as leakage and low thermal conductivity limit their applicability in a variety of settings. Carbon-based materials such as graphene and its derivatives can be utilized to surmount these obstacles. This study examines the recent advancements in graphene-based phase change composites (PCCs), where graphene-based nanostructures such as graphene, graphene oxide (GO), functionalized graphene/GO, and graphene aerogel (GA) are incorporated into PCMs to substantially enhance their shape stability and thermal conductivity that could be translated to better storage capacity, durability, and temperature response, thus boosting their attractiveness for TES systems. In addition, the applications of these graphene-based PCCs in various TES disciplines, such as energy conservation in buildings, solar utilization, and battery thermal management, are discussed and summarized.

Since the catalytic activity of most nanozymes is still far lower than the corresponding natural enzymes, there is urgent need to discover novel highly efficient enzyme-like materials. In this work, Co₃V₂O₈ with hollow hexagonal prismatic pencil structures were prepared as novel artificial enzyme mimics. They were then decorated by photo-depositing Ag nanoparticles (Ag NPs) on the surface to further improve its catalytic activities. The Ag NPs decorated Co₃V₂O₈ (ACVPs) showed both excellent oxidase- and peroxidase-like catalytic activities. They can oxidize the colorless 3,3’,5,5’-tetramethylbenzidine rapidly to induce a blue change. The enhanced enzyme mimetic activities can be attributed to the surface plasma resonance (SPR) effect of Ag NPs as well as the synergistic catalytic effect between Ag NPs and Co₃V₂O₈, accelerating electron transfer and promoting the catalytic process. ACVPs were applied in constructing a colorimetric sensor, validating the occurrence of the Fenton reaction, and disinfection, presenting favorable catalytic performance. The enzyme-like catalytic mechanism was studied, indicating the chief role of ⋅O₂^- radicals in the catalytic process. This work not only discovers a novel functional material with double enzyme mimetic activity but also provides a new insight into exploiting artificial enzyme mimics with highly efficient catalytic ability.