Hydrothermal synthesis of PdAu nanocatalysts with variable atom ratio for methanol oxidation

Bimetallic nanoparticles as pioneering eco-friendly catalysts for remediation of pharmaceuticals and personal care products (PPCPs)

The persistent presence of Pharmaceuticals and Personal Care Products (PPCPs) in aquatic environments poses a significant risk to both human health and ecosystems, with conventional water treatment methods often unable to effectively remove these contaminants. Recent research has identified bimetallic nanoparticles as a promising and eco-friendly solution for PPCP remediation, owing to their enhanced catalytic properties and the synergistic effects between the metals. This review critically examines the synthesis, characterization, and application of bimetallic nanoparticles for the degradation of PPCPs in water. Key synthetic approaches, particularly green synthesis methods, are explored, emphasizing their ability to control nanoparticle morphology, size, and composition. We highlight the novel catalytic mechanisms employed by bimetallic nanoparticles, including electron transfer, surface reactions, and adsorption processes, which contribute to efficient PPCP removal. Furthermore, the influence of critical factors such as nanoparticle size, composition, and surface functionalization on catalytic efficiency is analyzed. Key findings include the superior performance of bimetallic nanoparticles over monometallic counterparts, with specific emphasis on their ability to degrade a wide range of PPCPs under mild conditions. However, challenges such as scalability, stability, and environmental impact remain. This review also provides insights into the future directions for bimetallic nanoparticle development, stressing the importance of interdisciplinary research and collaborative efforts to optimize their design for large-scale, sustainable water treatment applications. Overall, this work offers a comprehensive understanding of how bimetallic nanoparticles can be optimized for sustainable water treatment solutions, highlighting their potential to mitigate the adverse effects of PPCPs on both ecosystems and public health.

Engineered Nanomaterials in Soil: Their Impact on Soil Microbiome and Plant Health

A staggering number of nanomaterials-based products are being engineered and produced commercially. Many of these engineered nanomaterials (ENMs) are finally disposed into the soil through various routes in enormous quantities. Nanomaterials are also being specially tailored for their use in agriculture as nano-fertilizers, nano-pesticides, and nano-based biosensors, which is leading to their accumulation in the soil. The presence of ENMs considerably affects the soil microbiome, including the abundance and diversity of microbes. In addition, they also influence crucial microbial processes, such as nitrogen fixation, mineralization, and plant growth promoting activities. ENMs conduct in soil is typically dependent on various properties of ENMs and soil. Among nanoparticles, silver and zinc oxide have been extensively prepared and studied owing to their excellent industrial properties and well-known antimicrobial activities. Therefore, at this stage, it is imperative to understand how these ENMs influence the soil microbiome and related processes. These investigations will provide necessary information to regulate the applications of ENMs for sustainable agriculture and may help in increasing agrarian production. Therefore, this review discusses several such issues.

Modification of boron-doped diamond electrodes with gold-palladium nanoparticles for an oxygen sensor

Modification of boron-doped diamond (BDD) with gold-palladium nanoparticles (Au@PdNPs) was successfully performed. Prior to the modification, BDD was modified with allylamine to provide active sites for the attachment of nanoparticles, while the synthesis of Au@PdNPs was performed by chemical reduction of a palladium salt solution in a colloidal solution of gold nanoparticles. Characterization using TEM images showed that by controlling the palladium concentration, flower and core-shell shaped Au@PdNPs can be prepared. XPS studies confirmed that the nanoparticles with a flower shape could be attached better on the BDD surface. The Au@PdNPs-modified BDD (Au@PdNPs-BDD) electrodes were then examined for the oxygen reduction reaction in comparison with gold and palladium-based electrodes. One order higher current response was observed at Au@PdNPs-BDD compared to AuNPs-BDD, indicating the contribution of palladium in the oxygen reduction reaction. Good linearity with comparable limits of detection suggested that Au@PdNPs-BDD electrodes are promising for use as oxygen sensors. Furthermore, their application as BOD sensors was demonstrated.

In-situ loading synthesis of graphene supported PtCu nanocube and its high activity and stability for methanol oxidation reaction

A perfect PtCu nanocube with partial hollow structure was prepared by hydrothermal reaction and its electrocatalytic methanol oxidation reaction (MOR) was studied. The appropriate concentration of shape-control additives KI and triblock pluronic copolymers, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO₁₉-PPO₆₉-PEO₁₉) (P123) play crucial roles in the final product morphology. The PtCu nanocubes can be perfectly in situ immobilizedonto graphene under the action of P123 while the structure and cubic morphologyremain unchanged. The electrochemical tests suggest that the obtained PtCu nanocube (PtCu-NCb) exhibits better MOR activity and stability than PtCu hexagon nanosheet (PtCu-NSt), PtCu nanoellipsoid (PtCu-NEs) and commercial Pt/C in alkaline medium. When in situ immobilized onto graphene, the MOR catalytic activity and stability of PtCu cubes are further improved. The markedly enhanced electrocatalytic activity and durability maybe attributed to the special cubic morphology with partial hollow structure enclosed by highly efficient facet and the probably the synergistic effect of PtCu and intermediate state CuI decorated on the surface and graphene.

Biomimetic Catalysts Based on Au@ZnO-Graphene Composites for the Generation of Hydrogen by Water Splitting

For some decades, the scientific community has been looking for alternatives to the use of fossil fuels that allow for the planet's sustainable and environmentally-friendly development. To do this, attempts have been made to mimic some processes that occur in nature, among which the photosystem-II stands out, which allows water splitting operating with different steps to generate oxygen and hydrogen. This research presents promising results using synthetic catalysts, which try to simulate some natural processes, and which are based on Au@ZnO-graphene compounds. These catalysts were prepared by incorporating different amounts of gold nanoparticles (1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%) and graphene (1 wt.%) on the surface of synthesized zinc oxide nanowires (ZnO NWs), and zinc oxide nanoparticles (ZnO NPs), along with a commercial form (commercial ZnO) for comparison purposes. The highest amount of hydrogen (1127 μmol/hg) was reported by ZnO NWs with a gold and graphene loadings of 10 wt.% and 1 wt.%, respectively, under irradiation at 400 nm. Quantities of 759 μmol/hg and 709 μmol/hg were obtained with catalysts based on ZnO NPs and commercial ZnO, respectively. The photocatalytic activity of all composites increased with respect to the bare semiconductors, being 2.5 times higher in ZnO NWs, 8.8 times higher for ZnO NPs, and 7.5 times higher for commercial ZnO. The high photocatalytic activity of the catalysts is attributed, mainly, to the synergism between the different amount of gold and graphene incorporated, and the surface area of the composites.

Core-shell structured PtRu nanoparticles@FeP promoter with an efficient nanointerface for alcohol fuel electrooxidation

In this study, a bottleneck was overcome for direct alcohol fuel cells using state-of-the-art PtRu catalysts for alcohol fuel oxidation. Herein, a core-shell structured PtRu catalyst system based on the emerging promoter FeP was developed that showed excellent catalytic performance for the oxidation of alcohol fuels. The surface spectrometric analysis and morphology observation confirmed the formation of a nanointerface of the PtRu shell and FeP core hybrid catalyst (PtRu@FeP), and efficient ligand effects and electronic effects were found to result from the noble metal active sites and adjacent promoter in the core-shell structure. The facile formation of oxygen-containing species and the strong electronic effects could activate the Pt active sites, leading to high catalytic performance. High anti-CO poisoning ability was found for this catalyst system when compared with the case of the benchmark commercial PtRu/C catalyst (110 mV less and 60 mV less as evaluated by the peak and onset potentials for CO oxidation, respectively). The PtRu@FeP catalysts also exhibited much higher catalytic activity and stability when compared with commercial and home-made PtRu/C catalysts; specifically, the peak current density of the PtRu@FeP 1 : 1 catalyst was about 2 and 3 times higher than those of the commercial PtRu/C catalyst and home-made PtRu/C for the oxidation of the alcohol fuels methanol and ethanol; moreover, high catalytic efficiency, improved by 2 times, was found, as expressed by the specific activity. Excellent catalytic stability as evaluated by 1000 cycles of cyclic voltammetry measurements was also demonstrated for the PtRu@FeP catalysts. The high catalytic performance could be attributed to the intimate nanointerface contact of the core-shell structured PtRu shell over the FeP core via a bi-functional catalytic mechanism and electronic effects based on the ligand effect in this catalyst system. The current study is a significant step to increase the PtRu catalytic performance via nanointerface construction by a core-shell structure on a novel promoter for direct alcohol fuel cells.

Au@PdAg core-shell nanotubes as advanced electrocatalysts for methanol electrooxidation in alkaline media

Developing active and cost-effective electrocatalysts for methanol electrooxidation is crucial to the commercialization of direct methanol fuel cells (DMFCs). In this study, Au@PdAg core-shell nanotubes are synthesized in an aqueous solution by sequential galvanic displacement between Ag nanowires and AuCl4 - and PdCl4 2-. High-resolution transmission electron microscopy studies demonstrate that the obtained Au@PdAg nanotubes consist of a Au-rich interior that is encapsulated with a three-dimensionally dendritic, porous PdAg alloy shell, forming a core-sheath nanostructure. Electrochemical studies indicate that the as-prepared Au@PdAg nanotubes exhibit apparent electrocatalytic activity and stability towards methanol electrooxidation in alkaline media. This remarkable high performance can be attributed to their large specific surface area and unique porous morphology.

Au-Pd bimetallic nanoparticles embedded highly porous Fenugreek polysaccharide based micro networks for catalytic applications

Currently, metallic nanoparticles possessing versatile heterogeneous catalytic functionality such as in hydrogenation, water splitting, hydrogen production and CO₂ reduction for global pollution remediation have been paid great attentions due to their high chemical stability, superior activity and unique electrical and optical properties. However, the gradual degradation of their catalytic activity on multiple usage limits the monometallic nanoparticles to industrial applications. Herein, we fabricated the highly porous fenugreek polysaccharide assisted green synthesis of AuPd nanostructures for heterogeneous catalytic hydrogenation of the industrial usable highly toxic 4-nitrophenol to the medicinally useful 4-aminophenol. The aqueous method developed in the present work is environmentally friendly, simple and low-cost procedure. The fabricated bimetallic porous AuPd nanostructures characterized using SEM, TEM, UV-Vis, XRD, XPS and FTIR analysis. The catalytic activity of the synthesized nanostructures was studied for the heterogeneous hydrogenation of 4-nitrophenol to 4-aminophenol in presence of NaBH₄, and the catalytic kinetic for the hydrogenation was analyzed via an UV-Vis spectrometer.

Gold nanocatalysts supported on carbon for electrocatalytic oxidation of organic molecules including guanines in DNA

Gold (Au) is chemically stable and resistant to oxidation. Although bulk Au is catalytically inert, nanostructured Au exhibits unique size-dependent catalytic activity. When Au nanocatalysts are supported on conductive carbon (denoted as Au@C), Au@C becomes promising for a wide range of electrochemical reactions such as electrooxidation of alcohols and electroreduction of carbon dioxide. In this mini-review, we summarize Au@C nanocatalysts with specific attention on the most recent achievements including the findings in our own laboratories, and show that Au nanoclusters (AuNCs, <2 nm) on nitrided carbon are excellent electrocatalysts for the oxidation of organic molecules including guanines in DNA. The state-of-the-art synthesis and characterization of these nanomaterials are also documented. Synergistic interactions among Au-containing multicomponents on carbon supports and their applications in electrocatalysis are discussed as well. Finally, challenges and future outlook for these emerging and promising nanomaterials are envisaged.