PtPdRh Mesoporous Nanospheres: An Efficient Catalyst for Methanol Electro-Oxidation

An aptasensor consisting of the integrated MOF-derived Zn-MOF-on-Co-MOF coupled with AuNPs nanocomposites and aptamer for ultrasensitive assay of fipronil

The conductivity of Zn-MOF-on-Co-MOF synthesized by one-pot method is improved by searching for the optimum carbonization temperature, which overcomes the limitation of traditional MOF. In order to further enhance electron transfer, the mesoporous PtPdCo trimetal was introduced, which provided considerable load capacity for methylene blue (MB) and reverse complementary DNA (sDNA), and also showed excellent catalytic activity for MB. In this study, the conductivity of aptasensor was improved by modifying carbonized MOF as the base material. In the presence of fipronil (FIP), Apt tended to bind to FIP and was separated from the electrode surface, so that the remaining single-stranded complementary DNA (cDNA) were hybridized with signal probe (MB@PtPdCo/sDNA) and amplified the electrochemical signal. By modifying the substrate, competitive amplification strategy and signal probe material to catalyze signal molecules, the sensor performs multiple signal amplification, and the electrical signal is significantly improved. The sensor has a wide detection range 100 pg/mL to 100 μg/mL and a low detection limit of 76 pg/mL.

Revealing the Effect of Anion Regulation in NiCo2X4 (X = O, S, Se, Te) on Photoassisted Methanol Electrocatalytic Oxidation

Designing nonprecious metal anode catalysts for photoassisted direct methanol fuel cells (PDMFCs) remains a challenge. As a semiconductor catalyst with a spinel structure, NiCo2O4 has good methanol catalytic oxidation activity and photocatalytic activity, making it a highly promising anode non-noble metal catalyst for PDMFCs. However, compared with the noble metal catalyst, the photoelectrocatalytic activity remained to be improved. In this report, an anion regulation strategy was adopted to improve the photoassisted methanol electrocatalytic activity. Using a CoNi-Aspartic (CoNi-Asp) nanorod as the precursor, the anion-regulated NiCo2X4 (X = O, S, Se, Te) was prepared by oxidation, sulfuration, selenization, and telluridation reactions. The regulation of anions and their effects on the electronic structure, intermediate product, and photoelectric catalytic performance of NiCo2X4 (X= O, S, Se, Te) was systematically discussed. Photoelectrochemical characterization and adsorption energy of •OH revealing the volcano-like correlation between the anion in NiCo2X4 (X = O, S, Se, Te) and their photoelectrocatalytic performance. The narrowest band gap (2.239 eV), the highest •OH adsorption energy (-3.32 eV), and the highest ratio of Co3+/Co2+ (2.19) ensure the best photoelectric catalytic performance of NiCo2S4, under the visible light irradiation, the photoresponse current density was 1.9 A g-1, the current density at 0.6 V was up to 21.9 A g-1. After 9 h of stability testing, the current retention rate was 80%. This report sheds an idea for the rational design of non-noble anode catalysts for PDMFCs.

Mechanisms and selectivity of methanol oxidation on PtRuM3/C-MWCNT (M = Fe and Co) electrocatalysts

Methanol oxidation efficiency and resistance to CO poisoning are the most challenging issues associated with direct methanol fuel cells. Much experimental effort has been undertaken, such as generating Pt-based binary and ternary nanoparticles, creating composite substrates, and fabricating nanoparticles with special shapes, to overcome these drawbacks. Our previous experiment showed that ternary PtRuM3/C-MWCNT (M = Fe and Co; C-MWCNT = carbon Vulcan-multiwalled carbon nanotube) electrocatalysts exhibited high methanol oxidation activity and tolerance to CO poisoning. However, reaction mechanisms on ternary PtRuM3/C-MWCNT (M = Fe and Co) electrocatalysts remain unknown. Therefore, this work is devoted to elucidating the problem using density functional theory calculations and thermodynamic models. Our present study showed that methanol oxidation proceeds via four possible reaction pathways on the surface of PtRuM3/C-MWCNTs, where the most favourable one follows a series of steps converting with a thermodynamic barrier of 0.513 eV for applied potentials of U = 0 V and 1.005 V on PtRuFe3/C-MWCNTs and 0.404 eV for U = 0 V and 0.167 eV for U = 1.005 V on PtRuCo3/C-MWCNTs. We also provide physical insights into the interaction between methanol oxidation intermediates and substrates' surface by analysing electronic properties. Our findings support the results of our previous experiment. The results of this study can be useful for rationally designing the anode for fuel cells.

An aptamer and flower-shaped AuPtRh nanoenzyme-based colorimetric biosensor for the detection of profenofos

A GO grafted SSM was prepared to load the freely mobile capture probe and novel flower-shaped AuPtRh nanospheres were synthesized to be a signal probe, which were constructed to form a colorimetric biosensor for the detection of profenofos.

Porous Noble Metal Electrocatalysts: Synthesis, Performance, and Development

Active sites (intrinsic activity, quantity, and distribution), electron transfer, and mass diffusion are three important factors affecting the performance of electrocatalysts. Composed of highly active components which are built into various network structures, porous noble metal is an inherently promising electrocatalysts. In recent years, great efforts have been made to explore new efficient synthesis methods and establish structural-performance relationships in the field of porous noble metal electrocatalysis. In this review, the very recent progress in strategies for preparing porous noble metal, including innovation and deeper understanding of traditional methods is summarized. A discussion of relationship between porous noble metal structure and electrocatalytic performance, such as accessibility of active sites, connectivity of skeleton structures, channels dimensions, and hierarchical structures, is provided.

A dual recognition strategy for accurate detection of CTCs based on novel branched PtAuRh trimetallic nanospheres

Accurate detection of circulating tumor cells (CTCs) has a pivotal role in the metastasis monitoring and prognosis of tumor. In this work, an ultrasensitive electrochemical cytosensor was developed based on excellent electrocatalytic materials and a dual recognition strategy. Herein, novel branched PtAuRh trimetallic nanospheres (b-PtAuRh TNS) were synthesized for the first time by a facile one-pot method, which had a huge specific surface area and outstanding catalytic activity. B-PtAuRh TNS linked with aptamers targeting mucin1 (MUC1) were served as signal tags to amplify the signal. As electrode modified material, the nanocomposites of Cabot carbon black (BP2000) and AuNPs were used to improve the electron transfer efficiency of electrode. In addition to using b-PtAuRh TNS labeled anti-MUC1 aptamers as signal probes, anti-EpCAM antibodies were worked as capture probes to achieve dual recognition of target cells. In other words, only cells expressing both MUC1 and EpCAM could produce electrochemical signal. The constructed cytosensor presented a wide linear range (5 - 1 × 10⁶ cells mL^-1) and a low detection limit (1 cell mL^-1). It was worth noting that the proposed cytosensor could detect CTCs in clinical blood samples. To sum up, the developed cytosensor might become a promising detection platform for cancer diagnosis and tumor metastasis.

A universal approach for the synthesis of mesoporous gold, palladium and platinum films for applications in electrocatalysis

High-surface-area mesoporous materials expose abundant functional sites for improved performance in applications such as gas storage/separation, catalysis, and sensing. Recently, soft templates composed of amphiphilic surfactants and block copolymers have been used to introduce mesoporosity in various materials, including metals, metal oxides and carbonaceous compounds. In particular, mesoporous metals are attractive in electrocatalysis because their porous networks expose numerous unsaturated atoms on high-index facets that are highly active in catalysis. In this protocol, we describe how to create mesoporous metal films composed of gold, palladium, or platinum using block copolymer micelle templates. The amphiphilic block copolymer micelles are the sacrificial templates and generate uniform structures with tunable pore sizes in electrodeposited metal films. The procedure describes the electrodeposition in detail, including parameters such as micelle diameters, deposition potentials, and deposition times to ensure reproducibility. The micelle diameters can be controlled by swelling the micelles with different solvent mixtures or by using block copolymer micelles with different molecular weights. The deposition potentials and deposition times allow further control of the mesoporous structure and its thickness, respectively. Procedures for example applications are included: glucose oxidation, ethanol oxidation and methanol oxidation reactions. The synthetic methods for preparation of mesoporous metal films will take ~4 h; the subsequent electrochemical tests will take ~5 h for glucose sensing and ~3 h for alcohol oxidation reaction.

Synergism of Multicomponent Catalysis: One-Dimensional Pt-Rh-Pd Nanochain Catalysts for Efficient Methanol Oxidation

Designing Pt-based alloy catalysts with multicomponent composition and a controllable structure is important to improve the utilization efficiency of precious metals and catalytic activity, but it still face a lot of challenges for simple preparation. Herein, we used insulin amyloid fibrils as templates and their own one-dimensional spiral structure to synthesize Pt-Rh-Pd ternary alloy nanochains under mild conditions. The prepared Pt-Rh-Pd alloy nanochains (NCs) have uniform diameter, and the particle size is only 2 nm. This ultrafine structure increases the specific surface area of the catalyst to a certain extent, and the synergistic effect of the three metals improves the catalytic performance. Compared with commercial Pt/C and binary Pt-Rh NCs, the as-presented Pt-Rh-Pd NCs show better methanol oxidation activity ability and stability against CO poisoning. The peak current density of front sweep is 1.48 mA cm-2, which is 1.7 times higher than that of commercial Pt/C (0.89 mA cm-2) and 1.4 times higher than that of the Pt-Rh NCs (1.07 mA cm-2), indicating great application potential as high-performance electrocatalysts in fuel cells.

Three-Dimensional PdPtCu Nanoalloys with a Controllable Composition and Spiny Surface for the Enhancement of Ethanol Electrocatalytic Properties

Pt-based nanomaterials have been proven to be effective catalysts for direct alcohol fuel cells (DAFCs). Specifically, the ternary nanoalloys (NAs) composed of Pt with other noble metals and transition metals can not only reduce the component of Pt but also enhance the electrocatalytic property and durability for alcohol oxidation. Herein, ternary PdPtCu NAs were synthesized through the solvothermal method using ethylene glycol as the solvent and reducing agent. The morphology and composition of PdPtCu NAs can be effectively controlled via selecting suitable surfactants and adjusting the proportion of precursors. The three-dimensional (3D) PdPtCu NAs with spiny rambutan-like morphology were obtained using the triblock copolymer Pluronic F-127 (PF-127) as the surfactant and adding three precursors with an equal molar ratio. The unique structure of PdPtCu NAs and the synergistic effect between the components significantly improved the electrocatalytic activity toward ethanol oxidation. Compared with different atomic ratio binary or ternary nanomaterials, 3D PdPtCu NAs manifested the best electrocatalytic performance.

3D highly branched PtCoRh nanoassemblies: Glycine-assisted solvothermal synthesis and superior catalytic activity for alcohol oxidation

Advanced Pt-based ternary nanocatalysts display dramatically enhanced utilization efficiency of Pt alternative to mono- and bi-counterparts, owing to the synergistic effects of the tri-metals. Herein, multicomponent uniform 3D PtCoRh highly branched nanoassemblies (HBNAs) were prepared by glycine-assisted one-pot solvothermal method in oleylamine (OAm). The effects of the precursor types, reaction time and amount of glycine were critically investigated in this synthesis. The as-prepared PtCoRh HBNAs displayed outstanding electrocatalytic activity and improved stability towards ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR) in 1 M KOH electrolyte, whose mass/specific activities were 1.75 A mg^-1/4.03 mA cm^-2 and 0.98 A mg^-1/2.34 mA cm^-2, respectively, which were remarkably higher than commercial Pt/C (0.85 A mg^-1/4.03 mA cm^-2 and 0.47 A mg^-1/0.89 mA cm^-2). This study provides some novel guidelines to fabricate advanced multimetallic electrocatalysts for practical applications in direct alcohol fuel cells (DAFCs).

Synthesis and characterization of size controlled bimetallic nanosponges

Metallic and bimetallic nanosponges with well-defined size and form have attracted increasing attention due to their unique structural properties and their potential for many applications. In this chapter, the recently developed methods for the synthesis and preparation of metallic and bimetallic nanosponges are presented. These methods can be mainly cataloged in two groups: dealloying-based methods and reduction reaction-based methods. Different topographical reconstruction methods for the investigation of their structural properties are then reviewed briefly. The optical properties of the metallic nanosponges are clearly different from those of the solid counterparts due to the tailored disordered structure. The recent advances in the exploration of the distinct linear and non-linear optical properties of the nanosponges are summarized.

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