Well-dispersed Pt nanoparticles on polydopamine-coated ordered mesoporous carbons and their electrocatalytic application

One-Pot Synthesis of Ultra-Small Pt Nanoparticles-Loaded Nitrogen-Doped Mesoporous Carbon Nanotube for Efficient Catalytic Reaction

In this study, Pt nanoparticles-loaded nitrogen-doped mesoporous carbon nanotube (Pt/NMCT) was successfully synthesized through a polydopamine-mediated "one-pot" co-deposition strategy. The Pt source was introduced during the co-deposition of polydopamine and silica on the surface of SiO2 nanowire (SiO2 NW), and Pt atoms were fixed in the skeleton by the chelation of polydopamine. Thus, in the subsequent calcination process in nitrogen atmosphere, the growth and agglomeration of Pt nanoparticles were effectively restricted, achieving the in situ loading of uniformly dispersed, ultra-small (~2 nm) Pt nanoparticles. The method is mild, convenient, and does not require additional surfactants, reducing agents, or stabilizers. At the same time, the use of the dual silica templates (SiO2 NW and the co-deposited silica nanoclusters) brought about a hierarchical pore structure with a high specific surface area (620 m2 g-1) and a large pore volume (1.46 cm3 g-1). The loading process of Pt was studied by analyzing the electron microscope and X-ray photoelectron spectroscopy of the intermediate products. The catalytic performance of Pt/NMCT was investigated in the reduction of 4-nitrophenol. The Pt/NMCT with a hierarchical pore structure had an apparent reaction rate constant of 0.184 min-1, significantly higher than that of the sample, without the removal of the silica templates to generate the hierarchical porosity (0.017 min-1). This work provides an outstanding contribution to the design of supported noble metal catalysts and also highlights the importance of the hierarchical pore structure for catalytic activity.

Preparation of novel HKUST-1-glucose oxidase composites and their application in biosensing

Copper-based metal-organic frameworks (MOF) and multi-walled carbon nanotubes (HKUST-1-MWCNTs) composite were synthesized by one-step hydrothermal method, and PDA-enzyme-HKUST-1-MWCNTs composite was prepared by one-pot method for the construction of glucose biosensors, which realized the sensitive amperometric detection of glucose at 0.7 V (vs. SCE). The sensitivity of the sensor for glucose detection was 178 μA mM^-1cm^-2 in the wide linear range of 0.005 ~ 7.05 mM, the detection limit was 0.12 μM and the corresponding RSD was 3.8%. Its high performance is mainly benefitted from the high porosity and large specific surface area of HKUST-1, the good conductivity of MWCNTs, and the excellent adhesion and dispersion of PDA. The strategy of combining PDA and MWCNTs to improve the dispersion and conductivity of MOF is expected to achieve a wider application of MOF-based materials in the electrochemical biosensing field.

Platinum Nanoparticle-Based Microreactors as Support for Neuroblastoma Cells

Excitotoxicity is a common phenomenon in several neurological diseases, associated with an impaired clearance of synaptically released glutamate, which leads to an overactivation of postsynaptic glutamate receptors. This will, in turn, start an intracellular cascade of neurotoxic events, which include exacerbated production of reactive oxygen species and ammonia toxicity. We report the assembly of microreactors equipped with platinum nanoparticles as artificial enzymes and polymer terminating layers including poly(dopamine). The biological response to these microreactors is assessed in human neuroblastoma cell culture. The microreactors' function to deplete hydrogen peroxide (H₂O₂) and ammonia is confirmed. While the proliferation of the cells depends on the number of microreactors present, no inherent toxicity is found. Furthermore, the microreactors are able to ameliorate the effects of excitotoxicity in cell culture by scavenging H₂O₂ and ammonia, thus having the potential to provide a therapeutic approach for several neurological diseases in which excitotoxicity is observed.

Enhancing electrical energy storage capability of dielectric polymer nanocomposites via the room temperature Coulomb blockade effect of ultra-small platinum nanoparticles

Introducing a high dielectric constant (high-k) nanofiller into a dielectric polymer is the most common way to achieve flexible nanocomposites for electrostatic energy storage devices. However, the significant decrease of breakdown strength and large increase of dielectric loss has long been known as the bottleneck restricting the enhancement of practical energy storage capability of the nanocomposites. In this study, by introducing ultra-small platinum (<2 nm) nanoparticles, high-k polymer nanocomposites with high breakdown strength and low dielectric loss were prepared successfully. Core-shell structured polydopamine@BaTiO₃ (PDA@BT) and core-satellite ultra-small platinum decorated PDA@BT (Pt@PDA@BT) were used as nanofillers. Compared with PDA@BT nanocomposites, the maximum discharged energy density of the Pt@PDA@BT nanocomposites is increased by nearly 70% because of the improved energy storage efficiency. This research provides a simple, promising and unique way to enhance energy storage capability of high-k polymer nanocomposites.

Electrochemical Detection of Hydrazine Using Poly(dopamine)-Modified Electrodes

We have developed a simple and selective method for the electrochemical detection of hydrazine (HZ) using poly(dopamine) (pDA)-modified indium tin oxide (ITO) electrodes. Modification with pDA was easily achieved by submerging the ITO electrode in a DA solution for 30 min. The electrocatalytic oxidation of HZ on the pDA-modified ITO electrode was measured by cyclic voltammetry. In buffer solution, the concentration range for linear HZ detection was 100 µM–10 mM, and the detection limit was 1 µM. The proposed method was finally used to determine HZ in tap water to simulate the analysis of real samples. This method showed good recovery (94%–115%) and was not affected by the other species present in the tap water samples.

Self-assembly synthesis of reduced graphene oxide-supported platinum nanowire composites with enhanced electrocatalytic activity towards the hydrazine oxidation reaction

Pt-NWs-P can self-assemble on the GO@NH₂ surface. After NaBH₄ reduction, Pt-NWs/RGO show improved electrocatalytic activity for the hydrazine oxidation reaction.

Mycofabrication of common plasmonic colloids, theoretical considerations, mechanism and potential applications

A coupling of the plasmon on the surface of metal nanoparticles with an incident photon enhances a broad range of useful optical phenomena, such as resonant light scattering (RLS), surface plasmon resonance (SPR) or Raman scattering. Due to these unique optical properties plasmonic nanostructures of different sizes and shapes have gained increasing popularity in areas such as cancer diagnosis, photothermal therapy as well as the imaging of living cells, detection of pathogens, biomolecules, metal ions, and the catalysis of various reactions in wet chemistry. This article reviews the current trends in the synthesis of plasmonic nanoparticles, particularly gold (AuNPs) and silver (AgNPs), using fungi as well as the proposed mechanisms for their mycofabrication. We provide an overview of the theoretical concepts of plasmonic nanoparticles which are sensitive electromagnetic responses that determine these nanoparticles applications.

High performance of electrocatalytic oxidation and determination of hydrazine based on Pt nanoparticles/TiO2 nanosheets

In this work, highly dispersed Pt nanoparticles (PtNPs) were deposited on the surface of the TiO2 nanosheets (TiO2NSs) by the photodeposition method in the presence of methanol as holes scavengers. The results indicated that PtNPs were distributed on TiO2NSs successfully with the diameter of ca. 5-9 nm. The electrochemical experiments such as electrochemical impedance spectroscopy and cyclic voltammetry were used to study the electrochemical properties of the PtNPs/TiO2NSs modified glassy carbon electrode (GCE). The as-prepared PtNPs/TiO2NSs/GCE presents excellent electrocatalytic activity for hydrazine. The sensor can be used to determine hydrazine at low potential with a wide linear range, high sensitivity, and fast response time. Moreover, the sensor exhibits good selectivity and reproducibility. In addition, the recoveries were 100.1-105.3% for hydrazine in the tap water, indicating the PtNPs/TiO2NSs/GCE should be a promising sensor for the determination of hydrazine in real samples.

Polydopamine and graphene oxide synergistically modified Prussian blue electrochemical immunosensor for the detection of alpha-fetoprotein with enhanced stability and sensibility

In this paper, a simple and highly sensitive amperometric immunosensor for the determination of alpha-fetoprotein based on multi-functional gold nanoparticles–polydopamine-Prussian blue–graphene oxide nanocomposites (Au–PDA-PB–GO) was fabricated.