Electrocatalytic reactivity for oxygen reduction of palladium-modified carbon nanotubes synthesized in supercritical fluid

New Au/chitosan nanocomposite modified carbon paste sensor for voltammetric detection of nicotine

A profoundly touchy voltammetric sensor for detection of nicotine (NIC) in urine and tobacco specimens has been developed in light of the boosted electrochemical response of NIC at gold and chitosan nanocomposite modified carbon paste electrode (ACMCPE). Material characterization techniques Scanning Electron Microscope and Energy Dispersive X-ray (SEM & EDX) were utilized to describe the ACMCPE surface material. The impedance spectroscopy technique (EIS), cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed to explore the electrochemical sensing of NIC at ACMCPE. The created sensor exhibits an exceptional electrochemical sensitivity to NIC in a universal Britton-Robinson (B-R) buffer solution with a pH range of 2.0 to 8.0. The sensor shows a linear response over NIC concentration ranges of 4.0-320.0 µM, with the detection limit (LOD) of 7.6 µM. The prepared sensor has been shown to be exceptionally viable in detecting NIC with amazing selectivity and reproducibility. We suggest it as a trustworthy and useful electrochemical sensor for NIC location.

Favoring the Selective H2O2 Generation of a Self-Antibiofouling Dissolved Oxygen Sensor for Real-Time Online Monitoring via Surface-Engineered N-Doped Reduced Graphene Oxide

Dissolved oxygen (DO) is a key parameter in assessing water quality, particularly in aquatic ecosystems. The oxygen reduction reaction (ORR) has notable prevalence in energy conversion and biological processes, including biosensing. Nevertheless, the long-term usage of the submersible DO sensors leads to undesirable biofilm formation on the electrode surface, deteriorating their sensitivity and stability. Recently, the reactive oxygen species (ROS), such as the two-electron pathway ORR byproduct, H2O2, had been known for its biofilm-degradation activity. Herein, for the first time, we reported N-doped reduced graphene oxide (N-rGO) for H2O2 selectivity as the self-antibiofouling DO sensor. Introducing foreign atom doping could reorient the electron network of graphene by the electronegativity gap, which facilitated highly selective and efficient two electron pathway of ORR. Mitigating the N content of N-rGO had enhanced the H2O2 selectivity (57.5%) and electron transfer number (n = 2.84) in neutral medium. Moreover, the N-rGO could be integrated to a wireless DO monitoring device that might realize an applicable device in the aquatic fish farming.

Advanced Nanocarbons for Enhanced Performance and Durability of Platinum Catalysts in Proton Exchange Membrane Fuel Cells

Insufficient stability of current carbon supported Pt and Pt alloy catalysts is a significant barrier for proton-exchange membrane fuel cells (PEMFCs). As a primary degradation cause to trigger Pt nanoparticle migration, dissolution, and aggregation, carbon corrosion remains a significant challenge. Compared with enhancing Pt and PtM alloy particle stability, improving support stability is rather challenging due to carbon's thermodynamic instability under fuel cell operation. In recent years, significant efforts have been made to develop highly durable carbon-based supports concerning innovative nanostructure design and synthesis along with mechanistic understanding. This review critically discusses recent progress in developing carbon-based materials for Pt catalysts and provides synthesis-structure-performance correlations to elucidate underlying stability enhancement mechanisms. The mechanisms and impacts of carbon support degradation on Pt catalyst performance are first discussed. The general strategies are summarized to tailor the carbon structures and strengthen the metal-support interactions, followed by discussions on how these designs lead to enhanced support stability. Based on current experimental and theoretical studies, the critical features of carbon supports are analyzed concerning their impacts on the performance and durability of Pt catalysts in fuel cells. Finally, the perspectives are shared on future directions to develop advanced carbon materials with favorable morphologies and nanostructures to increase Pt utilization, strengthen metal-support interactions, facilitate mass/charge transfer, and enhance corrosion resistance.

Phyllanthus emblica seed extract mediated synthesis of PdNPs against antibacterial, heamolytic and cytotoxic studies

Ecofriendly synthesis of Palladium nanoparticles (PdNPs) were achieved using Phyllanthus emblica (P. emblica) seeds as reducing agent. Further the ecofriendly synthesized PdNPs were subjected for various analytical techniques like UV-Vis, FT-IR, XRD, Zeta potential, SEM and TEM. The results indicated that green synthesized PdNPs were spherical in shape with average particle size of 28±2nm with moderate stability. Further the synthesized PdNPs and extract were subjected for its antibacterial studies against various disease causing pathogens by agar well diffusion method. Seed extract resulted in 8.9±1.46mm against B. subtilis and PdNPs showed 9.6±1.10mm against S. aureus and synthesized PdNPs and extract were tested for hemolytic which resulted in 20% and 10% respectively. Toxicity studies were done against Artemia salina (A. salina). The LC₅₀ value of green synthesized P. emblica capped PdNPs and the P. emblica seed extract were found to be less toxic for A. salina with a value of 1.00μg/mL and 1.25μg/mL. In addition samples were checked for in vitro cytotoxicity assays on HeLa cell lines.

Facile preparation of a highly sensitive nonenzymatic glucose sensor based on multi-walled carbon nanotubes decorated with electrodeposited metals

Preparation of Ni/CuAg/MWCNT hybrid composite modified electrode: (a) bare, (b) MWCNT, (c) CuAg/MWCNT, and (d) Ni/CuAg/MWCNT modified electrodes.

Electrochemical post-treatment of infinite coordination polymers: an effective route to preparation of Pd nanoparticles supported onto carbon nanotubes with enhanced electrocatalytic activity toward ethanol oxidation

This study describes an effective method to prepare highly dispersed palladium nanoparticles supported onto single-walled carbon nanotubes (SWNTs) with high electrocatalytic activity toward the oxidation of ethanol. This method is essentially based on electrochemical post-treatment of Pd-based infinite coordination polymer (ICP). The Pd-based ICP is synthesized through the coordination reaction between Zn(2+) and metallo-Schiff base (MSB) to form Zn-MSB-Zn (ZMZ) ICP that precipitates from ethyl ether. The as-formed Zn-MSB-Zn ICP is then subjected to an ion-exchange reaction with Pd(2+) to obtain the Zn-MSB-Pd (ZMP) ICP. To prepare Pd/SWNT nanocomposite, the ZMP ICP is mixed into the SWNT dispersion in N-dimethylformamide (DMF) to form a homogeneous dispersion that is then drop-coated onto a glassy carbon (GC) electrode. Electrochemical post-treatment of ZMP ICP to form Pd/SWNT nanocomposite is thus performed by polarizing the coated electrode at -0.2 V for 600 s in 0.5 M H2SO4. The results obtained with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that the resulting Pd nanoparticles are highly dispersed onto SWNTs and the particles size are small and narrowly distributed (2.12 ± 0.32 nm). X-ray photoelectron spectroscopy (XPS) analysis shows that, after the electrochemical post-treatment, no detectable ZMP ICP precursors are left on the surface of SWNTs. The electrocatalytic activity of the as-formed Pd/SWNT nanocomposite toward ethanol oxidation is investigated by cyclic voltammetry and chronoamperometry. The results show that the Pd/SWNT nanocomposite prepared here shows a more negative potential and higher mass catalytic activity, as well as higher stability for the oxidation of ethanol than the commercial Pd/C catalyst. This work demonstrates a novel approach to the formation of ultrasmall and highly dispersed Pd/SWNT nanocomposite with enhanced electrocatalytic activity toward ethanol oxidation.

Improvement of catalytic water oxidation on MnOx films by heat treatment

Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Electrodeposited MnOx films from aqueous electrolytes have previously been shown to exhibit a lower catalytic action than films deposited from ionic liquids when tested in strongly alkaline conditions. In this study, we describe a thermal treatment that converts the MnOx films deposited from aqueous electrolytes to highly catalytic films with comparable activity to ionic-liquid-deposited films. The films deposited from aqueous electrolytes show a remarkable improvement in the catalysis of water oxidation after heat treatment at a low temperature (≤120 °C) for 30 min. The films were characterised by using XRD and SEM, and energy-dispersive X-ray (EDX), FTIR and Raman spectroscopy, which indicate that dehydration occurs during the heat treatment without significant change to the microstructure or bulk composition. The X-ray absorption spectroscopy (XAS) results show the growth of small amounts (ca. 3-10 %) of reduced Mn species (Mn(II) or Mn(III) ) after heat treatment. The dehydration process removes structural water and hydroxyl species to result in a conductivity improvement and a more active catalyst, thereby contributing to the enhancement in water oxidation performance.

Hybrid materials based on Pd nanoparticles on carbon nanostructures for environmentally benign C-C coupling chemistry

The combination of different nanomaterials such as metallic nanoparticles and carbon nanostructures in a new hybrid material should give rise to interesting properties that combine the advantages of each of the nanocomponents. This review highlights the latest advances in the synthetic design of these hybrid materials where carbon nanostructures act as supports as well as stabilizing agents for very reactive metallic nanoparticles. The striking applications of Pd nanoparticles anchored on the surface of carbon nanostructures in C-C coupling chemistry are analyzed. Special emphasis is placed on the stability of these materials, which is linked to their recyclability. Numerous examples are given that involve the use of these catalysts in Heck, Suzuki and Sonogashira coupling reactions.