Nitrogen-doped graphene-silver nanodendrites for the non-enzymatic detection of hydrogen peroxide

In-operando electrochemical detection of hydrogen peroxide during bacteria damage using ZIF-67 derived electrocatalysts

In this study, ZIF-67 derived materials were obtained calcinating the ZIF-67 from 500 °C to 700 °C, and they were employed for the in-operando electrochemical detection of hydrogen peroxide formed during the bacterial damage of E. coli induced by the ZIF-67 as antibacterial agent. Transmission electron microscopy (TEM) micrographs revealed a shape transition during the calcination of ZIF-67 from a Co@C core@shell structure (500 °C) to a hollow carbon structure (600 °C). At 700 °C, the hollow structure unfolded to a laminar structure, forming a Co-N-C structure with Co-aggregated particles. The activity for H2O2 detection was shape-sensitive, finding that Co-N-C at 700 °C performed better by displaying a lower detection limit (LOD) of 1.64 ppm (48 μM) and a limit of quantification (LOQ) of 5.47 ppm (in phosphate buffer). The in-operando electrochemical tests confirmed that bacterial death can be followed by the detection of H2O2, finding a significant antibacterial activity until 1.5 h, after which the current dropped. These results were corroborated using the spread-plate method. Further tests with S. Aureus as a Gram-positive bacterium indicated that the proposed method can be extended to other bacteria.

Sensitive electrochemical determination of hydrogen peroxide in milk and water utilizing AgNPs@Sn MOF nanozyme

The detection of H2O2 by a non-enzymatic electrochemical sensor is demonstrated using the deposition of silver nanoparticles on a tin metal-organic framework (AgNPs@Sn MOF). Coupling Sn MOF with the AgNPs significantly amplifies the electro-analytical performance due to the higher porosity, synergistic effect, and enhanced active surface area for the analyte interaction, entailing the faster interfacial transfer of electrons. The synthesized material was explored using different characterization techniques, revealing the surface morphology, crystalline size and nature, and availability of different functional groups. Additionally, AgNPs@Sn MOF nanozyme effectively oxidizes 3,3',5,5'-tetramethylbenzidine (TMB) to oxidized-TMB(oxTMB) and o-phenylenediamine (OPD) to oxidized-OPD(oxOPD) product along with the generation of •OH radicals posing an excellent peroxidase-like activity in an acidic medium. Under the optimized experimental conditions, the colorimetric detection and the electrochemical sensing of H2O2 are facilitated with the LOD of 70 nM in the linear range 0.1-50 µM and 37 nM in the linear range of 0.1-30 µM, respectively. Notably, the practical utility of the sensor was demonstrated by sensing H2O2 in a real sample, achieving a recovery range of 97-106% and 96-106% for milk and water, respectively.

Hydrogen Peroxide and Dopamine Sensors Based on Electrodeposition of Reduced Graphene Oxide/Silver Nanoparticles

In this work, silver nanoparticles (AgNPs)/reduced graphene oxide (rGO) nanocomposites were electrodeposited on glassy carbon electrodes (GCE) to construct electrochemical sensors for the detection of hydrogen peroxide (H2O2) and dopamine (DA). The AgNPs were synthesized on graphene oxide (GO) by the hydrothermal method, followed by the reduction of the GO during the electrodeposition process, resulting in the formation of the nanocomposites on the surface of the electrodes. The generation of AgNPs on the graphene sheets was verified by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The AgNPs/rGO/GCE showed a linear response to H2O2 in the range of 5 μM to 620 μM, with a sensitivity of 49 μA mM-1cm-2 and a limit of detection (LOD) of 3.19 μA. The linear response of the AgNPs/rGO/GCE to DA ranged from 1 μM to 276 μM, the sensitivity was 7.86 μA mM-1cm-2, and the LOD was 0.18 μM. Furthermore, DA and H2O2 were detected simultaneously in the same solution without interferences, and the sensors displayed good stability over time. The preparation method for the sensors is relatively eco-friendly, convenient, and efficient, exhibiting great potential for sensitive detection of DA and H2O2.

Insights into Structural Behaviors of Thiolated and Aminated Reduced Graphene Oxide Supports to Understand Their Effect on MOR Efficiency

It is essential to develop novel catalysts with high catalytic activity, strong durability, and good stability for further application in methanol fuel cells. In this work, we present for the first time the effect of the chemical functional groups (thiol and amine) with different electron affinity in reduced graphene oxide supports on the morphology and catalytic activity of platinum nanoparticles for the methanol oxidation reaction. Hydroxyl groups on graphene oxide were initially brominated and then transformed to the desired functional groups. The good dispersion of metal nanoparticles over functionalized carbon substrates (particle size less than 5 nm) with good durability, even at a limited functionalization degree (less than 7%) has been demonstrated by morphological and structural studies. The durability of the catalysts was much improved via strong coordination between the metal and nitrogen or sulfur atoms. Impressively, the catalytic activity of platinum nanoparticles on aminated reduced graphene oxide was found to be much better than that on thiolated graphene oxide despite the weaker affinity between amine and noble metals. These findings support further developing new graphene derivatives with the desired functionalization for electronics and energy applications..

Recent Progress in Emerging Novel MXenes Based Materials and their Fascinating Sensing Applications

Early transition metals based 2D carbides, nitrides and carbonitrides nanomaterials are known as MXenes, a novel and extensive new class of 2D materials family. Since the first accidently synthesis based discovery of Ti₃ C₂ in 2011, more than 50 additional compositions have been experimentally reported, including at least eight distinct synthesis methods and also more than 100 stoichiometries are theoretically studied. Due to its distinctive surface chemistry, graphene like shape, metallic conductivity, high hydrophilicity, outstanding mechanical and thermal properties, redox capacity and affordable with mass-produced nature, this diverse MXenes are of tremendous scientific and technological significance. In this review, first we'll come across the MXene based nanomaterials possible synthesis methods, their advantages, limitations and future suggestions, new chemistry related to their selected properties and potential sensing applications, which will help us to explain why this family is growing very fast as compared to other 2D families. Secondly, problems that help to further improve commercialization of the MXene nanomaterials based sensors are examined, and many advances in the commercializing of the MXene nanomaterials based sensors are proposed. At the end, we'll go through the current challenges, limitations and future suggestions.

Noble metal nanodendrites: growth mechanisms, synthesis strategies and applications

Inorganic nanodendrites (NDs) have become a kind of advanced nanomaterials with broad application prospects because of their unique branched architecture. The structural characteristics of nanodendrites include highly branched morphology, abundant tips/edges and high-index crystal planes, and a high atomic utilization rate, which give them great potential for usage in the fields of electrocatalysis, sensing, and therapeutics. Therefore, the rational design and controlled synthesis of inorganic (especially noble metals) nanodendrites have attracted widespread attention nowadays. The development of synthesis strategies and characterization methodology provides unprecedented opportunities for the preparation of abundant nanodendrites with interesting crystallographic structures, morphologies, and application performances. In this review, we systematically summarize the formation mechanisms of noble metal nanodendrites reported in recent years, with a special focus on surfactant-mediated mechanisms. Some typical examples obtained by innovative synthetic methods are then highlighted and recent advances in the application of noble metal nanodendrites are carefully discussed. Finally, we conclude and present the prospects for the future development of nanodendrites. This review helps to deeply understand the synthesis and application of noble metal nanodendrites and may provide some inspiration to develop novel functional nanomaterials (especially electrocatalysts) with enhanced performance.

Novel synthesis of multicomponent porous nano-hybrid composite, theoretical investigation using DFT and dye adsorption applications: disposing of waste with waste

Extensive studies have shown that doping can enhance the properties of graphene, but the application to real industrial wastewater treatment and theoretical calculations are limited. In this study, the hybrid nanoadsorbent Cu, N co-doped graphene (Cu@NG) was successfully synthesized via green route using carbon rods from waste dry batteries, human urine and copper nitrate, then multiple characterizations, detailed density functional theory (DFT) theoretical calculations and comprehensive actual wastewater tests are performed in environmental applications to investigate the adsorption properties and mechanism. The results showed that Cu@NG surface is mesoporous, decorated with CuO crystals and doped with N atoms. The isotherms and kinetics were simulated by Langmuir and pseudo-second-order models, respectively. The theoretical maximum sorption for MB and CV on Cu@NG is 116.28 mg·g^-1 and CV is 86.96 mg·g^-1, respectively. Pilot tests with Cu@NG on real textile wastewater showed that COD, BOD and color were removed by 54.2%, 55.2% and 86.4%, respectively. The desorption rate of Cu@NG is approximately above 90% for both MB and CV on Cu@NG after six cycles of treatment. The DFT calculations confirmed the experimental results as MB is more reactive than CV molecules. Besides, interactions have been systematically investigated via topology and natural bond orbital (NBO) analyses. The process mechanism involved mainly electrostatic adsorption, π-π stacking interactions and H-bonding interactions and ion exchange.

A dopamine electrochemical sensor based on a platinum–silver graphene nanocomposite modified electrode

A platinum–silver graphene nanocomposite was synthesized and characterized. A nanocomposite modified electrode was fabricated in order to investigate the electrochemical detection of dopamine.

Voltammetric sensing of formaldehyde by using a nanocomposite prepared by reductive deposition of palladium and platinum on polypyrrole-coated nitrogen-doped reduced graphene oxide

The study presents the synthesis of polypyrrole-coated palladium platinum/nitrogen-doped reduced graphene oxide nanocomposites (PdPt-PPy/N-rGO NC) via direct the reduction of Pd(II) and Pt(II) in the presence of pyrrole monomer, N-rGO and L-cysteine as the reducing agent. X-ray diffraction confirmed the presence of metallic Pd and Pt from the reduction of Pd and Pt cations. Transmission electron microscopy images revealed the presence of Pd, Pt and PPy deposition on N-rGO. Impedance spectroscopy results gave a decreased charge transfer resistance due to the presence of N-rGO. The nanocomposites were synthesized with different Pd/Pt ratios (2:1, 1:1 and 1:2). A glassy carbon electrode (GCE) modified with the nanocomposite showed enhanced electrochemical sensing capability for formaldehyde in 0.1 M sulfuric acid solution. Cyclic voltammetry showed an increase in the formaldehyde oxidation peak current at the GCE modified with Pd₂Pt₁ PPy N-rGO. At a typical potential of 0.45 V (vs. SCE), the sensitivity in the linear segment was 345.8 μA.mM ^-1. cm^-2. The voltammetric response was linear between 0.01 and 0.9 mM formaldehyde concentration range, with a 27 µM detection limit (at S/N = 3). Graphical abstract Schematic presentation of formaldehyde detection by Pd₂Pt₁-PPy/nitrogen-doped reduced Graphene Oxide Nanocomposite (Pd₂Pt₁-PPy /N-Gr NC). The decrease of charge transfer resistance and the agglomeration of deposited metals in the presence of N-rGO enhance the current response of the electrochemical sensor.

In Situ Synthesis of Silver Nanospheres, Nanocubes, and Nanowires over Boron-Doped Graphene Sheets for Surface-Enhanced Raman Scattering Application and Enzyme-Free Detection of Hydrogen Peroxide

An effective in situ synthesis strategy is demonstrated for the preparation of silver nanostructures (nanospheres (NSs), nanocubes (NCs), and nanowires (NWs)) on the surface of boron-doped graphene (BG). Further, these functional nanomaterials are employed for the surface-enhanced Raman scattering (SERS) and non-enzymatic electrochemical detection of H₂O₂. The results confirm the superior performance of BG-Ag nanostructures as SERS platform. Among various geometries of silver nanoparticles studied in this work, we find that the AgNCs over BG (BG-AgNC) present outstanding SERS performance for detecting 4-mercaptobenzoic acid, with a limit of detection of 1.0 × 10^-13 M. Furthermore, BG-AgNC exhibits excellent capability to detect melamine as low as 1.0 × 10^-9 M. Electrochemical results confirm that the BG-AgNW-based platform exhibits a superior biosensing performance toward H₂O₂ detection. The enhanced performance is due to the presence of graphene, which improves the conductivity and provides more active sites. The synthesis of doped graphene with metallic nanoparticles described in this work is expected to be a key strategy for the development of an efficient SERS and electrochemical sensor that offers simplicity, cost-effectiveness, long-term stability, and better reproducibility.

Preparation of a nanocomposite material consisting of cuprous oxide, polyaniline and reduced graphene oxide, and its application to the electrochemical determination of hydrogen peroxide

A method is described for the preparation of a nanocomposite material consisting of cuprous oxide/polyaniline/reduced graphene oxide (Cu₂O/PANI/rGO). Aniline was employed as both the precursor for PANI and the reducing agent for Cu²⁺ and graphene oxide. A glassy carbon electrode was modified with the nanocomposite material. Chronoamperometric studies with the modified electrode showed it to enable an efficient electroreduction of hydrogen peroxide at -0.2 V vs. saturated calomel electrode. All measurements were performed in the absence of oxygen. Figures of merit include a wide linear response range (0.8 μM to 12.78 mM) and a low limit of detection of 0.5 μM (S/N = 3). Graphical abstract Cuprous oxide/polyaniline/reduced graphene oxide nanocomposites were synthesized through one-step process for fabricating an nonenzymatic electrochemical sensor for hydrogen peroxide.

An ultrasensitive electrochemical immunosensor based on C60-modified polyamidoamine dendrimers and Au NPs for co-catalytic silver deposition

C₆₀-Modified polyamidoamine dendrimers and Au NPs for the co-catalytic deposition of silver, used for ultrasensitive electrochemical immunosensing.

Signal amplification biosensor based on DNA for ultrasensitive electrochemical determination of metronidazole

The biosensor (PDDA-GN/DNA/GCE) showed remarkable signal amplification performance toward the reduction of metronidazole, and was applied to determinate metronidazole in urine and lake water samples with satisfactory results.

Nanocomposites of nitrogen-doped graphene decorated with a palladium silver bimetallic alloy for use as a biosensor for methotrexate detection

Pd₁Ag₁/NG–GCE is a promising platform for the highly sensitive electrochemical detection of MTX.

Hierarchical polystyrene@reduced graphene oxide–Pt core–shell microspheres for non-enzymatic detection of hydrogen peroxide

A non-enzymatic electrochemical sensor based on polystyrene@reduced graphene oxide (RGO)–Pt core–shell microspheres was developed for sensitive detection of hydrogen peroxide (H₂O₂).

Electrochemical synthesis and photoelectrochemical properties of a novel RGO/AgNDs composite

A novel RGO/AgNDs composite was prepared by a one-step electrodeposition method. The RGO/AgNDs composite exhibited excellent photoelectrical conversion and sensitive electrochemical response to H₂O₂.