Revisiting Some Recently Developed Conducting Polymer@Metal Oxide Nanostructures for Electrochemical Sensing of Vital Biomolecules: A Review

Electrochemical Probing the Site Reactivity in Iron Single-Atom Catalysts for Electrocatalytic Nitrate Reduction to Ammonia

Single-atom catalysts (SACs), specifically iron single atoms dispersed on nitrogen-doped carbon (Fe-NC), have shown promising potential in the electrocatalytic reduction of nitrate to ammonia (NitRR), but there is a lack of understanding of their intrinsic activity. The conventional measurements often overlook the intrinsic performance of SACs, leading to significant underestimation. This study presents an in situ electrochemical probing protocol, using two poisoning molecules (SCN- and NO2-), to characterize the reactivity of Fe sites in Fe-NC SACs for NitRR. The technique aids in quantifying the yield rate of ammonia on Fe sites and the active site number. The findings reveal the intrinsic turnover frequency (TOF) based on the number and ammonia yield rate of Fe sites, challenging the current understanding of SACs' inherent performances. This unique approach holds considerable potential for determining the intrinsic activity of other SACs in complex reactions, opening new avenues for the exploration of electrocatalytic processes.

TiO2-guanine as a new amalgamation compound for fabrication of a disposable biosensor with high sensitivity and rapid detection of H1N1 swine flu virus

A TiO2-guanine nanocomposite (TG NC)-based electrochemical biosensor was immobilized with hemagglutinin (HA) gene specific probe with 5' NH2 group on screen-printed gold electrode (probe(ss)DNA-TG-SPGE). The modified biosensor was examined for H1N1 swine flu virus. TG NCs along with precursors were characterized spectroscopically and morphologically by employing several approaches. Electrochemical investigations were performed with the help of cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer saline (PBS; pH 7.4) with 1 µM methylene blue (MB) redox indicator. For better detection of single-stranded virus DNA, the modified electrode was optimized at various concentrations, pH, and scan rates. The modified biosensor showed high sensitivity (40.32 μA/ng.cm2), low LOD (0.00024 ng/6 µL), and broad linear range 0.0002-20 ng/6µL with coefficient of determination of R2=0.9981 for H1N1 virus detection. The HA gene-modified biosensor presented decent stability and specificity against different infectious pathogens including H3N2 virus and human DNA with negative response. Furthermore, the modified biosensor also responded well for real sample target DNA detection with a recovery of >96%. The simply designed HA gene-modified biosensor transduces decreased current response towards target-specific (ss)DNA binding and could be used as a rapid detection tool for H1N1 swine flu virus diagnosis.

Polyvinylpyrrolidone/TiO2 composites' preparation via sol-gel procedure furthered with non-enzymatic glucose sensing and antibacterial effectiveness

An amperometric non-enzymatic glucose sensing based on polyvinylpyrrolidone and titanium dioxide nanocomposites (PVP-TiO2 NCs) fabricated over stainless-steel (SS) electrode was experimented. The electrode was fabricated of PVP-TiO2 NCs onto SS surface through drop casting coating. The NCs and the electrode were analyzed using Fourier transform infrared (FTIR) and UV-visible (UV-Vis) spectroscopy, X-ray diffraction spectra (XRD), X-ray photoelectron spectra (XPS), particle analyzer, scanning electron microscopy (SEM), EDS and transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis for surface. For electrochemical investigation, cyclic voltammetry, electrochemical impedance spectra, including Nyquist plots and Bode plots, and chronoamperometry were adopted. PVP-TiO2/SS-modified electrode manifested high sensitivity of 360.13 µA/mM.cm2, lower detection limit of 756.8 µM and 0 to 13 mM linear range with regression coefficient of R2 = 0.992. The electrode exhibited high stability with good anti-interference tendency against fructose, uric acid, ascorbic acid and sucrose. The modified electrode also performed well in real sample glucose detection. Further, PVP-TiO2 NCs performed appreciably toward antibacterial studies against some Gram-positive and Gram-negative deleterious bacteria, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Shigella flexneri microbes.

Ppy/TiO2-SiO2 nanohybrid series: synthesis, characterization, photocatalytic activity, and antimicrobial potentiality

A series of polypyrrole doped TiO₂-SiO₂ nanohybrids (Ppy/TS NHs) were synthesized thru in-situ oxidation polymerization by varying weight ratio of pyrrole. The structural analysis of NHs were characterized by X-ray Diffraction (XRD) spectra, UV-visible (UV-Vis) spectra and X-ray Photoelectron spectra (XPS) confirmed synthesis of nanomaterials. Surface and morphological study done by adopting, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Transmittance Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis confirmed the homogenous distribution, nano range size formation and mesoporous nature of nanohybrids. Further, electrochemical behavior of synthesized NHs investigated by adopting Electrochemical Impedance Spectroscopy (EIS) showed good kinetic behaviour and electron transport tendency. The nanohybrids and precursors were examined for photocatalytic degradation of methylene blue (MB) dye and revealed enhanced degradation tendency for the NHs series photocatalysts. It was found that variation of pyrrole (0.1 to 0.3 g) to TS nanocomposites (TS Nc) increased the photocatalytic potential of TS Nc. The maximum photodegradation efficacy was found to be 90.48% in 120 min for Ppy/TS0.2 NHs under direct solar light. Additionally, Ppy/TS0.2 NHs performed appreciably towards antibacterial studies against some Gram-positive and Gram-negative deleterious bacteria, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Shigella flexneri microbes.

Electrochemical Sensing of Dopamine Using Polypyrrole/Molybdenum Oxide Bilayer-Modified ITO Electrode

The electrochemical sensing of biomarkers has attracted more and more attention due to the advantages of electrochemical biosensors, including their ease of use, excellent accuracy, and small analyte volumes. Thus, the electrochemical sensing of biomarkers has a potential application in early disease diagnosis diagnosis. Dopamine neurotransmitters have a vital role in the transmission of nerve impulses. Here, the fabrication of a polypyrrole/molybdenum dioxide nanoparticle (MoO3 NP)-modified ITO electrode based on a hydrothermal technique followed by electrochemical polymerization is reported. Several techniques were used to investigate the developed electrode's structure, morphology, and physical characteristics, including SEM, FTIR, EDX, N2 adsorption, and Raman spectroscopy. The results imply the formation of tiny MoO3 NPs with an average diameter of 29.01 nm. The developed electrode was used to determine low concentrations of dopamine neurotransmitters based on cyclic voltammetry and square wave voltammetry techniques. Furthermore, the developed electrode was used for monitoring dopamine in a human serum sample. The LOD for detecting dopamine by using MoO3 NPs/ITO electrodes based on the SWV technique was around 2.2 nmol L-1.

Recent Advances in Nanomaterial-Based Chemiluminescence Probes for Biosensing and Imaging of Reactive Oxygen Species

Reactive oxygen species (ROS) play important roles in organisms and are closely related to various physiological and pathological processes. Due to the short lifetime and easy transformation of ROS, the determination of ROS content in biosystem has always been a challenging task. Chemiluminescence (CL) analysis has been widely used in the detection of ROS due to its advantages of high sensitivity, good selectivity and no background signal, among which nanomaterial-related CL probes are rapidly developing. In this review, the roles of nanomaterials in CL systems are summarized, mainly including their roles as catalysts, emitters, and carriers. The nanomaterial-based CL probes for biosensing and bioimaging of ROS developed in the past five years are reviewed. We expect that this review will provide guidance for the design and development of nanomaterial-based CL probes and facilitate the wider application of CL analysis in ROS sensing and imaging in biological systems.

Prolific intercalation of VO2 (D)/polypyrrole/g-C3N4 as an energy storing electrode with remarkable capacitance

VO2 (D)/polypyrrole/g-C3N4 composites are synthesized through in situ chemical oxidation polymerization, and used as an electrode material for excellent energy storage.