Investigating the thermo-physical properties of a new kind of graphitic carbon nitride included ternary hybrid nanofluids and the property correlations

In this work, a simple and facile approach was employed for the preparation of the ternary hybrids comprising of titanium dioxide, zinc oxide and graphitic nitride (designated as TZG-TH) with varying compositions of the components. In the context of complex and multi-stages involved for preparation of many of the THs in the literature, the present work uses the much simpler mythology for the preparation of TH. Nanofluids (NF) were formulated in ethylene glycol: water base fluid using TZG TH as the solid particles. Scanning electron microscope of TZG TH informs that the particles are agglomerated. High resolution transmission electron microscopy image of TZG-TH reveals the presence narrowly distributed spherical particles (having the sizes in the range 40 nm-100 nm) in sheet like structure The core level X-ray photoelectron spectrum of carbon and nitrogen elements reveal the existence of sp2 -bonded C in the C[bond, double bond]N and pyridinic and graphitic nitrogen in TZG-TH. X-ray diffraction patterns of TZG TH show the existence of anatase and hexagonal phase wurtzite crystalline structure in TH. The thermo-physical properties were determined for of the THNFs in order to elucidate the influence of compositions of the component and concentration ofof TZG-TH on the thermophysical properties. The TZG TH containing larger proportions of ZnO showed the maximum of 9.11 % and 12.1 % higher increase in viscosity than the binary and base fluid, respectively. The density of TZG THs varies from 1.079 to 1.095 cp, which is closer to the base fluid. The influence of TZG TH composition on refractive index and ultrasonic velocity indicates the existence of molecular level interactions between the nanoparticles in the TH and base fluid. The ∼210 % thermal conductivity enhancement was witnessed for the TZG TH, which is significantly higher than that of ZnO mono NF (26.9%) and TiO2 mono NF (33.0%). The influence of composition and concentration of TZG- TH on molecular interaction parameters like adiabatic compressibility, intermolecular free length, free volume, internal pressure and specific acoustic impedance are reported. The TZG TH based NF showed adequate dispersion stability as inferred from dynamic light scattering and UV-visible spectroscopy results. The results on TZG TH included THNF are new to the literature and would be helpful in exploring multifunctional properties with heat transfer capabilities for applications.

Hybridization of Co3S4 and Graphitic Carbon Nitride Nanosheets for High-performance Nonenzymatic Sensing of H2O2

The development of efficient H₂O₂ sensors is crucial because of their multiple functions inside and outside the biological system and the adverse effects that a higher concentration can cause. This work reports a highly sensitive and selective non-enzymatic electrochemical H₂O₂ sensor achieved through the hybridization of Co₃S₄ and graphitic carbon nitride nanosheets (GCNNS). The Co₃S₄ is synthesized via a hydrothermal method, and the bulk g-C₃N₄ (b-GCN) is prepared by the thermal polycondensation of melamine. The as-prepared b-GCN is exfoliated into nanosheets using solvent exfoliation, and the composite with Co₃S₄ is formed during nanosheet formation. Compared to the performances of pure components, the hybrid structure demonstrates excellent electroreduction towards H₂O₂. We investigate the H₂O₂-sensing performance of the composite by cyclic voltammetry, differential pulse voltammetry, and amperometry. As an amperometric sensor, the Co₃S₄/GCNNS exhibits high sensitivity over a broad linear range from 10 nM to 1.5 mM H₂O₂ with a high detection limit of 70 nM and fast response of 3 s. The excellent electrocatalytic properties of the composite strengthen its potential application as a sensor to monitor H₂O₂ in real samples. The remarkable enhancement of the electrocatalytic activity of the composite for H₂O₂ reduction is attributed to the synergistic effect between Co₃S₄ and GCNNS.

Electrochemical Immunosensor for Detection of H. pylori Secretory Protein VacA on g-C3N4/ZnO Nanocomposite-Modified Au Electrode

A g-C₃N₄/ZnO (graphitic carbon nitride/zinc oxide) nanocomposite-decorated gold electrode was employed to design an antigen-antibody-based electrochemical biosensor to detect Helicobacter pylori specific toxin, vacuolating cytotoxin A (VacA). The thermal condensation method was used to synthesize the g-C₃N₄/ZnO nanocomposite, and the nanocomposite was deposited electrochemically on a gold electrode. The morphology as well as the structure of the synthesized nanocomposite were confirmed by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, and Fourier transform infrared techniques. The nanocomposite efficiently increased the sensor performance by amplifying the signals. EDC-NHS chemistry was exploited for attachment of VacA antibodies covalently with the g-C₃N₄/ZnO-modified gold electrode. This modified electrode was exploited for immunosensing of H. pylori-specific VacA antigen. The immunosensor was stable for up to 30 days and exhibited good sensitivity of 0.3 μA^-1 ng mL^-1 in a linear detection range of 0.1 to 12.8 ng mL^-1. Apart from this, the fabricated sensor showed unprecedented reproducibility and remarkable selectivity toward the H. pylori toxin VacA. Thus, the highly sensitive immunosensor is a desirable platform for H. pylori detection in practical applications and clinical diagnosis.