Investigation on photocatalytic degradation of crystal violet dye using bismuth ferrite nanoparticles

Enhanced photocatalytic degradation of crystal violet dye and high-performance electrochemical supercapacitor applications of hydrothermally synthesised magnetic bifunctional nanocomposite (Fe3O4/ZnO)

The present investigation employed a facile hydrothermal approach for the fabrication of Fe3O4/ZnO dual-functional magnetic nanocomposite. Supercapacitor and visible-light-driven photocatalytic applications of the material were explored. X-ray diffraction, Fourier transform infrared spectra, ultraviolet-visible diffuse reflectance spectra (UV-vis/DRS), field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray spectroscopy, and vibrating sample magnetometer were used to analyse the nanocomposite's structural, morphological, optical, and magnetic properties. The FE-SEM analysis demonstrated that the surface morphology of Fe3O4, ZnO, and the Fe3O4/ZnO nanocomposite consisted of nanoparticles, nanoflakes, and nanoparticles adhered to the nanoflakes, respectively. The maximum specific capacitance of the electrode based on the Fe3O4/ZnO nanocomposite was measured to be 736.36 Fg-1at a scan rate of 5 mVs-1. The electrode also demonstrated remarkable cycling stability, retaining 86.5% of its capacitance even after 3000 cycles. The Fe3O4/ZnO nanocomposite was found to have an optical bandgap of 2.7 eV, an average particle size of 22.5 nm, and a saturation magnetization of 68.7 emu g-1. The photocatalysis experiment was conducted using the optimised settings, which included a pH of 7.0, a dye concentration of 30 mg l-1, a catalyst dose of 1 g l-1, and a contact time of 120 min. The Fe3O4/ZnO nanocomposite exhibited a notable degradation efficiency towards crystal violet dye upon exposure to visible light, achieving a degradation efficiency of 96.9%. This performance surpassed that of pure ZnO, which attained a degradation efficiency of 70.2%. The nanocomposite exhibited a rate constant of 2.80 × 10-2min-1, which was found to be notably higher than that of pure ZnO (0.8 × 10-2min-1), as determined through modelling (pseudo-first order linear fit). The radical scavenger experiments indicated that the superoxide radicals and hydroxyl radicals are the primary reactive species. The Fe3O4/ZnO photocatalyst can be effectively isolated using a bar magnet. Remarkably, the photocatalytic efficiency of the material remained almost entirely intact even after undergoing four cycles of recycling. In addition, this research opens up exciting new possibilities for use in fields like energy storage and pollution control.

Highly Efficient Sulfur and Nitrogen Codoped Graphene Quantum Dots as a Metal-Free Green Photocatalyst for Photocatalysis and Fluorescent Ink Applications

The demand for modern organic pollutant treatment has prompted the development of environmentally acceptable photocatalytic processes. In this work, we report novel nitrogen and sulfur codoped graphene quantum dot (S,N-GQD) based photocatalysts and fluorescent ink for the first time. For the degradation of organic dyes under visible irradiation, a hydrothermal technique was employed to generate S,N-GQD green nanomaterials. The synthesized samples were examined using XRD, HR-TEM, EDX, FT-IR, PL, and UV-vis spectroscopy. UV-DRS was used to determine the energy band gap of S,N-GQDs, and it was obtained to be around ∼2.54 eV. To explore the catalytic behavior of the produced S,N-GQDs as green nanomaterials, organic dyes (i.e., crystal violet and Alizarin yellow) have been used as a reference dye in this study. Using several radical scavenging agents, the photocatalytic mechanism was examined. This novel photocatalyst offers a promising alternative for the breakdown of organic pollutants. Moreover, these S,N-GQDs can also be used as fluorescent ink for imaging purposes and security reasons.