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Multifunctional magnetic composite nanoparticles (NPs) with antibiotics have demonstrated symbiotic effects because of their promising antimicrobial properties. The antimicrobial agent reduces side effects and dosage, and increases drug delivery efficiency. In this study, SiO2 coated over Fe3O4 magnetic nanoparticles (MNPs) were prepared by a solvothermal method. The MNPs were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), and Fourier transform infrared spectroscopy (FTIR). The antimicrobial tests were carried out using the disk diffusion method. The electrochemical sensing was investigated by cyclic voltammetry with varying As(III) concentrations from 1–10 ppb. The microstructural results showed the formation of spherical-shaped Fe3O4@SiO2 MNPs with 15–30 nm diameters. UV-vis results showed that Fe3O4 NPs promote visible light absorption of Fe3O4@SiO2 MNPs because of well-structured and unvarying shell thickness which is beneficial for the absorption of organic dyes. With an increase in the concentration of As(III), there was a shift in potential and an increase in oxidation peak current, showing the electrocatalytic capacity of the modified electrode. The SiO2 deposited on Fe3O4 displayed an admirable microbial operation. These Fe3O4@SiO2 MNPs are easily absorbed by cells and have the potential to influence bacterial cells both within and outside of the cell membrane, making them an intriguing candidate for use in a variety of biological applications in the future. [ABSTRACT FROM AUTHOR]

We report the solvothermal synthesis of MoS2 based quantum dots (QDs) and the performance evaluation of bare QDs for the detection of aqueous As (III) oxidative state at room temperature and neutral pH over a vast range (0.1−1000 ppb). Concentration-dependent photoluminescence (PL) of the QDs enhances up to 50 ppb and then suppresses till 1000 ppb. It shows two distinctive slopes for enhancement and suppression. The enhancement is possibly due to the passivation of trap states or defects. The formation of tiny glassy As2S3 particles on the QD surface may be the possible reason for suppression. The pattern of optical absorption of QDs follows the similar patterns of PL. Still, it shows an enhanced absorbance in the near UV range below ≤300 nm, which increases with As (III) concentration up to 50 ppb and then decreases following the PL pattern. The MoS2 QDs were characterized by using transmission electron microscopy, x-ray diffraction, UV−Vis, and PL spectroscopy. The enhancement and suppression results were excellently fitted with the modified Stern−Volmer equation. The detection of arsenic is possible using these linear fit equations as calibration curves. [ABSTRACT FROM AUTHOR]