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The detection of volatile organic compounds (VOCs) in ambient environments has opened up a new field for the quick, risk-free, and potentially low-cost identification of respiratory illnesses. In this context, CeO2-doped ZnO nanocomposites were produced through the sol–gel technique at various ratios (CeO2:ZnO at 1:4, 4:4, and 4:1, respectively), and their gas-sensing capability was evaluated and shown using a clad-modified fiber optic sensor to study its potential as a VOC detector. The study was based on the concepts of evanescent wave absorption. The modified cladded optical fiber was exposed to ammonia, ethanol, and methanol gas medium in the testing laboratory. At room/chamber temperature, the sensor's sensitivity is tested for various ratios and their spectral response was recorded, and was observed that CeO2-doped ZnO at 4:1 ratio exhibited better sensitivity towards ammonia gas vapor, with a sensitivity of 2.6 counts/10 ppm and a sensitivity percentage of about 26% for the maximum of 100 ppm. Thus, the RT ammonia gas-sensing capability of CeO2-doped ZnO (4:1) is well suited to industrial applications. [ABSTRACT FROM AUTHOR]

Undoped and Co-doped (0.5 and 3 at. %) SnO2 nanoparticles were synthesized by the co-precipitation method and the structural characterization done by X-Ray diffraction revealed the tetragonal rutile structure with a weak CoO phase in 3 at. % Co-doped sample. TEM and high-resolution transmission electron microscope images of Co-doped (3 at. %) SnO2 nanoparticles showed the presence of almost spherical nanoparticles with the particle size in the range of 7–9 nm. Pure SnO2 showed mixed phases of ferro and diamagnetism while Co-doped (3 at. %) SnO2 nanoparticles showed only ferromagnetism at room temperature. The room temperature ferromagnetism (RTFM) in the Co-doped sample is due to the interaction of the localized spins of the Co ions with the oxygen vacancies, which are introduced due to the substitution of Co2+ ions for Sn4+ ions (bound magnetic polarons). The presence of oxygen vacancies and the small particle size are responsible for the slightly enhanced ethanol sensitivity of Co-doped (3 at. %) SnO2 nanoparticles compared to SnO2 nanoparticles. From the results, it is concluded that the nanoparticles showing RTFM have potential applications in detecting ethanol. [ABSTRACT FROM AUTHOR]

(MnNi)Fe2O4 nanoparticle was prepared by auto-combustion method and its composites with poly(o-phenylenediamine) (PoPD) were synthesized through in-situ oxidative polymerization method. FTIR and XRD studies confirmed the formation of PoPD/(MnNi)Fe2O4 nanocomposites. The crystalline size of PM1, PM2 and PM3 are 44 nm, 45 nm and 16 nm respectively. The dispersion of (MnNi)Fe2O4 nanoparticles in PoPD reduces their crystalline size. In PoPD/(MnNi)Fe2O4 nanocomposites, spherical morphology of PoPD is modified by (MnNi)Fe2O4 nanoparticles. TEM images showed that (MnNi)Fe2O4 nanoparticles are dispersed in PoPD matrix. The hysteresis loops of (MnNi)Fe2O4 nanoparticles and PoPD/(MnNi)Fe2O4 nanocomposites indicated that they are ferrimagnetic in nature. The saturation magnetization value of (MnNi)Fe2O4, PM1, PM2 and PM3 are 29.871 emu/g, 3.342 emu/g, 4.298 emu/g and 7.877 emu/g respectively. The thermal stability and saturation magnetization value of PoPD/(MnNi)Fe2O4 nanocomposites increases with increase in concentration of (MnNi)Fe2O4 nanoparticles. Dielectric properties of PoPD/(MnNi)Fe2O4 nanocomposites were studied at different frequencies and temperature. The Mn2+ substitution in NiFe2O4 has improved the ethanol sensitivity of PoPD/(MnNi)Fe2O4 nanocomposites. The dielectric constant of PoPD/(MnNi)Fe2O4 nanocomposites increases with increase in frequency, temperature and concentration of nanoparticles. Theoretical investigations of the metal oxide complex were done by utilizing a DFT/ B3LYP/LANL2DZ basis set. The optimized bond parameters (bond lengths, bond angles and dihedral angles) were determined using identical level of basis set. The NLO properties of the title compound was calculated using first-order hyperpolarizability calculation. The HOMO-LUMO, which clarifies the possible charge transfer, happens inside the molecule. [ABSTRACT FROM AUTHOR]