Irfan H. Lone

Citrate precursor synthesis and multifunctional properties of YCrO3 nanoparticles

Monophasic and highly crystalline YCrO3 nanoparticles with an average grain size of 22 nm and a high surface area of 344 m2 g−1 have been prepared successfully by using a citrate precursor route for the first time. The two as obtained band gap values of 1.98 eV and 2.95 eV may be associated with the transition of chromium ions. The wedge shaped ferromagnetic loop with a saturation magnetization of 2.48 emu g−1, a remanent magnetization of 0.83 emu g−1 and a coercive field of 12.78 kOe as well as room temperature ferroelectricity with a remanent polarization of 0.009 μC cm−2, a saturation polarization of 0.026 μC cm−2 and a coercive field of −0.66 kV cm−1 establish the multiferroic characteristics of YCrO3 nanoparticles. In addition, humidity sensing characteristics with little repeatability sensor output and the response–recovery time were observed at a significance pace.

Structural characterization and multiferroic properties of hexagonal nano-sized YMnO3 developed by a low temperature precursor route

Multiferroic YMnO3 nanoparticles with a narrow size distribution and high specific surface area (304 m2 g−1) were synthesized using a low temperature polymeric citrate precursor route for the first time. The crystal structure of the monophasic hexagonal YMnO3 nanoparticles was estimated by powder X-ray diffraction studies. The transmission and scanning electron microscopic studies revealed nearly hexagonal nanostructures with an average grain size of ∼48 nm. The optical band gap was found to be 3.7 eV and photoluminescence studies also suggest the wide band gap semiconducting nature of YMnO3. DC-magnetization studies of YMnO3 nanoparticles show ferromagnetic hysteresis with saturation magnetization of 21.19 emu g−1. The appearance of a room temperature ferroelectric loop at 50 kHz has been observed for the first time with an improved remanent polarization of 0.0084 μC cm−2. The dielectric properties on sintered disks were also investigated as a function of frequency and temperature.

Dielectric, optical and enhanced photocatalytic properties of CuCrO2 nanoparticles

Herein, delafossite CuCrO2 nanoparticles were synthesized through a polymeric citrate precursor method, followed by heating at 900 °C in air. The BET surface area of the CuCrO2 nanoparticles was found to be 235 m2 g−1, which was more than 500 times that of bulk CuCrO2 (0.47 m2 g−1) and 2–4 times that of the reported CuCrO2 nanoparticles (50–100 m2 g−1) (Y.-T. Nien et al., Mater. Chem. Phys., 2016, 179, 182–188 and D. Xiong et al., J. Mater. Chem., 2012, 22, 24760–24768). In the photoluminescence spectra of the CuCrO2 nanoparticles, a strong luminescent emission peak was observed at ∼460 nm in the blue light region. The resulting transmittance value of the CuCrO2 nanoparticles was found to be 77% in the visible region, and the direct band gap energy was determined to be 3.09 eV via UV-vis spectroscopy. The dielectric properties as a function of frequency and temperature and photocatalytic degradation of the organic pollutants in an aqueous solution were also investigated. CuCrO2 nanoparticles also showed remarkable enhancement in the catalytic degradation of methylene blue in H2O under sunlight irradiation. The plausible fragmentation and the structural changes in the methylene blue molecule were further demonstrated via mass spectrometry.