A. Manikandan

Fundamental study of LaMg x Cr1−x O3−δ perovskites nano-photocatalysts: Sol-gel synthesis, characterization and humidity sensing

Nanocrystalline perovskite oxides, LaMgxCr1−xO3−δ (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1) were prepared by sol-gel method. The samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption isotherms at 77 K, respectively, to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the samples. Also, it was investigated the humidity sensing characteristics of the samples. The composites were sintered at 800 °C for 5 h and subjected to dc electrical conductivity studies at room temperature. The resistance measurements as a function of relative humidity (RH) in the range of 5-98% were done and the humidity sensing factors (Sf =R5%/R98%) calculated. The activation energy of the compounds were determined from the temperature-dependent electrical conductance experiments in the temperature range of 120-300 °C. LaMgCr-3 (x=0.4) had the highest humidity sensing factor 21407±431, while LaCr-1 (x=0) the lowest sensitivity factor 27.27±2. The response and recovery characteristics were studied for LaMgCr-3, which exhibited good linearity and a very narrow hysteresis loop. The photocatalytic activity of LaMgxCr1−xO3−δ was investigated by using the photo-decomposition of 4-chlorophenol (4-CP) under UV-visible light. The sample LaMgCr-3 (x=0.4) showed the highest photocatalytic degradation efficiency (93.05%) than other samples, due to their smaller size of particles with higher surface area.

Comparative study of structural, morphological, magneto-optical and photo-catalytic properties of magnetically reusable spinel mnfe2O4 nano-catalysts

Spinel MnFe2O4 nanostructures were synthesized by simple, economical and eco-friendly microwave combustion (MCM) and conventional combustion (CCM) methods using metal nitrates and glycine used as the fuel, instead of toxic inorganic/organic catalyst, template and surfactant. Powder XRD and FT-IR, EDX and SAED results were confirmed the products have a cubic phase spinel structure. EDX and SAED results confirmed purity and high crystallinity without any other secondary phase impurities. HR-SEM and HR-TEM analysis indicate that the MCM and CCM products consist of nano- and microstructures, respectively. The optical band gap (Eg) was measured using Kubelka-Munk model and it shows higher value (2.37 eV) for MnFe2O4-MCM than MnFe2O4-CCM (2.15 eV), due to the smaller particle size of MnFe2O4-MCM. VSM results showed a superparamagnetic behavior and the magnetization (Ms) value of MnFe2O4-MCM is higher i.e., 39.68 emu/g than MnFe2O4-CCM (33.59 emu/g). It was found that the sample MnFe2O4-MCM have higher surface area than MnFe2O4-CCM, which in turn leads to the improved performance towards the photocatalytic degradation (PCD) of methylene blue (MB) and it was found that the sample MnFe2O4-MCM show higher PCD efficiency (96.48%) than MnFe2O4-CCM (84.95%). Also, MnFe2O4 show higher activity with good reusability, and eco-friendly materials for industrial and technological applications.

Size-controlled synthesis of chalcogen and chalcogenide nanoparticles using protic ionic liquids with imidazolium cation

Green synthesis of selenium (chalcogen) nanoparticles (SeNPs) has been successfully attained by simple wet chemical method that involves the reaction of six different protic ionic liquids with imidazolium cations and sodium hydrogen selenide (NaHSe) in the presence of poly ethylene glycol-600 (PEG-600) as an additional stabilizer. The obtained SeNPs were characterized using UV spectral (UV), Fourier transform infra-red (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscope (SEM) with energy dispersive X-ray (EDX) and high resolution transmission electron microscope (TEM) analysis. The results illustrate that the synthesized SeNPs are spherical in shape with size ranging 19-24 nm and possess good optical property with greater band gap energy, high thermal stability up to 330 °C, low melting point of 218-220 °C comparing to precursor selenium. Using the synthesized SeNPs, two chalcogenides such as ZnSe and CdSe semiconductor nanoparticles were synthesized and characterized using XRD, SEM with EDX and TEM analysis. The fabricated CdSe and ZnSe nanoparticles appeared like pebble and cluster structure with particle size of 29.97 nm and 22.73 nm respectively.

Okra (Abelmoschus esculentus) Plant Extract-Assisted Combustion Synthesis and Characterization Studies of Spinel ZnAl2O4 Nano-Catalysts

Spinel ZnAl2O4 nano-catalysts were synthesized by a simple, economical and eco-friendly microwave irradiation (MIM) and conventional heating methods (CHM), using metal nitrates and Okra (Abelmoschus esculentus) plant extract, which play a dual role of both oxidizing and reducing nature. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) and selected area electron diffraction (SAED) pattern results were confirmed that the samples have a single-phase cubic spinel structure with high crystalline nature of ZnAl2O4. Surface morphology of the samples was revealed by high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) techniques and they are confirmed particle-like structure with grain size below 50 nm. The optical band gap (Eg) was measured using Kubelka-Munk model by UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) and the Eg value is higher for MIM product than CHM, due to the smaller particle size of ZnAl2O4-MIM. The magnetic property of the samples was determined by vibrating sample magnetometer (VSM) and showed a superparamagnetic behavior. Spinel ZnAl2O4 nano-catalysts are magnetically recyclable and could be reused with no significant loss in catalytic activity. Both the samples were successfully tested as catalysts for the conversion of alcohols into respective carbonyl compounds using H2O2 (as oxidant) and acetonitrile (as a solvent) system. It was found that the ZnAl2O4-MIM nanocatalysts show best performance of conversion of alcohols into a carbonyl compounds than that of ZnAl2O4-CHM, due to the smaller particle size and higher surface area of ZnAl2O4-MIM samples.

Novel Synthesis and Characterization Studies of Spinel Nix Co1−x Al2O4 (x = 0.0 to 1.0) Nano-Catalysts for the Catalytic Oxidation of Benzyl Alcohol

Ni-doped cobalt aluminate NixCo1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) spinel nanoparticles were successfully synthesized by a simple microwave combustion method using urea as the fuel and as well as reducing agent. X-ray powder diffraction (XRD) was confirmed the formation of single phase, cubic spinel cobalt-nickel aluminate structure without any other impurities. Average crystallite sizes of the samples were found to be in the range of 18.93 nm to 21.47 nm by Scherrers formula. Fourier transform infrared (FT-IR) spectral analysis was confirmed the corresponding functional groups of the M-O, Al-O and M-Al-O (M = Co and Ni) bonds of spinel NixCo1-xAl2O4 structure. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images was confirmed the particle like nanostructured morphology. Energy band gap (Eg) value was calculated using UV-Visible diffuse reflectance spectra (DRS) and the Eg values increased with increasing Ni2+ dopant from x = 0.2 (3.58 eV) to x = 1.0 (4.15 eV). Vibrating sample magnetometer (VSM) measurements exposed that undoped and Ni-doped CoAl2O4 samples have superparamagnetic behavior and the magnetization (Ms) values were increased with increasing Ni2+ ions. Spinel NixCo1-xAl2O4 samples has been used for the catalytic oxidation of benzyl alcohol into benzaldehyde and was found that the sample Ni0.6Co0.4Al2O4 showed higher conversion 94.37% with 100% selectivity than other samples, which may be due to the smaller particle size and higher surface area.

Preparation and Characterizations of PVP–TiO 2 NPs Calcined at 500, 600 and 700 °C by the Hydrothermal Method and Their Properties

The effect of the crystalline phase PVP encapsulated titanium dioxide (TiO2) nanoparticles (NPs) to optimize the optical properties and photocatalytic activity were comparatively investigated at different calcination temperatures. The synthesized products were characterized using instrumental techniques, such as powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscope, energy dispersive X-ray, ultraviolet–visible (UV–visible), photoluminescence (PL) and vibrating sample magnetometer. The functional groups were identified by the FT-IR analyses. XRD result showed that the anatase and rutile phase structure of TiO2 NPs was confirmed. The spherical shaped morphology is predicted by the SEM analysis. The optical properties of the TiO2 NPs were studied by the UV–visible and PL analysis. The magnetic behavior of the TiO2 NPs was studied. Photocatalytic activity of TiO2 NPs was tested by the degradation of MeB dye under UV light irradiation. In addition, the chemical oxygen demand removal follows the photo degradation in behaviour was observed.

Investigation of Phase Transition in Some Ferroelectrics Calcium and Zinc Doped Diammonium Dibromodichlorinate

Single crystals such as diammonium dibromodichloro calcinate(II), (NH4)2CaBr2Cl2, and diammonium dibromodichloro zincate(II), (NH4)2ZnBr2Cl2, abbreviated as DADBDC-Ca and DADBDC-Zn, respectively, were grown successfully by solution growth method. Single crystal X-ray diffraction, thermal analysis, AC conductivity; Fourier transform infra-red (FT-IR) spectroscopy, Differential scanning calorimetry were used to characterize the grown crystals. The surface morphology and chemical composition of the compound were analyzed by SEM and EDX studies. The cell parameters and crystallinity of the grown crystals were determined using single crystal and powder X-ray diffraction analysis. FT-IR spectra are used to confirm the presence of various functional groups in the sample. The phase transition of the sample was analyzed by differential scanning analysis. The electrical conductivity for the grown crystals has been calculated through impedance at various temperatures. It can be foreseen that the transition temperature reveals the ferroelectricity of the compound. The ferroelectric characteristics of the grown crystals have been studied by PE loop tracer.

Enhanced catalytic activity, facile synthesis and characterization studies of spinel Mn–Co aluminate nano-catalysts

Undoped and Mn2+ doped CoAl2O4 (MnxCo1-xAl2O4; x = 0.0 to 1.0) spinel nanoparticles were successfully synthesized by a microwave heating method using glycine as the fuel. X-ray powder diffraction (XRD) was confirmed the cubic spinel structure. The average crystallite size of the samples was found to be in the range of 16.46 nm to 20.25 nm calculated by Scherrers formula. The nano-sized particle-like morphology of the samples was confirmed by high resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (HR-TEM) analysis. Energy dispersive X-ray (EDX) results showed the pure form of spinel aluminate structure. The band gap energy (Eg) of pure CoAl2O4 was estimated to be 3.68 eV from UV-Visible diffuse reflectance spectroscopy (DRS), and the Eg values increased with increase of Mn2+ ions, due to the smaller grain size. The magnetic hysteresis (M-H) loop showed the superparamagnetic nature, and the magnetization and coercivity values increased with increasing Mn2+ ions, which was confirmed by vibrating sample magnetometer (VSM). All compositions of the nano-catalysts were tested as catalyst successfully for the conversion of benzyl alcohol into benzaldehyde and observed good catalytic activity.

Advanced nanofibrous textile-based dressing material for treating chronic wounds

In the present work, an electrospun nanofibrous textile composed of polyurethane (PU), sodium bicarbonate (