A. H. Naqvi

Comparative study of the cytotoxic and genotoxic potentials of zinc oxide and titanium dioxide nanoparticles

Nanoparticles (NPs) of zinc oxide (ZnO) and titanium dioxide (TiO2) are receiving increasing attention due to their widespread applications. The aim of this study was to evaluate the toxic effect of ZnO and TiO2 NPs at different concentrations (50, 100, 250 and 500 ppm) and compare them with their respective salts using a battery of cytotoxicity, and genotoxicity parameters. To evaluate cytotoxicity, we have used human erythrocytes and for genotoxic studies human lymphocytes have been used as in vitro model species. Concentration dependent hemolytic activity to RBCs was obtained for both NPs. ZnO and TiO2 NPs resulted in 65.2% and 52.5% hemolysis at 250 ppm respectively indicating that both are cytotoxic to human RBCs. Antioxidant enzymes assays were also carried out in their respective hemolysates. Both nanoparticles were found to generate reactive oxygen species (ROS) concomitant with depletion of glutathione and GST levels and increased SOD, CAT and lipid peroxidation in dose dependent manner. ZnO and TiO2 NPs exerted roughly equal oxidative stress in terms of aforementioned stress markers. Genotoxic potential of both the NPs was investigated by in vitro alkaline comet assay. DNA damage induced by the NPs was concentration dependent and was significantly greater than their ionic forms at 250 and 500 ppm concentrations. Moreover, the nanoparticles of ZnO were significantly more genotoxic than those of TiO2 at higher concentrations. The toxicity of these NPs is due to the generation of ROS thereby causing oxidative stress.

SYNTHESIS, STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF IN-SITU SYNTHESIZED POLYANILINE/SILVER NANOCOMPOSITES

Polyaniline (PANI) is recognized as one of the most important conducting polymers due to its high conductivity and good stability. In this paper, polyaniline/silver (PANI/Ag) nanocomposites were synthesized by in-situ polymerization of aniline using ammonium peroxydisulphate (APS) as oxidizing agent with varying concentration of Ag nanoparticles colloids (0 ml, 25 ml and 50 ml). Silver nanoparticles were synthesized separately in colloidal form from silver nitrate (Ag2NO3) with the help of reducing agent sodium borohydride (NaBH4). The PANI/Ag nanocomposites were characterized by XRD, SEM, AFM, UV-visible, temperature dependent resistivity and dielectric measurements. All samples show a single phase nature of the nanoparticles. The electrical resistivity as function of temperature was measured in the temperature range 298–383 K, which indicates a semiconducting to metallic transition at 373 K and 368 K for 25 ml and 50 ml silver colloid samples, respectively.

Graphene based magnetic nanocomposites as versatile carriers for high yield immobilization and stabilization of β-galactosidase

The present study demonstrates an efficient method for high yield immobilization of Aspergillus oryzae β-galactosidase onto graphene-iron oxide nanocomposites (Gr@Fe3O4 NCs) by a simple adsorption mechanism. The synthesized nanocomposites were characterized by X-ray diffraction and FT-Raman spectroscopy, and by vibrating sample magnetometry. The binding of the enzyme onto the nanocomposites was confirmed by transmission electron microscopy, scanning electron microscopy, and Fourier transform-infrared spectroscopy. The bound enzyme showed 90% immobilization yield. The adsorbed and free enzyme both exhibited the same pH-optima at pH 4.5. However, the immobilized enzyme showed enhanced pH stability toward acidic and basic extremes, as well as increased temperature resistance as compared to native β-galactosidase. The Michaelis constant, Km decreased, while Vmax increased, which indicates a higher affinity and activity retention by immobilized β-galactosidase. The bound enzyme retained 83% activity even after its 8th successive reuse. The adsorbed enzyme lost only 21% of its initial activity during storage at 4 °C, while the free β-galactosidase retained only 49% activity under similar storage conditions. The genotoxicity assessment revealed that the nanocomposites showed negligible toxicity to pBR322 DNA plasmid and human lymphocytes. In view of its easy production, non-toxic nature, improved stability against various denaturants and excellent reusability, the versatile Gr@Fe3O4 NCs can serve as an ideal support for the immobilization of other enzymes as well, and it may find applications in constructing biosensors and producing lactose-free dairy products to feed lactose intolerant patients.

SYNTHESIS AND CHARACTERIZATION OF Al DOPED ZnO NANOPARTICLES

Undoped and Al-doped ZnO (AZO) nanoparticles (NPs) have been successfully synthesized by the simple sol-gel method. The NPs have been characterized by a number of techniques as x-ray diffraction (XRD), UV-visible spectroscopy and scanning electron microscopy (SEM) at room temperature for 0%, 0.5%, 1% and 2% of Al concentration. The structural characteristics were examined using XRD and SEM with EDS. XRD analysis reveals that all samples crystallizes in polycrystalline nature with wurtzite lattice and exhibit no other impurity phase. The average crystallite size decreases with increase in Al concentration. The absorption spectra indicate increase in optical energy gap (Eg) with increase in Al ion doped into the ZnO lattice site.

Structural, optical and transport properties of transition metals doped (A: Co, Ni and Cu) BiFe0.9A0.1O3

Nanoparticles of pure and Transition metals doped (Co, Ni and Cu) BiFeO3 of the composition BiFe0.9A0.1O3 (A = Co, Ni and Cu) have been successfully synthesized by sol gel auto combustion method using citric acid as a chelating agent and calcinated at 300°C. Microstructural analyses were done by XRD, TEM and SEM techniques. The crystallite size was resolute by powder X-ray diffraction technique whereas, UV-VIS technique was used to study the optical properties and band gap (Eg) of all samples. The variation of a. c. conductivity has been studied as function of frequency. It was observed that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. It was also observed that doping of Transition Metals affects the optical properties effectively and band gaps were also increased.

Auto-combustion synthesis and characterization of Mg doped CuAlO2 nanoparticles

The synthesis of pure and Mg doped Copper aluminumoxide CuAlO2nanoparticles, a promising p-type TCO (transparent conducting oxide) have been done bysol gel auto combustion method using NaOH as a fuel, calcinated at 600°C. The structural properties were examined by XRD and SEM techniques. The optical absorption spectra of CuAlO2 sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The crystallite size was determined by powder X-ray diffraction technique. The electrical behavior of pure and Mg doped CuAlO2 has been studied over a wide range of frequencies by using complex impedance spectroscopy.The variation of a.c. conductivity has been studied as function of frequency and temperature. The data taken together conclude that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. Mg doping affects the optical properties and band gap.

Fabrication of transparent cellulose acetate/graphene oxide nanocomposite film for UV shielding

In this work, we have fabricated transparent cellulose acetate/graphene oxide nanocomposite (CAGONC) films for ultraviolet radiations (UVR) shielding. Graphene oxide (GO) was synthesized by modified Hummer’s method and CAGONC films were fabricated by solvent casting method. The films were analyzed using characterization techniques like x-ray diffraction (XRD), energy dispersive x-ray (EDX) equipped scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and ultra-violet visible (UV-VIS) spectroscopy. Four films were prepared by varying the wt% of GO (0.1wt%, 0.2wt% and 0.3wt%) with respect to cellulose acetate (CA). UV-vis measurements exhibit optical transparency in the range of 76-99% for visible light while ultra-violet radiation was substantially shielded.

Influence of Ce doping on optical and dielectric properties of TiO2

Rare earth ion (Ce) doped TiO2 and pure TiO2 nanostructured were prepared by sol gel acid modified technique and calcinated at 450°C. Microstructural studies and thermal analysis were carried by XRD and TGA respectively. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.04 eV and 3.14 eV for pure and Ce doped TiO2 respectively. Room temperature dielectric constant (e’) decreases abruptly at lower frequencies owing to the charge transport relaxation. The observed behavior of the dielectric properties can be attributed on the basis of Koop’s theory based on Maxwell-Wagner’s two layer model in studied nanoparticles.

Microstructural, optical and electrical properties of LaFe0.5Cr0.5O3 perovskite nanostructures

Perovskite nanocrystalline powder of LaFe0.5Cr0.5O3 was synthesized by sol-gel combustion route and characterized by x-ray diffractometer (XRD), scanning electron microscopy (SEM) equipped with EDS, UV-visible and LCR meter at room temperature Rietveld refinement of the XRD data confirms that the sample is in single phase-rhombohedral structure with space group R-3C. SEM micrograph shows clear nanostructure of the sample and EDS ensures the presence of all elements in good stoichiometric. The optical absorption indicates the maximum absorption at 315 nm and optical band gap of 2.94 eV was estimated using Tauc’s relation. Dielectric constant (e’) and loss were found to decrease with increase in frequencies. The dielectric behavior was explained on the basis of Maxwell-Wagner’s two layer model.

Room Temperature Optical and Dielectric Properties of Sr and Ni Doped Lanthanum Ferrite Nanoparticles

Strontium and nickel doped lanthanum ferrite (LaFeO3) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (e’) decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop’s theory based on Maxwell-Wagner’s two layer model in studied nanoparticles.