ZnO nanoparticles (NPs) with size less than 100 nm were successfully prepared by a hybrid electrochemical-thermal method using metallic zinc and NaHCO 3 without the use of any zinc salt, template or surfactant. The NPs were characterized by Fourier transform infra-red (FT-IR) spectroscopy, UV-visible spectroscopy, photoluminescence spectroscopy (PL), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. UV-visible spectral analysis indicated that the particle size increased with increasing calcination temperature. The band gap (3.91-3.83 eV) was higher for synthesized ZnO NPs than their bulk counterparts (3.37 eV). The FT-IR spectra at different calcination temperatures showed the characteristic band for ZnO at 450 cm -1 to be prominent with increasing temperature due to the conversion of precursor into ZnO. The wurtzite hexagonal phase was confirmed by XRD analyses for ZnO NPs calcined at 700 o C. The green photoluminescent emission from ZnO NPs at different calcination temperatures is considered to be originated from the oxygen vacancy or interstitial related defects in ZnO. SEM images clearly showed that the NPs are granular and of almost uniform size when calcined at higher temperatures. EDX spectra further confirmed the elemental composition and purity of ZnO obtained on calcination at 700 o C. The NPs are well dispersed near or above calcination temperature of 700 o C.

Activated carbon was prepared from vegetable wastes collected from the residential halls of University of Dhaka, Bangladesh. The carbon, produced by pyrolysis of vegetable wastes at 400 o C to 600 o C for 30 min under N 2 atmosphere, was chemically activated with zinc chloride. The activated carbon samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR). Topographical and morphological characteristics were examined by Scanning Electron Microscopy (SEM). The surface area of the activated charcoal was determined by adsorption of Methylene Blue from alcoholic solution and was found to be 53 m 2 g -1 . The zero point charge (pH zpc ) was also determined by pH titration means and obtained to be 6.10±0.1 at ambient temperature. Analyses of these experimental data lead us to conclude that the activated carbon prepared from vegetable wastes materials is a high grade active carbon in comparison with commercially available one. Activity of generated active carbon as an adsorbent was tested through adsorption of Pb(II). The results indicate that adsorption of Pb(II) on active charcoal was very fast and it followed Langmuir type of adsorption isotherm, and the dimensionless separation parameter, R L , was found to be 0

Polyaniline-silica (PAni-silica) composite material with 40% silica was prepared by polymerization of aniline in a medium consisting of colloidal silica, freshly prepared by hydrolysis of sodium silicate at room temperature at pH 6.5. The physico-chemical properties of both PAni and the composite material, PAni-silica were studied by FT-IR and transmission electron microscopy and measurements of BrunauerEmmett-Teller (BET) isotherms. PAni-silica composites showed inhomogeneous pore distribution, although PAni has no significant pores.Average pore size of PAni-silica was 280 and 175 Å during adsorption and desorption of nitrogen, respectively. The interactions of PAnisilica composite and PAni with saturated hydrocarbons were investigated by inverse gas chromatography. The composite material was found to be efficient for separation of a mixture of hydrocarbons, in the range of C 5 -C 9 , owing to large BET surface area. Enthalpy of adsorption of the individual hydrocarbons was evaluated from an analysis of the retention time and the flow rate of the carrier gas. For PAni, the enthalpy of adsorption was very low; however, the value for the composite material was found to be comparable to the enthalpy of evaporation of the individual hydrocarbons.

Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014

Nanocrystalline Fe3O4 and Fe2O3 particles were successfully synthesized by an innovative hybrid electrochemical-thermal method. The as-prepared compound was calcined for an hour from 100 to 600oC temperatures. The crystallinity, morphology and chemical state of the synthesized powders were characterized by XRD, TG-DTA, SEM/EDS, FT-IR, and UV–Vis spectral techniques after calcinations. The Brunauer–Emmett–Teller (BET) plots confirmed that iron oxide nanoparticles (NPs) calcined at 400oC has a surface area of 18.28 m2 g-1 with a total pore volume of 0.2064 cc g-1. From XRD pattern it is revealed that the precursor calcined at lower temperature (100-400oC) correspond to Fe3O4,while the ones calcined at higher temperature follow Fe2O3 pattern. The morphology of iron oxide NPs calcined at different temperatures were studied with scanning electron microscope (SEM) and exhibits spherical shaped geometries with average diameters of 80-150nm. Bangladesh J. Sci. Ind. Res.55(3), 221-228, 2020