Mohammad Mahbub Rabbani

Photocatalytic Activity of Electrospun PAN/TiO₂ Nanofibers in Dye Photodecomposition

Poly(acrylonitrile) (PAN) nanofibers containing different amounts of titanium dioxide (TiO₂) have been prepared by electrospinning technique. Photocatalytic activity of these electrospun PAN/TiO₂ nanofibers and the effect of TiO₂ content on the photocatalytic efficiency of PAN/TiO₂ nanofibers have been evaluated by monitoring the photodecomposition of fluorescein dye, rhodamine B and methylene blue under UV irradiation with respect to irradiation time. Moreover, the effect of hydrogen peroxide (H₂O₂) on the photocatalytic behavior of PAN/TiO₂ nanofibers has also been investigated. The results showed that PAN/TiO₂ nanofibers are effective photocatalyst and their photocatalytic efficiency increases with the increase of TiO₂ content in the PAN/TiO₂ nanofibers. It is also observed that the presence of H₂O₂ significantly enhances the photocatalytic ability of PAN/TiO₂ nanofibers. The morphology and the photocatalytic behavior of the PAN/TiO₂ nanofibers containing different amounts of TiO₂ nanoparticles have been investigated by field-emission scanning electron microscopy (FE-SEM) and UV/Visible spectroscopy, respectively.

Synthesis and Characterization of Methyltriethoxysilyl-Mediated Mesoporous Silicalites

A series of mesoporous silicalites was synthesized using different compositions of tetraethylorthosilicate and methyltriethoxysilane (MTES) as the silica source. Cetyltrimethylammonium bromide was used as the organic template. Their detailed pore structures were investigated by transmission electron microscopy, X-ray diffraction, and N2 adsorption method. The thermal properties of these silicalites were studied by thermogravimetric analysis. The increased amount of MTES destroyed mesoporous channels and reduced pore sizes from 3.4 nm to 2.8 nm in calcined silicalites. The calcined silicalite transformed completely into an amorphous state at 30% MTES loading. Methyl pending groups of MTES hindered the structural ordering of ≡Si-O- frameworks, resulting in an amorphous structure. This was caused by the insufficient formation of supramolecular assembly with the organic template. No capillary condensation step was found in MS 7/3 silicalite. The other capillary condensation steps shifted toward the lower relative pressure with increasing MTES content, indicating the reduction of pore sizes.

Electrospinning Fabrication of Poly(vinyl alcohol)/TiO 2 Nanofibers

Poly(vinyl alcohol) (PVA)/titanium dioxide () composite nanofibers were produced at different concentrations (0.5, 1 and 1.5 wt.%) using the electrospinning method. The parameters of electrospinning including polymer contents, voltage and tip-to-collector distance (TCD) were optimized for fabrication process. The study showed that 7.5 wt.% PVA, 15 kV applied voltage and 15 cm TCD are the best condition to obtain uniform PVA/ nanofibers. nanoparticles give significant effect in fiber morphology. content increases the diameter of the fibers and roughen the fiber surfaces. The PVA/ nanofibers were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD).

Optimum Conditions for the Fabrication of Zein/Ag Composite Nanoparticles from Ethanol/H2O Co-Solvents Using Electrospinning

The optimum conditions for the fabrication of zein/Ag composite nanoparticles from ethanol/H2O cosolvents using electrospinning and the properties of the composite were investigated. The zein/Ag nanoparticles were characterized using field-emission scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis. The antibacterial activity of the zein/Ag composite nanoparticles was also investigated. The XRD patterns and TEM images indicate the coexistence of a zein matrix and well-distributed Ag nanoparticles.

Electrochemical Characterization of Multilayered CdTe/ PSS Films Prepared by Electrostatic Self-assembly Method

Multilayered CdTe/PSS films were prepared by the electrostatic self-assembly method in an aqueous medium. Positively-charged cadmium telluride (CdTe) nanoparticles and anionic polyelectrolyte, poly (sodium 4-styrene sulfonate) (PSS) were assembled alternately in order to build up a multilayered film structure. A linear proportion of absorbance to the number of bilayers suggests that an equal amount of CdTe was adsorbed after each dipping cycle, which resulted in the buildup of a homogenous film. The binding energies of elements (Cd and Te) in multilayered CdTe/PSS film shifted from those of the CdTe nanoparticles in the pure state. This result indicates that the interfacial electron densities were redistributed by the strong electrostatic interaction between the oppositely-charged CdTe and PSS. Electrochemical properties of the multilayered CdTe/PSS films were studied in detail by cyclic voltammetry (CV).

Preparation and Characterization of CdSe-Decorated Multiwalled Carbon Nanotube Composites

Composites of carboxylated multiwalled carbon nanotubes (c-MWNTs) and CdSe nanoparticles were prepared by the electrostatic interaction. CdSe nanoparticles were stabilized by 2-(dimethylamino)ethanethiol hydrochloride to develop positive charges on their surfaces in aqueous solution. The structural characteristics of these composites were analyzed using X-ray diffraction (XRD), and transmission electron microscopy (TEM). Ultraviolet/visible (UV/vis) spectra of c-MWNT–CdSe composites showed the characteristic bands at ~250 nm. These results indicate that the energy state of c-MWNTs is significantly modified, which was caused by the homogeneous distribution of CdSe nanoparticles in c-MWNTs, and the bond formation between c-MWNTs and CdSe nanoparticles. The photoluminescence (PL) of CdSe nanoparticles in the composites was characterized in comparison with that of CdSe nanoparticles. PL of CdSe in c-MWNT–CdSe composites was collected at ~568 nm in solution, but disappeared in powder state.