Journal of Nano Structures
Volume:1 Issue: 3, Autumn 2012

Fabrication and electrochemical characterization of a sensor for the determination of epinephrine (EP), uric acid (UA) and folic acid (FA) is described. The sensor was prepared using carbon paste electrode (CPE) modified with 3,4-dihydroxybenzaldehyde-2,4- dinitrophenylhydrazone (DDP) and carbon nanotubes (CNTs), which makes the modified electrode highly sensitive for the electrochemical detection of these compounds. Cyclic voltammetry (CV) at various scan rates was used to probe the fabrication and characterization of the modified electrode. In order to characterize these new modified electrode, the electroanalytical response was evaluated for EP performing cyclic voltammetry, differential pulse voltammetry and chronoamperometry experiments. Under the optimum pH of 7.0, the oxidation of EP occurs at a potential about 215 mV less positive than that of the unmodified CPE. Differential pulse voltammetry (DPV) of EP at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 70 nM. DPV was used for simultaneous determination of EP, UA and FA at the modified electrode, and quantification of EP in some real samples by the standard addition method.

Silica coated magnetite nanoparticles were covalent grafted with 3- aminopropyl trimethoxysilane to give APTSCMNPs. Reaction of the resulted nanomaterial with 4-formyl benzo-12-crown-4 ether afforded FB12C4/APTSMNPs nanocomposite material in which the crown ether moiety was attached through propyl chain spacer. Characterization of the prepared nanocomposite was performed with different physicochemical methods such as FT-IR spectroscopy, thermogravimetric analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM).

Beryllium oxide (BeO) nanopowder was synthesized using sol-gel method and the effects of changes of chemical reagents were investigated. Because of tissue equivalence and other outstanding thermoluminescence (TL) properties of the bulk material in X and γ dosimetry, the applicability of this nanostructure in TL dosimetry was studied following irradiation to the 137Cs source. The TL glow curve of this nanoparticle shows 3 component glow peaks at 391, 429 and 481 K. Computerized glow curve deconvolution program was used for obtaining the number of constituent glow peaks and trapping parameters. Activation energies of three components were obtained to be 1.4, 1.39 and 1.39 eV with kinetic orders of 2.03, 2.12 and 2.09 respectively. TL dose response of this phosphor is also investigated.

The interaction between nano-SiO2 and lysozyme was investigated by the method of UV-Visible detection and fluorescence spectroscopic techniques. The thermal denaturation of lysozyme has been investigated in the presence and absence of nano-SiO2 over the temperature range (293-373) K in different buffers and pH values, using temperature scanning spectroscopy. The presence of nano-SiO2 caused the destabilization of lysozyme resulting in a decrease in the temperature of unfolding with an increase in nano-SiO2 concentration.

The effective parameters of (5, 0) and (5, 5) single-wall carbon nanotubes during the interaction with carbon dioxide as sensors are determined. The interaction of carbon dioxide molecules with internal and external walls of the nanotubes is studied using Gaussian 03 coding by density functional theory (DFT) at the B3LYP/6-311G level of theory. CO2 rotation around tube axles vertically and parallel to the internal and external walls has been investigated. The carbon dioxide molecule is predicted to bind only weakly to nanotubes, and the tube-molecule interactions can be identified as physisorption. CO2 adsorption is stronger on external wallsthan on internal walls, and adsorption on the external wall of (5, 0) is stronger than on the external wall of (5, 5); the adsorption energies are exothermic and equal to -0.8884 and -0.0528 kcal/mol, respectively. The rotation energy barrier for (5, 5) is lower than that for (5, 0) in all rotations, therefore in these interactions (5, 5) is more active. The energy gap significantly changes in the presence of carbon dioxide molecules on the inside surface of (5, 0) and the electric conductivity is affected, but no remarkable change is observed in the electronic structure of (5, 5).

Intercalation of lithium into Ag-CNTs sample is reported here. We have used a nano-porous silver foam as a frame for deposition of the CNTs inside the pores by electrophoresis deposition (EPD) technique. By using chronopotentiometry method, we have noticed that the Li storage capacity of the prepared Ag-CNTs electrode was improved noticeably in comparison with literature. In addition, a very good functional stability for the prepared electrode has been tested during subsequent cycles of charge / discharge (C&D) procedures. By scanning the cycle's regulated current from 0.2 up to 1.0 mA, it was shown that in the range of 0.4–0.6 mA reversibility of the C&D capacity became optimum and the voltage profiles were converged, as well.

ZnS nanoparticles were synthesized via a simple surfactant free microwave route. In this synthesis, thioacetamide was used as sulfur source. The effects of different parameters such as type of zinc precursor, time and power of irradiation on the morphology and particle size of the products have been investigated. The nanostructures were characterized by means of X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopy.

In this study, the TiO2 nanorods were synthesized from P25 TiO2 nanoparticles by hydrothermal method in 10 M NaOH solution. The effects of annealing temperatures on produced nanorods were investigated by scanning electron microscopy (SEM) X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Diameter growth and changes of surface oxygen defects of synthesized nanorods are studied with increasing annealing temperatures.

The efficient and environmentally friendly method for the one-pot synthesis of polyhydroquinolines has been developed in the presence of CuO nanoparticles. The multi-component reactions of aldehydes, dimedone, ethyl acetoacetate andammonium acetate were carried out under solvent-free conditions to afford some polyhydroquinoline derivatives. This method provides several advantages including high yields, low reaction times and little catalyst loading.

CoNi nanowires were deposited by pulsed electrodeposition technique into porous alumina templates. The effect of off time between pulses (toff) and reductive/oxidative time (treduc/oxid) on the microstructure and magnetic properties of the CoNi nanowires were investigated. Maximum coercivity and squareness were obtained for samples fabricated at treduc/oxid= 0.5 ms and toff =400 ms. The coercivity increases in the range of 930–1990Oe by increasing of off time from 20 to 400 ms. The initially hcp structure of the nanowires was converted to an amorphous structure by increasing of off time between the pulses.