| Nanomaterials exihibit unique electrical, optical, magnetic, and catalytic properties. Template synthesis method is an effective way to obtain nanomaterials with uniform size and regular morphology. This method possess many advantages when it was used to prepare ordered porous nanomaterials and semiconductor nanomaterials. Colloidal crystal is a common template used to to prepare oriented macroporous nanomaterials. DNA, a specific biological molecule, can also be used as template to prepare semiconductor nanomaterials. Ordered macroporous gold array (MGA) has many advantages when used as optical transparent electrode (OTE) materials, such as excellent light transmission performance, simplicity in preparation, and wide application in different solvents. Semiconductor CdS nanomaterials synthesized using DNA as a template exihibit excellent solubility, good biocompatility and high luminescence quantum yield, being superior to those synthesized in organic solvents. The CdS nanomaterials have been successfully utilized for heavy metal ion monitoring. We have carried out the following studies:(1) Oriented two-dimensional (2D) gold array was prepared through electrodepostion of gold in colloid crystal template assembled on the surface of ITO glass through vertical deposition method. The effect of electrodeposition time and means of eliminating microspheres on morphology, macroporous structure and optical property has been investigated.2D macroporous gold array was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV-vis spectrophotometry. The optimized experimental conditions involve electrodeposition of gold at-0.8V for30s and elimination of microspheres with tetrahydrofuran. As a result, ordered gold array with regular hemispherical holes and transmittance of20%have been obtained. The ordered gold pore array possesses good light permeability, and can be used as a good OTE material.(2) Thin-layer cell was fabricated using MGA as OTE. The cell thickness was estimated by thin-layer cyclic voltammogram of Fe(CN)63-/Fe(CN)64-couple and UV-vis spectrophotometry. Thin-layer electrochemical and spectroelectrochemical experiments in aqueous and nonaqueous solutions were carried out. E0’ value and n of N, N, N, N’-tetramethyl-p-phenylenediamine (TMPD) were calculated to be0.200V,0.191V (vs. Ag), respectively, and n was estimated to be1.05. Similarly, E0’ value and n of o-tolidine were determined to0.660V,0.659V (vs. Ag/AgCl), respectively, and n=1.7. The electrochemical results were consistent with the spectroelectrochemical ones. The results also indicate that the electrolytic efficiency of the macroporous gold film is higher than that of the ITO electrode. The2D MGA has good electrochemical and spectroelectrochemical properties, and can be used in various solvent systems.(3) Spectroelectrochemical measurement of TMPD was carried out using new MGA thin-layer cell. Linear extraction method was used to estimate the diffusion coefficient of the TMPD/TMPD+· couple. In the same time, the followed chemical reaction mechanism has been discussed. Do and DR of TMPD were determined to be9.29×10-6cm2/s and8.11×10-6cm2/s, respectively, using a double potential step techninque (-0.1V～0.3V～-0.1V). The rate constant was determined to be3.04×10-3s-1in acid medium.(4) CdS/DNA nanocomposites was synthesized using DNA as a template through two kinds of method. Cd2+and S2-were absorbed alternately onto the negtively charged DNA backbone via electrostatic interaction. As a result, CdS nanomaterials with good solubility and stability were obtained. The nanomaterials exhibit a strong emission peak at330nm. AFM and SEM results indicate that the nanoparticles exist mainly as rods or ellipses. The methods described herein might be extended to other types of DNA-semiconductor conjugates with tailored properties for diverse applications.(5) A highly sensitive and selective Hg2+sensor based on the use of CdS-encapsulated DNA nanocomposite has been developed. The nanocomposite exihibits a strong emission peak at330nm, which can be significantly quenched by Hg2+. Experimental conditions (e.g., pH, temperature, reaction time, and Hg2+concentration) that govern the extent of fluorescence quenching have been optimized. A detection limit of4.3nM was estimated at50℃. This novel material possesses high selectivity towards Hg2+, as a number of metal ions and anions were found to either not quench or quench the fluorescence at an insignificant level. The feasibility of the method for analysis of a waste water sample has been demonstrated. |
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