The Fabrication Of Nano-wire Arrays By AAO Template And Its Application In SERS Technique

Nano-materials are widely recognized as the most promising new materials in the 21th century, whose preparation, investigation and application are the most active field. For their especial structure, the nano-materials exhibits excellent properties in many aspects, such as mechanics, optics, electricity, acoustics, magnetics, calorifics, hydrogen saving, wave absorbing. Nowadays, many preparation methods for nano-materials have been developed, for example, arc process, catalysis thermal, laser ablation process, chemistry vapor deposition process, molecular beam epitaxy (MBE) process and template synthesis method. Template synthesis method, which can control the size and shape of the nano-materials, becomes an important method for nano-materials preparation. It expands the space and opportunity for the preparation of new functional materials, such as nano-wires or nano-tubes of metals, conduction macromolecules, magnetic materials, semiconductors. Also, this method can be used for the preparation of multilayer nano-wires, superlattice and quantum dots, which are available in the large scale integration functional materials.The surface of porous alumina template distributes holes uniform in nanometer size, and we can control diameter of the pores and hole density conveniently by changing oxidization conditions. Template is made of inorganic material and possesses heat stability and mechanical properties, so the further treatment of nano-structure is permitted, such as chemical modification, deposition, corrosion and machining property, which make it the most effective template for nano-materials. In recent years, the preparation technique and growth mechanics of AAO template and the nano-wire arrays synthesized by AAO template have become hot in the nano-materials research.The preparation of substrate is the most important in the study of surface enhanced Raman scattering (SERS). At the present time, the common methods for substrate preparation are ORC, metal-sol, chemical deposition silver island film, vacuum coating, metal-sol of laser etching and mechanical polishing. Each active substrate has both merit and drawback, such as nonuniform surface roughness, high price, disturbance of impurity ion and difficulty to control the size of nano-particles and its stabilities.In this paper, the electrochemical deposition technique was used to assemble high active metal nano-wires into the AAO nano-pores, which was uniform in the roughness, and the length can be controlled by changing parameters. This paper investigated the enhanced properties of SERS substrates with different parameters by changing pore sizes and deposition time. The CdS nano-wire arrays were prepared by AAO template and its especial optical properties were systematically studied by its phonon vibration modes.This paper consists of four chapters as follows:The first chapter briefly introduces nano-materials and nano-science, including several typical nano-materials, the properties and preparation of nano-materials, and the research history of nano-wire arrays synthesized by AAO template. The recent research situation of SERS active substrates was presented in this chapter. In the end, we introduced the value and main research content of this paper.The preparation and characterization of AAO template were presented in the second chapter. AAO templates with uniform nano-pores were prepared by the home-made electrolyte-cell, and we can control pore diameter and density conveniently by changing oxidization conditions. The scanning electron microscope (SEM) micrographs showed that the AAO template was a good tool for the preparation of uniform nano-wire arrays.The third chapter mainly investigated the preparation of silver nano-wires and their SERS spectra. Silver nano-wires were deposited into AAO nano-pores by AC deposition method, and then it was used as SERS substrate for the detection of 4-MPy molecules. The micrograph of atomic force microscope (AFM) indicated that the silver nano-wires were parallel to each other and vertical to the alumina. Good-quality SERS spectra of 4-MPy were observed, which demonstrated that the SERS intensity depended on the length of silver nano-wires emerging from the surface. However, the Raman shift was not affected by the surface conditions. The fourth chapter contains the preparation of CdS nano-wires and their SERS spectra study. The Raman spectra of CdS nano-wires demonstrated that the SERS intensity depended on the excitation wavelengths; SERS spectra of CdS nano-wires on silver substrate were observed, which indicated the signals of SERS were enhanced by silver substrate. In addition, SERS spectrum of CdS nano-wire showed that the SERS intensity was enhanced with the increasement of silver nano-wires's length, and then tended to saturable value.