Spectroscopic Studies Of Single Molecules And Halide Ions

Single-molecule spectroscopy was applied to the study of an important problem in surface-enhanced Raman scattering (SERS). One important consequence of this type of research is explaining of adsorption mechanism; then, the key important problem is that improve enhance of substrate in single-molecule. Several experiments have shown that added halide anions into silver sol can dramatically affect the SERS intensity of detected single-molecule. this paper discuss enhance substrate of single-molecule in two aspects.SERS is a highly sensitive technique for probing the interfacial phenomena and the behavior of molecules adsorbed on metal nanoparticles surface. It shows from the experiments that the vibrational modes of molecules were greatly increased, especially appeared and even split as prediction of electromagnetic enhancement (EM) theory. It may provide a good reason for us to be optimistic that the template synthesis will be an advantageous tool to fabricate the new SERS active substrates which applied to the single molecule field.In recent years, observation of the surface-enhanced Raman scattering (SERS) effect at the surfaces of silver particles have aroused new interest in re-investigating the characteristics of silver sol. Furthermore, recent studies have demonstrated that the SERS enhancement factor excited in the near-infrared (NIR) region is even higher than that in the visible range. However, some experiments approved that the observations of SERS and the surfaces plasmon resonance absorption (SPA) band changed by adding halide ions.Different chemical reduction methods and laser ablation method were used to prepare Ag nanoparticles, and by transmission electron microscope (TEM), Raman detector, UV-Vis absorption and fluorescence spectrometers, we analyzed the influences of size, shape, concentration and added species to their absorptions, luminescence and SERS signals.The influence of adding halogen anion to the gray silver sol on light absorption of the colloid was studied. It was found that a new absorption band appeared on the longer wavelength region at about 1000 nm with the addition of ion to the modified silver particles, and that the original surfaces plasmon resonance absorption band was reduced. Synchronously, the linear-chain aggregation caused by adding ion leads to an apparent blue shift of the surfaces plasmon resonance absorption peak, and the surfaces of colloidal silver particles were covered with an atomic group layer which had some kind of structure. Furthermore, it is noted that different halogen ions bring the affect of the Raman spectra in the silver colloids, then can be deduced probable mechanism in the process.In this paper, we have independently measured that the SERS enhancement for single RhB molecules adsorbed on silver tips. With this the silver-gilt Anodic Aluminum Oxide (AAO) substrate which was made completely by pulsed laser deposition (PLD) deposited and electrochemical eroded. This non-aqueous substrate provides new possibility for studying adsorption behavior of many other molecules with high activity.