Preparation And Propertities Of Gold/Silver Low-dimensional Nanomaterials And Their Composites

As the body's inherent chromophores such as hemoglobin, water, almost have no absorption in the near-infrared light (NIR) (650-900nm), Irradiated by the NIR,we can get the maximum penetration depth and the smallest damage to healthy cell. Hence the NIR therapy and imaging methods are applied to the field of biology. However, highly efficient of the transformation from the light to heat is the key factor for thermotherapy. The properties of light absorption and light scattering of noble metal nanomaterials depends on the shape, size, composition of the nanomaterials . The superficial plasma resonance absorption (SPA) peak can be turned to the NIR region by the regulation the parameters of the nanomaterials, which is providing a new mean for the tumor thermotherapy.In this paper, in order to achieve nanomaterials for the purpose of biological functions, The adjustable SPA of noble metal nanoparticles were synthesized by a simple and effective wet chemical method. We had prepared gold nanorods with biological hyperthermia value, by controlling the aspect ratio gold nanorods, the longitudinal SPA peak of gold nanorods shifted to NIR region; At the same time, A new mesoporous silica drug carrier with the function of light-control drug delivery was synthesized through coating mesoporous silica on the surface of the gold nanorods ; Furthermore we studied the influence of concentration effect and Au coating on photoluminescent properties of YVO4:Eu3+ NPs Colloids. The main results are as follows:1. The silver and gold nanorods were prepared by seed growth method. First, The small spherical noble metal nanoparticles were prepared by reduction of the noble metal salt solution with NaBH4 in the presence of sodium citrate. The sodium citrate served as a stabilizing agent and sodium borohydride as a reducing agent. This seed solution was used for the synthesis of noble metal nanorods. We made use of CTAB surfactant and the weak reducing agent AA to reduce the metal salt solution. As the seeds provide attachment points for the growth of nanorods, the one dimensional rod like structure of nanomaterials were synthesized under the control of CTAB. By controlling the reaction conditions, we obtained high yields of pure gold and silver nanorods materials. The surface morphology of the nanomaterials were measured with field emission scanning microscope (FESEM), transmission electron microscopy (TEM). Ultravioiet-visible-nearinfrared(UV-Vis-NIR) absorption spectra were measured to explore its near-infrared absorption characteristics. The experimental results show that SPA of gold nanorods was turned to the NIR region, which is a good material for thermotherapy.2. By the hydrolysis of TEOS in alkaline conditions (PH = 10), the surfaces of gold nanorods were coated with layers of SiO₂ shell. the thickness of the SiO₂ shell can be controlled by changing the growth time or the concentration of TEOS. Furthermore through the two-step synthesis method, reasonably controlling of the critical micelle concentration of CTAB reaction temperature, time, concentration of reactants, PH value and other factors, We have successfully synthesized gold nanorods coated with mesoporous silica. The FESEM, TEM, absorption spectra, XRD, adsorption-desorption characterization methods show that we have successfully prepared AuNRs @ MCM-41. This material not only has the drug carrying pore of mesoporous silica, but also has SPA characteristics of gold nanorods .The gold nanorods can absorb NIR and convert it to heat, this heat can affect the rate of drug release , achieving light controlled drug release purposes. This is a new dual functional materials, which is not reported in any literatures whether at home or abroad. It is an innovative point of our experiments, this new material is expected to apply in NIR controling drug delivery .3.The YVO₄:Eu³⁺ and YVO₄:Eu³⁺@Au nanoparticles (NPs) colloids were prepared by a wet chemistry method and characterized by X-ray diffraction (XRD), field emission scanning electron microscope(FE-SEM),transmission electron microscopy (TEM) and UV-vis absorption spectra. The influence of particle concentration and Au coating on the photoluminescence properties of the colloids was studied on emphasis. It was interesting to observe that in the colloid phase the location of excitation bands induced by the energy transfer (ET) from the VO₄^3- groups to Eu³⁺ gradually shifted to red with the concentration increase of YVO₄:Eu³⁺ NPs, while the intensity of the bands demonstrated an optimum value and the luminescent decay dynamics gradually deviated from exponential functions owing to the strong interactions among YVO₄:Eu³⁺ NPs. After coating with Au shells, the luminescent intensity for the ET excitation at 269-nm increased nearly 2 times, which was mainly attributed to the isolation effect among YVO₄:Eu³⁺ NPs. This work is very helpful of understanding the photoluminescence properties of rare earth (RE) doped NPs in the colloids. Here, we should point out that in molecular solutions of Eu(TTA)₃·2H₂O complex, the concentration effect induced spectral change was also observed.28 The present NPs are much larger than the complex molecules, it is interesting to observe such a significant spectral change induced by concentration effect. Herein, we can claim that the variation of excitation band location and the emission intensity of ⁵D₀-⁷F_J are definitely induced by the change of YVO₄:Eu³⁺ NPs concentration. Here, we highlight that such a significant spectral change on concentration of NPs has never been literatured in previous references related to RE-doped NPs solutions, to the best of our knowledge.