Synthesis Of Gold And Silver Nanoparticles And Application In SERS And Textile Colouration

Localized Surface Plasmon Resonance (LSPR) is the unique optical character of noblenanoparticles (NPs). The LSPR of noble nanoparticles mainly depend on thecomposition, shape, size and surrounding environment. Among all the strategy tofabricate noble NPs, Photo-induced method is considered to be an effective strategy toproduce anisotropic metal NPs. The thermal effect in a photo-induced process isderived from light. To learn about the effect of temperature in a photo-inducedreaction is of importance for obtaining uniform and mono-disperse NPs. In addition tophoto-induced reaction, wet chemical method is also a popular way to synthesizemetal NPs. However, developing simple and efficient methods remain a challenge.Surface Enhanced Raman Scattering (SERS) is one application of noble NPs,however, SERS enhancement of anisotropic metal nanoparticles depends on manyfactors, including shape, size and aggregation extent, which are complex andentangled in most cases. To fairly compare difference in enhancement ability andgetting rid of interlacement of other factors, it is significant to develop a simplestrategy to probe the SERS properties of metal nanoparticles. The stabilizer play animportant role in the synthesis and application of metal NPs. Hydroxy carboxylate,citrate, malate and tartrate are nontoxic reagents and gold NPs stabilized by all aboveprove better biocompatible, which facilitates the application of metal NPs. Based onabove view, the thesis is outlined as follows:1. The role of temperature in synthesizing anisotropic silver nanoparticlesby photoinduced method.Exploring the themal and light effects in photo-induced reaction is important forfurther developing photo-induced method. Products of a photo-induced reactionstrongly depend on many factors, including the intensity and wavelength of lights, the pH and temperature and so on. We systematically investigated the effect oftemperature on photochemical reaction, which was carried out by a home-madedevice at exact temperatures. Extinction spectroscopy was used to monitor thephotochemical reaction process of synthesizing silver NPs at different temperature(10-90℃). The morphologies of resulant silver nanoparticles were characterized bytransmission electron microscopy (TEM). The results showed that the temperatureplayed an important role in the particle growth, the shape/size control and the stabilityin a photochemical reaction; the main product is nanoprisms with much faster growthrate and better stability at90℃.2. Fast synthesis of gold nanoparticles with different shape and theirapplications in SERS.A fast and easy method to synthesize gold NPs was developed by wet chemicalmethod at room temperature, resulting in dendritic and discal nanoparticles withnanometers to microns in size. Gold NPs with different sizes and shapes can beprepared by adjusting the ratio between the reducer (Coumarin480) and the precursor(HAucl4). Fixing chloroauric acid concentration (9.8×10-5M) and the reducing agentis increased, the as-prepared particles are similar to spherical, however, increasing theconcentration of chloroauric acid continuously to2.94×10-4, discal NPs are obtainedand the particle size became smaller. In contrast, increasing the amount of chloroauricacid, the main product is dendritic NPs. By comparing SERS intensity of the threedifferent shaped gold nanoparticles, we find the dendritic structure displayed thestrongest enhancement to4-MPY.3. Comparison of Surface-Enhanced Ramans scattering spectra on twokinds of silver nanoplate films.The shape of noble metal NPs has great impact on SERS Substrates. Weexplored the relationship between LSPR and SERS activity of assembled silver filmwith different shape. Shape conversion from silver nanoprisms to nanodisks on slideswas in situ carried out by heating. SERS spectra on silver nanoprisms and nanodiskswere compared under different excitation lines and the difference in SERS intensitieswas discussed. It is demonstrated that SERS signals were greatly enhanced when theSPR band of a SERS substrate overlapped with the wavelength of excitation laser; theEM mechanism dominated SERS enhancement. The observation about therelationship of LSPR and SERS enhancement is in favor of further development of SERS mechanism and fabrication of optimal SERS substrates.4. Using hydroxy carboxylate to synthesize gold nanoparticles in heating andphotochemical reactions and their application in textile colouration.Citrate, malate and tartrate can be used to synthesize gold NPs using heating andphotochemical methods. NPs synthesized by the heating method from citrate weremore uniform than those from malate and tartrate by the same method. The formationrates of gold NPs by heating were influenced considerably by the pH of solutions; therate increased with a decrease of pH. NPs from photochemical synthesis were eggshaped and non-uniform regardless of the ligand used. The colour of the NPs may betuned by particle size, which is affected by ligand and synthesis method. Gold NPscan be used to colour wool fabric, silk and nylon fibres using conventional exhaustdyeing from a slightly acidic bath.