The Preparation Of Nanoparticles And Its Application In Surface Enhanced Raman Spectroscopy Used (sers) On Application Research

Raman scattering is a kind of vibration spectroscopy．The intensityof the normal Raman is very weak，which limits the application ofdetecting actual samples．Surface-Enhanced Raman Scattering (SERS)can improve Raman signal to4~7orders of magnitude and has highersensitivity． Moreover， SERS shows the advantage of giving theinformation of molecular detection on the surface of substrate，so it hasimproved the application of Raman spectroscopy in the scientificresearch field．The synthesis of metal nanoparticles as SERS substrates isthe key to SERS applications．Rough surface of electrode，nanoparticlesand the nano-island film are usually used as the SERSsubstrates． Particularly, metal nanoparticles due to the betterenhancement factor are good substrates．The stability of nanoparticleswill be strengthened after adding stabilizer which preventsnanoparticles from aggregation． Phytic acid (IP6) and its salts areeconomical and ‘green’ reagents and liable to chelate with metalions because of its structure containing six phosphates separately onboth sides of the cyclohexane．On the other hand，IP6molecules canform into the micelle themselves and some free phosphates remainingon the outside of the micelle．IP6micelles act as a stabilizer andcontroller in the process of synthesis of nanoparticles．The main contentsof this article are as follows：In chapter2，the tri-sodium citrate is used as the reduction regent，and IP6acts as a stabilizer and controller to synthesize the bigger Agnanoparticles (d=80nm)，then this Ag nanoparticles are used as thereduction regent to reduce HAuCl4． By altering the feed ratio ofAg-seed and additional HAuCl4we obtain some differentsamples(sample1, sample2, sample3, sample4)．The as-made samples are investigated by Uv-vis spectroscopy， transmission electronmicroscope (TEM) and SERS．The sample3which is synthesized byadding5mL HAuCl4has the main SPR absorption at520nm, showingthat the sample3is gold-nanoparticles．TEM image for sample3showsthat the morphology of the as-made gold nanomaterials is spherical，and the diameter is40-50nm with uniform size．In addition，this goldnanostructure with high sensitive Raman detection is applied as SERSsubstrate with a long-term stability of4months and the limit of detection(LOD) of7×10-9mol.L for R6G．In chapter3，using IP6as stabilizer and controller，L-ascorbic acidacts as the reduction regent to synthesize the Ag nanoparticles．The Agnanoparticles are then used as reduction regent to reduceHAuCl4． With different dosage of HAuCl4we prepare differentsamples(sample1, sample2, sample3)．TEM images show that sample3which is prepared adding1mL HAuCl4is shell structure with thediameter100nm and reasonably uniform size．Uv-vis spectroscopicexperiment is conducted to demonstrate the SPR property．R6G is usedas the probe molecular to investigate the SERS property of thosenanoparticles，and result shows that the shell nanoparticles possess SERSactivity．So，the shell structure alloy nanoparticles could be used as thecarrier to detect drug molecules．In chapter4， preparation of Au-Ag alloy nanoparticles usingone-step method is the main content of the work．IP6acts as a stabilizerand tri-sodium citrate is used as the reduction regent．Different samplesare reached with adding different ratio of AgNO3and HAuCl4．Theresulting alloy nanoparticles are investigated by transmission electronmicroscopy (TEM) and Uv-vis spectroscopy．TEM images show that theas-made alloy nanoparticles are spherical Structure and the diameter(d=20nm) is reasonably uniform．The nanoparticles which are reached by adding more HAuCl4（Au:Ag=3:1）present a certain aggregation,and produce lots of ‘hot spot’ which can enhance the SERSsignals．From the Uv-vis spectra，we can find that the SPR of alloynanoparticles is tunable． Using R6G as the probe molecular toinvestigate the SERS activity， result demonstrates that the alloynanoparticles which contain higher ratio Au exhibit good SERS activity，which is in accord with TEM．The method that is used in this work is verysimple and time-efficiency．The resulting colloidal alloy nanoparticlesexhibit large enhancement for SERS signal．...