Preparation Of Ultra-small Gold Nanoparticles By Flash Nanoprecipitation

Flash nanoprecipitation(FNP),is a new technology for rapidly preparing nanoparticles.Compared with traditional preparation method,FNP can quickly prepare nanoparticles with more uniform dispersion and smaller size,which has the advantages of strong controllability,rapid preparation and multiple batches.Due to gold nanoparticles’(AuNPs)high specific surface area,high efficiency and mild catalytic capacity,wide application range,the preparation of AuNPs with ultra-small size in aqueous phase has special significance.Firstly,our purpose is to study a simple synthesis strategy,namely,FNP based on multi-inlet vortex mixer,for the preparation of AuNPs less than 5 nm in size.On this basis,the effects of different parameters such as gold salt concentration,reducing agent concentration,stabilizer concentration and injection velocity on the morphology and optical properties of AuNPs were studied,which introduces adjustable properties,enlarge its application range.Therefore,FNP not only provides a reliable method for the synthesis of AuNPs,but also give AuNPs the adjustable function,which has a variety of potential application values.In this thesis,FNP was used as preparation method to study the effect of three capping agents(sodium citrate,HS-PEG1000-COOH,HS-PEG1000-NH2)on the morphology of AuNPs.The results showed that the size of AuNPs stabilized by sodium citrate was about 3-5 nm,and that of AuNPs stabilized by HS-PEG1000-R was about 1-2 nm.It was found that the preparation of AuNPs by FNP can significantly shorten the preparation time.By adjusting the injection speed,reducing agent concentration,and concentration of HAuCl4,the particle size can be fine-tuned within a certain range.Finally,the effect of different capping agent on the morphology of AuNPs was compared.HS-AuNPs have different catalysis ability because of their different terminal group-COOH and-NH2.The quasi-first-order reaction rate of AuNPs with the terminal group of-NH2 was 9.02 x 10-3 s-1,and its catalytic activity was significantly higher than that of AuNPs with the terminal group of-COOH,which did not even show the catalytic effect of quasi-first-order reaction.Under the same conditions,the former completed the catalytic reaction in 8min,while the latter completed in 30min.