Research On Microwave Syntheses Of Fluorescent Silver Nanoclusters And 1D Silver Nanoparticles By Poly(Methacrylic Acid) Template And Its Application

Noble mental nanoclusters have received much attention owing to their novel optical and electronic properties.Reduction in size often does more than simply make things smaller.There are many properties of materials that undergo qualitative,often sudden,changes below a certain size scale.Researches point out that silver particles, when their sizes decrease to comparable to the Fermi wavelength of an electron (＜0.5nm),the quantum effect becomes apparent and the silver nanoclusters start to exhibit semiconductor electronic characteristics.The band gap begins to evolve,and luminescence will be observed under excitation.Compared to traditional fluorescent labels,Ag nanoclusters have lots of advantages.Dye molecules are limited by photobleaching.Semiconductor nanocrystals,which have recently been introduced as labels,require toxic precursors and should be prepared under inert atmosphere.On the contrary,the Ag nanoclusters can be easily synthesized under mild conditions and show size-dependent emission. As an appealing optical label,Ag nanoclusters have great potential to be used in imaging,biological labeling and chemical sensor fields.1.In this study,we report a new approach for the synthesis of fluorescent and water-soluble nanoclusters(Ag_2-8),using the common polyelectrolyte poly(methacrylic acid) template without adding reduced agents by microwave heating method.2.We also prepared 3～10 nm diameter of non-fluorescent silver nanoparticles by prolonged the time of microwave heating.Herein,a self-assembly system with the polyelectrolyte poly(methacrylic acid) has been built up.For the first time,we developed a practical approach for assembling silver nanoparticles into well-defined arrays.The mechanism was discussed preliminarily:Ag⁺ binds tightly to the carboxylate groups of the poly(methaerylic acid) chains,this interaction neutralizes the polyanions to a large extent,which leads to a collapse of the hydrophobie polyelectrolyte chains and forms necklace-like structure.Ag particles assembling into well-defined 1D and 2D arrays. 3.The fluorescence quenching properties of the Ag nanoclusters were also investigated.Trace amount of copper(â…¡) and glutathione(GSH) can be selectively detected in HEPS buffer with fluorescent Ag nanoclusters.The minimal detection limit of Cu²⁺ is 0.4μM and the linear range of detection is 0～8.0μM.The minimal detection limit of glutathione(GSH) is 38.0μM and the linear range of detection is 50μM～200μM.