Preparation Of Functionalized Metal Nanomaterials And Their Application In Detection And Catalysis

The rapid development of nanoscience and nanotechnology has greatly promoted the wide application of nanometer materials in the field of detection and catalysis.In particular,metal nanoparticles,due to their good properties such as biocompatibility,surface plasmon resonance absorption（SPR）,surface enhanced Raman Scattering（SERS）,fluorescence and catalysis,have attracted extensive attention in the application field of colorimetric and fluorescent nanosensors,SERS detection and catalysis.In addition,bimetallic nanoparticles,magnetic composite metal nanoparticles and films assembled by metal nanoparticles have been further developed and expanded,which effectively improved the utilization efficiency of precious metals.In this study,the surface functionalized gold nanoparticles,fluorescent silver nanoclusters,flower-like silver nanofilms,bimetallic Cu-Ag nanoparticles and magnetic bimetallic Fe₃O₄@CuAg NPs hybrid nanoparticles were prepared,and used as colorimetric or fluorescent probes and catalysts based on the properties of the as-synthesized materials.The studies in this thesis include the following seven aspects:（1）Three-dimensional flower like Ag microstructures were assembled in situ on the substrate to fabricate Ag micro-flower（Ag NFs）film.The morphology and size of the Ag structures of these Ag NFs can be easily controlled by changing the reaction time.And the mechanism of growth of Ag NFs was also investigated by SEM.The shape evolution revealed the Ag NFs was assembled with thin nanosheets which composed of Ag nanoparticles,and the elemental composition of the nanoparticles was evidenced by X-ray spectroscopy analysis.Its potential as a catalyst in the reaction of reduction of nitrophenols was investigated.The reusability of the catalyst of the Ag NFs film was also estimated by recycling catalysis of 4-nitrophenol.Moreover,the Ag NFs film could be used as a versatile SERS substrate for detection of the R6G molecules.The results demonstrated that the Ag NFs film exhibited excellent SERS enhancement ability and catalytic activity.（2）We have reported a facile,cost-effective approach for the preparation of Ag NPs in aqueous medium using uric acid（UA）as reducing and stabilizing agent.The synthesized UA-AgNPs were thoroughly characterized using UV-visible spectroscopy,Transmission electron microscopy（TEM）and X-ray spectroscopy（EDS）.The UA-Ag NPs exhibited excellent specifity towards Ba²⁺and Sr²⁺that could be monitored by UV-visible spectrophotometer and naked eyes with lowest detection limit of 52.1 nM and 27.5 nM for Ba²⁺and Sr²⁺respectively.The proposed method provided rapid and sensitive detection of Ba²⁺and Sr²⁺ions at nM level in water samples,which were much lower than the U.S.EPA standard for the safety limit of metal ions in drinking water.The UA-Ag NPs can be applied to the analysis of trace Ba²⁺and Sr²⁺in lake water,indicating its potential applicability for detection in real samples.As far as we know,this is the first report for the colorimetric detecting Sr²⁺by using noble metal nanoparticles as a probe.Otherwise,the UA-Ag NPs exhibited excellent catalytic activity towards the reduction of nitrophenols and potassium hexacyanoferrate（III）.（3）The bimetallic uric acid functionalized copper and silver nanoparticles（UA-CuAg NPs）as well as magnetic bimetallic Fe3O4@CuAg NPs hybrid nanoparticles were synthesized.In order to improve the utilization efficiency of the precious metal nanoparticles,the magnetic composite structure was constructed based on the bimetallic nanoparticles with the flower magnetic ferroferric oxide as the center.These two kinds of nanoparticles were used as catalyst in the reducing reaction of nitrophenols and potassium hexacyanoferrate（III）.Compared with UA-Ag NPs nanoparticles,the bimetallic nanoparticles UA-CuAg NPs and bimetallic Fe3O4@CuAg NPs hybrid nanoparticles exhibited much higher catalytic activity in same reaction.The reusability of the catalyst of the Fe3O4@CuAg NPs was also estimated by recycling catalysis of 4-nitrophenol.Magnetic bimetallic nanoparticles（Fe₃O₄@CuAg NPs）could recycle at least 5 turns with high conversion efficiency at96%.（4）The galactosamine-functionalized gold nanoparticles（Galn-Au NPs）was prepared according to the reported method and used as detection probe to monitor the heavy metal ions Cd²⁺and recognize the latent fingerprints in this work.The Galn-Au NPs can be used as a colorimetric probe for the detection of Cd²⁺ions through localized surface plasmon resonance.A linear response to the concentration of Cd²⁺ions was observed in the range 1 to 100 nM with the detection limit of 3 nM.This method is simple and fast and has also been successfully applied to the detection of Cd²⁺ions in lake-water samples.The Galn-Au NPs can present blood latent fingerprints with third level by silver enhancement.（5）The folic acid functionalized silver nanoclusters（FA-Ag NCs）were synthesized and used as the fluorescent probe to detect Hg²⁺in water environment.The FA-Au-NCs exhibited a strong emission maximum at 441 nm excited at 360 nm.The FA-Ag NCs solution showed bright blue fluorescence emission under UV light.When exposing with Hg²⁺,the emission of FA-Ag NCs shut off immediately.As fluorescent probe,FA-Ag NCs could be used for detecting Hg²⁺with the limit of detection at 176 nM.The detection in real water samples was also performed,and the experimental results showed that FA-Ag NCs exhibited good behavior for monitoring Hg²⁺.（6）The glutathione functionalized Au Nanoclusters（GSH-Au NCs）were synthesized and used as a fluorescent reagent to visualize the latent fingerprints.The GSH-Au NCs exhibited orange fluorescent emission at UV-light,the GSH-Au NCs covered fingerprint can be enhanced greatly.The latent fingerprints（both sebaceous and blood）can be developed by fluorescent GSH-Au NCs to form bright images at UV lamp.The IgG modified GSH-Au NCs improved the sensitivity of detection due to the function of target of the IgG.The detection of blood latent fingerprint which pressed by the solution of diluted 10000 times of blood can also imaged by IgG-GSH-Au NCs.（7）The cubic crystal forms of NENU-3a was prepared and used as a heterogeneous catalyst in the reaction of reducing 4-NP.The as-synthesized NENU-3a at 50-80oC with different reaction time exhibited different catalytic activity.The best condition of preparing NENU-3a is reacting at 80oC with 2 hours.The NENU-3a displayed excellent performance of catalysis with high kinetic rates in the reaction of reducing nitrophenols and potassium hexacyanoferrate（III）.The reusability of the catalyst of the NENU-3a was also estimated by recycling catalysis of 4-nitrophenol.The NENU-3a can be easily recycled,showing good reusability,and the conversion was higher than 97%after 9 cycles.