Preparation And Application Of Silver Nanoclusters/Polysaccharides Nanocomposite

Polysaccharides are abundant,renewable,biocompatible,and degradable natural materials that have been widely used in various fields such as food engineering,wastewater treatment as well as biomedicine.Silver nanoclusters（AgNCs）,an emerging fluorescent nanomaterial,have unique optical,chemical and electrochemical properties.It should be noted that many researchers have combined AgNCs with polysaccharides to construct their nanocomposite with good properties.In addition,some polysaccharides can be used as stabilizers and reducing agents for green synthesis of AgNCs.Thus,the nanocomposites of silver nanoclusters and polysaccharides show attractive applications in bioimaging and biosensing.In this work,a facile and green approach based on the coordinated electrodeposition of carboxymethyl cellulose（CMC）is developed to fabricate AgNCs and AgNCs/CMC nanocomposite films.In the approach,CMC not only serves as the electrodeposition polysaccharide,but also acts as the stabilizing agent and reducing agent for the synthesis of AgNCs,as well as the major component in the resulting AgNCs/CMC nanocomposite film.After the electrodeposition and incubation,a homogeneous film is generated on the anodic electrode,which exhibits a clear yellow florescence.Transmission electron microscope observation shows that there are nanoparticles with the average size of 1.7 nm in the nanocomposite film.X-ray photoelectron spectroscopy,UV-vis absorption spectroscopy and fluorescence spectroscopy both confirm that there are AgNCs in the nanocomposite film.The AgNCs/CMC nanocomposite film shows the capability for fluorescence detection by utilizing the fluorescence quenching features of AgNCs.Moreover,the AgNCs/CMC-modified ITO electrode can be conveniently and directly produced based on coordinated electrodeposition of CMC,which presents potential applications for electrochemical biosensors.Thus,this study provides a novel approach for the green synthesis of AgNCs and direct fabrication of the AgNCs/CMC nanocomposite film.This work also investigates the preparation and application of AgNCs/nitrogen-doped carbon dots（N-CDs）/agar nanocomposite.First,a water-soluble AgNCs are prepared by using lipoic acid as stabilizer and sodium borohydride as reducing agent.Then the microwave method is used for the synthesis of thermo-responsive N-CDs/agar nanocomposite via utilizing agar as the carbon precursor and ethanolamine as the nitrogen source.Next,the dual-emission AgNCs/N-CDs/agar nanocomposite is constructed by using the above two fluorophores for ratiometric fluorescence detection towards Cu²⁺.The nanocomposite has two fluorescence emission peaks at 630 nm and 467 nm.With the addition of Cu²⁺,the fluorescence emission peak at 630 nm is gradually quenched,and the fluorescence emission peak at 467 nm gradually recovered,where the fluorescence color of the nanocomposite changes from red to blue.Thus,the relationship between the fluorescence intensity ratio(I₆₃₀/I₄₆₇)and the concentration of Cu²⁺can be used to establish the determination method of Cu²⁺.The calculated detection limit is 0.16μM（S/N=3）.In addition,nanocomposite gels can be constructed using the thermo-responsive sol-gel transition property of AgNCs/N-CDs/agar nanocomposite for simple visual qualitative analysis of Cu²⁺.This work proposes a green approach to fabricate AgNCs and AgNCs/CMC nanocomposite film based on the electrodeposition of polysaccharides.The prepared AgNCs/CMC nanocomposite film can be used for fluorescence detection and electrochemical sensing.In addition,this work also constructs AgNCs/N-CDs/agar nanocomposite for ratiometric fluorescence detection.This work provides new methods for the preparation of AgNCs and nanocomposites of AgNCs and polysaccharides.The prepared nanocomposites of AgNCs and polysaccharides show good applications in functional composite materials,detectors,sensors and other fields.