Construction And Performance Regulation Of Carbon Dots Based Composite

As a new type of carbon-based fluorescent nanomaterials,carbon dots?CDs?have incomparable application value in catalysis,biosensors,light-emitting devices and other fields,because they have good biocompatibility,low toxicity and other merits.However,carbon dots are easy to agglomerate and have poor stability,which limit their application.In view of the limitation of single carbon dots,two kinds of carbon dots based composites in the paper were constructed to improve the photophysical and photochemistry properties of carbon dots,and the mechanism of performance regulation was studied in depth.The main contents and achievements of the paper are as follows:Firstly,we located sulfur and nitrogen co-doped carbon dots?SN-CDs?onto graphite carbon nitride nanosheets?g-C₃N₄?and achieved a novel SN-CDs/g-C₃N₄ composite.The morphology and structure of the nanocomposite were characterized by TEM,XRD,XPS and FTIR.The results showed that SN-CDs were successfully dispersed on g-C₃N₄ nanosheets.Photocatalytic reduction of 4-nitrophenol showed that the catalytic activity of the composite was much higher than that of pure SN-CDs and g-C₃N₄ nanosheets.The catalytic activity of the composite decreased by only 5%after three recycles.This was due to the combination of SN-CDs and g-C₃N₄ through chemical bonds,which made the composite system more stable.The good interfacial bonding played an important role in promoting the effective separation and faster transfer of photogenerated charges,therefore resulting in the improvement of catalytic performance.Secondly,using mechanical stirring and ultrasonic technology,nitrogen-doped carbon dots?NCDs?with negative potential were successfully assembled inside the two-dimensional hexagonal ordered mesoporous silica?SBA-15?channels with negative potential under the driving of capillary force.The obtained composite was named as NCDs-in-SBA-15.The results of TEM,FTIR,XPS,XRD and BET measurements showed that carbon dots were only located inside the mesopores of SBA-15.More importantly,compared with pure NCDs,NCDs-in-SBA-15 exhibited excellent structural stability,light stability,thermal stability,as well as resistance to acid/alkali solvents.In addition,the composite structure could detect and adsorb Fe³⁺simultaneously.These unique properties were mainly attributed to two potential reasons:one was that the confinement of mesoporous channels led to the interfacial reactions between confined carbon dots and the inner surface of SBA-15;the other was that the mesopore walls of SBA-15 showed a good protective effects on the NCDs inside the SBA-15channels.