Construction Of Fluorescent Carbon Dots/Biopolymer Nanocomposites Based On Microwave Method And Their Applications

Carbon dots(CDs),a new type of fluorescent nanomaterial,have drawn considerable attention due to their attractive applications in biolabeling,bioimaging,biosensors and optoelectronic devices.It is worth mentioning that CDs exhibit appealing properties such as highly stable and multicolor fluorescence,non-toxicity,and biocompatibility.To date,a variety of natural materials(e.g.,glucose,amino acid,plant leaf,orange juice and gelatin)that can be used as carbon sources to prepare CDs have drawn much attention owing to their attractive properties,such as wide source,low cost,environmentally friendly prepairation,and good biocompatibility.This work investigated the construction of fluorescent carbon dots/biopolymer nanocomposites(carbon dots/chitosan composite and carbon dots/gelatin composite)by a simple and novel in situ method based on a microwave treatment of the biopolymer.Moreover,their properties and applications was studied and evaluated.First,on the basis of microwave treatment of chitosan solution,a convenient and novel in situ method is established to form a fluorescent carbon dots/chitosan composite.This method has many benefits including prompt operation,simple equipment,simplified post-treatment,“green”process and low cost,and it allows a convenient way to gain carbon dots/chitosan nanocomposite that can be directly used for subsequent applications.The analysis results indicate that the carbon dots/chitosan composite solution is transparent and homogeneous.In addition,the carbon dots/chitosan composite solution displays brown color under visible light,while presents clear blue fluorescence under 365 nm UV light.Transmission electron microscopy test exhibits that carbon dots disperse well in the carbon dots/chitosan composite,and the average size of carbon dots presents a value about 7.0 nm.Specially,the obtained carbon dots/chitosan composite not only has attractive properties(e.g.,multicolor fluorescence)that belong to carbon dots,but also retains the favorable properties(e.g.,pH-responsive properties)of chitosan.Based on these combined properties,it is convenient to employ the carbon dots/chitosan composite to construct multicolor fluorescent films and fluorescent beads.Furthermore,the carbon dots/chitosan composite can be directly applied to cell imaging.Thus,this carbon dots/chitosan composite constructed by in situ method has potential applications in fluorescent materials,fluorescent coatings,bioimaging and biolabeling.Furthermore,the CDs/chitosan composite produced by the simple and novel in situ method based on one-step microwave treatment of chitosan solution was straightforward used for further electrodeposition and electrically controlled release of CDs.Importantly,the prepared CDs/chitosan composite is not only endowed with the multicolor fluorescence features comingfrom CDs,but also reserves pH-responsive film-forming properties of chitosan.On the basis of these favorable properties,we can straightforward employ the CDs/chitosan composite to construct fluorescent coatings,as well as a variety of multicolor-fluorescent patterns on different electrodes or substrates through electrodeposition technique.More interestingly,the release of CDs in the electrodeposited coatings or patterns can be controlled by electrical signals.Consequently,this CDs/chitosan composite with straightforward applications in electrodeposition and electrically controlled release of CDs has promising uses in photoluminescent coatings,fluorescent patterns,and controlled release.Besides,on the basis of a convenient and novel in situ method,we choose a gelatin solution as the only reactant for producing the CDs/gelatin composite,which can be directly used in subsequent applications.The analysis results indicate that the prepared CDs/gelatin composite is not only endowed with the multicolor fluorescence features coming from CDs,but also reserves temperature-responsive sol-gel transition of gelatin.On the basis of these favorable properties,we can conveniently employ the CDs/gelatin composite to construct a fluorecent patterns.In addition,this CDs/gelatin composite can be directly employed to build fluorescent beads.More interestingly,CDs in the fluorescent beads can release by control the temperature of water system.Thus,this fluorescent CDs/gelatin composite may has promising uses in the fields of drug carrier,controlled release and fluorescent labeling.In summary,this work constructed the fluorescent carbon dots/biopolymer nanocomposites(carbon dots/chitosan composite and carbon dots/gelatin composite)by a convenient and novel in situ method based on microwave treatment of the biopolymers,which can be directly used for subsequent applications without needing further post-processing and purification.Importantly,these obtained carbon dots/biopolymer composites not only have attractive properties(e.g.,multicolor fluorescence)that belong to carbon dots,but also retain the favorable properties of the biopolymers.Thus,this work may provide important theoretical and practical basis for construction and application of carbon dots/biopolymer composite,and may also offer new methods for fluorescent coatings and patterns,bio-electronic devices,controlled release,fluorescent labeling,bioimaging and so on.