Preparation Of Novel Carbon Dots And Their Applications In Heavy Metal Ions And Sulfite Detection

Carbon dots(CDs)as a newly developed class of nanomaterials,in virtue of their unique physicochemical,optical and electronic properties,have displayed tremendous momentum in numerous fields such as bioimaging,sensing and medical area.However,the reported CDs always involve single emission or short wavelength,which can not meet the needs of analyzing real samples.Therefore,it is of great significance to develop a simple method to prepare dual emission or long wavelength of CDs and apply them to the analysis of real samples.Based on the previous works,the following major researches were carried out.(1)Preparation of dual emissive carbon dots(DECDs)and their application in ratiometric fluorescent detection of chromium(VI)in real samplesHexavalent chromium(Cr(VI))was usually used as an additive to improve the color fastness during the printing and dyeing process,and exposure to excess Cr(VI)posed tremendous threat to our health and living quality.Therefore,it is very necessary to develop a highly sensitive and selective method for detection of trace Cr(VI)in real samples.Based on the above discussion,the DECDs were synthesized through hydrothermal treatment of m-aminophenol and oxalic acid and characterized their morphology and properties.These results indicated the obtained DECDs not only exhibited dual emission fluorescence peaks(430 nm,510 nm)under the single excitation wavelength of 380 nm,but also possessed good water solubility and excellent photostability.A ratiometric fluorescent method for the determination of Cr(VI)was developed based on the special optical properties of the DECDs.Under the optimal conditions,a linear range was obtained from 2 to 300?M with a limit of detection of 0.4?M.The proposed ratiometric fluorescent method was applied to the determination of Cr(VI)in textile,steel,industrial wastewater and chromium residue samples,the recoveries were 88.4%-106.8%.(2)Preparation of orange-emissive carbon dots and their application in highly selective detection of silver ionsSilver ion(Ag~+)is one of the highest toxicity in heavy metal pollution,thus measuring the level of Ag~+in aqueous solution and biological samples attracted increasing attention.The CDs were synthesized through hydrothermal treatment of p-aminobenzoic acid and p-aminophenol and characterized their morphology and properties.These results indicated the obtained CDs exhibited emission wavelength at580 nm,as well as excellent photostability and water solubility.Based on the phenomenon that the fluorescence intensity decreased,which is attributed to the interaction of Ag~+and the amino groups on the surface of as-prepared CDs to form a nonfluorescent complex,a fluorescent method was established for detection of Ag~+.Under the optimal conditions,a linear range was obtained from 5 to 100?M with a limit of detection of 1.4?M.The proposed fluorescent method was applied to the determination of Ag~+in water and serum samples.Compared with the previous nanoprobes,this nanoprobe showed excellent selectivity,which presents the potential practical application in environmental protection and biological assay.(3)Preparation of zinc and boron co-doped carbon dots(ZnB-CDs)and their application in sensing of sulfiteSulfite is often used as a food additive to inhibit enzymatic and non-enzymatic browning process and microbe growth,but excessive intake are harmful to the human.Therefore,it is necessary to develop a simple and rapid method for detection of trace sulfite in tap water and food samples.The ZnB-CDs were synthesized through hydrothermal treatment of o-aminophenylboronic acid and zinc chloride and characterized their morphology and properties.These results indicated the ZnB-CDs exhibited photoluminescence at 535 nm when excited at 460 nm.Based on the phenomenon that the fluorescence intensity increased,which may be attributed to the decreasing of surface defects of as-prepared ZnB-CDs,a fluorescent method was established for detection of sulfite.Under the optimal conditions,a linear range was obtained from 4 to 160?M with a limit of detection of 1.24?M.The proposed fluorescent method was applied to the determination of sulfite in tap water,ranulated sugar and crystal sugar samples,the recoveries were 96.7%-107.2%.