Metal Functionalized Carbon Dots For Detection Of Small Molecules And Degradation Of Organic Dyes

Carbon quantum dots(CDs)as New carbon nanomaterials,have become a research hotspot due to their low cytotoxicity,good water solubility,excellent optical properties,and broadband absorption.The metal functionalization of carbon dots can effectively change the band gap energy level of carbon dots and endow carbon dots with new physical and chemical properties.In this paper,zinc,iron and sodium doped carbon dots were prepared to construct different fluorescent probes for the detection of small molecules and the degradation of organic dyes.1.Zinc doped carbon dots(Zn-CDs)were synthesized by one-step hydrothermal method,and the fluorescence quantum yield was 34%.The fluorescence intensity of Zn-CDs could be effectively quenched by the hydroxyl radical(·OH)generated from hydrogen peroxide catalyzed by Cu²⁺,therefore a Zn-CDs-Cu²⁺fluorescence probe was constructed for detecting hydrogen peroxide and participating in the reaction metabolites of hydrogen peroxide generation.Under the optimal conditions,the(F₀-F)/F₀and H₂O₂concentrations reaction have a good linear relationship in the range of 1.0×10^-6-1.0×10^-5mol/L,and the detection limit is 7.2×10^-7mol/L;Since cholesterol can generate hydrogen peroxide in the oxidation of cholesterol enzyme,under optimal conditions,the(F₀-F)/F₀and cholesterol concentrations of the system are in the range of 9.0×10^-7-3.0×10^-5mol/L It has a good linear relationship with the detection limit of 6.8×10^-7mol/L.The method was applied to the determination of H₂O₂in Yanhe water samples and cholesterol concentration in milk,respectively.The recoveries were 98.55%-105.4%and 98.00%-103.0%,respectively,and the results were satisfactory.2.Sodium doped carbon dots(Na-CDs)and undoped carbon dots(CDs)were synthesized by one-step hydrothermal method,using sodium fluoride as metal source,ascorbic acid and citric acid as carbon source.Comparing the CDs before and after doping,the functional groups did not change significantly,but Na-CDs had better pH stability and photostability,and had higher selectivity in response to 2,4,6-trinitrophenol(PA).The results showed that the fluorescence quenching signal(F₀-F)/F₀of the system showed a good linear relationship with the PA concentration in the range of 7.0×10^-7-2.0×10^-5mol/L,and the detection limit was 3.5×10^-7mol/L.The method was used to detect the content of 2,4,6-trinitrophenol in Yanhe water,the recovery rate could reach97.60%-104.0%,and the results were satisfactory.3.Transition metal-doped Fe-CDs were synthesized by one-step hydrothermal method,and the structures of the Fe-CDs were characterized by transmission electron microscopy(TEM),Fourier transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS).It is confirmed that Fe is chelated with carbon dots by coordination,and the surface has abundant hydrophilic functional groups,and the fluorescence quantum yield is 17%.Taking advantage of the fluorescent properties of Fe-CDs and using?-CD-AgNPs as the absorber,an off-on fluorescent probe was constructed based on the inner filter effect(IFE)to realize the quantitative detection of L-Try.Cyclodextrin(?-CD)has the characteristics of external hydrophilicity and internal hydrophobicity,and can selectively recognize small molecules in the inner cavity,with high sensitivity detection.The L-Try concentration showed a good linear relationship with(F₀-F)/F₀in the range of 1.0×10^-6-9.0×10^-5mol/L.The detection limit was 6.4×10^-7mol/L.Using Fe-CDs-like peroxidase activity,Fe-CDs and H₂O₂were used to construct a Fenton system to achieve the degradation of Rhodamine B(Rh B)under natural light.Under the best optimized conditions,the degradation efficiency can reach 100%,and the effective repeatability is 3 times.