Properties And Applications Of Multicolor Fluorescent Carbon Dots With Dual-Dependence On Excitation And Concentration

Carbon dots（CDs）as a novel carbon-based fluorescence nanomaterial have attracted much attention due to excellent water solubility,low toxicity,unique optical properties,good biocompatibility and easy surface functionalization.Especially,CDs with multicolor emissions have promising applications in sensing,bioimaging,and photoelectric devices.However,multicolor luminescent color of CDs in practical applications tends to be limited to particle size,the structure and component of a specific material.Therefore,based on the tunable fluorescent color of multicolor carbon dots,multicolor fluorescent carbon dots with dual dependence of excitation and concentration were successfully synthesized,and the optical properties of the CDs and their applications were deeply studied.The main research works are as follows:（1）Both excitation and concentration dual-dependence multicolor fluorescent CDs using citric acid and formamide were successfully synthesized by a one-step solvothermal method.The tunable fluorescence CDs can achieve full-color fluorescence emission from blue to red by adjusting the excitation wavelength and concentration.We propose a new strategy of realizing efficient full-color emission from the double-dependence CDs through controlling conjugated sp² domain.The CDs can be mixed with polyvinyl alcohol（PVA）solution to fabricate multicolor CD@PVA films,and these fluorescent composites with multicolor emissions can be applied in light emitting diode（LED）.Moreover,the CDs can qualitatively detect Cr（VI）and Ni（II）by the change of fluorescence color,which provides a simple and convenient strategy for the detection of heavy metal ions.（2）A simple indicator displacement assay（IDA）-based array system was established by using Fe³⁺-responsive fluorescent carbon dots（CDs）and Fe³⁺to detect adenosine triphosphate（ATP）related physiological phosphates（PPs）and monitor ATP hydrolysis.The analysis was based on principal component analysis of differential CDs fluorescence regulated by Fe³⁺/PPs complexes.Two sensor arrays were established.That is,three CDs/one Fe³⁺concentration（Array1）and one CD/four Fe³⁺concentrations（Array2）.Compared with Array1,Array2 saved a lot of trouble in preparing the CD sensors and the analytical performance it is hardly affected.The Array2 can distinguish PPs in serum environment and from interfering substances,such as amino acids and metal salt.Besides,quantitative analysis of ATP single-component system and qualitative analysis of adenosine triphosphate/adenosine diphosphate（ATP/ADP）two-component system can be achieved.On this basis,ATP hydrolysis processes were monitored,and results suggested that ATP hydrolysis completed within 20 min under the catalysis of 24U/mL apyrase.As ATP hydrolysis works for 30 minutes,its main products were adenosine monophosphate（AMP）and orthophosphate（Pi）.