Functional Graphene Quantum Dot Induced Sytnthesis Of Precious Metal Nanoparticles And Its Application In Bioelectric Analysis

Precious metal nanoparticles combine the advantages of precious metals and nanomaterials,have unique optical,electrical and catalytic properties,and are widely used in electrochemical sensors,biological imaging,optical sensors and catalysts.A large number of research results have shown that the electrochemical performance is highly dependent on the morphology and crystal size of the precious metal nanoparticles.Therefore,in recent years,many methods have been developed for controllable multi-morphology and different sizes of precious metal nanocrystals.However,the functionality and catalytic activity of the precious metal nanoparticles synthesized in the prior art are still insufficient,which limits their wide application in certain fields.In this subject,a variety of functionalized graphene quantum dots are prepared by designing graphene quantum dots,using functional graphene quantum dots as reducing agents and stabilizers to induce the synthesis of precious metal nanomaterials with different sizes,morphologies and specific functions.The close combination of graphene quantum dots and precious metals has significantly improved the electrocatalytic activity of the composite materials,and thus build an electrochemical biosensing platform.Graphene quantum dots(GLu-GQD)were prepared by one-step pyrolysis with citric acid as the carbon source and glutamic acid as the functional reagent.Using GLu-GQD as a reducing agent and a stabilizer,a gold/graphene quantum dot hybrid(Au/GQD)is formed in a one-step reaction with a boiling chloroauric acid solution.The hybrid is combined with hairpin DNA probe 1(H1)and thionine(Thi),and the H1-Au/GQD-Thi complex serves as a redox probe to construct an electrochemical aptamer sensor for detecting VEGF165.A VEGF165 molecule can recognize and bind two DNA affinity probes by a specific aptamer-target to generate a molecular machine for signal amplification.At the same time,Au/GQD's redox probe can catalyze Thi's redox activity in situ and further enhance the detection signal.Based on the dual amplification strategy of molecular machine and Au/GQD,the detection of VEGF165 by aptamer sensors showed ultra-high sensitivity and selectivity.Relative to Ag/AgCl potential of-0.18V,the square wave voltammetric signal increases linearly within the concentration range of 1.0×10-15-1.2×10-10 mol·L-1 VEGF165,and the detection limit is 3.0×10-16 mol·L-1(S/N=3).If corresponding high-affinity aptamers are available,this method can be applied to the detection of other target proteins.In the presence of tannic acid,a glutelic acid functionalized graphene quantum dot(Glu-GQD)was used to induce the synthesis of a special shape and function of Glu-GQD/Au composite material.The obtained Glu-GQD/Au is covalently linked to the acetamiprid aptamer(Apt)to obtain an autocatalytic redox probe.The research results show that Glu-GQD/Au has a nanostar-like structure with an average particle size of 102.5 nm,which is composed of several nano-scale gold nanocrystals with sharp edges and corners.The unique structure endows the gold nanostar with good electrocatalytic activity,and its combination with Glu-GQD further improves its catalytic ability.In the redox probe,Glu-GQD can perform a reversible redox reaction on the electrode surface due to its high electrical activity.Gold nanostars catalyze the redox reaction of Glu-GQD in situ and improve its electrochemical behavior.In addition,the aptamer can be specifically combined with acetamiprid.Therefore,an electrochemical aptamer sensor based on Glu-GQD/Au-Apt/graphene aerogel is constructed,which has ultra-high sensitivity and selectivity for the detection of acetamiprid.The differential pulse voltammetric signal decreases linearly with the concentration of acetamiprid,the linear range is 1.0×10-15-1×10-10 mol·L-1,and the detection limit is 3.7×10-16 mol·L-1(S/N=3).The aptamer sensor has been successfully applied to the electrochemical detection of acetamiprid in vegetables.FA/Glu-GQD was prepared by thermolysis the mixture of citric acid,glutamic acid and folic acid.Then,it was used as a reducing agent and a stabilizer to induce the synthesis of folic acid and glutamic acid functionalized graphene quantum dot-palladium@gold(FA/Glu-GQD-Pd@Au).The obtained hybrid was used as a redox probe for constructing HepG2 electrochemical sensing platform.The results show that FA/Glu-GQD-Pd@Au has a core-shell nanostructure.The palladium nanocube is the core,and the gold nanocrystal is the shell.Pd@Au gives high electrocatalytic activity due to its unique structure as well as combination with FA/Glu-GQD.FA/Glu-GQD can specifically target recognize HepG2 and bind it tightly.FA/Glu-GQD occurs reversible redox reactions on the electrode surface and produces electrochemical signal after binding HepG2.Pd@Au catalyzes the redox of FA/Glu-GQD in situ and achieves significant signal amplification.Sensors based on FA/Glu-GQD-Pd@Au exhibit ultra-high sensitivity for HepG2 detection.With the increase of HepG2 in the range of 3-1×105 cells·mL-1,the differential pulse voltammetry peak current linearly decreases,and the detection limit is 2.0 cells·mL-1(S/N=3).The proposed analytical method has been successfully applied in electrochemical detection of circulating cancer cells in human blood.