The Synthesis Of Quantum Dots And Nanozyme And Their Application In Detection Of Small Biomolecules

The detection of small biomolecules is of great importance to clinical diagnosis,food safety and environmental monitoring.Though there are plenty of test kits existing in market,it still makes some false results due to low stability,complexity of biological samples and operation of difference experimenter.Therefore,developing more sensitive,selective and stable methods for detection of small biomolecules are in emergency cause of the need of markets.Owing to size-and shape-controlable,easy modification of surface function and unique optical and catalytic characteristic of nanomaterials,it plays an important role in the detection of small biomolecules.It is easy to design and synthesize nanomaterials with specific response of small biomolecules and establish nanomaterials-based method for the determination of small biomolecules.The study details are as follows:1.S-doped carbon dots capped ZnCdTe quantum dots for ratiometric fluorescence sensing of guanineQuantum dots?QDs?-based ratiometric fluorescence probe have drawn extensive attention in recent years.However,most of them were based on the metal doped QDs,and intrinsic dual-emitting QDs were rarely reported.Herein,an intrinsic dual-emitting ZnCdTe QDs were synthesized by using fluorescence S doped-carbon dots?CDs?as capping ligands for the first time in this work,two emission peaks?derived from CDs and QDs respectively?were observed in CDs-ZnCdTe QDs and the probe showed excellent stability and optical properties.Moreover,we found that the fluorescence emission of QDs could be quenched by guanine via excited state electron transfer or the aggregation of QDs,but the emission of CDs remained stable,thus we successfully developed a ratiometric probe for the determination of guanine.Under optimized conditions,the detection limit of guanine was 0.076?mol?L^-1?3?/k?,with a linear range from 0.25 to 40.0?mol?L^-1.The smart ratiometric fluorescence probe was demonstrated for the detection of guanine in DNA samples with satisfactory recoveries ranging from 96.95 to 102.50%,indicating it was a promising biosensor for highly selectively and sensitively determination of guanine.2.Quercetin@ZIF-90 as a novel antioxidant for label-free colorimetric ATP sensing at neutral pHQuercetin is a nature polyphenolic flavonoid compound,which act as antioxidant and radical scavengers in cells.However,such activities strongly depend on the intracellular microenvironment,which has become an urgency to develop a more stable method for better use of quercetin.Herein,we report a facile approach to fabricate Quercetin@ZIF-90?QZ?with a narrow size distribution about 100 nm,the synthesized QZ exhibits considerable antioxidant and radical scavenger ability comparing to bare quercetin.Moreover,the experiment results indicated that QZ was sensitive to adenosine 5?-triphosphate?ATP?and pH,thus QZ was applied as a novel antioxidant for the determination of ATP.In brief,though 3,3?, 5,5?-tetramethylbenzidine?TMB?could be oxidized to blue cation radical complex by oxidase-like BSA-MnO₂ nanosheets?MNs?at neutral pH,QZ could sufficiently protect against MNs-induced TMB cation radicals reaction,which means no obvious color change in MNs-TMB system after the addition of QZ.However,ATP could induced collapse of QZ due to the interaction between ATP and Zn²⁺allowing the release of quercetin from ZIF-90 shell,and the inhibition effect to the MNs was weakened,leading to the recovery of blue ox TMB.In this way,a novel“Off-On”colorimetric method for ATP sensing was established,and the method displayed a good linear relationship ranging from 2.0 to 80.0?mol?L^-1.The reported strategy is also capable of ATP sensing in MCF-7 cell lysates,which illustrated our method exhibited high sensitivity and selectivity.3.Regulating the enzymatic activity of metal-ATP nanoparticles and its application for the determination of H2O2Compared to natural enzyme,nanozyme possess the advantage of low cost,recyclable and more stable,thus it is important to design and synthesize high catalytic efficiency nanozyme.Herein,Cu_xMn_1-x-ATP nanoparticles with remarkable peroxidase-and laccase-like activity which were synthesized by de novo method are reported.The SEM results indicated that Cu_xMn_1-x-ATP nanoparticles possessed sphere-like shape and with 200.0 nm average size.It is demonstrated that when the x=1,Cu_xMn_1-x-ATP nanoparticles only show strong laccase-like activity and weak peroxidase-like activity,but with decreasing of x which mean the contents of Mn element increase,Cu_xMn_1-x-ATP nanoparticles could show strong laccase and peroxidase-like activity at the same time.CuMn-ATP nanoparticles could catalyze the oxidation of TMB?with the existence of H₂O₂?and 2,4-DP,kinetic studies indicated that CuMnATP nanoparticles exhibited rather strong affinities to TMB and 2,4-DP.Subsequently,CuMn-ATP NPs were employed to establish a facile colorimetric biosensing method for the determination of H₂O₂,the proposed method for H₂O₂ detection with a linear range from 0.5to 50.0?mol?L^-1,and the detection limit of H₂O₂ is 0.05?mol?L^-1.In conclusion,the dual enzyme-like CuMn-ATP nanoparticles provide a versatile tool for biosensing,but also show potential to the decomposition of phenols.