Contruction Of Several Fluorescence Silicon Quantum Dots Sensors And Their Applications

In recent years,quantum dots?QDs?have attracted considerable attention owing to their special optical and electronic properties including size-tunable emission spectra,high quantum yield?QY?and good photostability.Among them,silicon quantum dots?SiQDs?have attracted special interest owing to their special properties including excellent biocompatibility and low toxicity.These excellent properties make SiQDs widely employed in bioimaging and photoelectric device.Based on the excellent properties of SiQDs,several sensors have been built for detection of the heavy metal ion,poisonous gas and biomolecules with simplicity,inexpensive,label-free high sensitivityand good selectivity.The main contents are summarized as follows:1.A SiQDs-based sensing platform was established for effective and selective detection of Cr?VI?via the inner filter effect?IFE?and a fluorescence“on–off–on”strategy for the determination of H₂S based on the oxidation-reduction between Cr?VI?and H₂S.The fluorescence of SiQDs was effectively quenched by Cr?VI?via the inner filter effect.Upon addition of hydrogen sulfide,the fluorescence of SiQDs was recovered due to the oxidation-reduction between Cr?VI?and H₂S.Under optimal conditions,the wide linear response ranges were obtained over the range of 0.1-200?M and0.1-200?M with the low detection limits of 28 nM and 22 nM for Cr?VI?and H₂S,respectively.The sensing platform was successfully applied to determination of Cr?VI?and H₂S in real samples.2.We present a novel colorimetric and ratiometric fluorescent dual-readout strategy for detection of uric acid based on cascade catalysis and silicon quantum dots?SiQDs?.This sensing strategy involves the uricase-catalyzed oxidation of uric acid?UA?and iodide-catalyzed oxidation of a colorless peroxidase substrate o-phenylenediamine?OPD?to produce a yellow product?2,3-diaminophenazine?oxOPD??,thus cause colorimetric signals variation that could be distinguished by naked eyes or detected through absorbance at 417 nm.Moreover,oxOPD can effectively quench the fluorescence of SiQDs?450 nm?via the inner filter effect and exhibits emission at about 565 nm,which results in the change of the emission intensity ratio(I₅₆₅/I₄₅₀)for qualitatively and quantitatively detect UA.Under optimal conditions,the wide linear response ranges were obtained over the range of0.01-0.8 mM with the low detection limits of 8.4?M and 0.75?M by colorimetry and ratiometric fluorescence,respectively.Meanwhile,sensing platform was successfully applied to determination UA in human serum samples,suggesting the biosensor has potentially application in biomedical or clinical analysis.3.A novel fluorescent ratiometric SiQDs sensor was first established for detection of alkaline phosphatase?ALP?based on dual catalysis and the inner filter effect.This sensing strategy involves the ALP-catalyzed dephosphorylation of pyrophosphate anions?PPi?,inhibitory effects of pyrophosphate?PPi?on the oxidative ability of Cu²⁺and the yellow product quenching the fluorescence of SiQDs.The rapid complexation between copper ions and PPi to form PPi-Cu complex can inhibite the redox reaction between OPD and Cu²⁺.In the presence of ALP,the PPi is hydrolyzed to phosphate ions by ALP,and then copper ions are released from PPi-Cu complex into the solution.The free copper ions trigger oxidation of OPD to produce a yellow product?2,3-diaminophenazine?oxOPD??.The oxOPD can effectively quench the fluorescence of SiQDs?450 nm?via the inner filter effect.Meanwhile,oxOPD exhibits emission at about 565 nm under excitation at 380 nm,which results in the change of the emission intensity ratio(I₅₆₅/I₄₅₀)for qualitatively and quantitatively detect ALP.The sensing platform was successfully applied to determination ALP in human serum samples.