Construction And Application Of Fluorescence Biosensing Systems Based On Silicon Quantum Dots

As a new kind of fluorescence nanomaterials,semiconductor quantum dots（QDs）have received extensive attention as a consequence of a series of excellent optical properties.However,most semiconductor quantum dots contain heavy metal elements and can cause environmental pollution and potential biological toxicity,which greatly limits the practical application of semiconductor quantum dots.Silicon quantums dots（SiQDs）,which are a kind of zero-dimensional nanostructured fluorescent material,can be promising alternatives to heavy metal-containing QDs in biological analysis,because SiQDs have no toxicity to the human body and are environmentally friendly.In addition,SiQDs possess many advantages including low cost,high natural abundance,controllable surface modification,strong luminescence,high photostability and good biocompatibility.In recent years,SiQDs have been used as fluorescent probes for analysis and detection.Fluorescence detection methods have the advantages of simple operation,high sensitivity,good selectivity and short response time.Therefore,we chose SiQDs as probes and constructed several fluorescent sensing systems for the detection of biological molecules.In the first chapter,we first introduced quantum dots,and then mainly introduced the synthesis methods,optical properties and applications of SiQDs in various fields.Finally,the main content and significance of this research are described.In the second chapter,we established a simple,sensitive and highly selective fluorescence method based on SiQDs and manganese dioxide（MnO₂）nanosheets for the determination ofα-glucosidase and its inhibitor acarbose.The fluorescence of SiQDs was effectively quenched by MnO₂nanosheets due to the inner filter effect.α-glucosidase could catalyze the hydrolysis of 2-O-α-D-Glucopyranosyl-L-ascorbic acid（AAG）to produce ascorbic acid（AA）,which can reduce the MnO₂nanosheets to Mn²⁺,resulting in the recovery of the fluorescence of the system.Acarbose could inhibit the activity of the enzyme and lead to the fluorescence quenching again.The detection ofα-glucosidase and its inhibitor acarbose can be achieved through changes of the fluorescence intensity of the system.The linear range of the sensing platform forα-glucosidase determination was 0.02-2.5 U m L^-1and the limit of detection was0.007 U m L^-1.The established fluorescence platform has been successfully used for the detection ofα-glucosidase in human serum with satisfactory results.In the third chapter,we designed a sensitive fluorometric and colorimetric dual-mode assay based on SiQDs and 5,5’-dithiobis-（2-nitrobenzoic acid）（DTNB）to effectively detect D-Penicillamine（D-PA）.The sulfhydryl group in the D-PA molecule can react with DTNB to form 5-thio-2-nitrobenzoate（TNB）,which has an obvious absorption peak at around 407 nm.Due to the inner filter effect（IFE）,the fluorescence intensity of SiQDs significantly decreased.Meanwhile,the color of the detection system changed from colorless to yellow.Consequently,the quantitative determination of D-PA can be achieved by both fluorometric and colorimetric methods at the same time.The fluorometric and colorimetric sensing platform could detect D-PA in 1-20μM and 2-20μM concentration range,respectively,and the limits of detection were 0.48μM and 0.68μM,accordingly.Furthermore,the designed sensing platform was utilized to detect D-PA in real biological samples and the experimental results were satisfactory,suggesting the feasibility and potential applications of the sensing platform.