Synthesis,Modification And Application Of Fluorescent Silicon Quantum Dots

Silicon quantum dots?SiQDs?are a kind of very important quasi-zero-dimensional semiconductor materials.They not only have unique photoelectric characteristics,but also have many advantages such as non-toxic,harmless,low cost and good biocompatibility,which has attracted the considerable attentions of many researchers.The application of SiQDs is very extensive.They have been applied in the fields such as detection,biomarkers,photocatalysts,photodiodes and solar cells,and have more widespread prospects for development.This paper is focus on the synthesis,modification and application of fluorescent silicon quantum dots?F-SiQDs?.The main contents are as follows:1.We have prepared green fluorescent silicon quantum dots?GF-SiQDs?by hydrothermal method with?3-aminopropyl?trimethoxysilane?APTMS?and sodium L-ascorbate.Absorption spectra show that the GF-SiQDs have no obvious absorption peak.Fluorescence spectra show that the maximum excitation wavelength and the maximum emission wavelength of the GF-SiQDs are 420 nm and 517 nm,respectively.Infrared spectra show that the GF-SiQDs contain a large number of amino groups on the surface.Transmission electron microscopy photographs show that the GF-SiQDs are spherical particle with good dispersibility and uniform particle size.X-ray diffraction results show that the GF-SiQDs are amorphous.Experimental studies show that the GF-SiQDs also have good salt stability.In addition,the reaction conditions and pH of solution may affect the luminescence properties of GF-SiQDs.Finally,we have studied the SiO₂ modified GF-SiQDs by slowly oxidizing the surface of GF-SiQDs with hydrogen peroxide.The SiO₂ modified GF-Si QDs have smaller particle diameters,enhanced stability,and the maximum emission wavelength are blue-shifted.2.We have prepared blue fluorescent silicon quantum dots?BF-SiQDs?by hydrothermal method with N-[3-?trimethoxysilyl?propyl]ethylenediamine?DAMO?and citric acid monohydrate.Absorption and fluorescence spectra indicate that the maximum absorption wavelength,the maximum excitation wavelength and the maximum emission wavelength of the BF-SiQDs are 360 nm,370 nm and 448 nm,respectively.Infrared spectra indicate that the BF-SiQDs contain a large number of amino groups on the surface.Transmission electron microscopy photographs indicate that the BF-SiQDs are spherical particle with good dispersion and uniform particle size.X-ray diffraction results indicate that the BF-Si QDs are amorphous.Experimental studies indicate that the BF-SiQDs have good light and salt stability,and they have a fluorescence lifetime of 14.2 ns and a quantum yield of 70.4%.Besides,the reaction conditions and pH of solution may affect the luminescence properties of BF-SiQDs.Finally,we have used the BF-SiQDs to detect copper?II?ion,azobenzene and4-?phenylazo?benzoic acid.The experimental results show that the linear range for the determination of copper?II?ion is 0¹ mM and the low detection limit is 0.091 mM,the linear range for the determination of azobenzene is 0¹ mM and the low detection limit is 0.043 mM,the linear range for the determination of 4-?phenylazo?benzoic acid is 0⁰.75 mM and the low detection limit is 0.040 mM.