Fluorescence Manipulation Of Semiconductor Quantum Dots By Photonic Crystal Structure And Its Analytical Application

Photonic crystal is a structure formed by periodic arrangement of substances with different refractive indexes.The study of light regulation by photonic crystals is usually applied to the design of optical devices,such as the preparation of low threshold lasers and high efficiency LED lights.In addition,photonic crystals can also be used to amplify fluorescent signals to prepare photonic crystal fluorescence sensors to improve the sensitivity of the detection method,so as to obtain better detection results.In this thesis,semiconductor quantum dots with fluorescence properties were introduced into the photonic crystal structure,and the manipulation and mechanism of the photonic band gap of photonic crystals on the fluorescence of quantum dots were studied.Fluorescence-enhanced semiconductor quantum dot sensing films were obtained to detect nitrite ions and mercury ions in aqueous solution.The specific content includes the following aspects:1.Water-soluble HPEI-Cd S quantum dots and MPA-Cd Te quantum dots were prepared and filled into the photonic crystal template after mixing with hydrogel precursor solution.By optimizing the amount of monomer,cross-linking agent and initiator,the hydrogel films with complete structure,photonic band gap and fluorescence properties were prepared.The fluorescence regulation of different kinds of quantum dots by photonic band gap of photonic crystal was studied and it is found that the photonic crystal structure can effectively enhance the fluorescence intensity of quantum dots.For HPEI-Cd S quantum dots with emission wavelength at487 nm,when the photon band gap is located at 496 nm,because the emission wavelength overlaps with the edge of the photon band gap,the interaction time between light and matter is enhanced,so the enhancement effect is the best.Similarly,for MPA-Cd Te quantum dots with emission wavelength at 543 nm,they effectively overlap with the red edge of the 504 nm and the blue edge of the 629 nm photonic band gap,respectively.The photon state density at the edge of the photonic band gap is higher and the fluorescence intensity is enhanced.The analysis and application of the above two fluorescence enhanced hydrogel films were explored.2.The application of fluorescence enhanced HPEI-Cd S quantum dots hydrogel films for detecting nitrite ion in aqueous solution was investigated.By optimizing the detection conditions,the fluorescence enhanced HPEI-Cd S quantum dot hydrogel films for the determination of nitrite ions was realized.The detection linear range was from 2×10^-6mol/L to 10^-5mol/L,and the detection limit was 0.25μmol/L,showing a good selectivity.It was observed under 365 nm UV lamp that the sensing film showed light blue fluorescence after interacting with nitrite ion.The mechanism of fluorescence quenching was discussed.The sensor film can be recovered after fluorescence quenching and can be reused which has practical application prospect.3.The performance of fluorescence enhanced MPA-Cd Te quantum dots hydrogel sensing film for detection of Hg²⁺ions was investigated.The optimal p H and equilibrium time were determined.Under the optimal conditions,Hg²⁺ions can quench the fluorescence of MPA-Cd Te quantum dot sensing film,and the fluorescence intensity decreases gradually with the increase of Hg²⁺concentration.The detection linear range is from 0.01μmol/L to 0.1μmol/L.It was observed under365 nm UV lamp that when the hydrogel film was immersed in the solution of Hg²⁺ions,it showed a fluorescence change from bright green to light blue,providing a feasible method for visual detection of mercury ions.