Interaction Between Quantum Dots And L-Aapartic Acid, Metalion And Pefloxacin Complex, DNA And Its Analytical Application

In our study, glutathione (GSH) capped CdTe QDs and glyphosate (Glyp) capped CdTe/CdS QDs were synthesized in aqueous solution, the sizes and shaps of the prepared QDs were characterized by transmission electron microscope (TEM) and fluorescence microscope (FM). The interactions of QDs with L-Aapartic acid, metal ion and metal-fluoroquinolones chelates, DNA were investigated by fluorescence spectrum (FL)、ultraviolet-visible absorption spectra (UV-vis), Fourier transform infrared (FT-IR) spectroscopy and resonance Rayleigh scattering (RRS) spectra assisted with chemical thermodynamics methods. A novel fluorescent probe for Cu2+determination based on the fluorescence quenching of Glyp-functionalized CdTe/CdS QDs was firstly reported. The interaction between Al(III)-pefloxacin complex and double-stranded DNA (dsDNA) was discussed based on reversible control of CdTe QDs fluorescence. So a novel fluorescence biosensor for sensitive and selective detection of dsDNA based on dual-fluorescence of QDs-Al3+-PFLX ensemble was developed.The main results are as follows:1. Interaction between GSH-CdTe QDs and L-Aapartic acid and Its analytical applicationGlutathione (GSH) capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous solution. The mechanism of interaction between GSH-CdTe QDs and L-Aapartic acid (L-Asp) was studied by UV-vis absorption, resonance Rayleigh scattering (RRS), fluorescence and infrared spectra. In pH5.3BR buffer solution, L-Asp could be combined with the GSH-CdTe QDs by the electrostatic attraction and hydrogen bond, forming a bigger diamete aggregate, which resulted in RRS increased markedly and the fluorescence of GSH-CdTe QDs quenched sharply. The increased RRS intensity and the quenched fluorescence intensity were directly proportional to the concentration of L-Asp in a certain range and the sensitivity of RRS method was higher (the detection limit for L-Asp was14.2ng-mL-1) than the fluorescence method, so a new sensitive RRS method for the determination of L-Aapartic acid was established by using GSH-CdTe QDs as a probe. In addition, the optimum conditions of the reaction and the influences of coexisting substances were tested by RRS method, which could be satisfactorily applied to the determination of L-Asp residues in urine samples.2. Fluorescence enhancement of CdTe/CdS QDs by coupling of glyphosate and its application for sensitive detection of copper ionA novel fluorescent probe for Cu2+determination based on the fluorescence quenching of Glyphosate (Glyp)-functionalized quantum dots (QDs) was firstly reported. A strong fluorescence intensity increment of TGA-CdTe/CdS QDs was generated by Glyp. The enhancement of the fluorescence was attributed to the passivation of trap states of TGA-CdTe/CdS QDs through the chelation of P=O group with Cd2+and the hydrogen bonds with thioglycolic acid. Under the optimal conditions, the response was linearly proportional to the concentration of Cu2+between2.4×10-2μg·mL-1and28μg·mL-1, with a detection limit of1.3×10-3μg·mL-1(38). The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu2+. The fluorescent probe was successfully used for the determination of Cu2+in environmental samples. The mechanism of reaction was also discussed.3. Detection of double-stranded DNA by dual-fluorescence quantum dot-Al3+-PFLX complex as biosensorsWe highlight a novel fluorescence biosensor for sensitive and selective detection of double-stranded DNA (dsDNA) based on dual-fluorescence of quantum dot-Al3+-pefloxacin mesylate (QDs-Al3+-PFLX) ensemble. The biosensor was based on a fluorescence "OFF-ON" mode. A13+-PFLX complex was used as a dual-function probe, as both the quencher to QDs and a receptor to dsDNA. In this paper, the A13+-PFLX complex was first employed as an effective fluorescence quencher to QDs through photoinduced electron transfer (PET), while the fluorescence of A13+-PFLX complex was also quenched by QDs when forming the ionic ensemble. Therefore, the mixed solution of these two fluorescent materials in the state of "off-off". Because of its strong binding affinity with A13+-PFLX complex, the dsDNA can break up the low fluoresced ionic ensemble, recovering the fluorescence of QDs and Al3+-PFLX complex, enabling them to display the signal output at558nm and421nm, respectively. The state of the two kinds of fluorescent material was converted into "on-on". Thus, the simultaneously quantitatively determination of dsDNA by QDs-Al3+-PFLX complex can be realized via both the restoration of QDs and the Al3+-PFLX complex fluorescence with a single excitation light, while ribonucleic acid, bovine albumin serum, and biological relevant metal ions cannot produce the similar results. The detection limits (38/K) for herring sperm (hs) DNA are0.0153(QDs) and0.0480(A13+-PFLX complex) μg-mL-1, respectively. The entire experimental process does not require any chemical modification and coupling of CdTe QDs and DNA, greatly simplifying the experimental process, to achieve highly sensitive and specific detection of the DNA, and has great practical value and application prospect.