Preparation And Analytical Application Of Fluorescent Sensors Based On Inner Filter Effect On Quantum Dots

Fluorescence analysis method refers to the application of certain substances which can emit fluorescence after excited by specific wavelength of light in qualitative and quantitative analysis of the analytes.It has the advantages of simple operation,high sensitivity,good selectivity,wide linear range,low detection limit and visualization in some methods etc.It has been widely used in drug analysis,biological analysis,environmental monitoring,mineral analysis and so on.As is known to all,fluorescent quantum dots have a lot of advantages when compared to conventional organic dyes or fluorescent proteins,such as better stability to photobleaching,relatively high quantum yields,the narrow and nearly symmetrical emission peaks,the broad absorption spectrum.In addition,desired excitation and emission wavelength can be easily obtained through careful adjustment of diameter and composition of quantum dots and different functional groups can be easily decorated on quantum dots.Due to these excellent features,fluorescent quantum dots are used as a very effective fluorescent probe in sensing application.The extinction coefficient of gold nanoparticles?AuNPs?is large and it is several orders of magnitude larger than the extinction coefficient of conventional organic chromophores.In addition,the surface plasmon resonance band of AuNPs is very sensitive to the distance between AuNPs and when AuNPs are close to each other and aggregated,the color of AuNPs changes from red to blue.Because of these excellent features,AuNPs are often used in visual detection.In this paper,water-soluble 3-mercaptopropionic acid modified cadmium telluride quantum dots?CdTe QDs?were synthesized.Based on the synergetic effect of inner filter effect and dynamic quenching of propranolol on CdTe QDs,propranolol can be fast and conveniently detected.In addition,we synthesized dithiocarbamate-modified gold nanoparticles?DTC-AuNPs?.Based on the inner filter effect of DTC-AuNPs on GQDs and the Pb²⁺triggered aggregation of DTC-AuNPs,Pb²⁺can be effectively and visually detected.?1?Fluorescence quenching of 3-mercaptopropionic acid stabilized CdTe QDs for direct determination of propranololIn this work,a sensitive,convenient and rapid fluorescence sensor for detection of propranolol was proposed based on the fluorescence quenching of propranolol on3-mercaptopropionic acid stabilized CdTe QDs.And the fluorescence quenching mechanism between CdTe QDs and propranolol was studied by time-resolved fluorescence spectroscopy?UV-Vis spectroscopy and fluorescence spectroscopy.And the results indicated that the fluorescence quenching of CdTe QDs was attributed to the simultaneous action of inner filter effect and dynamic quenching effect.The effects of concentration of quantum dots,pH value of buffer solution and incubation time on fluorescence signal of propranolol/CdTe QDs system were also investigated.Results indicated that,under the optimal experimental conditions,the linear range of this assay was 0.1?M to 2?M and 5?M to 200?M,with a corresponding detection limit of 0.055?M.Moreover,some common drug excipients and analogues of propranolol and stimulants had no apparent effect on the determination of propranolol.The proposed fluorescence sensor could be readily used for detecting propranolol in biological samples.?2?Visual detection of lead ions based on inner filter effect of functionalized gold nanoparticles on the fluorescence of graphene quantum dotsIn this work,dithiocarbamate-modified gold nanoparticles?DTC-AuNPs?were synthesized,and a convinient,selective and sensitive method for visual and fluorescent detection of Pb²⁺was proposed based on inner filter effect of DTC-AuNPs on the fluorescence of GQDs.And the fluorescence quenching mechanism was studied by transmission electron microscope?UV-Vis spectroscopy and fluorescence spectroscopy.The fluorescence of GQDs was quenched remarkably by DTC-AuNPs through the inner filter effect.And Pb²⁺can specifically combine with DTC-AuNPs,which triggered the aggregation and color change of DTC-AuNPs.Therefore,the inner filter effect of DTC-AuNPs on the fluorescence of GQDs was weakened and the fluorescnece intensity was recovered.And the effect of incubation time,concentration of GQDs and DTC-AuNPs on fluorescence signal of Pb²⁺/DTC-AuNPs/GQDs system were also investigated.Results indicated that,under the optimal experimental conditions,the linear range of this assay was 0.5?M to 100?M,with a corresponding detection limit of 0.35?M.Moreover,some common metal ions had no apparent effect on the determination of Pb²⁺.The proposed fluorescence sensor could be readily used for sensitive?convenient and rapid detecting Pb²⁺in practical samples.