Based On Water-soluble Cdte Nanocrystals Functional Fluorescent Probe Design, Synthesis And Analysis Applications

Semiconductor nanocrystals, or quantum dots (QDs), have emerged as an importantnew class of materials over the past decade. Compared with organic fluorophores,QDs possess many advantages, such as size-tunable fluorescence emission, largeabsorption across a wide spectral range, narrow emission spectra, high brightness,long-term photostability and single-light source excitation for multi-colored QDs.Traditionally, these QDs are synthesized in organic solvents using organometallicprecursors at high temperature. In recent years, water-soluble QDs have gainedincreasing attention because QDs have to be water-soluble for biological and mostlychemical applications. So it is necessary to synthesis high quality water soluble QDs.Here, the direct synthesisβ-cyclodextrin (CD) coated water-soluble CdTe QDs byusing a new'one pot'method is reported. At the artificially designed water-oilinterface using Cd(Ac)2, NaHTe, oleic acid andβ-cyclodextrin as precursors, theobtained CdTe QDs were stabilized byβ-CD, which is different from many previousreports. Compared to the organometallic route to obtain water-soluble QDs, the newstrategy is simple, cost-effective, and only need'one step'. Compared to the aqueoussynthesis route to obtain water-soluble QDs with thiols as stabilizers, our method isalso simple and requires no necessary to synthesize complicated thiols ligands. Thenew synthetic pathway which is easily handled can probably be expanded tosynthesize other receptor modified QDs.In this paper, different sizes of glutathione-capped CdTe (GSH/CdTe) QDs havebeen prepared derectly in aqueous solution. The biocompatible QDs have tunablefluorescence in the range of 510～670nm, and they also have high photoluminescencequantum yield (PLQY) without any post preparative treatment. In addition, folic acidwas covalently conjugated to the GSH/CdTe QDs for imaging of cancer cells,demonstrating their potentially broad application as biolabels.In a simple mixture solution of thioglycolic acid modified CdTe QDs and citrate-capped gold nanoparticles (AuNPs), fluorescence resonance energy transfer(FRET) was observed and studied. The steady state photoluminescence of CdTe QDsis quenched in the presence of AuNPs. The results suggest that it was hydrogen bondthat connected CdTe QDs and AuNPs together. More interestingly, the formed FRETcan be specificly broken by fluoride anion (F-) due to its unique and strongnucleophilic character. The results present here construct the hydrogen bond basednano-assemblies for the direct determination of F-in aqueous solution, which is highlysimple and practical.Since the affinity of boronic acid for diol is well known, a new FRET nanoprobe ofQDs-diol-MPBA-AuNPs was reported in aqueous solution. 3-amino-1,2-propanediol(diol) is selected to bind carboxyl on the surface of CdTe QDs.Mercaptophenyl-boronic acid(MPBA) is selected to modify AuNPs. The highextinction coefficient of AuNPs and the active boronate esters formed betweenphenylborinic acid and diol facilitate the efficient FRET. Meanwhile, F-anion, astrongly hard lewis base, specificly reacts with boron center and disassembles theAuNPs segment, resulting in the fluorescence recovery of the quenched QDs. Thenew nanoprobe responds well to aqueous F-with high selectivity and sensitivity in thepresence of a higher amount of other anions. In addition, the nanoprobe is low toxicityand effective for the highly selective detection of F~-in live cell.