| Compared to traditional organic fluorescent dyes, colloidal semiconductor nanocrystals (also referred to as quantum dots, QDs) possess many unique properties, such as high-quality luminescence, the broad excitation, size-tunable photoluminescence (PL) spectra, relatively high quantum yield and photochemical stability, which make QDs an attractive alternative to organic dyes in applications. These excellent properties exhibit great foreground in potential fields, including chemistry, medicine, materials, cell biology, molecule biology, and so forth. In the past few years, QDs-based PL sensors have generated an increasing interest because they can give birth to a distinct target signal for qualitative and quantificational analysis of various substances. The dissertation aimed to this advanced research direction, summarized a refined development of QDs and established a basic research method, that is, the following works have mainly been performed by taking QDs synthesis, characterization, particular PL behavior and PL sensors applied in chemical analysis as the line of this dissertation:One:A near-infrared-emitting CdTe/CdS core/shell quantum dots-based OFF-ON photo-luminescence sensor for highly selective and sensitive detection of Cd2+. Herein, near-infrared-emitting CdTe/CdS QDs were synthesized and regularly characterized in aqueous media with3-mercaptopropionic acid as a stabilizer. PL of the as-prepared QDs was quenched due to the addition of ammonium pyrrolidine dithiocarbamate, and became enhanced after adding Cd2+Furthermore, the relationship between PL intensity and the concentration of Cd2+was almost linear. Therefore, a novel QDs sensor based on a PL "OFF-ON" mode could be designed. Experimental results confirmed that this sensor of Cd2+was of high selectivity and sensitivity over other metal ions, and exhibited perfect analysis performance in real and complicate samples. This proposed method could even substitute the ICP-AES for the determination of Cd2+in the concentration range from0.1to2μM. Compared to conventional sensors based on a PL quenching mode, the "OFF-ON" PL sensor in our case presented a superior reliability and a lower detection limit, which was only6nm.Two:Rhodamine6G (R6G) conjugated-CdTe quantum dots used for a highly sensitive and selective ratiometric fluorescent sensor of glutathione (GSH). By electrostatic interactions in aqueous solution,3-mercaptopropionic acid capped-CdTe QDs and R6G were conjugated to form R6G-QDs conjugates, together with a systemic characterization. The addition of GSH (0～80μM) induced regular PL response of conjugates, and PL intensity of R6G (lR6G) to that of QDs (IQDS) in conjugates was near linear toward the concentration of GSH, which could be developed as a ratiometric PL sensor of GSH. Related experiments testified that the sensor was of high selectivity and sensitivity over other thiols and amino acids. In comparison with other single-intensity-based PL sensors and traditional analytical techniques, this ratiometric PL sensor was more facile, rapid, low-cost, and exhibited a lower limit detection of15nM. The proposed method could be applied to develop other types of QDs-based molecular or ionic probes for ratiometric PL sensing, and was beneficial to the in-depth research of GSH levels in biological samples and biomedical systems.Three:Fluorescein isothiocyanate (FITC) conjugated-CdTe quantum dots as novel dual-functionally ratiometric fluorescence sensors of pH and cadmium ions. In aqueous solution, FITC and2-mercaptoacetic acid capped-CdTe QDs were conjugated by hydrogen bonding, and formed FITC-QDs conjugates. With the pH increasing, both PL intensity of FITC (520nm) and QDs (595nm) in these conjugates showed regular enhancement. The ratiometric PL intensity (lFITC/IQDS) was near linear toward the pH from5.3to8.7. In addition, S2-induced PL quenching of QDs and the addition of Cd2+resulted in PL enhancement of S2--modified QDs. Thus, based on this PL "OFF-ON" mode, a ratiometric PL sensor of Cd2+could be achieved. Experimental results suggested that/lFITC/IQDS was almost linear toward the concentration of Cd2+in the range from0.1to15μM. Meanwhile, the addition of S2-and Cd2+hardly affect PL intensities of FITC. This proposed method for detecting pH and Cd2+was highly sensitive and selective in real and complicated samples, and could replace ICP-AES at the same condition. This proposed sensor can help to develop other related QDs-based ratiometric PL sensors of ions or molecules for the in-depth analysis of complex systems.Four:Preparation, luminescence properties and applications of quantum dots-micro gels conjugates. In this chapter,3-mcrcaptopropionic acid capped-CdTe QDs and polymers of N-isopropylmethacylamide and2-methylacrylic acid (that is, P(NIPAM-MAA)) were utilized as PL reagent and microgels, respectively. Due to electrostatic interactions, QDs were entrapped into microgels network to form QDs-P(NIPAM-MAA) hybrid microgels, whose configuration, particular PL properties and applications in PL imaging and sensors were seriously studied in following experiments. According to experimental results, hybrid microgels displayed fully reversible PL behavior between25℃and45℃. The PL intensity was reduced with the each increment of temperature, and then PL was recovered because of temperature dropping. In addition, there was bright PL imaging detected by the confbcal fluorescence microscope. The PL response of hybrid microgeis to Cu2+(0～2μM) was highly selective, and the relationship between PL intensity and the concentration of Cu2+was linear proportion, which could be used as a hybrid micro gels-based sensor for qualitative and quantitative detection of Cu2+... |
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