Study On The Fabrication Of Chemical/Biological Sensors Based On Gold, Silver Nanoclusters

Novel and stable fluorescent probes play an important role in the rapid development of biological sensing. Noble metal nanoclusters, such as gold nanoclusters(Au NCs) and silver nanoclusters, have received much attention recently owing to the ultra-small size, non-toxicity, good optical stability, and fluorescent properties. In this thesis, we synthesize a series of fluorescent gold, and silver nanoclusters stabilized by glutathione, and then the applications of these as-synthesized nanoclusters as fluorescent probes in the chemical/biological sensors were performed. The main contents are listed as follows:1. Au NCs stabilized by GSH could catalyzes the reaction between 3,3’,5,5’-tetramethylbenzidine(TMB) and H2O2 to produce a blue color for colorimetric analysis. The colorimetric determination of H2O2 and glucose is accomplished based on this phenomenon. Moreover, an ultra-sensitive fluorescent assay for the detection of H2O2 and glucose is developed, which results from the efficient fluorescence resonance energy transfer(FRET) between the Au NCs and oxidized TMB. This assay was further applied to detect the glucose in human serum.2. The fluorescent Au NCs can be quenched by some metal ions including Hg2 +,Fe3 + and Cu2 +, and then an assay for determining Hg2+, Fe3+ and Cu2 +was developed. One, two or all the three metal ions may be selectively detected by using the masking agent EDTA and NH4 F. This fluorescent probe was applied to detect trace amount of elements g Hg2 +, Fe3 + and Cu2+ in fish.3. A new gold and silver composite nanoclusters(Au Ag NCs) exhabiting unique characteristics such as high fluorescence intensity, non-toxic, good water solubility and biocompatibility was synthesized. A fluorescence assay for determining Fe3+ and Cu2+ with high selectivity and sensitivity has been developed based on the quenching fluorescence of Au Ag NCs. With wide detection range and no other interference, this method can be applied to detect trace amounts of Fe3 +and Cu2 + in serum and has a potential application in clinical diagnosis.4. A kind of composite Ag Au S/Ag2 S nanoclusters with special physical and chemical properties was prepared, which shows tunable luminescence depending on the nanocluster size. The cytotoxicity and biocompatibility are investigated by the MTT assay. The composite nanoclusters exhibit selective detection of mercury including Hg2 + and undissociated mercury complexes. On the other hand, rhodamine B can be photo-degraded under the irradiation of ultraviolet or visible in the presence of Ag Au S/Ag2 S nanoclusters.Based on the quenching fluorescent Au Ag S/Ag2 S nanoclusters resulted from mercury, this fluorescence sensor was applied to detect trace amounts of Hg2 + in the fish samples.5. Au NCs enzyme mimetic exhibit intrinsic enzyme activity similar to that found in natural horseradish peroxidase, overcoming the drawbacks of nature enzymes subjected to environmental conditions and low stability. We developed a plasmonic nanosensor that well accommodates conventional immunoassays and dramatically improves their sensitivity and stability. This plasmonic nanosensor directly employs Au NCs enzyme mimetic to mediate growth or aggregation of Au NPs resulting in different color as the readout. This colorimetric sensor shows ultrasensitivity and the protein avidin at ultralow concentration 1.0?10-22 g/m L can be detected by naked eye. The breast cancer biomarker, cancer antigen 15-3(CA15-3), and thyroid hormone(3,5,3′-L-triiodothyronine) in human sera were detected.6. An ultra-sensitive assay to detect cysteine based on one-dimension self assembly of core-shell gold nanorods has been developed. The investigation shows that the longitudinal plasmon wavelength of the core-shell nanorods is larger; the higher sensitivity of this developed method. The determination of Hg2 + was performed based on the affinity between core-shell nanostructure and mercury to form a nanocomposite induced by Hg2 + in the presence of Na BH4. The longitudinal bands shift to shorter wavelengths and realize the detection of Hg2 +.