Sensing Technology Based On Gold And Silver Nanoclusters And Phenylboronic Functional Materials

Noble metal nanoclusters(NCs), such as gold nanoclusters(AuNCs), silver nanoclusters(AgNCs) and bimetallic gold and silver nanoclusters(Au / AgNCs) possess unique chemical and physical properties, and are widely used in chemical sensors and biosensors to achieve the sensitive and specific detection of multiple targets. In this thesis, strong fluorescence Au / AgNCs were synthesized to develop several sensing systems for detecting pesticides and heavy metal ions. Moreover, the specific recognition of phenylboronic acid to polyols was employed to develop a height-readable analysis method for sugars and other polyols in samples.(1) A “lab-on-a-drop”-based fluorimetric protocol has been proposed using strong fluorescent nanoprobes of gold nanoclusters(AuNCs) for the label-free analysis of organophosphorus residue in vegetables(Chapter 2). Based on the AChE-catalyzed hydrolysis of ATC releases thiocholine to cause the aggregation of the AuNCs towards a fluorescence quenching, which could be curbed by the inhibition of ACh E activity once exposed to DDVP, a rapid, ultrasensitive and specific fluorimetric assay has been tailored for the detection of pesticide residues(linear concentrations ranging from 0.032 nM to 20 nM and the detection limit of 13.67 pM). Particularly, pesticide residues of DDVP in vegetable samples were quantified down to about 36 pM. Such a label-free “lab-on-a drop”-based fluorimetry may promise a new method for monitoring the direct phosphorylation biomarkers of free OPs towards early infectious warning, and the evaluation of the physiological catalytic activity of enzymes.(2) Bimetallic alloying gold-silver nanoclusters(Au-AgNCs) have been synthesized with strong fluorescence by a one-pot biomineralization synthesis route at a vital molar ratio of Au/Ag precursors in the protein matrix. A rapid, specific, and ultrasensitive fluorimetric method has thereby been developed using Au-AgNCs as the fluorescent probes for the detections of Hg2+ and Cu2+ ions in blood(Chapter 3). The as prepared Au-AgNCs could exhibit “silver effect”-enhanced red fluorescence, which is about 6.5-fold and 4.7-fold higher than that of common AuNCs and core-shell Au@AgNCs, respectively. Particularly, the “silver effect” endowed the Au-AgNCs probes the improved responses to Hg2+ ions, especially, the strong capacity of specifically sensing Cu2+ ions. Moreover, aided by a Cu2+ chelating agent, the separate detections of Hg2+ ions and Cu2+ ions could also be expected. Such an Au-AgNCs-based fluorimetric method can allow for the analysis of Hg2+ and Cu2+ ions down to 0.30 nM and 0.60 nM in blood, respectively, promising the detection applications in the clinical laboratory.(3) A visual height measurement technology was developed based on the capillary effects and the specific recognition of functionalized phenylboronic acid derivatives to sugars and other polyols including monosaccharides and polysaccharides in blood, natural products, agricultural and chemical products and other polyols containing 1,2- or 1,3-diol group(Chapter 4). Functionalized phenylboronic acid derivatives were firstly immobilized on the inner surface of a scaled capillary, which was pretreated by amino silane reagents. When the sample was automatically sucked into the capillary by the capillary effect, the reaction between the phenylboronic acid derivatives and polyhydroxy compounds containing 1,2- or 1,3-diol group could occur to form the phenylboronic compound that might become swelled, leading to the change of the hydrophilicity of the capillary walls. As result, the liquid levels of the capillary could rise, which heights could be visually determined to achieve the rapid analysis of the content of sugars and other polyhydroxy compounds in the samples. This developed method using functionalized phenylboronic acid derivatives that could identify sugars and other polyols, showing some advantages over most traditional enzymology technology, of which the inactivation of enzymes might happen, and have the advantages of less-consumption(about 20μL) sample, easy operation, and on-site applications.