Luminescent Sensors Based On Gold Nanoclusters

Gold nanoclusters (Au-NCs) are a new type of luminescent and ultra-small gold nanoparticles (core diameter<2 nm). Au-NCs have many excellent optical, electric and catalytic properties, and have thus attracted more and more attention in many fields scuh as materials, catalysis and sensing. The synthsis of Au-NCs by simple, low-cost, and environmentally friendly methods and the construction of sensitive and selective chemical sensors based on Au-NCs are of considerable research and application interest.In this thesis, two new types of Au-NCs were prepared using glutathione (GSH), P-cyclodextrin (β-CD) and polyethyleneimine (PEI) as the molecular templates and capping reagents. The UV absorption, fluorescence (FL) and electrochemiluminescence (ECL) properties of the Au-NCs, and the interactions with iorganic cations and anions were studied, based on which new luminescent sensors with specific recognition abilities towards Ag+and CN- ions were developed. The thesis consists of following five chapters.In the first chapter, literatures related to Au-NCs were investigated and reviewed, from which the synthesis methods, the properties and applictions of Au-NCs were briefly introduced. Addtionally, the content of this thesis and the significance of the work were stated.In the second chapter, study was focused on the synthesis and characterization of P-cyclodextrin-capped and glutathione-etched Au-NCs (Au13(SG)8@β-CD NCs or Au13). Their particle size, composition, and number of gold atoms and the capping molecules were characterized by scanning electron microscopy, fluorescence, UV-Vis absorption, FT-IR spectroscopy and mass spectrometry.In the third chapter, a selective and sensitive fluorescent method for the determination of Ag+ in water was developed by the enhancing fluorescence of Au13. There was a good linear response between the logarithmic of fluorescence intensity and the logarithmic of Ag+ concentration in the concentration range betwween 0.5 nM and 0.1 uM, with a detection limit at 0.3 nM (at an SNR of 3).In the fourth chapter, study was focused on an ultra-rapidly and "green" synthesis of PEI-capped Au clusters (AuNCs@PEI). AuNCs@PEI not only showed the red fluorescence, but also emitted the good stable ECL. Moreover, the addition of Ag+ ions into the TEA/AuNCs@PEI system resulted in significant enhancement in ECL production.In the fifth chapter, a cyanide ion sensor was developed by the quenching fluorescence of AuNCs@PEI. The sensor exhibited high sensitivity, specific selectivity and low limit of detection.