Synthesis Of Gold Nanoclusters And Their Applications For Fluorometric Sensing

Noble-metal nanoclusters, can exhibit molecule-like electronic transitions between HOMO-LUMO energy level due to their small size (less than 10 nm), usually consist of several to tens of atoms, with properties regulated by their subnanometer dimensions. Particularly, owing to their fascinating features including ease of preparation and conjugation, good water solubility, biocompatibility, excellent stability, gold nanoclusters (AuNCs) have drawn wide attention in recent years. Emerging as a new type of fluorescent material, AuNCs have been considered as a satisfactory candidate for biosensing, catalysis, and imaging. Therefore, considering their satisfactory optical charaters, in this study we attempt to develop sensing for antibiotic and heavy metal ions based on AuNCs. The main contains are listed as follows:Part 1 Metal-enhanced fluorescence (MEF), usually generated by the interactions of fluorophores with metal. Tetracycline and Eu3+, while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. AuNCs, emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu3+-Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01-5 μmol/L, with a detection limit of 4 nmol/L (3σ). Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. This system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence.Part 2 Mercury, as a widespread pollutant with distinct toxicological profiles, exists in water, soil, and food. Mercury ions (Hg2+), one of the most stable inorganic forms of mercury, is a caustic and carcinogenic species with high cellular toxicity. Hence, it is important to monitor Hg2+levels in aquatic ecosystem as a potential source of contamination. Herein, we have successfully synthesized AuNCs templated with DNA (5’-CCCCCCCCCCCCTTTTTT-3’), and subsequently employed this fluorescent AuNCs as a novel probe for sensitive detections of Hg2+. Basically, the procedure is due to the formation of thymidine-Hg2+-thymidine duplexes between AuNCs and Hg2+, thus leading to aggregations of AuNCs described here occurring, and facilitating their fluorescence decrease. Significantly, this decrease of fluorescent signals permitted sensitive detections of Hg2+ in a linear range of 0.1-100 μmol/L, with a detection limit of 0.083 μmol/L at a signal-to-noise ratio of 3. Additionally, the practicality of this probe for assaying Hg2+ in human urine and lake water samples was further validated, and showed various advantages including simplicity, low cost, sensitivity and selectivity, demonstrating its potential to broaden ways for assaying Hg2+ in real samples.In summary, we suppose that the research results describes above would be beneficial for us to understand deeply their characters of AuNCs, and developed effective platforms for pharmaceutical analysis.