The Study About Preparation And Characterization Of The New Noble Metal Nanoclusters And The Application As Sensors

New fluorescent noble metal nanoclusters are made of gold, silver and platinum group (such as, ruthenium, rhodium, palladium, osmium, iridium, platinum) noble metal elements. According to the composition, the fluorescent noble metal nanoclusters are divided into three types, namely, a single metal nanoclusters, bimetallic nanoclusters and polymetallic nanoclusters. Due to its good optical properties, the noble metal nanoclusters have been used in drug delivery, gene detection, food and environmental monitoring, catalysis, living biological imaging and other fields. However, given the demand for fluorescence sensors and fluorescence ratio-metric sensor and the flaw and the insufficiency of the fluorescent noble metal nanoclusters, the new fluorescence noble metal nanoclusters need further to be investigated in synthesis and sensor developing aspects. Main contents and results are listed as follows:1. Fluorescent gold nanoclusters (Au-NCs) were synthesized by a one-pot method using 11-mercaptoundecanoic acid as a reducing and capping reagent. It is found that the red fluorescence of the Au-NCs is quenched by the introduction of Eu3+ at pH 7.0, but that fluorescence is restored on addition of phosphate. The Au-NCs were investigated by transmission electron microscopy and fluorescence photographs. The effect of pH on fluorescence was studied in the range from pH 6 to 10 and is found to be strong. Based on these findings, we have developed an assay for phosphate. Ions such as citrate, Fe(CN)63-, SO42-, S2O82-, Cl-, HS-, Br-, acetate, NO2-, SCN-, ClO4-,HCO3-, NO3-, Cd2+, Ba2+, Zn2+, Mg2+ and glutamate do not interfere. The fluorescent nanocluster probe responds to phosphate in the range from 0.18 to 250 ?M, and the detection limit is 180 nM. The probe also responds to pyrophosphate and ATP.2. A sensitive and selective phosphorescence "turn-off-on" nanosensor to detect heparin by gold nanoclusters (Au-NCs) modulated with protamine was developed. The carboxyl groups on the surface of Au-NCs can interact with amino groups in protamine via electrostatic interactions and hydrogen bonding to induce the aggregation of Au-NCs, which results in the photoluminescence to "turn-off". However, in the presence of heparin, protamine prefers to combine with heparin to release Au-NCs, which results in the photoluminescence to "turn-on". The photoluminescence lifetime measurements demonstrate that the photoluminescence belongs to phosphorescence, and that the quenching progress is dynamic. The concentration of heparin can be determined by measuring the Au-NCs phosphorescence recovery. The linear response range was obtained from 0.006 to 25.0 ?g mL-1 with the detection limit of 6 ng mL-1. Moreover, the proposed phosphorescence nanosensor was used to detect heparin in fetal bovine serum samples with satisfactory results.3. Dual-emitting bovine serum albumin-erbium (?) complex-modulated gold-silver bimetallic nanoclusters (BSA-Er/Au/Ag-NCs) have been synthesized for the first time by a simple one-pot synthesis route. The BSA-Er/Au/Ag-NCs show unique and well-resolved dual emission bands at 400 nm corresponding to the emission of the BSA-Er complex and 585 nm related to the emission of Au/Ag-NCs under a single wavelength excitation at 340 nm, respectively. Interestingly, with the addition of sulfide ions (S2"), the emission intensity at 400 nm (I400) increases, while the emission intensity at 585 nm (I585) decreases, which could be due to the formation of an Ag2S layer on Au/Ag-NCs. The Ag2S layer not only quenches the fluorescence of Au/Ag-NCs due to the surface capping phenomenon, but also separates the BSA-Er complex and Au/Ag-NCs. The enlarging distance blocks the fluorescence energy transfer (ET) from the BSA-Er complex to Au/Ag-NCs, leading to an enhancement of the photoluminescence intensity at 400 nm. The opposite effect makes the ratio of the two emission intensities (I400I585) ultrasensitive to the existence of S2". Accordingly, a ratio-metric fluorescent nanosensor for the determination of S2- was established. Under optimum conditions, the fluorescence intensity ratio (I400/I585) of the nanosensor against the concentration of S2" shows a good linear range from 0.02 ?M to 180 ?M with a lower detection limit of 6.0 nM and excellent anti-interference performance.