Highly selective visual sensing of copper based on fluorescence enhanced glutathione-Au nanoclusters.

A blue emission glutathione stabilized Au nanoclusters prepared by an Au/Histidine complex with ligand-exchanges method was used for sensing of copper ions. We found that the glutathione stabilized Au NCs which has fluorescence emission hundred times higher than the Au/Histidine complex and has a highly selective fluorescence quenching response to copper ion. Other common metal ions, such as mercury, lead, iron and zinc, which could obviously quench or enhance the fluorescence of Au/Histidine complex, do not interfere the sensing of copper using glutathione stabilized Au nanocluster. The possible quenching mechanism and the dynamic quenching process for copper detection were also discussed. The results indicated that copper in the range from 0.5 to 300.0µM could be linearly detected and the detection could be finished quickly in 5min. A visual detection method for copper ion that may be used to fast warn copper pollution in waters by naked eyes observation was also be developed using the glutathione stabilized Au NCs probe.

An irreversible temperature indicator fabricated by citrate induced face-to-face assembly of silver triangular nanoplates.

Assembly of anisotropic nanoparticles which need well controlling of assembly direction and spatial arrangement is more interesting than one-dimensional nanoparticles assemblies. As confirmed by observing of transmission electron microscopy images and analysis of plasmon resonance spectrum transformations, we found that silver triangular nanoplates (TNPs) without further modification could be face-to-face assembled by citrate. The face-to-face assembly of silver TNPs could be disassembled quickly by heating at a wide temperature range from 30 to 80 °C. In this process, an obvious localized surface plasmon resonance (LSPR) peak shift and a color change of solution from pink to purple could be observed. Moreover, the disassembled silver TNPs suspension is very stable that no significant peak shift of silver TNPs spectrum was observed in 8 h after removing of silver TNPs from a hearing area. Therefore, we fabricated an irreversible temperature indicator by measuring the relationship between the shift of LSPR peak and heating temperature, and by watching the color change of the solution in a certain environment. The irreversible temperature indicator has potential to develop a temperature label for revealing temperature history of a thermosensitive product which cannot expose to excessive temperature.