A one-step method for successfully fabrication of water-soluble and alkanethiol-stabilized Au nanoclusters (NCs) was demonstrated. The novel and facile method was based on simply placing histidine (His), HAuCl4 and 11-mercaptoundcanoic acid (MUA) together at room temperature. The resulting Au NCs were exclusively composed of Au17MUA4His22 (AMH), as demonstrated by the photoluminescence, UV-Vis absorption, electrospray ionization mass and X-ray photoelectron spectroscopy. AMH exhibited intense red fluorescence (λem = 600 nm), a long fluorescence lifetime (7.11 μs), considerable stability, and a large Stoke's shift (320 nm). Based on the excellent properties of the AMH, cell experiments were conducted. Cytotoxicity studies showed that the Au NCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. Cancer cell imaging of HeLa cell lines indicated that the obtained AMH could serve as a promising fluorescent bioprobe for bioimaging. This strategy, based on the one-step method, may offer a novel approach to fabricate other water-soluble and alkanethiol-stabilized metal nanoclusters for application in biolabelling and bioimaging.

A simple and novel method for the colorimetric detection of Co(2+) was developed based on controlling the oxidation level of methylene blue (MB). After a complex was formed between MB, 2-aminothiophenol (ATP) and copper nitrate (MB-ATP-Cu(2+)), the sensing of Co(2+) showed high selectivity. The mechanism of sensing has also been discussed.

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Three kinds of morphological gold nanoparticles (Au NPs), including gold nanospheres, gold nanosheets, and gold nanostars were easily synthesized using Tryptophan (Trp) modified with glutaraldehyde (GA) as reducing agent and stabilizer. This method can avoid using of seed and surfactant during the whole preparation process. The molar ratio of Trp-GA to chloroaurate ions plays a significant role in controlling the morphology of the Au NPs in aqueous environment. By adjusting the molar ratio of Trp-GA to chloroaurate ions, gold nanospheres, nanosheets, and nanostars can be easily obtained. Moreover, the as-prepared gold nanosheets and nanostars possess excellent SERS efficiency, demonstrating their potential as SERS tags for practical application.