Reliable and sensitive methods to monitor mercury levels in real samples are highly important for environment protection and human health. Herein, a label-free colorimetric sensor for Hg2+ quantitation using gold nanostar (GNS) has been demonstrated, based on the formation of Au-Hg amalgamate that leads to shape-evolution of the GNS and changes in its absorbance. Addition of ascorbic acid (AA) to GNS solution is important for quantitation of Hg2+, mainly because it can reduce Hg2+ to Hg to enhance amalgamation on the GNSs and stabilize GNSs. In addition to transmission electron microscopy images, the distribution of circular ratios of GNSs in the presence of 2 mM AA and various concentrations of Hg2+ are used to show the morphology changes of the GNSs. Upon increasing the concentration of Hg2+, the average circular ratio of GNSs decreases, proving GNS is approaching to sphere. The morphology change alters the longitudinal localized surface plasmonic resonance (LSPR) absorbance of the GNSs significantly. Under the optimum conditions, our sensor exhibits a dynamic response for Hg2+ in the range of 1–4,000 nM with a detection limit of 0.24 nM. Upon Increasing Hg2+ concentration, the solution color changes from greenish-blue, purple to red, which can be distinguished by the naked eye when the Hg2+ concentration is higher than 250 nM. Owing to having a high surface-to-volume ratio and affinity toward Hg0, the GNS is sensitive and selective (at least 50-fold over tested metal ions like Pb2+) toward Hg2+ in the presence of AA. Practicality of this assay has been validated by the analysis of water samples without conducting tedious sample pretreatment.

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Background: Cancer causes millions of deaths and huge economic losses every year. The currently practiced methods for cancer therapy have many defects, such as side effects, low curate rate, and discomfort for patients. Objective: Herein, we summarize the applications of gold nanorods (AuNRs) in cancer therapy based on their photothermal effect-the conversion of light into local heat under irradiation. Methods: The recent advances in the synthesis and regulation of AuNRs, and facile surface functionalization further facilitate their use in cancer treatment. For cancer therapy, AuNRs need to be modified or coated with biocompatible molecules (e.g. polyethylene glycol) and materials (e.g. silicon) to reduce the cytotoxicity and increase their biocompatibility, stability, and retention time in the bloodstream. The accumulation of AuNRs in cancerous cells and tissues is due to the high leakage in tumors or the specific interaction between the cell surface and functional molecules on AuNRs such as antibodies, aptamers, and receptors. Results: AuNRs are employed not only as therapeutics to ablate tumors solely based on the heat produced under laser that could denature protein and activate the apoptotic pathway, but also as synergistic therapies combined with photodynamic therapy, chemotherapy, and gene therapy to kill cancer more efficiently. More importantly, other materials like TiO2, graphene oxide, and silicon, etc. are incorporated on the AuNR surface for multimodal cancer treatment with high drug loadings and improved cancer-killing efficiency. To highlight their applications in cancer treatment, examples of therapeutic effects both in vitro and in vivo are presented. Conclusion: AuNRs have potential applications for clinical cancer therapy.

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