Gold nanorods (AuNRs) with their plasmonic properties are becoming indispensable in the field of chemical sensing. There is particular interest in AuNRs for the detection of the mercury ion, Hg2+, owing to the affinity for Hg0 to amalgamate with Au0 . This system has previously been explored using cetyltrimethylammonium bromide coated AuNRs (CTAB@AuNRs), with modest success due to interference from CTAB and the general instability of CTAB@AuNRs. This investigation examines the detection of Hg2+ using polyethylene glycol thiol coated AuNRs (PEG@AuNRs). It was first determined that the CTAB could be exchanged for PEG-Thiol efficiently and with little effect on the features of the AuNRs. This was confirmed by analysis with 1H NMR, STEM and UV-Vis spectroscopy. The PEG@AuNRs used in the detection of Hg2+ showed only a moderate increase in sensitivity over CTAB@AuNRs. However, it was discovered that due to the increased stability of the PEG@AuNR the ratio of AuNRs to Hg2+ could be optimized increasing the range and sensitivity of detection. It was also discovered that incubation of the PEG@AuNRs with Hg2+ increased their sensitivity to Hg2+. This was attributed to the preferential liganding of PEG-thiol to Hg2+ over the AuNR surface and was verified with 1H NMR, STEM, and HR-TEM. The results were particularly interesting for the Hg2+ selectivity. Samples incubated with Hg2+ demonstrated a near 3-fold increase in sensitivity to Hg2+ while showing no detectable change in incubation with selected interfering ions.

Plasmonic detection of mercury via amalgamation on gold nanorods coated with PEG-thiol

ACS Spring Meeting 2021

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