Highly Selective and Reversible Optical, Colorimetric, and Electrochemical Detection of Mercury(II) by Amphiphilic Ruthenium Complexes Anchored onto Mesoporous Oxide Films

Abstract

The colorimetric, fluorimetric, and electrochemical detection of mercury ions by functionalized ruthenium sensitizers in aqueous and non‐aqueous solutions and on anchored TiO2 films are investigated. Mercury ions coordinate reversibly to the ruthenium sensitizers, inducing a color change and increasing the phosphorescence intensity significantly. The electrochemical data of the adsorbed sensitizer on TiO2 films show a reversible couple, owing to the percolation through electronic couplings between –NCS ligands of neighboring molecules; upon exposure to a Hg2+‐containing solution, the electrical signal is appreciably reduced. The detection limit for mercury(II) ions using UV‐vis spectroscopy in homogeneous aqueous solutions is estimated to be ∼ 20 ppb. The results presented herein have important implications in the development of reversible colorimetric, fluorimetric, and electrochemical on–off sensors based on nanocrystalline semiconductor films for the simple, swift, and selective detection of mercury ions in solution.

Phosphonate-Substituted Ruthenium(II) Bipyridyl Derivative as a Photoelectrochemical Probe for Sensitive and Selective Detection of Mercury(II) in Biofluids

“…As previously reported, when NCS was coordinated between two metal centers as a bridging group, a shift of 30 cm –1 toward high energy in the position of the v (CN) band was observed. The phenomenon is well-consistent with our data, indicating the NCS as a bridging ligand coordinated with Ru 2+ by the lone pair on the nitrogen and with Hg 2+ via the lone-pair electrons on the sulfur, respectively Figure B), while the addition of Hg­(NO 3 ) 2 blue-shifted the MLCT transition band to 460 nm (curve b, Figure B).…”

“…To further elucidate the PEC detection mechanism, the DRIFTS of Ru-1 /TiO 2 and UV–vis spectra and CVs of Ru-1 with and without the combination of Hg 2+ were investigated. As shown in Figure A, exposure of Ru-1 /TiO 2 /FTO to 0.1 mg/mL Hg­(NO 3 ) 2 solution decreased the v (NCS) group intensity at 2103 cm –1 by a factor of one-half and generated a new peak at 2144 cm –1 . As previously reported, when NCS was coordinated between two metal centers as a bridging group, a shift of 30 cm –1 toward high energy in the position of the v (CN) band was observed.…”

“…The CVs in Figure C showed that the addition of Hg 2+ positively shifted the first redox peak of Ru-1 from 0.859 to 0.909 V (vs Ag/AgCl) and slightly increased the anodic current. The positive shift in the CV agreed well with the blue shift in UV–vis spectra, indicating that the specific interaction between Hg 2+ and NCS increased the energy level of the HOMO and caused the dπ–π* transition to occur at higher energies, while the current increase was attributed to the improved conductivity after Hg 2+ coordination (Figure S5). The emission lifetimes of Ru-1 and Ru-1 /Hg 2+ (Figure D) were 39 and 33 ns, respectively, indicating that the e – –hole + recombination in the Hg 2+ -coordinated complex was more serious .…”

A colorimetric probe for the detection of Ni2+ in water based on Ag-Cu alloy nanoparticles hosted in electrospun nanofibres

“…If Ag and Cu ions are reduced simultaneously in the same solution, Ag-Cu alloy nanoparticles are expected to form. The alloy formation could be concluded from the fact that the optical absorption spectrum showed only one plasmon band, in agreement with literature reports (Mulvaney, 1996;Papavassiliou, 1976;Torigoe et al, 1993). Two bands would be expected if there was a mixture of Ag and Cu nanoparticles.…”

High-Efficiency Upconversion Luminescent Sensing and Bioimaging of Hg(II) by Chromophoric Ruthenium Complex-Assembled Nanophosphors

“…As shown in Figure , the spectral overlap between the green upconversion luminescence emission from Er 3+ -doping UCNPs and the absorbance of the complex N719 indicates the possibility of the energy transfer process from emissive Er 3+ to the complex N719. As reported by Palomares et al , − addition of Hg 2+ induces a significant blue shift for the absorption maximum of the complex N719, from 541 to 485 nm (Figure ), leading to a decrease in the spectral overlap between the green upconversion luminescence emission of UCNPs and the absorption band of the complex N719, and resulting in a recovery of the upconversion luminescence emission of UCNPs at 541 nm. As a result, the nanosystem is expected to sense Hg 2+ over other metal cations.…”