Colorimetric Detection of Sulfide Anions via Redox-Modulated Surface Chemistry and Morphology of Au-Hg Nanorods

Dual-mode fluorescence and colorimetric sensing of sulfide anion in natural water based on near-infrared Ag2S quantum dots and MnO2 nanosheets complex

Near infrared (NIR) emission Ag2S quantum dots (QDs) are of great value for biochemical sensing with strong anti-interference and low toxicity. Herein, NIR fluorescence Ag2S QDs were synthesized successfully. Combined with the excellent oxidase-like characteristics of manganese dioxide (MnO2) nanosheets, a fluorescence and colorimetric dual-mode sensor for sulfide anion was developed. MnO2 nanosheets could effectively catalyze the oxidation of TMB to produce blue TMB oxide (ox TMB), at the same time, the fluorescence of Ag2S QDs could be effectively quenched by fluorescence internal filtration effect (IFE) and dynamic quenching effect. The enzyme-like activity was weakened and the NIR fluorescence of Ag2S QDs was restored when sulfide anion (S2-) was added, due to the reduction of MnO2 to Mn2+.The linear ranges for fluorescence and colorimetric analysis of S2- were 2-250 μM and 0.3-50 μM, with detection limits of 0.6 and 0.215 μM, correspondingly. The dual-mode sensor had a wider detection range, higher sensitivity and shorter reaction time, which could be used for highly selective detection of S2- in different concentration ranges. In addition, it had been successfully applied to the determination of sulfide in water samples with satisfactory accuracy and sensitivity.

Ag0 decorated Cr2S3 NPs embedded on PVP matrix: A colorimetric probe for selective and rapid detection of sulphide ions from environmental samples

Globally, the environmental pollution is one of the major issues causing toxicity towards human and aquatic life. We have developed a facile and innovative sensing approach for detection of sulphide ions (S^2-) present in the aqueous media using Ag⁰ decorated Cr₂S₃ NPs embedded on PVP matrix (Ag/Cr₂S₃-PVP). Based on the SPR phenomena, the detection of S^2- ions was established. The nanohybrid was characterized using various techniques such as UV-vis spectrophotometer, High-Resolution Transmission Electron Microscopy (HR-TEM), Thermal Gravimetric Analysis (TGA), X-ray diffraction analysis(XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The yellowish colour of Ag/Cr₂S₃-PVP nanohybrid turned to brown colour in presence of S^2- ions. The selectivity and sensitivity of the prepared probe was studied against the other interfering metal ions. In addition, the effect of different concentration of S^2- ions in the nanohybrid solution was investigated and the Limit of detection (LOD) was found to be 6.6 nM. The good linearity was found over the range of 10 nM to 100 μM with R² value of 0.981. The paper strip based probe was developed for rapid onsite monitoring of S^2- ions. The proposed method is found to be cost-effective, rapid, and simple. We have validated the practical applicability of the prepared probe for determining the concentration of S^2- ions in real water samples.