Highly sensitive and selective determination of hydrogen sulfide by resonance light scattering technique based on silver nanoparticles.

We have developed a green approach to prepare DNA-templated silver nanoparticles (Ag-NPs) from the direct reaction between Ag+ and ascorbic acid in the presence of DNA and sodium hydroxide. The Ag-NPs showed strong resonance light scattering (RLS) intensity property. Then, the interaction between hydrogen sulfide (H2S) and Ag-NPs was studied by measuring their RLS spectra. The results showed that there is a strong interaction between Ag-NPs and H2S, which resulted in a decrease in the size of Ag-NPs and a decrease in the RLS intensity of the Ag-NPs solution at the wavelength of 467 nm. The results demonstrated that the RLS technique offers a sensitive and simple tool for investigating the interaction between Ag-NPs and H2S, which can be applied to detect H2S with high sensitivity and selectivity without complex readout equipment. The linear range for H2S determination was found to be the range from 5.0 × 10-9 to 1.0 × 10-7 mol L-1, and the detection limit (3σ/k) was 2.8 × 10-9 mol L-1. Moreover, the proposed method was applied for the determination of H2S in natural water samples with satisfactory results. Graphical abstract The application of Ag-NPs in H2S detection.

Silver nanoclusters stabilized with denatured fish sperm DNA and the application on trace mercury ions detection.

In this study, fluorescent silver nanoclusters (Ag NCs) were synthesized using denatured fish sperm DNA as the template. In contrast to other methods, this method did not use artificial DNA as the template. After their reaction with denatured fish sperm DNA, Ag+ ions were reduced by NaBH4 to form Ag NCs. The Ag NCs showed a strong fluorescence emission at 650 nm when excited at 585 nm. The fluorescence intensity increased fourfold at pH 3.78, controlled with Britton-Robinson buffer solution. The fluorescence of the Ag NCs was quenched in the presence of trace mercury ions (Hg2+ ) in a weakly acidic medium and nitrogen atmosphere. The extent of the fluorescence quenching of Ag NCs strongly depends on the Hg2+ ion concentration over a linear range from 2.0 nmol L-1 to 3.0 µmol L-1 . The detection limit (3σ/k) for Hg2+ was 0.7 nmol L-1 . Thus, a sensitive and rapid method was developed for the detection of Hg2+ ions.

Copper ion detection using novel silver nanoclusters stabilized with amido black 10B.

Novel fluorescent silver nanoclusters (AgNCs) were synthesized using amido black 10B (AB) as a stabilizing agent and then employed for the detection of copper ions (Cu(2+)). The AB-stabilized AgNCs (AB-AgNCs) were well dispersed in aqueous solution with an average diameter of around 1.3 nm and exhibited illustrious blue fluorescence emission. Moreover, the fluorescence of AB-AgNCs could be quenched efficiently by Cu(2+), which might be a result of the coordination between Cu(2+) and the free recognition group of AB on surfaces of AB-AgNCs, inducing the aggregation of AB-AgNCs. Based on the linear decrease of fluorescence intensity, the Cu(2+) concentration was determined in the range of 0.01-1.1 µmol L(-1) and the limit of detection (LOD) was 4.0 nΜ. In addition, the detection of Cu(2+) could be performed with AB-AgNCs in the presence of other ions, including 13 kinds of conventional metal ions and 11 kinds of anions. Based on the above experiment, the developed AB-AgNC probe was successfully further applied to detect Cu(2+) in three electroplating effluents, which showed high accuracy.

A sensitive spectrofluorometric method for detection of berberine hydrochloride using Ag nanoclusters directed by natural fish sperm DNA.

A novel DNA-directed AgNCs (DNA-AgNCs) was synthesized with economical raw material (natural fish sperm DNA) through a simple and rapid approach, and it first showed high and stable fluorescence emission as a AgNCs stabilized by natural DNA at about 635nm. Moreover, its emission intensity could be enhanced tremendously in acetic acid (HAc) medium. Whereas, when berberine hydrochloride (BRH) entered the solution system, it would interact and combine efficiently with DNA on the surface of AgNCs, which could lead to subtle change of charge distribution on its surface, and make it more lyophobic, inducing aggregation of DNA-AgNCs. As a result, fluorescence of the system was quenched visually; the process represented a color variance from yellow to hot pink under HAc medium, then back to yellowish-brown when BRH worked. Based on above phenomenon, a selective and accurate spectrofluorometric method for BRH detection was established. It can be applied to detect trace amounts of BRH in aqueous solution in the linear range from 1.0nM to 2000.0nM; and the detection limit (3σ/k) was 0.3nM, which is pretty lower compared to most reported spectral methods. Simultaneously, a semi-quantitative determination by visual evaluation from 5.0nM to 2000.0nM was also achieved. This method provided excellent selectivity for the detection of BRH in the presence of ten kinds of common natural amino acids and nine kinds of common mental ions. Furthermore, the BRH content in compound berberine tablets from drugstore was successfully investigated by this method and the results showed high accuracy.