Shu Chen

Silver nanoplates-based colorimetric iodide recognition and sensing using sodium thiosulfate as a sensitizer

A colorimetric method for the recognition and sensing of iodide ions (I(-)) has been developed by utilizing the reactions between triangular silver nanoplates (TAg-NPs) and I(-) in the presence of sodium thiosulfate (Na2S2O3). Specifically, I(-) together with Na2S2O3 can induce protection of TAg-NPs owing to the formation of insoluble AgI, as confirmed by the high-resolution transmission electron microscopy (HRTEM). In the absence of Na2S2O3, the etching reactions on TAg-NPs were observed not only by I(-) but also other halides ions. The Na2S2O3 plays as a sensitizer in this system, which improved the selectivity and sensitivity. The desired colorimetric detection can be achieved by measuring the change of the absorption peak wavelength corresponding to localized surface plasmon resonance (LSPR) with UV-vis spectrophotometer or recognized by naked eye observation. The results show that the shift of the maximum absorption wavelength (Δλ) of the TAg-NPs/Na2S2O3/I(-) mixture was proportional to the concentration of I(-) in the range 1.0×10(-9)-1.0×10(-6) mol L(-1). Moreover, no other ions besides I(-) can induce an eye discernible color change as low as 1.0×10(-7) mol L(-1). Finally, this method was successfully applied for I(-) determination in kelp samples.

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.

Visual determination of trace Cysteine based on promoted corrosion of triangular silver nanoplates by sodium thiosulfate

In this study, triangular silver nanoplates (TAg-NPs) were used to detect trace Cysteine concentration in the presence of sodium thiosulfate (Na2S2O3). Study showed that the TAg-NPs could be gently etched by Cysteine with the concentration of 1.0×10(-7) mol L(-1) through forming Ag-S covalent bond at the three corners. However, in the presence of Na2S2O3 (only 3.0×10(-6) mol L(-1)), the corrosion of Cysteine on TAg-NPs can be promoted significantly. It was also found that the color, morphology, and the maximum absorption wavelength of TAg-NPs change clearly with the concentrations of Cysteine as low as 2.5×10(-8) mol L(-1). Furthermore, the wavelength shift values (Δλ) of TAg-NPs solution were proportional to the concentrations of Cysteine in the range of 1.0×10(-9)-1.0×10(-7) mol L(-1), and the linear regression equation is Δλ=-0.89+319.94 c (c, μM, n=5) with the correlation coefficient of 0.990. At the same time, the color change of the TAg-NPs solution could be observed clearly by the naked eyes with increasing Cysteine concentrations in the range of 2.5×10(-8)-1.0×10(-7) mol L(-1). Thus, a novel method for the detection of Cysteine by either UV-vis spectrophotometry detection or naked eyes observation is established. It allows determination of Cysteine content in compound amino acid injection sample of 18AA-V.

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

AbstractNovel fluorescent silver nanoclusters (AgNCs) were synthesized using amido black 10B (AB) as a stabilizing agent and then employed for the detection of copper ions (Cu2+). The AB-stabilized AgNCs (AB–AgNCs) were well dispersed in aqueous solution with an average diameter of around 1.3xa0nm and exhibited illustrious blue fluorescence emission. Moreover, the fluorescence of AB–AgNCs could be quenched efficiently by Cu2+, which might be a result of the coordination between Cu2+ 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 Cu2+ concentration was determined in the range of 0.01–1.1xa0μmolxa0L−1 and the limit of detection (LOD) was 4.0xa0nΜ. In addition, the detection of Cu2+ 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 Cu2+ in three electroplating effluents, which showed high accuracy.n Graphical abstractThe process of synthesised silver nanoclusters and the application for Cu2+ detection.

A near-infrared fluorescent sensor with large Stokes shift for rapid and highly selective detection of thiophenols in water samples and living cells

AbstractThe development of simple methods with high sensitivity and selectivity to differentiate toxic aromatic thiols (thiophenols) from aliphatic thiols (cysteine, homocysteine, and glutathione) and hydrogen sulfide (H2S) is of great significance. Herein, we report on the fabrication of a novel near-infrared (NIR) fluorescent sensor for rapid and highly selective detection of thiophenols through the photoinduced electron transfer (PET) mechanism. In the presence of the thiophenols, an obvious enhancement of NIR fluorescence at 658xa0nm could be visualized with the aid of nucleophilic aromatic substitution (SNAr) reaction. The sensor displays large Stokes shift (~u2009227xa0nm), fast response time (<u200930xa0s), high sensitivity (~u20098.3xa0nM), and good biocompatibility. Moreover, the as-prepared sensor possesses an excellent anti-interference feature even when other possible interferents exist (aliphatic thiols and H2S) and has been successfully utilized for thiophenol detection in both water samples and living cells.n Graphical abstractIllustration of the sensor for thiophenol imaging in living cells

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

AbstractWe 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 isxa0a strong interaction between Ag-NPs and H2S, which resulted inxa0a decreasexa0in the size of Ag-NPs andxa0a decrease in the RLS intensity of the Ag-NPs solution at the wavelength of 467xa0nm. 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 5.0xa0×xa010−9 to 1.0xa0×xa010−7xa0molxa0L−1, and the detection limit (3σ/k) was 2.8xa0×xa010−9xa0molxa0L−1. Moreover, the proposed method was applied for the determination of H2S in natural water samples with satisfactory results.n Graphical abstractThe application of Ag-NPs in H2S detection

Visual detection of trace copper ions based on copper-catalyzed reaction of ascorbic acid with oxygen

A visual detection method for trace Cu(2+) in aqueous solutions using triangular silver nanoplates (abbreviated as TAgNPs) as the probe was developed. The method is based on that TAgNPs could be corroded in sodium thiosulfate (Na2S2O3) solutions. The absorption spectrum of TAgNPs solution changed when it is corroded by Na2S2O3. The reaction of oxygen with ascorbic acid (Vc) in the presence of a low concentration of Cu(2+) generates hydrogen peroxide that reacts with Na2S2O3, which leads the concentration of Na2S2O3 in the solution to be decreased. Therefore, the reaction between TAgNPs and the reacted mixture of Na2S2O3/Vc/Cu(2+) was prevented efficiently. When the Na2S2O3 concentration and reaction time are constant, the decrease in the concentration of Na2S2O3 is directly proportional to the Cu(2+) concentration. Thus, morphology, color, and maximum absorption wavelength of TAgNPs changed with the change of Cu(2+) concentration. The changed maximum absorption wavelength of TAgNPs (Δλ) is proportional to Cu(2+) concentration in the range from 7.5×10(-9) to 5.0×10(-7) M with a correlation coefficient of r=0.9956. Moreover, color change of TAgNP solution was observed clearly over a Cu(2+) concentration range from 7.5×10(-8) to 5.0×10(-7) M. This method has been used to detect the Cu(2+) content of a human hair sample, and the result is in agreement with that obtained by the atomic absorption spectroscopy (AAS) method.

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 650xa0nm when excited at 585xa0nm. The fluorescence intensity increased fourfold at pHxa03.78, 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 2.0xa0nmolxa0L-1 to 3.0xa0μmolxa0L-1 . The detection limit (3σ/k) for Hg2+ was 0.7xa0nmolxa0L-1 . Thus, a sensitive and rapid method was developed for the detection of Hg2+ ions.

Visual detection of trace copper(II) based on its catalytic action in the dissociation of thiosulfate

In this study, we report a new method for the detection of Cu2+ based on triangular silver nanoplates (TAg-NPs), which could be corroded by sodium thiosulfate (Na2S2O3). TAg-NPs with blue color can be changed to yellow color in the presence of a certain concentration of Na2S2O3, however, its color change is unclear when Na2S2O3 was heated in the presence of Cu2+. The reason may be that Na2S2O3 dissociates on heating in the presence of Cu2+, which leads the concentration of Na2S2O3 to be decreased. Furthermore, when the heating time is fixed, the decrease in the concentration of Na2S2O3 is proportional to the concentration of Cu2+. As a result, the color of the mixture solution of TAg-NP/Cu2+/Na2S2O3 and the absorbance at the position of the maximum absorption peak of TAg-NPs changed with the change in the concentration of Cu2+. The changes in the values of absorbance (ΔA, the absorbance of TAg-NP/Cu2+/Na2S2O3 subtracted from that of TAg-NP/Na2S2O3 at the position of the maximum absorption peak) were proportional to the concentrations of Cu2+. Thus, a new method was established by studying the UV-vis absorption spectrum or the naked eye observation, which is simple, fast and of low cost for copper ion detection. Using this method, the concentration of Cu2+ could be detected accurately in the range of 2.5 × 10−9 to 7.5 × 10−7 mol L−1 with the correlation coefficient of r = 0.9983. Moreover, the color change of TAg-NPs could be observed in the Cu2+ concentration of 2.5 × 10−8 to 7.5 × 10−7 mol L−1.

Trace copper ion detection by the suppressed decolorization of chromotrope 2R complex

Chromotrope 2R (CR) is a monoazo dye, which can be easily degraded under ultraviolet C (UVC) light irradiation. However, the degradation extent of CR is suppressed after it is chelated with Cu2+ ions to form a coordination complex (Cu2+–CR). This phenomenon was developed as a novel method for the quantitative detection of Cu2+ ions, which is based on determining the change in absorbance (ΔA, the absorbance of Cu2+–CR complex subtracted by that of CR after UVC light irradiation) by UV-visible absorption spectrum. Under the optimal detection conditions, ΔA at 509 nm highly depends on the concentration of Cu2+ ions in the range from 5.0 × 10−9 to 1.0 × 10−6 M as expressed by the following equation: ΔA = 0.3066 + 0.03605u2006lgu2006c with the correlation coefficient of r = 0.9912. The limit of detection (ld) is 3.4 nM as calculated by the formula 3σ = 0.3066 + 0.03605u2006lgu2006ld. This method provides affordable and selective detection of Cu2+ ions and was used to detect Cu2+ ions in a human hair sample.