Dejiang Gao

Determination of malachite green in environmental water using cloud point extraction coupled with surface-enhanced Raman scattering

A novel, simple and ultra-sensitive method, for rapid detection of trace malachite green (MG) in environmental water using cloud point extraction (CPE) coupled with surface-enhanced Raman scattering (SERS) is described. The colloidal gold nanoparticles (AuNPs) were synthesized by reduction of chloroauric acid (HAuCl4) with trisodium citrate and were used as SERS substrates. The SERS substrates were found to produce enhancement factors of 1.52 × 106 for MG by employing the SERS peak at 1175 cm−1. After the optimization of SERS conditions including the volumes of ethanol, colloidal AuNPs and HCl, the present method was linear for MG at 1175 cm−1 and 1618 cm−1 over the concentration range of 0.5–35.0 μg L−1 and 2.5–40.0 μg L−1, with the correlation coefficients (r) of 0.9971 and 0.9960. The limits of detection (LODs) were 0.10 μg L−1 and 0.70 μg L−1, and the intra- and inter-day relative standard deviations (RSDs) of detection were in the range of 2.0–2.5% and 1.9–3.2% at 1175 cm−1 and 1618 cm−1, respectively. Recoveries obtained by analyzing 4 spiked environmental water samples at 2 levels were between 93.1 and 106.0%.

A FRET-based fluorescent probe for mercury ions in water and living cells

On the basis of fluorescence resonance energy transfer (FRET), a new rhodamine derivative (DRh) was synthesized as a ratiometric fluorescent probe for detecting Hg(2+) in water and living cells samples. The recognition properties of the probe DRh with metal ions had been investigated in H2O/CH3CN (9:1, v/v; Tris-HCl 50mmolL(-1); pH=7.0) solution by the UV-Vis spectrophotometry and the fluorescence spectrophotometry. The results showed that the probe DRh exhibited the selective recognition of Hg(2+). Upon the addition of Hg(2+), the spirolactam ring of probe DRh was opened. The 1:1 stoichiometric structure between DRh and Hg(2+) were supported by Jobs plot, MS and DFT theoretical calculations. The linearly fluorescence intensity ratio (I582/I538) is proportional to the concentration of Hg(2+) in the range 0-30μmolL(-1). The limit of detection (LOD) of Hg(2+) is 0.008μmolL(-1) (base on S/N=3). The present probe was applied to the determination of Hg(2+) in neutral water samples and gave recoveries ranging from 104.5 to 107.9%. Furthermore, the fluorescent probe also can be applied as a bioimaging reagent for Hg(2+) detection in HeLa cells.

Selective and sensitive SERS sensor for detection of Hg2+ in environmental water base on rhodamine-bonded and amino group functionalized SiO2-coated Au–Ag core–shell nanorods

Here, we designed a new type of SERS sensor with high selectivity and sensitivity for the determination of Hg2+ at picomolar concentrations based on hydrolysis reactions. The Rhodamine 6G-derived Schiff base bonded and amino group functionalized SiO2-coated Au–Ag core–shell nanorods (Au@Ag@SiO2–NH2-R6G, NR-Rs), which show extraordinary enhancement factors (EF) and good stability, were employed as the SERS substrate of the sensor. The tunable ability of the chemical bonding of the substrate generates appropriate probe molecules bound to the surface of the nanorods (NRs) and improves the selectivity and sensitivity of the SERS sensor dramatically. The limit of detection (LOD) of Hg2+ obtained using the present SERS sensor was 0.33 pmol L−1. Furthermore, the proposed substrate has pH-responsive ability. The present sensor is suitable for the on-site determination of pH and Hg2+ by combining with a portable Raman spectrometer.

Determination of protein by resonance light scattering technique using dithiothreitol–sodium dodecylbenzene sulphonate as probe

The resonance light scattering (RLS) spectra of bovine serum albumin (BSA)-dithiothreitol (DTT)-sodium dodecylbenzene sulphonate (SDBS) and its analytical application were investigated. The RLS intensity of this system can be effectively enhanced in the presence of BSA. Based on the enhanced RLS intensity, a simple assay for BSA was developed. The experimental results indicate that the enhanced RLS intensity is proportional to the concentration of BSA in the range from 1.0 x 10(-8) to 7.5 x 10(-7) mol L(-1) with the determination limit of 5.0 x 10(-9) mol L(-1). The effects of pH, concentration of SDBS and DTT on the RLS enhancement were discussed. Most metal ions have little interference on the determination of BSA. Some synthetic and real samples were analyzed, and the results obtained were in good agreement with those obtained by Bradford method.

Simultaneous determination of thiocyanate ion and melamine in milk and milk powder using surface-enhanced Raman spectroscopy

In this study, a simple and efficient method based on surface-enhanced Raman spectroscopy (SERS) was developed to detect thiocyanate ion (SCN−) and melamine in milk and milk powder. Silver nanoparticles (AgNPs), sodium chloride (NaCl) and sodium hydroxide (NaOH) were used as the substrate, the aggregating agent and the alkaline adjusting agent for the SERS process, respectively. The SERS peak intensity at 445 cm−1 was measured under low NaCl concentration for determining SCN−, followed by the measurement of the SERS peak intensity at 704 cm−1 under high NaCl concentration for determining melamine. The determination conditions for SERS, including the amount of AgNPs, NaCl and NaOH, and the mixing time before measurement, were optimized. By the present method, good linear responses were obtained for SCN− and melamine in the concentration ranges of 2.00–191.00 mg L−1 and 0.01–4.80 mg L−1 respectively, with correlation coefficients higher than 0.998. The present method was successfully applied to the simultaneous determination of SCN− and melamine in four spiked milk samples and three certified milk powder samples. The recoveries of SCN− and melamine in spiked milk samples were 95.15–100.47% and 94.43–102.84%, respectively. The relative standard deviations (RSDs) for determining melamine in certified milk powder samples were lower than 1.6%.