Yongchao Lai

A colorimetric and surface-enhanced Raman scattering dual-signal sensor for Hg2+ based on Bismuthiol II-capped gold nanoparticles

The addition of Bismuthiol II to the gold nanoparticles (AuNPs) solution led to the aggregation of AuNPs with a color change from red to blue. As a result, hot spots were formed and strong surface-enhanced Raman scattering (SERS) signal of Bismuthiol II was observed. However, the Bismuthiol II-induced aggregation of AuNPs could be reversed by Hg(2+) in the system, accompanied by a remarkable color change from blue to red. As evidenced by UV-vis and SERS spectroscopy, the variation in absorption band and SERS intensity was strongly dependent on the concentration of Hg(2+), suggesting a colorimetric and SERS dual-signal sensor for Hg(2+). The sensor had a high sensitivity, low detection limits of 2nM and 30nM could be achieved by UV-vis spectroscopy and by SERS spectroscopy, respectively. Other environmentally relevant metal ions did not interfere with the detection of Hg(2+). The method was successfully applied to detect Hg(2+) in water samples. It was simple, rapid and cost-effective without any modifying or labeling procedure.

Silver nanoparticles decorated filter paper via self-sacrificing reduction for membrane extraction surface-enhanced Raman spectroscopy detection

Silver nanoparticles (AgNPs) decorated filter papers combining solid-phase extraction (SPE) with surface enhanced Raman spectroscopy (SERS) achieved rapid collection of analytes and in situ detection. The AgNPs were fabricated by cellulose self-sacrificing reduction. Aqueous Ag(NH3)2OH was reduced by hydroxyl groups in cellulose under alkaline conditions. The AgNPs were highly uniform and firmly adhered to the microfibers. Reaction conditions were optimized by the probe molecule p-aminothiophenol (PATP) to attain the best Raman enhancement. Methylene blue trihydrate (MB) and 6-thioguanine (6-TG) were detected by flow-through method. The results exhibited outstanding SERS effect and an obvious improvement in detection limit was observed compared to common immersion methods. SERS detection was quantitative as the log-log plot of Raman intensity against MB and 6-TG concentrations showed a linear relationship. The SERS-active paper is degradable because it could be burned after analyte detection.

Magnetic nanoparticles and quantum dots co-loaded imprinted matrix for pentachlorophenol.

In this study, an imprinted silica matrix of pentachlorophenol (PCP) co-loaded with Fe(3)O(4) nanoparticles and ZnS:Mn(2+) quantum dots (QDs) was fabricated. The introduction of Fe(3)O(4) nanoparticles to the imprinted matrix provided an easy way to separate PCP under an external magnetic field. ZnS:Mn(2+) QDs offered a readout signal to monitor the amount of PCP bound to the imprinted matrix and evaluate the efficiency of imprinting. X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy were used to characterize the imprinted matrix. The low angle X-ray diffraction and N(2) adsorption-desorption analysis indicated a periodic mesoporous structure. The as-synthesized imprinted matrix preferred to adsorb PCP rather than the other aromatic compounds like 2,4-dichlorophenoxy acetic acid, 2,4-dichlorophenol and phenol. The recoveries of spiked PCP in spring water and tap water with Fe(3)O(4)-ZnS:Mn(2+) co-loaded MIPs are 101% and 97%, respectively.

Surface-enhanced Raman spectroscopy detection of polybrominated diphenylethers using a portable Raman spectrometer.

Polybrominated diphenylethers (PBDEs), one of the most common brominated flame retardants, are toxic and persistent, generally detected by the chromatographic method. In this work, qualitative and quantitative detection of PBDEs were explored based on surface-enhanced Raman spectroscopy (SERS) technique using a portable Raman spectrometer. Alkanethiol modified silver nanoparticle aggregates were used as the substrate and PBDEs could be pre-concentrated close to the substrate surface through their hydrophobic interactions with alkanethiol. The effect of alkanethiols with different chain length on the SERS detection of PBDEs was evaluated. It was shown that 1-hexanethiol (HT) modified substrate has higher sensitivity, good stability and reusability. Qualitative and quantitative SERS detection of PBDEs in real sea water was accomplished, with the measured detection limits at 1.2×10(2) μg L(-1). These results illustrate SERS could be used as an effective method for the detection of PBDEs.