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The core of the surface-enhanced Raman spectroscopy (SERS)-based techniques for dynamic monitoring is to realize rapid and reversible adsorption. Herein, the integration technology of electro-enhanced adsorption, solid-phase microextraction, and surface-enhanced Raman spectroscopy (EE-SPME-SERS) was developed to obtain sensitive, ultrafast, and reversible SERS response toward in situ monitoring of pharmaceuticals and personal care products (PPCPs). In the EE-SPME-SERS method, a roughened Ag fiber with Au modification (r-Ag/Au fiber) was used as the SERS substrate, SPME sorbent, and working electrode. The r-Ag/Au fiber displayed good SERS sensitivity, ultrahigh photostability, and adsorption properties. The adsorption efficiency of benzidine was 76 times accelerated in EE-SPME-SERS compared to that in static adsorption. The whole process of "sampling and detection" in EE-SPME-SERS can be finished within 1 s. Reversible adsorption and desorption can be achieved in situ by switching the direction of electric field, and the regeneration process takes only a few minutes. Simulated release of benzidine from household wastewater was in situ and dynamically monitored using this strategy. EE-SPME-SERS was proved universal for ionized PPCPs and can detect multicomponents simultaneously. In addition, EE-SPME-SERS showed very good analytical properties. Great potential of EE-SPME-SERS can be expected in environmental monitoring.

Arsenic speciation analysis is important for pollution and health risk assessment. Surface-enhanced Raman Spectroscopy (SERS) is supposed to be a promising detection technology for arsenic species owing to the unique fingerprints. However, further application of SERS is hampered by its poor repeatability. Herein, the role of surface silver ions on colloidal Ag was revealed in SERS analysis of arsenic species. Arsenic species were adsorbed on Ag nanoparticles (Ag NPs) driven by surface silver ions and were simultaneously sensed by the SERS "hot spots" generated from the aggregation of Ag NPs. So, the inconsistent SERS activities of Ag NPs synthesized from different batches can be significantly improved by modifying external silver ions onto Ag NPs (AgNPs@Ag

Surface-enhanced Raman spectroscopy (SERS) of semiconducting TiO2 was used for studying binding modes and surface reactions of molecules bound at the interface but is generally limited by low signa...

Carbonaceous shell-coated γ-Fe2O3 nanoparticles (γ-Fe2O3@CNM) were synthesized from glucose caramelization and used as a novel magnetic solid-phase extraction medium for malachite green and crystal violet in environmental water. Malachite green and crystal violet were absorbed on to γ-Fe2O3@CNM by electrostatic and π-interactions. The morphologies, pore structures, surface functional groups, and magnetic properties of γ-Fe2O3@CNM were characterized by TEM, FTIR, hysteresis regression, Brunauer-Emmet-Teller analysis, zeta potential, XPS, and XRD. The magnetic solid-phase extraction procedure was optimized by extraction pH, absorption time, desorption solvent, and desorption time. The absorption capacities (qmax values) for malachite green and crystal violet were 34.2 and 27.9 mg g−1, respectively. After magnetic solid-phase extraction, malachite green and crystal violet were determined by LC-MS/MS. The analytical method was validated with a linear range of 0.02–20 ng mL−1, enrichment factor of 25.8 and 25.4, method detection limit of 0.004 ng mL−1, and intra-day precisions of 2.1% and 2.6% for malachite green and crystal violet, respectively. The relative recovery was found to be 73.4–101.5% for malachite green and 83.1–102.7% for crystal violet upon the application of the magnetic solid-phase extraction method to real water samples from lake, spring, sea, fishpond, and industrial waste.

The development of solid phase extraction (SPE) combined with the sensitive detection of surface-enhanced Raman spectroscopy (SERS) has been successfully applied for the analysis of complex environmental samples. In this work, a silver nanoplate-decorated copper membrane was fabricated as a recyclable SERS-active SPE substrate. The membrane was fabricated via modified galvanic displacement on a commercial copper membrane. Compared with filter paper SERS substrates, the as-synthesized substrate has relatively rapid heat conduction, which can lead to a greater temporal stability under continuous laser irradiation conditions. The relative standard deviation (RSD) value of the intensity change is 0.31%. The experimental results also showed that these substrates have a long life and are reproducible even after 5 cycles. The RSD was calculated to be 12.13%, which indicates that this method was recyclable. The signal intensity of filtering is almost 28 times higher than that of the traditional dropping method, which proves that the membrane has rapid extraction ability. The qualitative and quantitative detection of phorate was investigated based on a flow-through method. A good linearity (R2 = 0.98) was achieved for phorate in the concentration range of 3.84 to 288 nmol L−1. In addition, the simulated detection of phorate in actual water such as underground water, surface water, and drinking water was also studied. These results demonstrated its practical application to rapidly detect phorate in the real environment.

The nanoFe3O4-biochar (Fe3O4-BC) heterogeneous catalyst was synthesized by coprecipitation method and the mechanism of Fe3O4-BC/peroxymonosulfate (Fe3O4-BC/PMS) system adsorption and synergistic catalysis for the removal of bisphenol A (BPA) were studied. The effect of initial pH, Fe3O4-BC load, PMS concentration on the catalyst activity were systematically evaluated. The results showed the synergistic effect between BC and Fe3O4 can greatly improve the removal efficiency of BPA in the Fe3O4-BC/PMS system. BPA removal efficiency gained 100% in 90 min at pH 3.0 with PMS 5 mM, Fe3O4-BC load 2.0 g/L and BPA 20 mg/L. Sulfate radical (SO4•−) and hydroxyl radicals (•OH) was determined as the reactive species in the Fe3O4-BC/PMS system, and SO4•− was the major reactive species. Fe3O4-BC remained high active and the iron loss was only 2.13 mg/L when the pH was 3.0 after five recycles, which indicates that Fe3O4-BC catalyst has a good reusability potential and practical applications.

Novel SERS substrates is urgently in demand for rapid and sensitive analysis of toxic agrochemicals from food. In this work, a monodispersed tungsten disulfide quantum dots modified silver nanosphere (Ag@WS2QD) was prepared and used as SERS substrate. Ag@WS2QD generated uniform and stable SERS signals within 2 min, displaying great promise in “mixing and reading” detection. Compared to unmodified colloidal silver nanoparticles, 4 times higher analytical enhancement factor was found in Ag@WS2QD. Density functional theory calculation verified the enhanced charge transfer within the coupling systems of molecule-Ag@WS2QD. Besides, the unique surface properties are beneficial for the enrichment of specific molecule. Both the chemical extraction and enhanced charge transfer contributes to rapid and sensitive SERS detection of Ag@WS2QD. A “mixing and reading” SERS method for thiram from honey and four kinds of juice was developed from Ag@WS2QD, showing great promise for rapid and direct SERS detection for toxic agrochemicals and further applications.

The migration of solid samples from the interior to the surface of materials has raised serious concerns due to the increasing environmental health hazards in recent years. The convenient in situ detection of polycyclic aromatic hydrocarbons (PAHs) is especially needed. Surface-enhanced Raman spectroscopy (SERS) has emerged as an effective tool for spectroscopic detection and gives unique spectroscopic fingerprints of analytes. In this study, a hydrophobic 1-propanethiol-modified Ag nanowire membrane (PTH-Ag NMs) coupled with a portable Raman spectrometer was developed for the flexible on-site swabbing extraction and detection of typical PAHs. The swabbing process using an extracting agent was similar to the contact between a baby's mouth and toys. The SERS substrate suggested high uniformity, stability, and reusability. The curve of the normalized SERS intensity against the fluoranthene concentration displayed a good linear relationship (R2 = 0.98). The detection levels of fluoranthene, anthracene and pyrene reached 40.45, 35.65, and 45.45 ng cm−2, respectively. In addition, the simulated detection of these three PAHs on children's toys was demonstrated. The prepared hydrophobic PTH-Ag NMs have potential applications in the field of the inspection of toys by a simultaneous processing with simple pretreatment and a short total analysis time.

Pentachlorophenol (PCP) is a very high toxicity and slowly biodegraded organic pollutant. People may be exposed to PCP in environmental media through the inhalation of contaminated air, and ingestion of water and hazardous waste. Even low PCP intake will have serious effects on renal, metabolic and neurological functions, particularly in terms of carcinogenicity. Here, an electrostatic interaction driven solid phase microextraction (SPME) combined with surface enhanced Raman spectroscopy (SERS) was proposed for rapid detection of PCP in environmental water. The nanoporous Ag coating was in-situ electrochemically synthesized and modified by cysteamine to form a positive stationary phase on a fiber surface. The PCP was extracted using the DI-SPME mode and its SERS spectra were investigated; the characteristic bands at 338 cm−1, 378 cm−1 and 480 cm−1 were identified as the fingerprint peaks. The extraction procedure was optimized, and the adsorption mechanism was also discussed by the electric double layer model. The good stability and uniformity of the substrate provide a high enhancement factor of 3.7 × 105 and low LOD of 6.4 × 10−9 M for quantitative determination. This work provides a versatile strategy for rapid on-site detection of ionic or polar organic pollutants in environmental media.

The combined applications of solid phase microextraction coupled with surface enhanced Raman spectroscopy (SPME-SERS) detection have been successfully used in environmental analysis. In this work, ZnO nanorods (ZnO NRs) decorated with Au@4-ATP@Ag core–shell nanoparticles (NPs) were fabricated on a stainless steel fiber. The inclusion of an internal reference significantly improved the quality of the quantitative SERS measurements of the analytes. The obtained SERS-active SPME fiber resulted in a better reproducibility of the SERS signals. The relative standard deviation (RSD) value of the SERS-active SPME fiber was found to be 6.7% using malachite green (MG) as a probe molecule. A RSD value of 6.8% was observed when the SERS-active SPME fiber was exposed to laser irradiation continuously for about 10 min. These results suggest that the fiber was prepared with good stability and uniformity. Quantitative SERS measurements of the SERS-active SPME fiber showed an excellent quantitative ability for the detection of MG and crystal violet (CV) in aquaculture water. In CV, the results showed a good linear relationship in the concentration range of 5 × 10−8 M to 5 × 10−6 M, and the limit of detection (LOD) can reach 1.9 × 10−9 M (S/N = 3). This result indicates that the inclusion of an internal reference can effectively correct the signal fluctuation. This work provides versatile detection capability for rapid on-site quantitative SERS detection of different molecular species in environmental media.

A sponge inspired three dimensional flexible aluminum foil based ZnO nanosheet array substrate is described for use in real-world surface enhanced Raman spectroscopic detection. Gold and silver nanoparticles were employed to form numerous hot spots on uniformly grown ZnO nanosheets on the substrate. This flexible spongy substrate can extract analytes (such as the fungicide thiram) from various complex sample surfaces by physical swabbing. Specifically, this substrate was applied to detect thiram on the surface of fruits and vegetables. Non-destructive recycling detection with a relative standard deviation of 6.1% was accomplished by monitoring the characteristic Raman peak at 1382 cm−1. This modified substrate has a low detection limit (0.2 ng cm−2 of thiram for apple and tomato), outstanding uniformity (relative standard deviation = 8.9%) and thermal stability (relative standard deviation = 0.9%).

This work describes the integration of solid-phase microextraction (SPME) and surface-enhanced Raman spectroscopy (SERS) by codeposition of a hybrid consisting of reduced graphene oxide and silver on silver-copper alloy fibers. The morphology and structure of the coating were characterized by a variety of microscopic and spectroscopic techniques that confirmed the hybrid structure of the material. A galvanic-displacement-induced process is assumed to be involved during the codeposition of the hybrid coating on the alloy. In this process, Ag(I) is reduced to Ag(0) by Cu(0), and the presence of conjugated domains in GO facilitates the long-range transfer of electrons from Cu to Ag+. Simultaneously, GO accepts electrons and is converted into RGO. The hybrid coating exhibits a high SERS enhancement factor and good spatial uniformity. The needle-like coated alloy fibers are shown to be a viable tool for non-destructive sampling and SERS-based determination of trace levels of the antibiotics sulfadiazine and sulfamethoxazole in a spiked tissue mimic. The SERS peaks at 1149 cm−1 for sulfadiazine and 1144 cm−1 for sulfamethoxazole are selected as the reference peaks in the quantitative analysis. The linear range is from 0.01 to 100 μg·cm−3. The detection limits are 1.9 ng·cm−3 for sulfadiazine and 4.4 ng·cm−3 for sulfamethoxazole.

Highly bioaccumulated polycyclic aromatic hydrocarbons (PAHs) have cause health concerns because of their carcinogenic properties. PAHs could migrate to food from contaminated food contact materials. In this study, a hyphenated technique combining surface enhanced Raman spectroscopy (SERS) with surface microextraction was developed for in-situ on site screening of PAHs on food contact materials. Methanol and 1-propanethiol-modified silver nanoparticles (PTH-Ag NPs) were used to perform the in-situ microextraction and detection of PAHs, respectively. The SERS spectra can be obtained by a portable Raman spectrometer. The vibration of the C-C bond of PTH at 1030cm(-1) was chosen as an internal standard peak. The PTH-Ag NPs showed high uniformity with an RSD of 2.96%. A plot of the normalized SERS intensity against fluoranthene concentration showed a linear relationship (R(2)=0.98). The detection limit could reach 0.27ngcm(-2). The in-situ microextraction-SERS hyphenated technique for the detection of three PAHs at five food contact materials was demonstrated. The method can be also applied to detect PAH mixtures. This in-situ microextraction-SERS hyphenated method demonstrated its ability to rapidly screen PAHs on contaminated food contact materials free from complex sample pretreatment.

The sensitive and on-site detection of inorganic explosives has raised serious concerns regarding public safety. However, high stability and non-volatility features currently limit their rapid on-site detection. Surface-enhanced Raman spectroscopy (SERS) is emerging as a powerful technique for the trace-level detection of different molecules. Plasmonic Ag nanowires were produced by a hydrothermal synthesis method using polyvinylpyrrolidone (PVP) as a negatively charged stabilizer. Here, we report a rapid detection method for inorganic explosives based on a simple surface swab with a positively charged diethyldithiocarbamate-modified Ag nanowire membrane coupled with SERS. This membrane, serving as an excellent SERS substrate with high uniformity, stability, and reusability, can capture both typical oxidizers in inorganic explosives and organic nitro-explosives, via electrostatic interaction. The detection level of perchlorates (ClO4−), chlorates (ClO3−), nitrates (NO3−), picric acid, and 2,4-dinitrophenol is as high as 2.0, 1.7, 0.1, 45.8, and 36.6 ng, respectively. In addition, simulated typical inorganic explosives such as black powders, firecrackers, and match heads could also be detected. We believe that this membrane represents an attractive alternative for rapid on-site detection of inorganic explosives with high efficiency.

The indoors volatile organic compounds (VOCs), which can be classified into seven groups as oxy hydrocarbons, halogenated hydrocarbons, aromatic hydrocarbons, aliphatic hydrocarbons, terpenes, esters and aldehydes, have been brought to the forefront because millions of people are suffering from indoor air pollution. In this study, well-dispersive Au nanoparticles were deposited on porous single-crystalline ZnO nanoplates (Au@ZnO) via photodeposition free from additives for the gas sensing detection of the seven-group VOCs. The structure and morphology of Au@ZnO nanoplates were characterized by TEM, HRTEM, mapping and XRD. Comparing to pure ZnO nanoplates, the Au@ZnO sensor has prominent enhanced performance at 360 °C with high sensitivity (about 2–9 times for each group of VOCs), fast response/recovery time (less than 30/14 s) and stable repeatability (relative standard deviation less than 0.039) in the gas sensing tests. The fluctuation range of relative humidity is less than 80% and the contribution ratios of oxy hydrocarbons, halogenated hydrocarbons, aromatic hydrocarbons, aliphatic hydrocarbons, terpenes, esters and aldehydes were 0.1678, 0.0989, 0.0826, 0.0739, 0.2396, 0.1887, 0.1495, respectively. Finally, the possible sensing mechanism was discussed based on these results.

A formaldehyde gas sensor with high sensitivity and superior selectivity has been fabricated successfully with NiO–SnO2 hybrid nanospheres, which consisted of n-type porous SnO2 nanospheres and p-type NiO dopants. It has been characterized by X-ray diffraction (XRD), high-resolution electron microscopy (HRTEM), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and energy-dispersive X-ray spectroscopy (EDS). Compared with pure SnO2, the NiO-doped SnO2 nanospheres sensor exhibited significantly enhanced formaldehyde-sensing performances, including lower optimum sensing temperature (about 100 °C), lower detectable threshold (0.5 ppm), higher sensitivity (response = 26.03 to 50 ppm HCHO) and superior selectivity. Based on our experimental results, the role of the addition of NiO and a possible sensing mechanism has also been discussed.

Perchlorate, which causes health concerns because of its effects on the thyroid function, is highly soluble and mobile in the environment. In this study, diethyldithiocarbamate (DDTC)-modified silver nanoplates were fabricated on a copper wire to perform the on-site microextraction and detection of perchlorate. This fiber could be inserted into water or soil to extract perchlorate through electrostatic interaction and then can be detected by a portable Raman spectrometer, owing to its surface-enhanced Raman (SERS) activity. A relatively stable vibrational mode (δ(HCH)(CH3), (CH2)) of DDTC at 1273 cm(-1) was used as an internal standard, which was negligibly influenced by the absorption of ClO4(-). The DDTC-modified Ag/Cu fiber showed high uniformity, good reusability and temporal stability under continuous laser radiation each with an RSD lower than 10%. The qualitative and quantitative detection of perchlorate were also realized. A log-log plot of the normalized SERS intensity against perchlorate concentration showed a good linear relationship. The fiber could be also directly inserted into the perchlorate-polluted soil, and the perchlorate could thereby be detected on site. The detection limit in soil reached 0.081 ppm, which was much lower than the EPA-published safety standard. The recovery of the detection was 105% and comparable with the ion chromatography. This hyphenated method of microextraction with direct SERS detection may find potential application for direct pollutant detection free from complex sample pretreatment.

The persistent toxic substances (PTS), pollutants that have environmental persistence and toxic effects such as carcinogenicity and endocrine disruption, are generally detected by the chromatographic method. In this work, hydrophobic gold nanostructures were fabricated via simple electrochemical deposition and could be used for direct SERS detection of PTS with a portable Raman spectrometer. The obtained hydrophobic substrates free from modification show high affinity towards PTS, such as polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). According to the Cassie equation, the wetting properties of the surface changed from hydrophilic to hydrophobic when the contact angle changed from 77° to 123°, increasing the deposition time. The SERS signals collected on sixteen randomly selected points show that the relative standard deviation of the SERS intensity is 9.0%, indicating the substrate had good uniformity. Quantitative SERS detection of PTS was achieved, as the log–log plot of SERS intensity to PTS concentration exhibited a good linear relationship in view of the Freundlich equation. Quantitative analysis of fluoranthene, BDE-15 and PCB-15 was accomplished in the concentration range of 0.02–200 μM, 0.02–200 μM, 0.04–440 μM, with the detection limits of 6.7 nM, 2.6 nM and 5.3 nM, respectively. The effective SERS substrates provide a rapid and sensitive platform for trace level detection of hydrophobic contaminants in the environment.

That intense demand for both high sensitivity and high reliability has been a key factor strengthening the surface enhanced Raman spectroscopy (SERS) in the analytical application, particular in the hyphenation with pre-concentration technique. Credible data acquisition and processing is very dependent on the stable and uniform performance of SERS-active substrate. Here, a reliable and uniform ultrathin-layer Au was proposed for protecting the porous Ag fiber (porous Ag@Au) and applied in the solid phase microextraction coupled with SERS. The Au layer was carefully deposited on porous Ag surface to form the uniform film by a galvanic-free displacement reaction. This coating endowed the substrate with high oxidation-resistance under heating and good durability in the atmosphere condition. The extraction and SERS performance of Nitrofurazone and Semicarbazide were investigated on this fiber, the bands at 1350 cm −1 and 1387 cm −1 were selected as the characteristic peaks for quantitative determination, respectively. This robust and sensitive substrate provide the high enhancement factor of 1.3 × 10 6 and low LOD of 5.1 ppb for the extraction and identification of Nitrofurazone compounds. Importantly, this work develops a versatile strategy for rapid detection of prohibited antibiotic and its marker residue in a complex matrix.

A disordered silver nanowires membrane combining solid-phase extraction (SPE) with surface-enhanced Raman spectroscopy (SERS) was used for the rapid collection and detection of food contaminants. The membrane was fabricated via filtration of the silver nanowires colloid solution, which was prepared by a solvothermal polyol process. Analytes in 5 mL of liquid phase were concentrated in less than 10 s due to their affinity for the silver nanowires on the filter membrane. The membrane combined the advantages of SPE and SERS technology for the analysis of food safety contaminants. The use of the SERS-active extraction membrane eliminated the procedure of elution, which shortened the time of analysis. It has been shown that the as-prepared membrane had good uniformity and high temporal stability under continuous laser irradiation. Qualitative and quantitative detection of phorate and melamine was further performed based on a flow-through method. The characteristic SERS intensity plotted against phorate and melamine concentrations exhibited a good linear relationship over the concentration range of 2.5 to 10 μg mL(-1) (phorate) and 2.5 to 100 μg mL(-1) (melamine).

To better understand experimentally observed surface-enhanced Raman Scattering (SERS) of polychlorinated biphenyls (PCBs) adsorbed on nanoscaled silver substrates, a systematic theoretical study was performed by carrying out density functional theory and time-dependent density functional theory calculations. 2,2′,5,5′-tetrachlorobiphenyl (PCB52) was chosen as a model molecule of PCBs, and Agn (n = 2, 4, 6, and 10) clusters were used to mimic active sites of substrates. Calculated normal Raman spectra of PCB52–Agn (n = 2, 4, 6, and 10) complexes are analogical in profile to that of isolated PCB52 with only slightly enhanced intensity. In contrast, the corresponding SERS spectra calculated at adopted incident light are strongly enhanced, and the calculated enhancement factors are 104 ~ 105. Thus, the experimentally observed SERS phenomenon of PCBs supported on Ag substrates should correspond to the SERS spectra rather than the normal Raman spectra. The dominant enhancement in Raman intensities origins from the charge transfer resonance enhancement between the molecule and clusters. Copyright © 2014 John Wiley & Sons, Ltd.

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.

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.

Solid phase microextraction-surface enhanced Raman spectroscopy (SPME–SERS), combining the pretreatment and determination functions, has been successfully used in environmental analysis. In this work, Au-coated ZnO nanorods were fabricated on stainless steel fiber as a self-cleaning SERS-active SPME fiber. The ZnO nanorods grown on stainless steel fiber were prepared via a simple hydrothermal approach. Then the obtained nanostructures were decorated with Au nanoparticles through ion-sputtering at room temperature. The obtained SERS-active SPME fiber is a reproducible sensitivity sensor. Taking p-aminothiophenol as the probe molecule, the RSD value of the SERS-active SPME fiber was 8.9%, indicating the fiber owned good uniformity. The qualitative and quantitative detection of crystal violet and malachite green was also achieved. The log–log plot of SERS intensity to crystal violet and malachite green concentration showed a good linear relationship. Meanwhile, this SERS-active SPME fiber can achieve self-cleaning owning to the excellent photocatalytic performance of ZnO nanorods. Crystal violet was still successfully detected even after five cycles, which indicated the high reproducibility of this SERS-active SPME fiber.

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.

In this paper, a simple and novel method for the determination of polychlorinated biphenyls (PCBs), using silver nanoparticles (AgNPs) as a resonance light scattering (RLS) probe, is proposed. Under optimized conditions, there existed linear relationships between the enhancing RLS intensity of the system and the concentrations of PCBs in the range 8.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 2,4,4'-trichlorbiphenyl (PCB28), 9.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 2,2',5,5'-tetrachlorbiphenyl (PCB52) and 4.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 3,3',4,4'-tetrachlorobiphenyl (PCB77). The corresponding detection limits (S/N = 3) were 2.6 × 10(-8) g mL(-1) for PCB28, 3.3 × 10(-8) g mL(-1) for PCB52 and 6.3 × 10(-9) g mL(-1) for PCB77, respectively. Finally, the mechanism of RLS enhancement was also studied. The results indicated that PCBs were adsorbed on the surface of AgNPs to form larger AgNP-PCB aggregates, resulting in the RLS enhancement of the system.

Lomefloxacin has been increasingly used in veterinary medicine to treat microbial infections. To avoid using a complicated instrumental method to detect lomefloxacin residue in food, a simple and convenient indirect competitive enzyme-linked immunosorbent assay method has been developed in this study. The antibody generated from immunogen of bovine serum albumin-lomefloxacin showed high sensitivity toward lomefloxacin with an IC50 value of 0.35 ppb in PBS buffer and was suitable to be used as a screening assay to detect lomefloxacin residue in food products. The ELISA (Enzyme-Linked ImmunoSorbant Assay) developed in this study was compared with a commercial ELISA kit and significant improvement was achieved in terms of sensitivity and specificity. The antibody prepared showed excellent specificity with certain cross-reactivity with only two drugs including norfloxacin (17.5%) and fleroxacin (8.8%) among commonly used (fluoro)quinolones. The assay measured drug residue in defatted milk spiked with lomeflox...

Cd1−xZnxS nanoparticles were prepared by a one-pot solvothermal process from Zn(CH3COO)2, Cd(CH3COO)2 and NaS2CNEt2·3H2O (sodium diethyldithiocarbamate, DDTC). The Cd1−xZnxS nanoparticles were characterized by X-ray powder diffraction, transmission electron microscope and high-resolution transmission electron microscope equipped with an energy-dispersive X-ray spectrometer. The absorption spectra of the Cd1−xZnxS nanoparticles can be tuned into visible region by modulating stoichiometric ratio between Zn and Cd. With the increase of Zn content, the Cd1−xZnxS nanoparticles showed an enhanced photocatalytic activity on degradation of 4-chlorophenol. The Cd1−xZnxS prepared under the optimal experimental condition (initial Zn/Cd = 3:1, 210 °C, 24 h, in ethanol) possessed the best photocatalytic activity. The conversion ratio could reach up to 84% after 12 h under irradiation of visible light for Cd1−xZnxS prepared in ethanol, which was obviously superior to those of products prepared in water. These results showed that both crystallinity and synthetic medium were responsible for the enhanced photocatalytic activity for 4-chlorophenol.

An indirect competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) for detection of gatifloxacin residue in milk was developed in this study. Compared with conventional colorimetric ELISA using the same antibody, the developed CL immunoassay shows a significant improvement in sensitivity and detectability with an IC50 of 0.4 ng mL−1 and a detection limit of 0.001 ng mL−1 and thus is suitable to be used as a highly sensitive screening method to detect and regulate illegal use of gatifloxacin in food and food products. The test kit was applied to detect milk samples spiked by gatifloxacin, and satisfactory results were obtained.

A facile one-pot microwave irradiation reduction route has been developed for the synthesis of highly luminescent CdTe quantum dots using Na2TeO3 as the Te source in an aqueous environment. The synthesis parameters of this simple and rapid approach, including the reaction temperature and time, the pH of the reaction solution and the molar ratio of the 3-mercaptopropionic acid (MPA) stabilizer to Cd2+, have considerable influence on the particle size and photoluminescence quantum yield of the CdTe quantum dots. The photoluminescence quantum yield of CdTe quantum dots prepared using relatively short reaction times (10–40 min) reached 40%–60% (emission peaks at 550–640 nm). Furthermore, the resulting products could be used as fluorescent probes to detect Hg2+ ions in aqueous media. The response was linearly proportional to the concentration of Hg2+ ion in the range 8.0×10−9 mol/L to 2.0×10−6 mol/L with a detection limit of 2.7×10−9 mol/L.

Solid phase microextraction (SPME), a solvent free technique for sample preparation, has been successfully coupled with GC, GC-MS, and HPLC for environmental analysis. In this work, a method combining solid phase microextraction with surface enhanced Raman spectroscopy (SERS) is developed for detection of polycyclic aromatic hydrocarbons (PAHs). Silver nanoparticle aggregates were deposited on the Ag-Cu fibers via layer-by-layer deposition, which were modified with propanethiol (PTH). The SERS-active SPME fiber was immersed in water directly to extract PAHs and then detected using a portable Raman spectrometer. The pronounced valence vibration of the C-C bond at 1030 cm(-1) was chosen as an internal standard peak for the constant concentration of PTH. The RSD values of the stability and the uniformity of the SERS-active SPME fiber are 2.97% and 5.66%, respectively. A log-log plot of the normalized SERS intensity versus fluoranthene concentration showed a linear relationship (R(2) = 0.95). The detection limit was 7.56 × 10(-10) M and the recovery rate of water samples was in the range of 95% to 115%. The method can also be applied to detection of PAH mixtures, and each component of the mixtures can be distinguished by Raman characteristic peaks. The SERS-active SPME fiber could be further confirmed by GC-MS.

We have assigned the (31)P high-resolution spectrum of octacalcium phosphate by (31)P double quantum and HETCOR spectroscopy. The (31)P peaks at -0.2, 2.0, 3.3 and 3.7 ppm are assigned to P5/P6, P3, P2/P4 and P1, respectively. Our data reveal that substantial amount of the PO(4)(3-) groups at the P2 and P4 sites have been transformed to HPO(4)(2-) in our octacalcium phosphate sample.

Uniform micro-sized alpha- and beta-Si(3)N(4) thin ribbons have been achieved by a high-temperature thermal-decomposition/nitridation route. As-grown ribbons were characterized by using powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and cathodoluminescence. These alpha- and beta-Si(3)N(4) ribbons are structurally uniform micro-sized single crystals, and have a width of approximately 2-3 microns, a thickness of approximately 20-60 nm, and a length, that ranges from several hundreds of microns to the order of millimeters. A room-temperature cathodoluminescence spectrum recorded from these ribbons shows one intensive blue emission peak at approximately 433 nm. The growth for the new ribbon form of this material is believed to be dominated by a vapor-solid process.

Cysteamine-modified silver nanoparticle aggregates has been fabricated for pentachlorophenol (PCP) sensing by surface-enhanced Raman spectroscopy (SERS) using a portable Raman spectrometer. The cysteamine monolayers could preconcentrate PCP close to the substrate surface through the electrostatic interaction, which makes the SERS detection of PCP possible. Moreover, the Raman bands of cysteamine could be used as the internal spectral reference in the quantitative analysis. Qualitative detection of PCP was carried out by SERS without any sample pretreatment. Quantitative analysis of PCP was further realized based on the prepared substrate, as the log-log plot of normalized SERS intensity of PCP versus its concentrations exhibits a good linear relationship. The SERS signals collected on 20 randomly selected points show that the relative standard deviation of the normalized Raman intensity is 5.8%, which indicates the substrate had good uniformity. The PCP sensor also shows good long-term stability in the analyte solution. The substrate was cyclic immersed into PCP and methanol solution; after several cycles, the sensor still had good adsorption to PCP, which revealed the sensor has good reusability. Coupling with a portable Raman spectrometer, the cysteamine-modified silver nanoparticle aggregates have the potential to be used for in situ and routine SERS analysis of PCP in environmental samples.

A surface-enhanced Raman spectroscopy (SERS)-active extraction column based on propanethiol modified silver dendrites was fabricated. The column, which combines the advantages of solid phase extraction and SERS, may facilitate the development of rapid analysis with high reliability and accuracy. High temporal stability (under a continuous and intensive laser radiation) and excellent repeatability (repeated extraction and elution) were also achieved using this column. As an example, the quantitative analysis of fluoranthene was accomplished in the concentration range of 0.01-100 μg mL(-1) with this column. The extraction process could be accomplished in 10 s and the total time of one sample analysis including extraction, spectral acquisition, elution and intermediate process could be less than 30 s. This method can greatly simplify the sample preparation and reduce the total analysis time.

Silver nanoparticle aggregates were synthesized on copper foil, which was used for the surface-enhanced Raman spectroscopy (SERS) detection of polycyclic aromatic hydrocarbons (PAHs) with a portable Raman spectrometer. Silver nanoparticle aggregates were prepared by immersing copper foil in the solution of Sn(2+) and AgNO(3) in a cyclic fashion. A four-cycle process was selected for the following experiments due to its high enhancement and relatively convenient experimental procedure. The substrate has greater temporal stability under continuous laser radiation, good uniformity and reproducibility, which indicated that the substrate could provide reliable measurements. The relationship between SERS intensity and concentrations of PAHs was studied. Quantitative analysis of PAHs in aqueous solution was further performed based on the prepared substrate. The log-log plot of normalized SERS intensity to PAHs concentration exhibited a good linear relationship, with the detection limits in the range of 5-500 μg L(-1). Thus, due to the stability, reproducibility and quantitative results, the prepared substrate could be used as a potential SERS sensor for the analysis of environmental pollutants.

A mono-6-thio-β-cyclodextrin-modified silver film was synthesized via galvanic displacement on copper foil. The prepared silver films could enrich non-polar polychlorinated biphenyls (PCBs) molecules from hydrophilic phase using thiolate β-cyclodextrins (SH-β-CDs) as receptors. The components of as-prepared Ag-coated-Cu (Ag-Cu) film were confirmed by powder X-ray diffraction (XRD). Both surface-enhanced Raman spectroscopy (SERS) and energy dispersive X-ray spectroscopy (EDS) measurements gave strong evidences that the thiolated β-cyclodextrins (SH-β-CDs) had been immobilized on the surface of silver film. Compared to the substrates prepared in the absence of SH-β-CD, the surface morphology of the CD-modified Ag films was obviously changed. The interfacial enrichment and the capability of substrates to form inclusion complexes with PCBs molecules were tested by using PCB-15 (4,4'-dichlorobiphenyl) as the probe molecules via SERS technique. The measured SERS spectra could distinguish the PCB-15 molecules at micro-molar level according to the most intense CCC bending in-plane mode of PCBs. The enhancement factor (EF) of the SERS substrates for PCB-15 was 1.2×10(5), which was comparable with a number of previous reports.

This paper described an investigation of a novel eco-friendly fluorescence sensor for Hg(2+) ions based on N-acetyl-l-cysteine (NAC)-capped ZnS quantum dots (QDs) in aqueous solution. By using safe and low-cost materials, ZnS QDs modified by NAC were easily synthesized in aqueous medium via a one-step method. The quantitative detection of Hg(2+) ions was developed based on fluorescence quenching of ZnS QDs with high sensitivity and selectivity. Under optimal conditions, its response was linearly proportional to the concentration of Hg(2+) ions in a range from 0 to 2.4 × 10(-6) mol L(-1) with a detection limit of 5.0 × 10(-9) mol L(-1). Most of common physiologically relevant cations and anions did not interfere with the detection of Hg(2+). The proposed method was applied to the trace determination of Hg(2+) ions in water samples. The possible quenching mechanism was also examined by fluorescence and UV-vis absorption spectra.

Silver nanoplates were prepared by modified galvanic displacement on commercial copper foil. SEM, TEM, UV-vis and XPS were employed to analyze those closely packed silver nanoplates. This type of surface-enhanced Raman spectroscopy substrates showed strong surface plasmon absorption and reliable surface-enhanced Raman activity.

Though polychlorinated biphenyls (PCBs) have distributed as threats in the environment to human beings for several decades, monitoring of trace level PCBs in-field is still a challenge. As a potential method for monitoring PCBs at trace levels, Raman spectroscopy has been used to detect several PCBs in the laboratory. To facilitate the development of rapid detection of PCBs by Raman spectroscopy, it is essential to investigate the Raman spectra of all PCB congeners. Herein, the stable configurations and vibrational spectra of all the PCB congeners were calculated by Gaussian 03 program package. Based on molecular symmetry, PCBs are classified into seven groups. The structural features and the normal vibration modes for each group are discussed. Taking the C(2)-2 group as an example, the wavenumber ranges of the various normal vibration modes in the Raman spectra of PCBs were analyzed. The accuracy of calculated results was verified by experimental Raman spectra of PCB77 standard. This study can elucidate further information to promote the development of Raman spectroscopy in environmental monitoring.

Porous SnO(2) nanospheres with high surface areas have been synthesized through a solvothermal method in the absence of any templates. The structure and morphology of the resultant products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption technique. The as-prepared SnO(2) porous nanospheres with the diameters ranging from 90-150 nm are composed of small nanocrystals with average sizes of less than 10 nm. Results demonstrated that the formation of porous SnO(2) nanospheres is ascribed to etching the center part of the nanospheres. It was found that hydrochloric acid and NaClO played important roles in determining the final morphologies of the porous SnO(2) nanospheres. The gas sensing properties of the as-prepared porous SnO(2) nanospheres were investigated. By the comparative gas sensing tests, the porous SnO(2) nanospheres exhibited a superior gas sensing performance toward ppb level 2-chloroethanol and formaldehyde vapor, implying promising applications in detecting toxic volatile organic compounds (VOCs).

(Cu2Sn)x/3Zn1-xS (0 ≤ x ≤ 0.75) nanocrystals with widely tunable bandgaps (1.23—3.48 eV) are solvothermally synthesized from stoichiometric mixtures of CuCl2, SnCl2, ZnCl2, and thiocarbamide in ethanol.

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.