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Nanoplastics are emerging pollutants that pose potential threats to the environment and organisms. However, in-depth research on nanoplastics has been hindered by the absence of feasible and reliable analytical methods, particularly for trace nanoplastics. Herein, we propose a hyphenated method involving membrane filtration and surface-enhanced Raman spectroscopy (SERS) to analyze trace nanoplastics in water. In this method, a bifunctional Ag nanowire membrane was employed to enrich nanoplastics and enhance their Raman spectra in situ, which omitted sample transfer and avoided losing smaller nanoplastics. Good retention rates (86.7% for 50 nm and approximately 95.0% for 100-1000 nm) and high sensitivity (down to 10

A filtration-based SERS platform was proposed to separate and analyse AgNPs in antibacterial products.

The use of Chinese herbs containing aristolochic acid can induce the exchange of adenine and thymine in gene mutations and even cause liver cancer. To eliminate the harm of aristolochic acids (AAs) to humans, a rapid and robust method of AAs screening is a prerequisite. In this work, a facile and robust Surface-enhanced Raman spectroscopy (SERS) method was used for the qualitative and quantitative detection of AAs in Chinese medicinal herbal preparations based on the mandelic acid modified Ag nanoparticles SERS substrate. Qualitative and quantitative SERS detection of Aristolochic acid I (AAI) was achieved with a good linear relationship ranging from 0.2 - 120.0 μM and a limit of detection (LOD) of 0.06 μM. The proposed method demonstrates a refined strategy for sensitivity analysis of AAs with the advantages of easy operation, time-saving, high sensitivity, and molecular specificity, making it a preferred platform for the screening of AAI in regular inspections of herbal products and regulatory supervision of the supply chain.

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) has been widely used for chemical and biological analyses because of its ultrahigh sensitivity and label-free molecular specificity. However, SERS analysis of analytes with weak affinity for a substrate must rely on substrate surface modifications that trap analytes into the active sites. The interference from the Raman signal of the modified layer limits the improvement in the detection limit. Herein, we report a surface modification strategy for the enrichment and SERS detection of fluoranthene, which involves the functionalization of silver nanoplates on copper foil with thioctic acid. The modified SERS substrate provides high analyte enrichment and low interference from the modified layer. The fixed position of Raman peaks for fluoranthene enables quantitative detection from a minimum detectable concentration of 0.1 ng/mL up to 0.1 mg/mL. This study based on a simple and cost-effective method affords unique insights into the surface enrichment of analytes, wh...

Despite being an emerging risk to the environment and human health, little is known about the occurrence, formation, transport, and environmental impact of nanoplastics owing to the lack of quantitative and sensitive sensing techniques. Herein, a surface-enhanced Raman spectroscopy (SERS) method was developed for quantitative sensitive nanoplastics analysis, in which KI was added to Ag nanoparticles as a coagulant and cleaner to remove surface impurities. Polystyrene (PS) nanoplastics with four sizes (50, 100, 200, and 500 nm) were used to evaluate the proposed method, which exhibited high sensitivity (detection limit of 6.25 μg/mL for 100 nm PS nanoplastics), interference resistance, good repeatability, and quantitative analysis ability (R

The development of high-quality flexible surface-enhanced Raman spectroscopy (SERS) substrates is crucial for developing rapid SERS analysis in situ. Silver nanowire membranes as novel flexible substrates could benefit from the high collection efficiency of analytes by wrapping complex surfaces or wiping the surfaces of samples. However, their low SERS performance impedes further applications of silver nanowire membranes in analyte detection. Herein, we report an ultra-high-sensitivity silver nanowire membrane synthesized by a simple and time-saving cyclic voltammetry (CV) method. After CV treatment, a part of the silver nanowires on the silver nanowire membrane turned into small nanoparticles and nanorods. This nanostructure’s reconstitution increased the analytical enhancement factor of silver nanowire membranes by 14.4 times. Scanning and transmission electron microscopy, UV-vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were employed to investigate the transformation in the membrane nanostructure. The CV-treated substrates exhibited high surface-enhanced Raman activity and good temporal stability. The limits of detection (LODs) for p-aminothiophenol, crystal violet, tetramethylthiuram disulfide, sodium perchlorate, malachite green, fluoranthene, and potassium nitrate are 3.7 × 10−12 M, 5.1 × 10−11 M, 5.4 × 10−11 M, 6.3 × 10−9 M, 0.00693 ng, 0.0810 ng, and 0.0273 ng on this substrate, respectively. Additionally, the developed substrate is feasible for the detection of crystal violet in real samples. These results certify that CV-treated substrates possess broad application prospects in on-site SERS analysis.

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@WS

In this study, superparamagnetic β-CD-MnFe

Hexavalent chromium (Cr(VI)), a highly toxic heavy metal ion, poses a serious threat to human health, and the demand of rapid detection still on-going. Herein, we propose a surface-enhanced Raman spectroscopy (SERS)-based method for rapid and cost-effective quantification of Cr(VI) in aqueous solutions with direct signal of Cr(VI) rather than indirect signals of Raman reporter molecules exploited in previous studies. This method demonstrates high sensitivity (the detection limit of 0.72 ppb), high reproducibility (the batch-to-batch variation was less than 10 %), and excellent selectivity. The results of this proposed method are fairly in good agreement (R2 = 0.991) with those of the UV colorimetric method promulgated by the United States Environmental Protection Agency (USEPA). We demonstrated the potential of our novel method for practical application in determining Cr(VI) concentrations in drinking and environmental water samples, in which adequate recovery, and high interference resistance were observed. This method has the advantages of being faster and suitable for on-site inspection as no pretreatment process is required and the equipment is portable. The excellent performance promises a great prospective toward a rapid, reliable, and on-site detection for Cr(VI).

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.

In this study, superparamagnetic β-CD-MnFe2O4 with a large surface area was synthesized via a facile co-precipitation method, with β-cyclodextrin (β-CD) acting as a coating agent. The as-prepared β-CD-MnFe2O4 exhibited better catalytic performance than bare MnFe2O4 in terms of activating peroxymonosulfate (PMS) to degrade 2,4-dichlorophenol (2,4-DCP) over a broad pH range of 5-11. Electron spin resonance spectroscopy (ESR) and free radical quenching experiments indicate that various active species (SO4-/OH/O2-/1O2) are generated in the β-CD-MnFe2O4/PMS system and that pollutants trapped in the cyclodextrin cavity are quickly degraded. Various reaction parameters of the β-CD-MnFe2O4/PMS system and the stability of β-CD-MnFe2O4 were also investigated. The results indicate that β-CD-MnFe2O4 is promising for use in water purification owing to its excellent magnetic separation and recovery properties and good resistance to humic acid (HA).

Raman spectra that reflect the actual interactions of molecular complexes in solution can be obtained in situ, and the dominant intermolecular interactions can be determined via comparison with the calculated Raman spectra of all the possible configurations of the molecular complexes. In this study, we investigated the intermolecular interactions between C6F5Br and SCN− in solution using this method. The dominant intermolecular interaction in this di-molecular complex is identified as anion-π interaction, rather than halogen bonding. This method may find further applications in many fields, especially in biology.

Copper–silver or copper–gold galvanic displacement could induce the reduction of graphene oxide, resulting in a fast and effective removal of the oxygen-containing groups in graphene oxide and formation of silver or gold nanoparticles on graphene sheets. A graphene oxide mediated long-range electron transfer process between copper and silver or chloroauric ions is proposed for the occurrence of the reactions.

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.

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.

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.

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.

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.

Water-solublel-arginine-capped Fe3O4 nanoparticles were synthesized using a one-pot and green method. Nontoxic, renewable and inexpensive reagents including FeCl3,l-arginine, glycerol and water were chosen as raw materials. Fe3O4 nanoparticles show different dispersive states in acidic and alkaline solutions for the two distinct forms of surface bindingl-arginine. Powder X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the structure of Fe3O4 nanocrystals. The products behave like superparamagnetism at room temperature with saturation magnetization of 49.9 emu g−1 and negligible remanence or coercivity. In the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride, the anti-chloramphenicol monoclonal antibodies were connected to thel-arginine-capped magnetite nanoparticles. The as-prepared conjugates could be used in immunomagnetic assay. (See supplementary material 1) Electronic supplementary material The online version of this article (doi:10.1007/s11671-009-9480-x) contains supplementary material, which is available to authorized users. Click here for file