A Novel Thin-Layer Flow Cell Sensor System Based on BDD Electrode for Heavy Metal Ion Detection.

An electrochemical sensor based on a thin-layer flow cell and a boron-doped diamond (BDD) working electrode was fabricated for heavy metal ions determination using anodic stripping voltammetry. Furthermore, a fluidic automatic detection system was developed. With the wide potential window of the BDD electrode, Zn2+ with high negative stripping potential was detected by this system. Due to the thin-layer and fluidic structure of the sensor system, the electrodepositon efficiency for heavy metal ions were improved without using conventional stirring devices. With a short deposition time of 60 s, the system consumed only 0.75 mL reagent per test. A linear relationship for Zn2+ determination was displayed ranging from 10 µg/L to 150 µg/L with a sensitivity of 0.1218 µA·L·µg-1 and a detection limit of 2.1 µg/L. A high repeatability was indicated from the relative standard deviation of 1.60% for 30 repeated current responses of zinc solution. The system was applied to determine Zn2+ in real water samples by using the standard addition method with the recoveries ranging from 92% to 118%. The system was also used for the simultaneous detection of Zn2+, Cd2+, and Pb2+. The detection results indicate its potential application in on-site monitoring for mutiple heavy metal ions.

Gut microbiota influences feeding behavior via changes in olfactory receptor gene expression in Colorado potato beetles.

The Colorado potato beetle (CPB) is an internationally recognized plant quarantine pest that causes serious losses to potato agricultural production. The gut microbiota plays an important role in its growth and development, and the olfactory system plays an important role in insect feeding behavior. The gut microbiota is known to be capable of inducing changes in the olfactory systems of insects. However, the way these associated gut microbes influence the feeding-related behaviors of CPBs remains unclear. To explore the relationship between them, fresh potato leaves immersed in a mixture of five antibiotics (tetracycline, penicillin, ofloxacin, ciprofloxacin, and ampicillin) at specific concentrations for 1 h were fed to adult CPBs to reduce the abundance of gut microbes. We found that the feeding behavior of CPBs was significantly affected by the gut microbiota and that Pseudomonas was significantly higher in abundance in the control group than in the antibiotic group. We then used transcriptome sequencing to explore the differences in olfactory receptor genes in the heads of non-treatment and antibiotic-fed CPBs. Through Illumina Hiseq™ sequencing and screening of differential genes, we found that the olfactory receptor gene LdecOR9 was significantly upregulated and LdecOR17 was significantly downregulated after antibiotic feeding. A real-time polymerase chain reaction was used to verify the changes in olfactory receptor gene expression in the non-treatment groups and antibiotic-treated groups. The feeding behavior was partially rescued after CPBs were re-fed with intestinal bacteria. These results indicate that a certain amount of gut microbiota can result in the loss of the olfactory discrimination ability of CPBs to host plants. In summary, this study investigated the relationship between gut microbiota and olfactory genes, providing a reference for research on microbial control.

A biodegradable, flexible photonic patch for in vivo phototherapy.

Diagnostic and therapeutic illumination on internal organs and tissues with high controllability and adaptability in terms of spectrum, area, depth, and intensity remains a major challenge. Here, we present a flexible, biodegradable photonic device called iCarP with a micrometer scale air gap between a refractive polyester patch and the embedded removable tapered optical fiber. ICarP combines the advantages of light diffraction by the tapered optical fiber, dual refractions in the air gap, and reflection inside the patch to obtain a bulb-like illumination, guiding light towards target tissue. We show that iCarP achieves large area, high intensity, wide spectrum, continuous or pulsatile, deeply penetrating illumination without puncturing the target tissues and demonstrate that it supports phototherapies with different photosensitizers. We find that the photonic device is compatible with thoracoscopy-based minimally invasive implantation onto beating hearts. These initial results show that iCarP could be a safe, precise and widely applicable device suitable for internal organs and tissue illumination and associated diagnosis and therapy.

Beyond Photosynthesis: H2O/H2O2/O2 Self-Circulation-Based Biohybrid Photoelectrochemical Cells for Direct and Sustainable Solar-to-Fuel-to-Electric Power Conversion.

Solar-to-fuel conversion followed by secondary utilization in fuel cells provides an appealing approach to alleviating global energy shortages but is largely restricted by the complex design of power systems and the development of functional catalysts. Herein, we presented a biohybrid photoelectrochemical cell (BPEC) to implement sustainable solar-to-fuel-to-electric power conversion in a single compartment, by ingeniously combining reliable photoelectrochemical H2O2 generation with efficient bioelectrochemical H2O2 consumption. Specifically, the BPEC is composed of a Mo-modified BiVO4 (Mo:BiVO4) photoanode and a horseradish peroxidase (HRP)/pyrene-modified 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (bis-Pyr-ABTS)/carbon nanotubes with an encapsulated Co nanoparticle (Co/CNTs) biocathode. Upon photoexcitation, two-electron H2O oxidation can be carried out at the Mo-BiVO4 photoanode to produce H2O2, followed by electroenzymatic reduction of H2O2 to H2O by HRP with the help of a bis-Pyr-ABTS redox mediator at the biocathode. Besides, in response to the insufficient Faradaic efficiency of H2O2 generation at the photoanode, the functional Co/CNTs catalysts, possessing prominent electrocatalytic selectivity toward two-electron O2 reduction (electron transfer number = 2.6), are modified on the biocathode, thus clearly defining effective H2O/H2O2/O2 self-circulation in this device. This developed BPEC obtains an open-circuit potential of 1.03 ± 0.02 V and a maximum power density of 0.18 ± 0.02 mW cm-2. Moreover, inspired by the particular advantage of enzymatic biofuel cells for easy miniaturization, an enclosed "sandwich-like" BPEC of approximately 1 cm3 size is fabricated and delivers a power output of 0.13 ± 0.03 mW cm-2. Our work represents a controllable approach for meaningful solar energy utilization, beyond traditional artificial photosynthesis, and can further provide a significant paradigm shift in building an energy-sustainable society.

Comparison of Microbial Communities in Colorado Potato Beetles (Leptinotarsa decemlineata Say) Collected From Different Sources in China.

Microbial communities in insects are related to their geographical sources and contribute to adaptation to the local habitat. The Colorado potato beetle (Leptinotarsa decemlineata) (CPB) is a potato pest that causes serious economic losses in Xinjiang Uygur Autonomous Region (XJ) and Heilongjiang Province (HL), China. The influence of microorganisms in the invasion and dispersal of CPB is unclear. We studied microbial communities of CPB collected from nine geographic sources in China using high throughput sequencing technology. Bacteroidetes, Firmicutes, and Proteobacteria were the most dominant phyla, Clostridia, Bacteroidetes, and γ-Proteobacteria were the most dominant classes, Enterobacterales, Lactobacillales, Clostridiales, and Bacteroidales were the most dominant orders, and Enterobacteriaceae, Streptococcidae, Verrucomicrobiaceae, and Rikenellaceae were the most dominant families. There were significant differences, among sources, in the relative abundance of taxa at the genus level. A total of 383 genera were identified, and the dominant bacteria at the genus level were compared between XJ and HL. Pseudomonas was the unique dominant microorganism in the HL area, and the other four microorganisms (Lelliottia, Enterococcus, Enterobacter, and Lactococcus) were common within the 2 regions. Bacterial community diversity in CPB from Urumqi, Jimunai, and Wenquan was higher than diversity in other regions. T-Distributed Stochastic Neighbor Embedding (tSNE) analysis indicated that order and genus were appropriate taxonomic levels to distinguish geographical sources of CPB. These findings provide insight into the diversity of microorganisms of CPB in the differences among geographically isolated populations.

A naked-eye readout self-powered electrochemical biosensor toward indoor formaldehyde: On-site detection and exposure risk warning.

The determination of indoor formaldehyde is of great importance to protect individuals against its well-known adverse impact on health. Here, we report on a design of a naked-eye readout self-powered electrochemical biosensor (SPEB) toward gaseous formaldehyde based on the efficient catalytic activity of the formaldehyde dehydrogenase/poly (methylene green)/buckypaper bioanode and the excellent electrochromic property of the Prussian blue (PB) cathode. The SPEB has a planar configuration and is covered with poly(vinyl alcohol) (PVA) as gel electrolyte to provide an inner lateral resistance large enough to enable the progressive discoloration of the patterned PB at cathode, which in turn, making the determination of gaseous formaldehyde feasible by measuring the distance consumed after 10-min exposure. The use of PVA gel electrolyte can also facilitate the observation of the color change due to its excellent transparency. The SPEB shows obvious responses to gaseous formaldehyde in a broad concentration range of 80 and 3000 ppb, covering the important permissible limits of indoor formaldehyde related to human health. The SPEB also exhibits satisfactory results in sensing gaseous formaldehyde released from the real plywood that is one of the dominating sources of the gaseous indoor formaldehyde. The results shown here demonstrate the good potential of the naked-eye readout SPEB as a fast, reliable, and portable tool for on-site determination of gaseous formaldehyde, with the appealing characteristics such as ease of operation, simplicity of configuration, and no requirement of external power sources.

Recent development of biofuel cell based self-powered biosensors.

Self-powered biosensors (SPBs) based on enzymatic biofuel cells (EFCs) and microbial fuel cells (MFCs) have attracted considerable attention due to their obvious advantages such as simple configuration and ease of miniaturization, and potential applications including clinical diagnosis, environmental monitoring, industrial process control, etc. In this review, we will summarize the recent advances in SPBs, focusing on the use of EFC-SPBs as power sources in combination with microelectronic and electrochromic devices, and the applications of MFC-based SPBs as sensors for detecting toxicity, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and assimilable organic carbon (AOC). The efforts in, for example, boosting the energy, reducing the cost, and improving the sensing performance in terms of sensitivity, accuracy and dynamic detection range are discussed. Finally, future prospects for the development of MFC-based SPBs are presented.

A respiration substrate-less isolation method for acute toxicity assessment.

Respiration substrate (RS)-less isolation method was developed for enhancing the sensitivity of acute toxicity assessment of heavy metal ions. RS was removed from the first step of previous isolation method, which was an effective strategy for improving acute toxicity assessment. 50% inhibiting concentration (IC50) values of Cu2+, Cd2+, Zn2+, Hg2+ and Ni2+ were 0.39 mg L-1, 5.99 mg L-1, 3.99 mg L-1, 0.23 mg L-1 and 5.74 mg L-1, respectively. Beyond that, the complicacy of organic toxicants assessments was investigated by choosing 3,5-dichlorophenol (DCP) as model toxicant. Biofilm sensor, morphology method and suspended microbes-based methods including one-pot method, RS-isolation method, RS-less isolation method, RS-less isolation method with added potassium ferricyanide (+F), were compared. The sensitivity to DCP can be ranked as morphology method > suspended microbes-based methods > biofilm method. The difference of the present results implicated that the methodological interference, leading in different detection mechanisms of these methods. The relative investigations can provide theoretical guidance for developing comprehensive detection methods of pollutants.

How to Identify the "LIVE/DEAD" States of Microbes Related to Biosensing.

In this work, we fabricated a microbial biosensor with long-term stability, which relied on microbial activity. Activity of the microbe was commonly estimated by LIVE/DEAD assay and the propidium iodide (PI)-stained one was judged as dead. Herein, we proposed the utilization of a physiological state of microbes, which was neither live nor dead but between them. In this state, microbes represented a high PI-stained ratio but still had catalytic ability. This microbial state was obtained by forming the biofilm under the conditions of poor nutrition and low temperature. Thus, the dividing and proliferating ability of the microbes in the biofilm was weak, which was beneficial for long-term stability. This mechanism was further confirmed by the biosensors made from multifarious substrate materials, including graphene-based gel, biomass-based gel, graphite felt, and poly(vinyl chloride). This biosensor was applied to water pollution monitoring in the laboratory for 2 years and then was integrated into a multiparameter water quality monitoring station on a local lake for 2.5 years.

Water/Oxygen Circulation-Based Biophotoelectrochemical System for Solar Energy Storage and Release.

Fabricating an artificial photoelectrochemical device to provide electric power on demand is highly desirable but remains a challenge. In response to the intermittent nature of sunlight, we develop a water/oxygen circulation-based biophotoelectrochemical system (BPECS) by integrating a polypyrrole (PPy) capacitor electrode into a photobiofuel cell (PBFC). Unlike traditional PEC devices, the modular and integrated system design of BPECS can not only improve compatibility among PEC cells, BFCs, and capacitor devices, but also offers a feasible way for tackling the intermittent nature of sunlight. In this system, the molecules of water and oxygen can form a self-circulation, thus making this device intrinsically safe and cost-effective. Through the alternate two-step energy conversion (i.e., solar-to-chemical/electric and chemical-to-electric), this conceptual model obtains maximum power output densities of 0.34 ± 0.01 and 0.19 ± 0.02 mW cm-2 in light and dark conditions, respectively, and presents stable long-term cycling performance for solar energy storage and release. Our results demonstrate that such a BPECS achieves high-effective solar energy utilization, which carries great significance to the development of artificial BPECS and provides research opportunities to explore a deployable route for grid-scale photovoltaic energy storage.

A Self-Powered Biosensor with a Flake Electrochromic Display for Electrochemical and Colorimetric Formaldehyde Detection.

The formaldehyde biosensors with the features of cost effectiveness, high specificity, easy operation, and simplicity are urgently desired in routing and field detection of formaldehyde. Here, we report a new design of an enzymatic self-powered biosensor (ESPB) toward formaldehyde detection. The ESPB involves a formaldehyde dehydrogenase/poly-methylene green/buckypaper bioanode as the sensing electrode and a Prussian blue/Au nanoparticles/carbon fiber paper cathode as the electrochromic display. Formaldehyde acts as the fuel to drive the ESPB, relying on that the concentration of formaldehyde can be determined with the ESPB by both directly measuring the variance in short circuit current and observing the color change of the cathode. By measuring the variance in short circuit current, a linear detection range from 0.01 to 0.35 mM and a calculated detection limit of 0.006 mM are obtained, comparable to or better than those reported before. The color change of the cathode can be distinguished easily and exactly via the naked eye after immersing the ESPB in formaldehyde solution for 90 s with the concentration up to 0.35 mM, covering the permissive level of formaldehyde in some standards associated with environmental quality control. Specially, the formaldehyde concentration can be precisely quantified by analyzing the color change of the cathode digitally using the equation of B/(R + G + B). In the following test of real spiked samples of tap water and lake water, the recovery ratios of formaldehyde with the concentrations from 0.010 to 0.045 mM are tested to be between 95 and 100% by both measuring the variance in short circuit current and analyzing the color change of the cathode digitally. In addition, the ESPB exhibits negligible interference from acetaldehyde and ethanol and can be stored at 4 °C for 21 days with a loss of less than 8% in its initial value of short circuit current. Therefore, the ESPB with the capability of working like disposable test paper can be expected as a sensitive, simple, rapid, cost-effective colorimetric method with high selectivity in routing and field formaldehyde detection.

S100A4 promotes inflammation but suppresses lipid accumulation via the STAT3 pathway in chronic ethanol-induced fatty liver.

S100A4, a member of the S100 calcium-binding protein family, has been identified in a subpopulation of liver macrophages and promotes liver fibrosis via hepatic stellate cell activation. However, the specific role of S100A4 in alcoholic liver disease (ALD) has not been well investigated. Here, S100A4 knockout (S100A4-/-) mice were used in a chronic-binge ethanol model for studying the role of S100A4 and its related molecular mechanism in ALD. S100A4 expression was increased in ethanol-induced liver tissues of wild-type (WT) mice. Macrophage-derived S100A4 promoted liver inflammation but suppressed lipid accumulation under the ethanol feeding condition. S100A4 deficiency promoted ethanol-induced liver injury and hepatic fat accumulation. Further mechanistic studies found that S100A4 inhibited liver fat accumulation mainly by activating the STAT3 pathway and downregulating lipogenic gene expression, especially that of SREBP-1c. In AML-12 cells, a STAT3 inhibitor abolished STAT3 levels and decreased the expression of SREBP1c. Furthermore, the administration of a neutralizing S100A4 antibody to WT mice significantly promoted ethanol-induced liver injury and fatty accumulation. Thus, S100A4 may represent a potential candidate target for the prevention and treatment of ethanol-induced fatty liver. In this study, we discovered the special role of S100A4 in alcoholic liver disease. S100A4 deficiency attenuated ethanol-induced hepatitis and promoted hepatic fat accumulation in ethanol-induced liver tissues. Further mechanistic studies have found that S100A4 promotes early alcoholic hepatitis mainly by activating the STAT3 pathway and its downstream proinflammatory gene expression. Interestingly, activation of the STAT3 pathway downregulates lipogenic gene expression, especially SREBP-1c. KEY MESSAGES: In this study, we discovered the special role of S100A4 in alcoholic liver disease. S100A4 deficiency attenuated ethanol-induced hepatitis and promoted hepatic fat accumulation in ethanol-induced liver tissues. Further mechanistic studies have found that S100A4 promotes early alcoholic hepatitis mainly by activating the STAT3 pathway and its downstream proinflammatory gene expression. Interestingly, activation of the STAT3 pathway downregulates lipogenic gene expression, especially SREBP-1c.

Metallic and plasmonic MoO2 monocrystalline ultrathin mesoporous nanosheets for highly sensitive and stable surface-enhanced Raman spectroscopy.

Structure and size control are always considered as effective routes to enhance sensitive performance. Different from common polycrystalline porous nanosheets, herein, the general synthesis of monocrystalline ultrathin porous nanosheets (MUPNSs) by a facile decompressing decomposition (DPD) route is reported. Accompanied with the properties inherited from MUPNSs, i.e., high adsorption and strong plasma resonance, these MoO2 MUPNSs presented high sensitive activity as a surface enhanced Raman spectrum (SERS) substrate. The SERS sensitivity of MoO2 MUPNSs was about 1000 times higher than MoO2 polycrystalline ultrathin porous nanosheets (PUPNSs).

Alternative to Noble Metal Substrates: Metallic and Plasmonic Ti3O5 Hierarchical Microspheres for Surface Enhanced Raman Spectroscopy.

Compared with noble metals, improving the sensitivity of semiconducting surface-enhanced Raman scattering (SERS) substrates is of great significance to their fundamental research and practical application of Raman spectroscopy. In this paper, it is found that the SERS sensitivity is increased by 10 000 times by reducing the semiconducting TiO2 microspheres to quasi-metallic Ti3O5 microspheres. Its lowest detectable limit is up to 10-10 M, which may be the best among the non-noble metal substrates and even reaches or exceeds certain Au/Ag nanostructures to the best of our knowledge. This new type of non-noble metal SERS substrate breaks through the bottleneck of poor stability of conventional semiconductor substrate and can withstand high temperature oxidation at 200 °C and strong acid-base corrosion without performance degradation. Benefiting from its excellent ability of visible-light photocatalytic degradation of organic molecules, the substrate can be reused. Moreover, the new material also exhibits excellent photothermal conversion properties.

Characterization and analysis of non-ionic surfactants by supercritical fluid chromatography combined with ion mobility spectrometry-mass spectrometry.

Comprehensive separation and analysis of non-ionic surfactants have been conducted by coupling supercritical fluid chromatography (SFC) with ion mobility spectrometry-mass spectrometry (IMS-MS). Representative non-ionic surfactants were investigated, including alkylphenol ethoxylates (APEOs), e.g., octylphenol ethoxylates (OPEOs) and fatty alcohol ethoxylates (FAEs), e.g., lauryl alcohol ethoxylates (LAEs). A sub-2-µm high-density diol column was used for chromatographic separation by the first-dimensional SFC due to the differences in ethoxy chain prior to electrospray ionization (ESI). Maintaining the fidelity of pre-ionization separation in the first dimension, the introduction of IMS provided additional post-ionization resolution by broadly fractionating the oligometric ethoxymers based on their size and electric charge within 13.78 ms. Distinguishable series of singly and multiply charged non-ionic species could be clearly observed. The millisecond timescale ion mobility separation perfectly fits the elution time of a chromatographic peak, while effectively feeding components into the fast-scanning time-of-flight (TOF) mass analyzer for characterization and analysis. The orthogonality of the developed separation and analysis system was evaluated, revealing a correlation coefficient and peak spreading angle of 0.2729 and 74.16° for the studied OPEOs and 0.1962 and 78.69° for LAEs. Significant enhancement in peak capacity was achieved for the developed SFC-IMS-MS system with the actual peak capacity measured to be approximately 41 and 160 times higher than that of the dimensions of SFC and IMS, respectively, when used alone. Graphical abstract.

[Rapid on-site screening of five prohibited ingredients in cosmetics using thermal desorption-corona discharge ionization coupled with ion mobility spectrometry].

A rapid on-site analytical method is developed for screening lidocaine and four other types of prohibited ingredients in cosmetics using thermal desorption-corona discharge ionization together with ion mobility spectrometry. Performing no pretreatment, we dropped or sprayed cosmetic samples onto a Nomex sampling swab. The sampler was placed into a compartment for thermal desorption and corona discharge ionization; then, ion mobility spectrometry analysis was performed. The limits of detection (LODs) for the five analytes ranged from 10 to 50 ng. The instrumental analysis time for a single run was less than 20 ms, and the total sample analysis period was within 1 min. The proposed method is simple, fast, and has low cost, and could be used as an analytical tool for rapid on-site screening of prohibited ingredients in cosmetics.

Comprehensive screening of 63 coloring agents in cosmetics using matrix solid-phase dispersion and ultra-high-performance liquid chromatography coupled with quadrupole-Orbitrap high-resolution mass spectrometry.

An analytical methodology for comprehensive screening of 63 coloring agents of great concern for regulatory control in cosmetics has been established using ultra-high-performance liquid chromatography (UHPLC) coupled with quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). An effective, rapid, and simple sample pretreatment protocol with low sample and reagent consumption was developed based on matrix solid-phase dispersion (MSPD). The selection of the most suitable extraction conditions was made using statistical tools of factorial multifactor experimental design and analysis of variance (ANOVA). In the final conditions, 0.1 g of cosmetic sample was blended with 0.3 g of anhydrous sodium sulfate and 0.4 g of sand, and the MSPD column was eluted with 2 mL of methanol. The extract was analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS1/dd-MS2) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS1 and 17,500 FWHM for dd-MS2 stage with the experimentally measured mass deviations of less than 3 ppm (parts per million) for quasi-molecular ions and 5 ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 63 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. Method performance was evaluated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, precision, recovery, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the simultaneous analysis of 63 target coloring agents in 69 genuine cosmetic samples. Eleven legally prohibited coloring agents were detected in 26 cosmetic samples in total. The proposed method exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class coloring agent substances in cosmetics.

Development of an analytical method for twelve dioscorea saponins using liquid chromatography coupled to Q-Exactive high resolution mass spectrometry.

A rapid method using liquid chromatography coupled to Q-Exactive high resolution mass spectrometry was developed for determination of twelve dioscorea saponins in Polygonti Rhizome. The separation was performed on a Alorich Ascentis C8 column (100 mm × 4.6 mm, 3 µm) with gradient elution of water and acetonitrile. All calibration curves showed good linear regression (r2 >0.9947) within the linear range. The limits of detection and quantitation were in the range of 0.3-1.0 ng/mL and 1.0-3.0 ng/mL, respectively. The intra- and inter-day precision (RSD) were below 8.85% (n = 6) and 9.15% (n = 6), respectively. The recovery for the target compounds was within the range of 80.34-108.05%. The fragmentation pathways of twelve saponins were summarized in both positive and negative modes. The saponins which contain the same substituent groups and the different skeletons showed the same precursor ions and the similar fragmentation patterns in positive mode. However, different types of saponins can be distinguished in negative mode by the characteristic ions. The proposed method was applied to analyze six batches of Polygonti Rhizome samples for target compounds. This work promoted the quality control method for raw material or preparations which contain dioscorea saponins.

Metallic carbide nanoparticles as stable and reusable substrates for sensitive surface-enhanced Raman spectroscopy.

We demonstrate for the first time that metallic carbide nanoparticles with a strong localized surface plasmon resonance (LSPR) effect could be used as SERS substrates to detect trace substances. They achieve a noble metal-comparable enhancement factor of 6.4 × 107.

Improved Surface-Enhanced Raman Spectroscopy Sensitivity on Metallic Tungsten Oxide by the Synergistic Effect of Surface Plasmon Resonance Coupling and Charge Transfer.

Increasing the sensitivity of non-noble metal surface-enhanced Raman spectroscopy (SERS) is an urgent issue that needs to be solved at present. Herein, metallic W18O49 nanowires with a strong localized surface plasmon resonance (LSPR) effect are prepared. Interestingly, the LSPR peaks of these nanowires would undergo a strong blue shift from near-infrared (NIR) to visible light regions as the aggregation degree of the nanowires increases. By narrowing the gap between the LSPR absorption peak and the Raman excitation wavelength (532 nm), the oriented W18O49 bundles with a LSPR peak centered at 561 nm have greatly improved SERS sensitivity compared with that of the dispersed nanowires with a LSPR peak centered at 1025 nm. Enhancement mechanism investigation shows that the high sensitivity can be attributed to the synergistic effect of LSPR coupling among the oriented ultrathin nanowires and oxygen vacancy (Vo)-assisted charge transfer.