Search

Although homogeneous detection of some biomolecules has been of great significance in clinical assay, it faces great challenges in achieving precise in situ imaging of biomolecules. In addition, nonspecific adsorption between probes and biomolecules and low sensitivity are still unfathomed problems. Herein, we developed a promoted "Click" surface enhanced Raman scattering (SERS) strategy for realizing highly selective homogeneous detection of biomolecules by simultaneous dual enhanced SERS emissions, obtaining mutually confirmed logical judgment. Taking caspase-3 as one of the biotargets, we have realized highly selective homogeneous detection of caspase-3 using this strategy, and precise intracellular imaging of caspase-3 can be in situ monitored in living cells or during cell apoptosis. In detail, polyA-DNA and the Asp-Glu-Val-Asp (DEVD)-containing peptide sequence were modified into alkyne and nitrile-coded Au nanoparticles (NPs). During the cell apoptosis process, the generated caspase-3 would lead to the cleavage of the tetra-peptide sequence DEVD, thereby removing the negative protection part from the peptide on Au NPs. Interestingly, two different triple bond-labeled Au NPs can be connected together through DNA hybridization to form SERS "hotspot", resulting in simultaneously enlarged triple bond Raman signals. Moreover, we found that the SERS intensity was positively related with caspase-3 concentration, which has a wide linear range (0.1 ng/mL to 10 μg/mL) and low detection limit (7.18 × 10-2 ng/mL). Remarkably, these simultaneously enlarged signals by "Click" SERS could be used for more precise imaging of caspase-3, providing mutually confirmed logical judgment based on two spliced SERS emissions, especially for their relative intensity.

The reliability and reproducibility of surface-enhanced Raman scattering (SERS) technology is still a great challenge in bio-related analysis. Prussian blue (PB)-based SERS tags have attracted increasing interest for improving these deficiencies due to its unique Raman band (near 2156 cm−1) in the Raman-silent region, providing zero-background bio-Raman labels without interference from endogenous biomolecules. Moreover, the stable PB shell consisting of multiple layers of CN− reporters ensure a stable and strong Raman signal output, avoiding the desorption of the Raman reporter from the plasmonic region by the competitive adsorption of the analyte. More importantly, they possess outstanding multiplexing potential in biological analysis owing to the adjustable Raman shift with unique narrow spectral widths. Despite more attention having been attracted to the structure and preparation of PB-based SERS tags for their better biological applications over the past five years, there is still a great challenge for SERS suitable for applications in the actual environment. The biological applications of PB-based SERS tags are comprehensively recounted in this minireview, mainly focusing on quantification analysis, multiple-spectral analysis and cell-imaging joint phototherapy. The prospects of PB-based SERS tags in clinical diagnosis and treatment are also discussed. This review aims to draw attention to the importance of SERS tags and provide a reference for the design and application of PB-based SERS tags in future bio-applications.

Here, it reports a high-throughput detection method for reliably quantitative analysis of illegal drugs in complex biological samples by means of a surface-enhanced Raman scattering (SERS) active microcavity and rapid pretreatment device. Based on the well-made hemispherical microcavities that regularly distributed on a glass array, the quality-controllable microcavity device is fabricated by the compact self-assembly of core-shell nanopeanuts (CSNPs) onto the inside surface. Both the CSNPs with a quantifiable internal standard signal of crystal violet acetate anchored inside their gap and the well-made microcavity referred to the physical amplification of the microscale groove surface will do well in trace analysis, which will allow us to realize the accurately quantitative SERS analysis of targeted analytes spread on the bottom area of the microcavity array. As an example, 0.8 nM malachite green and 160 ppb methamphetamine (MATM) have been successively detected in a wide range as standard, while even 0.01 ppm MATM mixed in the urine/serum samples has been efficiently tested by the microcavity device equipped with a rapid pretreatment device (manual monolithic column syringe needle). All of the above suggest that the SERS-active microcavity equipped with a rapid pretreatment device has potential in the on-site quick test of trace amounts of illegal drugs in bodily fluid samples or other field analysis of food sanitation, environmental safety, and public health.

A reliable and sensitive sensing of multiple foodborne pathogens is critical for timely diagnosis and human health. To meet this need, herein, we designed a sandwich immunoassay platform, using functionalized SERS probes and magnetic beads, for the interference-free simultaneous detection of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in food samples by surface-enhanced Raman scattering (SERS) technology. The signal of two SERS probes coded by triple bonds (C[triple bond, length as m-dash]C and C[triple bond, length as m-dash]N) located at 2105 and 2227 cm-1, respectively, could perfectly avoid the spectral overlap with coexisting materials in the Raman fingerprint region, which ensured the accuracy of the immunoassay platform. The application of functional magnetic beads, integrating enrichment and separation, greatly improved the sensitivity of the detection system. Under magnetic force, due to the mature interaction between the antigen and antibody, the sandwich immunoassay platform could be fabricated. Its limit of detection (LOD) for the simultaneous detection of E. coli and S. aureus was as low as 10 and 25 cfu mL-1, respectively, and the sandwich immunoassay platform was successfully applied for the detection of E. coli and S. aureus in bottled water and milk. As a sensitive and highly selective analytical technique for the simultaneous multiple detection of pathogens, this SERS-based method has great potential to be applied in the field of food safety.

High-throughput optical labeling technologies have become increasingly important with the growing demands for molecular detection, disease diagnosis, and drug discovery. In this thought, a series of CN-bridged coordination polymer encapsulated gold nanoparticles have been developed as a universal and interference-free optical label through a facile and auxiliary agent-free self-assembly route. Moreover, surface-enhanced Raman scattering (SERS) emissions of CN-bridge can be tuned flexibly by simple replacement of Fe2+/Fe3+ with other metal ions relying on the synthesis of three Prussian blue analogues encapsulated gold nanoparticles (Au@PBA NPs). Thus, three distinct Raman frequencies have been acquired, which merely replaced the metal irons. On the basis of the potential supermultiplex optical label, space-confined surface-enhanced Raman scattering (SERS) emissions have been realized. Relying on "Abbe theorem", the focused laser allows the pure and single triple bond-coded SERS emissions to be combined into a unique and independent output, so-called "combined SERS emission" (c-SERS), if the Au@PBA NPs were confined into one micrometer-scale object. This study demonstrated c-SERS may simultaneously provide 2n - 1 optical labels only using n single emissions in the Raman-silent region for micrometer-size objects.

Materials with surface wrinkles at a micro/nanoscale possess extraordinary fascinating properties, and various techniques have been employed to create controllable wrinkles. Herein, natural polysaccharide was used to construct the surface wrinkled microsphere with controllable wrinkling patterns. A robust microsphere with an average size of about 55 μm fabricated from chitosan in alkali/urea aqueous solution was swelled and then coated orderly by introducing rigid silver nanoparticles (Ag NPs) with an average size of about 5 nm as the shell onto the surface through electrostatic layer-by-layer (LBL) self-assembly followed by deswelling, resulting in a surface wrinkled microsphere. The significant difference in the swelling behaviors between the stiff Ag shell and swelled chitosan microsphere could generate enough driving forces to form 3D micro- and nanoscale wrinkling surface topography. The surface wrinkled microspheres exhibited the hierarchically porous structure and hydrophobicity, and the topographical patterns could be adjusted by controlling the thickness of the Ag NP layer to achieve the sizes of wrinkling ranging from 60 to 300 nm. It was demonstrated that the wrinkled microspheres were superior as 3D surface-enhanced Raman spectroscopy (SERS) substrates, in which the wrinkled structure with spatial periodicity was proved to be effective for enhancing the SERS signal. The microsphere with controllable wrinkled surface topography could be applied to be a miniature 3D device, which promises potential technological applications in various areas.

We describe a novel biosensing strategy for sensitive detection of methylamphetamine (MAMP) based on surface enhanced Raman scattering (SERS) by the mediation of spacing between 4-mercaptobenzoic acid (4-MBA) labeled Au@Ag core-shell nanoparticles (Au@Ag). To achieve a favorable SERS substrate, Au@Ag shell-core nanoparticle was synthesized with seeds growth method and well characterized by SEM, TEM and UV–vis spectrometer. The uniform Au@Ag shows an excellent dispersion ability for SERS detection. Under the optimized conditions, the novel biosensor shows a good logarithm linear correlation with the concentration of MAMP ranging from 0.5 ppb to 40 ppb (R2 = 0.986), with a limit of detection at 0.16 ppb of MAMP (3σ). Furthermore, our biosensors hold an excellent selectivity, demonstrated by the negligible interference from the detection of other illicit drugs and metabolites. The concentrations determined with our biosensor from spiked MAMP in human urine sample fell within the same range with the results from mass spectrometry. This indicates that our sensor has a clear potential for the rapid detection of illicit drug in real samples.

It is highly vital in automotive body, high-speed rail overhead line parts and water distribution systems to use hot-dip galvanized steel (HDGS) coatings for efficiency and ease of synthesis. Various novel coating systems could surpass the technical restrictions of traditional anticorrosion techniques. In consequence, inorganic or organic coating systems must be chosen accurately and suitably. Meanwhile, these coating systems should be evaluated in accordance with their unique material characteristics and synergistic electrochemical parameters. From this view, we summarize an overview of recent developments of anticorrosive coating systems researches for HDGS. First, we demonstrate the traditional protective coatings to match the use of HDGS. Likewise, emerging and state-of-the-art protective coatings are summarized as well. Subsequently, methods for the assessment criteria of traditional and emerging protective coatings are displayed and illustrated through electrochemical analysis. Concluding, we make a proposal about the future developments of protective coating systems for HDGS.

Surface-enhanced Raman scattering (SERS) is an important, highly sensitive technique for chemical and biological analysis, which is critically dependent upon high-performance metallic substrates. Anisotropic gold (Au)–silver (Ag) alloy nanoboxes are attractive SERS substrates because of the greatly enhanced Raman signals from the strong electromagnetic fields on the sharp corners. Yet, the routine approach of Au–Ag alloy nanobox synthesis is still challenging because of the complicated procedures and use of biologically/environmentally unfriendly reagents. To facilitate the usage of Au–Ag alloy nanoboxes for broad SERS applications, we propose a facile green strategy to synthesize Au–Ag alloy nanoboxes with superior single-particle SERS sensitivity. Our novel straightforward strategy involves HAuCl4 and AgNO3 reduction by ascorbic acid, which is achieved in an aqueous one-pot reaction at ambient temperature. Significantly, the surfaces of the prepared Au–Ag alloy nanoboxes are judiciously designed to intr...

Layered double hydroxide (LDH) films have been used to protect metal substrates because of their superior barrier performance and capability of capturing corrosive anions (such as Cl−) by exchange with interlayer anions. In this preliminary work, we determined that some photoactive LDHs (such as NiAl-LDH) can also provide cathodic protection to metals under light illumination, stemming from the light-generated electrons of semiconducting LDHs, if the energy level of the conduction band of LDHs is higher than the Fermi level of the metal. The current experimental results prove that the corrosion resistance of stainless steel is enhanced by the attached NiAl-LDH films in the dark and is further increased under light illumination due to photogenerated cathodic protection.

Unbiodegradable toxic Hg2+ accumulates in ecological systems and results in contaminated food chain, exposing us to high level pollution and healthy risk. Here, monolayer 2,5-Dimercapto-1,3,4-thiadiazole (DMcT) functionalized Au@Ag nanoparticles (NPs) were controllably constructed as a label-free SERS probe. Based on them, we can perform rapid and easy Hg2+ identification with high sensitivity and selectivity over competing analytes. Remarkably, DMcT acted as both interior label and target acquisition. Since DMcT showed intrinsic Raman signal when attached to substrates surface, it can be employed for quantification instead of extra conventional signal label. Also, we've demonstrated that DMcT coordinated on the surface of Au@Ag NPs as bidentate ligand with both the thiocarbonyl sulfur atoms while the nitrogen atoms on the different sides of the molecule were devoted to Hg2+ recognition. Owing to the strong coordination between Hg2+ and nitrogen atoms, as low as 10pM Hg2+ can be detected. The probe responded a good linear relationship ranging from 0.05 to 100nM and the limit of detection is ~3 orders of magnitude lower than the United States Environmental Protection Agency (USEPA)-defined limit (10nM) in drinkable water (EPA: Washington, DC, 2001). Furthermore, our suggested platform is highly effective to perform real samples detection. Utilizing the environmental water from East Lake, Wuhan, it resulted in better accuracy over the conventional standard method.

Establishing an accurate, simple, and rapid serodiagnosis method aiming for specific cancer antigens is critically important for the clinical diagnosis, therapy, and prognostication of cancer. Currently, surface-enhanced Raman scattering (SERS) readout techniques challenge fluorescent-based detection methods in terms of both optical stability and more importantly multiple detection capability, which become more desirable for clinical diagnostics. We thus started using an interference-free mixing SERS emission (m-SERS) readout to simultaneously indicate, for the first time, three specific liver cancer antigens, including α-fetoprotein (AFP), carcinoembryonic antigen (CEA), and ferritin (FER), even in one clinical serum sample. Here, three triple bonds (C≡N and C≡C) coded SERS tags contribute separate SERS emissions located at 2105, 2159, and 2227 cm–1, respectively; must have one-to-one correspondence from AFP, to FER, to CEA, In the process of detection, the mature double antibody sandwich allows the form...

Since 1, 2, 3-Benzotriazole (BTA) is one of the most commonly used metal passivators in transformer oil, on-site and quantitative detection of BTA plays a significant role in fast evaluation of the performance of the insulating oil. Herein, we proposed a cycle-growth synthetic protocol for yielding two-dimensional (2D) plane-based surface-enhanced Raman scattering (SERS) substrates with tunable optical property and controllable interparticle distance, and an extraction material, so called colloidal lignin particles (CLPs), for the fast separation of BTA from oil matrix. After BTA from transformer oil were adsorbed by hydrophilic CLPs, highly reproducible SERS signal of BTA can be obtained by dropping on the substrate. The characteristic Raman shift at 1386 cm−1 of BTA has been selected to establish a good linearity between its relative intensity and concentration in the range of 1–300 mg/L, and the detection limit for BTA was down to 0.12 mg/L. Moreover, the time consumption for the whole detection process of real sample including sample pretreatment and SERS measurements was less than 30 min. It is highly expected that the combination of CLPs with SERS can accomplish the on-site detection of trace BTA in transformer oil.

Nitrites (NO2(-) ions) in food and drink play an important role in human health but require complicated operations before detection. Herein, we present a rationally designed SERS-enabled micro-chamber that comprised a drawn glass capillary with a tiny orifice (∼50 μm) at the distal tip, wherein the gold nanoparticles (Au NPs) are compactly coated on the inner wall surface. In this chamber, nitrites specifically trigger a pH and laser irradiance-dependent diazotization starting from p-aminothiophenol (PATP) absorbed onto the surface of Au NPs to form p,p'-dimercaptoazobenzene (DMAB) molecules, in which the presence of NO2(-) ions above 30.7 μM (1.38 ppm) in the siphoned liquid sample can be identified relying on SERS peak (1141 cm(-1)) intensity of the emerging azo moiety. Except for pH conditions, laser irradiance is more important but easily neglected in previous studies, which is capable of preventing generation of errors when the detection sensitivity was pursued through increasing the laser power. In this case, several real samples (rather than simple water samples), including honey, pickled vegetable and fermented bean curd, had been successfully detected accurately through such a convenient sampling micro-chamber. The SERS-enabled device could potentially be facilely incorporated with portable Raman instruments for a special application of food inspection in rapid and field analysis of NO2(-) ions.

We herein present a simple and surfactant-free synthetic strategy for the preparation of core–shell Fructus Broussonetia-like Au@Ag@Pt nanoparticles (FBNPs) via a combination of galvanic replacement and reagent reduction, in which a chitosan (CS)-mediated epitaxial growth of Pt multi-branches occurs on cresyl violet labeled Au core–Ag shell nanoparticles (NPs) at room temperature. The as-prepared novel nanostructures exhibit an enzyme mimetic activity due to the formation of a Fructus Broussonetia-shaped Pt shell, the absence of surfactants and the positively charged CS molecules intertwined within the outermost Pt NPs. Relying on the high sensitivity of resonance-enhanced Raman scattering and the highly efficient intrinsic peroxidase-like activity of FBNPs, H2O2 was detected with a wide detection window from 10 pM to 100 μM when utilizing 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate. Based on the H2O2–TMB catalytic oxidation system a simple, sensitive, selective and universal platform has been extended for the detection of all peroxidase-related analytes. For example, glucose at a concentration range of 1 nM to 200 μM was detected in the presence of glucose oxidase with a limit of detection of 1 nM.

Bacillus cereus, a common soil bacterium, has been shown to act as a biogeochemical indicator for concealed mineralisations, e.g., vein-type Au deposits. Field and cultivation-free detection of Bacillus cereus in the presence of Au3+ and other metal ions is significantly important but still almost blank in current biogeochemical prospecting of gold mine system. Herein, a self-established simple approach was slightly improved to make silver nanoparticles (Ag NPs) rapidly concentrated on every bacterial cell, and highly strong and distinct surface-enhanced Raman scattering (SERS) signals of Bacillus cereus free from any native fluorescence have been obtained in a so called ‘mixing-and-measuring’ manner. Furthermore, SERS was used for the first time to our knowledge to investigate the impacts of different concentrations of metal ions on Bacillus cereus, and successfully utilized for distinguishing Au3+ ions from other species. A more convincing multi-Raman criterion based on Raman bands, and further the entire Raman spectrum in combination with statistical analysis (e.g., principal component analysis (PCA)) were found capable of detecting spectral differences of Bacillus cereus in the presence of metal ions (Au3+, Ag+, Cu2+ and Zn2+) with different concentrations. An interesting phenomenon has been found that except for Au3+ ions, the highest permissive concentration of other metal ions for the detected Bacillus cereus is up to 10 μg/mL possibly due to their resistance to Au. The results also indicate that an effective biogeochemical exploration technique of SERS spectral response may be developed, where Bacillus cereus spore counts are measured in the field and used as a pre-screening method to target areas useful for further sampling and complete geochemical analysis.

Here, a completely new readout technique, so-called “Click” SERS, has been developed based on Raman scattered light splice derived from nanoparticle (NP) assemblies. The single and narrow (1–2 nm) emission originating from triple bond-containing reporters undergoes dynamic combinatorial output, by means of controllable splice of SERS-active NPs analogous to small molecule units in click chemistry. Entirely different to conventional “sole code related to sole target” readout protocol, the intuitional, predictable and uniquely identifiable “Click” SERS is relies on the number rather than the intensity of combinatorial emissions. By this technique, 10-plex synchronous biomarkers detection under a single scan, and accurate cellular imaging under double exposure have been achieved. “Click” SERS demonstrated multiple single band Raman scattering could be an authentic optical analysis method in biomedicine.

Methane-oxidizing bacteria (MOB), a unique group of Gram-negative bacteria utilizing methane as a sole source of carbon and energy, have been proved to be a biological indicator for gas prospecting. Field and cultivation-free detection of MOB is important but still challenging in current microbial prospecting of oil and gas (MPOG) system. Herein, SERS was used for the first time to our knowledge to investigate two species of methanotrophs and four closely relevant bacteria that universally coexisted in the upper soil of natural gas. A special but very simple approach was utilized to make silver nanoparticles (Ag NPs) sufficiently contact with every single bacterial cell, and highly strong and distinct Raman signals free from any native fluorescence have been obtained, and successfully utilized for distinguishing MOB from other species. A more convincing multi-Raman criterion based on single Raman bands, and further the entire Raman spectrum in combination with statistical analysis (e.g., principal component analysis (PCA)), which were found capable of classifying MOB related bacterial cells in soil with an accuracy of 100%. This study therefore demonstrated sensitive and rapid SERS measurement technique accompanied by complete Raman database of various gas reservoirs related bacteria could aid field exploration of natural gas reservoir.

We report the first microsampling device for reliably quantitative, label-free and separation-free detection of multicomponents of surface organic residues (SORs) by means of a quality controllable surface-enhanced Raman scattering (SERS)-enabled micropipette. The micropipette is comprised of a drawn glass capillary with a tiny orifice (∼50 μm) at the distal tip, where the specially designed nanorattles (NRs) are compactly coated on the inner wall surface. SERS signals of 4-mercapto benzoic acid (MBA) anchored inside the internal gap of NRs could be used to evaluate and control the quality of micropipettes and, therefore, allow us to overcome the limitations of a reliably quantitative SERS assay using traditional substrates without an internal standard. By dropping a trace extraction agent on targeting SORs located on a narrow surface, the capillary and SERS functionalities of these micropipettes allow on-site microsampling via capillary action and subsequent multiplex distinction/detection due to their molecularly narrow Raman peaks. For example, 8 nM thiram (TMTD), 8 nM malachite green (MG), and 1.5 μM (400 ppb) methyl parathion (MPT) on pepper and cucumber peels have been simultaneously detected in a wide detection range. The portable SERS-enabled device could potentially be facilely incorporated with liquid-liquid or solid phase micro-extracting devices for a broader range of applications in rapid and field analysis of food/public/environment security related SORs.

Herein, we presented a novel logic gate based on an INHIBITION gate that performs parallel readouts. Logic gates performing INHIBITION and YES/OR were constructed using surface-enhanced Raman scattering as optical outputs for the first time. The strategy allowed for simultaneous reading of outputs in one tube. The applicability of this strategy has been successfully exemplified in the construction of half-adder using the two-output logic gates as reporting gates. This reporting strategy provides additional design flexibility for dynamic DNA devices.

In this work, we suggest a chitosan-modified popcorn-like Au–Ag nanoparticles (CSPNPs) based assay for high sensitive detection of melamine, in which CSPNPs not only provide with an intrinsic peroxidase-like activity but also act as surface enhanced Raman scattering (SERS) substrates. CSPNPs can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H 2 O 2 to the charge transfer complex (CTC), which contributes to a tremendous surface-enhanced resonant Raman scattering (SERRS) signals with 632.8 nm laser excitation. The target molecule melamine can generate an additional compound with H 2 O 2 , which means the available amount of H 2 O 2 for the oxidation of TMB reduced. Correspondingly, the SERRS intensity of CTC is decreased. The decreased Raman intensity is proportional to the concentration of melamine over a wide range from 10 nM to 50 μM ( R 2 =0.989), with a limit of detection (LOD) of 8.51 nM. Moreover, the proposed highly selective method is fully capable of rapid, separation-free detection of melamine in milk powder.

Field, reliable and ultrasensitive detection of dipicolinic acid (DPA), a general biomarker of bacterial spores and especially Bacillus anthracis, is highly desirable but still challenging in current biometric security emergency response system. Herein we report an environmentally safe mercury (II) ions-mediated and competitive coordination interaction based approach for rationally designed surface-enhanced Raman scattering (SERS)-active gold nanoparticles (AuNPs), enabling rapid, ultrasensitive and zero-background detection of DPA without the pretreatment of samples. By means of competitiveness, these papain capped gold nanoparticles (P-AuNPs) are induced to undergo controllable aggregation upon the addition of Hg2+ ions and DPA with a concentration range (1 nM~8 μM), which correspondingly cause quantitative changes of SERS intensity of cresyl violet acetate (CVa) conjugated AuNPs. The decreased Raman intensity obtained by subtracting two cases of additives that contain only Hg2+ and the mixture of Hg2+ ...

The first appeal of clinical assay is always accurate and rapid. For alkaline phosphatase (ALP) monitoring in medical treatment, a rapid, reliable surface-enhanced Raman scattering (SERS) test kit is designed based on a “hot spots” amplification strategy. Consisting of alkyne-tagged Au nanoparticles (NPs), Ag+, and enzyme substrate, the packaged test kit can achieve one-step clinical assay of ALP in human serum within several minutes, while the operation is simple as it directly inputs the sample into the test kit. Here, Ag+ ions are adsorbed onto the surface of Au core due to electrostatic interaction between Ag+ and the negatively charged donor surface, then enzymatic biocatalysis of ALP triggers the reduction of Ag+ and subsequently silver growth occurs on every Au core surface in a controllable manner, forming “hot spots” between the Au core and Ag shell, in which the SERS signal of alkyne Raman reporters would be highly amplified. Meanwhile, ALP mediates a redox reaction of Ag+ as well as the dynamic...

Both accurate tumor navigation and nanostructures with high photothermal (PT) conversion efficiency are important but remain challenging to achieve in current biomedical applications. This study reports an anion exchange-based facile and green approach for synthesizing Au@Cu2- x S core-shell nanoparticles (NPs) in an aqueous system. In addition to the PT effect of the suggested NPs, the surface-enhanced Raman scattering (SERS) is also significantly improved due to the tailored localized surface plasmon resonance coupling between the Au metal core and the Cu2- x S semiconductor shell. Using an epitaxial strategy, Au@Cu2 O NPs are first obtained by the in situ reduction of cupric hydroxide on a cresyl violet acetate-coated Au core; then, Au@Cu2- x S NPs are obtained via anion exchange between the S2- and Cu2 O shell. Both the Cu/S atomic ratio and the Cu2- x S shell thickness can be adjusted conveniently. Hence, the ideal integration of the plasmonic Au core and Cu2- x S shell into a single unit is conducive not only to highly efficient PT conversion but also to the construction of a SERS-based navigator. This new type of SERS-guided NP, with enhanced photoacoustic signals, is an important candidate for both accurate tumor navigation and nondestructive PT treatment guided in vivo by two modes of optical imaging.

Herein we describe a novel ‘‘turn-off’’ biosensing strategy for thrombin detection based on Surface Enhanced Raman scattering (SERS) and the mediation of spacing between 4-mercaptobenzoic acid (4-MBA) labeled gold nanoparticles (AuNPs). The multiple arginine peptides that initiated gold nanoaggregates incorporating Raman reporter molecules due to the formation of ‘‘Hot Spots’’, are induced to disband by the addition of thrombin in which the peptides are catalytically cleaved into fragments and thus SERS signals of 4-MBA are sharply declined because of the weakened ability of fragments to induce aggregation. Through this strategy, a novel ‘‘turn-off’’ SERS biosensor for thrombin based on enzymatic amplification is established with sensitivity, selectivity and simplicity as AuNPs and peptides are easily accessible. Compared with non-enzymatic amplification based methods, this newly proposed method has improved sensitivity. The limit of detection was 160 fM (at the ratio of signal to noise, S/N ¼ 3:1). Further, controlled experiments showed that the method exhibited good selectivity over other proteases. The method demonstrated the capability and the potential for application in complex matrix and future biomarker development. The results also presented the potential and superiority of SERS biosensor based on signal amplification.

The present work reports a novel painting system for mild steels using electrodeposited silica (E-SiO 2 ) film as the pretreatment layer. The electrodeposition is based on basic catalysis of sol–gel processes (hydrolysis and condensation reactions) of tetraethoxysilane by applying a negative potential. The highly porous E-SiO 2 layer obtained ensures good adhesion to the topcoat. The painting system constructed on E-SiO 2 pretreatment layer is superior in its corrosion performance to traditional phosphating process. It is believed that such environmentally friendly and low-cost pretreatment layer can be used to fabricate highly corrosion resistant painting system for a variety of structural metal substrates.

A novel method using feature selection is proposed to classify Alzheimer's disease using Raman spectra. The method first find all the significant peak from the preprocessed spectrum as the feature candidates for classification. We select the most discrimination peak as a reference feature and compute the correlation coefficients between the reference and every peaks chosen. Then we discard highly correlated features to reduce the number of possible feature candidates. With the peak value and their ratio of the remaining features, we carry out the preliminary classification experiments and examine top 10% cases to seek the most frequently appearing features. Among them, we choose top 2 features, intensity of 1658 cm − 1 and ratio of intensity of 757 and 743 cm − 1 . These features correspond to protein bands of Amide I mode and cytochrome c, which are also considered important for the detection of Alzheimer's disease by other researchers. The classification result using 278 spectra achieved 95.8% classification rates for MLP (multi-layer perceptron) with these two features. It confirms that the features chosen with the proposed method could be effectively used for the diagnosis of Alzheimer's disease.

Field and pretreatment-free detection of heavy-metal ions in organic polluted water is important but still challenging in current water pollution emergency response systems. Here we report a polyadenine–DNA-mediated approach for a rationally designed alkyne-coded surface-enhanced Raman scattering (SERS) test kit, enabling rapid and simultaneous detection of Hg2+ and Ag+ by a portable spectrometer, impervious to organic interferences. Because of the formation of thymine (T)–Hg2+–T and cytosine (C)–Ag+–C, highly recognizable SERS signals are rapidly detected when two different alkyne-labeled gold nanoparticles (AuNPs) are induced to undergo controllable bridging upon the addition of low-volume targets. For multiplex detection through a portable spectrometer, the limits of detection reach 0.77 and 0.86 nM for Hg2+ and Ag+, respectively. Of particular significance, the proposed C≡C-containing Raman reporters provide an extremely effective solution for multiplex sensing in a spectral silent region, when the hy...

We report on a continuous and non-invasive approach in vivo to monitor arterial blood pH based on the laser trapping and Raman detection of single live erythrocytes. A home-built confocal laser tweezers Raman system (LTRS) is applied to trace the live erythrocytes at different pH values of the extracellular environment to record their corresponding Raman changes in vitro and in vivo. The analysis results in vitro show that when the extracellular environment pH changes from 6.5 to 9.0, the Raman intensity ratio (R1603, 1616 = I1603/I1616) of single erythrocytes decrease regularly; what is more, there is a good linear relationship between these two variables, and the linearity is 0.985, which is also verified successfully via in vivo Raman measurements. These results demonstrate that the Raman signal of single live erythrocytes is possible as a marker of the extracellular pH value. This in vivo and quantitative Raman-pH sensor of arterial blood will be an important candidate for monitoring the acid-base status during the treatment of ill patients and in some major surgeries because of its continuous and non-invasive characters.

In combination with morphological evaluation tests, we employ Raman spectroscopy to select higher potential reproductive embryos during in vitro fertilization (IVF) based on chemical composition of embryos culture medium. In this study, 57 Raman spectra are acquired from both higher and lower quality embryos culture medium (ECM) from 10 patients which have been preliminarily confirmed by clinical assay. Data are fit by using a linear combination model of least squares method in which 12 basis spectra represent the chemical features of ECM. The final fitting coefficients provide insight into the chemical compositions of culture medium samples and are subsequently used as criterion to evaluate the quality of embryos. The relative fitting coefficients ratios of sodium pyruvate/albumin and phenylalanine/albumin seem act as key roles in the embryo screening, attaining 85.7% accuracy in comparison with clinical pregnancy. The good results demonstrate that Raman spectroscopy therefore is an important candidate for an accurate and noninvasive screening of higher quality embryos, which potentially decrease the time-consuming clinical trials during IVF.

In the present study, silica nanoparticles with resonance Raman scattering (RRS) properties were utilized to construct a novel resonance Raman scattering tag for in vivo cellular imaging. β-Carotene, a native pigment insoluble in water, was for the first time encapsulated in silica nanoparticles through a simple one-step procedure in which β-carotene was enriched in the micelle of cetyltrimethylammonium bromide (CTAB) and simultaneously enclosed during the hydrolysis of tetraethylorthosilicate (TEOS). The particles were characterized by using X-ray diffraction, transmission electron microscopy (TEM), and Raman spectroscopy. Results showed that the size distribution of β-carotene doped silica nanoparticles (CSNPs), which were highly dispersible in aqueous solution, was fairly uniform in the range of 60 to 200 nm. Due to the advantages of highly stable and repeatable RRS signals of doped β-carotene, a simple cellular imaging approach based on this novel Raman tag has been preliminarily achieved. This paper demonstrated that resonance Raman scattering tags are important candidates for biological applications considering their high biocompatibility and spectral stability.

Early diagnosis is the key of the improved survival rates of oral cancer. Raman spectroscopy is sensitive to the early changes of molecular composition and structure that occur in benign lesion during carcinogenesis. In this study, in situ Raman analysis provided distinct spectra that can be used to discriminate between normal and malignant tissues, as well as normal and cancer cells. The biochemical variations between different groups were analyzed by the characteristic bands by comparing the normalized mean spectra. Spectral profiles of normal, malignant conditions show pronounced differences between one another, and multiple Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discrimination power for cancer sample identification. Statistical analyses of the Raman data and classification using principal component analysis (PCA) are shown to be effective for the Raman spectral diagnosis of oral mucosal diseases. The results indicate that the biomolecular differences between normal and malignant conditions are more obviously at the cellular level. This technique could provide a research foundation for the Raman spectral diagnosis of oral mucosal diseases.

In this work, four-second order nonlinear optical (NLO) azobenzene-containing materials are studied in-depth by using vibrational spectra and density functional theory (DFT). The Fourier transform infrared (FT-IR) spectra and FT-Raman spectra are recorded in the range of 50–4000 and 100–3600 cm−1, respectively. Meanwhile, the DFT computations are performed at B3LYP/6-31G (d, p) level to derive equilibrium geometry, vibrational wavenumbers and intensities, and first hyperpolarizability, and the scaled theoretical wavenumbers are also shown to be in good agreement with experimental data. The calculated results show that these four azobenzene-containing compounds are good materials and the compound with nitro substituent groups possesses a larger first molecular hyperpolarizability (β) value. Moreover, the simultaneous infrared and Raman activation of R1 group and C C stretching suggest that the charge transfer interaction might occur between the R1 group and phenyl ring, and the HOMO–LUMO gap analysis also supports this viewpoint.

Biological rhythms, which regulate the biological cycles of life, are of great interest in biomedicine. The effect of biological rhythms on bone is controversial at the moment. Raman spectroscopy was applied to assess the bone compositional information of hamsters under different photoperiods, designed as long day photoperiod of 16 h light and 8 h dark (LD, 16L : 8D) and short day photoperiod of 8 h light and 16 h dark (SD, 8L : 16D). After three months under such well-defined conditions, the hamsters in the two groups exhibited differences in body weight, fur color and testis size. In addition, for the first time to our knowledge bone compositional variations were observed in both mineral constituents and collagen secondary structures in hamsters conditioned under the different photoperiods. The collagen secondary structure in the SD hamsters was characterized by a higher ratio of mature intra-fibril cross-links indicating a more stable form of collagen. It is hypothesized that increased bone turnover rate and resorption led to the alteration of collagen cross-links in the SD group.

In surface-enhanced Raman scattering (SERS), the scattered intensity is drastically increased due to a resonant interaction with surface plasmons of coin metals. SERS is a nondestructive spectroscopic method applied also to biomedical samples. It inherits the advantages of normal Raman spectroscopy and at the same time overcomes the inherent low sensitivity problem. These properties endow SERS with exciting opportunities to be a successful analytical tool for cell analysis. SERS can be used to detect only molecules located on or close to the metallic nanostructures which can support surface plasmon resonances for the enhancement of the Raman signals. Therefore, these metallic nanostructures play a key role in the application of SERS in cell analysis. By incorporating the SERS substrates into the biosamples, molecular structural probing and cellular imaging become possible. In the past decade, analysts worldwide have developed many schemes to study the chemical changes and component distribution in cells by using SERS. In this paper, the application of SERS in cell analysis is reviewed. Copyright © 2011 John Wiley & Sons, Ltd.

This paper presents, for the first time, noninvasive imaging of a livingplant using biocompatible carbon-encapsulated AuAg nanoparticles (NPs) using micro-Raman spectroscopy (MRS). A convenient and controllable hydrothermal synthetic route was developed to synthesize the layer-by-layer triplex AuAgC core–shell NPs, which can incorporate the reporter molecule 4-mercapto benzoic acid (4-MBA). A unique approach was devised to deliver the carbon-encapsulated surface-enhanced Raman scattering (SERS) tags into the leaf of Nicotiana benthamiana. In vivo SERS mapping was subsequently performed to monitor the distribution of tags inside the leaf, which successfully avoided interference of autofluorescence from plant tissue. The imaging modality reported here and further the bio-functionalized carbon-encapsulated SERS NPshold significant potential as a strategy forbiochemical imaging in living plantsin a noninvasive and nontoxic manner, whichmight open up exciting opportunities for plant sciences. Copyright © 2010 John Wiley & Sons, Ltd.

In this study, β-carotene, a resonance Raman active substance, was introduced into the large pore channel of rod-like SBA-15 for the first time. This novel resonance Raman active material has been characterized by small angle X-ray scattering (SAXS) and Brunauer–Emmett–Teller (BET) surface area analysis. The adsorption process did not show any influence on the microstructure of SBA-15 as well as its physicochemical characters. Excited by 514.5 nm laser, the resonance Raman signals of the products were demonstrated as well-defined Raman peaks at 1009, 1158 and 1514 cm −1 , which should be assigned to the methyl rock (C–CH 3 ), carbon single-bond stretch (C–C) and carbon double-bond stretch (C C) normal modes, respectively. In addition, the internal standard method was utilized by resonance Raman spectroscopy to determine the adsorption capacity of mesoporous silicas for β-carotene using the results of UV–vis spectroscopy as a reference.

Monodispersed, readily-grafted, and biocompatible surface-enhanced Raman spectroscopic (SERS) tagging materials are developed; they are composed of bimetallic Au@Ag nanoparticles (NPs) for optical enhancement, a reporter molecule for spectroscopic signature, and a carbon shell for protection and bioconjugation. A controllable and convenient hydrothermal synthetic route is presented to synthesize the layer-by-layer triplex Au―Ag―C core―shell N Ps, which can incorporate the Raman-active label 4-mercapto benzoic acid (4-MBA). The obtained gold seed―silver coated particles can be coated further with a thickness-controlled carbon shell to form colloidal carbon-encapsulated Au core/ Ag shell spheres with a monodisperse size distribution. Furthermore, these SERS-active spheres demonstrated interesting properties as a novel Raman tag for quantitative immunoassays. The results suggest such SERS tags can be used for multiplex and ultrasensitive detection of biomolecules as well as nontoxic, in vivo molecular imaging of animal or plant tissues.

In this paper, we consider a new background elimination method for Raman spectra. The proposed method is based on peak detection, smoothing, and interpolation. Since the background is usually slowly varying with respect to wavelength, we could estimate the background by eliminating significant peaks. For this purpose, we seek the peaks by inspecting the smoothed derivative of a given spectrum. After clipping out the corresponding peak regions, we estimate the background by applying a modified linear interpolation. Then the background is eliminated from the measured Raman spectrum by simple subtraction. The experimental results showed that the proposed method gave satisfactory results for real Raman spectra as well as synthetic data. As the proposed method requires no prior knowledge of spectrum, we expect that the method could be applied to other spectral data as well.

Micro-Raman spectroscopy (MRS) was utilized for the first time to evaluate the effect of indole-3-carbinol (I3C) on acute alcoholic liver injury in vivo. In situ Raman analysis of tissue sections provided distinct spectra that can be used to distinguish alcoholic liver injury as well as ethanol-induced liver fibrosis from the normal state. Sixteen mice with liver diseases including acute liver injury and chronic liver fibrosis, and eight mice with normal liver tissues, and eight remedial mice were studied employing the Raman spectroscopic technique in conjunction with biomedical assays. The biochemical changes in mouse liver tissue when liver injury/fibrosis occurs such as the loss of reduced glutathione (GSH), and the increase of collagen (α-helix protein) were observed by MRS. The intensity ratio of two Raman peaks (I1450/I666) and in combination with statistical analysis of the entire Raman spectrum was found capable of classifying liver tissues with different pathological features. Raman spectroscopy therefore is an important candidate for a nondestructive in vivo screening of the effect of drug treatment on liver disease, which potentially decreases the time-consuming clinical trials. Copyright © 2008 John Wiley & Sons, Ltd.

Five triphenyl phosphonium salts including N -phenylacetamidyl triphenyl phosphonium chloride ( 1 ), N -phenylpropanamidyl triphenyl phosphonium chloride ( 2 ), ethyl 2-methylacetatyl triphenyl phosphonium chloride ( 3 ), ethyl butyryl triphenyl phosphonium chloride ( 4 ) and hexadecyl triphenyl phosphonium bromide ( 5 ) were synthesized and then were characterized by FT-Raman spectroscopy. Surface-enhanced Raman spectroscopy (SERS) in conjunction with electronic absorption spectroscopy was employed to study their interaction with DNA. The decreasing of Raman intensity at 1000, 1029, 1103 and 1588 cm −1 from compound 5 indicated that this compound has affinity for DNA. This was probably because compound 5 inserted into DNA and a new conjugated system was formed. The results of electronic absorption spectra were coincident with those of SERS. On the other hand, compound 5 showed a significant higher inhibitory rate on human cervix cancer cells. The targets of the compounds in the anti-cancer process were discussed. The mechanism of the anti-cancer process of compound 5 might be related to its interaction with DNA.

Bis(pyrrol-2-ylmethyleneamine) ligands and their mononuclear monomeric and dinuclear dimeric self-assembly complexes with Cu(II) were investigated by means of IR and Raman spectroscopies and density functional theory. The ground-state geometries were calculated by using the BeckeLeeYangParr composite exchange-correlation functional (B3LYP) and a combined basis set (LanL2DZ for Cu; 6–31G(d) for C, H, N), and they were compared with the single-crystal X-ray diffraction (XRD) structures. The DFT-calculated CuN bond lengths are generally higher by 0.001–0.040 A than those determined through XRD. The vibrational spectra were also calculated at the same level of theory for the optimized geometries. The calculated wavenumbers were scaled by a uniform scaling factor and compared with the experimental fundamentals. The predicted spectra are in good agreement with the experimental ones with the deviations generally less than 30 cm−1. In comparison with the spectra of the ligands, the coordination effect shifts the υ(CN) wavenumber by about 50 cm−1 toward a lower value. Because of the weak intermolecular CH···Cu hydrogen bond, the CuN stretching mode is shifted toward a lower wavenumber. Copyright © 2006 John Wiley & Sons, Ltd.

A new hybrid algorithm is proposed to eliminate the varying background of spectral signals. The method is based on the use of multiresolution, which is one of the main advantages provided by wavelet transform. Compared with the analyte signal, the background has a low frequency. The new method firstly split the signals into different frequency components, and then removes the varying low-frequency background. The method is successfully applied to simulated spectral data set and experimental Raman spectral data. The results showed that the wavelet transform technique could handle all kinds of background and low signal-to-background ratio spectra, and required no prior knowledge about the sample composition, no selection of suitable background correction points, and no mathematical assumption of the background distribution. The proposed procedure was illustrated, by processing real spectra, to be an effective and practical tool for background elimination in Raman spectra. In addition, the proposed strategy can be applied to other spectral signals as well.

Four ancient colored drawings (CDs), namely in black, blue, white and green, of Wuying Hall in the Imperial Palace, China, were analyzed by micro-Raman spectroscopy (MRS) in combination with energy dispersive X-ray spectroscopy (EDX) in order to identify the pigments in each case. The pigments lampblack (a pigment based on amorphous carbon), ultramarine blue/lapis lazuli (Na8[Al6Si6O24]Sn), dolomite (CaMg(CO3)2), emerald green (Cu(C2H3O2)2·3Cu(AsO2)2), gypsum (CaSO4·2H2O) were detected in the CDs, and these will be useful with regard to the restoration of the paintings at Wuying Hall. Furthermore, it is important to take into account the dating of some rare pigments, i.e., ultramarine blue and emerald green, in order to validate that there was a fire that destroyed more than 30 houses of Wuying Hall in 1869 (Tong-Zhi, 8th year of Qing Dynasty). The results demonstrate that micro-Raman spectroscopy can provide valuable information for the characterization, restoration and preservation of the cultural relic. Copyright © 2006 John Wiley & Sons, Ltd.

The Ni(II) complex with bis(2,4-dimethyldipyrrin-3-yl)methane, (NiL)2, has been synthesized and characterized by 1H-NMR, UV–Vis, FT-IR, FT-Raman, MS, and elemental analysis. X-ray diffraction analysis at room temperature indicates that the complex crystallizes in triclinic system, space group P−1 with a = 11.344(4), b = 12.703(4), c = 14.936(5) A, α = 87.017(6)°, β = 75.379(5)°, γ = 75.318(5)°, M r = 826.31, V = 2014.5(11) A3, Z = 2. The crystal structure of the title complex reveals that it is a dinuclear double-stranded helical entity. The ligands perform as tetradentate ligands and the ratio of Ni(II) to ligand is 2:2. The central Ni(II) atom is tetracoordinated by four nitrogen donors of two ligands and the coordination geometry of Ni(II) can be considered as a distorted tetrahedron configuration. The IR and Raman spectral analysis, assignment, and discussion are presented.

The ground-state geometries and electronic structures of 2-nitrotetraphenylporphyrin (H 2 -2-NO 2 -TPP) and zinc 2-nitrotetraphenylporphyrin (Zn-2-NO 2 -TPP) with C s and C 1 symmetry have been determined from density functional theory, using the Becke-Lee-Yang-Parr composite exchange-correlation functional (B3-LYP) and ab initio RHF method and 6-31G(d) basis set. The optimized geometries are then compared with the crystallographic data of related compounds. The energy and electronic structures of different conformers are analyzed and compared with each other. The conformers with C 1 symmetry are found to be more stable than that of C s symmetry. The relative order of the highest occupied a 2 u and a 1 u orbitals determined by B3LYP (a 2 u > a 1 u ) is reversed by RHF (a 1 u > a 2 u ). The vibrational wavenumber, IR, and Raman intensities are also calculated at B3LYP/6-31G(d) optimized geometries. The calculated wavenumbers are scaled by a uniform scaling factor and compared with the experimental one. Most of the scaled modes are found to be in good agreement with the observed fundamentals. A single β-NO 2 substitution slightly changes the geometries, the vibrational wavenumbers, and the frontier orbitals energy level.

The effect of acetonitrile (ACN) on the low-affinity interaction between human serum albumin (HSA) and ibuprofen (IBP) was studied using H-1-NMR techniques. Both chemical shift and relaxation measurements showed the addition of ACN to the solutions decreased the binding affinity of IBP to HSA and reduced the hydrophobic interaction between them. The self-diffusion coefficients of IBP were measured as a function of the drug concentration at different ACN concentrations. The association constant, K-a, for ligand-HSA complexes and the number of binding sites, n, are evaluated by the application of Langmuir isotherm. The results indicated that the value of n was about 38 without ACN, and about 26 with ACN concentration 12% (v/v%). The decreased binding capacity of IBP to HSA in the presence of ACN was mainly attributed to the competition of ACN with IBP to the low-affinity binding sites of HSA molecule. (C) 2002 Elsevier Science B.V. All rights reserved.

The low-affinity interaction between human serum albumin (HSA) and Diclofenac sodium (DCF) was studied using NMR techniques. Both 13C-NMR chemical shift and linewidth show that the dichlorophenyl ring in DCF molecule plays a primary role in its interaction with HSA. Langmuir adsorption isotherm was applied to evaluate the association constant K and the number of binding sites n of the drug/HSA complex through (1)H-NMR spin-lattice relaxation measurement. The results indicate that Langmuir isotherm can perfectly explain the capacity of low-affinity binding of proteins for the ligands.

Two kinds of enamels, including Chinese cloisonne wares from Fuwang chamber and gourd-shaped painted enamels decorations from the Forbidden City, in the Imperial Palace of China, are investigated by micro-Raman spectroscopy in combination with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy-dispersive X-ray fluorescence (EDXRF) in order to examine and analyze the composition of the glaze layer in each case. In this study the excitation is employed with either a NIR laser (785 nm) or a red laser (632.8 nm) in order to effectively eliminate the interference of background fluorescence and resonance effect. We have identified that the major matrix ingredients of the cloisonne wares are lead-based potash-lime silicate glasses while lead-potash silicate glass matrix is the main constituent for the painted enamels. Eight different colored areas of glaze layer also have been discussed in detail due to the distinct colors including turquoise, deep blue, yellow, white, red, pink, deep green and pale green. Their identification based on Raman data will be useful with regard to rapid and on site analysis and the restoration of the enamel decorations.

We describe herein a novel' "turn-on" SERS-based strategy for protease detection based on surface enhanced Raman scattering (SERS) and the mediation of spacing between 4-mercaptobenzoic acid (4-MBA) labeled gold nanoparticles (AuNPs) through enzyme assays. The method employed non-cross-linking aggregation of 4-MBA-modified AuNPs by peptides after treatment with target protease. Thus, SERS signals of 4-MBA are sharply increased because of the decreased electrostatic stability of AuNPs that initiated gold nanoaggregates incorporating Raman reporter molecules due to the formation of "Hot Spots". Through this strategy, a novel and facile "turn-on" SERS biosensor for trypsin and thrombin based on enzymatic cleavage activity is established with sensitivity, selectivity and simplicity as AuNPs and peptides are easily accessible. Compared with other methods, this newly proposed method has improved sensitivity. The limit of detection was 85fM (at the ratio of signal to noise, S/N=3:1) for trypsin. Controlled experiments showed that the method exhibited good selectivity over other proteases. We also proved that this principle could be easily adapted to detection of other proteases such as thrombin. The method demonstrated the capability for application in complex matrix samples. The results also presented the potential and superiority of SERS biosensor as a general approach for proteases based on enzyme activity.