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Block copolymer brush layer-templated gold nanoparticles on nanofibers for surface-enhanced Raman scattering optophysiology
摘要： A nanothin block copolymer (BCP) brush-layer film adsorbed on glass nanofibers is shown to address the long-standing challenge of forming a template for the deposition of dense and well dispersed nanoparticles on highly curved surfaces, allowing the development of an improved nanosensor for neurotransmitters. We employed a polystyrene-block-poly(4-vinylpyridine) BCP and plasmonic gold nanoparticles (AuNPs) of 52 nm in diameter for the fabrication of the nanosensor on pulled fibers with diameters down to 200 nm. The method is simple, using only solution processes and a plasma cleaning step. The templating of the AuNPs on the nanofiber surprisingly gave rise to more than one order of magnitude improvement in the surface-enhanced Raman scattering (SERS) performance for 4-mercaptobenzoic acid compared to the same AuNPs aggregated on identical fibers without the use of a template. We hypothesize that a wavelength-scale lens formed by the nanofiber contributes to enhancing the SERS performance, to the extent that it can melt the glass nanofiber under moderate laser power. We then show the capability of this nanosensor to detect the co-release of the neurotransmitters dopamine and glutamate from living mouse brain dopaminergic neurons with a sensitivity one order of magnitude greater than with aggregated AuNPs. The simplicity of fabrication and the far superior performance of the BCP-templated nanofiber demonstrates the potential of this method to efficiently pattern nanoparticles on highly curved surfaces and its application as molecular nanosensors for cell physiology.
关键词： block copolymer brush,neurosciences,SERS optophysiology,nanofiber,neurotransmitters
更新于2025-09-23 15:23:52
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Au@Cu Nanoarrays with Uniform Long-Range Ordered Structure: Synthesis and SERS Applications
摘要： The nanostructures with uniform long-range ordered structure are of crucial importance for performance standardization of high-quality surface-enhanced Raman scattering (SERS) spectra. In this paper, we described the fabrication and SERS properties of Au decorated Cu (Au@Cu) nanoarrays. The Cu nanoarrays with uniform long-range ordered structure were first synthesized by in-situ electrochemistry assembly on insulated substrate. The Cu nanoarrays can reach a size of centimeters with strictly periodic nano-microstructure, which is beneficial for the production and performance standardization of SERS substrates. Then Au nanoparticals were decorated on the Cu nanoarrays by galvanic reaction without any capping agent. The obtained Au@Cu nanoarrays exhibit excellent SERS activity for 4-Mercaptopyridine, and the sensitivity limit is as low as 10?8 M. Therefore, this facile route provides a useful platform for the fabrication of SERS substrates based on nano ordered arrays.
关键词： Au nanoparticles,Cu nanoarrays,surface decoration,surface-enhanced Raman scattering (SERS)
更新于2025-09-23 15:23:52
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Silver nanoparticles with reduced graphene oxide for surface-enhanced vibrational spectroscopy of DNA constituents
摘要： Composite of silver nanoparticles with reduced graphene oxide flakes is proposed for surface enhanced vibrational spectroscopy, particularly for detection of adenine and thymine as constituents of deoxyribonucleic acid. Composite was formed by original method implying simultaneous reduction of silver ions and graphene oxide by discharge plasma at the gas–liquid interface. Combination of nanosized silver with reduced graphene oxide provided greater enhancement of Raman light scattering and infrared light absorption in comparison with separately used components. Addition of the composite to water solutions of adenine and thymine allowed detection of these analytes at micromolar concentrations. Composite of nano-silver with reduced graphene oxide can be prospective for surface enhanced spectroscopy as an alternative to the expensive lithographically prepared noble metal substrates.
关键词： Adenine,Surface Enhanced InfraRed Absorption (SEIRA),Thymine,Reduced graphene oxide,Discharge plasma,Silver nanoparticles,Surface Enhanced Raman Scattering (SERS)
更新于2025-09-23 15:23:52
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Surface-enhanced Raman scattering (SERS) imaging of bioactive metabolites in mixed bacterial populations
摘要： Bacteria frequently live in mixed multispecies communities, shaped by the action of bioactive metabolites that are secreted by the residing microbial species. The identification and tracking of such chemical exchange processes is fundamental toward understanding how these particular extracellular molecules modulate microbial communities and functions. In this context, most chemical imaging approaches so far have focused on the analysis of metabolic interactions occurring between microbial populations co-cultured separately. We demonstrate here the application of surface-enhanced Raman scattering (SERS) spectroscopy as a valuable imaging tool for the non-invasive detection and visualization of metabolites secreted by Escherichia coli and Pseudomonas aeruginosa bacteria, cultured as mixed populations and thereby mimicking the complexity of natural microbial communities. SERS enabled the simultaneous detection and in situ visualization of indole and pyocyanin, revealing the down-regulation of pyocyanin expression due to indole signaling. The successful detection of chemical interactions in mixed bacterial populations shows the potential of SERS for the investigation of the chemistry underpinning multispecies microbial communities.
关键词： Quorum sensing,Plasmonics,Indole,SERS imaging,Pyocyanin
更新于2025-09-23 15:23:52
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Determination of 17β-estradiol by surface-enhanced Raman spectroscopy merged with hybridization chain reaction amplification on Au@Ag core-shell nanoparticles
摘要： The authors describe an aptamer-based assay for 17β-estradiol. It relies on the combined use of surface enhanced Raman scattering (SERS) and hybridization chain reaction (HCR). The aptamer against 17β-estradiol is applied as the recognition probes, and this results in excellent specificity. Specific recognition of target 17β-estradiol induce the freedom of DNA 2, which will open the stem-loop structure of probe 1 on the Au@Ag and form the partial dsDNA structure. With the nicking enzyme, the partial dsDNA will be hydrolyzed and the reside ssDNA on Au@Ag will form a small stem-loop structure. With the help of the other probe 2 modified Au@Ag and pre-immobilized probe 3 on the well of the microplate, an enzyme-free HCR can occur and tremendous Au@Ag can be assembled along the formed dsDNA in HCR, which can act as the excellent substrate for Raman measurement and greatly amplify the Raman signal of R6G on the Au@Ag. Afterwards, the key factor, ratio between probe 2-Au@Ag (P2) and probe1-Au@Ag (P1), affects the detection sensitivity is systematically optimized for the best sensing performance. The SERS signal of R6G, best measured at 1651 cm?1, increases linearly in the wide range from 1 pM to 10 nM. The detection limit can be as low as 0.1 pM.
关键词： Estrogen,Hybridization chain reaction,SERS,Food safety,Aptamer,Gold nanoparticle,Signal amplification,Environment monitoring
更新于2025-09-23 15:23:52
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Electronic Structure and Room Temperature Ferromagnetism in Gd-doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting
摘要： Enhanced visible light photocatalytic activity of Gd-doped CeO2 nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping. All-pure and Gd-doped CeO2 NPs are synthesized using a coprecipitation method and characterized using X-ray diffraction (XRD), absorption spectroscopy, surface-enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). The effect of Gd-doping on properties of CeO2 is discussed along with defects and oxygen vacancies generation. The XRD confirms the incorporation of Gd3+ at the Ce3+/Ce4+ site by keeping the crystal structure same. The average particle size from transmission electron microscopy (TEM) images is in the range of 5–7 nm. The XPS spectra of Ce 3d, O 1s, and Gd 4d exhibits the formation of oxygen vacancies to maintain the charge neutrality when Ce4+ changes to Ce3+. The gradual increase in hydrogen production is observed with increasing Gd concentration. The observed results are in good correlation with the characterization results and a mechanism of water splitting is proposed on the basis of analyses. The absorption spectra reveal optical band gap (2.5–2.7 eV) of samples, showing band gap narrowing leads to desired optical absorbance and photoactivity of NPs.
关键词： water splitting,hydrogen generation,SERS,XPS
更新于2025-09-23 15:23:52
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In situ synthesis of gold nanoparticles on pseudo-paper films as flexible SERS substrate for sensitive detection of surface organic residues
摘要： Surface enhanced Raman scattering (SERS) substrates that can be attached to rough, irregular surfaces and directly collect samples is especially useful for the detection of surface organic residues. Herein, novel AuNPs-pseudo-paper films (APPFs) with uniform structure, flexible properties and wicking capabilities were first fabricated and used as SERS substrate for the sensitive detection of surface pesticides residues. Gold nanoparticles (AuNPs) were in situ synthesized on pseudo-paper films (PPFs) by iterative seeding method to create lots of “hot-spots”, accordingly exhibiting high SERS activity (SERS enhancement factor of 3.02×106). By virtue of polyethylenimine (PEI) grafted onto the dissolved microcrystalline cellulose (MCC), AuCl4- and AuNPs can firmly be bonded to the surfaces of PPFs. The prepared APPFs show high reproducibility (relative standard deviation of 6.13 %), which is attributed to the uniform surface of the films. The fabricated APPFs SERS substrate allows rapid detection of surface pesticides residues by a facile “swabbing-measure” detection mode avoiding tedious and time-consuming sampling and separation processes. Based on their inherent SERS spectra, thiram, parathion methyl, and malachite green (MG) can be simultaneously detected on apple peel, which demonstrates the potential applicability of this developed protocol for surface organic residues analysis in agriculture and food security.
关键词： surface pesticides residues,pseudo-paper,in situ synthesis,SERS
更新于2025-09-23 15:23:52
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Porous SiO2-coated Au-Ag alloy nanoparticles for the alkyne-mediated ratiometric Raman imaging analysis of hydrogen peroxide in live cells
摘要： We prepared an ultrathin porous silica shell-coated Au-Ag alloy nanoparticle (AuAg@p-SiO2NP) and developed it as a novel alkyne-based surface-enhanced Raman scattering (SERS) nanoprobe for the ratiometric Raman imaging of exogenous and endogenous H2O2 in live cells. The AuAg@p-SiO2NPs functionalized with 4-mercaptophenylboronic acid (MPBA) and 4-mercaptophenylacetylene (MPAE, 1,986 cm-1) as internal standard were first incubated with dopamine (DA) to incorporate the bridging molecules through the formation of borate bond between DA and MPBA on the surface of nanoparticle. Then, the signaling alkyne molecules of 3-(4-(phenylethynyl) benzylthio) propanoic acid (PEB, 2,214 cm-1) were conjugated to the surface of nanoparticle through the formation of amide bond between the carboxyl group on the PEB and the amino group on the DA, forming the ratiometric SERS nanoprobe. In the presence of H2O2, the alkynyl on the PEB is released from the surface of the Au-Ag alloy nanoparticle due to the boronate-to-phenol switch, decreasing the Raman signal at 2,214 cm-1 significantly. Since the Raman signal of MPAE at 1,986 cm-1 remains unchanged, quantitative analysis of H2O2 concentration can be achieved based on the ratiometric value of I1986/I2214. Under the optimized conditions, the plot of the ratiometric value of I1986/I2214 versus the H2O2 concentration in the range from 0.12 to 8 m M revealed a good linear response with a detection limit of 52 nM based on a signal-to-noise ratio of S/N = 3. The porous SiO2-coated Au-Ag alloy nanoparticle provides a novel SERS substrate with excellent biocompatibility, high stability, and effective anti-interference ability. Together with the alkynyl derivatives as internal standard, the SERS nanoprobe reported here allows the ratiometric detection of H2O2 in live cells and can be further applied to quantify many other biomolecules by using different signaling agents.
关键词： porous SiO2-coated Au-Ag alloy nanoparticle,SERS,alkyne,cell imaging,hydrogen peroxide
更新于2025-09-23 15:23:52
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Silver Nanostructures on Graphene Oxide as the Substrate for Surface-Enhanced Raman Scattering (SERS)
摘要： Nanosized surface-enhanced Raman scattering (SERS) substrates fabricated by the controlled growth of metal nanostructures on water-dispersed two-dimensional nanomaterials can open a new avenue for SERS analysis of liquid samples in biological fields. In this work, regular and uniform Ag nanostructures were grown on the surface of graphene oxide (GO) through a microwave-assisted hydrothermal method. Polyamidoamine (PAMAM) dendrimers were assembled on the surface of GO to form GO/PAMAM templates for growing Ag nanostructures, which are primarily comprised of Ag dimers and trimers. The prepared Ag/GO nanocomposites are highly dispersed and stable in aqueous solution and may be used as substrates for enhanced Raman detection of rhodamine 6 G (R6G) in aqueous solution. This special substrate provides high-performance SERS and suppresses R6G fluorescence in aqueous solution and is promising as a nanosized material for the enhanced Raman detection of liquid samples in biological diagnostics.
关键词： graphene oxide (GO),Surface-enhanced Raman scattering (SERS),polyamidoamine (PAMAM) dendrimers,transmission electron microscopy (TEM),Fourier transform infrared (FTIR) spectroscopy,rhodamine 6G (R6G)
更新于2025-09-23 15:23:52
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PVP-assisted thermal annealing of thin Au layer for creation of effective and reproducible SERS substrates
摘要： Creation of SERS substrate with the large active area and homogeneous distribution of hot spots is now one of the most important tasks in the field of SERS practical implementation. This problem has been solved by various techniques, but the most applicable of them are expensive due to highly technical nature. In this work, a simple alternative approach based on thermal annealing of sputtered Au layer has been proposed. Usually, the thermal annealing of the thin Au layer leads to the formation of gold clusters array with high plasmon efficiency but with too wide size distribution and highly disordered arrangement. To overcome this drawback the previous soaking of Au layer in the poly(vinylpyrrolidone) (PVP) solution was proposed, with the aim to affect clusters formation and achieve the more homogeneous distribution of created hot spots array. Annealed Au and Au-PVP thin layers were characterized by AFM, XRD, XPS, UV–Vis and Raman spectroscopy techniques. Present results indicate that the PVP treatment before thermal treatment significantly affect the growth of the clusters and provide the perspective way for increasing of SERS efficiency and reproducibility.
关键词： Thin gold film,SERS,Annealing,Reproducibility
更新于2025-09-23 15:23:52