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Raman Tracking the Activity of Urease in Saliva for Healthcare
摘要： The detection of urease activity in the oral cavity is considered to be an efficient way to prevent dental caries and also to screen for helicobacter pylori infection. Herein, a rapid surface enhanced Raman scattering (SERS) method is proposed to determine the activity of urease by using inositol hexaphosphate (IP6) stabilized silver nanoparticles (AgNPs@IP6) as an efficient SERS-active substrate. The determination was achieved by monitoring the SERS peak intensity of urea at 1003 cm-1. With urease increase, the response of urea at 1003 cm-1 decreases gradually, indicating the two has good correlation. A linear relationship between the absolute value of signal drop and urease concentration is observed in a range from 2.35 to 37.5 μg/mL. In addition, the rapid SERS method was used to evaluate the activity of urease in real sample of saliva without any pretreatment, exhibiting a promising potential for biomedical application.
关键词： Urease activity,Surface-enhanced Raman scattering,Urea,Healthcare
更新于2025-09-19 17:15:36
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A simple approach for the ultrasensitive detection of paraquat residue in adzuki beans by surface-enhanced Raman scattering
摘要： Paraquat (PQ), a broad-spectrum contact herbicide, has been used in many countries for controlling weed growth in agriculture because of its quick-acting and nonselective contact with green plant tissue. PQ is also toxic to humans, and even contributes to the development of neurodegenerative diseases. However, PQ is generally excluded from pesticide residue monitoring programs due to the lack of suitable determination methods. Thus, this study developed a detection method combined with simple extraction and surface-enhanced Raman spectroscopy (SERS) to rapidly determine and quantify the PQ residue on legumes without destructive procedures and high-cost instruments. Following the extraction procedure of the QuPPe-method, however, we took whole adzuki beans (Vigna angularis) extracted via a mixture of methanol and 1% formic acid at room temperature and followed by a 1 min cleanup by SPE. The PQ values for adzuki beans determined by LC/MSMS showed that regardless of whether extraction was followed by the QuPPe-method or the method we proposed, a consistent and low relative standard deviation (RSD) below <22% was found. In this study, we proposed to extract PQ on the surface of the beans by shaking briefly with solvent, and then the PQ molecules were detected and quantified by depositing Ag nanoparticles (AgNPs) and performing SERS within 10 min. Using a coating of deposited Ag nanoparticles, SERS can achieve a limit of detection (LOD) for PQ on the order of 1 μg L?1 (～4 × 10?9 M) and a method detection limit (MDL) for adzuki beans of 0.8 μg kg?1 (～3.3 × 10?9 M). This sensitivity at the ppb level absolutely met the maximum residue limit (MRL) for PQ in dried beans as declared by most countries, including the US (0.3 mg kg?1), Australia (1.0 mg kg?1) and Taiwan (0.2 mg kg?1). Taiwan will ban the use of PQ as a defoliating agent for harvest in adzuki bean fields in 2019; therefore, developing a method for detecting PQ residues in the field or in import markets is necessary for consumer health and for authorities. This study provided an opportunity to utilize SERS in the field of on-site pesticide residue screening.
关键词： pesticide residue,paraquat,surface-enhanced Raman scattering,adzuki beans,detection method
更新于2025-09-19 17:15:36
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Overcurrent Electrodeposition of Fractal Plasmonic Black Gold with Broad-Band Absorption Properties for Excitation-Immune SERS
摘要： The dependence of plasmon resonance on the size, shape, and interparticle spacing of single, isolated nanostructures inherently limits their light-harvesting capability to a narrow spectral band. Here, we report a facile overcurrent electrodeposition strategy to prepare fractal plasmonic black gold (B-Au) with broad-band absorption properties (over 80% throughout the range of 300?1800 nm). The broad-band absorption properties are attributed to the excitation of multiple plasmons in the B-Au, which results in strong light?matter interaction over a broad-band spectral window. Consequently, the B-Au can produce strong broad-band surface-enhanced Raman scattering (SERS) regardless of the excitation light used. These ?ndings demonstrate that the fractal B-Au allows e?cient utilization of broad spectral photons and opens up exciting opportunities for highly sensitive SERS detection, photocatalysis, and photovoltaic devices.
关键词： broad-band absorption,surface-enhanced Raman scattering,fractal plasmonic black gold,photocatalysis,SERS,photovoltaic devices
更新于2025-09-19 17:13:59
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Direct bandgap opening in sodium-doped antimonene quantum dots: an emerging 2D semiconductor
摘要： Antimonene, which is similar to two-dimensional (2D) phosphorene, has recently gained considerable attention because of its thickness-dependent energy band structure. However, unlike phosphorene, undoped antimonene has an indirect bandgap only at the monolayer limit. In this work, an electrochemical sodium doping strategy was proposed to tune the energy band structure of antimonene. First-principles calculations indicated that a direct bandgap of 0.88 eV formed in 5.55% Na-doped antimonene, while undoped antimonene had an indirect bandgap of 2.38 eV. Optical and electrical measurements provided clear evidence for such a reconstruction of the energy band. We experimentally demonstrated p-type conduction in antimonene quantum dots (QDs)-based field-effect transistors. Furthermore, the induced direct bandgap enabled electric-field control of the surface-enhanced Raman scattering on plasmonic-free antimonene QDs. This allowed for detection of Rhodamine 6G with a detection limit down to the sub-femtomolar level. Our study highlights the potential of doped antimonene as an emerging 2D semiconductor.
关键词： Direct Bandgap,Quantum Dots,Antimonene,Field-Effect Transistors,Surface-Enhanced Raman Scattering,Sodium Doping
更新于2025-09-19 17:13:59
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Hierarchical Laser-Patterned Silver/Graphene Oxide Hybrid SERS Sensor for Explosive Detection
摘要： We demonstrate an ultrafast laser-ablated hierarchically patterned silver nanoparticle/graphene oxide (AgNP/GO) hybrid surface-enhanced Raman scattering (SERS) substrate for highly sensitive and reproducible detection of an explosive marker 2,4-dinitrotoluene (2,4-DNT). A hierarchical laser-patterned silver sheet (Ag?S) is achieved by ultrafast laser ablation in air with pulse energies of 25, 50, and 100 μJ. Multiple laser pulses at a wavelength of 800 nm and a pulse repetition rate of 50 fs at 1 kHz are directly focused on Ag?S to produce and deposit AgNPs onto Ag?S. The surface morphology of ablated Ag?S was evaluated using atomic force microscopy, optical pro?lometry, and ?eld emission scanning electron microscopy (FESEM). A rapid increase in the ablation rate with increasing laser energy was observed. Selected area Raman mapping is performed to understand the intensity and size distribution of AgNPs on Ag?S. Further, GO was spin-coated onto the AgNPs produced by ultrafast ablation on Ag?S. The hierarchical laser-patterned AgNP/GO hybrid structure was characterized using FESEM, high-resolution transmission electron microscopy, X-ray di?raction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Further, hierarchical laser-patterned AgNP/GO hybrid structures have been utilized as SERS-active substrates for the selective detection of 2,4-DNT, an explosive marker. The developed SERS-active sensor shows good stability and high sensitivity up to picomolar (pM) concentration range with a Raman intensity enhancement of ～1010 for 2,4-DNT. The realized enhancement of SERS intensity is due to the cumulative e?ect of GO coated on Ag?S as a proactive layer and AgNPs produced by ultrafast ablation.
关键词： silver nanoparticle/graphene oxide (AgNP/GO) hybrid,ultrafast laser ablation,explosive detection,surface-enhanced Raman scattering (SERS),2,4-dinitrotoluene (2,4-DNT)
更新于2025-09-19 17:13:59
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Controlled Fabrication of Optical Signal Input/Output Sites on Plasmonic Nanowires
摘要： Silver nanowires have attracted considerable attention as sub-diffraction limited diameter waveguides in a variety of applications including cell endoscopy and photonic integrated circuitry. Optical signal transport occurs by coupling light into propagating surface plasmons which scatter back into light further along the wire. However these inter-conversions only occur efficiently at wire ends, or at defects along the wire, which are not controlled during synthesis. Here we overcome this limitation, demonstrating the visible laser light-induced fabrication of gold nanostructures at desired positions on silver nanowires, and their utility as efficient in/out coupling points for light. The gold nanostructures grow via plasmon-induced reduction of Au(III) and are shown to be excellent ‘hotspots’ for surface-enhanced Raman scattering.
关键词： optical antenna,surface enhanced Raman scattering,Chemically synthesized noble metal nanowires,gold nanoparticle,laser direct writing
更新于2025-09-19 17:13:59
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Plasmon–Induced Dimerization of Thiazolidine-2, 4-Dione on Silver Nanoparticles - Revealed by Surface-Enhanced Raman Scattering Study
摘要： Surface-enhanced Raman scattering (SERS) study carried on thiazolidine-2, 4-dione (TZD), pharmacologically active heterocyclic compound, points to the presence of TZD dimer formed by plasmon-induced dimerization reaction of TZD on the surface of silver nanoparticles (Ag NP) at TZD concentrations of 10-3 M and above. The evidence for the presence of dimer was obtained from the appearance of a prominent band at 1566 cm-1 corresponding to ν C=C band (a characteristic vibrational band observed for the Knoevenagel condensation reaction products) which is absent in the normal Raman scattering (NRS) spectra of TZD solid/solution. The observed spectrum compares well with the calculated spectrum of dimer obtained using density functional theory (DFT) calculations. The dimerization reaction is plausibly induced by the transfer of hot electrons generated by the non-radiative plasmon decay of Ag NP and the proposed reaction mechanism is discussed. However, at lower concentrations (10-4 to 10-6M), the characteristic dimer peak (1566 cm-1) is absent and the SERS spectra resemble more with the NRS spectrum of TZD with few changes. The spectral analysis supported by DFT calculations showed that TZD molecules undergo deprotonation and get adsorbed on Ag NP surface as enolate forms. The proximity of TZD molecules on the surface of Ag NP is a necessary factor for the dimerization to occur. At lower concentrations, most molecules lie apart and reactions between molecules become less feasible and they remain as monomers on the surface, while at higher concentrations the molecules are closer to each other on Ag NP surface favouring the dimerization reaction to take place leading to the formation of the dimer.
关键词： density functional theory,thiazolidine-2, 4-dione,silver nanoparticles,plasmon-induced dimerization,Surface-enhanced Raman scattering
更新于2025-09-19 17:13:59
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a??Burning Lampa??-like Robust Molecular Enrichment for Ultrasensitive Plasmonic Nanosensors
摘要： Enriching and locating target analytes into specific “hot spot” are vital for ultrasensitive molecular identification and detection using plasmonic-based techniques. Inspired by mass transportation in lamp wicks, we develop an effective enrichment strategy for highly diluted analytes, in which analytes and Au nanoparticles are transported via solution microflow under the capillarity driving force of glass fiber papers to a heated region. After evaporation, a large volume of solution contained analytes and Au nanoparticles are condensed into a very limited area, and thus, analyte molecules are effectively enriched and located into SERS hot spots. Using this enrichment strategy, the sensitivity and detection limits of SERS are remarkably improved. Detection levels of crystal violet and anthracene are down to 10-16 M and 10-10 M, respectively. This enrichment strategy is very robust and easy to implement, and it can potentially be exploited in various plasmonic-based molecular detection and identification techniques.
关键词： enrichment,ultrasensitive detection,heating evaporation,capillary force,surface enhanced Raman scattering
更新于2025-09-19 17:13:59
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Hollow Porous Gold Nanoshells with Controlled Nanojunctions for Highly Tunable Plasmon Resonances and Intense Field Enhancements for Surface-Enhanced Raman Scattering
摘要： Plasmonic metal nanostructures with nanogaps have attracted great interest owing to their controllable optical properties and intense electromagnetic fields that can be useful for a variety of applications, but precise and reliable control of nanogaps in three-dimensional nanostructures remains a great challenge. Here, we report the control of nanojunctions of hollow porous gold nanoshell (HPAuNS) structures by a facile oxygen plasma-etching process and the influence of changes in nanocrevices of the interparticle junction on the optical and sensing characteristics of HPAuNSs. We demonstrate a high tunability of the localized surface plasmon resonance (LSPR) peaks and surface-enhanced Raman scattering (SERS) detection of rhodamine 6G (R6G) using HPAuNS structures with different nanojunctions by varying the degree of gold sintering. As the neck region of the nanojunction is further sintered, the main LSPR peak shifts from 785 to 1350 nm with broadening because the charge transfer plasmon mode becomes more dominant than the dipolar plasmon mode, resulting from the increase of conductance at the interparticle junctions. In addition, it is demonstrated that an increase in the sharpness of the nanojunction neck can enhance the SERS enhancement factor of the HPAuNS by up to 4.8-fold. This enhancement can be ascribed to the more intense local electromagnetic fields at the sharper nanocrevices of interparticle junctions. The delicate change of nanojunction structures in HPAuNSs can significantly affect their optical spectrum and electromagnetic field intensity, which are critical for their practical use in a SERS-based analytical sensor as well as multiple-wavelength compatible applications.
关键词： sintering,plasma etching,nanoporous gold,nanocrevice junction,surface-enhanced Raman scattering,plasmonic nanostructure
更新于2025-09-16 10:30:52
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Remarkable surface-enhanced Raman scattering on self-assembled {201} anatase
摘要： Semiconductors exhibit great potential as a surface-enhanced Raman scattering (SERS) substrate due to their low cost, stability, and biocompatibility. However, their application has been essentially restricted by their intrinsically low SERS sensitivity (10–102). Herein, sea urchin-like TiO2 was obtained by a self-assembled growth of crystals enclosed with the {201} facet. The high-symmetric spiny spheres exhibited appreciable Raman enhancement factors (EFs) of 1.6 (cid:2) 106, three orders of magnitude higher than those asymmetric TiO2 with exposed {101}, {001}, and {100} facets. The greatest charge transfer upon dopamine adsorption occurred on {201} TiO2 due to its high density of unoccupied t2g orbitals, partly contributing to the excellent SERS performance. More importantly, the sea urchin-like spheres created high-density hotspots evenly distributed in the vicinity of sharp tips and at narrow gaps between the spines, enabling a strong electromagnetic field enhancement (1.4 (cid:2) 104). Benefiting from the specific electronic and morphologic properties, the self-assembled {201} TiO2 exhibited superior SERS performance in terms of both intensity and reproducibility. The insights gained from this study open a new avenue to improve the SERS performance of semiconductors for applications in biomedical analysis, food detection, and toxicity tests.
关键词： SERS,{201} facet,self-assembled,surface-enhanced Raman scattering,electromagnetic field enhancement,TiO2,charge transfer
更新于2025-09-16 10:30:52