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Transition from discrete patches to plasmonic nanohole array by glancing angle deposition on nanosphere monolayers
摘要： By combining nanosphere lithography and glancing angle deposition, a morphological transition from disconnected patchy silver (Ag) coated nanosphere particles to a connected Ag nanohole sheet on close-packed nanosphere monolayers has been demonstrated, which significantly changes the optical property of the Ag nanostructure deposited. For different sized nanosphere monolayers, when the vapor incident angle was set to be 55o, the transmission spectra showed complicated features when the Ag deposition thickness was less than 60 nm. When the thickness was large enough (> 60 nm), a distinguished extraordinary optical transmission (EOT) peak was observed. The EOT peak wavelength position is independent of the Ag thickness deposited and is proportional to the nanosphere diameter. The obtained EOT peaks possess a high quality factor and have high transmission values compared to those reported in the literature for similar structures. Such a high quality EOT response could be used for constructing better sensors or developing other plasmonic applications.
关键词： extraordinary optical transmission,nanosphere lithography,glancing angle deposition,silver nanoparticles,plasmonic nanohole array
更新于2025-09-19 17:13:59
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Synthesis and Deposition of Ag Nanoparticles by Combining Laser Ablation and Electrophoretic Deposition Techniques
摘要： Silver nanostructured thin films have been fabricated on silicon substrate by combining simultaneously pulsed laser ablation in liquid (PLAL) and electrophoretic deposition (ED) techniques. The composition, topography, crystalline structure, surface topography, and optical properties of the obtained films have been studied by energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-visible spectrophotometry. The coatings were composed of Ag nanoparticles ranging from a few to hundred nm. The films exhibited homogenous morphology, uniform appearance, and a clear localized surface plasmon resonance (LSPR) around 400 nm.
关键词： pulsed laser ablation in liquid,electrophoretic deposition,silver nanoparticles
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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Silver nanoparticles on graphene quantum dots as nanozyme for efficient H <sub/>2</sub> O <sub/>2</sub> reduction in a glucose biosensor
摘要： In this work, we developed graphene quantum dot-supported silver nanoparticles (AgNPs@GQDs) as Nanozyme for efficient electrocatalytic reduction of H2O2. We applied this composite material in a glucose oxidase-based glucose sensor, by drop casting a mixture of AgNPs@GQDs and chitosan (CS) on glassy carbon electrodes (GCE). Various conditions such as thickness of the AgNPs@GQDs/CS film, pH and temperatures were optimized. The proposed sensor presented excellent selectivity and sensitivity, a linear dependence on glucose concentration in the range 0.1–10 mM and a limit of detection of ca. 0.01 mM.
关键词： hydrogen peroxide reduction,electrochemical sensor,graphene quantum dots (GQDs),silver nanoparticles (AgNPs),glucose oxidase (GOx)
更新于2025-09-19 17:13:59
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Generation of High Quality, Uniform and Stable Plasmonic Colorants via Laser Direct Writing
摘要： Brilliant plasmonic colors with long-standing stability are generated via laser direct writing. This plasmonic coloring system is made of silver nanoparticles (Ag NPs) layer embedded in the quartz glass formed by ion implantation. The laser-induced plasmonic heating merges the small Ag NPs into larger ones, which modifies the plasmon resonances. The plasmon resonances can be further tuned via changing the irradiation time and power, which shows scattering colors ranging from red to green and cyan. By scanning the laser across the Ag NPs layer, sophisticated plasmonic patterns and images with high resolution (≈105 DPI) can be obtained and preserved over long time (several months). This plasmonic coloring system via laser printing is facile, cost-effective, accurate, and highly stable with rich hue, compared to other plasmonic color systems, which bears significant potentials for industrial applications such as optics, displays, decorations, data storage, and anti-counterfeiting.
关键词： color printing,photothermal,silver nanoparticles,ion implantation
更新于2025-09-19 17:13:59
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<p>Filter-Membrane-Based Ultrafiltration Coupled with Surface-Enhanced Raman Spectroscopy for Potential Differentiation of Benign and Malignant Thyroid Tumors from Blood Plasma</p>
摘要： The objective of this study is to evaluate the performance and feasibility of surface-enhanced Raman spectroscopy coupled with a filter membrane and advanced multivariate data analysis on identifying and differentiating benign and malignant thyroid tumors from blood plasma. We proposed a membrane filter SERS technology for the differentiation between benign thyroid tumor and thyroid cancer. That is to say, by using filter membranes with optimal pore size, the blood plasma samples from thyroid tumor patients were pretreated with the macromolecular proteins being filtered out prior to SERS measurement. The SERS spectra of blood plasma ultrafiltrate obtained using filter membranes from 102 patients with thyroid tumors (70 thyroid cancers and 32 benign thyroid tumors) were then analyzed and compared. Two multivariate statistical analyses, principal component analysis-linear discriminate and Lasso-partial least squares-discriminant analysis (Lasso-PLS-DA), were performed on the SERS spectral data after background subtraction and normalization, as well as the first derivative processing, to analyze and compare the differential diagnosis of benign thyroid tumors and thyroid cancer. SERS measurements were performed in blood plasma acquired from a total of 102 thyroid tumor patients (benign thyroid tumor N=32; thyroid cancer N=70). By using filter membranes, the macromolecular proteins in blood plasma were effectively filtered out to yield high-quality SERS spectra. 84.3% discrimination accuracy between benign and malignant thyroid tumor was achieved using PCA-LDA method, while Lasso-PLS-DA yields a discrimination accuracy of 90.2%. Our results demonstrate that SERS spectroscopy, coupled with ultrafiltration and multivariate analysis has the potential of providing a non-invasive, rapid, and objective detection and differentiation of benign and malignant thyroid tumors.
关键词： thyroid tumor,silver nanoparticles,filter membrane,blood plasma,surface-enhanced Raman spectroscopy
更新于2025-09-19 17:13:59
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Highly Sensitive Detection of Salbutamol by ALP-mediated Plasmonic ELISA Based on Controlled Growth of AgNPs
摘要： Salbutamol (SAL), a short-acting β-2 adrenergic receptor agonist, is an undesirable addition to livestock farming and used to improve the growth rates. A direct competitive colorimetric immunoassay for SAL was developed. The alkaline phosphatase (ALP)-mediated controlled growth of the prereduction silver nanoparticles (AgNPs) was used to achieve the highly sensitive, colorimetric detection of SAL through the plasmonic ELISA. Click chemistry reaction was used to synthesize salbutamol biotin label (SAL-Bio) to achieve signal amplification and specific binding with antibody. ALP can efficiently hydrolyze sodium L-ascorbyl-2-phosphate and generate L-ascorbic acid, thereby reducing Ag+ and forming AgNPs. The plasmon resonance absorption signals of AgNPs were enhanced along with a distinct color change. The limit of detection of SAL can be decreased to 26.14 pg/mL. The method offers a good technique for the detection of many small molecular contaminants, such as pesticide residues and veterinary drug residues in food and edible water.
关键词： Salbutamol,alkaline phosphatase,colorimetric detection,direct competitive immunoassay,plasmonic ELISA,silver nanoparticles
更新于2025-09-19 17:13:59
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Laser-Generated Ag Nanoparticles in Mesoporous TiO2 Films: Formation Processes and Modeling-Based Size Prediction.
摘要： Controlling the formation of nanoparticles (NPs) by direct laser writing ensures an efficient way of engineering the optical responses of nanocomposite materials through adjusting laser parameters such as power, focusing and writing speed. The process of NP’s growth, photo-oxidation, and reduction affect the light absorption by an ensemble of laser-activated NPs. However, those self-consistent processes are not well understood. Previous studies explained the growth or shrinkage of silver NPs by neglecting heat diffusion. It remained unclear, however, how the NP size can be controlled by the laser writing speed. In this work, based on the coupled calculations of size-variation, light absorption, and heat diffusion by an emsemble of NPs, we propose a two-dimensional model taking account of spatial information of size and temperature to have a further investigation into the process. The spatial size distribution is revealed to be non-uniform leading to the transmission inhomogeneity along the laser written lines. This fact is confirmed by the in-situ transmission experiments. The performed study also depicts a novel view in which NPs grow ahead of the laser beam center due to the heat diffusion. The nonlinear growth never stops until it exhausts the majority of the free Ag0 in the matrix, while the amount of Ag0 by reduction cannot compensates the consumption. After that, the photo-oxidation dominates the process and finally acts as the controlling role in NP size depending on the writing speed. The simulations also show that it is not the activation energy of Ag0 diffusion but the ionization efficiency affect the final NP size, which helps understand in how to improve the laser processing of differently prepared samples.
关键词： photo-oxidation,silver nanoparticles,nanoparticles,TiO2 films,laser writing,heat diffusion
更新于2025-09-16 10:30:52
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Engineering carbon quantum dots for enhancing the broadband photoresponse in a silicon process-line compatible photodetector
摘要： Realization of heterojunction based broadband photodetectors (ultraviolet to near-infrared) compatible with existing silicon process technology has great promise for advanced optoelectronic applications. In this report, we demonstrate the application of carbon quantum dots (CQDs) synthesized from organic waste via a facile fabrication technique as a potential broadband photodetector in a hybrid (organic–inorganic) heterostructure with Si. The broadband photoresponse is further improved by impregnating the CQDs with reduced graphene oxide (rGO) and silver nanoparticles (AgNPs). The results show that the optimized incorporation of rGO aids in enhancing the photoresponse due to effective carrier transport, whereas AgNPs intensify the optical absorption due to localized surface plasmon resonance. The maximum responsivity and detectivity for the engineered CQDs are found to be around 1 A W?1 and 2 × 1012 Jones, respectively. This work demonstrates an economic, effective and feasible approach to harness natural resources for technological purposes, which can efficiently be adopted with presently available industry scale technologies.
关键词： silver nanoparticles,reduced graphene oxide,carbon quantum dots,silicon process technology,broadband photodetector
更新于2025-09-16 10:30:52
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Plasmonics of Diffused Silver Nanoparticles in Silver/Nitride Optical Thin Films
摘要： Metal-dielectric multilayers are versatile optical devices that can be designed to combine the visible transmittance of dielectrics with the electronic properties of metals for plasmonic and meta-material applications. However, their performances are limited by an interfacial optical absorption often attributed entirely to the metal surface roughness. Here, we show that during deposition of AlN/Ag/AlN and SiNx/Ag/SiNx multilayers, significant diffusion of Ag into the top dielectric layer form Ag nanoparticles which excite localized surface plasmon resonances that are primarily responsible for the interfacial optical absorption. Based on experimental depth profiles, we model the multilayer’s silver concentration profile as two complementary error functions: one for the diffused Ag nanoparticles and one for the interface roughness. We apply the Maxwell-Garnett and Bruggeman effective medium theories to determine that diffusion characteristics dominate the experimental absorption spectra. The newfound metal nanoparticle diffusion phenomenon effectively creates a hybrid structure characteristic of both metal-dielectric multilayer and metal-dielectric composite.
关键词： Plasmonics,Metal-dielectric multilayers,Optical thin films,Silver nanoparticles,Localized surface plasmon resonances
更新于2025-09-16 10:30:52