Search Results (5,503)

In this study, a cellulose nanocrystal (CNC)-supported Ag–ZnO nanocomposite was synthesized via a hydrothermal route as a polymeric photocatalyst for efficient UV-A light-driven dye degradation. The renewable CNC framework provides abundant hydroxyl functional groups for nanoparticle anchoring, enhancing dispersion and interfacial charge transfer. Structural (XRD, FTIR, TEM, PL, and XPS) and thermal (TGA and DTG) analyses confirm successful incorporation of Ag nanoparticles and retention of CNC crystallinity. The composite exhibits a reduced optical bandgap (3.02 eV) and demonstrates superior photocatalytic activity, achieving 96% methylene blue (MB) degradation within 120 min. Enhanced performance is attributed to the synergistic effect of Ag-induced plasmonic excitation and CNC-facilitated charge migration, effectively suppressing ZnO photocorrosion. Moreover, the optimization of the parameters was conducted and found to be pH 7, a catalyst dose of 0.3 g L⁻¹, and an initial MB concentration of 10 ppm, which shows the best photocatalytic degradation reaction. The CNC/Ag–ZnO catalyst maintains 87% activity after five reuse cycles, showing good stability and reusability. The photostability of the CNC/Ag–ZnO catalyst was evaluated by ICP-MS, which measured Zn²⁺ concentration in the aqueous solution. Additionally, the degraded MB compounds were identified using GC-MS/MS analysis. This work highlights the potential of polymer-based biogenic supports for sustainable photocatalyst design and bridges polymer science with environmental remediation technology. Full article

Background/Objectives: Beta amyloid (Aβ) aggregates play a central role in the pathophysiology of Alzheimer’s disease (AD), and their detection and modulation remain major challenges in developing effective therapeutic and diagnostic strategies. Previously, gold nanoparticles with plasmonic and optical properties in the near-infrared (NIR) region and photothermal capabilities have been designed for detecting and disaggregating Aβ aggregates. However, these systems often face limitations related to biodegradability, long-term accumulation, and safety. In this work, a degradable NIR-responsive nanosystem based on small gold nanoparticles (sAuNPs), potentially excretable due to their small size, encapsulated within bovine serum albumin (BSA) and functionalized with the all-D peptide D3, was developed to inhibit Aβ aggregation. Methods: sAuNPs (~5–6 nm), functionalized with HS-PEG-NH₂, were encapsulated into BSA nanoparticles using a desolvation method and subsequently conjugated to D3, resulting in the nanosystem f-sAuNPs-BSANPs-D3. The nanosystem was characterized by UV–Vis–NIR spectroscopy, dynamic light scattering, zeta potential analysis, electron microscopy, and nanoparticle tracking analysis. The effects of the nanosystem on Aβ_1–42 aggregation were evaluated using a thioflavin T assay and electron microscopy. Additionally, the effects of f-sAuNPs-BSANPs-D3 on cell viability and its stability against trypsin digestion were assessed. Results: The nanosystem exhibited a measurable photothermal response under NIR irradiation and significantly reduced fibril formation. It did not affect the viability of SH-SY5Y neuronal cells at the tested concentrations. Trypsin incubation experiments demonstrated that the nanosystem remained stable at low enzyme concentrations mimicking plasma conditions, whereas higher enzyme concentrations induced degradation of the albumin matrix and subsequent disaggregation of sAuNPs. Conclusions: Overall, this study presents a degradable, albumin-based sAuNP nanosystem with NIR-responsive properties and potential for nanomedicine applications to inhibit Aβ aggregation in AD. Full article

Surface plasmon resonance (SPR) is a label-free, real-time biosensing technology with high sensitivity for the detection of biomolecular interactions. This review highlights recent advances in SPR biosensors for the detection of SARS-CoV-2. First, we outline design strategies, especially advanced plasmonic nanostructures and precise surface functionalization, that improve the specificity and binding affinity to viral targets. Next, we cover signal amplification methods, such as nanoparticle conjugation and plasmonic photothermal effects, which enhance the sensitivity for low-abundance viral components. Subsequently, we conducted a comparative analysis of SPR biosensors alongside traditional and emerging detection approaches for SARS-CoV-2, elucidating their individual merits and drawbacks. We also discuss how machine learning improves data interpretation and diagnostic accuracy. Finally, we discuss the current challenges and future development directions, particularly for clinical diagnostics, epidemic monitoring, and public health security. These advances support faster, more reliable, and accessible diagnostics for current and future viral outbreaks. Full article

Noble metal nanostructures provide versatile platforms for light manipulation through localized surface plasmon resonances (LSPRs). Among them, triangular silver nanoplates (AgNPTs) exhibit strong field-enhancement and spectral tunability, yet assembling them reproducibly on solids is challenging. We report a two-step functionalization strategy for constructing ordered AgNPT dimers on silica substrates, combining 3-aminopropyltriethoxysilane (APTES) anchoring with 1,4-butanedithiol bridging. AFM reveals face-to-face dimers with well-defined sub-nanometer gaps. Large-area AFM statistics collected over multiple regions (N = 80 nanoplates per condition) confirm reproducible and selective vertical dimerization. Extinction spectroscopy reveals sequential dielectric and coupling effects: thiol adsorption red-shifts the main resonance from 700 to 780 nm because of increased local refractive index and near-field damping, whereas dimerization partially restores it to ≈750 nm, consistent with plasmon hybridization within rigid ∼0.7 nm molecular gaps, where nonclassical moderation may occur but classical hybridization fully explains the observed shifts. Concomitantly, the extinction intensity doubles, following an exponential growth toward saturation during assembly. Surface-enhanced Raman scattering (SERS) measurements using 4-mercaptobenzoic acid (4-MBA) confirm a fourfold increase in the SERS enhancement factor from monolayer to bilayer, consistent with near-field coupling and hotspot formation at interplate junctions. Quantitative plasmon sensitivity analysis yields comparable results between experiments and finite-difference-time-domain simulations, confirming that the observed spectral shifts arise from near-field coupling and dielectric modulation rather than ensemble effects. This reproducible methodology enables precise tuning of NPT orientation, spacing, and optical response, providing a robust platform for enhanced sensing, SERS, and nanophotonic device engineering. Full article

Attenuated total reflection (ATR) has long relied on a familiar trio—prism, metal film, and substrate—to unlock insights into material properties. In this work, we demonstrate the possibility and limitations of a prismless ATR system that utilizes the relative permittivity of air in place of a prism, followed by a plasmonic test material, which is in turn followed by a novel material characterized by low real relative permittivity and near-zero imaginary relative permittivity. We show that such measurements are possible in the visible IR and UV frequency ranges. In addition, we illustrate the advantages of prismless ATR. Full article

Environmental contamination by persistent industrial dyes such as Amido Black demands highly efficient photocatalysts for advanced water treatment. Structural, chemical, and optical strategies based on TiO₂ nanotube engineering are widely explored for this purpose. In this work, highly ordered TiO₂ nanotube arrays were fabricated by electrochemical anodization and subsequently decorated with Pd nanoparticles via potentiostatic electrodeposition (10–300 s), enabling precise control of Pd nanoparticle size and loading. The resulting materials were systematically characterized by SEM, TEM, XRD, XPS, UV–vis DRS, and PL spectroscopy, and their properties were correlated with the photocatalytic degradation of Amido Black under both UV and visible light irradiation. The study reveals a clear size-dependent duality in the role of Pd. For intermediate Pd nanoparticles (≈9 nm, 20 s), Pd behaves predominantly as an electron sink, forming an efficient Schottky junction with anatase TiO₂ that markedly suppresses charge carrier recombination. This configuration yields ≈ 97% Amido Black removal after 120 min of UV irradiation, with an apparent rate constant about three times higher than that of bare TiO₂ nanotubes. In contrast, for ultra-small Pd nanoparticles (≈6 nm, 10 s), interfacial defect states sensitize TiO₂ to visible light, enabling ≈ 65% degradation after 270 min and a rate constant roughly four times higher than that of undecorated nanotubes under visible illumination. At long deposition times (≥150 s), Pd agglomeration leads to enhanced photoluminescence and markedly reduced photocatalytic activity, indicating increased recombination and less effective utilization of photogenerated charges. This provides a practical design rule to rationally tailor Pd–TiO₂ nanotube photocatalysts for targeted UV or visible light applications in dye removal and broader environmental remediation scenarios Full article

Green synthesis is an eco-friendly, simple, and cost-effective process for the synthesis of metal nanoparticles from plant extracts that are rich in bioactive compounds. In the current study, the antioxidant potential and total soluble polyphenol content (TPC) of different parts of Ligusticum mutellina (L.) Crantz were evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays, and the results indicated that the seed extract was the most active plant part. HPLC analysis indicated the presence of phenolic compounds such as gallic acid, protocatechuic acid, and catechin, which may contribute to the reduction and stabilization of AgNPs. Silver nanoparticles (AgNPs) were synthesized from the aqueous seed extract of L. mutellina. The formation of nanoparticles was confirmed by UV–Vis spectroscopy, FT-IR analysis, powder X-ray diffraction (PXRD), and transmission electron microscopy (TEM). The UV–Vis spectrum indicated a surface plasmon resonance peak at around 411 nm, and PXRD analysis indicated an average crystallite size of around 13 nm. TEM analysis revealed predominantly spherical nanoparticles with an average size of 25.36 ± 10.76 nm. The synthesized AgNPs exhibited strong antibacterial activity against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. Overall, the results demonstrate that L. mutellina seed extract represents an effective natural source of reducing and stabilizing agents for green nanoparticle synthesis and highlight the potential of the obtained AgNPs as environmentally friendly antimicrobial materials. Full article

Microfluidics enables spatially controlled nanostructure synthesis by coupling confined flows with surface reactions. In this work, we study how geometry-induced laminar microenvironments govern the in situ formation of Au and Ag nanostructures inside 3D-printed microfluidic reactors. Proof-of-concept fish-scale valves were fabricated by masked stereolithography in three architectures designed to define three recurring zones in the microreactor, inside the fish-scales (zone 1), between the fish-scales (zone 2), and along the rows of fish-scales (zone 3). A Cu thin film was deposited on the inner walls of the channel to serve as the sacrificial surface for galvanic replacement using AgNO₃ or HAuCl₄. Distinct 0D, 1D, and 2D nanostructures were simultaneously obtained in a zone-dependent manner across the valves, including nanoparticle and nanopore-rich regions, nanowires, nanoflakes and clustered 2D features. COMSOL simulations were used to solve the Navier–Stokes equation and extract specific-zone flow descriptors, including Reynolds number, velocity, and wall shear stress, and relate them to the nanostructure morphologies observed by SEM. The flow throughout the devices is strongly laminar, with local Reynolds numbers up to 0.04, exhibiting systematic spatial gradients imposed by the valve geometry. These results provide a design-guided route to tune nanostructure morphology through microchannel architecture under constant global operating conditions. Full article

The high morbidity and mortality of cancer pose a severe challenge to human health. Traditional diagnostic and therapeutic strategies still exhibit obvious limitations in early diagnostic sensitivity, therapeutic precision, and real-time monitoring of treatment efficacy. The development of nanotechnology has provided novel solutions for precision cancer theranostics. Among nanomaterials, gold nanoparticles (AuNPs) have become a research hotspot in tumor nanomedicine due to their tunable size and morphology, excellent localized surface plasmon resonance (LSPR) effect, and favorable biocompatibility. However, despite encouraging preclinical outcomes, several challenges hinder their clinical translation, including an incomplete understanding of long-term toxicity, complex in vivo biological interactions, the lack of standardized evaluation protocols, and regulatory uncertainties and manufacturing reproducibility issues. This paper systematically reviews the physicochemical and biological mechanisms of AuNPs in cancer theranostics, and summarizes the latest research advances of AuNPs in cancer detection and diagnosis (including biomarker detection and multimodal imaging) as well as in therapeutic fields, covering photothermal therapy (PTT), photodynamic therapy (PDT), radiosensitization, targeted drug and nucleic acid delivery, and immunotherapy-assisted strategies. Furthermore, we discuss the development of intelligent and stimuli-responsive theranostic nanoplatforms based on AuNPs, and outline their future prospects in precision medicine and personalized cancer therapy, with particular emphasis on the requirements for clinical translation, including safety evaluation, large-scale production, and regulatory approval pathways. Full article

The detection of glucose is a critical aspect of healthcare and biomedical research, particularly for the management of diabetes mellitus. Among various sensing technologies, surface plasmon resonance (SPR)-based optical fiber sensors have emerged as a promising platform due to their high sensitivity, real-time monitoring capabilities, and miniaturization potential. This paper explores the development and application of a molecularly imprinted polymer (MIP)-coated eccentric core optical fiber SPR sensor for glucose concentration detection. The integration of MIP technology with SPR sensing enables enhanced specificity and selectivity towards glucose molecules, while the eccentric core structure of the optical fiber contributes to improved light–matter interaction and sensitivity. The amplitude sensitivities are calculated as 0.88771 [mmol/mL]⁻¹ for the 3% glucose solution, 0.35161 [mmol/mL]⁻¹ for the 3.5% solution, 0.20425 [mmol/mL]⁻¹ for the 4% glucose solution, 0.89041 [mmol/mL]⁻¹ for the 5% solution, and 1.55825 [mmol/mL]⁻¹ for the 7% solution. The proposed sensor exhibits a simple geometry and presents itself as a promising candidate for glucose solution concentration detection. Full article

Nano-tweezers, especially those based on photonic crystals and plasmonic structures, are powerful tools for trapping, manipulating, or accelerating nano-sized objects. However, the precise control of the inter-distance between trapped nanoparticles has rarely been considered. In this paper, we propose a mirror-symmetric optical conveyor belt, in which each unit contains three graded nano-slots. Through the optimized design of spacing between these nano-slots, the structure generates multiple trapping centers, enabling wavelength-selective control over trapping positions. The results show that, through dynamically shifting excitation wavelengths, the programmable bidirectional optical manipulation of nanoparticles can be achieved. Also, the inter-distance between trapped particles can be tuned with subwavelength precision. The proposed structure provides a versatile solution for lab-on-a-chip systems, especially for systems aiming to study the interactions between objects. Full article

Recent advances in metasurface-based research have enabled significant reductions in the size and weight of optical devices. By employing metallic nanostructures with subwavelength dimensions, color filtering can be achieved through phenomena such as extraordinary optical transmission (EOT), which allows specific bands of visible light to pass through. However, conventional EOT-based color filters often suffer from strong side peaks outside the desired transmission band, degrading color purity and hindering accurate color reproduction. In this study, we propose an ultrathin, polarization-independent color filter based on a nanohole array that utilizes the EOT effect while effectively suppressing unwanted side peaks. To achieve this, we introduce a modified design in which additional metallic triangular edges are placed around a hole in a conventional hole array. This configuration suppresses higher-order diffraction modes and enables selective transmission at RGB wavelengths, thereby improving spectral selectivity and overall color performance. Full article

Surface-enhanced Raman spectroscopy (SERS) amplifies Raman scattering by placing molecules in the near-field of plasmonic nanostructures, enabling label-free molecular fingerprinting. While attractive for living cell phenotyping, many cellular SERS works rely on internalized colloidal nanoparticles, leading to variable uptake/localization, aggregation-driven hotspot fluctuations, and potential cellular perturbation. Here, we report a chip-like Au/SiO₂ nanolaminate SERS substrate that supports direct culture and label-free measurements of living cells on spatially defined hotspots without nanoparticle uptake. The periodic nanolaminate forms dense nanogaps and is engineered for 785 nm excitation, providing uniform enhancement over a large, culture-compatible area with high hotspot uniformity. By engineering the cell–substrate nano–bio interface, the platform enables reproducible acquisition of intrinsic cellular vibrational fingerprints under physiological conditions without Raman tags. Using MCF-7 and MDA-MB-231 breast cancer cells, we collected hundreds of spectra per line, and MDA-MB-231 exhibited broader spectral variations, indicating greater heterogeneity. Principal component analysis and linear discriminant analysis achieved 99% classification accuracy for MCF-7 and MDA-MB-231, and bright-field imaging confirmed preserved adhesion and canonical morphologies. This chip-based, label-free living cell SERS platform enables scalable, nonperturbative phenotyping and may support rapid malignancy classification and treatment response screening across subtle cancer states. Full article

Silver films are key building blocks for plasmonic and nanophotonic devices, whose optical performance and device reliability are highly sensitive to particulate contamination introduced during fabrication and operation. Herein, a non-destructive surface cleaning strategy specifically applicable to silver film systems is proposed, based on the synergistic regulation of the mechanical properties of a polymer layer and its interfacial adhesion to the silver film. Such regulation is achieved by tuning hydrogen-bond-mediated interactions within a modified poly(vinyl alcohol) (PVA) layer, enabling effective control over the locus of fracture during peeling, such that fracture preferentially occurs at the polymer/silver interface. Unlike conventional polymer-assisted cleaning methods that suffer from an inherent trade-off between bulk cohesion and interfacial adhesion, this approach decouples the two properties through molecular-level hydrogen-bond redistribution. As a result, particulate contaminants can be efficiently removed from the silver surface while preserving the structural integrity of the silver film. The proposed method achieves a particle removal efficiency of up to 98% for contaminants larger than 30 nm and can be stably applied to silver films with lateral dimensions ranging from 1 inch to 12 inches, demonstrating excellent scalability. By further adjusting the processing parameters and compositional ratios of the polymer layer, this strategy is expected to be adaptable to silver films with different thicknesses and structural configurations, providing a reliable surface cleaning solution for improving the performance and reliability of plasmonic and optoelectronic thin-film devices. Full article

This study presents a statistically optimized protocol for the green synthesis of gold nanoparticles (Au NPs) using aqueous Kalanchoe pinnata leaf extract (AKPLE). An integrated experimental strategy, transitioning from preliminary one-factor-at-a-time (OFAT) screening to a five-factor Box–Behnken Design, was employed to model and simultaneously optimize two critical optical responses derived from surface plasmon resonance: the peak position (λ_max) and its absorbance intensity. Highly predictive quadratic models (R² > 0.97) revealed that synthesis outcomes are governed by significant nonlinear curvature, with minimal interaction effects. Multi-response optimization via a desirability function identified a harmonized set of conditions (HAuCl₄: 0.44 mM, AKPLE: 3.50% v/v, temperature: 80.6 °C, pH: 7.2, time: 66.7 min) predicted to minimize λ_max at 540 nm while maximizing absorbance to 0.61. Synthesis under these optimized conditions successfully produced spherical, crystalline Au NPs, as confirmed by characterization (average TEM size: 26.3 ± 4.1 nm; zeta potential: –30.45 mV). This work demonstrates that a hybrid OFAT-RSM approach is superior for the precise, multivariate optimization of plant-mediated Au NP synthesis, providing a validated and scalable framework to balance nanoparticle size and plasmonic intensity—an outcome unattainable through conventional OFAT methods. Full article