Search Results (987)

Herein, a high-performance Ta₂O₅/AgNPs composite Surface-Enhanced Raman Scattering (SERS) substrate is engineered for highly sensitive detection of microplastics. Through morphology modulation and band-gap engineering, the semiconductor Ta₂O₅ is structured into spheres and composited with silver nanoparticles (AgNPs), facilitating efficient charge transfer and localized surface plasmon resonance (LSPR). This architecture integrates electromagnetic (EM) and chemical (CM) enhancement mechanisms, achieving an ultra-low detection limit of 10⁻¹³ M for rhodamine 6G (R6G) with excellent linearity. Furthermore, the three-dimensional “pseudo-Neuston” network structure exhibits superior capture capability for microplastics (PS, PET, PMMA). To address spectral interference in simulated complex environments, a multi-scale deep-learning model combining wavelet transform, Convolutional Neural Networks (CNN), and Transformers is proposed. This model achieves a classification accuracy of 98.7% under high-noise conditions, significantly outperforming traditional machine learning methods. This work presents a robust strategy for environmental monitoring, offering a novel solution for precise risk assessment of microplastic pollution. Full article

Traditional colloid SERS substrates are mostly based on metal nanoparticles (MNPs), which have complex and time-consuming fabrication processes, poor structural control, and are susceptible to oxidation. As a result, solid-state SERS substrates have emerged as an effective alternative. Here, we propose using two-step mild and hard anodization to fabricate ordered anodic aluminum oxide (AAO) substrates with high total pore circumference for SERS detection. Hybrid pulse anodization (HPA) enables the fabrication of AAO at room temperature using 40 V in the first step and 40, 110, and 120 V in the second step of anodization. The different voltages applied in the second step effectively control the pore diameter, thereby achieving various nanostructures. The enhancement mechanism primarily originates from the high total pore circumference of nanostructures, which generates abundant hot spots around the pore peripherals, thereby significantly amplifying the SERS signal. Sorbic acid is a common preservative widely used in food products and employed as a test substance on high regularity AAO substrates at concentrations of 1000 ppm to 10 ppb. The resulting SERS spectra exhibited distinct characteristic peaks at 1640–1645 cm⁻¹. The analytical enhancement factor is calculated as 1.02 × 10⁵ at the AAO substrate prepared by 110 V with the Si substrate as the reference. By appropriately tuning the process parameters, a limit of detection (LOD) as low as 10 ppb of sorbic acid was achieved. Full article

Single exosomes are detected via surface-enhanced Raman scattering (SERS) due to electromagnetic field accumulation on a specially designed flexible metasurface. This metasurface is a modulated silver nanofilm deposited on a thin, flexible plastic substrate. An explicit Equation for calculating the local electric field is given. The field reaches extremely high values under plasmon resonance conditions and fills the depressions of the metasurface. The thin, flexible metasurface can be incorporated into automated Lab-On-Chip analytical systems and used for spectroscopic studies of exosomes. We propose a method to distinguish individual exosomes from the HEK293T cell line on the metasurface and then obtain and assign their SERS spectra. An important advantage of the plasmonic metasurface presented in this work is its spatial complementarity to exosomes and other vesicle-like objects. The plasmonic metasurface is fabricated using holographic lithography and further investigated using a correlation approach combining atomic force microscopy, scanning spreading resistance microscopy, and surface-enhanced spectroscopy. Full article

Surface-enhanced Raman scattering (SERS) is a highly sensitive analytical technique capable of single-molecule detection, yet its performance strongly depends on the underlying plasmonic architecture. In this study, we developed a robust SERS platform based on long-range–ordered bullseye plasmonic nano-gratings with tunable period and filling fraction, fabricated via electron beam lithography and reactive ion etching and uniformly coated with a thin gold film. These concentric nanostructures support efficient surface plasmon resonance and radial SPP focusing, enabling intense electromagnetic field enhancement across the substrate. Using this platform, we achieved quantitative detection of Rhodamine 6G with enhancement factors of ${10}^5$. Notably, our results reveal a previously unrecognized mechanistic insight: the geometric configuration producing the strongest local electric fields does not yield the highest SERS enhancement, due to misalignment between the dominant field orientation and the molecular polarizability tensor. This finding explains the non-monotonic dependence of SERS performance on grating geometry and introduces a new design principle in which both field strength and field–molecule alignment must be co-optimized. Overall, this work provides a mechanistic framework for rationally engineering plasmonic substrates for sensitive and quantitative molecular detection. Full article

Background/Objectives: Nanoparticles have emerged as indispensable tools in modern biomedicine, enabling precise diagnostics, targeted therapy, and controlled drug delivery. Despite their rapid progress, the translation of nanoparticle-based systems critically depends on the ability to detect, quantify, and track them across complex biological environments. Over the past two decades, a wide spectrum of detection modalities has been developed, encompassing optical, magnetic, acoustic, nuclear, cytometric, and mass spectrometric principles. Yet, no comprehensive framework has been established to compare these methods in terms of sensitivity, spatial resolution, and clinical applicability. Methods: Here we show a systematic analysis of all broadly applicable nanoparticle detection strategies, outlining their mechanisms, advantages, and drawbacks, and providing illustrative examples of practical applications. Results: This comparison reveals that each modality occupies a distinct niche: optical methods offer high sensitivity but limited penetration depth; magnetic and acoustic modalities enable repeated non-invasive tracking; nuclear imaging ensures quantitative, whole-body visualization; and invasive biochemical or histological assays achieve ultimate detection limits at the cost of tissue integrity. These findings redefine how each technique contributes to nanoparticle biodistribution and mechanistic studies, clarifying which are best suited for translational and clinical use. Conclusions: Placed in a broader context, this review bridges fundamental nanotechnology with biomedical applications, outlining a unified methodological framework that will guide the rational design, validation, and clinical implementation of nanoparticle-based therapeutics and diagnostics. By synthesizing the field into a single comparative framework, it also provides an accessible entry point for newcomers in nanotechnology and related biomedical sciences. Full article

Wide band gap (WBG) oxide and metal nanocomposites can possess bifunctionality from combining tightly coupled nanoobjects with different physicochemical properties. Adjusting synthesis conditions tunes these properties through modulating the process–morphology–function relationship. However, the controllable synthesis of such nanocomposites and their related applications are still underexplored. Here, we present a novel process flow to synthesize crystalline ZnO nanosheaves dotted with silver nanoparticles. The uniqueness of our strategy lies in the use of a silver mask for vertical growth of ZnO nanosheaves and thermal evaporating/dewetting Ag film to form a photocatalytic/plasmonic heterostructure. Upon combining a huge specific surface area and nanocrystallinity of ZnO nanosheaves, we enabled its surface-enhanced Raman scattering (SERS)-activity free of plasmonic components, yet their Ag modification resulted in improving detection limit in relation to Ellman’s reagent. Ag/ZnO nanosheaves showed dramatic photocatalytic activity to clean SERS-active surface. The systematic approach to synthesize Ag/ZnO heterostructure holds great promise in practical applications associated with interest in both photocatalytic and plasmonic properties. Full article

This study focused on the measurement requirements of Digital Image Correlation (DIC) in high-temperature environments of aero-engines and systematically investigated the applicability and stability of high-temperature speckle materials. Five common coating materials (Ti, TiN, Ta, NiCr alloy, and SiC) were selected. Corresponding thin films were deposited on Al₂O₃ ceramic substrates using magnetron sputtering technology, and their surface color evolution from room temperature up to 1200 °C was examined. The film compositions were analyzed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), revealing the mechanisms behind the color changes. The results indicate that Ti, TiN, Ta, and NiCr alloy exhibit significant color variations, which leads to insufficient color contrast for high-temperature speckle patterns. Further investigation shows that depositing an outer SiO₂ coating can improve surface scattering and reflection, while also inhibiting oxygen penetration, thereby enhancing oxidation resistance and improving speckle contrast. The SiC/SiO₂ composite structure demonstrates excellent thermal stability, making it an ideal speckle material for high-temperature DIC measurements. Full article

This study presents the synthesis and comprehensive characterization of tin dioxide nanoparticles (SnO₂NPs). SnO₂NPs were obtained using a conventional wet-chemistry route and an environmentally friendly green-chemistry approach employing plant extracts from rooibos leaves (Aspalathus linearis), pomegranate seeds (Punica granatum), and kiwifruit peels (family Actinidiaceae). The thermal stability and decomposition profiles were analyzed by thermogravimetric analysis (TGA), while their structural and physicochemical properties were investigated using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), Raman spectroscopy, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Transmission electron microscopy (TEM) confirmed the nanoscale morphology and uniformity of the obtained particles. The photocatalytic activity of SnO₂NPs was evaluated via the degradation of methyl orange (MeO) under UV irradiation, revealing that nanoparticles synthesized using rooibos extract exhibited the highest efficiency (68% degradation within 180 min). Furthermore, surface-enhanced Raman scattering (SERS) spectroscopy was employed to study the adsorption behavior of L-phenylalanine (L-Phe) on the SnO₂NP surface. To the best of our knowledge, this is the first report demonstrating the use of pure SnO₂ nanoparticles as SERS substrates for biologically active, low-symmetry molecules. The calculated enhancement factor (EF) reached up to two orders of magnitude (10²), comparable to other transition metal-based nanostructures. These findings highlight the potential of SnO₂NPs as multifunctional materials for biomedical and sensing applications, bridging nanotechnology and regenerative medicine. Full article

This research focused on the synthesis of triangular silver nanoplates (TSNPs) with sharp corners using a photomediated seed growth method. The TSNPs produced had an average edge length of 27.2 ± 9.2 nm and a (110) crystalline plane structure. In terms of optical properties, the TSNPs displayed three key absorbance peaks at approximately 400 nm, 500 nm, and 660 nm, which correspond to out-of-plane dipolar resonance, in-plane quadrupolar resonance, and in-plane dipolar resonance, respectively. The prepared TSNP colloidal solutions served as surface-enhanced Raman spectroscopy (SERS)-active materials for detecting paraquat residue in aqueous samples. We optimized the mixing time of the liquid SERS with the sample, maintaining a 1:1 volume ratio. The findings showed a remarkable enhancement of the Raman signal with 10 min mixing time using laser excitation at a wavelength of 785 nm. This study achieved the development of novel SERS-active substrates capable of detecting pesticides with excellent accuracy, sensitivity, and reproducibility for both qualitative and quantitative analysis in tap water, river water, drinking water, and cannabis water. Additionally, it paved the way for using the SERS technique as a promising approach in the areas of food safety and environmental monitoring, especially in the organic farming field. Full article

Raman spectroscopy has become a key tool for resolving the molecular behavior of interfaces due to its non-invasiveness, fingerprinting ability and in situ detection advantages. Surface-enhanced Raman scattering (SERS) and its derivative techniques (including SHINERS and TERS) have significantly overcome the challenges of weak interfacial signals and strong water interference through the synergistic effect of electromagnetic field enhancement and chemical enhancement. They have realized highly sensitive molecular detection at various interfaces such as solid–liquid, gas–liquid, water–oil, and so on. Despite the challenges of substrate stability and signal quantization, the deep integration of multi-technology coupling and theoretical computation will further promote the breakthrough of this technology in interface science. In this review, we systematically review the applications of Raman spectroscopy and SERS techniques in interface resolution, including key research directions such as analyzing interfacial molecular structures, detecting material reactions at water–oil interface, and tracking the evolution of electrochemical interfacial species, as well as exploring the technological bottlenecks and future development directions. Full article

Neonicotinoids are a novel class of insecticides that exhibit environmental persistence and off-target effects on both humans and ecosystems. Therefore, there is a need for sensitive and selective sensors to monitor concentrations of neonicotinoids in environmental water and soil systems. Molecularly imprinted polymer (MIP)-based sensors are an emerging technology with strong potential for reliable, sensitive, and selective detection of neonicotinoids. Moreover, MIPs are versatile and compatible with a wide range of analytical techniques, which can further enhance measurement capabilities in the development of practical and robust sensors. Despite this promise, many routes remain underexplored for neonicotinoid detection. This review reports on the current state of neonicotinoid chemical sensors and detection methods using MIPs and highlights potential applications of MIP-based approaches as cost-effective and easy-to-operate solutions for monitoring neonicotinoids. Recent sensors incorporating MIPs and electrochemical or optical techniques for neonicotinoid detection are described and compared. Approaches employing magnetic solid-phase extraction and quartz crystal microbalance are also discussed. Additionally, the influence of monomer choice for MIP synthesis, as well as the use of additives and nanomaterials for sensor construction and analyte detection, is reviewed. These methods may promote sustainability, reusability, ratiometric or simultaneous detection of neonicotinoids, and sensor portability for on-site monitoring. Full article

Food safety has recently attracted increasing attention, underscoring the need for timely and accurate on-site testing technologies. Optical detection, among various methods, offers notable advantages, including ease of use and rapid results, making it a promising approach for food safety applications. This paper reviews the fundamental principles of optical inspection for food field examination and explores its practical applications, including techniques such as surface-enhanced Raman scattering, UV–visible absorption spectroscopy, and fluorescence detection. Furthermore, this review discusses the integration of detection technologies with nanotechnology and smartphone-based systems. In addition, this review discusses the current applications, challenges, and potential solutions associated with optical detection in on-site food inspections. Full article

Tea, a worldwide prevalent beverage, is continually contaminated by pesticide residues and heavy metals, presenting considerable health concerns to consumers. Nonetheless, effective monitoring is limited by conventional detection techniques—such as gas chromatography (GC) and inductively coupled plasma mass spectrometry (ICP-MS)—which, despite their high precision, necessitate intricate pretreatment, incur substantial operational expenses, and are inadequate for swift on-site analysis. Biosensors have emerged as a viable option, addressing this gap with their exceptional sensitivity, rapid response, and ease of operation.This review rigorously evaluates recent advancements in biosensing technologies for the detection of pesticide residues and heavy metals in tea, emphasizing the mechanisms, analytical performance, and practical applicability of prominent platforms such as fluorescence, surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), colorimetric, and electrochemical biosensors. Electrochemical and fluorescent biosensors provide the highest promise for portable, on-site use owing to their enhanced sensitivity, cost-effectiveness, and flexibility to intricate tea matrices. The paper further emphasizes upcoming techniques such multi-component detection, microfluidic integration, and AI-enhanced data processing. Biosensors provide significant potential to revolutionize tea safety monitoring, with future advancements dependent on the synergistic incorporation of sophisticated nanomaterials, intelligent microdevices, and real-time analytics across the whole “tea garden-to-cup” supply chain. Full article

A three-dimensional Ag/TiO₂/Ti foam was fabricated via thermal annealing followed by pulsed laser deposition (PLD), providing a simple and scalable fabrication strategy. The porous Ti foam framework allows for the uniform dispersion of Ag nanoparticles (NPs), while the thermally formed TiO₂ interlayer promotes synergistic electromagnetic and chemical enhancement mechanisms. The localized electromagnetic field amplification at Ag-TiO₂ interfaces was simulated using the finite-difference time-domain (FDTD) method. Density functional theory (DFT) calculations confirmed that TiO₂ enhances both rhodamine 6G (R6G) adsorption on the substrate and charge transfer (CT) between the substrate and R6G, increasing the SERS activity. The optimized substrate demonstrates exceptional surface-enhanced Raman scattering (SERS) performance with an enhancement factor of 1.9 × 10⁷ and a detection limit of 2.24 × 10⁻¹¹ M for rhodamine 6G, with good reproducibility (RSD = 8.4%). Practical applicability is validated through sensitive detection of food colorants (brilliant blue and allura red). The synergistic combination of CT and electromagnetic enhancement in the easily fabricated Ag/TiO₂/Ti foam enables its application as a promising platform for food safety monitoring, effectively bridging laboratory innovation and practical applications. Full article

The objective of this study was to determine the most stable conformation of L-tryptophan (L-Tryp) on gold and silver nanoparticles. Additionally, this work investigated how these parameters were influenced by analyte concentration, nanoparticle size, and pH. The purpose of this study was to establish whether L-Tryp molecules interact with the nanoparticles through the carboxylate end, the amino group end, or both. This research has diverse applications in biophysics and medical diagnostics, potentially opening up new avenues in these fields. Moreover, it may enrich the disciplines of chemistry and nanotechnology by offering innovative approaches for future research. These findings represent a significant advancement in understanding the interactions between L-Tryp and nanoparticles, making a meaningful contribution to biophysics and medical diagnostics. Surface-Enhanced Raman Scattering (SERS) spectra of L-Tryp in the 100–4000 cm⁻¹ spectral range were obtained using a 785 nm laser for excitation. Gold (Au) and silver (Ag) nanoparticles (NPs) were synthesized using the citrate reduction method. The experimental procedure involved the use of electrolytes (such as NaCl) for colloid activation, which resulted in very high SERS signals. Modification of nanoparticle surface charge was achieved by adjusting the pH of Au and Ag colloidal suspensions between 2 and 11. The SERS spectra indicate that small-sized nanoparticles require high concentrations of L-Tryp to achieve high sensitivity, whereas larger nanoparticles perform effectively at lower concentrations. The pronounced enhancement of stretching vibrations in the COO⁻ group in the SERS spectra strongly suggests that the carboxylate group attaches to silver nanoparticles (AgNPs). Conversely, for gold nanoparticles (AuNPs), a new band at approximately 2136 cm⁻¹ was observed, indicating that the amino group of L-Tryp interacts with Au in its neutral form. These analyses were complemented by theoretical modeling, employing Density Functional Theory (DFT) calculations run using the Gaussian program to study molecular models in which L-Tryp interacted with AgNP and AuNP substrates in neutral, cationic, and anionic forms. Full article