Search Results (450)

Effective in situ pH sensing holds exciting prospects in environmental and biomedical applications, but still faces a great challenge. Until now, pH sensors with small size, high sensitivity, good stability and repeatability, great biosafety, wide detection range, and flexible structure have rarely been reported. Herein, we propose a novel dual-emission ratiometric fluorescent pH sensor by decorating ethyl cellulose (EC)-encapsulated CdSe/ZnS quantum dots (QDs) and oxazine 170 perchlorate (O170 dye) on the surface of the spider silk. When a 473 nm excitation light is coupled into the pH sensor, the evanescent wave transmitting along the surface of the spider silk will excite the CdSe/ZnS QDs and then the O170 dye based on the fluorescence resonance energy transfer (FRET) effect from the QDs; thus, the pH sensing of the surrounding liquid environment can be achieved in real time by collecting the photoluminescence (PL) spectra of the pH sensor and measuring the emission intensity ratio of the two fluorescent materials. The sensor has also demonstrated a high sensing sensitivity (0.775/pH unit) within a wide pH range of 1.92–12.11, as well as excellent reusability and reversibility, structure and time stability, biocompatibility, and biosafety. The proposed pH sensor has a potential application in an in situ monitor of water microenvironments, cellular metabolism, tumor microenvironments, etc. Full article

Medicinal plants are a rich source of diverse secondary metabolites (SMs) with significant industrial and medicinal applications. However, the natural content of these compounds is often low and influenced by various environmental and biological factors, making large-scale extraction from conventionally cultivated plants challenging. This review comprehensively examines the efficacy and benefits of plant in vitro culture techniques, specifically, callus, cell suspension, and hairy root cultures, for enhanced SMs production. A primary focus is placed on the elicitation effects of various nanomaterials and their mechanisms of action in boosting SMs synthesis. We present successful case studies utilizing different classes of nanomaterials, including metal oxides, non-metal oxides, carbon-based materials, polysaccharides, and quantum dots, as nano-elicitors. Furthermore, the review discusses the advantages and current challenges of nanomaterial-based elicitation, as well as its future applications and prospects. The insights consolidated in this review underscore the potential of nanoparticle-mediated elicitation as a robust strategy for the efficient production of valuable SMs in plant cell cultures. Finally, we emphasize the broad utility of diverse nanomaterials and highlight critical areas requiring further investigation in this field. Full article

Thanks to both endogenous and exogenous antioxidants (AOs), the antioxidant defense system ensures redox homeostasis, which is crucial for protecting the body from oxidative stress and maintaining overall health. The food industry also exploits the antioxidant properties to prevent or delay the oxidation of other molecules during processing and storage. There are many classical methods for assessing antioxidant capacity/activity, which are based on mechanisms such as hydrogen atom transfer (HAT), single electron transfer (SET), electron transfer with proton conjugation (HAT/SET mixed mode assays) or the chelation of selected transition metal ions (e.g., Fe²⁺ or Cu¹⁺). The antioxidant capacity (AOxC) index value can be expressed in terms of standard AOs (e.g., Trolox or ascorbic acid) equivalents, enabling different products to be compared. However, there is currently no standardized method for measuring AOxC. Nanoparticle sensors offer a new approach to assessing antioxidant status and can be used to analyze environmental samples, plant extracts, foodstuffs, dietary supplements and clinical samples. This review summarizes the available information on nanoparticle sensors as tools for assessing antioxidant status. Particular attention has been paid to nanoparticles (with a size of less than 100 nm), including silver (AgNPs), gold (AuNPs), cerium oxide (CeONPs) and other metal oxide nanoparticles, as well as nanozymes. Nanozymes belong to an advanced class of nanomaterials that mimic natural enzymes due to their catalytic properties and constitute a novel signal transduction strategy in colorimetric and absorption sensors based on the localized surface plasmon resonance (LSPR) band. Other potential AOxC sensors include quantum dots (QDs, <10 nm), which are particularly useful for the sensitive detection of specific antioxidants (e.g., GSH, AA and baicalein) and can achieve very good limits of detection (LOD). QDs and metallic nanoparticles (MNPs) operate on different principles to evaluate AOxC. MNPs rely on optical changes resulting from LSPR, which are monitored as changes in color or absorbance during synthesis, growth or aggregation. QDs, on the other hand, primarily utilize changes in fluorescence. This review aims to demonstrate that, thanks to its simplicity, speed, small sample volumes and relatively inexpensive instrumentation, nanoparticle-based AOxC assessment is a useful alternative to classical approaches and can be tailored to the desired aim and analytes. Full article

Scandium-modified carbon dots (Sc-oCDs) were synthesized in this work through a solid-phase approach. The prepared Sc-oCDs exhibited excitation-independent emission properties, as well as photostability against pH, ionic strength, and UV irradiation. Their fluorescence quantum yields significantly exceeded those of unmodified counterparts, confirming effective Sc modification. The Sc-oCDs also possessed upconversion fluorescence at 542 nm with 980 nm excitation. Additionally, the as-prepared Sc-oCDs functioned as an effective fluorescent sensor for Cu²⁺, demonstrating selective fluorescence quenching. A linear correlation was observed between the quenching efficiency and Cu²⁺ concentration from 1 to 600 μM, achieving a detection limit of 0.167 μM. Operating via dynamic quenching, this sensing system achieved highly selective and rapid (<1 min) detection of Cu²⁺, enabling sensitive Cu²⁺ monitoring in aqueous samples. Full article

Since the introduction of the DNA origami technology by Seeman and Rothemund, the integration of functional entities (nanoparticles, quantum dots, antibodies, etc.) has been of huge interest to broaden the area of applications for this technology. The possibility of precise functionalization of the DNA origami technology gives opportunity to build up complex novel structures, opening up endless opportunities in medicine, nanotechnology, photonics and many more. The main advantage of the DNA origami technology, namely the self-assembly mechanism, can represent a challenge in the construction of complex mixed-material structures. Commonly, DNA origami structures are purified post-assembly by filtration (either spin columns or membranes) to wash away excess staple strands. However, this purification step can be critical since these functionalized DNA origami structures tend to agglomerate during purification. Therefore, custom production and purification procedures need to be applied to produce purified functionalized DNA origami structures. In this paper, we present a workflow to produce functionalized DNA origami structures, as well as a method to qualify the successful hybridization of a quantum dot to a square frame DNA origami structure. Through the utilization of a FRET fluorophore–quencher pair as well as a subsequent assembly, successful hybridization can be performed and confirmed using photoluminescence measurements. Full article

Graphitic nanomaterials have emerged as foundational components in nanoscience owing to their exceptional electrical, mechanical, and chemical properties, which can be tuned by controlling dimensionality and structural order. From zero-dimensional (0D) quantum dots, carbon nano-onions, and nanodiamonds to one-dimensional (1D) nanoribbons, two-dimensional (2D) nanowalls, and three-dimensional (3D) graphene foams, these architectures underpin advancements in catalysis, energy storage, sensing, and electronic technologies. Among various synthesis routes, chemical vapor deposition (CVD) provides unmatched versatility, enabling atomic-level control over carbon supply, substrate interactions, and plasma activation to produce well defined graphitic structures directly on functional supports. This review presents a comprehensive, dimension-resolved overview of CVD-derived graphitic nanomaterials, examining how process parameters such as precursor chemistry, temperature, hydrogen etching, and template design govern nucleation, crystallinity, and morphological evolution across 0D to 3D hierarchies. Comparative analyses of Raman, XPS, and XRD data are integrated to relate structural features with growth mechanisms and functional performance. By connecting mechanistic principles across dimensional scales, this review establishes a unified framework for understanding and optimizing CVD synthesis of graphitic nanostructures. It concludes by outlining a path forward for improving how CVD-grown carbon nanomaterials are made, monitored, and integrated into real devices so these can move from lab-scale experiments to practical, scalable technologies. Full article

Fluorescent nanoprobes operating in the NIR-II window have gained considerable attention for biomedical imaging because of their deep-tissue penetration, reduced scattering, and high spatial resolution. Their tunable optical behavior, flexible surface chemistry, and capacity for multifunctional design enable sensitive detection and targeted visualization of biological structures in vivo. This review highlights recent advances in the design and optical engineering of four widely studied NIR-II nanoprobe families: quantum dots, carbon dots, upconversion nanoparticles, and dye-doped silica nanoparticles. These materials were selected because they offer well-defined architectures, controllable emission properties, and substantial mechanistic insight supporting discussions of imaging performance and translational potential. Particular focus is placed on emerging strategies for activatable, targeted, and ratiometric probe construction. Recent efforts addressing biosafety, large-scale synthesis, optical stability, and early preclinical validation are also summarized to clarify the current progress and remaining challenges that influence clinical readiness. By outlining these developments, this review provides an updated and focused perspective on how engineered NIR-II nanoprobes are advancing toward practical use in biomedical imaging and precision diagnostics. Full article

Cationic gemini surfactants, which constitute a unique class of amphiphilic molecules composed of two hydrophilic ammonium groups and two hydrocarbon tails connected by a spacer, have emerged as highly versatile functional agents with superior interfacial activity and self-assembly behavior compared to conventional monomeric analogs. Their structural tunability enables precise control over physicochemical properties, making them attractive for applications across diverse scientific and industrial domains. In biomedical sciences, gemini surfactants act as potent antimicrobial and anti-biofilm agents, as well as efficient carriers for drug and gene delivery. In nanotechnology and optoelectronics, they facilitate the synthesis and stabilization of nanoparticles, quantum dots, and perovskite nanocrystals, leading to improved colloidal stability, enhanced photophysical performance, and extended material lifetimes. Within the petroleum industry, gemini surfactants have proven effective in enhanced oil recovery (EOR) by reducing interfacial tension and in crude oil transportation as drag-reducing agents (DRAs), significantly lowering viscosity, turbulence, and pipeline energy losses. This review summarizes recent advances in the chemistry, mechanisms of action, and applications of gemini surfactants, highlighting their multifunctionality and emphasizing their potential in the development of next-generation sustainable technologies. Full article

Quantum dots (QDs) are a class of nanomaterials with unique fluorescent properties that have gained significant attention in the research of Chinese herbal medicines (CHMs). Due to their exceptional optical characteristics, stability, biocompatibility, and other advantages, QDs are increasingly utilized in CHM studies. This review explores the diverse applications of QDs, including their use in detecting active ingredients and common exogenous pollutants in CHMs, as well as in assessing the degradation of such pollutants in both CHMs and their growing environments. Furthermore, the paper discusses the potential of QDs synthesized from CHMs as tools for analyzing other substances and modulating their pharmacological effects. The review also highlights the preparation methods, detection principles, and specific research strategies related to QDs. Integrating QDs into CHM research is poised to drive the modernization and internationalization of the CHM industry. Full article

In this work, Clar’s rule was employed to predict changes in stability and energy gap of graphene quantum dots (GQDs) following the attachment of an epoxy functional group at various positions, using coronene as a model molecule. To evaluate the applicability of this approach, quantum-chemical calculations were performed within the framework of density functional theory (DFT). It was established that Clar’s rule enables highly accurate prediction of the most reactive sites on GQDs, as well as corresponding changes in energy gap. The obtained results hold particular value for studying GQDs of varying sizes. Full article

One-pot hydrothermal synthesis of boron nitride quantum dots (BNQDs) offers a simple and widely accessible approach to produce nanoparticles with tailored properties for biomedical purposes, including bioimaging and drug delivery. However, growing evidence suggests that most reported BNQD syntheses yield products with insufficient purity and poorly defined structures, limiting their bioapplications where precise composition and controlled synthesis are paramount. In this study, we present a formation mechanism and demonstrate multiple BNQD synthesis pathways that can be precisely controlled by modulating the reaction equilibrium during hydrothermal synthesis under varying experimental conditions. We demonstrate that carbon-related defects shift BNQD photoluminescence (PL) from the UV to the 400–450 nm region, making them suitable for bioimaging, while BO₂⁻ enrichment introduces additional phosphorescence. Furthermore, we show that as-synthesized BNQD suspensions contain significant contamination by non-luminescent ammonium polyborate salts, which is overlooked in prior studies, and disclose the mechanism of their formation as well as effective purification method. Finally, we assess the biocompatibility of purified BNQDs with tuned PL properties and demonstrate their application in bioimaging using Vero cells. The elucidated nanoparticle formation mechanisms, combined with methods for precise control of optical properties, structural defects and sample purity, enable the reproducible production of reliable and effective BNQDs for bioimaging. Full article

Local droplet etching and subsequent refilling enables the fabrication of highly symmetric quantum dots with low fine structure splitting, suitable for generating polarization entangled photons. While well established in GaAs/Al_xGa_1−xAs, this approach does not yield emission in the telecom bands required for low loss fiber-based quantum communication. To achieve emission at 1.55 μm, local droplet etching must be adapted to alternative material platforms such as InP. Here, we systematically investigate how the etching material deposition rate and etching time influence nanohole morphology in In_0.52Al_0.48As layers lattice-matched to InP. In the first experiment, InAl was deposited at fluxes of 0.2–4.0 Å s⁻¹ at $T_{etch} = 350 °\mathrm{C}$ and 460 °C. Lower fluxes produced nanoholes with lower density and larger ring diameters, indicating fewer and larger initial droplets, consistent with scaling theory. The average nanohole diameter decreased monotonically with increasing flux, whereas the average depth showed no clear dependence on flux. In the second experiment, etching times of 30–600 s were tested for InAl, In, and Al droplets. Average nanohole diameters remained constant for Al across all etching times, but decreased for In and InAl with increasing etching time, suggesting sidewall redeposition during etching. For all droplet types, depths peaked at intermediate times and decreased for prolonged etching, consistent with material diffusion into the nanohole after droplet consumption. Full article

This study focused on the abnormal phosphorylation of tau and its aggregation process, characteristic of Alzheimer’s disease, and aimed to compare the morphology and formation process of phosphorylated tau aggregates produced by four kinases: Cdk5/p25, GSK3β, MARK4, and p38α. Using quantum dots for 2D and 3D structural analysis, tau aggregates were confirmed in non-phosphorylated tau (non p-tau), as well as tau phosphorylated by GSK3β and MARK4. Aggregation initiation times were observed around 72 h for non-p-tau, and around 96 h for GSK3β and MARK4 phosphorylated tau. The thickness of non-p-tau aggregates was approximately 11 μm, while GSK3β aggregates were significantly thicker (13 μm) and exhibited increased density. TEM analysis suggested that tau forming wavy filaments was less prone to forming large aggregates. ThT assays and CD spectra showed an increased β-sheet structure for all kinases. Non-p-tau and GSK3β exhibited an increased right-twisted β-sheet structure, while Cdk5/p25, MARK4, and p38α showed an increased left-twisted β-sheet structure. The direct correlation between kinase activity and tau aggregate morphology revealed in this study provides a potential mechanistic basis for understanding disease heterogeneity and establishing novel therapeutic targets for AD specifically or for other neurodegenerative diseases as well. Full article

With the recently acquired knowledge of the use of a multiphase mixture of precursors under electron beam irradiation (EBI), new possibilities were opened for this technique. In the present work, we obtained quantum dots, nanocrystals, nanoparticles, and grains of PbSe with a sintered appearance using a biphasic mixture of PbSe and PbSeO₃ under EBI. High-energy milling was used to obtain the biphasic mixture of precursors, which is composed of agglomerates with sizes ranging from ~400 to ~1700 nm, but nanoparticles were also present. The structural details of the biphasic mixture were studied using X-ray diffraction and the Rietveld method. The driving force of the EBI caused instantaneous physical and chemical changes due to the high internal energy of the biphasic mixture of precursors. The abrupt release of high internal energy, due to localized heating effects during EBI, gave way to the formation of multi-scale PbSe structures. Large particles with a sintered appearance formed near the electron beam impact point and in regions between ~800 nm and ~1400 nm, while well-defined faceted nanostructures were predominantly observed beyond ~1400 nm. The latter tended to be surrounded by {200} facets as the main growth direction. Furthermore, coalescence was anticipated to occur during EBI. It occurred simultaneously with the sublimation mechanism when the particle size was below the critical size of 10 nm. Multi-scale PbSe structures, obtained via EBI, are promising for developing thermoelectric devices due to their crystallinity and nanostructured features. Full article

The development of quantum-enhanced technologies requires single-photon sources, as well as methods for their characterization and verification. Here, we describe a methodology for measuring the correlation function of a single-photon source using an experimental setup that comprises a laser-excited fluorescence microscope equipped with a Hanbury Brown–Twiss intensity interferometer as one of the detection systems. Measurements of the response function of the device and the reference samples are performed. The second-order autocorrelation function of the exciton state of GaAs quantum dots in AlGaAs nanowires is obtained and reveals a single-photon emission. Full article