Thiram (Thr) residues pose potential risks to ecological environment and human health. Herein, a simple multi-channel colorimetric assay for Thr detection was proposed. Cu2+ served as the colorimetric probe, and coordinated with Thr, forming Cu2+-Thr complex with satisfactory oxidase (OXD)-like and laccase (LAC)-like activity. The catalytic kinetics of Cu2+-Thr complex well fitted Michaelis-Menten model. Leveraging Thr activated OXD and LAC-like activities of Cu2+, colorimetric assays for Thr detection were developed. The detection range and limit of detection of this method were comparable to those methods involving nanomaterials. By integrating smartphone with test papers and test swabs, two portable sensing platforms were developed to achieve on-site detection of Thr. The concentrations of Thr in food and water samples were successfully determined via multiple channels with satisfactory recoveries and relative standard deviation. The simple and low-cost multi-channel colorimetric sensing platforms showed potential for food safety analysis and environmental monitoring.
Achieving a circular plastics economy requires the high-purity identification of plastic flakes among diverse non-plastic contaminants in recycling streams. To this end, the accurate and rapid measurement of impurity levels in flake feedstock is crucial for the industry to ensure high-quality secondary raw materials. Short-wave infrared hyperspectral imaging (HSI) is well-suited to this task because structure-specific CH vibrational overtones provide chemical fingerprints, yet the large spectral dimensionality of HSI imposes substantial acquisition and computational demands that have limited its practical deployment. Here, we present a filter-wheel-based band-target imaging (BTI) framework in which the multispectral band set is rationally derived from spectroscopic and hyperspectral analysis. By relating the hydrogen distribution of five plastic monomer units and two contaminants to their second- and first-overtone absorption features in the 1100-1700 nm region, six diagnostic bands are selected to maximize inter-class spectral variance. The implemented BTI system, coupled with a deep learning-based object detector, reduces the per-frame acquisition time to under 2 s for the entire 2D region while achieving a mean average precision (mAP@0.5) of 91.8% across the seven target classes. Ultimately, this integrated approach demonstrates the potential for chemically specific identification of plastic flakes, offering a promising step toward the sustainable recovery of high-purity plastic resources.
Herein, a novel fluorescence "off-on" sensing system was developed for ultrasensitive detection of H2O2 by integrating carbon dots (CDs) with Au@Ag core-shell nanorods (Au@Ag NRs). The detection mechanism lies in the H2O2-triggered etching of the silver shell on Au@Ag NRs, which enables reversible modulation of the fluorescence resonance energy transfer (FRET) between CDs (donor) and Au@Ag NRs (acceptor). Initially, the fluorescence of CDs is efficiently quenched (turn-off) by Au@Ag NRs via FRET. Upon addition of H2O2, the Ag0 shell is gradually oxidized into Ag+, including a red shift in the UV-vis absorption spectrum of Au@Ag NRs and thus weakening the FRET effect, leading to fluorescence recovery (turn on). The fluorescence recovery value (ΔF) is linearly correlated with H2O2 concentration in the range of 0.1-50 μM (R2 = 0.996), with a detection limit as low as 0.01 μM. The CDs-Au@Ag NRs nanoprobe exhibits excellent selectivity toward H2O2 over other potential interferents. The proposed system was successfully applied to detect H2O2 in real food samples, including sausages and pickled chicken feet, demonstrating its practical utility for routine monitoring of H2O2 residues in complex processed meat products.
Apoptosis is accompanied by dynamic alterations in lysosomal microenvironmental parameters including polarity; therefore, real-time monitoring of these changes is essential for elucidating apoptotic mechanisms. Herein, a tetrahydrocarbazole-based fluorescent probe TC-AP-ID with a D-π-A structure was rationally designed and synthesized for polarity detection. The probe exhibited a remarkable solvatochromic effect: the maximum emission wavelength was red-shifted from 606 nm to 653 nm as the 1,4-dioxane/water ratio decreased from 99/1 to 1/99 (v/v), accompanied by a gradual decrease in fluorescence intensity. The probe demonstrated excellent emission stability over a wide pH range of 3-11. Colocalization experiments with Lyso-Tracker Green in HeLa cells yielded a high Pearson correlation coefficient of 0.95. The probe successfully realized real-time imaging of apoptosis induced by cisplatin (0-50 μM) and polarity changes during H2O2-mediated oxidative stress in live HeLa cells and zebrafish larvae. These findings indicated that probe TC-AP-ID was an effective tool for investigating lysosomal microenvironmental alteration in apoptotic progression and drug-induced cytotoxicity.
Opals are hydrated amorphous to poorly crystalline silica phases that form in a wide range of geological environments. Recent studies have shown that the shape of water-related absorption bands in the near infrared domain can be used as a potential proxy for deciphering opal genesis processes. However, the physicochemical parameters controlling the shape of the absorption, and thus its use as a criterion for genesis studies, have not yet been experimentally constrained. We examined whether temperature, pH, and the resulting microstructures independently influence the CRC (Concavity Ratio Criterion), which quantifies whether the low-frequency side of the absorption band is concave or convex. In this study, amorphous silica analogous to opal-A was synthesized under controlled laboratory conditions using the Stöber routine, varying in temperature (25-70 °C) and pH (≈0.6-12). The resulting materials were imaged by scanning electron microscopy to assess microstructural changes, and by near-infrared spectroscopy (4000-8000 cm-1) to investigate the speciation and bonding state of water. The results show that temperature primarily influences particle size and size distribution, with only a minor effect on the Near InfraRed (NIR) spectral signature. In contrast, pH exerts a strong control on both silica structure and water speciation, leading to significant variations in CRC values. These experimental results demonstrate that the CRC is mainly governed by fluid chemistry rather than microstructure. The CRC therefore constitutes a robust proxy for constraining the chemical conditions of opal formation, with important implications for interpreting terrestrial deposits and remote sensing observations of hydrated silica on planetary surfaces, including Mars.
Walnut oil is a high-value edible oil with complex lipid composition, but its adulteration with lower-cost vegetable oils remains difficult to identify because different edible oils share highly similar Raman vibrational fingerprints. In particular, low-level adulteration induces only weak and localized spectral variations, while the major lipid-related Raman bands are strongly overlapped. To address these challenges, this study developed RamanFusionNet, a multi-level feature fusion-enhanced Net for weak Raman spectral fingerprint analysis of multi-source walnut oil adulteration. Unlike conventional approaches that rely primarily on a single spectral representation or a single model, RamanFusionNet combines raw spectral-band features, local differential descriptors, multiscale statistical features, and fast Fourier transform-based frequency-domain features. These complementary representations characterize changes in peak intensity, peak shape, and local spectral profiles caused by low-level adulteration. Ensemble modeling was further used to reduce the sensitivity of individual models to spectral noise and data partitioning, thereby enabling the identification of adulterant oil types and the prediction of adulteration levels. Experimental results show that RamanFusionNet can effectively distinguish between pure walnut oil and various adulterated oils, with an AUC of up to 0.996, a Spec of up to 0.993, and optimal regression performance of RMSE = 0.021 and R2= 0.991. For samples adulterated at a low concentration of 1%, the model achieved an RMSE of 0.0328 and an MAE of 0.0278.
AIE-based biological probes have attracted extensive research attention owing to their remarkable merits, such as high fluorescence brightness, long-term in-situ retention capacity, outstanding photostability and low cytotoxicity. Meanwhile, lipid droplets (LDs) have been proven to participate in a variety of vital biological processes. Accordingly, we rationally designed and synthesized an intramolecular charge transfer (ICT) fluorescent probe Py-TM featuring typical aggregation-caused quenching (ACQ) characteristics, and further modified its molecular skeleton to construct an AIE-active probe Py-TM-Me. The as-synthesized Py-TM-Me exhibits excellent polarity responsiveness, a large Stokes shift, favorable photostability and superior biocompatibility. It also possesses high detection sensitivity and precise lipid droplet-targeting capacity, enabling high-contrast fluorescence imaging of intracellular lipid droplets, and simultaneously shows specific lysosome-targeting performance. Moreover, Py-TM-Me can be applied to monitor intracellular microenvironmental polarity fluctuations and in vivo fluorescence imaging in zebrafish, which offers a novel tool for future investigations on human lipid droplet-related diseases.
UV-Vis spectroscopy is widely used for the determination of nitrate nitrogen (NO3-N) and chemical oxygen demand (COD) in water. However, the determination results are susceptible to interference from temperature and turbidity, leading to reduced detection accuracy for NO3-N and COD. Existing studies have primarily focused on correcting individual interference factors, but research on the effects of temperature-turbidity coupled interference on the spectra of NO3-N and COD mixed solutions, as well as corresponding compensation methods, remains relatively scarce. To address this issue, this paper proposes a Sequential Double EPO strategy, which achieves stepwise separation and correction of interference information by sequentially constructing subspaces for temperature and turbidity interference. First, this study evaluated the compensation capabilities of EPO for single-type temperature and turbidity interference under individual interference conditions. Subsequently, the impact of temperature-turbidity coupled interference on the spectra of mixed solutions was analyzed to determine the interference correction sequence under dual interference conditions. Second, based on this analysis, the Sequential Double EPO compensation strategy was proposed to sequentially separate and compensate for temperature and turbidity interferences. Finally, partial least squares regression (PLS) was used to establish quantitative prediction models for NO3-N and COD. Experimental results indicate that the Sequential Double EPO strategy can compensate for temperature and turbidity interferences, effectively reducing spectral bias and improving spectral consistency. Compared with other methods, the PLS models established using SDEPO-compensated spectra achieved coefficients of determination (R2) of 0.9160 and 0.9441 for NO3-N and COD prediction, respectively, with RPD values of 3.4866 and 4.2040, demonstrating superior predictive stability and model robustness.
Metal-peptide frameworks (MPFs) have gained considerable attention due to their advantages and properties, particularly in the field of biomedicine. In the current study in situ synchrotron powder X-ray diffraction (XRD) and Raman spectroscopy measurements under high pressure-room temperature conditions were conducted on Cd(Gly-L-Phe)2 MPFs. The compound crystallizes in a monoclinic structure from C2 space group. Computational calculations were performed to assign the vibrational modes, yielding good agreement with the experimental data. High-pressure XRD analysis showed no structural phase transition, but hinted at a possible conformational change. After compression in the Raman spectroscopy experiment, vibrational analysis suggests a conformational rearrangement of Cd(Gly-L-Phe)2 in the 1-2 GPa pressure range, corroborating the changes observed in the high-pressure XRD analysis. Upon decompression, the changes in the Cd(Gly-L-Phe)2 sample proved to be reversible. These investigations contribute to a better understanding of the behavior of MPFs under pressure, which is highly relevant for their potential applications in the biomedical field.
The detection performance of surface-enhanced Raman scattering (SERS) substrates is closely related to their three-dimensional plasmonic nanostructures. In this work, a series of three-dimensional porous hovenia acerba-like silver nanostructure-decorated polyvinyl alcohol hydrogel (HA-AgNPs@PVA) SERS substrates were fabricated by a facile in-situ chemical reduction strategy. Three-dimensional porous plasmonic nanostructures possess numerous nanopores, capable of forming multi-level and high-density hot spots. Additionally, the porous nanostructures can accommodate a greater number of probe molecules, significantly enhancing SERS performance. Using crystal violet as probe molecule, the optimized HA-AgNPs@PVA SERS substrate achieves a detection sensitivity of 10-10 M and an enhancement factor of 1.6 × 108. Moreover, flexible HA-AgNPs@PVA SERS substrate was applied for the detection of thiram on various fruit surfaces using a "stick-and-read" approach, delivering a high detection sensitivity of 10-8 M and demonstrating excellent quantitative detection capability. The developed flexible SERS platform exhibits great potential for on-site food safety monitoring.
Nitroreductase (NTR) can efficiently reduce the nitro group of compounds to an amino group using nicotinamide adenine dinucleotide (NADH) as an electron source. Its expression is upregulated under hypoxic conditions, making it a reliable marker for the degree of hypoxia in tumor cells. Herein, we designed and synthesized a dual-functional iridium complex-based fluorescent probe Ir-NO2 that targets mitochondria, specifically recognizes NTR, and serves as an NTR-activatable photosensitizer for photodynamic therapy (PDT) of tumor cells. The probe is capable of detecting both endogenous and exogenous NTR in cells, as well as enabling NTR recognition in zebrafish. Upon NTR detection, the singlet oxygen yield increased from 0.71 to 0.83. Moreover, both the probe and its NTR-recognized strongly fluorescent produce (Ir-OH) function as dual Type I/II PDT photosensitizers.
Five flavonols bearing electron-donating and electron-withdrawing substituents were synthesized and characterized by NMR spectroscopy, mass spectrometry, UV-Vis spectroscopy, and cyclic voltammetry. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were performed to investigate their molecular geometries, frontier molecular orbitals, electronic structures, and excited-state properties. The optimized geometries revealed that flavonols containing substituents at both the C2' and C6' positions adopt non-planar conformations, whereas the remaining derivatives are essentially planar. Potential energy surface calculations showed that steric interactions between the 3-hydroxyl group and the ortho substituents stabilize the twisted conformations and reduce π-conjugation. The HOMOs were predominantly localized on rings B and C, while the LUMOs were distributed over rings A and C, indicating similar oxidation and reduction centres throughout the series. Electron-donating substituents raised the HOMO energies, resulting in lower oxidation potentials and red-shifted UV-Vis absorption bands. TDDFT calculations accurately reproduced the experimental absorption spectra and confirmed that the lowest-energy electronic excitation is dominated by the HOMO→LUMO transition. Strong correlations were observed between the experimental electrochemical energy gap and the DFT-calculated HOMO-LUMO energy gap (R2 = 0.92), while excellent agreement was obtained between the calculated and experimental absorption maxima (R2 = 0.98). The excellent agreement between experimental and computational parameters establishes quantitative structure-electronic property relationships for flavonols by integrating DFT, TDDFT, UV-Vis spectroscopy and electrochemistry, and provides a predictive basis for the rational design of flavonol-based functional materials and biologically active derivatives.
Surface-enhanced Raman scattering (SERS) is a powerful tool for rapid on-site detection of pesticide residues, but its performance heavily relies on the substrate. Herein, a gelatin‑silver nanocube (Ag NC) composite hydrogel SERS substrate was developed via mild EDC-NHS crosslinking coupled with low-temperature gelation. The three-dimensional porous hydrogel efficiently enriches target molecules, while the sharp edges of Ag NCs generate abundant electromagnetic hotspots. Using rhodamine 6G as a probe, the optimized substrate (20% gelatin, Ag NC/gelatin volume ratio 3:1) exhibited good uniformity, reproducibility, and stability. For thiram detection, a linear response was obtained from 10-4 to 10-7 M with a limit of detection (LOD) of 4.45 × 10-8 M in standard solution. Practical applicability was demonstrated in orange juice, where thiram was detected down to 1.0 × 10-6 M (LOD = 4.78 × 10-7 M) with recoveries of 96.9-97.9%. This work provides a gelatin-based, stable and sensitive SERS platform for food safety monitoring.
Spinal cord injury (SCI) triggers a devastating secondary cascade of neuroinflammation and metabolic failure that extends functional deficits well beyond the initial impact site. Mitigating this progressive degeneration remains a critical challenge in regenerative medicine. This study investigated the neuroprotective efficacy of a 14-day 808-nm infrared photobiomodulation (PBM) regimen in a rat spinal cord contusion model. To objectively characterize microenvironmental molecular dynamics, Fourier-transform Raman (FT-Raman) spectroscopy was coupled with Principal Component Analysis (PCA) and validated via Hematoxylin and Eosin (H&E) and Luxol Fast Blue (LFB) histology. The results demonstrated that PBM effectively stabilizes the biochemical microenvironment 1 cm cranial to the lesion epicenter. Spectroscopic profiling is consistent with the finding that PBM preserves protein structural integrity (Amide I, 1660 cm-1) and mitigates lipid disorder associated with myelin sheath degradation (2929-2859 cm-1). Furthermore, PBM normalized glucose-related vibrational signatures (1123 cm-1), thereby reducing the accumulation of unmetabolized substrates and suggesting improved tissue homeostasis. Moreover, spatial analysis revealed a differential therapeutic response: the cranial segment showed significant tissue sparing, whereas the distal segment exhibited higher resistance to treatment. Together, these findings indicate the potential of PBM as a targeted, non-invasive strategy to limit SCI propagation while highlighting FT-Raman spectroscopy as an effective, label-free platform for monitoring molecular neural repair.
For ATP detection, indicator displacement assays with multicationic macrocyclic hosts and anionic fluorescent dye guests represent an intuitive design strategy. However, such systems typically exhibit turn-off responses. For biological samples with strong background- and autofluorescence, ratiometric or turn-on signaling is preferred, which requires more sophisticated assay architectures. In the present work, the host-guest complexation of fluorescent pH indicator dye trisodium 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) with a cationic ammonium-pillar[6]arene (AP6) was employed in the design of indicator displacement assays featuring two distinct detection modes for the fluorescent sensing of nucleotide ATP. In the first approach, AP6-assisted deprotonation of HPTS enabled the development of a colorimetric and a fluorescent ratiometric assay. In the second strategy, fluorescence turn-on sensing was achieved by exploiting the FRET-type quenching of HPTS fluorescence by AP6-modified reduced graphene oxide (rGO-AP6). Both sensing platforms demonstrated high selectivity toward ATP over structurally similar nucleotides and other biologically relevant anions, a broad dynamic range and a low limit of detection. The performance of the turn-on ATP sensor was validated in the complex biological matrix of human serum, demonstrating its applicability for practical bioanalytical applications.
Bone infections remain diagnostically challenging because current standard methods rely on microbiological and histopathological testing, which are time-consuming and may delay treatment decisions. This study evaluated handheld near-infrared spectroscopy for detecting spectral changes associated with staphylococcal inoculation in ex vivo human bone. An ex vivo bacterial inoculation model was established using human trabecular bone specimens inoculated with Staphylococcus aureus and Staphylococcus epidermidis. Spectra were acquired using a handheld NIR spectroscopy platform and analysed after standard normal variate preprocessing combined with either smoothing or first-derivative transformation. In total, 120 averaged spectra derived from 40 donors were included. Principal component analysis revealed partial clustering by inoculation status, particularly after derivative preprocessing, but substantial overlap remained. Linear discriminant analysis indicated stronger discrimination between inoculated and uninoculated bone than between the two staphylococcal species. However, classification performance depended on preprocessing and validation strategy; therefore, donor-wise dataset partitioning was used to reduce the risk of overly optimistic performance estimates caused by donor-level information leakage. These findings suggest that handheld NIR spectroscopy may provide rapid, non-destructive information on inoculation-associated spectral alterations in controlled ex vivo bone models. Further studies with sham-incubated controls, repeated donor-level cross-validation, independent external validation, additional pathogens, and clinically realistic confounders are required before clinical translation.
The potential of silica-based materials for sensing applications has long been underestimated. In this work, several strategies were explored to synthesize sol-gel materials suitable for carbonyl monitoring using fluorescence. The materials were designed to incorporate both a free amino group for the reaction with carbonyl compounds and a fluorescent core. The first and simplest strategy involved a single functional monomer, 4-trimethoxysilylaniline, which fulfilled both of the required criteria. To allow for a braoder choice of reactants , particularly in changing the fluorescent core, a second approach was employed using two functional monomers: one bearing an amino group (3-aminopropyltrimethoxysilane) and the other providing fluorescence (1-naphthyltrimethoxysilylaniline). Finally, a third strategy was developed to broaden the range of usable probes. This method involved solubilizing conventional fluorescent compounds (such as anthracene or fluorescein) into oil-in-water micelles, followed by polymerization of a silica matrix around them. Using these three strategies, four different materials were synthesized. Their potential for carbonyl sensing was evaluated based on their toxicity, adsorption capacity, and fluorescence response after interaction with hexanal. Although the materials synthesized via the third strategy exhibited fluorescence intensities up to 1000 times higher than those from the two other approaches, they also showed significant leakage of both the surfactant and the fluorescent probe. The results highlight the trade-offs associated with each synthesis route and identify candidates requiring subsequent concentration-dependent analytical characterization.
In this work, a multi-technique diagnostic analysis integrating spectroscopic/spectrophotometric and 3D imaging methods was successfully applied for the characterization of a large eighteenth-century Vergine Assunta wooden statue by Filippo Colicci, located within the apse of the right aisle of the Cathedral of Santa Maria Assunta in Novara di Sicilia, Italy. To this aim, an in situ, non-invasive survey, by applying X-ray fluorescence (XRF) spectroscopy, micro-Raman (μ-Raman) spectroscopy, Fourier transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR) and visible reflectance spectrometry (Vis-RS), was conducted to: (i) shed light on the nature of the raw materials and color palette used for the realization/decoration of the artwork; (ii) retrieve insights into execution technique; (iii) identify possible nondocumented interventions starting from the discrimination between original and modern constituents and (iv) evaluate potential degradation patterns associated to changes in microclimatic conditions and mechanical stress induced by liturgical handling and transportation. At the same time, a 3D LiDAR survey was implemented to assess damaged or weakened areas of the statue and to identify regions that may have undergone undocumented restoration handling. The achieved results represent useful and essential tools to address management issues of the artwork, providing valuable insights for planning and monitoring targeted and minimally invasive restoration strategies for its long-term safeguarding.
