Search Results (423)

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

Zn_1−xFe_xO nanocomposites (NCs) with varying Fe concentrations (x = 0, 0.1, 0.2, 0.3, and 0.4) were effectively prepared using the hydrothermal approach, and their morphology, structural, optical, and magnetic properties were systematically analyzed. XRD analysis confirmed Fe doping reduced crystallinity and crystallite size. TEM images of Zn_1−xFe_xO NCs exhibited smaller and more agglomerated nanostructures compared to the pure ZnO NPs. Raman and XPS analyses indicated increased lattice disorder, oxygen vacancies, and the coexistence of Fe²⁺/Fe³⁺ species. UV–Vis spectra showed enhanced visible light absorption and a tunable band gap, while PL results reflected defect-induced emission shifts and quenching, associated with zinc vacancies, interstitials, and oxygen-related defects. Magnetic measurements revealed a transition from diamagnetism to ferromagnetic-like behavior at room temperature for Fe content x ≥ 0.2, with magnetization strongly dependent on doping level. These results highlight Zn_1−xFe_xO for advanced optoelectronic and spintronic applications. Full article

Manganese(II) halide complexes with the general formula [MnX₂{(PhN=PPh₂)CH₂}], where X is bromine or iodine and (PhN=PPh₂)CH₂ is the bis-phosphanimine ligand 1,1′-methylenebis-(N,1,1-triphenylphosphanimine), were prepared and isolated. The structure of the two compounds was determined by single-crystal X-ray diffraction, revealing an approximately tetrahedral geometry at the metal centre. Unlike structurally comparable compounds containing phosphine oxides or related [O=P]-donors in the coordination sphere, which commonly show green emissions, solid samples of [MnBr₂{(PhN=PPh₂)CH₂}] and [MnI₂{(PhN=PPh₂)CH₂}] exhibited orange emissions upon irradiation with UV light. The emission spectra resulted excitation-independent. Superimposable steady-state luminescence spectra were collected for both compounds as powders and crystals suitable for X-ray diffraction. The excitation spectra and the ligand→metal antenna effect were affected by the coordinated halide, and only [MnBr₂{(PhN=PPh₂)CH₂}] showed bright luminescence under near-UV irradiation. Either ligand- or metal-centred transitions can account for the observed luminescence, and the luminescence decay curves were consistent with a multiplicity change from the excited to the ground state, with excited-state lifetimes in the range of hundreds of microseconds. Attempts to rationalize the unexpected luminescence were carried out based on DFT calculations. Full article

Monodisperse mesoporous hollow silica microcapsules present unique opportunities for advanced optical characterization due to their tunable nanostructure, high porosity and easy functionalization. A critical and challenging parameter in the optimization of these applications is the accurate determination of the effective refractive index, which governs light propagation and confinement within the nanostructured matrix of such mesoporous materials. In this study, individual mesoporous hollow silica microcapsules doped with Rhodamine B dye were analysed optically by exploiting whispering gallery mode (WGM) resonances, enabling non-destructive, single-particle refractometry with nanostructural sensitivity. Fourier Transform analysis of the fluorescence emission spectra revealed sharply defined, periodically spaced WGM peaks. For microcapsules with an 88 $\mu$m diameter, the measured intermodal spacing ($\Delta \lambda = 1.296$ nm) yielded an effective refractive index of 1.164. The measured value of the effective refractive index was cross-validated using Lorenz–Lorentz and Bruggeman effective medium models, both predicting porosity values (~63%) that closely match independent Brunauer–Emmett–Teller (BET) nitrogen adsorption measurements. The excellent agreement between optical and adsorption-based porosity demonstrates that WGM spectroscopy combined with Fourier analysis is a powerful, label-free, and non-invasive technique for correlating nanoscale porosity with macroscopic optical properties. This approach is widely applicable to single-particle analyses of nanostructured dielectric materials and opens new possibilities for in situ optical metrology in the development of advanced photonic, catalytic, and biomedical platforms. Full article

Perovskite light-emitting diodes (PeLEDs) have garnered significant interest owing to their exceptional color purity, broadly tunable emission spectra, and cost-effective solution processability. However, blue PeLEDs continue to underperform in efficiency and operational stability compared to their red and green counterparts, primarily due to defect-induced non-radiative recombination losses and inefficient exciton management. Herein, we demonstrate a synergistic approach that integrates multi-cation compositional engineering with triplet exciton management by incorporating a high-triplet-energy material, mCBP (3,3-Di(9H-carbazol-9-yl)biphenyl), during film fabrication. Temperature-dependent photoluminescence reveals that mCBP incorporation significantly enhances the exciton binding energy from 49.36 meV to 68.84 meV and reduces phonon coupling strength, indicating improved exciton stability and suppressed non-radiative channels. The corresponding PeLEDs achieve a peak external quantum efficiency of 10.2% and a maximum luminance exceeding 12,000 cd/m², demonstrating the effectiveness of this solution-based triplet management strategy. This work highlights the critical role of scalable, solution-processed triplet exciton management strategies in advancing blue PeLED performance, offering a practical pathway toward high-performance perovskite-based display and lighting technologies. Full article

Contemporary science is seeking simple and scalable methods of producing stable colloidal solutions of carbon nanomaterials that have favorable optical properties. Pyrolytic carbon (PyC), a by-product of methane pyrolysis, is a promising sustainable material. This study developed a method of obtaining stable PyC colloids using ultrasonic homogenization and investigated the effects of solvent polarity on dispersion, stability, and photoluminescence. Mechanically fragmented PyC was ultrasonically treated in ethanol, acetonitrile, and cyclohexane. Characterization using dynamic light scattering, UV-Vis spectroscopy, photoluminescence, Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and electron microscopy revealed that solvent polarity significantly influenced fragmentation and colloid stability. Polar solvents, especially ethanol, promoted better dispersion of aggregates, whereas nonpolar cyclohexane produced smaller, yet unstable aggregates. Raman and FT-IR analyses confirmed graphitic domains and oxygen-containing surface groups, which are critical to colloidal stability. UV-Vis spectra displayed solvent-dependent shifts in absorption edges, while photoluminescence spectra showed blue emission centered at ~490 nm, which is linked to surface states. Electron microscopy verified the presence of spherical nanoparticles with a diameter of ~20 nm and high carbon purity after sedimentation. These results demonstrate that ultrasonic treatment combined with solvent selection provides a straightforward route to photoluminescent PyC colloids with potential applications in sensors, bioimaging, and optoelectronics. Full article

TiO₂ nanoparticles were synthesized by a nitric acid-assisted sol–gel route using three different amounts of nitric acid (NA) (0, 0.05, and 0.10 mL HNO₃) to investigate how controlled acid addition influences their structural, optical, and photocatalytic behavior under visible-light irradiation. X-ray diffraction and Raman spectroscopy confirmed the formation of phase-pure anatase TiO₂, with slightly increased crystallinity and crystallite size upon NA incorporation. UV–Vis absorption and Tauc analysis revealed a systematic blue shift in the absorption edge accompanied by band-gap widening, attributed to electron–hole confinement and defect-state modification. Photoluminescence spectra showed enhanced visible emission with increasing acid content, indicating a higher density of oxygen vacancies and Ti³⁺ centers. SEM–EDX analysis verified homogeneous morphology, Ti–O stoichiometry, and the absence of extrinsic impurities. Although the TiO₂ sample prepared with 0.10 mL of HNO₃ (FNA) showed a wider band gap and slightly larger crystallite size, it still delivered the highest photocatalytic performance in methylene blue degradation, reaching about 74.8% removal after 240 min of visible-light exposure. This unexpected behavior can be explained by a defect-related mechanism in which NA promotes the formation of surface oxygen vacancies and Ti³⁺ sites. Because of these defects, new electronic states appear between the valence and conduction bands, allowing the material to absorb lower-energy light and improving how electrons interact with the dye. Full article

Oligo(arylene ethynylene)s (OAEs) containing 4,5-(diethynylaryl)-1,2,3-triazoles with 3(OMe) and NR₂ substituents at the 5-position and bis-1,4-dialkoxybenzene moieties as spacers at the 4-position were obtained using the retro-Favorskii reaction as a key step. The most intense fluorescence was observed for OAEs with a trimethoxyphenyl substituent in THF solutions, with a quantum yield of up to 88%. Increasing the solvent polarity had minimal effect on the emission of trimethoxyphenyl substituted derivatives. A notable red shift in emission spectra was observed with increasing solvent polarity for OAEs 10a,g containing para-dimethylaminophenyl group. Their emission spectra in aqueous organic solutions revealed that an increase in water fraction in THF/water mixtures led to a bathochromic shift in emission spectra maxima accompanied by a hypochromic effect. An increase in intensity was observed in aqueous acetonitrile and DMSO. The maximum intensity was observed in DMSO solutions containing 30% water, which is attributed to aggregate-induced emission enhancement. Dynamic light scattering data also confirmed the formation of nanoscale aggregates in aqueous organic mixtures. Full article

Roasting intensity and cultivar shape the physicochemical composition and sensory characteristics of date seed-based coffee alternatives. This study evaluated quality traits among eight date seed cultivars (Zahidi, Medjool, Deglet nour, Thoory, Halawi, Barhee, Khadrawy, Bau Strami) roasted at three intensities (light: 180 °C; medium: 200 °C; dark: 220 °C) using digital technologies, including near-infrared spectroscopy (NIR), electronic nose (e-nose), and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), supported by machine learning (ML) modeling. NIR spectra showed distinct chemical fingerprints for date seed powders and beverages, with key absorption bands from 1673–2396 nm and 1720–1927/2238–2396 nm, respectively. E-nose outputs showed higher volatile emissions in dark-roasted samples, particularly for ethanol and NH₃. GC-MS identified 25 volatile compounds, mainly pyrazines and furanic compounds. Pyrazine concentration was greatest in Bau Strami and Medjool cultivars, whereas Halawi and Thoory cultivars had greater content of furfural. Two ML classification models achieved high accuracy in classifying cultivars (NIR inputs: 99%; e-nose inputs: 98%) and roasting levels, while regression models (NIR inputs: R = 0.88; e-nose inputs: R = 0.90) effectively predicted volatile aromatic compounds obtained using GC-MS. Dark roasting resulted in a significant pH reduction and intensified browning, with furfural persisting as a stable aroma contributor. These findings highlight the potential of date seeds as a coffee alternative, with roasting level and cultivar selection influencing flavor profiles. The findings also demonstrate the utility of digital sensing technologies as an efficient, low-cost tool for rapid quality assessment and process optimization in the development of novel beverages. Full article

This study presents the development of a portable DOBI meter prototype designed for the rapid, low-cost evaluation of crude red palm oil (RPO) quality. The device employs two narrow-spectrum LEDs (UV at 269 nm and visible at 446 nm) as light sources, paired with a broadband photodiode (PD) detector to measure light absorption in a quartz cuvette containing 95% hexane-diluted oil samples. Dedicated LED driver circuits, a PD receiver module, and microcontroller-based data acquisition and display systems were integrated into a compact enclosure. Calibration procedures involved the measurement of LED emission spectra and PD responses, followed by standard curve generation using known RPO concentrations. The results from the DOBI meter were validated against a commercial spectrophotometer (Merck Prove 600), demonstrating high accuracy with less than 5% deviation. Further analysis of RPO extracted from microwave-treated mesocarps showed consistent DOBI values and carotenoid concentrations across both instruments. The developed device offers a reliable, accessible alternative for assessing palm oil quality, particularly in field or small-scale industrial settings. Full article

Liposomal systems are advanced carriers of active substances which, thanks to their ability to encapsulate these substances, significantly improve their pharmacokinetics, bioavailability, and selectivity. This article presents the results of spectroscopic studies for a selected compound from the 1,3,4-thiadiazole group, namely 4-[5-(naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD, see below in the text), in selected liposomal systems formed from the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Detailed spectroscopic analyses were carried out using electronic absorption and fluorescence spectroscopy; resonance light scattering (RLS) spectra measurements; dynamic light scattering (DLS); as well as time-resolved methods—fluorescence lifetime measurements using the TCSPC technique. Subsequently, based on the interpretation of spectra obtained by FTIR infrared spectroscopy, the preliminary molecular organization of the above-mentioned compounds within lipid multilayers was determined. It was found that NTBD preferentially occupies the region of polar lipid headgroups in the lipid multilayer, although it also noticeably interacts with the hydrocarbon chains of the lipids. Furthermore, X-ray diffraction (XRD) techniques were used to study the effect of NTBD on the molecular organization of DPPC lipid multilayers. Monomeric structures and aggregated forms of the above-mentioned 1,3,4-thiadiazole analogue were characterized using X-ray crystallography. Interesting dual fluorescence effects observed in steady-state fluorescence measurements were linked to the excited-state intramolecular proton transfer (ESIPT) effect (based on our earlier studies), which, in the obtained biophysical systems—liposomal systems with strong hydrophobicity—is greatly enhanced by aggregation-induced emission (AIE) effects. In summary, the research presented in this study, concerning the novel 1,3,4-thiadiazole derivative NTBD, is highly relevant to drug delivery systems, such as various model liposomal systems, as it demonstrates that depending on the concentration of the selected fluorophore, different forms may be present, allowing for appropriate modulation of its biological activity. Full article

Nanocrystalline CoWO₄ sampled were synthesized using a simple mechanochemical approach and a solid-state reaction, respectively. The formation of nanocrystalline CoWO₄ was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The optical properties of the obtained samples were explored by diffuse reflectance UV–visible (DRS) and photoluminescence (PL) techniques. A milling speed of 850 rpm led to the direct synthesis of monoclinic CoWO₄ with a short reaction time (1 h). The complete reaction did not occur in the solid-state synthesis. The obtained samples had monoclinic crystal systems with different lattice parameters. The average crystallite sizes of CoWO₄ were in the range of 20 to 180 nm. The TEM investigation showed that the morphology of the CoWO₄ particles differed depending on the preparation conditions. The values of the determined optical bandgap of CoWO₄ were the range of 1.89 to 2.18 eV, according to diffusion reflectance spectroscopy in the ultraviolet-to-visible range. Broader blue–green emission spectra with peaks at 430 nm were observed for samples prepared via both routes. The CIE color coordinates of the CoWO₄ samples lay in the blue and purple regions. The quantum yields of the CoWO₄ samples synthesized after 1 h and 5 h milling times at 850 rom were 0.34 and 0.67%, respectively. This study proposes an affordable mechanochemical approach for blue–green phosphors that could possibly be used in various light-emitting diodes (LEDs). Full article

This paper presents a test and analysis of a lateral-offset optical fiber Mach-Zehnder interferometer (MZI) employed as a chloride ion concentration sensor using a near-infrared light source (amplified spontaneous emission, wavelength = 1520–1620 nm). An 8 cm optical fiber MZI sensor was fabricated and fusion-spliced using a lateral-offset process. We used this 8 cm lateral-offset optical fiber MZI to measure chloride ions in samples of sodium chloride solutions with different weight concentrations ranging from 0.015% to 25% and then analyzed the interference spectra regarding their normalized intensity and wavelength shift and three integral area ranges (1520–1580 nm, 1540–1600 nm, and 1520–1620 nm). The comparative spectral analysis results show that the lateral-offset optical fiber MZI sensor exhibited a linear decrease in its normalized intensity as well as a wavelength shift when the concentration increased. The lateral-offset optical fiber MZI sensor displayed a sine wave plot in the three integral area ranges when the concentration increased. Other than sensing parameters such as the normalized intensity (adjusted R-squared = 0.98223) or wavelength shift (adjusted R-squared = 0.94209), the three integral area ranges (adjusted R-squared = 0.96425, 0.91621, and 0.9577, respectively), which possessed adjusted R-squared values greater than 0.9, are also recommended for use as sensing parameters for the testing and analysis of a lateral-offset optical fiber MZI employed as a chloride ion concentration sensor using a near-infrared light source. Full article

Skin cancer is the most frequently diagnosed form of cancer worldwide. Diagnostic uncertainty can arise when macroscopic or dermoscopic evaluations do not clearly differentiate between benign and malignant lesions. Laser-induced plasma spectroscopy (LIPS), traditionally used in fields like materials science and environmental analysis, has recently gained attention for its applications in human tissue assessment. LIPS works by generating a (micro)plasma when a laser interacts with tissue, producing element-specific light emissions that can be analyzed in real time. In this study, we explored the potential of LIPS to differentiate between benign and malignant skin lesions using the Spectra-Scope^® Score (SSS). Our results revealed a clear distinction: benign lesions showed a median SSS of 1.7, while suspicious and malignant lesions had a significantly higher median score of 8.1 (p < 0.001). Receiver operating characteristic (ROC) curve analysis demonstrated strong diagnostic performance, with an area under the curve (AUC) of 0.82 (p < 0.001). The findings of this preliminary study support the high accuracy of LIPS in identifying malignancy and underscore its promise as a non-invasive, real-time diagnostic aid. Integrating SSS into clinical workflows could enhance the early detection of skin cancer and reduce reliance on invasive diagnostic procedures. However, further validation is needed to fully establish its role in routine dermatological practice. Full article

Cd-based perovskite materials have the advantages of high emission efficiency and tunable emission, as well as broad application prospects in the field of optoelectronics. However, achieving multimode dynamic luminescence under UV light excitation in a single system is a great challenge. Here, we successfully prepared Sb³⁺/Pb²⁺ co-doped Cs₇Cd₃Br₁₃ crystals by a simple hydrothermal method. Tunable emission from orange to white and then to blue, covering the wavelength range between 370 and 800 nm, was achieved by varying the doping concentration of Pb²⁺ ions in Cs₇Cd₃Br₁₃:0.5%Sb³⁺. Temperature-dependent photoluminescence (PL) spectra and density functional theory (DFT) calculations confirm that the wide-band white-light emission of Cs₇Cd₃Br₁₃: Sb³⁺/Pb²⁺ crystal comes from the first self-trapped exciton (STE1) of undoped Cs₇Cd₃Br₁₃ intrinsic capture state and the emission of free excitons (FEs) and STE2 induced by the confining effect and the Jahn–Teller effect by Pb²⁺ incorporation, as well as the Sb triplet self-trapped exciton (STE3). More specifically, the samples with the best co-doped ratio exhibit significant excitation-wavelength-dependent luminescence characteristics and can realize the conversion of the emission color from white and blue to orange. Based on the tunable emission characteristics of three emission colors, the material has good prospects in encryption and anti-counterfeiting applications. This work provides a new strategy for the application of Cd-based halides in the field of anti-counterfeiting. Full article