Search Results (792)

Modifications in leaf architecture disrupt optical properties and internal light-scattering dynamics. Accurate modeling of leaf-scale light scattering is therefore essential not only for understanding how disease affects the availability of light for chlorophyll absorption, but also for evaluating its potential as an early optical marker for plant disease detection prior to visible symptom development. Conventional ray-tracing and radiative-transfer models rely on high-frequency approximations and thus fail to capture diffraction and coherent multiple-scattering effects when internal leaf structures are comparable to optical wavelengths. To overcome these limitations, we present a GPU-accelerated finite-difference time-domain (FDTD) framework for full-wave simulation of light propagation within plant leaves, using anatomically realistic dicot and monocot leaf cross-section geometries. Microscopic images acquired from publicly available sources were segmented into distinct tissue regions and assigned wavelength-dependent complex refractive indices to construct realistic electromagnetic models. The proposed FDTD framework successfully reproduced characteristic reflectance and transmittance spectra of healthy leaves across the visible and near-infrared (NIR) ranges. Quantitative agreement between the FDTD-computed spectral reflectance and transmittance and those predicted by the reference PROSPECT leaf optical model was evaluated using Lin’s concordance correlation coefficient. Higher concordance was observed for dicot leaves ($C_b=0.90$) than for monocot leaves ($C_b=0.79$), indicating a stronger agreement for anatomically complex dicot structures. Furthermore, simulations mimicking an early-stage fungal infection in a dicot leaf—modeled by the geometric introduction of melanized hyphae penetrating the cuticle and upper epidermis—revealed a pronounced reduction in visible green reflectance and a strong suppression of the NIR reflectance plateau. These trends are consistent with experimental observations reported in previous studies. Overall, this proof-of-concept study represents the first full-wave FDTD-based optical modeling of internal light scattering in plant leaves. The proposed framework enables direct electromagnetic analysis of pre- and post-penetration light-scattering dynamics during early fungal infection and establishes a foundation for exploiting leaf-scale light scattering as a next-generation, pre-symptomatic diagnostic indicator for plant fungal diseases. Full article

To investigate the treatment performance of a CuTiO₃ photocatalytic system for organic peroxide production wastewater under visible light, CuTiO₃ powder prepared through the hydrothermal method was used for this experiment. The light absorption properties of the CuTiO₃ catalyst were analyzed using Uv-Vis diffuse reflectance spectroscopy (Uv-Vis DRS). The effects of the initial pH, photocatalyst dosage, light intensity, and reaction duration on the photocatalytic reaction were examined. Before and after the reaction, the changes in pollutant components in water were characterized via three-dimensional excitation–emission matrix fluorescence spectrometry (3D-EEM) and gas chromatography–mass spectrometry (GC-MS); the changes in the concentrations of some pollutants were analyzed via wavelength scanning. The results indicated that CuTiO₃ has a good response to visible light. Under the optimized conditions (initial pH = 5, CuTiO₃ dosage = 1.2 g/L, light intensity = 1300 W/m², duration = 4 h), the COD removal rate reached 58%, and the B/C (BOD₅/COD) ratio of wastewater increased from 0.112 to 0.221, demonstrating a good pretreatment effect. GC-MS analysis demonstrated significant degradation effects on amide and hydride substances. Radical capture experiments verified hydroxyl radicals as the dominant species in CuTiO₃ photocatalysis. Visible-light photocatalysis using CuTiO₃ provides an efficient pretreatment pathway for organic peroxide production wastewater. Full article

Organic optoelectronic devices receive appreciable attention due to their low cost, ecology, mechanical flexibility, band-gap engineering, brightness, and solution process ability over a broad area. In this study, we designed and studied organic light-emitting diodes (OLEDs) consisting of an assembly of natural dyes, extracted from noble fir leaves (evergreen) and blue hydrangea flowers mixed with poly-methyl methacrylate (PMMA) as light emitters. We experimentally demonstrate the effective conversion of blue light emitted by an inorganic laser/photodiode into longer-wavelength red and green tunable photoluminescence due to the excitation of natural dye–PMMA nanostructures. UV-visible absorption and photoluminescence spectroscopy, ellipsometry, and Fourier transform infrared methods, together with optical microscopy, were performed for confirming and characterizing the properties of light-emitting diodes based on natural dyes. We highlighted the optical and physical properties of two different natural dyes and demonstrated how such characteristics can be exploited to make efficient LED devices. A strong pure red emission with a narrow full-width at half maximum (FWHM) of 23 nm in the noble fir dye–PMMA layer and a green emission with a FWHM of 45 nm in blue hydrangea dye–PMMA layer were observed. It was revealed that adding monolayer MoS₂ to the nanostructures can significantly enhance the photoluminescence of the natural dye due to a strong correlation between the emission bands of the inorganic–organic emitters and back mirror reflection of the excitation blue light from the monolayer. Based on the investigation of two natural dyes, we demonstrated viable pathways for scalable manufacturing of efficient hybrid OLEDs consisting of assembly of natural-dye polymers through low-cost, purely ecological, and convenient processes. Full article

Hyperspectral imaging (HSI) is a noncontact camera-based technique that enables deep learning models to learn various plant conditions by detecting light reflectance under illumination. In this study, we investigated the effects of four light sources—halogen (HAL), incandescent (INC), fluorescent (FLU), and light-emitting diodes (LED)—on the quality of spectral images and the vase life (VL) of cut roses, which are vulnerable to abiotic stresses. Cut roses ‘All For Love’ and ‘White Beauty’ were used to compare cultivar-specific visible reflectance characteristics associated with contrasting petal pigmentation. HSI was performed at four time points, yielding 640 images per light source from 40 cut roses. The results revealed that the light source strongly affected both the image quality (mAP@0.5 60–80%) and VL (0–3 d) of cut roses. The HAL lamp produced high-quality spectral images across wavelengths (WL) ranging from 480 to 900 nm and yielded the highest object detection performance (ODP), reaching mAP@0.5 of 85% in ‘All For Love’ and 83% in ‘White Beauty’ with the YOLOv11x models. However, it increased petal temperature by 2.7–3 °C, thereby stimulating leaf transpiration and consequently shortening the VL of the flowers by 1–2.5 d. In contrast, INC produced unclear images with low spectral signals throughout the WL and consequently resulted in lower ODP, with mAP@0.5 of 74% and 69% in ‘All For Love’ and ‘White Beauty’, respectively. The INC only slightly increased petal temperature (1.2–1.3 °C) and shortened the VL by 1 d in the both cultivars. Although FLU and LED had only minor effects on petal temperature and VL, these illuminations generated transient spectral peaks in the WL range of 480–620 nm, resulting in decreased ODP (mAP@0.5 60–75%). Our results revealed that HAL provided reliable, high-quality spectral image data and high object detection accuracy, but simultaneously had negative effects on flower quality. Our findings suggest an alternative two-phase approach for illumination applications that uses HAL during the initial exploration of spectra corresponding to specific symptoms of interest, followed by LED for routine plant monitoring. Optimizing illumination in HSI will improve the accuracy of deep learning-based prediction and thereby contribute to the development of an automated quality sorting system that is urgently required in the cut flower industry. Full article

This work demonstrates a three-step method for the synthesis and production of submicron spherical gold particles using laser ablation in liquid (LAL), laser-induced fragmentation in liquid (LFL), laser-induced nanochain formation, and laser melting in liquid (LML). The nanoparticles were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV–visible spectroscopy. In the first stage, spherical gold nanoparticles with a size of 20 nm were obtained using LAL and LFL. Subsequent irradiation of gold nanoparticle colloids with radiation at a wavelength of 532 nm leads to the formation of gold nanochains. Irradiation of nanochain colloids with radiation at a wavelength of 1064 nm leads to the formation of large spherical gold particles with a size of 50 to 200 nm. The formation of submicron gold particles upon irradiation of 2 mL of colloid occurs within the first minutes of irradiation and is complete after 480,000 laser pulses. Increasing the laser pulse energy leads to the formation of larger particles; after exceeding the threshold energy (321 mJ/cm²), fragmentation is observed. Increasing the concentration of nanoparticles in the initial colloid up to 150 μg/mL leads to a linear increase in the size of submicron nanoparticles. The use of picosecond pulses for irradiating nanochains demonstrates the formation of the largest particles (200 nm) compared to nanosecond pulses, which may be due to the effect of local surface melting. The described technique opens the possibility of synthesizing stable gold nanoparticles over a wide range of sizes, from a few to hundreds of nanometers, without the use of chemical reagents. Full article

Background: Phototherapy utilizes targeted irradiation to inactivate bacteria or treat various medical conditions. Depending on the therapeutic goal, wavelengths from violet to infrared (IR) are applied. Within the visible and near-IR spectrum, photodynamic therapy (PDT) combines light with photosensitizers that generate reactive oxygen species (ROS), leading to bacterial inactivation. Optimizing photodynamic efficacy can involve either enhancing ROS formation through specific topical agents that modulate ROS generation or employing dual-wavelength light irradiation (DWLR) to achieve synergistic excitation. Established DWLR protocols typically combine blue and red light or IR to activate distinct photosensitizers. Materials and Methods: This study investigates whether a similar synergistic effect can be achieved within the green spectral range by simultaneously exciting a single photosensitizer—coproporphyrin III (CP III)—at 496 nm and 547 nm. Results: Convolution analysis and in vitro bacterial reduction experiments with Cutibacterium acnes subsp. elongatum revealed that cyan irradiation (496 nm) achieved the strongest photoreduction (2.31 log steps at 1620 J/cm²), whereas PC-lime irradiation (547 nm) produced a smaller effect (0.74 log steps). DWLR protocols (simultaneous and sequential irradiation) resulted in intermediate reductions (1.64 and 1.73 log steps, respectively), exceeding PC-lime but not surpassing cyan irradiation alone. Conclusions: These findings demonstrate that excitation efficiency at the local absorption maximum of CP III is the primary determinant of ROS generation, while spectral broadening through DWLR does not enhance bacterial inactivation within this wavelength range and in vitro setup. Full article

This work addresses the challenge of realizing broadband, low-loss fiber-to-waveguide coupling in the short-wavelength near-infrared range (700–1050 nm), where the required fine structural dimensions and taper tips approach or even exceed current fabrication limits, resulting in tight fabrication tolerances and degraded coupling efficiency. We propose a broadband trilayer adiabatic edge coupler on a thin-film lithium tantalate platform that requires only two standard lithography and etching steps. The design integrates a crossed bilayer taper and a dual-core mode converter to achieve adiabatic mode transformation from a ridge to a thin strip waveguide, ensuring excellent fabrication tolerance and process simplicity. Simulations predict a minimum coupling loss of 0.57 dB at 850 nm, which includes the transmission through the complete edge-coupler structure, along with a 0.5-dB bandwidth exceeding 140 nm. The proposed structure provides a broadband, low-loss, and fabrication-tolerant interface for short-wavelength photonic systems such as quantum photonics, biosensing, and visible-light communications. Full article

Estimating the depth of a fluorescently labeled tumor is beneficial in tumor resection. In this study, we proposed a method for the three-dimensional position estimation of fluorescent tumors using Monte Carlo simulations. A limited proof-of-concept experiment was conducted, and the two-dimensional position of a tumor was estimated by calculating the centroid of the fluorescence distribution, which was obtained by using excitation light to scan the surface of the model. The depth of the tumor was estimated by fitting the analytical equation based on Beer’s law to the diffuse fluorescence profile on the surface of the model. In the estimation of the two-dimensional position, the distance between the embedded and estimated tumor coordinates was 0.71 mm. The estimated tumor depths of 2–6 mm closely matched the embedded depths, with an error rate of approximately 20%. In previous studies, depth estimation was limited to 1–5 mm using visible light, whereas for the simulation used in the present study, the use of longer wavelengths enabled estimation at slightly greater depths. Full article

The synergistic combination of the ruthenium-based tetranuclear dendrimer photosensitizer with the highly efficient water oxidation catalyst Ru(bda)(pic)₂ enables effective water oxidation under low-energy light irradiation in phosphate buffer 20 mM/acetonitrile 3% (pH 7). This study demonstrates that the integrated system can produce a significant amount of oxygen using visible light at wavelengths greater than 650 nm (up to 160 nmol), achieving quite good turnover number (3.5 × 10⁻³), high quantum yields (0.23) and enhanced stability. These results highlight the potential of this approach to efficiently drive solar water splitting for fuel production, even with low-energy illumination, thereby advancing the development of sustainable photochemical systems for solar energy conversion. Full article

Singlet oxygen is a type of reactive oxygen species that is typically generated via type II photosensitization reactions. Since 1,3-diphenylisobenzofuran (DPBF), a commonly used chromogenic probe, exhibits peak absorbance at 410 nm for singlet oxygen detection, it severely interferes with blue light irradiation and compounds that absorb in this wavelength region. This study investigated developing and validating a fluorescence-based method using DPBF to quantitatively analyze the type II photosensitizing property of riboflavin (RF) and its heterocyclic flavin derivatives. DPBF fluorescence-based analysis provided more sensitive and practical results than traditional colorimetric methods. It effectively overcomes spectral interference from colored photosensitizers, such as RF and its derivatives, under blue light irradiation (λ peak 447 nm). This method permitted more effective measurement of their activity without interference from their intrinsic color and maintained high linearity and low variation across different sample concentrations, even with short irradiation times. The type II photosensitizing potency of the tested compounds under blue light was consistently ranked as follows: RF > flavin mononucleotide > flavin adenine dinucleotide > lumiflavin > lumichrome. The results suggest that the DPBF fluorescence-based assay is a more effective approach than colorimetric analysis, making it a practical and reproducible tool for assessing the type II photosensitizing properties of diverse compounds. This study also provides a refinement of an existing probe-based assay for relative comparisons under visible light conditions. Full article

Wavelength-shifting (WLS) materials are used in radiation detectors to convert ultraviolet photons into visible light, enabling improved photon detection in systems such as scintillators and optical diagnostics for nuclear fusion devices. However, the long-term performance of these materials under radiation is still a critical issue in high-dose environments. In this work, we investigated the radiation tolerance of three WLS compounds (TPB, NOL1, and SB2001), each deposited on reflective substrates (ESR and E-PTFE), resulting in six distinct WLS/substrate systems. The samples underwent gamma irradiation at absorbed doses of 100 kGy, 500 kGy, and 1000 kGy, as well as fast neutron (14.1 MeV) irradiation up to a fluence of 1.9 × 10¹³ n/cm². Qualitative photoluminescence and reflectance measurements were performed before and after irradiation to assess changes in optical performance. Gamma exposure caused spectral broadening in several samples, particularly those with TPB and SB2001, with variations of the two metrics used to compare the performance of the materials exceeding 10% at the highest doses. Neutron-induced effects were generally weaker and did not exhibit a clear fluence dependence. Reflectance degradation was also observed, with variations depending on both the WLS material and the deposition method. These findings contribute to the understanding of WLS material stability under radiation and support their qualification for use in optical components exposed to harsh nuclear environments. Full article

The influence of ZnO nanolayers as a passivating layer prevents electrons from recombining with the electrolyte or oxidized dye molecules at the interface by acting as a blocking layer for semiconducting materials. At 300 °C, it was observed that FTO-ZnO 500-cycle samples recorded the lowest Rq and Ra values of 1210 nm and 0.877 nm, respectively, resulting in homogeneous, crystalline, and smooth surface thin films. SEM images of FTO-ZnO 500 cycles-300 °C (150.00 KX) show a much more crystalline and homogeneous layer, while FTO-ZnO 500 cycles-100 °C (150.00 KX) show an irregular and agglomerated surface. Energy-dispersive spectroscopy also revealed that ALD successfully deposited ZnO on the FTO glass substrates, especially at 300 °C, resulting in uniform layers. In visible light wavelength (400 nm–800 nm), FTO-ZnO 500 cycles-300 °C exhibited the highest stable transmittance value of 0.78 a.u. However, it can be observed that the temperature with the slowest grain growth at 500 cycles of ZnO deposition was 200 °C, with a layer thickness of 60 nm. The device efficiency increased progressively with deposition temperature, reaching a maximum power conversion efficiency of 4.63% for ZnO films deposited at 300 °C with 500 ALD cycles. The observed enhancement is attributed to improved crystallinity, grain growth, and film uniformity at elevated deposition temperatures, which collectively enhance charge transport and reduce recombination losses. These results demonstrate that optimizing the ALD temperature is a key factor in achieving high-quality ZnO films and improved DSSC performance. Full article

This paper presents a cascaded imaging method that combines low-light enhancement and visible–long-wavelength infrared (VIS-LWIR) image fusion to mitigate image degradation in dark environments. The framework incorporates a Low-Light Enhancer Network (LLENet) for improving visible image illumination and a heterogeneous information fusion subnetwork (IXNet) for integrating features from enhanced VIS and LWIR images. Using a joint training strategy with a customized loss function, the approach effectively preserves salient targets and texture details. Experimental results on the LLVIP, M³FD, TNO, and MSRS datasets demonstrate that the method produces high-quality fused images with superior performance evaluated by quantitative metrics. It also exhibits excellent generalization ability, maintains a compact model size with low computational complexity, and significantly enhances performance in high-level visual tasks like object detection, particularly in challenging low-light scenarios. Full article

The article deals with the creation of a calibration model of lactic acid content in an aqueous solution. The research concept included the preparation of a control tool for the process of modifying the properties of the food fraction for methane fermentation bacteria. The thesis was formulated that it is possible to prepare a systemic solution for real-time observation and monitoring of lactic acid secretion during the digestion of a hydrated mixture of food fractions. The scientific aim of the work was to develop and verify a calibration model of lactic acid content in an aqueous mixture with limited transparency for visible light waves. The research methodology was based on near-infrared spectroscopy with multivariate analysis. Stochastic modeling with noise reduction based on orthogonal decomposition was used. A calibration model was created using Gaussian processes (GP) to predict the lactic acid concentration in an aqueous solution or mixture using an NIR-Vis spectrophotometer. The design of the calibration model was based on absorbance spectra and computational data from selected wavelength ranges from 450 nm to 1900 nm. The measurement data in the form of spectra were limited from the initial wider range (400–2250 nm) to reduce interference. The generated calibration model achieved a mean error level not exceeding 2.47 g∙dm⁻³ of the identified lactic acid fraction. The coefficient of determination R² was 0.996. The effect of absorbing the emitter waves was achieved despite the limited transparency of the mixture. Full article

The use of photocatalytic CO₂ reduction as a green technology has attracted the attention of scholars. Nevertheless, the lower visible-light utilisation and photocatalytic efficiency of catalysts remain a challenge. In this work, Bi_xO_yBr_z photocatalysts were synthesised using a hydrothermal method by adjusting the molar ratio of Bi(NO₃)₃·5H₂O and C₁₉H₄₂BrN (Bi:Br ratio) and the pH value of the precursor solution. The obtained samples were characterised, and the CO₂ reduction performance was tested. The results showed that the phase composition for most of the samples was Bi₄O₅Br₂, and BiOBr or Bi₅O₇Br was also confirmed in a small number of samples. Owing to the effects of pH and the Bi:Br ratio on the reaction process, BiOBr→Bi₄O₅Br₂→Bi₅O₇Br transformation occurred. Acidic conditions are conducive to the formation of BiOBr. In alkaline environments, bismuth-rich Bi₄O₅Br₂ or even Bi₅O₇Br easily forms. Bi₄O₅Br₂ has self-assembled microsphere and irregular polyhedron morphologies. The polyhedron Bi₄O₅Br₂ results in CO and CH₄ yields of 10.34 μmol·g⁻¹·h⁻¹ and 1.86 μmol·g⁻¹·h⁻¹ in CO₂ reduction, respectively. Although the microsphere Bi₄O₅Br₂ has a maximum light absorption wavelength of 438 nm, the polyhedron Bi₄O₅Br₂ has the best photocatalytic CO₂ reduction performance and CO selectivity. This work describes the controllable preparation of Bi₄O₅Br₂ at various pH values and Bi:Br ratios and the optimisation of its photocatalytic performance. Full article