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- 2018
- imgae sensor
- internet of things
- drone
- visible light ID
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- Tohoku University
- University of Northumbria
- University of Huddersfield
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Optical Filter Designs for Multi-Color Visible Light Communication
摘要： In visible light communication (VLC), using multiple colors is an efficient way to enhance data rate, leading to multi-color VLC (MC-VLC). However, the performance of MC-VLC is jeopardized by the spectral overlaps of different colors. Thin-film optical filters, as the key component of MC-VLC systems, are usually adopted to separate colors. The passband bandwidth (BW) and center wavelength (CWL) of optical filters are critical to mitigate the crosstalk among colors, and thus must be carefully designed. Moreover, due to the intrinsic wavelength shift of the CWL with the varying of the angle of incidence (AoI), it is challenging to support mobility for MC-VLC. In this paper, we consider a joint design of multiple optical filters for MC-VLC by properly selecting the BW and CWL of each filter. We first investigate the optical filter design for a fixed receiver location. Then, to support mobility, we propose two robust optical filter designs, namely statistically and worst-case robust designs, which do not rely on the exact receiver location. Efficient methods are developed to solve the corresponding design problems and obtain the optimized optical filters. Compared with the existing optical filters, the proposed optical filters exhibits much better performance in various scenarios.
关键词： robust design,optical filter,spectrum shift,Mobility,multi-color LED,visible light communication,spectral overlap
更新于2025-09-09 09:28:46
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Tuning the optical properties of ZnO:Cd by doping La and Y
摘要： Zinc oxide doped with Cadmium and rare earth elements synthesized by solgel auto combustion route is reported in this work. The studies have been carried out to analyze the structural, morphological and optical properties of Cd doped ZnO and rare earth doped ZnCdO. The XRD analysis reveals that the addition of rare earth impurity decreases the particle size of ZnCdO. La doped ZnCdO has the least particle size among the samples of ZnCdO and rare earth doped ZnCdO. The morphological changes due to the addition of rare earth impurities have been found. Samples of La doped ZnCdO shows a pillar like morphology. The hexagonal structures are prominently seen in the SEM micrographs of the samples of ZnCdO. The UV-Visible spectral analyses show that the bandgap reduces when ZnCdO is doped with the rare earth impurities. The photoluminescence spectra show the broad spectrum in visible region exhibited by ZnO and a scanty UV emission. The UV emission of rare earth doped samples decreases due to the destruction in the crystal structure. The rare earth doped ZnCdO shows a small peak in green emission that decreases when rare earth impurities are doped. There is a uniform spectral response other than a small Gaussian like green peak. The overall analyses show that the samples can be used in optoelectronic applications to work in the visible region.
关键词： rare earth elements,structural properties,optical properties,UV-Visible spectral analyses,Cadmium,SEM micrographs,photoluminescence spectra,XRD analysis,Zinc oxide,solgel auto combustion,morphological properties
更新于2025-09-09 09:28:46
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Insight into Reinforced Photocatalytic Activity of CNT-TiO <sub/>2</sub> nanocomposite for CO <sub/>2</sub> Reduction and Water Splitting
摘要： Using titanium dioxide (TiO2) and its modified forms for photocatalytic reduction of CO2 reduction and production of hydrogen are promising routes for providing solutions to the world energy demand in the foreseeable future. Here, we report the synthesis of a series of efficient, stable TiO2 nanoparticles modified with multi-walled carbon nanotubes (CNT) via a simple, combined sonothermal method followed by a hydrothermal treatment. In comparison to bare TiO2, the synthesized CNT-TiO2 photocatalysts showed improved photocatalytic activities for CO2 reduction under UVA as well as under visible light; and water (H2O) splitting under visible light at ambient temperature and pressure. The 2.0CNT-TiO2 has performed the best for methanol, hydrogen and formic acid production from the reduction of CO2 with yield rates of 2360.0, 3246.1 and 68.5 μmol g-1 h-1 under UVA, respectively. Its potential was further tested under visible light for methanol production, 1520.0 μmol g-1 h-1. Also, the highest rate of hydrogen yield from water splitting was 69.41 μmol g-1 h-1 with 2.0CNT-TiO2 under visible light at pH 2. The primary photocatalytic reactions of CNT-TiO2 composites and their intimate structure were studied computationally. It was demonstrated that the binding of CNT to TiO2 nanoparticles are preferable at (101) surfaces compared to (001) facets. Interaction of CNT with TiO2 results in common orbitals within TiO2 band gap that enables visible light excitation of the CNT-TiO2 composites can lead to charge transfer between TiO2 and CNT; while UV light excitation can result in charge transfer in any direction, from CNT to TiO2 and from TiO2 to CNT. The latter process is operative in the presence of sacrificial electron donor TEOA.
关键词： photocatalytic reduction,CO2 reduction,UVA light,water splitting,visible light,CNT-TiO2 nanocomposite,hydrogen production
更新于2025-09-09 09:28:46
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Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control
摘要： Pathogenic biofilms raise significant health and economic concerns, because these bacteria are persistent and can lead to long-term infections in vivo and surface contamination in healthcare and industrial facilities or devices. Compared with conventional antimicrobial strategies, photocatalysis holds promise for biofilm control because of its broad-spectrum effectiveness under ambient conditions, low cost, easy operation, and reduced maintenance. In this study, we investigated the performance and mechanism of Staphylococcus epidermidis biofilm control and eradication on the surface of an innovative photocatalyst, graphitic carbon nitride (g-C3N4), under visible light irradiation, which overcame the need for ultraviolet (UV) light for many current photocatalysts (e.g., titanium dioxide (TiO2)). Optical coherence tomography (OCT) and confocal laser scanning microscopy (CLSM) suggested that g-C3N4 coupons inhibited biofilm development and eradicated mature biofilms under the irradiation of white light-emitting diodes (LEDs). Biofilm inactivation was observed occurring from the surface towards the center of the biofilms, suggesting that the diffusion of reactive species into the biofilms played a key role. By taking advantage of scanning electron microscopy (SEM), CLSM, and atomic force microscopy (AFM) for biofilm morphology, composition, and mechanical property characterization, we demonstrated that photocatalysis destroyed the integrated and cohesive structure of biofilms and facilitated biofilm eradication by removing the extracellular polymeric substances (EPS). Moreover, reactive oxygen species (ROS) generated during g-C3N4 photocatalysis were quantified via reactions with radical probes, and 1O2 was believed to be responsible for biofilm control and removal. Our work highlights the promise of using g-C3N4 for a broad range of antimicrobial applications, especially for the eradication of persistent biofilms under visible light irradiation, including photodynamic therapy, environmental remediation, food industry applications, and self-cleaning surface development.
关键词： graphitic carbon nitride,mechanical properties,extracellular polymeric substances,biofilms,visible light
更新于2025-09-09 09:28:46
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Fabrication and Performances of Graphene/TiO2 Composites Derived from Graphenes and Titanium(IV) Alkoxide Precursors
摘要： Graphene/TiO2 composites were synthesized by sol-gel technique using titanium(IV) n-butoxide (TNB), titanium(IV) isopropoxide (TIP) and titanium(IV) propoxide (TPP) as different titanium alkoxide precursors. The as-prepared composites were characterized by BET surface area, SEM, XRD, EDX and UV-visible absorption spectroscopy. The samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under UV irradiation. The results indicated that the sample GTNB had best excellent photocatalytic activity among the three kinds of samples. According to the photocatalytic results, methylene blue removal by a treatment with graphene/TiO2 composites seems to have an excellent removal effect as order of GTIP, GTNB and GTPP composites due to a photolysis of the supported TiO2, the radical reaction and the adsorptivity and absorptivity of the graphene.
关键词： TiO2,Visible light,Graphene,Photocatalytic,TEM
更新于2025-09-09 09:28:46
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Visible-Light-Driven Conversion of CO2 to CH4 with an Organic Sensitizer and an Iron Porphyrin Catalyst
摘要： Using a phenoxazine-based organic photosensitizer and an iron porphyrin molecular catalyst, we demonstrated photochemical reduction of CO2 to CO and CH4 with turnover numbers (TONs) of 149 and 29, respectively, under visible light irradiation (λ > 435 nm) with a tertiary amine as sacrificial electron donor. This work is the first example of a molecular system using an earth-abundant metal catalyst and an organic dye to effect complete 8e-/8H+ reduction of CO2 to CH4, as opposed to typical 2e-/2H+ products of CO or formic acid. The catalytic system continuously produced methane even after prolonged irradiation up to four days. Using CO as the feedstock, the same reactive system was able to produce CH4 with 85% selectivity, 80 TON and a quantum yield of 0.47%. The redox properties of the organic photosensitizer and acidity of the proton source were shown to play a key role in driving the 8e-/8H+ processes.
关键词： methane,organic photosensitizer,CO2 reduction,iron porphyrin,visible light
更新于2025-09-09 09:28:46
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Determination of Nitrogen Concentration in Fresh Pear Leaves by Visible/Near-Infrared Reflectance Spectroscopy
摘要： A rapid and reliable method is required to determine the N status of pear (Pyrus communis L.) leaves during the growing season for timely fertilization to improve the yields and fruit quality. In the present study, we evaluated visible and near-infrared reflectance (Vis/NIR) spectra of fresh pear leaves using partial least squares (PLS) regression to determine the N concentration of fresh pear leaves. In addition, we studied the performance of modified spectra generated using different preprocessing techniques. A total of 450 leaf samples were collected from 6-yr-old pear trees of two cultivars, and randomly separated into two subsets (calibration subset [294 samples] and validation subset [180 samples]) after excluding outliers by using principle component analysis. Results showed that the model built using full spectra performed better than that developed using characteristic wavelength segments. In addition, we found that original spectral proved to provide better accuracy than derivative spectra. Among the studied preprocessing techniques, moving average smoothing (MAS) technique improved accuracy the most. Overall results suggested that PLS regression with preprocessing of full spectra using MAS is optimal method for modeling N concentration of fresh pear leaves which yielded 0.961 and 0.953 coefficient of determination (R2) for calibration and cross-validation, respectively. The validation of this method resulted high R2 value (0.847) and low mean relative error (4.48%). In conclusion, this model could provide a rapid and more reliable method to determine the total N concentration in fresh pear leaves and could be useful for fertilization management in pear orchards.
关键词： partial least squares regression,preprocessing techniques,pear leaves,Nitrogen concentration,visible/near-infrared reflectance spectroscopy
更新于2025-09-09 09:28:46
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Synthesis of Self-Gravity Settling Faceted-Anatase TiO2 with Dominant {010} Facets for the Photocatalytic Degradation of Acetaminophen and Study of the Type of Generated Oxygen Vacancy in Faceted-TiO2
摘要： In this study, faceted TiO2, predominately exposed with {010} facets (T-{010}), was synthesized with a two-step hydrothermal reaction and used for the degradation of acetaminophen (ACE) in an aqueous solution. T-{010} showed considerable photocatalytic reactivity, and its easy-settling (gravity-settling, ~97% of T-{010} settled after 30 min) property demonstrated acceptable reusability. A solid-state chemical reduction approach (NaBH4) at a mild temperature (300 ?C) was used for generation of an oxygen vacancy in T-{010} and P25 (commercial TiO2). The oxygen vacancy concentrations of the samples were investigated by electron paramagnetic resonance (EPR). It was also found that NaBH4 reduction induced the generation of both surface and subsurface Ti3+ on colored P25, but only surface Ti3+ species were formed on colored T-{010}. The prepared colored TiO2 samples were successfully used for photocatalytic degradation of ACE in an aqueous solution under visible light illumination.
关键词： photocatalytic degradation,visible light,{010} facet,oxygen vacancy,settling
更新于2025-09-09 09:28:46
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Photocatalytic performance of Ag2S/ZnO/ZnS nanocomposites with high visible light response prepared via microwave-assisted hydrothermal two-step method
摘要： A series of different ratios of Ag2S/ZnO/ZnS nanocomposites with visible light response were prepared by a microwave-assisted hydrothermal two-step method, whose composition, crystalline structure, morphology and surface physicochemical properties were well-characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), photoluminescence spectrum (PL), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and N2 adsorption–desorption measurements. Results showed that as-composites mainly consisted of ZnS crystal phase, whose grain size increased obviously compared with non Ag2S samples. At the same time, due to the introduction of narrow band gap Ag2S, the synthesized composite can effectively increase the visible optical absorption of ZnO/ZnS composites. Among them, 1% Ag2S/ZnO/ZnS showed a mixed structure of nano-line and nano-particle, of which BET value increased significantly, and the morphology was more excellent. Photocatalytic activities of a series of Ag2S/ZnO/ZnS composites under different light sources were studied using methyl orange as a model molecule, and 1% Ag2S/ZnO/ZnS was taken as the best one. Meanwhile, 1% Ag2S/ZnO/ZnS also showed a good degradation effect on other dyes with different structures, and its degradation efficiency did not change significantly after three cycles, showing certain stability. In addition, composites with Ag2S loading of 1% possessed the highest hydrogen production ability of photolysis water, indicating that the introduction of Ag2S had significantly enhanced the catalytic performance.
关键词： microwave-assisted,Ag2S,photocatalysis,visible light,photolysis of water to hydrogen,ZnO/ZnS
更新于2025-09-09 09:28:46
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Construction of Ternary rGO/Ag <sub/>2</sub> CO <sub/>3</sub> /AgBr Heterostructured Photocatalyst for Improved Photocatalytic Activity and Stability
摘要： Novel ternary rGO/Ag2CO3/AgBr heterostructured photocatalyst have been successfully fabricated through in-situ anion exchange synthesis route. The morphology, crystal structure, component and optical property of the as-obtained products were fully characterized by various technologies. The photocatalytic performances of the as-obtained products were measured by degrading rhodamine B (RhB) under visible light irradiation. The rGO/Ag2CO3/AgBr heterostructured photocatalyst exhibits higher photocatalytic activity than that of the pure Ag2CO3 and rGO/Ag2CO3, indicating the presence of a synergic effect between three components. The superior photocatalytical activity for the rGO/Ag2CO3/AgBr heterostructured photocatalyst is due to the formation of multi-heterojunction with rGO acting as electron mediation, which facilitate the separation of photogenerated electron and hole pairs. The possible transfer path of photogenerated carriers and mechanism for the improved photocatalytic activity are also supposed.
关键词： AgBr,Ternary Heterojunction,Ag2CO3,Photocatalysis,Visible Light Driven
更新于2025-09-09 09:28:46