Light-emitting Diode Illumination Research Articles

B‐doping mediated formation of oxygen vacancies in Bi2Sn2O7 quantum dots with a unique electronic structure for efficient and stable photoelectrocatalytic sulfamethazine degradation

This study devised a straightforward one-step approach that enabled simultaneous boron (B) doping and oxygen vacancies (OVs) production on Bi2Sn2O7 (BSO) (B-BSO-OV) quantum dots (QDs), optimizing the electrical structure of the photoelectrodes. Under light-emitting diode (LED) illumination and a low potential of 1.15 V, B-BSO-OV demonstrated effective and stable photoelectrocatalytic (PEC) degradation of sulfamethazine (SMT), achieving the first-order kinetic rate constant of 0.158 min−1. The surface electronic structure, the different factors influencing the PEC degradation of SMT, and the degradation mechanism were studied. Experimental studies have shown that B-BSO-OV exhibits strong visible light trapping ability, high electron transport ability, and superior PEC performance. DFT calculations show that the presence of OVs on BSO successfully reduces the band gap, controls the electrical structure, and accelerates charge transfer. This work sheds light on the synergistic effects of the electronic structure of B-doping and OVs in heterobimetallic oxide BSO under the PEC process and offers a promising approach for the design of photoelectrodes.

Photoantimicrobial and photocatalytic hydrogen evolution activities of seleno-Chevrel phases

Chevrel phases are triclinic crystal structures consisting of a refractory metals and chalcogenides, which present unique properties in many applications. Herein, structural, mechanical, dynamical and electronic properties of Fe2Mo6Se8 and Cu2Mo6Se8 seleno-Chevrel phases were theoretically and experimentally investigated. The theoretical studies revealed the mechanical and dynamical stabilities of these phases that lead to the experimental synthesis. These seleno-Chevrel phases were used for photothermal and photodynamic antibacterial and antibiofilm applications, in the absence and presence of near infrared (NIR) and white light-emitting diode (LED) illuminations on Staphylococcus aureus (S. aureus) and Escherichia coli (E.coli) strains. Fe2Mo6Se8 and Cu2Mo6Se8 displayed enhanced antibacterial activities (73.1% and 60.0%, respectively) and biofilm inhibition effects (93.9% and 88.7%, respectively) on S. aureus. For E. coli bacterium, Fe2Mo6Se8 and Cu2Mo6Se8 showed also antibacterial effects (60.0% and 67.5%, respectively) and biofilm inhibition activities (88.7% and 78.1%, respectively). The increased photothermal and photodynamic activities of Fe2Mo6Se8 and Cu2Mo6Se8 can be attributed to the enhanced ROS production, which triggered probably the denaturation of bacterial proteins and nucleic acids by producing photoinduced electrons to obtain super oxide anion (•O₂̄) radical under light irradiation. Therefore, seleno-Chevrel phases could be a good alternative for medical antibacterial surface applications. Moreover, Fe2Mo6Se8 and Cu2Mo6Se8 were also used as catalysts for photocatalytic hydrogen evolution reactions. Fe2Mo6Se8 showed 1.8-fold higher photocatalytic hydrogen evolution rate than that of Cu2Mo6Se8, which can be explained by the bonding properties of catalysts. This article paves the way that Chevrel phases can be effectively used for different photocatalytic and photoantimicrobial applications.

On the photoresponse regulations by deep-level traps in CsPbBr3 single crystal photodetectors

The all-inorganic halide perovskite CsPbBr3 has attracted significant attention owing to its excellent opto-electronic properties. However, deep-level traps within the material are significant for the properties of CsPbBr3 based opto-electronic devices. In this study, the effects of deep-level traps on the photoresponse characteristics of CsPbBr3 photodetectors were thoroughly studied. By tailoring the illumination combinations where 532 nm light emitting diode (LED) illumination corresponds to the band-to-band excitation of photo-carriers and 648 nm LED illumination corresponds to sub-band excitation by the deep-level traps, it is proven that the device photoresponse performance is improved by the existence of deep-level traps. The photoresponsivity was enhanced by ∼63.64% (from 0.44 to 0.72 A W−1) under 3.18 μW cm−2 532 nm LED illumination. The rise/fall time was reduced by 21.95% (from 20.5 to 16.0 ms)/25.47% (from 21.2 to 15.8 ms). The underlying physical mechanisms of deep level trap-induced modulations on the photoresponse performance of the CsPbBr3 photodetector were revealed and discussed. By further systematic simulation of the effects of material properties on the photoresponse regulation, it was concluded that a shorter carrier lifetime, higher carrier mobility, higher trap concentration, and deeper trap level could improve the photoresponse of the CsPbBr3 photodetector. This study aims to clarify the physical relation between material properties and device performance and provide guidance for high-performance CsPbBr3 photodetector design.

Combined antibacterial effect of 460nm light-emitting diode illumination and chitosan against Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes on fresh-cut melon, and the impact of combined treatment on fruit quality.

This study evaluated the combined antibacterial effect of 460nm LED illumination and chitosan on Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes on fresh-cut melon surface and its impact on the quality of melon at a total dose of 2.4kJ/cm2 at 4 and 10 °C. Results showed that the antibacterial effect of LED illumination in combination with chitosan (0.5 and 1.0%) was much better than that of LED illumination alone, showing their synergistic effect. Among the pathogens, L. monocytogenes was the most susceptible pathogen to LED illumination. Although the color of melons became paler after LED illumination, there was little to no change in ascorbic acid content, total flavonoid content, or antioxidant capacity of the illuminated fruits compared with non-illuminated fruits. Thus, these results suggest that chitosan-mediated 460nm LED illumination could be applied to inactivate foodborne pathogens on fresh-cut melons during storage at food establishments.

Effect of 450 nm Visible Blue Light from Light-Emitting Diode on Escherichia coli O157:H7 in Agar Gels: Optimizing the Lighting Array and Quantitative Microbial Exposure Assessment

Visible blue light emitting diodes (LED) have been studied to inactivate Escherichia coli (E. coli) O157:H7 in agar gels. The LED array was optimized to attain uniform light illumination, and the light intensity distribution was visualized through optical simulation. The uniformity of LED light intensity was assessed, and the evenly spaced array showed the best uniformity with a Petri factor of 0.99. Microbial populations in agar gels prepared with and without a dye were analyzed after light irradiation. Each segment of the gels with different heights was taken to measure microbial reduction, and the results indicated that optical properties, such as opaqueness, played an important role in microbial reduction. The agar gel without and with a dye showed a maximum reduction of <3.4 and <2.1 log CFU/g, respectively. An exposure assessment for E. coli O157:H7 was conducted based on the assumption for the agar gel product after LED illumination. The probability results indicated that a risk (>5 log CFU/g) existed mainly in the bottom layer of the sample, despite the average contamination being <5 log CFU/g. This study provides a suitable approach for designing the LED photoinactivation process and subsequent exposure assessment to avoid risk.

Flexible Solution-Processed Electron-Transport-Layer-Free Organic Photovoltaics for Indoor Application

Organic photovoltaics (OPVs) have unique advantages of low weight, mechanical flexibility, and solution processability, which make them exceptionally suitable for integrating low-power Internet of Things devices. However, achieving improved operational stability together with solution processes that are applicable to large-scale fabrication remains challenging. Their major limitation arises due to the instable factors that occur both inside the thick active film and from the ambient environment, which cannot be completely resolved via the current encapsulation techniques used for flexible OPVs. Additionally, thin active layers are highly vulnerable to point defects, which result in low yield rates and impede the laboratory-to-industry translation. In this study, flexible fully solution-processed OPVs with improved indoor efficiency and long-term operational stability than that of conventional OPVs with evaporated electrodes are achieved. Benefiting from the oxygen and water vapor permeation barrier of the spontaneously formed gallium oxide layers on the exposed eutectic gallium-indium surface, fast degradation of the OPVs with thick active layers is prevented, maintaining 93% of its initial Pmax after 5000 min of indoor operation under 1000 lx light-emitting diode (LED) illumination. Additionally, by using the thick active layer, spin-coated silver nanowires could be directly used as bottom electrodes without complicated flattening processes, thereby substantially simplifying the fabrication process and proposing a promising manufacturing technique for devices with high-throughput energy demands.

Stability of SARS-CoV-2 in cold-chain transportation environments and the efficacy of disinfection measures.

Low temperature is conducive to the survival of COVID-19. Some studies suggest that cold-chain environment may prolong the survival of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and increase the risk of transmission. However, the effect of cold-chain environmental factors and packaging materials on SARS-CoV-2 stability remains unclear. This study aimed to reveal cold-chain environmental factors that preserve the stability of SARS-CoV-2 and further explore effective disinfection measures for SARS-CoV-2 in the cold-chain environment. The decay rate of SARS-CoV-2 pseudovirus in the cold-chain environment, on various types of packaging material surfaces, i.e., polyethylene plastic, stainless steel, Teflon and cardboard, and in frozen seawater was investigated. The influence of visible light (wavelength 450 nm-780 nm) and airflow on the stability of SARS-CoV-2 pseudovirus at -18°C was subsequently assessed. Experimental data show that SARS-CoV-2 pseudovirus decayed more rapidly on porous cardboard surfaces than on nonporous surfaces, including polyethylene (PE) plastic, stainless steel, and Teflon. Compared with that at 25°C, the decay rate of SARS-CoV-2 pseudovirus was significantly lower at low temperatures. Seawater preserved viral stability both at -18°C and with repeated freeze-thaw cycles compared with that in deionized water. Visible light from light-emitting diode (LED) illumination and airflow at -18°C reduced SARS-CoV-2 pseudovirus stability. Our studies indicate that temperature and seawater in the cold chain are risk factors for SARS-CoV-2 transmission, and LED visible light irradiation and increased airflow may be used as disinfection measures for SARS-CoV-2 in the cold-chain environment.

Development and optimization of LED systems for surface fungal decontamination of fresh produce

Uneven irradiation is the major challenge of light-emitting diode (LED) antimicrobial technology. This study developed different LED illumination systems with multi-directional light sources, spotlight reflector (SR), and parabolic reflector (PR) to ensure the high antifungal efficiency of LED on artificially inoculated litchi fruit. Results showed that multi-light LEDs enable multi-angle irradiation, therefore, could reach higher inactivation rates under the comparable energy output. Integrating LED with SR could gather the scattering light and improve the inactivation efficiency (LEDs < LEDs + SR). The addition of PR enhanced bottom irradiation, leading to a comparable effect with an extra light source (LED + SR + PR = dual-LEDs). Moreover, when comparing the energy consumption required for 90 % inactivation of fungi, the LED systems combined SR and/or PR required less power consumption than those of LEDs alone. The antifungal effects of developed systems were further validated by natural samples. These results suggest several feasible solutions to improve the antifungal efficiency of LED and also provide practical system designs to broaden the LED application in the food industry.

The molecular regulation of folate accumulation in pakchoi by low intensity white light-emitting diode (LED) illumination

The objective of the present study was to determine the effect of white LED illumination on the level of folate and its precursors, synthesis-related enzymes, and the expression of their corresponding genes in pakchoi stored at 20 °C. Results indicated that LED (10 μmol m−2 s−1) illumination decreased the level of 7,8-dihydroneopterin (DHN), 6-hydroxymethyl-7.8-dihydropterin (HMDHP), 7,8-dihydrofolate (DHF), chorismate, and 4-amino-4-deoxychorismate (ADC), and increased the level of folate 7.8-dihydroneopterin 3’-triphosphate (DHN-P3), 6-hydroxymethyldihydropterin pyrophosphate (HMDHP-P2), dihydropteroate (DHP), Tetrahydrofolate (THF), polyglutamyl tetrahydrofolatein (THF-Glu(n)) and p-aminobenzoate (pABA). Additionally, the level of guanosine triphosphate cyclohydrolase I (GTPCHI), 7,8-dihydrofolate reductase (DHFR), and folylpolyglutamate synthetase (FPGS) were also reduced, as was the expression level of their corresponding genes. LED illumination also increased the level of 7,8-dihydrofolate synthetase (DHFS), amino deoxychorismate synthetase (ADCS), and amino deoxychorismate lyase (ADCL), and the expression of their corresponding genes. The LED treatment, however, did not have much impact on the level of guanosine triphosphate (GTP) and γ-glutamyl hydrolase (GGH). The analysis of differentially expressed genes (DEGs) indicated that the white LED illumination treatment had a significant impact on folate biosynthesis. In summary, white LED illumination had a regulatory impact on folate metabolism in harvested pakchoi and extended its postharvest quality.

Recent Progress in Visible Light Positioning and Communication Systems

In this paper, we report the recent progress in visible light positioning and communication systems using light-emitting diodes (LEDs). Due to the wide deployment of LEDs for indoor illumination, visible light positioning (VLP) and visible light communication (VLC) using existing LEDs fixtures have attracted great attention in recent years. Here, we review our recent works on visible light positioning and communication, including image sensor-based VLP, photodetector-based VLP, integrated VLC and VLP (VLCP) systems, and heterogeneous radio frequency (RF) and VLC (RF/VLC) systems.

Natural Bioactive Substances in Fruits of Aronia melanocarpa (Michx.) Elliott Exposed to Combined Light-Type, Chitosan Oligosaccharide, and Spent Mushroom Residue Treatments.

Greenhouse culture is a practical approach to obtain non-wood forest products from berry fruit at a higher efficacy than resource silviculture in natural understory. In this study, three-year old black chokeberry (Aronia melanocarpa (Michx.) Elliott 1821) seedlings were transplanted to a greenhouse where sunlight was complemented by red- (69.4% red, 30.2% green, 0.4% blue) and blue-color (15.3% red, 64.9% green, 19.8% blue) light-emitting diode (LED) illuminations. Half of the planting soils were amended by spent mushroom residue (SMR) (not amendment as the control) and half the seedlings were sprayed by chitosan oligosaccharide (CO) on leaves. All treatments can increase seedling height, but only blue light reinforces the basal diameter growth. Compared to sunlight, exposure to blue light can promote leaf nitrogen and phosphorus concentrations, superoxide dismutase activity, and fruit proanthocyanidin content. The combination with CO addition will further increase chlorophyl a content, acid phosphatase activity, and total phenolics in fruit. SMR amended can induce the steady state uptake of nutrients but failed to impact fruit quality. Overall, we recommend the combination of blue light LED illumination plus CO addition to culture black chokeberry for the purpose to gain natural bioactive compounds.

Effect of White Light-Emitting Diode Illuminants Recommended by the CIE on Colors of Dental Ceramic Materials

The aim of this study was to evaluate color inconstancy of dental ceramics under the white light-emitting diode illuminants recently proposed by the CIE. From spectral reflectance factors of 18 dental ceramics (VST, NSP, and IEC; shades A1, A2, A3, A3.5, B2, and C2), the corresponding colors under illuminant D65 and CIE 1931 Standard Colorimetric Observer were computed for all samples, using the chromatic adaptation transform CIECAT16. CIEDE2000 color differences between dental ceramics illuminated by CIE D65 standard illuminant and different white LED illuminants were calculated. Perceptibility and acceptability thresholds (PT00 and AP00) in dental ceramics were used to analyze color changes. Color gamut size was within the same range for all illuminants and for all ceramics, since MCDM computed values were 4.1–4.4 for VST, 4.0–4.2 for NSP, and 4.3–4.6 for IEC. For all ceramics and shades, the color inconstancies were higher than 50:50% PT00 and, in general, lower than 50:50% AT00. The effect of CIE-proposed LED illuminants on dental ceramic is perceptible and slightly lower than on natural teeth. Dental clinicians should consider these lighting effects on the visual appearance of dental ceramics.

In vitro and in vivo phototoxicity on gastric mucosa induced by methylene blue.

Methylene blue (MB) is used endoscopically to demarcate tumors and as a photosensitizer in photodynamic therapy (PDT). However, there are few in vivo studies about its toxicity in healthy stomach tissue. We performed sequential in vitro and in vivo analyses of MB-induced phototoxicity. We performed in vitro experiments using the AGS human gastric cancer cell line treated with light-emitting diode (LED) irradiation (3.6 J/cm2) and MB. Cytotoxicity was evaluated using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. In vivo toxicity was evaluated in the stomach of beagles using the same dose of fiber-optic LED via gastroscopy, after spraying 0.1% and 0.5% MB solutions. Stomach tissue was also evaluated using the TUNEL assay. In vitro, increased concentrations of MB led to higher TUNEL scores. However, cell viability was significantly lower after MB plus LED irradiation than after treatment with MB alone (P < 0.001). In vivo, the TUNEL score was highest immediately after treatment with 0.1% or 0.5% MB plus light irradiation, and the score was significantly higher in the LED illumination plus MB group than in the control group (P < 0.05). The elevated TUNEL score was maintained for 3 days in the MB plus light irradiation group but returned to normal levels on day 10. : Endoscopic light application with MB 0.5% concentration to the stomach may be regarded as a safe procedure despite some DNA injuries in the early period.

Highly stable β-Bi2O3/Ag decorated nanosilica as an efficient Schottky heterojunction for ciprofloxacin photodegradation in wastewater under LED illumination

A novel mesopours SiO2/β-Bi2O3/Ag plasmonic heterojunction was first fabricated by a simple multi-step approach. The fabricated heterojunction was applied for ciprofloxacin (CIP) degradation in wastewater. The ternary SiO2/β-Bi2O3/Ag photocatalyst exhibited a wide absorption in the visible region (400–700 nm) with the assistance of the surface plasmonic resonance (SPR) behavior of Ag0 metal. Furthermore, the experimental results indicated that 96% of CIP was degraded with a TOC removal efficiency of 65% in 105 min under 140 W of light-emitting diode (LED) irradiation. The kinetics studies showed that the degradation rate of SiO2/β-Bi2O3/Ag is 0.02651 min−1, which is 3.17, 2.62, and 1.99 times higher than that of pure β-Bi2O3, SiO2/β-Bi2O3, and β-Bi2O3/Ag, respectively. The impacts of operational parameters like solution pH, CIP concentration, and SiO2/β-Bi2O3/Ag dosage were also assessed. The trapping experiments suggested that the main reactive species is the •OH radical, which can be easily generated on the valence band of β-Bi2O3. The Schottky heterojunction between β-Bi2O3 and Ag nanoparticles was well depicted based on trapping tests and characterization techniques. The stability experiments suggested that the SiO2/β-Bi2O3/Ag nanocomposite possessed high stability in five consecutive cycles and could be applied for CIP removal with acceptable photodegradation performance. Finally, it can be concluded that the nanosilica exhibited an efficient support structure, which can significantly improve the surface properties of SiO2/β-Bi2O3/Ag by inhibiting the agglomeration effects of β-Bi2O3/Ag nanoparticles as well as enhance the adsorption and stability of nanocomposite.

Chitosan enhances antibacterial efficacy of 405 nm light-emitting diode illumination against Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella spp. on fresh-cut melon

This study aimed to evaluate the influence of chitosan on the antibacterial efficacy of 405 nm LED illumination against Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on fresh-cut melons. The antibacterial efficacy of LED illumination (a total dose of 1.3 kJ/cm2) with or without chitosan (0.5 and 1.0 %) against these three pathogens was determined at 4 and 10 °C, respectively. Non-illuminated and chitosan-treated fruits were stored in the dark for 36 h under the same temperature. Color changes, ascorbic acid content, and total flavonoid content of illuminated and non-illuminated fruits were also analyzed. The results showed that the populations of all three pathogens on the non-illuminated and chitosan-treated fruits remained unchanged during storage. Regardless of bacterial species and chitosan concentrations, LED illumination in combination with chitosan greatly reduced the bacterial populations by 1.5 – 3.5 log/cm2, which was greater than LED illumination alone. Among the three pathogens, L. monocytogenes was the most susceptible to chitosan-mediated LED illumination. However, the whiteness index of illuminated fruits significantly increased by 1.3-fold compared to that of non-illuminated fruits, regardless of the presence of chitosan. Unlike color, no significant difference was observed in ascorbic acid and total flavonoid contents between illuminated and non-illuminated fruits. Although the fruit color was changed by LED illumination, these results indicate that adding chitosan could enhance the antibacterial efficacy of 405 nm LED illumination against major foodborne pathogens on fresh-cut melons without changing nutritional quality.

Covalent Grafting of 5-Aminolevulinic Acid onto Polylactic Acid Films and Their Photodynamic Potency in Preserving Salmon.

A novel photodynamic inactivation (PDI)-mediated antimicrobial film of polylactic acid/5-aminolevulinic acid (PLA/ALA) was successfully fabricated by a covalent grafting method using low-temperature plasma. The chemical structure, surface morphology, hydrophilic ability, and mechanical and barrier properties of the films were characterized, and their antibacterial, anti-biofilm potency and preservation effects on ready-to-eat salmon were investigated during storage. Results showed that the amino group of ALA was covalently grafted with the carboxyl group on the surface of PLA after the plasma treatment, with the highest grafting rate reaching ∼50%. The fabricated PLA/ALA films displayed an enhanced barrier ability against water vapor and oxygen. Under blue light-emitting diode illumination, the PLA/ALA films generated massive reactive oxygen species from the endogenous porphyrins in cells induced by ALA and then fatally destroyed the cell wall of planktonic cells and the architectural structures of sessile biofilms of the pathogens (Listeria monocytogenes and Vibrio parahaemolyticus) and spoilage bacterium (Shewanella putrefaciens). More importantly, the PDI-mediated PLA/ALA films potently inhibited 99.9% native bacteria on ready-to-eat salmon and significantly suppressed the changes of its drip loss, pH, and lipid oxidation (MDA) during storage, and on this basis, the shelf life of salmon was extended by 4 days compared with that of the commercial polyethylene film. Therefore, the PDI-mediated PLA/ALA films are valid in inactivating harmful bacterial and preserving the quality of seafood.

Multispectral imaging of nailfold capillaries using light-emitting diode illumination.

The capillaries are the smallest blood vessels in the body, typically imaged using video capillaroscopy to aid diagnosis of connective tissue diseases, such as systemic sclerosis. Video capillaroscopy allows visualization of morphological changes in the nailfold capillaries but does not provide any physiological information about the blood contained within the capillary network. Extracting parameters such as hemoglobin oxygenation could increase sensitivity for diagnosis and measurement of microvascular disease progression. To design, construct, and test a low-cost multispectral imaging (MSI) system using light-emitting diode (LED) illumination to assess relative hemoglobin oxygenation in the nailfold capillaries. An LED ring light was first designed and modeled. The ring light was fabricated using four commercially available LED colors and a custom-designed printed circuit board. The experimental system was characterized and results compared with the illumination model. A blood phantom with variable oxygenation was used to determine the feasibility of using the illumination-based MSI system for oximetry. Nailfold capillaries were then imaged in a healthy subject. The illumination modeling results were in close agreement with the constructed system. Imaging of the blood phantom demonstrated sensitivity to changing hemoglobin oxygenation, which was in line with the spectral modeling of reflection. The morphological properties of the volunteer capillaries were comparable to those measured in current gold standard systems. LED-based illumination could be used as a low-cost approach to enable MSI of the nailfold capillaries to provide insight into the oxygenation of the blood contained within the capillary network.

The Effect of Short-Wavelength White LED Illumination throughout the Night on the Milk Fatty Acid Profile of High-Yielding Dairy Cows.

Fatty acid levels in milk vary between day and night milking. Many dairy cows are still kept under white light-emitting diode (W-LED) illumination throughout the night, although it is known to disrupt endogenous circadian rhythms. We investigated the effects of whole-night W-LED illumination (125 lux) on milk yield and circadian composition, compared to a natural light-dark (LD) cycle of 10 h light. Mid-late lactation cows (n = 34) that were exposed to natural LD cycle showed circadian variation in milk fat composition, characterized by higher health-promoting monounsaturated fatty acid (MUFA; 24.2 ± 0.4 vs. 23.2 ± 0.4 g/100 g fat, p &lt; 0.001) and lower saturated fatty acid levels (71.2 ± 0.4 vs. 72.5 ± 0.4, p &lt; 0.001) at 13:30 h (day milk) than at 03:30 h (night milk). Compared to natural LD (n = 16), W-LED (n = 18) did not affect milk production or milk fat yields, yet abolished the milking time variation in milk fat composition towards a less healthy fatty acid profile. This lowered MUFA levels of day milk (23.8 ± 0.4 vs. 26.7 ± 0.4, p &lt; 0.01). Therefore, W-LED has no commercial advantage over the tested natural LD cycle, and conversely, even shows circadian disruption. Accordingly, a natural LD cycle of 10 h light is preferable over W-LED from the perspective of cost savings, the cows' well-being, and preserving the natural milk fat profile, as the nutritional value of the day milk is slightly higher.

Large‐Area Wide Bandgap Indoor Organic Photovoltaics for Self‐Sustainable IoT Applications

Superior spectral responsivity, low open‐circuit voltage losses, and good scalability make organic photovoltaics (OPVs) potential power generating contenders for low‐power consumption electronic devices for indoor self‐sustainable applications. Herein, large‐area organic photovoltaic devices with PBTZT‐stat‐BDTT‐8: PC71PM photoactive layer are fabricated to develop indoor power sources for low‐power, portable, and wireless electronic devices. The better spectral matching of PBTZT‐stat‐BDTT‐8‐based photoactive absorber layer with light‐emitting diode (LED) emission spectra translates a power conversion efficiency (PCE) over 18% for single‐cell (0.38 cm2) device. Whereas, PCEs over 17% and 16% are observed for mini‐module (18.63 cm2) and submodule (40 cm2) under 1000 lux LED (2700 K) illumination, respectively. The emission powers of the LED lamps are carefully analyzed, and integral current densities of photovoltaics cells are calculated with the help of external quantum efficiency and photon flux spectrum to assure the reliability of photovoltaic measurements. Finally, the commercially available programmable Arduino boards and Bluetooth‐based Internet of Things devices integrated with OPVs to build a self‐sustainable communication system that can function well under indoor environment are demonstrated.

Enhanced Photoredox Activity of BiVO4/Prussian Blue Nanocomposites for Efficient Pollutant Removal from Aqueous Media under Low-Cost LEDs Illumination

Bismuth vanadate (BiVO4, BV) is a widely explored photocatalyst for photo(electro)chemical applications, but its full photocatalytic potential is hindered by the fast recombination and low mobility of photogenerated charge carriers. Herein, we propose the photodeposition of different amounts of Prussian blue (PB) cocatalysts on the surface of monoclinic BV to obtain BV-PB composite photocatalysts with increased photoactivity. The as-prepared BV and BV-PB composites were characterized by an array of analytic techniques such scanning eletron microscopy (SEM), transmission eletron microscopy (TEM), X-day diffraction (XRD), and spectroscopic techniques including Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and Raman spectroscopy. The addition of PB not only increases the absorption of visible light, as indicated by DRS, but also improves the charge carriers’ transfer across the photocatalysts/solution interface and hence reduces electron-hole (e−-h+) recombination, as confirmed by EIS and PL measurements. Resultantly, the BV-PB composite photocatalysts with optimum PB loading exhibited enhanced Cr(VI) photoreduction efficiency as compared to pristine BV under visible light illumination from low-power blue light-emitting diodes (LEDs), thanks to the cocatalyst role of PB which mediates the transfer of photoexcited conduction band (CB) electrons from BV to Cr(VI) species in solution. Moreover, as compared to pristine BV and BV + H2O2, a drastic increase in the methylene blue (MB) photo-oxidation efficiency was observed for BV-PB in the presence of a minute quantity of H2O2 due to a synergic effect between the photocatalytic and Fenton-like processes. While pure BV photodegraded around 70% of MB dye within 120 min, the BV-PB/H2O2 and BV/H2O2 system could degrade almost 100% of the dye within 20 min (kobs. = 0.375 min−1) and 40 min (kobs. = 0.055 min−1), respectively. The practical approach employed in this work may pioneer new prospects for synthesizing new BV-based photocatalytic systems with low production costs and high photoredox efficiencies.