Diode Illumination Research Articles

Curcumin and carvacrol mediated photodynamic inactivation with 405 nm light emitting diodes (LEDs) on Salmonella Enteritidis.

Photodynamic inactivation (PDI) has a potential application for food preservation that can minimize food pathogens posing risks to consumer health. This study aimed to evaluate the antibacterial activity of 405 nm light-emitting diodes (LEDs) illumination in the presence of carvacrol and curcumin against Salmonella Enteritidis and S. Enteritidis PT4 at different temperatures (4 °C, 25 °C and 37 °C) and time parameters (15 min, 30 min and 45 min) in the illumination system. Compared to their individual treatment, the decrease in the bacterial population was stronger in bacteria treated with LEDs + carvacrol or LEDs + curcumin. Co-application of carvacrol or curcumin with LEDs at 37 °C showed strong antibacterial activity against both bacteria depending on the application time. Co-application at 37 °C for 45 min completely inhibited the growth of S. Enteritidis. LEDs, curcumin, carvacrol applications alone or LEDs + curcumin, LEDs + carvacrol applications caused a decrease in bacterial population in proportion to the increase in the storage temperature and application times. These results showed that carvacrol or curcumin potentiates LEDs illumination therapy against both bacteria. Future studies on adapting the PDI system to control bacteria in a variety of foods may help develop novel strategies to fight against foodborne bacterial pathogens.

Improvement of Water Quality by Light-Emitting Diode Illumination at the Bottom of a Field Experimental Pond

Remediation of water quality by stimulating algal photosynthesis using light-emitting diodes (LEDs) has attracted attention, but few studies have examined this in outdoor freshwater environments. To understand the effects of LED illumination on water quality, the dissolved oxygen (DO), temperature, pH, and electric conductivity were monitored over 5 months in three depressions with or without a red/blue LED light at the bottom of an experimental pond. The effects of the blue LED on water quality were evident in the period with less rainfall after the change of water quality to an equilibrium state; DO and pH were higher, and EC was lower for the blue LED than for the control. The diel changes of these variables were also lower for the blue LED. The effects of the red LED on DO and pH were also evident, but to a lesser extent compared to those of the blue LED. A vertical mixing of water associated with a nighttime cooling of the surface water was suggested by a rapid DO increase after a temperature decrease in the control. Such internal water circulation and an inflow of water after rainfall might have obscured the LED effects in the rainy period. The bottom water of the blue LED had a higher density and species richness of phytoplankton than that of the control at the end of the experiment. A lower density of phytoplankton and higher nutrient concentrations in the red LED might have been due to a higher density and feeding activity by zooplankton. Our results confirmed the applicability of LED illumination in stimulating algal photosynthesis, and in improving the oxygen condition of the bottom water in freshwater ponds.

Efficacy of 405 nm Light-Emitting Diode Illumination and Citral Used Alone and in Combination for Inactivation of Vibrio parahaemolyticus on Shrimp

Vibrio parahaemolyticus is a widely distributed pathogen, which is frequently the lead cause of infections related to seafood consumption. The objective of the present study was to investigate the antimicrobial effect of the combination of 405 nm light-emitting diode (LED) and citral on V. parahaemolyticus. The antimicrobial effect of LED illumination and citral was evaluated on V. parahaemolyticus not only in phosphate-buffered saline (PBS) but also on shrimp. Quality changes of shrimp were determined by sensory evaluation. Changes in bacteria cell membrane morphology, cell membrane permeability, cell lipid oxidation level, and DNA degradation were examined to provide insights into the antimicrobial mechanism. The combination of LED treatments and citral had better antimicrobial effects than either treatment alone. LED combined with 0.1 mg/mL of citral effectively reduced V. parahaemolyticus from 6.5 log CFU/mL to below the detection limit in PBS. Combined treatment caused a 3.5 log reduction of the pathogen on shrimp within 20 min and a 6 log reduction within 2 h without significant changes in the sensory score. Furthermore, combined LED and citral treatment affected V. parahaemolyticus cellular morphology and outer membrane integrity. The profile of the comet assay and DNA fragmentation analysis revealed that combination treatment did not cause a breakdown of bacterial genomic DNA. In conclusion, LED may act synergistically with citral. They have the potential to be developed as novel microbial intervention strategies.

Convolutional Neural Network for Measurement of Suspended Solids and Turbidity

The great potential of the convolutional neural networks (CNNs) provides novel and alternative ways to monitor important parameters with high accuracy. In this study, we developed a soft sensor model for dynamic processes based on a CNN for the measurement of suspended solids and turbidity from a single image of the liquid sample to be measured by using a commercial smartphone camera (Android or IOS system) and light-emitting diode (LED) illumination. For this, an image dataset of liquid samples illuminated with white, red, green, and blue LED light was taken and used to train a CNN and fit a multiple linear regression (MLR) by using different color lighting, we evaluated which color gives more accurate information about the concentration of suspended particles in the sample. We implemented a pre-trained AlexNet model, and an MLR to estimate total suspended solids (TSS), and turbidity values in liquid samples based on suspended particles. The proposed technique obtained high goodness of fit (R2 = 0.99). The best performance was achieved using white light, with an accuracy of 98.24% and 97.20% for TSS and turbidity, respectively, with an operational range of 0–800 mgL−1, and 0–306 NTU. This system was designed for aquaculture environments and tested with both commercial fish feed and paprika. This motivates further research with different aquatic environments such as river water, domestic and industrial wastewater, and potable water, among others.

Effects of Light-Emitting Diode Illumination on Sediment Surface Biological Activities and Releases of Nutrients and Metals to Overlying Water in Eutrophic Lake Microcosms

The release of nutrients and metals from the sediment to the overlying water induced by oxygen depletion is an important issue in eutrophic aquatic systems. Effects of light-emitting diode (LED) illumination on oxygen conditions and release of nutrients and metals from the sediment were examined by comparing with those effects of aeration in microcosms using water and sediment of Lake Taihu, China. Periphyton with filamentous algae developed on the sediment surface in the LED (blue wavelength) treatment. Dissolved oxygen became rapidly saturated and gradually supersaturated in the aeration and LED treatments, respectively, but remained low in the control. A thicker oxic layer developed on the sediment for the LED than aeration but was poorly developed with a blackened surface in the control. Invertebrate burrows were distributed deeper and the bacterial community was more dominated by aerobic species in the LED, indicating deeper penetration of oxygen into the sediment. Nutrients (e.g., N and P) and some metals (e.g., Hg, As, and Mn) in water were lower for the LED and aeration than in the control; nutrients and other solutes that increased electric conductivity (e.g., Ca, Mg) were lower for the LED than aeration. These results suggest that LED can effectively oxygenate the bottom water by stimulating algal photosynthesis and benthic invertebrate activity, resulting in greater retention of nutrients and metals in/on sediment compared to aeration.

Low-cost and high-performance poly(thienylene vinylene) derivative donor for efficient versatile organic photovoltaic cells

The utilization of donor materials with complex structures obviously increases the costs of organic photovoltaic (OPV) cells. Therefore, low-cost and high-performance are two issues that must be considered when designing polymer donors for the preparations of large-area OPV cells. Here, a poly(thienylene vinylene) derivative, named PTVT-BT was reported. PTVT-BT has a very simple completely non-fused molecular structure. PTVT-BT shows planar molecular structure and obvious solution aggregation effect. Besides, PTVT-BT demonstrates a high hole mobility up to the magnitude of 10-2 cm-2 V-1 s-1. The external quantum efficiency of electroluminescence of PTVT-BT is 7 × 10-3. As a result, the OPV cell based on PTVT-BT:eC9 demonstrates a power conversion efficiency (PCE) of 16.31%, which is the highest value among the poly(thienylene vinylene)- and polythiophene-based OPV cells. The tandem OPV cell with PTVT-BT as the donor of the sub-cell yields an outstanding PCE of 18.49%. Besides, the indoor OPV cell based on PTVT-BT:BTA3 exhibits a PCE of 27.30% under a light-emitting diode (LED) illumination of 1000 lux (2700 K). This study indicates that PTV-derivative is a kind of promising material for the future OPV industrialization.

Color-temperature dependence of indoor organic photovoltaic performance

Organic materials are uniquely suited for indoor light energy harvesting because they absorb mostly in the visible spectrum and the absence of ultraviolet light minimizes their degradation. However, the performance of photovoltaic devices under indoor lighting depends on the correlated color temperatures (CCTs) of the light sources but has not been examined previously. Here we study organic photovoltaics with different combinations of donor and acceptor materials under white light-emitting diode (LED) illumination. The current density – voltage (J - V) measurements were performed under illuminance of 1000 lx at nominal LED CCTs of 3000 K, 4000 K, and 6000 K. Absorption spectra of neat and blended films and device external quantum efficiency were measured. Our results show that active layer absorption in the blue LED emission region determines the short-circuit current density (J sc ) increase from 3000 K to 6000 K CCT; the more the active layer absorbs at 450 nm, the larger the J sc increase under higher CCTs. We find that the normalized fractional absorption of the active layer at 450 nm needs to be > 0.85 to eliminate a decrease in power conversion efficiency as the CCT is varied from 3000 K to 6000 K. This work highlights the unique tunability of organic absorbers that is difficult to achieve in inorganic materials and provides guidance on how to select organic absorbers for specific applications under different indoor illumination conditions. • Study color-temperature dependence of organic photovoltaic performance under white light-emitting diode illumination. • Active layer absorption at 450 nm determines the power conversion efficiency (PCE) under cool white light. • A threshold exists in the 450-nm absorption to eliminate PCE decrease as color-temperature increases. • Analyze color-temperature behavior of high-performance organic photovoltaics.

Award-Winning LED Illumination for Fluorescence from Fura-2 to Cy7.5 and Beyond

Abstract:Light-emitting diode (LED) illumination for fluorescence microscopy systems has come a long way since the turn of the century, when the LED sources available had low optical power and a limited range of wavelengths. While the benefits of LED technology were attractive, their limitations prevented large-scale adoption. Twenty years later, advances in the semi-conductor industry have eliminated many of those fundamental hurdles. Today, LED technology is rapidly replacing the lamps used in microscopy and fluorescence imaging, even for applications on the extreme ends of the light microscopy spectrum. This article describes the latest advances in illumination for fluorescence imaging, from near-UV to near-IR fluorophores. Case studies demonstrate the new X-Cite® NOVEM™ as successful replacements for traditional arc lamps in calcium imaging applications, producing equivalent results with the convenience of LEDs. For its usefulness to the microscopy community, the X-Cite NOVEM system was awarded the prestigious 2021 Microscopy Today Innovation Award.

Heterosubstrate Illumination Effects in III-V Solar Cells.

Reference cell based current vs voltage (IV) measurements assume that the effect of an illumination spectrum on a solar cell's performance can be fully captured by the multiplication of the spectrum with the device's spectral response and subsequent integration. This is based on a fundamental understanding that sub-bandgap light will be minimally absorbed, if at all, in the active layers of the solar cell and therefore not contribute to the power generation. In this work we show a novel phenomenon in which illumination of the substrate is required for good performance in solar cells with III-V active layers and germanium substrates, despite negligible contribution to the short circuit current or open circuit voltage, or increase of generated power beyond that expected from the III-V junction. Discovered in the course of characterizing cells for low-light conditions, we confirm the observation with additional IV and electroluminescence measurements and modeling that reproduces experimental results. This phenomenon has implications for device characterization under non-standard light sources, the development of solar cells for conditions lacking long-wavelength light such as indoor photovoltaics under light-emitting diode illumination, and the prediction of device performance under spectra that differ from the test conditions.

Efficient Green Light Acclimation of the Green Algae Picochlorum sp. Triggering Geranylgeranylated Chlorophylls.

In analogy to higher plants, eukaryotic microalgae are thought to be incapable of utilizing green light for growth, due to the “green gap” in the absorbance profiles of their photosynthetic pigments. This study demonstrates, that the marine chlorophyte Picochlorum sp. is able to grow efficiently under green light emitting diode (LED) illumination. Picochlorum sp. growth and pigment profiles under blue, red, green and white LED illumination (light intensity: 50–200 μmol m−2 s−1) in bottom-lightened shake flask cultures were evaluated. Green light-treated cultures showed a prolonged initial growth lag phase of one to 2 days, which was subsequently compensated to obtain comparable biomass yields to red and white light controls (approx. 0.8 gDW L−1). Interestingly, growth and final biomass yields of the green light-treated sample were higher than under blue light with equivalent illumination energies. Further, pigment analysis indicated, that during green light illumination, Picochlorum sp. formed unknown pigments (X1-X4). Pigment concentrations increased with illumination intensity and were most abundant during the exponential growth phase. Mass spectrometry and nuclear magnetic resonance data indicated, that pigments X1-X2 and X3-X4 are derivatives of chlorophyll b and a, which harbor C=C bonds in the phytol side chain similar to geranylgeranylated chlorophylls. Thus, for the first time, the natural accumulation of large pools (approx. 12 mg gDW −1) of chlorophyll intermediates with incomplete hydrogenation of their phytyl chains is demonstrated for algae under monochromatic green light (Peak λ 510 nm, full width at half maximum 91 nm). The ability to utilize green light offers competitive advantages for enhancing biomass production, particularly under conditions of dense cultures, long light pathways and high light intensity. Green light acclimation for an eukaryotic microalgae in conjunction with the formation of new aberrant geranylgeranylated chlorophylls and high efficiency of growth rates are novel for eukaryotic microalgae. Illumination with green light could enhance productivity in industrial processes and trigger the formation of new metabolites–thus, underlying mechanisms require further investigation.

Impacts of Colored Light-Emitting Diode Illumination on the Reproductive Performance and Bioactive Constituents and the Molecular Mechanism of Hypothalamus Gland in Zi-geese.

Goose is a seasonal breeding animal. Its reproduction is regulated by hypothalamus-pituitary-gonad axis and also affected by environmental factors such as light and location. Zi-goose is characterized with long egg-laying period and high egg-laying potential and belongs to the long-day type of seasonal breeding. In this study, the regulation mechanism of different lighting on reproductive performance of Zi-goose by using metabonomics analysis technology. In addition, 1,481 differential metabolites were screened out totally. 583 differential metabolites were identification in hypothalamus of Zi-goose. 196 differential metabolites were identification in pituitary of Zi-goose. 692 differential metabolites were identification in ovary of Zi-goose. Under red light condition for 12 h, expression of 433 differential metabolites were down-regulated and expression of 150 differential metabolites were up regulated in hypothalamus of Zi-goose, expression of 125 differential metabolites were down-regulated and expression of 71 differential metabolites were up-regulated in pituitary of Zi-goose, expression of 355 differential metabolites were down-regulated and expression of 337 differential metabolites were up-regulated in ovary of Zi-goose. 33 differential metabolites were closely associated with 1,264 transcripts and 400 homologous genes of related enzymes in hypothalamus of Zi-goose. 15 differential metabolites were closely associated with 163 transcripts and 47 homologous genes of related enzymes in pituitary of Zi-goose. 55 differential metabolites were closely associated with 1,255 transcripts and 360 homologous genes of related enzymes in ovary of Zi-goose. It was confirmed that four metabolic pathways were closely related to light regulation of reproductive performance of Zi-goose, namely GnRH signaling pathway, prolactin signaling pathway, thyroid hormone synthesis and ovarian steroidogenesis. Typical differential metabolites of arachidonic acid, glucose-6-phosphate, progesterone, glutathione, oxidized glutathione, testosterone, deoxyepiandrosterone and their related protein genes would play an important role in light regulation of reproductive performance of Zi-goose.

ITO‐Free Indoor OPV Modules from Nonhalogenated Solvents

The growing market of the internet‐of‐things (IoT) accelerates the development of indoor organic photovoltaics. Very high performances up to 29% are already achieved under illumination with white light‐emitting diodes with intensities in the range of 500–1000 lux. However, topics relevant for mass production such as large area coating, use of nontoxic solvents, and inexpensive electrodes are hardly addressed thus far. Herein this work, an indium‐tin‐oxide‐free device stack is presented, which shows very good performance with many novel absorber materials under both full sun light as well as indoor illumination. Furthermore, lab‐scale cells are upscaled to small modules that can power typical IoT devices. This includes the transition from spin coating to slot‐die coating as well as the use of green solvents. Further, as the parallel resistance (RP) is crucial for the performance under low illumination intensities, a detailed analysis is carried out and it is found that a one‐diode model with the RP being determined from the dark current–voltage characteristics reproduces the behavior quite accurately. Efficiencies of 19.3% on cell level and above 17% on an 8.1 cm2 module with eight interconnected cells are achieved under 500 lux cold white light‐emitting diode illumination.

Effect of differences in light source environment on transcriptome of leaf lettuce (Lactuca sativa L.) to optimize cultivation conditions.

When used in closed-type plant factories, light-emitting diode (LED) illumination systems have the particular advantages of low heat emission and high luminous efficiency. The effects of illumination quality and intensity on the growth and morphogenesis of many plant species have been examined, but improvements are needed to optimize the illumination systems for better plant products with lower resource investments. In particular, new strategies are needed to reduce the wastage of plant products related to leaf senescence, and to better control the ingredients and appearance of leafy vegetables. Although the quality of light is often altered to change the characteristics of plant products, the transcriptional status underlying the physiological responses of plants to light has not been established. Herein, we performed a comprehensive gene expression analysis using RNA-sequencing to determine how red, blue, and red/blue LEDs and fluorescent light sources affect transcriptome involved in the leaf aging of leaf lettuce. The RNA-sequencing profiling revealed clear differences in the transcriptome between young and old leaves. Red LED light caused large variation between the two age classes, while a pure or mixed blue LED light spectrum induced fewer transcriptome differences between young and old leaves. Collectively, the expression levels of genes that showed homology with those of other model organisms provide a detailed physiological overview, incorporating such characteristics as the senescence, nutrient deficiency, and anthocyanin synthesis of the leaf lettuce plants. Our findings suggest that transcriptome profiles of leaf lettuce grown under different light sources provide helpful information to achieve better growth conditions for marketable and efficient green-vegetable production, with improved wastage control and efficient nutrient inputs.

Low-Trap-Density CsPbX3 Film for High-Efficiency Indoor Photovoltaics.

The continuous advancement of the Internet of Things (IoT) and photovoltaic technology has promoted the development of indoor photovoltaics (IPVs) that powers wireless devices. Nowadays, the CsPbX3 perovskite has received widespread attention because of its high power conversion efficiency (PCE) in an indoor environment and suitable band gap for IPVs. In this work, we regulated the thickness of the photoactive layer (to optimize the carrier transport process without affecting indoor absorption) and bromine substitution (to adjust the band gap and improve the quality of the film) to reduce trap-assisted carrier recombination. A CsPbI2.7Br0.3 perovskite cell with excellent performance was obtained, which is superior to c-Si cells in a low-light environment. The optimized device achieved PCE values of 32.69 and 33.11% under a 1000 lux fluorescent lamp and white light-emitting diode (WLED) illumination. The J-V hysteresis of the device is also effectively suppressed. Moreover, it has a steady-state output power of 7.76 μW (0.09 cm2, and can be enhanced by enlarging the areas), which can meet the consumption of many small wireless devices. It is worth noting that the optimized device has excellent applicability to be used in a complex indoor environment.

Architecting Silk Protein and Melanin for Photoresponsive and Self‐Healable Optoelectronic Skins

AbstractThe central processes driving biological phenomena are based on the conduction of ions and electrons in biomaterials, implying the possibility of achieving a fully biomaterial‐based electronic skin. However, finding the appropriate biomaterials for electronic skins is still challenging. Here, a photoresponsive, self‐healable, and biomaterial‐based optoelectronic skin (OE‐skin) fabricated with melanin nanoparticles and silk protein is proposed and the electronic properties and their mechanisms in the artificially generated OE‐skin are reported. Not only does silk protein hydrogel provide a transparent and skin‐compatible platform for use as OE‐skin but it also provides the appropriate environment for melanin to demonstrate high electrical conductivity. The OE‐skin can be considered a p‐type semiconducting material showing high conductivity of up to 6 mS cm−1 in addition to a 40% enhancement in the conductivity by green laser and ultraviolet light emitting diode illuminations. Additionally, the OE‐skin autonomously heals itself from multiple cuts, allowing the restoration of its electrical properties. These material properties enable applications for strain‐sensors, humidity sensors, and ultraviolet light sensors, as well as image pixels to convert light‐lettering into electrical signals. The proposed fully biomaterial‐based OE material platform offers a new way for next‐generation electronic skins to achieve a seamless interface with the human body.

Ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella-based photo-fermentation with optimal light-emitting diode illumination: From laboratory to pilot plant

To achieve ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella pyrenoidosa-based photo-fermentation, light-emitting diode (LED) spectrum was firstly evaluated in 5-L glass photo-fermenter with surrounding LED panels. Results showed that warm white LED was favorable to improve biomass yield and recovery rate of nutrients than mixed white LED. When scaling up from laboratory (50-L, 500-L) to pilot scale photo-fermenter with inner LED panels, the maximum recovery rates of NO3- (5.77 g L-1 d-1) and PO43- (0.44 g L-1 d-1) were achieved in 10,000-L photo-fermenter, along with high productivity of biomass (11.06 g L-1 d-1), protein (3.95 g L-1 d-1) and lipids (3.79 g L-1 d-1), respectively. This study demonstrated that photo-fermenter with inner warm white LED illumination is a superhigh-efficient system for nitrate and phosphate recovery with algal biomass coproduction, providing a promising application in pilot demonstration of wastewater bioremediation and facilitating novel facility development for green manufacturing.

Obtain full visible spectrum light-emitting diode illumination via bismuth-activated cyan phosphors

Developing highly efficient cyan-emitting fluorescent materials is essential to bridge the cyan gap in phosphor-converted white light-emitting diodes for full-spectrum white illumination. Here, a Bi-doped cyan phosphor has been reported to solve this gap. The phase purity, photoluminescence emission/excitation spectra, concentration quenching, lifetime decay curves, and temperature-dependent photoluminescence emission spectra were systematically investigated. SrLaGaO4:Bi3+ exhibits a broad excitation band (250–400 nm), which matches with the emission of a commercial near-ultraviolet light-emitting diode chip. The cyan light peaked at 475 nm is observed, which is attributed to the 3P1→1S0 transition of Bi3+. The thermal quenching experiment was performed, and the activation energy was calculated as 0.36 eV. Finally, full-spectrum white light-emitting diode devices were fabricated using SrLaGaO4:Bi3+ phosphors, commercial blue BaMgAl10O17:Eu2+ phosphor, green (Ba, Sr)2SiO4:Eu2+ phosphor, and red CaAlSiN3:Eu2+ phosphor, which displayed an International Commission on an illumination coordinate of (0.3732, 0.3850), a correlated color temperature of 4290 K, and a color rendering index of 93.2 at a drive current of 20 mA. This result indicates that SrLaGaO4:Bi3+ plays an essential role in bridging the cyan gap, providing new inspiration for applying cyan-emitting phosphors in full-spectrum white lighting.

Survival Analysis to Predict How Color Influences the Shelf Life of Strawberry Leather.

Color change of fruit-based products during storage is an important quality parameter to determine their shelf life. In this study, a combination of relative humidity (RH) and illumination was evaluated on the stability of strawberry leathers. Samples were conditioned at 25 °C, in chambers with RH of 22.5% and 52.3% and under two levels of illumination (no illumination and with a light-emitting diode (LED) illumination at 1010 lx). Samples were analyzed during storage by instrumental color measurements, total anthocyanin content, and consumers’ acceptance/rejection of the product color. Current-status survival analysis was performed to estimate the sensory-based shelf-life of the strawberry leather. The chromatic parameters (a* and ΔE* values) and anthocyanin content changed with increasing storage time and RH, fitting a first-order fractional conversion model. Samples conditioned at the higher RH showed a higher reduction of a* values and anthocyanins losses when stored under LED illumination than those without illumination. The increase of RH resulted in a faster increase of the consumer rejection probability and a shorter shelf life of the strawberry leather. For 50% of consumers’ rejection, the sensory shelf life of the strawberry leather equilibrated at 22.5% RH was estimated as at least 54 days, while it was reduced to approximately 2 days at 52.3% RH. The red chromatic parameter (a* value) strongly correlated to the percentage of consumer rejection in all storage conditions, suggesting that this analytical parameter can be useful as a predictor of strawberry leather’s shelf life. Therefore, the results of this study show the applicability of an approach that integrates instrumental and sensory data to acquire faster information on color changes during the storage of strawberry leather and product shelf-life prediction.

Expanding the Angle of Incidence Tolerance of Unclonable Anticounterfeiting Labels Based on Microlens Arrays and Luminescent Microparticles

Unclonable anticounterfeiting labels can be based on micrometer‐scale randomness created by stochastic processes like the distribution of luminescent microparticles in a transparent layer. Adding a microlens array to the layer can simplify the hardware needed for authentication in that magnification is no longer required. The bright point‐pattern generated under light‐emitting diode illumination can be captured by a standard digital camera. Shifting the angle of incidence (AOI) relocates the microlens foci changing the bright point‐pattern. This provides unclonability, as several distinct bright point patterns at different AOI can be required for authentication. However, it also imposes technical requirements for the authentication setup in terms of the tolerance with which the AOI must be controlled. Herein, the AOI tolerance, the deviation of angle between reference and test image for which sufficiently similar bright point patterns are recorded that they are considered matching by the authentication algorithm, is investigated. Using microlens arrays with a focal length of 550 μm, the average size of the phosphor particle was varied from 9 ± 1 to 32.5 ± 2 μm, resulting in a relaxation of tolerance from 0.8° to 3.6°. Methods to further increase the AOI tolerance and facilitate the practical implementation of these labels are discussed.

Multifunctional high entropy oxides incorporated functionalized biowaste derived activated carbon for electrochemical energy storage and desalination

Nano-sized high entropy oxides (particle size < 10 nm) are expected to possess enhanced stability, electrochemical properties and increased potential in versatile applications than bulk metal oxides. In this study, nano-sized high entropy oxides incorporated surface functionalized coconut shell derived activated carbon (HEO/f-CSAC) is synthesized, characterised and used as an advanced multifunctional material for electrochemical energy storage and desalination. Attributed to its unique microstructure and extraordinary properties, HEO/f-CSAC shows an excellent salt adsorption capacity of 241 mg g−1 at 1.2 V in 500 mg L−1 concentration of NaCl solution, which is very high as compared to previous reports. The reason behind high salt adsorption capacity is its outstanding specific capacitance of 147.5 F g−1 at current density 1 A g−1. Moreover, the assembled lab-scale CDI unit demonstrates extremely good performance upto 20 adsorption-desorption cycles due to the long cycle life with good capacitance retention of fabricated HEO/f-CSAC based two-electrode supercapacitor. Additionally, a red light-emitting diode illumination by connecting three supercapacitors in series, indicates the high efficiency and potential of HEO/f-CSAC for real life energy-related application. These results prove that HEO/f-CSAC can be implemented for water desalination with enhanced supercapacitive performance manifesting its multifunctionality for energy and environmental applications.