LED Illumination Research Articles

Comparing Practical Spectral Imaging Methods for Cultural Heritage Studio Photography

Two practical methods for implementing spectral imaging within the framework of museum studio photography were investigated. Imaging was carried out using a consumer RGB digital camera paired with either (1) colored glass filters and a broadband source or (2) optimized multichannel LED illumination, yielding five or six spectral image bands, respectively. Color targets were used to develop and verify profiles for transforming between the multiband camera signals and final color managed images. The filter-based and LED-based profiles were assessed quantitatively for color accuracy using color difference statistics, and several paintings were imaged and rendered using the profiles as a visual demonstration of the differences. While both were superior to conventional RGB imaging, the LED-based method outperformed the filter-based method for accurate reproduction of independent data. This supplements practicality and cost considerations that are informing the development of accessible spectral imaging strategies for highly color accurate museum studio photography.

Impact of Light with Different Spectra on the Photosynthetic Activity of Cucumber Plants under Fusarium Wilt

The photosynthetic activity of 28-day-old cucumber plants of the Kustovy variety formed under LED illumination with the predominance of red light (RL) or far red light (FRL) and infected with the fungus Fusarium oxisporum sp. (F.ox.) was studied. The predominance of RL or FRL contributed to an increase in the content of chlorophyll and carotenoids per dry leaf weight compared to the plants grown under white light (WL). In the infected plants grown under WL and RL regimes, an increase in the total content of chlorophyll and carotenoids was observed relative to healthy plants, and a decrease in the same parameters for FRL was noted. In healthy cucumber leaves grown under RL and FRL regimes, an increase in the activity of photosystem (PS)1 and PS2 in comparison with WL was observed. Infection of cucumber plants grown under WL did not cause any changes in the functional parameters of PS2 against the background of a slight reduction in PS1 complexes. Under RL and FRL regimes, a decrease in the photochemical activity of PS 1 and PS 2 in infected leaves was noted. The activity of ascorbate peroxidase - one of antioxidant enzymes in chloroplasts decreased in healthy cucumber leaves under RL and FRL compared to WL and increased in infected leaves compared to the healthy ones under all light regimes, especially strongly under RL. The results obtained demonstrate different response mechanisms for cucumber chloroplasts to the infection with a fungal pathogen, depending on the light conditions of growing.

Molecularly understanding and regulating carrier injection behavior of ETL/perovskite towards high performance PeLEDs

Effectively balancing carrier injection of perovskite LEDs (PeLEDs) for next-generation display and illumination urgently needs for molecularly understanding carrier injection behavior of electron transport layer (ETL)/perovskite toward further developing high performance PeLEDs. Here, we molecularly reveal the electron injection behaviors of PeLEDs by theoretically-experimentally decoupling the electron transport of ETLs and electron injection of TmPyPB/perovskite and TPBi/perovskite. Resulted, the better molecular planarity bridging effect (MPBE) of TmPyPB than TPBi can effectively increase electronic-coupling for the improved electron transport ability and significantly decrease injection barrier for the enhanced electron injection capability, intrinsically leading to a more balanced carrier injection and a less electron accumulation of PeLEDs. Compared to TPBi-based PeLEDs, the TmPyPB-based PeLEDs present the obviously-increased average EQE, current efficiency, power efficiency and luminance by 44 %, 63 %, 43 % and 100 %, respectively. Meanwhile, this PeLED shows a higher voltage tolerance characteristic of 7.5 V than that of TPBi-based PeLEDs (6.25 V). Therefore, this work may provide a fundamental insight into carrier injection behavior of PeLEDs for effectively-regulating its carrier injection balance and further for its greatly-facilitated commercialization.

Simultaneous photoautotrophic production of DHA and EPA by Tisochrysis lutea and Microchloropsis salina in co-culture

Marine microalgae have received much attention as a sustainable source of the two health beneficial omega-3-fatty acids docosahexaenoic acid (DHA, C22:6) and eicosapentaenoic acid (EPA, C20:5). However, photoautotrophic monocultures of microalgae can only produce either DHA or EPA enriched biomass. An alternative may be the photoautotrophic co-cultivation of Tisochrysis lutea as DHA-producer with Microchloropsis salina for simultaneous EPA production to obtain EPA- and DHA-rich microalgae biomass in a nutritionally balanced ratio. Photoautotrophic co-cultivation processes of T. lutea and M. salina were studied, applying scalable and fully controlled lab-scale gas-lift flat-plate photobioreactors with LED illumination for dynamic climate simulation of a repeated sunny summer day in Australia [day–night cycles of incident light (PAR) and temperature]. Monocultures of both marine microalgae were used as reference batch processes. Differences in the autofluorescence of both microalgae enabled the individual measurement, of cell distributions in co-culture, by flow cytometry. The co-cultivation of T. lutea and M. salina in artificial sea water with an inoculation ratio of 1:3 resulted in a balanced biomass production of both microalgae simultaneously with a DHA:EPA ratio of almost 1:1 (26 mgDHA gCDW−1, and 23 mgEPA gCDW−1, respectively) at harvest after depletion of the initially added fertilizer. Surprisingly, more microalgae biomass was produced within 8 days in co-cultivation with an increase in the cell dry weight (CDW) concentration by 31%, compared to the monocultures with the same amount of light and fertilizer. What is more, DHA-content of the microalgae biomass was enhanced by 33% in the co-culture, whereas EPA-content remained unchanged compared to the monocultures.Graphical

Photodegradation of tetracycline antibiotic by ternary recyclable Z-scheme g-C3N4/Fe3O4/Bi2WO6/Bi2S3 photocatalyst with improved charge separation efficiency: Characterization and mechanism studies

This article argues the design of the recyclable Z-scheme g-C3N4/Fe3O4/Bi2WO6/Bi2S3 (CNFBB) photocatalyst as an efficient concept to obtain photogenerated charge carriers with high redox potential. A cost-effective magnetic CNFBB nanocomposite was fabricated via a multistep method by decorating Fe3O4, Bi2WO6, and Bi2S3 on the surface of pure g-C3N4 nanosheets. The photocatalytic capability was demonstrated for the visible-light degradation of tetracycline antibiotic (TC) in an aqueous solution. Sophisticated analytical techniques such as XRD, FTIR, elemental mapping, EDS, SEM, AFM, TEM, VSM, DRS, PL, and BET were employed for the characterization of synthesized nanomaterials. The CNFBB catalyst showed improved TC degradation activity (98 % in 105 min) under LED illumination with a remarkable degradation rate of 0.0341 min−1, which is 2.27 times higher than that of ternary CNFB. The improved photocatalytic ability was ascribed to the synergistic impacts of g-C3N4, Fe3O4, Bi2WO6, and Bi2S3 by developing a quaternary CNFBB nanostructure with a high surface area, lower band gap energy, high stability, easily recycled, excellent redox potential, and an efficient charge separation mechanism. Interestingly, the CNFBB hybrid displayed good reusability and high stability after six cycles of experiments. The photodegradation mechanism was charge migration pathways, and band locations were systematically explained by the Z-scheme heterojunction system verified by radical quenching experiments, ESR results, and band structure calculation. This work can open new horizons in designing other Bi-based systems supported by g-C3N4 nanosheets for wastewater purification.

Methyl Aminolaevulinic Acid versus Aminolaevulinic Acid Photodynamic Therapy of Actinic Keratosis with Low Doses of Red-Light LED Illumination: Results of Long-Term Follow-Up.

Photodynamic therapy (PDT) treatment for multiple actinic keratosis (AK) has been found effective when lower doses of red light were used with methyl aminolaevulinic acid (MAL). The aim of this study was to compare the results of lower doses of red light conventional PDT (h-PDT, 16 J/cm2) with MAL and aminolaevulinic acid (ALA) in a long-term follow-up. Patients with more than five symmetrical AK on the scalp who were candidates for PDT were selected and divided randomly between MAL and ALA treatment and patients were followed at 3 and 12 months. The responses were assessed by counting the total AK and the AK per patient. Pain and adverse events were also compiled. A total of 46 patients were treated, 24 with MAL, and 22 with ALA. The two groups were comparable at baseline (p > 0.005). No significant differences were found in the results of both treatments at 12 months, despite ALA exhibiting slightly better results at 3 months. No differences in pain and adverse events were assessed. Both ALA and MAL were effective when lower doses of red light were used in c-PDT. Long term efficacy was also documented. Further studies are necessary to determine the inferior point of red-light illumination without losing efficacy.

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 < 0.001) and lower saturated fatty acid levels (71.2 ± 0.4 vs. 72.5 ± 0.4, p < 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 < 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.

Working smarter with optical filters and LED illumination

Working smarter with optical filters and LED illumination

A Photoinduced, Nickel-Catalyzed Reaction for the Stereoselective Assembly of C-Linked Glycosides and Glycopeptides.

C-Alkyl glycosides and glycoproteins exist in natural products and are prized for their role as carbohydrate mimics in drug design. However, a practical strategy that merges glycosyl donors with readily accessible reagents, derived from abundant carboxylic acid and amine feedstocks, is yet to be conceived. Herein, we show that a nickel catalyst promotes C-C coupling between glycosyl halides and aliphatic acids or primary amines (converted into redox-active electrophiles in one step), in the presence of Hantzsch ester and LiI (or Et3 N) under blue LED illumination to deliver C-alkyl glycosides with high diastereoselectivity. Mechanistic studies support the photoinduced formation of alkyl radicals that react with a glycosyl nickel species generated in situ to facilitate cross-coupling. Through this manifold, innate CO2 H and NH2 motifs embedded within amino acids and oligopeptides are selectively capped and functionalized to afford glycopeptide conjugates through late-stage glycosylation.

A Photoinduced, Nickel‐Catalyzed Reaction for the Stereoselective Assembly of C‐Linked Glycosides and Glycopeptides

AbstractC‐Alkyl glycosides and glycoproteins exist in natural products and are prized for their role as carbohydrate mimics in drug design. However, a practical strategy that merges glycosyl donors with readily accessible reagents, derived from abundant carboxylic acid and amine feedstocks, is yet to be conceived. Herein, we show that a nickel catalyst promotes C−C coupling between glycosyl halides and aliphatic acids or primary amines (converted into redox‐active electrophiles in one step), in the presence of Hantzsch ester and LiI (or Et3N) under blue LED illumination to deliver C‐alkyl glycosides with high diastereoselectivity. Mechanistic studies support the photoinduced formation of alkyl radicals that react with a glycosyl nickel species generated in situ to facilitate cross‐coupling. Through this manifold, innate CO2H and NH2 motifs embedded within amino acids and oligopeptides are selectively capped and functionalized to afford glycopeptide conjugates through late‐stage glycosylation.

Green Upconversion of a SrLaAlO4:Yb,Er Phosphor and Its Application for LED Illumination

Green Upconversion of a SrLaAlO4:Yb,Er Phosphor and Its Application for LED Illumination

Some recent advances in color science

We will discuss some of main topics in two recent publications on color from the International Commission on Illumination (CIE): CIE 015:2018 and CIE 248:2022. Regarding CIE 015:2018, it is the 4th edition of the most important CIE general publication on colorimetry, generally known as ‘CIE publication 15’. Among main novelties in CIE 015:2018 with respect to its previous 2004 edition, we can mention the introduction of the next four topics: 1) Cone-fundamental-based colorimetric observers; 2) New CIE illuminants (indoor daylight illuminants, smoothed daylight illuminants, illuminant E, and white LED illuminants); 3) The CIE colour appearance model CIECAM02; 4) The CIE 2017 color fidelity index. As a consequence of the active research on color appearance during the past few years, CIE 248:2022 proposed the CIECAM16 color appearance model for related colors and CIE 1931 standard colorimetric observer. In general, color appearance models provide a viewing-condition-specific method for the transformation of the tristimulus values X, Y, Z, to or from perceptual attribute correlates. CIECAM16 replaces CIECAM02 and may be useful for color management systems and image industries. CIECAM16 is simpler and maintains the predictions of experimental visual data made by CIECAM02. Finally, we will discuss advances in two issues related to color included in the current CIE Research Strategy: 1) A roadmap toward a new CIE colorimetry based on cone fundamentals, currently studied by CIE Technical Committee 1-98; 2) Color differences in tri-dimensional object colors and spatio-chromatic complexity, currently studied by CIE Technical Committees 8-17 and 8-14, respectively. In overall, we can conclude that color science is an active inter- and multi-disciplinary research field where optics continues playing a key role.

Photo-rechargeable all-solid-state lithium − sulfur batteries based on perovskite indoor photovoltaic modules

Photovoltaic technologies for indoor energy harvesting have attracted considerable attention because of the unique power requirements associated with the Internet of Things. However, intermittent power supplies, low light intensities, and security issues are barriers to the development of indoor photovoltaic technology. Herein, we demonstrate an all-solid-state photo-rechargeable battery system for indoor energy harvesting and storage based on an all-inorganic CsPbI2Br perovskite solar cell module and an all-solid-state lithium − sulfur battery. This energy conversion and storage unit exhibits an excellent overall energy conversion and storage efficiency of 11.2 % under LED illumination, as well as a high electrochemical storage capacity of 1585.3 mAh g−1. Moreover, the unit also shows good safety and stability after 200 h of photo-charge and galvanostatic discharge cycles due to the thermal stability of the solid-state CsPbI2Br perovskite and sulfide electrolyte. Even in the thermal aging tests at 60°C and 90°C, the photo-rechargeable battery still delivers superior high and steady performance for 200 h.

Influence of Pulsed, Scanning and Constant (16- and 24-h) Modes of LED Irradiation on the Physiological, Biochemical and Morphometric Parameters of Lettuce Plants (Lactuca sativa L.) while Cultivated in Vertical Farms

In city farming, when growing green crops, a significant part of the production cost is the cost of electricity for lighting. The physiology, biochemistry, morphology and productivity of plants can be affected by changing irradiation modes and these changes reduce electricity costs. However, the results of studies in the literature are contradictory. In this work, we investigated the effect of impulse (frequency 1000 Hz and duty cycle 67%), scanning (the principle of running lights) and constant 16 h and 24 h modes of operation of white light LED irradiators on the physiological, biochemical and morphometric parameters of lettuce with red and green leaves. The daytime integral of light in all variants remained unchanged ~15.6 mol m−2 day−1. Daily electricity consumption also did not differ significantly. Plants were grown on racks in a climatic chamber up to 35 days of age. For lettuce with red leaves, the most optimal for biomass accumulation and synthesis of anthocyanins was the impulse illumination mode, while for lettuce with green leaves, no statistically significant differences in biomass were observed under different irradiation modes. For red-leaved lettuce, it was found that the highest concentration of carotenoids in the leaf was observed under constant (24 h) and scanning irradiation, which is associated with a more active reaction of the photosynthetic system to prolonged irradiation and increased intensity during scanning irradiation. Also, increased photosynthetic activity was found in both varieties of lettuce at 16 h of operation of LED irradiators, which, however, did not affect their final productivity. The results may be useful for the development of LED illuminators for use in rack growing.

Confined Fe single atomic sites on (100) plane of anatase TiO2 nanofibers boost white LED driven Fenton-like norfloxacin degradation

Developing efficient and sustainable photocatalyst is crucial for antibiotic degradation in water treatment. Iron (Fe) species modified semiconductor photocatalysts have been widely used in visible-light driven Fenton-like systems. However, the limited dispersion of Fe sites and low redox rate of the Fe(III)/Fe(II) restrict the catalytic performance. Herein, the atomic Fe sites with highly dispersed coordination centers were confined (100) facets exposed titania nanofibers (Fe-TNFs) for efficient photocatalytic Fenton-like norfloxacin (NOR) degradation. The optimized Fe-TNFs catalyst could achieve 95% NOR removal after 5 h of white LED illumination, which is 15% higher than that of nanostructured Fe species. The high performance is credited for the enhanced visible light absorption, and the efficient electron transfer through Fe–O bonds in Fe-TNFs enables the fast cyclic transformation of Fe(III)/Fe(II), which can promote the continuous production of •OH in the photocatalytic Fenton-like system. This study can provide technical support for the developing a feasible and sustainable wastewater treatment solution, and provide reference for the fate and risk assessment of antibiotics in the environment.

479 Introduction of a Novel Multispectral Imaging Screening Algorithm to Distinguish Malignant Melanoma from Seborrheic Keratosis

Malignant melanoma (MM) is in the background of the majority of skin cancer-related mortality. On the other hand, seborrheic keratosis (SK) is a common benign lesion that in certain cases can mimic MM. In this work, we utilized a multispectral imaging device prototype with LED illumination to differentiate MM from SK, with the use of 405 nm autofluorescence and 525 and 660 nm diffuse reflectance imaging. Intensity descriptors of the captured images were analyzed, including the ratios, standard deviation and minimum and maximum of intensity values of the lesions in the investigated channels.

Drastically enhanced tetracycline degradation performance of a porous 2D g-C3N4 nanosheet photocatalyst in real water matrix: Influencing factors and mechanism insight

Porous 2D nanosheets are an emerging class of materials with exciting physical, chemical, optical, and electronic characteristics. This study reported the facile synthesis of a porous 2D g-C3N4 nanosheet photocatalyst through a simple chemical exfoliation route. The morphological characterization of the samples confirmed its porous 2D nanosheet structure with an approximate thickness of 2.5 nm. The as-prepared photocatalyst displayed a 4.2-fold enhanced tetracycline (TC) degradation rate coefficient compared to the pristine g-C3N4 under LED illumination. Further, the porous 2D g-C3N4 nanosheet photocatalyst exhibited superior TC degradation efficacy in a real water matrix. The synergistic effect of higher pH, presence of carbonate and bicarbonate anions, and the existence of humic substances could have elevated the degradation performance in the real water matrix. Moreover, the as-synthesized catalyst demonstrated remarkable stability and recyclability even after the four-cycle recycling experiment. A possible photocatalytic mechanism has been proposed following the findings of the radical trapping experiment. It is believed that this study would inspire further fabrication of other porous 2D nanosheet photocatalysts.

State of the Art and Elucidation of Postharvest LED Lighting on the Metabolism of Brassica Sprouts

Brassicaceae sprouts are important sources of vitamins, phenolic compounds, minerals, glucosinolates, and isothiocyanates. LEDs illumination have been demonstrated to increase yield and the phytochemical content of young plants. In the present work, rocket, radish, and tatsoi seeds were germinated in darkness for 7 days at 20 °C and 90% RH. After harvesting, sprouts were stored for 5 days at 5 °C under different LEDs treatments: White, Blue, Green, Orange, and Red. Darkness was used as control. The respiration rate and the sulforaphane content were monitored as a reference of the primary and secondary metabolism changes to evaluate the influence of LEDs. The application of Blue and Green LEDs increased the CO2 emission by ~25–45% compared to Darkness while no C2H4 emission was detected. The biosynthesis of sulforaphane was also increased by ~15–25%, under different wavelengths, although a clear tendency was not found among species. The state of the art of this research field was reviewed to elucidate the knowledge on it. Conclusively, the primary and secondary metabolism of plants, specifically in sprouts, can be stimulated using postharvest LED lighting.

Effect of Functionalized Benzene Derivatives as Potential Hole Scavengers for BiVO4 and rGO-BiVO4 Photoelectrocatalytic Hydrogen Evolution.

Sustainable hydrogen production is one of the main challenges today in the transition to a green and sustainable economy. Photocatalytic hydrogen production is one of the most promising technologies, amongst which BiVO4-based processes are highly attractive due to their suitable band gap for solar-driven processes. However, the performance of BiVO4 alone in this role is often unsatisfactory. Herein we report the improvement of BiVO4 performance with reduced graphene oxide (rGO) as a co-catalyst for the photoelectrochemical water splitting (PEC-WS) in the presence of simple functionalized benzene derivatives (SFBDs), i.e., phenol (PH), benzoic acid (BA), salicylic acid (SA), and 5-aminosalicylic acid (5-ASA) as potential photogenerated hole scavengers from contaminated wastewaters. Linear sweep voltammetry and chronoamperometry, along with electrochemical impedance spectroscopy were utilized to elucidate PEC-WS performance under illumination. rGO has remarkably improved the performance of BiVO4 in this role by decreasing photogenerated charge recombination. In addition, 5-ASA greatly improved current densities. After 120 min under LED illumination, 0.53 μmol of H2 was produced. The type and concentration of SFBDs can have significant and at times opposite effects on the PEC-WS performance of both BiVO4 and rGO-BiVO4.

Aggregation-Induced Emission Poly(meth)acrylates for Photopatterning via Wavelength-Dependent Visible-Light-Regulated Controlled Radical Polymerization in Batch and Flow Conditions.

A robust wavelength-dependent visible-light-regulated reversible-deactivation radical polymerization protocol is first reported for the batch preparation of >20 aggregation-induced emission (AIE)-active polyacrylates and polymethacrylates. The resulting polymers possess narrow molar mass distributions (Đ ≈ 1.09-1.25) and high end-group fidelity at high monomer conversions (mostly >95%). This demonstrated control provides facile access to the in situ generation of complex sequence-defined tetrablock copolymers in one reactor, even while chain extending from less reactive monomers. Polymerizations can be successfully carried out under various irradiation conditions, including using UV, blue, green, and red LED light with more disperse polymers obtained at the longer, less energetic, wavelengths. We observe a red shift and wavelength dependence for the most efficient polymerization using LED illumination in a polymerization reaction. We find that the absorption of the copper(II) complex is not a reliable guide to reaction conditions. Moreover, the reported protocol is readily translated to a flow setup. The prepared AIE-active polymers are demonstrated to exhibit good photopatterning, making them promising materials for applications in advanced optoelectronic devices.