Search Results (47)

Herein, we study a method for developing a broad-emission emitter that can emit radiation from the visible light to NIR regions. Firstly, an NIR phosphor’s optical properties (e.g., scattering vs. weight concentration, conversion efficiency, and emission spectra under blue and red light excitation) are investigated. Then, pcW-LEDs encapsulated with NIR down-conversion phosphor samples are prepared to test these optical properties. The results show that pcW-LEDs encapsulated with the NIR phosphor at different weight concentrations of 10.0%, 12.5%, and 15.5%, respectively, emit a broadband emission from 400 nm to 900 nm. The EQE values of the pcW-LEDs encapsulated with NIR phosphor at weight concentrations of 10%, 12.5%, and 15.0% are 26%, 23%, and 19%, respectively. The correlated color temperatures of these samples are 5767 K, 5940 K, and 6068 K, respectively. The obtained radiant fluxes of the samples are 26 mW, 22 mW, and 18 mW, respectively, at an injection current of 50 mA. Full article

Spiropyran has an attractive and mysterious fluorescence switch and dual-color conversion characteristics, as it exhibits both aggregation-caused quenching (ACQ) in solvents and fluorescence enhancement in polymer matrices. The explanation for this phenomenon has always been of great controversy. Hence, the solvent effect on the emission of spiropyran (SP) was investigated in 16 solvents. By means of molecular orbital theory and the Jablonski diagram, several special parameters (e.g., Hansen solubility parameters and viscosity) were selected for this analysis, with excellent goodness of fit. Subsequently, the main factors that affected the blue shift, red shift, and luminescence efficiency of the emission of the ring-opened form merocyanine (MC) were found to be the hydrogen bonding and polarity, aggregation effect, and viscosity, respectively. A newly modified Jablonski diagram was proposed to clarify the emission behaviors of spiropyran influenced by solvent polarity and isomerization. Meanwhile, the solvent effect could also be extended to a solid polymer matrix (six kinds of polyethylene glycol (PEG) with different molecular weights), which is proposed to be defined as the generalized solvent effect. Accordingly, we have demonstrated that the unique fluorescence properties of spiropyran are dominated by the generalized solvent effect. The security information storage capacity of the simulated quick response (QR) code sensor combined with SP for anti-counterfeiting was significantly improved to six dimensions in taking advantage of the former theoretical analysis. Full article

The agri-food processing industry predominantly relies on fossil fuels, contributing significantly to greenhouse gas emissions and extensive water use. Climate change requires a conversion of food processing technologies towards sustainability. Our research focuses on testing and validating pulsed electric field (PEF) technology as a mild processing method for stabilizing freshly squeezed, not from concentrate, blood orange juice. Experiments were carried out on a continuous pilot plant endowed with a patented treatment chamber that ensures a constant flow of product without “hot spots” for a homogeneous treatment. Once the operative conditions of the process in terms of energy density were optimized, PEF-treated blood orange juice was tested in order to evaluate the effects on physico-chemical parameters (total soluble solids, total acidity, pH, CIE L*, a*, b*, C*, h color indices, cloud, bioactive compounds (ascorbic acid, total anthocyanins, total and individual flavanones), antioxidant activity (ORAC units, total phenolic content), microbial communities (aerobic mesophilic viable count, yeasts and molds, acid-tolerant microorganisms), residual enzymatic pectinmethylesterase activity, and sensory attributes (flavor, off-flavor, off-odor, color, intensity of odor, acidity, sweetness, bitter, freshness, cooked flavor). Then, in order to simulate the commercial refrigerated distribution of PEF-treated blood orange juice and define its refrigerated shelf-life, the PEF-treated freshly squeezed, not from concentrate, blood orange juice was subjected to physico-chemical, antioxidant, microbiological, and sensory evaluations over twenty days of refrigerated storage at 4 ± 1 °C. The PEF treatment effectively ensured excellent microbial inactivation and enhanced the nutritional and health characteristics of the juice, thereby extending its shelf-life. This study demonstrates the significant potential of the PEF treatment to produce blood orange juice suitable for a new retail segment—freshly squeezed juices with superior health quality, fresh-like characteristics, and extended refrigerated shelf-life. Full article

Effectively utilizing deep red to near-infrared (DR-NIR) phosphors to achieve the optimal performance of NIR phosphor-converted white LEDs (DR-NIR pc-wLEDs) is currently a research hotspot. In this study, an optical model of DR-NIR pc-wLEDs with virtual multilayer fluorescent films was established based on the Monte Carlo ray-tracing method. Different gradient distributions of the particles were assigned within the fluorescent film to explore their impact on the optical performance of pc-LEDs. The results show that, for the case with single-type particles, distributing more DR-NIR particles far from the blue LED chip increased the overall radiant power. The distribution of more DR-NIR particles near the chip increased the conversion ratio from blue to DR-NIR light. The ratio of the 707 nm fluorescence emission intensity to the 450 nm excitation light intensity increased from 1:0.51 to 1:0.28. For multiple-type particles, changes in the gradient distribution resulted in dual-nature changes, leading to a deterioration in the color rendering index and an increase in the correlated color temperature, while also improving the DR-NIR band ratio. The reabsorption caused by the partial overlap between the excitation band of the DR-NIR particles and the emission band of the other particles enhanced the radiant power at 707 nm. Distributing DR-NIR phosphor particles closer to the chip effectively amplified this effect. The proposed model and its results provide a solution for the forward design of particle distributions in fluorescent films to improve the luminous performance of DR-NIR pc-wLEDs. Full article

A special micro LED whose light emitting area is laid out in a U-like shape is fabricated and integrated with colloidal quantum dots (CQDs). An inkjet-type machine directly dispenses the CQD layer to the central courtyard-like area of this U-shape micro LED. The blue photons emitted by the U-shape mesa with InGaN/GaN quantum wells can excite the CQDs at the central courtyard area and be converted into green or red ones. The U-shape micro LEDs are coated with Al₂O₃ by an atomic layer deposition system and exhibit moderate external quantum efficiency (6.51% max.) and high surface recombination because of their long peripheries. Low-temperature measurement also confirms the recovery of the external quantum efficiency due to lower non-radiative recombination from the exposed surfaces. The color conversion efficiency brought by the CQD layer can be as high as 33.90%. A further continuous CQD aging test, which was evaluated by the strength of the CQD emission, under current densities of 100 A/cm² and 200 A/cm² injected into the micro LED, showed a lifetime extension of the unprotected CQD emission up to 1321 min in the U-shape device compared to a 39 min lifetime in the traditional case, where the same CQD layer was placed on the top surface of a squared LED. Full article

Metal halide perovskite semiconductors have emerged as promising materials for various optoelectronic applications due to their unique crystal structure and outstanding properties. Among different forms, perovskite nanowires (NWs) offer distinct advantages, including a high aspect ratio, superior crystallinity, excellent light absorption, and carrier transport properties, as well as unique anisotropic luminescence properties. Understanding the formation mechanism and structure–property relationship of perovskite NWs is crucial for exploring their potential in optoelectronic devices. In this study, we successfully synthesized all-inorganic halide perovskite NWs with high aspect ratios and an orthorhombic crystal phase using the hot-injection method with controlled reaction conditions and surface ligands. These NWs exhibit excellent optical and electrical properties. Moreover, precise control over the halogen composition through a simple anion exchange process enables the tuning of the bandgap, leading to fluorescence emission, covering a wide range of colors across the visible spectrum. Consequently, these perovskite NWs hold great potential for efficient energy conversion and catalytic applications in photoelectrocatalysis. Full article

Malpighian tubules (MTs) are arthropod excretory organs crucial for the osmoregulation, detoxification and excretion of xenobiotics and metabolic wastes, which include tryptophan degradation products along the kynurenine (KYN) pathway. Specifically, the toxic intermediate 3-hydroxy kynurenine (3-HK) is metabolized through transamination to xanthurenic acid or in the synthesis of ommochrome pigments. Early investigations in Drosophila larval fat bodies revealed an intracellular autofluorescence (AF) that depended on tryptophan administration. Subsequent observations documented AF changes in the MTs of Drosophila eye-color mutants genetically affecting the conversion of tryptophan to KYN or 3-HK and the intracellular availability of zinc ions. In the present study, the AF properties of the MTs in the Asian tiger mosquito, Aedes albopictus, were characterized in different stages of the insect’s life cycle, tryptophan-administered larvae and blood-fed adult females. Confocal imaging and microspectroscopy showed AF changes in the distribution of intracellular, brilliant granules and in the emission spectral shape and amplitude between the proximal and distal segments of MTs across the different samples. The findings suggest AF can serve as a promising marker for investigating the functional status of MTs in response to metabolic alterations, contributing to the use of MTs as a potential research model in biomedicine. Full article

In this study, all-inorganic perovskite quantum dots (QDs) for pure blue emission are explored for full-color displays. We prepared CsPbBr₃ and Cs₃NdCl₆ QDs via hot injection methods and mixed in various ratios at room temperature for color blending. Nd-doped CsPb(Cl/Br)₃ QDs showed a blueshift in emission, and the photoluminescence quantum yields (PLQY, Φ_PL) were lower in the 460–470 nm range due to surface halogen and Cs vacancies. To address this, we introduced a silane molecule, APTMS, via a ligand exchange process, effectively repairing these vacancies and enhancing Nd doping into the lattice. This modification promotes the PLQY to 94% at 466 nm. Furthermore, combining these QDs with [1]Benzothieno[3,2-b][1]benzothiophene (BTBT), a conjugated small-molecule semiconductor, in a composite film reduced PLQY loss caused by FRET in solid-state QD films. This approach achieved a wide color gamut of 124% National Television System Committee (NTSC), using a UV LED backlight and RGB perovskite QDs in a BTBT-based organic matrix as the color conversion layer. Significantly, the photostability of this composite was enhanced when used as a color conversion layer (CCL) under blue-LED excitation. Full article

Briefly, 0.005-mol Sm³⁺-doped (Ba_0.85Ca_0.15)(Ti_0.9Hf_0.1)O₃ ([(Ba_0.85Ca_0.15)_0.995Sm_0.005](Ti_0.9Hf_0.1)O₃, BCTH:0.005Sm³⁺) lead-free ceramics were prepared via hydrothermal method and powder injection molding using paraffin and oleic acid as binders, and the effects of preparation method and sintering conditions on microstructure, dielectric behavior and optical properties were investigated. XRD Rietveld refinement reveals the coexistence of orthogonal, rhombohedral and tetragonal phases, in which the crystal structure and phase fraction are influenced greatly by sintering temperature and holding time. The ceramics present enhanced relaxor behavior and frequency dispersion phenomenon as compared with those prepared by the solid-state sintering method, and the diffusive index γ value is within 1.421–1.673. The transition mechanism and luminescence performance of BCTH:0.005 Sm³⁺ were analyzed by Blasse formula, photoluminescence spectrum and fluorescence lifetimes, where emission peaks show slight blueshift, fluorescence decay lifetime becomes shorter, electric multipole interaction dominates the energy transfer mechanism, and the down-conversion luminescence is one-photon absorption process. The CIE chromaticity color coordinate (0.4746, 0.5048), correlated color temperature 3134 K and color purity 93.58% are achieved, which reveals that the BCTH:0.005 Sm³⁺ ceramics express high quality yellow emission rather than orange-red light of the hydrothermal method synthesized nano-powder, and have potential application in optical field. Full article

Perovskite nanocrystals (PeNCs) have emerged as a promising class of luminescent materials offering size and composition-tunable luminescence with high efficiency and color purity in the visible range. PeNCs doped with Yb³⁺ ions, known for their near-infrared (NIR) emission properties, have gained significant attention due to their potential applications. However, these materials still face challenges with weak NIR electroluminescence (EL) emission and low external quantum efficiency (EQE), primarily due to undesired resonance energy transfer (RET) occurring between the host and Yb³⁺ ions, which adversely affects their emission efficiency and device performance. Herein, we report the synergistic enhancement of NIR emission in a CsPbCl₃ host through co-doping with Yb³⁺/Nd³⁺ ions for perovskite LEDs (PeLEDs). The co-doping of Yb³⁺/Nd³⁺ ions in a CsPbCl₃ host resulted in enhanced NIR emission above 1000 nm, which is highly desirable for NIR optoelectronic applications. This cooperative energy transfer between Yb³⁺ and Nd³⁺ can enhance the overall efficiency of energy conversion. Furthermore, the PeLEDs incorporating the co-doped CsPbCl₃/Yb³⁺/Nd³⁺ PeNCs as an emitting layer exhibited significantly enhanced NIR EL compared to the single doped PeLEDs. The optimized co-doped PeLEDs showed improved device performance, including increased EQE of 6.2% at 1035 nm wavelength and low turn-on voltage. Our findings highlight the potential of co-doping with Yb³⁺ and Nd³⁺ ions as a strategy for achieving synergistic enhancement of NIR emission in CsPbCl₃ perovskite materials, which could pave the way for the development of highly efficient perovskite LEDs for NIR optoelectronic applications. Full article

The adsorption of the lipase B from Candida antarctica (CALB) over polyethylene terephthalate (PET), polypropylene (PP), and derivatives, abundant components of urban solid waste (USW), was investigated. The characterization of the supports and biocatalysts synthesized by SEM-EDS and FTIR is presented. Two immobilization strategies were evaluated, conventional and total adsorption. The adsorbed protein was determined by Bradford and through high-resolution inductively coupled plasma atomic emission spectroscopy (ICP-AES). In this sense, the adsorption of CALB in all the proposed supports was evidenced, obtaining the highest protein loads in bis-(2-hydroxyethyl) terephthalate (BHET). Subsequently, the biocatalysts were applied to the esterification of rac-ibuprofen with ethanol. CALB immobilized in BHET showed remarkable activity, achieving conversions of 30%. In this context, immobilization on this support was optimized, studying the addition of sorbitol-glycerol. Thus, in the presence of 0.91 g of polyols, a catalyst with a protein load of 33.3 mg·g⁻¹ was obtained, achieving productivity of 0.298 mmol min⁻¹ mg⁻¹. Additionally, no differences were found when using BHET from USW bottles of various colors. This research shows the potential of materials derived from PET as enzymatic supports, unreported materials, that we can use as tools to achieve sustainable biotechnological applications. Full article

Red color conversion materials have often been used in conventional white LEDs (light-emitting diodes) to enhance the insufficient deep-red component and thus improve the color-rendering property. Quantum dots (QDs) are one of the candidates for this due to their flexibility in controlling the emission wavelength, which is attributed to the quantum confinement effect. Two types of remote QD components, i.e., QD films and QD caps, were prepared and applied to conventional white LED illumination to improve the color-rendering properties. Thanks to the red component near 630 nm caused by the QD components, the color rendering indices (CRIs) of both Ra and R9 could be increased to over 95. It was found that both the diffusing nature of the reflector and the light recycling process in the vertical cavity between the bottom reflector and the top optical films play important roles in improving the color conversion efficiency of remote QD components. The present study showed that the proper application of remote QDs combined with a suitable optical cavity can control the correlated color temperature of the illumination over a wide range, thus realizing different color appearances of white LED illumination. In addition, a high CRI of over 95 could be achieved due to the sufficient excitation from fewer QDs, due to the strong optical cavity effect. Full article

The design and production of biodegradable and sustainable non-toxic materials for solar-energy harvesting and conversion is a significant challenge. Here, our goal was to report the preparation of novel protein/lipid hydrogels and demonstrate their utility in two orthogonal fundamental studies—light harvesting and white-light emission. Our hydrogels contained up to 90% water, while also being self-standing and injectable with a syringe. In one application, we loaded these hydrogels with suitable organic donor-acceptor dyes and demonstrated the energy-transfer cascade among four different dyes, with the most red-emitting dye as the energy destination. We hypothesized that the dyes were embedded in the protein/lipid phase away from the water pools as monomeric entities and that the excitation of any of the four dyes resulted in intense emission from the lowest-energy acceptor. In contrast to the energy-transfer cascade, we demonstrate the use of these gels to form a white-light-emitting hydrogel dye assembly, in which excitation migration is severely constrained. By restricting the dye-to-dye energy transfer, the blue, green, and red dyes emit at their respective wavelengths, thereby producing the composite white-light emission. The CIE color coordinates of the emission were 0.336 and 0.339—nearly pure white-light emission. Thus, two related studies with opposite requirements could be accommodated in the same hydrogel, which was made from edible ingredients by a simple method. These gels are biodegradable when released into the environment, sustainable, and may be of interest for energy applications. Full article

Rivers are vital water sources for humans and homes for aquatic organisms. Conversely, they are well known as the route of plastics into the ocean. Despite being the world’s number one emitter of riverine plastics into the ocean, microplastics (MPs), or plastic particles less than 5 mm, in the Philippines’ rivers are relatively unexplored. Water samples were collected from six sampling stations along the river channel of the Cagayan de Oro River, one of the largest rivers in Northern Mindanao, Philippines. The extracted microplastics’ abundance, distribution, and characteristics were analyzed using a stereomicroscope and Fourier transform infrared spectroscopy (FTIR). The results showed a mean concentration of 300 items/m³ of MPs dominated by blue-colored (59%), fiber (63%), 0.3–0.5 mm (44%), and polyacetylene (48%) particles. The highest concentration of microplastics was recorded near the mouth of the river, and the lowest was in the middle area. The findings indicated a significant difference in MP concentration at the sampling stations. This study is the first assessment of microplastic in a river in Mindanao. The results of this study will aid in formulating mitigation strategies for reducing riverine plastic emissions. Full article

The conversion of waste into a valuable product is regarded as a promising alternative to relieving the burden of solid waste management and could be beneficial to the environment and humans. This study is focused on utilizing eggshell and orange peel enriched with banana starch to fabricate biofilm via the casting technique. The developed film is further characterized by field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The physical properties of films, including thickness, density, color, porosity, moisture content, water solubility, water absorption, and water vapor permeability, were also characterized. The removal efficiency of the metal ions onto film at different contact times, pH, biosorbent dosages, and initial concentration of Cd(II) were analyzed using atomic absorption spectroscopy (AAS). The film’s surface was found to have a porous and rough structure with no cracks, which can enhance the target analytes interactions. EDX and XRD analyses confirmed that eggshell particles were made of calcium carbonate (CaCO₃), and the appearance of the main peak at 2θ = 29.65° and 2θ = 29.49° proves the presence of calcite in eggshells. The FTIR indicated that the films contain various functional groups, such as alkane (C-H), hydroxyl (-OH), carbonyl (C=O), carbonate (CO₃²⁻), and carboxylic acid (-COOH) that can act as biosorption materials. According to the findings, the developed film exhibits a notable enhancement in its water barrier properties, thereby leading to improved adsorption capacity. The batch experiments showed that the film obtained the maximum removal percentage at pH = 8 and 6 g of biosorbent dose. Notably, the developed film could reach sorption equilibrium within 120 min at the initial concentration of 80 mg/L and remove 99.95% of Cd(II) in the aqueous solutions. This outcome presents potential opportunities for the application of these films in the food industry as both biosorbents and packaging materials. Such utilization can significantly enhance the overall quality of food products. Full article