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Photoaligned Liquid Crystalline Structures for Photonic Applications
With the advancement of information display technologies, research on liquid crystals is undergoing a tremendous shift to photonic devices. For example, devices and configurations based on liquid crystal materials are being developed for various applications, such as spectroscopy, imaging, and fiber optics. One of the problems behind the development of photonic devices lies in the preparation of patterned surfaces that can provide high resolution. Among all liquid crystal alignment techniques, photoalignment represents a promising non-contact method for the fabrication of patterned surfaces. In this review, we discuss the original research findings on electro-optic effects, which were mainly achieved at the Department of Electronic and Computer Engineering of the Hong Kong University of Science and Technology and the collaborating research laboratories. 2023 by the authors. -
Photoaligned nematic liquid crystals doped with palladium-immobilised carbon nanospheres for advanced low-voltage display and energy storage devices
This study presents a nematic liquid crystal (NLC), D30-17, doped with palladium-immobilised carbon nanospheres (CNS) Pd/ON10 at two different concentrations. The composites were prepared with 0.1 and 0.4 wt/wt% dopant concentrations and are referred to as Mix 1 and Mix 2, respectively. The palladium-immobilized carbon nanospheres were employed because they function as advanced materials for catalysis and energy applications owing to the catalytic properties of palladium. The sample holder used in this experiment consisted of photo-aligned cells coated with a photosensitive alignment layer, Cibacron brilliant yellow (CBY). The textural studies revealed improved alignment in the doped mixtures. The frequency- and temperature-dependent dielectric behaviour was analysed for the pure and doped systems in both the planar (at 0 V) and homeotropic (at 12 V) states. Dielectric studies showed that the relative permittivity, dielectric loss, and conductivity of the doped material increased with increasing dopant concentration compared with that of pure NLC. Compared with the pure NLC and Mix 2, Mix 1 exhibited greater dielectric anisotropy, leading to a lower threshold voltage. A reversal in the dielectric anisotropy was also observed, which was attributed to the bistable inversion in the CBY alignment layer of the photo-aligned cells. Optical studies indicated that there was no significant shift in wavelength with respect to the dopant concentration. These composites are expected to find applications in liquid-crystal-based electronic and photonic devices. This journal is The Royal Society of Chemistry, 2026 -
Photocatalytic activity of bismuth silicate heterostructures synthesized via surfactant mediated sol-gel method
A surfactant mediated sol-gel method is employed to synthesize bismuth silicate heterostructures with tunable morphologies and properties. The synthesized nanoparticle samples were characterized by XRD, FTIR Spectroscopy, SEM-EDAX and UV-DRS. The synthesized bismuth silicates exhibit excellent photodegradation against malachite green and rhodamine B dyes in the aqueous medium. Bismuth silicates (10% SiO2-Bi2O3) show superior photocatalytic property and outstanding reusability compared to pure bismuth oxide. The kinetics of the photodegradation of the dyes shows that the reaction follows first-order kinetics with the regression coefficient of 0.99. Thus, enabling Bismuth silicates heterostructures practical application as a photocatalyst for clean water. 2019 Elsevier Ltd -
Photocatalytic and antimicrobial properties of Boerhavia diffusa bio-callus synthesized Silver nanoparticles
Plant tissue culture plays a pivotal role in plant biotechnology, and offers innovative and reliable avenues for synthesizing nanoparticles. The approach is safe, replicable, and efficient for therapeutic and environmental sustainability. Despite the proven efficiency of green synthesis approaches, plant callus extracts for nanoparticle synthesis remain moderately investigated. The current study bridges the gap by synthesizing ecofriendly silver nanoparticles (Ag-NPs) using callus extracts of Boerhavia diffusa (Punarnava), an important medicinal plant with proven potential pharmacological properties. These synthesized Boerhavia diffusa-mediated Ag-NPs (BD-Ag-NPs) were characterized using UV-Vis spectroscopy, SEM, FTIR, and XRD. Spectral analysis showed spherical-shaped BD-Ag-NPs with an average size of 9 nm at wavelength 420 nm. Energy-dispersive X-ray (EDX) analysis revealed that silver ions constituted 51.78 % of the total weight of the nanoparticle solutions, while the crystalline structure of the BD-Ag-NPs was confirmed through XRD. Phytoconstituents present in the callus were utilized for capping and the reduction of Ag ions to Ag-NPs was confirmed through FTIR analysis. In addition, BD-Ag-NPs exhibited functional properties like textile dye degradation and broad-spectrum antimicrobial activities against bacterial and fungal pathogens. The current study highlights the potential of employing callus-derived nanoparticles for sustainable environment and biomedical applications. This study advances the application of green nanoparticle synthesis using tissue culture systems and makes significant contributions to addressing global challenges. 2025 The Authors -
Photocatalytic and antioxidant potential of silver nanoparticles biosynthesized using Artemisia stelleriana leaf extracts
The antioxidant and photocatalytic activity of Artemisia stelleriana-based silver nanoparticles (AS-AgNPs) was investigated in this study. Microscopic, X-ray diffraction and spectroscopic studies were used to characterize the synthesized AS-AgNPs. UVvisible spectrophotometric examination revealed a peak at 425 nm. The phytocompounds involved in the transformation of silver ions into AS-AgNPs were confirmed using Fourier-transform infrared spectroscopy analysis. The crystalline nature of the AS-AgNPs was verified using the X-ray powder diffraction technique. Spherical-shaped AS-AgNPs with a size of 22.7 nm were proved using field emission scanning electron microscopy. The AS-AgNPs were top-notch photocatalysts for the degradation of Reactive Blue-222A (RB-222A) and Reactive Blue-220 (RB-220) dyes. After 80 min of UV light exposure, AS-AgNPs degraded RB-222A and RB-220 dyes by 94.6 and 90.8%, respectively. The phytotoxicity investigation in Vigna radiata and Arte-mia salina indicated that the hazardous dye can be degraded into innocuous chemicals by AS-AgNPs. The results suggest that AS-AgNPs are an excellent antioxidant and photocatalyst for the degradation of synthetic dyes. 2023 The Authors. -
Photocatalytic and eco-emission applications of green synthesized ZnO-CB nanoparticles
Herein, we report the synthesis of ZnO nanoparticles (ZnO-CB NPs) by employing the solution combustion method using an aqueous extract of brinjal calyxes as fuel. Characterization techniques, such as X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), UVvisible spectroscopy, and Scanning electron microscopy (SEM), were used to investigate the structural, optical, and morphological properties of synthesized nanoparticles, respectively. Highly porous hexagonal crystalline ZnO-CB NPs with less than 7 nm particle size were obtained. The photocatalytic performance of synthesized material is measured with Malachite green (MG), Basic brown 1 (BB1), and Acid orange 36 (AO36) as benchmark dyes. It showed that the synthesized material worked effectively under pH 10 with UV light irradiation. The synthesized ZnO-CB NP shows good removal effectiveness of the MG, BB1, and AO36 dyes with 99.3 %, 99.6 %, and 99.5 %, respectively, which can be promising photocatalysts for ecological applications such as wastewater remediation. Further, the synthesized ZnO-CB NP was used as blends in the methyl ester of Millettia pinnata oil (MPME), which is blended 20 % with commercial diesel (MPME20). The synthesized ZnO-CB NP was added to the MPME20 in varying amounts to ascertain its effects on the quality of emissions of various greenhouse gases such as hydrocarbons, COx, and NOx. Moreover, brake thermal efficiency (BTHE) and brake-specific fuel consumption (BSFC) were studied for the blends. The blend MPME20 with 25 mg of ZnO-CB NP, i.e., MPME20-25 mg, ZnO-CB, displays the best performance and reduced emissions. 2024 The Author(s) -
Photocatalytic degradation of methylene blue and metanil yellow dyes using green synthesized zinc oxide (Zno) nanocrystals
In this work, ZnO nanocrystals (NCs) have been effectively synthesized by a simple, efficient and cost-effective method using coconut husk extract as a novel fuel. The synthesized NCs are characterized by UV-Vis, XRD, FT-IR, SEM, EDX, Raman and PL studies. The obtained ZnO were found to be UV-active with a bandgap of 2.93 eV. The X-ray diffraction pattern confirms the crystallinity of the ZnO with hexagonally structured ZnO with a crystallite size of 48 nm, while the SEM analysis reveals the hexagonal bipyramid morphology. Photocatalytic activities of the synthesized ZnO NCs are used to degrade methylene blue and metanil yellow dyes. 2021 by the authors. Licensee MDPI, Basel, Switzerland. -
Photocatalytic Degradation of Textile Dyes Using Artemisia stelleriana Besser Mediated Nanoparticles
Artemisia stelleriana is widely used as an ornamental plant and belongs to the family Asteraceae. In the current study, A. stelleriana-mediated Zinc oxide newlinenanoparticles (AS-ZnONPs), Silver nanoparticles (AS-AgNPs) and Silver/Zinc oxide bimetallic nanoparticles (AS-Ag/ZnONPs) were synthesised using one-pot method. The UV-Vis spectral analysis revealed characteristic peaks at 358 nm for AS-ZnONPs, newline425 nm for AS-AgNPs, and 357 nm and 473 nm for AS-Ag/ZnONPs. Fourier transform infrared spectroscopy (FTIR) analysis identified phytoconstituents taking part in newlinenanoparticle synthesis, manifesting the presence of alkaloids, phenols, saponins, and newlineflavonoids. The synthesised AS-ZnONPs, AS-AgNPs, and AS-Ag/ZnONPs have a crystalline nature and were confirmed using X-ray diffraction (XRD) analysis. The crystallite sizes of the AS-ZnONPs, AS-AgNPs, and AS-Ag/ZnONPs were 22.54 nm, 18.67 nm, and 10.4 nm, respectively. Spherical-shaped Ag nanoparticles and hexagonal, cylindrical, and spherical-shaped ZnO nanoparticles were synthesized from the leaf extract of A. stelleriana. The average size of the synthesised nanoparticles was 37.6 nm and 71.2 nm for AS-ZnONPs and AS-AgNPs, respectively. On the other hand, spherical-shaped AS-Ag/ZnONPs were synthesized with an average size of 35.3 nm. The photocatalytic degradation activity of AS-ZnONPs showed 93.44%, 47%, 94.76%, 99.9%, and 74.82% degradation for Reactive Blue 220 (RB220), Reactive Blue 222A (RB222A), Reactive Red 120 (RR120), Reactive Yellow 145 (RY145) and newlineReactive Yellow 86 (RY86) dyes respectively after 320 min of UV light exposure. ASZnONPs showed positive results for all five dyes and a better percentage of degradation was observed in a 5 ppm concentration of dye treated with 1 mg/mL concentration of newlineAS-ZnONPs. In the case of AS-AgNPs, RB220 and RB222A dyes showed positive results but no degradation was observed in the remaining three dyes. After 320 min of UV light exposure, AS-AgNPs showed 95.98%, and 100% degradation of RB220 and RB222A dyes respectively. -
Photocatalytic Degradation of Textile Dyes Using Quassia india (Gaertn.) Noot. Mediated Nanoparticles
Prognostic research points at the necessity and relevance of revamping polluted newlineenvironments. The toxic effect of textile dyes released into waterbodies can be reduced newlineby the degradation process and alternate methods in nanotechnology are used to lessen newlinethe gravity of the situation. Compared with chemical and physical nanoparticle synthesis, plant extract-based nanoparticle synthesis is an environmentally friendly alternative method. UV-visible spectrum analysis validated the production of nanoparticles (NPs), revealing unique peaks at 430 nm for Quassia indica (QI)- mediated Silver nanoparticles (QI-Ag NPs), 368 nm for QI-mediated Cobalt oxide nanoparticles (QI-Co3O4 NPs), 348 nm for QI-mediated Zinc oxide nanoparticles (QIZnO NPs, 350 nm and 408 nm for QI-mediated Silver/Zinc oxide nanoparticles (QIAg/ZnO NPs), 415 nm and 675 nm for QI-mediated Cobalt oxide/Zinc oxide newlinenanoparticles (QI-Co3O4/ZnO NPs). Fourier Transform Infrared Spectroscopy (FTIR) newlineinvestigation identified phytochemicals involved in nanoparticle synthesis. The X- Ray Diffraction (XRD) examination unveiled the crystalline structures of QI-mediated NPs. Dynamic Light Scattering (DLS) study revealed information on the hydrodynamic newlinediameter and colloidal stability of the NPs, which showed average particle size. Field newlineEmission Scanning Electron Microscopy (FE-SEM) and Energy-Dispersive X-Ray newlineSpectroscopy (EDX) were used to investigate the morphology and elemental composition of NPs. The morphological shapes of QI-Ag NPs were spherical, QI-ZnO NPs showed hexagonal, QI-Co3O4 NPs displayed octahedral, QI-Ag/ZnO NPs exhibited spherical structure, and QI-Co3O4/ZnO NPs unveiled a mixture of octahedral and hexagonal shaped NPs. The High-resolution Transmission Electron Microscopy (HR-TEM) validated the NPs size and Selected Area Electron Diffraction (SAED) newlineconfirmed the crystalline characteristics. -
Photocatalytic Degradation of Textile Dyes Using Strobilanthes Species Mediated Nanoparticles
Discharge of dye pollutants from textile industries jeopardizes ecosystem by leading to grave threats like contamination of water resources and hazardous health effects. The current study points and focuses at the synthesis, characterization, dye degradation and toxicity analysis of zinc oxide nanoparticles (ZnO NPs) and silver nanoparticles (Ag NPs) derived from Strobilanthes barbatus and Strobilanthes hamiltoniana leaf extracts. UV-visible spectrum analysis validated the biogenesis of ZnO and Ag NPs, revealing unique peaks at 359 nm for ZnOSB NPs, 360 nm for ZnOSH NPs, 428 nm for AgSB NPs, and 432 nm for AgSH NPs. Fourier transform infrared spectroscopy (FTIR) investigation identified phytochemicals involved in nanoparticle synthesis, manifesting the presence of flavonoids, saponins and alkaloids. The X-ray diffraction (XRD) examination disclosed the crystalline structures of ZnOSB NPs, ZnOSH NPs, AgSB NPs and AgSH NPs displayed an average crystalline size of 22.29 nm, 26.9 nm, 23.5 nm and 20.6 nm. Dynamic Light Scattering (DLS) study revealed information on the hydrodynamic diameter and colloidal stability of the NPs, which showed average particle size for ZnOSB NPs, ZnOSH NPs, AgSB NPs and AgSH NPs as 91.6 nm, 165.4 nm, 142.3 nm and 255.3 nm. Field Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDS) were used to investigate the morphology and elemental composition of ZnO NPs and Ag NPs, revealing particle shape and size variations. The morphological shapes of ZnOSB NPs were spherically shaped NPs, ZnOSH NPs showed rod-shaped NPs, AgSB NPs and AgSH NPs both showed spherical-shaped NPs. The High-resolution Transmission Electron Microscopy (HRTEM) validated the nanoparticles' size and crystalline characteristics, similar to FESEM. The photocatalytic degradation of textile dyes using ZnO NPs and Ag NPs were researched, and the results revealed that diverse dyes degraded efficiently under UV light exposure. The ZnO NPs and Ag NPs showed excellent catalytic degradation at dye (Reactive Blue 220, Reactive Blue 222A, Reactive Yellow 145, and Reactive Yellow 86) concentrations of 1 ppm, 5 ppm, and 10 ppm with NP concentrations of 1 mg/ml. Chemical kinetics research unveiled that the degrading processes had pseudo-first-order kinetics. It has been observed that nanoparticles such as ZnO NPs and Ag NPs can maintain their photocatalytic activity across multiple cycles of dye degradation. Phytotoxicity tests conveyed that ZnO and Ag NPs were beneficial in lowering seed germination inhibition and toxicity in Vigna radiata. The brine shrimp lethality experiment indicated that the synthesized nanoparticles were not hazardous. This comprehensive work gives insight and sheds light on the synthesis, characterization, and use of ZnO and Ag NPs utilizing plant extracts, highlighting their promise for environmental remediation and sustainable nanoparticle synthesis. -
Photocatalytic Degradation of Toxic Textile Dyes by Biosynthesized Silver Nanoparticles Synthesized from Strobilanthes hamiltoniana Leaf Extract
Biocompatible nanoparticle synthesis from Strobilanthes hamiltoniana leaf extracts is an ecologically friendly, cost-effective and long-lasting technique for wastewater treatment, particularly for textile dye degradation. S. hamiltoniana mediated silver nanoparticles (SH-Ag NPs) showed a maximum absorbance of 432 nm. Based on the FESEM analysis, the SH-Ag NPs were usually spherical with an average diameter of nm. The FTIR analyses revealed the significance of functional groups in the formation of SH-Ag NPs. Degradation and rate of degradation for textile dyes after 320 min, SH-Ag NPs displayed 88.4%, 79.49%, 0.0059 min-1 and 0.00495 min-1 for reactive blue 220 (RB-220) and reactive blue 222A (RB-222A) dyes. The phytotoxicity study of SH-Ag NPs treated dye solutions demonstrated a significant decrease in inhibitory efficiency when compared to dye effluents. The biosynthesized SH-Ag NPs could represent a viable catalyst alternative for treating textile dye degradation both before and after it enters aquatic environments. 2024 Asian Publication Corporation. All rights reserved. -
Photocatalytic driven self-cleaning IPN membranes infused with a host-guest pair consisting of metal-organic framework encapsulated anionic nano-clusters for water remediation
Traditional water treatment membranes frequently encounter challenges in attaining an ideal equilibrium between permeability and selectivity. The performance of membranes is further hampered by hydrophobicity, scalability, and fouling problems, as well as excessive energy consumption. Hence, the current research is dedicated to the development of highly effective antifouling membranes, aiming for a significant balance between water permeance and separation efficiency, and featuring exceptional photocatalytic self-cleaning properties to ensure the sustainable reuse of membranes. In this study, a unique nanocomposite-based membrane is designed containing metal-organic frameworks (MOFs) MIL-101 (Fe) encapsulated copper-containing polyoxometalate (Cu-POM) incorporated into an interpenetrating polymer networks (IPNs) membrane. POMs are highly electronegative, oxo-enriched nanosized metal-oxygen cluster species and when composited with MOF yields POMOF which can help in the removal of pollutants from water through electrostatic site-specific binding. The IPN membrane designed by polymerizing aniline in the presence of polyvinylidene fluoride (PVDF) offers tunable pores of the membrane. The infusion of POMOF imparts a strong negative charge to the membrane surface, improving membrane hydrophilicity. This enhances pollutant removal through the Donnan exclusion principle and adds anti-fouling properties. Furthermore, the reduced pore size achieved by the IPN architecture in the POMOF@IPNs membrane effectively sieves out both cationic and anionic dyes, as well as pharmaceutical pollutants. Additionally, POMOF enhances the photocatalytic degradation of CR and MB dyes, coupled with essential self-cleaning attributes vital for separation processes. The IPNs structure, apart from housing POMOF, fortifies the membrane's mechanical strength with its distinctive network-like configuration. Furthermore, these advanced membranes showcase robust antibacterial and antiviral characteristics, while remaining non-cytotoxic to mammalian cells. Our findings indicate that the state-of-the-art POMOF@IPNs membrane is scalable and holds substantial promise for industrial wastewater treatment. 2024 Elsevier B.V. -
Photocatalytic nanomaterials: Applications for remediation of toxic polycyclic aromatic hydrocarbons and green management
Nanomaterials (NMs) have piqued the attention of scientists and researchers across many biomedical sciences due to their superior physical, chemical, and magnetic properties. The efficacy and efficiency of NMs depend on adapting to specific site conditions and soil composition. NMs have lately received much attention in the context of polycyclic aromatic hydrocarbons (PAHs) polluted soil remediation and water mitigation because of their unique properties resulting from their nanoscale sizes. The remediation of hazardous PAHs in water and soil is a hot research subject. Because the exposure of PAHs in water and soil results in pollution, which raises major human health concerns. The current review reports novel advancements in NMs that subsidize enhancement for degradation of PAHs. Challenges to the fabrication of high activity-based photocatalytic materials are also discussed. Furthermore, this review delivers exclusive and wide-ranging perspectives on the fabrication of nanomaterial-based photocatalytic systems. The knowledge of both soil remediation and water mitigation is also updated. 2022 -
Photocatalytic seawater splitting for hydrogen fuel production: impact of seawater components and accelerating reagents on the overall performance
The future fuel, hydrogen, is a clean, sustainable energy source with a substantial density of energy per unit volume/weight. Breakthroughs in hydrogen production, storage, and transportation are essential to meet the sustainable global energy demands. Solar-to-hydrogen conversion through water-splitting reactions (via photo/electro/photoelectro-processes) is a promising strategy for producing green hydrogen fuel. Specifically, the photocatalytic hydrogen generation reaction, mimicking artificial photosynthesis, is a simple and cost-effective method adopted for solar-hydrogen production. Various semiconductor photocatalysts and hybrid photocatalytic systems have been developed to address the sluggish kinetics and selectivity of pristine water/seawater splitting reactions. Recently, seawater has been used as feedstock for large-scale hydrogen production to advance the field and alleviate the scarcity of freshwater sources. This review article, therefore, aims to highlight the importance of seawater splitting reactions using different photocatalytic systems. A brief introduction to the fundamentals, historical progress, and mechanism of the seawater splitting reaction is presented. The impact of seawater components and accelerating reagents on the intrinsic performance of water splitting catalysts is discussed in detail, followed by an elaborate discussion of natural water and artificial seawater splitting with emphasis on onerous photocatalyst designs. Finally, the current challenges and opportunities of saltwater electrolysis for sustainable hydrogen fuel generation and applications are discussed. 2023 The Royal Society of Chemistry. -
Photoisomerization Dynamics of 2-[(E)-(4-fluorophenyl)diazenyl]- 1H-imidazole: A Theoretical and Experimental Insight
This study investigates the photoresponsive behavior of substituted azobenzenes with a specific focus on their nonlinear optical response. This study suggests that azoimidazole substitution is a better alternative to azobenzene derivatives for nonlinear optical responses. The synthesis, characterization, photophysical property and isomerization pathway of 2-[(E)-(4-fluorophenyl)diazenyl]-1H-imidazole (E-2g) are presented as an optical limiter through a comprehensive blend of experimental and theoretical approaches. Notably, E-2g exhibited a lower energy barrier than reported azobenzenes. The trans-to-cis photostationary state was reached in 75 min, while the cis-to-trans state was achieved in 60 min at 354 nm. The study further explores the photoisomerization pathway of E-2g, highlighting its nonlinear absorption, which has a nonlinear absorption coefficient (?eff) of 8.8 10?11 m/W at 20 ?J, as determined by Z-scan measurements. The results suggest that E-2g exhibits significant nonlinear absorption characteristics, which helps in applications requiring protection from intense light sources. This study explores the photoresponsive behavior of substituted azobenzenes derivative, azoimidazole, over unsubstituted azobenzene derivatives for nonlinear optical properties. Through experimental and theoretical analyses, the title compound was synthesized, characterized, and shown to have a lower energy barrier and efficient photoisomerization in solution. Its strong nonlinear absorption properties make it a promising candidate for optical limiting applications, such as eye protection and safeguarding sensitive optical sensors. 2025 World Scientific Publishing Company. -
Photoisomerization Dynamics of 2-[(E)-(4-fluorophenyl)diazenyl]-1 H -imidazole: A Theoretical and Experimental Insight
This study investigates the photoresponsive behavior of substituted azobenzenes with a specific focus on their nonlinear optical response. This study suggests that azoimidazole substitution is a better alternative to azobenzene derivatives for nonlinear optical responses. The synthesis, characterization, photophysical property and isomerization pathway of 2-[(E)-(4-fluorophenyl)diazenyl]-1H-imidazole (E-2g) are presented as an optical limiter through a comprehensive blend of experimental and theoretical approaches. Notably, E-2g exhibited a lower energy barrier than reported azobenzenes. The trans-to-cis photostationary state was reached in 75 min, while the cis-to-trans state was achieved in 60 min at 354 nm. The study further explores the photoisomerization pathway of E-2g, highlighting its nonlinear absorption, which has a nonlinear absorption coefficient (?eff) of 8.8 10-11 m/W at 20 ?J, as determined by Z-scan measurements. The results suggest that E-2g exhibits significant nonlinear absorption characteristics, which helps in applications requiring protection from intense light sources. 2024 World Scientific Publishing Company. -
Photoluminescence studies of non-toxic monoclinic yttrium oxide quantum dots synthesized at low temperature for live cell imaging applications
Synthesis of monoclinic Y2O3 remains a challenging task due to complex formation conditions such as high pressure or high temperature environments. Monoclinic yttria exhibits better photoluminescence characteristics compared to the cubic phase and hence can be a better host for nanophosphors. Reports are available predicting the stability of monoclinic phase at low temperature in extremely fine particles. But experimental preparation of this phase at low temperature is not yet reported. Here we report the first-time preparation of monoclinic Y2O3 at 90 C using simple laboratory hot air oven. The synthesized nanoparticles exhibit intense PL emission in the blue region and hence can find applications in display industry. The band structure calculations were carried out using density functional theory and the excitonic Bohr radius was estimated using the electron as well as hole effective masses determined from band structure. The cytotoxicity studies reveal non-toxic nature the particles. The fluorescence imaging experiments show that the material is capable of emitting blue fluorescence in L6 skeletal cell lines and it ensures the applicability of this material in the biomedical field. 2022 Elsevier Ltd and Techna Group S.r.l. -
Photoluminescence, Judd-Ofelt and Thermoluminescence studies on bright red emitting CaY2O4:Eu3+ phosphor for display applications
The Eu3+-doped CaY2O4 phosphors were synthesised via high-temperature solid-state method. The XRD analysis suggests an Orthorhombic-like phase of the phosphor, with Eu3+ ions effectively substituting Y3+ sites, while the crystallite size analysis (Scherrer and W-H) reveals dopant-induced grain growth accompanied by strain relaxation. The photoluminescence spectra show an intense red-emission at 610 nm under a broad UV-to-blue excitation, with 466 nm emerging as the most efficient excitation wavelength, highlighting compatibility with blue LED sources. Concentration quenching behaviour suggests excitation-wavelength dependence, with optimum Eu3+ concentration at 1.5 mol% under deep UV-excitation (257 nm), and 2 mol% under near-UV/visible (393532 nm) excitations. Dexter analysis indicates the dipole-dipole interactions dominated quenching in the visible region, while the unusually low Q value under deep UV-excitation suggests the host-activator transfer. The Judd-Ofelt analysis indicates a non-centrosymmetric Eu3+ environment, and CIE coordinates (x = 0.643, y = 0.356) with ?94 % high colour purity demonstrates the saturated red emission. Thermoluminescence study exhibits multiple traps with near-linear UV dose response, supporting dosimetric potential. The combined broad excitation, high emission intensity, and colour purity make the CaY2O4: Eu3+ a promising red phosphor for display and LED applications. 2025 Elsevier B.V. -
Photometric and spectroscopic study of candidate be stars in the magellanic clouds
[No abstract available] -
Photometric identification of objects from galaxy evolution explorer survey and sloan digital sky survey
We have used Galaxy Evolution Explorer (GALEX) and Sloan Digital Sky Survey (SDSS) observations to extract seven band photometric magnitudes for over 80 000 objects in the vicinity of the North Galactic Pole. Although these had been identified as stars by the SDSS pipeline, we found through fitting with model spectral energy distributions that most were, in fact, of extragalactic origin. Only about 9 per cent of these objects turned out to be mainsequence stars and about 11 per cent were white dwarfs and red giants collectively, while galaxies and quasars contributed to the remaining 80 per cent of the data. We have classified these objects into different spectral types (for the stars) and into different galactic types (for the galaxies). As part of our fitting procedure, we derive the distance and extinction to each object and the photometric redshift towards galaxies and quasars. This method easily allows for the addition of any number of observations to cover a more diverse range of wavelengths, as well as the addition of any number of model templates. The primary objective of this work is to eventually derive a three-dimensional extinction map of the Milky Way Galaxy. 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.