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A series of Sm3+-activated strontium hexaborate (SrB6O10) red phosphors has been synthesized using a soluble salt reaction (SSR) method and the correlation between their trap states and decay kinetics was studied in detail.

Luminescent double perovskite phosphor Sr

Natural extracts have been of very high interest since ancient time due to their enormous medicinal use and researcher’s attention have further gone up recently to explore their phytochemical compositions, properties, potential applications in the areas such as, cosmetics, foods etc. In this present study phytochemical analysis have been done on the aqueous and methanolic Moringa leaves extracts using Gas Chromatography-Mass spectrometry (GCMS) and their free radical scavenging potency (FRSP) studied using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical for further applications. GCMS analysis revealed an extraction of range of phytochemicals in aqueous and methanolic extracts. In aqueous, extract constituents found with high percent peak area are Carbonic acid, butyl 2-pentyl ester (20.64%), 2-Isopropoxyethyl propionate (16.87%), Butanedioic acid, 2-hydroxy-2-methyl-, (3.14%) (also known as Citramalic acid that has been rarely detected in plant extracts) and many other phytochemicals were detected. Similarly, fifty-four bio components detected in methanolic extract of Moringa leaves, which were relatively higher than the aqueous extract. Few major compounds found with high percent peak area are 1,3-Propanediol, 2-ethyl-2- (hydroxymethyl)- (21.19%), Propionic acid, 2-methyl-, octyl ester (15.02%), Ethanamine, N-ethyl-N-nitroso- (5.21%), and 9,12,15-Octadecatrienoic acid etc. FRSP for methanolic extract was also recorded much higher than aqueous extract. The half-maximal inhibitory concentration (IC50) of Moringa aqueous extract observed is 4.65 µl/ml and for methanolic extract 1.83 µl/ml. These extracts can act as very powerful antioxidants, anti-inflammatory ingredient for various applications in diverse field of food, cosmetics, medicine etc.

A facile method for feasible industrial production of long afterglow phosphor nanocomposites, in the form of small beads were developed that continuously emit visible light for >7 h to realize many innovative applications involving hard and soft surfaces. Green emitting SrAl2O4:Eu2+, Dy3+ (SRA) long afterglow phosphor was uniformly dispersed in the epoxy resin (ER) matrix in presence of organic surfactant as hardener to make phosphor-embedded viscous fluid that could then be solidified at room temperature (~25 °C) within few minutes. As ethyl alcohol (solvent) started evaporating, ethylene glycol (surfactant), which is the simplest amongst glycols, started adhering with SRA phosphor particles via van der Waals attraction. The homogeneity of dispersion strongly depends on the shape of SRA phosphor added to ER matrix and confirmed that the near-spherical is the best. The SRA phosphor–ER beads demonstrated an optimum ultraviolet (UV) excitation wavelength at 375 nm and a green-emission peak at 517 nm, where the latter one is due to the transitions from 4f65d1 to 4f7 energy levels of Eu2+ ions. The appearance of SRA phosphor–ER beads in translucent yellow-green color, bright green and green under ambient light, UV (375 nm) irradiation and in dark conditions, respectively was indicated using photoluminescence and colorimetric measurements. The SRA phosphor–ER beads exhibited highly durable, reversible and reproducible afterglow luminescence for longer durations. Photoluminescence, structural, morphological and afterglow properties of the prepared SRA phosphor–ER beads were investigated thoroughly. Moreover, these afterglow beads have several designing and crafting applications such as interior design, glowing toys, ornaments and tracking lights etc.

In the present study, CaZrO3 nanophosphors were sensitized with lanthanum (La) at different concentrations (0.5, 1.0, 1.5, 2.0, and 2.5) prepared using polyvinyl alcohol as the chelating agent through the sol-gel method. To study their structural and optical properties, samples were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL). The XRD results revealed that samples were well crystallized and average crystallite sizes were calculated. The average crystallite size value was in good agreement with the value obtained from TEM analysis. Energy dispersive spectroscopy and FE-SEM confirmed the existence of La in the prepared samples. In the PL spectra, La-sensitized samples exhibited three bands at 402 nm, 438 nm, and 463 nm in the visible range when excited at the 260 nm wavelength. As the proportion of La increased, the intensity of bands at 438 nm and 463 nm decreased, whereas the band at 402 nm remained stable. Time-resolved PL spectra illustrated the lifetime of the samples. Corresponding CIE co-ordinates for La-sensitized CaZrO3 were calculated.

Semiconductor assisted photocatalysis is one of the most efficient methods for the degradation of complex organic dyes. A major limiting factor of semiconductor assisted photocatalysis is the requirement of a continuous source of light to perform a redox reaction. One of the upcoming solutions is photon energy-storing long afterglow/persistent phosphors. They are an unusual kind of rechargeable, photon energy capturing/trapping phosphors that can trap charge carriers (electrons/holes) in their meta-stable energy levels, thereby resulting in persistent luminescence. Persistence luminescence from such materials can range from minutes to hours. The coupling of long afterglow phosphors (LAP) with the conventional semiconductor is a promising way to support the photocatalytic process even in dark. In addition, dissimilar band structures of LAPs and semiconductor results in formation of heterojunction which further suppresses the recombination of charge. Such an encouraging idea of LAP for round-the-clock working photocatalytic system is in its premature stage; which is required to be investigated fully. Thus, we present a state-of-art review on the potential materials for assisting round-the-clock photocatalysis, trapping-detrapping mechanism in LAP materials, fabrication strategies and their associated characterization tools. Review also covers LAP materials and their photocatalytic mechanism briefly.

A new self-activated green-yellow emitting Gd2CaZnO5 (GCZO) phosphor was synthesized using solid-state reaction method at high-temperature. XRD analysis confirmed the orthorhombic structure of the sample with the Pbnm space group. SEM micrographs reveal the irregular morphology with micron sized particles. Detailed photoluminescence (PL) analysis revealed that the excitation of the phosphor lies in the UV range (˜377 nm) with the related broad green-yellow emission centered at 530 nm. The broad band emission ranging from ˜450 nm to 650 nm can be attributed to the surface defects and oxygen vacancies. The calculated luminescence decay lifetime for the optimized phosphor was found to be 2.925 μs. Furthermore, the color-coordinate (x, y) were calculated and found to be (0.44, 0.45), which lies in the green-yellow (˜540 nm) region of the electromagnetic spectrum. The values of color coordinates and Color correlated temperature of 3289 K support the synthesized phosphor for the emission of warm white-light. These results perfectly established the suitability of this green-yellow emitting GCZO phosphor for Ultra-Violet Light-Emitting Diodes (LEDs) excited white-LED applications.

An unconventional red-shift but enhanced photoluminescence (PL) under ultraviolet A (UV-A) irradiation of Eu2+ doped Barium Magnesium Aluminate (BAM) phosphor prepared in both bulk and nanoforms useful for modern lighting applications has been presented. The solid-state reaction and solution combustion approaches were used for the preparation of phosphors with post-annealing step in reduced atmosphere. A significant broad blue-green (˜500 nm) PL associated with the transition of Eu2+ from 4f6 5d1 excited state to the 4f7 ground state has been observed. The observed shifts and PL intensities were found to be extremely reliant on the thermal processing parameters during the synthesis of phosphor/nanophosphormaterials. It’s also important to note that the size of the phosphor particles have significant role in defining the red-shift of PL due to quantum confinement effect. Detailed structural and morphological characterizations were also done in this paper. The results are promising and suggest that the BAM phosphor is highly desirable for enhancing the brightness levels in modern lighting and display systems.

A novel color-tunable phosphor of BaZnO2:xEu3+ (x = 0–20 mol%) has been successfully prepared via high-temperature calcination method using alkaline earth metal as the charge compensator. Uncommonly, BaZnO2:Eu3+ is a multi-wavelength excitable phosphor due to its wide absorption spectrum ranging 250–550 nm. It shows broad white (400–700 nm), orange (∼580 nm) and red (∼611 nm) photoluminescence (PL) under 370 nm, 395 nm and 467 nm excitations, respectively and were assigned to one or more 5D0→7FJ (J = 1 to 4) transitions of Eu3+ ion. An efficient energy transfer between Zn2+ and Eu3+ has been observed upon systematically increasing the concentration of Eu3+ ion. Scanning Electron Microscopy images indicated elongated rod-like structures with an average diameter of ∼20 nm. The chromaticity coordinates (x, y) were found to be positioned at white (0.33, 0.42), orange (0.51, 0.42) and red (0.65, 0.34) regions correspond to 370 nm, 395 nm and 467 nm excitations, respectively. The temperature-dependent luminescence spectrum of BaZnO2:Eu3+ under the excitation of 467 nm was also studied. It exhibited good thermal stability and a marginal drop in photoluminescence intensity by 4.29% at 150 °C was observed. The mathematical calculation of the activation energy was approximately 0.20 eV. The results indicate the suitability of the phosphor for LEDs applications, which is otherwise difficult to obtain in single-component system.

In this report, energy harvesting properties of Nafion films were investigated using piezoionic generator (PIOG) and triboelectric generator (TEG) devices. Nafion films were prepared by simple doctor blade deposition of a Nafion ionomer solution onto the aluminum electrode. The Nafion films were characterized for their surface morphology, composition, and crystallinity. Furthermore, the Nafion film exhibited strong substrate adhesion, a smooth surface, and amorphous nature. The deposited Nafion film was used directly as an active layer to fabricate the PIOG and TEG devices with ITO electrodes. Output voltages of ∼450 mV and ∼1.9 V have been observed for the PIOG and TEG devices against biomechanical energy. The maximum instantaneous power produced by these devices is approximately ∼0.205 μW cm−2, and ∼0.128 μW cm−2 for the PIOG and TEG, respectively. The PIOG performance can be further improved using Nafion composite films. Similarly, the TEG performance can be enhanced with other friction layers such as PVDF, PDMS, PMMA, and PVC films instead of ITO. Therefore, the proposed nanogenerators can be used as touch sensors and energy sources for wearable electronic devices in the future.

Calcium aluminozincate phosphor, Ca3Al4ZnO10 (CAZ) doped with Eu3+ has been synthesized using solid-state reaction (SSR), combustion (CS) and sol-gel (SG) methods for relatively improved luminescence performance and to optimize synthesis method. The X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and PL decay measurements have been recorded for the detailed investigation of the luminescence properties of the as-synthesized phosphor. The thermoluminescence (TL) spectral study has been done to estimate the trap depth of the defect centres. The XRD peaks confirm the complete matching of the diffraction peaks of the as-synthesized sample with the standard data for Ca3Al4ZnO10. The morphology of the sample synthesized via SG method shows agglomerated particles with average particle size smaller than the samples synthesized via CS and SSR method. The detailed investigation shows significant red emission enhancement in Eu3+ doped CAZ phosphor synthesized via SG method. The obtained results suggest that the Eu3+ doped CAZ phosphor synthesized via SG method could be a great choice as red emitter for applications in solid state lighting.

Oxy-fluoro tellurophosphate glasses with molar composition (40-x)P2O5-20TeO2-20ZnF2-20RO-xEu2O3 (where R = Ca, Sr, and Ba and x = 1) were prepared by melt quenching technique. The structural, optical, and photoluminescent properties were studied for the prepared glass. The Fourier transform infrared (FT-IR) studies revealed the presence of poly-phosphate structure and maximum depolymerization was observed for BaO network modifier mixed glass. The band gap and Urbach energy values were calculated based on the absorption spectra. The intense emission peak was observed at 613 nm (5D0→7F2) under the excitation of 392 nm, which matches well with the emission of commercial near ultraviolet (n-UV) LED chips. The highest emission intensity and quantum efficiency were observed for BaO network modifier mixed glass. Based on these results, BaO network modifier glass samples with molar composition (40-x)P2O5-20TeO2-20ZnF2-20BaO-xEu2O3 (x = 3, 5, 7, and 9) were prepared to optimize the emission intensity. The optimized doping concentration of Eu2O3 was 5 mol% and the Commission International de l’Eclairage (CIE) chromaticity coordinates fall in the red region. The interaction among Eu3+ ions was dipole-dipole in nature, which was confirmed by Dexter theory and Inokuti-Hirayama (I-H) model. The above results suggest the applicability of the glass as a potential red photoluminescent material in photonic devices.

In the contemporary days, non-linear optical materials (NLO) are getting higher attention as per the increasing demand in optical communication and data storage technology. Consequently, they explore various physical properties of the NLO material for their industrial applications. In current report, l-arginine p-nitrobenzoate monohydrate (LANB) single crystals were obtained by adopting slow cooling technique. The structural confirmation of grown single crystal was carried out using single crystal X-Ray diffractometer. Presence of strain within single crystal was deduced using Hall–Williamson relation. Various defects associated within single crystal were assessed using high resolution XRD. Additionally, its crystalline quality was again confirmed by time resolved photoluminescence spectroscopy (TRPL). Using transmission spectra, the cut off wavelength and band gap of the host material was determined to be nearly 420 nm and 2.9 eV respectively. The dielectric property has been recorded by varying the frequency ranging from 50 Hz to 100 kHz. The curve suggests that dielectric loss value is less at high frequency ensures the suitability of crystal in photonics and NLO based devices. The laser damage threshold values were also measured for single and multiple shots. Thermal parameters of the titled compound were calculated using PPE. In photoconductivity measurement, negative photoconductivity has been observed in titled compound. Microhardness studies were also performed on single crystal to explore its mechanical properties.

Recent studies have shown that, Eu3+ doped silicates have gained lot of importance as an ideal red phosphor material in White Light Emitting Diode (WLED) application, due to Eu3+ electronic configuration. Studies have been carried out in the literature to observe the effect of charge compensation on photoluminescence properties of silicates. Alkali metals (Li+, Na+, K+, Cl−) and other halogens are used as charge compensators. The Li+ ion is known to be a good charge compensator because of its small size and such studies are well documented. Keeping this in view, we wanted to carry out such compensation using alkali metals but also curious to understand, the way a combination of alkali pair for such compensation process and the effect of charge compensator on the PL properties of this phosphor. We specifically chose the alkali pair, where charges are same but their size and mass ratio being vastly different. Europium doped calcium silicate (Ca2SiO4: Eu3+) has been prepared with charge compensators using alkali metals such as Li, Rb and Li-Rb. To start with, β-dicalcium silicate (Ca2SiO4) has been prepared by solution combustion technique in the muffle furnace at a temperature of 500 °C. Diformyl hydrazine (DFH) was used as a fuel. In the second step, we synthesized Ca2SiO4 mixed with Eu3+ and their mixture with required alkali metals by solid state reaction followed by calcinations at 900oC for 2 h. Subsequently obtained β-Ca2SiO4: Eu3+ phosphor powders were characterized by powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Fourier transform Infra-Red (FTIR) spectroscopy. PXRD analysis confirmed the monoclinic phase with P2/m space group. However, SEM observation revealed agglomerated wafer and stony cluster morphology. The PL spectra of Ca2SiO4: Eu3+ was carried out with varying concentration of Eu3+. The samples with 5 mol% showed maximum PL intensity peak compared to other concentrations and spectra revealed PL at 588, 611, 620, 648, 685 and 701 nm. The same procedure was adapted for β-Ca2SiO4: Eu3+, Li where Li act as a charge compensator. Surprisingly a new intense luminescent peak is observed at 574 nm and 588 nm, besides the intense red luminescent peak. The Hyper Sensitive Transition (HST) peaks around 612 nm and 621 nm have got their intensity pattern inverted indicating the effect of charge compensation on the Eu3+ environment which is a result of crystallographic effects and splitting of energy levels with changed transition probability.

For the first time, single-step fabrication of two-dimensional nanosheets of zinc sulfide (ZnS) was achieved employing flexible aluminum (Al) foil substrate using hydrothermal technique at 140 °C for ∼4 h. Indium doped Tin Oxide (ITO) coated on PET (Polyethylene Terephthalate) substrate and ZnS deposited Al foil as a top and bottom electrodes were used to fabricate a piezoelectric device. To generate an electric potential, the top ITO electrode was tapped on the ZnS nanosheets. The open-circuit voltage, VOC of ∼400 mV was obtained and analyzed for ZnS nanosheets based nanogenerator with gentle finger taping. However, the highest output for the single nanogenerator was found to be ∼600 mV by applying toe pressure. Additionally, switching polarity and superposition experiments were utilized to confirm the nanogenerator's performance, with the findings confirming piezo-electric voltage output. This study investigates the new potential for a ZnS-based high-efficient energy harvester that can scavenge biomechanical energy for next-generation flexible self-powered electronics devices as well as a good replacement for ZnO nanosheets in 2D nanostructured based nanogenerator devices due to its simple single-step production process, low cost, and high output gain.