Blue-violet Region Research Articles

Irradiation for improving Violet-Blue Light Contribution of tri- and Polychromatic Polysulfone Host-guest systems

Herein, we explored the effect of light irradiation on polysulfone films dopped with highly emissive guests. We report irradiation promoted interactions in a polysulfone membrane functionalized with a fluorinated β-diketone species leading to an improved Violet-Blue Light Contribution in Polychromatic Polysulfone Host-Guest Systems.We suggest that irradiation at higher UV wavelengths, leads to an amorphous-to-monomer phase transformation of the fluorinated boron guest, BF2dbm (dbm as dibenzoylmethanoate), to which corresponds conversion of part of the green emission from aggregates to cyan-blue fluorescence, characteristic of the monomeric form. Also, irradiation at lower wavelength promotes host-guest BF2dbm@PSU strong interaction giving rise to increased emission in the violet-blue region by sacrificing the contribution from the intense blue-cyan emission from BF2dbm molecules.In the current work we also prepared combinations of Tb3+ and Eu3+ highly fluorinated complexes and evaluated its tuneable emission due to light driven ligand interaction with host matrix. The judicious choice of molecular ratio between Tb3+ and Eu3+ complexes allow rationally designed preparation of triple-emissive flexible films when irradiated at 300, 320 and 330 nm, to be used in highly advanced anti-counterfeiting technologies.In short, we propose a simple and new powerful approach for emission colour tuning of polysulfone dopped films.

Optical whispering gallery mode resonators: analysing thermo-optic tuning in a silicon sphere

ABSTRACT In this work, we discuss and experimentally investigate the whispering gallery modes (WGMs) in a 500 μm radius silicon sphere. We begin by reviewing the basics of WGM resonators, followed by simulations and experimental results obtained with the aforementioned silicon spherical WGM resonator. The recorded WGM signatures in the transmission and scattering spectra excited, in the near-infrared (near-IR) region, agree well with the simulations. Thermo-optic tuning of these WGMs is achieved by introducing a pump laser in the violet-blue region. Red-shifts in wavelength are observed, which increase with the increase in the pump power. A shift of 0.63 nm is observed at a pump power of 6.32 mW. We also study switching by analysing the transient response of the WGM spectra. The measured WGMs exhibit high quality factors ( Q ∼ 10 5 ), which along with the aforesaid tunability, demonstrates the potential of spherical silicon resonator as a platform for photonic applications, e.g. sensing and communication. In summary, this work contributes towards the understanding of the fundamental physics of WGMs and provides insights into silicon WGM resonators.

Synthesis, optical properties, and applications of Eu3+, Na+-doped high-color-purity Sr3MgNb2O9 red phosphors for w-LEDs and the detection of latent fingerprints

A series of novel phosphors, doping Eu3+ and Na+ ions in the Sr3MgNb2O9 (SMNO) crystal lattice (SMNO:xEu3+, xNa+, x = 0.5–30 mol%), was successfully synthesized through high-temperature solid-state reaction. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the successful synthesis of SMNO:Eu3+, Na+. The phosphor belongs to the hexagonal crystal system and the P3¯m1 (No.164) space group. The bandgap energy of SMNO was calculated with Materials Studio and measured with the use of diffuse reflectance spectroscopy. The excitation spectrum of SMNO:Eu3+, Na+ displays multiple narrow absorption peaks in the violet-blue region as well as a charge transfer band (CTB) near 300 nm, exhibiting the highest peak at 394 nm. Four distinct characteristic peaks are observed in the emission spectrum of SMNO:Eu3+, Na+. Notably, the peak at 601 nm shows the highest emission intensity due to the radiative transition from 5D0→7F2. By varying doping concentrations, it was determined that an optimal concentration of 5 mol%Eu3+ resulted in phosphors, with high color purity exceeding 99 %. Concentration quenching is attributed to the nearest neighbor ions interaction. Furthermore, SMNO:Eu3+, Na+ exhibited good stability in 300–480 K, with luminescent intensity remaining 68.6 % at 420 K and 54.4 % at 480 K compared to room temperature (300 K). The internal quantum efficiency (IQE) of SMNO:5%Eu3+, 5 %Na+ is 65.0 %. Both red and white light-emitting diodes (LEDs) were prepared using SMNO:Eu3+, Na+. The chromaticity coordinates of w-LED were measured as (0.357, 0.376), correlating to a correlated color temperature (CCT) of 4685 K and exhibiting a good color rendering index (CRI, Ra = 88). Additionally, the latent fingerprint (LFP) development demonstrated clear visualization of Levels I-III characteristic structures of fingerprints when utilizing SMNO:Eu3+, Na+. These findings suggest promising applications for SMNO:Eu3+, Na+ in w-LED lighting and LFP development.

Diatom Biosilica Functionalised with Metabolically Deposited Cerium Oxide Nanoparticles.

This study introduces a novel approach to synthesising a three-dimensional (3D) micro-nanostructured amorphous biosilica. The biosilica is coated with cerium oxide nanoparticles obtained from laboratory-grown unicellular photosynthetic algae (diatoms) doped metabolically with cerium. This unique method utilises the ability of diatom cells to absorb cerium metabolically and deposit it on their silica exoskeleton as cerium oxide nanoparticles. The resulting composite (Ce-DBioSiO2) combines the unique structural and photonic properties of diatom biosilica (DBioSiO2) with the functionality of immobilised CeO2 nanoparticles. The kinetics of the cerium metabolic insertion by diatom cells and the physicochemical properties of the obtained composites were thoroughly investigated. The resulting Ce-DBioSiO2 composite exhibits intense Stokes fluorescence in the violet-blue region under ultraviolet (UV) irradiation and anti-Stokes intense violet and faint green emissions under the 800 nm near-infrared excitation with a xenon lamp at room temperature in an ambient atmosphere.

Preparation and characterization of TiO2 photocatalyst films and their application for preservation of Agaricus bisporus in combination with blue-violet LEDs

This study aims to prepare and characterize non-metallic nitrogen-modified titanium dioxide (N–TiO2), film and expand its photocatalytic excitation wavelength to the visible blue-violet region. The film uses corn starch as a carrier. It is combined with blue-violet LED light to explore the effect of this combination on the quality of Agaricus bisporus during storage. This study found that the mechanical properties and hydrophobicity of the corn starch film with nano-TiO2 added were improved; the effect of adding N–TiO2 was more pronounced; the tensile strength increased by 65% while the water contact angle increased by 11%. In the application of A. bisporus storage, the film combined with blue-violet LED light can slow down the loss of moisture, reduce the respiratory rate, delay the appearance of the respiratory peak, and maintain the color and hardness of A. bisporus. After 15 d of storage, compared to the control group, the hardness decreased by 69%, browning index (BI) increased by 221%, the CS-N group hardness decreased by only 23%, and the BI increased by 89%. Under blue-violet LED light, the accumulation of secondary metabolites in A. bisporus increased, and the polyphenol content also showed an increasing trend during storage.

ZnO-Based Materials: From Pauli’s Nonsense to a Key Enabling Technology

In this work, we aim to highlight the increasing interest in semiconductors, particularly ZnO. A revision of the evolution of the scientific production on three selected topics has been conducted. As an indicator of scientific production, the number of publications indexed in the Web of Science Data Base has been used. The search terms selected range from the general to the particular: semiconductors, oxide semiconductors, and ZnO. The period considered is from 1 January 1900 to 6 June 2023. The importance of doping processes in tailoring the properties of these materials, and the relevance of the most recently derived applications are also revised. Since many of the most recent applications that have been developed or are under development refer to optoelecronic properties, doping with rare earth elements has a central role. This was the reason behind choosing the system ZnO doped with Rare Earth elements (Eu, Gd, and Ce) and codoped with Ru to illustrate the materials’ tuning potential of doping processes. Morphology, crystal structure, and luminescent properties have been investigated. Upon doping, both the Near Band Edge and the Deep Level emissions show a remarkable difference due to the change in the relative weight of the components constituting these bands. The spectra in all cases extend over the whole visible range, with a main emission in the violet-blue region corresponding to the Near Band Edge, and a broad band extending from the blue-green to orange-red region associated with the presence of different defects.

Investigations of structural, optical and electrical properties of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder

The Pb2+ doped ZnAl2O4 ceramic with different concentrations (0–2 mol %) has been prepared via the fast citrate sol-gel technique. Crystalline size of prepared samples was found in the range of 26–32 nm using XRD data. The X-ray pattern revealed that all samples are polycrystalline in nature with cubic phase and Fd͞3 m space group. The preferred orientation and structure parameter of spinel ZnAl2O4 has been tailored significantly after doping Pb2+ ions. The FTIR technique was used to identify the characteristic functional group of the prepared spinel structure.The optical band gap of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder was found to increase from 3.65 eV to 4.36 eV with an increase in Pb2+ content. The prominent emission was observed in the violet-blue region (387 nm) after exciting the sample at 270 nm. The impedance data has been analyzed to explore the dielectric constant (k), dissipation loss factor (DF), and ac conductivity. The observed violet-blue emission and improved dielectric behavior endorse the potential applications of Zn1-xPbxAl2O4 (0 ≤ x ≤ 2 mol %) ceramic powder in UV sensors.

An investigation about the ability to change color and the way energy is transferred of NaYMgWO6:RE3+ (RE3+ = Tm3+, Dy3+, Tm3+/Dy3+): A new type of single-phase white phosphor for WLEDs

Novel NaYMgWO6:Tm3+, Dy3+ phosphor is synthesized by solid-state reaction method in air. The phase structure was meticulously analyzed through XRD and Rietveld refinement techniques. Dy3+ doped NaYMgWO6 phosphors emitted yellowish-white light, which was observed. Surprisingly, the introduction of Tm3+ ions resulted in white-emitting, which was further studied with the aid of a spectrometer. By fixing the concentration of Tm3+ ions and subsequently adjusting the co-doping concentration of Dy3+ ions or altering the excitation wavelength, the CIE coordinates of NaYMgWO6:Dy3+, Tm3+ phosphors shifted from the blue-violet region to the yellowish-white region. In particular, when b = 0.2 mol, there was efficient energy transfer from Tm3+ to Dy3+, with an energy transfer efficiency of 95.1 %. The gradual decrease of the lifetime at 454 nm monitoring implies that there is indeed an energy transfer process from Tm3+ to Dy3+ and that the probability of energy transfer from Tm3+ to Dy3+ gradually increases with increasing Dy3+ concentration. These findings indicate that NaYMgWO6: aTm3+, bDy3+ phosphors offer a novel approach to researching single-phase white phosphors.

Organosulfur and Organoselenium Functionalized Benzimidazo[1,2-a]quinolines: From Experimental and Theoretical Photophysics to All-Solution-Processed OLEDs.

In this study, we present the synthesis of benzimidazo[1,2-a] quinoline-based heterocycles bearing organosulfur and organoselenium moieties through transition-metal-free cascade reactions involving a sequential intermolecular aromatic nucleophilic substitution (SNAr). Both sulfur and selenium derivatives presented absorption maxima located around 355nm related to spin and symmetry allowing electronic 1π-π* transitions, and fluorescence emission at the violet-blue region (~440nm) with relatively large Stokes shift. The fluorescence quantum yields were slightly influenced by the chalcogen, with the sulfur derivatives presenting higher values than the selenium analogs. In this sense, the quantum yields for selenium derivatives can probably be affected by the intersystem crossing or even the photoinduced electron transfer process (PET). The compounds were successfully applied in all-solution-processed organic light-emitting diodes (OLEDs), where poly(9-vinylcarbazole) was employed as a dispersive matrix generating single-layer device cells. The obtained electroluminescence spectra are a sum of benzimidazo[1,2-a]quinolines and PVK singlet and/or triplet emissive states, according to their respective energy band gaps. The best diode rendered a luminance of 25.4cd⋅m-2 with CIE (0.17, 0.14) and current efficiency of 20.2 mcd⋅A-1, a fivefold improvement in comparison to the PVK device that was explained by a 50-fold increase of charge-carriers electrical mobility.

Optical and dielectric behaviors of polyvinyl chloride incorporated with MgFe2O4/MWCNTs

Casting and wet chemical methods have been used to produce polyvinyl chloride/magnesium ferrite/multi-walled carbon nanotubes (PVC-MgFe2O4-MWCNTs) polymer nanocomposites. Full characterization was carried out applying x-ray diffraction (XRD), scanning electron microscope (SEM/EDS), and Fourier transform infrared (FTIR) techniques. MWCNTs disclosed high crystalline nature and Rietveld refinement revealed nanostructure for MgFe2O4 with average size 16 nm. Optical properties were inferred by diffused reflectance spectrophotometry, fluorescence (FL), and chromaticity (CIE). Upon loading PVC with MgFe2O4/MWCNT, both direct and indirect bandgaps were reduced, the absorbance was enhanced greatly, while transmittance and reflectance were reduced. The refractive index was reduced except for PVC/MgFe2O4 where it enhanced for λ > 450 nm and increased with incident photon energy. The optical conductivity is highly enhanced for the whole wavelength range. According to FL and CIE results, the FL peak intensity of pure PVC polymer decreased upon loading MgFe2O4 and quenched further upon adding MWCNTs to the polymer. PVC emitted in the blue range while doped PVC emitted in blue-violet regions. The effect of MgFe2O4 and/or MWCNTs on the ac conductivity, electrical dielectric constant and electric modulus of PVC was investigated at room temperature. Based on the characterization data, the synthesized polymer nanocomposites have potential applications in several different optoelectronic settings.

Comparative Study on Gemmological Characteristics and Luminescence of Colorless and Yellow Scapolites

The orange fluorescence of scapolite has been confirmed to be caused by (S2)−, but the frequent blue fluorescence in gem-quality scapolite has not been well explained. An energy dispersive X-ray fluorescence spectrometer (XRF), electron probe microanalyzer (EPMA), X-ray powder diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Raman spectrometer, ultraviolet-visible spectrophotometer, fluorescence spectrometer, and conventional gemological test methods were used to study the gemological characteristics, chemical composition, coloration mechanism, spectral characteristics, and luminescence of colorless and yellow scapolite. The results show that both yellow and colorless scapolites are mizzonite and that they share the same gemological and spectroscopic characteristics. The results of XRD, FIRT, and Raman spectra show that the yellow scapolite has the same structure as the colorless scapolite. The yellow color of scapolite is caused by Fe3+ and when the Fe content is low it is colorless. Yellow scapolite has about three times the Fe content of colorless scapolite. Under the excitation of long-wave and short-wave ultraviolet light, scapolite forms a strong and wide excitation peak in the blue-violet region centered at approximately 410 nm, which is due to the 4f1 → 5d1 of Ce3+, resulting in blue fluorescence.

Crystal growth, structural and DFT study of novel single crystal (E)-N’-(2-chlorobenzylidene)-4-fluorobenzohydrazide for nonlinear optical applications

Nonlinear optical (NLO) material, (E)-N'-(2-chlorobenzylidene)-4-fluorobenzohydrazide (CBBH) novel single crystal was grown via a Schiff base chemical reaction. A single crystal X-ray diffraction technique was utilized for the recognition of the crystal structure of the CBBH. The imperfection of novel CBBH crystal was checked by high resolution X-ray diffraction (HRXRD) study. Hirshfeld surface study through colour coding was applied to know the intra and intermolecular force interactions. Fourier transforms infrared (FTIR), proton 1H and carbon 13C nuclear magnetic resonance (NMR) spectra were employed to elucidate the various functional groups and structure of the crystal. The absorption maxima from UV–Vis plot for the CBBH molecule was found at 314 nm, which reveals the π-π* transition. Photololuminescence (PL) study reveals that emission observed in the blue-violet region. The HOMO and LUMO energies were investigated using the density functional theory (DFT) method. Natural bond orbital (NBO) analysis explored the donor-acceptor exchanges and it's endurance into intra-molecularly. The first-order hyperpolarizability value, β0 = 23.73 × 1030 esu was observed for CBBH crystal, which is ∼64 times larger than that of urea molecule (0.3728 × 1030 esu). Z-scan experiment on CBBH crystal supports its third-order nonlinear optical (NLO) properties. Optical limiting analysis indicates reverse saturation absorption behavior of CBBH crystal.

Dual polymer electrochromic sunglasses with black to anti-blue-ray conversion based on new anti-blue-ray transparent polymer

Smart electrochromic (EC) glasses with visible light modulation have attracted considerable attention due to their unique advantages, but EC sunglasses with anti-blue-ray function have not yet been reported. Herein, a series of wide-bandgap electrochromic conjugated polymers P2–P4 based on 3,4-propylenedioxythiophene (ProDOT) and naphthalene units were designed and synthesized using direct arylation polymerization. Among them, polymers P2 exhibit a satisfactory yellow hue and outstanding overall electrochromic performances. By tuning the intramolecular torsion between ProDOT and naphthalene units in the polymer structure, the absorption spectra of polymers P3 were entirely shifted to the high-energy violet-blue spectra region relative to the anti-blue-ray function. New dual conjugated polymer electrochromic devices based on P3 and black-to-transmissive electrochromic polymer were fabricated, which exhibited the fast transformation between black and anti-blue-ray transmissive color with a switching time of < 5.0 s, high contrast of 49% at 400–700 nm and a high coloring efficiency of 470.8 cm2/C. Moreover, an EC prototype sunglasses device with an anti-blue-ray function was fabricated to demonstrate the practical suitability based on the dual conjugated polymer ECDs. This work contributes to the application of EC technology to the smart glasses field.

A Study of the Structural and Surface Morphology and Photoluminescence of Ni-Doped AlN Thin Films Grown by Co-Sputtering.

Aluminum nitride (AlN) is a semiconductor material possessing a hexagonal wurtzite crystal structure with a large band gap of 6.2 eV. AlN thin films have several potential applications and areas for study, particularly in optoelectronics. This research study focused on the preparation of Ni-doped AlN thin films by using DC and RF magnetron sputtering for optoelectronic applications. Additionally, a comparative analysis was also carried out on the as-deposited and annealed thin films. Several spectroscopy and microscopy techniques were considered for the characterization of structural (X-ray diffraction), morphological (SEM), chemical bonding (FTIR), and emission (PL spectroscopy) properties. The XRD results show that the thin films have an oriented c-axis hexagonal structure. SEM analysis validated the granular-like morphology of the deposited sample, and FTIR results confirm the presence of chemical bonding in deposited thin films. The photoluminescence (PL) emission spectra exhibit different peaks in the visible region when excited at different wavelengths. A sharp and intense photoluminescence peak was observed at 426 nm in the violet-blue region, which can be attributed to inter-band transitions due to the incorporation of Ni in AlN. Most of the peaks in the PL spectra occurred due to direct-band recombination and indirect impurity-band recombination. After annealing, the intensity of all observed peaks increases drastically due to the development of new phases, resulting in a decrease in defects and a corresponding increase in the crystallinity of the thin film. The observed structural, morphological, and photoluminescence results suggest that Ni: AlN is a promising candidate to be used in optoelectronics applications, specifically in photovoltaic devices and lasers.

Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics

The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.

Lophine-cinnamoyl hybrids: Synthesis, photophysical properties and a spectroscopic and molecular dynamics approach towards interactions with bovine serum albumin

Lophine and cinnamic acid derivatives have gained considerable attention due their chemical, biological and fluorescence emission properties. Herein we reported the synthesis of a new family of lophine-cinnamoyl hybrids connected by a methylene chain with two to nine carbon atoms. The hybrids show absorption in the ultraviolet and emission in the blue-violet region independent of the length of the alkyl chain spacer. Non-covalent interactions of the hybrids to bovine serum albumin (BSA) were investigated by UV–Vis absorption and fluorescence spectroscopy. Overall, the hybrids display moderate affinities for BSA (binding constants in the range 10–14 × 104 M−1) and can be effectively employed as protein probes using BSA as a model. The theoretical calculations showed preferential interactions of the hybrids with the binding pocket located near to Trp213 and the number of binding sites equal to 1 are in agreement with the experimental data obtained through the Stern-Volmer approach.

Te2 absorption spectrum from 19000 to 24000 cm−1

A Fourier-transform absorption spectrum of 130Te2 has been recorded from 19000 to 24000 cm−1 at approximately 620 °C; a transmission spectrum is made available in ASCII format. The spectrum is intended to aid spectral calibration in the blue-violet region. It extends slightly beyond the paper version of the Tellurium atlas, published in 1980 (J. Cariou and P. Luc, 'Atlas du spectre d'absorption de la molécule de tellure', Laboratoire Aime-Cotton (1980)).

Atto 465 Derivative Is a Nuclear Stain with Unique Excitation and Emission Spectra Useful for Multiplex Immunofluorescence Histochemistry.

Multiplex immunofluorescence (mIF) is an effective technique for the maximal visualization of multiple target proteins in situ. This powerful tool is mainly limited by the spectral overlap of the currently available synthetic fluorescent dyes. The fluorescence excitation wavelengths ranging between 405 and 488 nm are rarely used in mIF imaging and serve as a logical additional slot for a fluorescent probe. In the present study, we demonstrate that the addition of 2,3,4,5,6-pentafluoroaniline to Atto 465 NHS ester, creating Atto 465-pentafluoroaniline (Atto 465-p), generates a bright nuclear stain in the violet-blue region of the visible spectrum. This allows the 405 nm excitation and emission, classically used for nuclear counterstains, to be used for the detection of another target protein. This increases the flexibility of the mIF panel and, with appropriate staining and microscopy, enables the quantitative analysis of at least six targets in one tissue section. (J Histochem Cytochem XX: XXX-XXX, XXXX).

Synthesis and luminescent properties of rare earths doped Gd&lt;sub&gt;2&lt;/sub&gt;Te&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;11&lt;/sub&gt; tellurite phosphors

A series of rare earth Dy&lt;sup&gt;3+&lt;/sup&gt;, Tb&lt;sup&gt;3+&lt;/sup&gt;, Eu&lt;sup&gt;3+&lt;/sup&gt; singly doped Gd&lt;sub&gt;2&lt;/sub&gt;Te&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;11&lt;/sub&gt; (GTO) tellurite phosphors with intrinsic polarity are prepared by hydrothermal method. The phase structures, morphologies and thermal stabilities of these phosphors are characterized. Their luminescence properties are tested in detail. The results show that all those phosphors are crystalized into single phase of digadolinium tellurite with short rod-like shape. The maximum size in the axial direction is microns. The phosphor has good thermal stability. For the GTO:Dy&lt;sup&gt;3+&lt;/sup&gt;, the fluorescence emission under UV excitation is mainly located in the yellow-green region. The optimal doping concentration corresponding to the strongest excitation and emission is 2.5%, and the CIE color coordinates are (0.39, 0.43). The fluorescence decay curve shows that the lifetime of the GTO:Dy&lt;sup&gt;3+&lt;/sup&gt; on &lt;sup&gt;4&lt;/sup&gt;F&lt;sub&gt;9/2&lt;/sub&gt; energy level decreases gradually with doping concentration of Dy&lt;sup&gt;3+&lt;/sup&gt; increasing, which may be related to the cross relaxation (CR) between Dy&lt;sup&gt;3+&lt;/sup&gt; ions. For the GTO:Eu&lt;sup&gt;3+&lt;/sup&gt;, the fluorescence emission under UV excitation is mainly located in the red region and orange-red region. The emission intensity is enhanced with the doping concentration of Eu&lt;sup&gt;3+&lt;/sup&gt; increasing. When the doping concentration is 10%, the CIE color coordinates are (0.62, 0.38), which are located in the orange-red region with high color purity. The fluorescence lifetime of Eu&lt;sup&gt;3+&lt;/sup&gt; on &lt;sup&gt;5&lt;/sup&gt;D&lt;sub&gt;0&lt;/sub&gt; energy level is hardly affected by the change of Eu&lt;sup&gt;3+&lt;/sup&gt; doping concentration. For the GTO:Tb&lt;sup&gt;3+&lt;/sup&gt;, with the increase of the Tb&lt;sup&gt;3+&lt;/sup&gt; concentration, the fluorescence emission under UV excitation changes from blue-violet region to yellow-green region, which can be ascribed to the influence of CR between Tb&lt;sup&gt;3+&lt;/sup&gt; ions. The fluorescence decay behavior reveals that the Tb&lt;sup&gt;3+&lt;/sup&gt; ions on &lt;sup&gt;5&lt;/sup&gt;D&lt;sub&gt;4&lt;/sub&gt; excited state may undergo energy transfer and reabsorption, which can deviate the fluorescence decay from the single exponential model. When the concentration of Tb&lt;sup&gt;3+&lt;/sup&gt; is 0.5%, the sample exhibits white light emission with the CIE color coordinates of (0.33, 0.35) and color rendering index of 86. The measurements of temperature-dependent emission spectra show that the above-mentioned phosphors have good luminescent thermal stability. The internal quantum efficiencies (IQEs) of those three types of phosphors are measured, and the IQE of GTO:Eu&lt;sup&gt;3+&lt;/sup&gt; is better than those of GTO:Dy&lt;sup&gt;3+&lt;/sup&gt; and GTO:Tb&lt;sup&gt;3+&lt;/sup&gt;. There is still much room for improvement in the luminescent performance of all these phosphors. These phosphors have potential to be used in UV-excited white LEDs.

Manganese ions substituted ZnO nanoparticles: Synthesis, microstructural and optical properties

Nanocrystalline Mn ions doped ZnO powder samples with a generic formula Zn1-xMnxO (x = 0.00, 0.02, 0.04, and 0.06) were prepared using conventional co-precipitation method. Confirmation of pure single-phase formation of all the ZnO samples was obtained by x-ray diffraction profiles. An average crystallite size in between 25 nm and 30 nm was calculated using Scherrer's formula. Williamson-Hall plots verified the existence of microstrain within the nanocrystals. Presence of bivalent, trivalent and tetravalent Mn ions in ZnO matrix was confirmed by x-ray photoelectron spectra analysis. Room temperature UV–Vis spectra studies confirmed that all the samples showed strong absorption near violet-blue region of EM spectrum. Photoluminescence spectra analysis confirmed the presence of both zinc and oxygen vacancies in doped samples.