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In this study, YOF:Pr3+ nanophosphors were synthesized using the microwave-assisted hydrothermal route. The structural and morphological properties of the nanophosphors calcined at different temperatures were studied in detail to optimize the synthesis conditions. The visible region and near-infrared (NIR) photoluminescence (PL) properties of the nanophosphors were obtained. Intense emission bands were observed in the blue and red regions under 250 nm excitation. The CIE chromaticity diagram showed that the color coordinates of the nanophosphors were located in the yellow region. The optimum Pr3+-concentration was found to be 0.002 mol fraction. The application of YOF: 0.002 Pr3+ nanophosphor for latent fingerprint detection was examined and evaluated on different types of surfaces. The nanophosphor demonstrated excellent adherence to the ridge patterns and sufficient sensitivity required for distinguishing between the ridges and the furrows. Different levels of detail were also observed that provided necessary information for the individualization of the fingerprints. The results suggest that the prepared YOF:Pr3+ nanophosphor can be a potential candidate for the rapid visualization and detection of latent fingerprints.

To get high quality white light from the combination of blue light emitting diode (LED) and yellow emitting YAG phosphor is still an issue. Herein, we report a self-emitting Zn3(VO4)2 yellow phosphor synthesized by combustion method (CM) and co-precipitation method (CPM). Urea was used as a fuel for combustion and sodium hydroxide was used as precipitating agent for co-precipitation route. Under near UV excitation, the phosphors emit in the yellow region with an asymmetric emission band towards the higher wavelength in the range from 400 nm to over 800 nm due to the charge transfer transition of an electron from the oxygen to the tetrahedra VO4 with Td symmetry. The luminescence intensity for the CPM synthesized phosphor was much higher than the CM synthesized phosphor. Temperature dependent PL results suggested that the phosphor is thermally stable and retain its 80 % of the initial brightness at 353 K. The quantum efficiency of the CPM synthesized phosphor (∼ 33 %) is also most double the CM synthesized phosphor. The overall results suggest that a UV converted yellow emitting phosphor could be a potential alternative for the combination of blue and green phosphor used in WLED. As a result, the efficiency of the white LED can be enhanced by reducing the probability of the reabsorption.

The pyrochlore-structured (A2B2O7) compounds have emerged as a focal point in contemporary research and materials science, captivating attention for their intriguing properties such as photoluminescence, superconductivity, ionic mobility, and potential applications in high-temperature barrier coatings. Their potential application in up- or down-conversion photoluminescence further positions them for integration into a myriad of optoelectronic and sensing devices. Building on extensive prior research, this review delves into the upconversion (UC) luminescence properties of numerous pyrochlore-structured host materials (titanates, zirconates, hafnates, and ytterbium pyrochlores), specifically those doped with rare earth ions. While these materials may share similar chemical and structural characteristics, their luminescent capabilities exhibit significant variation upon rare earth ion doping. The phase transitions of various pyrochlore-structured compounds with respect to cation ratio, the relationship between crystal structure, doping concentrations, and UC luminescent properties in pyrochlore-structured compounds are summarized in detail. Through controlled doping strategies and structural adjustments, researchers have been able to tailor the luminescence properties of pyrochlore structured compounds to meet specific application requirements. The intricate exploration of the UC luminescence properties of pyrochlore-structured compounds, especially when doped with rare earth ions, showcases the rich potential for these materials in a wide array of applications across various fields, from advanced sensing technologies to innovative optoelectronic devices, paving the way for exciting advancements in materials science and beyond.

A series of Na4Ca (PO3)6: xmol% Eu3+ (x = 1, 2, 3, 4 and 5) was synthesized using a solid-state method and characterized using various techniques. The X-ray powder diffraction data confirmed that the phosphors crystalized in the monoclinic phase. The Fourier-transform infrared spectroscopy confirmed the presence of phosphate groups and an HO-H peak. The optical bandgaps got smaller as the Eu3+ concentration went up as seen in the diffuse reflectance data. The photoluminescence excitation spectra obtained when monitoring the 613 nm emission line showed peaks assigned to 4f→4f Eu3+ transitions. When the excitation was monitored at 394 nm, the emission exhibited strong narrow bands at 591, 613, 651 and 698 nm owing to the 5D0 → 7FJ (J = 0 - 4) transitions of Eu3+. The main emission peak increased with Eu3+ concentration from 1 mol% to 4 mol% and decreased significantly as the Eu3+ concentration reached 5 mol%. The concentration quenching effect is responsible for the drop in PL intensity at concentrations higher than the optimum Eu3+ concentration. The International Commission on Illumination (CIE) chromaticity coordinates of the phosphors displayed colour response in the orange- red region, suggesting that they have potential application in the orange-red colour-emitting light displays.

An undoped and a series of orange-red emitting LiCaBO3:Sm3+ (x = 0.5–3 mol%) phosphors have been synthesized using a highly reliable and cost-effective combustion method. The synthesized phosphors were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL), and Diffuse Reflectance spectroscopy (DRS). The structural studies of the LiCaBO3:Sm3+phosphor confirm the single-phase orthorhombic structure with space group Pbca and the presence of borate anionic groups. Upon near-UV excitation at 405 nm, the PL emission spectra show four emission peaks centered at 564 nm, 602 nm, 650 nm, and 708 nm corresponding to the 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 transitions respectively resulting in the emission of orange-red light. The optimum dopant concentration of Sm3+ion was 1 mol% and the main mechanism of concentration quenching was calculated using Dexter's theory. The bandgap of the undoped phosphor was found to be 5.31 eV. The CIE chromaticity coordinates are (0.56, 0.40) which confirms the orange-red emission. The obtained results indicate that the synthesized phosphor can be a potential candidate for application in solid-state lighting devices.

A novel technique was created to quickly evaluate the impact of various ratios on the efficiency of up-conversion emission using a combination of up-conversion nanophosphors (UCNPs) and gold nanoparticles (Au NPs). Four different types of Y2O3 UCNPs with different Er3+ or Er3+/Yb3+ doping, which affects the emission colour as well as the up-conversion mechanism, were prepared via the microwave-assisted hydrothermal method. Au NPs were produced independently using the reduction technique. Different ratios of UCNPs were mixed with the Au NPs in water. The mixed powder composites were extracted for analysis. X-ray powder diffraction was utilized to study the structure of UCNPs with and without Au NPs, while transmission electron microscopy was used to study the morphology and size of Au NPs. Absorption and up-conversion measurements were also made. The novel protocol allowed rapid evaluation of four different Y2O3 UCNPs of Er3+ and Er3+/Yb3+ doped with concentrations optimized for red and green emission over a range of Au/UCNP concentrations, which might usually be done in four separate studies. Despite the wide range of variables, only a decrease in UC emission was measured in the presence of Au NPs, suggesting that the conditions for plasmonic enhancement are limited and not easy to attain. In spite of this, in many phosphor/metal NP systems, the innovative prototyping process can enable quick assessment of possible plasmonic enhancement.

This article reports on the development of a new Web-based application software for calculating Judd-Ofelt intensity parameters and derived quantities from the emission spectra of Eu3+ doped compounds. The application was entirely developed in JavaScript, and it is compatible with all major browsers. The web application can be accessed via the following link https://sciapps.sci-sim.com/judd_ofelt_analysis_Eu.html. Test samples of ZnO doped with different amounts of Eu3+ were synthesized using the combustion method, and their radiative properties and the chemical environment in the Eu surroundings were thoroughly investigated by Judd-Ofelt intensity and the derived parameters using the online application. In contrast to the tediousness and time-consuming process of these types of calculations, by using this online software, all intensity parameters and the derived quantities can be obtained within a short time.

Thin films of Bi3+ doped LaOCl and LaOF phosphors prepared via the pulsed laser deposition (PLD) technique in vacuum and different argon (Ar) pressures were compared in order to assess their luminescence properties. All peaks of the X-ray diffraction patterns of the films were consistent with the tetragonal structure of the LaOCl and LaOF, but in the case of LaOF the signal was weaker and not all peaks were present, suggesting some preferred orientation. Photoluminescence measurements revealed that the films exhibited emission around 344 nm for LaOCl:Bi and 518 nm for LaOF:Bi under excitations of 266 nm and 263 nm, respectively. The luminescence from the LaOF:Bi sample was less intense compared to the LaOCl:Bi sample prepared under the same conditions, which was also the case for the powder samples. The amount of ablated material present on the substrate was much less for LaOF:Bi compared to LaOCl:Bi, which is attributed to the greater bandgap and hence weaker absorption of the laser pulses for LaOF:Bi. Therefore phosphors based on LaOCl as the host material were found to be preferable over LaOF under the PLD conditions used in this study.

Zinc sulfur-selenide (ZnSxSe1-x) (0 ≤ x ≤ 1.0) thin films were grown on glass substrates using photo-assisted chemical bath deposition technique and the deposited samples were annealed in an open-air furnace at 250 ℃ for 3 h. X-ray diffraction analysis revealed a phase transition from hexagonal ZnSe to cubic ZnS as x changes from 0 to 1.0. Raman scattering showed two longitudinal optical modes due to ZnSe structure. The effects of S and Se ions variation is observed by the change in surface morphology from nanoflakes to spherical particles as x increased. The presence of the expected elementary composition was confirmed by the energy dispersive x-ray spectroscopy. The bandgap of the films was found to increase from 2.68 to 3.50 eV with a corresponding decrease in crystallite size (11.9 – 7.1 nm) as x varied from 0 to 1.0. Photoluminescence excitation and emission showed defect emission peaks ascribed to intrinsic and extrinsic deep level defects such as Zn2+ or S2- ions vacancies and interstitials. The emission colours were tuned from red to yellowish-green with increased x values as confirmed from Commission Internationale de L’Eclairage analysis. The tunability of the ZnSxSe1-x structural, optical and morphological properties makes it a good candidate for optoelectronic applications.

Pulsed laser deposited films on glass substrate deposited at different substrate temperatures (Ts) and partial pressures of oxygen, Ho3+-doped Bi2O3 films were produced. The degradation capability of the Rhodamine B dye using the Bi2O3:Ho3+ films was explored. The impact of the Bi2O3:Ho3+ content on the dye degradation performance was analyzed. The X-ray powder diffraction patterns showed that the films deposited at 400 °C had an α-Bi2O3 phase. The impacts of various Ts and O2 partial pressures were correlated with the surface morphology and the thickness of the films using results of field emission scanning electron microscope. The thin films deposited at a low O2 partial pressure of 5–20 mTorr at Ts = 400 °C exhibited nano-needles with an average size of 80 nm and a length of ∼750 nm. The estimated band gap of the prepared films was found to vary between 2.6 and 3.0 eV. The photoluminescence (PL) of the Bi2O3:Ho3+ thin films excited at 450 nm showed an intense green band emission observed at 548 nm, and the feeble emissions at 654 and 753 nm were ascribed to the transitions of Ho3+. The nano-needle particles of the α-Bi2O3:Ho3+ exhibited a maximum PL intensity for the 20 mTorr O2 partial pressure thin film. The films prepared in vacuum and with an O2 partial pressure of 5 mTorr exhibited a 41 % dye degradation efficiency during a duration of 270 min of the photocatalysis experiment.

The effect of preparation conditions, Ar/H2 and air atmospheres, on structural and luminescent properties of CaF2:Tb thin films was investigated. The structure of the CaF2:Tb thin films was confirmed by X-ray powder diffraction. Cracks and big grain sizes on the thin film's surface, prepared in air atmosphere, were observed in the scanning electron microscopy images. Atomic force microscopy images for the film prepared under air atmosphere showed big particle sizes with some cracks on the surface, while a dense and smaller particle size was formed for the film prepared under Ar/H2 atmosphere. The measured transmittance showed that the thin film prepared under Ar/H2 exhibited slightly higher transmittance in the visible to near infrared regions. Weak emission intensity from the Tb3+ ion with a decrease in lifetime was observed from the film prepared under air. Whereas the film prepared under an Ar/H2 atmosphere showed a homogenous surface morphology with intense luminescence intensity from the Tb3+ ion. The variation in the Tb3+:5D4 lifetime was analysed using rate equation analysis. The presence of Tb4+ ions in the thin films was confirmed by X-ray photoelectron spectroscopy. This work highlighted the importance of the preparation atmosphere on the photoluminescence properties of CaF2:Tb3+ thin films.

Ion beam modification is a one-of-a-kind approach for engineering nanomaterials to change their chemical and physical properties. Ion beam engineering of metal oxide semiconductor nanoparticles has been performed to improve their optoelectronic properties considering their energy applications. Zinc Oxide (ZnO) is one of these developing wide band gap semiconductor materials with remarkable optoelectronic features that has piqued the scientific community's curiosity for a number of energy applications. Through the implantation of distinct ions at varied parameters, the low energy ion beam approach has been widely used to modify the structural, morphological, and optoelectronic features of ZnO thin film-based devices (i.e. dose, energy etc.). It offers a promising approach for controlling implantation-induced defects and associated emission in ZnO thin films. On the one hand, inert ion bombardment causes consistent surface patterning to form on ZnO, while on the other, it creates nucleation centers for the creation of nanostructures. Due to the significant radiation resistance of ZnO thin films, tuning of different properties can be studied with little to no irreparable damage to the crystal lattice. In this context, rare earth metal ion implantation in ZnO thin films represents an alternate option for study in the realm of luminescent-based applications, such as solar cells and lighting. This paper focuses on the utility of such ion implantation procedures in optoelectronic devices such as solid-state lighting and solar cells, using ZnO as a prototype material. A correlation amongst the ion implantation induced defects, conductivity and optical behaviour has also been highlighted for in-depth understanding of implantation related effects in ZnO thin film based optoelectronic devices for solar cells and lighting applications.

ZnTiO3:Er3+,Yb3+ thin film phosphors were successfully deposited by pulsed laser deposition (PLD) at different substrate temperatures. The distribution of the ions in the films was investigated and the chemical analysis showed that the doping ions were homogeneously distributed in the thin films. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO3:Er3+,Yb3+ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. Under 980 nm diode laser excitation, the ZnTiO3:Er3+,Yb3+ film phosphors displayed up-conversion emission from the Er3+ electronic transitions, with violet, blue, green, and red emission lines at 410, 480, 525, 545 and 660 nm from 2H9/2 → 4I15/2, 4F7/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. The up-conversion emission was enhanced by increasing the silico (Si) substrate temperature during the deposition. Based on the photoluminescence properties and decay lifetime analysis, the energy level diagram was established and the up-conversion energy-transfer mechanism was discussed in detail.

Gallium-doped zinc oxide nanoparticles (GZO NPs) were synthesized using reflux precipitation method and annealed at temperatures ranging from 300 to 600 °C. X-ray diffraction study exhibited a highly crystalline GZO NPs with hexagonal wurtzite structure. The highest diffraction peak intensity was displayed by GZO NPs annealed at 300 °C. The crystallite size of the NPs increased from 12 to 25 nm with the increase in annealing temperature (AT) indicating the tendency of large grain growth in the nanoparticles due to annealing. SEM micrographs showed tiny hexagonal particles for unannealed samples which turned into bigger rods with increasing AT. Photoluminescence spectra displayed the highest excitonic peak luminescence for the sample annealed at 300 °C among its annealed counterparts. The minimum reflection was also observed for the sample annealed at 300 °C. The red shift in the UV emission with increasing particle size due to annealing closely followed the red shift in the band edge emission of the reflectance spectra, indicating that the two complement each other. The band gap of GZO NPs decreased from 3.3 to 3.1 eV with an increase in AT, implying that the optical properties of these materials were clearly affected by thermal annealing. We were able to produce better quality GZO NPs with high crystallinity, minimum lattice stress, and lowest % reflectance in both the visible and UV–Vis range at a relatively lower AT of 300 °C using the reflux method which, to the best of our knowledge, is less reported on to synthesize GZO NPs. Keywords: GZO NPs, Optical properties, Temperature, Transparent conducting oxide (TCO)

Bismuth is a non-toxic posttransition metal with a large number of possible valence states which, together with to its tendency to form clusters, make it a versatile but complex dopant for possible luminescence applications. The outer orbitals responsible for luminescence are unshielded and strongly influenced by the surrounding environment, so that their energies are host dependent. In this review article we surveyed models that have been developed to understand the optical properties of bismuth based materials and compiled a few case studies on the luminescence of bismuth doped materials, with some emphasis on trivalent Bi3+ and simple oxide hosts (e.g. CaO:Bi; Y2O3:Bi; ZnO:Bi; La2O3:Bi; SrO:Bi; YPO4:Bi and LaPO4:Bi). Special emphasis was given to the compilation of simplified energy diagrams under different conditions. For the most stable trivalent Bi3+ state it has been experimentally found by many researchers that the absorption spectra consist of medium, weak and strong bands in order of increasing energy (designated the A, B and C bands, respectively), which were interpreted in terms of transitions to the states associated with the 3P1, 3P2 and 1P1 levels of the excited 6s1p1 configuration. Traditionally above the C band energy, but before the host absorption, a further D band is generally encountered, which is attributed to a metal-to-metal charge transfer (MMCT) transition corresponding to the transfer of an electron from the Bi3+ ion to the bottom of the conduction band. Recent modelling of this MMCT band in different materials has clarified that it may occur at energies below the C band and be an important influence on excitation spectra at lower energies. The challenge of unambiguously identifying the nature of emissions is still an ongoing challenge, as illustrated by some of the case studies. Keywords: Bi doped, Luminescence, Stokes shift, Metal-to-metal charge transfer, CaO:Bi, Y2O3:Bi, ZnO:Bi, La2O3:Bi, SrO:Bi, YPO4:Bi and LaPO4:Bi

Oxide materials (ZnO, TiO2) doped with noble metals were synthesized using the combustion technique. The results of the addition of Ag, Au, and Pd up to a concentration of 2 mol% on the structural, optical, morphological and antimicrobial properties was considered. X-ray diffraction experiments revealed that the crystal structure of the host materials remained unaltered despite doping with noble metals. From the scanning electron microscopy results, it was evident that the doped nanoparticles aggregated in clusters of different sizes in the host matrix. The plasmonic effect was also observed in the absorbance spectra of the different doped materials. The obtained materials have shown promising antimicrobial features. All ZnO materials exhibited a high antimicrobial activity, with very low minimum inhibitory concentration values, against the planktonic growth of all tested Gram-positive and Gram-negative bacterial strains. All doped materials exhibited very good anti-biofilm activity, the lowest minimal biofilm eradication concentration values being registered for ZnO doped with Au and Pd toward Escherichia coli and for ZnO doped with Ag against Candida albicans. These results indicate the potential that these materials have for antimicrobial applications in the fields of biomedicine and environmental protection.

The synthesis of polyvinylpyrrolidone seed mediated Ag/Pd allied nanobimetallic particles was successfully carried out by the simultaneous reduction of the metal ions in ethylene glycol, diethylene glycol, glycerol, pentaerythritol and sodium borohydride solution. The optical measurement revealed the existence of peak broadening that causes diffusion processes of the metal sols to decrease making it possible to monitor the changes spectrophotometrically. This, together with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution TEM measurements strongly support the conclusion that intimately alloyed clusters were formed and the particle growth anisotropy is diffusion limited. Finally, the catalytic potential of the nanocomposites was investigated using 4-nitrophenol in the presence of sodium borohydride at 299 K; a good linear fitting of ln(A/A0) versus the reaction time was obtained, indicating pseudo-first-order kinetics.