Fluorescent Phosphors Research Articles

Boosting the red emission and luminescent thermostability of GdPO4:Eu3+ phosphors by coating with graphitic carbon nitride

Due to the fact that the luminescence of Eu3+ belongs to orbital forbidden f→f transition, the luminous intensity of Eu3+-activated phosphors is relatively weak. In this work, in order to increase the luminous intensity of GdPO4:Eu3+, a series of GdPO4:Eu3+@g-C3N4 phosphors was obtained via conventional solid-state reaction, with GdPO4:0.05Eu3+@0.005 g-C3N4 identified as the optimal sample. The characterization results indicate that: (a) The coating of g-C3N4 not only enhances the luminescence, but also unexpectedly induces a relatively weak negative thermal quenching (NTQ) effect, thereby obviously improving its luminescence thermal stability. The mechanisms behind the enhanced luminescence and luminescence thermal stability are explored, and attributed energy transfer from g-C3N4 to Eu3+ and phonon electron interaction, respectively. (b) The WLED prepared with GdPO4:0.05Eu3+@0.005 g-C3N4 and yellow fluorescent phosphor (YAG:Ce3+) forms warm-white light under excitation of ultraviolet light. The findings reveal that GdPO4:0.05Eu3+@0.005 g-C3N4 is a potential candidate for using in the field of warm WLEDs excited by ultraviolet light.

Modulation and Enhancement of Red Luminescence in Ca2GdSbO6: Eu3+ Phosphor by Co-Doping with Bi3.

The double perovskite structure of Ca2GdSbO6 as a fluorescent phosphor matrix material possesses a stable structure, making it an excellent candidate for a matrix material. In this study, single-doped Ca2GdSbO6: Eu3+ fluorescent phosphors and Bi3+ sensitized Ca2GdSbO6: Eu3+, Bi3+ fluorescent phosphor materials were synthesized using the high-temperature solid-state method. The luminescence of this phosphor is based on the 5D0→4F2 transition emission of Eu3+ ions, which occurs at 612nm. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, high-temperature fluorescence spectra, and fluorescence decay lifetimes to study the phase structure, optical properties, crystal structure, and chemical purity of the samples. The performance of the single-doped phosphor was significantly improved by the addition of Bi3+ sensitizer. The luminescence intensity increased by nearly 100% compared to Ca2GdSbO6: Eu3+ phosphor, with a quantum efficiency increase of 124%. The thermal quenching activation energy was found to be 0.299eV, and the luminescence intensity remained at 70.3% of room temperature at 453K. These results indicate that the co-doping of Bi3+ has a modulation and enhancement effect on the luminescence of Ca2GdSbO6: Eu3+ red phosphor, showing great potential for application in near-ultraviolet-excited white LED devices.

Luminescence properties and energy transfer of broadband NIR phosphor Li2MgZrO4: 1.0%Cr3+, y%Yb3+

The discovery of high thermal stability, broad-band near-infrared (NIR) fluorescent phosphors holds significant potential in applications such as non-destructive testing, promoting plant growth, and night vision devices. In this study, a novel broad-band NIR phosphors Li2MgZrO4 (LMZ): 1.0 %Cr3+, y%Yb3+ were synthesized via a high-temperature solid-state reaction method, with the optimal doping concentration found to be y = 1.5. These phosphors exhibited broad NIR emission in the range of 700–1050 nm by effective energy transfer from Cr3+ to Yb3+. The maximum full width at half maximum (FWHM) of the Cr3+/Yb3+ co-doped LMZ phosphor is 270 nm. The thermal stability of the phosphors was improved with Yb3+ co-doping. Additionally, energy transfer from Cr3+ to Yb3+ was confirmed through luminescence spectra and lifetime analysis. Finally, NIR pc-LED devices composed of a 460 nm ultraviolet chip and LMZ: 1.0 %Cr3+, 1.5 %Yb3+ phosphors were fabricated, offering a highly promising source of invisible light. These results demonstrate the wide-ranging potential applications of this novel, high thermal stability, and ultra-broad NIR emitting fluorescent phosphor.

Mn5+-doped BaAl2O4, Ba3Al2O6, and Ba7Al2O10 phosphors emitting in the second near-infrared biological window

In recent years, NIR-II-type fluorophores with emission wavelengths within the 1000–1700 nm range have garnered widespread attention in the field of bioimaging due to their high tissue penetration ability. Here, Mn-doped BaAl2O4, Ba3Al2O6, and Ba7Al2O10 with NIR-II-type luminescence were synthesized by solid-phase or liquid-phase methods. Confirmed by XPS and EDS analysis, Mn is found uniformly distributed in the structure in the valence state of + 5. The optimal doping concentration of Mn5+ in the three matrices was analyzed by PLE and PL spectroscopy. In addition, the samples exhibit a wide excitation range spanning from 600 to 900 nm, coupled with a narrow emission band peaking between 1150 and 1200 nm. As both the excitation and emission wavelengths have excellent penetration capabilities in biological tissues, the synthesized fluorescent phosphors in this study hold potential for meaningful applications in the realm of fluorescence imaging.

Designing ultra-highly efficient Sm3+ activated SrLaAlO4 orange-red emitting phosphor towards security encoding, hydro-gels, flexible displays and personal identification

SrLaAlO4:Sm3+ (1–5 mol %) nanophosphors (SLAO:Sm3+ NPs) has been developed. Under stimulation at 402 nm, the Sm3+ ions shows the transition of 4G5/2→ 6H7/2 enabled the phosphor to emit a powerful orange-red light at 602 nm. Based on the photoluminescence emission (PLE) profiles, the International Commission on Illumination calculated the colour coordinates (CC), correlated colour temperature (CCT) and colour purity (CP) values. Comparisons were made between the acquired CC and the normal National Television System Committee (NTSC) coordinates. Additionally, the applicability of the SLAO:2Sm3+ NPs was evaluated to visualize the latent fingerprints on smooth surfaces using the powder dusting method. The obtained latent fingerprint images exhibited good sensitivity, high contrast, and appreciable ridge details. To develop anti-counterfeiting inks that mark on multiple surfaces with high resolution without spreading and tracing, fluorescent phosphor was fabricated with the required thickening agent. The created pattern in the ink above immediately formed and lighted with bright orange and red fluorescence emission when exposed to UV light. The findings showed that the optimized NPs can generate a lot of interest for application in security encoding and personal identification.

Biorecovery of rare earth elements from fluorescent lamp powder using the fungus Aspergillus niger in batch and semicontinuous systems

Rare earth elements (REE) are essential in the manufacture of high-technology goods. Tons of wastes containing REE are yearly accumulated; however, environmentally friendly recycling methods are poorly studied. The use of heterotrophic microorganisms could be particularly relevant in the bioleaching of wastes transforming insoluble REE-bearing compounds into more soluble forms which are directly and/or indirectly involved in their metabolism. In this study, bioleaching of rare earth elements from fluorescent phosphor powder in fluorescent tubes using Aspergillus niger CECT2807 was investigated. Bioleaching experiments were performed in batch cultures at 1% pulp density. The concentrations in solution reached 122 mg/l of Y, 8.50 mg/l of Eu, 0.95 mg/l of Ce, 0.40 mg/l of Tb and 1.11 mg/l of La, after 7 days. Then, REE precipitated due to the generation of oxalic acid by the fungus. The residues generated were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and the lamp powder biotransformation was evidenced. Additionally, semicontinuous experiments were conducted and evidenced significant increase of REE dissolution rate in static conditions. The amount of extracted REE under static conditions reached 16.5 mg of Y and 0.75 mg of Eu per gram of fluorescent lamp powder.

Designing orange-red emitting luminescent platform for data security and information encryption based Sm3+ doped BLAO phosphor

Due to the features of great difference and invariability, latent fingerprint (LFP) and lip print (LP) detection has grown to be a vital part of criminal investigation. Due to its environmental friendliness, powder dusting is now the method of choice for visualizing LFPs. The uses of this technology are severely constrained by essential flaws like limited resolution, low sensitivity, and high background interference. To address these issues, a novel orange red emitting BaLaAlO4:Sm3+ (1–5 mol %) (BLAO:Sm) phosphor has been fabricated via solution combustion route. The 4G5/2 → 6H7/2 transition of Sm3+ ions caused the phosphor to generate intense orange-red light at 601 nm under stimulation at 402 nm. The optimal Sm3+ concentration in BLAO is 2 mol % (BLAO:2Sm). The International Commission on Illumination evaluated the colour coordinates (CC), correlated colour temperature (CCT), and colour purity (CP) values based on the photoluminescence emission (PLE) profiles. The acquired CC and the typical National Television System Committee (NTSC) coordinates are compared. Additionally, the usefulness of the phosphor is assessed for the powder dusting technique to detect fingerprints (FPs) on various surfaces. The level 1–3 structure of LFPs and the distinct features of lip prints (LPs) are clearly visible utilizing the BLAO:2Sm phosphor under 402 nm, UV illumination. Fluorescent phosphor is fabricated with the necessary thickening agent in order to create AC inks that mark on various surfaces with high resolution without spreading and tracing. When exposed to UV light, the above ink's drawn design instantly developed and is illuminated with vivid orange red fluorescence emission. The results revealed that the optimized phosphor can garner significant interest for use in personal identification, and security encoding.

Optimizing Leaching of Rare Earth Elements from Red Mud and Spent Fluorescent Lamp Phosphors Using Levulinic Acid

Although various hydrometallurgical and solvometallurgical efforts have been made to extract REEs from end-of-life (EoL) products and waste, a systematic and statistical analysis of the impacts of leaching parameters to optimize the leaching process using organic acids is necessary, but lacking in the literature. This study employed the response surface methodology to develop mathematical models for optimal leaching by levulinic acid (LevA) of REEs in two waste materials, namely red mud and spent fluorescent lamp phosphors. The established models exhibited excellent statistical properties, in terms of significance, fitting, prediction, and error distribution. For red mud, the optimal conditions of liquid-to-solid ratio (L/S; v/w) of 40, temperature of 70 °C, and duration of 60 h led to 100% leaching of REEs excluding Sc. At the same L/S and temperature, >98.7% of REEs were leached from fluorescent phosphors after 96 h. The SEM–EDS analysis of the waste materials revealed and confirmed morphological and compositional changes after leaching under the optimal conditions.

In‐doped LiCa2.98MgV3O12 rare‐earth‐free phosphor with a high photoluminescence quantum yield of 67.4%

AbstractRare earth resources applied in numerous novel materials, are increasingly scarce in worldwide. Meanwhile, great attention has been focused on the blue rare‐earth‐free fluorescent phosphors as an excitation source of near‐ultraviolet (NUV) chips, which are available in white‐light‐emitting diodes (WLEDs) that combined with yellow commercial phosphors. Many solutions have been found to improve the photoluminescence quantum yield (PLQY) of phosphor. In this study, we effectively increased PLQY by introducing indium ion to vanadate garnet phosphor forming a series of LiCa3−XMgV3O12: xIn3+ (x = 0.01, 0.02, 0.04, 0.06, 0.08, and 0.10). The resultant In‐doped vanadate garnet phosphors exhibit a relative increase in PLQY, and the optimal phosphors is LiCa2.98MgV3O12: 0.02In3+ with a PLQY as high as 67.4%. These In‐doped vanadate garnet phosphors have a broad emission at 480 under 320 nm where near UV‐light excitation. It is revealed that the distortion of V‐V and V‐O bond length in [VO4] crystal structure and unit cell volume data of phosphors have an extensive influence on PLQY. Therefore, these novel vanadate garnet phosphors can be the essential blue color choice for WLED devices application in illumination.

Red-emission analysis, Judd–Ofelt intensity parameters and laser properties of CdMgZnO:xEu3+ nanocrystals: the effects of Eu3+ concentration

In this paper, we discuss a strong red Eu3+-concentration-dependent emission line associated with an electric dipole transition (5D0 → 7F2) at 616 nm in CdMgZnO:xEu3+ nanocrystals made via a sol–gel synthesis route. Oxygen interstitial defects created by the presence of a mixed-valence state of Eu 3+ and Eu2+ ions as rare-earth cations lead to a structural distortion which is confirmed by x-ray photon electron spectroscopy. The Judd–Ofelt intensity parameters, Ω2 and Ω4, obtained from the emission spectra, show a trend for Ω2 > Ω4 that translates to stronger covalence and a stable local structure surrounding the Eu3+ ions in CdMgZnO nanocrystals. The asymmetry ratio (R o), radiative lifetime (), branching ratio , stimulated emission cross-section, and the gain bandwidth (δ e× Δλ eff) for 5D0 are computed and analysed. A radiative lifetime ranging from 789 to 984 µs points to a suitable material for orange-red fluorescent phosphors for lighting and display technologies. The gain bandwidth (δ e× Δλ eff), which is dependent on the Eu3+ concentration, suggests the use of the CdMgZnO:xEu3+ nanocrystal material in fibre amplifiers, while the sample with x = 1.5%, which yields the largest emission cross-section (15.79 × 10−22 cm2), the highest gain bandwidth (28.8 × 10−28 cm3), and a high branching ratio (71%), is the best candidate for red laser applications.

Synthesis, characterization and the fluorescent enhancement mechanism of bonded poly(Eu(TTA)2(phen)MAA-co-VA) nanofibers by electrospinning

A novel bonded phosphor poly(Eu(TTA)2(phen)MAA-co-VA) (Eu-PVA, for short) was prepared employing the technology of coordination-polymerization-alcoholysis. The bonded Eu-PVA fluorescent nanofibers were prepared by electrospinning, having the initial decomposition temperature of 290 °C higher 51 °C than that of the doped nanofibers. A relationship is established between the fiber morphology and the fluorescence intensity of the bonded fiber Eu-PVA, predicting fluorescence quenching according to the morphological evolution. Compared with the corresponding fluorescent phosphors, both doped and bonded fluorescent fibers exhibit obvious fluorescence enhancement effects in that nanofibrosis increase the specific surface of the fibers and decrease the diffuse reflection and the light loss owing to the smoother surface of the fibers than that of the phosphors. Furthermore, security paper with both masking and security has been fabricated applying the bonded fluorescent nanofibers into pulp, being extended to the development of banknotes, bills, and securities.

Mg3Y2Ge3O12:Bi3+ UV fluorescent phosphor as the TiO2 “sensitizer” for enhancing the heavy oil viscosity reduction

Abstract Nowadays, visible fluorescent materials based on rare earth (RE) and non-RE ions doping have been extensively explored for white LEDs. As for the UV fluorescent materials, it is well known that they are not suitable for the lighting applications. As a result, when compared to the visible fluorescent materials, previous works paid little attention to the UV fluorescent materials. In this work, we report a type of Mg3Y2Ge3O12:Bi3+ UV fluorescent phosphor. To understand the crystal structural information and photoluminescence (PL) properties of samples, we have used the X-ray diffraction (XRD), scanning electronic microscope (SEM), UV–visible diffuse reflectance and PL spectra to characterize them. The structural results reveal that the Bi3+ doped sample show their particle size at about 30 μm. The PL results show that the Bi3+ doped sample upon excitation at 230 nm can show a broad emission band that can almost cover the whole UV spectral region from 290 nm to 410 nm. Since this UV fluorescent band is exactly in agreement with the UV absorption region of TiO2 semiconductor, we have fabricated several Mg3Y2Ge3O12:Bi3+/TiO2-based ceramic plates and proposed used them to serve as an efficient UV irradiation source for photocatalytic application. As a result, we find that the TiO2 can exhibit the significantly enhanced photocatalytic property for the heavy oil viscosity reduction after adding the Mg3Y2Ge3O12:Bi3+ UV fluorescent phosphor.

Dual-emitting film with cellulose nanocrystal-assisted carbon dots grafted SrAl2O4, Eu2+, Dy3+ phosphors for temperature sensing

In this study, we synthesized a novel dual-emitting fluorescent phosphor from cellulose nanocrystal (CNC)-assisted carbon dots (CDs)-grafted SrAl2O4, Eu2+, Dy3+ (SAO) through a facile core-shell process. The CNC-CDs-coated SAO presents excellent scattered dual-emission and improved water resistance without destruction of the SrAl2O4 crystals. The phosphors were then reacted with coupling amino-silane and assembled with nanofibrillated cellulose skeletons to create flexible isotropic films. The obtained phosphors and hybrid films were characterized via electron microscopy, photoluminescence analysis, and X-ray photoelectron spectroscopy. The results demonstrate that the optical signals of phosphors can be controlled by CDs content. The assembled cellulose films exhibit strong temperature responses, high light-induced scattering, and good flexibility. The luminescent emission of films is highly sensitive to surrounding temperature variation (243–383 K) and good linearity behavior was obtained for such a sensitive sensor. Such flexible nanofibrillated cellulose films are excellent candidates for temperature sensor devices in industrial applications.

Screening and selection of technologically applicable microorganisms for recovery of rare earth elements from fluorescent powder

Rare Earth Elements (REE) are essential elements in many new technology products. Up to now, recycling is poorly established and no environmentally friendly strategies are applied. Modern biotechnologies like bioleaching can contribute to overcome the current limitations. In this study, we investigated bioleaching approaches exemplary for fluorescent phosphor (FP), which is accumulated during the recycling of fluorescent tubes and energy saving bulbs. A broad spectrum of different microorganisms were tested regarding their potential to leach REE from FP. Among them were classical acidophilic microorganisms, as well as various heterotrophic ones, producing organic acids or metal complexing metabolites, or having a high metal tolerance. Larger amounts of REE were leached with the strains Komagataeibacter xylinus, Lactobacillus casei, and Yarrowia lipolytica. Besides the COOH-functionality, also other biotic processes contribute to metal leaching, as comparison with indirect leaching approaches showed. Among the different REE components of the FP preferably the oxidic red dye yttrium europium oxide (YOE) that contain the critical REE yttrium and europium was leached. The results provide the basis for the development of an environmentally friendly recycling process for REE from waste materials.

Carbon-ZnO alternating quantum dot chains: electrostatic adsorption assembly and white light-emitting device application.

Aggregation-induced quenching (ACQ) in carbon nanodots (CNDs) impede their applications in solid devices. Herein, the concept of alternating quantum dot (QD) chains was proposed to overcome the common issue of fluorescence quenching in CNDs; in this study, CNDs and ZnO QDs were interlinked to form carbon-ZnO alternating quantum dot chains (CZA-QDCs), which overcame the ACQ of CNDs and hence ensured efficient full-spectrum fluorescence for white light-emitting devices (WLEDs) without excessive blue emission. Under the excitation of 365 nm lines, white emission resulting from the combination of blue emission from the CNDs and yellow emission from the ZnO QDs has been achieved from these powders. The quantum efficiency of the CZA-QDC powders can reach 49% and remain stable for two months. By coating the powders onto an ultraviolet chip as phosphors, WLEDs with a luminous efficiency of 20.1 lm W-1, color coordinate of (0.30, 0.35), correlated color temperature of 5205 K, and a color rendering index of 84 have been fabricated. Due to the relatively high abundance and eco-friendly characteristics of both carbon and ZnO, the results reported herein may provide a promising alternative to fluorescent phosphors that are widely used in WLEDs.

Recycling of Florescent Phosphor Powder Y<sub>2</sub>O<sub>3</sub>:Eu by Leaching Experiments

Due to the advancing development of new technologies and consumer goods the future demand for raw materials will rise significantly. The finite primary raw materials will not be able to meet the demand quickly enough or the prices for the extraction will rise enormously. In consequence, a recycling of process waste and end of life products will be in future an essential step in order to meet the demand. Y2O3:Eu fluorescent phosphor was identified as the main composition in phosphor waste fractions and was chemical leached and bioleached with A. ferrooxidans. A selective leaching towards Y in bioleaching batches was observed and already after four days 100 % could be leached. The bioleaching with the bacteria showed no significant differences in comparison to the abiotic control without microorganism. Initial Fe3+ in the medium was identified as the driving force and lower extraction efficiencies of the biotic batches were attributed to a biosorption process and to high pH-values. This work showed that the extraction of yttrium out of waste products with high Y2O3:Eu content by chemical leaching with Fe-addition under mild conditions offers a good perspective to support the material demand of Y in the future growing market. In comparison to bioleaching of other fluorescent phosphors and waste fractions leaching efficiencies up to 100% were achieved and it was identified that the microorganisms can positively influence the leaching effect. Furthermore, it became obvious that the leaching behavior of microorganisms was highly dependent on the sample material. As relevant parameters mainly the structural composition of the phosphor was identified.

Investigation of a Bioflotation Interface with Infrared Spectroscopy

In this paper we report an approach for the structural analysis of mineral-collector interfaces of (bio) flotation systems by means of attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR). The extraction of rare earth metals from electronic waste materials is an important challenge for the recycling industry. In a current project bacteriophage are used as biocollectors to develop a bioflotation model system for the separation of lanthanum phosphate doped with cerium and terbium (LaPO4:Ce3+,Tb3+) from mixed fluorescent phosphors. As an initial analytical concept fluorescence microscopy was successfully applied to investigate particles of spent fluorescent lamp powders and to visualize the bacteriophage on the surface of the waste material. However, due to the restrictions of this technique we are not able to identify the molecular interactions of the bacteriophage with the recycled material. ATR FT-IR was found to be an effective tool to detect the major coat protein of the bacteriophage biocollectors on the surface of the LaPO4:Ce3+,Tb3+ and sense their specific bonding interaction opening the gates for the high level chemical characterization of the interface.

Identification of lanthanum-specific peptides for future recycling of rare earth elements from compact fluorescent lamps.

As components of electronic scrap, rare earth minerals are an interesting but little used source of raw materials that are highly important for the recycling industry. Currently, there exists no cost-efficient technology to separate rare earth minerals from an electronic scrap mixture. In this study, phage surface display has been used as a key method to develop peptides with high specificity for particular inorganic targets in electronic scrap. Lanthanum phosphate doped with cerium and terbium as part of the fluorescent phosphors of spent compact fluorescent lamps (CFL) was used as a target material of economic interest to test the suitability of the phage display method to the separation of rare earth minerals. One random pVIII phage library was screened for peptide sequences that bind specifically to the fluorescent phosphor LaPO4 :Ce3+ ,Tb3+ (LAP). The library contained at least 100 binding pVIII peptides per phage particle with a diversity of 1 × 109 different phage per library. After three rounds of enrichment, a phage clone containing the surface peptide loop RCQYPLCS was found to bind specifically to LAP. Specificity and affinity of the identified phage bound peptide was confirmed by using binding and competition assays, immunofluorescence assays, and zeta potential measurements. Binding and immunofluorescence assays identified the peptide's affinity for the fluorescent phosphor components CAT (CeMgAl11 O19 :Tb3+ ) and BAM (BaMgAl10 O17 :Eu2+ ). No affinity was found for other fluorescent phosphor components such as YOX (Y2 O3 :Eu3+ ). The binding specificity of the RCQYPLCS peptide loop was improved 3-51-fold by using alanine scanning mutagenesis. The identification of peptides with high specificity and affinity for special components in the fluorescent phosphor in CFLs provides a potentially new strategic approach to rare earth recycling. Biotechnol. Bioeng. 2017;114: 1016-1024. © 2016 Wiley Periodicals, Inc.

Leaching of rare earth elements from fluorescent powder using the tea fungus Kombucha

In most modern technologies such as flat screens, highly effective magnets and lasers, as well as luminescence phosphors, Rare Earth Elements (REE) are used. Unfortunately no environmentally friendly recycling process exists so far. In comparison to other elements the interaction of microorganisms with REE has been studied to a less extent. However, as REE are ubiquitously present in nature it can be assumed that microorganisms play an important role in the biogeochemistry of REE. This study investigates the potential of organic acid-producing microbes for extracting REE from industrial waste.In Germany, 175 tons of fluorescent phosphor (FP) are collected per year as a distinct fraction from the recycling of compact fluorescent lamps. Because the FP contains about 10% of REE-oxides bound in the so-called triband dyes it is a readily accessible secondary resource of REE. Using the symbiotic mixed culture Kombucha, consisting of yeasts and acetic acid bacteria, REE were leached at a significant rate. The highest leaching-rates were observed in shake cultures using the entire Kombucha-consortium or its supernatant as leaching agent compared to experiments using the isolates Zygosaccharomyces lentus and Komagataeibacter hansenii as leaching organisms. During the cultivation, the pH decreased as a result of organic acid production (mainly acetic and gluconic acid). Thus, the underlying mechanism of the triband dye solubilisation is probably linked to the carboxyl-functionality or a proton excess. In accordance with the higher solubility of REE-oxides compared to REE-phosphates and –aluminates, the red dye Y2O3:Eu2+ containing relatively expensive REE was shown to be preferentially solubilized.These results show that it is possible to dissolve the REE-compounds of FP with the help of microbial processes. Moreover, they provide the basis for the development of an eco-friendly alternative to the currently applied methods that use strong inorganic acids or toxic chemicals.

Polymer nano-composite films with inorganic upconversion phosphor and electro-optic additives made by concurrent triple-beam matrix assisted and direct pulsed laser deposition

Abstract The work was to investigate polymer nano-composite films with two inorganic additives: upconversion fluorescent phosphor NaYF4:Yb3+, Er3+ and aluminum doped ZnO (AZO). The films were deposited using a new method of concurrent evaporation of the frozen solution of polymer poly(methyl methacrylate) (PMMA) using the matrix assisted pulsed laser evaporation (MAPLE) and the ablation of the phosphor and AZO targets using the pulsed laser deposition (PLD). Three laser beams, an infrared 1064-nm beam for the MAPLE and two 532-nm beams for the PLD targets, were concurrently used in the process. A new target holder with remote control of the target tilt was designed to provide overlapping of the plumes from the three targets and uniform mixing of the additives in the polymer film. The fabricated nano-composite films were characterized using X-ray diffraction, scanning electron microscopy (SEM), and the measurement of the quantum efficiency (QE) of the upconversion fluorescence. The films retained the crystalline structure of the inorganic additives. The size of the nano-particles varied in the range 10–200 nm. Upconversion QE of the films was an order of magnitude less than that of the bulk phosphor, which can be explained by lesser number of the rare-earth ions in the nano-particles in the polymer film than in the micro-grains of the bulk phosphor. The AZO additive increased QE by 1.6 times to (0.072 ± 0.022) % more likely due to the plasmonic enhancement of the local optical infra-red pump (980 nm) field. The proposed triple-beam triple-target MAPLE/PLD method can be potentially used for making a wide variety of nano-composite films.