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A series of Gd1 – x – yEuxTbyAlO3 (x = 0.01, 0.03, 0.05, 0.07 mol, y = 0.03 mol) tunable color emanating phosphors were synthesized by simplistic low temperature solution combustion process at 600°C. The X-ray powder diffraction and Rietveld refinement analysis confirmed the formation of single-phased co-doped nanophosphor at 1000°C. The synthesized nanophosphors were crystallized in orthorhombic crystal system having Pnma (62) space group. The morphological and photoluminescence characteristics of Gd1 – x – yEuxTbyAlO3 phosphors were validated using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, excitation, and emission spectra studies. The optical band gap values of co-doped nanocrystalline phosphors were also evaluated. The detailed analysis of excitation and emission spectra of synthesized nanophosphors revealed that Tb3+ effectively sensitized Eu3+ ion and the energy transfer can be controlled by carefully adjusting the amounts of Eu3+ to achieve color-tunable emission. The non-radiant energy loss phenomenon was observed at x = 0.05(Eu3+) in Gd1 – x – 0.03AlO3: xEu3+, 0.03Tb3+ phosphors. Commission International de I'Eclairage 1931 color coordinates (x, y) of co-doped samples have been extracted from emission spectra avail of photoluminescent data. The result suggested that hue could have been vigilant in greenish, orangish red and dark red color region with divergences in Eu3+ (x = 0, 0.01, 0.03, 0.05, 0.07). Other pertinent photometric assets, i.e. correlated color temperature and color purity of synthesized co-doped nanocrystalline materials were determined as well. This study advances understanding of rare earth ion co-doping effects, also providing new design opportunities for enhanced luminous materials for usage in light emitting diodes, lasers, displays, and solid-state technological innovations. [ABSTRACT FROM AUTHOR]

Detailed analysis covered the optical and structural properties of Eu3+-doped NaY9Si6O26 oxyapatite phosphors, which were obtained via hydrothermal synthesis. X-ray diffraction patterns of NaY9Si6O26:xEu3+ (x = 0, 1, 5, 7, 10 mol% Eu3+) samples proved a single-phase hexagonal structure (P63/m (176) space group). Differential thermal analysis showed an exothermic peak at 995 °C attributed to the amorphous to crystalline transformation of NaY9Si6O26. Electron microscopy showed agglomerates composed of round-shaped nanoparticles ~53 nm in size. Room temperature photoluminescent emission spectra consisted of emission bands in the visible spectral region corresponding to 5D0 → 7FJ (J = 0, 1, 2, 3, 4) f-f transitions of Eu3+. Lifetime measurements showed that the Eu3+ concentration had no substantial effect on the rather long 5D0-level lifetime. The Eu3+ energy levels in the structure were determined using room-temperature excitation/emission spectra. Using the 7F1 manifold, the Nv-crystal field strength parameter was calculated to be 1442.65 cm−1. Structural, electronic, and optical properties were calculated to determine the band gap value, density of states, and index of refraction. The calculated direct band gap value was 4.665 eV (local density approximation) and 3.765 eV (general gradient approximation). Finally, the complete Judd–Ofelt analysis performed on all samples confirmed the experimental findings. [ABSTRACT FROM AUTHOR]

The present study deals with the synthesis and characterization of the Gd2O3:Eu3+ nanophosphors and the impact of Y3+ co-doping on the structural and optical properties of the Gd2O3:Eu3+. All nanophosphors are synthesised by facile low temperature solution combustion method using citric acid as a chelating agent. The XRD pattern of as-synthesised Gd2O3:Eu3+ confirmed the presence of mixed-phase crystallites and upon annealing, it transforms to a cubic phase. The images of TEM and FE-SEM confirm that the samples are spherical after annealing. From the perspective of the emission spectra of Gd2O3:Eu3+, the 5D0 to 7F2 (613 nm) optical transition is the most important among the different narrow emission peaks observed in the visible region. Optimal doping concentration of Eu3+ was 7 wt%. Y3+ ions were incorporated into this Gd2O3:7 wt%Eu3+ nanophosphors. Y3+ co-activated samples crystallized in the cubic structure and exhibited a threefold enhancement in emission intensity and considerable improvement in lifetime and quantum efficiency compared to Gd2O3:Eu3+ nanophosphors. Temperature-dependent PL spectra indicate that the obtained nanophosphor exhibits excellent thermal stability and the activation energy was observed to be 0.4773 eV. Beyond that, red CIE coordinates, with excellent colour purity (greater than 95%) and suitable colour-correlated temperature (below 5000 K) suggest that the prepared red-emitting nanophosphors have immense potential in phosphor converted LED (pc-LED) applications. [ABSTRACT FROM AUTHOR]

We present the band gap engineering and morphological tuning of BaAl2O4:0.1% Sm3+, x% Tb3+ nanophosphors synthesized by citrate sol–gel method. Herein, the samarium (Sm3+) concentration is kept constant at 0.1%, while the concentration of terbium (Tb3+) is tuned from 0.5 to 2.5% with steps of 0.5%. X-ray diffraction confirms the hexagonal crystal structure of the BaAl2O4:0.1% Sm3+, x% Tb3+ nanophosphors. The reduction in crystallite size from 38 to 31 nm is noticed after doping and co-doping. Scanning electron microscope micrographs display evolution in morphology from multimodal grain-like structures to agglomerated pointy nanorods. Energy dispersive X-ray spectroscopy confirms all the main elements, although Sm is not detected due to the low content incorporated into the lattice. Transmission electron microscope results reveal that the particle size and shape can be controlled by varying concentrations of Tb3+. Diffuse reflectance spectra with the aid of the Kubelka–Munk function, reveal the energy band gap in the range of 2.6–5.3 eV. Under the excitation wavelength of 235 nm, photoluminescence studies reveal eight emission peaks located between 380 and 641 nm characteristic of Tb3+ ions. Upon the excitation wavelength of 402 nm, the emission spectra show four peaks positioned at 564, 601, 648 and 708 nm attributed to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2,4G5/2 → 6H9/2 and 4G5/2 → 6H11/2 transitions of Sm3+ ions, respectively. From the colour coordinate results, this nanophosphor can successfully play a significant role in green, yellow and red LED applications. [ABSTRACT FROM AUTHOR]

In this work, calcium silicate nanophosphors (CaSiO3) doped with Sm 3 + ions were prepared at 9 0 0 ∘ C by a simple solution combustion synthesis technique. The particle size, functional groups and morphology of the prepared phosphors were identified by X-Ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. The monoclinic phase of the nanophosphors was confirmed by X-ray diffraction studies. The effective excitation of the nanophosphors near the UV region and their yellow emission were confirmed by photoluminescence studies. [ABSTRACT FROM AUTHOR]

The present investigation describes the synthesis of luminescent terbium‐doped strontium aluminate nanoparticles emitting bright green light, which were synthesized through a solid‐state reaction method assisted by microwave radiation. Various samples containing different concentrations of Tb were synthesized, and an analysis of their structural and morphological features was conducted using powder x‐ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The band gaps of the samples were determined utilizing the Kubelka–Munk method. The quenching mechanism observed was identified to be due to dipole–dipole interaction using the Dexter theory. The optimized sample with a terbium concentration of 4 at.% has a luminescence lifetime of 1.05 ms with 20.62% quantum efficiency. The results of this study indicate that the terbium‐doped strontium aluminate fluorescent nanoparticles exhibit promising potential for a wide range of applications, including bioimaging, sensing and solid‐state lighting. [ABSTRACT FROM AUTHOR]

Ho3+-doped MgAl2O4 nanophosphors (1–11 mol%) were synthesized via solution combustion method and oxalyldihydrazide used as fuel. The findings revealed a range of band gap energies between 4.86 and 5.42 eV. Ho3+ ions in the host undergo f-f transitions that are triggered at 406 nm, and as a result, exhibit discrete photoluminescence emission peaks between 406 and 605 nm. Enhanced MgAl2O4 has chromaticity diagram (CIE) coordinates from orange–red to yellow region and 97% color purity. Photocatalytic properties of NPs under UV light led to the discovery that a rapid orange–red dye is activated at 493 nm. Fast orange–red dye removal using the new photocatalysts and MgAl2O4:Ho3+ nanophosphors has been demonstrated. The investigation showed that 89.02% of the dye lost its color after being exposed to radiation for 120 min. The cyclic voltametric method can detect lead pollution using the modified MgAl2O4:Ho3+ carbon paste electrode. Based on their electrochemical performance, we conclude that MgAl2O4:Ho3+ nanophosphors are effective lead detecting electrode materials. [ABSTRACT FROM AUTHOR]

The current study involves the synthesis and characterisation of europium doped strontium aluminate nanophosphors using the solid-state reaction method with varying concentrations of europium. The existence of the SrAl2O4 phase in all samples was verified using X-ray diffraction and FTIR analysis. The lattice parameters as well as phase fractions were determined using Rietveld refinement. Surface morphology was studied using field emission scanning electron microscope. Using the Tauc plot method acquired from the diffuse reflectance spectra, the band gaps of the samples were determined and it was found that the doped samples possess lower band gaps compared to the host. Our findings demonstrate that these nanophosphors exhibiting bright orange-red emission under UV excitation with quantum efficiency 70.68%, can be applied for display and fluorescence imaging. [ABSTRACT FROM AUTHOR]

The ongoing ambitious progression in the illumination sector to design the iconic WLEDs has bestowed an impetus to manufacture novel and eco-friendly nanophosphors (NPs). In this pursuit, we have presented cool white light-emitting single-phase crystalline Dy3+ -doped Ca9Y(PO4)7 i.e., CYP:Dy3+ nanophosphors synthesized via a facile, economical, and non-toxic solution combustion (SC) technique. The crystal structural details regarding phase formation and crystallite size of CYP:Dy3+ was inferred using powder x-ray diffraction (PXRD), which suggests the structures are in a rhombohedral phase with the R3c space group. The Kubelka–Munk model was used to evaluate the optical band gap of 4.18 eV, thus revealing their desired optical quality and semiconductor nature. Transmission electron microscopy (TEM) showed agglomerated particles with irregular dimensions with an average size ranging from 40 nm to 65 nm. Photoluminescence studies indicated the emission of visible photons under high energy irradiation with the bands at 4F9/2 → 6H13/2, 15/2, due to intra-configurational transitions of Dy3+ ions. The phosphor was located in the white region with the Commission Internationale de I'Eclairage (CIE) chroma coordinates of (0.295, 0.336). Thus, the presented work carves an avenue for the synthesis of single-phase nanophosphors with economical and environmental advantages, along with a proposal to boost the advancement in WLEDs relevant to industrial prospects, thus generating more revenue. [ABSTRACT FROM AUTHOR]

In this work, we investigated the potential of Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphors to visualize latent fingermarks. We prepared these nanophosphors with various doping concentrations by the conventional coprecipitation reaction. The crystal structure, morphology, luminescence properties, and energy transfer mechanisms were studied. The crystalline phase was characterized by X-ray diffraction and crystal structure refinement using the Rietveld method. XRD measurements showed that the samples crystallized in the pure single pyrochlore phase with few more peaks originated from secondary phases and impurities generated during phosphor production, and that Eu3+ ions occupied D3d symmetry sites. The average crystallite size after mechanical grinding was less than 100 nm for all compositions. The optical characterization showed that, when excited under 532 nm, the Eu3+/Dy3+-codoped Y2Sn2O7 samples' main intense emission peaks were located at 580–707 nm, corresponding to the 5D0→7Fj (j = l, 2, 3, and 4) transitions of europium. In fact, the 5D0→7F2 hypersensitive transition is strongly dependent on the local environment and was quite weak in Eu3+:Y2Sn2O7 at low Eu3+ doping levels. We found that the presence of Dy3+ as a codopant permitted enhancing the emission from this transition. The calculated PL CIE coordinates for the synthesized nanophosphors were very close to those of the reddish-orange region and only slightly dependent on the doping level. Various surfaces, including difficult ones (wood and ceramic), were successfully tested for latent fingerprint development with the prepared Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphor powder. Thanks to the high contrast obtained, fingerprint ridge patterns at all three levels were highlighted: core (level 1) islands, bifurcation, and enclosure (level 2), and even sweat pores (level 3). [ABSTRACT FROM AUTHOR]

In the realm of anti-counterfeiting (AC) measures, the focus has increasingly turned towards fluorescent inks, appreciated for their practicality and environmentally friendly nature. However, their susceptibility to wear and vulnerability to moisture damage has hindered their widespread application. Additionally, most available fluorescent inks are single-colored, toxic, and skin-irritating, making them ill-suited for real-world use. In light of these challenges, this article delves into the impact of introducing Sm3+ ions into the La 2 MoO 6 host lattice. The green solution combustion method is employed to synthesis 1–11 mol % Sm3+ doped La 2 MoO 6 :Sm3+ nanophosphors (LMO:Sm3+ (1–11 mol %) NPs. The effects of rare earth doping are examined through X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, and photoluminescence (PL) analysis. The PL spectra reveal four emission bands, with a prominent 603 nm wavelength band emitting an orange-red hue attributed to the electronic transition of Sm3+ ions. Notably, the impact of Sm3+ ion doping on the phosphor's luminescence spectra is prominently featured. The optimal concentration is found to be 5 mol % (LMO:5Sm3+), with concentration quenching primarily attributed to exchange-type interactions. The luminescent properties are evidenced by Commission Internationale de l'éclairage (CIE) color coordinates (0.6063, 0.3901), color purity (CP = 99.10 %), and correlated color temperature (CCT = 1383 K). Furthermore, the study delves into optical parameters such as energy band gap and refractive index, revealing values of 2.313 and 2.252 eV, respectively, for the optimal molar concentration. These findings hold promise in the development of AC inks suitable for screen-printing and writing on a variety of surfaces. The resultant patterns exhibit vivid orange-red fluorescence under UV 365 nm irradiation, showcasing potential applications in encryption, security marking, and optical authentication. [ABSTRACT FROM AUTHOR]

The solution combustion synthesis method is employed to prepare Magnesium, Zinc, Aluminate doped with dysprosium (Dy3+) using the general formula Mg(1‐x‐y) Zn(y)Al2O4:xDy (x = 0.05 and y = 0.3 mol%). From X‐ray diffraction studies, the crystal structure belongs to a cubic close‐packed spinel structure with space group Fd3ˉm and an average crystallite size is 26.18 nm. In the Fourier transform infrared spectra, the peaks at 683.69 cm−1, 503.12 cm−1 correspond to the AlO6 groups. The peak temperature (Tm) from the Thermoluminescent glow curve is recorded at 235°C, 237°C, and 235°C, at irradiation doses of 600 Gy, 800 Gy, and 1000 Gy, respectively. The kinetic parameters are evaluated from the thermoluminescent glow curve by calculating the activation energy (E), order of kinetics (b), and frequency factor (s−1). Nanophosphor Mg0.65Zn0.3Al2O4:0.05Dy shows sub linear dose relationship at doses 600–675 Gy and 925–1000 Gy. Further, at doses between 675 and 925 Gy, it shows a super linear relationship. The optimum activation energy (E) of 0.77–0.82 eV and negligible fading make it suitable for high radiation thermoluminescent dosimetry. [ABSTRACT FROM AUTHOR]

A series of Sr1−xZr4(PO4)6:xPr (x = 0, 0.01, 0.03, 0.05, 0.07, and 0.09) nanophosphors were prepared by simple sol–gel technique. The crystal structure, vibrational properties, surface morphology, elemental composition, and particle size were investigated using X-ray diffraction-Rietveld refinements, FTIR, SEM-EDAX, and TEM techniques. The effect of dopant concentration of Pr3+ ions in SrZr4(PO4)6 nanophosphors was analysed, and their photoluminescence properties were investigated along with lifetime measurements. Under 448 nm excitation, due to 3P0–3F2 transition of Pr3+ ions, it shows intense reddish emission at 650 nm. Energy-level diagram explains energy transfer mechanisms and concentration quenching mechanisms in detail. The appropriate incorporation of dopant ions (x = 0.03 mol%) showed potential candidates for efficient plant growth n-UV LED. Further, thermoluminescence properties of UV light, Ag and Ni ions irradiated Pr3+ ions doped SrZr4(PO4)6 phosphors were analysed, and glow curves were recorded. The TL studies reveal that SrZr4(PO4)6:Pr3+ phosphors may be a potential candidate as dosimetry materials for low radiation measurement. [ABSTRACT FROM AUTHOR]

Herein a versatile and scalable method to prepare periodically corrugated nanophosphor surface patterns displaying strongly polarized and directional visible light emission is demonstrated. A combination of inkjet printing and soft lithography techniques is employed to obtain arbitrarily shaped light emitting motifs. Such predesigned luminescent drawings, in which the polarization and angular properties of the emitted light are determined and finely tuned through the surface relief, can be used as anti‐counterfeiting labels, as these two specific optical features provide additional means to identify any unauthorized or forged copy of the protected item. The potential of this approach is exemplified by processing a self‐standing photoluminescent quick response code whose emission is both polarized and directionally beamed. Physical insight of the mechanism behind the directional out‐coupled photoluminescence observed is provided by finite‐difference time‐domain calculations. [ABSTRACT FROM AUTHOR]

Luminescence thermometry has emerged as a very versatile optical technique for remote temperature measurements, exhibiting a wide range of applicability spanning from cryogenic temperatures to 2000 K. This technology has found extensive utilization across many disciplines. In the last thirty years, there has been significant growth in the field of luminous thermometry. This growth has been accompanied by the development of temperature read-out procedures, the creation of luminescent materials for very sensitive temperature probes, and advancements in theoretical understanding. This review article primarily centers on luminescent nanoparticles employed in the field of luminescence thermometry. In this paper, we provide a comprehensive survey of the recent literature pertaining to the utilization of lanthanide and transition metal nanophosphors, semiconductor quantum dots, polymer nanoparticles, carbon dots, and nanodiamonds for luminescence thermometry. In addition, we engage in a discussion regarding the benefits and limitations of nanoparticles in comparison with conventional, microsized probes for their application in luminescent thermometry. [ABSTRACT FROM AUTHOR]

Lanthanide-doped nanophosphors have emerged as promising optical labels for high-resolution, "multicolor"electron microscopy. Here, we develop a library of 11 unique lanthanide-doped nanophosphors with average edge lengths of 15.2 ± 2.0 nm (N = 4284). These nanophosphors consist of an electron-stable BaYF5 host lattice doped at 25% atomic concentration with the lanthanides Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Ce3+, Ho3+, Er3+, Tm3+, and Yb3+. Under â 100 pA/nm2 beam current in a transmission electron microscope, each nanophosphor species exhibits strong cathodoluminescence spectra with sharp characteristic emission lines for each lanthanide. The bright emission and stability of these nanoparticles enable not only ensemble, but also single-particle cathodoluminescence spectroscopy, which we demonstrate with BaYF5:Ln3+, where Ln3+ = Tb3+, Ho3+, Er3+, Sm3+, Eu3+, or Pr3+. Single-particle cathodoluminescence corresponds directly with HAADF intensity across nanoparticles, confirming high spatial localization of the measured cathodoluminescence signal of lanthanide-doped nanophosphors. Our synthesis and characterization of sub-20 nm, electron-stable nanophosphors provides a robust material platform to achieve single-molecule labeled correlative cathodoluminescence electron microscopy, a critical foundation for high-resolution correlation of single molecules within the context of cellular ultrastructure.

The extraordinary and unique properties of persistent luminescent (PerLum) nanostructures like storage of charge carriers, extended afterglow, and some other fascinating characteristics like no need for in-situ excitation, and rechargeable luminescence make such materials a primary candidate in the fields of bio-imaging and therapeutics. Apart from this, due to their extraordinary properties they have also found their place in the fields of anti-counterfeiting, latent fingerprinting (LPF), luminescent markings, photocatalysis, solid-state lighting devices, glow-in-dark toys, etc. Over the past few years, persistent luminescent nanoparticles (PLNPs) have been extensively used for targeted drug delivery, bio-imaging guided photodynamic and photo-thermal therapy, biosensing for cancer detection and subsequent treatment, latent fingerprinting, and anti-counterfeiting owing to their enhanced charge storage ability, in-vitro excitation, increased duration of time between excitation and emission, low tissue absorption, high signal-to-noise ratio, etc. In this review, we have focused on most of the key aspects related to PLNPs, including the different mechanisms leading to such phenomena, key fabrication techniques, properties of hosts and different activators, emission, and excitation characteristics, and important properties of trap states. This review article focuses on recent advances in cancer theranostics with the help of PLNPs. Recent advances in using PLNPs for anti-counterfeiting and latent fingerprinting are also discussed in this review.

The possibility to precisely control reaction outcomes for pursuing materials with well-defined features is a main endeavor in the development of inorganic materials. Confining reactions within a confined space, such as nanoreactors, is an extremely promising methodology which allows to ensure control over the final properties of the material. An effective room temperature inverse miniemulsion approach for the controlled synthesis of undoped and Eu3+-doped calcium molybdate crystalline nanophosphors was developed. The advantages and the efficiency of confined space in terms of controlling nanoparticle features like size, shape, and functional properties are highlighted by systematically comparing miniemulsion products with calcium molybdate particles obtained without confinement from a typical batch synthesis. A relevant beneficial impact of space confinement by miniemulsion nanodroplets is observed on the control of size and shape of the final nanoparticles, resulting in 12 nm spherical nanoparticles with a narrow size distribution, as compared to the 58 nm irregularly shaped and aggregated particles from the batch approach (assessed by TEM analysis). Further considerable effects of the confined space for the miniemulsion samples are found on the doping effectiveness, leading to a more homogeneous distribution of the Eu3+ ions into the molybdate host matrix, without segregation (assessed by PXRD, XAS, and ICP-MS). These findings are finally related to the photoluminescence properties, which are evidenced to be closely dependent on the Eu3+ content for the miniemulsion samples, as an increase of the relative intensity of the direct f–f excitation and a shortening of the lifetime (from 0.901 ms for 1 at. % to 0.625 ms for 7 at. % samples) with increasing Eu3+ content are observed, whereas no relationship between these parameters and the Eu3+ content is evidenced for the batch samples. All these results are ascribed to the uniform and controlled crystallization occurring inside each miniemulsion nanodroplet, as opposed to the less controlled nucleation and growth for a classic nonconfined approach. [ABSTRACT FROM AUTHOR]

In the biomedical field, the use of fluorescence imaging in the second near‐infrared (NIR‐II) region is growing rapidly because it imparts the advantages of reduced autofluorescence and low photon scattering. The advantage of reduced scattering is that it increases penetration depth in vivo and improves imaging clarity. Herein, this work uses mesoporous silica, a biocompatible template that can be easily modified, functionalized, and loaded with drugs for use in several bioapplications. The ZnGa2O4 spinel oxide system is integrated into mesoporous silica and different concentrations of Cr3+ and Ni2+ are loaded in octahedral sites to obtain the highest emission intensity in the NIR‐II region at 1285 nm via energy transfer from Cr3+ to Ni2+. Given that only a few nanophosphor systems with emission in the NIR‐II region are available, this work attempts to establish emission in the NIR‐II and NIR‐I regions to obtain images in vivo with an increased penetration depth to 5 mm and improved clarity for bioimaging purposes. This system will open the door for biomedical research on other NIR‐II nanophosphors. [ABSTRACT FROM AUTHOR]

• The TL dosimetry characteristics of BaSO 4 : Eu including reusability, response to varying heating rates, signal fading, dose response and order of kinetics were studied for low dose irradiations. • The optimal Eu doping concentration and heating rate were found to be 0.5 mol % and 5 K/s, respectively. • The TL reusability and fading rate were found to be only 1.2% and 0.14 % per day, respectively, demonstrating the promising dosimetric properties of the nanophosphor. Thermoluminescence (TL) dosimetry is used in radiation protection and for measuring absorbed dose to patients in diagnostic radiology and radiotherapy. The main aim of the study herein was to assess the TL properties of BaSO 4 : Eu nanophosphors following irradiation with low dose γ- and X-rays. BaSO 4 phosphors activated with various concentrations of Eu were prepared by the co-precipitation method. The highest radiation sensitivity was obtained for an Eu concentration of 0.5 mol%. The TL properties in terms of glow curve, heating rate, reusability, fading and order of kinetics were studied. Optimized BaSO 4 : Eu irradiated with doses from 1.25 to 50 mGy displayed a major TL peak at ≈ 220 °C and exhibited a linear response with absorbed dose. The reusability test was performed for ten consecutive irradiations, readings, and annealing cycles, and showed a slight decrease in TL after the first cycle after which it was stabilized. Signal fading measurements were performed for irradiated samples over 50 days, where a signal loss of about 0.14 % per day was observed. [ABSTRACT FROM AUTHOR]

The copper doped ZnO (CuxZn1-xO, where x = 0, 0.01, 0.02, 0.04, 0.05) nanoflowers were produced by using co-precipitation process. Hexagonal wurtzite nanocrystalline phase of both pure and Cu-doped samples was confirmed by X-ray diffraction analysis. Field emission scanning electron microscopy results confirmed the emergence of fully dispersed nanoflower like morphologies in the Cu-doped ZnO and uniform dispersion of particles. Band gap energies of the prepared samples were calculated using the Tauc’s plot. All of the generated samples’ room temperature photoluminescent spectra show two emission peaks, one excitonic peak in the UV region and another broad defect level peak in the visible area. The yellow and green luminescence characteristics of both pure and doped samples were analysed via the PL spectra in visible light region, making them appropriate for optoelectronic applications. The antibacterial potential of the produced nanostructures against the bacterial strains of Enterococcus Faecalis (gram positive) and Pseudomonas Aeruginosa (gram negative) were assessed. When compared to the pure ZnO nanostructures, the doped samples exhibit enhanced antibacterial activity. For the samples with 5 at.%Cu, the greatest zone of inhibition against Pseudomonas Aeruginosa was noted to be 25mm. For the samples doped with 5 at.% Cu, the largest zone of inhibition against Enterococcus Faecalis was 21mm. The findings indicate that the obtained samples have higher antibacterial potential against gram negative than gram positive bacteria. The prepared doped ZnO nanoflowers were therefore recommended as excellent green nanophosphors for the production of white LEDs and effective nanoantibiotics against gram-negative bacteria.

A low temperature‐assisted and oxalyl dihydrazide fuel‐induced combustion synthesized series of uncalcined MgAl2O4:Eu3+ nanophosphors showed an average crystallite size of ~20 nm, and bandgap energy (Eg) of 4.50–5.15 eV, and were validated using density functional theory and found to match closely with the experimental values. The photoluminescence characteristic emission peaks of Eu3+ ions were recorded between 480 and 680 nm. The nanophosphors excited at 392 nm showed f–f transitions assigned as 5D0→7FJ (J = 0, 1, 2, and 3). The optimized MgAl2O4 phosphors had Commission Internationale de l'Eclairage coordinates in the red region, a correlated colour temperature of 2060 K, and a colour purity of 98.83%. The estimated luminescence quantum efficiency (η) was observed to be ~63% using Judd–Ofelt analysis. Electrochemical and photocatalytic performance were explored and indicated its multifunctional applications. Therefore, MgAl2O4:Eu3+ nanophosphors could be used for the fabrication of light‐emitting diodes, industrial dye degradation, and as electrodes for supercapacitor applications. [ABSTRACT FROM AUTHOR]

In this study, LiZr2(PO4)3 nanophosphors with varying concentrations of Sm3+ (0.25 ≤ x ≤ 3.0 mol%) utilizing urea as an organic fuel were synthesized via combustion method. Here, we investigated the fluctuations in the various parameters of lattice and verified the phase (trigonal) examined by the powder X-ray diffraction system. The elemental analysis was done with energy dispersive X-ray spectroscopy and the morphology was obtained using scanning electron microscope as well as transmission electron microscope. The electrical and optical characteristics of nanophosphor were determined using UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The bandgap adjustment in the region of 4.065–4.462 eV was achieved by doping LiZr2(PO4)3 with Sm3+ from 0.25 to 3 mol%. PL characteristics of undoped and Li(1–x)Zr2(PO4)3:xSm3+ (x = 1.5 mol%) were explored using a 405 nm excitation source to look into the viability of employing it for displays. In the visible spectrum, the PL spectra exhibit three distinct peaks at 566, 601 and 649 nm. The findings showed that synthesized phosphor might be investigated as a potential material for various display technology. [ABSTRACT FROM AUTHOR]

ZnS, a semiconductor material with a bandgap in the range of 3.6–3.8 eV, can be employed as a scintillator. We herein report on the preliminary results obtained from the thermoluminescence (TL) emission of ZnS and ZnS:La nanophosphors synthesized by chemical route. The samples were characterized by X-ray diffraction, scanning electron microscopy and TL. ZnS samples show a TL maximum centred at 87°C, while the ZnS:La sample shows two groups of components appearing between 70–160°C and 190–330°C. The dose–response displays a good linearity in the range of 10–17 Gy. [ABSTRACT FROM AUTHOR]

The design of nanoprobes in the second window near‐infrared region has grasped a substantial amount of attention due to the flexible emission in the second near‐infrared region (NIR‐II) region (1,000–1,700 nm). In addition, this region provides the advantage of reduced photon scattering with less autofluorescence for improvement during in vivo fluorescence imaging. NIR‐II nanoprobes such as quantum dots, AIEgens, carbon nanotubes, and polymers are in a constant state of evolution for improved NIR‐II emission. Among these probes, lanthanides are explored the most for NIR‐II imaging applications. Moreover, nanophosphors, although in their nascent form, are interesting compounds due to their good luminescence properties with efficient energy transfer processes. Our review aims to give insight into nanophosphors, mainly for biological imaging applications. We will also provide a comparative study of lanthanides and nanophosphors for understanding the mechanism and importance of nanophosphors in the future bio‐imaging field. [ABSTRACT FROM AUTHOR]

Novel mixed phase BaAl2O4/CaAl4O7 (BC) and BC: x% Dy3+ (0 ≤ x ≤ 3) nanophosphors were synthesized by the citrate sol-gel method. The morphology changed as x%Dy3+ varied. The patterns showed that the BC nanophosphors matched well with the monoclinic CaAl4O7 and hexagonal BaAl2O4 structures. Moreover, the structure of BC was not influence by the dopant. The dopant is mainly located in the BaAl2O4 phase. The crystallite sizes were estimated to be in the nanoscale order. The photoluminescence (PL) results showed that the emission was quenched for BC: x% Dy3+ (x > 2.4) be due to the quadrupole-quadrupole interaction. The emission peaks at 325, 482 and (563 and 576) nm were assigned to the bandgap defects of BC, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The International commission on illumination (CIE) showed the dopant (Dy3+) had changed the emission color from blue to white. This showed that the BC: x% Dy3+ (1.2 ≤ x ≤ 3) nanophosphors were potential candidates for white-light LEDs.

In this work, we investigated the potential of Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphors to visualize latent fingermarks. We prepared these nanophosphors with various doping concentrations by the conventional coprecipitation reaction. The crystal structure, morphology, luminescence properties, and energy transfer mechanisms were studied. The crystalline phase was characterized by X-ray diffraction and crystal structure refinement using the Rietveld method. XRD measurements showed that the samples crystallized in the pure single pyrochlore phase with few more peaks originated from secondary phases and impurities generated during phosphor production, and that Eu3+ ions occupied D3d symmetry sites. The average crystallite size after mechanical grinding was less than 100 nm for all compositions. The optical characterization showed that, when excited under 532 nm, the Eu3+/Dy3+-codoped Y2Sn2O7 samples’ main intense emission peaks were located at 580–707 nm, corresponding to the 5D0→7Fj (j = l, 2, 3, and 4) transitions of europium. In fact, the 5D0→7F2 hypersensitive transition is strongly dependent on the local environment and was quite weak in Eu3+:Y2Sn2O7 at low Eu3+ doping levels. We found that the presence of Dy3+ as a codopant permitted enhancing the emission from this transition. The calculated PL CIE coordinates for the synthesized nanophosphors were very close to those of the reddish-orange region and only slightly dependent on the doping level. Various surfaces, including difficult ones (wood and ceramic), were successfully tested for latent fingerprint development with the prepared Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphor powder. Thanks to the high contrast obtained, fingerprint ridge patterns at all three levels were highlighted: core (level 1) islands, bifurcation, and enclosure (level 2), and even sweat pores (level 3).

In this study, we synthesized NaYF4-based downshifting nanophosphors (DSNPs), and fabricated DSNP-polydimethylsiloxane (PDMS) composites. Nd3+ ions were doped into the core and shell to increase absorbance at 800 nm. Yb3+ ions were co-doped into the core to achieve intense near-infrared (NIR) luminescence. To further enhance the NIR luminescence, NaYF4:Nd,Yb/NaYF4:Nd/NaYF4 core/shell/shell (C/S/S) DSNPs were synthesized. The C/S/S DSNPs showed a 3.0-fold enhanced NIR emission at 978 nm compared with core DSNPs under 800 nm NIR light. The synthesized C/S/S DSNPs showed high thermal stability and photostability against the irradiation with ultraviolet light and NIR light. Moreover, for application as luminescent solar concentrators (LSCs), C/S/S DSNPs were incorporated into the PDMS polymer, and the DSNP-PDMS composite containing 0.25 wt% of C/S/S DSNP was fabricated. The DSNP-PDMS composite showed high transparency (average transmittance = 79.4% for the visible spectral range of 380–750 nm). This result demonstrates the applicability of the DSNP-PDMS composite in transparent photovoltaic modules. [ABSTRACT FROM AUTHOR]

A series of Dy3+ doped Gd2O3 nanophosphors was synthesized by combustion method using urea. The crystallite sizes of the samples are found to be in the range of 9–16 nm. Photoluminescence emission spectra of the doped samples show two intense peaks at 487 nm and 575 nm corresponding to 4F9/2–6H15/2 and 4F9/2–6H13/2 transitions, respectively. The intensity of the emission spectra increases with the increase of dopant concentration upto 1at% of Dy3+ due to the energy transfer from Gd3+ of the host to Dy3+ and decreases due to concentration quenching. The electric dipole–dipole interaction mechanism is the main mechanism for concentration quenching. The decay curves are well fitted with bi exponential equation. The CIE co-ordinates and CCT values of the doped samples are found to be closed to that of white light. [ABSTRACT FROM AUTHOR]

Herein, the fabrication of eccentric Ag@Void@Y2SiO5:Pr3+ plasmonic yolk‐shell nanophosphors (PYSNPs) with high up‐conversion efficiency, and their incorporation on photochromic WO3 layers, is demonstrated to fabricate photochromic smart windows with high coloration contrast and swift color change. The up‐conversion efficiency of the Pr3+ ion‐doped Y2SiO5 (Y2SiO5:Pr3+) nanoshells is enhanced by about 50% through the incorporation of carefully designed plasmonic Ag cores placed inside their hollow cavities. Introduction of these geometry‐optimized plasmonic nanophosphors at the surface of photochromic WO3 films results in about 24‐fold and tenfold enhancements of their coloration rate and kinetic constant, respectively. The strategy adopted for designing and fabricating the Ag@Void@Y2SiO5:Pr3+ PYSNPs and their subsequent incorporation in conventional photochromic films offers an exciting approach for fabricating photochromic smart windows with dynamically controlled transmission of solar radiation, which is a promising technology for reducing energy consumption associated with heating, ventilation, and air‐conditioning of buildings. [ABSTRACT FROM AUTHOR]

[Display omitted] • YAlO:Cr3+ phosphor was prepared and modified with CDs and SiO 2 coating for multifunctional applications. • The PL intensity increases by 48.73 % and 19.29 % in the SiO 2 @CDs/YAlO:Cr3+ and CDs/YAlO:Cr3+ NCs, respectively, compared to the YAP:Cr3+ nanophosphor. • Improving fluorescence sensing for Fe3+ ions (0–350 µM) and achieves high sensitivity (0.2 µM) with low detection limit (4.93 µM). • The optimized composite holds promise for applications in white LEDs, Fe3+ sensors, latent fingerprint detection, and temperature probes for FIR thermometry. This study focuses on the synthesis of SiO 2 -coated carbon dots (CDs) grafted onto YAlO 3 :Cr3+ (YAP:Cr3+) nanophosphors (NPs) through a combustion method. The CDs enhance the absorption cross-section of Cr3+ ions, significantly boosting the luminescence of YAP:Cr3+ by 19.29-fold. Further improvement is achieved with a SiO 2 coating, leading to a 48.73-fold increase in photoluminescence intensity. The NCs are colour tunable, with emissions ranging from pinkish-red to blue, depending on the concentration of CDs and the excitation wavelength. These properties make them suitable for diverse applications, such as ratio metric fluorescence sensors for detecting Fe3+ ions within the 0–350 µM range, with high sensitivity (0.2 µM) and a low detection limit (4.93 μM). Additionally, they serve as material for white light-emitting diodes (W-LEDs), achieving CIE coordinates of (0.31, 0.30) and a rendering index of 94. The NCs also function as an optical thermometer with a sensitivity of 0.31 % K−1 at 320 K, making them ideal for temperature sensing applications. Moreover, their stability and dual-emissive nature make them highly effective in latent fingerprints (LFPs) detection, enabling high-resolution, level III fingerprint analysis. The dual emission properties of CDs and Cr3+ ions position these NCs as multifunctional materials, suitable for optical sensing, lighting, and security applications. [ABSTRACT FROM AUTHOR]

• Novel CDs@ZnAl 2 O 4 :Pr3+NCs were prepared using solution combustion method. • CDs incorporation shows a dramatic 39.02 fold enhancement in the PL intensity. • The colour purity of 5Wt% CDs@ZnAl 2 O 4 :Pr3+NCs is 98.3% and has a broad temperature domain of 300 K to 460 K, making it suitable for optical thermometry. • The imaged FPs display superior contrast, high sensitivity, minimal background interference and stability. • For high-end security encryption, the prepared fluorescent ink is highly beneficial. The remarkable optical properties of carbon dots (CDs) render them highly promising as a versatile group of carbon-based nanomaterials. Integrating hydrothermally synthesized CDs into zinc aluminate doped with Pr3+ ions (ZnAl 2 O 4 :Pr3+) nanophosphors (ZAO:Pr3+ NPs) fabricated via the solution combustion (SC) technique holds great potential. The aim of synthesizing these nanocrystals (NCs) is to explore their potential uses in optical thermometry and anti-counterfeiting (AC) measures. The synthesized nanoparticles (NPs) and nanocomposites (NCs) underwent characterization using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra to verify their phase, morphology, particle size, oxidation state, and chemical composition. When excited at 447 nm, the Pr3+ doped ZAO: NPs exhibited an orange-red emission band at 614 nm. A remarkable enhancement in PL intensity, by a factor of 39.02 folds, is noted upon embedding CDs into the ZAO:Pr3+ NPs (CDs@ ZAO:Pr3+). The enhanced PL intensity can be ascribed to the Förster resonance energy transfer (FRET) mechanism. Even at a temperature of 423 K, the NPs retains 95.4% of its emission intensity compared to that at room temperature, showcasing exceptional thermal stability. The 5 wt% CDs@ZAO:1Pr3+ NCs demonstrate a high colour purity (CP) of 98.3%. Moreover, these NCs hold promise for optical thermometry applications across a broad temperature range spanning from 303 to 463 K. Utilizing the exceptional ZAO:1Pr3+ NPs and 5 wt% CDs@ZAO:1Pr3+ NCs, two representative white light emitting diodes (w-LEDs) have been successfully developed, boasting satisfactory luminous efficacy and colour-rendering index (CRI). This underscores their potential for high-performance w-LED applications. Simultaneously, a highly sensitive, non-contact optical thermometer has been engineered, featuring maximum relative sensitivities of approximately 44.51×10−4 K −1 and 75.48×10−4 K −1 at the emission intensities corresponding to 673, 693, 712 and 735 nm, respectively. We have developed a simple brush mode technique for creating a variety of patterns using the manufactured AC security ink. The latent fingerprints (LFPs) visualized using 5 wt% CDs@ZAO:1Pr3+ NCs exhibit excellent resolution and contrast, enabling the easy identification of fingerprint characteristics from levels I-III. Employing deep learning utilizing the YOLOv8x algorithm, fluorescence images of the revealed LFPs demonstrate remarkable alignment with standard controls, suggesting a high degree of similarity. In addition, the fabricated white light emitting diode (w-LED) boasts a favorable colour rendering index (R a =87) alongside Commission International de L′Eclairage (CIE) coordinates (0.617, 0.376). Consequently, the inclusion of 5wt% CDs@ZAO:1Pr3+NPs showcases remarkable luminescent attributes and holds promising prospects across various applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction: The gold standard for diagnosis of active lupus nephritis (ALN), a kidney biopsy, is invasive with attendant morbidity and cannot be serially repeated. Urinary ALCAM (uALCAM) has shown high diagnostic accuracy for renal pathology activity in ALN patients. Methods: Lateral flow assays (LFA) for assaying uALCAM were engineered using persistent luminescent nanoparticles, read by a smartphone. The stability and reproducibility of the assembled LFA strips and freeze-dried conjugated nanoparticles were verified, as was analyte specificity. Results: The LFA tests for both un-normalized uALCAM (AUC=0.93) and urine normalizer (HVEM)-normalized uALCAM (AUC=0.91) exhibited excellent accuracies in distinguishing ALN from healthy controls. The accuracies for distinguishing ALN from all other lupus patients were 0.86 and 0.74, respectively. Conclusion: Periodic monitoring of uALCAM using this easy-to-use LFA test by the patient at home could potentially accelerate early detection of renal involvement or disease flares in lupus patients, and hence reduce morbidity and mortality. [ABSTRACT FROM AUTHOR]

A single‐phase perovskite LaAlO3:Dy3+ phosphor was synthesized using a gel‐combustion method at 600°C utilization with hexamethylenetetramine as a fuel. Further calcination of the samples was carried out (800 and 1000°C) to investigate the resultant effect on the crystalline and luminescence behaviour. The crystal structure had a cubic unit cell (space group Pm3̅m) and was examined using the Rietveld refinement and X‐ray diffraction data. Additionally, Debye–Scherrer and Williamson–Hall equations were applied to determine other structural features. The particle size and morphology of phosphors were evaluated using transmission electron microscopy. Diffraction measurements were supported by the various metal–oxygen vibration modes studied with the help of Fourier transform infrared spectroscopy. Energy‐dispersive X‐ray analysis verified the chemical composition of synthesized sample. Luminescence spectra of the LaAlO3:Dy3+ phosphors exhibited intense bands for 4F9/2→6H15/2 (482 nm, bluish region) and 4F9/2→6H13/2 (574 nm, yellowish region) transitions. Commission Internationale de L'Eclairage and correlated colour temperature data confirmed the cool‐white emission of the samples under ultraviolet light excitation. The interesting and advantageous luminescence characteristics of LaAlO3:Dy3+ phosphors make them potential materials for white light‐emitting diodes. [ABSTRACT FROM AUTHOR]

IntroductionThe gold standard for diagnosis of active lupus nephritis (ALN), a kidney biopsy, is invasive with attendant morbidity and cannot be serially repeated. Urinary ALCAM (uALCAM) has shown high diagnostic accuracy for renal pathology activity in ALN patients.MethodsLateral flow assays (LFA) for assaying uALCAM were engineered using persistent luminescent nanoparticles, read by a smartphone. The stability and reproducibility of the assembled LFA strips and freeze-dried conjugated nanoparticles were verified, as was analyte specificity.ResultsThe LFA tests for both un-normalized uALCAM (AUC=0.93) and urine normalizer (HVEM)-normalized uALCAM (AUC=0.91) exhibited excellent accuracies in distinguishing ALN from healthy controls. The accuracies for distinguishing ALN from all other lupus patients were 0.86 and 0.74, respectively.ConclusionPeriodic monitoring of uALCAM using this easy-to-use LFA test by the patient at home could potentially accelerate early detection of renal involvement or disease flares in lupus patients, and hence reduce morbidity and mortality.