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• Ca 0.5 Y 1.90-x O 3 :xHo3+ (0.5 ≤ x ≤ 3 moles %) nanophosphor was successfully prepared by solution combustion method • The synthesized nanophosphor was characterized by XRD, TEM, FTIR, UV–Visible and PL techniques. • The synthesized nanophosphor display instance green emission corresponds to 5 S 2 → 5 I 8 transition of Ho3+ ions. • Nanophosphor display good thermal stability with high color purity (98%) with CCT values in the 5000-6000 K range. • Ca 0.5 Y 1.90-x O 3 :xHo3+ nanophosphor also have the good thermal stability with activation energy of 0.23 eV. • Ca 0.5 Y 1.90-x O 3 :xHo3+ nanophosphor can be commercialized for solid state lightening and various optoelectronic devices. This paper presents a series of Ho3+activated Ca 0.5 Y 1.90-x O 3 green-emitting nanophosphors using the facile solution combustion method. X-ray diffraction (XRD) and Transmission electron microscope (TEM) confirm the phase purity, structural morphology with cubic phase, and irregular shape particle with the average particle size of 21 nm. Diffuse reflectance spectra of the recorded and band gap estimated by Tauc's equation which is 5.78 eV, 4.90 eV for direct and indirect band gaps for 2 mol% of Ho3+, respectively. Under the excitation of 448 nm wavelength (5I 8 → 3G 6), the doped samples display characteristic emission of Ho3+ ions correspond to 5S 2 → 5I 8 (at 551 nm) transition, which fall in a strong green region. The optimal concentration for Ho3+ doping is found as 2 mol%, after this quenching of photoluminescence (PL) intensity occurred and this is accredited due to dipole-dipole interaction. The proposed nanophosphor also displays the good thermal stability with activation energy of 0.23 eV. The nanophosphor confirms the excellent color purity (98%), CRI (98.36%), and CCT value (5724 K). With this, nanophosphor also exhibits good quantum efficiency of 81.1% under the 448 nm excitation wavelength. These results direct that the Ho3+activated Ca 0.5 Y 1.90-x O 3 nanophosphor may have potential applicability for green-emitting LEDs, display device and optoelectronic applications. [Display omitted]. [ABSTRACT FROM AUTHOR]

[Display omitted] • This report features facile combustion with a mixing approach for the synthesis of Eu:Y 2 O 3 nanophosphor and Eu:Y 2 O 3 -PVA film (EYF). • EYF is highly selective for the arsenic ion (As3+) over the various cations and anions present in real water samples. • EYF display a limit of detection (LOD) as 57 ng/L (=0.057 ppb) for 0–100 µg/L linear range. • Fluorescent change of the sensor could be visually observed with naked eyes under UV–Vis light. • This sensing probe provides sensitive, selective and a label-free fluorescence-based detection of arsenic ions in real water samples. The present article reports the synthesis and characterization of Eu:Y 2 O 3 nanophosphor (EYN) and EYN dispersed polyvinyl alcohol (PVA) fluorescent film (EYF), with subsequent studies of sensing behavior for the detection of heavy metal ions particularly arsenic ions (As3+) in real water samples. Various characterization techniques have been employed to confirm the successful phase formation/stability of EYF. The maximum emission peak for EYF with excitation wavelength 394 nm has been obtained as 612 nm and hence picked for the demonstration of PL (Photoluminescence) response with arsenic ions solution in natural pH range (at ∼ 7 pH). Fluorescence intensities of EYF have been found to decrease quickly with As3+ ion contents due to the reduction in the population of Eu3+ ions in the 5D 0 level and also due to formation of direct or indirect coordinate bonds with Eu3+. The PL intensity of the EYF nanoprobe has completely been quenched at 260 µg/L concentration of As3+ ions with the limit of detection 57.5 ng/L (=0.057 ppb) for 0–100 µg/L linear range. The selectivity of EYF probe is also investigated for various common cations and ions present in real water samples. Moreover, sensing probe has been examined with different river water samples and shows recovery percent in between 98 and 105 & maximum % RSD value as 5.76 with n = 5 tests. Furthermore, the EYF sensing probe shows a visible color change with the contaminated water under UV–Vis light which useful for the onsite detection of arsenic concentration. Hence, EYF endows a promising pathway for a flexible, portable, low-cost sensing device for the sensitive and selective detection of arsenic ions in real water samples. [ABSTRACT FROM AUTHOR]

In the present paper, we have reported the variation of CaWO 4 :Eu 3+ nano phosphors with different compositions of Li + , (LEC) (Li + = 2, 5, 7 and 10 at%). The as-prepared (ASP) samples are annealed at 900 °C to eliminate unwanted organic moieties present in the sample and to improve crystallinity. These nanoparticles are characterized by X-ray diffraction (XRD), Thermogravimetric Analysis (TGA) , X-ray photoelectron spectroscopy (XPS), Fourier transform IR spectroscopy (FTIR), Raman spectroscopy, photoluminescence studies. FTIR gives the absorption band at ~832 cm −1 , which corresponds to antisymmetric vibrations due to O-W-O band in the WO 4 2- tetrahedron. This is also confirmed by the Raman Spectroscopy. CaWO 4 has a crystal of the Scheelite type having C 4 h point group symmetry and I 4 1/a space group symmetry. The surface/ particle morphology of 900 °C annealed samples studied using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) and show the formation of nanosheet like structure. Annealed samples of lithium co-doped CaWO 4 :Eu 3+ nanoparticles have shown the red luminescence which is attributed due to the strong host contribution and different energy transfers from Li + ions to host matrix under 392 nm excitations. Li + ion improves the crystallinity and radiative transition rate and these materials may be potential candidates for white light emitting diodes and may be widely used as optoelectronic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The luminescent divalent (Ca2+) doped Eu:Y 2 O 3 @SiO 2 core–shell nanophosphors have been synthesised and characterized. • The fluorescence intensity of phosphor increases by 34 % for the SiO 2 coted (10 vol%) sample. • The nanophosphor could be utilized for security ink, latent fingerprints, warm LEDs, and other optoelectronic devices. • The developed fingerprints have first and second-level ridge features appropriate for a forensic lab. The divalent (Ca2+)-doped Eu:Y 2 O 3 @SiO 2 core–shell luminescent nanophosphors have been synthesised by a cost-effective combustion technique. Various characterizations were carried out to confirm the successful formation of the core–shell structure. The TEM micrograph reveals the thickness of the SiO 2 coating over Ca-Eu:Y 2 O 3 as ∼25 nm. The optimal value of silica coating over the phosphor has been obtained as 10 vol%(TEOS) of SiO 2 , with this value increasing fluorescence intensity by 34 %. Phosphor exhibits CIE coordinates as x = 0.425, y = 0.569 and a CCT value as ∼2115 K with color purity and the respective CRI of 80 % and 98 %, respectively, which make the core–shell nanophosphor suitable for warm LEDs, and other optoelectronic applications. Further, the core–shell nanophosphor has been investigated for the visualisation of latent finger prints and as security ink. The findings point towards the prospective future application of nanophosphor materials for anti-counterfeiting purposes and latent finger prints for forensic purposes. [ABSTRACT FROM AUTHOR]