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Europium doped Y2O3 nanophosphors have been prepared by the solution combustion method. The prepared nanophosphors were characterized by powder x-ray diffraction (XRD). XRD revealed that the cubic phase with crystallite size in the range 25–37 nm formed. Surface morphology of the samples was studied by field emission scanning electron microscopy and the particles were observed as spherical in nature, having an average size ~30 nm. The electron spin resonance spectrum of the irradiated nanophosphor exhibited a signal having peaks at g = 2.1646 and 2.0035 which are attributed to and defect centers, respectively. Thermoluminescence (TL) emission showed a strong red (611 nm) emission at 417 K. The prominent TL glow (417 K) peak exhibited low fading, good reproducibility and linear dose response in the range 0.01–2.0 kGy. This behavior is favorable for TL dosimetry applications. The Y2O3:Eu3+ nanophosphor has prodigious potential as a dosimeter to be use for monitoring high dose ionizing radiation fields.

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

A detailed investigation of the thermoluminescence (TL) properties of γ-ray and C5+ ion beam irradiated K2CaMg(SO4)3:Dy (KCM) phosphor was carried out. KCM was irradiated by 50 and 75 MeV energy C5+ ion beams with a fluence range of 15 × 1010 ions cm−2 to 30 × 1012 ions cm−2. The TL glow curves along with the response curves of these phosphor samples were analyzed and compared with commercial CaSO4:Dy phosphor. The TL glow curves of the phosphor exposed to γ-rays from 60Co and 137Cs sources were also examined in this study for comparative analysis. Theoretical analysis of the glow curves of the C5+ ion beam and γ-ray irradiated samples was performed using the glow curve deconvolution method. SRIM/ TRIM simulations were performed in order to identify the ion beam profile, range, distribution, etc. The enhancement in the intensity of the low temperature glow peak is explained with the help of an energy level model and the decrease in TL intensity with increasing ion fluence is also explored in detail. The radicals produced after irradiation were verified using the electron paramagnetic resonance (EPR) technique. The effects of temperature and microwave power on the EPR signal are also studied.

Sm3+ doped Ca3B2O6 phosphors have been synthesized by combustion method. X-ray diffraction (XRD), photoluminescence (PL), UV–Vis spectroscopy and thermoluminescence (TL) have been used to study the structural, luminescence and optical properties of the phosphors. Under 400 nm excitation, the phosphor shows characteristic emission for Sm3+ ion (4G5/2 → 6Hj/2, j = 5, 7, 9 and 11) with the main orange-red emission peak at 600 nm corresponding to the 4G5/2 → 6H7/2 transition state of the Sm3+ ion. The optimum molar concentration and maximum critical distance between the Sm3+– Sm3+ ions were found to be 3 mol.% and 20.098 A, respectively. The phosphor can be efficiently excited by near UV chips for their potential use in solid state lighting. The calculated CIE coordinates (0.60, 0.40) were found to be in the orange-red spectrum region. The thermoluminescence studies were carried out after irradiating the phosphor by gamma rays in the dose range of 10–5000 Gy. The glow peak was deconvoluted by the TLAnal program and the kinetic parameters associated with the deconvoluted peaks were evaluated.

In this paper, the combustion synthesis and photoluminescence properties of Sm3+ doped KSrVO4 nanophosphors are reported. The samples were characterized by different techniques such as x-ray powder diffraction, transmission electron microscopy, UV?vis spectrophotometry and photoluminescence spectroscopy. The lattice parameters were calculated as and ?3. The average grain size of the samples was estimated as 42 nm using the modified Scherrer?s equation. Under near UV excitation, the sharp emission line at 560, 600, 646 and 704 nm due to characteristic transitions of Sm3+ were observed. The maximum PL emission intensity was observed at 1.5 mol.% of the Sm3+ ions. The band gap of the phosphor was calculated from diffused reflectance data and was found to be 3.74 eV. The CIE 1931 chromaticity coordinates (x, y) of the phosphor were (0.61, 0.39), in a shade of orange-red color. The potential applications of this material as a down conversion phosphor under blue light excitation were evaluated for possible application as a high color-purity phosphor in light emitting diodes (LEDs) that can fill the 590?600 nm gap.

A report on the sol–gel preparation of nanosized ZnAl2O4:0.01% Cr3+ at a relatively low temperature (~80 °C) is presented. The catalyst/Zn mole fraction in the solution was varied from 0–3 during the synthesis. The x-ray diffraction (XRD) data show that the annealed samples were pure cubic crystalline structures at the lower catalyst/Zn mole fractions. However, minor diffraction peaks associated with ZnO were detected at the higher catalyst/Zn mole fractions. An increase in the mole fraction led to transformation of morphology from spherical particles to rod-like-structures. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and elemental mapping revealed the presence of Zn, Al, O and Cr. In addition, the catalytic mole fraction influenced the band-gap of the ZnAl2O4 host. Photoluminescence (PL) spectra indicated that the undoped and 0.01% Cr3+-doped powders exhibit a bluish-violet emission at slightly different peak positions, suggesting that the emission could either be originating from the host or the Cr3+ dopant ion. The emission from the host was attributed to oxygen vacancies (Vo*), while emissions from the Cr3+ were attributed to the transitions from different energy levels in the Cr3+ ion. It was also noted that the PL emission intensity was dependent on the catalyst/Zn mole fraction. The colour chromaticity showed that the emission colour of the ZnAl2O4:0.01% Cr3+ phosphor could be tuned by varying the catalyst/Zn mole fraction.

Orange-red emitting NaCaBO3:Sm 3+ nanophosphors were prepared by combustion method using metal nitrates and urea as initial materials. The phase of the product was identified by x-ray diffraction technique (XRD) and was found to be orthorhombic with a space group Pmmn and lattice parameters a=16.12 A, b=10.25 A, c=3.52 A and V=581.60 A 3 calculated with the POWD program. The average particle size of the nanophosphor calculated from the XRD data and cross verified by TEM was 34 nm. The spectral properties of the NaCaBO3: Sm 3+ nanophosphors were studied under near UV and electron excitation, which shows characteristic emission lines assigned to the transition ( 4 G5/2 to the 6 Hj, j=5/2, 7/2, 9/2, 11/2) of the Sm 3+ ion. The optimal Sm 3+ ion concentration and its critical energy distance were determined as x=2 mol% and 59.97 A, respectively and the dipole–dipole interactions were responsible for concentration quenching in the present phosphor. The band gap of the phosphor was calculated to be 5.82 eV. The phosphorescence decay curve was also measured.