Morphology and photoluminescence of self-assembled CaWO4:Sm3+ microspheres: effect of pH and surfactant concentration

Abstract

Self-assembled CaWO 4 :Sm 3? microspheres were prepared via surfactant (sodium dodecyl sulfate) mediated hydrothermal method. The effect of pH and the concentration of surfactant on the morphology and photoluminescence of the synthesized phosphors have been studied. Samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence spectroscopy. The microspheres were found to have an average size of 1-2 lm. They were mesoporous in nature and constituted of nanocrystals of about 10-30 nm dimension. The TEM images revealed the interlinking framework of the nano-sized constituents which consequently lead to the formation of mesoporous microspheres. The lowering of pH causes a slight reduction in the size of microspheres which could have been attributed to loss of OH from the nanoparticle surface and subsequent retardation in the adsorption of growing molecular CaWO 4 :Sm 3? units. Also, as pH increases, crystallinity decreases. The increase in amount of SDS reduced the crystallinity of the materials, destroyed the monodispersity of microspheres and lowered the luminescence output. It was found that lower pH and higher monodispersity of microspheres are quite favourable for high luminescence output.

Enhancement of Eu3+ Emission in YVO4:Eu3+ Nanocrystals by Li+ Codoping: An Oxidant-Resistant Dispersion and Polymer Film

“…This could suggest that Li + occupies the interstitial sites rather than the Y 3+ lattice sites similar to that. in YPO 4 :Eu 3+ as reported by Parchur et al 24,26 In Figure 1c, the variation of the fwhm and unit cell volumes are presented. The fwhm values are decreased with increasing Li + ion codoping.…”

“…17−19 There are also reports on methods to enhance the luminescence emission such as codoping with certain metal (mono-, di- or tri-valent) ions in appropriate stoichiometry, tuning of synthetic parameters and morphological variations. 20−24 The enhancement is effective when the codopant acts as a sensitizer or improves the crystallinity of the materials. The codoping of Li + in the YPO 4 :Dy 3+ system has improved the crystallinity and emissions of Dy 3+ including its near infrared band at 872 nm.…”

Structural and Optical Properties of Ca0.9Cu0.01WO4 Solid Solution Synthesized by Sonochemistry Method at Room Temperature

“…CaWO 4 nanocrystals are interesting and promising materials due to their excellent physical, chemical, and optical properties, such as intense photoluminescent emission at 420 nm. 1 Moreover, they are not toxic, when obtained by conventional methods of synthesis, and have a lower cost preparation, when compared with other semiconductors. Thus, the CaWO 4 material can be considered an important candidate for drug delivery or light-emitting devices (LEDs).…”

“…Calcium tungstate (CaWO 4 ) is a well-known semiconductor and an important member of the class of scheelite minerals. CaWO 4 nanocrystals are interesting and promising materials due to their excellent physical, chemical, and optical properties, such as intense photoluminescent emission at 420 nm . Moreover, they are not toxic, when obtained by conventional methods of synthesis, and have a lower cost preparation, when compared with other semiconductors.…”

Correlating Structure and Luminescence Properties of Undoped and Eu3+-Doped La2Hf2O7 Nanoparticles Prepared with Different Coprecipitating pH Values through Experimental and Theoretical Studies

“…In recent years, our group has developed a combined coprecipitation and molten-salt synthesis (MSS) procedure to synthesize A 2 B 2 O 7 NPs size-controllably. The pH value of the coprecipitation step is a very important factor that governs the physical and microstructural properties of the synthesized NPs. − While our synthesis procedure has many advantages, such as simplicity, greenness, reliability, scalability, and generalizability, , to the best of our knowledge, no study has been reported on the systematical investigation of the influence of the pH value during the synthesis of these NPs on their structural characteristics, defect chemistry, and luminescence properties.…”