Abstract
Mesoporous silica nanoparticles (mSiO2) have been used in many applications including drug delivery, catalysis, sensing. In drug delivery, tracing of mSiO2 needs incorporation of organic dyes or radio nuclei, etc. However, organic dyes are unstable under various mediums or in longer duration. To overcome this, one of ways is use of lanthanide ions (Ln3+) such as Eu3+, Tb3+ or Dy3+, which show luminescence in visible as well as near infrared (NIR) regions. In this work, nanocomposites of mSiO2 and Y2O3:Ln3+ have been prepared. These are characterized by several techniques. mSiO2 is stable up to 500 °C and microstructure of mesoporous collapses at 900 °C. Interestingly, mSiO2 reacts with Y2O3 to form Y2Si2O7 phase at 900 °C. On the other hand, such phase was not formed from Y2O3 and amorphous SiO2 at same temperature. This finding of the formation of highly crystalline Y2Si2O7 at lower temperature 900 °C is the first report to the best of authors’ knowledge. Their luminescence studies are performed by single or multi doping of Ln3+ ions. Their energy transfer processes are discussed. The crystallinity of Y2O3 or Y2Si2O7 is improved after co-doping of Ce3+ to Ln3+. Such nanocomposites are highly dispersible in distilled water, methanol and PBS (Phosphate Buffered Saline).
Highlights
In recent years, mesoporous silica has been subject of research for various properties viz. stable mesoporous structure, pore size tunability, high specific surface area and well modified surface
X-ray diffraction (XRD) patterns of nanocomposites of mesoporous silica and Y2O3:Eu co-doped with Dy or Tb are shown in Figure S2(a - b)
In cases of nanocomposites of mesoporous silica and Y2O3:Tb or Dy co-doped with Ce, their XRD patterns (Figure S2(c - d), see the supplementary material) of as-prepared and 500 oC heated samples are similar to those of mesoporous SiO2 (mSiO2)-Y2O3:Ln (Ln = Eu or Dy or Tb)
Summary
Mesoporous silica has been subject of research for various properties viz. stable mesoporous structure, pore size tunability, high specific surface area and well modified surface. Ln3+ doped Y2O3 based luminescent materials are preferable over others due to very high thermal stability, high luminescence intensity as well as solid solution solubility at any composition.[15,16,17,18,19,20,21] Studies on the chemical bonding in structure of a compound (e.g., mSiO2) and surface functionalization on particles are necessary to understand their properties and this can be analyzed by Fourier Transform Infrared (FTIR) and Raman Spectroscopy.[22,23,24]. At this same temperature, amorphous silica-Y2O3:Ln composite do not form any compound Such prepared nanocomposites will be useful in drug delivery and other biomedical applications.
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