Colloidal Stability and Optical Thermometry in Mesoporous Silica Coated Phosphate Based Upconverting Nanoparticles

Core@shell nanoparticles (NPs) have been synthesized by using the chemical co- precipitation technique and St.ber method. The XRD, TGA, HRTEM, FTIR, Raman and XPS analysis have been carried out to characterize the core and core@shell NPs. The HRTEM analysis shows the evidence of silica coating with shell thickness similar to 5 nm and size similar to 17 nm of the core NPs. The colloidal stability and band gap have been estimated by using the UV-Vis absorption analysis. The enhancement of about 12 times in upconversion emission intensity of the core@shell NPs as compared to that of the core NPs has been reported due to reduce surface defect after silica coating. The optical thermometry and security ink performance of the prepared NPs have been investigated. The core@shell NPs have been found to exhibit better thermal stability, colloidal stability, improved sensitivity and temperature range as compared to the bare core NPs. (C) 2021 Elsevier B.V. All rights reserved.