Mesoporous NaGdF₄/Ho–Yb@m-SiO₂ Upconversion Nanophosphors as a Potent Theranostic Probe

Abstract

Nearly monodispersed NaGdF4/Ho–Yb upconversion nanoparticles (UCNPs) are synthesized by thermolysis of respective rare earth oleates. UCNPs are made biocompatible by mesoporous silica (m-SiO2) coating. These particles exhibit red and green bands in the visible range upon excitation at 980 nm laser. Interestingly, because of the presence of Ho3+ ions, these UCNPs can be excited via UV–vis light in addition to the 980 nm near infrared light. A systematic study is carried out to demonstrate the use of these UCNPs as drug (DOX) carriers. Toxicity studies and bio-imaging using DOX-loaded UCNPs have been demonstrated. UCNPs are also radiolabeled with 177Lu using m-SiO2 coating to demonstrate its potential application as a carrier of the therapeutic radionuclide in vivo for radionuclide therapy. Lu-177 adsorption studies are carried out extensively in order to understand the nature of adsorption, and it is found to be a combination of Langmuir and Freundlich isotherm models. Kinetics of adsorption of Lu3+ ions on the m-SiO2 coating of UCNPs is studied. Overall, the synthesis and physicochemical characterization of NaGdF4/Ho–Yb@m-SiO2 upconversion nanocrystals and their potential utilities in multimodal biomedical applications are amply demonstrated.

Codoping of Yttria (Y2O3): Ho–Yb Nanoparticles with Li Increase Emitted Green Light Intensity for Security Ink and Bioimaging

“…Emission spectra show the doublet emission peaks at 530 nm (lower intensity) and 550 nm (higher intensity), which are assigned to transitions from the excited-state levels ( 5 F 4 , 5 S 2 ) of Ho 3+ to the ground-state level ( 5 I 8 ). 31,32 We observed a decrease in the luminescence intensity of Ho 3+ with codoping with Yb 3+ or Yb 3+ −Li + . This decrease in intensity is related to the followings: Yb/Li ions act as quenchers or there is energy transfer from Ho 3+ to Yb 3+ .…”

Lanthanide molecular cluster-aggregates as the next generation of optical materials

“…8). 94 Although widely demonstrated for nanoparticles, glasses, and other classes of low-phonon materials, [220][221][222][223][224] Ho 3+ UC was never observed with a molecular system. The main reason is the mismatching between Yb 3+ (donor) and Ho 3+ (acceptor) electronic states.…”

Chitosan–poly(vinyl alcohol)–ionic liquid-grafted hydrogel for treating wastewater

“…The Freundlich adsorption isotherm is expressed as follows:where q e represents the equilibrium adsorption capacity of the dye adsorbed on the dried gel surface, and C e is the equilibrium concentration of the adsorbate (mg L −1 ). 38 K f and n are the Freundlich isotherm constant and the heterogeneity factor, respectively. The kinetic study on murexide adsorption was performed at room temperature at different intervals.…”