Investigation on the structure and upconversion fluorescence of Yb3+/Ho3+ co-doped fluorapatite crystals for potential biomedical applications

Abstract

Rare-earth Yb3+ and Ho3+ co-doped fluorapatite (FA:Yb3+/Ho3+) crystals were prepared by hydrothermal synthesis, and their structure, upconversion properties, cell proliferation and imaging were investigated. The synthesized crystals, with a size of 16 by 286 nm, have a hexagonal crystal structure of classic FA and a Ca/Yb/Ho molar ratio of 100/16/2.1. Several reasonable Yb3+/Ho3+ -embedding lattice models along the fluorine channel of the FA crystal cell are proposed for the first time, such as models for (Ca7YbHo©)(PO4)6F2 and (Ca6YbHoNa2)(PO4)6F2. The activated FA:Yb3+/Ho3+ crystals were found to exhibit distinct upconversion fluorescence. The 543- and 654-nm signals in the emission spectra could be assigned, respectively, to the 5F4 (5S2) - 5I8 and 5F5 - 5I8 transitions of holmium via 980-nm near-infrared excitation and the energy transfer of ytterbium. After the surfaces were grafted with hydrophilic dextran, the crystals displayed clear fluorescent cell imaging. Thus, the prepared novel FA:Yb3+/Ho3+ upconversion fluorescent crystals have potential applications in the biomedical field.

(La0.97RE0.01Yb0.02)2O2S Nanophosphors Converted from Layered Hydroxyl Sulfate and Investigation of Upconversion Photoluminescence (RE=Ho, Er)

“…Another type of widely investigated UC phosphors is RE 2 O 3 (such as Y 2 O 3 :Yb/Er), whose relatively high phonon energy (ℏω ~ 600 cm −1 ; ~ 591 cm −1 for Y 2 O 3 and 612 cm −1 for Lu 2 O 3 ) [15], however, lowers the efficiency of UC luminescence due to photon-phonon coupling. From the view point of biocompatibility, Li et al [16] synthesized Yb 3+ - and Ho 3+ -codoped fluorapatite crystals (nanorods of 16 by 286 nm) via hydrothermal reaction, and UC luminescence of Ho 3+ at 543 and 654 nm was attained through a two-photon process under 980-nm laser excitation. The crystals also exhibited clear fluorescent cell imaging after the surfaces were grafted with hydrophilic dextran [16].…”

“…From the view point of biocompatibility, Li et al [16] synthesized Yb 3+ - and Ho 3+ -codoped fluorapatite crystals (nanorods of 16 by 286 nm) via hydrothermal reaction, and UC luminescence of Ho 3+ at 543 and 654 nm was attained through a two-photon process under 980-nm laser excitation. The crystals also exhibited clear fluorescent cell imaging after the surfaces were grafted with hydrophilic dextran [16]. …”

The Change in Antioxidant Properties of Dextran‐Coated Redox Active Nanoparticles Due to Synergetic Photoreduction–Oxidation

“…The peaks corresponding to OH stretch (3343.16 cm −1 ), CH 2 stretch (2916.70 cm −1 ), COH vibration (1340.46 cm −1 ), CO stretch (1028.81 cm −1 ) and CC stretch (915.74 cm −1 ) are present in case of dextran, Dex–CNPs dark and Dex–CNPs light samples as depicted in Figure 3 B. It is evident that the peak corresponding to CO stretch (1642.01 cm −1 ) is exclusively present in Dex–CNPs light which indicates the possible presence of an aldehyde or a ketone bond that may have been formed as a result of potential oxidation of dextran in the presence of CNPs 16. The oxidation of dextran leading to formation of aldehyde bonds are further discussed in later sections through NMR proton spectra analysis…”

Effects of crystalline growth on structural and luminescence properties of Ca(10−3x)Eu2x(PO4)6F2 nanoparticles fabricated by using a microwave driven hydrothermal process

“…The success of rare-earth doping is expected in view of similarity in ionic radius of lanthanide ions and calcium ion and high affinity to PO 4 3-. Moreover, it is important to note that substitution of OH -groups by F -ions could contribute to the enhancement of luminescence efficiency 18 . C for 24 h in order to get the final product.…”