Dual Stimuli-Responsive Block Copolymers for Controlled Release Triggered by Upconversion Luminescence or Temperature Variation

Abstract

An amphiphilic block copolymer (BCP) which contains both photoresponsive and thermoresponsive blocks was synthesized by the atom transfer radical polymerization approach. Meanwhile, a new core/shell type of the upconversion nanoparticle (UCNP) LiYF 4 :Yb 3+ 0.25 ,Tm 3+ 0.01 @LiYF 4 :Yb 3+ 0.2 was successfully synthesized. By encapsulating UCNPs inside the micelles of the BCP and incorporating Nile red (NR) into the UCNP@BCP hybrid nanoparticles as a model drug, controlled release of the drug by the dual-stimuli BCP could be studied. After exposing the UCNP-loaded micellar solution to near-infrared (NIR) light, it was found that the UV light pumped from UCNPs could disrupt the polymer micelles and the fluorescence intensity of NR decreased with the increase of the irradiation time of the NIR light. The thermoresponsive study indicated that the fluorescence intensity of NR decreased with the increase of temperature of the micellar solution because of the release of NR into water arising from the contraction of the amphiphilic BCP.

Interaction of LiYF4:Yb3+/Er3+/Ho3+/Tm3+@LiYF4:Yb3+ upconversion nanoparticles, molecularly imprinted polymers, and templates

“…Nanoparticles of LiYF 4 doped with Yb 3+ , Er 3+ , Ho 3+ , and Tm 3+ ions were synthesized by the thermal decomposition of the lanthanide and lithium triuoroacetate precursors in the presence of oleic acid coordinating ligands and noncoordinating 1octadecene solvent molecules, according to our previously reported procedure. [18][19][20] Briey, a batch of Yb 3+ -, Er 3+ -, Ho 3+ -, and Tm 3+ -doped LiYF 4 (74 mol% Y, 20 mol% Yb, 2 mol% Er, 2 mol% Ho, and 2 mol% Tm) was obtained as follows: Li 2 CO 3 (1.48 mmol), Y 2 O 3 (0.74 mmol), Yb 2 O 3 (0.2 mmol), Er 2 O 3 (0.02 mmol), Ho 2 O 3 (0.02 mmol), and Tm 2 O 3 (0.02 mmol) were dissolved in 50% triuoroacetic acid (TFA) at 80 C in a three-necked ask. Then, the solutions were evaporated to dryness under an argon gas purge.…”

LiYF4:Yb/LiYF4 and LiYF4:Yb,Er/LiYF4 core/shell nanocrystals with luminescence decay times similar to YLF laser crystals and the upconversion quantum yield of the Yb,Er doped nanocrystals

“…This is usually done in high boiling oleic acid-based solvent mixtures, similar to the synthesis of NaYF4 upconversion nanocrystals [62][63][64][65][66]. Since the particles have a small size and display a relatively strong luminescence, they have been proposed for a variety of biomedical and bioimaging applications [79,80,83,87], as well as for transparent displays [70,74] and chemosensing [86]. Due to their large surfaceto-volume ratio, however, surface quenching of the luminescence presents a severe problem, often reducing the photoluminescence quantum yield of the nanocrystals by several orders of magnitude compared to the bulk material.…”

“…Core particle synthesisHOA-based synthesis procedures for nanocrystalline LiYF4 are usually based on the thermal decomposition of trifluoro acetates[63,64,66,67,[78][79][80][81][82][83][84][85][86][87][88][89] or on the reaction of yttrium oleate with either ammonium fluoride and lithium oleate[77] or ammonium fluoride and lithium hydroxide[62,65,[68][69][70][71][72][73][74][75][76]. Here, we prepared the LiYF4 nanoparticles at temperatures above 200 °C via the reaction of ammonium fluoride with rare earth oleates and lithium oleate dissolved in oleic acid/octadecene[62,65,[68][69][70][71][72][73][74][75][76][77].…”

Synthesis, Optical Properties, and Sensing Applications of LaF3:Yb3+/Er3+/Ho3+/Tm3+ Upconversion Nanoparticles

“…More importantly, to synthesize a kind of UCNPs that can emit UV light and can be applied as a trigger for photoresponsive materials, some preliminary experiments were conducted. As our previous study indicated that UV-emissive LiYF 4 -type UCNPs can be obtained by the single doping of Tm 3+ [ 38 , 44 ], we optimized the doping concentrations of Yb 3+ and Tm 3+ to synthesize LaF 3 UCNPs with luminescence characteristics in the UV region. As the UC emission is strongly related to the cross-relaxation of the doping ions, we increased the concentration of Yb 3+ (sensitizer) and decreased the concentration of Tm 3+ (activator) based on the doping concentrations shown in Figure 5 b.…”