Aufwärtskonvertierende NaYF 4 :Yb,Er/NaYF 4 ‐Kern/Schale‐Nanokristalle mit hoher Lumineszenzquantenausbeute

Emerging Design Principle of Near-Infrared Upconversion Sensitizer Based on Mitochondria-Targeted Organic Dye for Enhanced Photodynamic Therapy

Upconversion luminescent (UCL) triggered photodynamic therapy (PDT) affords superior outcome for cancer treatment. However, conventional UCL materials which all work by a multiphoton absorption (MPA) process inevitably need extremely high power density far over the maximum permissible exposure (MPE) to laser. Here, a one-photon absorption molecular upconversion sensitizer Cy5.5-Br based on frequency upconversion luminescent (FUCL) is designed for PDT. The unusual super heavy atom effect (SHAE) in Cy5.5-Br strongly enhances its spin-orbit coupling (0.23 cm^-1 ), triplet quantum yield (11.1 %) and triplet state lifetime (18.8 μs) while the potential hot-band absorption of Cy5.5-Br is well maintained. Importantly, Cy5.5-Br can efficiently target the tumour site and kill cancer cells by destroying mitochondria under a biosafety MPE to 808 nm laser. The photostability and antitumor results are obviously superior to that of a Stokes process. This work provides a design criterion for FUCL dyes to realize effective PDT upon a biosafety optical density, possibly bringing more clinical benefits than conventional MPA materials.

Lanthanide-Doped Nanoparticles for Near-Infrared Light Activation of Photopolymerization: Fundamentals, Optimization and Applications

Photopolymerization refers to a type of polymerization process in which light is utilized as excitation source to initiate polymerization of monomers and oligomers. Despite great progress, photopolymerization is typically induced by ultraviolet or visible light, which still greatly restrains its applications. Upconversion nanoparticles (UCNPs) represent a class of optical nanomaterials that are able to convert low-energy near-infrared (NIR) light into high-energy ultraviolet (or visible light) emissions. In this context, UCNP-assisted photopolymerization has recently attracted extensive attentions due to its unique advantages. In this account, recent advances in the fundamentals, optimization and emerging applications of UCNP-based photopolymerization are reviewed. Fundamental theories of upconversion luminescence and photopolymerization will be introduced first. Various optimization approaches to improve UCNP-assisted photopolymerization are then summarized, followed by diverse emerging applications. Challenges and future perspectives in this area will be provided as a conclusion.

Homo–hetero/core–shell structure design strategy of NaYF4 nanocrystals for superior upconversion luminescence

A comprehensive strategy has been developed to construct nano-sized homogeneous and heterogeneous core/shell structures of NaYF₄ host. Synthesis conditions of cubic phase/α-NaYF₄ and hexagonal phase/β-NaYF₄ are discussed. Pure cubic NaYF₄:Yb,Er nanocrystals were synthesized with different average sizes extending from 7 nm to 15 nm by varying the reaction time. Temperature and time thresholds of hexagonal nucleation were determined and utilized for controlled core/shell structures of different phases. α-NaYF₄:Yb,Er@α-NaYF₄, α-NaYF₄:Yb,Er@β-NaYF₄, β-NaYF₄:Yb,Er@α-NaYF₄, and β-NaYF₄:Yb,Er@β-NaYF₄ core/shell structures were prepared by adopting the required conditions to achieve the desired phase. Excess sodium was used to grow hexagonal shell over metastable cubic core under controlled conditions of reaction time and temperature to prevent the structural transition of the core. Upconversion emission spectra have also been obtained. UCL integrated intensities demonstrated about 5-fold enhancement for α-shell over α-core as compared to the core alone and 22-fold enhancement with β-shell. On the other hand, α-shell over β-core exhibited 5-fold enhancement and β-shell over β-core exhibited 6-fold enhancement.

Establishment of essential conditions of different phases of NaYF₄ and their utilization for the synthesis of core/shell structures to achieve the enhancement of UCL intensities.

Luminescent Ratiometric Thermometers Based on a 4f-3d Grafted Covalent Organic Framework to Locally Measure Temperature Gradients During Catalytic Reactions

Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials, are a new type of support for grafting lanthanide ions (Ln³⁺ ), which can be employed as ratiometric luminescent thermometers. In this work we have shown that COFs co-grafted with lanthanide ions (Eu³⁺ , Tb³⁺ ) and Cu²⁺ (or potentially other d-metals) can synchronously be employed both as a nanothermometer and catalyst during a chemical reaction. The performance of the thermometer could be tuned by changing the grafted d-metal and solvent environment. As a proof of principle, the Glaser coupling reaction was investigated. We show that temperature can be precisely measured during the course of the catalytic reaction using luminescence thermometry. This concept could be potentially easily extended to other catalytic reactions by grafting other d-metal ions on the Ln@COF platform.

Bright Infrared-to-Ultraviolet/Visible Upconversion in Small Alkaline Earth-Based Nanoparticles with Biocompatible CaF2 Shells

Upconverting nanoparticles (UCNPs) are promising candidates for photon-driven reactions, including light-triggered drug delivery, photodynamic therapy, and photocatalysis. Herein, we investigate the NIR-to-UV/visible emission of sub-15 nm alkaline-earth rare-earth fluoride UCNPs (M1-x Lnx F2+x, MLnF) with a CaF2 shell. We synthesize 8 alkaline-earth host materials doped with Yb3+ and Tm3+ , with alkaline-earth (M) spanning Ca, Sr, and Ba, MgSr, CaSr, CaBa, SrBa, and CaSrBa. We explore UCNP composition, size, and lanthanide doping-dependent emission, focusing on upconversion quantum yield (UCQY) and UV emission. UCQY values of 2.46 % at 250 W cm-2 are achieved with 14.5 nm SrLuF@CaF2 particles, with 7.3 % of total emission in the UV. In 10.9 nm SrYbF:1 %Tm3+ @CaF2 particles, UV emission increased to 9.9 % with UCQY at 1.14 %. We demonstrate dye degradation under NIR illumination using SrYbF:1 %Tm3+ @CaF2 , highlighting the efficiency of these UCNPs and their ability to trigger photoprocesses.

A DNA-Azobenzene Nanopump Fueled by Upconversion Luminescence for Controllable Intracellular Drug Release

Stimulus-responsive drug release possesses considerable significance in cancer therapy. This work reports an upconversion-luminescence-fueled DNA-azobenzene nanopump for rapid and efficient drug release. The nanopump is constructed by assembling the azobenzene-functionalized DNA strands on upconversion nanoparticles (UCNPs). Doxorubicin (DOX) is loaded in the nanopump by intercalation in the DNA helix. Under NIR light, the UCNPs emit both UV and visible photons to fuel the continuous photoisomerization of azo, which acts as an impeller pump to trigger cyclic DNA hybridization and dehybridization for controllable DOX release. In a relatively short period, this system demonstrates 86.7 % DOX release. By assembling HIV-1 TAT peptide and hyaluronic acid on the system, targeting of the cancer-cell nucleus is achieved for perinuclear aggregation of DOX and enhanced anticancer therapy. This highly effective drug delivery nanopump could contribute to chemotherapy development.