Xiaoqi Zhao

All-in-one thermometer-heater up-converting platform YF3:Yb3+,Tm3+ operating in the first biological window

Achieving the combination of real-time diagnosis and therapy in one up-converting platform with sensitive thermometry and efficient heat production is a critical step towards photo-thermal therapy (PTT). Here, the potentiality of truncated octahedral YF3:Tm3+/Yb3+ micro-crystals as thermometers operating in the first biological window (BW-I) was evaluated on the basis of a thermo-responsive fluorescence intensity ratio (FIR) of far-red to NIR emission from completely separated 3F2,3/3H4 → 3H6 transitions. The probabilities of cross-relaxation (CR) processes related to 3F2,3/3H4 levels were greatly enhanced by increasing the Yb3+ content, leading to an increase of more than three times in the absolute sensitivity within the physiological temperature range. Photo-thermal effects were also assessed by monitoring the variation of temperature around the samples as functions of the Yb3+ dosage, excitation time and density of 980 nm laser diodes. These results offer a promising strategy to optimize the thermal sensitivity and optical heating ability, which indicates that the present UC platform has great potential applications in PTT as real-time thermometers and photo-thermal agents.

808 nm Light-Triggered Thermometer–Heater Upconverting Platform Based on Nd3+-Sensitized Yolk–Shell GdOF@SiO2

The realization of real-time and accurate temperature reading at subcutaneous level during the photothermal therapy (PTT) could maximally avoid the collateral damages induced by overheating effects, which remains a formidable challenge for biomedical applications. Herein, 808 nm light-driven yolk-shell GdOF:Nd3+/Yb3+/Er3+@SiO2 microcapsules were developed with thermal-sensing and heating bifunctions. Under 808 nm excitation, sensitive thermometry was implemented by monitoring thermoresponsive emission from 2H11/2/4S3/2 levels of Er3+; meanwhile, the addition of Nd3+ with rich metastable intermediate levels and the yolk-shell configuration with large specific surface area triggered efficient light-to-heat conversion via enhanced nonradiative channels. The potentiality of dual-functional samples for controlled subcutaneous photothermal treatment was validated through ex vivo experiments, and the antibacterial activity against Escherichia coli was also elaborately evaluated. Results open a general avenue for designing and developing upconverting platforms with sensitive thermal-sensing and efficient heating bifunctions, which makes a significant step toward the achievement of real-time controlled PTT.

NIR-to-NIR Deep Penetrating Nanoplatforms Y2O3:Nd3+/Yb3+@SiO2@Cu2S toward Highly Efficient Photothermal Ablation

A difunctional nano-photothermal therapy (PTT) platform with near-infrared excitation to near-infrared emission (NIR-to-NIR) was constructed through core-shell structures Y2O3:Nd3+/Yb3+@SiO2@Cu2S (YRSC), in which the core Y2O3:Nd3+/Yb3+ and shell Cu2S play the role of bioimaging and photothermal conversion function, respectively. The structure and composition of the present PTT agents (PTAs) were characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectra. The NIR emissions of samples in the biological window area were measured by photoluminescence spectra under the excitation of 808 nm laser; further, the penetration depth of NIR emission at different wavelengths in biological tissue was also demonstrated by comparing with visible (vis) emission from Y2O3:Yb3+/Er3+@SiO2@Cu2S and NIR emission from YRSC through different injection depths in pork muscle tissues. The photo-thermal conversion effects were achieved through the outer ultrasmall Cu2S nanoparticles simultaneously absorb NIR light emission from the core Y2O3:Nd3+/Yb3+ and the 808 nm excitation source to generate heat. Further, the heating effect of YRSC nanoparticles was confirmed by thermal imaging and ablation of YRSC to Escherichia coli and human hepatoma (HepG-2) cells. Results indicate that the YRSC has potential applications in PTT and NIR imaging in biological tissue.

Controllable fabrication of BaF2 self-assembled 3D Rubik's cube-like architectures emitting blue luminescence

Uniform barium fluoride (BaF2) micro-crystals with Rubiks cube-like structure have been prepared through a facile and environmentally friendly hydrothermal approach assisted by citric acid as the chelating agent. The crystal structures, morphologies and optical properties of the obtained samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The influential factors on the morphologies and size of BaF2 particles, including pH values and the molar ratio of Ba2+/Cit3−, were systematically investigated and the possible growth mechanism for BaF2 three-dimensional (3D) Rubiks cube-like architectures was proposed on the basis of time-dependent experiments. Moreover, the BaF2 micro-cubes prepared with different amounts of Cit3− exhibit an intense blue band emission centered at around 423 nm with the excitation of 336 nm ultraviolet (UV) light and the origin of this strong blue light was analyzed in detail. Results provide an effective strategy to fabricate uniform micro-crystals with controllable morphology and excellent optical properties.

Self-calibrated optical thermometer LuNbO4:Pr3+/Tb3+ based on intervalence charge transfer transitions

A Pr3+/Tb3+ co-doped LuNbO4 phosphor was synthesized as a self-calibrated optical thermometer using a high-temperature solid-state method, and its structure and luminescent property were elaborately investigated. Under intervalence charge transfer (IVCT) excitation at 305 nm, the sample LuNbO4:Pr3+/Tb3+ exhibited several bands in the green and red regions, originating from characteristics transitions of Pr3+ and Tb3+ ions. Through monitoring thermo-responsive emission intensity ratios from the 1D2 → 3H4 (Pr3+) and 5D4 → 7F5 (Tb3+) transitions, sensitive thermometry with good signal discriminability was achieved in phosphor LuNbO4:Pr3+/Tb3+ owing to a significant difference in thermal activation energy between Pr3+ and Tb3+ under IVCT excitation. Moreover, the maximum absolute sensitivity and relative sensitivity reached about 0.024 K−1 at 493 K and 1.26% K−1 at 463 K, respectively, for the LuNbO4:Pr3+/Tb3+ sample, which implies that the present phosphor could be considered as a promising candidate for self-calibrated optical thermometers.