Core–shell structured nanoparticles for near-infrared (NIR) photocatalysis were synthesized by a two-step wet-chemical route. The core is composed of upconversion luminescence NaYF4:Yb,Tm prepared by a solvothermal process, and the shell is anatase TiO2 nanocrystals around NaYF4 particles formed via a method similar to a Stöber process. Methylene blue compound as a model pollutant was used to investigate the photocatalytic activity of NaYF4:Yb,Tm@TiO2 composites under NIR irradiation. To understand the nature of NIR-responsive photocatalysis of NaYF4:Yb,Tm@TiO2, we investigated the energy transfer process between NaYF4:Yb,Tm and TiO2 and the origin of the degradation of organic pollutants under NIR radiation. Results indicate that the energy transfer route between NaYF4:Yb,Tm and TiO2 is an important factor that influences the photocatalytic activity significantly and that the degradation of organic pollutants under NIR irradiation is caused mostly by the oxidation of reactive oxygen species generated in the photocatalytic reaction, rather than by the thermal energy generated by NIR irradiation. The understanding of NIR-responsive photocatalytic mechanism helps to improve the structural design and functionality of this new type of catalytic material.

We report the novel near-infrared (NIR) photocatalysis of YF(3) : Yb(3+),Tm(3+)/TiO(2) core/shell nanoparticles. The core/shell nanoparticles show photocatalytic activity under the NIR irradiation. This study demonstrates that the NIR energy can be used as the driving source for photocatalysis besides the UV and visible energy.

A general and versatile biomimetic approach to synthesize water dispersible and functionalizable upconverting nanoparticles (UCNPs) for selective imaging of live cancer cells is reported. The approach involves coating the surface of UCNPs with a monolayer of phospholipids containing different functional groups, allowing for conjugation of many molecules for a wide range of applications in fields such as bioinspired nanoassembly, biosensing, and bio-medicine.

Fluorescence probes in the NIR‐IIa region show drastically improved imaging owing to the reduced photon scattering and autofluorescence in biological tissues. Now, NIR‐IIa polymer dots (Pdots) are developed with a dual fluorescence enhancement mechanism. First, the aggregation induced emission of phenothiazine was used to reduce the nonradiative decay pathways of the polymers in condensed states. Second, fluorescence quenching was minimized by different levels of steric hindrance to further boost the fluorescence. The resulting Pdots displayed a fluorescence QY of ca. 1.7 % in aqueous solution, suggesting an enhancement of ca. 21 times in comparison with the original polymer in tetrahydrofuran (THF) solution. Small‐animal imaging by using the NIR‐IIa Pdots exhibited a remarkable improvement in penetration depth and signal to background ratio, as confirmed by through‐skull and through‐scalp fluorescent imaging of the cerebral vasculature of live mice.

Under 980 nm excitation, unusual 3P2-->3H6 (approximately 264 nm) and 3P2-->3F4 (approximately 309 nm) emissions from Tm3+ ions were observed in hexagonal NaYF4:Yb3+ (20%)/Tm3+ (1.5%) microcrystals. In comparison with the strong emissions from 1D2 and 1I6, the emissions from 1G4 and 3H4 almost vanished due to the efficient cross-relaxation of 1G4 + 3H4-->3F4 + 1D2(Tm3+). Double logarithmic plots of the upconversion emission intensity versus the excitation power are neither straight lines nor typical saturation curves. Theoretical analysis indicated that the complicated dependent relationships were mainly caused by phonon-assisted energy transfers and nonradiative relaxation.

Small molecules participate extensively in various life processes. However, specific and sensitive detection of small molecules in a living system is highly challenging. Here, we describe in vivo real-time dynamic monitoring of small molecules by a luminescent polymer-dot oxygen transducer. The optical transducer combined with an oxygen-consuming enzyme can sensitively detect small-molecule substrates as the enzyme-catalyzed reaction depletes its internal oxygen reservoir in the presence of small molecules. We exemplify this detection strategy by using glucose-oxidase-functionalized polymer dots, yielding high selectivity, large dynamic range, and reversible glucose detection in cell and tissue environments. The transducer-enzyme assembly after subcutaneous implantation provides a strong luminescence signal that is transdermally detectable and continuously responsive to blood glucose fluctuations for up to 30 days. In view of a large library of oxygen-consuming enzymes, this strategy is promising for in vivo detection and quantitative determination of a variety of small molecules.

Yb,Tm hybrid nanostructures. This demonstrates that the plasmon field enhancement effect is the main reason for the improved UC emission efficiency.

This paper described the energy-transfer amplified singlet oxygen generation in semiconductor polymer dots (Pdots) for in vitro and in vivo photodynamic therapy. Hydrophobic photosensitizer tetraphenylporphyrin was facilely doped in the nanoparticles consisting of densely packed semiconductor polymers. Optical characterizations indicated that the fluorescence of Pdots was completely quenched by the photosensitizer, yielding an energy transfer efficiency of nearly 100% and singlet-oxygen generation quantum yield of ∼50%. We evaluated the cellular uptake, dark toxicity, and photodynamic therapy of the Pdot photosensizer in human gastric adenocarcinoma cells. The in vitro studies indicated that cancer cells were efficiently destroyed at very low dose of the Pdots such as 1 μg/mL by using the light dose of 90 J/cm(2), which is considerably less than that in clinical practice. The antitumor effect of the Pdots was further evaluated in vivo with human gastric adenocarcinoma xenografts in Balb/c nude mice, which show that the xenograft tumors were significantly inhibited and eradicated in some cases. Our results indicate the energy transfer amplified Pdot platforms have great therapeutic potential for treating malignant cancers.