Low-power upconverting nanoparticles are presented that display highly efficient, temperature-dependent green to blue upconversion under aerated aqueous conditions. These features are useful for live cell and in vivo temperature sensing.

Low‐power light upconversion by triplet–triplet annihilation (TTA‐UC) was only recently demonstrated in glassy polymers and the upconversion efficiency in these materials is typically much lower than in solution. As aggregation of the chromophores was thought to be the culprit, we here report the covalent tethering of a suitable chromophore pair to a polymeric backbone. The new materials were based on the sensitizer‐bearing monomer palladium meso‐phenoxy‐tris(heptyl)porphyrin‐ethylmethacrylate (PdmPH3PMA), which was copolymerized with a diphenylanthrancene methacrylate (DPAMA), as the emitter‐bearing monomer, and methyl methacrylate (MMA) as an optically inert comonomer. The DPA content was kept within a narrow range of 30–37 wt %, while the PdmPH3PMA content was varied between 0.73 and 0.012 wt %. To explore additional compositions, blends of a high‐porphyrin‐content terpolymer with a DPAMA‐MMA copolymer were also prepared. All of the materials studied were processed into thin films by solution‐casting and displayed blue TTA‐UC emission. The UC emission intensity was found to strongly depend on the composition and the underlying effects were investigated through a systematic study. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1629–1639

Lanthanide-containing nanoparticles have attracted much attention due to their unique optical properties and potential in nanotechnological applications. An amphiphilic block copolymer of poly(ethylene glycol)-b-poly(ε-caprolactone) methyl ether (mPEG-PCL) was functionalized with a dipicolinic acid (dpa) moiety and coordinated to lanthanide ions to afford [Ln(dpa-PCL-PEG-OCH3)3](HNEt3)3 (Ln = Eu(3+), Tb(3+)). Micelle-like nanoparticles of dpa-PCL-PEG-OCH3 macroligand and metal-centered polymers were prepared by solvent displacement methods. Dynamic light scattering analysis (DLS) and cryogenic transmission electron microscopy images confirmed the presence of solid sphere (<47 nm in diameter) and vesicle (>47 nm in diameter) morphologies. The viability and stability of the lanthanide complexes in micelle-like nanoparticles was explored by DLS and luminescence spectroscopy, and found to be stable for several weeks.