Enhancing the upconversion of Er incorporated BaTiO by introducing oxygen vacancies.

Lanthanide-incorporated crystals display the phenomenon of upconversion (UC), wherein near-infrared (NIR) light is converted into ultraviolet-visible (UV-Vis) emission with a narrow bandwidth. This unique photophysical property renders lanthanide UC materials highly promising for diverse applications. However, the limited quantum efficiency (∼3%) hinders the broader utilization of UC materials.

Power-dependent photophysical pathways of upconversion in BaTiO:Er.

Lanthanide incorporated perovskite is one of the most promising systems for efficient energy conversion or light-emitting materials in terms of upconversion (UC). Investigation of the photophysical mechanism of UC in the lanthanide-doped system is here continued. However, research on the 4I13/2 energy state in Er3+ is rare and more is still needed.

Upconversion properties in lanthanide doped layered-perovskite, CsBiNbO.

Despite advances of lanthanide-doped upconversion (UC) materials, the applications such as light-emitting diode and biological imaging are limited by low quantum efficiency. For this context, the understanding of unique interactions between the doped-lanthanides and the host crystals has attracted a huge amount of the researcher's interest. In particular, it was revealed that doping lanthanide ions in a non-centrosymmetric site of host lattice is the cause of relaxation of the Laporte selection rule in the 4f-4f transition of lanthanide ions.

Effect of tetragonal to cubic phase transition on the upconversion luminescence properties of A/B site erbium-doped perovskite BaTiO.

With the increasing number of applications for upconversion materials, a more detailed understanding of the intrinsic mechanisms of their optical processes is required. Thus far, various lanthanide-doped host materials or nanoparticle systems have been investigated as representative upconversion systems owing to their major advantage as optical probes. As for the energetics of upconversion and the associated upconversion pathways, the role of the host material is very important because it provides a unique microscopic environment; for example, a unique local lattice structure in the case of crystalline samples.

Cellular uptake efficiency of nanoparticles investigated by three-dimensional imaging.

Understanding the interaction of nanoparticles with living cells on the basis of cellular uptake efficiency is a fundamental requisite in biomedical research. Cellular internalization of nanoparticles takes place by mechanisms like ATP hydrolysis-driven endocytosis that deliver nanoparticles to the cytoplasm, organelles and nuclei. Despite its importance in nanomedicine, this uptake procedure is not understood in-depth because of the complexity of the biochemical mechanisms and the lack of available experimental methods for quantitative analysis.

Upconversion Luminescence Sensitized pH-Nanoprobes.

Photon upconversion materials, featuring excellent photophysical properties, are promising for bio-medical research due to their low autofluorescence, non-cytotoxicity, low photobleaching and high photostability. Upconversion based pH-nanoprobes are attracting considerable interest due to their superiority over pH-sensitive molecular indicators and metal nanoparticles. Herein, we review the advances in upconversion based pH-nanoprobes, the first time in the seven years since their discovery in 2009.