Upconverting Materials: Synthesis, Characterizations and Applications

Dear Colleagues,

Photon upconversion processes that generate emissions at shorter wavelengths than the excitation wavelength (generally near infrared light) constitute a research topic in the fields of the physics and chemistry of materials, with increasing development over the last 50 years.

Among trivalent lanthanide (Ln)-based upconversion (UC) materials, for which the sequential absorption of two or more photons per emitted photon occurs within discrete, long-lived Ln energy levels, fiber and bulk glasses and bulk crystals were early investigated, mainly by their possible applications as upconversion laser systems.

A completely new scenario appeared in the early 2000s, with the development of effective chemical strategies to prepare Ln-doped nanosized materials with enhanced UC efficiency. Current extensive research concerning these UC nanocrystalline materials is driven by the abundance of envisaged applications, ranging from color displays and lighting technologies, to sensing, security, and photovoltaics, and importantly, to bioimaging and biomedicine.

Another recent approach to achieve UC emission and most of the indicated applications is based on triplet-triplet annihilation (TTA) mechanisms in molecule-based chromophores, with their triplet states as the intermediate excited states.

This thematic issue will include i) the preparation and strategies of chemical synthesis of both Ln-UC and TTA-UC systems with enhanced UC efficiency, ii) the characterization of the above materials, and iii) the study and results concerning applications of UC materials as well as envisaged future developments in this research field. Considered applications should include, but are not be limited to bioimaging (including multimodal bioimaging by magnetic resonance imaging MRI, X-ray computed tomography CT, etc.), detection applications (UC materials as sensors and biosensors of temperature, pH as well as of ions and small molecules), drug delivery and therapies, lighting sources, photocatalysis and photovoltaics.

Prof. Dr. Concepción Cascales
Guest Editor

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• Lanthanide-based UC materials
• TTA-based UC materials
• Synthesis and preparation of UC materials
• Strategies of enhancement of UC efficiency
• Functionalization of nanosized UC materials
• Bioimaging
• Multimodal bioimaging
• UC-based (nano)thermometers
• Drug delivery and UC-based therapies
• UC-based lighting sources
• UC-based color displays
• UC-based materials for solar cells.