Dye Sensitization for Ultraviolet Upconversion Enhancement

Upconversion nanocrystals that converted near-infrared radiation into emission in the ultraviolet spectral region offer many exciting opportunities for drug release, photocatalysis, photodynamic therapy, and solid-state lasing. However, a key challenge is the development of lanthanide-doped nanocrystals with efficient ultraviolet emission, due to low conversion efficiency. Here, we develop a dye-sensitized, heterogeneous core–multishelled lanthanide nanoparticle for ultraviolet upconversion enhancement. We systematically study the main influencing factors on ultraviolet upconversion emission, including dye concentration, excitation wavelength, and dye-sensitizer distance. Interestingly, our experimental results demonstrate a largely promoted multiphoton upconversion. The underlying mechanism and detailed energy transfer pathway are illustrated. These findings offer insights into future developments of highly ultraviolet-emissive nanohybrids and provide more opportunities for applications in photo-catalysis, biomedicine, and environmental science.

Upconversion lanthanide nanomaterials: basics introduction, synthesis approaches, mechanism and application in photodetector and photovoltaic devices

Upconversion (UC) of lanthanide-doped nanostructure has the unique ability to convert low energy infrared (IR) light to high energy photons, which has significant potential for energy conversion applications. This review concisely discusses the basic concepts and fundamental theories of lanthanide nanostructures, synthesis techniques, and enhancement methods of upconversion for photovoltaic and for near-infrared (NIR) photodetector application. In addition, a few examples of lanthanide-doped nanostructures with improved performance were discussed, with particular emphasis on upconversion emission enhancement using coupling plasmon. The use of UC materials has been shown to significantly improve the NIR light-harvesting properties of photovoltaic devices and photocatalytic materials. However, the inefficiency of UC emission also prompted the need for additional modification of the optical properties of UC material. This improvement entailed the proper selection of the host matrix and optimization of the sensitizer and activator concentrations, followed by subjecting the UC material to surface-passivation, plasmonic enhancement, or doping. As expected, improving the optical properties of UC materials can lead to enhanced efficiency of photodetectors and photovoltaic devices.