NaYbF4:Tm3+ based-nanostructured materials have been synthesized by solvothermal method and sol-gel technique. Observed high intense UV-blue up-conversion luminescence, under low-power commercial 980 nm laser irradiation, have been applied to enhance photocatalytic activity. Thus, photocatalytic degradation of methylene blue, as an organic pollutant model, was proved as a unique photonic effect, converting incident NIR radiation before reaching the contaminated solution
Ultimate generation of luminescent security inks have been used to detect counterfeiting including applications in banknotes, quick response codes (QR codes), barcodes, security documents, drug packaging and food security. Anti counterfeiting strategies are competitively developed against fast-growing counterfeit markets. So far, most security inks are based on the down-conversion effect, that is transforming UV incident radiation into visible light. But the substrates are sensitive to this UV “reading light”, which leads to a reduction of the contrast between the substrate and the printed sample. Therefore, rare-earth doped upconversion luminescent materials present significant advantages compared to standard fluorescent dyes, such as invisibility in ambient light, excitation by low cost commercial NIR irradiation and a lack in background noise, due to negligible auto-fluorescence from the surface. However, more attention needs to be paid on the codification of overall emitted luminescence, so it will be more difficult to mimic by ever increasing sophisticated counterfeiters. Thus, we present upconversion emissions in rare-earth doped nano-glass-ceramics (nGCs) under NIR excitation at 980 nm. Intensity ratios among UV and VIS upconversion emission bands can be tailored by modifying doping concentration level. Specific doping level, excitation wavelength and focusing conditions give rise to additional security features based on light-responsive encryption security patterns. A multi-digit code based on these intensity ratios can be set from resulting spectra, providing a proof-of-concept test for light-responsive encryption security patterns.
Enhancing the efficiency of solar energy harvesting schemes, particularly photocatalytic processes, by means of spectral converting materials stands up as an emerging route not yet fully explored. In this context, there is a growing interest in harvesting energy from the large near-infrared (NIR) range of solar radiation (approx. 60% in terms of the photon number or 40% of the energy from the sun’s total incoming radiation) for various energy and environmental applications. The immediate goal is to bridge the gaps of photocatalysts by shifting NIR photons into UV-VIS ones through up-conversion photonic mechanisms. Here we present different photonic materials (glasses, crystals and solvothermal core-shell nanocrystals) showing high intense NIR-to-UV-VIS upconversion luminescence. Photocatalytic degradation of organic dye methylene blue as a pollutant model has been successfully attained under NIR radiation. We have also successfully achieved hydrogen and oxygen evolution via water-splitting using Al-doped SrTiO3 (STO:Al) photocatalyst, loaded with rhodium-chromium oxide (RhCrOx) as a hydrogen evolution cocatalyst in order to enable the overall water-splitting reaction. Both experiments have been carried out under low-power commercial 980 nm laser irradiation. Up-conversion driven photocatalysis is proved, as a solely photonic effect, converting incident NIR radiation before reaching the contaminated solution. We also explore the implementation of rare-earth doped upconversion materials with the performance of luminescent solar concentrators (LSC), as a promising option for enhancing the efficiency of optical devices
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.