Visible‐to‐Ultraviolet Light Conversion: Materials and Applications

Abstract

Photon frequency conversion using optical materials is a common strategy for light generation and utilization. Materials capable of visible‐to‐ultraviolet (UV) light conversion have attracted particular attention due to their potential applications in nonlinear optics, biophotonics, as well as environmental sciences. There are four main mechanisms of visible‐to‐UV light conversion processes, including second‐harmonic generation, two‐photon absorption, lanthanide‐based upconversion, and triplet–triplet annihilation. Herein, recent developments in visible‐to‐UV light conversion materials are collectively reviewed and the emerging applications are presented. The prospects and challenges for further development in this field are also highlighted.

Special Education Student Teachers’ Opinions about Online Supervision amidst COVID-19

“…In addition to this, feedbacks were rapidly provided to student teacher for their lesson plans and their instruction by supervisors during the online supervision. This finding is consistent with the findings of previous studies conducted with web 2.0 tools which provided facilities in file sharing and feedback (Duncan, 2021;Du et al, 2021). Moreover, the study demonstrates that online supervision contributes student teachers' technological literacy development.…”

Purely organic Vis-to-UV upconversion with an excited annihilator singlet beyond 4 eV

“…Hence, converting two visible photons into UV light or high-lying excited states with energies exceeding 4 eV, which corresponds to UVB photons with wavelengths shorter than 310 nm, would most likely enable several applications under mild reaction conditions. 1…”

“…Several photochemical processes such as water splitting, [1][2][3] waste-water treatment 4 and the photocatalytic activation of inert molecules [5][6][7] require more energy than a single visible photon 5,[8][9][10][11][12][13] can provide. In principle, highly energetic UV light could be exploited for all these applications, but the efficient and mercury-free generation of UV light below 320 nm by artificial light sources is challenging 14,15 and the solar spectrum sharply drops in that region.…”

“…Hence, converting two visible photons into UV light or high-lying excited states with energies exceeding 4 eV, which corresponds to UVB photons with wavelengths shorter than 310 nm, would most likely enable several applications under mild reaction conditions. 1 The sTTA mechanism is highly attractive for converting visible 16,17 or even NIR 18,19 photons into radiation of higher energy at non-coherent low photon fluxes. [20][21][22][23] Vis-to-UV upconversion via sTTA was initially observed by Castellano in 2009.…”

Multi-responsive deep-ultraviolet emission in praseodymium-doped phosphors for microbial sterilization

“…The natural defects and substitution defects of the host lattice, as well as the charge compensation effects will make for the generation and regulation of energy traps, thus contributing to the emergence of PersL and photo-stimulated luminescence (PSL) [18,19]. On the other hand, as preferred luminescence centers, lanthanide dopants with 4f-4f electronic transitions possess abundant absorption and emission energy levels, which enables the generation of photoluminescence (PL) and UCL [17,20,21]. Hence, coupling the interactions of host lattice, energy traps and luminescent centers provide the possibility of creating multimode luminescence in a synergetic fashion.…”