Multiphoton Upconversion Materials for Photocatalysis and Environmental Remediation

Abstract

Solar‐driven photocatalysis holds great potential for energy conversion, environmental remediation, and sustainable chemistry. However, practical applications of conventional photocatalytic systems have been constrained by their insufficient ability to harvest solar radiation in the infrared spectrum. Lanthanide‐doped upconversion materials possess high photostability, tunable absorption, and the ability to convert low‐energy infrared radiation into high‐energy emission, making them attractive for infrared‐driven photocatalysis. This review highlights essential principles for rational design of efficient photocatalysts. Particular emphasis is placed on current state‐of‐the‐arts that offer enhanced upconversion luminescence efficiency. We also summarize recent advances in lanthanide‐doped upconversion materials for photocatalysis. We conclude with new challenges and prospects for future developments of infrared‐driven photocatalysts.

Exploiting the upconversion luminescence, Lewis acid catalytic and photothermal properties of lanthanide-based nanomaterials for chemical and polymerization reactions

“…To improve the intensity of upconversion luminescence without the need for increasing laser intensity or concentration of UCNC, several strategies including plasmon-assisted upconversion, core-shell structure design, dye-sensitized UCNC, and host lattice distortion have been proposed. 1,[9][10][11]23,103,113 This is particularly useful when overheating, due to the photothermal effect of lanthanide-based UCNC or absorption of excitation light by the solvent, is not desired in a photochemical/photopolymerization reaction. In this case, it is advantageous to be able to produce strong upconversion emission using as low an excitation intensity as possible.…”

“…7,[19][20][21][22] The energy of light emitted from UCNCs, covering a wide spectrum range from UV to NIR, can be selectively tuned to excite various photosensitizers. For example, semiconductors excited by upconverted UV photons from UCNCs have been used in water splitting, 6,23,24 wastewater treatment, 6,[25][26][27] nitrogen photofixation [28][29][30] and photoelectrocatalysis. 6,23,[31][32][33][34] To date, most photocatalytic reactions are driven by photoredox catalysts that absorb UV/visible light (Fig.…”

“…For example, semiconductors excited by upconverted UV photons from UCNCs have been used in water splitting, 6,23,24 wastewater treatment, 6,[25][26][27] nitrogen photofixation [28][29][30] and photoelectrocatalysis. 6,23,[31][32][33][34] To date, most photocatalytic reactions are driven by photoredox catalysts that absorb UV/visible light (Fig. 1a).…”

“…For example, semiconductors excited by upconverted UV photons from UCNCs have been used in water splitting, 6,23,24 wastewater treatment, 6,25–27 nitrogen photofixation 28–30 and photoelectrocatalysis. 6,23,31–34…”

Degradation of upconverting nanoparticles in simulated fluids evaluated by ratiometric luminescence

“…[1][2][3][4][5][6][7][8][9][10][11] The proposal and application of core-shell upconversion nanostructures is a milestone in the development of upconversion nanomaterials, which provides exciting new opportunities for their wide application in the biomedical, [12][13][14][15][16] environmental, and photocatalysis fields. [17][18][19][20][21] Notably, Liu's group proposed an energy transfer-mediated upconversion mechanism, in which activators without long-life intermediate energy states (Tb 3+ , Eu 3+ , Dy 3+ and Sm 3+ ) were doped in separated layers to achieve tunable upconversion emission by controlling gadolinium sublattice-mediated energy migration. 22 The rational design of a core-shell nanostructure not only enhances the luminescence [23][24][25] but also integrates multiple functional units into a single UCNP, [26][27][28] thus providing great flexibility for the construction of UCNPs.…”