Manipulating the Low-Energy Photons by an Upconversion Fluorescent Hybrid Photocatalyst for Water Oxidation

Abstract

Upconversion fluorescence (NaYF 4 /Yb, Er) is a promising technique employed by solar cells for enhancing light harvesting, especially for manipulating the lowenergy photons. Here, we report a semiconductor/NaYF 4 /Yb, Er hybrid structure applied to photoelectrochemical (PEC) water oxidation. Three emission peaks in visible wavelengths at 522.5, 541.5, and 655.5 nm are observed for NaYF 4 /Yb, Er under 980 nm excitation due to a nonlinear anti-Stokes process. Owing to the overlap between the upconversion fluorescent emission of NaYF 4 /Yb, Er and the UV−vis absorption edge of Fe 2 O 3 , the hybrid structure Fe 2 O 3 /NaYF 4 /Yb, Er presents 70% enhancement of the photocurrent density compared with the pristine Fe 2 O 3 and 19% improvement in the carrier concentration. The charge-transfer kinetics at the electrode/electrolyte interface is also reinforced. Through the radiationreabsorption mechanism, this hybrid semiconductor integrated with upconversion fluorescence reveals efficient energy conversion effect and presents valuable reference for PEC applications.

Multisignal optical temperature‐sensing properties of Eu3+‐doped NaYF4 nanoparticles

“…However, the emissions from 5 D 1 level can be clearly observed in Figure 1(c), because the nonradiative transition and cross‐relaxation from 5 D 1 to 5 D 0 are of relatively low probability due to the low photon energy of NaYF 4 . [ 28 ] These emissions from 5 D 0 and 5 D 1 levels covered the visible spectrum of green light (I G , 526 nm and 536 nm), yellow light (I Y , 555 nm), orange light (I O , 592 nm and 615 nm), and red light (I R , 651 nm and 696 nm). [ 29 ]…”

“…[27] Finally, the ions at 5 D 0 and 5 D 1 relaxed radiatively to 7 F J (J = 0-4). As mentioned in the introduction, the [28] These emissions from 5 D 0 and 5 D 1 levels covered the visible spectrum of green light (I G , 526 nm and 536 nm), yellow light (I Y , 555 nm), orange light (I O , 592 nm and 615 nm), and red light (I R , 651 nm and 696 nm). [29] The emission spectra of NaYF Conversely, I 0 reaches the maximum while the Eu 3+ concentration is 12%.…”

Photon upconversion of Nd3+–Yb3+–Tb3+ doped core–shell–shell–shell nanoparticles

“…1 Anti-Stokes-shifted luminescent materials have been widely applied in displays, anti-counterfeiting, biological labelling, and other fields due to their sharp emission bands, high light stability, and low biological toxicity. [2][3][4][5][6][7] Compared to typically 980 nm excited NaYF 4 :Yb/Er or NaYF 4 :Yb/Tm UCNPs, in which Er 3+ or Tm 3+ ions serve as activators and Yb 3+ ions are used as sensitizers to absorb 980 nm NIR light, 6,[8][9][10][11][12][13][14] Nd 3+ doped UCNPs can be excited by an 808 nm laser and then transfer energy to the activator (for example, Er 3+ ) through Yb 3+ as an energy transfer bridge (Nd 3+ → Yb 3+ → Er 3+ ), 15,16 greatly reducing the thermal effect caused by the strong absorption of water under 980 nm excitation. However, the inherently weak energy transfer efficiency limits their further applications.…”

Direct large-scale synthesis of water-soluble and biocompatible upconversion nanoparticles for in vivo imaging

“…12 The Yb 3+ ion emerges as a frequently utilized sensitizer owing to its substantial absorption cross-section in the near-infrared region, facilitating effective absorption of near-infrared light. [13][14][15][16][17][18] Notably, the NaYF 4 :Ln 3+ nanoparticles have emerged as pivotal luminescent nanomaterials for various applications, including bioimaging, optical data storage, and anti-counterfeiting measures, owing to their exceptional upconversion properties. However, the large specic surface area of NaYF 4 :Ln 3+ nanoparticles oen leads to signicant non-radiative transitions, posing challenges for the exploration and application of new optical functionalities.…”