TiO₂-Coated CsPbI₃ Quantum Dots Coupled with Polyoxometalates for On/Off Fluorescent Photoswitches

Abstract

Lead halide perovskite quantum dots (QDs) have attracted significant attention because of their excellent optoelectronic properties. In this study, we focused on reversibly modulating the photoluminescence (PL) emission of perovskite QDs using a redox cluster of polyoxometalates (POMs). Three different CsPbBr x I3–x (x = 0, 0.4, and 0.7) QDs of 9.6∼12.8 nm diameter were synthesized, stabilized by TiO2 coating, and coupled with (Bu4N)4[W10O32] (tetra-n-butylammonium decatungstate: TBADT) in organic solution. The TiO2-coated CsPbBr x I3–x (CsPbBr x I3–x @TiO2 core/shell) QDs showed bright PL emissions at 705, 678, and 605 nm, which were efficiently quenched by one-electron-reduced W10O32 5– (POM–) via photoinduced electron transfer (PET). Particularly, the PL emission at 705 nm of CsPbI3@TiO2 QDs was most efficiently quenched by 95% via PET and Förster resonance energy transfer (FRET) because of a large spectral overlap between the QD emission and POM– absorbance. The quenching mechanism was analyzed by steady-state and time-resolved PL measurements. CsPbI3@TiO2 QDs was found to photocatalytically reduce POM to POM– by visible light. The PL emission from CsPbI3@TiO2 QDs was reversibly switched between On and Off states by alternately exposing the QD–POM system to intense visible light (PL quenching via PET and FRET) and reoxidation of POM– in ambient air (PL recovery). The obtained results open the possibility of constructing perovskite QD-based photoswitches for super-resolution imaging, optical data storage, smart display, and bioimaging.

Encapsulation of Pb-Free CsSnCl3 Perovskite Nanocrystals with Bone Gelatin: Enhanced Stability and Application in Fe3+ Sensing

“…As shown in Figure b, with an increase of the Fe 3+ concentrations, the PL intensity of bone gelatin- CsSnCl 3 NCs decreased accordingly, which can be fitted by the Stern–Volmer equation where F 0 and F represent the PL emission intensities of the bone gelatin–CsSnCl 3 NCs in the absence and presence of a Fe 3+ ion, respectively, [C] is the concentration of Fe 3+ , and K sv is a Stern–Volmer constant. Linear regression yields the relationship F 0 / F = 0.735 + 4.609­[C], with a correlation coefficient ( R 2 ) of 0.97022 and a quenching constant ( K sv ) of 4.6 × 10 3 M –1 .…”

Selective fluorescence sensor for Fe3+ based on in situ synthesis of CsSnCl3 perovskite quantum dots with bone gelatin

“…τ 0 and τ are the average (amplitude‐weighted) lifetimes of the donor with and without the acceptor, respectively. According to the Förster theory, E depends on the donor‐acceptor distance ( r ) and the Forster distance ( R 0 ), which is defined as the distance at which half of the energy is transferred to the acceptor 26 : …”

“…In the range of 0.1–1 mM, the F 0 /F shows a strong linear relationship with Fe 3+ concentration (Figure 7c), where F 0 and F indicate the PL emission intensities of the bone gelatin‐CsSnCl 3 QDs in the absence and presence of Fe 3+ ion, respectively. The Stern–Volmer (SV) equation can be used to fit the linear correlation equation, 26 and the fitting result is F 0 /F = 1.068 + 1.539 C (Fe 3+ ). R 2 has a correlation coefficient of 0.979, and Ksv has a quenching constant of 1.539 × 10 3 M −1 .…”

Cubic CsPbI3 Nanoarchitectonics with High and Stable Photoluminescence toward White Light-Emitting Diodes

“…Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) are widely applied in the fields of solar cells, photodetectors, liquid crystal televisions, and other optoelectronics − due to their high photoluminescence quantum yields (PLQYs), , narrow spectral widths, tunable PL spectrum in the whole visible light region, adjustable band gaps, and high color purity. − In addition, low-dimensional perovskite NCs have been continuously studied. , However, the surface ligands of these NCs are easily desorbed during the purification process, resulting in the aggregation and growth of NCs into large particles, which decreases the stability and PLQYs . In particular, cesium lead iodide (CsPbI 3 ) NCs can accelerate degradation under the conditions of water, heat, and strong light.…”