Stress-Induced Photoluminescence Change of Monolayer Nanosheet Prepared by Delamination of Aurivillius-Phase Layered Perovskite

Abstract

A comprehensive investigation was performed on the photoluminescence properties of monolayer Bi 3+ -substituted ATa 2 O 7 2− (A = Ca, Sr, Bi 0.5 Na 0.5 ). The Bi 3+ center in the A−Ta−O perovskite framework functioned as a luminescence center (λ max = 470−520 nm) under UV-light illumination (λ ex = 250−340 nm). Comparison of the photoluminescence spectra of Bi 3+ in several types of layered ATaand free-standing ATa 2 O 7 2− nanosheet membranes, revealed that the positions of the emission and excitation bands were greatly influenced by the interlayer cation species. The results implied that the photoluminescence properties of Bi 3+ in ATa 2 O 7 2− were sensitive to changes in the electric field surrounding Bi 3+ because of the ultimate thinness of the monolayer ATa 2 O 7 2− nanosheets (1.1−1.2 nm). To further explore the relationship between mechanical stress in Bi 3+ -substituted ATa 2 O 7 2− nanosheets and the emission band of Bi 3+ , changes in the photoluminescence and Raman spectra in response to the curvature radius of free-standing ATa 2 O 7 2− nanosheet membranes were compared. The present study confirmed that two-dimensional nanomaterials could help further the understanding of mechanochromic phenomena in Bi-containing inorganic materials.

Controlling Thickness of Aurivillius Phase Perovskite Nanosheets Obtained by Delaminating Bi2SrNan–2NbnO3n+3 (n = 2–5) Layered Crystal

“…EDS spectra were used to determine the composition of the BSN2, BSNN3, BSNN4, and BSNN5 nanosheet free-standing membranes (Figure S4–S6): Bi 0.13 Sr 0.64 Nb 2.00 O 7−δ , Bi 0.25 Sr 0.90 Na 0.83 Nb 3.00 O 10−δ , and Bi 0.27 Sr 0.92 Na 1.69 Nb 4.00 O 13−δ for n = 2, 3, 4, respectively (Table S1). These results confirmed that 9–13% of the A site was occupied by Bi. , Because the SrNa 3 Nb 5 O 16 2– nanosheet free-standing membrane contained SrNa 2 Nb 4 O 13 2– nanosheets as an impurity, the molar ratio of (Bi+Sr+Na)/Nb was much smaller than the theoretical value.…”

“…Aurivillius-phase layered perovskites have exhibited unique physicochemical properties including oxygen ion conductivity, − Bi 3+ -based mechanochromic photoluminescence, , and visible-light driven photocatalysis. − Aurivillius-phase layered perovskites are composed of two alternating components: an anionic perovskite nanosheet layer ([ A n ‑1 B n O 3 n +1 ] 2– ) and a cationic bismuth oxide layer ([Bi 2 O 2 ] 2+ ). The general formula of Aurivillius-phase layered perovskites can be written as Bi 2 A n –1 B n O 3 n +3 , where n corresponds to the number of perovskite units along the stacking direction per perovskite nanosheet layer.…”

Tunable Photoluminescence of Bismuth‐ and Trivalent‐Lanthanide‐Doped Monolayer Perovskite Oxide Nanosheets

“…These results agree with the situation for Bi 3+ ‐substituted perovskite nanosheets in previous studies. [ 3 ] On the other hand, the position of the emission bands for Eu 3+ ( 5 D 0 → 7 F j , j = 0, 1, 2, 3, …) is not dependent on the R value. The result clearly indicated that the energy levels for the ground and excited states of Bi 3+ are more easily influenced by change of R values than those of Eu 3+ .…”

“…have great potential for application in optical sensors with high thermal, mechanical, and chemical stability. [1][2][3][4][5] The lanthanide and bismuth centers in perovskite nanosheets show strong visible-light emission under UV-light illumination, in which energy transfer occurs due to bandgap absorption in the perovskite framework to the luminescent centers by O 2− -Ln 3+ or O 2− -Bi 3+ charge-transfer transitions. [6] Because all luminescent centers in the perovskite nanosheet framework are located within ≈1 nm of the outermost surface of the nanosheet, the PL properties of the luminescent centers are sensitively influenced by changes in the environment surrounding the nanosheet, including humidity, pH, and mechanical stress.…”

“…[13] Considering previous literature on Eu 3+ and Tb 3+ -based PL perovskite nanosheets, the Ta-O framework can be a good photosensitizer for not only bismuth but also trivalent lanthanides. [3,14,15] Delamination of the Aurivillius-phase layered perovskite is performed by multistep cation exchange reactions. However, the strong electrostatic interactions among perovskite layers and bismuth oxide layers due to their high charge densities have greatly hampered further investigation of the PL properties of these perovskite nanosheets.…”