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224 results on '"Di, Yunsong"'

4. Lead‐Free Perovskites with Photochromism and Reversed Thermochromism for Repeatable Information Writing and Erasing.

Author

Sheng, Yuhang, Gui, Qingfeng, Zhang, Yi, Yang, Xingru, Xing, Fangjian, Liu, Cihui, Di, Yunsong, Wei, Shibiao, Cao, Guiyuan, Yang, Xifeng, Zhang, Xiaowei, Liu, Yushen, and Gan, Zhixing

Subjects
THERMOCHROMISM, PEROVSKITE, WRITING processes, EXCITON theory, SONICATION, PHOTOCHROMISM
Abstract

Recently, novel optical information writing strategies have been developed based on fluorescent change of halide perovskites generated by light induced structural transformation. However, to date, the repeatable writing and erasing of fluorescent patterns are still a major challenge. Herein, lead‐free Cs3InCl6:Sb3+ perovskite with photochromism and reversed thermochromism is developed for repeatable information writing and erasing. The original Cs3InCl6:Sb3+ perovskite synthesized by a modified hot‐injection method exhibits green photoluminescence (PL), which is caused by recombination of self‐trapped excitons. After treating with ultrasonication and heating, the green PL gradually turns to blue emission, which is related to surficial Cl vacancies that are generated or exposed due to the desorption of surfactants. Under continuous UV light irradiation, due to the photo repairing effect, the blue emission gradually vanishes, the fluorescent color recovers to green. Based on this photochromic effect, fluorescent patterns are drawn by UV exposure with mask. Moreover, the green PL color can again return to blue by heating at 100 °C. Thus, the photochromism‐induced fluorescent patterns can be simply erased based on the reversed thermochromism effect. Therefore, repeatable optical information writing and thermal erasure are demonstrated based on reversible PL change of Cs3InCl6:Sb3+. [ABSTRACT FROM AUTHOR]

Published
2024
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19. High-Contrast Optical Coherence Tomography Angiography Based on Normalized Complex Decorrelation

Author

Shi, Junpeng, Guo, Zixian, Dong, Chunyu, Xing, Fangjian, Di, Yunsong, Gan, Zhixing, Liu, Cihui, Liu, Jianhua, and Zhu, Hui

Abstract

In this letter, a Sigmoid-shaped curve is proposed to enhance the contrast between blood vessels and static tissue in optical coherence tomography angiography. Different from the conventional parabolic curve, the Sigmoid-shaped function biases the decorrelation histogram towards both ends, which suppresses the static tissue background as well as enhances the flow signal in the blood vessels region. An intensity mask is generated to remove the decorrelation signal at the noise level and then the filtering method is used to improve the image quality. A white diffuse plate has been used and verified to remove the static background deeper when our method is applied, and the z-axis range of static signal increases from $27.3~\mu $ m to $31.9~\mu $ m, indicating the extent of decorrelation has been improved by 17%. We demonstrate that the contrast of vascular image of the mouse ear has been improved from 32.6 to 43.1, compared with the conventional decorrelation method.

Published
2024
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21. Bioinspired hierarchical colloidal crystal paper with Janus wettability for oil/water separation and heavy metal ion removal

Author

Zhang, Lihao, primary, Chen, Yufei, additional, Cao, Yue, additional, Li, Sunlong, additional, Lu, Weipeng, additional, Cao, Wei, additional, Zhu, Jialiang, additional, Bao, Weiting, additional, Shao, Ming, additional, Gan, Zhixing, additional, Di, Yunsong, additional, Xing, Fangjian, additional, Li, Xiang, additional, Zhang, Liang, additional, and Liu, Cihui, additional

Published
2023
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40. Laser‐Triggered Vapor‐Phase Anion Exchange on All‐Inorganic Perovskites for Multicolor Patterns and Microfabrications.

Author

Sheng, Yuhang, Zha, Yanfang, Feng, Xuying, Xing, Fangjian, Di, Yunsong, Liu, Cihui, Zhang, Xiaowei, and Gan, Zhixing

Subjects
PEROVSKITE, VISIBLE spectra, ANIONS, EXCHANGE reactions, MICROFABRICATION, FLUORESCENCE
Abstract

Anion exchange reaction is a facile postsynthesis approach to modulate the bandgaps of perovskites to meet the demands in full visible spectrum. However, conventional anion exchanges are usually conducted in solutions, limiting their applications in fabricating high‐quality blue‐emitting perovskites and multicolor fluorescent patterns. Herein, a laser‐triggered vapor‐phase anion exchange (LTVAE) method is developed to convert CsPbBr3 perovskites with different morphologies (nanocrystal films/solution, microcrystals, and microplatelets) into CsPb(BrxCl1‐x)3 and CsPb(BrxI1‐x)3 perovskites. Thus, the green fluorescence is converted into blue and red fluorescence. Moreover, the deep‐blue fluorescence obtained by LTVAE shows a high quantum yield (QY) of 67.2%. Based on the mask‐assistant LTVAE, multicolor fluorescent patterns are fabricated, which are very significant for anticounterfeit and multicolor displays. Furthermore, a polymer‐assistant LTVAE method is developed to improve the stability of the multicolor fluorescent patterns. More importantly, micro‐heterojunctions with two different fluorescent colors are successfully constructed on a single CsPbBr3 microplatelet, which paves the way for microfabrications. [ABSTRACT FROM AUTHOR]

Published
2023
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45. Structural characterizations on the degradation of 2D organicâ€"inorganic hybrid perovskites and its enlightenment to improved stability.

Author

Zha, Yanfang, Wang, Yun, Sheng, Yuhang, Wu, Shuyi, Zhang, Jinlei, Ma, Kewei, Yang, Lun, Liu, Cihui, Di, Yunsong, and Gan, Zhixing

Subjects
PEROVSKITE, SOLAR cells, CHEMICAL decomposition, ENLIGHTENMENT, PHOTOVOLTAIC power systems, CHEMICAL reactions
Abstract

Despite the demonstrated high-efficiency of solar cells and light-emitting devices based on two-dimensional (2D) perovskites, intrinsic stability of the 2D perovskites is yet far from satisfactory. In this work, we find the 2D (BA)2PbI4 perovskite crystals rapidly degrade in the ambient conditions and the photoluminescence (PL) nearly completely quenches in 6 d. Moreover, the PL shoulder band due to defects and absorption band of PbI2 gradually rise during degradation, suggesting the precipitation of PbI2. Besides, rod structures are observed in the degraded crystals, which are attributed to the formation of one-dimensional (1D) (BA)3PbI5 perovskites. And the degradation can be largely retarded by decreasing the humidity during storage. Therefore, a chemical reaction for the degradation of (BA)2PbI4 is proposed, revealing the interactions between water molecules and undercoordinated defects are very critical for understanding the degradation. Enlightened by these findings, dimethyl itaconate (DI) treatment is developed to passivate the defects and block the intrusion of moisture to improve the stability of the (BA)2PbI4. After storage in the ambient environment for 16 d, the DI treated (BA)2PbI4 only shows a slight surface degradation without formation of any nanorod-like structures, and the PL intensity retains about 70%. Therefore, our systematic study provides a comprehensive understanding on the degradation dynamics of 2D perovskites, which will promote future development of intrinsically stable 2D perovskites. [ABSTRACT FROM AUTHOR]

Published
2022
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46. Growth and Optical Properties of Lead‐Free Cs3Bi2Br9 Perovskite Microplatelets.

Author

Deng, Fang, Zhang, Jinlei, Wu, Shuyi, Liu, Cihui, Xing, Fangjian, Xu, Jiaqing, Di, Yunsong, Yu, Liyan, Dong, Lifeng, and Gan, Zhixing

Subjects
OPTICAL properties, OPTICAL resonance, WHISPERING gallery modes, OPTICAL resonators, RAMAN scattering
Abstract

Lead‐free halide perovskites are drawing increasing interest due to their environmental friendliness, good thermal stabilities, and unique optoelectronic properties. Herein, a simple and rapid wet‐chemical approach is developed to synthesize the lead‐free Cs3Bi2Br9 microplatelets (MPs) with regular hexagonal shapes (side length of ≈5–12 μm). A strong photoluminescence (PL) emission located at 425 nm and a very weak PL band located at 576 nm are observed, which are ascribed to the intrinsic band‐edge transition and the emissive deep level defects, respectively. The weak emission at 576 nm implies the good crystalline quality of the as‐prepared Cs3Bi2Br9 MPs. Spatially resolved PL and Raman mappings exhibit inhomogeneous distributions. Both the PL emissions and Raman scatterings at the edges are remarkably stronger than those at the center, which are interpreted by the formation of whispering‐gallery modes (WGMs) due to the optical resonance of cavity, as supported by our finite‐difference time‐domain (FDTD) simulations. Therefore, the hexagonal Cs3Bi2Br9 MPs can act as optical cavities, which will play important roles in micro‐waveguides and micro‐lasers that are significant for the development of integrated photonic chips. [ABSTRACT FROM AUTHOR]

Published
2022
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