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Zhou J, Ma F, Chen K, Zhao W, Yang R, Qiao C, Shen H, Su WS, Lu M, Zheng Y, Zhang R, Chen L, Wang S. The luminescence mechanism of ligand-induced interface states in silicon quantum dots. NANOSCALE ADVANCES 2023; 5:3896-3904. [PMID: 37496620 PMCID: PMC10368006 DOI: 10.1039/d3na00251a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 06/17/2023] [Indexed: 07/28/2023]
Abstract
Over decades of research on photoluminescence (PL) of silicon quantum dots (Si-QDs), extensive exploratory experiments have been conducted to find ways to improve the photoluminescence quantum yield. However, the complete physical picture of Si-QD luminescence is not yet clear and needs to be studied in depth. In this work, which considers the quantum size effect and surface effect, the optical properties of Si-QDs with different sizes and surface terminated ligands were calculated based on first principles calculations. The results show that there are significant differences in the emission wavelength and emission intensity of Si-QD interface states connected by different ligands, among which the emission of silicon-oxygen double bonds is the strongest. When the size of the Si-QD increases, the influence of the surface effect weakens, and only the silicon-oxygen double bonds still localize the charge near the ligand, maintaining a high-intensity luminescence. In addition, the presence of surface dangling bonds also affects luminescence. This study deepens the understanding of the photoluminescence mechanism of Si-QDs, and provides a direction for both future improvement of the photoluminescence quantum efficiency of silicon nanocrystals and for fabricating silicon-based photonic devices.
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Affiliation(s)
- Jian Zhou
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Fengyang Ma
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Kai Chen
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Wuyan Zhao
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Riyi Yang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Chong Qiao
- School of Mathematics and Physics, Nanyang Institute of Technology Nanyang 473004 China
| | - Hong Shen
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Wan-Sheng Su
- National Taiwan Science Education Center Taipei 111081 Taiwan
- Department of Electro-Optical Engineering, National Taipei University of Technology Taipei 106344 Taiwan
- Department of Physics, National Sun Yat-sen University Kaohsiung 804201 Taiwan
| | - Ming Lu
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Yuxiang Zheng
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
- Yiwu Research Institute of Fudan University Chengbei Road Yiwu City 322000 Zhejiang China
| | - Rongjun Zhang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
- Yiwu Research Institute of Fudan University Chengbei Road Yiwu City 322000 Zhejiang China
| | - Liangyao Chen
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
| | - Songyou Wang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Center, Department of Optical Science and Engineering, Fudan University Shanghai 200433 China
- Yiwu Research Institute of Fudan University Chengbei Road Yiwu City 322000 Zhejiang China
- Key Laboratory for Information Science of Electromagnetic Waves (MoE) Shanghai 200433 China
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Wu C, Zhang S, Zheng Y, Wang A, Zhao Q, Sun W, Liu W, Long C, Wang Q. Solvent-Type Passivation Strategy Controls Solid-State Self-Quenching-Resistant Behavior in Sulfur Dots. Inorg Chem 2022; 61:21157-21168. [PMID: 36520141 DOI: 10.1021/acs.inorgchem.2c04002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Treatment of sulfur dots with polyethylene glycol (PEG) has been an efficient way to achieve a high luminescence quantum yield, and such a PEG-related quantum dot (QD)-synthesis strategy has been well documented. However, the polymeric insulating capping layer acting as the "thick shell" will significantly slow down the electron-transfer efficiency and severely hamper its practical application in an optoelectric field. Especially, the employment of synthetic polymers with long alkyl chains or large molecular weights may lead to structural complexity or even unexpected changes of physical characteristics for QDs. Therefore, in sulfur dot preparation, it is a breakthrough to use short-chain molecular species to replace PEG for better control and reproducibility. In this article, a solvent-type passivation (STP) strategy has been reported, and no PEG or any other capping agent is required. The main role of the solvent, ethanol, is to directly react with NaOH, and the generated sodium ethoxide passivates the surface defects. The afforded STP-enhanced emission sulfur dots (STPEE-SDs) possess not only the self-quenching-resistant feature in the solid state but also the extension of fluorescence band toward the wavelength as long as 645 nm. The realization of sulfur dot emission in the deep-red region with a decent yield (8.7%) has never been reported. Moreover, a super large Stokes shift (300 nm, λex = 345 nm, λem = 645 nm) and a much longer decay lifetime (109 μs) have been found, and such values can facilitate to suppress the negative influence from background signals. Density functional theory demonstrates that the surface passivation via sodium ethoxide is dynamically favorable, and the spectroscopic insights into emission behavior could be derived from the passivation effect of the sulfur vacancy as well as the charge-transfer process dominated by the highly electronegative ethoxide layer.
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Affiliation(s)
- Chuqiao Wu
- School of Chemistry, Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, South China Normal University, Guangzhou510006, China
| | - Shuting Zhang
- Department of Pharmacy, Huizhou Health Sciences Polytechnic, Huizhou516025, China
| | - Yuhui Zheng
- School of Chemistry, Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, South China Normal University, Guangzhou510006, China
| | - Aiqi Wang
- Department of Pharmacy, Huizhou Health Sciences Polytechnic, Huizhou516025, China
| | - Qiming Zhao
- School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan411201, China
| | - Wenjie Sun
- School of Chemistry, Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, South China Normal University, Guangzhou510006, China
| | - Wanqiang Liu
- School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan411201, China
| | - Chenggang Long
- Ruide Technologies (Foshan) Inc, Foshan, Guangdong528311, China
| | - Qianming Wang
- School of Chemistry, Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, South China Normal University, Guangzhou510006, China
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