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Shi W, Guan L, Ren X, Zhang J, Luo T, Liu C, Lan Y, Chen Z, Chen X, Li X. Effect of aggregation configuration of molecular fluorophore CZA on photoluminescence properties of carbon dots. J Colloid Interface Sci 2024; 659:213-224. [PMID: 38176231 DOI: 10.1016/j.jcis.2023.12.058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/03/2023] [Accepted: 12/09/2023] [Indexed: 01/06/2024]
Abstract
The effect of aggregation configuration of molecular fluorophore citrazinic acid (CZA) on the photoluminescence (PL) properties of carbon dots (CDs) has been investigated using first-principles method. The structural stability of all aggregates has been analyzed, and the results show that the most stable structures are J-type CZA aggregates with head-to-tail configurations and the CZA/CD aggregates are bonded by replacing H atoms on the CD edges with de-OH from the pyridine ring of CZA. The luminescent properties of CZA/CD aggregates are mainly affected by the binding modes and binding sites. When the sites belong to electron-donating groups, electron-withdrawing groups or sp2 domain, the PL spectra of CDs are shifted and the luminescent intensities are significantly enhanced. The results suggest that covalently bonded CZA/CD aggregates are responsible for the high fluorescence quantum yield of CD. Moreover, the distance between the centers of the two pyridine rings in H-type CZA dimers less than 3.5 Å is prone to π-π stacking, leading to fluorescence quenching of aggregates. The present work is helpful in understanding the effect of molecular fluorophores on the PL properties of CDs and provides theoretical guidance for the controllable synthesis of CDs.
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Affiliation(s)
- Weicai Shi
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Li Guan
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China.
| | - Xiaojie Ren
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Jianen Zhang
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Tao Luo
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Chunzhi Liu
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Youshi Lan
- Department of Radiochemistry, China Institute of Atomic Energy, Beijing 102413, PR China
| | - Zhijuan Chen
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China
| | - Xiaobo Chen
- Division of Energy, Matter, and Systems, School of Science and Engineering, University of Missouri - Kansas City, KS, MO 64110, United States.
| | - Xu Li
- Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China.
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Olla C, Cappai A, Porcu S, Stagi L, Fantauzzi M, Casula MF, Mocci F, Corpino R, Chiriu D, Ricci PC, Carbonaro CM. Exploring the Impact of Nitrogen Doping on the Optical Properties of Carbon Dots Synthesized from Citric Acid. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1344. [PMID: 37110929 PMCID: PMC10141696 DOI: 10.3390/nano13081344] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/07/2023] [Accepted: 04/09/2023] [Indexed: 06/19/2023]
Abstract
The differences between bare carbon dots (CDs) and nitrogen-doped CDs synthesized from citric acid as a precursor are investigated, aiming at understanding the mechanisms of emission and the role of the doping atoms in shaping the optical properties. Despite their appealing emissive features, the origin of the peculiar excitation-dependent luminescence in doped CDs is still debated and intensively being examined. This study focuses on the identification of intrinsic and extrinsic emissive centers by using a multi-technique experimental approach and computational chemistry simulations. As compared to bare CDs, nitrogen doping causes the decrease in the relative content of O-containing functional groups and the formation of both N-related molecular and surface centers that enhance the quantum yield of the material. The optical analysis suggests that the main emission in undoped nanoparticles comes from low-efficient blue centers bonded to the carbogenic core, eventually with surface-attached carbonyl groups, the contribution in the green range being possibly related to larger aromatic domains. On the other hand, the emission features of N-doped CDs are mainly due to the presence of N-related molecules, with the computed absorption transitions calling for imidic rings fused to the carbogenic core as the potential structures for the emission in the green range.
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Affiliation(s)
- Chiara Olla
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Antonio Cappai
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Stefania Porcu
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Luigi Stagi
- Laboratory of Materials Science and Nanotechnology, CR-INSTM, Department of Chemical, Physics, Mathematics and Natural Sciences, University of Sassari, Via Vienna 2, 07100 Sassari, Italy
| | - Marzia Fantauzzi
- Department of Chemistry and Geological Science, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Maria Francesca Casula
- Department of Mechanical, Chemical, and Materials Engineering, CINSA and INSTM, University of Cagliari, Via Marengo 2, I-09123 Cagliari, Italy
| | - Francesca Mocci
- Department of Chemistry and Geological Science, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Riccardo Corpino
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Daniele Chiriu
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Pier Carlo Ricci
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
| | - Carlo Maria Carbonaro
- Department of Physics, University of Cagliari, Cittadella Universitaria, I-09042 Monserrato, Italy
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