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5. Tuning Perovskite Nanocrystal Synthesis via Amphiphilic Block Copolymer Templates and Solvent Interactions

Author

Sun, Ya-Sen, Wu, Kuan-Wei, and Shih, Orion

Abstract

Amphiphilic block copolymer (a-BCP) micelles offer morphological diversity and dimensional tunability, making them suitable for the fabrication of perovskite nanocrystals. However, precise control over the nucleation and growth of perovskite nanocrystals using a-BCP colloidal templates remains underexplored. This study investigates the effects of toluene, methanol, and polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) on the formation of cesium lead bromide (CsPbBr3) nanocrystals. The process involves four stages: (i) PS-b-P2VP micellization, (ii) PbBr2complexation, (iii) coordination interaction with P2VP, and (iv) burst nucleation of CsPbBr3nanocrystals. Toluene, a good solvent for PS but a nonsolvent for P2VP, PbBr2, and CsBr, facilitates the formation of PS-b-P2VP spherical micelles. Adding PbBr2to these micelles in toluene results in multiple emulsion, dispersing PbBr2microstructures (microemulsion) and forming [PbBr3]−complexes encapsulated by the micelles (nanoemulsion). Prolonged stirring enhances this nanoemulsion. CsBr, insoluble in toluene, must be dissolved in methanol before being mixed with micelle-encapsulated complexes, promoting quick crystal nucleation. However, excess methanol weakens micellization, leading to the formation of fused micelles and irregular nanocrystals. At a high methanol content, [PbBr4]2–complexes also form, driving CsPbBr3to CsPb2Br5transformation via Ostwald ripening, resulting in large CsPb2Br5microcrystals that precipitate due to gravitational forces overcoming Brownian motion, destabilizing their dispersion in the solution.

Published
2024
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12. Analysis of factors affecting KOH protein solubility of cottonseed meal.

Author

SUN Ya-sen, HAN Wen-jie, WANG Ru-nan, and ZHANG Yang

Subjects
*COTTONSEED meal, *COTTONSEED, *FACTOR analysis, *SOLUBILITY, *DENATURATION of proteins, *SEED proteins, *SOLVENT extraction
Abstract

The experiment was to analysis the factors affecting KOH protein solubility of cottonseed meal. The factors affecting the solubility of KOH protein in the processing process of low-temperature cottonseed meal were studied by laboratory experiment and production practice. The results showed that the main loss of KOH protein solubility in the stages of degreasing, dephenolization, drying and evaporation. In the laboratory experiment stage, the countercurrent extraction method had higher solubility than soaking method, and the extraction temperature cannot exceed 55 °. The long-term storage of dephenolization solution had higher solubility to KOH protein of the material. In the process of production, the solubility of KOH protein could be improved by increasing the concentration of new methanol and circulating liquid as far as possible under the condition that gossyrol was qualified. In the drying stage to improve the 1#-3# pan dryer drying temperature, reduce the effect of organic solvents on material protein denaturation. The direct steam pressure and the temperature of the four layers of the evaporator should be reduced as far as possible in the evaporation and drying stage, to reduce the influence of hot and humid steam on the solubility of KOH protein of the material. With the increase of storage time, the solubility of KOH protein of cotton seeds and cotton embryos decreased, but the decrease was not large. The study indicates that higher KOH protein solubility of cottonseed meal could be obtained by selecting fresh raw materials, adopting countercurrent extraction and strictly controlling the technological parameters of solvent extraction. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Chain Length Effects of Added Homopolymers on the Phase Behavior in Blend Films of a Symmetric, Weakly Segregated Polystyrene-block-poly(methyl methacrylate)

Author

Hong, Jia-Wen, primary, Chang, Jung-Hong, additional, Hung, Hsiang-Ho, additional, Liao, Yin-Ping, additional, Jian, Yi-Qing, additional, Chang, Iris Ching-Ya, additional, Huang, Tzu-Yen, additional, Nelson, Andrew, additional, Lin, I-Ming, additional, Chiang, Yeo-Wan, additional, and Sun, Ya-Sen, additional

Published
2022
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40. Effects of Graphitization and Bonding Configuration in Iron–Nitrogen-Doped Carbon Nanostructures on Surface-Enhanced Raman Scattering.

Author

Chang, Iris Ching-Ya, Sun, Ya-Sen, Yang, Yaw-Wen, Wang, Chia-Hsin, Cheng, Shao-Liang, and Hu, Wei-Wen

Abstract

The development of carbon materials as highly efficient and durable substrates for surface-enhanced Raman scattering (SERS) is of great importance for realizing practical application of molecular sensing through Raman spectroscopy. In this report, we demonstrate the fabrication, by low-temperature pyrolysis, of high-quality, iron–nitrogen-doped carbon nanosheets and nanorods from spin-coated poly-(4-vinylpyridine) (P4VP) polymer thin films and electrospun polymer nanofibers, respectively. As P4VP chains have functional pyridine rings available to bind with metal precursor ions through favorable interactions, iron (Fe) atoms can be incorporated into the carbon nanostructures with the aid of Fe-(II) acetate during the synthesis. The incorporation of a metal salt can decrease the thermal stability of pyridinic groups so that the pyrolysis produces carbon nanostructures with high degree of graphitization and with iron- and nitrogen-doped species. The codopants in these carbon nanostructures introduce surface dipole moments, affect the DOS of valence bands, and decrease the work function. The electronic structure of carbon nanomaterials can be finely tuned to enable the vibronic coupling of the conduction band and valence band states of carbon nanostructures with the excited and ground states of the probed molecules of Rhodamine 6G and crystal violet. The vibronic coupling enables a superior enhancement in SERS with the detection limit concentration being as low as 10–7 M and the maximum enhancement factor being 3.8 × 104 through a charge transfer (CT) process. The polymer-templated carbon nanostructures offer great promise for the implementation of this system in a next-generation SERS substrate for molecular sensing. [ABSTRACT FROM AUTHOR]

Published
2020
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46. Membranes with Highly Ordered Straight Nanopores by Selective Swelling of Fast Perpendicularly Aligned Block Copolymers

Author

Yin, Jun, Yao, Xueping, Liou, Jiun-You, Sun, Wei, Sun, Ya-Sen, and Wang, Yong

Abstract

Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In this work, we reported on an extremely simple and efficient strategy to produce such well-defined membranes. We demonstrated that neutral solvents were capable of annealing amphiphilic block copolymer (BCP) films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with thicknesses up to 600 nm to the perpendicular orientation within 1 min. Annealing in neutral solvents was also effective to the perpendicular alignment of block copolymers with very high molecular weights, e.g., 362 000 Da. Remarkably, simply by immersing the annealed BCP films in hot ethanol followed by drying in air, the originally dense BCP films were nondestructively converted into porous membranes containing highly ordered, straight nanopores traversing the entire thickness of the membrane (up to 1.1 μm). Grazing incident small-angle X-ray spectroscopy confirmed the hexagonal ordering of the nanopores over large areas. We found that the overflow of P2VP chains from their reservoir P2VP cylinders and the deformation of the PS matrix in the swelling process contributed to the transformation of the solid P2VP cylinders to empty straight pores. The pore diameters can be tuned by either changing the swelling temperatures or depositing thin layers of metal oxides on the preformed membranes viaatomic layer deposition with a subnanometer accuracy. To demonstrate the application of the obtained porous membranes, we used them as templates and produced centimeter-scale arrays of aligned nanotubes of metal oxides with finely tunable wall thicknesses.

Published
2024
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