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Impacts of structural asymmetry on the magnetic response of excitons and biexcitons in single self-assembled In(Ga)As quantum rings
(2009-08-01)
Lin, Ta-Chun
;
Lin, Chia-Hsien
;
Ling, Hong-Shi
;
Fu, Ying-Jhe
;
Chang, Wen-Hao
The diamagnetic shifts of neutral excitons and biexcitons confined in single self-assembled In(Ga)As/GaAs quantum rings are investigated. Unlike quantum dots, quantum rings reveal a considerably large biexciton diamagnetic shift, about two times larger than that of single excitons. Based on model calculations, we found that the inherent structural asymmetry and imperfection, combined with the interparticle Coulomb interactions, is the fundamental cause of the more extended biexciton wave function in the quantum rings. The exciton wave function tends to be localized in one of the potential valleys induced by structural imperfections of the quantum ring due to the strong localization of hole and the electron-hole Coulomb attraction, resembling the behavior in single dots. Our results suggest that the phase coherence of neutral excitons in quantum rings will be smeared out by such wave function localizations.
以無機分子改質雙性機丁聚糖之自組裝混成複合材料及其生醫特性之研究
(2009)
劉典謨
;
Liu Dean-Mo
;
國立交通大學材料科學與工程學系(所)
幾丁聚醣(chitosan)為直鏈多糖體，是廣泛應用在醫學、藥學、化學分離、環境工程等領域的天然高分子；幾丁聚醣具備生物相容性、生物可降解性、無毒等性質，但是他難溶於中性溶劑，因此限制了其發展潛力。隨著合成化學的進步，將有機官能基作疏水性改質已有效合成兩性衍生物，也常運用作藥物載體、組織工程的支架等，現有許多研究在幾丁聚醣中加入無機物，也致力發展有別於一般合成化學、材料化學、膠體化學、醫學、生物科技等想法的創新思維。因此，利用有機無機複合物增加材料效能和特殊性質也更顯重要。本實驗室在幾丁聚醣的骨架上利用親水性羧甲基酸 (carboxymethyl)和疏水性己醯基(hexanoyl)作幾丁聚醣的雙配位基改質，成功合成出兩性幾丁聚醣，稱作CHC。CHC 可透過自組裝形成奈米顆粒或是中空的奈米微胞，也可控制其尺寸和疏水程度。藉由控制CHC 的化學親和力，可以調控包覆不同性質的藥物，以用做特殊醫療效果。另外，越來越多的技術和研究截取無機配位基的優點，製備出多功能複合材料，這也是此次計畫的中心思想。因此，接下來我們將進一步用無機配位基，如矽烷、氧化鐵做分子內改質。值得一提的本實驗室已經合成出新的無機兩性CHC 複合物，且初步觀察到次奈米的形貌結構，我們可以樂觀地預期無機CHC 複合物具前瞻性的應用價值，且本研究計畫將深入探討此複合材料的化學、物理、生醫特性並提供一個有效可行的合成方法。
Characteristics of emission polarization in a-plane nanorods embedded with InGaN/GaN multiple quantum wells
(2010-09-15)
Li, J. C.
;
Lu, T. C.
;
Huang, H. M.
;
Chan, W. W.
;
Kuo, H. C.
Nonpolar (a-plane) GaN nanorod arrays with embedded In(x)Ga(1-x)N/GaN (x=0.09, 0.14, 0.24, and 0.30) multiple quantum wells (MQWs) grown on r-plane sapphire have been fabricated successfully by self-assembled Ni nanomasks and subsequent inductively coupled plasma reactive-ion etching. After nanorod fabrications, the polarization ratio of the emission from MQWs with lower indium composition (x=0.09 and 0.14) slightly decreases but apparently increases by at most 79% for the samples with higher indium composition (x=0.24 and 0.30). Competition between the effect of multiple scattering, strain relaxation and reduction in localized centers, expected in a-plane MQW samples, are attributed to the variations in the polarization ratios after the nanorod formation. (c) 2010 American Institute of Physics. [doi:10.1063/1.3483239]
Three-Dimensional Block Copolymer Nanostructures by the Solvent-Annealing-Induced Wetting in Anodic Aluminum Oxide Templates
(2014-09-01)
Chu, Chiang-Jui
;
Chung, Pei-Yun
;
Chi, Mu-Huan
;
Kao, Yi-Huei
;
Chen, Jiun-Tai
Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this work, the fabrication and morphologies of three-dimensional polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures confined in the nanopores of anodic aluminum oxide (AAO) templates are studied. It is discovered that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates (SAINT) method. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b -PDMS nanostructures can be controlled by changing the wetting conditions. Different solvents are used as the annealing solvent, including toluene, hexane, and a co-solvent of toluene and hexane. When the block copolymer wets the nanopores in toluene vapors, a perpendicular morphology is observed. When the block copolymer wets the nanopores in co-solvent vapors (toluene/hexane = 3:2), unusual circular and helical morphologies are obtained. These three-dimensional nanostructures can serve as naontemplates for refilling with other functional materials, such as Au, Ag, ZnO, and TiO2.
Intramolecular Interactions of a Phenyl/Perfluorophenyl Pair in the Formation of Supramolecular Nanofibers and Hydrogels
(2014-02-10)
Hsu, Shu-Min
;
Lin, Yu-Chun
;
Chang, Jui-Wen
;
Liu, Yu-Hao
;
Lin, Hsin-Chieh
A new system for the incorporation of a phenyl/perfluorophenyl pair in the structure of a peptide hydrogelator was developed. The strategy is based on the idea that the integration of an end-capped perfluorophenyl group and a phenylalanine with a phenyl moiety in the side chain forms an intramolecular phenyl/perfluorophenyl pair, which can be used to promote the formation of the supramolecular nanofibers and hydrogels. This work illustrates the importance of structure-hydrogelation relationship and provides new insights into the design of self-assembly nanobiomaterials.
Self-supporting Polymer from a POSS Derivative
(2011-06-16)
Cheng, Chih-Chia
;
Yen, Ying-Chieh
;
Chang, Feng-Chih
;
應用化學系
;
Department of Applied Chemistry
A new polyhedral oligomeric silsesquioxane macromer, octakis[N-(6-aminopyridin-2-yl)-undecanamide-10-dimethyl-siloxy]silsesquioxane (POSS-C11-Py), containing eight diaminopyridine arms, is able to self-assemble to form a physically crosslinked polymer-like structure with good mechanical properties (tensile strength = 46.1 MPa, tensile modulus = 0.58 GPa, elongation = 49.3%) through quadruple hydrogen bonding interactions between these arms. POSS-C11-Py is the first organic/inorganic supermolecule possessing polymer-like mechanical properties as a result of self-complementary interactions, providing a potential route toward the design and fabrication of polymer-like supramolecular materials.
Influences of the Non-Covalent Interaction Strength on Reaching High Solid-State Order and Device Performance of a Low Bandgap Polymer with Axisymmetrical Structural Units
(2013-05-07)
Jheng, Jyun-Fong
;
Lai, Yu-Ying
;
Wu, Jhong-Sian
;
Chao, Yi-Hsiang
;
Wang, Chien-Lung
A high organic field-effect transistor mobility (0.29 cm(2)V(-1)s(-1)) and bulk-heterojunction polymer solar cell performance (PCE of 6.82%) have been achieved in a low bandgap alternating copolymer consisting of axisymmetrical structural units, 5,6-difluorobenzo-2,1,3-thiadiazole. Introducing the fluorine substituents enhanced intermolecular interaction and improved the solid-state order, which consequently resulted in the highest device performances among the 2,1,3-thiadiazole-quarterthiophene based alternating copolymers.
A Supramolecular "Double-Cable" Structure with a 129(44) Helix in a Columnar Porphyrin-C-60 Dyad and its Application in Polymer Solar Cells
(2012-11-01)
Wang, Chien-Lung
;
Zhang, Wen-Bin
;
Sun, Hao-Jan
;
Van Horn, Ryan M.
;
Kulkarni, Rahul R.
A novel porphyrin-C-60 dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C-60)] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 degrees C with a latent heat (Delta H) of 18.5 kJ mol(-1). The phase formation is majorly driven by the cooperative intermolecular PorPor and C60C60 interactions. Structural analysis reveals that this stable phase possesses a supramolecular double-cable structure with one p-type Por core columnar channel and three helical n-type C-60 peripheral channels. These double-cable columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, alpha = beta = 90 degrees and gamma = 120 degrees. The column repeat unit is determined to possess a 129(44) helix. With both donor (D; Pro) and acceptor (A; C-60) units having their own connecting channels as well as the large D/A interface within the supramoleculassr double-cable structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]-phenyl-C-61-butyric acid methyl ester. A phase-separated columnar morphology is observed in a bulk-heterojunction (BHJ) material made by the physical blend of a low band-gap conjugated polymer, [poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothia-diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.
Hierarchical Superstructures with Control of Helicity from the Self-Assembly of Chiral Bent-Core Molecules
(2012-07-01)
Lin, Shih-Chieh
;
Ho, Rong-Ming
;
Chang, Chin-Yen
;
Hsu, Chain-Shu
;
應用化學系
"Herein, two asymmetric chiral bent-core molecules, 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1R)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7R) and 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1S)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7S), were synthesized to demonstrate control of the helicity of their self-assembled hierarchical superstructures. Mirror-imaged CD spectra showed a split-type Cotton effect after the formation of self-assembled aggregates of BC7R and BC7S, thereby suggesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical ribbons with preferential helicity that corresponded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The formation of helical ribbons was attributed to the merging of twisted ribbons through an increase in width to improve morphological stability. As a result, control of the helicity of hierarchical superstructures from the self-assembly of bent-core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale."
Synthesis and applications of a novel supramolecular polymer network with multiple H-bonded melamine pendants and uracil crosslinkers
(2012-03-01)
Patra, Dhananjaya
;
Ramesh, Mohan
;
Sahu, Duryodhan
;
Padhy, Harihara
;
Chu, Chih-Wei
A conjugated main-chain copolymer (PBT) consisting of bithiazole, dithieno[3,2-b:2',3'-d]pyrroles (DTP), and pendent melamine units was synthesized by Stille polymerization, which can be hydrogen-bonded (H-bonded) with proper molar amounts of bi-functional p-conjugated crosslinker F (i.e., two uracil motifs covalently attached to a fluorene core through triple bonds symmetrically) to develop a novel supramolecular polymer network (PBT/F). The effects of multiple H-bonds on light harvesting capabilities, HOMO levels, and photovoltaic properties of polymer PBT and H-bonded polymer network PBT/F are investigated. The formation of supramolecular polymer network (PBT/F) between PBT and F was confirmed by FTIR and XRD measurements. Because of the stronger light absorption, lower HOMO level, and higher crystallinity of H-bonded polymer network PBT/F, the solar cell device containing PBT/F showed better photovoltaic properties than that containing polymer PBT. The preliminary results show that the solar cell device containing 1:1 weight ratio of PBT/F and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) offers the best power conversion efficiency (PCE) value of 0.86% with a short-circuit current density (Jsc) of 4.97 mA/cm2, an open circuit voltage (Voc) of 0.55 V, and a fill factor (FF) of 31.5%. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

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