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1.
Clive Eley Tong Li Fenglin Liao Simon Michael Fairclough Jason M. Smith George Smith Shik Chi Edman Tsang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(30):7972-7976
A series of highly efficient semiconductor nanocrystal (NC) photocatalysts have been synthesized by growing wurtzite‐ZnO tetrahedrons around pre‐formed CdS, CdSe, and CdTe quantum dots (QDs). The resulting contact between two small but high‐quality crystals creates novel CdX/ZnO heterostructured semiconductor nanocrystals (HSNCs) with extensive type‐II nanojunctions that exhibit more efficient photocatalytic decomposition of aqueous organic molecules under UV irradiation. Catalytic testing and characterization indicate that catalytic activity increases as a result of a combination of both the intrinsic chemistry of the chalcogenide anions and the heterojunction structure. Atomic probe tomography (APT) is employed for the first time to probe the spatial characteristics of the nanojunction between cadmium chalcogenide and ZnO crystalline phases, which reveals various degrees of ion exchange between the two crystals to relax large lattice mismatches. In the most extreme case, total encapsulation of CdTe by ZnO as a result of interfacial alloying is observed, with the expected advantage of facilitating hole transport for enhanced exciton separation during catalysis. 相似文献
2.
Nanojunction‐Mediated Photocatalytic Enhancement in Heterostructured CdS/ZnO,CdSe/ZnO,and CdTe/ZnO Nanocrystals
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Clive Eley Dr. Tong Li Fenglin Liao Dr. Simon Michael Fairclough Dr. Jason M. Smith Prof. George Smith Prof. Shik Chi Edman Tsang 《Angewandte Chemie (International ed. in English)》2014,53(30):7838-7842
A series of highly efficient semiconductor nanocrystal (NC) photocatalysts have been synthesized by growing wurtzite‐ZnO tetrahedrons around pre‐formed CdS, CdSe, and CdTe quantum dots (QDs). The resulting contact between two small but high‐quality crystals creates novel CdX/ZnO heterostructured semiconductor nanocrystals (HSNCs) with extensive type‐II nanojunctions that exhibit more efficient photocatalytic decomposition of aqueous organic molecules under UV irradiation. Catalytic testing and characterization indicate that catalytic activity increases as a result of a combination of both the intrinsic chemistry of the chalcogenide anions and the heterojunction structure. Atomic probe tomography (APT) is employed for the first time to probe the spatial characteristics of the nanojunction between cadmium chalcogenide and ZnO crystalline phases, which reveals various degrees of ion exchange between the two crystals to relax large lattice mismatches. In the most extreme case, total encapsulation of CdTe by ZnO as a result of interfacial alloying is observed, with the expected advantage of facilitating hole transport for enhanced exciton separation during catalysis. 相似文献
3.
Cytotoxicity of nanoparticle-loaded polymer capsules 总被引:1,自引:0,他引:1
Cytotoxic effects of micrometer-sized polymer capsules composed out of alternating layers of polystyrenesulfonate (PSS) and polyallylamine hydrochloride (PAH) on a fibroblast cell line have been investigated with an adhesion assay. For the purpose of visualization with fluorescence nanometer-sized CdTe nanoparticles have been embedded in the walls of the capsules. Similar to free CdTe nanoparticles, toxic Cd-ions are also released from CdTe nanoparticles that have been embedded in capsules. At high capsule concentrations, the capsules start to sediment on top of the cells and thus impair cell viability. 相似文献
4.
Jagadeesh B Prabhakar A Sarma GD Chandrasekhar S Chandrashekar G Reddy MS Jagannadh B 《Chemical communications (Cambridge, England)》2007,(4):371-373
Residue based control of specific helical folding is explored in hybrid peptide oligomers consisting of alternating L-Ala and cis-beta-furanoid sugar amino acid (FSAA) residues as building blocks; two series of these hybrid oligomers are designed, synthesized and extensively characterized by using NMR, CD, FT-IR and MD simulation studies; results show the co-existence of left-handed 11- and 14/15-helical conformations in these short oligomers of Boc-(alpha/beta) and Boc-(beta/alpha) series. 相似文献
5.
Zhongsheng Zhang 《Tetrahedron letters》2006,47(5):665-669
Peptidotriazoles, unnatural oligomers with alternating amide and triazole linkages, are synthesized efficiently on solid support. The key transformations involve multiple cycles of 1,2,3-triazole formation, using soluble Cu(I) catalyst and conditions that do not generate precipitate on solid support nor require exclusion of oxygen. Our synthetic protocol will enable the preparation of other unnatural oligomers with multiple triazoles using solid phase methodologies. 相似文献
6.
[reaction: see text] Conjugated oligomers with an alternating phenylene-pyrimidine structure have been synthesized by the successive Suzuki coupling reaction starting from 2-bromo-5-iodopyrimidine. The photoluminescence properties and quasi-reversible redox behavior of these oligomers make them applicable as an active material for a light-emitting device. Blue light-emitting electroluminescent devices with an external quantum efficiency up to 1.8% have been fabricated. 相似文献
7.
Unprecedented Chain‐Length‐Dependent Conformational Conversion Between 11/9 and 18/16 Helix in α/β‐Hybrid Peptides
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Dr. Baptiste Legrand Dr. Christophe André Laure Moulat Emmanuel Wenger Dr. Claude Didierjean Dr. Emmanuel Aubert Dr. Marie Christine Averlant‐Petit Prof. Jean Martinez Dr. Monique Calmes Dr. Muriel Amblard 《Angewandte Chemie (International ed. in English)》2014,53(48):13131-13135
α,β‐Hybrid oligomers of varying lengths with alternating proteogenic α‐amino acid and the rigid β2,3,3‐trisubstituted bicyclic amino acid ABOC residues were studied using both X‐ray crystal and NMR solution structures. While only an 11/9 helix was obtained in the solid state regardless of the length of the oligomers, conformational polymorphism as a chain‐length‐dependent phenomenon was observed in solution. Consistent with DFT calculations, we established that short oligomers adopted an 11/9 helix, whereas an 18/16 helix was favored for longer oligomers in solution. A rapid interconversion between the 11/9 helix and the 18/16 helix occurred for oligomers of intermediate length. 相似文献
8.
Ioannis Kanelidis Yi Ren Vladimir Lesnyak Jan‐Christoph Gasse Ronald Frahm Alexander Eychmüller Elisabeth Holder 《Journal of polymer science. Part A, Polymer chemistry》2011,49(2):392-402
Four alternating arylamino‐functionalized copolymers were synthesized in a Suzuki copolymerization applying 4, 4′‐(2,7‐dibromo‐9H‐fluorene‐9,9‐diyl)dianiline, 4,4′‐(2,7‐dibromo‐9H‐fluorene‐9,9‐diyl)bis(N,N‐diphenylaniline), 4‐(3,6‐dibromo‐9H‐ carbazol‐9‐yl)aniline and 4‐(3,6‐dibromo‐9H‐carbazol‐9‐yl)‐N,N‐diphenylaniline in combination with 2,2′‐(9,9‐dioctyl‐9H‐fluorene‐2,7‐diyl)bis(1,3,2‐dioxaborinane). The resulting novel alternating copolymers were fully characterized. The copolymers revealed blue light emission and wide optical bandgaps of at least 2.93 eV for the fluorene‐based and 3.07 eV for the carbazole‐based polymers. The amino‐functions allow to tie semiconducting CdTe nanocrystals (NCs) and to synthesize a series of composites with CdTe NCs. Moreover, tuning the emission color over a wide range by tying these CdTe NCs results in a facile preparation of organic–inorganic semiconductor composites with emission colors “à la carte.” © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
9.
Hui Liu Xiao-Feng Zhang Li-Hong Wang Yan Chen Dong-Nai Ye Long Chen He-Rui Wen Shi-Yong Liu 《中国化学》2021,(3):577-584
A series of all-donor type alternating (D1-D2) monodisperse oligomers based on cyclopentadithiophene (CPDT) and 1,4-difluorobenzene (DFB) with gradually increas... 相似文献
10.
In recent years, clean and sustainable energy generation by photocatalytic water splitting has gained enormous attention from researchers. Two-dimensional Cd-based structures play a central role in the research of semiconductor-based photocatalysis. Here, a few layers of cadmium monochalcogenides (CdX; X=S, Se, and Te) are theoretically investigated using density functional theory (DFT). For their potential applicability in photocatalysis, it is proposed that they are exfoliated from the wurtzite structure with an electronic gap that depends on the thickness of the proposed systems. Our calculations address a long-standing doubt about the stabilities of free-standing CdX monolayers (ML). Induced buckling removes the acoustic instabilities in 2D planar hexagonal CdX structures (due to interlayer interactions) that depend on the number of neighboring atomic layers present. All studied (and stable) systems have an electronic gap of >1.68 eV, calculated with hybrid functionals (HSE06). A band-edge alignment plot about the water‘s oxidation-reduction potential is constructed, and a potential energy surface is constructed for the hydrogen evolution reaction. Our calculations suggest that the chalcogenide site is most favorable for hydrogen adsorption, and the energy barrier falls within the experimentally achievable limits. 相似文献
11.
Chinwon Rim 《Tetrahedron letters》2009,50(28):4161-79
A facile and efficient synthetic approach to tripodal star-shaped oligomers is described. Several generations of hydroxyl-terminated tripodal star-shaped oligomers were prepared in high yield from 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) as a core by alternating amine-catalyzed thiol-ene and acrylate esterification reactions. The compounds were fully characterized by 1D and 2D NMR spectroscopy, ESI-MS, and elemental analysis. The combination of thioether groups and hydrogen bonding moieties suggests that these products can be used as metal chelating ligands. 相似文献
12.
Hong Ming ZHANG Xian Hong WANG Xiao Jiang ZHAO Ji LI Fo Song WANG 《中国化学快报》2006,17(4):437-440
A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity. 相似文献
13.
A new class of materials was prepared from aniline-containing oligomers that are covalently linked to the nucleobases of duplex DNA. Oligomers composed of repeating aniline (PANI) or 4-aminobiphenyl (PAB) units having the properties of conducting polymers conjoined to the DNA were prepared by the reaction of horseradish peroxidase and H2O2 with DNA having the appropriate monomers aligned within the major groove. These oligomers exhibit the spectral and chemical properties typical of para-linked polyanilines. This method of preparation enables utilization of the unique self-recognizing properties and sequence programmability of DNA to create tailored oligomers. This ability was demonstrated experimentally by preparation of PAB oligomers from alternating benzene and aniline monomers. Conjoined conducting polymers carrying the sequence information of DNA may have applicability as nanowires. 相似文献
14.
A. A. Collyer D. W. Clegg M. Morris D. G. Parker G. W. Wheatley G. C. Corfield 《Journal of polymer science. Part A, Polymer chemistry》1991,29(2):193-200
High molecular weight alternating block copolymers of polyethesulphone (PES) and polydimethylsiloxane (PDMS) were prepared by the condensation of dimethylamino-terminated PDMS oligomers and hydroxy-terminated PES oligomers in 1,2-dichlorobenzene. Microphase separation of the block copolymers at exceptionally short block lengths was observed by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The Si? O? C intersegment linkage in these materials appeared to display poor hydrolytic stability which is contrary to results obtained for other block copolymers. 相似文献
15.
Seong-Ho Kim Yong-Kyun Sim Bum-Tae Kim Yong Hwan Kim Yeong-Joon Kim Seongsoon Park Hyuk Lee 《Tetrahedron: Asymmetry》2011,22(14-15):1499-1504
A synthetic method for lactic acid oligomers via solid-phase synthesis under mild reaction conditions with up to 99% yield is presented. The fine control of the chirality on each lactic acid unit of the oligomers was easily achieved by the substitution of (R)-THP-protected lactic acid (R)-2 by (S)-2 without alternating the procedure. The overall synthesis of the trimer and tetramer was completed in one and two days, respectively. Intramolecular cyclizations of enantio-controlled lactic acids were also attempted through the Yamaguchi macrolactonization or the Mitsunobu reaction. However, we were unable to isolate single cyclic oligomers but always obtained a mixture of cyclic oligomers. 相似文献
16.
Olsen CA Bonke G Vedel L Adsersen A Witt M Franzyk H Jaroszewski JW 《Organic letters》2007,9(8):1549-1552
[structure: see text] We describe the synthesis and characterization of the first generation of oligomers consisting of alternating repeats of alpha-amino acids and chiral N-alkyl-beta-alanine (beta-peptoid) residues. These chimeras are stable toward proteolysis, non-hemolytic, and possess antibacterial activity comparable to well-known antimicrobial agents. Moreover, the chimeras exhibit length-dependent, concentration-dependent, solvent-dependent, and ion-strength-dependent ellipticity, indicating the presence of a secondary structure in solution. Thus, alpha-peptide/beta-peptoid oligomers represent a promising novel peptidomimetic backbone construct for biologically active ligands. 相似文献
17.
Giovanna Di Pasquale Angela La Rosa Antonino Mamo 《Macromolecular rapid communications》1997,18(4):267-272
A new alternating block copolymer was synthesized from dihydroxy-terminated poly-(ether ketone sulfone) and bis(dimethylamino)-terminated polydimethylsiloxane oligomers. The chemistry and the thermal properties are discussed. Surface chemical composition of films was analyzed by ESCA. Quantitative calculations showed a noticeable siloxane enrichment at the surface. 相似文献
18.
M. E. Rogers T. E. Glass S. J. Mecham D. Rodrigues G. L. Wilkes J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2663-2675
New strategies for the synthesis of perfectly alternating segmented polyimide-polydimethyl siloxane copolymers were developed by utilizing a transimidization method. Imide oligomers endcapped with 2-aminopyrimidine were reacted with aminopropyl terminated (dimethyl siloxane) oligomers to afford perfectly alternating segmented imide siloxane copolymers. The polymerization was conducted in solvents such as chlorobenzene and chlorofrom. High molecular weight, fully imidized perfectly alternating segmented imide siloxane copolymers were obtained within 2 h at temperatures of 60-110°C. The mechanism of the reaction was further elucidated via model compounds and NMR characterization. The block copolymers exhibited two Tgs due to the microphase separation of the polyimide and polysiloxane phases. The Tg of the polyimide phase was a function of the length of the polyimide block. However, partial phase mixing was also evident from the DSC results on the imide siloxane copolymers prepared with low molecular weight polyimide segments. Thermooxidative stability and tensile properties of the perfectly alternating segmented imide siloxane copolymers were found to be principally dependent on the amount of poly (dimethyl siloxane) incorporated in the copolymer and did not correlate with the poly (dimethyl siloxane) or polyimide block lengths. The stress-strain behavior of both solvent cast films or molded films is also reported. © 1994 John Wiley & Sons, Inc. 相似文献
19.
Bouillère F Feytens D Gori D Guillot R Kouklovsky C Miclet E Alezra V 《Chemical communications (Cambridge, England)》2012,48(14):1982-1984
Small α/γ-peptides alternating α-aminoisobutyric acid and cyclic γ-amino acid residues are described. NMR studies together with restrained simulated annealing revealed that an extended backbone conformation largely dominates in solution for as short as 4-residues long oligomers. This new fold type is devoid of any hydrogen bond and characterized by a four-fold symmetry. 相似文献
20.
A range of alternating furanylene-meta-phenylene oligoaryls of different chain lengths is synthesized by a convergent/divergent protocol from the annulation of a propargylic dithioacetal and an aldehyde with a propargylic dithioacetal moiety as a substituent. The emission properties of these oligomers showed chain-length dependent in poor solvent such as cyclohexane. Time resolved fluorescence spectroscopic analyses indicate that there might be intramolecular interaction between the chromophores in 2c-e and such interaction became more prominent as the chain-lengths increased from 9 to 21. Since oligomers 2 have meta-phenylene and 2,5-furnaylene linkages, the oligomers 2e, may likely be folded to enable intrachain chromophore-chromophore interactions. In addition, these oligomers are electrochemically active and the first oxidation potentials are chain-length dependent. 相似文献