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Theoretical study on self-assembly in organic
materials
Jianming CHEN, Qikai LI, Lingyi MENG, Zhigang SHUAI,
Front. Chem. China. 2010, 5 (1): 2-10.
https://doi.org/10.1007/s11458-009-0204-7
Theoretical work related to the self-assembly of organic materials was dealt with, and the various mechanisms leading to self-assembly, such as transition metal mediated self-assembly, constraint induced self-assembly, covalent bond based self-assembly and van der Waals interaction driven self-assembly, etc., were discussed. The formation of ordered structures could be attributed to the competition between short range attractive forces and long-range repulsion, which was arising from dipole interaction or may result from a different mechanism based on a purely repulsive isotropic short-range pair potential with two characteristic length scales. Such mechanism could be exploited in the study of self-assembly process. First principles SAPT(DFT) interaction energy calculations, combined with the Williams-Stone-Misquitta method, offer the ability to improve the molecular dynamics (MD) accuracy which could in turn be used in the prediction of crystal structures and self-assembly tendency. The combination of experimental and theoretical studies could open new breakthroughs over the design, synthesis, and characterization of self-assembled materials.
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Semiconducting nanocrystals, conjugated polymers,
and conjugated polymer/nanocrystal nanohybrids and their usage in
solar cells
Lei ZHAO, Jun WANG, Zhiqun LIN
Front. Chem. China. 2010, 5 (1): 33-44.
https://doi.org/10.1007/s11458-009-0112-x
As one of the major renewable energy sources, solar energy has the potential to become an essential component of future global energy production. With the increasing demand in energy, the harvesting of solar energy using inexpensive materials and manufacturing methods has attracted considerable attention. Organic/inorganic (i.e., conjugated polymer/nanocrystal (CP/NC)) nanohybrid solar cell, including both physically mixed CP/NC composites and covalently linked CP-NC nanocomposites, is one of the several most promising alternative, cost-effective concepts for solar-to-electric energy conversion that has been offered to challenge conventional Si solar cells over the past decade. It has low fabrication cost and capability of large-scale production. However, to date, the highest power conversion efficiency (PCE) of organic/inorganic nanohybrid solar cells has been reported to be only 5.5%, which is still lower than the theoretical prediction of more than 10%. Several problems, i. e., microscopic phase separation of semiconducting CPs and NCs, low charge injection, and low carrier collection, have not been well addressed. More research remains to be done to improve the efficiency of CP/NC nanohybrid solar cells. In this review article, the recent advances in solving these problems were discussed. For the CP/NC solar cells prepared by physically mixing electron donating CP and electron accepting NC (i.e., forming CP/NC composites), methods involving the use of solvent mixtures and ligand modification to control the phase separation at the nanoscale are discussed; the implications of intriguing anisotropic NCs as well as their assemblies (i.e., NC arrays) on improving the charge collection are presented. For newly developed CP/NC solar cells prepared by chemically tethering CP chains on the NC surface (i.e., yielding CP-NC nanocomposites, thereby preventing microscopic phase separation of CP and NC and improving their electronic interaction), recent strategies on the synthesis of such nanocomposites and their photovoltaic performance are discussed.
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Organic photovoltaic materials and thin-film
solar cells
Xin WANG, Jiuyan LI, Di LIU,
Front. Chem. China. 2010, 5 (1): 45-60.
https://doi.org/10.1007/s11458-009-0208-3
Organic photovoltaic materials are of interest for their future applications in solar cells. Compared to inorganic or dye-sensitized solar cells, organic photovoltaic (OPV) cells offer a huge potential for low-cost large-area solar cells because of their low material consumption per area and easy processing. In the last few years, there have seen an unprecedented growth of interest in OPVs with power conversion efficiency of over 5% attainable. However, OPV’s performance is limited by the narrow light absorption, poor charge carries mobility, and low stability of organic materials, all of which confine its large-scale commercial applications. This review will develop a discussion on the OPV device configuration and operational mechanism after an introduction of the general features of OPV materials. Subsequently, the typical progresses in materials development and performance evolution in recent years will be summarized. The future challenges and prospects faced by organic photovoltaics will be discussed. Finally, the innovative strategy on research of molecular design and device optimization will be suggested with the aim for practical application.
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Derivated titanate nanotubes and their hydrogen
storage properties
Zheng CHANG, Jing LIU, Xiaoming SUN, Junfeng LIU,
Front. Chem. China. 2010, 5 (1): 71-75.
https://doi.org/10.1007/s11458-009-0095-7
Titanate nanotubes and their derivates, Pd-loaded and Co2+, Zn2+, Cu2+, and Ag+ ion-exchanged titanate nanotubes, were respectively prepared and characterized by XRD, HR-TEM, and EDS. Their hydrogen storage properties were investigated, and the results revealed that the derivated titanate nanotubes had better hydrogen storage characters. Pd-loaded titanate nanotubes exhibited the highest hydrogen storage capacity of 1.03 wt%, which is three times higher than that of raw titanate nanotubes. The ion-exchanged titanate nanotubes also showed enhanced capacity. Especially, Co-TiNT reached a storage capacity of 0.80 wt%. The reason why hydrogen storage capacity was enhanced in titanate nanotubes was a pilot study. These results indicated that oxide nanotubes provided some new opportunities for hydrogen energy applications.
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QSAR study on fluoroquinolones as antibacterial
agents active for Pseudomonas aeruginosa
Xiaohong LI, Ruizhou ZHANG, Xiangdong YANG,
Front. Chem. China. 2010, 5 (1): 80-87.
https://doi.org/10.1007/s11458-009-0102-z
Density functional theory (DFT) was used to calculate the properties of a set of molecular descriptors for 14 fluoroquinolone with anti-Pseudomonas aeruginosa activity. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed in order to reduce dimensionality and investigate the effectiveness of variables, i. e., which subset of variables should be more effective for classifying fluoroquinolones according to their antibacterial activities against P. aeruginosa. The PCA results showed that the variables ELUMO, ΔEHL, Q5, Q6, logP, MR, and MP are responsible for the separation between compounds with higher and lower anti-P. aeruginosa activity. The HCA results were similar to those obtained using PCA. By using the chemometric results, four synthetic compounds were analyzed through the PCA and HCA. Two of them are proposed as active molecules against P. aeruginosa. The result is consistent with the observations of clinic experiments. The methodologies of PCA and HCA provide a reliable rule for classifying new fluoroquinolones with anti-P. aeruginosa activity.
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Purification and characterization of two major
selenium-containing proteins in selenium-rich silkworm pupas
Qiong LIU, Xueying LIANG, Jing TIAN, Decong HU, Ping CHEN, Hong ZHANG,
Front. Chem. China. 2010, 5 (1): 88-98.
https://doi.org/10.1007/s11458-009-0109-5
Selenium (Se) is an essential trace element in vivo involved in the defense against oxidative stress. Se deficiency is associated with many human diseases. The bioactivity of Se is dose- and species-dependent. Silkworm pupa has been reported to accumulate Se mainly in proteins. Thus the characterization of major Se-containing proteins is very important in the application of Se-rich silkworm pupas in food and drugs. In this study, crude proteins were extracted from Se-rich silkworm pupas, followed by DEAE-Sepharose and Sephedex G-75 chromatography. Se content was measured after each step to determine the highest Se-containing fraction for the next step of separation. The proteins obtained were analyzed using SDS-PAGE, followed by in-gel digestion with trypsin, and were characterized by MALDI-TOF MS and ESI-MS/MS. These data showed two proteins mainly accumulated Se in the silkworm pupas. Those two proteins were proven by mass spectrometry to be arylphorin and sex-specific storage-protein 2 precursor (SP-2), respectively. Both of them belong to the storage proteins of amino acids during metamorphosis and the non-feeding pupal stage. The results suggest that Se could be enriched by storage proteins and be supplied to silkworm pupas in accompany with amino acids for the synthesis of new Se-containing proteins and peptides.
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Catalytic synthesis of methylene diphenyl dicarbamate
from methyl phenyl carbamate and trioxane over sulfuric acid catalyst
Tao LI, Guotong QIN, Huiquan LI, Haitao LIU, Yixia PEI,
Front. Chem. China. 2010, 5 (1): 99-103.
https://doi.org/10.1007/s11458-009-0207-4
Methylene diphenyl dicarbamate (MDC) was synthesized from methyl phenyl carbamate (MPC) and trioxane using sulfuric acid (H2SO4) as catalyst. The effects of reaction temperature, reaction time, molar ratio of reactants and the content of catalyst have been studied in details. The results showed that H2SO4 exhibited high catalytic activity with the merits of moderate reaction velocity. Under the conditions of n(MPC)/n(trioxane)=3:1, reaction temperature of 95°C, reaction time of 3.5 h and 30% H2SO4, the conversion of MPC reached 99.0% with the selectivity of MDC 81.6%. Moreover, the H2SO4 catalyst was reused five times without obviously activity decrease. Based on the identification of byproducts, a possible reaction mechanism was proposed.
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Investigation into ramie whisker reinforced arylated
soy protein composites
Rakesh KUMAR, Lina ZHANG,
Front. Chem. China. 2010, 5 (1): 104-108.
https://doi.org/10.1007/s11458-009-0206-5
Whiskers were prepared from ramie fibers and were characterized using atomic force microscopy to evaluate their dimensions. SPI/whiskers composites (SW) were prepared by incorporating different weight contents (wt.%) of the whiskers into soy protein isolate (SPI). Thiodiglycol was used as a plasticizer for the preparation of SW composites. The SW composites were arylated with 2,2-diphenyl-2-hydroxyethanoic acid through the process of “dip-coating” and coded as SW-B. In this paper, the characterization of SW and SW-B composites, such as their morphologies, mechani- cal properties, thermal stability, optical transmittance, and water uptake, are discussed. The results indicated substantial improvement in the water resistance, thermal stability, and the modulus of the SW-B composites after arylation due to the formation of hydrophobic diphenylhydroxymethane (DPHM) microparticles on the surface. This work provides a novel method to increase the water resistance of protein based composites.
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