Terahertz plasmon and surface-plasmon modes in cylindrical metallic nanowires

We present a theoretical study on collective excitation modes associated with plasmon and surface-plasmon oscilla- tions in cylindrical metallic nanowires. Based on a two-subband model, the dynamical dielectric function matrix is derived under the random-phase approximation. An optic-like branch and an acoustic-like branch, which are free of Landau damp- ing, are observed for both plasmon and surface-plasmon modes. Interestingly, for surface-plasmon modes, we find that two branches of the dispersion relation curves converge at a wavevector qz = qrnax beyond which no surface-plasmon mode exists. Moreover, we examine the dependence of these excitation modes on sample parameters such as the radius of the nanowires. It is found that in metallic nanowires realized by state-of-the-art nanotechnology the intra- and inter-subband plasmon and surface-plasmon frequencies are in the terahertz bandwidth. The frequency of the optic-like modes decreases with increasing radius of the nanowires, whereas that of the acoustic-like modes is not sensitive to the variation of the radius. This study is pertinent to the application of metallic nanowires as frequency-tunable terahertz plasmonic devices.     

PO43-掺杂Bi2O2CO3/Bi0的制备及其可见光催化性能

构建氧空位以及附着金属单质Bi(Bi⁰)是增强半导体材料光吸收性能、促进半导体光生载流子分离的有效方法。通过简单的共沉淀法及氢气热还原成功制备了PO₄^3-掺杂Bi₂O₂CO₃附着Bi⁰(Bi-P-BOC)的可见光催化剂,并对其在可见光下催化降解氧氟沙星(OFX)的性能及机理进行了研究。材料表征结果表明BOC随着PO₄^3-的均匀掺杂,可见光吸收能力增强,表面缺陷增多,比表面积增大。而随着氢气热还原,BOC表面形成 Bi⁰的同时也原位构建了大量的氧空位。可见光催化性能测试表明,Bi-P-BOC可以在180 min内降解约85%的OFX,降解速率为0.013 0 min^-1,是BOC降解速率的8倍。Bi-P-BOC光催化降解机理表明其具有更好的可见光吸收能力,Bi⁰以及氧空位的存在促进了光生载流子的分离,h+是其光催化降解过程中的主要的活性氧物种(ROS),此外,¹O₂和·O₂^-也对降解有一定贡献。     

Synthesis and anti-HIV-1 activity of the conjugates of gossypol with oligopeptides and D-glucosamine

A series of novel gossypol derivatives were synthesized and screened for their in vitro anti-HIV- 1I activity. The results showed that replacing the aldehyde groups of gossypol with certain oligopeptides and Dglucosamine not only reduced the cytotoxicity of gossypol derivatives but also enhanced their antiviral activity against HIV-1. Interestingly, D-glucosamine derivative of gossypol that lacked the COONa group also exhibited the same potent anti-HIV-1 activity as oligopeptide derivatives with the COONa group. These compounds blocked the entry of HIV-1ⅢB into target cell. which was similar to T20. Furthermore, the molecular docking analysis rationalized their anti-HIV-1 activity. The results also implied that certain oligopeptides and D-glucosamine were important moities to prepare gossypol derivatives as HIV- 1 entry inhibitors besides certain amino acids.     

Low-redshift cosmic baryon fluid on large scales and She-Leveque universal scaling

We investigate the statistical properties of cosmic baryon fluid in the nonlinear regime, which is crucial for understanding the large-scale structure formation of the Universe. With the hydrodynamic simulation sample of the Universe in the cold dark matter model with a cosmological constant, we show that the intermittency of the velocity field of cosmic baryon fluid at redshift z = 0 in the scale range from the Jeans length to about 16 h(-1) Mpc can be extremely well described by She-Leveque's universal scaling formula. The baryon fluid also possesses the following features: (1) for volume weight statistics, the dissipative structures are dominated by sheets, and (2) the relation between the intensities of fluctuations is hierarchical. These results imply that the evolution of highly evolved cosmic baryon fluid is similar to a fully developed turbulence.     

Facile synthesis of cyclopentapeptide,cyclo[Arg(NO2)-Gly-Asp(OBn)-D-Phe-Lys(Fmoc)], and its application in synthesis of integrin-targeting anticancer conjugate

An efficient approach for integrin-targeting cRGDfK conjugate synthesis has been developed using a new protected cyclopentapeptide, cR(NO₂)GD(Bn)fK(Fmoc), as the key intermediate. cR(NO₂)GD(Bn)fK(Fmoc) was conveniently prepared in high yield. The Fmoc group of this cyclopentapeptide was selectively removed under mild conditions which makes it an ideal intermediate for cRGDfK conjugate synthesis as was well demonstrated in this paper by the synthesis of cRGDfK chlorambucil conjugate.     

Enantioselective trapping of oxonium ylide intermediates by N-benzhydryl-α-imino ester:Synthesis of β-tetrasubstituted α-amino acids

A synergistic rhodium(Ⅱ)/phosphoric acid catalyzed three component reaction of 3-diazooxindoles,alcohols and N-benzhydryl-α-imino ester is developed for the efficient construction of chiral β-alkoxy C~β-tetrasubstituted α-amino acid derivatives in good yields and with excellent diastereoselectivities and high enantioselectivities.The synthetic application of the resulting products was illustrated by reducing with Pd/C under H_2 atmosphere followed reacting with CSCl_2 at room temperature to rapid afford 3-spirocyclic oxindole in a good yield with a chirality retainment.The three-component reaction is proposed to proceed through an electrophilic trapping of the oxonium ylides by N-benzhydryl-α-imino ester.     

在Ni-B非晶态催化剂作用下生物油水相加氢制备饱和醇

采用化学还原法制备了Ni-B和Ni-Co-B非晶态催化剂, 并采用X射线衍射(XRD)、BET比表面积、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电感耦合等离子体光谱(ICP)进行了结构表征. 结果表明, 在110 ℃及氢冷压4.0 MPa时, 在Ni-B或Ni-Co-B催化下, 丙酮、糠醛和苯酚的转化率和饱和醇的选择性分别达到99.99% 和95.00%以上. 对于Ni-B催化生物油真实体系, 在150 ℃及氢冷压4.0 MPa下, 饱和醇的收率达到47.54%. 温度过高易导致催化剂转晶从而降低反应活性. 为生物油的有效利用和饱和多元醇的制备提供了新思路.     

生物质定向热解制取高品质液体燃料、化学品和碳材料研究进展

生物质定向热解制备高品质液体燃料、化学品和碳材料是目前全球研究的前沿和热点.本文首先综述了生物质定向热解机理和目标产物富集机制等方面的最新研究进展.然后分别针对生物质定向热解制备高品质液体燃料(芳烃类、醇醚类和酯类)、高附加值化学品(左旋葡聚糖、左旋葡聚糖酮、糠醛和4-乙烯基苯酚)和高性能碳材料(特殊生物质、改性生物炭和生物油等为原料制备)等三类高值产品的研究现状进行了系统的概述.最后对生物质定向热解未来发展方向进行了展望,为其高效转化利用提供了一定的依据和借鉴.     

Ni/HZSM-5的结构及催化木糖醇水相加氢合成液体烷烃的性能研究

采用浸渍法制备了Ni/HZSM-5双功能催化剂,采用BET、XRD、NH3-TPD、H2-TPR、FTIR和TG等方法表征了催化剂比表面、孔结构、酸性、还原能力及骨架结构等信息,研究了其催化木糖醇水相加氢合成液体烷烃的性能及催化剂失活的原因。结果表明,在优化的金属中心/酸中心的协同作用下,木糖醇可通过水相加氢高选择性地合成C5-C6烷烃;过高的金属中心或酸中心均会导致C-C键断裂形成轻质烷烃,以2%Ni/HZSM-5催化剂上木糖醇水相加氢活性最高,木糖醇C转化率为94%液体烷烃总收率可达90%,这与其具有较大的比表面积、合适的孔径分布、较多的金属活性中心、适中的酸量和强酸量有关。催化剂6次重复使用后活性明显降低,其骨架部分脱铝和表面积碳是其失活的主要原因。