基于Si-rich SiNx/N-rich SiNy多层膜结构的量子点构筑及发光特性

利用等离子体增强化学气相沉积法制备Si-rich SiN_x/N-rich SiN_y多层膜,分别使用热退火和激光辐照技术对多层膜进行退火,以构筑三维限制、尺寸可控、有序的硅纳米晶.实验结果表明,经退火后,纳米硅晶粒在Si-rich SiN_x子层内形成,其尺寸可由Si-rich SiN_x子层厚度调控.实验还发现,激光辐照技术相比于热退火能更有效地改善多层膜的微结构,提高多层膜的晶化率,以激光技术诱导晶化的Si-rich SiN_x/N-rich SiN_y多层膜作为有源层构建电致发光器件,在室温下观察到了增强的电致可见发光,并且发光效率较退火前提高了40%以上. 关键词： 氮化硅 多层膜 限制结晶 纳米晶硅     

分层掺B和吸附H2O碳纳米管的结构稳定性及电子场发射性能

运用基于第一性原理的密度泛函理论,系统研究了处于外电场中分层掺B并吸附不同数目H₂O碳纳米管体系的结构稳定性和电子场发射性能. 研究表明:第3层掺B并吸附5个H₂O的B₃CNT+5H₂O体系结构最稳定,管帽处Mulliken电荷最密集,尤其与单独掺B的B₃CNT和单独吸附H₂O的B₃CNT+5H₂O相比,其Fermi能级处态密度分别     

硼掺杂单壁碳纳米管吸附甲醛的电子结构和光学性能研究

应用基于第一性原理的密度泛函理论研究了硼原子取代掺杂的（8,0）碳纳米管吸附甲醛气体分子的束缚能、电子结构以及光吸收和反射性质.研究发现,硼原子掺杂的碳纳米管对甲醛气体具有较强的敏感性,其束缚能大大增加,电荷转移更加显著,吸收峰和反射峰增多,峰值减小,且在低能区发生蓝移现象,在能量约为172 eV处均出现一特征峰.对计算结果进行了讨论,期望利用硼掺杂碳管来制作检测甲醛的纳米传感器和光电器件. 关键词： 碳纳米管 甲醛 硼原子取代掺杂 光学性能     

界面势垒对碳纳米管场发射特性的影响

以界面势垒对碳纳米管(CNT)场发射的影响为研究目的,在硅衬底上引进很薄的二氧化硅层,以二氧化硅层作为绝缘势垒,然后在二氧化硅界面层上直接生长CNT,来研究二氧化硅绝缘势垒层对CNT场发射的影响。场发射结果为:Fowler-Nordheim(F-N)曲线分为两部分,高电场下偏离F-N曲线并趋于饱和。在双势垒模型的基础上,从电场在两势垒上的分布不同及电子在两势垒上的隧穿几率不同,理论上分析了界面势垒对场发射的影响:低电场下电子在界面势垒的隧穿几率大于在表面势垒的隧穿几率,界面势垒对场发射不起阻碍作用,场发射遵守F-N规律;高电场下电子在界面势垒的隧穿几率小于在表面势垒的隧穿几率,场发射偏离F-N规律。理论对实验结果进行了合理的解释。     

Microstructure and strain films using in-plane grazing analysis of GaN epitaxial incidence x-ray diffraction

This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.     

Photoelectrochemical cells using metal-decorated carbon nanotube electrodes

We fabricated the photoelectrochemical (PEC) cells using n-type TiO₂ and metal (Pt, Pd)-decorated carbon nanotubes (CNTs) as an anode and a cathode, respectively. Photovoltaic effects were clearly observed. Compared with conventional PEC cell with Pt cathode, a larger photo-voltage was found in the PEC cells with the metal-decorated CNT cathode due to p-type semiconducting properties of CNTs. Additionally, we connected two PEC cells in series to decompose water into oxygen and hydrogen. Indeed, the connected PEC cells yielded the photo-voltage of about 1.35 V, which is larger than 1.23 V required for water splitting. This result demonstrates the possibility of hydrogen generation using the connected PEC cells without an external bias.     

Amperometric determination of bovine insulin based on synergic action of carbon nanotubes and cobalt hexacyanoferrate nanoparticles stabilized by EDTA

A simple approach is proposed for the synthesis of cobalt hexacyanoferrate nanoparticles (CoNPs) with uniform shape and size controlled by ethylene diamine tetraacetic acid (EDTA) as a stabilizer. A sensitive amperometric biosensor for insulin has been prepared using glassy carbon electrodes by solubilization of carbon nanotubes (CNTs) in chitosan (CHIT) together with CoNPs synthesized by the new methodology. The CoNP-CNT-CHIT organic–inorganic system exerts a synergistic effect, resulting in the remarkably enhanced insulin currents owing to the superior electron-transfer ability of CNTs and the excellent reversible redox centers of CoNPs. High-resolution transmission electron microscopy (HRTEM) was used to provide closer inspection of the CoNPs. The effects of alkali metal cations and the concentrations of CNTs and CoNPs on the voltammetric behavior of the film-modified electrode were also investigated. In pH 6.98 phosphate buffer (PB) at +0.7 V (vs. SCE) the insulin biosensor exhibits a linear response range of 0.1–3 μM with a correlation coefficient of 0.98, and the detection limit (S/N=3) is determined to be 40 nM, the stability of the biosensor was tested and found satisfactory. There is great promise for in vivo measurements of this important hormone.     

Capillary electrophoresis–electrospray mass spectrometry and HR–ICP–MS for the detection and quantification of 10B-boronophenylalanine (10B–BPA) used in boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a bimodal radiotherapeutic treatment based on the irradiation of neoplastic tissues with neutrons after the tissues have selectively accumulated molecules loaded with nuclides with large neutron capture cross-sections (such boron-10). Boron-10 carriers have been tested to a limited extent, and clinical trials have been conducted on sulfhydryl borane (¹⁰B-BSH) and boronophenylalanine (¹⁰B-BPA). However, precise and accurate measurements of boron-10 concentrations (0.1–100 μg/g) in specimens and samples of limited size (μg scale) are needed in order to be able to biologically characterise new compounds in predictive tissue dosimetry, toxicology and pharmacology studies as well as in clinical investigations. A new approach based on fast separation and detection of ¹⁰B-BPA performed by coupling capillary electrophoresis to electrospray mass spectrometry is reported. This method allows the quantitative analysis and characterisation of ¹⁰B-BPA in a short time with a high separation efficiency. Detection limits of 3 μM for ¹⁰B-BPA and 30 ng/mL for ¹⁰B were obtained with CE–ESI–MS. A quantification limit of 10 μM for ¹⁰B-BPA (100 ng/mL for ¹⁰B) was attained. The total boron-10 concentration was determined by high-resolution inductively coupled mass spectrometry in order to validate the method. Boron-10 isotope measurements were carried out by HR–ICP–MS at medium resolution (R=4000) due to the presence of an isobaric interference at mass 10. Good agreement was obtained between the values from CE–ESI–MS and those from HR–ICP–MS. The method has been successfully used to determine the ¹⁰B-BPA in two lines of cultured cells.     

Nanostructured electrochemical DNA biosensors for detection of the effect of berberine on DNA from cancer cells

Multi walled carbon nanotubes (MWNT) in dimethylformamide (DMF) or aqueous sodium dodecyl sulfate (SDS) solution, colloidal gold nanoparticles (GNP) in phosphate buffer solution (PBS), and a GNP–MWNT mixture in aqueous SDS solution have been investigated for chemical modification of a screen-printed carbon electrode used as the signal transducer of a dsDNA-based biosensor. Differential pulse voltammetry of the DNA redox marker and the guanine moiety anodic oxidation and cyclic voltammetry with K₃[Fe(CN)₆] as indicator revealed substantial enhancement of the response of the biosensor, particularly when MWNT in SDS solution was used. The biosensor was used in testing of berberine, an isoquinoline plant alkaloid with significant antimicrobial and anticancer activity. Berberine had a very strong, concentration-dependent, effect on the structural stability of DNA from the human cancer cells (U937 cells) whereas non-cancer cells were changed only when berberine concentrations were relatively high 75 and 50 μg mL⁻¹. Figure Schematic illustration of preparation of the nanostructured films: (a) layer-to-layer coverage (DNA/nanomaterial/SPE); (b) mixed coverage (DNA-nanomaterial/SPE)