Studying (n, 0) and (m,m) GaP nanotubes (n = 3–10 and m = 2–6) through DFT calculations of Ga-69 quadrupole coupling constants

We investigated properties of representative zigzag and armchair gallium phosphide (GaP) nanotubes by performing density functional theory (DFT) calculations. To achieve our purpose, eight models of (n,0) zigzag GaP nanotubes with n = 3–10 and five models of (m,m) armchair GaP nanotubes m = 2–6 were considered. Each model was firstly optimized and quadrupole coupling constants (C_Q) were subsequently calculated for gallium-69 atoms of the optimized structures. The results indicated that the optimized properties including dipole moments, energy gaps, binding energies, and bond lengths could be mainly dependent on the diameters of GaP nanotubes, which are directly determined by n or m indices. Moreover, comparing the values of C_Q parameters indicated that the narrower GaP nanotubes could be considered as more reactive materials than the wider nanotubes, in which the reactivities are very important in determining the applications of nanotubes. And finally, the atoms at the sidewalls of nanotubes could be divided into atomic layers based on the similarities of properties for atoms of each layer, in which the properties of Ga atoms at the edges of nanotubes are significantly different from other layers only for wider nanotubes.     

Synthesis and Magnetic Properties of Manganese-Doped GaP Nanowires

We characterized the structure and magnetic properties of Mn-incorporated GaP nanowires synthesized by thermal evaporation of GaP/Mn powders. The nanowires consist of twin-crystalline zinc blende GaP grown with the [111] direction and doped with about 1 at. % Mn. They are often sheathed with the bumpy amorphous outerlayers containing high concentrations of Mn and O. The ferromagnetic hysteresis curves at 5 and 300 K and temperature-dependent magnetization provide evidence for the ferromagnetism with the Curie temperature higher than room temperature. Magnetic properties of individual nanowires have been measured, showing a large negative magnetoresistance equal to about -5% at 5 K. We suggest that the Mn doping of GaP nanowires would form a dilute magnetic semiconductor.     

Synthesis of high-purity GaP nanowires using a vapor deposition method

High-purity gallium phosphide (GaP) nanowires were successfully synthesized on the nickel monoxide (NiO) or the cobalt monoxide (CoO) catalyzed alumina substrate by a simple vapor deposition method. To synthesize the high-purity GaP nanowires, the mixture source of gallium (Ga) and GaP powder was directly vaporized in the range of 850–1000 °C for 60 min under argon ambient. The diameter of GaP nanowires was about 38–105 nm and the length was up to several hundreds of micrometers. The GaP nanowires have a single-crystalline zinc blend structure and reveal the core-shell structure, which consists of the GaP core and the GaPO₄/Ga₂O₃ outer layers. We demonstrate that the mixture of Ga/GaP is an ideal source for the high-yield GaP nanowires.     

The thermostability and reactivity of GaP nanocrystals in oxygen: from GaP nanocrystals to Ga2O3 nanocrystals

The thermostability and reactivity of GaP nanocrystals in O(2) were investigated using the thermogravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis techniques. alpha-Ga(2)O(3) nanoparticles, nano-hollow-particles, or nanorods and nanotubes can be separately obtained from the oxidation of nanocrystalline GaP at 400 degrees C for 30 min in dry O(2) atmosphere via manipulating different heating rates. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) analysis showed that the products were all alpha-Ga(2)O(3) but with different morphologies when different heating rates were applied. The formation mechanisms of the different morphological alpha-Ga(2)O(3) nanocrystals were discussed.     

Highly luminescent InP/GaP/ZnS nanocrystals and their application to white light-emitting diodes

Highly stable and luminescent InP/GaP/ZnS QDs with a maximum quantum yield of 85% were synthesized by in situ method. The GaP shell rendered passivation of the surface and removed the traps. TCSPC data showed an evidence for the GaP shell. InP/GaP/ZnS QDs show better stability than InP/ZnS. We studied the optical properties of white QD-LEDs corresponding to various QD concentrations. Among various concentrations, the white QD-LEDs with 0.5 mL of QDs exhibited a luminous efficiency of 54.71 lm/W, Ra of 80.56, and CCT of 7864 K.     

Non-innocent Dissociation of H(2)O on GaP(110): Implications for Electrochemical Reduction of CO(2)

The structural and electronic properties of the GaP(110)/H(2)O interface have been investigated by first-principles density functional theory calculations. Our results suggest that hydride-like H atoms are present on the surface as a consequence of the dissociation of water in contact with the GaP surface. This feature opens up a new feasible reduction pathway for CO(2) where the GaP(110) surface is the electrochemically active entity.     

Electronic structure and related properties for quasi-binary (GaP)1−x (ZnSe) x crystals

The results of pseudopotential calculations of the band structure and related electronic and optical properties of quasi-binary (GaP)_1?x (ZnSe) _x crystals in the zinc blende structure are presented. Trends in bonding and ionicity are discussed in terms of electronic charge densities. Moreover, the composition dependence of the refractive index and dielectric constants are reported. The computed values are in reasonable agreement with experimental data. The results suggest that for a proper choice of the composition x, (GaP)_1?x (ZnSe) _x could provide more diverse opportunities to achieve the desired electronic and optical properties of the crystals which would improve the performances of devices fabricated on them.     

(GaP)n和(GaP)n－ (n＝10～16)团簇的结构与稳定性研究

采用密度泛函理论B3LYP/Lanl2dz方法对(GaP)_n和(GaP)_n^－ (n＝10～16)团簇的一系列异构体的结构和稳定性进行了研究. 讨论了中性团簇得到一个电子之后, 几何结构和电子性质的变化. 频率分析预测出最强吸收峰位于341～390 cm^－1区域. 从能隙、结合能和能量二次差分等方面综合考虑, 具有T_h对称性的(GaP)₁₂和(GaP)₁₂^－分别是中性(GaP)_n和阴离子(GaP)_n^－团簇中最稳定的, 而具有T_d点群结构的(GaP)₁₆也比较稳定, 究竟哪种结构易于合成还有待于实验的进一步证实. 在相同理论水平上计算了基态(GaP)_n (n＝10～16)的绝热电子亲合势(AEAs)及其基态阴离子的垂直电离能(VDEs), 这对以后的实验数据分析将有一定的参考价值.     

磷化镓纳米粒子的固氮

Under mild ambient conditions gallium phosphide （GAP） nanoparticles were employed to carry out the reduction of nitrogen. By using Nessler＇s reagent ammonia was detected in the slurry where the aggregated GAP particles were suspended in water and bubbled by pure nitrogen. Dependence of the concentration of ammonia upon bubbring time, velocity of the flow of nitrogen, and dosage of GAP particles was investigated. In comparison with the original GAP nanoparticles, the Raman scattering of the GAP particles undergoing the process of nitrogen fixation reveals that two sharp lines at 138 and 182 cm^-1, respectively, emerged from the broad continuum around 100-200 cm^-1. These two lines might be assigned to the translational motions of ammonia adsorbed on the surface of the GAP particles. An assessment of the infrared spectra of the two GAP particles led to the conclusion that the environment of the two H2O molecules was not identical. Analysis of the electron spin resonance results showed that the structure defect, gallium self-interstitial, was not involved in the nitrogen fixation of the GAP nanoparticles.     

Direct observation of the release of phenylalanine from diphenylalanine nanotubes

The core recognition motif of the amyloidogenic beta-amyloid polypeptide is a dipeptide of phenylalanine. This dipeptide readily self-assembles to form discrete, hollow nanotubes with high persistence lengths. The simplicity of the nanotube formation, combined with ideal physical properties, make these nanotubes highly desirable for a range of applications in bionanotechnology. To fully realize the potential of such structures, it is first necessary to gain a comprehensive understanding of their chemical and physical properties. Previously, the thermal stability of these nanotubes has been investigated by electron microscopy. Here, we further our understanding of the structural stability of the nanotubes upon dry-heating using the atomic force microscope (AFM), and for the first time identify their degradation product utilizing time-of-flight secondary-ion mass spectrometry. We show that the nanotubes are stable at temperatures up to 100 degrees C, but on heating to higher temperatures begin to lose their structural integrity with an apparent collapse in tubular structure. With further increases in temperature up to and above 150 degrees C, there is a degradation of the structure of the nanotubes through the release of phenylalanine building blocks. The breakdown of structure is observed in samples that are either imaged at elevated temperatures or imaged following cooling, suggesting that once phenylalanine is lost from the nanotubes they are susceptible to mechanical deformation by the imaging AFM probe. This temperature-induced plasticity may provide novel properties for these peptide nanotubes, including possible applications as scaffolds and drug delivery devices.     

Characterization of the chemical interaction between single-walled carbon nanotubes and titanium dioxide nanoparticles by thermogravimetric analyses and resonance Raman spectroscopy

Raman spectroscopy is a powerful technique that is used to characterize or observe alterations in the structure or properties of carbon nanotubes and its composites. This method can provide information about electronic changes or quantify them. We used Raman spectroscopy to study the chemical and electronic changes in a composite formed by titanium dioxide nanoparticles and single-walled carbon nanotubes. This composite was characterized by scanning electron microscopy to investigate the morphology and by thermogravimetric analyses to assess the thermal stability of the isolated carbon nanotubes as compared with the nanotubes by titanium dioxide nanoparticles. The Raman results showed that the modification of the nanotubes with the TiO₂ nanoparticles generates a new material with different structure of the nanotubes, resulting in a decrease in defects. The charge transfer from the TiO₂ nanoparticles to the nanotubes alters the electronic properties of both moieties in the hybrid material. The interaction between the nanotubes and nanoparticles decreases the CC bound order of the nanotubes and decreases their thermal stability.     

The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes

Polyaniline (PANI) nanotubes were prepared by the oxidation of aniline in solutions of acetic or succinic acid, and subsequently carbonized in a nitrogen atmosphere during thermogravimetric analysis running up to 830 °C. The nanotubular morphology of PANI was preserved after carbonization. The molecular structure of the original PANI and of the carbonized products has been analyzed by FTIR and Raman spectroscopies. Carbonized PANI nanotubes contained about 8 wt.% of nitrogen. The molecular structure, thermal stability, and morphology of carbonized PANI nanotubes were compared with the properties of commercial multi-walled carbon nanotubes.     

尼龙/碳纳米管复合材料研究进展

碳纳米管(CNTs)由于其独特的结构,较高的长径比,较大的比表面积,且具有超强的力学性能和良好的导热性,已经证明是塑料的非常优异的导电填料,聚合物基碳纳米管复合材料可望应用于材料领域的多个方面,尤其在汽车、飞机及其它飞行器的制造等军事和商业应用上带来革命性的突破。本文介绍了碳纳米管的结构形态和碳纳米管的制备、纯化、修饰方法及聚合物基碳纳米管复合材料的制备、性能,并综述了近几年来尼龙/碳纳米管复合材料的研究进展及应用前景。     

碳纳米管基气体传感器研究进展

碳纳米管具有灵敏度高、响应快和工作温度低等优异的气敏特性,近年来碳纳米管基气体传感器的研究成为研究热点.概述了碳纳米管基气体传感器的种类、结构特点、气敏性能和未来的发展方向,着重介绍了纯的碳纳米管包括单壁碳纳米管、多壁碳纳米管和碳纳米管阵列的气敏特性,以及碳纳米管的修饰或碳纳米管与高分子材料、氧化物等复合对其气敏性能的影响.     

功能化碳纳米管的电磁性能研究及进展

碳纳米管是最近发展起来的一种结构独特,性能优异的新材料,已成为当今物理、化学、材料等领域共同关注的课题.而碳纳米管的功能化更是为我们开辟了一个广阔的研究领域.本文总结了近十多年来功能化碳纳米管的研究进展,并侧重对功能化碳管的合成方法及电磁特性以及应用进行了评述.     

Aligned Nanotubes

Since the discovery of carbon nanotubes by Iijima in 1991, various carbon nanotubes with either a single‐ or multilayered graphene cylinder(s) have been produced, along with their noncarbon counterparts (for example, inorganic and polymer nanotubes). These nanostructured materials often possess size‐dependent properties and show new phenomena related to the nanosize confinement of the charge carriers inside, which leads to the possibility of developing new materials with useful properties and advanced devices with desirable features for a wide range of applications. In particular, carbon nanotubes have been shown to exhibit superior properties attractive for various potential applications, ranging from their use as novel electron emitters in flat‐panel displays to electrodes in electrochemical sensors. For many of the applications, it is highly desirable to have aligned/patterned forms of carbon nanotubes so that their structure/property can be easily assessed and so that they can be effectively incorporated into devices. In this Review, we present an overview on the development of aligned and micropatterned nanotubes, with an emphasis on carbon nanotubes.     

Synthesis and Application of Carbon Nanotubes

Owing to the unique structure, the superior physical and chemical properties, the super strong mechanical performances, and so on, carbon nanotubes have attracted the attention of researchers all over the world. In this article, the basic properties and the main production processes of carbon nanotubes are introduced in brief, and the progress of applied research for carbon nanotubes is reviewed.     

Fabrication and optical properties of gallium phosphide nanoparticulate thin film

The gallium phosphide (GaP) nanoparticulate thin films were fabricated by colloidal suspensions deposition with GaP nanoparticles dispersed in N,N-dimethylformamide (DMF). The microstructure and optical properties of the film have been studied by scanning electron microscopy, high resolution transmission electron microscope, and optical absorption and fluorescence spectra. The morphology of the film was found to be composed of nanoparticle aggregates, and with an irregularly rough surface. From the result of fluorescence, it can be established that the film not only retains the violet and blue light emissions which ascribed to transition from conduction band to valence band of gallium phosphide particles, but has an excellent luminescence property. The correlation between the optical properties and the microstructure of the thin film is discussed.     

Self-assembled light-harvesting peptide nanotubes for mimicking natural photosynthesis

Light-harvesting peptide nanotubes are synthesized by the self-assembly of diphenylalanine with THPP and platinum nanoparticles (nPt; see picture; TEOA = triethanolamine). The light-harvesting peptide nanotubes are suitable for mimicking photosynthesis because of their structure and electrochemical properties that are similar to the ones of photosystem?I in natural photosynthesis.     

The structure of nanotubes formed by diphenylalanine, the core recognition motif of Alzheimer's beta-amyloid polypeptide

Alzheimer's beta-amyloid diphenylalanine motif has previously been shown to self-assemble into discrete and extraordinary stiff nanotubes; these nanotubes were initially thought to be distinct from the single crystal structure of diphenylalanine, but it is now shown that the X-ray powder diffraction pattern of the nanotubes is identical to the simulated pattern for the single crystal structure, affording a new foundation for understanding and rationalizing the properties of this remarkable organic material.