Au@TiO2纳米管阵列的制备及光催化性能

利用一种简单易行、可控的方法制备了均匀的Au@TiO₂纳米管阵列。首先在室温下通过阳极氧化的方法形成TiO₂纳米管，再在氧化后的TiO₂纳米管上用磁控溅射沉积不同厚度的Au膜，最后将沉积Au膜后的TiO₂纳米管在空气中450℃退火2h。热处理过程导致了Au向TiO₂纳米管的扩散，在纳米管表面形成了Au“岛”包裹的Au@TiO₂纳米管。对制备的Au@TiO₂纳米管的微观结构利用了扫描电子显微镜、能谱、X射线衍射和透射电子显微镜进行表征。并且用光电流、紫外可见光光漫反射光谱、荧光光谱和降解亚甲基蓝溶液的方法分析测量了Au@TiO₂纳米管的光电性能及光催化性能。结果表明：当可见光照射含Au@TiO₂纳米管催化剂的亚甲基蓝水溶液时，其光催化性能远远高于纯TiO₂纳米管，这是由于Au颗粒表面等离子体共振效应（LSPR）增加了电子-空穴对的分离并且延缓了其重组所致。     

Preparation and photocatalytic properties of RuO2/TiO2 composite nanotube arrays

RuO₂/TiO₂ composite nanotube arrays were prepared using an anodic oxidation method combined with dipping. The photocatalytic properties of RuO₂/TiO₂ nanotube arrays in methylene blue solution were investigated under visible light irradiation. The results showed that Ru existing in the form of RuO₂ was dispersed uniformly on the surface of TiO₂ nanotubes, and the RuO₂ did not change the crystal structure of TiO₂ nanotubes. The load of RuO₂ on TiO₂ had a little influence on the band-gap energy and the absorption band edge, but could increase the amount of Ti-OH functional groups on the surface of TiO₂ nanotubes. The RuO₂/TiO₂ nanotube arrays with the optimal photocatalytic activity were formed in the ruthenium chloride solution with a concentration of 0.0030 mol/L. The 2 h photocatalytic degradation rate of methylene blue increased from 38% for pure TiO₂ nanotubes to 69% for RuO₂/TiO₂ nanotube arrays. This work demonstrated that RuO₂/TiO₂ nanotube arrays showed an improved photocatalytic property over pure TiO₂ nanotubes due to the fact that RuO₂ could capture the photo-generated holes, which greatly decreased the recombination of the photo-generated electrons and holes, and hence lengthen the lifetime of photo-induced electrons and increased the amount of hydroxyl groups absorbed on the TiO₂ nanotubes surface.     

N、Mn共掺杂TiO_2的制备、表征及光催化性能研究

应用溶胶凝胶法,以尿素、氯化锰和钛酸丁酯为原料制备了纯Ti O2、N掺杂、Mn掺杂及N、Mn共掺杂的Ti O2纳米粉体。采用XRD、SEM、EDS、UV-VIS等分析手段对样品的物相、形貌、成分和吸光性能进行了表征,并且以亚甲基蓝溶液为模拟污染物在阳光下进行了光催化实验。结果表明,样品主要为锐钛矿相二氧化钛及少量的金红石型二氧化钛;样品呈颗粒状,有一定程度的团聚;N掺杂、Mn掺杂及N、Mn共掺杂样品的吸收光谱分别红移至470、440、490 nm;光催化实验表明,在可见光照射下的光催化能力由强到弱依次为N、Mn共掺杂N掺杂Mn掺杂纯Ti O2。     

Nanoflower-like CdS and SnS2 loaded TiO2 nanotube arrays for photocatalytic wastewater treatment and hydrogen production

In this work, nanoflower-like CdS/SnS₂/TiO₂ NTs ternary heterojunction photocatalysts were synthesized by a hydrothermal method, the relationship between the morphology, microscopic morphology, crystallinity, elemental presence state and hydrogen production performance of the ternary photocatalysts were investigated by SEM, TEM, XRD and XPS, respectively. The photocatalytic performance, electrochemical property and hydrogen production capacity of CdS/SnS₂/TiO₂ NTs were compared with pure TiO₂ NTs, CdS/TiO₂ NTs and SnS₂/TiO₂ NTs. After 2 h of photocatalytic reaction, the removal efficiency of MB wastewater reached 100%, and the photocatalytic efficiencies toward RhB and Cr(VI) removal reached 86.08% and 80.93% after 3 h, respectively. The electron spin resonance (ESR) technique certified the active radical groups that played a role in the catalytic process and further investigated the possible photocatalytic mechanism. Hydrogen production per unit time achieved 97.14 μmol h^?1 cm^?2, this work provides the new technique to achieve solar energy conversion for hydrogen generation.     

Physical properties of carbon nanotube sheets drawn from nanotube arrays

We report mechanical, thermal, and electrical properties of novel sheet materials composed of multiwalled carbon nanotubes, drawn from a CNT array. At low loading there is some slippage of CNTs but at higher loading tensile strength σ₀ = 7.9 MPa and Young’s modulus E = 310 MPa. The room-temperature thermal conductivity of the CNT sheet was 2.5 ± 0.5 W m^?1 K^?1, giving a thermal conductivity to density ratio of κ/ρ = 65 W m^?1 K^?1 g^?1 cm³. The heat capacity shows 1D behavior for T > 40 K, and 2D or 3D behavior at lower temperatures. The room-temperature specific heat was 0.83 J g^?1 K^?1. The iV curves above 10 K have Ohmic behavior while the iV curve at T = 2 K is non-Ohmic, and a model to explain both ranges is presented. Negative magnetoresistance was found, increasing in magnitude with decreasing temperature (?15% at T = 2 K and B = 9 T). The tensile strength, Young’s modulus and electrical conductivity of the CNT sheet are low, in comparison with other CNT materials, likely due to defects. Thermal conductivity is dominantly phononic but interfacial resistance between MWCNTs prevents the thermal conductivity from being higher.     

Growth and electrical characterization of high-aspect-ratio carbon nanotube arrays

The remarkable properties of carbon nanotubes (CNTs) make them attractive for microelectronic applications, especially for interconnects and nanoscale devices. In this paper, we describe a microelectronics compatible process for growing high-aspect-ratio CNT arrays with application to vertical electrical interconnects. A lift-off process was used to pattern catalyst (Al₂O₃/Fe) islands to diameters of 13 or 20 μm. After patterning, chemical vapor deposition (CVD) was involved to deposit highly aligned CNT arrays using ethylene as the carbon source, and argon and hydrogen as carrier gases. The as-grow CNTs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the CNTs have high purity, and form densely-aligned arrays with controllable array size and height. Two-probe electrical measurements of the CNT arrays indicate a resistivity of ∼0.01 Ω cm, suggesting possible use of these CNTs as interconnect materials.     

有序TiO_2纳米管阵列光催化性能研究进展

高度有序TiO₂纳米管阵列由于具有结构的有序性及尺寸的可控性,已成为近年来光催化材料领域的研究热点之一。本文针对有序TiO₂纳米管阵列特殊的结构形貌特点,阐述了管壁粗糙度、管长、管壁厚度、管径及表面积对其光催化性能的影响。在不同的催化剂载体（透明玻璃基底、无基底、钛丝网基底、非平面钛片基底）生长TiO₂纳米管阵列是有效地提高其光催化性能的途径之一,介绍了这些新型结构的TiO₂纳米管阵列的研究进展。最后总结了现阶段主要掺杂改性TiO₂纳米管阵列的方法及掺杂效果。在此基础上,指出了当前研究中存在的主要问题,并展望今后的研究方向。     

One-step production of monolith-supported long carbon nanotube arrays

Aligned carbon nanotube (CNT) arrays over 150 μm long have been grown by catalytic chemical vapour deposition on the walls of bare cordierite monoliths in a single step. The method described avoids the need for the multiple pre-treatment steps currently applied, and is coupled with an increase in the thickness of the carbon layer obtained by an order of magnitude compared to literature. Uniform CNT growth has been obtained over different lengths of monolith. The resulting CNT/cordierite monoliths have a high surface area and low pressure drop, making them a viable support for use in industrial catalysis.     

N-doped anodic titania nanotube arrays for hydrogen production

Titanium dioxide (TiO₂) nanotube arrays are grown in a mixed electrolyte by anodizing process. The anodic nanotubes for N-doping were calcinated at 773 K in a tube furnace with a mixture of NH₃ and Ar gas. The photocatalytic activity of N-doped TiO₂ nanotubes was carried out in a water-splitting reaction under UV and visible light irradiation. Various characterization techniques (Scanning electron microscopy, X-ray diffractometry, X-ray photo-electron spectroscopy, etc.) are used to study the surface morphology, phase of structure, and binding energy.     

Fabrication and characterization of copper doped TiO2 nanotube arrays by in situ electrochemical method as efficient visible-light photocatalyst

Highly ordered copper doped TiO₂ nanotube arrays (CuTiO₂NTs) thin-film were prepared in an aqueous solution containing NH₄F and different concentrations of copper nitrate via the electrochemical oxidation of titanium substrates. The resulting nanotubes were characterized by FE-SEM, XRD, XPS and EDX. The CuTiO₂NTs showed a tube diameter of 40–90 nm and wall thickness of 20–30 nm. Diffuse reflectance spectra showed a shift toward longer wavelengths relative to pure TiO₂ nanotubes (TiO₂NTs). The visible light photo-catalytic activity of the CuTiO₂NTs electrodes was evaluated by the removal of methylene blue (MB) dye and the production of hydrogen. The results showed that CuTiO₂NTs samples exhibited better photo-catalytic activity than the TiO₂NTs. This work demonstrated a feasible and simple anodization method to fabricate an effective, reproducible, and inexpensive visible-light-driven photo-catalyst for hydrogen evolution and environmental applications.     

Preparation of CdS/TiO2 nanotube arrays and the enhanced photocatalytic property

In this paper, a series of CdS/TiO₂ NTs have been synthesized by SILAR method. The as-prepared CdS/TiO₂ NTs have been analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), and ultraviolet–visible (UV–vis). And their photocatalytic activities have been investigated on the degradation of methylene blue under simulated solar light irradiation. XRD results indicate that TiO₂ NTs were anatase phase, CdS nanoparticles were hexagonal phase. FESEM results indicate that low deposition concentration can keep the nanotubular structures. UV–vis results indicate that CdS can be used to improve the absorbing capability of TiO₂ NTs for visible light, and the content of CdS affects the band gap. Photocatalytic results indicate that CdS nanoparticles are conducive to improve the photocatalytic efficiency of TiO₂ NTs, and the highest degradation rate can reach 93.8%. And the photocatalytic mechanism of CdS/TiO₂ NTs to methylene blue is also described.     

The physical and photocatalytic properties of thallium doped cobalt ferrites for efficient hydrogen fuel production

Herein, a series of CoFe_2-xTl_xO₄ (0.03 ≤ x ≤ 0.15) nanoceramics were prepared via a meso-2,3-dimercaptosuccinic acid assisted solvothermal route. The influence of a thallium ion dopant on the structural, magnetoptical, electrical, and photocatalytic characteristics has been scrutinized. The X-ray diffraction demonstrated that CoFe_2-xTl_xO₄ nanoceramics have a cubic structure at all Tl ions concentrations. The Raman scattering spectroscopy revealed the reshuffling of the iron cation between the tetrahedral and octahedral sites of the structure of ferrite due to the substitution with Tl ions. The magnetic properties showed an increase of the saturation magnetization from 59.5 emu/g to 67.4 emu/g and an increase of the coercive field from 344.2 Gauss to 583.1 Gauss with increasing the amount of Tl cations. The optical band gap decreases with the increase of Tl ion concentration. The activation energy decreases from 0.44 eV to 0.26 eV with increasing the Tl ion concentration. These unique physical properties gave rise to the outstanding capability of the as-synthesized CoFe_2-xTl_xO₄ nanoceramics for the photocatalytic production of hydrogen fuel.     

Tribological properties of vertically aligned carbon nanotube arrays

Carbon nanotubes (CNTs) are a promising material for the fabrication of biomimetic dry adhesives. The dimensions of single CNTs are in the range of those of terminal elements of biological dry hairy adhesion systems, such as the setal branches on the toe of the gecko. Here, the tribological properties of densely packed arrays of vertically aligned and up to 1.1 mm long multi-walled CNTs (VACNTs) synthesized by chemical vapor deposition are examined. The coefficient of friction μ is as high as 5–6 at the first sliding cycle, and decreases down to stable values between 2 and 3 at the fourth to fifth sliding cycles. Such high values of μ can only be explained by the strong contribution of adhesion induced by applied shear force. After the tests, wear-induced deformations of the VACNT surface are observed, which strongly depend on the amount of normal force applied during the friction experiments. Interestingly, the plastic deformation of the VACNTs does not significantly affect μ after a preconditioning by a few sliding cycles. However, a strong decrease of μ during the initial wear cycles has to be taken into account for the development of applications, such as non-slip surfaces and pick-and-place techniques for manufacturing.     

Surface properties of vertically aligned carbon nanotube arrays

This study focuses on the structural changes of vertically aligned carbon nanotube (CNT) arrays while measuring their adhesive properties and wetting behaviour. CNT forests grown by chemical vapor deposition with a height of ~ 100 µm, an outer CNT diameter of ~ 10 nm and a density of the order of ~ 10¹⁰ CNTs/cm² show an average adhesion of 4 N/cm² when pressed against a glass surface. The applied forces lead to the collapse of the regular CNT arrays which limits their reusability as functional dry adhesives. Goniometric water contact angle (CA) measurements on CNT forests show a systematic decrease from an initial value of ~ 126° to a final CA similar to highly orientated graphite. Environmental scanning electron microscopy shows that this loss of hydrophobicity is due to an evaporation induced compaction of CNTs together with the loss of their vertical alignment. We observe the formation of cellular patterns for controlled drying.     

Synthesis,characterization, and visible-light photocatalytic activity of transition metals doped ZTO nanoparticles

Transition metals doping has been proved to be a feasible way for tuning the physical properties on the surface and bulk of nanomaterials and also for the good performance in decontamination of emerging pollutants. In this context, doped samples of zinc tin oxide or zinc stannate nanoparticles (ZTO NPs) by several transition metals were synthesized in order to enhance the optical absorbance with the aims of reducing the band gap and therefore ameliorated their photocatalytic activity. They were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence. The XRD patterns and the microscopic observations showed the formation of spherical nanoparticles with an average size of about 30 nm and highly pure ZTO phase with an inverse spinel structure. The Raman spectra were dominated by bands relatives to the F2g (2) and A1g symmetries modes of inverse spinel structure. The band gap Eg is estimated to be 3.75 eV for the undoped sample, and 3.67, 3.64, 3.78 and 3.21 eV, for 2% Fe, 2% Mg, 2% Gd, and 2% Mn doped ZTO samples, respectively.Furthermore, the undoped ZTO NPs have the intrinsic problem of recombination of photogenerated charge carriers. We have shown that the reduction of the band gap and oxygen vacancies resulting from the doping effect could be a useful tool for trapping and avoid the recombination of electrons coming from photosensitized rhodamine B (RhB) under visible light irradiation. Owing to the structural advantages and low band gap, 2% Mn doped ZTO NPs, with the kinetic rate constants k of 0.024 min⁻¹, show enhanced performance for the elimination of RhB in aqueous solution compared to undoped and other doped ZTO NPs.     

Structural,optical and photocatalytic properties of hafnium doped zinc oxide nanophotocatalyst

A series of novel hafnium (Hf) doped ZnO nanophotocatalyst were synthesized using a simple sol–gel method with a doping content of up to 6 mol%. The structure, morphology and optical characteristics of the photocatalysts were characterized by XRD, SEM, TEM, FTIR, XPS, DRS and PL spectroscopy. The successful synthesis and chemical composition of pure and doped ZnO photocatalysts were confirmed by XRD and XPS. DRS confirmed that the spectral responses of the photocatalysts were shifted towards the visible light region and showed a reduction in band gap energy from 3.26 to 3.17 eV. Fluorescence emission spectra indicated that doped ZnO samples possess better charge separation capability than pure ZnO. The photocatalytic activity of Hf-doped ZnO was evaluated by the methylene blue (MB) degradation in aqueous solution under sunlight irradiation. Parameters such as irradiation time and doping content were found effective on the photoactivity of pure ZnO and Hf-doped ZnO. The photocatalysis experiments demonstrated that 2 mol% Hf-ZnO exhibited higher photocatalytic activity as compared to ZnO, ZnO commercial and other hafnium doped ZnO photocatalysts and also revealed that MB was effectively degraded by more than 85% within 120 min. The enhanced photoactivity might be attributed to effective charge separation and enhanced visible light absorption. It was concluded that the presence of hafnium within ZnO lattice could enhance the photocatalytic oxidation over pure ZnO.     

Multiwalled carbon nanotube/polybenzoxazine nanocomposites: Preparation, characterization and properties

A novel nanocomposite composed of polybenzoxazine (PBZ) and multiwalled carbon nanotubes (MWNT) was prepared successfully. The surface modification of MWNT, including nitric acid modification followed by toluene-2,4-diisocyanate (TDI) treatment, introduced hydroxyl, carboxyl, and isocyanate groups on the MWNT surface. The surface carboxyl groups catalyzed the ring-opening reaction of benzoxazine and thus decreased the curing temperature of the system. The isocyanate groups reacted with the phenolic hydroxyl groups generated by the ring opening of benzoxazine resulting in the significant improvement of the adhesion between PBZ and MWNT. Dynamic mechanical analyses indicated the increase of storage modulus as well as T_g by the addition of MWNT into PBZ. A well dispersed modified-MWNT on nanoscale level inside PBZ matrix was observed by TEM and SEM.     

Cu掺杂镍基MOF复合物的制备及光催化性能研究

采用水热法合成了Cu掺杂镍基金属有机框架催化剂（Ni-BDC）复合催化剂，使用傅里叶红外光谱（FT-IR）、X射线粉末衍射分析（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）及N2-吸附脱附等技术对催化剂的结构、形貌进行了表征，并以亚甲基蓝（MB）为目标降解物，对Cu/Ni-BDC光催化性能进行研究。表征结果显示，Cu/Ni-BDC催化剂呈现多孔结构且具有较大的孔径尺寸及比表面积。在可见光的照射下，0.5g·L^-1的Cu/Ni-BDC催化剂投入量在150min内对100mL质量浓度为10mg·L^(-1)的MB溶液的降解率达84.8%，且催化剂经过5次循环实验其光催化降解率仍保持在77%以上。     

Synthesis,characterization and photocatalytic activity study of aluminium doped BiSbO4 microflakes

Metal oxides have an extraordinary ability to generate charge carriers with significant importance in environmental remediation. For the degradation of different dyes, a one-step hydrothermal method was adopted to synthesize Al-doped BiSbO_4. While bismuth antimonate composite with reduced graphene oxide was synthesized by the simple ultra-sonication method. To investigate the structural confirmation, X-ray diffraction (XRD) was used. For studying morphology, scanning electron microscopy (SEM) was conducted. UV–Visible spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR) were used to observe the optical properties and vibrational modes of the as-synthesized BiSbO₄ nanoparticles and doped Al–BiSbO₄. The above-mentioned studies verify the formation of nanoparticles of Al-doped BiSbO₄. The synthesized composite was used to degrade the organic dyes such as methylene blue and crystal violet. The degradation efficiency of doped, undoped and composite is studied and compared. The results indicate the extraordinary efficiency of BiSbO₄/rGO composite to doped and bare samples for the degradation of dyes. It is confirmed by the degradation of different dyes that the BiSbO₄/rGO composite shows the best catalytic efficiency.     

Europium (Eu3+) - doped ZnO nanostructures: Synthesis,characterization, and photocatalytic,chemical sensing and preliminary assessment of magnetic properties

We have successfully synthesized single-phase wurtzite hexagonal ZnO:Eu³⁺ (1, 5 and 10 mol %) nanoparticles via facile co-precipitation method. The samples have been characterized by powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), fourier transform infrared (FTIR) and UV–visible spectroscopy. Change in optical band gap is explained by invoking the existence 4f electronic states of Eu³⁺ in the band gap of ZnO. Photocatalytic performance of these samples for degradation of methyl orange (MO), rhodamine B (Rh B) and picric acid (PA) under UV illumination is found to be 3–3.5 times higher than pure ZnO. However, 5 mol% doping exhibited the highest catalytic efficiency. This sample was also highly sensitive and selective for PA, and the limit of detection was: 1.790 μM, 1.140 μM and 1.751 μM for 1, 5 and 10 mol% Eu³⁺ doped ZnO samples respectively. Finally, all samples behave weak ferromagnetically at room temperature, but a systematic increase in the ferromagnetic-like response is noticed with Eu³⁺ concentration, despite finding no evidence of secondary magnetic phases; EuO and Eu₂O₃ from XRD measurements. Conceivably, the observed ferromagnetic order is attributed to defect induced f⁷– ferromagnetism. Indeed, low concentration of Eu³⁺ dopant is found to be more significant, as reported by different groups.