Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties

We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of −2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density.     

Effects of coffee ring via inkjet printing seed layers on field emission properties of patterned ZnO nanorods

Inkjet printing, a fast, simple, efficient graphical deposition technology, is first applied to achieve high-quality emission arrays. Patterned arrays of ZnO nanorods have been successfully synthesized via hydrothermal method after inkjet printing the ZnO seed layer. During printing, different substrate temperatures were found to affect the morphology, microstructure and field emission (FE) properties of ZnO arrays. The results showed that the FE performance was improved when the coffee ring effect was eliminated by raising the substrate temperature due to higher aspect ratio of the nanorods. Both the compensating flow characteristics inside the droplets and the mechanism of regulating the rheological behavior of the solution during inkjet printing were analyzed to inhibit the effect of coffee ring, which played an important role in the later patterning electrode construction of emission arrays. The selective growth of the emitter material can be easily realized by introducing the direct patterning technology of inkjet printing in the preparation of field emission electron source.     

Controllable growth of ZnO nanorod arrays with different densities and their photo-electric properties

ABSTRACT: Since the photo-electric response and charge carriers transport can be influenced greatly by the density and spacing of the ZnO nanorod arrays, controlling of these geometric parameters precisely is highly desirable but rather challenging in practice. Here, we fabricated patterned ZnO nanorod arrays with different density and spacing distance on silicon (Si) substrate by electron beam lithography (EBL) method combined with the subsequent hydrothermal reaction process. By using the EBL method, patterned ZnO seed layers with different areas and spacing distances were obtained firstly. ZnO nanorod arrays with different density and various morphologies were obtained by the subsequent hydrothermal growth process. The combination of EBL and hydrothermal growth process was very attractive and made us could control the geometric parameters of ZnO nanorod arrays expediently. Finally, the vertical transport properties of the patterned ZnO nanorod arrays were investigated through the micro probe station equipment and the I-V measurement results indicated that back-to-back Schottky contacts with different barriers height were formed in dark conditions. Under UV light illumination, the patterned ZnO nanorod arrays showed a high UV light sensitivity, and the response ratio was about 104. The controllable fabrication of patterned ZnO nanorod arrays and understanding for their photo-electric transport properties were helpful to improve the performance of nanodevices based on them.     

High improvement of interfacial and mechanical properties in reinforced PP composite by grafting polyethyleneimine modified carboxylic multi-walled carbon nanotubes on short carbon fiber

The properties of carbon fiber reinforced polymer composites (CFRPs) will benefit greatly from improving interfacial performance. In this study, the interfacial properties of the PEI-CNT-CF/PP composite was improved by coating polyethyleneimine (PEI) modified carboxylic multi-walled carbon nanotubes (CNTs) in aqueous solution (PEI-CNT) onto the surface of the CF (PEI-CNT-CF) to form a network structure. The network formation changed the chemical characteristics and compatibility of CF surface by introducing amine (imine) groups, and could induce transcrystallization (TC) at interface of composite. These positive factors led to a 24.6% increasement in the interfacial shear strength (IFSS) of PEI-CNT-CF/PP, and further resulted in 16.2% and 5.3% improvement in tensile and flexural strength, respectively. SEM images of the fracture surface demonstrated a significant improvement in the interfacial adhesion between PEI-CNT-CF and PP resin. These results indicated that the PEI-CNT was a great choice to strengthen the interface of CF/PP system.     

Preparation and electrochemical properties of polyaniline doped with benzenesulfonic functionalized multi-walled carbon nanotubes

Nanocomposite of benzenesulfonic functionalized multi-walled carbon nanotubes doped polyaniline (PANi/f-MWCNTs) was synthesized via a low-temperature in situ polymerization method. The PANi/f-MWCNTs composite has a thin film of PANi coating uniformly on the surface of the f-MWCNTs. The electrochemical results show that PANi/f-MWCNTs nanocomposite possesses good rate response, which could ascribe to the uniform structure and the better conductivity of composite as well as the in situ doping/de-doping process between the benzenesulfonic acid groups of f-MWCNTs and PANi chain. In addition, the composite also has better capacity and cyclability than PANi/p-MWCNTs composite. It could attribute to the presence of f-MWCNTs, which makes more electrolyte contact with PANi to participate in faradaic redox reactions and dopes with the PANi polymer chain through the benzenesulfonic acid groups to form stable polyemeraldine salts.     

Structural,optical and photocatalytic properties of ZnO nanorods: Effect of aging time and number of layers

ZnO thin films were prepared by sol–gel dip coating method onto glass substrates. The effects of aging time of the starting solution (2, 10 and 30 days) and the number of coats (2, 5 and 10 coatings) on structural, morphological and optical properties were investigated. Photocatalytic efficiency was also assessed. X-ray diffraction analysis indicates that all the films exhibit a Zincite-type structure with a preferred grains orientation along the [002] direction. The preferred orientation factor (POF) increases with aging time while the crystallite size decreases. The field emission scanning electron microscopy observations reveals nanorods morphology. The length of ZnO nanorods increase with increasing number of layers whereas their length decreases as a function of aging time while adopting a random orientation. A high optical transparency is observed for all ZnO thin films, ranging from 90 up to 96%. Methylene Blue (MB) dye photocatalytic degradation was found increases with aging time, reaching almost 94% after 10 h under UV irradiation. The apparent reaction rate (K_app) obtained by Langmuir-Hinshelwood model increases with increasing aging time from, from 0.218 h⁻¹ for 2 days to reach a steady state around 0.270 h⁻¹. Nevertheless, a small variation of K_app was recorded when varying the number of coats; 0.223–0.226 h⁻¹.     

Structural and optical properties of doped ZnO/SiO2 nanocomposite

The synthesis of ZnO/SiO₂ nanocomposite doped with Co, Cu and Mn nanoparticles were performed using sol-gel method. Rietveld refinement analysis was done for the X-ray diffraction data and results showed that all samples are single wurtzite hexagonal phase and have an average crystallite size ~14 nm. The lattice parameters, bond length, crystallite size, microstrain, dislocation density and the system volume were studied in details. Transmission electron microscopy technique showed that nanoparticles characterized by an elliptical shape. Fourier transform infrared and scanning electron microscope techniques proved the presence of SiO₂ in the system. The energy gap values of both undoped and doped samples with Co, Mn and Cu were 2.84, 2.47, 2.71 and 2.8 eV, respectively. Photoluminescence spectra for undoped and doped ZnO/SiO₂ were investigated in details.     

多壁碳纳米管吸附处理柴油废水的动力学特性

通过静态吸附实验研究了多壁碳纳米管(MWCNTs)对柴油废水中油的吸附特性,并与活性炭进行了比较。表明MWCNTs和活性炭对柴油的吸附量均在前10 min上升迅速60 min左右可达到吸附平衡,但MWCNTs的吸附能力远大于活性炭。在动力学分析中发现准二级动力学模型能较好地符合研究体系,且随温度的升高,吸附速率增加。根据Arrhenius公式,算得MWCNTs吸附柴油2^#的活化能(E_a)的值为14.21 kJ·mol^-1,可推断吸附应是物理吸附。利用颗粒内扩散模型发现MWCNTs吸附分外表面吸附、碳管间大空隙的内扩散和管间小空隙内扩散3阶段,而活性炭对柴油2^#的吸附分为外表面吸附和颗粒内扩散两个阶段,且受边界层的影响较大。MWCNTs对柴油的吸附存在初始吸附行为。在298 K下MWCNTs对3种柴油的吸附及在288、298和308 K下对柴油2^#的吸附,都是中等起始吸附,柴油2^#的吸附,随温度的升高,起始吸附行为增强,在318 K时吸附过程具有较强烈的起始吸附行为。     

碳纳米管在电化学传感器中的应用进展

综述了碳纳米管(Carbon Nanotube,CNT)在电化学传感器研究中的应用进展。重点介绍了CNT电极和CNT修饰电极的制备、电化学特性及应用,并对其在DNA电化学生物传感器方面的应用前景与挑战进行了展望。     

Characterization and gas sensing properties of bead-like ZnO using multi-walled carbon nanotube templates

We report bead-like ZnO nanostructures for gas sensing applications, synthesized using multi-walled carbon nanotube (MWCNT) templates. The ZnO nanostructures are grown following a two-step process: in the first, ZnO nanoparticles are synthesized on MWCNTs by thermal evaporation of a Zn powder; and in the second, the hybrid nanostructures are heat-treated at 800 °C. Scanning and transmission electron microscopy images indicate that the bead-like ZnO nanostructures have surface protuberances with nanoparticle sizes ranging from 20 to 60 nm, and a well-crystallized hexagonal structure. Gas sensors based on multiple-networked bead-like ZnO showed considerably enhanced electrical responses and better stability to both oxidizing (NO₂) and reducing (CO) gases compared with previously reported nanostructured gas sensors, even if the response to CO gas was slow to increase. Both the NO₂ and CO gas sensing properties increased dramatically when the working temperature was increased up to 300 °C. The response sensitivities measured were 2953%, 5079%, 9641%, 3568%, and 3777% to 20 ppm NO₂ at 200, 250, 300, 350 and 400 °C, respectively. For CO gas on the other hand, the response sensitivities were 107%, 110%, 114%, 118%, and 122% at 5, 10, 20, 50, and 100 ppm concentrations, respectively. For concentrations between 5 and 20 ppm, the recovery time of the oxidizing gas was much shorter than the response time. The origin of the NO₂/CO gas sensing mechanism of the bead-like ZnO nanostructures is discussed.     

表面活性剂分散多壁碳纳米管机理及性能评价

十二烷基硫酸钠(SDS)、十六烷基三甲基溴化铵(CTAB)、壬基酚醚璜基琥珀酸单酯二钠盐(HT A-103)、辛基酚聚氧乙烯醚(OP-10)分别与质量分数为0.1％的多壁碳纳米管(MWCNTs)复配,制备出4种表面活性剂-MWCNTs分散体系.利用UV-Vis光谱、Zeta电位及SEM对其分散性进行了评价,分析了各类表...     

Growth and optical properties of ZnO nanorod arrays on Al-doped ZnO transparent conductive film

ZnO nanorod arrays (NRAs) on transparent conductive oxide (TCO) films have been grown by a solution-free, catalyst-free, vapor-phase synthesis method at 600°C. TCO films, Al-doped ZnO films, were deposited on quartz substrates by magnetron sputtering. In order to study the effect of the growth duration on the morphological and optical properties of NRAs, the growth duration was changed from 3 to 12 min. The results show that the electrical performance of the TCO films does not degrade after the growth of NRAs and the nanorods are highly crystalline. As the growth duration increases from 3 to 8 min, the diffuse transmittance of the samples decreases, while the total transmittance and UV emission enhance. Two possible nanorod self-attraction models were proposed to interpret the phenomena in the sample with 9-min growth duration. The sample with 8-min growth duration has the highest total transmittance of 87.0%, proper density about 75 μm⁻², diameter about 26 nm, and length about 500 nm, indicating that it can be used in hybrid solar cells.     

ZnO nanorod array-coated mesh film for the separation of water and oil

Dense and vertically aligned ZnO nanorod arrays with a large area have been fabricated successfully on the stainless steel mesh by a simple chemical vapor deposition method. The coated mesh exhibited both superoleophilic and superhydrophobic properties, even if it was not modified by low surface energy materials. The separation efficiencies were more than 97% in the filtration of water and oil. Besides, the wettability of the coated mesh was still stable after it was soaked in the corrosive solutions for 1 h. A detailed investigation showed that the coated mesh has the best superhydrophobic property when the stainless steel mesh pore size was about 75 μm.     

多壁碳纳米管的有机修饰与表征

为了增加多壁碳纳米管(MWCNTs)表面活性,通过浓H2SO4和浓HNO3处理过的MWCNTs与SOCl2回流进而与合成的N-乙基-3,6-二氨基咔唑反应,得到了有机修饰的MWCNTs.用傅立叶变换红外(FTIR)光谱对有机修饰的MWCNTs结构进行研究.研究结果结构表明:有机修饰的MWCNTs红外光谱在1617和16...     

多壁碳纳米管的氨表面改性及其臭氧催化降解草酸

采用水热方法制备了一系列用浓氨水改性的多壁碳纳米管催化剂,该催化剂的活性通过非均相催化臭氧化降解水溶液中的草酸来进行评价。降解过程符合零级反应动力学模型,且催化剂的表观动力学常数与其表面碱性基团数量以及零电位pH值（pHPZC）呈正相关。为此,可断定用浓氨在水热条件下处理多壁碳纳米管能明显提高催化臭氧降解草酸能力是因为提高了催化剂的表面碱性基团数量和pHPZC。     

Structural and optical properties of a radio frequency magnetron-sputtered ZnO thin film with different growth angles

This study introduces optical properties of a columnar structured zinc oxide [ZnO] antireflection coating for solar cells. We obtained ZnO films of columnar structure on glass substrates using a specially designed radio frequency magnetron sputtering system with different growth angles. Field-emission scanning electron microscopy was utilized to check the growth angles of the ZnO films which were controlled at 0°, 15°, and 30°. The film thickness was fixed at 100 nm to get a constant experiment condition. Grain sizes of the ZnO films were measured by X-ray diffraction. A UV-visible spectrometer was used to measure the transmittance and reflectance of the ZnO film columnar structures as a function of the growth angles.     

单壁碳纳米管显著增强的ZnO可见光催化活性

利用醋酸锌为原料,采用溶胶-凝胶法制备了单壁碳纳米管（SWMTs）和氧化锌的纳米复合物（ZnO/SWNTs）。用X射线衍射光谱（XRD）、拉曼光谱、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、热重分析（TGA）、傅里叶变换红外光谱（FT-IR）以及紫外-可见吸收光谱（UV-Vis）对复合物进行了表征。结果显示,粒径为10～20 nm的ZnO粒子均匀地负载在SWNTs表面,且在可见光区具有很好的光吸收性能。研究了ZnO/SWNTs光催化剂在太阳光照射下对甲基橙和亚甲基蓝的光催化降解情况。结果表明,复合物的催化活性明显高于ZnO。对于甲基橙,光照200 min后,降解率为99.8%,是纯ZnO（4.8%）的20倍;对于亚甲基蓝,仅光照20 min,降解率就达到了98.4%,是纯ZnO（4.0%）的25倍。     

TPU/PLA nanocomposites with improved mechanical and shape memory properties fabricated via phase morphology control and incorporation of multi-walled carbon nanotubes nanofillers

Shape memory polymer nanocomposites based on thermoplastic polyurethane (TPU)/polylactic acid (PLA) blends filled with pristine multi-walled carbon nanotubes (MWCNTs) and modified MWCNTs─COOH were fabricated by direct melt blending technique and investigated for its morphology, mechanical, thermal, electrical, and shape memory properties. Morphological characterizations by using transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM) revealed better dispersion of MWCNTs─COOH in the polymer blend, which is attributed to the improved interfacial interactions between the polymer blends and MWCNTs-COOH. Loading of the MWCNTs-COOH in the TPU/PLA blends resulted in the significant improvements in the mechanical properties such as tensile strength and elastic modulus and these effects are more pronounced on increasing the MWCNTs─COOH loading amount, when compared to the pristine MWCNTs filled system. Thermal analysis showed that the glass transition temperature of the blends increases slightly with increasing loading of both pristine and modified MWCNTs in the system. The resistance of nanocomposites decreased from 2 × 10¹² Ω to 3.2 × 10¹⁰ Ω after adding 3% MWCNTs─COOH. The shape memory performance tests showed that the enhancement of shape recovery by 252% could be achieved at 3% MWCNTs loading, when compared to that of TPU/PLA blends.     

A close correlation between nucleation sites,growth and final properties of ZnO nanorod arrays: Sol-gel assisted chemical bath deposition process

Different ZnO seed layers are synthesized by changing sol-gel parameters, including precursor concentration, type of solvent, and type of additive in order to systematically investigate the importance of seed layer properties on the nucleation, growth, and final properties of zinc oxide (ZnO) nanorod (NR) arrays. The X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) show the importance of the seed layer on ZnO NRs properties. Results verify that the relative intensity (RI factor) of (002) polar planes in the XRD patterns of ZnO nanoparticles (NPs) together with the aspect ratio, density, and alignment of ZnO NRs control the structural characteristics of those arrays. For instance, the RI factor of ZnO NPs and NRs follow the same trend when changing precursor concentration in sol preparation step. However, the importance of other parameters, including aspect ratio, density, and alignment of NRs is confirmed by changing solvent and additive. In addition, FESEM images show that the density of ZnO NRs is proportional to NPs density and inversely proportional to the size of ZnO NPs in the seed layers. Besides, the significant role of wrinkled inter-layer on NRs properties, together with the formation mechanism of that inter-layer are profoundly investigated.     

Photocurrent detection of chemically tuned hierarchical ZnO nanostructures grown on seed layers formed by atomic layer deposition

We demonstrate the morphological control method of ZnO nanostructures by atomic layer deposition (ALD) on an Al₂O₃/ZnO seed layer surface and the application of a hierarchical ZnO nanostructure for a photodetector. Two layers of ZnO and Al₂O₃ prepared using ALD with different pH values in solution coexisted on the alloy film surface, leading to deactivation of the surface hydroxyl groups. This surface complex decreased the ZnO nucleation on the seed layer surface, and thereby effectively screened the inherent surface polarity of ZnO. As a result, a 2-D zinc hydroxyl compound nanosheet was produced. With increasing ALD cycles of ZnO in the seed layer, the nanostructure morphology changes from 2-D nanosheet to 1-D nanorod due to the recovery of the natural crystallinity and polarity of ZnO. The thin ALD ZnO seed layer conformally covers the complex nanosheet structure to produce a nanorod, then a 3-D, hierarchical ZnO nanostructure was synthesized using a combined hydrothermal and ALD method. During the deposition of the ALD ZnO seed layer, the zinc hydroxyl compound nanosheets underwent a self-annealing process at 150 °C, resulting in structural transformation to pure ZnO 3-D nanosheets without collapse of the intrinsic morphology. The investigation on band electronic properties of ZnO 2-D nanosheet and 3-D hierarchical structure revealed noticeable variations depending on the richness of Zn-OH in each morphology. The improved visible and ultraviolet photocurrent characteristics of a photodetector with the active region using 3-D hierarchical structure against those of 2-D nanosheet structure were achieved.