Micro & Nano Letters
Volume 11, Issue 4, April 2016
Volumes & issues:
Volume 11, Issue 4
April 2016
Respiratory tract toxicity of titanium dioxide nanoparticles and multi-walled carbon nanotubes on mice after intranasal exposure
- Author(s): Patinya Sukwong ; Koravit Somkid ; Supunsa Kongseng ; Dakrong Pissuwan ; Krongtong Yoovathaworn
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 183 –187
- DOI: 10.1049/mnl.2015.0523
- Type: Article
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Titanium dioxide nanoparticles (TiO2-NPs) and multi-walled carbon nanotubes (MWCNTs) have been used in various industrial and household products. Due to their small size they may be able to penetrate into the body and interfere with cell function and biological structure, which raises serious concerns regarding the possible adverse health effects on human beings from inhalation exposure to TiO2-NPs and MWCNTs. To evaluate the toxicological effects of TiO2-NPs and MWCNTs on the respiratory system, intranasal exposure of TiO2-NPs and MWCNTs in mice was performed. The release of lactate dehydrogenase (LDH), total protein content, and pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-6) into the bronchoalveolar lavage fluid of mice was measured at 24 h post-intranasal instillation. The ICR (Institute for Cancer Research) mouse strain was used as a model. A significant induction of LDH was found in ICR mice treated with TiO2-NPs and MWCNTs at a concentration of 500 µg (kg bw)−1. However, a higher degree of induction was detected in mice treated with TiO2-NPs than the ones that were treated with MWCNTs. In contrast, MWCNTs at the same concentration had more effect on the release of protein content and pro-inflammatory cytokines. The results in this work also suggest that the toxic effects of both TiO2-NPs and MWCNTs on the respiratory tract depend on their concentration. A higher concentration of both particles mostly induced the production of inflammatory signals.
Flexible route to fabricate excellent adsorbents for vitamin B12 by specially designed oil-drop process
- Author(s): Bingzhi Guo ; Yilun Huang ; Qianming Gong ; Junjie Wang ; Daming Zhuang ; Ji Liang
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 188 –191
- DOI: 10.1049/mnl.2015.0491
- Type: Article
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This work presented the preparation of an excellent adsorbent composed of carbon nanotubes (CNTs) and activated carbon (AC) with hierarchical porous structure by specially designed oil-drop process. In this process, CNTs were pre-dispersed in the ethanol diluted phenolic formaldehyde resin and subsequently, the uniform suspension was injected dropwise into the stratified liquids. These liquids were composed of paraffin, polydimethyl siloxane and poly(ethylene glycol) (PEG)-6000 aqueous solution with different densities. After being semi-cured in the three-layered liquids at 70°C, the spheres were carbonised at 600°C and further activated at 800°C with steam. Scanning electron microscope observations indicated that compared with those prepared by two-layered oil bath in the authors’ previous work, the CNTs/phenolic resin spheres acquired by the modified oil-drop method would absorb PEG-6000 instead of polydimethyl siloxane and hence no residue of silica spheres produced in the final CNTs/AC spheres. Meanwhile, pore structure analyses indicated that the average diameter of the pores in the CNTs/AC spheres increased from 8.1 to 23.3 nm, which could be ascribed to the pore forming effect of PEG-6000. The adsorption capacity for vitamin B12 by the porous CNTs/AC spheres reached 52.98 mg/g, which was much higher than commercial AC beads and macroporous resin spheres. This implied that the CNTs/AC spheres could have potential applications in hemoperfusion.
Morphology control and characteristics of ZnO/ZnS nanorod arrays synthesised by microwave-assisted heating
- Author(s): Ming-Kwen Tsai ; Wei Huang ; Sheng-Yao Hu ; Jyh-Wei Lee ; Yueh-Chien Lee ; Min-Hung Lee ; Ji-Lin Shen
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 192 –195
- DOI: 10.1049/mnl.2015.0331
- Type: Article
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The morphology control investigations on ZnO/ZnS core/shell nanorod fabricated by microwave-assisted in-situ surface sulphidation of ZnO nanorod arrays is presented. First, the ZnO nanorod arrays are grown on ZnO/Si substrate by microwave heating of a mixed zinc nitrate hexahydrate and hexamethylenetetramine precursors in deionised water. Then, the grown ZnO nanorod arrays on ZnO/Si substrate are immersed in thioacetamide (TAA) aqueous solution to undergo sulphidation process to form ZnS shell on ZnO core. The morphological, structural, and optical characteristics of the as-prepared ZnO nanorods and ZnO/ZnS core/shell nanorods are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) measurements, respectively. The SEM images and XRD patterns show that the ZnS shell becomes thicker due to more and more ZnS nanoparticles formed with increasing the concentration of TAA solution. The PL spectra demonstrate that the thicker ZnS shell results in more oxygen vacancies occupied by S atom, and would decrease the intensity ratio of the deep-level emission to the ultra-violet emission for the ZnO/ZnS core/shell nanorods synthesised with the higher concentration of TAA solution.
Extension and denature temperature of dsDNA molecules at various magnetic forces by using magnetic tweezers
- Author(s): Yung-Chiang Chung ; Cheng-Wei Tsai ; Shih-Hao Lin
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 196 –201
- DOI: 10.1049/mnl.2015.0388
- Type: Article
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Stretching experiments on lambda-deoxyribonucleic acid (DNA) were carried out in microfluidic channel using a microscope, micro-flow pump, and electromagnet. The micro-flow channel was fabricated by using micro electromechanical technology, and the electromagnet was analyzed by software to simulate the magnetic field distribution. The magnetic field was 248.6 gauss at a current of 0.5 A, and the system could exert 20.4 pN of force on a magnetic bead with diameter of 2.8 μm. When the buffer temperature was 25 °C, the average length of lambda-DNA molecules was 1.9 μm without magnetic field. In a magnetic field of 248.6 gauss, the extension was 7.2 μm, the total length was 9.1 μm, and the coefficient of elasticity was 2.83 × 10−6 N/m. When the buffer temperature was 45 °C, the average length was 4.6 μm without magnetic field. At 45 °C in a magnetic field of 248.6 gauss, the extension was 11.9 μm, the total length was 16.5 μm, and the coefficient of elasticity was 1.71 × 10−6 N/m. Besides, the denature temperature of dsDNA decreases with increasing magnetic force, and the temperature difference can be higher than 7 °C. This system can be used to measure the related properties of macromolecules.
Photocatalytic performance of thermally prepared TiO2/C photocatalysts under artificial solar light
- Author(s): Agnieszka Wanag ; Ewelina Kusiak-Nejman ; Joanna Kapica-Kozar ; Antoni Waldemar Morawski
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 202 –206
- DOI: 10.1049/mnl.2015.0507
- Type: Article
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A simple method of preparation of artificial solar light-active TiO2 photocatalysts is presented. The new TiO2/C samples were obtained by thermal treatment (150, 250, 350 and 450 °C) of industrial titanium dioxide (TiO2-starting) in the presence of naphthalene vapours. The obtained nanomaterials were investigated by means of UV-vis/DR, Fourier transform infrared spectroscopy/diffuse reflectance infrared and X-ray powder diffraction methods. Brunauer–Emmett–Teller (BET) specific surface area and carbon content were also measured. The photocatalytic activity of the photocatalysts was investigated on the basis of phenol degradation under artificial solar light. TiO2/C photocatalysts show higher photocatalytic activity in comparison with TiO2-starting and commercial KRONOClean 7000 photocatalysts. It was noted that the highest decomposition and mineralisation degree of phenol and its degradation co-products were found for sample obtained at 450 °C and contained 0.19 wt.% of carbon. The carbon content, BET surface area and anatase crystallite size are the mean features, which strongly contribute the photocatalytic activity of new carbon-modified TiO2 photocatalysts under artificial solar light. Modification of TiO2 with naphthalene vapours is a promising method, especially taking the mineralisation of phenol and the co-products of its degradation into account.
Preparation of GO/PUF hybrid shell microcapsules using GO sheets as the particulate emulsifier
- Author(s): Chuanjie Fan ; Tian Wei ; Chengyuan Hu ; Xiaodong Zhou
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 207 –211
- DOI: 10.1049/mnl.2015.0445
- Type: Article
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Hexadecane microcapsules with graphene oxide (GO)/poly (urea-formaldehyde) (PUF) hybrid shells were prepared by a simple one-step microencapsulation process in this work. The GO sheets here play dual roles that as an emulsifier and the functional filler. The morphology, shell thickness, and thermal stability of the prepared microcapsules were characterised using scanning electronic microscopy, transmission electron microscopy, and thermal gravimetric analysis, respectively. The results showed that the GO sheets exhibited good emulsifying ability and were successfully introduced into the microcapsule's shell. The hexadecane-loaded microcapsules with GO/PUF shells exhibited excellent thermal and barrier properties.
Nitrate sensing based on Pd-Sn bimetallic composite: a comparison between a bulk electrode and a microband electrode array
- Author(s): Yexiang Fu ; Chao Bian ; Jian Kuang ; Yang Li ; Shanghong Xia
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 212 –214
- DOI: 10.1049/mnl.2016.0002
- Type: Article
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This work presents a bulk electrode and a microband electrode array for electrochemical nitrate sensing in acidic medium. The microelectrode array is fabricated on silicon wafer by micro electro-mechanical system technique. Electrodepostion was carried out to modify tin onto the bulk palladium electrode and thus formed Pd-Sn bimetallic composite. On the microelectrode array, Pd and Sn were successively deposited to obtain a double-layer composite. The performance of the two kinds of electrodes towards nitrate sensing was investigated and compared. The microelectrode array showed better sensitivity and repeatability than the bulk electrode. The results are consistent with the unique properties of the microelectrode array in electrochemical analysis such as high current density and low background noise.
Influence of reducing reagent combination in graphene oxide reduction
- Author(s): Chengyuan Hu ; Rong Zhou ; Chuanjie Fan ; Xiaodong Zhou
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 215 –220
- DOI: 10.1049/mnl.2014.0623
- Type: Article
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Large-scale production of high-quality graphene nanosheets has been considered to be an interesting and significant challenge. A new approach is reported regarding the fabrication of high-quality graphene nanosheets via chemical reduction with the combination of reducing reagents from graphene oxide (GO). High-conducting reduced GO (RGO) was provided with the combination of hydrazine hydrate and hydroiodic acid. RGO was characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman, thermo gravimetric analysis, atomic force microscopy and four-probe conductivity tester. Characterisation results indicated that oxygenated functional groups were removed from GO, and high graphitisation has occurred in GO reduction process. The electrical conductivity of RGO was considerably improved and the C/O ratio of RGO was higher than that prepared by single reducing reagent. Combination of hydrate hydrazine and hydroiodic acid have showed high reduction efficiency and good synergistic effect in GO reduction process. The findings in this work can promote research on prepared graphene-based nanosheets composites by a quick and effective processing technique.
Method for fabricating polymethylmethacrylate micro-nanotube arrays based on spin-coating method and PAA templates
- Author(s): Wei-min Kang ; Zhi-xia Jia ; Hao Liu ; Bo-wen Cheng
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 221 –223
- DOI: 10.1049/mnl.2015.0432
- Type: Article
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A novel and low-cost method for fabricating poly(methyl methacrylate) micronanotube arrays (PMMA-MNAs) using a porous anodic aluminium (PAA) template and spin-coating method was presented. PMMA-MNAs with different length micronanotubes were fabricated by changing the temperature of electric heating drying oven and heating time, then characterised by field-emission scanning electron microscope. Experimental results showed that the poly(methyl methacrylate) (PMMA) liquid membrane was obtained by means of spin coating at the spin velocity of 4000 r/min, and can further grow into PMMA-MNAs using an all-through-pore PAA film as template at a certain temperature. The length of PMMA-MNAs increased nonlinearly with the increasing of the oven temperature and trended to a stable value (about 6.51 μm) at 150°C for 1.5 h. Flexible PMMA-MNAs with characteristics of hollow structure will have wide application prospects in catalyst carrier, high precise sensor, drug sustained release and so on. The presented experimental results could facilitate understanding the growth mechanism of polymer nanotube arrays.
Photolithographically definable SU-8–alumina composite for W-band dielectric resonator antennas
- Author(s): Najeeb Al-Khalli ; Mohammad Alduraibi ; Nacer Debbar ; Muhammad Saleem ; Majeed Alkanhal ; Abdelrazik Sebak ; Mohamed Abdel-Rahman
- Source: Micro & Nano Letters, Volume 11, Issue 4, p. 224 –229
- DOI: 10.1049/mnl.2015.0389
- Type: Article
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A novel process has been developed for fabricating ceramic dielectric structures with dimensions applicable to W-band millimetre wave dielectric resonator antennas. The ceramic dielectric structures are based on composites of SU-8 2150 photoresist and alumina (Al2O3)-alpha nanopowder. The effects of increasing the weight percentage of Al2O3 nanopowder on the photo-polymerisation of the SU-8–Al2O3 composite were systematically investigated. Cylindrical structures with thicknesses up to 500 µm have been fabricated using single casted conventional ultraviolet lithography. The relative permittivity of SU-8–Al2O3 composites at different weight percentages of Al2O3 was studied showing an increase from a relative permittivity of 4.5 to 5.66 with increasing the Al2O3 weight percentage from 0 to 35%. Also, finally, double layer manufacturing of ceramic SU-8–Al2O3 composite structures was demonstrated.
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