Micro & Nano Letters
Volume 13, Issue 7, July 2018
Volumes & issues:
Volume 13, Issue 7
July 2018
Optical absorption theoretical analysis for thin film crystalline silicon solar cells fabricated on the hexagonal close-packed dome arrays
- Author(s): Kun Huang ; Xingyu Han ; Yunbo Shi ; Huiliang Cao ; Jinyang Gao ; Zongmin Ma ; Kim Heng
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 892 –895
- DOI: 10.1049/mnl.2017.0245
- Type: Article
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In this work, the low aspect ratio hexagonal close-packed dome arrays were designed to trap light for c-Si thin film solar cells. The optical performance of the designed solar cell was theoretically studied via simulation based on the rigorous coupled wave analysis in detail. The result of the simulation showed the model of the solar cell with arrays exhibited absorptivity enhancement in the longer wavelength range. Simultaneously, the integral for the AM 1.5 absorbance spectrum of each model showed that the absorption gains reach up to the highest point of 45.13% in the periodicity of 0.7 μm.
Reversible lossless manipulation of water droplets with large-range volume
- Author(s): Liu Huang ; Xuyue Wang ; Changlin Zhao ; Jiyu Liu ; Ziai Liu ; Yankui Sun ; Xin Liu ; Jinlong Song
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 896 –901
- DOI: 10.1049/mnl.2017.0789
- Type: Article
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The lossless manipulation of microdroplets has great promising applications in the fields of such as liquids transportation. In recent years, superhydrophobic surfaces with low adhesion have been utilised as an effective solid surface to realise the lossless transfer of liquids. However, the present methods using superhydrophobic surfaces are hard to realise the reversible lossless manipulation of water droplets with a large-range volume. Here, a special transfer pipette composed of a superhydrophobic hole and an optimised pressure-generation device is developed to realise the lossless manipulation of water droplets. The superhydrophobic surfaces are obtained by electrochemical etching, boiling-water immersion and stearic acid modification, showing an excellent superhydrophobicity with a water contact angle of ∼165° and roll-off angle of ∼2°. The capture and release of water droplets are realised via controlling the resultant force of the vertical component of capillary force and gravity of droplets. The applied pressure is far less than the threshold pressure which guaranties the lossless property in the manipulation processes. The operable limiting volume of water droplets even reaches to 1404 µL, showing a large-range operable volume. Moreover, the strategy can easily realise the reversible and repeatable manipulation showing potential applications in the biological and microfluidic fields.
Synthesis, characterisation, and evaluation of core–shell Fe3O4/SiO2/polypyrrole composite nanoparticles
- Author(s): Bei Li ; Yongsheng Qiao ; Jinhui An ; Lazhen Shen ; Qi Ma ; Yong Guo
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 902 –906
- DOI: 10.1049/mnl.2017.0907
- Type: Article
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This work reported a facile synthetic approach to synthesise core–shell Fe3O4/SiO2/polypyrrole composite nanoparticles with the superparamagnetic Fe3O4 nanoparticles as the inner core. The core–shell Fe3O4/SiO2/polypyrrole composite nanoparticles were prepared through a three-step approach involving co-precipitation for the synthesis of Fe3O4 nanoparticles, Stöber method for SiO2 intermediate layer coating and solvothermal methods for polypyrrole shell. The as-prepared nanoparticles were characterised using transmission electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses and vibration sample magnetometer. The particle size of the inner core Fe3O4 nanoparticles was found to be 15 ± 3 nm, and the thicknesses of the SiO2 shell and polypyrrole shell were ∼2.5 and ∼5 nm, respectively. From Fe3O4 nanoparticles to Fe3O4/SiO2 and then to Fe3O4/SiO2/polypyrrole composite nanoparticles, the magnetic saturation gradually decreases from 67 to 34 emu/g, then dropped to 7 emu/g. The as-prepared Fe3O4/SiO2/polypyrrole composite nanoparticles showed potential applications in drug and gene delivery systems.
Facile synthesis of TiO2 hollow spheres via aerosol-assisted spray drying for photocatalysis
- Author(s): Shumin Wang ; Xiaoxia Yan ; Yan Zhu ; Dongmei Deng ; Haibo He ; Hua Chen ; Liqiang Luo
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 907 –910
- DOI: 10.1049/mnl.2017.0817
- Type: Article
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A simple and feasible aerosol-assisted spray-drying method was developed. High-resolution transmission electron microscopy images demonstrated the as-prepared TiO2 possessed hollow structure with large cavity formed by the accumulation of numerous nanoparticles. Moreover, the obtained TiO2 hollow spheres could lead to the improved light-harvesting and low recombination of photo-generated electron–hole carriers, as well as large specific surface area. These excellent properties contributed to the superior photocatalytic activity in degrading Rhodamine B.
Manual control of optical tweezer switching for particle trapping and injection
- Author(s): Nithiroth Pornsuwancharoen ; Phichai Youplao ; Khomyuth Chaiwong ; Prateep Phatharacorn ; Surasak Chiangga ; Victor Koledov ; Jalil Ali ; Muhammad Safwan Aziz ; Senee Suwandee ; Preecha Yupapin
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 911 –914
- DOI: 10.1049/mnl.2017.0891
- Type: Article
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This work presents an optical switching model that the tweezer probe uses for manually switching the controlled by an external switch, in which the upward and downward switching can be operated and simultaneously switched. By using the microring resonator incorporated with the two non-linear phase modulators, the optical tweezer can be generated and the switching probes controlled. The switching time with the table force of ∼2 fs is obtained. The tweezer force and torque are calculated and interpreted for molecule trapping and injecting from and to the trapping and the target surfaces. The relative forces and torques are calculated and plotted. In applications, the specific forces and torques can be controlled to perform the appropriate trapping and injecting. The switching time depends on the external switching module, which may be electronically controlled.
Li4Ti5O12/Ti4O7/carbon nanotubes composite anode material for lithium-ion batteries
- Author(s): Xiaoyan Zhang ; Wen Xu ; Xing Li ; Xiaoxi Zhong ; Wanying Liu ; Yuanhua Lin ; Ruochen Xia
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 915 –918
- DOI: 10.1049/mnl.2017.0799
- Type: Article
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The work describes a method for preparing Li4Ti5O12 (LTO)/Ti4O7/carbon nanotubes (CNTs) composite as anode material for lithium-ion batteries (LIBs). The electrochemical tests make sure that LTO/Ti4O7/CNTs composite provides excellent electrochemical performance compared with spinel LTO. Notably, the LTO/Ti4O7/CNTs composite exhibits good cycle stability, retaining over 78.5% of its initial capacity after 100 cycles at 20°C, whereas that of spinel LTO is 32.6 mAh g−1 (35.4% retention). The significantly improved electrochemical performance of the LTO/Ti4O7/CNTs electrodes can be mainly ascribed to the improvement of electronic conductivity and faster electron transfer from the CNTs and Ti4O7. The outstanding electrochemical performance makes it a promising anode material for high-rate and long life LIBs.
t-ZrO2 prepared by a novel zirconium oxalate synthesised solvothermally
- Author(s): Siyu Ni and Yafeng Li
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 919 –922
- DOI: 10.1049/mnl.2017.0711
- Type: Article
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In this work, the authors intentionally employ the oxalic acid (OA) to replace terephthalic acid to synthesise a novel zirconium oxalate under the similar reaction condition with UIO-66. The powder X-ray diffraction and thermal gravimetric analysis confirm that as-synthesised zirconium oxalate is a pure phase and oxalate serves as bridging ligand. Scanning electron microscope indicates that zirconium oxalate is aggregated together by several micrometres of needle-like crystals. After zirconium oxalate is calcined at 500°C, the product is the pure tetragonal zirconia (ZrO2) with high crystallinity. The morphology and particle size of ZrO2 are basically unmodified with a comparison with the zirconium oxalate. X-ray photoelectron spectroscopy reveals that the structural carbon acts as a phase transformation promoter to stabilise the tetragonal ZrO2.
Fabrication of large-scale Ag micro/nanostructures using electrochemical migration
- Author(s): Teruki Nakakura and Masumi Saka
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 923 –926
- DOI: 10.1049/mnl.2017.0913
- Type: Article
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Fabrication of Ag micro/nanostructures was studied because of their excellent chemical, electrical, and optical properties. Ag micro/nanostructures are usually produced via chemical methods, but these methods require the processing of waste liquid and multiple devices. The work proposes a fabrication method using electrochemical migration (ECM), which is a simple and environmentally friendly method because this method requires only metal electrodes, water, and a DC bias without chemical agents. A fabrication method for Ag micro/nanostructures using ECM with a large separation between the electrodes is demonstrated, and the deposition behaviour of Ag micro/nanostructures and the factors influencing the deposition are determined.
Effect of surfactant type on buckypaper electrochemical performance
- Author(s): Nadia Farsaei Vahid ; Mohammad Reza Marvi ; Mohammad Reza Naimi-Jamal ; Seyed Morteza Naghib ; Ali Ghaffarinejad
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 927 –930
- DOI: 10.1049/mnl.2017.0691
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In this work, buckypapers (BPs) were synthesised by different types of non-ionic surfactants. The prepared BPs were characterised by different methods. Using of non-ionic and also non-toxic surfactant, Tween 20, made the surface possible to immobilise the biological molecules on the surface for measuring the electrochemical properties changes. Moreover, this surface showed better electrochemical behaviour, higher conductivity, and better charge transfer kinetics than BP which was synthesised by conventional Triton X100. To our knowledge, this is the first research on the effect of surfactant type on the BP synthesis and characteristics.
Carbon composite coatings on Ti for corrosion protection as bipolar plates of proton exchange membrane fuel cells
- Author(s): Pingping Gao ; Zhiyong Xie ; Chun Ouyng ; Xiaobo Wu ; Ting Lei ; Chunbo Liu ; Qizhong Huang
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 931 –935
- DOI: 10.1049/mnl.2018.0076
- Type: Article
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A highly corrosion resistant and conductive composite coating on Ti bipolar plates was prepared by the hydrothermal and impregnation method. The composite coating consisted of amorphous carbon immersed in suspension solution [polytetrafluoroethylene (PTFE) 10 wt.% + TiN nanoparticles 3 g/l]. The surface of coating was completely smooth and nano-holes on the surface of coatings were filled by PTFE and TiN particles. TiN particles were uniformly distributed in the coating when 0.1 mol/l of glucose was used as carbon source. The composite coating exhibited excellent conductivity and corrosion resistivity. It was revealed that corrosion current density, interfacial contact resistance, and contact angle were 0.009 µA/cm2, 13 mΩ cm2, and 115.53°, respectively. Meanwhile, it was shown that the corrosion current density of the coating was below 1 µA/cm2 with a potentiostatic polarisation test (0.6 and −0.1 V). In summary, the Ti substrate with a carbon composite film immersed in suspension solution showed a great potential application in bipolar plates of proton exchange membrane fuel cells.
Photophysical performances and morphology of phosphorescent electrospun fibres fabricated from iridium complex/PMMA blends
- Author(s): Aihui Liang ; Tian Cao ; Xiulan Yang ; Yi Chen ; Han Wang ; Zhiping Wang ; Dewang Liu ; Ming Luo
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 936 –940
- DOI: 10.1049/mnl.2017.0840
- Type: Article
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Yellow phosphorescent electrospun (ES) fibres were successfully fabricated from a binary blend of iridium complex/poly(methyl methacrylate) (PMMA) by a single spinneret, whose diameters range from 350 to 1300 nm. Owing to the geometrical confinement of the electrospinning process, the aggregation of iridium complex Y1 in the ES fibres is much smaller than that in the spin-coated films. Moreover, the photoluminescence quantum efficiency of the ES fibres is much higher than that of the spin-coated films. The lifetimes of ES fibres become shorter and the diameters of ES fibres become larger with increasing the ratio of Y1 in Y1/PMMA blend from 1 to 10%. In the scanning electron microscope images, the surface structure on the Y1/PMMA blend fibres was smooth and non-porous, which probably because the high boiling point solvent of N,N-dimethylformamide was used in the electrospinning process. The present work demonstrates that phosphorescent ES fibres can be prepared from the binary blend of iridium complexes/PMMA, which could be used in wearable organic light-emitting diodes.
Preparation of anti-corrosive high-conductivity copper–graphene composite film
- Author(s): Pengzhong Liu ; Xiaohong Chen ; Ping Liu
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 941 –946
- DOI: 10.1049/mnl.2018.0188
- Type: Article
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Copper matrix/graphene composite films were prepared using copper foil as a growth matrix and ethylene as a carbon source. Research results showed that when the concentration of carbon decreased, nucleation density was low and the graphene grains were larger with better boundaries to other grains. A moderate amount of hydrogen assisted decomposition of the hydrocarbons, but also etched some nucleation sites, favourable for the growth of high-quality graphene. The H2, Ar and carbon source gas (0.931 vol% C2H4–Ar mixture) with the flow rates of 70, 4000 and 5 sccm and the growth time of 10 s were the parameters chosen to obtain the copper matrix bilayer graphene composite films. The resulted composite film demonstrated electrical conductivity better than copper. Addition of graphene can greatly improve the corrosion resistance of matrix material. This is true whether in the electrochemical corrosion or immersion corrosion in the oxidation and alkaline environments.
Pressureless densification and properties of TiB2–B4C composite ceramics with Ni as additives
- Author(s): Li Ma ; Jincheng Yu ; Xue Guo ; Yujun Zhang ; Hongyu Gong
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 947 –950
- DOI: 10.1049/mnl.2017.0709
- Type: Article
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Titanium diboride–boron carbide (TiB2–B4C) composite ceramics were prepared using different amounts of Ni as sintering aids by pressureless sintering at 2100°C for 60 min under an argon atmosphere. This study focused on the effects of different amounts of Ni as additives on densification and mechanical and thermal properties of TiB2–B4C composite ceramics. Results showed that the relative density, hardness, flexural strength and thermal conductivity of obtained composite ceramics with 1.3 wt% Ni addition were 98%, 20.4 GPa, 330 MPa and 30 W/m K, respectively. However, fracture toughness was 6 MPa m1/2 when the content of Ni was fixed at 2.2 wt%.
Alternating and semicontinuous chemical reduction method for high production of silver nanoparticles
- Author(s): Miguel A. Pedroza-Toscano ; Susana Lopez-Cuenca ; Edgar D. Moreno-Medrano ; Martin Rabelero-Velasco ; Rodolfo Salazar-Peña
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 951 –954
- DOI: 10.1049/mnl.2018.0085
- Type: Article
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Synthesis of silver nanoparticles (AgNPs) was carried out in aqueous solutions. Silver nitrate was used as precursor, carboxymethyl cellulose (CMC) as stabilising agent, and sodium borohydride as reducing agent. The reaction was semicontinuous by feeding both the precursor and reducing agent into the stabilising agent aqueous solution in an alternated fashion. Weight ratios of 1:1 AgNO3:CMC were used in the reduction reactions. AgNPs were characterised by UV–vis spectroscopy, transmission electronic microscopy (TEM), and X-ray diffraction. The formation of AgNPs was confirmed by the presence of an absorption peak about 400 nm using UV–vis spectrophotometry. Spheroidal nanoparticles with an average diameter between 5 and 90 nm were observed by TEM. High productivity of AgNPs was obtained at lower reaction times and at low temperature compared with others previously reported in the literature.
Multistep synthesis of AgBr quantum dots coupled porous BiOBr spheres for enhanced photocatalysis
- Author(s): Rui-Juan Qi ; Li-Xia Yang ; Chen-Yu Yi ; Chun-Liang Hang ; Qian Liu
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 955 –958
- DOI: 10.1049/mnl.2017.0815
- Type: Article
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A three-step route has been adopted for the synthesis of AgBr quantum dots coupled porous BiOBr spheres. Firstly, porous Bi spheres were obtained through a simple solvothermal method employing ethylene glycol as a reducing agent. Sequentially, a redox reaction of Bi spheres with NH4Fe(SO4)2 as an oxidiser was employed to prepare porous BiOBr spheres. Finally, AgBr quantum dots were loaded on BiOBr spheres through in situ precipitation. The obtained powders were characterised by employing powder X-ray diffraction for phase confirmation and transmission electron microscopy for microstructure evolution. BiOBr hierarchical spheres with a diameter of ca. 500 nm were made up by two-dimensional nanosheets. AgBr quantum dots were deposited on BiOBr petals and did not influence the microstructure and morphology of the BiOBr host. The BiOBr/AgBr composite exhibited higher photocatalytic activity than pure BiOBr porous spheres in degrading Rhodamine B dyes.
Spectroscopic-ellipsometry measurement of the optical properties of zinc oxide thin films prepared by sol–gel method: coating speed effect
- Author(s): Maryam Motallebi Aghgonbad and Hassan Sedghi
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 959 –964
- DOI: 10.1049/mnl.2017.0882
- Type: Article
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In this work, thin films of zinc oxide were prepared by sol–gel spin coating method with different coating speeds of 3600, 4800 and 6000 rpm. Spectroscopic ellipsometry analysis was used to extract the optical constants such as refractive index n, and extinction coefficient k, in the wavelength range of 300–800 nm. The knowledge of both n and k allows the calculation of the important properties such as real and imaginary parts of the dielectric function, the absorption coefficient and the optical bandgap energy. Ellipsometric measurements were collected at an incidence angle of 70°. Also, a computer programming of Kramers–Kronig (KK) relations was used to calculate the optical properties. The ellipsometric results were compared with the parameters obtained by the KK method. It was found that the coating speed in sol–gel method, noticeably affect optical properties of the films. The films were found to exhibit high transmittance and low absorbance in the visible region. The direct optical bandgap of the films was obtained in the range of 3.4–3.7 eV using the ellipsometric method. A decrease in the void fraction of layers with an increment in the coating speed had been seen.
Enhancing the delay performance of junctionless silicon nanotube based 6T SRAM
- Author(s): Shubham Tayal and Ashutosh Nandi
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 965 –968
- DOI: 10.1049/mnl.2017.0867
- Type: Article
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This work investigates the delay performance of junctionless silicon nanotube (JLSiNT) field-effect transistor (FET) based 6T SRAM cell. The study demonstrates that the delay performance of symmetric drain/source DS-JLSiNT FET (inner gate covers drain, channel, and source regions) based 6T SRAM gets improved when the inner gate of nanotube covers only either drain and channel regions (D-JLSiNT FET) or source and channel regions (S-JLSiNT FET) because of improved I on/C gg. The improvement in read (write) access time is ∼22% (17%) and ∼9% (20%) when DS-JLSiNT FET is replaced by D-JLSiNT FET and S-JLSiNT FET, respectively, in DS-JLSiNT FET based 6T SRAM. Furthermore, due to partial covering of inner gate, the gate electrostatic integrity is reduced which decreases the ratio of on-current to off-current (I on/I off) resulting in degraded static noise margin (SNM). However, the deterioration in write SNM, hold SNM, and read SNM are almost minimal (∼0.3, 0.9, and 2%, respectively) for S-JLSiNT FET based SRAM as compared to DS-JLSiNT FET based SRAM. However, the deterioration in SNMs is aggravated for D-JLSiNT FET based SRAM as compared to DS-JLSiNT FET based SRAM. Thus, S-JLSiNT FET is the best configuration for designing of JLSiNT FET based 6T SRAM cell.
Fabrication and application of porous Pd@Mt/PC composite as an efficient green heterogeneous catalyst for Suzuki cross-coupling reaction
- Author(s): Li Tian ; Sun Yunlong ; Zhou Rui ; Long Mudi ; Liu Yufan
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 969 –973
- DOI: 10.1049/mnl.2017.0511
- Type: Article
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The palladium-loaded montmorillonite (Pd@Mt) was mixed with polycarbonate (PC) solution to obtain Pd@Mt/PC composite. A different solvent was used to treat the Pd@Mt/PC coating so as to induce crystallisation of PC and fabricate a porous surface. The scanning electron microscopy and surface area measurement results proved this successful change. The Pd@Mt/PC that was treated by isopropanol fabricated a porous surface coating on glass microsphere (Pd@Mt/PC-M), which was found to be a conveniently obtained environment-friendly catalyst in the Suzuki reaction, as the Pd content was only 0.2012 ppm in the product solution. Notably, it exhibited high efficiency, affording the corresponding product in good to excellent yields for 20 reactants (in the range of 78–99%, only two reactants gained yield below 90%). As a heterogeneous catalyst, it could be easily recovered by simple filtration from the reaction mixture and a high yield of more than 90% at a third run was remained.
Structure, magnetic and microwave studies of mechanically alloyed powders Fe45Ni35Co20
- Author(s): Ahmed Haddad ; Insaf Ouldbrahim ; Mohamed Azzaz
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 974 –978
- DOI: 10.1049/mnl.2017.0655
- Type: Article
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Nanocrystalline Fe-35 wt%Ni-20 wt%Co has been prepared by using a high-energy planetary ball mill with increasing milling time from 4 to 36 h. Microstructural characterisations showed the development of an face-centred cubic nanostructured Fe-35 wt%Ni-20 wt%Co alloy with an average crystallite size of 8 nm. The magnetic investigation revealed that the nanostructures obtained from a milling time of 36 h have the highest magnetic saturation and the lowest coercive field. In addition, the hardness and the electromagnetic absorption of the Fe-35 wt%Ni-20 wt%Co alloy were found to increase with the milling time. These evolutions could be attributed to the crystallite size and the strain variations in the samples during milling.
Synthesis and characterisation of Fe3O4 at MPTMS at Au nanocomposite by sol–gel method for the removal of methylene blue
- Author(s): Maryam Mohebbi ; Alireza Allafchian ; Seyed Amir Hossein Jalali ; Parviz Kameli
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 979 –984
- DOI: 10.1049/mnl.2018.0127
- Type: Article
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New magnetic nanocomposite core-shell–shell Fe3O4 at 3-mercoptopropyltrimethoxysilan (s) at Au has been synthesised by the sol–gel method. First magnetite nanoparticles are synthesised by co-precipitation method, then the obtained particles are coated by MPTMS coating with the sol–gel method. At final step, gold nanoparticle has been used to coat Fe3O4 at MPTMS. New magnetic nanocomposite has been characterised by using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and vibrating sample magnetometer, UV–vis spectroscopy. The new nanocomposite has been studied for its efficiency in adsorption of methylene blue (MB) as a model for azo paints which has been widely used in aquatic solutions of textile industry. The adsorption test has been carried out at various contact time of adsorbent and dye, temperature and stirring speed under visible light. The results indicate that the adsorption capacity of MB dye rises by the increase in the temperature, stirring speed and the contact time between MB and adsorbent. This nanocomposite easily separated from the solution with help of week magnetic field. Therefore this new adsorbent could be regarded as a very good adsorbent for MB removal.
Controllable synthesis of cuprite (Cu2O) microcrystals and their shape-dependent photocatalytic performances
- Author(s): Peili Liu ; Xu Zhang ; Li Yao ; Chengliang Han
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 985 –988
- DOI: 10.1049/mnl.2017.0495
- Type: Article
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Microcrystals of cuprite (Cu2O) samples exhibiting octahedral and spherical morphologies were synthesised via a facile chemical method and were then characterised by X-ray powder diffraction and scanning electron microscopy. It was observed that the potassium sodium tartrate (KNaC4H4O6·4H2O, PST) and gelatin addition had a prominent effect on the morphologies. The possible formation mechanism of Cu2O microcrystals was discussed based on the effects of PST and gelatin. Furthermore, the photocatalytic activities of the prepared Cu2O microcrystals were investigated by UV–vis spectrophotometry, demonstrating that their behavior was influenced by the different morphologies, and the Cu2O microspheres possessed the highest activity.
Fabrication and modal characterisation of large-area polymer membranes for acoustic micro-electromechanical systems devices
- Author(s): Luca Camellini ; Alberto Torin ; Asaad K. Al-mashaal ; Graham S. Wood ; Michael J. Newton ; Rebecca Cheung ; Enrico Mastropaolo
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 989 –992
- DOI: 10.1049/mnl.2018.0089
- Type: Article
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Bilayer polymer/metal suspended membranes made of poly(methyl methacrylate) (PMMA) and aluminium (Al) have been fabricated using a wet transfer technique where a polyelectrolyte (polydiallyldimethylammonium chloride – PDAC) has been employed as sacrificial layer to facilitate the detachment of the thin PMMA/Al layers from the substrate holders. In this way, free-standing PMMA/Al membranes with outstanding diameter (3.5 mm) to thickness (400 nm) ratios of ∼104 have been obtained. The membranes have been actuated mechanically and electrothermally and their modal behaviour characterised using laser Doppler vibrometry. The first five modes of vibrations have been detected in the range of 2–25 kHz. The second and fifth degenerate modes have been seen to split, probably due to non-uniform tension or mass density. The membranes can achieve vibration amplitudes in the order of few tens of microns. When performing electro-thermal actuation, it has been observed that the amplitude of a single mode can be tuned by controlling the path of the electric current across the membrane.
Self-assembled 3D NiCo2S4 nanotubes-graphene aerogel composites as an excellent anode for Li-ion batteries
- Author(s): Lixin Zhang ; Qi Wang ; Hongfang Jiu ; Chunmei Xie ; Shaomei Zhang
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 993 –997
- DOI: 10.1049/mnl.2017.0920
- Type: Article
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Three-dimensional nickel cobalt sulphide (NiCo2S4) nanotubes-graphene aerogel composites (NGAs) are firstly assembled by an electrostatic interaction between the diallyldimethylammonium chloride-modified NiCo2S4 nanotubes and graphene oxide (GO) sheets, followed by a steerable hydrothermal and freeze-drying process. The final samples are characterised by scanning electron microscope, transmission electron microscopy, X-ray diffraction and Brunauer–Emmett–Teller. The results reveal that the NiCo2S4 nanotubes with a uniform diameter of about 200 nm tightly anchor onto the crumpled surface of graphene sheets and GO sheets self-assemble into an interconnected porous structure. When the composites are evaluated as an anode for lithium-ion batteries (LIBs), presenting an extremely admirable cycling stability (967.5 mAh g−1 after 100 cycles at a current density of 100 mA g−1) and excellent rate capability (as high as 654.7 mAh g−1 at a large rate of at 2000 mA g−1). This work proved that the NGAs may have a great application in LIBs.
Preparation of microencapsulated phase change materials based on expanded polystyrene foam wastes
- Author(s): Yifei Shao ; Haifeng Jiang ; Shu Li ; Jiaqi Yang ; Mingyue Zhang ; Junfeng Li
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 998 –1000
- DOI: 10.1049/mnl.2017.0868
- Type: Article
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The ‘white pollution’ caused by expanded polystyrene (EPS) foam wastes has become a difficult problem in the world. In this study, the wasted EPS foam material was reused to prepare phase change material (PCM) in order to reduce its pollution to the environment. The phase separation method was adopted to build microencapsulated PCM and the paraffin wax was used as core material in this work. Their results showed that the impurities contained in polystyrene foam wastes almost had no impact on the samples. The particles had continuous surface and regular spherical structure. Compared to other PCMs, the latent heat of the PCM in this study is significantly increased, which is about 72.52 J/g. As mentioned above, the material prepared in this work can be considered as a potential phase change material.
Friction performance and optimisation of diamond-like texture on hydraulic cylinder surface
- Author(s): Xiaolan Chen ; Liangcai Zeng ; Feilong Zheng
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1001 –1006
- DOI: 10.1049/mnl.2018.0026
- Type: Article
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For the ring surface of a hydraulic cylinder, grid and striped textures have been demonstrated in many previous works to easily provide a conductive oil path, which increases the difficulty of generating converging wedges and are harmful to the formation of dynamic pressure lubrication, especially for full lubrication. Moreover, these studies used an orthogonal design method to study the hydrodynamic lubrication effect and friction performance of the surface without considering the comprehensive effect of multiple parameters with simultaneous changes, which may introduce errors into the simulation analysis. In this work, a diamond-like, non-conductive texture, which mimics shark skin, is developed and optimised to determine the optimal texture morphology while simultaneously considering the influence of multiple parameters, including the diamond angle, axial length ratio, and area occupancy, to optimise the surface of the friction pair. The results show that under the same working conditions, the lift of the diamond texture is nine times greater than that of the striped texture, while its friction coefficient is only one-quarter of that of the striped texture, which will greatly improve the friction and responsiveness of the hydraulic cylinder.
Effect of gate dielectric on electrical parameters due to metal gate WFV in n-channel Si step FinFET
- Author(s): Rajesh Saha ; Brinda Bhowmick ; Srimanta Baishya
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1007 –1010
- DOI: 10.1049/mnl.2018.0189
- Type: Article
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p.
1007
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This work reports the statistical impact of dielectric constant (k) of gate dielectric materials on various electrical parameters in step-FinFET (fin field-effect transistor) and conventional FinFET (C-FinFET) due to the gate metal work function variability (WFV). 3D technology computer-aided design simulations showed that several performance parameters are more affected by the WFV in C-FinFET than in step-FinFET. It was observed that the fluctuation of parameters like subthreshold swing (σSS), on current (σI on), and off current (σI off) are noticeably affected by dielectric materials. However, for both the structures, there is no significant variation in the threshold voltage (σV T) with variation in k values for varying grain size.
Durable antibacterial and hydrophobic polyester fibres and wearable textiles
- Author(s): Bin Zhang and Yujie Jiang
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1011 –1016
- DOI: 10.1049/mnl.2018.0197
- Type: Article
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1011
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This work reports a novel environmentally friendly antibacterial and hydrophobic polyester [polyethylene terephthalate (PET)] fibre finished with ZnO containing quaternary ammonium compounds (QACsZnO). The results show that the QACsZnO can be coated onto the PET fibre surface, imparting perdurable antibacterial activity. It was found that the hydrophobicity and mechanical properties were improved greatly after the PET fibre was finished with QACsZnO. Additionally, the QACsZnO-finished PET fibre exhibited good antibacterial activities against Staphylococcus aureus, Escherichia coli and Bacillus subtilis. Moreover, QACsZnO-finished PET fibre was still capable of restoring its hydrophobicity, and it did not induce damage after dry-cleaning. These remarkable features of QACsZnO-finished PET fibre that were suitable for development of multi-function and textile applications on the market had increased dramatically.
Effect of calcination temperature on the structure and photocatalytic performance of BiVO4 prepared via an improved solution combustion method
- Author(s): Yuanxin Qi ; Min Wang ; Yu Zhang ; Tong Zhu
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1017 –1020
- DOI: 10.1049/mnl.2017.0564
- Type: Article
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1017
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The bismuth vanadate (BiVO4) photocatalysts were synthesised via an improved solution combustion method. The effects of different calcine temperatures on microstructure and photocatalytic properties of BiVO4 were studied. The samples were characterised by X-ray diffraction, X-ray phototelectron spectroscopy, transmission electron microscope, ultraviolet–visible and photoluminescence analyses. Furthermore, the photocatalytic activity of the sample was evaluated by photocatalytic decomposition of rhodamine B (rhB). The results showed that all samples were monoclinic structures with high purity. Moreover, the calcination temperature had significant effects on both morphology and photocatalytic properties of BiVO4. The sample obtained at 500°C had the narrowest bandgap energy and presented the best photocatalytic activity for the rhB photodegradation rate reached up to 86.67% after 50 min under visible-light irradiation.
Nano-Bi2MoO6/calcined mussel shell composites with enhanced photocatalytic performance under visible-light irradiation
- Author(s): Dongjiao Jiang ; Lu Cai ; Lili Ji ; Hailong Zhang ; Wendong Song
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1021 –1025
- DOI: 10.1049/mnl.2017.0905
- Type: Article
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1021
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A novel visible-light-driven nano-Bi2MoO6/calcined mussel shell (CMS) photocatalyst composite was designed and synthesised by a facile hydrothermal method and characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscope and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic degradation of Rhodamine B (RhB) under visible-light (λ > 420 nm) irradiation. The results indicated that 5% nano-Bi2MoO6/CMS photocatalysts composite exhibited the highest activity, and its RhB degradation efficiency reached 98.7% within 60 min, which was 1.2 times higher than that of the pure Bi2MoO6 photocatalyst. This work demonstrated that CMS powder could be utilised to fabricate Bi2MoO6/CMS photocatalyst nanocomposites for water-treatment applications and this study could provide a solution to the abandoned mussel shell resources from waste and environmental pollution.
Microstructure and dynamic mechanical properties of magnetorheological elastomer based on ethylene/acrylic elastomer prepared using different manufacturing methods
- Author(s): Tianming Gao ; Ruihong Xie ; Kyungho Chung
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1026 –1030
- DOI: 10.1049/mnl.2017.0372
- Type: Article
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1026
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Magneto-rheological elastomer (MRE) is a kind of smart material based on elastomer matrix and it is divided into isotropic (i-MRE) and anisotropic MRE (a-MRE) depending on the magnetic particle arrangement. In the i-MRE, carbonyl iron particles (CIP) are randomly dispersed, while they form a chain-like structure in the a-MRE. Two manufacturing procedures of a-MRE have been introduced. The a-MRE-1 was manufactured by one-step process involving application of magnetic field and curing of matrix simultaneously. On the other hand, a-MRE-2 was manufactured by two-step process in which the magnetic field was applied to induce CIP orientation and then the matrix was cured. The microstructure and mechanical properties of MRE were characterised by scanning electron microscope, universal testing machine and dynamic mechanical analysis. The results showed that the CIP content in MRE had no effect on the cure properties. A chain-like structure existed in a-MRE-1, whereas the orientation structure of CIP in the a-MRE-2 was not as clear as that in a-MRE-1. The tensile strength of a-MRE-1 was the lowest because no interfacial reaction occurred between the CIP and the rubber molecules chain, whereas i-MRE had the highest tensile strength.
Free longitudinal vibration of a nanorod with elastic spring boundary conditions made of functionally graded material
- Author(s): Mustafa Özgür Yayli
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1031 –1035
- DOI: 10.1049/mnl.2018.0181
- Type: Article
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1031
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The elastic spring boundary conditions play an important role in dynamical analysis of functionally graded (FG) nanorods. However, these special issues have not been properly paid attention to in the previously developed non-local models. In this work, longitudinal vibration analysis of FG restrained nanorods is presented via non-local elasticity theory. Two axial springs are attached to a FG nanorod at both ends. By considering the non-local differential relations for the FG nanorod, a coefficient matrix is derived and analysed via an exact eigenvalue method. Finally, the results calculated from finite-element method are used to validate the present method. The influence of FG index, non-local parameter and boundary conditions on the axial frequencies of FG nanorods is discussed.
Investigation on preparation and formation mechanism of copper antimony sulphide particles by microwave irradiation
- Author(s): Wei Wang ; Lingyun Hao ; Guowei Zhi ; Qing Lin ; Zhengxia Tang
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1036 –1039
- DOI: 10.1049/mnl.2018.0099
- Type: Article
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1036
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In this work, copper antimony sulphide (CuSbS2) particles were synthesised by a microwave irradiation method. The effects of Cu/Sb ratio in the precursor solution and microwave irradiation power on properties of CuSbS2 particles were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that the sphere-like CuSbS2 particles with single phase and stoichiometric composition was synthesised at 400 W for 4 min first and then 240 W for 6 min, when the ratio of Cu/Sb was 1:2. The formation mechanism of CuSbS2 particles was also investigated through evaluation of as-prepared particles with different reaction time.
Facile synthesis of Bi decorated 2D and 3D BiOBr micro-nanostructures with enhanced photocatalytic activity
- Author(s): Yingliu Li ; Jianzhong Zhu ; Ruihong Yang ; Min Shao
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1040 –1045
- DOI: 10.1049/mnl.2017.0787
- Type: Article
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BiOBr nanoplates and microflowers decorated with Bi nanoparticles were synthesised by a one-pot catalytic-solvothermal method. Using SbCl3 as additive agent, it can not only shorten the synthesis time but also control the morphology and composition of the product. The samples were characterised by various analytical techniques, indicating enhanced optical absorption and effective charge separation properties as well as abundant oxygen vacancies. The products were employed for the degradation of rhodamine B and phenol solution under visible-light irradiation, exhibiting significantly improved photocatalytic efficiency in comparison with pure BiOBr. An investigation into the photocatalytic mechanism of Bi/BiOBr showed that peroxy radical was the main active species in the degradation process. This study provided a facile and energy saving preparation of controllable Bi/BiOBr heterojunction with oxygen vacancies.
Design and analysis of hairpin piezoresistive pressure sensor with improved linearity using square and circular diaphragms
- Author(s): Mohsen Hayati ; Morteza Fathipour ; Hamid Sherafat Vaziri
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1046 –1051
- DOI: 10.1049/mnl.2018.0149
- Type: Article
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1046
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A novel structure for piezoresistive pressure sensors is proposed. The structure comprises two piezo-resistors, one mounted on a flat diaphragm and the other mounted outside of the diaphragm so that a hairpin-shaped structure is formed. As a result, one of the piezo-resistors will be affected by the input pressure and the other one will not. Also an inverting Operational Amplifier (OP-AMP) amplifier is utilised. The proposed pressure sensor can be designed using both square diaphragm or circular diaphragm and it has the advantage of higher linearity for input pressure range of 1 MPa in comparison with conventional structures. The value of nonlinearity (NL) is decreased from 0.5515% full-scale (FS), for the conventional sensor, to 0.1138% FS (for the proposed sensor with square diaphragm) and 0.0761% FS (for the proposed sensor with circular diaphragm), which shows an improvement in reducing NL about 80% in square diaphragm and about 86% when circular diaphragm is employed. The proposed structure is analysed and simulated using COMSOL multiphysics software.
Fabrication of seamless roller mould with smooth surface microstructures by rotation lithography and reflow process
- Author(s): Chao Ji ; Mujun Li ; Jinfeng Qiu ; Junjie Zhu ; Huichun Ye
- Source: Micro & Nano Letters, Volume 13, Issue 7, p. 1052 –1056
- DOI: 10.1049/mnl.2018.0155
- Type: Article
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In this work, the authors conducted a versatile approach for an innovative fabrication of a seamless micro-stripes array on the roller which is as a mould for roller imprinting lithography. The major steps in the proposed fabrication method include an uniform speed PR-coating process, followed by a digital micromirrors device based maskless lithography projection and an incremental step-and-rotate exposure process. In addition to above-mentioned steps, a following thermal reflow process was performed to transform the micro-stripes into smooth surface microstructures. The study also analysed the mechanism of the reflow process by numerical simulations and experiments. The mechanism includes the gravitational effect and the definition of the four stages of the reflow process. Study results show that the reflow process on the roller is feasible and the proposed method is a promising approach for fabricating three-dimensional smooth surface microstructures on the roller with different requirements.
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