Micro & Nano Letters
Volume 13, Issue 9, September 2018
Volumes & issues:
Volume 13, Issue 9
September 2018
Biomedical applications of aluminium oxide nanoparticles
- Author(s): Peyman Hassanpour ; Yunes Panahi ; Abbas Ebrahimi-Kalan ; Abolfazl Akbarzadeh ; Soodabeh Davaran ; Aygun N. Nasibova ; Rovshan Khalilov ; Taras Kavetskyy
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1227 –1231
- DOI: 10.1049/mnl.2018.5070
- Type: Article
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Aluminium oxide (Al2O3) nanoparticles (AlNPs) are class of metal oxide nanoparticles that have diverse biomedical applications owing to their exceptional physicochemical and structural features such as resistance towards wear, chemicals, mechanical stresses as well as their favourable optical properties and a porous vast surface area. Other reasons for widespread applications of AlNPs are their low cost of preparation and easy handling. Therefore, owing to the economic importance, the recent achievements and possible health risks associated with the biomedical applications of AlNPs are overviewed in this work.
Eliminate the transmission feedthrough of thermal-piezoresistive I2-BAR MEMS resonators based on reverse-biased PN junction
- Author(s): Zhuang Xiong ; Zhaoyun Zhang ; Li Zhang ; He Yang
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1232 –1235
- DOI: 10.1049/mnl.2017.0774
- Type: Article
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The thermally driving and piezo-resistive sensing I2-BAR resonators have attracted substantial attentions due to its promising features which could be widely applied for radio frequency) applications. However, one major drawback of the I2-BAR resonators is that the thermal driving and the piezoresistive sensing signals are highly coupled which results in an excessive transmission feedthrough floor, masking thus the real resonance behaviours. In this work, a simple and effective approach to eliminate the feedthrough effect using reverse-biased PN junction is presented. The device was fabricated on a p-type silicon-on-insulator wafer with locally doped n-type regions. With proper bias voltages, the thermal driving current and the output piezoresistive current were confined inside the p-type layer and the n-type layer, respectively. With such design concept, an improvement of 50 dB feedthrough reduction was observed comparing with the conventional measurement. The resonance behaviour can thus be physically obtained without further post data processing. This research also shows that such measurement methods can be transferred to other domains where integrated thermal driving and piezoresistive sensing transductions are required.
AgNPs uniformly doped onto PVA microspheres for optical recognition application
- Author(s): Bei Yang ; Xue Bai ; Lihong Xue ; Lizhang Yang
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1236 –1239
- DOI: 10.1049/mnl.2017.0859
- Type: Article
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Via surface aldolisation or semi-aldolisation, the surface of poly(vinyl alcohol) (PVA) microspheres was uniformly doped with sliver nanoparticles (AgNPs). Scanning electron microscope (SEM) revealed the spherical shape of the AgNPs@PVA microspheres. Fourier transform infrared spectra and X-ray photoelectron spectra (XPS) provided information on the surface interactions between AgNPs and PVA microspheres. The AgNPs@PVA microspheres offered simple and rapid qualitative detection of Hg2+ ions and pH values through a colour change in aqueous solution. The AgNPs@PVA microspheres also showed off–on behaviour.
Synthesis of low shrinkage monolith alumina aerogels by surface modification and ambient pressure drying
- Author(s): Chi Li ; Zheng Gong ; Likang Ding ; Donglai Guo ; Wenbin Hu
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1240 –1244
- DOI: 10.1049/mnl.2018.5077
- Type: Article
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The authors have synthesised a kind of low shrinkage alumina (Al2O3) aerogel using an inexpensive salt of aluminium (AlCl3·6H2O) via tetraethoxysilane modification and an ambient pressure drying process. The morphology, pore structure, surface group, crystal phase and thermal properties of the Al2O3 aerogel are analysed by X-ray diffractometer, scanning electron microscopy, Fourier transform infrared spectra and nitrogen adsorption test. Further improvement in thermal stability and thermal shrinkage are obtained by incorporation of silicon (Si) atoms during the aerogel preparation. The specific surface area of modified aerogel is 480 m2/g and the diameter shrinkage is 8% after drying, and reach 304 m2/g and 16.5% after heating at 1000°C. The approach, which is straightforward, inexpensive and safe, can be employed to prepare a monolithic mesoporous material with low shrinkage and high-temperature resistance. This will further promote the potential application of packaging and thermal insulation materials.
Single-mask fabrication of micro-probe electrode array with various tip heights and sharpness using isotropic and anisotropic etching
- Author(s): Young-min Shin ; Yong-Kweon Kim ; Seung-Ki Lee ; Jae-Hyoung Park
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1245 –1247
- DOI: 10.1049/mnl.2018.5064
- Type: Article
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In this work, a silicon-based micro-probe array was fabricated using multi-step deep reactive ion etching (DRIE) and reactive ion etching (RIE) processes. The micro-probe structure was implemented using a micromachining technique through a combination of two anisotropic DRIE and two isotropic RIE processes with a single etch mask. The cone-shaped tip height and tapered tip-end angle were experimentally varied with respect to the first DRIE depth. As the first DRIE depth was decreased, the micro-probe tip height increased and the sharpness consequently improved. The conductive layer was exposed only at the tip ends of the micro-probe to form a conical ultra-micro electrode, and it was characterised via cyclic voltammetry measurements.
Characteristics of signal propagation in multiferroic majority logic gates subjected to thermal noise
- Author(s): Bo Wei ; Li Cai ; Bao Jun Liu ; Xiao Kuo Yang ; Cheng Li
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1248 –1251
- DOI: 10.1049/mnl.2018.5065
- Type: Article
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The error rates of multiferroic majority logic gate (MLG) in the presence of thermal noise fluctuation are evaluated via solving the Landau–Lifshitz–Gilbert equations. It is found that in the pre-stress condition, magnetisation orientations of nanomagnets in the MLG denote an initial 4°–10° departure from the easy axis direction due to random thermal noise field. This phenomenon may be the main origin of switching errors of multiferroic logic gates at high temperature. Specifically, in the post-stress condition, it has been seen that larger spacing between nanomagnets leads to a high error rate, up to 50%, which arises from weak dipolar coupling interactions and strong thermal fluctuations. However, opposed to their expected, small spacing between nanomagnets leads to a higher error rate, up to 90%, which mainly arises from spontaneous magnetisation reversal induced by weak stress anisotropy energy. Therefore, moderate spacing is very important to MLG switching at room temperature, for example the optimal spacing is 250–310 nm for MLG constructed with nanomagnets having shape anisotropy energy of 623 kT. These findings can provide guides on multiferroic logic circuit design.
Electromagnetic interference shielding properties of graphene/MWCNT hybrid buckypaper
- Author(s): Shaowei Lu ; Dandan Chen ; Junyan Shao ; Yaoyao Bai ; Caijiao Tian ; Keming Ma ; Xiaoqiang Wang
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1252 –1254
- DOI: 10.1049/mnl.2018.5066
- Type: Article
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A type of lightweight and flexible graphene/multi-walled carbon nanotube (MWCNT) hybrid buckypaper (BP) is fabricated, which show superior shielding effectiveness (SE) of electromagnetic interference and without polymer. The EMI SE of graphene/MWCNT hybrid BP with thickness of 130 μm is up to ∼51 dB at 8 GHz, which is much higher than that of pure MWCNT BP with same thickness (∼32.5 dB) and the best electrical conductivity is up to 10,000 S/m. More important, the improvement in EMI SE is contributed to the SE absorption, while the SE reflection is almost unchanged. This paper-like material is smooth, tough, and flexible enough to be attached on the complex curved surface structure. A facile way to fully develop graphene and MWCNT in lightweight and flexible EMI shielding materials and devices is provided here.
GaN LEDs fabricated using SF6 plasma RIE
- Author(s): Wasif Khan ; Xiaopeng Bi ; Bin Fan ; Wen Li
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1255 –1259
- DOI: 10.1049/mnl.2018.5083
- Type: Article
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In this work, the authors report a cost-effective fabrication method for making gallium nitride (GaN) light emitting diode (LED) arrays using SF6 plasma in a conventional reactive-ion etching (RIE) system. The etch rates for GaN were investigated with different radio-frequency power and carrier substrates. The surface roughness due to the etching was also determined for the various recipes used. The optical intensity and the temperature change during operation of the fabricated LED's were investigated. The effect of post-fabrication annealing on enhancement in the electrical and optical properties of the LED's was investigated.
Graphite carbon coated TiN nanoparticles as high durable oxygen reduction reaction catalyst in alkaline electrolyte
- Author(s): Ce Liang ; Nian Tao ; Bowen Wang ; Sen Lin ; Ming Lei
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1260 –1264
- DOI: 10.1049/mnl.2018.5100
- Type: Article
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The novel composite structure of TiN nanoparticles enclosed by graphite carbon coating (TiN/C) has been successfully prepared through a facile one-step solid state method under N2 atmosphere using the TiO2 powder and melamine as raw materials. TiN nanoparticles with size ranging from 12 to 15 nm are covered by filmy graphite carbon layer, and their electrocatalytic properties towards oxygen reduction are further investigated. Benefiting from the surface chemical bonding of oxide and oxynitride components, TiN/C nanocomposite exhibit a considerable catalytic activity. The current density of TiN/C nanocomposite (4.65 mA cm−2 at 0.2 V) is comparable to that of commercial Pt/C catalyst, in spite of a little more negative gap in onset potential. Moreover, the TiN/C nanocomposite has excellent long time durability and methanol tolerant performance with the protection of graphite carbon coating.
Tunable surface plasma resonance of gold nanorods superstructure and their SERS properties
- Author(s): Yufei Sun ; Liwei Wang ; Junhui Liu ; Ruoping Li ; Mingju Huang
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1265 –1268
- DOI: 10.1049/mnl.2018.5103
- Type: Article
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High-quality gold nanorods (GNRs) with different aspect ratios and uniform morphology were synthesised using the seed-mediated growth method. The GNRs were assembled into two different type superstructures: the one is arranged vertically to the substrate (V-GNR superstructure); the other is arranged parallel to the substrate (P-GNR superstructure). Their work at present is devoted to study the Raman enhancement effect and signal repeatability of GNR superstructures. The influence of GNRs arrangement on surface-enhanced Raman scattering (SERS) was investigated experimentally. In addition, the electromagnetic field coupling of GNR superstructures with different arrangement modes was simulated by the finite-different time-domain method. Both experiments and theories have proved that the required resonance wavelength of Raman laser can be obtained by adjusting the aspect ratio of GNRs. Furthermore, the P-GNR superstructure can bring high and repeatable SERS signal intensity of molecules compared with V-GNR superstructure and other nanostructures. It can be concluded that P-GNR superstructure is a good substrate mode for SERS technique.
Facile one-step synthesis of SnS2 nanoscale hollow spheres for enhanced lithium-ion storage performance as anode
- Author(s): Yani Guo ; Xiufeng Wang ; Weizhi Shao
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1269 –1271
- DOI: 10.1049/mnl.2018.5125
- Type: Article
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The SnS2 hollow nanospheres are successfully fabricated using SnCl4·5H2O, thiourea and urea as raw materials via a mild one-step hydrothermal process. The size of SnS2 hollow nanosphere is about 400 nm, and the shell thickness of it is about 50 nm, consisting of nanoparticles with the size of 3 nm. The formation of such hollow structure could be mainly ascribed to the soft template effect of carbon-dioxide and ammonia bubbles decomposed from urea. The obtained hollow nanospheres possess a higher specific surface area of 142 m2 g−1 compared with that of the SnS2 granular aggregate sample (34 m2 g−1), presenting better cycling stability and rate capability.
Label-free immunosensor based on interdigitated electrodes with Ni–Co nanowires
- Author(s): Fu-Yuan Siao ; Yaw-Jen Chang ; Hung-Ju Shih
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1272 –1275
- DOI: 10.1049/mnl.2018.5135
- Type: Article
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This work presents a label-free immunosensor consisting of interdigitated electrodes and Ni–Co nanowires (NWs) to determine the relative amount of analyte, using electroanalytical measurement. Interdigitated electrodes were fabricated by the conventional printed circuit board treatment and Ni–Co NWs were synthesised by the electrodeposition method using a porous anodic alumina oxide membrane as the template. The experimental results showed that Ni–Co NWs can provide specific binding with histidine-tagged capture agent based on the method of immobilised metal affinity chromatography. Due to the large surface-to-volume ratio of NWs, this immunosensor had 2.6-fold the immobilisation ability of flat Ni–Co film to absorb histidine-tagged capture agent. Moreover, this immunosensor exhibited sensitivity in detecting low amounts of analyte. The electrical responses of the electroanalytical measurement of analyte, from 1000 to 625 ng/mL, could be discriminated; however, the fluorescence intensities became indiscriminative. This label-free immunosensor has the potential to immobilise various capture agents through the use of histidine for different analyte analyses.
Tunable hybrid metal–graphene frequency selective surfaces based on split-ring resonators by leapfrog ADI-FDTD method
- Author(s): Meng-Lin Zhai and De- Min Li
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1276 –1279
- DOI: 10.1049/mnl.2017.0857
- Type: Article
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A tunable hybrid metal–graphene frequency selective surface (FSS) based on split-ring resonators at mid-infrared frequencies is proposed and numerically investigated by an improved leapfrog alternating direction implicit (ADI)-finite-difference time-domain (FDTD) method. The graphene conductivity described by a new closed-form approximate expression is incorporated into the leapfrog ADI-FDTD through the vector-fitting technique and auxiliary differential equation approach. Numerical simulations show that the proposed method has good computational accuracy and higher efficiency compared to conventional FDTD method and analytical solutions. Besides, the transmission and reflection coefficients of the FSS can be effectively adjusted by changing the chemical potential of graphene, the layer number of graphene patch and operating temperature. This work provides a novel method for designing tunable devices for optical plasmonic applications.
Understanding the performance of corona aged epoxy nano micro composites
- Author(s): Belaguppa Manjunath Ashwin Desai ; Palash Mishra ; Nilesh J. Vasa ; Ramanujam Sarathi ; Takahiro Imai
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1280 –1285
- DOI: 10.1049/mnl.2018.0164
- Type: Article
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Corona ageing of the epoxy nanocomposites surface exhibits a high influence on contact angle of the material. A reduction in corona inception voltage due to water droplet, upon corona ageing, is less with epoxy composites, which has Wollastonite as filler followed with nano-micro silica filler added epoxy composites. Charge accumulation studies indicate that charge retention time drastically reduces with corona aged epoxy composite specimen. Epoxy composites with Wollastonite as filler have shown higher mean charge lifetime. Adoption of laser induced breakdown spectroscopy (LIBS) technique for characterisation of samples is unique. Measure of threshold fluence and plasma temperatures through LIBS studies enables to classify the ageing condition of the composite material. Plasma temperature and threshold fluence are clear indicators to classify different materials. Plasma temperature is also an indicator of the hardness of the material. Epoxy composite with Wollastonite as filler is not affected by laser abrasion, which is in accordance with its superior performance with corona ageing, proving as discharge resistant material.
Synthesis and characterisation of polymer containing dye-affinity ligand grafted to magnetic nanoparticles for enteric insulin delivery
- Author(s): Babak Izadi Vahedi ; Amir Heydarinasab ; Homayon Ahmad Panahi ; Mohsen Jahanshahi
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1286 –1290
- DOI: 10.1049/mnl.2017.0384
- Type: Article
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In the present work, a novel technique is reported for the surface grafting of polymer containing famous dye-affinity, Procion blue MX-R, onto modified iron oxide nanoparticles with 3-mercaptopropyltrimethoxysilane. The grafted nanocarrier was synthesised by free radical polymerisation followed by coupling with Procion blue and then characterised by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and also transmission electron microscopy. The grafted magnetic nanocarrier was used for enteric insulin delivery. The profile of the insulin uptake by synthesised nanocarrier indicated excellent accessibility of the polymer contains Procion blue. Scatchard analysis reflected that the capacity of the polymer containing dye-affinity ligand nanocarrier was about 12 µmol g−1 at pH 5. The balance sorption information of insulin by polymer contains Procion blue nanocarrier which were verified by Freundlich, Temkin, Langmuir and Redlich–Peterson models. The magnetic nanocarrier showed maximum of 95% drug release in acidic medium of pH 1.2, and about 80% drug release was recorded in intestine medium of pH 7.4.
Numerical analysis of film-loaded silicon nanowire optical rectangular waveguide: an effective optical sensing
- Author(s): Ritu Raj Singh and Vishnu Priye
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1291 –1295
- DOI: 10.1049/mnl.2018.0140
- Type: Article
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Subwavelength waveguide using silicon nanowires is investigated for its compatibility with silicon-on-insulator platform. A layer of silicon film over SiO2 substrate is employed to construct silicon nanowire waveguides that complies with standard 220 nm silicon height technology. The proposed structure is further investigated for its utility as an optical sensing element in photonic integrated circuits. Film-loaded silicon nanowire optical rectangular waveguide (SNORW) allows light to be guided inside low refractive indexed gapping region with optimised dimension. Fully numerical analysis is performed using finite-element method as evidence to support the guiding phenomena of this waveguide. Eventually, confinement factor and waveguide sensitivity is found to be linear with measurand refractive index. As a result, the purpose of this SNORW leads to an effective sensing in the new era of photonics.
Facile and low-cost fabrication of uniform silicon micro/nanostructures by nanopitting-assisted wet chemical etching
- Author(s): Feng Wang ; Shulan Jiang ; Jinghui Han ; Guangran Guo ; Bingjun Yu ; Weiqing Yang ; Linmao Qian
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1296 –1301
- DOI: 10.1049/mnl.2018.0185
- Type: Article
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Silicon micro/nanostructures are promising building blocks for high-performance solar cells, lithium-ion batteries, sensors and so on. Great challenges like high cost and complex fabrication process still exist for the fabrication of silicon micro/nanostructures, especially for the fabrication of uniformly distributed silicon micro/nanostructures. In this study, the generally unwelcome failure of materials, nanopitting, was introduced and demonstrated to be effective in micro/nanofabrication for the first time. Together with wet chemical etching, uniformly distributed silicon micro/nanostructures were obtained. Ag islands were formed by the nanopitting of chloridion, which will be used as mask and catalyser in the chemical etching process. The silicon micro/nanostructures, especially, uniformly distributed p-type silicon micro/nanostructures were fabricated with the low-cost and facile fabrication approach. In addition, the application of the silicon micro/nanostructures was demonstrated as microsupercapacitive electrodes with the integration of MnO2 nanostructures. The results show that the electrochemical performance of silicon micro/nanostructures was much better than that of silicon microstructures. The proposed approach is cost-effective to fabricate silicon micro/nanostructures, and the silicon micro/nanostructures have great potentials in miniaturised energy storage devices, sensors and photodevices.
Rapid prototyping of PET microfluidic chips by laser ablation and water-soaking bonding method
- Author(s): Zhifu Yin
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1302 –1305
- DOI: 10.1049/mnl.2018.0193
- Type: Article
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The solution to the commercialisation of polymer microfluidic chips lies in the chosen of a low-cost and concise method. CO2 laser is an excellent tool for ablating arbitrary-shaped microchannels in most of thermoplastics. However, upheaval area is usually generates along the microchannel due to high temperature during laser ablation process which leads to the difficulty in fully bonding polymer microchannels. In this work, a new bonding method for fully bonding uneven substrates with homogenous surface property was developed based on water-soaking treatment. To prevent edge separating, an extra laser welding on the lateral of the chip was conducted. The influence of laser current on the width and depth of poly(ethylene terephthalate) (PET) microchannel was investigated. The mechanism of water-soaking bonding was explained and the parameters of this method were optimised. The experiments showed that PET chip can be fully bonded without any block or leakage and the bonding strength of PET chip can be as high as 3.4 MPa.
Applied magnetic field effect on core mode properties of MFPCF
- Author(s): Seyhan Coşkun ; Yavuz Öztürk ; Gokalp Kahraman
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1306 –1309
- DOI: 10.1049/mnl.2018.0145
- Type: Article
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The work investigates a magnetic fluid filled photonic crystal fibre (MFPCF) at 1557 nm under applied magnetic field. They computed the refractive index change of the MF due to the magnetic field and used it in simulations to find the effective refractive indices of the core and the first cladding modes of the MFPCF. Then, they analytically computed the effective mode area and the confinement loss. The effective refraction index of the core mode increasing by 0.0341% under the applied field of 0–500 Oe, increases the effective mode area by 128% and the confinement loss by 866%. Thus, a rather small change in the effective refractive index gives rise to a rather large change in confinement loss. However, this effect saturates after about 500 Oe because the MF nanoparticles no longer change their magnetic orientation. It is also noteworthy that the confinement loss changes almost linearly with the effective area as the magnetic field change. These results suggest that MFPCF are suitable for a tunable attenuator and a field sensor.
Reduction of 2-nitrophenol using a hybrid C–Ni nanocomposite as a catalyst
- Author(s): Jeong W. Ko ; Jiulong Li ; Akira Suzuki ; Kazuyuki Takai ; Weon B. Ko
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1310 –1314
- DOI: 10.1049/mnl.2018.0171
- Type: Article
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Synthesis of hybrid carbon–nickel (C–Ni) nanocomposite was performed with [C60] fullerene and Ni hydroxide in an electric furnace at 700°C for 2 h. The resulting product was characterised by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and electron spin resonance spectroscopy. The catalytic reduction of 2-nitrophenol using the hybrid nanocomposite was investigated by ultraviolet–visible spectroscopy. Kinetic study showed that reduction of 2-nitrophenol in the presence of sodium borohydride with the hybrid C–Ni nanocomposite was followed a pseudo-first-order reaction law.
Preparation of γ-alumina/silica core–shell abrasives and their chemical mechanical polishing performances on sapphire substrates
- Author(s): Xin Wang and Hong Lei
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1315 –1320
- DOI: 10.1049/mnl.2018.0166
- Type: Article
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The chemical mechanical polishing (CMP) process has become a widely accepted global planarisation technology. The abrasive is one of the important influencing factors during the CMP process. In this work, γ-alumina/silica abrasives with a core–shell structure were synthesised. Time-of-flight secondary ion mass spectroscopy was used to characterise the composition of the obtained abrasives. The morphology and structure of the abrasives were measured by using scanning electron microscopy and transmission electron microscopy. The CMP performances of the γ-alumina/silica abrasives on sapphire substrates were investigated. Experimental results indicate that the γ-alumina/silica abrasives exhibit lower surface roughness and higher material removal rate than that of pure silica and γ-alumina abrasives under the same testing conditions. Furthermore, through the X-ray photoelectron spectroscopy test, this work investigated the chemical effect mechanism of the γ-alumina/silica core–shell abrasives in sapphire CMP. The results show that solid-state chemical reactions occur between the silica shell and sapphire surface during the CMP process. The study also established a wear model to investigate the mechanical friction mechanism.
Encapsulation of supported g-C3N4/Au with metal–organic frameworks for enhanced stability towards photocatalytic hydrogen evolution
- Author(s): Zewu Zhang ; Qikang Wang ; Qiong Wu ; Qingxu Rao ; Zusheng Hang ; Xiaohai Bu ; Haojun Shi
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1321 –1324
- DOI: 10.1049/mnl.2018.0206
- Type: Article
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The supported graphitic-carbon nitride (g-C3N4)/Au composite has attracted considerable attention as an alternative visible-light photocatalyst for hydrogen evolution reactions. However, the short-term photocatalytic durability greatly limits their practical application. In this work, porous [Zn(BDC)(H2O)2] n , which is a typical two-dimensional metal–organic frameworks (MOFs), was used as the protecting material to encapsulate g-C3N4/Au. The obtained g-C3N4/Au@[Zn(BDC)(H2O)2] n catalyst was composed of lamellar MOFs shells and g-C3N4/Au cores. The catalysts exhibited an excellent catalytic activity and particularly superior stability as compared to the bare g-C3N4/Au. The encapsulation method by using MOFs as the protective shell provides an alternative strategy for designing photocatalysts with high catalytic performance.
Molybdenum gratings as a high-temperature refractory platform for plasmonic heat generators in the infrared
- Author(s): Sara Nunez-Sanchez ; Hugo Dominguez Andrade ; Jan Harwood ; Ian Bickerton ; Neil A. Fox ; Martin J. Cryan
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1325 –1328
- DOI: 10.1049/mnl.2018.0156
- Type: Article
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The aim of this work is to study the heating efficiency of refractory microstructures by excitation of surface plasmon polaritons in the far infrared that can be used for high-temperature applications. The work has designed metal grating couplers on molybdenum films to maximise the absorption of a 10.6 µm CO2 laser light source. Molybdenum has been chosen since it is an industrial refractory metal combined with the fact that its optical properties in the far infrared are similar to gold but with stable high-temperature performance. Linear gratings have been used as plasmonic couplers on large area substrates produced by laser milling. Real-time absolute temperature measurements have been performed showing a 42% increase in the maximum achievable temperature from 702 to 985 K.
Polypeptide-based amphiphilic brush copolymers as unimolecular micelles: synthesis, characterisation, and encapsulation study
- Author(s): Yukui Zheng ; Miao Pan ; Chao Lu ; Daojun Liu
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1329 –1334
- DOI: 10.1049/mnl.2018.5094
- Type: Article
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Polypeptide-based amphiphilic brush copolymers PLL-g-(PBLG-b-PEG) and PLL-g-(PZLL-b-PEG) with a poly(L-lysine) (PLL) backbone and amphiphilic oligo(γ-benzyl-L-glutamate)-b-poly(ethylene glycol) (PBLG-b-PEG) or oligo(ε-benzyloxycarbonyl-L-lysine)-b-poly(ethylene glycol) (PZLL-b-PEG) side chains were synthesised, characterised, and evaluated as unimolecular nanocontainers to encapsulate hydrophobic guest molecules. The structure of these brush polymers was modulated by tuning the length of the PLL, PBLG/PZLL, and PEG segments. The final products were characterised with 1H nuclear magnetic resonance and gel permeation chromatography. The morphology and aggregation behaviours of brush copolymers were examined by using a transmission electron microscope and dynamic light scattering. It was revealed that these water-soluble brush copolymers resembled unimolecular micelles in an aqueous solution. An encapsulation study was performed using pyrene and oil red O as the model compounds, and the results showed that hydrophobic molecules could be solubilised in these unimolecular micelles with high loading capacities. The synthesised polypeptide-based amphiphilic brush copolymers could serve as promising unimolecular nanocarriers for the delivery of hydrophobic drugs.
Modulation of electronic conductivity and bandgap of electrochemically polymerised polycarbazole films using montmorillonite, multi-walled carbon nanotube and reduced graphene oxide as nanofillers
- Author(s): Aditi Srivastava and P. Chakrabarti
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1335 –1338
- DOI: 10.1049/mnl.2018.0139
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The effect of adding several nanofillers such as montmorillonite (nanoclay), multi-walled carbon nanotube (MWCNT) and reduced graphene oxide on electrical and optical properties of polycarbazole (PCz) has been experimentally characterised. Polymerisation and deposition of PCz-based nanocomposite films on Indium Tin Oxide (ITO) coated glass substrate were performed using electrochemical method. Different nanocomposite films were characterised with respect of morphology, bandgap, and conductivity. The effect of nanofillers on the electrical characteristics of Al/PCz Schottky diodes was subsequently studied with devices fabricated in the laboratory. The experimental results demonstrate a radical improvement in the electrical behaviour of the semiconducting polymer after incorporation of nanofillers. It is found from the experimental results that the conductivity is highest and the bandgap is smallest in the case of PCz nanocomposite film using MWCNT as a nanofiller.
Synthesis of LaTb x O y :Eu3+ nanowire arrays and study of performances on fluorescence enhancement and red shift
- Author(s): Qian Wang ; Jie Feng ; Guangzheng Peng ; Tong Zhang ; Ji Xiang ; Peng Li ; Lina Ye ; Xiaoyou Yuan
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1339 –1342
- DOI: 10.1049/mnl.2017.0923
- Type: Article
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Highly ordered LaTb x O y :Eu3+ nanowire arrays have been synthesised in anodic aluminium oxide template by chemical co-deposition at negative pressure suction, it is amorphous and with homogeneous morphologies. There are two peaks at 619 and 704 nm with excitation wavelength of 394 nm, which have red shift slightly relative to the 5D0–2F2 and 5D0–7F4 energy level transition of Eu3+, and Tb3+ exhibits strong fluorescence enhancement and sensitisation in LaTb x O y :Eu3+ nanowire arrays with the existence of La3+. The fluorescence intensity of LaTb x O y :Eu3+ nanowire arrays is related to the doping concentration of Eu3+ ion. When the doping concentration of Eu3+ is 8%, the fluorescence intensity reaches a maximum, and remarkably decreases at higher concentrations.
Fabrication of microparabolic reflector for infrared antenna coupled detectors
- Author(s): Mohamed H. Mubarak ; Othman Sidek ; Mohamed R. Abdel-Rahman ; Mohamed Tafir Mustaffa ; Ahmed Shukri Mustapa Kamal ; Saad M. Mukras
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1343 –1348
- DOI: 10.1049/mnl.2017.0826
- Type: Article
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The fabrication process of a microparabolic reflector using isotropic xenon difluoride etching technique is presented and analysed through this work for developing infrared antenna-coupled detectors. Although many parametric studies described the behaviour of this process in the literature, the non-linearity of the process and its dramatic dependency on the pattern definition result in great difficulties when adopting the process for developing a particular structure. The main focus of this work is, therefore, to present a detailed etching analysis as dictated in the proposed design providing the proper etching recipe according to the proposed structure design and its associated masking pattern. Deep insights into the process have been highlighted suggesting the necessity of the process assessment in terms of evaluating the three-dimensional etched volume rather than the etched depth. This will potentially solve the non-linearity behaviour and the pattern dependency problem. The optimum etching recipe yields approximately a total volume of 0.354 mm3 through the proper patterning mask. The resultant parabolic cavities have and in their diameter and depth, respectively, as required for the proposed structure. The integration of a microparabolic reflector with such detectors will potentially enhance the specific detectivity of these detectors.
High-reflection optical thin films based on SiO2/TiO2 nanoparticles multilayers by dip coating
- Author(s): Wang Yuehui and Yang Xing
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1349 –1351
- DOI: 10.1049/mnl.2018.0045
- Type: Article
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The alternately stacking layers of SiO2 and TiO2 nanoparticles with different refractive indices were fabricated to form the distributed Bragg reflectors on the silicon wafer by dip coating method. By appropriate design of the thickness of the quarter-wave layers, the peak reflectance region can be tuned from the blue-green to the infrared portion of the electromagnetic spectrum. The peak reflectance of 65% at 800 nm and at 1600 nm has been achieved using seven periods, respectively; meanwhile, compared with the simulation, 80% at 800 nm and 70% at 1620 nm for seven periods, respectively. The scanning electron microscopy and the atomic force microscope studies confirm the thickness uniformity achieved along the fabrication direction, and a good quality of surfaces and interfaces.
Development of in-flow label-free single molecule sensors using planar solid-state nanopore integrated microfluidic devices
- Author(s): Fatma D. Güzel and Benjamin Miles
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1352 –1357
- DOI: 10.1049/mnl.2018.5206
- Type: Article
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Nanopore biosensors have attracted attention due to their label-free single molecule detection capability. To date, different materials and applications have been shown in the field, varying from Si3N4 to graphene and biomolecule sensing to DNA sequencing. Classical nanopore devices are composed of Si3N4 material supported on a Si wafer and the detection is largely based on electrochemical sensing using chambers of ml volumes on both sides of the nanopore device. In this study, in-flow label-free electrochemical detection of DNA molecules at single molecule level is shown using a classical Si3N4 nanopore device integrated into a microfluidic device. The layout of the device given here set the basics for future works and discussions regarding future microfluidic integrated solid-state nanopores and the behaviour of the molecule under the influence of hydrodynamic flow.
AgCl/AgIO4 composites as an efficient photocatalyst for visible-light-driven degradation of rhodamine B
- Author(s): Xiang-Feng Wu ; Yi-Jin Wang ; Hui Li ; Chen-Xu Zhang ; Jia-Rui Zhang ; Jun-Zhang Su ; Yi-Wei Wang ; Zuo-Lin Cao ; Kai-Yuan Wang ; Mi Zhang
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1358 –1362
- DOI: 10.1049/mnl.2018.5185
- Type: Article
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A novel AgCl/AgIO4 composite was fabricated via an in-suit synthetic method. The as-prepared samples have been characterised by using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. Rhodamine B dilute solution was used to discuss the photocatalytic activities of the as-prepared composites under the visible light irradiation. Experimental results showed that with increasing the contents of AgIO4 the photocatalytic activity of the as-prepared hybrids was first increased and then decreased. When the molar ratio of AgCl to AgIO4 was 1:5, in 30 min, the as-prepared composites with the bandgap of 1.21 eV exhibited the highest photocatalytic activity and possessed 96.3% of degradation efficiency. That was increased by 71.5 and 27.9% compared with AgCl and AgIO4, respectively. Moreover, AgCl was linked with AgIO4 via chemical bonds rather than physical contact at the interfaces of these two semiconductors. In addition, a possible photocatalytic degradation mechanism for the as-prepared hybrids was also presented.
Core–shell-type polymer–lipid nanoparticles for the transdermal delivery of daidzein
- Author(s): Zaitongguli Wusiman ; Liang Sun ; Tiantian Zuo ; Yunzhi Yin ; Xiaoming Yang ; Qi Shen
- Source: Micro & Nano Letters, Volume 13, Issue 9, p. 1363 –1366
- DOI: 10.1049/mnl.2018.5095
- Type: Article
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Daidzein (DZ) is an ideal Chinese herb for treating cardiocerebrovascular disease. Despite its poor water solubility and limited application, DZ was successfully loaded, along with penetration enhancer azone, onto core–shell-type polymer–lipid nanoparticles through a two-step preparation method. The mean particle diameter, encapsulation efficiency, and drug-loading rate of DZ–polymer-azone–lipid nanoparticles (D-P-Azone-LNs) were 77.59 ± 2.26 nm, 79.91% ± 1.46%, and 1.50% ± 0.02%, respectively. In skin penetration experiment, the cumulative amount of DZ from D-P-Azone-LN reached 14.91 μg·cm−2 at 72 h. This amount was 1.44 and 6.01 times higher than those of DZ–polymer–lipid nanoparticles (D-P-LNs) and DZ solution, respectively. Confocal laser scanning microscopy was used to conduct a qualitative analysis. In vivo study, D-P-Azone-LN achieved better skin retention than those of D-P-LN and DZ. Furthermore, no significant irritation was observed in the skin irritation experiment. These results suggested that the core–shell polymer–lipid nanoparticles, which combined the properties of polymer and lipid nanoparticles, can offer a useful formulation for enhancing the skin permeation of drug for transdermal delivery.
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