Micro & Nano Letters
Volume 15, Issue 10, 19 August 2020
Volumes & issues:
Volume 15, Issue 10
19 August 2020
Effects of process parameters on Cu-nanoparticle synthesis in tetraethylene glycol through microwave irradiation
- Author(s): Woo Lim Choi and Jong-Hyun Lee
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 640 –644
- DOI: 10.1049/mnl.2019.0459
- Type: Article
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p.
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Copper nanoparticles were successfully synthesised through microwave irradiation of a copper-oxide particle precursor dispersed in tetraethylene glycol. Initial results obtained after 4–6 min of irradiation, without the use of a surfactant, indicated nanoparticle aggregation and particle-size bimodality by incomplete reduction. However, the said aggregation and bimodality were observed to be significantly suppressed with accelerated reduction upon addition of an alcohol-type surfactant. Consequently, Cu nanoparticles measuring 74 and 79 nm in size were successfully synthesised by performing short irradiations lasting 3 and 4 min, respectively.
Synthesis of iron-oxide magnetic nanoparticles coated with dextran of varied molecular mass using a facile ball-milling method
- Author(s): Bo-Wei Chen ; Shadie Hatamie ; Prabir Garu ; Pooyan Heravi ; Jiann-Yeu Chen ; Bo-Tau Liu ; Zung-Hang Wei ; Da-Jeng Yao
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 645 –650
- DOI: 10.1049/mnl.2019.0811
- Type: Article
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p.
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A simple ball-milling method was implemented to prepare dextran-coated superparamagnetic iron oxide nanoparticles (dextran-coated SPIONs, DSPIONs) by coating dextran (molecular mass, M dextran, 10, 40, 70 and 100 kDa) onto nanoparticles, which synthesised with co-precipitation methods. The size, saturation magnetisation and hydrodynamic diameters of the DSPIONs, composed of Fe3O4 and γ-Fe2O3 proved by X-ray diffraction and Raman spectra, were 11–14 nm, 55–65 emu g−1 and 200–300 nm using transmission electron microscope, superconducting-quantum-interference-device magnetometer and dynamic light scattering devices, respectively. The characteristic lines of surface coating were revealed in attenuated-total-reflection Fourier-transform infrared spectra. The saturation magnetisation and surface coating percentage (thermogravimetric analysis) of the ball-milled DSPIONs were independent on M dextran. The results were different from the statistical data from previous studies: DSPIONs using increasing M dextran were accompanied by decreasing saturation magnetisation and increasing surface coating in conventional co-precipitation protocols. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated the ball-milled DSPIONs exhibited low cytotoxicity in human hepatoma (SK-HEP1) cells, and the implementation of Prussian blue staining proved the DSPIONs were able to be uptaken by SK-HEP1. There was no obvious difference between the ball-milled DSPIONs with various M dextran. It demonstrated the ball milling process might be potential for SPION preparation in the biomedical field.
Photocatalytic potentiality of a two-dimensional Fe-doped C2N material in visible light
- Author(s): Wei Gu and ZhangE Peng
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 651 –656
- DOI: 10.1049/mnl.2019.0794
- Type: Article
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In this study, the phenotype of Fe-doped Nano-C2N monolayer (C2N monolayer) was analysed based on the Perdew-Burke-Ernzerh-solids (PBEsol) functional of First-principles. The results indicate that the length of Fe-C bonds is significantly higher than the C-N bond. For Fe atom doped, the band gap of C2N monolayer system is reduced from 1.811 to 0.384 ev, which increases the activity of electron hopping. Moreover, at Fe-doped C2N positions, the partial density of states (PDOS) of the C2N monolayer is well overlapped. That indicates that there has a strong interaction between the Fe atom and the C2N monolayer. Furthermore, after doping with Fe atom, C2N monolayer shows better light absorption ability in the ultraviolet and infrared regions. The corresponding conduction band minima (CBM) values in the Fe-doped C2N monolayer system are lower than that of the pristine C2N monolayer system. In particular, it was lower than the O2/O2 •− redox potential, which show that the electrons located in the conduction band have the potential to convert the oxygen molecules into superoxide radicals. Our findings suggest that Fe-doped C2N monolayer can be a promising material for the novel photocatalytic degradation materials.
Bactericidal effect of gentamicin conjugated gold nanoparticles
- Author(s): Bidhan Mohanta ; Anindita Chakraborty ; Subburaj Selvaraj ; Alok Roy
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 657 –661
- DOI: 10.1049/mnl.2020.0194
- Type: Article
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The authors explored the antibacterial activity of gentamicin conjugated gold nanoparticles against Escherichia coli bacteria by using the disk diffusion method. Gold nanoparticles were prepared by the reduction of tetrachloroauric acid with sodium citrate. Experiments were performed with relatively lower and higher doses of gentamicin, gold nanoparticles, and gentamicin conjugated gold nanoparticles. Atomic force microscopy (AFM) images of the bacterial colonies with and without treatment were taken. Results show that gentamicin used alone in a lower range of doses did not cause any growth inhibition, but when used in conjugation with gold nanoparticles, clear inhibition zones were visible. The ratios of inhibition areas of gold nanoparticles with gentamicin to only gentamicin were more in case of bigger sized gold nanoparticles. AFM images of the bacterial colonies also showed that gentamicin conjugated gold nanoparticles were more effective than other groups in inhibiting bacterial growth.
Two-step hydrothermal preparation of poor crystalline MoS2 and its enhanced performance for dibenzothiophene hydrodesulphurisation
- Author(s): He Huang ; Na Liu ; Jian Wei ; Xueying Wang ; Qinglong Luo ; Xueli Huang ; Xuefeng Wang ; Mei Zhong
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 662 –665
- DOI: 10.1049/mnl.2020.0234
- Type: Article
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p.
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Poor crystalline MoS2 was synthesised by a novel two-step hydrothermal method, including aging and hydrothermal stages. The structures were characterised by different analytical methods such as X-ray diffraction (XRD), Brunauer–Emmett–Teller, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The synthesised products were typical mesoporous materials with a high specific surface area (273 m2/g). XRD and XPS displayed that the products were poor crystalline MoS2 mixed with metal Mo and Mo4+/(Mo + Mo4+) was 72.6%. The electron microscopy results showed that the products were uniform bent nanosheets with150 nm diameter and 3–5 layers. Furthermore, the product displayed excellent hydrodesulphurisation performance of dibenzothiophene (DBT) and the DBT conversion reached 87.3%. Compared with the one-step hydrothermal method, the two-step one was able to shorten the reaction time by 12 h, create more active sites and affect crystalline, composition, specific surface area and morphology of products.
Anisotropic wet etching on the β-phase poly(vinylidene fluoride) film
- Author(s): Hirofumi Miki ; Ryota Sugii ; Taisuke Tominaga ; Shigeki Tsuchitani
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 666 –669
- DOI: 10.1049/mnl.2019.0304
- Type: Article
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p.
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The ability to fabricate micro patterns or micro structures directly on a flexible and piezoelectric β-phase poly(vinylidene fluoride) (PVDF) film, has potential applications in the field of micro-electro-mechanical systems. The authors realised several tens to several hundred of micro patterns directly on a 110-μm thick flexible β-phase PVDF film by wet-etching technology. Through experiments, the authors also found that the β-phase PVDF film shows anisotropic etching characteristic in the proposed wet-etching process. In this Letter, the authors reported β-phase PVDF film micropattern fabrication process and its anisotropic wet-etching properties for the first time.
Effects of deposition and annealing conditions on the crystallisation of NiTi thin films by e-beam evaporation
- Author(s): Hao Sun ; Jianjun Luo ; Zhongjing Ren ; Ming Lu ; Yong Shi
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 670 –673
- DOI: 10.1049/mnl.2020.0004
- Type: Article
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This Letter demonstrates the effects of deposition and annealing conditions on the crystallisation of nickel–titanium (NiTi) thin films deposited by the e-beam evaporation. NiTi thin films of 0.5 μm thick are fabricated on P-type (110) silicon substrates using the e-beam evaporation technique. With the characterisations using the X-ray diffraction method, the results indicate that low e-beam deposition rate and argon employed annealing procedures can be beneficial to the formation of NiTi crystalline structure. Additionally, the as-deposited NiTi thin films without annealing procedures are amorphous, when deposited on the substrates at low temperatures. The differential scanning calorimetry studies show NiTi thin films formed by the e-beam evaporation are Ni-rich. Furthermore, SEM images illustrate that high-precision patterned NiTi thin film microstructures can be fabricated by combining with the e-beam evaporation and lift-off resist methods, without any wet or dry etching procedures. The proposed fabrication process for NiTi thin film microstructures shows great potential for application in shape memory alloy medical devices, as well as the micro-robotics.
Green sol–gel synthesis of CoMnCrO4 spinel nanoparticles and their photocatalytic application
- Author(s): Farzaneh Moradnia ; Saeid Taghavi Fardood ; Ali Ramazani ; Samira Osali ; Ilnaz Abdolmaleki
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 674 –677
- DOI: 10.1049/mnl.2020.0189
- Type: Article
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p.
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CoMnCrO4 spinel nanoparticles were prepared using the green and efficient sol–gel method. The synthesised nanoparticles were fully characterised by Fourier-transform infrared spectroscopy, X-ray powder diffraction with Rietveld refinement, transmission electron microscopy, scanning electron microscopy, and diffuse reflectance spectroscopy analysis. The characterisation of the sample showed that the CoMnCrO4 NPs have a spinel cubic structure with a crystallite size of 14 nm, narrow bandgap (1.75 eV), and uniform spherical morphology with particle size about 25–30 nm. The CoMnCrO4 NPs demonstrated high photocatalysis capability towards the Congo red dye as a pollutant with a high and fast efficiency degradation of 90% after 30 min under the visible light irradiation. Also, the impacts of different parameters consisting of nanoparticle amount, initial dye concentration, irradiation time, light and dark on dye degradation efficiency were assessed.
Temperature effect on structural, mechanical properties and corrosion behaviour of CrN thin films deposited by magnetron sputtering
- Author(s): Bassam Abdallah ; Mahmoud Kakhia ; Walied Alssadat ; Walaa Zetoun
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 678 –683
- DOI: 10.1049/mnl.2019.0600
- Type: Article
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Chromium nitride (CrN) thin films have been synthesised on Si(100) and stainless steel (SS304) substrates by direct current (DC) magnetron sputtering at different temperatures (25–100–200°C). The effects of temperature on structural and mechanical properties of the prepared films have been investigated. The CrN thin films have been described by X-ray diffraction to reveal their crystalline quality and texture. Results indicate that the grain size decreases with the temperature. The thickness of CrN films have been determined by scanning electron microscopy and their stoichiometry was measured by energy dispersive X-ray spectroscopy. Atomic force microscopy was employed to characterise the morphology of the surface for thin films and to calculate the roughness value. The results show that the hardness of films depends strongly on the grain size of the film. The micro-hardness of these films decreased with the increase in temperature. The corrosion of the CrN coating deposited was studied with corrosion potential, polarisation resistance, as well as electrochemical impedance spectroscopy techniques.
Effect of micron aluminium powder on mechanical properties and microstructural in zirconia toughened alumina ceramics
- Author(s): Ruihao Zhang ; Bao Qi ; Jie Wang ; Xinwei She ; Zhende Ran ; Xianquan Jiang
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 684 –687
- DOI: 10.1049/mnl.2020.0053
- Type: Article
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p.
684
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Traditional powder metallurgy was employed to prepare alumina–zirconia (Al2O3–ZrO2) and alumina–zirconia–aluminium (Al2O3–ZrO2–Al) ceramics. It was found that as the sintering temperature increases, the flexural strength of both ceramics increases first and then decreases. The maximum flexural strength of Al2O3–ZrO2 appears to be 430.7 MPa when sintered at 1650°C, and Al2O3–ZrO2–Al appears to be 448.8 MPa when sintered at 1600°C. As the sintering temperature increases, the grain size of each phase grows up, the porosity increases, the content of intragranular phase and monoclinic ZrO2 (m-ZrO2) increases. The addition of Al powder improves the dispersion of ZrO2, reduces the porosity of zirconia toughened alumina ceramics, and improves the bending strength. Al powder increases the content of the intragranular ZrO2, restrains the t–m phase transformation, results in the decreases of the relative amount of m-ZrO2 in ZrO2 (Xm ). Adding Al powder during ball milling is a simple method to increase the content of intragranular ZrO2 in Al2O3–ZrO2 ceramics.
Microstructure and mechanical properties of Zr-modified Al–7Si–0.35Mg–0.2Ti cast alloy
- Author(s): Zhuang Zhang ; Xiaodong Du ; Pengcheng Zhuang ; Rong Chai ; Changjian Wang ; Hao Zhang
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 688 –692
- DOI: 10.1049/mnl.2019.0755
- Type: Article
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In this research, four specimens of hypo-eutectic Al–7Si–0.35Mg–0.2Ti–xZr (x = 0, 0.1, 0.2, 0.3 wt%) cast alloys were fabricated via a traditional casting method. The effect of different concentrations of Zr on the microstructure and mechanical properties of cast alloys was investigated through metallographic observation, SEM analysis, TEM observations, tensile strength testing, and Vickers hardness test. The results show that the plate-like shape eutectic Si phase is gradually transformed into fine fibrous eutectic Si phase, and is more evenly distributed as the content of Zr increased. The α-Al matrix grains are transformed from dendrites to isometric grains, of which the grains sizes became smaller. The results of the tensile test show that with the addition of 0.2% Zr, Al–7Si–0.35Mg–0.2Ti alloys obtain the best tensile properties. The ultimate tensile strength and elongation values are 221 MPa and 11%, the number of which is increased by 14.5 and 71.9% than base alloy, respectively. Additionally, the alloy's yield strength, Vickers hardness, and other comprehensive mechanical properties have also improved significantly.
Growth characteristics of tin sulphides crystals by the vapour transport method using SnS and sulphur powders: effect of temperature and pressure
- Author(s): Chaeeun Kim ; Jun-Cheol Park ; Ji-Hoon Ahn
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 693 –696
- DOI: 10.1049/mnl.2020.0032
- Type: Article
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p.
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Tin sulphide compounds have two different types of 2D layered crystal structures with different electrical conduction types. Tin disulphide with n-type semiconductor characteristics has a 2D crystal structure with hexagonal symmetry, while tin monosulphide (SnS) with p-type semiconductor characteristics has a 2D crystal structure with orthorhombic symmetry. These layered materials have many potential applications such as electronic and optoelectronic devices. Meanwhile, it is known that the growth products of tin sulphides are very sensitive to the process parameters. In this study, the authors investigated the growth phenomena of tin sulphides by the vapour transport method using SnS and sulphur powders because vapour transport reactions are relatively simple and facilitate the understanding of the effects of growth parameters. The growth behaviour of tin sulphides as a function of process temperature and pressure was observed, and the results can be explained in terms of the sulphurisation and reduction of SnS powder during the growth process.
Microfluidisation trends in the development of nanodelivery systems: characterisation and release study of resveratrol-loaded nanostructured lipid carrier prepared with high-pressure microfluidisation
- Author(s): Jianmin Wang ; Hao Sun ; Xin Liu
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 697 –702
- DOI: 10.1049/mnl.2020.0236
- Type: Article
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p.
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The release behaviour and kinetic evaluation of resveratrol (Res) from nanostructured lipid carrier (NLC) have been conducted after characterisation for Res-NLC in this study. High-pressure microfluidisation technique was successfully applied to manufacturing Res-NLC, and the morphology of nanoparticle was observed via freeze-fracture transmission electron microscopy. Photon correlation spectroscopy was used to characterise the NLC system for particle size (PS) and polydispersity index (PDI). The in vitro release research was implemented by the dialysis method with active ingredient determined by high-performance liquid chromatography. Fitting of release data to different kinetic models was carried out. The optimised Res-NLC was physically stable with the PS below 200 nm, PDI below 0.3 and zeta potential (ZP) above 50 mV. The encapsulation efficiency was above 80%. Moreover, an in vitro release analysis demonstrated the sustained release profile of contents from NLC formulation over 12 h, with about 90% of the active ingredient released. Res-NLC presented the best fit with the Weibull model accompanied by better correlation value. In conclusion, all the obtained results demonstrated that the release study of Res-loaded NLC exhibited the promising application of the NLC formulation system in active ingredient sustained release carrier.
Facile preparation of multiphosphonic acid functionalised multi-walled carbon nanotubes for enhanced adsorption properties for heavy metal ions from wastewaters
- Author(s): Zhihua Jia ; Ping Yin ; Zhenglong Yang ; Yanbin Xu ; Xiguang Liu ; Feng Wang ; Huawei Yang ; Wenjuan Sun
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 703 –708
- DOI: 10.1049/mnl.2019.0678
- Type: Article
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p.
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This work presents facile preparation processes of multiphosphonic acid functionalised multi-walled carbon nanotubes (HEDP-MWCNTs and ATMP-MWCNTs), which have been characterised by FT-IR, XPS, X-ray diffraction, TGA, and SEM, and have employed for heavy metal ions adsorption. The adsorption properties of MWCNTs, HEDP-MWCNTs, and ATMP-MWCNTs for gold ions, cadmium ions, copper ions, lead ions, nickel ions, cobalt ions, zinc ions, and chromium ions have been investigated, the experimental results reveal that the functionalised samples HEDP-MWCNTs and ATMP-MWCNTs have excellent adsorption properties for Pb(II) and Au(III), respectively. The investigation results on their adsorption selectivity represent that in the binary heavy metal ion systems, HEDP-MWCNTs/ATMP-MWCNTs has displayed a strong affinity for Pb(II)/Au(III) and even could exhibit 100% selectivity while coexisting with copper ions, nickel ions, cobalt ions, zinc ions, chromium ions, or cadmium ions. Furthermore, the adsorption kinetics of HEDP-MWCNTs for Pb(II) and ATMP-MWCNTs for Au(III) have also been studied at different solution temperatures. All these research work results show that two novel functionalised adsorbents HEDP-MWCNTs and ATMP-MWCNTs have shown excellent adsorption properties for heavy metal ions and they can be used in wastewater treatment, especially for lead/gold ions removal.
Pulsed plasma chemical synthesis of Fe2O3@TiO2 core–shell nanocomposites
- Author(s): Galina Kholodnaya ; Roman Sazonov ; Denis Ponomarev ; Alexander Sivkov ; Ivan Shanenkov ; Fedor Konusov ; Ruslan Gadirov
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 709 –712
- DOI: 10.1049/mnl.2020.0110
- Type: Article
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p.
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The Letter presents the results of the experimental investigation on the synthesis of core–shell structured nanocomposites. Iron oxide, which served as a nucleus in the composite, was synthesised using the plasma dynamic method. The composite shell was titanium oxide produced by the pulsed plasma chemical method. Average sizes of nanoparticles were estimated between 50 and 150 nm in the Fe2O3@TiO2 core–shell structured composite nanoparticles using TEM. A distinctive feature of the morphology of the synthesised Fe2O3@TiO2 core–shell is that the core entirely encapsulates clusters of titanium oxide nanoparticles. The wall thickness of the coating is 5–10 nm. The spectral dependence of the absorption coefficient α(hν) was calculated for the Fe2O3@TiO2 composite. The interband absorption parameters are determined in the energy intervals Δ′(hν) upon approximation of the absorption spectra. The bandgap for indirect and direct allowed transitions is 1.36 and 1.97 eV for and , respectively.
Relationship between secondary phase and photocatalytic activity in titanium-doped bismuth ferrite nanocrystals
- Author(s): Lili Wang ; Shuai Meng ; Guoli Chen ; Xiaodong Yang ; Yan Yan ; Rui Chen
- Source: Micro & Nano Letters, Volume 15, Issue 10, p. 713 –716
- DOI: 10.1049/mnl.2020.0223
- Type: Article
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p.
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Doping is an effective way to enhance photocatalytic activity. Herein, the authors have synthesised a series of BiFe1−x Ti x O3 (x = 0, 0.05, 0.10, 0.15, 0.20) nanocrystals through sol–gel methods. X-ray diffraction, Raman spectra, high-resolution transmission electron microscopy images and X-ray photoelectron spectroscopy characterisations indicate doping could facilitate the formation of Bi2Fe4O9 phase at low content, while inhibiting this formation at high content. Interestingly, the appearance of Bi2Fe4O9 improved the photocatalytic activity, which may be attributed to the spontaneous formation of heterostructure between Bi2Fe4O9 and BiFeO3 phases. The staggered energy bands between these two phases could effectively separate electrons and holes, resulting in enhanced photocatalytic performance.
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