Volume 9, Issue 10, October 2018

Recent advances in nanofibers fabrication and their potential applications in wound healing and regenerative medicine

Doaa M. Ragab;Nazik A. Elgindy

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 665-676
DOI: 10.5185/amlett.2018.1856

Nanofibers fabrication is generating considerable interest in terms of their biomedical applications. Recent development in nanofibers fabrication techniques resulted in controlled manipulation of nanofibers characteristics, such as their high surface to volume ratio, high porosity and their ability to encapsulate bioactive molecules. Development of biocompatible, polymer coated nanofibers can also provide an optimal environment for cell adhesion, proliferation and differentiation. This paper presents an overview on different applied techniques for nanofibers fabrication, in addition to the process variables to tailor their physico-chemical characteristics. Furthermore, the current review sheds a new light on the application of nanofibers on treatment of diabetic foot ulcers and artificial skin reconstruction. 

Hydrogen concentration behavior of y-grooved weld joint based on a coupled analysis of heat transfer - thermal stress - hydrogen diffusion

Go Ozeki; A. Toshimitsu Yokobori; Toshihito Ohmi; Tadashi Kasuya; Nobuyuki Ishikawa; Satoshi Minamoto; Manabu Enoki

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 677-683
DOI: 10.5185/amlett.2018.2160

It is important to predict the stress driven hydrogen induced cracking at the weld joint on the basis of computational mechanics from the view point of engineering problem. In this study, On the basis of proposed numerical analysis, behaviors of hydrogen diffusion and concentration during cooling process of y-grooved weld joint were analyzed and the mechanism of hydrogen induced cracking was investigated. One of authors has been proposed a multiplication method which magnifies the hydrogen driving term in the diffusion equation to realize correctly hydrogen concentration behaviors. In this study, the behaviors of hydrogen diffusion and concentration for the model of y-grooved weld joint was analyzed by combining a multiplication method with the coupled analyses of heat transfer – thermal stress – hydrogen diffusion. As a result, hydrogen was found to diffuse from weld metal to base metal through HAZ (Heat Affected Zone), and concentrate at the position of blunt angle side of weld groove bottom. It was found that hydrogen concentrates at the position of the local maximum value of hydrostatic stress gradient. This analytical result was found to well predict the actual hydrogen induced cracking of the y-grooved weld joint. Using this method of analysis, prediction of hydrogen induced cracking becomes possible. 

Radiation engineered copper nanoparticles immobilised catalytic reactor (Cu-NICaR) system

Swarnima Rawat; Nilanjal Misra; Virendra Kumar; Shubhangi Atmaram Shelkar; Narender Kumar Goel; Rakesh Kumar Singhal; Lalit Varshney

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 684-691
DOI: 10.5185/amlett.2018.2123

A robust and reusable Copper Nanoparticles Immobilised Catalytic Reactor (Cu-NICaR) system was fabricated by immobilising Copper Nanoparticles (Cu NPs) onto a radiation functionalized polymer support. Gamma radiation induced simultaneous irradiation grafting process was employed for introducing poly-glycidyl methacrylate (poly(GMA)) chains onto non woven PE-PP matrix. Optimization of the grafting process was carried out by studying the effect of experimental parameters, such as absorbed dose, monomer concentration and solvent polarity on grafting yield. The poly(GMA)-g-PE-PP matrix was used as a functional polymer support for Cu NPs, synthesised under optimized conditions using NaBH4 as reducing agent. Characterization of the samples was carried out by UV-Visible spectrophotometer, Fourier Transform Infrared (FTIR) Spectroscopy, X-ray fluorescence (XRF), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). Catalytic activity of Cu NPs immobilised poly(GMA)-g-PE-PP catalytic system was studied  by spectrophotometrically monitoring the catalytic reduction of p-nitrophenol (PNP), using NaBH4 as reducing agent. The Cu NPs-immobilised-poly(GMA)-g-PE-PP was observed to exhibit excellent catalytic activity both in batch process (12 cycles over a period of 30 days) as well as in fixed bed column reactor mode, without significant loss of activity. 

Design of a novel three arm electrothermal microgripper with multiple degrees of control

Muaiyd H. M. Al-Zandi; Changhai Wang

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 692-695
DOI: 10.5185/amlett.2018.2072

A novel three arm microgripper design is presented in this paper.  It is a SU-8 based design with integrated microheaters. It is composed of three microactuators: two are based on a design for bi-directional beam deflection and the other is a tri-directional actuator. The actuators are simulated and analyzed using COMSOL Multiphysics tool. The first actuator has displacement of about 12 μm and 35 μm respectively when heaters h1 and h2 are used in operation and the heater temperature is about 200°C. The second actuator has a displacement of about 12 μm in all three directions. This microgripper is flexible and can be used to grasp a wide range of sizes of micro-particles. In addition, it has more freedoms of control by using the different combinations of the 8 embedded microheaters for electrothermal actuation. 

Composites of AISI 316L stainless steel and nanocrystalline Ti-B-C ceramic powders

Slawomir M. Kaczmarek; Tomasz Bodziony; Vinh H. Tran; Pawal Figiel; Anna Biedunkiewicz; Grzegorz Leniec

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 696-702
DOI: 10.5185/amlett.2018.2161

Series of nanocrystalline and TiC, TiB2, and B4C powders as dopants (3%-20%) embedded in an AISI 316L austenitic steel have been prepared and investigated by ferromagnetic resonance and magnetic measurements. The homogeneous composites with the dopants up to x = 7 vol. % exhibit superparamagnetic properties, characterized by bifurcation between the field-cooled MFC(T) and zero-field cooled MZFC(T) magnetization below Tir and a maximum at Tmax in low-field MZFC(T) curves. We found that the Tir and Tmax values depend proportionally on the dopant concentrations x. The magnetization measurements in fields above 1000 Oe suggested an induced phase transition from superparamagnetic state to ferromagnetic one but presumably without long-range magnetic correlation. An analysis of magnetic anisotropic energy barrier distributions implied that different sizes and compositional types of dopants may contribute to the superparamagnetic relaxation process.  The results demonstrate the possibility of obtaining new steel-based materials with desired properties and potential applications as combining magnetic and mechanical advantages.

Effect of reaction time on LiMn2O4 nanostructures prepared by modified chemical bath deposition method

Lehlohonolo F. Koao; Setumo V. Motloung; Tshwafo E. Motaung

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 703-707
DOI: 10.5185/amlett.2018.2137

LiMn2O4 (LMO) powders were prepared by modified chemical bath deposition method. The effect of reaction time on the structure, morphology and optical properties of LMO nanostructures were investigated. The reaction time was varied from 1 - 120 min. The X-ray diffraction (XRD) patterns of the powders correspond to the various planes of a cubic spinel LMO phase. It was observed that the secondary phases decreases with an increase in reaction time. The diffraction peaks increase in intensity with an increase in reaction time up to 10 min. The estimated average grain sizes calculated using the XRD spectra were found to be in the order of 60 ± 1 nm. The scanning electron microscope (SEM) image suggested that the reaction time influences the morphology of the prepared powders. The irregular nanoparticle increased in size with an increase in reaction time. The UV-Vis spectra showed a red shift with an increase in reaction time up to 10 min. 

Visible light responsive TiO2 nanotubes synthesized by electrochemical anodization method

Elizabeta Stojcheva; Metka Benčina; Ita Junkar; Tomaž Lampe; Matjaz Valant; Veronika Kralj-Iglič; Aleš Iglič

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 708-714
DOI: 10.5185/amlett.2018.2024

The photocatalytic activity of TiO2 nanotubes (NTs) makes these materials promising candidates for a variety of applications, including photocatalytic degradation, water splitting and biomedical devices. The large band gap of TiO2 (anatase ∼3.2 eV; rutile ∼ 3.0 eV) requires excitation with UV light, which accounts for only a small fraction of solar light. In order to increase the light absorption in the visible region, reduction of the band gap is required. Here, TiO2 nanotubes (NTs) were fabricated by electrochemical anodization of Ti foil. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and X-ray photoemission spectroscopy (XPS) were used to determine morphology, crystal structure and surface composition of the TiO2 NTs. Different synthesis conditions influenced TiO2 NTs properties that allowed the tuning of the band gap. UV-Vis analysis of 61.54 µm long NTs showed light absorption over the whole visible range, while NTs with the length up to 0.21 µm are able to absorb only UV light. 61.54 µm long NTs exhibited band tailing up to 1.43 eV.

Impact of infrared radiation on oxide layer of ultrathin TiNi-based alloy wire

Gunther Sergey; Chekalkin Timofey; Hodorenko Valentina; Kang Ji-hoon; Kim Ji-soon; Gunther Victor

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 715-720
DOI: 10.5185/amlett.2018.1821

Despite the well-known advantages of TiNi-based alloys, the cost of production is still high. The alloys are traditionally made by vacuum induction melting technology followed by vacuum arc remelting to get ingots which are further worked mechanically to final or semi-finished items. The special attention is paid by a thin wire which can be used as a suture material or for a tissue grafting. Thin TiNi yarns are produced by cold drawing via dies with the intermediate annealing. When a diameter is about or over 1 mm, the existing solutions give clear insight into a general idea about how to change the structure and properties of the alloy. However, when the size is definitely scaled-down to 90 μm and less, serious difficulties appear because such yarn requires thoroughly care in mechanical processing steps and repeated heat treatment increases the expense making the product costly and unprofitable. As working steps and heat treatment of the ultrathin TiNi-based wire (UW) are to be more predictable and controllable, there was suggested an infrared (IR) drawing heater due to the radial warming system located prior to the die. In hope to provide a more comprehensive understanding of this issue, a study on how the IR heating method influences on surface properties of the UW, comparing the various effects of heat treatment was carried out using the designed IR heater. The study covers the effect of oxide layer composition and its modification on the properties of the wire IR-heat drawn. Strong correlations were observed between oxide layer thickness and strength characteristic of the resultant wire. These findings elucidate the role of the oxide layer and its composition on a quality of the UW drawing process. 

Enhancing absorption in thin film organometal trihalide perovskite solar cell by photon recycling

Abhinav Bhatnagar; Vijay Janyani

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 721-726
DOI: 10.5185/amlett.2018.2108

Over the past few years thin film planar heterojunctions solar cells have made much progress as a low cost with high power conversion efficiency photovoltaic devices. Among the materials used in fabricating such solar cells organometal trihalide perovskite (MAPbI3) has proven to be a promising absorber material due to cheaper organic-inorganic perovskite compounds, abundantly available in nature, ease of fabrication and compatible with low temperature large scale processing. In addition to the efficient absorption in ultra-violet range the material possess intriguing optoelectronic properties such as high crystallinity, high carrier mobility and large carrier diffusion lengths. Currently, the highest power conversion efficiency achieved by such perovskite solar cells is only 23.9% as reported in 2017. In this work we demonstrate a thin film organometal trihalide perovskite solar cell with hybrid interfaces between different materials which are selected after extensive study to achieve reduced recombination and high performance. Further, the absorption of the incident solar spectrum is enhanced by incorporating a 1D photonic crystal at the bottom of the cell facilitating the photon recycling process. The proposed solar cell parameters are numerically computed using rigorous coupled wave algorithm through SYNOPSYS RSOFT CAD tool. The thickness of each layer of the structure is optimized using MOST scanning and optimization module of RSOFT CAD tool to achieve highest power conversion efficiency at minimum device thickness (~2 µm). The power conversion efficiency thus obtained is 25.2% with a fill factor of 86.3% at AM 1.5, which is very promising. This demonstrates the remarkable potential of the proposed design to achieve efficiencies over 20% and compete with the existing crystalline silicon photovoltaic market. 

Reducing edge effect of temperature-field for large area thin film deposition in hot filament chemical vapor deposition system

Lin Li; Shibing Tian; Ruhao Pan; Chao Wang; Chi Sun; Junjie Li; Changzhi Gu

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 727-732
DOI: 10.5185/amlett.2018.2146

The uniformity in temperature-field of the hot filament chemical vapor deposition (HFCVD) system is of great importance since it is a critical parameter that determines the quality of the deposited films. In fact, the temperature-field is mainly filament distribution dependent. In conventional analysis method, the filament array usually has an equal-space distribution, which leads to a remarkable edge effect and consequently unable to obtain large area uniformity in temperature-field in HFCVD for high-quality thin film deposition. Here, we proposed theoretically an asymmetrical filament distribution to reduce the edge-effect of temperature field. The adjacent filament distance was optimized by using numerical simulation based on heat-transfer theory. Based the optimized condition, temperature difference as low as 13 K between the center and edge region of the filament arrays can be achieved in 100-mm substrate, which is only one tenth of the temperature difference of that in the case that the filaments were evenly distributed. Thus unequal-space distribution can be employed to enhance the uniformity in temperature field of the HFVCD system in favor of the growth of high quality thin films in large area.

Surface reinforcement of metals by carbon nanomaterials followed by high intense energy irradiation

Nuha Abusaif; Gregory S. Bocharov; Alexander V. Eletskii; Alexander V. Uvarov; Sergei D. Fedorovich

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 733-736
DOI: 10.5185/amlett.2018.2107

The metal surface modification by carbon nanostructures followed by high intense treatment has been realized. As carbon nanostructures were used: carbon soot formed in an arc discharge with graphite electrodes remained after extraction of fullerenes; fullerene C60; partially reduced graphene oxide. An intense pulsed laser and electron beam accelerator were used as high intense energy sources. Measurements performed indicate that the above described processing of the steel surface results in a considerable enhancement of the microhardness (up to 800%) and a notable decrease (up to 50%) in the friction coefficient. The degree of reinforcement depends on both the type of nanocarbon and the source of energy. The maximum effect of reinforcement is reached for fullerene C60 coverage and laser irradiation. The dependence of the microhardness of the treated surface on the irradiation energy has a non-monotone character reaching the maximum value of about 200 J/cm 2 at the laser irradiation and 400 J/cm 2 at the e-beam irradiation.

Redox-active cerium oxide based nanozyme abrogate the organophosphate mediated poisoning in mammalian cells

Kinjal D. Shah; Ragini Singh; Sanjay Singh

Advanced Materials Letters, 2018, Volume 9, Issue 10, Pages 737-747
DOI: 10.5185/amlett.2018.1939

Owing to the autocatalytic antioxidant activity, cerium oxide nanoparticle (CeNPs) has been extensively used in biomedical fields for treatment of neurodegenerative diseases, biosensing, and therapeutic applications. The redox-dependent interconversion between +3 and +4 oxidation states of CeNPs is suggested to be the reason of scavenging of free radical generated in the biological system. Herein we have explored the protective effect of CeNPs against the oxidative stress induced by organophosphate-based pesticide, 2,2-dichlorovinyl dimethyl phosphate (DDVP), in a normal human liver cell culture model (WRL-68). DDVP is known to cause the toxic effect in cells by inducing lipid peroxidation, cellular glutathione level depletion and DNA fragmentation by the caspase-dependent pathway. We followed the protection of cells by CeNPs against DDVP exposure using MTT and NRU assays. Exposure of DDVP to cells induced significant nuclear fragmentation, which could be avoided in cells pre-treated with CeNPs. Mechanistically, we observed that CeNPs induces an increase in cellular GSH level, which could assist in removal of excess of reactive oxygen species, generated in DDVP exposed cells, along with the superoxide dismutase (SOD)-like activity of CeNPs. The interaction study showed that there was no chemical interaction between DDVP and CeNPs, therefore, the intrinsic SOD-like activity of CeNPs was intact even in the complex cell culture media. Growing evidence suggest that excess use of DDVP could lead to the several diseases in cells/tissues, therefore our finding emphasizes that CeNPs can be used as a potent antioxidant agent to avoid the ramifications of DDVP and other commercial pesticides.