Issue 2


G4 self-assembly as an intrinsic nucleic acid function

Anna Varizhuk; Vyacheslav Severov; Galina Pozmogova

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 91-96
DOI: 10.5185/amlett.2018.2003

It is now commonly acknowledged that G-rich polynucleotide sites can fold into G-quadruplex (G4) structures in vivo. In terms of molecular programming, the G4-folding propensity can be regarded as a build-in nucleic acid function with multiple implications for genomic regulation. Here we review several important advances in the studies of G4 self-assemblies in genomic context. We discuss prerequisites and consequences of G4 formation upon transcription or replication and analyze recent data on G4-dependent genomic rearrangements, including translocation and recombination. Hypothetical mechanisms of those G4-dependent rearrangements suggest self-association of G-rich sites. We outline the general molecular basis for possible self-association pathways, i.e., formation of intermolecular G4 assemblies or interquadruplex stacking. Intermolecular G4s and multimeric G4 stacks attract widespread interest as scaffolds for the development of complex junctions in DNA nanotechnology and have prospects in aptamer design, but in this review we focus on fundamental aspects of such higher-order G4 assemblies.

Properties of the photochromic latexes based on spiropyran by emulsion polymerization

Ting Zhang; Liuwa Fu; Zhikang Chen; Yanyan Cui; Xiaoxuan Liu

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 97-100
DOI: 10.5185/amlett.2018.1677

The latexes based on 2-(3’, 3’-Dimethyl-6-nitro-3’H-spiro[chromene-2,2’-indol]-1’-yl)ethanol(SPOH) were prepared via emulsion polymerization, using a macromolecular surfactant that copolymerized by methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA). The photochromism of the latexes was characterized by UV-vis spectroscopy. Through the characterization of DLS and SEM, the sizes and morphological of the latexes were studied before and after UV light irradiation. During the thermal fading process, it appeared continuous variable pattern in the emulsion, which was related to the rearrangement of the stimulated latexes to meet the dynamic balance of ionic strength, due to the reversible isomerization of spirogyra.

Electroless deposition of nickel on biocompatible poly(dimethylsiloxane) after a laser processing as a pretreatment

Stephan Armyanov; Eugenia Valova; Konstantin Kolev; Dragomir Tatchev; Petar Atanasov; Nadya Stankova

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 101-106
DOI: 10.5185/amlett.2018.1818

Due to its biocompatibility poly(dimethylsiloxane) (PDMS) is an important material for the development of microelectromechanical systems or long-term, medical implants. The paper describes the morphology modifications and surface chemistry of PDMS during pulse laser treatment. SEM, μ-Raman spectroscopy, X-ray micro-tomography and XPS analyses are applied. PDMS decomposition takes place as a function of laser energy absorption. This leads to different oxidation degree of silicon, as shown by the curve fitting of Si 2p and O 1s. The irradiated parts become hydrophilic in contrast with the rest of the material, which remains hydrophobic. This is the condition enabling successful selective electroless deposition of Ni in the tracks, excluding the usual preceding sensibilization and chemical activation. This process is accomplished successfully after femtosecond laser irradiation and it is found that the time interval between laser treatment and metallization is not a critical parameter.

Composites of phenolic resin with expanded graphite and conductive carbon black

Carmen G. Renda; Jeferson A. Dias; Roberto Bertholdo; Alessandra A. Lucas

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 107-111
DOI: 10.5185/amlett.2018.1817

The phenolic resin (PR) is widely studied as matrix for composites due to its promising mechanical properties and chemical stability. However, which regard to electrical conduction, PR is a typical insulator (electrical conductivity around 10 -12 S.cm -1 ), limiting its utilization for electric conduction’ applications. Expanded graphite (EG) and conductive carbon black (CB) are fillers that have been utilized to increase the electrical conductivity of several polymers, but they have not yet been enough studied to composites materials with PR. Thus, this study aims at asses to produce composites of PR and EG or CB (2% w / w) and verify the influence these fillers on the composites’ electrical properties. The composites were analyzed by FT-IR (Fourier Transform-Infrared Spectroscopy), Impedance Spectroscopy (IS) and Scanning Electron Microscopy (SEM). It was verified that the electric conductivity of the PRs increased due to fillers. The composite PR/CB showed electric conductivity about five orders of magnitude higher than the PR. On the other hand, the composite PR/EG showed greatest electrical conductivity, about seven orders of magnitude higher than the PR (1.1x10 -5 S.cm -1 ). These results have shown the efficacy of those fillers in the increase of the electrical conduction in PR-based composites. Therefore, these composites materials have potential to be used as Electromagnetic Interference (EMI) shielding and electrostatic discharge (ESD). 

Narrow bandgap quantum dot diode structures and photoresistors for thermo-photovoltaic and infrared applications 

Karen M. Gambaryan

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 112-115
DOI: 10.5185/amlett.2018.1804

For the thermophotovoltaic (TPV) and other mid-infrared applications, the narrow bandgap quantum dot (QD) diode structures and photoresistors (PR) based on InAsSbP alloys and InAs industrial substrates are fabricated and investigated. For the nucleation of InAsSbP composition strain-induced QDs in Stranski–Krastanow growth mode, as well as at the growth of emitter epilayer lattice-matched with the InAs(100) substrate, the modified liquid phase epitaxy (MLPE) technique is employed. The HR-SEM and AFM microscopes are used for characterization. The grown QDs surface density equals to (3-8)×109 cm -2 , with height and width dimensions ranges from 4 nm to 15 nm and 10 nm to 35 nm, respectively. The current-voltage characteristics and photoresponse spectra of QD TPV and PR structures are also explored. The redshift of the absorption edge, as well as enlargement toward the short wavelength region is revealed for both QD-based devices. The quantitative calculations show increasing of QD-based TPV structures efficiency up to 16% compared with the same structures without QDs. 

Waveguide-detector system on silicon for sensor application

J. Alarcón-Salazar; G. V. Vázquez; A. A. González-Fernández; I. E. Zaldívar-Huerta; J. Pedraza-Chávez; M. Aceves-Mijares

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 116-122
DOI: 10.5185/amlett.2018.1552

A whole silicon monolithic waveguide-detector system is studied. Four different coupling electrophotonic devices are presented. One of them is analyzed in detail. The studied system consists of a planar p-n junction with a waveguide built in a cavity in front of it. The output port of the waveguide faces directly to the depleted layer maximizing absorbance of all photons. The waveguide is experimentally fabricated and characterized, and light on the visible range is transmitted in multimode. The simulation of the fabrication process considers an N-type silicon substrate, whose resistivity is varied from 10Ω×cm to 1000Ω×cm. The diode sensor is characterized by computational simulation, and the model is validated using characteristics of diodes previously fabricated. The dark current, the electric field and the characteristics of the depleted zone are obtained to optimize the design of the system. Electrical stimulations are performed for bias voltages of 0 V, -5 V, -10 V, -20 V and -30 V. The simulation results show that the proposed coupling scheme enhances the generation of photocurrent, which results from all the photons emerging from the waveguide and impinging directly on the space charge region.

Walking robot movement on non-smooth surface controlled by pressure sensor

T. K. Maiti; M. Miura-Mattausch;H. J. Mattausch; Y. Ochi; D. Navarro

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 123-127
DOI: 10.5185/amlett.2018.1878

In this letter, we focus on the robot movement on non-smooth ground-surface, detected by pressure sensor. A simulation tool has been developed to study the robot motion according to the ground-surface condition change. The effect of the robot-foot contact with the ground-surface is considered by elastic properties to the ground. We performed simulation analyses for various surface conditions to control the robot dynamics with respect to pressure sensing data that incorporates the two-way interactions between robot and ground. We upgraded the robot by implementing the pressure sensors under its foot, to measure the real-time contact force between foot and ground-surface. The obtained sensing data is used to analyse the surface condition, for controlling robot-leg movement horizontally along the ground-surface. Consequently, the analysis results guide us to improve the motion of a real self-controlled walking robot. 

Preparation of WS2 Nanosheets from Lithium Intercalation for Hydrogen Evolution 

Yu-Shun Chen; Chia-Wei Chang; Kuan-Bo Lin; Min-Hsiung Hon; Chao-Cheng Kaun; Yen-Hsun Su

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 128-131
DOI: 10.5185/amlett.2018.1923

In this content, the few-layered 1T-WS2 nanosheets were prepared by chemical exfoliation and applied to study hydrogen evolution reaction. Lithium were introduced from n-butyllithium in hexane solution and showed intercalation into the bulk WS2 powder to form the LixWS2 compound in a teflon lined autoclave at a temperature of 1000  o C for 5 hours. Different concentration of n-butyllithium solution were used with the intention of observing the as-prepared nanosheet properties and the influence on the hydrogen evolution reaction. After the LixWS2 powder reacted with DI-water and underwent ultrasonic treatment, the few-layered 1T-WS2 nanosheets were obtained. The size of the as-prepared nanosheets was in the scale of several hundred nanometers. The layer number of the sheets can be observed and determined as about the range of three to six layers. Furthermore, the measurements of UV-vis, TEM (Transmission Electron Microscope), AFM (Atomic Force Microscope) and hydrogen evolution reaction were carried out. In this report, the 1T-WS2 nanosheets show excellent catalytic activity for hydrogen evolution reaction. This indicates that 1T-WS2 nanosheets are promising in sustainable production of hydrogen fuel and increasing the efficiency of hydrogen production.

Generalized predictive control for DEAP flexible bionic actuator with fuzzy model

Yuan Li; Jinwen Zheng; Zhaoguo Jiang; Qinglin Wang

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 132-137
DOI: 10.5185/amlett.2018.1928

Dielectric electro-active polymer (DEAP) is novel type of flexible smart materials, which have advantages of lightweight, high energy density and fast response, making them especially suitable for the actuator material of bionic robots. However, DEAP materials generally have hysteresis effect, creep, uncertainty and nonlinear characteristic, and result in challenges for control strategies. To address this issue, an improved generalized predictive control (GPC) strategy based on T-S fuzzy model is presented in this paper. T-S model is adopted to model for DEAP actuator and GPC controller is developed based on the model. A position tracking experiment was conducted with the DEAP experiment platform. The experimental results show that this control strategy has high tracking accuracy and fast response speed, and the proposed model and control method for EAP flexible actuator were verified.

Effects of C60 film coating on the electrochemical performance of composite LiCoO2 cathodes for lithium secondary batteries

Arenst Andreas Arie; Joong Kee Lee

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 138-141
DOI: 10.5185/amlett.2018.6408

In this work, LiCoO2(LCO) composite electrodes were coated by fullerene C60 thin film with different thickness of 60, 100 and 200 nm using a plasma thermal evaporation technique. The surface morphology of bare and coated samples was observed by scanning electron microscope (SEM). The electrochemical characteristics of the coated electrodes as cathode materials in Lithium-Ion Batteries (LIB)were investigated by a galvanostatic charge-discharge test at various C-rates between 3.0 and 4.5 V and compared with those of uncoated samples. An improvement of the performances of the coated electrodes in terms of higher initial coulombic efficiency, higher capacity retention and better rate capability was shown by the 60 nm thick C60 coated LiCoO2 electrodes. It can be said that the thin C60 coating layer can minimize the dissolution of Co from the electrode to the electrolyte. As the thickness of coating layer was increased, the coated electrodes show a more severe capacity fade due to longer Li-ion diffusion path.

Selective adsorbtion of low density lipoprotein from blood using porous silicon

Praveen Kumar S; Ramesh R; Aravind T

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 142-147
DOI: 10.5185/amlett.2018.1952

This work presents the isolation of Low-Density Lipoprotein (LDL) from blood. The blood molecules with size less than 1µm are filtered in the size based crossflow filter technique. Filtered molecules are passed through the Porous Silicon (PSi). The immobilized Anti-Apolipoprotein B (AAB) on the surface of Porous Silicon is used to adsorb the LDL. Isolation of LDL based on Porous Silicon eliminates the calculation of the other lipoproteins and Triglycerides. Filter with AAB coated PSi is designed and simulated in COMSOL Multiphysics software. 

Templated synthesis of mesoscopic titania and its application in the solid-state dye-sensitized solar cells 

Yashwant Pandit; G. T. Harini; Deepa Landage; Chetan J. Bhongale

Advanced Materials Letters, 2018, Volume 9, Issue 2, Pages 148-152
DOI: 10.5185/amlett.2018.6911

The formation of mesoscopic titania is done by templated mechanism in which the films are prepared by co-assembly of titania precursor species and complexing agent acetyl acetone (acac) and an amphiphilic structure-directing agent, Pluronic F127 (a triblock copolymer). Thinner films of titania having well organized mesoscopic structure were prepared by doctor-blading method. These films were characterized by SEM, TEM, XRD, etc. UV-Vis absorption studies showed good dye intake in very thin mesoscopic titania layers. Prototype photovoltaic device fabricated utilizing the mesoscopic titania films showed reasonable power conversion efficiency and fill factor (FF). The device with mesoscopic TiO2 layer with thickness as low as 300 nm gave solar cell efficiency 0.31% and FF of 50.2%. This proves the utility of very thin layer of mesoscopic titania fabricated by doctor-blading technique. Such a thin layer may be useful in perovskite solar cells as well. Application of versatile dye molecules, polymers with suitable anchoring functionality could lead to desired high-performance photovoltaic devices.