Rapid thermal annealing of graphene-metal contact

Cataloged from PDF version of article.High quality graphene-metal contacts are desirable for high-performance graphene based electronics. Process related factors result large variation in the contact resistance. A post-processing method is needed to improve graphene-metal contacts. In this letter, we studied rapid thermal annealing (RTA) of graphene-metal contacts. We present results of a systematic investigation of device scaling before and after RTA for various metals. The results reveal that RTA provides a convenient technique to reduce contact resistance, thus to obtain reproducible device operation. (C) 2012 American Institute of Physics

Genistein-induced mir-23b expression inhibits the growth of breast cancer cells

Aim of the study: Genistein, an isoflavonoid, plays roles in the inhibition of protein tyrosine kinase phosphorylation, induction of apoptosis, and cell differentiation in breast cancer. This study aims to induce cellular stress by exposing genistein to determine alterations of miRNA expression profiles in MCF-7 cells. Material and methods: XTT assay and trypan blue dye exclusion assays were performed to examine the cytotoxic effects of genistein treatment. Expressions of miRNAs were quantified using Real-Time Online RT-PCR. Results: The IC50 dose of genistein was 175 μM in MCF-7 cell, line and the cytotoxic effect of genistein was detected after 48 hours. miR-23b was found to be up-regulated 56.69 fold following the treatment of genistein. It was found that miR-23b was up-regulated for MCF-7 breast cancer cells after genistein treatment. Conclusions: Up-regulated ex-expression of miR-23b might be a putative biomarker for use in the therapy of breast cancer patients. miR-23b up-regulation might be important in terms of response to genistein. © 2015, Termedia Publishing House Ltd. All rights reserved

Graphene based flexible electrochromic devices

Graphene emerges as a viable material for optoelectronics because of its broad optical response and gate-tunable properties. For practical applications, however, single layer graphene has performance limits due to its small optical absorption defined by fundamental constants. Here, we demonstrated a new class of flexible electrochromic devices using multilayer graphene (MLG) which simultaneously offers all key requirements for practical applications; high-contrast optical modulation over a broad spectrum, good electrical conductivity and mechanical flexibility. Our method relies on electro-modulation of interband transition of MLG via intercalation of ions into the graphene layers. The electrical and optical characterizations reveal the key features of the intercalation process which yields broadband optical modulation up to 55 per cent in the visible and near-infrared. We illustrate the promises of the method by fabricating reflective/transmissive electrochromic devices and multi-pixel display devices. Simplicity of the device architecture and its compatibility with the roll-to-roll fabrication processes, would find wide range of applications including smart windows and display devices. We anticipate that this work provides a significant step in realization of graphene based optoelectronics

Plasmon-polaritons on graphene-metal surface and their use in biosensors

Cataloged from PDF version of article.We studied excitation of surface plasmon-polaritons on graphene-metal surface. The metal surface is functionalized by transfer printing of graphene grown by chemical vapor deposition on copper foils. Surface plasmon resonance characteristics of monolayer and multilayer graphene on the metal surface are presented. We were able to obtain the dispersion relation of graphene-metal surface which reveals the essential feature of the plasmon-polaritons. As an application, we fabricated a surface plasmon resonance sensor integrated with a microfluidic device to study nonspecific physical interaction between graphene layer and proteins. (C) 2012 American Institute of Physics

Critical coupling in plasmonic resonator arrays

Cataloged from PDF version of article.We report critical coupling of electromagnetic waves to plasmonic cavity arrays fabricated on Moire surfaces. Dark field plasmon microscopy imaging and polarization dependent spectroscopic reflection measurements reveal the critical coupling conditions of the cavities. The critical coupling conditions depend on the superperiod of the Moire surface, which also defines the coupling between the cavities. Complete transfer of the incident power can be achieved for traveling wave plasmonic resonators, which have a relatively short superperiod. When the superperiod of the resonators increases, the coupled resonators become isolated standing wave resonators in which complete transfer of the incident power is not possible. Analytical and finite difference time domain calculations support the experimental observations. (C) 2011 Optical Society of Americ

Direct imaging of localized surface plasmon polaritons

Cataloged from PDF version of article.In this Letter, we report on dark field imaging of localized surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by plasmonic coupled cavities. We image the light scattered from SPPs in the plasmonic cavities excited by a tunable light source. Tuning the excitation wavelength, we measure the localization and dispersion of the plasmonic cavity mode. Dark field imaging has been achieved in the Kretschmann configuration using a supercontinuum white-light laser equipped with an acoustooptic tunable filter. Polarization dependent spectroscopic reflection and dark field imaging measurements are correlated and found to be in agreement with finite-difference time-domain calculations. (C) 2011 Optical Society of Americ

Graphene-enabled electrically switchable radar-absorbing surfaces

Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection. Resistive and/or magnetic composite materials are used to reduce the backscattered microwave signals. Inability to control electrical properties of these materials, however, hinders the realization of active camouflage systems. Here, using large-area graphene electrodes, we demonstrate active surfaces that enable electrical control of reflection, transmission and absorption of microwaves. Instead of tuning bulk material property, our strategy relies on electrostatic tuning of the charge density on an atomically thin electrode, which operates as a tunable metal in microwave frequencies. Notably, we report large-area adaptive radar-absorbing surfaces with tunable reflection suppression ratio up to 50 dB with operation voltages <5 V. Using the developed surfaces, we demonstrate various device architectures including pixelated and curved surfaces. Our results provide a significant step in realization of active camouflage systems in microwave frequencies. © 2015 Macmillan Publishers Limited. All rights reserved

Absorption enhancement of molecules in the weak plasmon-exciton coupling regime

Cataloged from PDF version of article.We report on the experimental and theoretical investigations of enhancing the optical absorption of organic molecules in the weak plasmon–exciton coupling regime. A metal–organic hybrid structure consisting of dye molecules embedded in the polymer matrix is placed in close vicinity to thin metal films. We have observed a transition from a weak coupling regime to a strong coupling one as the thickness of the metal layer increases. The results indicate that absorption of the self-assembled J-aggregate nanostructures can be increased in the weak plasmon–exciton coupling regime and strongly quenched in the strong coupling regime. A theoretical model based on the transfer-matrix method qualitatively confirms the experimental results obtained from polarization-dependent spectroscopic reflection measurements