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Frank P.,AIT Austrian Institute of Technology | Srajer J.,AIT Austrian Institute of Technology | Schwaighofer A.,AIT Austrian Institute of Technology | Kibrom A.,AIT Austrian Institute of Technology | And 3 more authors.
Optics Letters | Year: 2012

Here we present a surface based on double-layered nanoparticle stacks suitable for spectro-electrochemical applications. The structure is formed on a continuous gold layer by a two-dimensional periodic array of stacks of gold and tantalum pentoxide nanodisks. Reflection spectra in the visible wavelength region showed the multiple-resonant nature of surface plasmon (SP) excitations in the nanostructure, which is in good agreement with simulations based on a finite-difference-time-domain method. The multiple SP resonances can be tuned to various wavelength regions, which are required for simultaneous enhancement at excitation and emission wavelengths. Cyclic voltammetry measurements on the nanostructure proved the applicability of electrochemical methods involving interfacial redox processes. © 2012 Optical Society of America. Source

Potroz M.G.,Nanyang Technological University | Potroz M.G.,Center for Biomimetic Sensor Science | Cho N.-J.,Nanyang Technological University | Cho N.-J.,Center for Biomimetic Sensor Science
Molecules | Year: 2015

The neglected tropical disease (NTD) trachoma is currently the leading cause of eye disease in the world, and the pathogenic bacteria causing this condition, Chlamydia trachomatis, is also the most common sexually transmitted pathogenic bacterium. Although the serovars of this bacterial species typically vary between ocular and genital infections there is a clear connection between genital C. trachomatis infections and the development of trachoma in infants, such that the solutions to these infections are closely related. It is the unique life cycle of the C. trachomatis bacteria which primarily leads to chronic infections and challenges in treatment using conventional antibiotics. This life cycle involves stages of infective elementary bodies (EBs) and reproductive reticulate bodies (RBs). Most antibiotics only target the reproductive RBs and this often leads to the need for prolonged therapy which facilitates the development of drug resistant pathogens. It is through combining several compounds to obtain multiple antimicrobial mechanisms that we are most likely to develop a reliable means to address all these issues. Traditional and ethnobotanical medicine provides valuable resources for the development of novel formulations and treatment regimes based on synergistic and multi-compound therapy. In this review we intend to summarize the existing literature on the application of natural compounds for controlling trachoma and inhibiting chlamydial bacteria and explore the potential for the development of new treatment modalities. © 2015 by the authors; licensee MDPI. Source

Chen P.,Center for Biomimetic Sensor Science | Chen P.,Nanyang Technological University | Liedberg B.,Center for Biomimetic Sensor Science | Liedberg B.,Nanyang Technological University
Analytical Chemistry | Year: 2014

Localized surface plasmon resonance (LSPR) occurring in noble metal nanoparticles (e.g., Au) is a widely used phenomenon to report molecular interactions. Traditional LSPR sensors typically monitor shifts in the peak position or extinction in response to local refractive index changes in the close vicinity of the nanoparticle surface. The ability to resolve minute shifts/extinction changes is to a large extent limited by instrumental noise. A new strategy to evaluate LSPR responses utilizing changes in the shape of the extinction spectrum (the curvature) is proposed. The response of curvature to refractive index changes is investigated theoretically using Mie theory and an analytical expression relating the curvature to the refractive index is presented. The experimentally derived curvatures for 13 nm spherical gold nanoparticles (AuNPs) exposed to solvents with different bulk refractive indices confirm the theoretical predictions. Moreover, both the calculated and experimental findings suggest that the curvature is approximately a linear function of refractive index in regimes relevant to bio and chemical sensing. We demonstrate that curvature is superior over peak shift and extinction both in terms of signal-to-noise (S/N) ratio and reliability of LSPR sensors. With a curvature, one could readily monitor submonolayer adsorption of a low molecular weight thiol molecule (Mw = 458.6) onto 13 nm AuNPs. It is also worthwhile mentioning that curvature is virtually insensitive to instrumental instabilities and artifacts occurring during measurement. Instabilities such as baseline tilt and shift, shift in peak position as well as sharp spikes/steps in the extinction spectra do not induce artifacts in the sensorgrams of curvature. © 2014 American Chemical Society. Source

Jackman J.A.,Nanyang Technological University | Jackman J.A.,Center for Biomimetic Sensor Science | Knoll W.,Center for Biomimetic Sensor Science | Knoll W.,AIT Austrian Institute of Technology | And 2 more authors.
Materials | Year: 2012

The importance of cell membranes in biological systems has prompted the development of model membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment. Tethered lipid bilayers represent one of the most promising classes of model membranes and are based on the immobilization of a planar lipid bilayer on a solid support that enables characterization by a wide range of surface-sensitive analytical techniques. Moreover, as the result of molecular engineering inspired by biology, tethered bilayers are increasingly able to mimic fundamental properties of natural cell membranes, including fluidity, electrical sealing and hosting transmembrane proteins. At the same time, new methods have been employed to improve the durability of tethered bilayers, with shelf-lives now reaching the order of weeks and months. Taken together, the capabilities of tethered lipid bilayers have opened the door to biotechnology applications in healthcare, environmental monitoring and energy storage. In this review, several examples of such applications are presented. Beyond the particulars of each example, the focus of this review is on the emerging design and characterization strategies that made these applications possible. By drawing connections between these strategies and promising research results, future opportunities for tethered lipid bilayers within the biotechnology field are discussed. © 2012 by the authors. Source

Huang J.,Nanyang Technological University | Larisika M.,AIT Austrian Institute of Technology | Larisika M.,Center for Biomimetic Sensor Science | Fam W.H.D.,Nanyang Technological University | And 5 more authors.
Nanoscale | Year: 2013

We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of <5 layers. This newly grown RGO possesses lower defect density with larger and increased distribution of sp2 domains than chemically reduced RGO. Furthermore this method without optimization reduces the relative standard deviation of electrical conductivity between chips, from 80.5% to 16.5%, enabling RGO to be used in practical electronic devices. © The Royal Society of Chemistry 2013. Source

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