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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.


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.


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.


Larisika M.,AIT Austrian Institute of Technology | Larisika M.,Center for Biomimetic Sensor Science | Huang J.,Nanyang Technological University | Tok A.,Nanyang Technological University | And 4 more authors.
Materials Chemistry and Physics | Year: 2012

This article presents an improved graphene oxide synthesis method and its subsequent simple reduction technique with hydrazine vapour more efficiently to produce large area graphene flakes with a dramatic change in average sheet resistance of ∼145 k/ as compared to existing annealing methods. With the above characteristics, a high-performance and low-voltage operating graphene field-effect transistor (FET) was achieved with the potential to be used as detection platform for biomolecules. © 2012 Elsevier B.V. All rights reserved.


Chen P.,Nanyang Technological University | Chen P.,Center for Biomimetic Sensor Science | Yin Z.,Nanyang Technological University | Huang X.,Nanyang Technological University | And 5 more authors.
Journal of Physical Chemistry C | Year: 2011

Resonance Raman spectroscopy (RRS) often suffers from the large fluorescence background which obscures the much weaker Raman scattering. To address this fundamental problem, a novel Raman substrate has been fabricated by adsorption of Au 0.7Ag 0.3 alloy nanoparticles (NPs) on a graphene oxide (GO) coated SiO 2 surface, which offers both excellent Raman enhancement and fluorescence quenching. Our experimental data reveal that a Raman to fluorescence background intensity ratio of 1.6 can be obtained for a highly fluorescent dye like Alexa fluor 488. Moreover, we demonstrate that the Raman enhancement mainly originates from the Au 0.7Ag 0.3 alloy NPs and that the fluorescence quenching mainly arises from the underlying functionalized GO (FGO) substrate. © 2011 American Chemical Society.


Palaniappan Al.,Nanyang Technological University | Goh W.H.,Nanyang Technological University | Tey J.N.,Nanyang Technological University | Wijaya I.P.M.,Nanyang Technological University | And 7 more authors.
Biosensors and Bioelectronics | Year: 2010

A facile and high performance biosensing platform using aligned carbon nanotubes on quartz substrate is reported in this communication. Single walled carbon nanotubes are grown on quartz substrates by a chemical vapor deposition process and are characterized with field emission scanning electron microscopy and atomic force microscopy in order to verify the quality of the material. The quartz substrate is then directly used as a biosensor in a field effect transistor configuration. In order to demonstrate the sensing capabilities of the fabricated sensor devices, electronic detection of prostate specific antigen, a potential cancer biomarker, is carried out by adopting liquid gated configuration. A conductivity change due to the specific binding of target antigen with the immobilized receptor antibody demonstrates the sensing capabilities of the fabricated device. Sub-nM detection sensitivities have been obtained using the adopted direct immunoassay approach, which shows that the device responds to clinically relevant concentration regimes. © 2010 Elsevier B.V. All rights reserved.


Fam D.W.H.,Nanyang Technological University | Palaniappan A.,Nanyang Technological University | Palaniappan A.,Center for Biomimetic Sensor Science | Tok A.I.Y.,Nanyang Technological University | And 5 more authors.
Sensors and Actuators, B: Chemical | Year: 2011

Carbon nanotubes (CNTs) are one of the advanced functional materials of today and has been researched extensively since its discovery. Although much is still not known about the physical and chemical properties of CNTs, it has already found potential applications in many industries, from defense to electronics and even in environmental remediation. CNTs possess many desirable mechanical and chemical properties, which supercedes many of the advanced materials of today. It was also found that CNTs have excellent electronic properties like unprecedented mobilities of up to 100,000 cm2/V s, which can potentially result in a quantum leap in the electronics industry. Over the recent years, CNT and their derivatives (decorated/functionalized) were also intensively studied, especially in the field of bio and chemical sensing owing to the size similarity of nanotubes with the analytes such as biospecies that enable strong interactions between them. However, despite intensive research, commercialization of these potential applications still remains elusive mainly due to the lack of control in synthesis of specific chirality, diameter and length of CNTs, which influences the device performance. This short review focuses on addressing recent advances in CNT research especially on aspects such as controlled synthesis, decoration/functionalization for specific recognition, sensor device fabrication and commercialization strategies. © 2011 Elsevier B.V. All rights reserved.


Tu M.-C.,Nanyang Technological University | Tu M.-C.,Center for Biomimetic Sensor Science | Chen H.-Y.,Nanyang Technological University | Wang Y.,Tum Create | And 5 more authors.
Analytica Chimica Acta | Year: 2015

This article reports on carbon nanotube/manganese dioxide (CNT-MnO2) composites as electrochemical tags for non-enzymatic signal amplification in immunosensing. The synthesized CNT-MnO2 composites showed good electrochemical activity, electrical conductivity and stability. The electrochemical signal of CNT-MnO2 composites coated glassy carbon electrode (GCE) increased by nearly two orders of magnitude compared to bare GCE in hydrogen peroxide (H2O2) environment. CNT-MnO2 composite was subsequently validated as electrochemical tags for sensitive detection of α-fetoprotein (AFP), a tumor marker for diagnosing hepatocellular carcinoma. The electrochemical immunosensor demonstrated a linear response on a log-scale for AFP concentrations ranging from 0.2 to 100ngmL-1. The limit of detection (LOD) was estimated to be 40pgmL-1 (S/N=3) in PBS buffer. Further measurements using AFP spiked plasma samples revealed the applicability of fabricated CNT-MnO2 composites for clinical and diagnostic applications. © 2014.


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.


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.

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