Now showing 1 - 10 of 31
  • Publication
    Thermal and aqueous stability improvement of graphene oxide enhanced diphenylalanine nanocomposites
    Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular, their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to, e.g., biosensing, electrochemical, electromechanical or electronic applications.
  • Publication
    Nanoscale spectroscopy and imaging of hemoglobin
    Sub diffraction limited infrared absorption imaging of hemoglobin was performed by coupling IR optics with an atomic force microscope. Comparisons between the AFM topography and IR absorption images of micron sized hemoglobin features are presented, along with nanoscale IR spectroscopic analysis of the metalloprotein.
      412Scopus© Citations 9
  • Publication
    Nanoscale infrared absorption imaging permits non-destructive intracellular photosensitizer localization for subcellular uptake analysis
    The most immediate biological and medical advantages of therapeutic agent localization on the nanoscale arise from the increased understanding of targeted delivery, selectivity and intracellular distribution that are gained by imaging at the resolution scale of individual nanovectors and therapeutic agents themselves. This paper reports on the use of a nanoscale resolution chemical imaging method, infrared (IR) nanospectral absorption imaging, used to map the subcellular localization of a photoactive therapeutic agent - toluidine blue-conjugated gold nanoparticles (TBO) within nanoscale subsections of single colon adenocarcinoma cells. By comparison of photosensitizer distribution with diffraction limited optical imaging, the benefits of IR nanospectral localization are highlighted and the spatial and spectral accuracy of the non-destructive IR imaging method is confirmed. IR spectral ratio imaging is presented as a means to map intracellular nanoparticle density at sub 50 nm lateral resolution with IR nanospectroscopy enabling distinction of nanoparticle seeded cells from a control group with 95% confidence. In this way we illustrate that IR absorption nanoimaging combined with IR point source data does not only yield intracellular drug detection on the order of nanometres, but also permits extension of the AFM-IR technique from subcellular analysis up to studies of cell numbers that are statistically significant.
      395Scopus© Citations 29
  • Publication
    Surface-enhanced Raman scattering from small numbers of purified and oxidised single-walled carbon nanotubes
    Surface enhanced resonance Raman scattering (SERRS) has been applied to investigate defects in purified and carboxylated single-walled carbon nanotubes (SWCNTs). For both samples SERRS spectra with temporal fluctuating peak intensities and positions in the range of 1000 to 1350 cm-1 have been observed. A series of peaks in this window were observed to coincide with peak positions that have been assigned to arise from Stone-Thrower-Wales and heptagonal-pentagonal intramolecular junction defects on the nanotubes surface. Two possible origins for these fluctuating spectral features are discussed ie the presence of Stone-Thrower-Wales defects in SWCNTs or amorphous carbon impurities.
      409Scopus© Citations 28
  • Publication
    The Effect of Ag Nanoparticles on Surface-Enhanced Luminescence from Au Nanovoid Arrays
    Studies comparing the effect of adding two different nanoparticle compositions on the plasmonic properties of Au nanovoid arrays were undertaken. Surface-enhanced resonance luminescence and surface-enhanced resonance Raman studies comparing dispersed Ag nanoparticles and Ag nanoparticle aggregates on gold nanovoid arrays were undertaken. These studies showed that using Ag nanoparticle aggregates increased both luminescence and Raman efficiency relative to when dispersed nanoparticles were used; in addition, these studies also showed that adding dispersed Ag nanoparticles supported a more reproducible enhancement in luminescence and Raman across the substrate compared to using Ag nanoparticle aggregates. Finite element analysis simulations indicated that surface plasmon polariton distribution in the sample was affected by the presence of the Ag nanoparticles on the Au nanovoid array.
      361Scopus© Citations 24
  • Publication
    Single-Molecule Nonresonant Wide-Field Surface-Enhanced Raman Scattering from Ferroelectrically Defined Au Nanoparticle Microarrays
    Single-molecule detection by surface-enhanced Raman scattering (SERS) is a powerful spectroscopic technique that is of interest for the sensor development field. An important aspect of optimizing the materials used in SERS-based sensors is the ability to have a high density of "hot spots" that enhance the SERS sensitivity to the single-molecule level. Photodeposition of gold (Au) nanoparticles through electric-field-directed self-assembly on a periodically proton-exchanged lithium niobate (PPELN) substrate provides conditions to form well-ordered microscale features consisting of closely packed Au nanoparticles. The resulting Au nanoparticle microstructure arrays (microarrays) are plasmon-active and support nonresonant single-molecule SERS at ultralow concentrations (<10-9-10-13 M) with excitation power densities <1 × 10-3 W cm-2 using wide-field imaging. The microarrays offer excellent SERS reproducibility, with an intensity variation of <7.5% across the substrate. As most biomarkers and molecules do not support resonance enhancement, this work demonstrates that PPELN is a suitable template for high-sensitivity, nonresonant sensing applications.
      149Scopus© Citations 12
  • Publication
    Sub-wavelength infrared imaging of lipids
    (Optical Society of America, 2011-01) ; ; ;
    Infrared absorption spectroscopy of lipid layers was performed by combining optics and scanning probe microscopy. This experimental approach enables sub-diffraction IR imaging with a spatial resolution on the nanometer scale of 1, 2-dioleoyl-sn-glycero-3-phosphocholine lipid layers.
      295Scopus© Citations 18
  • Publication
    Electric Field-Induced Chemical Surface-Enhanced Raman Spectroscopy from Aligned Peptide Nanotube–Graphene Oxide Templates for Universal Trace Detection of Biomolecules
    Semiconductor-graphene oxide-based surface-enhanced Raman spectroscopy substrates represent a new frontier in the field of surface-enhanced Raman spectroscopy (SERS). However, the application of graphene oxide has had limited success because of the poor Raman enhancement factors that are achievable in comparison to noble metals. In this work, we report chemical SERS enhancement enabled by the application of an electric field (10-25 V/mm) to aligned semiconducting peptide nanotube-graphene oxide composite structures during Raman measurements. The technique enables nanomolar detection sensitivity of glucose and nucleobases with up to 10-fold signal enhancement compared to metal-based substrates, which, to our knowledge, is higher than that previously reported for semiconductor-based SERS substrates. The increased Raman scattering is assigned to enhanced charge-transfer resonance enabled by work function lowering of the peptide nanotubes. These results provide insight into how semiconductor organic peptide nanotubes interact with graphene oxide, which may facilitate chemical biosensing, electronic devices, and energy-harvesting applications.
      549Scopus© Citations 29
  • Publication
    3D-Printed Peptide-Hydrogel Nanoparticle Composites for Surface-Enhanced Raman Spectroscopy Sensing
    Precise control over the arrangement of plasmonic nanomaterials is critical for label-free single-molecule surface-enhanced Raman spectroscopy (SERS)-based sensing applications. SERS templates should provide high sensitivity and reproducibility and be cost-effective and easy to prepare. Additive manufacturing by extrusion-based three-dimensional (3D) printing is an emerging technique for the spatial arrangement of nanomaterials and is a method that may satisfy these SERS template requirements. In this work, we use 3D printing to produce sensitive and reproducible SERS templates using a fluorenylmethyloxycarbonyl diphenylalanine (Fmoc-FF) hydrogel loaded with silver or gold nanoparticles. The Fmoc-FF template allows the detection of low Raman cross-section molecules such as adenine at concentrations as low as 100 pM.
      486Scopus© Citations 16
  • Publication
    Application of AAO matrix in aligned gold nanorod array substrates for surface-Enhanced fluorescence and Raman scattering
    In this paper, we probed surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from probe molecule Rhodamine 6G (R6G) on self-standing Au nanorod array substrates made using a combination of anodization and potentiostatic electrodeposition. The initial substrates were embedded within a porous alumina template (AAO). By controlling the thickness of the AAO matrix, SEF and SERS were observed exhibiting an inverse relationship. SERS and SEF showed a non-linear response to the removal of AAO matrix due to an inhomogeneous plasmon activity across the nanorod which was supported by FDTD calculations. We showed that by optimizing the level of AAO thickness, we could obtain either maximized SERS, SEF or simultaneously observe both SERS and SEF together.
      480Scopus© Citations 28