Now showing 1 - 10 of 43
  • 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.
      512Scopus© Citations 28
  • Publication
    SERS Enhancement of Porphyrin-Type Molecules on Metal-Free Cellulose-Based Substrates
    (American Chemical Society, 2021-12-02) ; ;
    The detection of analytes using spectroscopy methods, such as surface-enhanced Raman spectroscopy (SERS), is crucial in the fields of medical diagnostics, forensics, security, and environmental monitoring. In recent years, a lot of focus has been directed toward organic polymer material-based SERS platforms due to their lower cost, controllable synthesis and fabrication, structural versatility, as well as biocompatibility and biodegradability. Here, we report that cellulose nanofiber-based substrates can be used as a metal-free SERS platform for the detection of porphyrin-type molecules. We report SERS signal enhancement for five different porphyrin molecules with exceptional 2 orders of magnitude peak intensity enhancement observed resulting in a detection limit of 10-5 M. We show that the cellulose-based platform is more suitable for porphyrin molecule detection than traditionally used semiconductor materials like graphene oxide. The observed enhancement is attributed to the disturbed growth of self-assembled structures on the cellulose nanofibers and the generation of disordered 3D clusters of porphyrin molecules.
      35Scopus© Citations 13
  • Publication
    Plasmon enhanced fluorescence studies from aligned gold nanorod arrays modified with SiO2 spacer layers
    Here we demonstrate that quasi self-standing Au nanorod arrays prepared with plasma polymerisation deposited SiO2 dielectric spacers support surface enhanced fluorescence (SEF) while maintaining high signal reproducibility. We show that it is possible to find a balance between enhanced radiative and non-radiative decay rates at which the fluorescent intensity is maximized. The SEF signal optimised with a 30 nm spacer layer thickness, showed a 3.5-fold enhancement with a signal variance of <15% thereby keeping the integrity of the nanorod array. We also demonstrate the decreased importance of obtaining resonance conditions when LSPR is positioned within the spectral region of Au interband transitions. Procedures for further increasing the SEF enhancement factor are also discussed.
      725Scopus© Citations 32
  • 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
    Flexing Piezoelectric Diphenylalanine-Plasmonic Metal Nanocomposites to Increase SERS Signal Strength
    Piezoelectric quasi-1D peptide nanotubes and plasmonic metal nanoparticles are combined to create a flexible and self-energized surface-enhanced Raman spectroscopy (SERS) substrate that strengthens SERS signal intensities by over an order of magnitude compared to an unflexed substrate. The platform is used to sense bovine serum albumin, lysozyme, glucose, and adenine. Finite-element electromagnetic modeling indicates that the signal enhancement results from piezoelectric-induced charge, which is mechanically activated via substrate bending. The results presented here open the possibility of using peptide nanotubes on conformal substrates for in situ SERS detection.
      558Scopus© Citations 22
  • Publication
    Self-energized organic-inorganic hybrid composite for surface enhanced Raman spectroscopy
    In this study, we integrate plasmonic metal nanomaterials with a piezoelectric polyvinylidene fluoride (PVDF) polymer and lithium niobate (LiNbO3) based composite to form an all-solid-state flexible self-energized sensor. We demonstrate that following the application of a load, the film enhances the surface-enhanced Raman spectroscopy (SERS) signal of an analyte molecule up to 14 times. The piezoelectric β-phase of PVDF in the film is optimized through the introduction of multi-walled carbon nanotubes and post-fabrication UV irradiation annealing. Additionally, the SERS signal enhancement can be further increased by the application of in situ UV light irradiation of the sample, resulting in the generation of photoexcited electrons from LiNbO3 microparticles introduced into the composite. Both the application of a mechanical displacement and the UV light-induced charge generation result in an improved charge transfer between the film and an analyte molecule. The piezoelectric PVDF/LiNbO3 film has been shown to be a suitable SERS platform for the detection of important biological molecules, demonstrating the potential of the substrate for fast on-site detection applications.
      39Scopus© Citations 4
  • Publication
    Effect of cavity architecture on the surface enhanced emission from site selective nanostructured cavity arrays
    Presented here are studies of the impact of incident angle on surface-enhanced emission from a dye that is located site selectively on a plasmon-active nanocavity array support. Studies were performed for a surface-active luminescent dye selectively assembled on the top surface or on the walls of the voids of nanocavity array substrates. Results show that emission intensities depend on where the dye is located with respect to the void or surface of the nanocavity array and on the dimensions of the cavity. This was interpreted to arise from the presence of void-localized plasmons and surface-localized and -delocalized plasmon modes.
      531Scopus© Citations 33
  • Publication
    Strong coupling in molecular exciton-plasmon Au nanorod array systems
    We demonstrate here strong coupling between localized surface plasmon modes in self-standing nanorods with excitons in a molecular J-aggregate layer though angular tuning. The enhanced exciton−plasmon coupling creates a Fano like line shape in the differential reflection spectra associated with the formation of hybrid states, leading to anti-crossing of the upper and lower polaritons with a Rabi frequency of 125 meV. The recreation of a Fano like line shape was found in photoluminescence demonstrating changes in the emission spectral profile under strong coupling.
      542Scopus© Citations 26
  • Publication
    Electric Field-Driven Catalytic Activity Using a Bioinspired Peptide and Titanium Dioxide Semiconductor Composite with Metal Nanoparticles
    Heterogeneous catalytic processes facilitated by the localized surface plasmon resonance excitation in plasmonic nanomaterials possess the potential to increase product yield and selectivity in a range of redox reactions beyond what is possible when using traditional catalysis-based approaches. In this article, we demonstrate electric field (that was generated by applying DC voltage)-driven redox catalysis (with and without UV irradiation) using plasmonic nanoparticles with a peptide nanotube/titanium dioxide hybrid semiconductor nanocomposite. The applied DC voltage reduces the bandgap of the peptide nanotubes, enabling control over the semiconductor–metal charge transfer rate. In the presence of the electric field, product formation from the hybrid semiconductor nanocomposite was c.a. 5 times faster than when using peptide nanotubes or titanium dioxide alone. The product formation was further enhanced in combination with UV irradiation with an overall 9-fold enhancement.
      312Scopus© Citations 2
  • Publication
    Wettability gradient-induced alignment of peptide nanotubes as templates for biosensing applications
    Self-assembled diphenylalanine (FF) peptide nanotubes (PNTs) have attracted significant attention due to their well-ordered supramolecular structure and wide range of functional capabilities that may enable potential nanobiotechnology applications. However, self-assembled PNTs are generally inhomogeneous at the macroscale, which has limited their potential use. Reproducibly controlling the assembly and alignment of PNTs is therefore critical to enable the widespread use of PNTs, e.g., in sensing applications. In this study, a surface patterning technique based on UV/ozone exposure through a mask is used to align PNTs. Exposed regions become hydrophilic, leading to directed spreading of the FF solution and alignment of the PNTs that improves as the difference in wettability between adjacent regions increases. Alignment was further found to depend on the concentration- and temperature-dependent diameter of the PNTs formed and the size of the hydrophilic area. Finally, aligned PNTs decorated with silver nanoparticles are used to sense an analyte molecule using surface enhanced Raman spectroscopy.
      332Scopus© Citations 33