Now showing 1 - 7 of 7
  • 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.
      530Scopus© Citations 18
  • Publication
    Energy harvesting with peptide nanotube-graphene oxide flexible substrates prepared with electric field and wettability assisted self-assembly
    Piezoelectric diphenylalanine peptide nanotubes (PNTs) have recently been demonstrated in energy harvesting applications, typically based on vertically aligned PNTs that generate charge when pressed. In this work, we use a wettability difference and an applied electric field to align PNTs and PNT-based composites on flexible substrates. Open-circuit voltages and short-circuit currents exceeding 6 V and 60 nA, respectively, are achieved by bending the substrate, opening up the use of horizontally aligned PNTs as flexible energy harvesting substrates.
      141Scopus© Citations 5
  • 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.
  • 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.
      278Scopus© Citations 29
  • 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.
      632Scopus© Citations 30
  • 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.
      371Scopus© Citations 17
  • Publication
    Nucleobase sensing using highly-sensitive surface-enhanced Raman spectroscopy templates comprising organic semiconductor peptide nanotubes and metal nanoparticles
    Templates formed from aligned diphenylalanine nanotubes with plasmon-active metal nanoparticles are a promising nanocomposite for large-scale, rapid, stable, and cost-effective surface-enhanced Raman spectroscopy (SERS) substrates. The high sensitivity of such templates arises from an arrangement of densely packed plasmon-active silver nanoparticles that enhance the localized electromagnetic field and allow the detection of the nucleobases adenine, cytosine, thymine, uracil, and guanine at concentrations in the range 10−5 to 10−9 M. Blinking of the SERS signal is observed, indicating sensitivity down to the single or few molecule limit. Such blinking could result from charge transfer process. These results demonstrate the potential for using aligned diphenylalanine nanotube-metal nanoparticle templates for practical monitoring of biomolecules and are promising initial steps toward the use of peptide nanotube-based in diagnostic sensing applications.
      344Scopus© Citations 7