Now showing 1 - 10 of 14
  • Publication
    Structural Transition-Induced Raman Enhancement in Bioinspired Diphenylalanine Peptide Nanotubes
    Semiconducting materials are increasingly proposed as alternatives to noble metal nanomaterials to enhance Raman scattering. We demonstrate that bioinspired semiconducting diphenylalanine peptide nanotubes annealed through a reported structural transition can support Raman detection of 10-7 M concentrations for a range of molecules including mononucleotides. The enhancement is attributed to the introduction of electronic states below the conduction band that facilitate charge transfer to the analyte molecule. These results show that organic semiconductor-based materials can serve as platforms for enhanced Raman scattering for chemical sensing. As the sensor is metal-free, the enhancement is achieved without the introduction of electromagnetic surface-enhanced Raman spectroscopy.
      38Scopus© Citations 10
  • 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.
      685Scopus© Citations 26
  • 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.
      42Scopus© Citations 5
  • Publication
    Metal-Free Cellulose-Based Platforms for Biomolecule Fluorescence Signal Enhancement
    (American Chemical Society, 2021-12-22) ; ;
    Fluorescence is a rapid and noninvasive technique for analyte detection. Green, sustainable, and safe materials that enhance the analyte fluorescence signal possess the potential to create new green photonic technologies for medical diagnostics. Here, we report that metal-free cellulose-based substrates can be used as platforms to enhance the fluorescence signal from a model immunoassay as well as a wide variety of molecules by over an order of magnitude. The cellulose-based sensing platforms are cost-effective, biocompatible, robust, and result in a reproducible signal variation as low as 16%. We show that molecules at concentrations as low as 100 nM can be detected on cellulose-based substrates. We attribute the observed enhancement to nanofiber-driven clustering of the analyte molecules, high surface roughness, as well as a charge-transfer process.
      39Scopus© Citations 4
  • 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.
      316Scopus© Citations 2
  • 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.
      427Scopus© Citations 8
  • 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.
      36Scopus© Citations 13
  • 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.
      334Scopus© Citations 33
  • Publication
    Thermally-controlled spherical peptide gel architectures prepared using the pH switch method
    Self-assembling nanostructured peptide gels are promising materials for sensing, drug delivery, and energy harvesting. Of particular interest are short diphenylalanine (FF) peptides modified with 9-fluorenylmethyloxycarbonyl (Fmoc), which promotes the association of the peptide building blocks. Fmoc-FF gels generally form fibrous networks and while other structures have been demonstrated, further control of the gelation and resulting ordered three-dimensional structures potentially offers new possibilities in tissue engineering, sensing, and drug release applications. Herein, we report that the structure tunability of Fmoc-FF gels can be achieved by controlling the water content and the temperature. We further explore the incorporation of metal nanoparticles in the formation of the gel to enable optical sensing applications based on hybrid Fmoc-FF-nanoparticle microspheres. Finally, fluorescence lifetime imaging microscopy reveals a correlation between lifetime and reduced bandgap, in support of a semiconductor-induced charge transfer mechanism that might also increase the stability of an excited state of a probe molecule. The observations potentially further widen the use of these peptide materials in bioimaging and sensing applications.
      40Scopus© Citations 1
  • Publication
    Electric Field Tunability of Photoluminescence from a Hybrid Peptide-Plasmonic Metal Microfabricated Chip
    Enhancement of fluorescence through the application of plasmonic metal nanostructures has gained substantial research attention due to the widespread use of fluorescence-based measurements and devices. Using a microfabricated plasmonic silver nanoparticle-organic semiconductor platform, we show experimentally the enhancement of fluorescence intensity achieved through electro-optical synergy. Fluorophores located sufficiently near silver nanoparticles are combined with diphenylalanine nanotubes (FFNTs) and subjected to a DC electric field. It is proposed that the enhancement of the fluorescence signal arises from the application of the electric field along the length of the FFNTs, which stimulates the pairing of low-energy electrons in the FFNTs with the silver nanoparticles, enabling charge transport across the metal-semiconductor template that enhances the electromagnetic field of the plasmonic nanoparticles. Many-body perturbation theory calculations indicate that, furthermore, the charging of silver may enhance its plasmonic performance intrinsically at particular wavelengths, through band-structure effects. These studies demonstrate for the first time that field-activated plasmonic hybrid platforms can improve fluorescence-based detection beyond using plasmonic nanoparticles alone. In order to widen the use of this hybrid platform, we have applied it to enhance fluorescence from bovine serum albumin and Pseudomonas fluorescens. Significant enhancement in fluorescence intensity was observed from both. The results obtained can provide a reference to be used in the development of biochemical sensors based on surface-enhanced fluorescence.
      36Scopus© Citations 3