Now showing 1 - 10 of 14
  • 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.
      835Scopus© Citations 37
  • 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.
      283Scopus© Citations 2
  • Publication
    Plasmonic photo-catalysis using a CdS-silver nanowire composite
    We examine the potential of cadmium sulfide when combined with plasmonic nanostructures to support photo-induced catalysis. Super-bandgap irradiation of a silver nanowire and cadmium sulfide composite for the probe molecule p-aminothiophenol (PATP) showed the formation of dimercaptoazobenzene (DMAB) from PATP. Our results demonstrate that cadmium sulfide can be used as an alternative material to semiconductors, such as titanium dioxide, for plasmonic photocatalysis applications.
      20Scopus© Citations 3
  • 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.
      21Scopus© Citations 3
  • 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.
      19Scopus© Citations 9
  • 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.
      21Scopus© Citations 4
  • 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.
      207Scopus© Citations 8
  • 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.
      638Scopus© 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.
      23Scopus© Citations 3
  • 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.
      18Scopus© Citations 13