Physics Research Collection

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Recent Submissions

Now showing 1 - 5 of 251
  • 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.
      10Scopus© Citations 1
  • 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.
    Scopus© Citations 3  10
  • Publication
    Cellulose Acetate-Based Plasmonic Crystals for Surface-Enhanced Raman and Fluorescence Spectroscopy
    (American Chemical Society (ACS), 2022-03-23) ; ;
    In order to meet environmental concerns, there is an increasing demand for biodegradable and sustainable materials in many areas, including photonics. Cellulose and its derivatives are potentially eco-friendly alternatives to conventional plastics, because of their abundance and lower environmental impact. Here, we report the fabrication of plasmonic structures by molding cellulose acetate into submicrometric periodic lattices, using soft lithography. The fabricated platforms can be used for the enhancement of Raman and fluorescence signals of a range of analytes including a model immunoassay utilizing a streptavidin-conjugated dye, which is characterized by a 23-fold enhancement in fluorescence signal intensity, which shows the potential of the platform to be further used for the assay-based development of diagnostic tools.
    Scopus© Citations 1  10
  • 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.
    Scopus© Citations 8  14
  • 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.
    Scopus© Citations 3  12