Aligned Peptide Nanotube–Metal Nanoparticle Templates for High Sensitivity Surface Enhanced Raman Spectroscopy-based Sensing

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Saudi Digital Library
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 optical sensing of biomolecules or energy harvesting applications. Templates formed from aligned FF-PNTs with plasmon-active metal nanoparticles or graphene oxide are a promising nanocomposite for large-scale, rapid, stable, sensitive, biocompatible, and cost-effective surface-enhanced Raman scattering (SERS) substrates. In this thesis, a novel method for directing alignment into arrays of an ordered structure is reported, using a wettability-based technique. A highly sensitive SERS template is reported in this thesis, which utilizes aligned FF-PNTs to form a dense packing arrangement of plasmon‐active silver nanoparticles (Ag NPs). Knowing that FF-PNTs are both pyro- and piezoelectric materials with a large band gap of around 4.6 eV, the template was further activated by introducing two novel mechanisms, firstly, super band gap UV irradiation and secondly, the application of an external electric field during SERS measurements. Both UV and electric field-induced charge transfer facilitates a chemical enhancement that provides up to a 10-fold increase in SERS intensity and allows the detection of a wide range of small molecules at concentrations as low as 10–13 M. Not only was an increase in SERS intensity seen with applied electric field or UV irradiation but also catalyst activity was reported. Both methods were found to work well with other systems that consisted of FF-PNT and graphene oxide (GO), enabling nanomolar detection sensitivity of glucose and nucleobases surpassing to metal-based substrates.