A colloidal system of polythiophene-grafted edge-gold-coated silver nanoprisms with enhanced optical properties and stability

Abstract

Silver nanoprisms (Ag-PRs) have been epitaxially edge-coated with gold and subsequently covered fully with P3HT chains to fabricate poly(3-hexylthiophene)-grafted edge-gold-coated silver nanoprisms (P3HT@AuAg-PRs) which are miscible with organic solvents; each AuAg-PR with a typical edge length of 122 nm is surrounded by 4.4 × 10³ P3HT chains. Both absorption and emission spectra have indicated that aggregated P3HT chains are bound on the surfaces of noble-metal nanoprisms. Picosecond emission kinetic profiles have suggested that the S₁ relaxation time of P3HT in P3HT@AuAg-PRs is reduced due to energy transfer to AuAg-PRs. From nanosecond transient-absorption kinetic profiles, the reduced amplitude and the increased decay time of T₁ excitons in P3HT@AuAg-PRs have been measured, indicating that neither the intersystem crossing of S₁ into T₁ nor the intersystem crossing of T₁ into S₀ occurs effectively in P3HT@AuAg-PRs owing to the stretched and rigid conformations of P3HT chains bound on the surfaces of AuAg-PRs. The surface-enhanced Raman scattering effect of P3HT@AuAg-PRs is as high as 4.6 because the sharp tips of AuAg-PRs which are maintained via gold coating serve as “hot spots”. The morphology deformation time of P3HT@AuAg-PRs in H₂O₂(aq) has been extended 48 times longer than that of Ag-PRs. Overall, our fabricated nanocomposites of P3HT@AuAg-PRs not only have feasible-process ability but also possess enhanced optical properties and high stability against oxidizing agents, extending the use of noble-metal nanoprisms for various optical applications.