Chitosan-luminol reduced gold nanoflowers: From one-pot synthesis to morphology-dependent SPR and chemiluminescence sensing

By reducing HAuCl4 with chemiluminescent (CL) reagent luminol in the presence of hydrophilic polymer chitosan, three-dimensional flowerlike gold nanostructures (AuNFs) were synthesized via a convenient one-pot method. As-prepared stable and monodisperse AuNFs were consisted of smaller-sized nanodots according to subsequent characterizations by high-resolution transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction. The size and morphology of AuNFs could be tailored by varying the amount of luminol or chitosan, which further influenced their surface plasmon resonance (SPR) properties in both visible and near-infrared regions. On the basis of the characterizations, a chitosan-assisted secondgrowth mechanism was proposed to explain their formations and morphology evolutions with the amount of reactants. Moreover, an electromagnetic simulation method, discrete dipole approximation, was introduced to calculate the morphology-dependent extinction spectra of geometrically irregular AuNFs. The simulations were consistent with the experimental results. Finally, because luminol was attached on the surface of AuNFs, as-prepared AuNFs could react with H2O2 to generate chemiluminescence. The functionalized AuNFs were immobilized on the solid supports by virtue of the film-forming property of chitosan solution to fabricate a reagent-free CL sensor for the determination of H2O2. Due to their shape-dependent SPR properties and specific surface structures, these AuNFs might also have great potential for the applications in biomedicine and surface enhanced Raman scattering.