Large-scale controllable fabrication of aluminum nanobowls for surface plasmon-enhanced fluorescence

Al nanoparticles (NPs) exhibit excellent localized surface plasmon resonance (LSPR) properties and have been considered a promising alternative to plasmonic Au or Ag NPs. However, it remains difficult to fabricate Al NPs with uniform size and controllable morphology over a large area on substrates, which seriously hinders the in-depth exploration of their properties and applications. Herein, we have developed a self-assembly nanoparticle template method to realize the controllable preparation of bowl-shaped Al NPs (Al nanobowls (Al NBs)) with tunable sizes from 36 to 131 nm on the substrate surface, accompanied by tunable LSPR spectral responses from 272 to 480 nm. Among them, 131 nm Al NBs exhibit superior fluorescence enhancement ability (1932.2-fold) and a low detection limit (78.6 pM) towards 5-carboxyfluorescein, exceeding comparable Ag NBs and Au nanospheres (NSs). This can be attributed to the strong electromagnetic enhancement induced by the LSPR effect and the effective inhibition of fluorescence quenching caused by the self-passivated oxide layer. Therefore, the successful fabrication of Al NBs on substrates is of vital significance for their promising applications, including surface-enhanced spectroscopy, sensitive fluorescence detection, light-harvesting devices, biosensing, and ultraviolet (UV) plasmonics.