Self-assembled colloidal gold nanoparticles as substrates for plasmon enhanced fluorescence

Decades of intense research in the field of nanoscience have led to the ability to produce nanoparticles (NPs) with controlled composition, shape, and size. One of the next key challenges is the self-assembly of appropriate NP building blocks into larger systems to obtain micro- or macroscale materials. To achieve this, self-assembly protocols must not only produce high-quality structures, but also deliver the assemblies of interest to desired locations on a substrate. In this review, we discuss different self-assembly strategies, focusing on colloidal gold NPs and applications as plasmon-enhanced fluorescence (PEF) platforms. These plasmonic substrates have been used for biosensing and cell imaging, based on the enhancement of fluorescent emitters, and applied to improve the emission efficiency of luminescent NPs. It is important to note that higher fluorescence enhancement relies on precise control of the location of gold NPs and fluorescent emitters on the plasmonic substrate. Despite the diversity of available self-assembly strategies, many of them provide similar levels of structural control over the placement of gold NPs on the substrate. To highlight this, we have organized the discussion according to strategies that result in similar degrees of structural control over the placement of gold NPs and its associated PEF effect.