Movable Au Microplates as Fluorescence Enhancing Substrates for Live Cells

Hexagonal and triangular Au microplates extending over an area of ~12, 000 μm² with thickness in the range 30–1000 nm have been synthesized using a single step thermolysis of (AuCl₄)⁻–tetraoctylammonium bromide complex in air. The microplates are self-supporting and can be easily manipulated using a sharp pin, a property which enables them to serve as substrates for living cells. The microplate surface is non-toxic to living cells and can enhance the fluorescence signal from fluorophores residing within the cell by an order of magnitude. In addition, the microplates are smooth and single-crystalline, and ideal as microscopy substrates and molecular electrodes. The growth of the microplates in the initial stages is interesting in that they seem to grow perpendicular to the substrate, as evidenced by in situ microscopy.