Smooth glass beads were purchased from Sigmund Linder (type P; borosilicate; radius, 3.175 mm). Smooth PS spheres were purchased from Cospheric (radius, 600 μm). Glass coverslips were purchased from Thermo Fisher Scientific thickness 1.4H. Spheres were inserted in a container with 240-grit sandpaper walls and then shaken for variable number of hours to obtain surfaces with different roughness. The fluorescent liquid was prepared as described in (18). It was purified with a Serlabo prestacked 220-g silica column and a LPLC (low-pressure liquid chromatography) device (Serlabo) using pressures up to 100 psi, which allows the efficient purification of 5 to 10 g of tetrazines.