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Flow chart for the preparation of foamed gold material with micro/nanoscale hollow spheres. Here, r1 is the radius of the PS sphere, t = r2 – r1 is the thickness of the Au shell, and d is the diameter of the hollow sphere. In step (4), the photo of the sample is shown. It is important to note that it is only a schematic of the sample fabrication process here. The details of the process are presented in Methods.
