One-pot preparation of thin nanoporous copper foils with enhanced light absorption and SERS properties

Abstract

A facile hydrothermal method has been presented to prepare free-standing nanoporous Cu foils (NPCFs) having a thickness of ~1.4 μm and an area of up to ~10 cm², which were grown on the inwall of a Teflon-lined autoclave by assembling and reducing Cu_xO nanoparticle intermediates and then peeling themselves off in the cooling period of the reaction. The pore sizes of NPCFs can be adjusted by varying the reaction time. It is observed that the NPCFs with water absorbed inside their nanopores show excellent flexibility while dried ones exhibit a highly hydrophobic nature. Compared with commercially available Cu foils, the as-synthesized NPCFs show enhanced ability to absorb light over a wide range of wavelengths from 200 to 1000 nm because of their nanoporosity. The highest absorbance and the biggest enhancement can reach 86% at 300 nm and 43% at 575 nm, respectively. The smooth side of NPCFs with a hemisphere-like surface demonstrates outstanding surface-enhanced Raman scattering performance by employing Rhodamine 6G as the probe molecule, which agrees well with the results of finite-difference time-domain simulation.