Construction of Carbon Nanotube Sponges to Have High Optical Antireflection and Mechanical Stability.

Antireflective (AR) materials are required to possess high optical antireflection and mechanical stability for their practical applications in optical, opto-electronic, and electron-optical devices. However, the AR materials developed so far can hardly meet these requirements. Here, we report the construction of a highly porous and sponge-like material based on carbon nanotubes (CNTs). This is achieved by continuous winding of a hollow cylindrical CNT assembly and subsequent modification with amorphous carbon (AC). The resultant material is shown to have very low optical reflectance at the visible and infra-red wavelengths over a wide range of incident angles and undergoes little degradation even after long-lasting compressive cycling between 0 and 90% strains or a large change of environmental temperature from -196 to 300 °C. Besides, the AR sponge material can recover fast after bending, stretching, and compression from high elastic strains. Such an excellent combination of broadband and omnidirectional antireflection, mechanical stability, and elastic flexibility results from the strong light absorption by the highly porous CNT structures strengthened by AC deposition on CNT surfaces and junctions, and the new AR material has potential applications in the renewable energy and military fields.