Dynamically modulating the mid-infrared localized surface plasmon resonance of Al-doped ZnO nanocrystals

Abstract The localized surface plasmon resonance (LSPR) regulation of semiconductor oxide nanocrystals (NCs) in the near-infrared region (0.8–2.5 μ m) of the solar spectrum has attracted much attention for its potential in applications such as electrochromism and sensing. However, the LSPR modulation properties of doped semiconductor oxide NCs in the mid-infrared region (2.5–25 μ m) have rarely been reported. Here, we synthesized aluminum-doped zinc oxide (AZO) NCs with various nominal Al doping contents (1–20at%). The LSPR absorption peaks of these films were regulated between ∼3.8 and 6.57 μ m depending on the doping content. AZO NC films with 1at% nominal Al doping and a 1316 nm film thickness exhibited the highest electrochemical infrared absorption regulation, achieving 35.9% regulation at 3–5 μ m and 32.5% at 7.5–13 μ m. The infrared absorption regulation mechanism of the AZO NCs involved changes in the LSPR absorption intensity caused by electron injection/extraction into/from the surface depletion layer of the AZO NCs. After applying different voltages, the AZO NC film on the Al substrates exhibited different apparent temperatures, demonstrating its potential applications in infrared displays and camouflage.