From Alcohol Ligand Content to Doping Level, Morphology, and Optical Absorption in the Synthesis Process of Aluminum-Doped Zinc Oxide Nanoparticles

Aluminum-doped zinc oxide (AZO) nanoparticles (NPs) with tunable composition, morphology, and localized surface plasmon resonance (LSPR) properties were synthesized via a high-temperature thermal injection method. While maintaining constant Zn and Al amounts, systematic alcohol-to-Zn ratio variations (2.5:1 to 10.0:1) enabled precise control over Al³⁺ doping levels, particle morphology, and optical characteristics. Increasing alcohol content enhanced Al³⁺ incorporation into the ZnO lattice while reducing particle size and blue-shifting LSPR absorption. The NPs exhibited strong NIR/MIR absorption (peaking at 2002 cm^-1 within the 6000-580 cm^-1 range), resulting from increased free carrier density through Al³⁺/Zn²⁺ heterovalent substitution. This work establishes a reliable approach for designing infrared plasmonic metal oxides, demonstrating how synthetic parameters govern dopant incorporation and optical responses. The tunable NIR/MIR properties of AZO NPs show significant potential for both fundamental research and practical applications in light-responsive technologies, pending further optimization of the synthesis process.