Enhancement of the upconversion photoluminescence of hexagonal phase NaYF₄:Yb³⁺,Er³⁺ nanoparticles by mesoporous gold films

Efficient enhancement of photoluminescence in rare-earth activated upconversion materials is of great significance for their practical applications in various fields. In this work, three-dimensional mesoporous gold films were fabricated by a low-cost and facile dealloying approach to improve the upconversion photoluminescence efficiency. The mesoporous Au films exhibit good chemical stability, large-area uniformity and abundant distribution of porous nanospaces. Varying the time of the dealloying process leads to modification of the pore size distribution, surface roughness and residual Ag content, resulting in effective tuning of the wavelength of the broadband localized surface plasmon resonance (LSPR). Enhancement factors were identified to be a function of the dealloying time. With the optimized upconversion photoluminescence enhancement, a 41-fold increase was achieved with the mesoporous gold substrate which had been dealloyed for 8 days. These results pave the way to overcome the limitation of poor upconversion efficiency for widespread practical applications in life science and energy fields.