Enhancement of NaYF4:Yb3+/Er3+up-conversionluminescence based on anodized alumina template

Up-conversion nanoparticle (UCNP) can collect near-infrared (NIR) light and convert it into visible light.Therefore, UCNP has potential applications in fields such as biomedicine, anti-counterfeiting, and solar cells.However, the efficiency of traditional UCNP in the above-mentioned fields is relatively low, greatly limiting itsuse in related fields. Therefore, enhancing the up-conversion luminescence intensity of up-conversionnanoparticles is particularly important and urgently needed. In this work, anodic alumina templates are used toenhance the luminescence intensity of up-conversion nanocrystals. NaYF4:Yb3+, Er3+with a diameter of 35 nm isprepared by using co-precipitation method. Single pass AAO templates with pore size and pore spacing of88 nm and 100 nm are prepared by using two-step anodization method. Finally, NaYF4:Yb3+, Er3+/AAOcomposite structures are formed by using spin coating method. The red green light emission intensity ofNaYF4:Yb3+, Er3+/AAO sample can increase 4.4 and 9.0 times that of NaYF4:Yb3+, Er3+/Al reference sample,respectively. The enhancement mechanism is explored by using the finite difference time domain method, andthe results show that the primary source of enhancement is the localized surface plasmon resonance effect of thepores in the anodic alumina template. At the same time, the relationship between the up-conversionluminescence intensity of NaYF4:Yb3+, Er3+/AAO sample and the incident angle is investigated. Theexperimental results show that as the incident angle increases, the luminescence intensity of the red and greenlight of NaYF4:Yb3+, Er3+/AAO samples first decrease and then increase. Due to the coupling of the localsurface plasmon resonance with the excitation wavelength and emission wavelength, the up-conversionluminescence intensity of the sample can be affected. The relationship of AAO channel enhancement factor withincident angle at excitation wavelength and emission wavelength is studied by using the finite difference timedomain method. The results indicate that as the incident angle increases, the enhancement factor at theexcitation wavelength decreases, while the enhancement factor at the emission wavelength increases after beingilluminated at an incident angle of 15 degrees. Therefore, when the incident angle is less than 20 degrees, the electric fieldintensity at 980 nm dominates, but when it is greater than 20 degrees, the electric field intensity at 540 nm and 650 nmtakes precedence. The above results provide a reference for putting them into practical applications in the fieldsof anti-counterfeiting and solar cells