Tweaking nanoscale structure to tune photoluminescence

Photoluminescent materials emit photons in the form of a light beam, but controlling the properties of this emission is challenging. Acosta et al. demonstrated how to precisely tune the intrinsic photoluminescence of nanoporous anodic alumina, an inorganic material that can be produced with a cost-effective and scalable industrial process—the anodization of aluminum.

The authors engineered the nanoscale structure of this material in the form of photonic crystals, which allow highly directional emission of light with tunable wavelength. Nanoporous anodic alumina is an ideal photonic crystal platform material because it has well-defined and controllable geometric features.

Using a combination of pulse and constant anodization, they produced a structure made of nanoporous anodic alumina photonic crystals consisting of two layers: a non-emitting, light-filtering layer on top and an intrinsically light-emitting layer underneath. The light-filtering layer allowed them to narrow the characteristically broad photoluminescent emission from the underlying light-emitting layer up to about 50 nanometers, as well as shift it about 15 nanometers.

“Our study is a step forward in engineering light-emitting materials through structural engineering,” said author Lluis Marsal. “This nanofabrication approach, which is compatible with conventional microfabrication techniques, makes it possible to tune the intrinsic emission of materials and narrow the spectral width of these emissions for specific applications.”

Potential applications of tunable, light-emitting nanoporous anodic alumina photonic crystals include photodetection and solar light harvesting. Next, the authors will explore the applicability of this technology in sensing and lasing, as well as test its limitations.

Source: “Tuning intrinsic photoluminescence from light-emitting multispectral nanoporous anodic alumina photonic crystals,” by Laura K. Acosta, Cheryl Suwen Law, Abel Santos, Josep Ferré-Borrull, and Lluis F. Marsal, APL Photonics (2022). The article can be accessed at https://aip.scitation.org/doi/full/10.1063/5.0078505 .