New advances in lanthanide-based luminescent materials promise to revolutionize fields such as photonics, information security, and biomedicine, enabling full-color emissions from single nanoparticles. Researchers have developed a multi-layer core-shell (MLCS) nanoparticle capable of switching between different colors of light with just one excitation source—a 980 nm laser—by intricately controlling how different lanthanide ions interact during the emission process.
Recent breakthroughs focus on the manipulation of the upconversion dynamics involving lanthanide ions called erbium (Er3+), thulium (Tm3+), and ytterbium (Yb3+). The collaboration of these elements allows the new nanoparticle structure to produce specific colors: red, green, and blue, depending on the excitation mode applied, simplifying the previous need for complex designs requiring multiple laser sources.
The pivotal nature of this research lies not just in the materials used, but the approach taken to realize this color variability. Traditionally, these advanced materials required multiple excitation wavelengths to achieve color changes. This work shifts the paradigm by enabling temporal control of the upconversion emissions, making it possible to achieve color-switchable outputs through innovative techniques like time-gated detection.
Er3+, which can emit both red and green light, is capable of switching between these colors under non-steady state conditions. The transitional effects happen through cooperative modulation enabled by the presence of Tm3+. By introducing Tm3+ at controlled concentrations, scientists can expedite the population of energy levels within Er3+, facilitating the manipulation of color outputs. For example, during longer pulse widths of excitation, red emissions dominate, whereas shorter pulse widths can yield everything from yellow to green. Particularly notable is the ability to achieve unexpected color outputs seamlessly from one nanoparticle using simple adjustments to the external excitation.
The MLCS nanoparticles' new design concept significantly reduces the need for complicated pump systems and suggests immense potential applications across various industries. The upconversion characteristics of these materials position them as exciting candidates for uses such as volumetric displays or anti-counterfeiting technologies, where distinct color outputs under controlled conditions are advantageous.
The results—published recently—confirm the team's hypothesis about the role of Tm3+ influencing the upconversion dynamics significantly beyond its typical use as merely a blue-emitter. This not only opens new avenues for full-color emission but enhances the scientific community's overall comprehension of lanthanide interactions.
One fascinating application of this technology is already visible: researchers were able to create artwork, showcasing colors from the same nanoparticle under varying excitation methods. A "butterfly-over-rose" image resulted from strategically switching laser modes, demonstrating the material's capacity for practical use and artistic expression.
The study concluded with the possibility of transitioning this technology toward the creation of optical devices and flexible, functional materials, urging continued examinations of lanthanide-based systems for future advancements. This contrived MLCS nanoparticle structure holds definitive promise, hinting at more efficient, high-performance luminescent materials across varied domains.