Abstract
Abstract We study the light emission of plasmonic-luminescent hybrid nanostructures consisting of Ag nanoparticles (NPs) embedded in europium oxide (EuOX). The Ag NPs present a bidimensional organization in the nanostructures and they optically behave as oblate spheroids. The photoluminescence (PL) spectral response of the nanostructures evolves from a narrow red emission characteristic of Eu3+ ions in absence of Ag NPs to a broad blue-green emission band associated with Eu2+ ions when the layer of Ag NPs is present. This behavior is not related to a change in the Eu2+/Eu3+ ratio, which is verified by compositional analysis. Instead, a detailed investigation of the PL emission of the nanostructures suggests that the coupling of the Ag NPs to the Eu2+ ions present in the EuOX layer, which manifests itself in an efficient sensitization of these ions, enhances their broad visible emission. In particular, the longitudinal mode of the Ag NPs surface plasmon is considered to be responsible for the efficient energy transfer for the non-normal incidence excitation PL configuration used. Finally, the use of a capping amorphous Al2O3 layer allows improving the robustness of hybrid nanostructures and further enhances their PL emission. These findings provide a new path to actively control the selective excitation of Eu2+ and Eu3+ ions via a controlled coupling with the surface plasmon resonance modes of the Ag NPs and points to these nanostructures as promising building blocks for the development of integrable white light sources.
Highlights
White light-light-emitting diodes (WL-LEDs) have almost completely replaced conventional lighting sources due to their high lifetime, superior efficiency, energy-saving, and safety
Experimental melting values in the range from ≈115 to 530 °C that are lower than the melting temperature of bulk Ag (Tm(Ag) = 962 °C), have been reported in the case of Ag nanoparticles (Ag NPs) with a diameter in the range of a few to 20 nm, such as those shown in Figure 1 [35, 36]
We have evaluated the chromatic coordinates (CIE 1931) of the Pl-L hybrid nanostructures and the Hybrid plasmonic-luminescent Ag NPs:europium oxide (EuOX) nanostructures have been produced in a single step by Pulsed Laser Deposition (PLD) in vacuum at room temperature
Summary
White light-light-emitting diodes (WL-LEDs) have almost completely replaced conventional lighting sources due to their high lifetime, superior efficiency, energy-saving, and safety. Among the alternatives to produce WL-LEDs, a usual approach consists of the combination of UV or blue excitation sources with different rare-earthdoped amorphous or crystalline phosphors [7] that emit light in the blue, green, and red wavelength ranges in order to obtain white light by their combination [1, 2, 6]. The use of different phosphors decreases the efficiency of the device and presents technical problems associated with the combination of phosphors with different excitation requirements and physical and chemical properties. An appropriate good absorption in the UV-Blue wavelength range, strong chemical and oxygen stability, along with a high conversion efficiency are required [1, 5]
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