Abstract
This work focuses on improving the fluorescence intensity of cerium oxide (ceria) nanoparticles (NPs) through added plasmonic nanostructures. Ceria nanoparticles are fluorescent nanostructures which can emit visible fluorescence emissions under violet excitation. Here, we investigated different added plasmonic nanostructures, such as gold nanoparticles (Au NPs) and Cadmium sulfide/selenide quantum dots (CdS/CdSe QDs), to check the enhancement of fluorescence intensity emissions caused by ceria NPs. Different plasmonic resonances of both aforementioned nanostructures have been selected to develop optical coupling with both fluorescence excitation and emission wavelengths of ceria. In addition, different additions whether in-situ or post-synthesis have been investigated. We found that in-situ Au NPs of a 530 nm plasmonic resonance wavelength provides the highest fluorescence emissions of ceria NPs compared to other embedded plasmonic structures. In addition to the optical coupling between plasmonic resonance of Au with the visible emissions fluorescence spectrum of ceria nanoparticles, the 530 nm in-situ Au NPs were found to reduce the bandgap of ceria NPs. We suggest that the formation of more tri-valent cerium ions traps energy levels along with more associated oxygen vacancies, which is responsible for increasing the fluorescence visible emissions intensity caused by ceria. As an application, the gold-ceria NPs is shown to optically detect the varied concentration of iron tiny particles in aqueous medium based on a fluorescence quenching mechanism. This work is promising in different applications such as biomarkers, cancer treatments, and environmental pollution monitoring.
Highlights
Cerium oxide NPs can be considered to be one of the most promising nanostructures developed in the last two decades due to its oxide storage capacity based on reduction-oxidation characteristics [1]
The plasmonic resonance emissions spectra of the used Au NPs is shown in Figure 1b, and both cadmium sulfide/zinc sulfide (CdS/ZnS), and CdSe/ZnS quantum dots (QDs) are shown together in Figure 1c [16,17]
All plasmonic-ceria NPs show an enhanced fluorescence visible emissions intensity compared to pure ceria NPs
Summary
Cerium oxide (ceria) NPs can be considered to be one of the most promising nanostructures developed in the last two decades due to its oxide storage capacity based on reduction-oxidation (redox) characteristics [1]. The formed oxygen vacancies inside the crystalline structure of ceria are adsorbing centers for oxygen, radicals, and charged tiny metallic particles Such vacancies are associated with the formation of tri-valent cerium ions trap energy levels, which are optically active through a reduced bandgap that is close to 3 eV. Such tri-valent ions are responsible for visible fluorescence emissions when excited through violet or near ultra-violet (UV) exposure and 5d–4f energy levels transitions [2,3,4,5] Both the oxygen vacancies and optical fluorescence characteristics of ceria lead to using the optical nanostructures in wide variety of applications such as optical sensors for.
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