Ceria nanoparticles have been proved to be one of the most promising optical conversion host structures, due to its low-phonon nature and non-stoichiometric structure. In up-conversion, erbium has been extensively used as the main optical center for converting low-photon energy into higher ones. This paper studies the effect of introducing plasmonic nanostructure, such as gold, for enhancing the optical upconversion quantum yield efficiency of erbium-doped-ceria nanoparticles. The numerical results show that the efficiency experienced a significant enhancement as a result of existence of metal nanostructures. In addition, the temperature influence upon the nanocomposite is studied in detail. The numerical calculations show that the temperature change has a remarkable influence on the luminescence parameters and quantum yield efficiency of the up-conversion structure.
Due to its optical and structural characteristics, cerium oxide (ceria) nanoparticles have been used in wide variety of applications. This paper introduces the enhancement of visible fluorescence emission of ceria nanoparticlesthrough adding plasmonicgold nanoparticles (Au NPs) under violet excitation. Au NPs lead to enhance the formation of tri-valent ionization states of cerium ions with corresponding oxygen vacancies formation. In addition, the coupling between plasmonic waves of gold and emission spectrum of ceria offers another contribution to the enhancement of fluorescence intensity.Then, gold-ceria nanoparticles have been applied as optical sensing material for dissolved oxygen in aqueous media based on fluorescence quenching mechanism.The sensed data is automatically collected and processed through a wireless sensor network-based communication infrastructure with smartdata and feedback management capability.
The work demonstrates an electrospun nanocomposite of recombinant spider silk protein (rSSp) nanofibers with embedded cerium oxide (ceria) nanoparticles. RSSP (MaSp1) has been produced, extracted from goat milk, and fabricated into nanofibers using an electrospinning process. The resulting electrospun nanofibers have a mean diameter of ∼50 nm. Furthermore, ceria nanoparticles of mean diameter <10 nm were added in the spinning dope to be embedded within the generated nanofibers. These nanoparticles show certain optical activity due to optical trivaliant cerium ions, associated with formed oxygen vacancies. The formed nanocomposite shows promising mechanical properties such as the Young’s modulus, elasticity (or elongation at break), and toughness. In addition, the electrospun mat becomes fluorescent with 520-nm emission upon exposure to UV light, due to excitation of the optically active ceria nanoparticles. Also, the formed nanocomposite shows a decay of its electric resistance over time upon exposure to cyclic loads at different humidity conditions. The synthesized nanocomposite can be utilized in different biomedical, textile, and sensing applications.
Ceria nanoparticles are studied as optical probe for different types of tiny metallic particles using fluorescence quenching technique. The synthesized ceria nanoparticles are characterized by having formed charged oxygen vacancies, which can be considered as the main receptors for the used tiny metallic particles to be sensed or absorbed. Under near-UV excitation, the visible fluorescent emission intensity is found to be reduced with increasing the concentration of the studied tiny metallic particles in an aqueous solution. To emphasize the optical sensing process, ceria nanoparticles fluorescence lifetime measurements were demonstrated before and after adding the tiny metallic particles. In addition, Stern–Volmer constants, which are considered as an indication for the sensitivity to quenchers, have been calculated for the used ceria nanoparticles and found to be 1.645, and 0.768 M−1 for both lead and iron sensing, respectively. This work could be further helpful as sensitive optical sensors in both biomedical and environmental applications.
This work investigates the relationship between the Q factor of a silica microsphere coated with nonlinear optical molecules and the surface density of the nonlinear molecules. Two types of nonlinear molecules are studied: poly{1-[p-(3′-carboxy-4′-hydroxyphenylazo) benzenesulfonamido]-1,2-ethandiyl} (PCBS), and Procion Brown MX-GRN (PB). In our experiments, we coat silica microspheres with ionic self-assembled multilayer films with different thicknesses as well as with different PCBS/PB chromophores densities. The Q factors of the coated microspheres are measured to be within the range of 106 to 107, which can be attributed to the optical absorption of the coated chromophores. This work can be used to experimentally determine the effective density of chromophores assembled on the silica microsphere. It may also find applications in chemical/biological sensing.
This work investigates the relationship between the Q factor of a silica-microsphere coated with nonlinear optical molecules and the surface density of the molecules. Two types of nonlinear molecules are studied: poly {1-[p-(3′-carboxy-4’-hydroxyphenylazo) benzenesulfonamido]-1, 2-ethandiyl} (PCBS), and Procion Brown MX-GRN (PB). In our experiments, we coat silica microspheres with ionic self-assembled multilayer (ISAM) films with different thickness values as well as different PCBS/PB chromophore densities. The Q factors of the coated microspheres are limited to the range of 106-107, which can be attributed to the optical absorption of the coated chromophores. This work can be used to experimentally determine the effective density of chromophores assembled on the silica microsphere. It may also find applications in chemical / biological sensing.
As an amorphous material with full inversion symmetry, silica-based microstructures cannot possess significant secondorder nonlinearity. We recently developed a method that can potentially overcome this deficiency by coating a silica fiber taper with layers of radially aligned nonlinear molecules. The coating process can be accomplished through layerby- layer self-assembly, where the alignment of the nonlinear molecules is maintained through electrostatic interaction. As a result, the nonlinear fiber structures are thermodynamically stable and can generate significant second-order nonlinear responses despite their full rotational symmetry. This prediction has been experimentally confirmed through SHG measurements. To further enhance the overall second-order nonlinearity, we have developed an UV-ablation-based approach that can generate second-order nonlinearity that is spatially periodic along the fiber taper. Our preliminary experiments suggest that SHG intensity can be enhanced by such quasi-phase-matching configurations.
We can also use the self-assembly approach to construct tunable plasmonic systems. As a proof-of-concept study, we assembled swellable polymer films over a planar Au substrate through layer-by-layer assembly and covered the swellable polymer with a monolayer of quantum dots. After immersing the swellable plasmonic structure in solution and adjusting its pH value, we used a fluorescence lifetime based approach to demonstrate that the thickness of the swellable polymers can be modified by almost 400%. The fluorescence lifetime measurements also confirmed that the plasmonic resonance can be significantly modified by the swellable polymers.
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