Abstract
We used Optically Stimulated Luminescence (OSL) from X-ray-irradiated sodium chloride nanocrystals to investigate how silver nanoparticle (AgNP) films enhanced luminescence. We controlled the emitter-AgNP distance and used the OSL intensity and decay times to explore the plasmonic interactions underlying the enhanced luminescence. Both intensity and decay times depended on the emitter-AgNP distance, which suggested that a mechanism involving energy transfer from the localized surface plasmons (LSPs) to the trapped electrons took place through a distance-dependent coupling. Compared to other plasmon-enhanced mechanisms, the energy transfer observed here occurred in the opposite bias: LSP relaxation stimulated electron transfer from non-optically active traps to optically active traps, which culminated in enhanced emission. Therefore, a different mechanism of plasmonic coupling converted optically unreachable electrons into useful luminescence information.
Highlights
We used Optically Stimulated Luminescence (OSL) from X-ray-irradiated sodium chloride nanocrystals to investigate how silver nanoparticle (AgNP) films enhanced luminescence
Such luminescence enhancement usually originates via two mechanisms: (1) the excitation mechanism, which results from amplification of the local electric field close to the metal surface; and (2) the metal-coupled emission mechanism, which involves energy transfer from the excited luminophore to the plasmons, to increase the radiative decay rates and reduce the lifetime of the plasmophore emission[7,8,9]
The excitation mechanism usually occurs at very short distances (
Summary
All the layers were rinsed with Mili-QTM water for 5 min between each deposition step (to remove nonspecifically adsorbed chitosan and AgNPs) and dried under nitrogen flow. This procedure was repeated several times, to grow films with 3, 5, and 10 chitosan/AgNP bilayers. The substrates were immersed in each solution for 20 min, rinsed with Mili-QTM water for 5 min, and dried under nitrogen flow This procedure was repeated several times, to grow films with 1, 2, 4, and 6 chitosan/poly(acrylic acid) bilayers. The probability of electron escape increases with increasing photon fluency (φ) and/or the photoionization cross-section (σ) For this reason, the decay time (τd) decreases, and the OSL intensity decays faster. Analysis of the shape and decay times of the OSL curves provides information regarding the charge de-trapping mechanism and rate
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