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Nonlinear Optical Investigations in Nine-Atom Silver Quantum Clusters and Graphitic Carbon Nitride Nanosheets
journal contribution
posted on 2015-07-16, 00:00 authored by Kishore Sridharan, P. Sreekanth, Tae Joo Park, Reji PhilipAbsorption saturation due to surface
plasmon resonance affects the optical limiting efficiency of metal
nanoparticles (NPs) by raising the limiting threshold to higher laser
fluences. It has been shown that in gold, compared to the larger NPs,
smaller quantum clusters (QCs) exhibit better optical limiting with
lower limiting thresholds due to the absence of absorption saturation.
Here we report optical limiting properties of two novel materials,
namely, nine-atom silver (Ag9) QCs and graphitic carbon
nitride (GCN) nanosheets. The relatively large nonlinear absorption
of Ag9 QCs compared to Ag NPs is revealed from open-aperture
Z-scan measurements carried out using 532 nm, 5 ns laser pulses. Optical
nonlinearity in the QCs arises mostly from free carrier absorption
and a relatively weak saturable absorption. The superior limiting
efficiency of Ag9 QCs is complemented by excellent chemical
stability, which makes silver quantum clusters ideal candidates for
optical limiting applications. The two-dimensional sheet-like structure
of GCN is ideal for grafting metals and semiconductors, and we show
that even though the nonlinearity of pristine GCN is low it can be
improved substantially by grafting lightly with Ag9 QCs.
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Keywords
Ag 9 QCsNonlinear Optical Investigationschemical stabilitycarrier absorptionnonlinear absorptionnovel materialsGCNlaser fluencesgraphitic carbon nitridesaturable absorptionabsorption saturationGraphitic Carbon Nitride NanosheetsAbsorption saturationquantum clustersOptical nonlinearitysilver quantum clusterssurface plasmon resonance532 nmAg NPsmetal nanoparticles5 ns laser pulses