Enhanced nonlinear absorption and efficient power limiting action of Au/Ag@ graphite core-shell nanostructure synthesized by laser ablation

Abstract

Here we report a drastic enhancement of nonlinear absorption behaviour and exceptional optical limiting action of two core-shell systems (Au@graphite and Ag@graphite) prepared by adopting a fairly easy way in which we did not use any graphitic substrate. We carried out pulsed laser ablation of Au and Ag targets in toluene, monosubstituted benzene from which graphite layers of nanometer thickness has emerged as a result of photochemical reactions. The prepared samples were characterized and analyzed by UV/Vis spectroscopy, Raman spectroscopy, and TEM. Theoretical simulations of the core-shell nanostructures were done by the finite-difference time-domain method underlined the quenching of SPR in the case of both Au and Ag NPs by the graphitic layers evolved from toluene. Au and/or Ag@graphite core-shell structure exhibited a huge improvement in the nonlinear absorption behaviour and the optical limiting efficiency of these systems is found to be better than that of many benchmark optical limiters. The enhancement in nonlinear absorption property and the limiting actions of these systems were attributed to the enhanced excited-state absorption as well as free-carrier absorption arose as a result of the modification in the electronic structure of graphite on core-shell formation. Moreover, the metallic NPs also enhances nonlinear absorption through free-carrier absorption free-carrier absorption. So we believe these results are quite useful for guiding the characterization, monitoring the synthesis of similar nanostructures and for, the development of nanohybrids with desired properties for nonlinear optical, optoelectronic and photocatalytic applications.

Laser Driven In Situ Growth of Metal Nanoparticles on Graphene Oxide Nanosheets for Plasmon-Enhanced Optoelectronic Responses

“…A large NLO enhancement (∼6-fold) is observed in the Au NPs–rGO NS hybrid due to strong activation of the LSPR effect at the laser excitation wavelength of 532 nm. We have also compared our results in Table with previous reports on various metal nanoparticle hybrids with GO/graphite/rGO in the nanosecond regime. − Zheng et al have studied hydrothermally synthesized Au, Pd, and Pt NPs hybrids with GO and estimated the effective β in the range of 0.83–1.1 cm/GW. Similarly, Nancy et al .…”

“…Thus, the reduction of oxygen functionalities in the GO NS plays a major role in enhancing the effective nonlinear absorption coefficients. However, Ag/Au NP–graphite core–shell structures synthesized by Shiju et al have pronouncedly enhanced β values through increased plasmon field interactions at the NP–graphite interfaces. It is worth mentioning that these graphite shells were obtained from laser-irradiated toluene, which is toxic in nature.…”

“…This charge transfer enables the additional photon absorption to facilitate the ESA process that improves the RSA behavior. In addition, FCA contributes to the ongoing nonlinear optical processes by electron excitation in the continuum states of metal NPs . In this way, FCA and ESA greatly influence the effective nonlinear optical absorption coefficients of the hybrid materials.…”

“…The obtained limiting thresholds are listed in Table and are much superior to reported values, where they demonstrated that the high concentration of NPs unfavorably affects the optical limiting properties of their rGO hybrids. The limiting threshold values of our hybrid materials are comparable with the metal NP–graphite matrix core–shell structures reported by Shiju et al The obtained lower limiting thresholds of rGO NS hybrids resulted from strong plasmon field interactions between rGO NS and NPs.…”

“…The bandgap of GO can be tuned from visible to NIR wavelengths by reduction approaches to transform GO into reduced graphene oxide (rGO). Over time, the structure of GO/rGO has been engineered with metal nanoparticles to boost the optical absorption at nanoscale thicknesses. − The performance of these devices depends mostly on the crystalline quality of NPs and their interaction with rGO. Metal nanoparticle–rGO hybrids are mostly synthesized by chemical routes, which produces chemical residues in the end product that causes the device’s poor performance.…”