In Situ Monitoring of Scale Effects on Phase Selection and Plasmonic Shifts during the Growth of AgCu Alloy Nanostructures for Anticounterfeiting Applications

Abstract

Tailoring of plasmon resonances is essential for applications in anticounterfeiting. This is readily achieved by tuning the composition of alloyed metal clusters; in the simplest case, binary alloys are used. Yet, one challenge is the correlation of cluster morphology and composition with the changing optoelectronic properties. Hitherto, the early stages of metal alloy nanocluster formation in immiscible binary systems such as silver and copper have been accessible by molecular dynamics (MD) simulations and transmission electron microscopy (TEM). Here, we investigate in real time the formation of supported silver, copper, and silver–copper-alloy nanoclusters during sputter deposition on poly­(methyl methacrylate) by combining in situ surface-sensitive X-ray scattering with optical spectroscopy. While following the transient growth morphologies, we quantify the early stages of phase separation at the nanoscale, follow the shifts of surface plasmon resonances, and quantify the growth kinetics of the nanogranular layers at different thresholds. We are able to extract the influence of scaling effects on the nucleation and phase selection. The internal structure of the alloy cluster shows a copper-rich core/silver-rich shell structure because the copper core yields a lower mobility and higher crystallization tendency than the silver fraction. We compare our results to MD simulation and TEM data. This demonstrates a route to tailor accurately the plasmon resonances of nanosized, polymer-supported clusters which is a crucial prerequisite for anticounterfeiting.

Gas-phase synthesis of nanoparticles: current application challenges and instrumentation development responses

“…Further, a significant target history effect was also clearly discernible, due to the redepositions. The temporal evolution of the phase separation of immiscible Ag–Cu nanoalloys was followed by another very recent study employing a combination of ex situ (Transmission Electron Microscopy, TEM) and in situ (optical spectroscopy, Grazing-Incidence Small- and Wide-angle X-ray Scattering, GISAXS/GIWAXS) methods, 101 and deducing the effective diffusion coefficients of the two elements (confirming previous simulation results on the same 102 and different systems 103 ). The nanoparticles reported within this study are promising for potential anti-counterfeiting applications.…”

Recent Developments in Plasmonic Alloy Nanoparticles: Synthesis, Modelling, Properties and Applications

“…However, this is not a comprehensive list of the many studies which, to date, involved plasmonic nanoalloys, sometimes also including photodetection, photovoltaics, chemical transformations, linear spectroscopy and circular dichroism. The possibility of tailoring the LSP, offered by alloying, is crucial also for applications in anticounterfeiting and electrochromic color switching [197] …”

“…The possibility of tailoring the LSP, offered by alloying, is crucial also for applications in anticounterfeiting and electrochromic color switching. [197] …”

Revealing the alloying and dealloying behaviours in AuAg nanorods by thermal stimulus

“…Bimetallic nanocrystals have attracted great interest as they offer an extra degree of freedom to fine-tune their structures, phases, and properties in comparison with the elemental ones. Diverse configurations and synergistic effects can be obtained in these nanocrystals, which frequently enable novel functionalities facilitating diverse applications in such as optics, [1][2][3][4][5][6] plasmonics, [7][8][9][10][11][12] catalysis, [13][14][15][16][17][18][19][20] sensor, [21][22][23][24][25][26][27][28] and biomedicine. [29][30][31][32][33] For example, Xu et al have reported that bimetallic AuAg core-shell catalysts show much higher catalytic activity than elemental Au and Ag catalysts in reducing 4-nitrophenol.…”