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<p>In the paper, a chemical-free, lithography-free route is reported for producing tunable bimetallic Au–Ag nanoparticles via nanosecond laser ablation of pre-deposited thin Au–Ag bilayers on BK7 glass. By systematically varying laser fluence, pulse number, bilayer thickness ratios (50:50 and 25:75), and employing the second harmonic of an Nd: YAG laser, the controlled transformation of thin films into curved, non-spherical bimetallic nanostructures with circular cross-sections is demonstrated. Morphological analysis reveals that nanoparticle height exceeds radius on BK7, indicating departures from spherical symmetry under the chosen processing conditions. Optical measurements reveal that LSPR features shift to longer wavelengths (up to ~ 800&#xa0;nm) as nanoparticles evolve, accompanied by sharper and more intense peaks under optimized fluence and pulse regimes. Notably, samples with higher silver content, which were provided by irradiation of bimetallic films with an Ag: Au thickness ratio of 75:25, exhibit sharper LSPR resonances than 50:50 films, attributed to the plasmonic contribution of silver. Complementary theory and simulation based on solving the heat equation by generalized finite-difference time-domain (G-FDTD) modeling provide insight into melting, ablation thresholds, etc. Our results indicate that laser-processed Au–Ag nanoarchitectures offer a chemical-free pathway for LSPR-guided sensing and plasmon-enhanced spectroscopy, with tunable optical responses and potential scalability. This work establishes a framework for integrating bimetallic plasmonic substrates into label-free sensing, SERS, and related photonic applications while aligning with sustainable development goals through reduced chemical waste and environmental impact.</p>

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Chemical-free method to produce Au–Ag bimetallic nanostructures on a glass substrate by nanosecond Nd: YAG laser pulses

  • 期刊论文

  • 发表日期：

    2026年5月21日

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  • Nader Javanmard,
  • Mahdi Sovizi,
  • Maryam Aliannezhadi

摘要

In the paper, a chemical-free, lithography-free route is reported for producing tunable bimetallic Au–Ag nanoparticles via nanosecond laser ablation of pre-deposited thin Au–Ag bilayers on BK7 glass. By systematically varying laser fluence, pulse number, bilayer thickness ratios (50:50 and 25:75), and employing the second harmonic of an Nd: YAG laser, the controlled transformation of thin films into curved, non-spherical bimetallic nanostructures with circular cross-sections is demonstrated. Morphological analysis reveals that nanoparticle height exceeds radius on BK7, indicating departures from spherical symmetry under the chosen processing conditions. Optical measurements reveal that LSPR features shift to longer wavelengths (up to ~ 800 nm) as nanoparticles evolve, accompanied by sharper and more intense peaks under optimized fluence and pulse regimes. Notably, samples with higher silver content, which were provided by irradiation of bimetallic films with an Ag: Au thickness ratio of 75:25, exhibit sharper LSPR resonances than 50:50 films, attributed to the plasmonic contribution of silver. Complementary theory and simulation based on solving the heat equation by generalized finite-difference time-domain (G-FDTD) modeling provide insight into melting, ablation thresholds, etc. Our results indicate that laser-processed Au–Ag nanoarchitectures offer a chemical-free pathway for LSPR-guided sensing and plasmon-enhanced spectroscopy, with tunable optical responses and potential scalability. This work establishes a framework for integrating bimetallic plasmonic substrates into label-free sensing, SERS, and related photonic applications while aligning with sustainable development goals through reduced chemical waste and environmental impact.