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Patterning of Metallic Nanoparticles over Solid Surfaces from Sessile Droplets by Thermoplasmonically Controlled
Chalikkara Farzeena1, Subramanyan Namboodiri Varanakkottu2
1School of Materials Science and Engineering, National Institute of Technology Calicut, Kozhikode 673601 Kerala, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 4, 2022
Summary
This study presents a new light-directed method for assembling gold nanoparticles using controlled liquid flow from evaporating droplets. This technique enables precise patterning of metallic nanoparticles, overcoming previous limitations.
Area of Science:
- Nanotechnology
- Materials Science
- Fluid Dynamics
Background:
- Evaporative assembly from sessile droplets is a promising technique for particle patterning on substrates.
- Current methods often require additives or surface modifications and struggle with nanoparticle patterning, especially for metallic nanoparticles.
- Achieving dynamic control over microparticle assembly is possible, but nanoparticle patterning remains a challenge.
Purpose of the Study:
- To demonstrate a simple, light-directed method for patterning gold (Au) nanoparticles using thermoplasmonically controlled liquid flow.
- To investigate the mechanism of particle assembly driven by light-induced thermocapillary flow.
- To explore the potential for creating diverse nanoparticle patterns and hybrid assemblies.
Main Methods:
- Utilizing 532 nm laser excitation to generate a temperature gradient and thermocapillary flow within an evaporating droplet containing Au nanoparticles.
- Employing particle streak velocimetry to analyze the fluid flow dynamics.
- Modulating illumination conditions to control pattern morphology and creating hybrid assemblies with polystyrene (PS) particles.
- Characterizing the assembled structures using optical microscopy, 3D profilometry, and scanning electron microscopy (SEM).
Main Results:
- Light excitation at the plasmonic wavelength induced thermocapillary flow, directing Au nanoparticle assembly at the irradiation zone.
- The thermocapillary flow effectively counteracted natural evaporative convection flows.
- Various pattern morphologies, including center deposit, off-center deposit, multi-spot deposit, and lines, were achieved by adjusting illumination.
- Closely packed hybrid assemblies of Au and PS particles were successfully created, with Au nanoparticles forming ordered structures within PS particle voids.
Conclusions:
- The developed light-directed strategy offers a simple and effective approach for programmable patterning of metallic nanoparticles.
- This method overcomes limitations of previous techniques in nanoparticle assembly.
- The findings significantly enhance the applicability of evaporative lithography for advanced nanoparticle patterning and hybrid material fabrication.
