Synthesis by picosecond laser ablation of ligand-free Ag and Au nanoparticles for SERS applications
Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra (MIFT), Università di Messina, 98166 Messina, Italy
2 CNR-Istituto per i Processi Chimico-Fisici, 98158 Faro Superiore, Messina, Italy
3 Dipartimento di Chimica, Materiali ed Ingegneria Chimica "G. Natta”, Politecnico di Milano, Milano, Italy
4 Dipartimento Energia & Centre for NanoEngineered Materials and Surfaces -NEMAS, Politecnico di Milano, 20133 Milano, Italy
* Corresponding author: email@example.com
Published online: 9 January 2018
The morphological and optical properties of noble metal nanoparticles prepared by picosecond laser generated plasmas in water were investigated. First, the ablation efficiency was maximized searching the optimal focusing conditions. The nanoparticle size, measured by Scanning Transmission Electron Microscopy, strongly depends on the laser fluence, keeping fixed the other deposition parameters such as the target to scanner objective distance and laser repetition frequency. STEM images indicate narrow gradients of NP sizes. Hence the optimization of ablation parameters favours a fine tuning of nanoparticles. UV-Visible spectroscopy helped to determine the appropriate laser wavelength to resonantly excite the localized surface plasmon to carry out Surface Enhanced Raman Scattering (SERS) measurements. The SERS activity of Ag and Au substrates, obtained spraying the colloids synthesized in water, was tested using crystal violet as a probe molecule. The good SERS performance, observed at excitation wavelength 785 nm, is attributed to aggregation phenomena of nanoparticles sprayed on the support.
© The Authors, published by EDP Sciences, 2018
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