Nanoplasmonics and surface enhanced spectroscopy

Application of laser ablated gold nanopartisles for enhancing the capabilities of LIBS analysis of stainless steel 
Kiris V.V., Nevar A.A., Butsen A.V., Pakhomenko R.A., Tarasenko N.V.
Plasma Physics Centre, B.I. Stepanov Institune of Physics of NAS of Belarus, Nezalezhnasci Ave. 68-2, 220072Minsk, Belarus. 
E-mail: a.nevar@ifanbel.bas-net.by

Laser-induced breakdown spectroscopy (LIBS) is elemental analysis technique based on recording microplasma spectra that is formed on the surface of the analyzed sample under the action of laser pulses. Recently it was shown that improvement in the analytical characteristics of LIBS can be achieved by deposition of nanoparticles on the surface of the analyzed sample before laser exposure.
In this work, gold nanoparticles synthesized by laser ablation in acetone were used for LIBS signal enhancement during analysis of stainless steel. 
Gold nanoparticles were synthesized by laser ablation in a liquid. The synthesis technique is described in more detail in the paper [1].
For LIBS investigations a Nd3+:YAG laser (1064 nm, 6-8 ns, 10 Hz) was used. Energy varied from 16 to 58 mJ/pulse. The emission spectra were registered by spectrometer coupled with a CCD detector Toshiba 1205D with 2048 photosensitive elements of 14 × 200 µm size. 
The 200 laser pulses were applied for ablation of stainless steel sample to be analyzed and the only last five pulses were accompanied by recording the spectrum after each pulse. The previous laser pulses were used for cleaning of the sample surface. Then 10 μl of the Au nanoparticles solution were deposited by drop-casting to this treated area. After drying five additional laser pulses were applied with registration the spectrum after each pulse. This procedure was repeated ten times. Results were averaged over 10 points.
In the studied wavelength range (280 – 400 nm), a significant enhancement (up to 30 times) was observed only for the first two pulses. It is worth noting that the amplification effect almost disappeared away at the third-fourth pulse. The effect of NELIBS was most strongly observed at low energy densities.
The work was financed by the Belarusian Foundation for Fundamental Researches under Grant F18SRBG-004.

1.	Tarasenko N., Butsen A. Laser synthesis and modification of composite nanoparticles in liquids // Quantum Electronics.-2010.-40.-P. 986-1003.