Optimally enhanced optical emission in laser-induced breakdown spectroscopy by combining a cylindrical cavity confinement and Au-Nanoparticles action

In order to study the characteristics of laser-induced breakdown spectroscopy(LIBS), the optimal size of cavity(D = 5 mm, H = 4 mm) was obtained using the aluminum cylindrical cavities with different diameters (from 2 mm to 6 mm)and heights(from 1 mm to 6 mm) in LIBS and the optimal size of Au-NPs(D = 20 nm) was obtained by depositing Au-NPs (10 nm, 20 nm, 30 nm in particle diameter) on the shot of pure copper sample surface that was cleaned by laser. The enhancement factor is about 22.5, 5.4, 34.3 under the confinement of the optimal cavity, the action of the optimal Au-NPs and the combination of the optimal cavity and optimal Au-NPs, respectively. The plasma temperatures, and SNR, were calculated and researched under different conditions. Experiments have shown that cavity confinement can increase the electron temperature of the plasma, while under the Au-NPs action, the electron temperature hardly changes. Compared with zero confinement, Au-NPs action and cavity confinement can all improve the SNR of the plasma spectrum, but the SNR is the best with the combination of the optimal cavity and optimal Au-NPs. The enhancement principle was analyzed by shock wave theory and properties of Au-NPs.