In order to realize sensitive elemental analysis of bismuth brass, especially under minimal sample ablation or high spatial resolution, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) in reheating scheme was studied. In the experiments, two electro-optically Q-switched Nd:YAG lasers were selected as the laser sources and their output beams were aligned orthogonally. The first laser was used to produce sample plasma and the second reheating laser was used to produce KHCO3 target plasma. The spectra were recorded with a compact spectrometer coupled with non-intensified CCD detectors. Bismuth brass samples were analyzed while 3 mJ and 30 mJ pulse energies were selected for the ablation and reheating laser pulse, respectively. Up to two-orders signal enhancement has been observed if compared TEODP-LIBS with LIBS without target-enhanced excitation. The calibration curves of bismuth and tin have been built in both TEODP-LIBS and LIBS analysis. 89 and 1002 ppm detection limit for bismuth and tin has been determined by TEODP-LIBS. And 6.5 and 3.8 enhancement factors have been achieved if compared with LIBS. Potential sensitive elemental analysis under high spatial resolution using TEODP-LIBS will be possible after optimizing the focusing condition.
Micro-laser-induced breakdown spectroscopy (μLIBS) has very important applications in elemental microanalysis of different samples. However, with the decreasing of ablated sample mass and plasma temperature, the detection sensitivity of μLIBS will decrease significantly. In order to solve this problem, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy (TEODP-LIBS) using an aluminum target was investigated in this work. In the experiments, 532 nm laser pulses with 12 ns pulse width were focused on the brass sample surface by a 10x microscope objective to ablate the sample; time-delayed 1064 nm reheating laser pulses with 12 ns pulse width were focused on the surface of an aluminum target to produce target plasma. The ablated sample was reheated and further broken down by this orthogonal target plasma and enhanced atomic emissions of the sample elements could be observed. The emission spectra were recorded with a compact spectrometer coupled with non-intensified charge-coupled device (CCD) detectors. The intensities of the optical emissions of the sample elements in μLIBS, ODP-LIBS as well as TEODP-LIBS were compared. Up to 3 orders and 16-folds signal enhancement have been observed in TEODP-LIBS if compared with μLIBS and ODP-LIBS, respectively. It is demonstrated that TEODP-LIBS is able to give much higher enhancement factor on the signal intensity than ODP-LIBS. TEODP-LIBS is able to significantly improve the detection sensitivity of μLIBS under minimal sample ablation and find important applications on the elemental microanalysis of different samples.
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