Although some kind of 3D mapping by registered stacking of 2D maps based on laser ablation of serial consecutive sections has been reported in the literature, this approach is only possible for “soft” material which can be microtomed. Very recently the Analytical Chemistry Laboratory, in collaboration with other institutions, has published a novel 3D mapping technique via a combined rastering / depth profiling approach [1], which allows for direct 3D mapping of “hard” materials. The 3D imaging procedure (see Figure 1) is based on laser drilling on a virtual grid on the surface, followed by extraction of depth maps along the z axis (for each element monitored). Using a burst of 50 laser pulses at 1 Hz on each point of the grid, a penetration rate of ca. 150 nm per pulse (in glass) was obtained and a lateral resolution in the order of the laser beam diameter. By ultrafast ICP-MS monitoring of individual ablation pulses (58 ms for a set of 19 elements) using a laser ablation cell with fast signal washout, the corresponding peak areas could be consistently integrated, resulting in spatial elemental data associated with individual pulses. After manipulation of the spatial elemental data sets and quantification, stacks of 50 2D depth maps (for each element monitored) were produced which could be visualized as volume images or time-lapsed movies (Figure 2).

Figure 1: Workflow for retrieval of 3D imaging data from laser ablation - ICP-MS analysis of the weathered area on a corroded archaeological glass artifact, illustrated for Na/Na2O (lower concentrations, “cool” colors; higher concentrations, “hot” colors). LA: NWR UP-213; ICP-MS: Agilent 7500ce

Figure 2: 3D images of the surface layer of an ancient weathered glass can be viewed for 19 elements simultaneously as time-lapsed movies (in avi format) with continuous scrolling in 50 steps (from the surface [step 1] to a depth of 7.5 μm [step 50]).

References

  1. ELTEREN, J.T. van, IZMER, A., ŠALA, M., ORSEGA, E.F., ŠELIH, V.S., PANIGHELLO, S., VANHAECKE, F. 3D laser ablation-ICP-mass spectrometry mapping for the study of surface layer phenomena : a case study for weathered glass. Journal of analytical atomic spectrometry, ISSN 0267-9477, 2013, vol. 28, issue 7, str. 994-1004. http://pubs.rsc.org/en/content/articlelanding/2013/ja/c3ja30362d, doi: 10.1039/C3JA30362D.