Prof. John Costello awarded an SFI IvP award for €640,000 for a project entitled: "Stagnation Layers in Laser Based Analytical Techniques"

Prof. John Costello from DCU's School of Physical Sciences has been awarded an SFI IvP award for €640,000 for a project entitled: "Stagnation Layers in Laser Based Analytical Techniques"

Laser ablation, leading to heated and partially ionized plasma plumes, underpins a number of key commercial analytical techniques employed across a wide range of domains including materials science, biopharmaceuticals, security/forensics, environmental monitoring, etc - namely LIBS, LA-ICP-MS and MALDI-TOF-MS. 

LIBS or laser induced breakdown spectroscopy allows elemental classification and quantification by analyzing the radiation emitted from a laser-produced plasma formed on the surface of (usually) a liquid or solid sample. LIBS can provide a limit-of-detection or LOD down to a few parts per million (ppm). 

In LA-ICP-MS or laser ablation-inductively coupled plasma-mass spectrometry, the laser plasma plume forms the traditional atomization step in ICP-MS, while the plume constituents are transported to the ICP torch via a flowing gas. One of the most recent developments in this technique is the 'designed formation' of nanoparticles in this 'atomization' step. It is well known that femtosecond laser plasmas tend to preferentially generate nanoparticles and so it is no surprise that this approach is now already employed in commercial LA-ICP-MS by e.g., Applied Spectra Inc. LA-ICP-MS improves significantly on LIBS to achieve a LOD in the parts per billion (or ppb) range, but it does so at an increase in both cost and complexity. However, we already have very preliminary evidence that nanoparticles are preferentially formed by colliding (nanosecond) laser produced plasmas in gases. Hence colliding plasmas in an ambient gas atmosphere could lead to a significant simplification of the laser ablation step over the femtosecond laser driver case and a concomitant reduction in cost. This will be just one area of laser ablation exploration and development tackled in the current proposal. 

In MALDI-TOF-MS or matrix assisted laser desorption ionization, combined with time of flight mass spectrometry, a biomolecule of interest, e.g., a protein is fixed in a protective host material (the matrix) and irradiated by an intense (usually) UV laser pulse. In recent years the technique has been enhanced by extension to mass spectrometric imaging or MSI [9]. The molecule of interest has to be fixed at very low density in the protective matrix limiting the MALDI signal. Although all of these techniques deal with entities of hugely different masses, they are each connected by a common entity - the plasma plume formed at the focus of a laser on the sample surface. The overarching goal of this proposal is to significantly increase the key performance parameters of LIBS, LA-ICP-MS and MALDI TOF by substituting the single ablated plasma plume by a stagnation layer of controllable density, temperature, geometry, composition, etc. formed at the collision front between two (or more) counter-propagating plumes.