Smaller nanoparticles vaporize more efficiently, yet larger ones give a stronger LIBS signal overall.
Why does total atom count win out, and what does that mean for applications like biomedical tagging, where particle size is already constrained?
The other two papers focused on two applications, one with LIBS and one with inductively coupled plasma–mass spectrometry (ICP-MS), laser ablation ICP-MS to be specific.
And I think that laser ablation is getting very mature for very advanced applications, and these papers show exactly this.
You’re also presenting your team’s in-flight LIBS system, mounted on a drone.
This is something that is not studied as deeply as the typical plasma characteristics. I think that this is something the community should be more focused on.
Smaller nanoparticles vaporize more efficiently, yet larger ones give a stronger LIBS signal overall. Why does total atom count win out, and what does that mean for applications like biomedical tagging, where particle size is already constrained?
Fortunately, smaller nanoparticles have a very high efficiency of vaporization, so they become mostly emitters. But clearly, the bigger nanoparticles have a higher amount of atoms, and they are more useful where the sensitivity of the technique is concerned.
At the same time, we should keep in mind that when we are tagging, for example, exosomes, which are particles that can be 100 nm or even smaller, we also have to keep in mind the steric effect that these nanoparticles could have. Therefore, you have to choose a nanoparticle that allows you to tag your system. Maybe you can do a multiple tag, which means multiplex analysis. In that case, you cannot use such big nanoparticles. It's always a compromise, depending on which kind of tag we are looking for.
As Editor-in-Chief of Spectrochimica Acta Part B, you organize the SAB session at SciX each year to honor the journal’s three best papers. What stood out to you in this year’s selections?
The selection is done by the whole editorial board and team. I'm talking about 35 international members of this jury. This year, one paper was selected that was very technical, on the use of intensified charge-coupled devices (ICCDs) , and it's aimed at making correct use of the instrumentation. The other two papers focused on two applications, one with LIBS and one with inductively coupled plasma–mass spectrometry (ICP-MS), laser ablation ICP-MS to be specific. And I think that laser ablation is getting very mature for very advanced applications, and these papers show exactly this.
You’re also presenting your team’s in-flight LIBS system, mounted on a drone. How does your self-calibrated approach make quantitative measurement possible despite flight vibration and refocusing lag?
The idea of using LIBS in a drone is not new. However, until now, there has not been an operating system because you have two main problems when you deal with a drone. The first is the positioning, which depends on the satellite connection and consequently has an uncertainty that, in the best case, can be some centimeters.
Then, we have to take into account that during the flight, we have oscillation and tilting, so using the traditional approach, based on the comparison of the measurement with some reference measurement, is not possible because you never know exactly. You are not able to reproduce your standard experiment exactly. With this self-calibration, everything is done in the measurement, so all the information, including the instrumental calibration and the quantification of the elements, comes directly from the measurement of the signal.
This gives a huge freedom in the use of the drone. I think this is why this is the first—from what I know, at least—the first operating system able to do in-flight measurements with quantitative information that is very acceptable, down to 0.1%.
We can detect even ppm, but we are not able to quantify with this method. But for drone applications, your sample is not just a few centimeters; we are talking about kilometers, so it is not that important to have such a small accuracy because the sample is so wide that if you shoot one meter after, you have a different composition, and you're interested in having an overview of the field that you are flying over.
What would you tell a student trying to build a career that spans both fundamental plasma physics and applied instrument development, the way yours has?
I've been a professor for 27 years, so for me, this is a very important question. The students should be formed on the fundamental aspects of science; sometimes, there is a trend of going directly to the application because now we have high-end technology, but this allows you to exploit a spectroscopic technique for several applications. It does not allow you to have an idea that can be a real revolution, so this is what we should teach our students because we don't need evolutionary work forever. We need revolutionary work. This is a crucial point that the institutions should understand when they manage students.
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