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Fields & Applications Spectroscopy

Ten Year Views: With Vassilia Zorba

To commemorate our 10th anniversary, we’re reflecting on the field of analytical science – speaking with leading figures and friends of The Analytical Scientist to understand how far the field has come over the past decade, what lessons have been learned, and where we go from here. In this installment, Vassilia Zorba, Group Leader for Laser Technologies Group at Lawrence Berkeley National Laboratory, and Associate Adjunct Professor in Mechanical Engineering at the University of California, talks us through the benefits of laser implementation in analytical science – and what the future holds for spectroscopy…

In your opinion, what has been the most significant development in spectroscopy over the past 10 years?

It’s difficult to pin down just one, as there have been so many great developments during that time. There have been some interesting advancements in nonlinear optics and their integration in the field of analytical chemistry. Specifically, the use of nonlinear ultrafast laser-matter interactions in the laser plasma formation regime, which has been instrumental in addressing issues like improving spatial and depth resolution. We’ve also made advances in our ability to propagate pulsed laser beams and deliver energy at long distances. With this development, we’re now able to suppress diffraction, which allows us to concentrate pulsed laser energy to a target at a remote location. This discovery has been a critical component in our ability to generate plasmas for remote spectroscopy applications.

Another pivotal moment has to be the ChemCam mission to Mars. This was a very challenging problem to tackle and ChemCam’s success has been extremely beneficial for the field of laser-induced breakdown spectroscopy (LIBS). This tremendous milestone has demonstrated the amazing possibilities of LIBS as well as introducing its capabilities to a wider audience. We’ve seen the flexibility of the technique and what can be achieved – which has encouraged many researchers to use LIBS in their work. Seeing such advancement in technology is always an exciting moment.

What are some of the key applications for lasers?

Energy conversion and storage are significant application areas – laser spectroscopy allows us to understand variations of chemical composition in solar cells and Li-ion batteries. Researchers have also been looking at biomedical imaging with laser spectroscopy, including LIBS.

Personally, I favor the recent direction towards all-optical isotopic techniques, which unlock completely different types of applications. The development of the laser ablation molecular isotopic spectrometry (LAMIS) technique in particular has opened up new horizons in terms of what is possible for many different areas in biomedical and environmental research. When it comes to nuclear security, the ability to detect isotopes optically is incredibly important for measuring the levels of enrichment in nuclear safeguards and forensics. Isotope ratio mass spectrometry has shown the tremendous information we can gather regarding when or where something was made – based on high precision measurements of Isotopic ratios. Transitioning even a few of these isotopic ratio measurement capabilities from mass spectrometry to laser spectroscopy can be a real game-changer for rapid analysis in the field.  It all comes down to the level of precision; for some applications, laser spectroscopy can already do very well – for others requiring very high levels of precision we’re not quite there yet, but we’re getting closer!

What about your own work with next-gen laser tools?

In the past, I worked on the utilization of ultrafast LIBS to analyze lithium ion batteries with high resolution. This involved using three-dimensional imaging to look at the composition of minor elements in complex matrices. Additionally, by looking at interfacial layers as thin as 50 to 100 nanometers, we can understand how chemical reactions during battery charging can affect the macroscale battery performance after electrochemical cycling.

More recently, I’ve been looking into applications in nuclear security and nonproliferation. By using ultra-fast laser tools and advanced optics, we can propagate a pulsed laser beam over long distances for remote sensing from solids. There are multiple forms of interesting spectroscopic information we are only now able to unveil as some of the technology components are becoming more mature. A lot of work goes into manipulating beam propagation and phase wavefront – for example, using laser filaments or orbital angular momentum beams to deliver a high amount of energy across a remote distance. The pulsed laser energy must be high enough to form a plasma from a solid sample so we can extract elemental and isotopic information. 

You mentioned lithium ion batteries – how can analytical science help us here?

In the semiconductor industry, we know that there is very tight control in standardization of the process – for example, fabrication is performed under clean room conditions. However, this is not the case for battery manufacturing – which means that batteries can often work successfully despite the presence of impurities or compositional variations. 

But when it comes to large format applications, such as electric vehicles, we need to better understand the composition of raw materials to be able to control the macroscale battery performance. Once you start charging a battery, electrochemical reactions take place which adds a layer of complexities. Understanding composition and mapping variations of composition as a function of space and depth can give electrochemists clues to making better batteries. This includes battery components such as anodes, cathodes, solid state electrolytes, and interfacial layers formed on battery electrodes.

What is most exciting to you about the future of spectroscopy?

A new concept that has been introduced in the laser-metal interaction community, which is called cold ablation or ablation cooling. Thanks to tremendous developments in laser technology, we have the capability to produce gigahertz (GHz) bursts of femtosecond laser pulses – these are nanosecond-spaced series of pulses of femtosecond duration. Recent research looked into the mechanisms of GHz burst ablation with femtosecond pulses for the first time, and the results showed significant differences to traditional femtosecond plasmas – both in terms of expansion of the ablation ejecta and what we do on the surface. I think this is a very exciting direction to go into – and it offers possibilities for improving our spatial and depth resolution even more as well as improving our analytical performance as a whole.

What would you personally like to achieve in the next 10 years?

I have two main goals. The first is to fuse advanced optics and nonlinear concepts with analytical spectroscopy to improve current capabilities in cross cutting applications. The second involves training the next generation of scientists to drive further progress in the spectroscopy field. Specifically, I want to make the field more appealing for students by giving them a taste of the possibilities within spectroscopy.

What advice do you have for someone who is new to the field of analytical science?

Perseverance is the number one thing to learn. It’s also useful to keep an open mind about learning and fusing different concepts – even those from other disciplines. Research is becoming more interdisciplinary, and by incorporating a diversity of ideas and principles from chemistry, physics, and engineering, you could unlock a multitude of possibilities. Overall, being prepared to work hard and not being afraid to expand your scientific horizons will help you advance in your career and contribute to the field.

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About the Author
Vassilia Zorba

Group Leader, Lawrence Berkeley National Laboratory, Berkeley, California, USA.

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