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Chemical Engineering

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The shortness of time . . .

| By Gerald Ondrey

As I get older, time seems to get shorter. Although many experience this feeling, the duration of time is not changing, only our perception of it. However, in the five decades I have been involved in science, the timescale at which we are able to measure phenomena has shortened by nine orders of magnitude.

When I was in college and graduate school, nanosecond (10–9 s) laser pulses were used to study molecular dynamics. For example, you could measure how long it took, after absorbing a photon, before a molecular bond was broken and the parts flew away from each other. Towards the end of my academic career, the duration of laser pulses had shortened to picoseconds (10–12 s) and femtoseconds (10–15 s). It was in 1999 that Ahmed Zewail from the California Institute of Technology received the Nobel Prize in Chemistry for his studies of the transition states of chemical reactions using femtosecond laser spectroscopy.

The 2023 Nobel Prize in Physics announced last month was about time, and the fact that the measurement timescale in physics and chemistry really is getting shorter over the years, and is now at the attosecond scale (10–18 s). It was for their ability to generate and measure attosecond laser pulses that the three winners — Anne L’Huillier, professor at Lund University; Ferenc Krausz, director at the Max Planck Institute of Quantum Optics and professor at Ludwig-Maximilians-Universität Munich; and Pierre Agostini, professor at The Ohio State University — were awarded the 2023 Physics Prize. With attoseconds, it is now possible to monitor the dynamics of the electrons within atoms or molecules.

One cannot predict the impact such research will have on the chemical process industries (CPI). For sure, the ability to study the motion of electrons is of interest today, with the growing importance of electrochemistry and materials science. The more we understand — at the fundamental level — how matter interacts with light and how electrons move in and out of molecules, the better will our chances be of developing the next generation of solar cells, electrolyzers and electronic devices. One only needs to look at the advancements in sensor technology and the role lasers play in gas detectors to see today’s “fruits” of yesterday’s basic research. The addition of attosecond spectroscopy to our analytical toolbox will certainly find its practical applications — it is only a matter of time.


… and space

As the measurement timescale has shrunk, so has the size of the particles in chemical powders. The 2023 Nobel Prize in Chemistry was awarded for the discovery and synthesis of quantum dots — nanoparticles that are so small that their size determines their physical properties, which are governed by quantum mechanical effects. The winners for the prize are Moungi Bawendi, professor at the Massachusetts Institute of Technology; Louis Brus, professor at Columbia University; and Alexei Ekimov, former chief scientist at Nanocrystals Technology, Inc. Their pioneering work over the last 20–30 years is already bearing fruit, with many commercial applications of quantum dots already realized, such as in computer and television screens, in some light-emitting diodes for illumination, and in biomedical applications for mapping cells and organs. A lot of research is underway to further develop other applications, such as in photocatalysis. (For more on quantum dots, see Chem. Eng., April 2019, pp. 14–17). ■

Gerald Ondrey, Senior Editor