Sitting Down With… Joel M. Harris, Distinguished Professor Emeritus in the Department of Chemistry at the University of Utah, USA.
Did you always know you wanted to be a scientist?
My father was a PhD organic chemist, so I was exposed to science early in life. I remember once when he brought home a microscope from the lab, and we sampled some water from our dog’s water dish outside. I was completely fascinated by all the microscopic organisms swimming around in that sample. Perhaps it’s not surprising that microscopes became a tool that my lab adapted for doing spectroscopy in small volumes in the past two decades.
My serious interest in science began when my father’s colleague – Warren Wise, an analytical chemist – gave me some surplus optics from Edmund Scientific. He also introduced me to electronics through Heathkit, which sold educational electronics kits.
I then started experimenting with optics and imaging and learning radio frequency electronics. As a young teenager, I built a super-heterodyned shortwave receiver, which taught me principles of signal mixing and isolation, noise rejection, and phase-sensitive detection.
When I started graduate school at Purdue and joined Fred Lytle’s lab, developing time-resolved spectroscopy methods with optics, pulsed lasers, and high-speed detectors, it felt like a return to my childhood, and I’ve stayed there ever since.
Did you have a (healthy) rivalry with your father?
I’m grateful that my father’s field was different enough from mine, so that I never really felt I was competing with him. He worked in research and development in the rubber chemical industry, developing compounds that improved tire wear and longevity.
Six months before I joined the faculty at the University of Utah, my father retired from industry at the age of 55. He had been offered a promotion that would have required relocation and more travel, so he declined the offer and started a second career in teaching. He accepted a position on the chemistry faculty of a small HBCU in South Carolina. Six months later, I began my teaching career at Utah, so we started teaching careers about the same time.
My father went on to teach for 20 years, and during those decades, we shared a lot of stories about preparing lectures, writing exams, developing laboratory exercises, and dealing with students. So rather than any kind of rivalry, we had a great deal to share during those 20 years.
How did your research interests evolve over the course of your career?
My early research at Utah, building on the work I did in Fred Lytle’s lab, was focused on time-resolved laser spectroscopy. My group studied electronically excited states of molecules and used their radiative and non-radiative decay pathways for detection and analysis. We developed fluorescence lifetime measurement techniques and new methods of photothermal spectroscopy, where heat generated by non-radiative decay could be detected through changes in the refractive index of the sample. With photothermal methods, we could detect ultra-trace level concentrations of non-fluorescent molecules and even follow decay pathways through the evolution of heat deposited in the sample.
About five years into my career, I started a collaboration with my former undergraduate advisor, Charles Lochmüller at Duke University, and began developing methods to probe the chemistry of liquid-solid interfaces. Lochmüller was studying the structure of liquid chromatographic stationary phases using fluorescent reporter molecules attached to silica surfaces. Since my lab had been developing nanosecond fluorescence lifetime measurements, we began applying time-resolved fluorescence techniques to investigate the kinetics of molecules at liquid-solid interfaces.
That work launched a 45-year quest to characterize the composition, reaction kinetics, and structure of molecules at the boundary between solids and liquids. Those interfaces are critically important in analytical chemistry. They govern chemical separations, modification of surfaces, immobilized ligands and their interfacial reactions, and surface-based biosensing.
Liquid-solid interfaces are difficult to study. There are comparatively few molecules at an interface relative to the bulk solution, so one needs high sensitivity to detect them. One also needs spatial selectivity so that the measurement is dominated by molecules at the interface, rather than being overwhelmed by molecules in solution. Quantification is another challenge. We routinely report solution concentrations based on the response of standard samples of known concentration. It is much harder to report concentrations of molecules at interfaces (molecules per unit area) because of the difficulty in preparing standard samples of known surface concentration.
The combination of scientific importance and measurement difficulty provided fertile ground for asking questions and developing new quantitative methods. The quest has been to understand interfacial chemical processes, where the measurement itself is a large part of the challenge.
Is there one contribution from your career that stands out as particularly satisfying?
One of the most satisfying breakthroughs was developing the capability to count individual molecules in order to quantify molecular populations at liquid-solid interfaces. We accomplished this using total internal reflection fluorescence microscopy, which confined the excitation to the interface. That allowed us to image fluorescent molecules at the interface and quantify their populations in fluorescence images.
To do that, we needed to distinguish the signal from a molecule versus detector noise. We used spatial criteria based on the diffraction limits of the microscope: if a spot in a detected image came from a fluorescing molecule, its size and shape were governed by diffraction characteristics of the microscope objective. That allowed us to develop spatial criteria to reject detector noise and lower the threshold well into the noise floor of the camera while still avoiding counting false events which would not satisfy the spatial criteria. As a result, we could quantify interfacial molecular populations by simply counting molecules.
Because we were interested in chemical kinetics at these interfaces, we also acquired movies and could observe individual molecules reacting at a surface and determine rates of reversible interfacial reactions. We applied this concept to measuring adsorption/desorption kinetics, peptide binding to lipid bilayers, and reactions of immobilized DNA strands. This was a very satisfying accomplishment, and it could not have been achieved without a focus on quantitative analysis of interfacial molecular populations.
Would you say your career has been driven more by curiosity, impact, or some combination of the two?
When writing a proposal, one is required to explain how the work might be applied and its potential impact. What was motivating for me, however, was doing experiments driven by curiosity and grounded in fundamental questions, where the findings might lead to chemical insight and deeper understanding of measurements.
The findings from such experiments connect to teaching. Whether writing a manuscript or giving a conference talk, the results could be used to teach new principles of measurement and new insights about interfacial chemistry. And perhaps that was the motivation of the work that I sought – a chance to do some teaching of new concepts.
What kind of research environment did you try to create for your students?
As a graduate student, my advisor – Fred Lytle – allowed me a great deal of freedom to try new ideas in the research lab. That experience shaped me, and I wanted that same kind of freedom of inquiry within my research group.
A way of achieving this goal was by keeping the group relatively small. I usually had five or six graduate students, but with enough support for every student to have their own unique project and responsibilities. Importantly, each student also had their own optical table and experimental setup. The goal was to create an environment where each student had the freedom to build and modify their own instrument, try new ideas, and make mistakes without impacting the progress and success of others.
That approach meant my lab did not produce a large number of publications, but a smaller group allowed me to participate in discovery and to share in the excitement of new experiments. Some of those experiments were based on ideas I was openly skeptical about – and the students had the freedom to prove me wrong, and they often did!
I believe that large research groups are harder to manage in that respect. In a large group, students may interpret unexpected results simply as mistakes, when there may actually be something important hidden in those observations. Discovery often happens at the edges of expectation, and that was exactly where I wanted to be. It was never about professional success or adding to my CV – it was about figuring things out.
Did you ever seriously consider an alternative career path within science?
As I was finishing graduate school, I interviewed in both industry and academia. But my heart was always in the latter – largely because of the pleasure I found in teaching and working with students.
At the time, in the mid-to-late 1970s, industry still supported fundamental research, so there were opportunities to make discoveries there. Those discoveries needed to connect eventually to a profitable product, but the fundamental science was still important. I’ve had students who went into industry and made very important fundamental discoveries, and those discoveries ultimately drove major advances in products and technologies. Their grounding in fundamental science helped them enormously, even in an applied environment.
I could have had a fulfilling career in industry. However, when the University of Utah offered me an appointment as their first faculty member in analytical chemistry, I realized this was a rare opportunity. The offer came with an expectation that I would develop undergraduate courses in analytical chemistry and start a graduate program in this area. While this was a major responsibility, the department gave me the freedom and support needed to make it a successful endeavor.
I joined the faculty at Utah straight out of graduate school, starting my appointment just four days after defending my dissertation. With no time to adjust to being a faculty member, I never felt like I left graduate school – I was still a student, just earning better pay. With the freedom to write new courses, build a research lab, and work with graduate students, I never worried about tenure. I was too busy and having too much fun to think about it.
Having seen analytical science develop over several decades, has the field evolved in the way you expected?
I think the field has done brilliantly well. The capabilities of modern instruments and the complexity of the problems now being solved would have been difficult to imagine 50 years ago.
What’s fun, though, is that the core principles of measurement science haven’t changed. The tools have expanded dramatically, from control systems and engineering to the sophistication of the ways we probe complex systems, especially in biology. But underneath it all, the fundamental measurement principles remain. So despite no longer running a lab, I still love going to seminars and hearing about new applications of those principles.
Fifty years ago, I would not have been able to predict where we would be today, and that means I shouldn’t try too hard to extrapolate into the future. Ultimately, the direction of the field will be shaped by the cleverness and creativity of thousands of brilliant people working on new problems. So I won’t speculate too much, but I will keep going to seminars so I can learn about the future as it unfolds.
As you move into retirement, what do you think you’ll miss most?
I miss teaching. In undergraduate courses, I always incorporated an independent project into the laboratory. Students would write proposals for a chemical analysis project of their own design. After consulting with them and helping them to refine their plans, they would carry out their analysis, typically involving environmental samples, consumer products, food and beverages, sometimes pharmaceuticals.
What I really enjoyed was working alongside them in the lab while they solved problems. That experience was rewarding because I was no longer the adversary, standing in front of the class asking questions. Instead, the students asked the questions, and the chemistry became the mystery, and we were both on the same side of the bench trying to figure things out together.
This was a wonderful way to teach measurement science and to build close working relationships with undergraduates. It was very time-consuming, but extremely rewarding, and I do miss it.
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