Bob Curl died on July 3, 2022. He is perhaps best known as a member of the team at Rice University that in 1985 discovered the carbon-60 molecule buckminsterfullerene and the class of all carbon molecules known collectively as the fullerenes. C60, which came to be known as buckyball, was found to spontaneously assemble from hot carbon vapor. This finding not only opened up a new chapter in the science of carbon, but it also prompted the search for other nanomaterials, ultimately providing an early foundation for the fields of nanoscience and nanotechnology.
Curl was born in 1933 in Alice, Texas. He was the son of a Methodist minister and spent much of his youth moving between small towns in South Texas. At age 9 he received a chemistry set for Christmas. Curl wrote that “within a week, I decided to become a chemist.” He attended Rice University (which charged no tuition at the time), and received a Bachelor of Science in Chemistry in 1954. Bob traveled to UC Berkeley to do his PhD[?] work in the physical chemistry laboratory of Kenneth Pitzer, where he investigated the thermodynamic properties of fluids. Pitzer helped him secure a postdoctoral fellowship in E. Bright Wilson’s microwave spectroscopy lab at Harvard, after which he returned to Rice as an Assistant Professor of Chemistry in 1958, where he remained for the duration of his career.
Bob built a molecular spectroscopy program that evolved over time from a focus on fundamental microwave studies of small molecules to technically demanding laser spectroscopies of transient species, including free radicals. Whenever a new radiation source made a previously unavailable frequency range accessible, Bob was ready with an interesting molecular physics problem, often utilizing quantitative spectroscopic measurements to address the thermodynamic properties of gases or to identify important reaction intermediates.
Bob delighted in collaborating with his peers, including his Rice colleagues Frank Tittel, Graham Glass, and Philip Brooks. Among the many scientists that Bob met outside the walls of Rice, he was particularly fascinated by Harry Kroto, who had built a molecular spectroscopy lab at the University of Sussex in the UK and was studying a unique class of transient cyanoacetylene molecules of composition H-(C)n-C≡N, which were hypothesized to form in the clouds of carbon rich stars.
In 1976 Rick Smalley brought to Rice the technology of supersonic molecular beams, which he had developed as a postdoctoral fellow in the University of Chicago laboratory of Donald Levy and Lennard Wharton. Molecules entrained within supersonic beams could be readily cooled down to a few degrees Kelvin, thus dramatically simplifying the associated molecular spectra, and opening up new physical chemistry studies of increasingly complex molecules. Among these complex molecules were clusters of refractory materials. Rick had found that molecular beams of such clusters could be formed through the laser vaporization of an appropriate target placed in the throat of a supersonic nozzle. Rick teamed up with Bob to collaborate on this unusual and exciting research. Bob knew of a problem for which this technique was ideally suited, and so he invited Harry Kroto to visit Rice. Bob’s basic hypothesis was that Rick’s cluster experiment might emulate the astrophysical conditions that yielded the cyanoacetylenes. One of us (JRH) was a graduate student in the Smalley lab and worked with Harry on these experiments, which led to the discovery of C60 and the fullerenes. Our experiments almost immediately established that C60 was a uniquely dominant carbon cluster with a lack of chemical reactivity that suggested it had no reactive ‘edges’, as might be expected from a (flat) graphene fragment. While Harry, Rick, and I had all spent an evening thinking about possible C60 molecular structures, it was Rick who came into the lab on a Tuesday morning with a beer-stained paper model of C60. Most of us were convinced that this simple structure had to be the explanation behind our striking data set. However, Bob’s nature was scientific caution. He worked that day to convince himself (and us) that C60 had at least some degree of resonance stabilization, similar to the Kekulè structure of benzene. We viewed Bob as our ‘insurance policy.’ If we could convince Bob of something, then we were probably right! For this discovery, and for its eventual role in launching the field of nanotech, Harry, Bob and Rick received the 1996 Nobel Prize in Chemistry.
Although Bob was credited as a cofounder of nanotechnology and often asked to speak on the topic, he did not consider himself an expert. In fact, his primary interests remained in developing and using new quantitative spectroscopic techniques with both old and new collaborators, and that is how he spent much of the rest of his career before retiring in 2012.
In parallel with his research career, Bob was a dedicated and nurturing educator. He remembered his humble beginnings, and he went out of his way to make new students to Rice feel welcome. He was the Master of Lovett College from 1968 to 1972, which was a particularly challenging era for the students and those guiding them. He understood the stresses that the Vietnam war and the intense academic atmosphere of Rice placed on his charges. While many students felt Bob’s classes were ‘too hard’, Bob himself was viewed as remarkably generous with the time he spent outside of the classroom helping students.
To those who made the transition from student to colleague, Bob was a special friend. He was genuinely modest about his own accomplishments and always ready to celebrate those of others. The story of a meeting with the Rice President after the Nobel Prize was announced is telling. The President asked Bob and Rick what he could do for them in recognition of the honor that they had brought to Rice. Bob asked if it might be possible to put a bicycle rack near the building where he had his office and labs. In both little and big ways, Bob made everyone around him better.
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Heath, J.R., Williams, R.S. Robert F. Curl (1933–2022). Nat. Nanotechnol. 17, 901 (2022). https://doi.org/10.1038/s41565-022-01195-0