Ssm Winter 2007 Engtech Daimondoids

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Diamondoids in the Rough

The Path to the Nanotechnology Revolution

by Jian Cui and Kellen Schefter Photos Credit: Nick Melosh

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anuary 3, 2003 may one day be remembered as a turning point in the “nanotechnology revolution.” On this day, researchers at oil giant Chevron published in Science a novel method for extracting from oil significant quantities of a special class of nanoparticles never before observed in nature—higher diamondoids. Three years later, on the campus of Stanford University, the Stanford-Chevron Program for Diamondoid Nanoscience was founded to explore the fundamental properties of these materials.

Diamond Nanoclusters

and though it took a long, long time, nature’s chemistry factory has done that for us.”

The Stanford-Chevron Program for Diamondoid Nanoscience Having unearthed sizable quantities of a previously unstudied material, Chevron made diamondoids available for scientific scrutiny by contacting various universities, including Stanford, UC-Berkeley, and MIT. According to Professor Shen, seven Stanford professors in various fields showed interest in pursuing diamondoid research. One of these professors is Dr. Nick Melosh in the Department of Materials Science. Following some preliminary experiments, Chevron determined that Stanford would be, according to Melosh, the “most fruitful location” to establish a center for university-based diamondoid research. Hence, the StanfordChevron Program for Diamondoid Nanoscience emerged. As part of the first stage in the collaboration with Stanford, Chevron is providing $1.2 million over the course of four years to support the research of three professors – Drs. Shen, Melosh, and Hari Manoharan in the Physics Department – who are investigating diamondoid properties. This collaboration could potentially expand in the future.

A diamondoid is a carbon and hydrogen-based nanoparticle that is structured like a diamond crystal lattice. The structure of a diamondoid is reminiscent of both diamond—carbon in its most stable form—and known carbon nanoclusters such as carbon nanotubes and the famous 60-carbon Buckminsterfullerene, or “Buckyball.” Both diamonds and nanoclusters possess properties that are unseen in other materials. The existence of a new carbon-based nanoparticle raises an intriguing question. Will diamondoids behave more like diamonds, other nanoclusters, or a superposition of the two? The reason higher diamondoids have not been heavily studied in the past is simple: they are very difficult to obtain. The simplest diamondoid, adamantane, is structurally Funding Basic Research analogous to a single cage of diamond’s lattice structure. While Why did Chevron turn to Stanford and other universities, adamantane has been heavily studied and is commercially rather than conduct the research entirely by itself? “Investing available today for low prices, diamondoids with more cages in Stanford research is actually very cost effective,” says are difficult and costly to Melosh, “because you get the produce. In fact, a single “[This collaboration] is relatively unusual… we’re best people, the best expertise, isomer of a four-caged and the best equipment right really exploring the fundamental properties of tetramantane is the most away, for a relatively small complicated diamondoid amount of capital funding.” these new materials instead of trying to refine a to ever be synthesized Tapping academic research process or to develop a particular material for an groups harnesses the collective by man. Scientists have searched for these higher expertise of each individual existing application.” - Melosh diamondoids that contain involved and the knowledge more than three cages in a variety of different arrangements, amassed over years of experience, aided generously by because they are predicted to have interesting and useful outside funding such as government grants. properties analogous to diamond—such as high thermal While on the surface this seems to be no different from stability and structural rigidity—but on the nanoscale level. most collaborations between industry and academia These higher diamondoids have only recently been today, the name of the program, Program for Diamondoid extracted from oil through processes that Chevron developed. Nanoscience, is the first sign of something special. Shen As Professor Zhi-Xun Shen of Stanford’s Departments of explains, “These days, fewer and fewer industries are willing Physics and Applied Physics notes, “It is much easier to to invest in something which is very basic. We used to have extract things that already exist than to synthesize them. places like Bell (AT&T Bell Laboratories) that were doing Basically, nature has spent millions of years with extreme long-term basic research.” This type of collaboration is less temperatures and extreme conditions to generate this oil, favored today in both business and academia, where high

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demand for immediate results and applications dominates. In the face of this trend, “[The Stanford-Chevron collaboration] is relatively unusual,” Melosh notes. “We’re really exploring the fundamental properties of these new materials instead of trying to refine a process or to develop a particular material for an existing application.” According to Melosh, Stanford will keep the patent rights to all of the intellectual property developed on campus, but Chevron can license these patents “as they see fit.” This opens the door for Chevron Technology Ventures, a subsidiary of Chevron Corp. aimed at commercializing promising technologies, to potentially launch startup companies for marketing any processes or applications that arise from the collaboration. Such companies could contribute to Chevron’s bottom line, but ultimately, “There’s no two year path to making a profit,” says Melosh. “It’s a high risk, high reward kind of investment.”

Photo Credit: Diamondoids internal structure © 2006 Chevron USA Inc.

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Diamondoids and the Nanotechnology Revolution The risk with diamondoid research is duallayered: not only are the applications of these materials unknown, but basic research remains to prove that diamondoids exhibit the predicted unique properties. Many of these predictions, even at this point, are speculative; this is characteristic of the “nanotechnology revolution” as a whole. The possibilities are big—such as designing nanoparticles as tiny machines that can perform particular functions at the molecular level—but so are the costs. Millions of dollars and incalculable human resources are being applied to studying these new materials. Critics have found fault in the exorbitant expenditure in light of the current minimal payoff associated with the “revolution” so far. Nevertheless, the researchers are patient. “Revolutions take time,” says Melosh. “It’s not going to happen overnight.”

Unique Properties of Diamonds and Nanoclusters:

Diamond has a very large bandgap, high hole mobility, very high thermal conductivity, is the hardest material known, is very chemically inert, and has negative electron affinity. The advantages of nanoclusters and other nanomaterials include known processing techniques, electronic quantization, high surface to volume ratio, doping during growth, and ease of functionalization. Professors Zhi-Xun Shen, Nick Melosh, and Hari Manoharan are exploring the degree to which diamondoids share properties of diamonds and nanoclusters, because the combination of diamond’s rare properties and the versatility of nanoclusters can yield unimaginably interesting and useful results. Possible applications of diamondoids include using them in a singlemolecule layer in field emitter displays, using them as an alternative detector for X-rays, and using them as doped superconductors.

layout design: Pam Bhattacharya

This figure illustrates the diamond cage structure of diamondoids and the different ways in which the diamondoid cages can be arranged.

Though it may not keep pace with hype-driven expectations, the best chance nanotechnology has to deliver on its promise is to take advantage of basic research capabilities of the modern university. “University research,” explains Shen, “is the core of our nation’s technological reserve, and even corporations in this case realize that.” S JIAN CUI is a junior majoring in chemistry who in his spare time likes to… who are we kidding, he doesn’t have spare time. KELLEN SCHEFTER is a junior majoring in mechanical engineering who is the greatest representative to come from San Luis Obispo since Chuck Liddell. They would like to thank Professor Zhi-Xun Shen and Professor Nick Melosh for their invaluable contributions to the article. Photos Credit: Nick Melosh

To Learn More: Visit http://www.chevron.com/moleculardiamond/

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