Diamond Rotors

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Project Summary The research in this proposal focuses on the development of methods for fabricating magic-angle spinning (MAS) rotors from single crystal diamond logs for applications (1) in ambient temperature MAS experiments, and (2) dynamic nuclear polarization (DNP) MAS experiments. In particular, there is an ever- increasing push towards rotors that attain higher spinning frequencies for MAS NMR in order to improve sensitivity and resolution. However, the spinning frequencies currently obtainable (~100 kHz) are limited by the strength of the material from which the rotors are fabricated – typically ZrO2 with flexural strength of ~800 MPa. Above ~120 kHz the ZrO2 rotors explode. Diamond is one of the strongest materials on earth with flexural strengths of 2-5 GPa for single crystal samples and therefore an ideal material to manufacture MAS rotors. Furthermore, diamond is transparent to terahertz radiation, so it is ideal for DNP experiments. Finally, it has excellent thermal properties – it thermal conductivity is 10x better than Cu. Thus, it is easy to compensate for the aerodynamic heating associated with MAS. Machining diamond cylinders to high tolerance required for rotors requires a novel laser machining processes which we have begun to develop to produce small (≤1.3 mm OD) diamond rotors. Here we propose to refine our processes and test them in our available instrumentation. The goal is to produce 1.3 mm, 0.7 mm and a new generation of 0.5 mm rotors that will attain ωr/2π>300 kHz and improve the resolution of MAS spectra by a factor of ~5 over what is currently available. In addition, we anticipate that diamond rotors will lead to larger DNP enhancements. We also describe some applications to amyloid fibrils and membrane proteins where we anticipate that diamond rotors will have a significant scientific impact.