Plasma assisted processing of nanomaterials can promote chemical reactions at near room temperature, even thermodynamically unfavorable ones which can not be run efficiently through conventional chemical routes. In this proposal, Adámas, Inc. in partnership with Rivis, Inc. proposes to use an atmospheric pressure plasma for the surface treatment of diamond nanoparticles (DNP) containing color centers in order to significantly enhance their performance as quantum sensors. Diamond particles containing optically active nitrogen-vacancy (NV) centers have gained significant attention due to their unique optoelectronic properties that facilitate their use as sensors across many fields. The implications for fossil energy applications are sweeping, where measurement of observables such as pressure, temperature, and pH/corrosion are envisioned for monitoring of power grids, oil refining processes, pipeline integrity, coal mine safety, among many others. The fundamental physical principle to all signal enhancement and detection schemes is manipulation of the electronic spin state of the NV center, which primarily has two charge states: a neutral state, NV0, and a negatively charged state, NV-, possessing an electron spin. It is desirable that the negative charge state exists for shallow NV centers for be utilized in sensing. Experimental and theoretical results indicate that surface termination is critical for the negative charge stabilization of these quantum centers to maximize sensitivity, where fluorination or nitridation (full-N) are the best terminations providing positive electron affinity preserving negative charge state of shallow NV centers. These functionalities are difficult to achieve via conventional wet chemistry methods, especially on nanoparticles. The plasma is generated via Rivis patented plasma self-tuning dielectric barrier system where a rapid risetime high voltage pulse creates an overvoltage allowing electric field applied across the gas filled dielectric electrode gap to reach values two to three times the breakdown value of the gas before discharge formation. These plasma conditions are well-suited for promoting formation of reactive species for fluorine and nitrogen functionalization. Thus, the major objectives of the project are to (1) Develop a deeper insight into the plasma conditions that promote generation of reactive species leading to the high level of functionalization of DNP; (2) Demonstrate the general applicability of the plasma system for the functionalization of nano-materials with the attachment of fluorine, and nitrogen groups to DNP; and (3) Develop approach for plasma treatment of large volumes of DNP suitable for quantum sensors to be pursued in Phase II.
