Tailored polymers as nucleation templates for the synthesis of fluorescing nanodiamonds

• Applicant: Professor Dr. Ulrich Ziener
• Subject Area: Preparatory and Physical Chemistry of Polymers
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 438523753

• The project will establish a robust protocol for the controlled synthesis of sub-10-nm fluorescing nanodiamonds (NDs) by a polymer templating process. The polymers will comprise adamantane-type diamondoid sites to facilitate efficient nucleation and growth as well as heteroatom-carrying moieties (mainly N but also Si, Ge) to achieve controlled implantation of heteroatom-vacancy defects (location, number). • The seed polymers will be applied in a high pressure high temperature (HPHT) process to grow NDs using carbon supply from “reactive hydrocarbons” (isocetane/tetracosane) as known for small molecular templates and as we used for the preliminary results on polymer templated NDs. • Vacancies will be introduced by electron beam irradiation or ion beam treatment performed in collaboration with local groups. Annealing will be done at temperatures around 800 °C in vacuum or under inert atmosphere in accordance to standard procedures. • We will analyze the obtained NDs first by electron microscopy and then by absorption and fluorescence spectra on an optical microscope to investigate the nature of the produced NV (and SiV, GeV) centers, photoluminescence quantum yield and lifetime to gain information about the concentration of defects. For the most promising samples, we will turn to autocorrelative techniques and investigate magneto-optical effects on samples with single colour centers in collaboration with the Institute for Quantum Optics. The polymeric approach allows a high local concentration of templating units with control over their location as well as precise incorporation of defects. The yield and quality of the NDs will be strongly improved compared to small molecular templates. The specific goals of this project are, increasing in complexity:1. Preparation of (hetero-)adamantyl monomers and their polymersPolymerization of seed macromolecules with defined monomodal and narrow molar mass distribution and a variety of N, Si, and Ge containing adamantyl monomers will be performed to present ideal nucleation sites for the HPHT process. 2. Production of highly fluorescing and stable NDs with multiple colour centersA controlled amount of aza-, sila- and germaadamantyl will be incorporated into the polymeric templates to steer the heteroatom-vacancy centers. For NV centers we will examine if we can control the nature of the NV center (NV0 or NV-) by controlling the electron-beam acceleration voltage and the annealing temperature. 3. Generation of small NDs with single colour centersEnd group functionalization with aza-, sila-, or germaadamantane or derivatives, respectively, will allow us to incorporate only one heteroatom species per polymeric templating unit to ultimately synthesize nanodiamonds in the range of a few nanometers with single colour centers, which are important as quantum sensors.The process shall be established as a new gold standard for the bottom-up synthesis of fluorescing nanodiamonds.

• DFG Programme: Research Grants
• Major Instrumentation: Diamantambosszelle mit Zubehör
• Instrumentation Group: 0850 Höchstdruckpressen, Tetraederpressen
• Co-Investigator: Professor Dr. Alexander Kühne