Functionalized Fluorescent Nanodiamonds with Millisecond Spin Relaxation Times

Abstract

Fluorescent nanodiamonds (FNDs) containing nitrogen-vacancy (NV) defects are useful probes for biological imaging and nanoscale sensing applications. Here, we explore the effect of chemical surface modifications and core–shell structures on the T1relaxation times of 100 nm FNDs hosting nitrogen-vacancy ensembles. The results show that surface oxidation and silica coating of FNDs using the Stöber method can dramatically increase the spin relaxation time from T1= 320 ± 9 μs to T1= 1.00 ± 0.06 ms. Using FT-IR and NEXAFS measurements conducted on air oxidized particles, we find that changes to surface functional groups and sp2carbon density may be responsible for the observed enhancements to the..