With the implementation of high-field solid-state NMR as a versatile spectroscopic technique for obtaining high-resolution 13 C spectral fingerprints of carbon-based nanoparticles, the key results of this study depict how the measurement of fundamental 13 C relaxation times offers crucial information on the spatial proximities of the core carbon moieties to surface-associated paramagnetic centers of diamond nanocrystals. Consequently, the results of this study also demonstrate that 13 C spin-lattice relaxation times of the core sp 3 carbons are interrelated with the geometric size of nanoparticles, elucidating fundamental physicochemical characteristics of carbon-based and organic nanoparticles. Evaluating 13 C T1 can provide information about implanted hetero-nuclei in the surface layers of diamond nanoparticles, and this experimental approach can be extended to investigating silicon-and phosphorus-containing nanoparticles.