High-Density Covalent Grafting of Spin-Active Molecular Moieties to Diamond Surfaces

Abstract

Functionalization of diamond surfaces with TEMPO and other surface paramagnetic species represents one approach to the implementation of novel chemical detection schemes that make use of shallow quantum color defects such as silicon-vacancy (SiV) and nitrogen-vacancy (NV) centers. Yet, prior approaches to quantum-based chemical sensing have been hampered by the absence of high-quality surface functionalization schemes for linking radicals to diamond surfaces. Here, we demonstrate a highly controlled approach to the functionalization of diamond surfaces with carboxylic acid groups via all-carbon tethers of different lengths, followed by covalent chemistry to yield high-quality, TEMPO-modified surfaces. Our studies yield estimated surface densities of 4-amino-TEMPO of approximately 1.4 molecules nm −2 on nanodiamond (varying with molecular linker length) and 3.3 molecules nm −2 on planar diamond. These values are higher than those reported previously using other functionalization methods. The ζ-potential of nanodiamonds was used to track reaction progress and elucidate the regioselectivity of the reaction between ethenyl and carboxylate groups and surface radicals.

Nanometer-Thick Carbon Coatings with Covalent Chemical Functionalization of Metal Oxide Nanoparticles for Environmental and Biological Applications

“…Further functionalization of Al 2 O 3 @C-COOH was done using EDC coupling, forming an amide linkage on the surface (Scheme ). The functionalization was adapted from previous literature, , as described in the Supporting Information. Details on the synthesis and characterization of a nanoruby and Fe 3 O 4 nanoparticles can be found in the Supporting Information, with particle characterization shown Figures S1 and S2.…”

Diamond surface engineering for molecular sensing with nitrogen—vacancy centers

“…Notably, the majority of NV biosensing research has thus far leveraged nanodiamonds rather than bulk substrates, which can directly utilize many of the diamond surface preparation and functionalization strategies described in this Review. Further supported by significant advancements in production and purification of nanodiamonds, this alternate platform has seen application in biomedical sensing and imaging, [361][362][363][364][365] drug delivery, 366 and reaction monitoring, 233,367 as discussed in recent reviews. 346,368,369 Specifically, these experiments have monitored physiological variables, such as concentration of ions, radicals, and biomolecules, in addition to pH, temperature, and redox potential or forces.…”