Ultrasmall Nanodiamonds: Perspectives and Questions

Abstract

Nanodiamonds are at the heart of a plethora of emerging applications in areas ranging from nanocomposites and tribology to nanomedicine and quantum sensing. The development of alternative synthesis methods, a better understanding, and the availability of ultrasmall nanodiamonds of less than 3 nm size with a precisely engineered composition, including the particle surface and atomic defects in the diamond crystal lattice, would mark a leap forward for many existing and future applications. Yet today, we are unable to accurately control nanodiamond composition at the atomic scale, nor can we reliably create and isolate particles in this size range. In this perspective, we discuss recent advances, challenges, and opportunities in the synthesis, characterization, and application of ultrasmall nanodiamonds. We particularly focus on the advantages of bottom-up synthesis of these particles and critically assess the physicochemical properties of ultrasmall nanodiamonds, which significantly differ from those of larger particles and bulk diamond.

Surface Control of Nanodiamond: From Homogeneous Termination to Complex Functional Architectures for Biomedical Applications

“…Unlike NDs made by detonation synthesis, diamondoids show a well-defined structure . To make them applicable, a large number of selective functionalization reactions have been carried out. , However, it will take some synthesis effort to close the gap between macromolecular diamondoids and the smallest known diamond nanoparticles …”

“…Among the plethora of carbon nanomaterials, nanodiamond represents an exciting prospect for a range of applications in the fields of biomedicine and bioanalytics owing to its low toxicity profile and the possibility for individual surface functionalization. − Consisting of an sp 3 -hybridized carbon core, ND combines the properties of macroscale diamond such as mechanical and thermal stability with extraordinarily diverse surface chemistry . ND particle sizes can range from subnanometer to ∼100 nm in diameter, depending on the synthesis technique and conditions employed .…”

“…45,47 However, it will take some synthesis effort to close the gap between macromolecular diamondoids and the smallest known diamond nanoparticles. 8…”

Carbon Surface Chemistry: New Insight into the Old Story

“…Even nanodiamonds with sp 3 hybridized core, expose a sp 2 hybridized carbon surface to decrease the surface energy. [ 4 ] With many examples of their chemical applications, the dominating “graphitic structure with hexagonal network” of carbon materials is somehow chemically inert, [ 5 ] which possesses mainly physical adsorption ability through dispersive forces. The chemical reactivity is primarily from the deviations of hexagonal motifs in the graphitic lattice.…”

Origins and Simulation of (002) Forbidden Reflections in Nanodiamonds: Implications for Sub-4 nm Nanodiamond Synthesis and Characterization

“…The ND also has many applications both in chemical and biomedical area, such as CO 2 reduction, kidney filtration system, and so forth. , Thus, it has been considered to have a bright future in the commercial application and fundamental chemical science. In 2021, our research group developed a low-temperature synthetic approach of sub-4 nm NDs based on graphene oxide and nitrated polycyclic aromatic hydrocarbons .…”