Electrostatic Grafting of Diamond Nanoparticles: A Versatile Route to Nanocrystalline Diamond Thin Films

Abstract

Nanodiamond (ND) seeding is a well-established route toward the CVD (chemical vapor deposition) synthesis of diamond ultrathin films. This method is based on the deposition onto a substrate of diamond nanoparticles which act as pre-existing sp(3) seeds. Here, we report on a straightforward method to disperse diamond nanoparticles on a substrate by taking advantage of the electrostatic interactions between the nanodiamonds and the substrate surface coated with a cationic polymer. This layer-by-layer deposition technique leads to reproducible and homogeneous large-scale nanoparticle deposits independent of the substrate's nature and shape. No specific functionalization of the nanoparticles is required, and low concentrated solutions can be used. The density of NDs on the substrate can be controlled, as shown by in situ ATR-FTIR (attenuated total reflection Fourier transform infrared) analysis and QCM (quartz crystal microbalance) measurements. Highly dense and compact ND deposits can be obtained, allowing CVD growth of nanocrystalline diamond ultrathin films (70 nm) on various substrates. The synthesis of 3D structured and patterned diamond thin films has also been demonstrated with this method.

Surface Modifications of Nanodiamonds and Current Issues for Their Biomedical Applications

“…Fullerenes or carbon nanotubes exhibit hydrophobic behavior and their stability in water suspension can only be obtained after their functionalization [178][179][180]. These colloids of NDs in water were also used to obtain homogeneous seeding of substrates for CVD growth of thin diamond films [181,182]. Some groups used surfactants like sodium oleate [98] or oleylamine [183] to improve the colloidal stability of NDs.…”

Nanodiamonds: From Synthesis and Purification to Deposition Techniques, Hybrids Fabrication and Applications

“…These polymers are soluble in water. Such layer by layer deposition was previously achieved for other nanoparticles [124,125] and later applied to NDs [126][127][128][129]. Negatively charged NDs were then deposited through a layer by layer process on substrates coated with PDDAC [126].…”

Metallic Seed Nanolayers for Enhanced Nucleation of Nanocrystalline Diamond Thin Films

“…Recent research 24 has shown that electrostatic grafting (or self-assembly) on surface modified substrates can result in very high ND particle densities by taking advantage of the electrostatic interactions between the ND particles and the substrate surface. Alternatively, by a heat treatment in air, the ND particle surface becomes mainly covered by carboxylic groups and a negative surface charge is obtained when suspended in water.…”

“…This is in line with several recent reports that focused on the seeding of ND particles by electrostatic self-assembly. [24][25][26]51,52 Electrostatic grafting on substrates (with or without surface modification) can result in a very high density and uniformity of ND particles if a properly selected surface modification and fractionalization of the ND particles are employed to improve their dispersion and to separate those particles into a more narrow range of particle sizes. 26,52 Ideally, ND particles are anchored to the substrate surface as seeds of single grain size for NCD film growth, but it is well known that the formation of ND particle agglomerates is difficult to avoid.…”