Nanodiamonds In Water Research Articles

Colloidal stability over months of highly crystalline high-pressure high-temperature hydrogenated nanodiamonds in water

In this study, milled nanodiamonds synthesized from HPHT diamond (MND) were successfully hydrogenated and stabilized in colloidal suspension in water over months. The optimal hydrogenation conditions correspond to a minimization of carbon/oxygen bonds and sp2/amorphous carbon at MND surface as shown by FTIR and XPS. Clean crystalline particles were observed by HR-TEM. The colloidal stability is discussed in terms of sp2 carbon and role of facets. The signature of a surface conductivity was identified by FTIR. A particular arrangement in colloidal suspension of H-MND was observed by Cryo-EM for H-MND with the formation of chain like structures extending over micron range.

Early dynamics of the emission of solvated electrons from nanodiamonds in water.

Solvated electrons are among the most reductive species in an aqueous environment. Diamond materials have been proposed as a promising source of solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from detonation nanodiamonds upon excitation with both deep ultraviolet (225 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination in the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. In particular, a transient response that we attribute to solvated electrons is observed on hydrogenated nanodiamonds upon visible light excitation, while it shows a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in an aqueous phase using nanodiamonds.

The effect of salt and particle concentration on the dynamic self-assembly of detonation nanodiamonds in water

Detonation nanodiamonds (DNDs) are becoming increasingly important in science and technology with applications from drug delivery to tribology. DNDs are known to self-assemble into fractal-like aggregates in water, but their colloidal properties remain poorly understood. Here, the effect of salt and particle concentration on the size and shape of these aggregates is investigated using dynamic light scattering and small-angle X-ray scattering. Our results suggest the existence of two particle aggregate populations with diameters on the scale of 50 nm and 300 nm, respectively. The concentration of NaCl, in the range 0.005-1 mM, does not have a significant effect on the size or shape of the particle aggregates. The hydrodynamic radius of both aggregate populations decreases as the DND concentration increases from 0.01 to 2 mg mL-1. At the same time, the particle aggregates become denser and their overall shape changes from disk-like to rod-like with increasing DND concentration. We identify unexpected similarities between the aggregate structures observed for DNDs and those commonly observed for concentrated colloidal particles in high salt environments, described by classical colloid aggregation theories. Our results contribute to the fundamental understanding of the colloidal properties of DNDs and pave the way for the engineering of novel nanoparticle-based systems that make use of DNDs' unique colloidal properties for future applications.

Tritium labelling to study humic substance-nanodiamond composites

Nanodiamonds produced by the detonation method are used as lubricants, polishing compositions, polymer composites, etc. To reveal how nanodiamonds differ in terms of surface properties and interact with natural organic matter, we used tritium-labelled humic substances to quantitively describe their adsorption onto the nanodiamond surface. It was shown that the adsorption of humic substances onto nanodiamonds resulted in fractionation of humic substances that was strongly dependent on the zeta potential of nanodiamonds in water but did not significantly affect the uptake of nanodiamonds by wheat seedlings. The uptake of nanodiamond particles by plants was determined by the functional composition of the particle surface.

Bilayer Adsorption of Lysozyme on Nanodiamonds in Aqueous Suspensions

The interactions of one of the most famous enzymes, lysozyme, with carboxylated nanodiamonds in water were studied. It was found that stable complexes are formed as a result of lysozyme adsorption ...

Electronic effects on the interfaces “nanodiamond - surface groups – water molecules”

In this paper an explanation of the dependence of photoluminescence of detonation nanodiamonds in water on the type of functional surface groups due to the manifestation of inductive and mesomeric electronic effects on the interface “nanodiamond - surface groups – water molecules” is proposed. This explanation based on the experimental results of the study of photoluminescence of detonation nanodiamonds with different surface functionalization and theoretical calculations of the electron density on the surface of nanoparticles. The hypothesis can be extended to other functionalizations of nanodiamonds, which will allow to control the stability and photoluminescent properties of colloidal systems “nanodiamonds-solvent” through the functionalization of the surface of nanoparticles.

Diprotic ammonium palmitate ionic liquid crystal and nanodiamonds in aqueous lubrication. Film thickness and influence of sliding speed

Ionic liquid based lubricants offer potential to reduce the sliding friction and wear of ferrous bearing surfaces such as those used in cutting and machining processes. In this study, two types of promising additives were investigated: (1) diprotic bis(2-hydroxyethyl)ammonium palmitate (DPA) ionic liquid crystal and (2) a 0.1 wt% dispersion of nanodiamonds (ND) in DPA. Both have been used at 1 wt% concentration in aqueous lubricants. Those were Water+DPA, and Water+DPA+ND. The stability of the dispersions has been studied by dynamic light scattering, finding that the interaction between the additives and water changes particle size distribution. Glass-against-steel optical interferometry using water film alone indicated that the film thickness decreased with number of sliding strokes and that in turn increased the friction coefficient. By comparison, Water+DPA and Water+DPA+ND showed lower friction coefficients and increased film thickness. In steel-steel pin-on-disk contacts lubricated only by water, electrical resistance increases at speeds higher than 100 mm/s. DPA and DPA+ND additives displace the electrical resistance increase to lower sliding speed, around 10 mm/s. The additives reduced the coefficients of sliding friction up to 82%, and wear rates of AISI 316L disks by more than two orders of magnitude. The combination of the palmitate ionic liquid crystal and nanodiamonds in Water+DPA+ND gave the lowest wear rates. The wear mechanism and surface analysis associated with these results are discussed.

Influence of hydrogen bonds on the colloidal and fluorescent properties of detonation nanodiamonds in water, methanol and ethanol

ABSTRACTThis paper presents the results of research of influence of hydrogen bonds with different strength on fluorescence and colloidal properties of detonation nanodiamonds with surface carboxylic groups in the solvents. It is established that the colloidal properties of detonation nanodiamonds are almost independent on hydrogen bonds strength in water, methanol and ethanol. The fluorescent properties of detonation nanodiamonds are dependent on the type of solvent: the more intensive fluorescent properties correspond to weaker hydrogen bonds in solvents.

Nanodiamond-enhanced MRI via in situ hyperpolarization

Nanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques, however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton–electron polarization transfer technique, can enable high-contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to 1H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time.

Synthesis of novel nanodiamonds–gold core shell nanoparticles

This work presents novel diamond-based nanostructures formed by a fluorescent nanodiamond core coated with a gold shell (ND@Au). Gold shell was grown on silicon-doped nanodiamonds in water by controlled reduction of gold chloride. The resulting gold-coated nanodiamond samples were characterized by means of scanning electron microscopy, UV–visible, Raman and luminescence spectroscopies. These gold-coated nanodiamonds showed a strong resonance absorption in the visible and near-infrared (NIR) range. When excited with green laser, the silicon doped nanodiamonds emit a stable fluorescence peaked at about 740nm due to the SiV centers with no photobleaching and photoblinking. In this work we demonstrate that optical properties of the silicon-doped nanodiamonds are retained after the formation of the gold shell.

Molecular dynamics-based refinement of nanodiamond size measurements obtained with dynamic light scattering

The determination of particle size by dynamic light scattering uses the Stokes-Einstein relation, which can break down for nanoscale objects. Here we employ a molecular dynamics simulation of fully solvated 1-5 nm carbon nanoparticles for the refinement of the experimental data obtained for nanodiamonds in water by using dynamic light scattering. We performed molecular dynamics simulations in differently sized boxes and calculated nanoparticles diffusion coefficients using the velocity autocorrelation function and mean-square displacement. We found that the predictions of the Stokes-Einstein relation are accurate for nanoparticles larger than 3 nm while for smaller nanoparticles the diffusion coefficient should be corrected and different boundary conditions should be taken into account.

Nanodiamond-based Nanolubricants: Experiment and Modeling

ABSTRACTOur recent efforts using primarily nanodiamonds as lubricant additives are discussed. For traditional high performance engine oils, our results show a reduction in friction for steel surfaces for both laboratory experiments under controlled conditions and in a pilot study of passenger cars under typical driving conditions. Examination of the surfaces suggests that surface polishing at the sub-micron scale may be responsible for these results. A separate set of experiments using a quartz crystal microbalance to measure dissipation and drag due to friction has shown that when added to water the charge of the nanodiamond acquired from surface functionalization can have a large influence on uptake and friction at the water-metal interface. More importantly, these results suggest the possibility of creating nanodiamonds with controllable frictional drag at the solid-liquid interface through surface processing. Companion simulation results for nanodiamonds in water sliding between diamond surfaces are also presented. Future possibilities for further understanding and tuning the properties of nanodiamonds as lubricant additives through synergistic experiments and modeling are also discussed.

Hydrogen and carbon monoxide generation from laser-induced graphitized nanodiamonds in water

Nanodiamonds (ND) were found to generate hydrogen (H2) and carbon monoxide (CO) from water at a remarkable rate under pulsed laser (532 nm) irradiation. The transformation of diamond structure into graphitic layers takes place to form an onion-like carbon structure. The CO generation suggests the oxidative degradation reaction of graphitic layers, C + H2O → CO + 2H(+) + 2e(-), which produced a unique laser-induced reaction: C + H2O → CO + H2. Au, Pt, Pd, Ag, and Cu nanoparticles on the ND enhance both gas evolution rates (~2 times for Au) and graphitization and, specifically, Au was found to be the most efficient amongst other nanoparticles. The enhancement effect was ascribed to effective charge separation between the metal nanoparticles and ND. The Au-ND hybrid on the reduced graphene oxide produced consistently a greater photocurrent than the ND upon visible light irradiation.

Surface modification of detonation nanodiamonds by the perfluorobutyl radical

The method was developed for surface defunctionalization of detonation nanodiamonds by substitution of a perfluorinated organic radical for hydroxyl and carboxyl groups. Size-mass distributions of modified particles of detonation nanodiamonds in water and toluene were studied

Poly(vinylpyrrolidone) as a tool: aqueous dispersion of nanodiamonds by wrapping in the solid state

AbstractAmong carbon‐based nanomaterials such as fullerenes, carbon nanotubes and nanodiamonds, the latter are good candidates as prospective materials in the future due to their potential physical, chemical and biological properties. Thus, nanodiamonds were wrapped with biocompatible polymers in the solid state. The dispersibility of the polymer‐wrapped nanodiamonds in water was investigated with respect to reaction time and mass ratio of the polymers during the wrapping process. The dispersibility of the materials was monitored using UV spectroscopy, and the size distribution of the polymer‐wrapped nanodiamonds was analyzed using high‐resolution transmission electron microscopy and dynamic light scattering measurements. In addition, molecular modeling calculations were performed. Finally, the best dispersion for the polymer‐wrapped nanodiamonds in water was found for a reaction time of 120 min. Copyright © 2012 Society of Chemical Industry