Nanodiamond Surface Research Articles

Amidated nanodiamonds prepared by mechanochemical technology and their dispersion properties

The effect of amide functional groups at the nanodiamond surface is of great significance. Herein, we develop a new facile, inexpensive, and contaminant-free approach to modify nanodiamond surface through the mechanochemical amidation of nanodiamond using ball milling technique in the presence of ammonium chloride (NH4Cl) as amidation reagent to introduce the amide functional groups on the nanodiamond surface. It is observed that the amidated nanodiamonds can uniformly disperse well in an aqueous solution. Moreover, the results indicated that the technique is easy to operate and scale-up for industrial application. Furthermore, the well-dispersed nanodiamond colloids can be used for numerous applications including lubrication, thermal interface materials, and drug delivery system. More interesting, the dried amidated nanodiamond can be re-dispersed back to the colloidal solution of a wide range of solvents including water, dimethylsulfoxide, dimethyl formamide and ethanol, which greatly expands the application and functionality of nanodiamond.

Humidity Sensors Realized via Negative Photoconductivity Effect in Nanodiamonds.

Herein, the negative photoconductivity (NPC) effect has been observed in nanodiamonds (NDs) for the first time, and with illumination under a 660 nm laser lamp, the conductivity of the NDs decreases significantly. The NPC effect has been attributed to the trapping of carriers by the absorbed water molecules on the ND surfaces. A humidity sensor has been constructed based on the NPC effect of the NDs, and the sensitivity of the sensor can reach 106%, which is the highest value ever reported for carbon-based humidity sensors.

Hyaluronic acid adsorption on nanodiamonds: Quantitative characteristics and mechanism

Formation of adsorption complex between hyaluronic acid and detonation nanodiamonds was studied. Nanodiamonds that possess negative and positive zeta-potential in an aqueous suspension were used. To determine the direct amount of hyaluronic acid on the nanodiamond surface tritium label was introduced into the polymer by means of tritium thermal activation method. It was found that hyaluronic acid irreversibly adsorbs on both positively and negatively charged nanodiamonds, but in different quantities. Adsorption of hyaluronic acid on nanodiamonds of positive zeta potential leads to the isoelectric point at the surface coverage close to 100 mg/g, while further increase in surface amount of hyaluronic acid results in the formation of negatively charged particles and the increase of its species diameter comparing with the initial material. In the case of negatively charged nanodiamonds adsorption of hyaluronic acid is also observed, but it was as much as 50 times lower than in the case of positively charged nanodiamonds. Even small amounts of hyaluronic acid adsorbed on nanodiamond surface results in the disaggregation of clusters of nanodiamonds that are formed in an aqueous suspension, while zeta potential was from − 50 to − 40 mV that is around of the value for non-modified material. On the basis of the experimental data, we can suggest that the adsorption mechanism of complex formation between hyaluronic acid and nanodiamonds includes both electrostatic interaction and formation of hydrogen bonds between surface functional groups and adsorbed water molecules.

Tritium-Probe Method in a Study of Adsorption Layers of Lysozyme on the Surface of Detonation Nanodiamonds

Tritium-labeled lysozyme was used to determine its adsorption on the surface of nanodiamonds produced by detonation synthesis. It was found that the amount of the adsorbed protein depends on the charge of the nanodiamond surface. A multilayer coating is formed on the originally positively charged nanodiamonds, with the adsorption becoming 4–5 times stronger on negatively charged nanodiamonds produced from the original nanodiamonds via their annealing in air. According to IR spectroscopic data, the adsorption of lysozyme results in that the number of loops and turns in the protein structure decreases in the adsorption on two types of nanodiamonds. The use of a tritium probe did not find any significant difference between the structures of protein molecules in their adsorption on nanodiamonds with different functional surface compositions. The orientation of molecules in the surface layer was found to be the same: Protein parts containing amino acid residues of phenylalanine are contacting with the sorbent, and the amino acid residues of proline, which are contained in the loops, are on the surface of the adsorption layer.

Formation of Active Centers of Nickel–Zinc Catalysts Deposited on the Nanodiamond for the Selective Hydrogenation of Phenylacetylene

A study is performed of bimetallic catalysts NiZn/ND with ratios Ni : Zn = 1 : 1 and 1 : 3 prepared by impregnation using detonation nanodiamond (ND) as a support. They were compared with monometallic Ni/ND and Zn/ND. It is shown by nitrogen adsorption/desorption, scanning and transmission electron microscopy that metal deposition does not affect the porous structure or morphology of a support. Coordination of metal precursors on a nanodiamond surface proceeds with the participation of functional groups, as is confirmed by a change in the electrokinetic charge of the surface. The reduction of metal precursors is studied by temperature-programmed reduction and in situ XAFS spectroscopy. In Ni-containing samples, two forms of Ni2+ are found that are bonded differently with the support. ZnO is not reduced in the samples upon treatment with hydrogen at temperatures up to 400°C. The fraction of reduced nickel is determined by analyzing XANES spectra. Virtually full reduction of nickel is observed in a catalyst with a Ni : Zn ratio of 1 : 1 after 4 h of in situ treatment with hydrogen inside a spectrometer cell at 400°C, but not at a Ni : Zn ratio of 1 : 3 under the same conditions. The highest selectivity of styrene formation in the reaction of phenylacetylene hydrogenation throughout the investigated range of temperatures (100–350°С) is ensured by NiZn/ND; NiZn3/ND is less active and selective, since ZnO closes the active nickel centers and prevents the adsorption of phenylacetylene.

Insight into the Metal‐Support Interactions between Ruthenium and Nanodiamond‐derived Carbon material for CO Oxidation

AbstractFor supported metal catalysts, metal‐support interactions (MSI) are vital for their catalytic performance, which can be regulated by controlling surface structures of supports. In this work, two kinds of nanodiamond (ND)‐derived carbon materials, i. e. ND@graphene (ND@G) and onion‐like carbon (OLC), were applied to support Ru catalyst. The characterization results show that compared with OLC supported Ru catalyst (Ru/OLC), ND@G supported Ru catalyst (Ru/ND@G) exhibits a higher Ru dispersity, large amount of nanoclusters and Ru single atoms with positive charges dispersing on the surface of ND@G, indicating a stronger MSI in Ru/ND@G. Ru/ND@G favors twin CO adsorbates, while Ru/OLC favors linear adsorbates. For CO oxidation reaction, it was found that Ru/OLC with more metallic Ru NPs exhibited higher catalytic activity compared to Ru/ND@G. Moreover, Ru/OLC showed better reusability and stability compared to Ru/ND@G during CO oxidation reaction. This work highlights the importance of having an adequate rather than an excessively strong MSI for some catalytic systems.

Nanodiamond surface chemistry controls assembly of polypyrrole and generation of photovoltage

Nanoscale composite of detonation nanodiamond (DND) and polypyrrole (PPy) as a representative of organic light-harvesting polymers is explored for energy generation, using nanodiamond as an inorganic electron acceptor. We present a technology for the composite layer-by-layer synthesis that is suitable for solar cell fabrication. The formation, pronounced material interaction, and photovoltaic properties of DND-PPy composites are characterized down to nanoscale by atomic force microscopy, infrared spectroscopy, Kelvin probe, and electronic transport measurements. The data show that DNDs with different surface terminations (hydrogenated, oxidized, poly-functional) assemble PPy oligomers in different ways. This leads to composites with different optoelectronic properties. Tight material interaction results in significantly enhanced photovoltage and broadband (1–3.5 eV) optical absorption in DND/PPy composites compared to pristine materials. Combination of both oxygen and hydrogen functional groups on the nanodiamond surface appears to be the most favorable for the optoelectronic effects. Theoretical DFT calculations corroborate the experimental data. Test solar cells demonstrate the functionality of the concept.

Surface Modification of Fluorescent Nanodiamonds for Biological Applications.

Fluorescent nanodiamonds (FNDs) are a new class of carbon nanomaterials that offer great promise for biological applications such as cell labeling, imaging, and sensing due to their exceptional optical properties and biocompatibility. Implementation of these applications requires reliable and precise surface functionalization. Although diamonds are generally considered inert, they typically possess diverse surface groups that permit a range of different functionalization strategies. This review provides an overview of nanodiamond surface functionalization methods including homogeneous surface termination approaches (hydrogenation, halogenation, amination, oxidation, and reduction), in addition to covalent and non-covalent surface modification with different functional moieties. Furthermore, the subsequent coupling of biomolecules onto functionalized nanodiamonds is reviewed. Finally, biomedical applications of nanodiamonds are discussed in the context of functionalization.

Detonation Nanodiamonds: A Comparison Study by Photoacoustic, Diffuse Reflectance, and Attenuated Total Reflection FTIR Spectroscopies.

The qualitative analysis of nanodiamonds by FTIR spectrometry as photoacoustic (FTIR–PAS), diffuse-reflectance (DRIFT), and attenuated total reflection (ATR) modalities was evaluated for rapid and nondestructive analysis and comparison of nanodiamonds. The reproducibility and signal-gathering depth of spectra was compared. The assignment of characteristic bands showed that only six groups of bands were present in spectra of all the modalities with appropriate sensitivity: 1760 (C=O stretch, isolated carboxyl groups); 1640–1632 (H–O–H bend, liquid water); 1400–1370 (non-carboxyl C–O–H in-plane bend and CH2 deformation); 1103 (non-carboxyl C–O stretch); 1060 (in-plane C–H bend, non-aromatic hydrocarbons and carbohydrates); 940 cm−1 (out-of-plane carboxyl C–O–H bend). DRIFT provides the maximum number of bands and is capable of measuring hydrogen-bonded bands and CHx groups. ATR provides the good sensitivity for water and C–H/C–C bands in the range 2000–400 cm−1. FTIR–PAS reveals less bands than DRIFT but more intense bands than ATR–FTIR and shows the maximum sensitivity for absorption bands that do not appear in ATR-IR spectra and are expedient for supporting either DRIFT or FTIR–PAS along with depth-profiling. Thus, all three modalities are required for the full characterization of nanodiamonds surface functional groups.

Experimental investigation of thermo-physical properties, heat transfer, pumping power, entropy generation, and exergy efficiency of nanodiamond + Fe3O4/60:40% water-ethylene glycol hybrid nanofluid flow in a tube

The synthesis method of in-situ/chemical co-precipitation was implemented for the addition of Fe3O4 nanoparticles on the surface of nanodiamond (ND) nanoparticles, and it is characterized by using x-ray diffraction, transmission electron microscopy and the magnetic property was estimated from the vibrating sample magnetometer. The 60:40% water-ethylene glycol mixture is used as a base fluid for the preparation of ND-Fe3O4 hybrid nanofluids. Experimental techniques are used to measure the thermophysical properties at various particle volume loadings, and temperatures and the obtained data is validated with literature data. The heat transfer, friction factor, and pumping power are evaluated at particle volume loadings from 0.05% to 0.2% and in the Reynolds number range from 2105 to 8126. The concepts of the second law of thermodynamics are used to evaluate the thermal entropy generation, frictional entropy generation and exergy efficiency of the hybrid nanofluids. The thermal conductivity enhancements are 5.03% and 12.79%, whereas, the viscosity enhancements are 108% and 50.84% at particle loading of 0.2% at temperatures of 20 °C and 60 °C in comparison with base fluid. The Nusselt number is augmented to 15.65%; thermal entropy generation is reduced to 20%, frictional entropy generation is augmented to 272.48% and exergy efficiency is increased to 38.24% with a maximum penalty in friction factor of 1.128-times at 0.2% particle loading and a Reynolds number of 7502 against base fluid data. New equations are modelled to evaluate the thermophysical properties, Nusselt number, and friction factor.

Nanosilver supported on inert nano-diamond as a direct plasmonic photocatalyst for degradation of methyl blue

Direct photocatalysis with plasmonic nanostructures represents a new and promising direction in pollutant disposal. In current practice, inert metal oxides are usually used as supports to load plasmonic nanoparticles. However, due to the lack of stabilizing functional groups on the surface of these metal oxides, the stability and dispersibility of the obtained nanostructures are poor. Herein, a nano-diamond (ND) material with easily functionalized surface was used as an inert support to load silver nanoparticles to prepare plasmonic nanostructures with direct photocatalytic ability. The plasmonic nanostructure can be easily prepared by modifying the surface of ND with pyridine groups and then reducing the silver precursor in-situ. Thanks to pyridine group's dual functions of complexing Ag nanocrystals and dispersing ND, the obtained plasmonic nanostructure not only has uniformly distributed Ag nanocrystals on ND surface, but also shows excellent multi-solvent dispersibility. we demonstrate that this novel plasmonic nanostructure can directly decolorization of methyl blue (MB) under visible light irradiation with a standard rate constant as high as 28.4 s−1 g−1. In addition, the catalyst can be easily recovered and recycled for at least five times while maintaining high catalytic activity. The mechanism study shows that the localized surface plasmon resonance energy transfer of Ag nanoparticles is the direct driving force of MB degradation. The inert ND support can not only ensure the physical stability of Ag nanoparticles, but also avoid the attenuation of plasmonic resonance energy to matrix, which plays an indispensable synergistic role in promoting the rapid degradation of MB.

Detonation nanodiamonds dispersed in polydimethylsiloxane as a novel electrorheological fluid: Effect of nanodiamonds surface

Using deagglomerated nanodiamond particles of 4–5 nm suspended in polydimethylsiloxane (PDMS) we have fabricated fluids demonstrated pronounced electrorheological effect. It has been revealed that the type of functional groups on nanodiamond particle surface plays a crucial role in the behavior of the suspensions under electric field. Suspension of hydrogenated nanodiamonds has demonstrated the most powerful electrorheogical effect. The high values of yield stress of the order of 80–90 Pa have been detected at extremely low concentrations of nanodiamond particles (3–4 wt%). The suspensions has outstanding sedimentation stability: the sedimentation ratio is more than 90% after 30 days. A power law dependence of the yield stress on the electric field, τ ∼ E1.0-1.5 indicates mainly the conduction mechanism of the effect. Suspensions of carboxylated nanodiamonds in PDMS reveal qualitatively different behavior and the electrophoresis occurs. The paper discusses the reasons of different rheological behavior depending on nanodiamond surface functionalization. The prospects of nanodiamonds application as filler for electrorheological fluids have been shown.

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.

Temperature dependence of the longitudinal spin relaxation time T1 of single nitrogen-vacancy centers in nanodiamonds

We report the experimental study of the temperature-dependence of the longitudinal spin relaxation time $T_1$ of single Nitrogen-Vacancy (NV) centers hosted in nanodiamonds. To determine the relaxation mechanisms at stake, measurements of the $T_1$ relaxation time are performed for a set of individual NV centers both at room and cryogenic temperatures. The results are consistant with a temperature-dependent relaxation process which is attributed to a thermally-activated magnetic noise produced by paramagnetic impurities lying on the nanodiamond surface. These results confirm the existence of surface-induced spin relaxation processes occurring in nanodiamonds, which are relevant for future developments of sensitive nanoscale NV-based quantum sensors.

Pomegranate like polypyrrole/nanodiamond hierarchical structures for metal-free ultrabroad-band electromagnetic absorptions

Exploring metal-free ultrabroad-band electromagnetic absorption materials is of great significance in practical application and theoretical research, which is, however, still challenging. Constructing hierarchical structures and seeking metal-free magnetic materials could be feasible ways to realizing stable, lightweight and metal-free ultrabroad-band electromagnetic absorption. In this work, pomegranate like polypyrrole/nanodiamond hierarchical structures, which could achieve metal-free ultrabroad-band electromagnetic absorptions, are synthesized through in situ polymerization. The optimal reflection loss peak reaches −53 dB at 10.5 GHz and the effective bandwidth below −10 dB could achieve 12.2 GHz, realizing 5.8–18 GHz full-coverage at a single thickness of 4.2 mm. The ultrabroad-band electromagnetic absorption results mainly from the π-p hybridization induced nanodiamond surface defect state, the multiple polarizations and interfaces, as well as the biomimetic pomegranate like hierarchical structures leading to the synergistic magnetic and dielectric dissipations. This work provides referencing path for designing metal-free ultrabroad-band electromagnetic absorption materials.

Pristine detonation nanodiamonds as regenerable adsorbents for metal cations

The usability of pristine (not functionalized by grafting) detonation nanodiamonds as reversible and repeatedly regenerated adsorbents for metal cations was shown by examples of sorption of cadmium, zinc, nickel, and copper from aqueous solutions. Various pristine nanodiamond surface treatments are discussed. The procedure of oxidative sintering with nitric acid at 250 °C provided a surface with an increased number of carboxyl groups with a sorption capacity above 100 μmol/g for all test cations. Sorption isotherms for test metals (copper, nickel, zinc, and cadmium) can be divided into two distinct parts: a lower part for concentrations of up to 10–15 mmol/L belong to the Langmuir L5 type by Giles and absorption free energies are 8–12 kJ/mol according to the Dubinin–Radushkevich model, evidencing a primarily chemisorption mechanism of the studied cations on micropores in ND surface. The parts of curves above 10–15 mmol/L are described with linear equations, free energies of absorption are 4–6 kJ/mol by Dubinin–Radushkevich that are assigned to physisorption in mesopores. A procedure for the surface regeneration, which is based a similar sintering treatment with nitric acid, was developed. It provided sorption parameters not degraded compared to the starting material; and the regeneration process is repeatable at least for 10 cycles.

Polymer coated nanodiamonds as gemcitabine prodrug with enzymatic sensitivity for pancreatic cancer treatment

The fabrication of Gemcitabine (GEM) prodrug was reported to be an effective method to enhance its pancreatic cancer treatment efficiency. Here, a kind of nanocarbon-based materials, nanodiamond (ND), was selected as the nanocarrier of GEM, owing to its outstanding surface properties and non-cytotoxicity. The polyelectrolytes, polyethyleneimine and polyacrylic acid, were used to self-assemble outside ND surface through electrostatic forces, followed by attachment of polyethylene glycol to address better biocompatibility. GEM was conjugated with an enzyme-sensitive peptide gly-phe-leu-gly to build up the controlled release platform. From characterization results of dynamic laser scattering, zeta potential and transmission electron microscope, the significant improvement of ND stability in physiological condition was proved. Non-cytotoxicity of this functionalized ND carriers and cytotoxicity of the prodrug against BxPC-3 pancreatic cancer cells were indicated by methylthiazolyl tetrazolium (MTT) assay. In vivo experiments also revealed its superior anticancer effect compared with free GEM treatment. Therefore, the combination of polymer coated NDs with high surface capability and enzyme-responsive intracellular GEM release make it possible to realize higher treatment efficiency on pancreatic tumor therapy.

Effect of polyethylene glycol surface modified nanodiamond on properties of polylactic acid nanocomposite films

Nanodiamond (ND) was surface modified by polyethylene glycol (PEG) to improve the interfacial adhesion between ND and the polylactic acid (PLA) matrix and achieve uniform nanoparticle dispersion in the matrix. PEG functionalized ND (ND-PEG) was successfully prepared by a novel and scalable modification method. Firstly, the ND particles oxidized by air was treated with dopamine, and then the hydroxyl groups on PEG and polydopamine (PDA) were covalently linked by isocyanate groups. The Fourier Transform Infrared spectroscopy, Thermogravimetric analysis and X-ray photoelectron spectroscopy reveal that PEG has been covalently boned on the surface of ND. Compared with those of pure PLA film, the tensile strength, tensile modulus and elongation at break of the nanocomposite films with PEG modified ND increase by 66.64%, 37.6% and 187.43%, respectively. In the meantime, the degradation temperature at the initial stage and the temperature at the maximum weight loss rate of the nanocomposite films are significantly increased. It is suggested that the incorporation of ND-PEG into PLA matrix is an effective method to improve the mechanical properties and thermal stability of PLA.

Front Cover: Hydrophobic Surface Coating of Nanodiamonds by Polyglycerol‐Based Polymers with Alkyl Chains for Dispersing in an Organic Solvent (ChemNanoMat 9/2020)

Dispersing nanodiamond (ND) in an organic solvent has been realized by surface functionalization with hydrophobic polymers. The following two types of “grafting from” processes are applied to the ND surface coating; 1) ring opening polymerization of 1,2-epoxyhexane giving ND functionalized with poly(1,2-hexylene glycol) (ND-PHG) and 2) ring opening polymerization of glycidol followed by Williamson ether synthesis giving ND functionalized with octyl and tetradecyl groups (ND-POPG and ND-PTPG, respectively). ND-POPG and ND-PTPG are found to show much higher dispersibility (∼5 mg/mL in chloroform) than ND-PHG (∼0.3 mg/mL). More information can be found in the Full Paper by Naoki Komatsu et al.

Nanoscale Dynamic Readout of a Chemical Redox Process Using Radicals Coupled with Nitrogen-Vacancy Centers in Nanodiamonds.

Biocompatible nanoscale probes for sensitive detection of paramagnetic species and molecules associated with their (bio)chemical transformations would provide a desirable tool for a better understanding of cellular redox processes. Here, we describe an analytical tool based on quantum sensing techniques. We magnetically coupled negatively charged nitrogen-vacancy (NV) centers in nanodiamonds (NDs) with nitroxide radicals present in a bioinert polymer coating of the NDs. We demonstrated that the T1 spin relaxation time of the NV centers is very sensitive to the number of nitroxide radicals, with a resolution down to ∼10 spins per ND (detection of approximately 10-23 mol in a localized volume). The detection is based on T1 shortening upon the radical attachment, and we propose a theoretical model describing this phenomenon. We further show that this colloidally stable, water-soluble system can be used dynamically for spatiotemporal readout of a redox chemical process (oxidation of ascorbic acid) occurring near the ND surface in an aqueous environment under ambient conditions.