Characterization of nanodiamonds for metamaterial applications

Several different types of nanodiamonds were characterized in order to find the best sample to be used in further experiments with metamaterials. In this work we present the results of optical analysis of aqueous suspensions containing nanodiamonds, SEM analysis of diamond particles dispersed on silicon substrates and measurements of photoluminescence from defects in nanodiamonds.     

Shock-wave sintering of nanodiamonds

A two-stage technology of compaction of ultrafine-dispersed diamonds (UDDs) is developed and successfully applied for ampoule-free sintering of dense UDD granules in lead under a pressure of up to 100 GPa. Standard strength tests of polycrystals (fractions 80/63, 125/80) thus obtained showed a wide spread in strength (from grade AS4 to AS80), which is indicative of highly inhomogeneous sintering conditions. A single-crystal diamond is obtained for the first time by using shock-wave compaction; the crystal is a transparent twinned octahedron 0.6 mm in size with an impurity content of less than 0.05%. This result is unexpected and encourages us to believe that this method can be used to manufacture jewellery-grade diamonds (larger than 2 mm in size). The pressure and temperature conditions of sintering are analyzed.     

Surface chemistry of nanodiamonds

The experimental data available in the literature and the results obtained by the author in research into the structure of nanodiamonds and the physicochemical and chemical properties of their surface are generalized. An account is given of the problems concerning the chemical state and modification of the nanodiamond surface in gaseous and liquid media and the infiuence of modification on the sorption and catalytic properties of nanodiamonds, their compactibility, and sintering. The similarity and difference in the behavior of nanodiamonds and diamond macrocrystals in oxidation processes are discussed. The activation energies of oxidation of nanodiamonds by different reagents are determined in the absence and presence of catalysts.     

Photochromic properties of modified nanodiamonds

A functionalization of the surface of detonation nanodiamonds by photochromic spirocompounds from the classes of spiropyrans and spirooxazines has been carried out for the first time. A comparative study of the interaction of nanodiamonds with positive and negative potential is performed by the spectral–kinetic method, which shows the possibility of surface modification by only functionalized molecules of spirocompounds with the formation of surface proton complexes. This is confirmed by the hypsochromic shift of the absorption bands of the photoinduced merocyanine forms of adsorbed molecules of spirocompounds and by the decrease of the speed of their dark relaxation to the initial state in the presence of nanodiamonds with a negative potential.     

Protective silicon coating for nanodiamonds using atomic layer deposition

Ultrathin silicon coating was deposited on nanodiamonds using atomic layer deposition (ALD) from gaseous monosilane (SiH₄). The coating was performed by sequential reaction of SiH₄ saturated adsorption and in situ decomposition. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to investigate the structural and morphological properties of the coating. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to compare the thermal stability of nanodiamonds before and after silicon coating. The results confirmed that the deposited cubic phase silicon coating was even and continuous. The protective silicon coating could effectively improve the oxidation resistance of nanodiamonds in air flow, which facilitates the applications of nanodiamonds that are commonly hampered by their poor thermal stability.     

Selective inhibition of the oxidation of nanodiamonds for their cleaning

The effect of selective inhibition of nanodiamond oxidation upon heating of detonation carbon in air is used to extract nanodiamonds from the detonation products. The methods for cleaning nanodiamonds from nondiamond carbon modifications are described depending on the synthesis conditions.     

Electron emission properties of detonation nanodiamonds

This paper summarizes the results of systematic studies of field electron emission from detonation nanodiamond coatings corresponding to nanodiamond powders of different modifications. The role of the chemical composition of the surface of detonation nanodiamond particles in field emission mechanisms is discussed. Field emission-related electronic properties of single diamond nanodots are studied using tight-binding calculations and continuum electrostatic simulations.     

Applications of optical duobinary in optical carrier suppression and separation labeling

A novel approach is used to implement optical carrier suppression and separation （OCSS） labeling. Then, the performance of 10/40-Gb/s duobinary payload with 2.5-Gb/s amplitude shift keying （ASK） or duobi- nary label by numerical simulations is studied. Influencing factors, such as demultiplexer bandwidth and fiber Bragg grating （FBG） filter bandwidth, are investigated. Simulation result shows that the received sensitivity of ASK label is higher than that of the duobinary label, while the received sensitivity of duobi- nary payload with duobinary label is higher than that with ASK label.     

The particle size-dependent photoluminescence of nanodiamonds

The intrinsic defects- and impurities-originated photoluminescence from nanodiamond particles of various sizes (5-500 nm) were observed. Luminescence spanning from 500 nm to 800 nm can be excited with 488 nm and 532 nm wavelengths lasers without any high-energy treatment to create the defects/impurities. The luminescence is found to be particle-size and laser-wavelength dependent, suggesting different kinds of defects/impurities predominantly sustain the luminescence from nanodiamonds of different sizes.     

Single step surface modification of highly stable magnetic nanoparticles for purification of His-tag proteins

The aim of this study was to develop a simple, cheap, and rapid method for purification of His-tag recombinant proteins with high yields. The new immobilized metal ion affinity adsorbent containing superparamagnetic nanoparticles and hydrophilic resins are proposed here to improve the purification of His-tagged recombinant proteins. In this report, we have described the preparation of nanosized superparamagnetic nanoparticles (Fe₃O₄) which were prepared by chemical precipitation method followed by surface modification using phosphonomethyl iminodiacetic acid. The stable surface functionalized nanoparticles were further linked with Ni²⁺ for purification of 6× His-tagged proteins. The phosphonate group of the N-phosphonomethyl iminodiacetic acid ligand acts as a surface anchoring agent on magnetite nanoparticles and the remaining free –COOH groups outside for binding with Ni²⁺ ions. The nanoparticles were approximately 6–8 nm in size and were stable and had negligible non-specific binding for protein. The proteins were purified within 1 h and observed on sodium dodecyl sulfate-polyacrylamide electrophoresis gel.     

Preparation of silica coated cobalt ferrite magnetic nanoparticles for the purification of histidine-tagged proteins

Surface modified cobalt ferrite (CoFe₂O₄) nanoparticles containing Ni–NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe₂O₄ nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe₂O₄ agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe₂O₄ particles were coated with silica and subsequently the surface of these silica coated particles (SiO₂–CoFe₂O₄) was modified by amine (NH₂) groups in order to add further functional groups on the silica shell. Then, carboxyl (–COOH) functional groups were added to the SiO₂–CoFe₂O₄ magnetic nanoparticles through the NH₂ groups. After that Nα,Nα–Bis(carboxymethyl)-l-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO₂–CoFe₂O₄ magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3.     

Quantum confinement and fullerenelike surface reconstructions in nanodiamonds

We present x-ray absorption and emission experiments and ab initio calculations showing that the size of carbon diamond must be reduced to at least 2 nm, in order to observe an increase of its optical gap, at variance with Si and Ge where quantum confinement effects persist up to 6-7 nm. In addition, our calculations show that the surface of nanodiamond particles larger than approximately 1 nm reconstructs in a fullerenelike manner, giving rise to a new family of carbon clusters: bucky diamonds. Signatures of these surface reconstructions are compatible with pre-edge features observed in measured absorption spectra.     

Structure of nanodiamonds prepared by laser synthesis

A study is reported of nanodiamonds obtained by a new method—pulsed laser ablation of a specially prepared carbon target. In the mechanism employed to produce a diamond phase, this method is similar to that of detonation synthesis of nanodiamonds. The main structural characteristics of the material have been determined and compared with the corresponding characteristics of detonation nanodiamonds.     

Synthesis,properties, and applications of fractionated nanodiamonds

The methods for dispersing nanodiamond powders of different purity grades and preparing nanodiamond powder suspensions suitable for fractionation are analyzed. The main physicochemical properties of fractions separated from the synthesis products (blends) and purified nanodiamonds are investigated. It is found that the size distribution of nanodiamonds in the blend is inhomogeneous: an increase in the particle size leads to a decrease in the fraction of these particles. The advantages of nanodiamonds fractionated in size are demonstrated for different applications.     

Preparation of nanodiamonds by laser irradiation of graphite

Graphite powders were irradiated by pulsed laser at room temperature and normal pressure and then boiled in perchloric acid. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction pattern (EDP), X-ray diffraction (XRD) pattern, and Raman spectroscopy.The analyses on the HRTEM images, EDP, and XRD show that the diamond particles with a size of about 5 nm are obtained. The shifting and broadening of the diamond peak in Raman spectrum indicate that there are high defect density and residual internal stress in synthetic diamond.     

Atomic and electronic structures and stability of icosahedral nanodiamonds and onions

The relative stability of alternative carbon nanoparticles with icosahedral symmetry, such as diamond-like nanocrystallites and multiwalled fullerenes (onions), is investigated using the parametric model and the density functional tight-binding (DFTB) method. It is demonstrated that an increase in the size of particles and their hydrogenation favor the stabilization of diamond-like nanocrystallites. The formation of “intermediate” nanostructures consisting of diamond-like nanocrystallites inside the fullerene cage is revealed. The electronic spectra of icosahedral carbon nanoparticles are calculated.     

Design of a luminescent biochip with nanodiamonds and bacterial luciferase

An “aluminum oxide film-adhesive layer-nanodiamond-luciferase” supramolecular structure is prepared on a flat plate. It is demonstrated that, in this structure, the enzyme retains the catalytic activity. The structure prepared can be treated as a luminescent biochip prototype for use in bioluminescent analysis.     

Application of modified nanodiamonds as catalysts of heterogeneous and electrochemical catalyses

The possible use of modified nanodiamond powders in heterogeneous and electrochemical oxidation catalyses is analyzed. It is shown that the efficiency of oxidation catalysis depends on the content of atomic oxygen. The inference is drawn that the electrochemical modification of the surface of nanodiamond powders in a hydrochloric solution and the promotion of the surface with palladium are promising for the preparation of both catalysts of the oxidation of CO to CO₂ and electrodes of low-temperature fuel elements.     

Radiative and nonradiative decay rates in chromium-related centers in nanodiamonds

We address for the first time the measurement of nonradiative decay rates in Cr-related centers in nanodiamonds. Compared to our previous quantum efficiency measurement of Cr centers created in bulk diamond, separate measurements of radiative and nonradiative decay rates in grown nanodiamonds prove more challenging due to size dependence effects. We demonstrate in this Letter that, using defocused dipole imaging and collection efficiency calculation via finite-difference time-domain (FDTD), a quantum efficiency up to 0.9 can be inferred to Cr-related centers showing a 2-level system photon statistics.