Absorption and scattering of light in nanodiamond hydrosols

Scattering and absorption of optical radiation in hydrosols of detonation nanodiamonds (DND) have been studied. Experimental data are presented on the spectral response of the optical density of DND hydrosols prepared by different techniques and in different concentrations. The size distribution of DND particles in these hydrosols was investigated by dynamic light scattering (DLS). The experimental data are compared with calculations. The calculations were performed on models including both the structure of a single DND particle made up of a diamond core and a thin graphite-like shell and the size distribution of the DND particles. A comparison of experiments with the calculation provided a possibility of refining the model of the DND particle and gaining insight into the nature of particle aggregation. It is demonstrated that the combined use of two methods of investigation, which deal with the spectral response of optical density and dynamic light scattering, offers valuable information on the nature of DND hydrosol coloring and the results of particle size determination.     

pH-Mediated fine-tuning of optical properties of graphene oxide membranes

We demonstrate a pH-mediated fine-tuning method for the transmittance and optical properties of graphene oxide membranes (GOMs) which are assembled at liquid/air interface starting from graphene oxide (GO) hydrosols. The transmittance of GOM continuously decreases with the increase of the pH value of the parent hydrosol. The size and surface chemistry of GO nanosheets are discussed to how to influence the transmittance of GO hydrosol and the optical properties of the resulting membrane since a size classification occurs in acidic condition and a deoxygenate reaction is initiated by basic environment. This study indicates an easy strategy for precisely adjusting the optical properties of graphene-based membrane, which is very important for developing novel optical devices.     

Dual‐bonding structured ternary composite film of poly(vinyl alcohol)–boric acid–nanodiamond

Ternary composite films of poly(vinyl alcohol) (PVA), boric acid (BA), and detonation nanodiamond (DND) were prepared by aqueous solution method. Because of its excellent mechanical/thermal properties and low friction coefficient, DND is expected to offer PVA film superior performance if the puzzles of particle agglomeration in polymer matrix and fragile interface reaction between DND and PVA can be settled. BA was used as a crosslinking agent to form a strong network structure between DND and PVA. Investigation on microstructure of PVA/BA/DND films and bonding mechanisms therein shows that BA, DND, and PVA may crosslink by oxo‐bridges owing to the interaction of hydroxyl groups. The Young's modulus (E) of composite films was enhanced by nearly 3.3 times with only 0.8 wt % DND loading, and the antiwear, thermal stability, and waterproof properties can be significantly improved after the crosslinking. Meanwhile, the transparency of composite films can be well preserved even with large DND content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45449.     

Effect of nanodiamond surface functionalization using oleylamine on the scratch behavior of polyacrylic/nanodiamond nanocomposite

Addition of hard particles such as nanodiamonds to polymers to improve their physical and mechanical properties is very common. However, nanodiamonds are usually hydrophilic so their tendency to form agglomerates in a polymeric matrix is quite strong. In this study, the effect of nanodiamond surface modification on its uniform dispersion in a polymeric matrix such as polyacrylic-base polymer clear coat was investigated. For this purpose, detonation nanodiamond (DND) with an average particle diameter of 4–6 nm was used. To improve dispersion of as-received DND (AR-DND) in the polymeric matrix, the surfaces of the particles were modified by heat treatment (oxidation) in air and followed by functionalization using oleylamine (OLA) as surfactant. So, nanocomposites with different contents of AR-DND, HT-DND and OLA treated HT- DND (OLA-HT-DND) particles were produced. Their characterizations were investigated by employing many analytical methods such as: Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermo-gravimetry analysis (TGA). Scratch resistance test and study of coating surfaces, using scanning tunneling microscopy (STM), were carried out on the polymeric nanocomposites. The results showed that the surface-functionalized nanodiamonds are highly dispersive and stable in the polymeric matrix. In addition, scratch resistance was increased with the addition of nanoparticles.     

Detonation nanodiamonds as UV radiation filter

The attenuation of ultraviolet radiation (UVR) by detonation nanodiamonds (DND) can be significant, depending on the concentration, composition of DND surface, size of DND particles and content of nitrogen defects in DND. The ability of DND to attenuate efficiently UVA (320–400 nm), UVB (290–320 nm) and UVC (190–290) radiation via absorption and scattering makes them attractive broad-spectrum UV-protecting agents. The studied DND exhibited red photoluminescence presumably due to the nitrogen-vacancy centers.     

Transparent niobate glass-ceramics for optical limiting

The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm²), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm²). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage.     

Chemical-mechanical polishing performance of core-shell structured polystyrene@ceria/nanodiamond ternary abrasives on sapphire wafer

Driven by electrostatic attraction, Ce⁴⁺ ions or/and positively charged detonation nanodiamond (DND) particles can absorb onto negatively charged polystyrene (PS) spherical colloids. Three types of core-shell structured composite abrasives, PS@CeO₂, PS@DND and PS@CeO₂/DND, can thus be assembled. When PS@CeO₂ and PS@DND were used to polish sapphire wafer at pad rotating speed of 120–150 r/min and load pressure of ~3 kg, the material removing rate (MRR) exceeded 1.0 μm h⁻¹, 10–20 % higher than unitary abrasives. The surface profile roughness (Ra) for wafer polished by these two composite abrasives was respectively 1.25 and 0.63 nm, which is superior to CeO₂ (Ra = 1.38 nm) and DND (Ra = 1.29 nm). When using PS@CeO₂/DND, the polishing interface area can be increased owing to the combined effect of elastic PS spheres and intensively coated CeO₂ and DND. Meanwhile, the synergistic mechanism of sapphire-CeO₂ chemical reaction and the strong mechanical abrasion of DND particles benefit the polishing efficiency. MRR for this ternary composite abrasive attained 1.4–1.7 μm h⁻¹ while sapphire can be smoothed to a sub-nanoscale roughness.     

Modification of detonation nanodiamonds by heat treatment in air

In order to readily utilize nanodiamond (ND) particulates produced by detonation synthesis in many nanotechnology applications, it is necessary to modify the surface chemistry and to separate the particles into a more narrow range of particle sizes. Surface functionalization and fractionalization are highly dependent upon the method of ND synthesis and purification. For example, when material purified through the use of strong liquid oxidizers is used to produce hydrosols, they are unstable and difficult to fractionalize. In this study we developed a method of preparation that overcomes these two barriers. ND powder previously purified with a mixture of sulfuric acid and chromic anhydride was treated as follows: annealed in air followed by dispersion in water using a high power sonicator and multi-step ultracentrifugation. This treatment resulted in stable hydrosols formed from the smallest particle-size fractions.     

Antimicrobial and Antioxidant Activity of Chitosan/Hydroxypropyl Methylcellulose Film-Forming Hydrosols Hydrolyzed by Cellulase

The aim of this study was to evaluate the impact of cellulase (C) on the biological activity of chitosan/hydroxypropyl methylcellulose (CH/HPMC) film-forming hydrosols. The hydrolytic activity of cellulase in two concentrations (0.05% and 0.1%) was verified by determination of the progress of polysaccharide hydrolysis, based on viscosity measurement and reducing sugar-ends assay. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging effect, the ferric reducing antioxidant power (FRAP), and microbial reduction of Pseudomonas fluorescens, Yersinia enterocolitica, Bacillus cereus, and Staphylococcus aureus were studied. During the first 3 h of reaction, relative reducing sugar concentration increased progressively, and viscosity decreased rapidly. With increasing amount of enzyme from 0.05% to 0.1%, the reducing sugar concentration increased, and the viscosity decreased significantly. The scavenging effect of film-forming solutions was improved from 7.6% at time 0 and without enzyme to 52.1% for 0.1% cellulase after 20 h of reaction. A significant effect of cellulase addition and reaction time on antioxidant power of the tested film-forming solutions was also reported. Film-forming hydrosols with cellulase exhibited a bacteriostatic effect on all tested bacteria, causing a total reduction.     

Structural properties of nanocomposites based on resole-type phenol-formaldehyde oligomers and detonation nanodiamonds

Using the methods of infrared spectroscopy (IRS) and X-ray photoelectron spectroscopy (XPS), it was shown that short-term high-energy machining of detonation nanodiamonds (DND) leads to structural changes in the crystal structure and functional composition of the surface layer on particles. The possibility of spontaneous formation for stable colloidal systems with a narrow size distribution of mechanically activated DND in phenol-formaldehyde oligomers (PFO) was established. By molecular spectroscopy it was revealed that π → π* interactions of the aromatic rings of PFO are caused by orientational phenomena as a result of hydrogen bonds between an activated DND surface and functional groups of PFO. The effect of DND concentration on the curing reaction parameters ofpsgr the phenol-formaldehyde oligomer was determined by differential scanning calorimetry (DSC). The concentration effect of mechanically activated nanodiamonds on the physical and mechanical characteristics of a composite material based on phenol-formaldehyde binder and polyamide paper (Nomex) was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48582.     

Synthesis of Yb:YAG Ceramics Without Sintering Additives and their Performance

High‐quality 10%Yb:YAG ceramics was successfully synthesized without sintering additives such as SiO₂ for the first time. Optical scattering loss of the Yb:YAG ceramics was 0.1%/cm and its transmitted wavefront distortion was λ/19.5 (t = 4.7 mm), which was very comparable to single crystal laser materials. Laser performance of thin disk made of this material (φ11 × t0.15 mm) was 74.1% of slope efficiency (optical‐to‐optical conversion efficiency: 68.1%) and the maximum output power reached 1.8 kW. Synthesis of high‐purity and high‐quality YAG ceramics without using sintering additives was demonstrated for the first time to our knowledge and we can discuss the technological meaning of high‐purity materials for the future.     

The Effect of Using Micro-Clustered Water as a Polymer Medium

The aim of the study was to investigate the changes within the physicochemical properties of gelatin, carrageenan, and sodium alginate hydrosols prepared on the basis of micro-clustered (MC) water. The rheological parameters, contact angle and antioxidant activity of hydrosols were investigated. Moreover, the pH, oxidation–reduction potential (ORP) and electrical conductivity (EC) were measured. The hydrosols with MC water were characterized by a lower pH, decreased viscosity, a lower contact angle, and only slightly lower antioxidant activity than control samples. The results showed that hydrosol’s properties are significantly changed by MC water, which can lead to enhancement of its applicability but requires further investigation.     

Structural study of detonation nanodiamonds

The structure of spherical hollow detonation nanodiamonds (DND) previously ground in a planetary mill for 10 min has been studied by synchrotron radiation diffraction. The interference contribution of the diffraction pattern from DND calculated using different structural parameters has been compared with the experimental pattern of DND after mechanical treatment. It was shown that after mechanical treatment of spherical hollow DND (r_inner=19.94 A, r_outer=25.47 A), two kinds of particles were observed: one was non-hollow spheres of r=13.9 A size at the same lattice parameters a=b=3.85 A, c=3.45 A and the others, of the size 5a×13b×5c at the parameters a=c=3.567 A, b=3.85 A, were particles of non-spherical shape.     

Nuclear spin-lattice relaxation in nanocarbon compounds caused by adsorbed oxygen

Nuclear spin-lattice relaxation measurement is an effective tool for studying electronic structure and magnetic properties of nanosized compounds. The present work deals with the effect of oxygen molecules, adsorbed onto the surface of carbon nanoparticles - in which the number of surface atoms is comparable with that in the sample's volume - on nuclear spin-lattice relaxation rate of the carbon nuclei. We measured ¹³C spin-lattice relaxation in as-prepared (air rich) and out-gassed samples of detonation nanodiamond (DND), activated carbon fibers (ACF) and glassy carbon (GC) samples having multishell onion-like structure.Our measurements showed that the paramagnetic oxygen molecules (the only magnetic agent in ambient air), being physisorbed onto the surface and in structural voids of ACF and GC, create an additional relaxation channel and definitely affect the ¹³C spin-lattice relaxation as do the unpaired electrons of the internal dangling bonds. Air removal results in 1.5-2 times elongation in T₁. In contrast, the relaxation time is nearly the same for as-prepared and out-gassed DND samples. The reason is that in DND oxygen molecules have access only to the surface carbon nuclei whereas the rest of carbons remain unaffected by oxygen. Thus the main relaxation agents in DND particles are dangling bonds with unpaired electron spins, which mask the relaxation effect of paramagnetic oxygen. These findings are in a good agreement with our EPR data, which show that oxygen affects the inherent paramagnetic defects in the aforementioned nanocarbons.     

Direct sector field ICP-MS determination of metal impurities in detonation nanodiamond

A simple, rapid, sensitive and accurate method for the determination of metal impurities in detonation nanodiamond (DND), based upon the direct aspiration of aqueous suspensions of nanodiamond into a sector field inductively coupled plasma mass spectrometer (ICP-MS) is proposed. Quantitative release, atomisation and ionisation of the nanodiamond coated and encased elements, within the plasma, and their detection free from spectral interference, was confirmed by comparing results obtained from the direct ICP-MS analysis of aqueous suspensions with results from the ICP-MS analysis of the acidic digests of pre-ashed DND, obtained through DND combustion in air at 723 K for 48 h. The developed direct method was capable of the quantification of more than 30 elements at concentration levels of 10⁻⁸ wt.%, with acceptable levels of precision and accuracy, from an aqueous suspension of just 0.1 mg mL⁻¹ DND.     

Locating inherent unpaired orbital spins in detonation nanodiamonds through the targeted surface decoration by paramagnetic probes

Detonation nanodiamond (DND) produced by explosive method has been successfully modified by divalent copper ions via their exchange with protons of neighboring carboxyl groups in water suspension. These ions interact magnetically with all diamond defect sites (both surface and bulk) causing changes in parameters of electron paramagnetic resonance (EPR) signal originating from spins (S = 1/2) of dangling C-C bonds — i.e. unpaired lone orbital paramagnetic centers (PC). EPR on the series of well purified aggregated and disintegrated DND samples in powders and suspensions showed that EPR parameters of PC in DND are unique features characterizing the nanodiamond particle as an isolated object. Surface Cu²⁺ ions located on the DND surface have been used for probing the location of PC. Double component analysis of PC's EPR spectra showed quasilinear dependence of line broadening for both EPR spectra components on probe concentration. The concentration changes for the broader component were found to be more prominent than that for the narrower one. It allows attributing PC characterized by the broader and narrower components to different types of defects located closer to the DND surface and deeper towards the diamond core. The estimated depths of occurrence for two types of intrinsic PC are ~ 0.8 nm and ~ 1.5 nm from the DND surface for the shallow and deeper PC, respectively.     

Enhanced non-linear optical properties of Eu3+ activated glasses by embedding silver nanoparticles

Tri-positive lanthanide ion (Eu³⁺) activated glasses doped with different concentrations of silver (Ag0₎ nanoparticles obtained using thermal reducing agent were fabricated by applying the method of melt quench. The formation of Ag⁰ nanoparticles in glasses was revealed by the surface plasmon resonance (SPR) peak in the absorption spectra. Transmission electron microscopic measurements confirmed the presence of spherically shaped Ag⁰ nanoparticles of different size distribution. The absorption spectra showed a red–shift of the SPR peak with an increase in AgNO₃ concentration occurring through Ostwald's ripening process because of the growth of particle size (as evidenced from microscope images). The non-linear optical (NLO) and optical limiting measurements were performed in the near infrared spectral region and femtosecond pulse excitation. The non-linear parameters were found to increase as the AgNO₃ concentration increased to 0.6 mol %, however, the parameters subsequently decreased at higher doping level. The optical limiting threshold values demonstrated a reverse trend. The increase in non-linear optical properties regarding Ag nanoparticles concentration attributed to the enhancement of polarizabilities of glasses that occurred through local field stimulated by SPR of Ag nanoparticles when exposed to laser radiation of high energy. The increase in NLO coefficients (particularly the non-linear absorption coefficient) and the decrease in optical limiting threshold values with AgNO₃ concentration (up to 0.6 mol %) indicated that these glasses containing 0.6 mol % AgNO₃ are useful for the construction of the power optical limiters that function at the infrared region in the femtosecond pulse regime.     

Seeding slurries based on detonation nanodiamond in DMSO

Identification of a solvent where nanodiamond particles form stable colloids is very important for a variety of applications including seeding of a substrate for diamond film growth. Dimethyl sulfoxide (DMSO) is one of the most powerful readily available organic solvents. We demonstrated that using DMSO as a solvent for detonation nanodiamonds (DND) provides significant advantages in achieving resistance to sedimentation in colloidal suspensions for DND with positive zeta potentials. Colloidal stability of DND with negative zeta potentials in DMSO, however, is low. Using DMSO allows for the effective fractionation of a variety of DNDs including those that cannot be fractionated using DI water, for example, as a solvent. We also present seeding results using different DMSO/alcohol seeding slurry compositions. Combination of DMSO and alcohol as a seeding slurry allows removal of the solvent without damaging uniformity of the seeds after their distribution over a substrate.     

Preparation and characterization of transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency

Transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency were reported in this paper. First, zinc oxide (ZnO) precursor was synthesized via the homogeneous precipitation method and ZnO nanoparticles were then made by calcination of the precursor at different temperature. The structural properties of the as-prepared ZnO nanoparticles were studied in detail using thermogravimetry (TGA), differential thermal analysis (DTA), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM), respectively. Transparent ZnO/epoxy nanocomposites were subsequently prepared from transparent epoxy (EP-400) and as-prepared ZnO nanoparticles via in situ polymerization. Optical properties of ZnO/epoxy nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet-visible (UV-vis) spectrophotometer. The optical properties of the as-obtained nanocomposites were shown to depend on ZnO particle size and content. The nanocomposite containing a very low content (0.07% in weight) of ZnO nanoparticles with an average particle size of 26.7 nm after calcination at 350 °C possessed the most optimal optical properties, namely high-visible light transparency and high-UV light shielding efficiency, that are desirable for many important applications.     

Preparation of silver hydrosols using polyethylene glycol modified with vinyl pyrrolidone

Hydrosols containing silver nanoparticles were prepared from copolymers of ethylene glycol (EG) and vinyl pyrrolidone (VPy). The copolymers were synthesized using a macro-azo-radical initiator appended with EG units. The hydrosols were prepared by simply stirring the copolymers with AgNO₃ in water at room temperature. The nanoparticles conferred thermal stability to the hydrosols, up to 80 °C. Spectroscopic, thermal, and gas chromatography analyses revealed that the silver nanoparticles were protected by EG and carbonyl groups with strong interaction between silver and the oxygen species of EG and VPy.