Study on the Modification of Nanodiamond with DN-10

Fourier transform infrared spectroscopy (FT-IR) and ζ-potential were introduced to study the effect of different modification parameters on the surface properties of nanodiamond (NO). Results showed that under stirring grinding conditions, ND hard aggregates were smashed and some active spots on them reacted with surfactant molecules, which led to the increase in its ζ-potential and stability. Different models of surface modification were also given in this study.     

Mechanochemical Dispersion of Nanodiamond Aggregates in Aqueous Media

A technology of mechanochemical treatment (MCT) is introduced to modify nanodiamond (ND) surface aiming to obtaining a stable suspension with well-dispersed ND particles in aqueous medium. ND investigated in this paper is a purified product of nanometer-sized diamond synthesized by explosive detonation. As obvious aggregation and sediment were observed when the sample was added into deionized water, it is crucial to conduct deaggregation and dispersion investigations. Amid a series of mechanical treatments, i.e. grinding, stirring, ultrasonic and classification, some reagents are introduced to modify the newly created surface during aggregates comminution. For the co-effects of mechanical forces and surfactants, the mean size of particles was reduced and a stable system containing ND with narrow size distribution was prepared. Mechanism of surface reaction and modification are discussed, while AFM, Zetasizer3000HS, XRD, XPS and FTIR are utilized for the analysis. The functional chemical structure of ND p     

On the ζ-Potential of Nanodiamond in Aqueous Systems

Several factors affecting the ζ-potential of nanodiamonds were studied. The Chemical Mechanical Modification (CMM) of surface, different surfactants and its dosage, and inorganic ions on the ζ-potential of nanodiamond sample L were studied using ZETASIZER3000HS and Nexus470. Results show that the ζ-potential changes with its parameters of detonation synthesis and purification. Results also suggest that CMM and subsequent treatments employed can alter apparently the ζ-potential and that some anionic surfactants increase the absolute value of the ζ-potential in the alkaline surrounding.     

Modification of dispersibility of nanodiamond by grafting of polyoxyethylene and by the introduction of ionic groups onto the surface via radical trapping

To improve the dispersibility of polycrystalline nanodiamond (ND) in solvents, the grafting of polymers and introduction of ionic groups onto ND surface via radical trapping by ND surface were investigated. The grafting of polyoxyethylene (POE) onto ND surface by trapping of POE radicals formed by the thermal decomposition of POE macro azo-initiator (Azo-POE) was examined. The polymer radicals formed by the thermal decomposition of Azo-POE were successfully trapped by ND surface to give POE-grafted ND. The effect of temperature on the grafting of POE onto ND was discussed. In addition, the introduction of cationic protonated amidine groups onto ND was achieved by the trapping of radicals bearing protonated amidine groups formed by thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AMPA). The anionic carboxylate groups was introduced onto ND surface by the trapping of the radicals bearing carboxyl groups formed by thermal decomposition of 4,4′-azobis(4-cyonovaleric acid) (ACVA) followed by the treatment with NaOH aqueous solution. The dispersibility of ND in water was remarkably improved by the grafting of POE, based on the steric hindrance of polymer chains and by the introduction of ionic groups, based on the ionic repulsion, onto ND surface.     

PTFE surface modification by Ar plasma and its characterization

Polytetrafluoroethylene (PTFE) samples were exposed to argon plasma discharge and the changes of the PTFE surface properties were studied by different methods. Surface wettability and aging of the plasma modified PTFE were derived from the contact angle measured by standard goniometry. Electrokinetical potential (ζ-potential) was determined by SurPASS Instrument. The ζ-potential and the contact angle characterize “chemistry” of the PTFE surface and also make possible to follow the aging of the PTFE surface after the plasma treatment. The surface morphology and roughness were examined by Atomic Force Microscopy (AFM). Surface concentrations of elements were determined by X-ray photoelectron spectroscopy (ARXPS). The contact angle of the modified PTFE decreases with increasing time of the plasma treatment. During the aging of the plasma modified PTFE the contact angle increases. After the plasma treatment dramatic changes in the PTFE surface morphology and roughness were observed. Also a significant increase of ζ-potential is observed, which indicates more hydrophilic surface of the modified PTFE in comparison with pristine one. With increasing time of the plasma treatment the total oxygen content in the polymer surface layer increases.     

Facile synthesis of cationic polymer functionalized nanodiamond with high dispersity and antibacterial activity

In this work, a cationic polymer, N-alkylated poly (4-vinylpyridine) was applied for the surface functionalization of nanodiamond (ND). The facile route not only settled the problems of agglomeration and poor dispersion stability of ND but also rendered the nanomaterial antibacterial property. Chemical modification of the particles was confirmed by FT-IR spectroscopy and ¹HNMR, and the cationic polymer contents were determined by TGA studies. The particle diameters and dispersity of functionalized NDs were investigated by TEM and DLS measurements. It was found that extremely tight core aggregates (100–200 nm) were broken into tiny nanoparticles (20–30 nm) through functionalization with NPVP-propyl or NPVP-hexyl, which gave stable and homogeneous functionalized ND particles in colloidal solution. The antibacterial tests against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) showed that the cationic polymer-modified ND exerted certain antibacterial activity. The FE-SEM images indicated that NPVP-hexyl-ND particles were attached to the cell wall surface of E. coli, which subsequently led to the formation of nanoscale holes on cell membrane and eventually the serious destruction of cell wall. We suspected that the interaction of NPVP-hexyl-ND with bacteria may come from the electrostatic interactions, the intermolecular and surface forces between functionalized nanoparticles and cell membranes, which may damage the outer membranes of bacteria and result in cell death.     

Controlled adhesion of human lymphocytes on electrically charged polymer surface having phosphorylcholine moiety

The human lymphocytes were interacted with polymer surfaces whose surface potential was controlled by the formation of a polyion complex (PIC) having a phosphorylcholine moiety. 3-(Methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit was copolymerized with 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate. PIC was made at the solid–liquid interface, that is, an aqueous solution containing an anionic polymer with different concentrations was contacted with a cationic polymer coated polymer membrane. The formation process of PIC was followed using a quartz crystal microbalance, and the PIC surfaces were analyzed by ζ-potential and X-ray photoelectron spectroscopy. The surface potential on the PIC was controllable from +20 to −16 mV, which increased in the amount of adsorbed anionic copolymer as the ζ-potential decreased toward the negative charge. The PIC surface in contact with human lymphocyte for 5 h was observed using a scanning electron microscopy and the density of the adherent human lymphocyte was determined by the lactate dehydrogenase method. The lymphocyte adhesion on the surface was gradually reduced with an increase in the negative value of the ζ-potential. The morphological change in the adherent lymphocytes was not observed on the polymer surfaces with MPC units. The adherent lymphocytes were not activated on the PIC surface. The lymphocyte adhesion with reduced activation could be controlled by changing the surface potential on the polymer with the MPC unit.     

Study on protein conformation and adsorption behaviors in nanodiamond particle-protein complexes

In the present research, the conformation of bovine serum albumin (BSA) in the nanodiamond particle (ND)-BSA complex was studied by Fourier transform infrared spectroscopy, fluorescence spectroscopy, UV-vis spectroscopy, and circular dichroism spectroscopy. The spectroscopic study revealed that most BSA structural features could be preserved in the complex though the BSA underwent conformational changes in the complex due to ND-BSA interaction. In addition, BSA adsorption isotherms and zeta-potential measurements were employed to investigate the pH dependence of the ND-BSA interaction. The changes in surface charge of the ND-BSA complex with pH variations indicated that the binding of BSA to ND might lead to not only the adsorption of BSA onto the ND surface but also the partial breakup of ND aggregates into relatively small ND-BSA aggregates because of the strong binding force between ND and BSA. The results show that ND is an excellent platform for protein immobilization with high affinity and holds great potential to be used for biosensor applications.     

Field electron emission from nanodiamond

Nanodiamond (ND) films on silicon substrates have been synthesized by plasmachemical deposition (PCD). Films with minimum differences in the structure and morphology, which were obtained by varying the PCD process parameters, exhibited significantly (several orders in magnitude) different field-emission currents. It was found that the surface of ND films showing by the maximum field-emission currents contains needle-like carbon structures. Based on the obtained experimental data, it is concluded that the field-emission properties of ND films are determined by the presence of non-diamond carbon inclusions.     

Development of docetaxel nanocapsules for improving in vitro cytotoxicity and cellular uptake in MCF-7 cells

The aim of this study was to fabricate docetaxel loaded nanocapsules (DTX-NCs) with a high payload using Layer-by-Layer (LbL) technique by successive coating with alternate layers of oppositely charged polyelectrolytes. Developed nanocapsules (NCs) were characterized in terms of morphology, particle size distribution, zeta potential (ζ-potential), entrapment efficiency and in vitro release. The morphological characteristics of the NCs were assessed using transmission electron microscopy (TEM) that revealed coating of polyelectrolytes around the surface of particles. The developed NCs successfully attained a submicron particle size while the ζ-potential of optimized NCs alternated between (+) 34.64?±?1.5 mV to (?) 33.25?±?2.1 mV with each coating step. The non-hemolytic potential of the NCs indicated the suitability of the developed formulation for intravenous administration. A comparative study indicated that the cytotoxicity of positively charged NCs (F4) was significant higher (p?in vitro on MCF-7 cells. Furthermore, cell uptake studies evidenced a higher uptake of positive NCs (≥1.2 fold) in comparison to negative NCs. In conclusion, formulated NCs are an ideal vehicle for passive targeting of drugs to tumor cells that may result in improved efficacy and reduced toxicity of encapsulated drug moiety.     

On the role of Nb-related sites of an oxidized β-TiNb alloy surface in its interaction with osteoblast-like MG-63 cells

β-Stabilized titanium (Ti) alloys containing non-toxic elements, particularly niobium (Nb), are promising materials for the construction of bone implants. Their biocompatibility can be further increased by oxidation of their surface. Therefore, in this study, the adhesion, growth and viability of human osteoblast-like MG 63 cells in cultures on oxidized surfaces of a β-TiNb alloy were investigated and compared with the cell behavior on thermally oxidized Ti, i.e. a metal commonly used for constructing bone implants. Four experimental groups of samples were prepared: Ti or TiNb samples annealed to 600 °C for 60 min in a stream of dry air, and Ti and TiNb samples treated in Piranha solution prior to annealing. We found that on all TiNb-based samples, the cell population densities on days 1, 3 and 7 after seeding were higher than on the corresponding Ti-based samples. As revealed by XPS and Raman spectroscopy, and also by isoelectric point measurements, these results can be attributed to the presence of T-Nb₂O₅ oxide phase in the surface of the alloy sample, which decreased its negative zeta (ζ)-potential in comparison with zeta (ζ)-potential of the Ti sample at physiological pH. This effect was tentatively explained by the presence of positively charged defects acting as Lewis sites of the surface Nb₂O₅ phase. Piranha treatment slightly decreases the biocompatibility of the samples, which for the alloy samples may be explained by a decrease in the number of defective sites with this treatment. Thus, the presence of Nb and thermal oxidation of β-stabilized Ti alloys play a significant role in the increased biocompatibility of TiNb alloys.     

Experimental and Numerical Investigation of Mechanical and Thermal Residual Strains in Adhesively Bonded Joints

Abstract:  This paper describes an investigation of residual and mechanical strains in aluminium/aluminium (Al/Al) and aluminium/carbon fibre-reinforced polymer (Al/CFRP) adhesively bonded double-lap joints. Residual strains were measured inside the adherends by means of neutron diffraction (ND) and modelled using finite element analysis (FEA). In the Al/Al joints the measured residual strains were negligible, showing good agreement with FE predicted results. However, considerable strains developed in the Al/CFRP joint because of differential thermal contraction of the two materials during joint manufacture. Although considerable scatter was seen in the ND results, the measured and predicted trends showed similar behaviour and were of comparable magnitude. The paper also reports measurements of internal strains in an Al/CFRP joint under tensile load using ND and of surface strains using moiré interferometry (MI). In general, good agreement was observed between FE predictions, surface strains measured with MI and internal strains measured with ND for the loaded Al/CFRP joint.     

Iontophoresis from a micropipet into a porous medium depends on the ζ-potential of the medium

Iontophoresis uses electricity to deliver solutes into living tissue. Often, iontophoretic ejections from micropipets into brain tissue are confined to millisecond pulses for highly localized delivery, but longer pulses are common. As hippocampal tissue has a ζ-potential of approximately -22 mV, we hypothesized that, in the presence of the electric field resulting from the iontophoretic current, electroosmotic flow in the tissue would carry solutes considerably farther than diffusion alone. A steady state solution to this mass transport problem predicts a spherically symmetrical solute concentration profile with the characteristic distance of the profile depending on the ζ-potential of the medium, the current density at the tip, the tip size, and the solute electrophoretic mobility and diffusion coefficient. Of course, the ζ-potential of the tissue is defined by immobilized components of the extracellular matrix as well as cell-surface functional groups. As such, it cannot be changed at will. Therefore, the effect of the ζ-potential of the porous medium on ejections is examined using poly(acrylamide-co-acrylic acid) hydrogels with various magnitudes of ζ-potential, including that similar to hippocampal brain tissue. We demonstrated that nearly neutral fluorescent dextran (3 and 70 kD) solute penetration distance in the hydrogels and OHSCs depends on the magnitude of the applied current, solute properties, and, in the case of the hydrogels, the ζ-potential of the matrix. Steady state solute ejection profiles in gels and cultures of hippocampus can be predicted semiquantitatively.     

The effect of micro-alloying addition of Cr on age hardening of an Mg–Zn alloy

This work reports a chemical method called “co-deposition route” for fabricating ND (nanodiamond)/Cu composite at a molecular-level mixing. The main procedure of “co-deposition route” includes four steps. ND particles have been functionalized by HF acid before co-deposition. SEM, HRTEM (high-resolution transmission electron spectroscopy), XRD (X-ray diffraction), EDS (energy-dispersive spectrum analysis) and optical microscope were carried out to characterize the as-prepared composite powders and bulk composites. Results indicated that copper matrix composite with a homogeneous dispersion of functionalized ND particles can be prepared. The modification of ND particles was performed by HF (30 vol%) acid at 70 °C, and CF bond was successfully detected by XPS (X-ray photoelectron spectrum) and IR (Infrared spectroscopy). The properties of relative density, microhardness and electric conductivity of ND/Cu composites have been measured. With the comparison of conventional methods, it showed that the as-prepared ND/Cu composites with good combined performances have a promising future for industry application.     

Boron-doped transparent conducting nanodiamond films

Boron-doped nanodiamond (ND) films on silica substrates have been obtained by the method of microwave plasma-enhanced chemical vapor deposition (MWPECVD). Using special technological regimes ensuring the growth of boron-doped ND films after the deposition of an initial ND nucleation layer with small roughness (<15 nm) and a large number of diamond phase nucleation centers per unit surface area (>10¹⁰ cm⁻²), it is possible to obtain conducting ND films transparent in the UV spectral range. Dependence of the transparency and conductivity of the obtained films on the boron concentration and methane content in the working methane-hydrogen mixture has been studied.     

Surface structure and properties of functionalized nanodiamonds: a first-principles study

The goal of this work is to gain fundamental understanding of the surface and internal structure of functionalized detonation nanodiamonds (NDs) using quantum mechanics based density functional theory (DFT) calculations. The unique structure of ND assists in the binding of different functional groups to its surface which in turn facilitates binding with drug molecules. The ability to comprehensively model the surface properties, as well as drug-ND interactions during functionalization, is a challenge and is the problem of our interest. First, the structure of NDs of technologically relevant size (～5 nm) was optimized using classical mechanics based molecular mechanics simulations. Quantum mechanics based density functional theory (DFT) was then employed to analyse the properties of smaller relevant parts of the optimized cluster further to address the effect of functionalization on the stability of the cluster and reactivity at its surface. It is found that functionalization is preferred over reconstruction at the (100) surface and promotes graphitization in the (111) surface for NDs functionalized with the carbonyl oxygen (C = O) group. It is also seen that the edges of ND are the preferred sites for functionalization with the carboxyl group (-COOH) vis-à-vis the corners of ND.     

Surface characterization of glass fibers made from silicate waste: Zeta-potential and contact angle measurements

The surface properties of three glass fibers made from silicate waste and of various commercial glass fibers have been characterized by zeta ()-potential and contact angle measurements. -Potential measurements indicate that the formation of the electrochemical double layer is clearly affected by the type and amount of network former and network modifier oxides in the glass structure. A high negative -potential is measured for fibers containing large amounts of network former oxides. The amount and type of network modifier cations leaching from the glass and adsorbing in the electrochemical double layer causes the negative -potential to decrease. pH-depending -potentials show that the Brønsted acidic surface character predominates. The ratio of network former to network modifier oxides affect the course of the = f(pH) function and, therefore, the acidity of the fiber surfaces. Contact angles of glass fibers against water and diiodomethane have been measured in order to estimate the fiber surface tensions. All investigated glass fibers are rather hydrophobic. The surface tension of the fibers is similar to polymer. The results of the present study are relevant for the use of such glass fibers as reinforcement for polymer matrix composites.     

Patient preferences for in-center intense hemodialysis

There is a lack of data on patient preferences for intense hemodialysis (IHD). In this study, we conducted a cross-sectional survey to identify patient preferences and patient-centered barriers for IHD. A questionnaire on preferences and anticipated barriers, anticipated benefits, and quality of life for three in-center IHD schedules (daytime 2 hr six times/week [DHD], nocturnal 8 hr three times/week [ND3], and nocturnal 8 hr six times/week [ND6]) was administered to 100 chronic hemodialysis patients. A majority of patients (68%) were willing to undergo DHD for symptomatic benefits or increase in survival. An increase in energy level (94%) and improvement in sleep (57%) were the most common potential benefits that would justify DHD, but only 19% would undergo DHD for an increase in survival of < or =3 years. Only 20% and 7% would consider ND3 and ND6, respectively. The most common reported barriers were inadequate time for self (50%) and family (53%), followed by transportation difficulties (53%). Most patients would undergo DHD for symptomatic or survival benefits, but not ND3 or ND6. Disruption of personal time, however, is an important consideration. Success of DHD program would depend on arrangements for transportation to dialysis unit.     

The effect of diamond nanoparticles on redox and immune parameters in rats

The objective of the study was to evaluate the effect of nanodiamond (ND) particles manufactured by detonation method (size of grains 2-10 nm) on organism health status. Wistar rats were administrated with diamond nanoparticles colloid by intravenous and intraperitoneal injection. Both routes of administration increased superoxide dismutase (SOD) activity and at the same time decreased activity of glutathione reductase (GR) and glutathione peroxidase (GPx) within erythrocytes. ND did not significantly affect neither total antioxidative state (TAS) nor thiobarbituric acid reactive substances (TBARS) in examined animals blood plasma. This study was also designed to examine the effect of ND on the phagocytosis activity and oxidative burst of innate immune cells. Both intravenous and intraperitoneal administration of ND hydrocolloid decreased the number of the phagocytosing neutrophiles stimulated by E. coli. Independently of the injection method nanodiamond increased the number of cells with stimulated oxidative burst and it suppressed the mechanism of oxygen dependent bacteria elimination.     

Preparation and characterization of stable aqueous higher-order fullerenes

Stable aqueous suspensions of nC?? and individual higher fullerenes, i.e. C??, C?? and C??, are prepared by a calorimetric modification of a commonly used liquid-liquid extraction technique. The energy requirement for synthesis of higher fullerenes has been guided by molecular-scale interaction energy calculations. Solubilized fullerenes show crystalline behavior by exhibiting lattice fringes in high resolution transmission electron microscopy images. The fullerene colloidal suspensions thus prepared are stable with a narrow distribution of cluster radii (42.7 ± 0.8 nm, 46.0 ± 14.0 nm, 60 ± 3.2 nm and 56.3 ± 1.1 nm for nC??, nC??, nC?? and nC??, respectively) as measured by time-resolved dynamic light scattering. The ζ-potential values for all fullerene samples showed negative surface potentials with similar magnitude ( - 38.6 ± 5.8 mV, - 39.1 ± 4.2 mV, - 38.9 ± 5.8 mV and - 41.7 ± 5.1 mV for nC??, nC??, nC?? and nC??, respectively), which provide electrostatic stability to the colloidal clusters. This energy-based modified solubilization technique to produce stable aqueous fullerenes will likely aid in future studies focusing on better applicability, determination of colloidal properties, and understanding of environmental fate, transport and toxicity of higher-order fullerenes.