Thermal conductivity and properties of cyanate Ester/nanodiamond composites

The aim of this study was to improve thermal conductivity, thermal stability, and mechanical properties of bisphenol A dicyanate ester with the addition of nanodiamond. Cyanate ester/nanodiamond composites containing various ratios of nanodiamond were prepared. Thermal stability and thermal conductivity of the samples were evaluated by thermogravimetric analysis, differential scanning calorimetry, and laser flash method, respectively. The samples were characterized with the analysis such as gel content, water absorption capacity, and stress–strain test. Hydrophobicity of the samples was determined by contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy. The obtained results prove that the cyanate ester/nanodiamond composites have good thermal and mechanical properties and can be used in many applications such as the electronic devices, materials engineering, and other emergent. Copyright © 2014 John Wiley & Sons, Ltd.     

Biological activity of detonation nanodiamond and prospects in its medical and biological applications

The present review summarizes and analyzes recent advances in the field of medical and biological applications of detonation nanodiamond and, on this basis, considers most promising ways of creation of anticancer and antimicrobial drugs, diagnostic agents, and nanocompositions for orthopedic surgery. In addition, progress in the surface chemistry of detonation nanodiamond is discussed and problems related to purposeful surface modification with a view to obtain detonation nanodiamond with desired properties ensuring their successful application in biology and medicine are considered.     

纳米金刚石的表面修饰及应用

纳米金刚石是一种新型的碳纳米粒子,具有硬度高、化学稳定、良好的生物相容性和热传导性等优点,有广阔的应用前景。对于纳米金刚石的应用,大多需要对其进行表面修饰。本文主要结合近年来国内外研究成果,阐述了氢化、羧酸化、羟基化及其他表面修饰等纳米金刚石的表面修饰方法,总结了纳米金刚石在润滑、抛光、生物医学、复合材料等领域的应用。     

Preparation and properties of Miramistin–hyaluronic acid coatings on the nanodiamond surface

Hyaluronic acid is a promising coating for imparting biocompatibility to nanodiamond–antibiotic composites. It has been found that the adsorption of Miramistin on nanodiamonds with an initial negative zeta-potential increases the adsorption of hyaluronic acid, which remains lower than on positively charged nanodiamonds that are not affected by the pre-adsorption of Miramistin. The highest adsorption of hyaluronic acid is observed when Miramistin neutralizes the surface charge of nanoparticles.     

Effect of silica nanoparticles on properties of waterborne polyurethanes

Waterborne polyurethane composites containing silica nanoparticles are synthesized successfully via the in situ polymerization.The structure,thermal stability,surface hardness,tensile strength,UV-Vis absorbance,dynamic mechanical properties and chemicals resistance of the resulting composites are investigated by FTIR,TEM,TGA,UV-Vis,DMA and chemicals soakage measurements.Results show that polyurethane molecules and silica nanoparticles are linked with covalent bonds.As a result,physical properties of polyurethane composites,such as thermal stability,surface hardness,weather and chemicals resistance are all improved when an appropriate concentration of silica nanoparticles are incorporated.     

Composites Based on Polytetrafluoroethylene and Detonation Nanodiamonds: Filler–Matrix Chemical Interaction and Its Effect on a Composite’s Properties

Specific properties of PTFE composites filled with ultradisperse detonation diamonds (UDDs) with different surface chemistries are studied. It is found for the first time that filler in the form of UDDs affects not only the rate of PTFE thermal decomposition in vacuum pyrolysis, but also the chemical composition of the products of degradation. The wear resistance of UDD/PTFE composites is shown to depend strongly on the UDD surface chemistry. The presence of UDDs in a PTFE composite is found to result in perfluorocarbon telomeres, released as a readily condensable fraction upon composite pyrolysis. The chemical interaction between PTFE and UDDs, characterized by an increase in the rate of gas evolution and a change in the desorbed gas’s composition, is found to occur at temperature as low as 380°C. It is shown that the intensity of this interaction depends on the concentration of oxygen-containing surface groups, the efficiency of UDDs in terms of the composite’s wear resistance being reduced due to the presence of these groups. Based on the experimental data, a conclusion is reached about the chemical interaction between UDDs and a PTFE matrix, its dependence on the nanodiamond surface chemistry, and its effect on a composite’s tribology.     

Characterizing protein activities on the lysozyme and nanodiamond complex prepared for bio applications

Recently, nanodiamond particles have attracted increasing attention as a promising nanomaterial for its biocompatibility, easy functionalization and conjugation with biomolecules, and its superb physical/chemical properties. Nanodiamonds are mainly used as markers for cell imaging, using its fluorescence or Raman signals for detection, and as carriers for drug delivery. For the success of these applications, the biomolecule associated with the nanodiamond has to retain its functionality. In this work, the protein activities of egg white lysozyme adsorbed on nanodiamond particles of different sizes is investigated. The lysozyme nanodiamond complex is used here as a protein model for analyzing its structural conformation changes and, correspondingly, its enzymatic activity after the adsorption. Fourier-transform infrared spectroscopy (FTIR) is used for the analysis of the sensitive protein secondary structure. To access the activities of the adsorbed lysozyme, a fluorescence-based assay is used. The process of adsorption is also analyzed using UV-visible spectroscopic measurements in combination with analysis of nanodiamond properties with FTIR, Raman spectroscopy, and ζ-potential measurements. It is found that the activity of lysozyme upon adsorption depends on the nanodiamond's size and surface properties, and that the nanodiamond particles can be selected and treated, which do not alter the lysozyme functional properties. Such nanodiamonds can be considered convenient nanoparticles for various bioapplications.     

Nanodiamond Thin Film Electrodes: Metal Electro‐Deposition and Stripping Processes

The properties of a nanodiamond thin film deposit formed on titanium substrates in a microwave‐plasma enhanced CVD process, are investigated for applications in electroanalysis. The nanodiamond deposit consists of intergrown nano‐sized platelets of diamond with a high sp² carbon content giving it high electrical conductivity and electrochemical reactivity. Nanodiamond thin film electrodes (of approximately 2 μm thickness) are characterized by electron microscopy and electrochemical methods. First, for a reversible one electron redox system, Ru(NH₃)₆^3+/2+, nanodiamond is shown to give well‐defined diffusion controlled voltammetric responses. Next, metal deposition processes are shown to proceed on nanodiamond with high reversibility and high efficiency compared to processes reported on boron‐doped diamond. The nucleation of gold is shown to be facile at edge sites, which are abundant on the nanodiamond surface. For the deposition and stripping of both gold and copper, a stripping efficiency (the ratio of electro‐dissolution charge to electro‐deposition charge) of close to unity is detected even at low concentrations of analyte. The effect of thermal annealing in air is shown to drastically modify the electrode characteristics probably due to interfacial oxidation, loss of active sp² sites, and loss of conductivity.     

Investigations on the recycling of hemp and sisal fibre reinforced polypropylene composites

Microscopic, mechanical, rheological and thermal tests were carried out in order to determine the recycling behaviour of PP/vegetal fibre composites. Different composites using hemp and sisal were characterized. All results were compared with PP-g-MA/hemp composites and PP/glass fibre composites.The results prove that mechanical properties are well conserved with the reprocessing of PP/vegetal fibre composites but that there is poor adhesion between the fibres and PP without any treatment. The addition of PP-g-MA shows an improvement of the bonding evidenced by MEB pictures. Vegetal fibres induce an increase in the percentage of crystallinity χ_c and in the crystallization temperature T_c which can be explained by the nucleating ability of the fibres improving crystallization of PP. The Newtonian viscosity η₀ decreases with cycles, indicating a decrease in molecular weight and chain scissions induced by reprocessing. The decrease of fibre length with reprocessing could be another reason for viscosity decrease.     

Mechanical and thermal properties of poly-ether ether ketone reinforced with CaCO3

CaCO₃/PEEK (poly-ether ether ketone) composites were prepared on a twin-screw extruder with different mass ratio of CaCO₃/PEEK from 0% to 30%. Four types of particles were used as filler in PEEK matrix. The influence of surface treatment with sulfonated PEEK (SPEEK) of the particles on the mechanical and thermal properties of the composites was studied. The experiments included tensile tests, flexural tests, notched Izod impact tests, TGA, DSC and SEM. The modulus and yield stress of the composites increased with CaCO₃ particles loadings. This increase was attributed to the bonding between the particles and the PEEK matrix, as can be proved by the SEM pictures of tensile fracture surface of the composites. The impact strength of the composites was modified by the SPEEK coated on the CaCO₃ particle surface. DSC experiments showed that the particle content and surface properties influenced the glass transition temperature (T_g) and melting temperature (T_m) of the composites. The T_g increased with the content of fillers while T_m decreased. In this study the fillers treated were found to give better combination properties, which indicated that SPEEK played a constructive role in the CaCO₃/PEEK composites.     

Influence of the preparation procedure on the properties of polyaniline based magnetic composites

A versatile process for the preparation of composite films consisting of magnetite (Fe₃O₄) nanoparticles embedded in a polyaniline (PANI) matrix is reported. Spectroscopic properties of polyaniline matrix (PANI-EB), polyaniline protonated with camphor sulfonic acid (PANI-CSA_0.5) PANI-ES and PANI/Fe₃O₄-CSA_0.5 composites were studied, both in the state of the solutions of m-cresol and in thin films processed from the same solvents. The results of these studies indicate that m-cresol can be used for PANI/Fe₃O₄ composite preparation. Such films show both reasonably high electrical conductivity and magnetic permeability. A controlled application of a magnetic field during the casting process resulted in the formation of the materials with an unusual combination of magnetic and transport properties. The obtained films show the behavior that can be explained by the presence of both ferromagnetic and paramagnetic phases. The superparamagnetic contribution, if any, is very small. Application of the external magnetic field during fabrication of the composites stimulates creation of the aggregates of magnetic particles which, although keeps conductivity at a relatively high level, leads to a small decrease of the conductivity value.     

Adsorption characteristics of a nanodiamond for oxoacid anions and their application to the selective preconcentration of tungstate in water samples.

A nanodiamond with a mean particle size of 4 nm, which was prepared by the detonation of a nanodiamond, has been characterized and used as a collector for tungstate in water samples. An aqueous solution of nanodiamond was found to be stable over the pH range from 3 to 10. Coagulation of the nanodiamond could be brought about by adding an electrolyte solution. The adsorption characteristics of nanodiamond have been elucidated to be attributable to amino groups on its surface by the elemental-analysis data and the zeta potential measured in weak acid media. The unique adsorption properties of the nanodiamond for oxoacid anions were applied to a selective preconcentration method for tungstate in water samples. An appropriate amount of nanodiamond was added to a sample solution at pH 5 and a calcium chloride solution was added to aggregate nanodiamond. The sample solution was then allowed to stand for 2 h and centrifuged. The nanodiamond was transferred onto a membrane filter, washed with a diluted calcium chloride solution and treated in advance of an ICP-AES measurement by either of the following procedures: (a) redispersion of the nanodiamond into dilute nitric acid with an ultrasonic washer and (b) ashing of the membrane filter and the coagulated nanodiamond at 700 degrees C, followed by a treatment of the ash with hydrochloric and tartaric acids. The average recovery of tungstate from 100-ml artificial river-water was found to be 99% at the 0.25 ppm level with an RSD of 2.2% (n = 3). The concentration factor at present is 10.     

Recent Development of Nano-Carbon Material in Pharmaceutical Application: A Review

Carbon nanomaterials have attracted researchers in pharmaceutical applications due to their outstanding properties and flexible dimensional structures. Carbon nanomaterials (CNMs) have electrical properties, high thermal surface area, and high cellular internalization, making them suitable for drug and gene delivery, antioxidants, bioimaging, biosensing, and tissue engineering applications. There are various types of carbon nanomaterials including graphene, carbon nanotubes, fullerenes, nanodiamond, quantum dots and many more that have interesting applications in the future. The functionalization of the carbon nanomaterial surface could modify its chemical and physical properties, as well as improve drug loading capacity, biocompatibility, suppress immune response and have the ability to direct drug delivery to the targeted site. Carbon nanomaterials could also be fabricated into composites with proteins and drugs to reduce toxicity and increase effectiveness in the pharmaceutical field. Thus, carbon nanomaterials are very effective for applications in pharmaceutical or biomedical systems. This review will demonstrate the extraordinary properties of nanocarbon materials that can be used in pharmaceutical applications.     

Magnetic properties and dye adsorption capacities of silica–hematite nanocomposites with well-defined structures prepared in surfactant solutions

Silica–hematite (α-Fe₂O₃) nanocomposites were synthesized by addition of aqueous solution containing ferrous ions (Fe²⁺), cetyltrimethylammonium bromide (CTAB) as a surfactant and tert-butanol (t-butanol) as a cosurfactant into colloidal silica solution. At alkaline atmosphere, silica surface with negative charges electrostatically attracts positively-charged iron hydroxide nuclei or particles which are stabilized by cationic CTAB molecules, and then silica–iron compound composites could be formed. Finally, the silica–hematite composite particles were obtained after calcination at 800 °C for 4 h. Through these processes, two types of composites having “core–shell type” or “decorated type” could be achieved. Morphology, BET surface area, crystallinity and magnetic properties of samples were analyzed by using TEM, BET, XRD and VSM, respectively. The “decorated type” composites had larger BET surface area and better magnetization. Also, to estimate the application in water treatment, adsorption properties of composites were studied through methylene blue (MB) adsorption which was characterized by UV–vis spectroscopy, involving collection of composites with neodymium magnet.     

Synthesis,characterization, biocompatibility,thermal and mechanical performances of sawdust reinforced composite

The work outlines the synthesis of a new and easy technique to develop sustainable composites of sawdusts reinforced polyester resin composites. For shaping a new approach we have found very rare approach for developing composites with sawdusts of Mahagoni wood (Swietenia mahagoni) reinforced polyester resin composites in open literatures. Due to this gap, a plan made to develop untreated and treated sawdusts (very common in Bangladesh and many other countries of the world) reinforced strong and durable composites with unsaturated polyester resins along with their biodegradability, thermal and mechnical properties where the material properties were revealed and corelations were elaborated in the subsequent sections. Specifically, the tensile strengths of virgin resin (VR), untreated sawdust reinforced composite (UTSDC) and 4% caustic soda treated sawdust reinforced composite (4TSDC) are 10.77, 15.83 and 21.64 N/mm², respectively. That means the observed reinforcement property for UTSDC and 4TSDC increased ~47% and 101%, respectively. Moreover, the binding phenomena were explained with the own schamatic presentation. The composite phenomena was explained sequentially by using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, etc. Between the developed composites 4TSDC was strong (25% as compared from tensile strength) and durable (8% as observed in biodegradability results) than the UTSDC of unsaturated polyester resin. The pattern of water uptake follows usual Fickian diffusion behavior. The observed properties of the developed convincible composites indicate that they can be considered for indoor to outdoor applications especially for using the fence, roof, furniture items like chair, table, park benches, etc.     

General Method to Increase Carboxylic Acid Content on Nanodiamonds

Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes.     

Size-dependent surface CO stretching frequency investigations on nanodiamond particles

In this work, the spectroscopic properties of surface functionalized nanodiamond particles are investigated via Fourier transform infrared spectroscopy. The functionalization of the nanodiamond surface was achieved chemically using strong acid treatment method. The size dependent C=O stretching frequency (between 1680 and 1820 cm(-1)) are studied for particle diameter sizes from the 5 to 500 nm range. The surface C=O stretching frequencies at approximately 1820 cm(-1), for large particle size (500 nm), down shifted to 1725 cm(-1) (5 nm) with decreasing particle sizes. We attributed the shift as a result of hydrogen bond formation between the COOH groups in the carboxylated nanodiamond surfaces. Particle size was characterized with dynamic light scattering method and surface morphology of the particles was investigated with scanning electron microscopy. The influence of pH value on C=O stretching frequency is also analyzed. This finding affords useful information for the studying of surface functionalized nanodiamonds with implications for their interaction with biomolecules.     

Role of triplet states of polymethine dyes in photogeneration of electron-hole pairs in poly(N-epoxypropylcarbazole) films

The external magnetic field effects on the spectral and luminescent properties of film composites based on photoconductive poly(N-epoxypropylcarbazole) doped with cationic polymethine and merocyanine dyes have been studied. The magnetic field effects on the intensity and kinetics of delayed fluorescence and recombination luminescence have been revealed. These effects are explained by participation in the photogeneration of charged pairs of singlet-triplet intersystem crossing in excited dye molecules.     

Quantification of nanodiamonds in aqueous solutions by spectrophotometry and thermal lens spectrometry

Spectrophotometry and thermal lens spectrometry were used to study solutions of several commercial detonation nanodiamonds. It was found that the absorption spectra of solutions of all studied nanodiamond samples obey the Bouger-Lambert-Beer law, which ensures the precise determination of the total mass concentration of unknown nanodiamond solutions using a calibration plot. It was shown that the absorption spectra of nanodiamond solutions exhibit both absorption and scattering components, both significantly affecting signal formation. Conditions were proposed for the spectrophotometric determination of nanodiamonds at 250 nm (l = 1.0 cm). The detection limits were from 60 ng/mL to 2 ??g/mL, depending on the nanodiamond type. Limits of detection of SDND nanodiamonds by spectrophotometry and thermal lens spectrometry were calculated for identical conditions of sample preparation and measurements (488 nm, l = 1.0 cm). These were 10 and 0.6 ??g/mL for spectrophotometry and thermal lens spectrometry, respectively (power of excitation radiation 150 mW).     

Structure and mechanical properties of thermoplastics modified with nanodiamonds

The structure and properties of composite materials based on amorphous thermoplastics and detonation nanodiamonds are studied. The conception of the “rheological method” is advanced for compatibilization of a polymer and a filler under the regime of elastic turbulence (spurt) for preparation of composites with a high level of dispersion and a homogeneous distribution of nanodiamond particles. As a rule, the dependences of strength and physicomechanical characteristics of the nanocomposites on the content of the dispersed phase are described by curves with an extremum or saturation. The concentration of the filler corresponding to the extremum or the approach to the plateau value for a specific parameter depends on the nature of the polymer matrix and is attained at filler contents below 2.5 wt %. The elastic modulus monotonically increases as the content of nanodiamonds is increased to 5 wt %.