Abstract  The modifications afforded by several chemical treatments to the main functional groups of a bituminous coal vv ere characterized by diffuse reflectance infrared spectroscopy. The starting materials were the polyanions and potassium coal adducts obtained from the parent coal, treated with potassium according to the Sternberg and Lazarov reactions. The results show the differences in the reactive sites involved in these reactions and in the behaviour of these sites during protonation or alkylation. Some of the typical functional groups introduced (or modified) can be active acceptor sites during hydrogen transfer from tetralin at low temperature (315 degrees C) in conditions avoiding thermal bond cleavage. Taking into account the semiquantitative results of the i.r. analysis, the participation of several active sites in the total hydrogen transfer was estimated, indicating the role of quinonic, aromatic and alkyl groups. Copyright (C) 1996 Elsevier Science Ltd.

Abstract  High quality graphene sheets were produced from graphite by liquid phase exfoliation using N-methyl-2-pyrrolidone (NMP) and a subsequent thermal treatment to enhance the exfoliation. The exfoliation was enhanced by treatment with organic solvent and high thermal expansion producing high yields of the high-quality and defect-free graphene sheets. The graphene was successfully deposited on a flexible and transparent polymer film using the vacuum filtration method. SEM images of thin films of graphene treated at 800 degrees C showed uniform structure with no defects commonly found in films made of graphene produced by other techniques. Thin films of graphene prepared at higher temperatures showed superior transmittance and conductivity. The sheet-resistance of the graphene film treated at 800 degrees C was 2.8 x 10(3) k Omega/square with 80% transmittance. (C) 2012 Elsevier B. V. All rights reserved.

Abstract  Sulfonated poly(ether ether ketone) (SPEEK), a strong polyelectrolyte, was investigated as an additive in polysulfone (PSU)/SPEEK/N-methyl-2-pyrrolidinone (NMP) systems. Membrane characterisation was carried out using filtration studies and by atomic force microscopy (AFM). The effect of SPEEK in the charged membrane formation was investigated through thermodynamic and viscosity studies and correlated with the structure and properties of the resulting membranes. A "Polyelectrolyte behaviour" of SPEEK was observed for the first time in the membrane forming systems. Charged ultrafiltration/nanofiltration membranes prepared from 20 wt.% PSU solutions with the ratio of SPEEK/PSU in the range of 0.005-0.05, have substantially increased permeability, salt rejection, porosity, and a greatly reduced fouling tendency compared to the base PSU membrane. The charged membranes offer the possibility of effective removal of humic substances from surface waters in a highly efficient manner.

Abstract  A nanocomposite of a chemically synthesized nanostructured aluminum nitride (AIN) and a polyimide has been studied. Using a nonaqueous polar solvent, N-methylpyrrolidinone (NMP), as the suspension media, the degree of particle agglomeration of AlN was reduced dramatically from micron to nanoscale size. Upon the addition of poly(amic acid) to the AlN/NMP suspension, a further deagglomeration of the particles was observed. The surface physicochemical interactions have been investigated by characteristic model reactions using FTIR spectroscopy. A mechanistic interpretation for the deagglomeration and stabilization behavior is discussed. The formation of the AlN/PI nanocomposite was achieved by the rapid solidification of the precursor suspension followed by compression molding. Such an approach for nanocomposites exhibits better homogeneity with ultrafine fillers and allows a tailorable composition and property at the nanoscale level. Finally, AlN/PI nanocomposites with an increased ceramic loading, up to 65% by volume, were attained and their thermal and mechanical properties, along with the compositional effects, have been investigated.

Abstract  In this study, we demonstrate a flexible method for functionalizing multiwalled carbon nanotubes (MWCNTs) with polyurea (PU) coatings using molecular layer deposition (MLD). Uniform and conformal PU films can be deposited on the surface of pristine MWCNTs without any surface treatment. The PU shell thickness and wrapping amount are precisely tunable by changing the number of MLD cycles. The present MLD functionalizing treatment provides better dispersion of the MWCNTs in highly polar solvents such as N,N-dimethylformamide, dimethyl sulfoxide, and 1-methyl-2-pyrrolidinone. Furthermore, the PU layers improve the compatibility between MWCNTs and the polyurethane matrix. Significant increases in tensile strength and modulus are obtained, resulting in greatly enhanced mechanical properties of PU-functionalized MWCNT/polyurethane composites. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract  The use of carbon nanotubes (CNTs) in radio frequency identification (RFID) applications offers a very large range of possibilities to exploit the incredible properties of CNTs. However, due to their entanglement state, their size and the different interacting forces between nanotubes bundles present at nanometric scale, CNTs debundling is very hard to achieve, requiring specific equipment and chemicals. Our purpose was to reduce as small as possible CNTs bundles, in order to realize ink to print on an RFID antenna. The size of the head printer nozzles required very small particles, about a few micrometers, in order to be able to print on the sensitive position of the antenna. To reduce the size of the bundles and stabilize the solution, an ultrasonic horn with an ultrasonic bath were combined as mechanical stress for CNT dispersion, and some chemicals such as sodium dodecyl sulfate (SDS)-a surfactant, N-methyl-2-pyrrolidone (NMP)-a solvent, or chitosan were used to meet our requirements.

Abstract  AA5182 aluminium alloy cold rolled samples were coated by thin films of emeraldine base (EB) obtained from a 5% solution in N-methylpyrrolidinone. Accelerated corrosion tests prove this coating very effective for corrosion protection of aluminium alloys in neutral environment. This study underlines the prominent role of surface cathodic intermetallic particles in pit initiation and coating break down in enhanced corrosion conditions and suggest that, beside the EB barrier properties, the enhanced corrosion resistance observed on the EB coated samples could partly arise from two other mains factors: a weak redox activity of the polymer which passivate the metal, a proton involving self-healing process taking place at the polymer-metal interface, which contributes to delay local acidification in first steps of corrosion on EB coated aluminium surfaces. (c) 2006 Elsevier Ltd. All rights reserved.

Abstract  This study investigates the effect of polyvinyl pyrrolidone (PVP) of different molecular weights on the structure and permeation properties of polysulfone (PSf) membranes. The membranes were prepared by phase inversion method using PSf in two solvents, viz. N-methyl-2-pyrrolidone (NMP) and dimethyl acetamide (DMAc) separately. The surface morphology of the resulting membranes was analyzed by scanning electron microscope (SEM) and liquid displacement method. The membranes were subjected to ultrafiltration characterizations such as measurement of pure water flux (PWF), compaction factor (CF), equilibrium water content (EWC), hydraulic resistance and bovine serum albumin (BSA) rejection. Results show that the morphological parameters and flux performance of the membranes have a significant inter-relationship with the molecular weight of PVP. The membrane pore number and pore area are seen to increase with molecular weight of PVP. However, at a constant pressure, the PWF is found to decrease while BSA rejection increases significantly for the membranes prepared with both the solvents. For the membrane composition considered in this study, the solvent DMAc is found to be more suitable than NMP, in terms of BSA rejection, irrespective of the pH of the BSA solution. The maximum rejection found in this study is 76% with PSf/DMAc membrane with PVP 360,000 (at pH 9.3). (c) 2008 Elsevier B.V. All rights reserved.

Abstract  We developed a simple drop-casting method via solvent extraction (SECG) to grow dense and uniform perovskite nanocrystals at room temperature for carbon-based mesoscopic solar cells free of an organic hole-transport layer. The CH3NH3PbI3/N-methyl-2-pyrrolidone (NMP) precursor solution (40%) was first dripped onto a substrate with film configuration TiO2/Al2O3/C and infiltrated at 70 degrees C for 10 min. The perovskite substrate was next immersed in a bath of diethyl ether at 25 degrees C for 30 min. Third, the solventextracted substrate was stored in a dry box (humidity 50%) at 25 degrees C for at least 100 h to complete the crystal growth. The device performance attained a power conversion efficiency (PCE) of 12.3%, which is significantly greater than that of DMF (6.3%) and NMP (8.3%) devices using traditional thermal annealing. The SECG device displayed a superior intrinsic enduring stability: the PCE exceeded 12% for 5000 h with a maximum value of 13.3% without light-soaking at 25 degrees C, but the performance degraded rapidly under one-sun irradiation without encapsulation. To understand the kinetics of charge transfer and defect relaxation for the devices under investigation, we recorded transient photoluminescence decays at an excitation wavelength of 635 nm and a probe wavelength of 770 nm.

Abstract  One stage fractional crystallization and solvent extraction techniques have been used to separate different microcrystalline waxes grades with different characteristics from Suez crude petrolatum. One stage fractional crystallization has been done using butyl acetate as solvent at ambient temperature of 20 degrees C, at different dilution solvent ratios (S/F by weight) ranging from 2:1 to 8:1 and constant washing ratio of 2:1. While, solvent extraction technique has been done at different extraction temperatures and different solvent feed ratios (S/F by weight). The extraction solvents used are dimethyl-sulfoxide (DMS), N, N, dimethyl-acetamide (DMA), and N-methyl-2-pyrrolidone (NMP). The wax products are evaluated according to TAPP1-ASTM equation and petroleum wax specifications. The data revealed that solvent extraction technique is more suitable for deoiling Suez crude petrolatum than one stage fractional crystallization technique. Also, the resulting data revealed that DMA and NMP are suitable extracting solvents for isolating of microcrystalline waxes from Suez crude petrolatum. But, according to petroleum wax specifications, DMS is not a suitable solvent for separation of microcrystalline wax from Suez crude petrolatum. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Two coal-derived pitch samples, one a medium temperature pitch from a Sasol-Lurgi gasifier and the other from a high temperature coking process, have been heat treated to induce polymerization, both separately and as a mixture of pitches (co-pyrolysis). The initial pitch samples and the heat-treated samples have been examined by size exclusion chromatography (SEC) in 1-methyl-2-pyrrolidinone (NMP), by UV-fluorescence spectroscopy (UV-F), by solid state C-13 NMR; elemental analyses of the initial pitch samples have been carried out. The Sasol-Lurgi pitch showed larger apparent sizes, more alkyl and carbonyl functions, and smaller polycyclic aromatic hydrocarbon (PAH) groups than the high temperature pitch. Co-pyrolysis of the two pitches indicated that polymerized product from the Sasol-Lurgi pitch can be used as an extender for high-temperature binder pitch. (C) 2007 Elsevier Ltd. All rights reserved.

Abstract  Membrane surface and cross-sectional morphology created during membrane formation is one of the most essential factors determining membrane separation performance. However, the complicated interactions between added nanoparticles and additives influencing membrane morphology and performance during building membrane architectures had been generally neglected. In this study, asymmetric PVDF composite ultrafiltration (UF) membranes containing graphene oxides (GO) were prepared by using N-methyl pyrrolidone (NMP) as solvent and polyvinylpyrrodione (PVP) as the pore forming reagent. In the first time, the effects of mutual interactions between GO and PVP on membranes surface compositions, morphology and performance were investigated in detail. The variation in chemical properties of different membranes and hydrogen bonds in the membrane containing GO and PVP were confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle (CA) were utilized to clarify the synergetic effects of GO and PVP on morphologies and surface hydrophilicity of membranes. Besides, water flux, bovine serum albumin (BSA) rejection and attenuate coefficient were also determined to investigate filtration performance of various membranes. Compared with pure PVDF membrane, the comprehensive performance of PVDF/GO/PVP membrane has been obviously improved. The surface hydrophilicity and anti-fouling performance were enhanced by the synergistic effects of incorporated GO and PVP. When the PVP content was 0.25 wt.% and the GO content was 0.5 wt.%, the optimized performance can be obtained due to the formation of hydrogen bonds between GO and PVP. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  The aggregation of coal derived material in solvents was investigated by size exclusion chromatography (SEC), using a polystyrene-divinylbenzene packed column and eluting with NMP, NMP/CS2 (1:1, v/v) and NMP containing anion additives. The SEC chromatogram of coal extract using NMP as the eluent shows two main peaks. One appears near the exclusion limit of the column (shorter retention time) and the other one at the longer retention time. Changing the eluent to NMP/CS2 (1:1, v/v) mixed solvent results in the disappearance of the material eluted near the exclusion limit. Instead, all the fractions appear at longer retention time. Adding anion additives (5-10 mM), e.g. tetrabutylammonium acetate and NMP 1,1,2,3,3-pentacyanopropenide, into NMP eluent also results in the disappearance of the material eluted near the exclusion limit. The observed changes are thought to be due to the disruption of coal molecular aggregation rather than changes in solvent properties. The material eluted near the exclusion limit is strongly aggregated, its size depends on the extent of aggregation and the solvent used. Disruption of the aggregated coal molecule was responsible for the changes in the SEC chromatogram. In addition, the aggregation of the coal extract was found to increase with decreasing coal rank. For the different extract fractions, the aggregation increases in the order: acetone soluble, pyridine soluble-acetone insoluble and pyridine insoluble-NMP/CS2 (1:1, v/v) mixed solvent soluble. (C) 2001 Elsevier Science Ltd. All rights reserved.

Abstract  Tetracyanoethylene (TCNE) is a very effective additive enhancing coal solubility in the N-methyl-2-pyrrolidinone (NMP)-CS2 (1:1, v/v) mixed solvents. It was found that TCNE generates 1,1,2,3,3-pentacyanopropene (PCNP) anion in NMP in the presence of water. The PCNP anion is not an electron acceptor but is as effective as TCNE at enhancing solubility. This rules out charge-transfer complexation between coal and TCNE as a main factor in increasing coal solubility. In addition, we have not found a correlation between the electron acceptor ability of additives and their ability to enhance coal solubility. These results do not support the proposal that formation of a charge-transfer complex between electron accepters and coal is responsible for the enhancement of coal solubility.

Abstract  The effect of cathode structures on the chemical stability of Nafion membranes is investigated. Membrane electrode assemblies (MEAs) were prepared by using Nafion 212 membrane and commercially available carbon supported Pt electro-catalysts. The cathode structures were controlled by the use of long side chain (LSC) and short side chain (SSC) perfluorosulfonic acids (PFSAs) as well as three dispersing solvents for the electrode fabrication (a water-isopropanol mixture, N-methyl-2-pyrrolidone, or glycerol). The membrane durability was evaluated by the H-2 crossover current density after a 200-hour open circuit voltage accelerated stress test. The MEA with a glycerol-processed SSC PFSA-bonded cathode exhibited a 200-fold less H-2 crossover current density than the MEA with a water-isopropanol-processed LSC PFSA-bonded cathodes. The analyzes by electrochemical impedance spectroscopy and microscopy suggest that the structural uniformity of cathodes play the most significant role in the chemical stability of the Nafion membranes. This study emphasizes the importance of cathode structures on the durability of Nafion membranes. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

Abstract  Multi-walled carbon nanotubes (MWCNTs) are functionalized at the sp(2) C-H defect sites with 3,4-diaminobenzoic acid by a "direct" Friedel-Crafts acylation reaction in a mild polyphosphoric acid/phosphorous pentoxide medium. Owing to enhanced surface polarity, the resulting 3,4-diaminobenzoyl-functionalized MWCNTs (DAB-MWCNT) are highly dispersible in polar solvents, such as ethanol, N-methyl-2-pyrrolidone, and methanesulfonic acid. The absorption and emission properties of DAB-MWCNT in solution state are qualitatively shown to be sensitive to the pH in the environment. The DAB-MWCNT is used as a stable platform on which to deposit platinum nanoparticles (PNP). The PNP/DAB-MWCNT hybrid displays high electrocatalytic activity with good electrochemical stability for an oxygen reduction reaction under an alkaline condition.

Abstract  A novel monomer diacid, 6,6'-methylenebis(2-oxo-8-{2-[(2-oxo-2H-chromen-7-yl)oxylacetoxy)-2H-chromene-3-carboxylic acid}, having two substituents (2-oxo-2H-chromen-7-yl)oxyacetate in the aromatic moiety, was synthesized and used in a direct polycondensation reaction with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents to give a series of new aromatic polyamides with photosensitive coumarin pendent groups. Polyamide properties were investigated by DSC, TGA, GPC (gel permeation chromatographic analysis), and wide-angle X-ray scattering, viscosity and solubility measurements. The introduction of bulky side chains in the structure of aromatic polyamides led to moderate inherent viscosity values (0.40-0.87 dLg(-1)) and increased solubility of these polymers in aprotic polar solvents such as NMP (N-methylpyrrolidone), DMAc, DMSO and DMF. and in less polar solvents like Py and THE The good solubility of these polyamides was in agreement with their amorphous character as evidenced by X-ray diffraction diagrams. Gel permeation chromatography evidenced high molecular weights (49,400-63,900 gmol(-1)) which allowed transparent, flexible and tough films to be cast from polymer solutions. These aromatic copolyamides showed good thermal properties associated with glass transition temperatures (Tg) in the range of 221-257 degrees C and the onset of decomposition in air above 390 degrees C. UV illumination (lambda > 300 nm) of the polymer films induced crosslinking between polyamide molecules through a [2 pi + 2 pi] photocycloaddition at the C=C bond of coumarin moieties. Information concerning the photoreactive property of coumarin-containing polymers was obtained by studying the changes in the UV absorption spectra and IR spectra of irradiated polymeric films. (c) 2008 Elsevier Ltd. All rights reserved.

Abstract  The binodal curves, tie-line compositions and cloud point data as a function of temperature and concentration were measured for aqueous two phase systems composed of acetonitrile (ACN) + K2CO3 + H2O, ACN + Na2CO3 + H2O, 1-methyl-2-pyrrolidone (NMP) + K2CO3 + H2O and NMP+ Na2CO3 + H2O. Additionally, salting-out ability of sodium sulfite, sodium thiosulfate and sodium tartrate was studied. The free energy, enthalpy and entropy of clouding point (CP) estimated using a simple method, and the driving force of the two-phase formation process was discussed on the base of the estimated free energy values. Also, an empirical equation was modified as a function of organic solvents density and dielectric constants and used for the simultaneous correlation of all experimental binodal data. Furthermore, e-NRTL and e-Wilson models were used for the correlation of tie-line compositions. The obtained results confirm the high performance of these models in the correlation of binodal and tie-line data. (C) 2013 Elsevier B.V. All rights reserved.

Abstract  Polyaniline base in the form of solution, powder and film was treated with aqueous solutions of three organic acids, toluenesulfonic acid (TSA), sulfosalicylic acid (SSA) and dodecylbenzenesulfonic acid (DBSA), and HClO4. The doping characteristics and stability of these salts were studied using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy and UV-Vis absorption spectroscopy. Polyaniline salts in N-methylpyrrolidinone (NMP) solution readily undergo deprotonation, whereas the DBSA-protonated salt in CHCl3 is stable even under near-UV irradiation. The protonation levels achievable when the base powder is treated with the organic acids are comparable with that obtained with HClO4. When the protonation of the base powder is carried out in mixtures of organic acids and HClO4, the organic acid anions are selectively incorporated into the salt. However, in the case of films, protonation by the organic acids is hampered by the large size of the anions. When salt films are cast from salt solutions, the larger anions are retained better than the CLO(4)(-) anions when these films are treated with water. The organic anions also decompose at a higher temperature than the ClO4- anions.

Abstract  Fabrication of polysulfone hollow-fiber microfiltration membranes through non-solvent induced phase separation (NIPS) by dry-wet spinning was studied. For all sample preparations, we used N-methylpyrrolidone (NMP) as solvent, polyethylene glycol (PEG) as additive, aqueous NMP solution as bore liquid, and water as coagulation bath. Particular focus was placed on the influence of PEG molecular weight (Mw) on membrane structure. Characterization of the obtained membranes was performed by measuring pure water permeate flux, tensile strength, and tensile elongation at break, and by analyzing scanning electron microscope (SEM) images of hollow-fiber cross-sections, outer surfaces, and inner surfaces. Dope viscosity increased sharply as PEG Mw was raised to 20,000 or higher, as did water permeate flux. SEM image analysis revealed that outer-surface pore size increased with PEG Mw. Morphology of the inner surface transformed markedly as PEG Mw was raised from 6000 to 20,000. (c) 2008 Elsevier B.V. All rights reserved.

Abstract  For separation of oil and water mixture using ultrafiltration (UF), polysulfone (Psf) membranes were synthesized by phase inversion method using N-methyl-2-pyrrolidone (NMP). In order to achieve both higher permeation flux and fouling resistance, modification of Psf has been done by adding polymeric additives such as polyvinylpyrrolidone (PVP), polyetherimide (PEI), polyethylene glycol (PEG) and polyethersulfone (PES). Pure Psf membrane showed a lower flux of about 0.26 L m(-2) h(-1) which on PVP addition helped to enhance flux to the highest value of 33.66 L m(-2) h(-1). The performance in oil and water separation in terms of rejection efficiency with respect to the concentration polarisation phenomenon was measured for each modified Psf membrane. The morphology and hydrophilicity of the modified membranes were investigated by a scanning electron microscopy (SEM) and contact angle analysis respectively. The UF experimental results using synthetic vegetable oil-water mixture showed that retention of oil over the membrane was nearly 99.8% for Psf/PVP membrane and also have excellent oil-fouling resistance ability even during dead-end batch UF under higher operation pressure. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  To explain certain phenomena occurring during thermal processing of coal, studies were made of hydrogen transfer to coals, their N-methyl-2-pyrrolidinone (NMP) extracts and residues, and tetrahydrofuran (THF)-soluble and -insoluble parts of the NMP extracts. The transfer of hydrogen to coals was found to be rank-dependent; the extraction products followed the same trend but with a poorer correlation. Much higher hydrogen acceptance reactivities were determined for NMP residues than for parent coals. The reactivity of extracts changed during prolonged storage. The FT-i.r. deconvoluted spectra, the correlation between oxygen content and hydrogen transfer and other data indicated that carbonyl (quinone) groups are the primary acceptor sites of hydrogen from tetralin at relatively low temperature (310-320-degrees-C). The relation between hydrogen acceptance and coke microtexture formation during carbonization is discussed.

Abstract  Chemical modification of a chloromethylated polysulfone (CMPS) was performed by reacting the chlorometyl group with P-H bond of 9,10-dihydro-oxa-10-phosphophenanthrene-10-oxide (DOPO). A kinetic study of phosphorylation of CMPS with different chlorine content was reported. The obtained polymers bearing cyclic bulky groups containing phosphorus were characterized by analytical methods; Fourier transforms spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). The thermal stability of phosphorus-modified polysulfone was evaluated by dynamic thermogravimetric analysis in nitrogen gas. The polymers were readily soluble in polar organic solvent, such as N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF). Differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA) proved an amorphous morphology of these polymers. POLYM. ENG. SCI., 50:48-56, 2010. (C) 2009 Society of Plastics Engineers

Abstract  Bleached shellac, a mixture of polyesters made up of sesquiterpenoid acids esterified with hydroxy aliphatic adds, is a well-known water-insoluble polymer. Owing to its high solubility in N-methyl pyrrolidone (NMP) it is interesting to apply as a polymer matrix for solvent-exchanged in situ forming gel. The aim of this research was to study the gel properties, drug release and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyromonas gingivalis of the in situ forming gels prepared from bleached shellac dissolving in NMP to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The solvent exchange between NMP and external aqueous simulated gingival crevicular fluid stimulated the dissolved bleached shellac transforming into the opaque rigid gel. Increasing the amount of bleached shellac increased the viscosity of the system while still exhibiting Newtonian flow and increased the work of syringeability whereas prolonging the drug release. The developed systems comprising 5% w/w antimicrobial agent showed antimicrobial activities against all test bacteria. Thus the solvent exchange-induced in situ forming gels comprising of bleached shellac-antimicrobial drugs exhibited potential use for periodontitis treatment (C) 2015 Elsevier Ltd. All rights reserved.

Abstract  We report the effect of temperature on the extent of graphene oxide reduction by hydrazine and the dispersibility of the resulting chemically converted graphene (CCG) in polar organic solvents. The extent of graphene oxide reduction at high temperatures was only slightly higher than at low temperatures (30-50 degrees C), while the dispersibility of the resulting CCG in organic solvents decreased markedly with increasing temperature. The low dispersibility of CCGs prepared at high temperatures was greatly affected by reduction and influenced by the formation of an irreversible agglomerate of CCG at high temperatures. The reduction of graphene oxide at low temperatures is necessary to prepare highly dispersible CCG in organic solvents. CCG prepared at 30 degrees C is dispersible in N-methyl-2-pyrrolidone concentrations as high as 0.71 mg/mL. The free-standing paper made of this CCG possessed an electrical conductivity of more than 22,000 S/m, one of the highest values ever reported.