DMF Systems Research Articles

Molecularly designed and synthesized of bright blue nitrogen-doped lignin-derived carbon dots applied in printable anti-counterfeiting

With the increased demand for green and sustainable development, the research of advanced biomass-based carbon dots (CDs) has drawn growing attention. Herein, a one-step green solvent integration strategy-assisted solvothermal method to preparing CDs from hydrolyzed lignin and ethylenediamine (EDA) in formamide (FA) was developed. The Schiff reaction between FA and EDA contributes to the formation of -C-N groups, further inducing the high photoluminescence quantum yield (up to 42.69 %)，obviously higher than NCDs prepared in H2O, EtOH and DMF systems (corresponding to H-NCDs, E-NCDs and D-NCDs, respectively). The analysis of structure, composition, photoluminescence (PL) behaviors and DFT calculations showed that F-NCDs have main blue fluorescent emission peak from 410 to 455 nm under 330–390 nm excitation due to the small sp2 structure in carbon core, and the large sp2 conjugated clusters and CO group related surface states leaded to the long wavelength emission. The F-NCDs with excellent optical properties was further used for preparing fluorescent film and invisible anti-counterfeiting ink, which exhibited outstanding fluorescence even at different temperatures and aging times. We provided a facile way for green facile preparation of lignin-based CDs and their sustainable anti-counterfeiting application.

Exploring the Microscopic Aspects of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Formamide, N-Methylformamide, and N,N-Dimethylformamide by Multiple Spectroscopic Techniques and Computations.

The microscopic aspects of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) mixtures with formamide (FA), N-methylformamide (NMF), and N,N-dimethylformamide (DMF) were investigated using spectroscopic techniques of femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), FT-IR, and NMR. Molecular dynamics simulations and quantum chemistry calculations were also performed. According to fs-RIKES, the first moment of the low-frequency spectrum bands mainly originating from the intermolecular vibrations in the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems changed gradually with the molecular liquid mole fraction XML but that in the [MOIm][BF4]/NMF system was constant up to XNMF = 0.7 and then gradually increased in the range of XNMF ≥ 0.7. Excluding the contribution of the 2D hydrogen-bonding network due to the presence of FA in the low-frequency spectrum band, the XML dependence of the normalized first moment of the low-frequency band in the [MOIm][BF4]/FA and [MOIm][BF4]/NMF systems revealed that the normalized first moment did not remarkably change in the range of XML < 0.7 but drastically increased in XML ≥ 0.7. FT-IR results indicated that the amide C═O band shifted to the low-frequency side with increasing XML for the three mixtures due to the hydrogen bonds. The imidazolium ring C-H band also showed a similar tendency to the amide C═O band. 19F NMR probed the microenvironment of [BF4]- in the mixtures. The [MOIm][BF4]/NMF and [MOIm][BF4]/DMF systems showed an up-field shift of the F atoms of the anion with increasing XML, and the [MOIm][BF4]/FA system exhibited a down-field shift. Steep changes in the chemical shifts were confirmed in the region of XML > 0.8. On the basis of the quantum chemistry calculations, the observed chemical shifts with increasing XML were mainly attributed to the many-body interactions of ions and amides for the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems. Meanwhile, the long distance between the cation and the anion was due to the high dielectric medium for the [MOIm][BF4]/NMF system, which led to an up-field shift.

Assessment of caries on the first permanent molars in a group of seven- to thirteen-year-old schoolchildren: Comparison of DMF and ICDAS systems.

The objective of this study wasto compare ICDAS and DMFT/S in the evaluation of caries status of the first permanent molar in 200 children aged 7 to 13years. This was a cross-sectional design study.Participants were selected from two private schools in Lebanon. The examinations were performed by two trained and calibrated examiners using a dental mirror and a WHO probe. The number of decayed (D), missing (M) and filled (F) teeth was recorded in DMFT/S form, and the numbers related to D, M and F were then added to record the DMFT/S value (D1MFT/S, D2MFT/S and D3MFT/S). In the ICDAS, the assessment of caries associated with restorations and sealant was recorded. Student t tests/and Mann-Whitney tests were used to compare the continuous variables. Chi-square tests and Fisher exact tests were used to compare the categorical variables. The average age of the participants was 9.21±1.927 (7-13years old). No significant difference was found between the mean time to score DMFT, DMFS and ICDAS indices (-p-value>0.05). The prevalence of caries with D1MFS, D2MFS and D3MFS was 80.5%, 54% and 30.5%, respectively. However, the prevalence of caries with ICDAS II was 77.5%. The DMF index is an international user-friendly system thatshows the carious history of teeth. However, the ICDAS assesses the different stages of cariesand describes the restorative status of the tooth,promoting new preventive approaches and curative needs. More studies should be done to confirm these findings.

Thermophysical study of the binary mixtures of triethyl phosphate with N-methylformamide, N,N-dimethylformamide and N,N-dimethylacetamide – Experimental and theoretical approach

Abstract Densities at (293.15, 298.15, 303.15 and 308.15) K, and viscosities and ultrasonic velocities at 298.15 K of binary liquid mixtures of triethyl phosphate with N-methylformamide, N,N-dimethylformamide and N,N-dimethylacetamide have been measured over the entire range of composition at p = 0.1 MPa. From the experimental data, values of excess molar volume, excess isentropic compressibility, viscosity deviation and excess Gibbs energy of activation for viscous flow have been calculated. These results were fitted to the Redlich-Kister-type polynomial equation. The viscosity deviations and the excess Gibbs energy were found to be positive for the all systems investigated, while the excess volumes and the excess isentropic compressibilities were negative for TEP + DMA and for TEP + DMF systems, and positive for mixtures TEP + NMF. These results were interpreted based on the strength of the specific interaction, size and shape of molecules. Molecular dynamics simulations were used to provide a detailed explanation of the differences between the TEP + NMF and other systems, which were ultimately traced to strong hydrogen bonding between NMF and TEP.

Numerical investigation of continuous droplet transport in parallel-plate electrowetting-on-dielectric digital microfluidics (EWOD DMF) with stripped electrodes

Electrowetting-on-dielectric digital microfluidics (EWOD DMF) has recently emerged as a promising technology for a variety of applications based on the manipulation of discrete microdroplets. A great deal of effort has been devoted to advancing this technology by means of enhancing droplet speed and stability. In this work, we numerically investigate the continuous droplet transport process in a parallel-plate EWOD DMF device with a previously proposed “stripped electrode” design and compare it with the transport motion of the conventional “square electrode” design. The microfluidic droplet motion is solved by a finite volume formulation on a fixed computational domain. The gas-liquid interface of a droplet is captured by a coupled level-set and volume-of-fluid scheme with the surface tension force at the interface computed by the continuum surface force method. A simplified viscous stress scheme reliant on the Hele-Shaw flow model is used to evaluate the viscous forces exerted by the parallel plates. The numerically simulated transport processes of the “stripped electrode” and “square electrode” designs show good agreement with the experimental results. Furthermore, a parametric study is conducted in which the influences of the strip number, activated contact angle, and gap spacing between the plates on droplet transport speed and stability are examined. It has been found that both the transport speed and stability can be noticeably improved by the “stripped electrode” design, which can be adopted for promoting the transport efficiency in a large number of droplet-based applications utilizing parallel-plate EWOD DMF systems.

Selective α-Monomethylation by an Amine-Borane/N,N-Dimethylformamide System as the Methyl Source.

A new and practical α-monomethylation strategy using an amine-borane/N,N-dimethylformamide (R3 N-BH3 /DMF) system as the methyl source was developed. This protocol has been found to be effective in the α-monomethylation of arylacetonitriles and arylacetamides. Mechanistic studies revealed that the formyl group of DMF delivered the carbon and one hydrogen atoms of the methyl group, and R3 N-BH3 donated the remaining two hydrogen atoms. Such a unique reaction pathway enabled controllable assemblies of CDH2 -, CD2 H-, and CD3 - units using Me2 NH-BH3 /d7 -DMF, Me3 N-BD3 /DMF and Me3 N-BD3 /d7 -DMF systems, respectively. Further application of this method to the facile synthesis of anti-inflammatory flurbiprofen and its varied deuterium-labeled derivatives was demonstrated.

Thermodynamics of amide + ketone mixtures. 2. Volumetric, speed of sound and refractive index data for N,N-dimethylacetamide + 2-alkanone systems at several temperatures. Application of Flory's model to tertiary amide + n-alkanone systems

Data on density, ρ, speed of sound, c, and refractive index, nD, have been reported at (293–303.15) K for the N,N-dimethylacetamide (DMA)+CH3CO(CH2)u−1CH3 (u=1, 2, 3) systems, and at 298.15K for the mixture with u=5. These data have been used to compute excess molar volumes, VmE, excess adiabatic compressibilities, κSE, and excess speeds of sound cE. Negative VmE values indicate the existence of structural effects and interactions between unlike molecules. From molar excess enthalpies, HmE, available in the literature for N,N-dimethylformamide (DMF), or N-methylpyrrolidone (NMP)+n-alkanone systems, it is shown: (i) amide-ketone interactions are stronger in DMF systems than in those with NMP; (ii) they become weaker when u increases in mixtures with a given amide. Structural effects largely contribute toHmE and are more relevant in mixtures containing NMP. The application of the Flory's model reveals that the random mixing hypothesis is valid in large extent for DMF solutions, while NMP systems are characterized by rather strong orientational effects. From values of molar refraction and of the product PintVm (where Pint is the internal pressure and Vm the molar volume), it is concluded that dispersive interactions increase with u, or when DMF is replaced by DMA in mixtures with a fixed ketone.

Three-dimensional digital microfluidic manipulation of droplets in oil medium.

We here develop a three-dimensional DMF (3D DMF) platform with patterned electrodes submerged in an oil medium to provide fundamental solutions to the technical limitations of 2D DMF platforms and water–air systems. 3D droplet manipulation on patterned electrodes is demonstrated by programmably controlling electrical signals. We also demonstrate the formation of precipitates on the 3D DMF platform through the reaction of different chemical samples. A droplet containing precipitates, hanging on the top electrode, can be manipulated without adhesion of precipitates to the solid surface. This method could be a good alternative strategy to alleviate the existing problems of 2D DMF systems such as cross-contamination and solute adsorption. In addition, we ascertain the feasibility of temperature-controlled chemical reaction on the 3D DMF platform by introducing a simple heating process. To demonstrate applicability of the 3D DMF system to 3D biological process, we examine the 3D manipulation of droplets containing mouse fibroblasts in the 3D DMF platform. Finally, we show detachment of droplets wrapped by a flexible thin film by adopting the electro-elasto-capillarity (EEC). The employment of the EEC may offer a strong potential in the development of 3D DMF platforms for drug encapsulation and actuation of microelectromechanical devices.

Vapor–liquid equilibrium measurements and assessments of fluoroethane + N,N-dimethylformamide and fluoroethane + dimethylether diethylene glycol systems for the hybrid refrigeration cycle

This study aimed to develop novel working pairs for the hybrid refrigeration cycle. To this end, the vapor–liquid equilibrium data of fluoroethane (R161) + N,N-dimethylformamide (DMF) and R161 + dimethylether diethylene glycol (DMEDEG) systems were obtained from 293.15 K to 353.15 K. Experimental data were correlated using the nonrandom two-liquid (NRTL) activity coefficient model. The average relative pressure deviations are 1.33% and 1.45%, and the maximum relative pressure deviations are 3.68% and 3.90%, respectively. Experimental results show that the two binary mixtures exhibit negative deviations from Raoult's law. Finally, the performance of R161 + DMF, R161 + DMEDEG, and R134a + DMF systems were simulated and evaluated based on the hybrid refrigeration cycle. Results show that both R161 + DMF and R161 + DMEDEG systems are potential working pairs for the hybrid refrigeration cycle, and the R161 + DMEDEG system is better.

Polymeric nanofiber composites with aligned ZnO nanorods

Abstract ZnO nanorods with high aspect ratio were synthesized and were dispersed in poly(vinyl alcohol) (PVA)–water, PVA–water-N,N-dimethylforamide (DMF) and poly(acrylonitrile) (PAN)–DMF systems. These mixtures were electrospun to understand their spinning behaviour. It was found that only PAN–DMF system could result in formation of nanofiber composites reinforced with aligned ZnO rods. PAN nanofibers reinforced with ZnO rods up to 50 wt% on the weight of polymer could be readily electrospun. The presence of aligned ZnO rods inside PAN nanofibers was confirmed using scanning electron microscopy (SEM) and scanning/transmission electron microscopy (STEM). Raman analysis revealed that such reinforced nanocomposites are enabled only when ZnO rods could interact with both the dispersant as well as the polymer. Both random and aligned ZnO–PAN reinforced nanofibers could be successfully produced to suit different applications.

Amide-induced phase separation of hexafluoroisopropanol–water mixtures depending on the hydrophobicity of amides

Amide-induced phase separation of hexafluoro-2-propanol (HFIP)-water mixtures has been investigated to elucidate solvation properties of the mixtures by means of small-angle neutron scattering (SANS), (1)H and (13)C NMR, and molecular dynamics (MD) simulation. The amides included N-methylformamide (NMF), N-methylacetamide (NMA), and N-methylpropionamide (NMP). The phase diagrams of amide-HFIP-water ternary systems at 298 K showed that phase separation occurs in a closed-loop area of compositions as well as an N,N-dimethylformamide (DMF) system previously reported. The phase separation area becomes wider as the hydrophobicity of amides increases in the order of NMF < NMA < DMF < NMP. Thus, the evolution of HFIP clusters around amides due to the hydrophobic interaction gives rise to phase separation of the mixtures. In contrast, the disruption of HFIP clusters causes the recovery of the homogeneity of the ternary systems. The present results showed that HFIP clusters are evolved with increasing amide content to the lower phase separation concentration in the same mechanism among the four amide systems. However, the disruption of HFIP clusters in the NMP and DMF systems with further increasing amide content to the upper phase separation concentration occurs in a different way from those in the NMF and NMA systems.

The specific character of the reaction of derivatives of 2-thioxo-2,3-dihydropyrimidin-4(1H)-one with iodomethane and alkyl chloromethyl sulfides

The alkylation of 5-alkyl-6-(2,6-dihalobenzyl)-2-thioxo-2,3-dihydropyrimidin-4(1H)-ones with MeI, AllSCH 2 Cl, and MeSCH 2 Cl in the K 2 CO 3 -DMF, NaOMe-MeOH, and KOH-EtOH systems was investigated. A hypothetical mechanism for the reaction is examined, and an explanation is proposed for the composition of the reaction products. The presence of high anti-HIV-1 activity was established in the obtained derivatives of 2-{[(allylsulfanyl)methyl]sulfanyl}pyrimidin-4(3H)-one.

The photodynamic activity of a novel porphyrin derivative bearing a fluconazole structure in different media and against Candida albicans

The spectroscopic properties and photodynamic activity of a novel porphyrin covalently linked to an antifungal fluconazole structure were investigated in DMF and different biomimetic systems, results being compared with those obtained for the non-fluconazole homologoue. Absorption and fluorescence studies indicated that the tetrapyrrolic macrocycle retained its individual spectroscopic properties. Photosensitization ability was first evaluated using 9,10-dimethylanthracene; in microheterogenic media, the porphyrin interacted with sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles and also β-cyclodextrin, photosensitized decomposition of l-tryptophan being observed in these systems. The in vitro photodynamic activity of the photosensitizers when associated with β-cyclodextrin, as tested against Candida albicans, revealed that growth delays imparted by fluconazole alone and the unsubstituted porphyrin were almost additive when the two compounds were used together. However, when the fluconazole was covalently linked to a porphyrin nucleus and exposed to light, reduction in growth delay efficacy was observed relative to the mixed system.

Reentrant swelling behavior of thermosensitive N-isopropylacrylamide nano-sized gel particles

The closed-loop phase diagram of poly N-isopropylacrylamide (PNIPA) in a water–N,N-dimethylformamide (DMF) system was measured by thermooptical analysis (TOA). The reentrant swelling behavior of N-isopropylacrylamide (NIPA) nano-sized gel particles in the water–DMF system was measured by using photon correlation spectroscopy (PCS) technique. Theoretically, a modified double lattice model (MDL) can be used to describe the closed-loop phase behavior of linear PNIPA in water–DMF systems. For crosslinked NIPA nano-sized gel particles in a water–DMF system, we combined MDL theory for the mixing contribution and Flory–Erman theory for the elastic contribution. Molecular interaction parameters obtained from the PNIPA solution were used to directly predict the swelling-ratio curves for the NIPA gel. Using our model, the calculated results were in good agreement with the experimental data using only one adjustable parameter.

Photogalvanic behaviour of [Cr 2O 2S 2(1-Pipdtc) 2(H 2O) 2] in aqueous DMF

The photogalvanic behaviour of [Cr 2O 2S 2(1-Pipdtc) 2(H 2O) 2] was performed in a Honda Cell using 100% DMF and different percentages of water–DMF systems. The maximum potential of 200 mV with 18 μA of current was generated in DMF. The experiments were performed at different pH conditions and added dyes. The system was found to generate a maximum potential of 86, 67 and 36 mV at pH∼4, 7 and 8, respectively, at 65 °C. Malachite green and methylene blue (10 −4 M) produced maximum potential of 100 and 82 mV, respectively. The system was reversible when the irradiated solution was aerated immediately. When the solution was kept in dark for a long time (12 h) and then aerated, the solution was found to be irreversible. The Cr(V) is photoreduced to Cr(IV) with the light irradiation and the unstable Cr(IV) reverts to Cr(V) by aerial oxidation.

A theoretical study of the interactions between N,N-dimethylformamide and xylenes

The ab initio and density functional (DFT) methods were performed on binary systems of N,N-dimethylformamide (DMF) with xylenes (o-, or m-, or p-xylene), and seven stable configurations were obtained with no imaginary frequencies. To obtain the interaction energies of these complexes, single-point energy calculations with basis set superposition error (BSSE) correction were carried out at B3LYP/6-31G* and MP2/6-31G* levels. The structures, Chelpg (charges from electrostatic potentials using a grid-based method) charge distribution and bond characteristics of the mentioned complexes were calculated. The results indicated the presence of double C–H···O hydrogen bonds between DMF and xylenes in these complexes and the interaction energies of hydrogen bonding between DMF and xylene systems decreased in the following sequence: DMF–o-xylene: a1 > DMF–m-xylene: b1 > DMF–p-xylene: c1.

Correlation of &lt;sup&gt;1&lt;/sup&gt;H NMR for Alcohol＋DMF Systems Based on SAFT

Correlation of &lt;sup&gt;1&lt;/sup&gt;H NMR for Alcohol＋DMF Systems Based on SAFT

Phase behavior and morphological studies of polyimide/PVP/solvent/water systems by phase inversion

AbstractThe solubility gaps for poly(vinyl pyrrolidone) (PVP) in four polyimide solutions (NMP, DMF, GBL, DMSO) were determined by cloud point measurement and correlated with χPI/Solvent and ΔδPVP/Solvent. Membranes prepared with NMP and DMF systems showed a tendency of suppressing fingerlike structure with addition of PVP. On the other hand, membranes prepared with GBL and DMSO systems showed an inclination toward inducing macrovoid formation. These effects of PVP on the membrane morphology were explained by means of miscibility gap, viscosity of the polymer solution, polymer–polymer phase separation, and overall porosity. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 81: 3481–3488, 2001

Swelling of poly[methacrylic acid‐co‐poly(oxytetramethylene) dimethacrylate

AbstractAn equation of swelling equilibrium is derived for crosslinked copolymer including incomplete network structures, to be applied to the swelling data on copolymer of poly(oxytetramethylene) dimethacrylate (POTMDM) with methacrylic acid (MAA). Poly(MAA‐co‐POTMDM)s with various monomer contents, is prepared by copolymerization in N,N‐dimethylformamide (DMF). The equation shows good applicability to the swelling behaviors of poly(MAA‐co‐POTMDM) for tetrahydrofuran (THF) and DMF systems. A difference in polymer‐polymer interaction parameter between THF and DMF systems, derived from the results of curve fitting is explained in terms of dependence of polymer‐solvent interaction parameter on crosslink density. © I993 John Wiley &amp; Sons, Inc.

Dielectric relaxation studies of some aliphatic alcohols and their mixtures in benzene solutions

Dielectric absorption of four aliphatic alcohols, viz., methyl alcohol, ethyl alcohol, n-propyl alcohol, tert-butyl alcohol and their binary mixtures, mixtures of these alcohols with dimethyl formamide and 2-fluoroaniline has been studied in the 3 cm microwave region at a temperature of 30°C in benzene. In alcohols and their mixtures the tan σ - concentration curve shows a marked increase in the concentration range 0.02 – 0.05 weight fraction. This behaviour has been explained as due to the formation of complex via self and hetero-association. The alcohols + DMF systems show complex formation at a very low concentration range. The study of systems alcohols + 2 - fluoroaniline indicate that the 2-fluoroaniline produces dissociating effects in these alcohols.