Dimethylformamide Solvent Research Articles

Investigation of ultrafast optical nonlinearity in a nickel-dithiolene complex: mechanism of pulse-selective response in different solvents

The ultrafast optical nonlinear of a dithiolene complex of nickel (bis(1,2-diphenyl-1,2-ethenedithiolato-S,S’)-nickel) (1) has been systematically investigated. Results of Z-scan with picosecond and nanosecond pulses show that compound 1 in N,N’-dimethylformamide (DMF) has a selective reverse saturable absorption (RSA), which could be observed with picosecond pulses and would be dramatically suppressed under ns pulses. The pulse-selective response vanishes in dichloromethane (DCM) and toluene solvents, indicating a connection with the decrease of solvent polarity. The ultrafast decay processes of excited state in different solvents are further investigated via femtosecond transient absorption (TA) experiment. The results are studied with global & target analysis and show that the excited state lifetime of 1 is remarkably shortened with the increasing polarity of the solvents, which suppresses the accumulation of excitons on excited-state and result in the substantially decrease of RSA in DMF solvent under nanosecond pulses. Our results are expected to shed light on the mechanism of selectively tuning optical nonlinearity in metal dithiolene complexes on an ultrafast time scale.

Surface and interface characteristics of hydrophobic lignin derivatives in solvents and films

Lignin is an abundant macromolecule available in large quantities in the world, but it is under-utilized. In this study, lignin was modified via methylation and grafting with dodecyl glycidyl ether (DGE), and films containing these lignin derivatives were generated following different routes and using solvents (water, ammonium hydroxide, and dimethylformamide). The impact of the solvent type, coating method, and temperature on the characteristics of the prepared films was studied using contact angle (sessile drop experiment), scanning electron microscopy, and Turbiscan stability index (TSI) analyses. Methylation and the subsequent DGE grafting improved the hydrophobicity of lignin by blocking the phenolic active site of lignin, which improved the surface tension, contact angle, and interfacial tension of solvents containing lignin derivatives. Such alternations in the hydrophobicity of lignin substantially decreased the water uptake (90 %) of the lignin derivatives analyzed by the powder test wettability analysis. Quartz crystal microbalance (QCM) analysis revealed that the modifications were successful in reducing the dissolution of lignin derivatives in water, and exhibited the fundamental absorption behavior of water by the films. The methylated and DGE grafted lignin derivative with the highest hydrophobicity may be more attractive than other lignin derivatives to be used potentially in coating and packaging applications.

Synthesis of Polycaprolactone Nanoparticles through Flow‐Focusing Microfluidic‐Assisted Nanoprecipitation

AbstractPolycaprolactone nanoparticles (PCL NPs) were produced by a liquid nonsolvent nanoprecipitation process in a flow‐focusing microfluidic device and optimized in terms of particle size, polydispersity index (PDI), and zeta potential ζ. The effects of flow rate ratio (FRR), total flow rate (TFR), the organic solvents tetrahydrofuran and dimethylformamide (DMF), the surfactants polyvinyl alcohol and Tween 80, and polymer molecular weight on the size, PDI, and ζ of PCL NPs were investigated. A stability study was performed to compare the effect of the surfactants on the characteristics of PCL NPs over 7 d. The smallest particles are produced at the highest FRR, TFR, and polymer molecular weight and lowest polymer concentration in DMF. The presence of both surfactants results in smaller NPs.

Study on hysteresis in perovskite solar cells fabricated using different solvents under ambient conditions

We have investigated the dependency of hysteresis in all-ambient-processed perovskite solar cells on the solvent used for the synthesization of perovskite. Methylammonium lead iodide (MAI) perovskite solar cells have been fabricated using the two-step sequential spin coating method. The influences of PbI2 precursor on the cell performance and its hysteresis are investigated using four different solvents of pure dimethylformamide (DMF), pure dimethyl sulfoxide (DMSO) and mixtures of DMF:DMSO with the ratios of (4:1) and (1:4). The results indicate that a small amount of DMSO in DMF leads to produce large grains of perovskite with proper coverages at the interfaces with hole and electron transport layers. The best conversion efficiency of 10.9% was obtained for the cell prepared by the solvent of (4:1) for DMF:DMSO. The best hysteresis was also obtained from the same cell with the hysteresis index of 0.009.

Studies on non-gelatinous & thermo-responsive chitosan with the N-isopropylacrylamide by RAFT methodology for control release of levofloxacin

The non-gelatinous and thermo-responsive properties were introduced in chitosan by incorporating the chain of poly(N-isopropylacrylamide) via reversible addition-fragmentation chain transfer (RAFT) polymerization. To achieve this, the reaction was carried out at 80 °C by modifying the chitosan(CS) with RAFT agent as a macroinitiator (CS-RAFT), where the amine group of CS was protected with phthalic anhydride and then reacted with 4-cyano-4-[(dodecyl sulfanyl thiocarbonyl)sulfanyl]-pentanoic acid (CDSTSP) to form CS-RAFT agent. Further, the addition of NIPAAm chains onto CS-RAFT was carried out in N,N′-dimethylformamide (DMF) solvent by using 2,2′-azobisisobutyronitrile (AIBN) as an initiator in N2 atmosphere. The controlled addition of NIPAAm chains on to CS was confirmed by 1H NMR spectroscopy, further, a kinetic study was performed to get the characteristic features of the RAFT reaction. The product was characterized by 1H NMR, FT-IR, UV–Visible spectroscopy, XRD, SEM, and TGA analyses. The product in aqueous solution showed LCST at 2.0 mg/mL on 33 ± 0.1 °C. Further, beads were prepared with the sodium alginate and loaded the water-soluble levofloxacin drug (60% w/w loading was achieved). The drug delivery process was studied in-vitro at 37 ± 0.1 °C & pH 7.4, which shown controlled release of drug up to 32 h and it was 71% of the loaded levofloxacin.

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Summary Carboxylation of terminal alkynes with CO2 via direct C–H bond activation is a highly appealing way to capture and convert CO2 but faces great challenges and difficulty. Here, we report an efficient catalyst that is prepared simply through introduction of p-tert-butylaniline into graphite oxide powders followed by localized growth of Ag nanoparticles (NPs). The bulky nature of p-tert-butylaniline facilitates the powder exfoliation, giving rise to mass production of uniform modified graphene oxide (tert-GO) nanosheets of 4 nm in thickness. Notably, Ag/tert-GO shows excellent catalytic activity for converting alkynes regardless of containing electron-donating or electron-withdrawing groups under mild reaction conditions. The synergy of the amide linkages on tert-GO nanosheets and the supported small-sized Ag NPs is recognized as the vital role in promoting adsorption of CO2 and subsequent conversion.

Electrospun drug blended poly(lactic acid) (PLA) nanofibers and their antimicrobial activities

In the present study, the influence of electrospinning parameters on poly(lactic acid) (PLA) nanofiber production and antimicrobial attitude of drug blending were investigated. The PLA concentrations (5 to 12% wt/v) were determined with solvent ratio variations of a triple solvent system (chloroform (CHL), dimethylformamide (DMF) and tetrahydrofuran (THF)). Flow rates were varied from 0.5 to 1 mL/h, while voltages were changed from 10 to 15 kV, and 10 kV voltage and 0.5 mL/h flow rate were selected as optimum electrospinning conditions. According to morphological investigations via scanning electron microscopy, the average PLA fiber diameters varied from 303 to 405 nm, for 5 and 8% wt/v PLA concentrations, respectively. The drug (ceftriaxone disodium) was blended into these concentrations and electrospun. Drug addition reduced the fiber diameters, and at 8% wt/v drug blended PLA concentrations homogeneous fiber distribution was obtained. Additionally, the antimicrobial attitude of drug blended PLA nanofibers was analyzed by using agar disc diffusion method and antimicrobial activity against Escherichia coli, and Listeria monocytogenes were observed.

Biocidal activity of curcumin and cationic polymer possessing composites

There is a growing interest in new type of biocidal compounds with antibacterial properties against bacteria. In this study, new antibacterial synthetic materials bearing curcumin and cationic polymers were synthesized. In the synthesis stage, the methacrylate functional cationic monomer was synthesized via the Michael addition route by using 3-acryloxy-2-hydroxypropyl methacrylate and 3-amino pyridine to obtain Monomer 1. Monomer 1 was further quaternized with hexyl bromide to obtain a cationic methacrylate functional monomer. Free-radical polymerization of Monomer 1 and methyl acrylate was conducted in the presence of azobisisobutyronitrile under dimethylformamide solvent. The composite formulation was conducted by using turmeric extract Curcuma longa (curcumin), hydroxyapatite, montmorillonite, and silver nitrate. The materials were analyzed by using the methods of X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and scanning electron microscopy. The biocidal activities against the bacteria Escherichia coli, Listeria monocytogenes, Salmonella, and Staphylococcus aureus were analyzed using agar well diffusion method. From the Fourier transform infrared, X-ray diffraction, and scanning electron microscopy analysis results of the synthesized nanocomposites, it is seen that they form strong connections with the components added to the composites and form an exfoliated structure. According to the antibacterial analysis results, the nanocomposites obtained have showed a strong antibacterial resistance against E.coli, L.monocytogenes, Salmonella, and S. aureus bacteria, and the high inhibition zone areas were obtained.

The Characteristics of Perovskite Solar Cells Fabricated Using DMF and DMSO/GBL Solvents

Organic solar cells are used in low-cost solar energy applications. Recently, organo-lead halide perovskite solar cells have attracted considerable interest. Low-temperature spin-coating is the simplest method to fabricate the low-cost solar cells; however, forming a continuous perovskite film by spin coating a precursor solution of lead iodide (PbI2) and methylammonium iodide (CH3NH3I) is challenging. This work investigated the characteristics of perovskite thin film, prepared using dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)/γ-butyrolactone (GBL) solvents in the direct mixing of PbI2 and CH3NH3I. Perovskite films prepared using the DMSO/GBL solvent had greater crystallinity and compactness than those using the DMF solvent. Cell performance was improved by a perovskite absorber using the DMSO/GBL solvent to a power conversion efficiency of 8.87%, an open-circuit voltage of 0.82 V, a current density of 17.13 mA/cm2, and a fill factor of 63.01%.

Flexible and transparent supercapacitors using electrospun PEDOT:PSS electrodes

Electrospun poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) nanofibers were deposited onto flexible polyethylene terephthalate (PET) substrates to obtain electrodes for flexible and all solid-state supercapacitors (SCs). The solution used for electrospinning contained a conducting polymer (PEDOT:PSS), an insulating polymer (polyethylene oxide or PEO), a solvent (dimethylformamide) and a surfactant (Triton-X).The nanofibers improved considerably their conductivity when they were immersed in ethylene glycol (EG), producing a removal of the excedent of PEO around the nanofibers, which causes that the PEDOT:PSS nanofibers became more conductive, then improving their electrochemical performance. The removal of PEO was observed by scanning electronmicroscopy (SEM) and corroborated by energy-dispersive X-ray spectroscopy (EDS). The PEDOT:PSS electrodes were used in supercapacitors, with poly (vinyl alcohol)/phosphoric acid (PVA/H3PO4) gel polyelectrolyte, forming an all solid-state SC. The SCs reach an areal capacitance of 1.8 m F/cm2 and a gravimetric capacitance of 3.6 F/g at a discharging current of 5μA/cm2 by galvanostatic charge discharge technique (GCD). The capacitances of the SCs were also calculated by cyclic voltammetry showing very similar results than GCD. These results using PEDOT:PSS nanofibers as electrodes showed better performance in comparison with doped PEDOT:PSS films with the same gel polyelectrolyte. The devices showed very good stability since they were charged and discharged at 20 μA /cm2 by 1000 cycles maintaining ∼92 % of the initial capacitance. These results open the possibility of fabricating wearable and 3-D interconnected electrodes for energy-storage devices that could be implemented on clothes and on any non-flat surface.

One-pot synthesis, crystal structure, hirshfeld, DFT and anticancer study of ethyl 2-(3-fluoro-4-methylphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxylate

Abstract In the present study, a novel ethyl 2-(3-fluoro-4-methylphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxylate was synthesized by an efficient one-pot nitro reductive cyclization method using sodium dithionite as reductive cyclizing agent in DMSO medium. Title compound was recrystallized in Dimethyl formamide solvent. Single crystal X-ray studies revealed that the title compound crystallized in monoclinic system (P21/c space group with Z = 4) and molecules are linked with C—H…O intermolecular hydrogen bonds. The Hirshfeld surfaces computational method applied to visualize and analyze the intermolecular interactions within the crystal structure. The theoretical structural optimization of the title compound was carried out using B3LYP/6-311++G (d,p) level of theory. Anticancer screening result of compound showed promising activity against human malenoma A375 and mouse malenoma B16F10 cancer cell line with IC50 value of 33.99 μM and 31.14 μM in comparison to the standard drug Cisplatin with IC50 12.99 μM and 20.33 μM respectively.

Ultrafast Exfoliation of 2D Materials by Solvent Activation and One-Step Fabrication of All-2D-Material Photodetectors by Electrohydrodynamic Printing.

Large-scale liquid exfoliation of two-dimensional materials such as molybdenum disulfide, tungsten disulfide, and graphene for the synthesis of printable inks is still inefficient due to many hours of exfoliation time needed to achieve a highly concentrated dispersion that is useful for printing. Here, we report that soaking the bulk 2D material powders in a variety of solvents (water, ethanol, isopropanol, acetone, methanol, dimethylformamide, N-methyl pyrrolidone, and hexane) briefly as short as 5 min "activates" them to be much more easily exfoliated afterward. The unsoaked powder yielded a negligible concentration of dispersed nanosheets (less than 0.01 mg/mL) even after long hours of sonication, while the powders soaked in water resulted in dispersed nanosheets of 1.21 mg/mL for MoS2 and 1.28 mg/mL for WS2 after 6 and 4 h of sonication, respectively, a more than 100 time increase. For graphene, soaking in methanol for 5 min prior to sonication for 6 h yielded an increase in the dispersed nanosheet concentration to 0.13 mg/mL, a more than 10 time increase in concentration. The enhanced exfoliation is originated not from the intercalated solvent molecules but from the slightly increased d-spacing of the bulk powders during soaking due to the different dielectric environments in the solvents, which assists in the exfoliation afterward. We further fabricated MoS2 and WS2 photodetectors with graphene as electrodes by one-step electrohydrodynamic (EHD) printing using highly concentrated inks (>2 mg/mL) obtained by ultrafast liquid exfoliation, which have light sensitivity down to 0.05 sun. We believe that this ultrafast exfoliation technique combined with the one-step device printing technique enables a big step toward the mass production of functional devices fabricated from solution-processed 2D material inks.

Effect of B-site doping on the phase and thermal stability of CsPbI3 perovskite

B-site doping has been regarded as an effective strategy to stabilize the desired perovskite phase of CsPbI3. However, on the basis of first-principles study, we demonstrate that only Sn2+ doping could enhance both the phase and thermal stability of CsPbI3 perovskite while doping with other cations such as Mn2+, Zn2+, Sr2+, Ca2+, Mg2+, Bi3+ and Sb3+ either decreases the phase or thermal stability of CsPbI3 host or has little influence. The experimentally observed improvement of stability should be ascribed to nanocrystallization or the use of dimethylformamide (DMF) solvent rather than B-site doping.

Influence of solvent and nanoparticles on the morphology and gas separation properties of copolyimide membranes

AbstractIn this study, the effect of solvent type and nanoparticles of silica and zeolite 4A on the gas separation properties of polyimide (PI) membranes were investigated. Gas separation of the membranes based on pure solvents of dimethylformamide (DMF), n‐methyl‐2‐pirrolidone (NMP), dimethylacetamide (DMAc), and dimethylsulfoxide (DMSO) were studied. The prepared PI membranes using DMAc and DMSO showed the highest selectivity and permeability, respectively. In this regard, the influence of their mixing on transport properties of the PI was evaluated. The prepared membrane using the mixture of DMSO/DMAc with the volume ratio of 1:3 showed the best gas separation performance in comparison to the Robeson's upper bound. Incorporation of 20 wt% of silica and zeolite 4A nanoparticles into the PI membrane indicated that the selectivity of CO2/CH4 increased from 39.4 to 57.6 and 68.5, respectively. Besides, gas transport properties of the PI‐based mixed matrix membranes were satisfactory predicted by modified Maxwell model. Furthermore, characteristic parameters of the encapsulated particles by interfacial layer were determined.

Solvent Switched Weak Interaction of a 4-Quinazolinone with a Cavitand Derivative.

Interaction of 4-quinazolinone with tetrakis (3,5-dicarboxylatophenoxy)-cavitand derivative has been studied in methanol and dimethylformamide media using fluorescence spectroscopy and molecular modeling methods. Results show temperature dependent complex formation: either the entropy gain or the high enthalpy changes are responsible for the formation of stable complexes in two separated temperature regions. However, different thermodynamic parameters are associated to different conformations of the complexes: while the high entropy gain associated to the formation of deeply included guest in methanol, the high entropy gain is associated with the formation of weakly included guest in dimethylformamide solvent. This finding highlights the importance of dynamic properties of the species interacted in different solvents.

Separation and recovery of materials from the waste light emitting diode (LED) modules by solvent method

Nowadays, a large quantity of Light Emitting Diodes (LEDs) have been produced and updated with the development of optoelectronic industry. At the same time, many waste LEDs are discarded. However, there are many metals and non-metals in waste LEDs, which may cause secondary pollution and waste of resources if disposed improperly. In this study, solvent method was used to dissociate the waste LED modules and recycle resources. Firstly, the components of the waste LED modules were analyzed. The main component of the transparent plastic part, usually used as packaging materials, is cured epoxy resin, and the main component of the white plastic part as the skeleton of LED modules is a mixture of polyphenylene oxide (PPO) and polystyrene (PS). Then, eight organic solvents, [EMIM+]BF4− ion liquid and sodium hydroxide (NaOH) inorganic reagent were tried to separate a 40 × 40 mm2 waste LED module respectively. The results showed that only three organic solvents—dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl-sulfoxide (DMSO) could dissociate the waste LED module very well. The used DMF solution was purified by rotary evaporation, and the regenerative DMF solution could be reused because its property has not changed. The solid residue obtained after rotary evaporating DMF was identified as polystyrene (PS). It was inferred that the waste LED module was dissociated through the DMF dissolving the PS of white plastic. In addition, the effect of DMF, DMA and DMSO dissociating the waste LED modules with the change of temperature was discussed. It was found that the choice of suitable solvent is a key for this method, and the heating temperature was also a very important factor. Finally, it was measured that the cured epoxy resin and the white plastic of the waste LED module accounted for about 31.4% (w/w) and 37.7% (w/w) respectively, which can be recycled. In short, the method not only separated completely the waste LED module and its each part was recycled easily, but the solvents can be reused. This study suggests a new route to recycle LEDs due to its environmentally friendly process, which may exert a significantly beneficial impact on our environment.

Synthesis and characterization of pyrrolo[1,2-a]quinoline derivatives for their larvicidal activity against Anopheles arabiensis

Certain tetrahydropyrido[1,2-a]quinolines and pyrroloquinoline homologs have shown various biological activities such as antimicrobials, crop-protectings, diuretics, antioxidants, anticoagulants, and antimalarial activities. Keeping this observation in mind, we envisaged to synthesize and characterize a series of novel ethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-3-carboxylates and dimethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-2,3-dicarboxylates (2a-k). Quaternary salts of lepidine such as 1-[2-(substituted phenyl)-2-oxoethyl]-4-methylquinolin-1-ium bromide (1a-f) were obtained by stirring lepidine with different phenacyl bromides in acetone at room temperature separately. These quaternary salts of lepidine (1a-f) were then treated with electron-deficient ethyl propiolate and dimethyl-but-2-yne-dioate separately, in the presence of anhydrous K2CO3 and dimethylformamide (DMF) solvent to obtain ethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-3-carboxylates and dimethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-2,3-dicarboxylates, respectively (2a-k). The newly synthesized compounds were assessed by spectroscopic techniques to determine their structures. Based on our previous study on the similar pharmacophore, the synthesized compounds 2a-k were screened for their larvicidal activity against Anopheles arabiensis using a standard World Health Organization larvicidal assay; compounds 2b and 2e at 8.12 and 9.2 μM exhibited the highest larval mortality at 78 and 89%, respectively, when compared with the negative control acetone, and it demonstrated less activity, which was similar to the positive control, temephos. Finally, the test compound 2e at 9.2 μM, resulted in an 89% mortality rate after 48 h of exposure, followed by compound 2b at 8.12 μM with a 78% mortality rate. Compounds 2f, 2d, and 2c showed intermediate toxicity, and the mortality rate was lower than 60% for larvae exposed to any of the remaining test compounds.

The positive effect of nitridation on CrNb49O124 nanowires for high-performance lithium-ion storage

Advanced electrode materials with excellent electrochemical properties have always been widely concerned in lithium-ion batteries (LIBs). In this work, two kinds of CrNb49O124 nanowires of different sizes are prepared via electrospinning technique with two different solvents (ethanol and dimethylformamide). Moreover, the obtained CrNb49O124 nanowires are nitrided by thermal ammonia gas to further improve the electrochemical performance. And it is pleasantly surprised to say that the nitrided CrNb49O124 nanowires perform better than our expectation. It exhibits an initial Coulombic efficiency up to 90.72%, and an eximious charge specific capacity (273.6 mAh g−1), which is apparently higher than that before nitridation. In addition, after 300 cycles at 1 C, it still maintains capacity of 224.4 mAh g−1 and the retention is up to 90.41%, indicating its excellent long cycling stability. The outstanding electrochemical properties of nitrided CrNb49O124 nanowires are proved to be much superior than most of anode materials in LIBs. Meanwhile, it is successfully confirmed that nitridation technique can be an efficient approach for high-performance energy storage applications to promote electrochemical properties of most electrode materials.

Ethylenediamine loading into a manganese-based metal-organic framework enhances water stability and carbon dioxide uptake of the framework.

Metal–organic frameworks (MOFs) based on 2,5-dihydroxyterepthalic acid (DOBDC) as the linker show very high CO2 uptake capacities at low to moderate CO2 pressures; however, these MOFs often require expensive solvent for synthesis and are difficult to regenerate. We have synthesized a Mn-DOBDC MOF and modified it to introduce amine groups into the structure by functionalizing its metal coordination sites with ethylenediamine (EDA). Repeat framework synthesis was then also successfully performed using recycled dimethylformamide (DMF) solvent. Characterization by elemental analysis, FTIR and thermogravimetric studies suggest that EDA molecules are successfully substituting the original metal-bound DMF. This modification not only enhances the material's carbon dioxide sorption capacity, increasing stability to repeated CO2 sorption cycles, but also improves the framework's stability to moisture. Moreover, this is one of the first amine-modified MOFs that can demonstrably be synthesized using recycled solvent, potentially reducing the future costs of production at larger scales.

Hydrogen bond capability tunable different “relay-race” mechanisms of the excited-state proton transfer process for 4′-methoxy-3-hydroxyflavone

Abstract The different “relay-race” mechanisms of proton transfer process are investigated for 4′-methoxy-3-hydroxyflavone (MHF) in methanol (MeOH) and dimethylformamide (DMF) characterized by different hydrogen bond (HB) capabilities. Based on the density functional theory and time-dependent density functional theory, we demonstrate that the asynchronous excited-state intermolecular double proton transfer via two intermolecular HBs happens for MHF in MeOH. Differently, in DMF solvent, it breaks the intramolecular HB and forms a single intermolecular HB. And the intermolecular single proton transfer occurs in DMF upon photoexcitation. The excited-state intermolecular HBs both in MHF-MeOH and MHF-DMF complex are proved to be significantly strengthened, which facilitate the proton transfer process. Importantly, it reveals that the higher electrostatic potential and the stronger proton capture ability of DMF than MeOH induce a faster proton transfer for MHF-DMF in experiment. The results highlight the significance of the solvent HB capability in effecting the proton transfer mechanism, and hence have potential to design and develop excellent fluorescent probes.