A general synthetic route to indenofluorene derivatives as new organic semiconductors

A series of 2,6-disubstituted indenofluorene derivatives were obtained in high purity via a general route involving the Suzuki coupling reaction. The potential of these conjugated indenofluorenes as new organic semiconductors was demonstrated by the light-emitting diode reaching a high luminance of 1400 Cd/m(2) below 10 V. [structure: see text]     

Polythiophene encapsulated inside(13, 0) CNT: A nano-hybrid system

We present a first-principles calculation on the electronic and optical properties of a hybrid nanotube system consisting of a （13, 0） single-walled carbon nanotube encapsulated by polythiophene. This hybrid-system represents a complete new type of matter and is known as the peapod system. We analyze bow the polythiophene changes the electronic and optical properties of the nanotube. In particular, we examine new features in the dielectric function due to the transitions between the states of the polymer and the nanotube. The electronic structure of the combined system appears to be a simple superposition of the individual constituents. The density functional theory calculations demonstrate van der Waals interaction as the bonding mechanism between the tube and the encapsulated molecule.     

Current Applications of Suzuki–Miyaura Coupling Reaction in The Total Synthesis of Natural Products: An update

Suzuki‐Miyaura Coupling Reaction (SMCR) has been extensively used in the total synthesis of natural products. We underscored these achievements in a report published in Tetrahedron up to 2012. Since then, there has been tremendous growth in this field and numerous articles have been published after 2012. In this review, we tried to go insight and highlight the current developments in the applications of SMCR as a key and strategic step (steps) in the total synthesis of biologically active natural products accomplished and reported from 2012 till date.     

Synergistic effect of graphene oxide nanoplatelets and cellulose nanofibers on mechanical,thermal, and barrier properties of thermoplastic starch

In recent years, because of the limited availability of oil resources and the increasing concerns regarding environment protection, much attention has been drawn to produce packaging films based on degradable biopolymers instead of synthetic polymers. On the other hand, because of the high costs of oil extraction, raw materials and film production, and disposing of the waste products of synthetic films, the need to replace these films with less pollutant and more cost‐effective films is growing globally. In this study, to answer the need for replacing synthetic polymer films, nanocomposite films based on thermoplastic starch reinforced with cellulose nanofibers and graphene oxide nanoplatelets were produced and characterized. The results implied that the synergistic effect of cellulose nanofibers and graphene oxide nanoplatelets has played an important role in improving the mechanical properties of the films. The results showed that with the addition of cellulose nanofibers and graphene oxide nanoplatelets, the tensile strength and elastic modulus of starch film were increased from 3 and 32 MPa to 13 and 436 MPa, which corresponds to 438% and 1435% improvement, respectively. In addition, the oxygen permeability resistance and the water vapor transmission for samples containing 3 wt% of graphene oxide nanoplatelets was decreased by 78% and 30% compared with the thermoplastic starch film, respectively. The permeability coefficient of the samples containing 3 wt% graphene oxide nanoplatelets for oxygen, nitrogen, and carbon dioxide have proved to be 0.051, 0.054, and 0.047 barrer, which shows that these films can perform well as packaging films.     

Application of a thiourea‐containing task‐specific ionic liquid for the solid‐phase extraction cleanup of lead ions from red lipstick,pine leaves,and water samples

Here, task‐specific ionic liquid solid‐phase extraction is proposed for the first time. In this approach, a thiourea‐functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid‐phase extraction column are used for the selective extraction and preconcentration of ultra‐trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5–40.0 ng/mL with the detection limit of 0.13 ng/mL (3s_b/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.     

An Efficient Isocyanide‐Based Three‐Component Diastereoselective Synthesis of Chromane‐3,4‐dicarboxamides

An efficient method for the diastereoselective synthesis of chromane‐3,4‐dicarboxamides via the three‐component reaction of 2‐oxo‐2H‐chromene‐3‐carboxylic acids, amines, and isocyanides in MeCN is reported.     

Investigation of cross-linked PVA/starch biocomposites reinforced by cellulose nanofibrils isolated from aspen wood sawdust

In this study, a bio-based composite prepared from cross-linked polyvinyl alcohol/starch/cellulose nanofibril (CNF) was developed for film packaging applications. For this purpose, CNF, as reinforcing phase, was initially isolated from aspen wood sawdust (AWS) using chemo-mechanical treatments, and during these treatments, hydrolysis conditions were optimized by experimental design. Morphological and chemical characterizations of AWS fibers were studied by transmission electron microscopy, scanning electron microscopy, Kappa number, and attenuated total reflectance-Fourier transform infrared spectroscopy, as well as National Renewable Energy Laboratory and ASTM procedures. Morphological images showed that the diameter of the AWS fibers was dramatically decreased during the chemo-mechanical treatments, proving the successful isolation of CNF. Moreover, chemical composition results indicated the successful isolation of cellulose, and Kappa number analysis demonstrated a dramatic reduction in lignin content. Mechanical, morphological, biodegradability, and barrier properties of biocomposites were also investigated to find out the influence of CNF on the prepared biocomposite properties. The mechanical results obtained from tensile analysis revealed that Young’s modulus and ultimate tensile strength of biocomposite films were enhanced with increasing CNF concentration, while a significant decrease was observed in elongation at break at the same concentration of CNF. Furthermore, with adding CNF, barrier properties and resistance to biodegradability were increased in films, whereas film transparency gradually declined.     

Synthesis of 2-amino-3-cyano 4-<Emphasis Type="Italic">H</Emphasis>-chromenes containing quinoline in water: computational study on substituent effects

An efficient, high yielding and environmentally benign strategy to the synthesis of new 2-amino-3-cyano-4-H-chromene derivatives, via one-pot three-component reaction involving malononitrile, various α- or β-naphthol and appropriate aromatic aldehydes including 2-chloroquinoline-3-carbaldehydes in the presence of morpholine in water, was achieved. During the development of the synthesis five new chromene derivatives were fruitfully synthesized. It was found that employing this approach, aromatic aldehydes bearing electron-withdrawing groups give higher yields of the corresponding products in shorter reaction times. This observation was in agreement with topological analysis of calculated electron density functions using density functional theory and quantum theory of atoms in molecules approaches.     

Isocyanide-based four-component synthesis of 1,3-indandionylamidinium betaines

An efficient approach for the synthesis of novel 1,3-indandionylamidinium betaines via four-component reaction of 1,3-indandione, aldehydes, amines, and isocyanides, without assistance of any catalyst and under mild reaction conditions has been reported. The structures of these compounds were confirmed by IR, mass spectroscopic, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies.     

Plasma oxidation and stabilization of electrospun polyacrylonitrile nanofiber for carbon nanofiber formation

The effect of plasma treatment on the stabilization of copolymer P(AN-MA) containing 6.1 mol% methyl acrylate (MA) prepared by an electrospinning technique has been investigated at various oxygen contents (10 %, 20 % and 30 %) and different exposure times. The morphology and chemical structural evolution of electrospun and oxidized nanofibers were studied using field–emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). FT-IR analysis indicated that the treated nanofibers were effectively oxidized under different contents of oxygen and prolonged plasma exposure times by increasing the peak intensities of polar groups at 1730 and 3400 cm^?1 corresponding to C=O stretching band and OH stretching vibration mode, respectively. Additionally, a reduction in the extent of the cyclization reaction is observed with further increase in exposure times and contents of oxygen, which implies lower conversion of C≡N bands into C=N ones in the copolymer chain. According to the FE-SEM studies, the surfaces of the treated nanofibers were completely etched after 15 min of treatment due to the existence of strong ion bombardment and a reduction in the average fiber diameters was observed.