Dielectric spectroscopy of polypyrrole–γ–Fe2O3 composites

In situ polymerization of pyrrole was carried out in the presence of γ–Fe₂O₃ (FE) to synthesize polypyrrole–γ–Fe₂O₃ composites (PPy/FE) by chemical oxidation method. The PPy/FE composites have been synthesized with various compositions viz., 10, 20, 30, 40 and 50 wt.% of γ–Fe₂O₃ in pyrrole. The AC conductivity was studied in the frequency range 10²–10⁷ Hz. The dielectric behaviour was also investigated in the frequency range 10²–10⁷ Hz. The dimensions of γ–Fe₂O₃ particles in the matrix have a greater influence on the conductivity values and the observed dielectric values.     

Crystal structure of a new organic dihydrogenomonophosphate (C6H8N3O)2(H2PO4)2

Chemical preparation, X-ray single-crystal, thermal behavior, and IR spectroscopy investigations are given for a new organic cation dihydrogenomonophosphate (C₆H₈N₃O)₂(H₂PO₄)₂ (denoted IAHP) in the solid state. This compound crystallizes in the orthorhombic space group P2₁2₁2₁. The unit cell dimensions are: a = 7.422(3) Å, b = 12.568(5) Å, c = 20.059(8) Å with V = 1871.1(13) Å³ and Z = 4. The structure has been solved using direct method and refined to a reliability R factor of 0.029. The atomic arrangement can be described as inorganic layers of H₂PO₄⁻ anions between which are located the organic groups (C₆H₈N₃O)⁺ through multiple hydrogen bonds.     

Self-assembled silver nanoprisms monolayers at the liquid/liquid interface

A crown ether derivative (4′-aminobenzo-15-crown-5 hydrotetrafluoroborate) can mediate the self-assembly of silver nanoprisms at the liquid/liquid interface in the form of a stable hybrid nanocomposite film. The metallic luster of the interfacial film results from the electronic coupling of Ag nanoprisms, suggesting the formation of closely packed nanoprism thin films. The interfacial film of nanoprisms could be transferred to solid substrates as a Langmuir–Blodgett film. The properties of films were studied by UV–vis spectroscopy and transmission electron microscopy.     

Synthesis of nanocrystalline MMoO4 (M = Ni,Zn) phosphors via a citrate complex route assisted by microwave irradiation and their photoluminescence

Nanocrystalline MMoO₄ (M = Ni, Zn) phosphors, which have wolframite-type structure, were successfully synthesized at low temperatures via a modified citrate complex route assisted by microwave irradiation. The citrate complex precursors were heat-treated from 300 to 600 °C for 3 h. Crystallization of the MMoO₄ (M = Ni, Zn) nanocrystallites were detected at 500 °C, and entirely completed at a temperature of 600 °C. The nanoparticles presented primarily dispersed and homogeneous morphology with particle size of 20–40 nm. The nanocrystalline MMoO₄ (M = Ni, Zn) phosphors prepared at 600 °C exhibited broad luminescence in green and blue wavelength region, respectively.     

Preparation and characterization of TiO2 bulk porous nanosolids

A novel TiO₂ bulk porous nanosolid (also called a “TiO₂ nanosponge”) was prepared by a solvothermal hot-press (SHP) technique, using TiO₂ nanoparticles (average particle size of 15 nm) and various solvents as the starting materials. The pore diameters of the nanosolids were rather uniform, and the maximum value of pore volume and specific surface area were 0.249 cm³/g and 59.455 m²/g, respectively. The pore volume and diameter of TiO₂ bulk porous nanosolid could be controlled by changing either the type or the amount of the solvent used in the experiment. No residual solvents could be detected by FTIR analysis, which means that the solvents had entirely escaped from the samples during the process of preparing TiO₂ bulk porous nanosolids.     

Characterization of LSMO/C60 spinterface by first-principle calculations

Spinterface between fullerene C₆₀ and La_{0 7}Sr_{0 3}MnO₃ (LSMO) was studied by means of density functional theory. Co-existence of many different configurations was shown, and probabilities of their appearance were estimated. Dependence of composite properties on configuration and temperature was also investigated. Key role of transition metal atoms in both binding between composite compartments and magnetic ordering in C₆₀ molecule was discussed. The latter was suggested to be responsible for spin-polarized charge transport while overall magnetic moment of fullerene molecule is relatively small.     

Effect of NaCl on the properties of Eu-doped Ca-α-SiAlON phosphors prepared by combustion synthesis

Eu-doped Ca-α-SiAlON phosphors, featuring high phase purity, uniform particle size of 3–5 μm and good luminescent properties with a yellow emission spectrum under blue light excitation, were prepared by a highly efficient combustion synthesis (CS) method. A certain amount of NaCl was applied as an innovative additive to regulate and control the properties of synthesized phosphors. Further, the effects of NaCl additive in the CS system were systematically investigated and rational proposed. It was found that the effect on accelerating nitridation and crystallization played a dominant role in the reaction as the content of NaCl was less than 6 wt%, while the effect of absorbing reaction heat through vaporization was dominant with the further-increased content of NaCl. The intensity of the emission spectrum for the sample doped with 6 wt% of NaCl was remarkably enhanced, nearly 40% more than the sample which was not NaCl-doped. Moreover, a continuous blue-shift phenomenon in emission spectra was observed with the increased content of NaCl.     

Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

Improvement of n-type OTFT electrical stability by gold electrode modification

N-type organic thin film transistors (OTFT) containing modified gold electrodes have been fabricated to investigate the influence of the self assembled monolayer on the transistor characteristics. We report on the effect of drain/source modification by thiol derivatives on the performances, electrical parameters uniformity and electrical stability of C₆₀ transistors. In the literature, electrical instability is often attributed to organic semiconductor (OSC), OSC-insulator interface and insulator. We found here that OSC-metal interfaces affect dramatically the operational stability for bottom gate/bottom contact structure. These effects have been attributed to morphological evolution at the interface metal-OSC induced by the self-assembled monolayers.     

An efficient nonfullerene acceptor for all-small-molecule solar cells with versatile processability in environmentally benign solvents

A new structure of dicyanodistyrylbenzene-naphthalimide-based nonfullerene acceptor NIDCSN was synthesized and characterized to have a favorable electron accepting property and versatile processability in various organic solvents. The nonfullerene all-small-molecule solar cells comprising p-DTS(FBTTh₂)₂ as the donor and NIDCSN as the acceptor exhibited a maximum power conversion efficiency of 3.45% with a remarkable open-circuit voltage of 1.04 V, together with similar device performances when fabricated in five different solvents including environmentally benign non-halogenated ones.