Negative differential resistance and memory effect in diodes based on 1,4-dibenzyl C60 and zinc phthalocyanine doped polystyrene hybrid material

Negative differential resistance (NDR) and memory effect were observed in diodes based on 1,4-dibenzyl C60 (DBC) and zinc phthalocyanine doped polystyrene hybrid material. Certain negative starting sweeping voltages led to a reproducible NDR, making the hybrid material a promising candidate in memory devices. It was found that the introduction of DBC enhanced the ON/OFF current ratio and significantly improved the memory stability. The ON/OFF current ratio was up to 2 orders of magnitude. The write-read-erase-reread cycles were more than 10(6), and the retention time reached 10 000 s without current degradation.

Preparation and electrical-magnetic properties of polyaniline doped with ionic ferrocenesulfonic acid

Conducting polyamline with electrical conductivity of 2.34 x 10(-1) S cm(-1) was obtained using ferrocenesulfonic acid as dopant. After the ferrocenesulfonic acid was oxidized with FeCl3, though the electrical conductivity of the doped polyaniline decreased by 1-2 orders of magnitude, the magnetic susceptibility (chi) increased with the increase of the oxidation degree of ferrocenesulfonic acid. EPR spectra showed not only a signal with a g value of around 2, but also a so-called half-field signal with a g value of about 4 even at room temperature. Coexistence of ferromagnetic intrachain interactions and antiferromagnetic interchain interactions in the materials has been suggested.

Electrochemical and bioelectrochemistry properties of room-temperature ionic liquids and carbon composite materials

Room-temperature ionic liquids (RTILs) are liquids at room temperature and represent a new class of nonaqueous but polar solvents with high ionic conductivity. The conductivity property of carbon nanotubes/RTILs and carbon microbeads/RTILs composite materials has been studied using ac impedance technology. Enzyme coated by RTILs-modified gold and glassy carbon electrodes allow efficient electron transfer between the electrode and the protein and also catalyze the reduction Of O-2 and H2O2,

A single ionic conductor based on Nafion and its electrochemical properties used as lithium polymer electrolyte

In an attempt to raise the transport number of Li+ to nearly unity in solid polymer electrolytes, commercial perfluorinated sulfonate acid membrane Nafion 117 was lithiated and codissolved with copolymer poly(vinylidene fluoride)hexafluoropropylene. The effect of fumed silica on the physical and electrochemical properties of the single ion conduction polymer electrolyte was studied with atom force microscopy, fourier transform infrared spectroscopy, differential scanning calorimetry, and electrochemical impedance spectroscopy. It was confirmed that the fumed silica has an obvious effect on the morphology of polymer electrolyte membranes and ionic conductivity. The resulting materials exhibit good film formation, solvent-maintaining capability, and dimensional stability. The lithium polymer electrolyte after gelling with a plasticizer shows a high ionic conductivity of 3.18 x 10(-4) S/cm.

An ionic liquid based on a cyclic guanidinium cation is an efficient medium for the selective oxidation of benzyl alcohols

A novel room temperature ionic liquid (RTIL) has been prepared containing a cyclic hexaalkylguanidinium cation. The selective oxidation of a series of substituted benzyl alcohols has been carried out in it, with sodium hypochlorite as the oxidant. The RTIL acts as both phase transfer catalyst (PTC) and solvent. The ionic liquid could be recycled after extraction of the benzaldehyde product with ether.

Ionic liquid solvent based on cyclic guanidinium cation for nucleophilic displacement reactions

The nucleophilic displacement reaction of n-bromooctane and potassium iodide in ionic liquid based on cyclic guanidinium cation(2) was investigated. The kinetic reasult shows that the rate of the reaction is enhanced in ionic liquid (2). The same reaction in [bmim][PF6](1)(where bmim = 1-butyl-3-methylimidazolium) was also studied. It was found that as a reaction medium ionic liquid (2) is better than (1) for nucelophilic displacement reactions.

A room-temperature ionic-liquid-templated proton-conducting gelatinous electrolyte

Novel proton-conducting gelatinous electrolytes templated by room-temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium-tetrafluoroborate (BMImBF(4)) have been prepared in methylsisesquioxane backbone containing H3PO4, and the influences of the RTIL on the structure, morphology, thermal stability, and electrochemical properties of the gelatinous electrolytes have been examined. X-ray diffraction and scanning electron microscopy proved that BMImBF(4) acted as structure-directing template during the sol-gel process of methyl-trimethoxysilane. X-ray photoelectron spectra and infrared spectroscopy demonstrated that the hydrogen-bonding was formed between BMImBF(4) and H3PO4. The electrolytes had good thermal stability up to 300 degreesC and showed superior mechanical and electrochemical properties. A room-temperature conductivity of 1.2 x 10(-3) S cm(-1) was obtained for the electrolyte at the molar ratio of RTIL/Si/H3PO4 0.3/1/1, and its electrochemical window was up to 1.5 V.

Electrochemical deposition of silver in room-temperature ionic liquids and its surface-enhanced Raman scattering effect

The use of room-temperature ionic liquids (RTILs) as media for electrochemical application is very attractive. In this work, the electrochemical deposition of silver was investigated at a glassy carbon electrode in hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) RTILs and in KNO3 aqueous solution by cyclic voltammetric and potentiostatic transient techniques. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of silver from AgBF4 in both BMIMPF6 and BMIMBF4, resembling the redox behavior of AgNO3 in KNO3 aqueous solution. A crossover loop was observed in all the cyclic voltammograms of these electrochemical systems, indicating a nucleation process. From the analysis of the experimental current transients, it was shown that the electrochemical deposition process of silver in these media was characteristic of 3D nucleation with diffusion-controlled hemispherical growth, and the silver nucleation closely followed the response predicted for progressive nucleation in BMIMPF6 and instantaneous nucleation in KNO3 aqueous solution, respectively.

Bronsted guanidine acid-base ionic liquids: Novel reaction media for the palladium-catalyzed Heck reaction

Bronsted acid-base ionic liquids (GILs) based on guanidine and acetic acid are efficient reaction media for palladium-catalyzed Heck reactions. They offer the advantages of high activity and reusability. GIL2 plays multiple roles in the reaction: it could act as solvent, as a strong base to facilitate beta-hydride elimination, and as a ligand to stabilize activated Pd species.

Negative differential resistance effect in organic devices based on an anthracene derivative

The authors observed a negative differential resistance (NDR) in organic devices consisting of 9,10-bis-(9,9-diphenyl-9H-fluoren-2-yl)-anthracene (DPFA) sandwiched between Ag and indium tin oxide electrodes. The large NDR shown in current-voltage characteristics is reproducible, resulting in that the organic devices can be electrically switched between a high conductance state (on state) and a low conductance state (off state). It can be found that the currents at both on to off states are space-charge limited and attributed to the electron traps at the Ag/DPFA interface. The large and reproducible NDR makes the devices of tremendous potential in low power memory and logic circuits.

The use of CE-electrochemiluminescence with ionic liquid for the determination of bioactive constituents in Chinese traditional medicine

CE/tris(2,2-bipyridyl) ruthenium(ll) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL), CEECL, with an ionic liquid (IL) detection system was established for the determination of bioactive constituents in Chinese traditional medicine opium poppy which contain large amounts of coexistent substances. A minimal sample pretreatment which involves a one-step extraction approach avoids both sample loss and environmental pollution. As the nearby hydroxyl groups in some alkaloid such as morphine may react with borate to form complexes and IL, as a high-conductivity additive in running buffer, could cause an enhanced field-amplified effect of electrokinetic injection. Running buffer containing 25 mM borax-8 mM 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) IL (pH 9.18) was used which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Sensitive detection could be achieved when the distance between the Pt working electrode and the outlet of separation capillary was set at 150 mu m and the stainless steel cannula was fixed approximately 1 cm away from the outlet of the capillary. Quantitative analysis of four alkaloids was achieved at a detection voltage of 1.2 V and a separation voltage of 15 kV in less than 7 min.