Friedel–Crafts alkylation of 2-naphthols with enamides and enethers induced by catalytic amount of triarylaminium salt

A novel and efficient regioselective Friedel–Crafts alkylation reaction of 2-naphthols with electron-rich enamides or enethers initiated by catalytic amounts of stable radical cation triarylaminium salt has been developed. The processes occur under mild conditions.     

Synthesis and acetone gas sensing properties of α-Fe2O3 nanotubes

α-Fe₂O₃ nanotubes was successfully prepared by single nozzle electrospinning method. Scanning electron microscope (SEM) was used to characterize the morphology of α-Fe₂O₃ nanotubes. The gas sensing properties of α-Fe₂O₃ nanotubes were investigated in detail. The results exhibit relatively good sensing properties to acetone at 240 °C. The response and recovery times are about 3 and 5 s, respectively. The structure of nanotubes is beneficial to the gas sensing properties, which will enlarge the surface-to-volume ratio of α-Fe₂O₃ and then be available for the transfer of gas, and thus improved the sensor performance consequentially.     

Sol–gel synthesis of NiFe2O4 with PVA matrices and their catalytic activities for one-step hydroxylation of benzene into phenol

Nickel ferrite (NiFe₂O₄) was synthesized using citric acid (CA) as a chelating agent and varying amounts of polyvinyl alcohol (PVA) as powder binder via a combustion process. The influence of PVA/NiFe₂O₄ blend composition on the phase, crystal structure, and morphology has been investigated by X-ray diffraction (XRD), scanning electron microscopy, and Fourier transform infrared spectroscopy, respectively. The probable assignments of the thermal degradation products of PVA/NiFe₂O₄ were studied by complementary thermogravimetric analysis and differential thermal analysis. The PVA/NiFe₂O₄ crystals preferentially oriented along the (311) plane as revealed by XRD, owing to diffusion of α-Fe₂O₃ particles into the lattice matrix where the rate of diffusion increased significantly with the PVA concentration increase from 0.1 to 0.3 mol%. A vibrational doublet at 1,644 and 1,609 cm^?1 for the ≡Fe–O–COOH complex was emitted in the spectra of PVA-impregnated NiFe₂O₄ to assure the attachment of Fe(III) to the chelating agents CA/PVA. Thermal kinetic consideration based on Coats–Redfern and Horowitz–Metzger equations at subsequent decomposition steps of CA/PVA/NiFe₂O₄ illustrated that the values of activation free energy ΔG* increase significantly, indicating the non-spontaneous behavior. The one-step direct hydroxylation of benzene toward phenol has been extensively investigated using hydrogen peroxide as an oxidant.     

The effect of framework functionality on the catalytic activation of supported Pd nanoparticles in the Mizoroki–Heck coupling reaction

Palladium nanoparticles (Pd-NPs) were supported on functional and nonfunctional Co-coordination polymers (Pd/CoBDCNH₂ and Pd/CoBDC). Advanced analytical techniques revealed that Pd-NPs are supported on the external surface of the polymer framework and the functionalized framework possesses effective influence to prevent Pd-NP aggregation. Supported Pd-NPs were effectively applied as heterogeneous recyclable catalysts in the Mizoroki–Heck C–C cross coupling reactions of iodobenzene and either aromatic or aliphatic terminal alkenes. Catalytic results exhibited that highly dispersed Pd-NPs with low loading (1%) on the functional polymer (Pd/CoBDCNH₂) are more effective than aggregated Pd-NPs with high loading (9%) on the nonfunctional polymer (Pd/CoBDC). Both catalysts can simultaneously provide high activity and selectivity to E-coupled products, high efficiency in low amounts, easy separation of heterogeneous catalyst and appropriate performance in the recycling reaction without addition of a reducing agent.     

Electrical and interface state density properties of polyaniline–poly-3-methyl thiophene blend/p-Si Schottky barrier diode

We have formed conjugated polymeric aniline–thiophene organic material on p-Si substrate by adding polyaniline–poly-3-methyl thiophene blend solution in acetonitrile on top of a p-Si substrate and then evaporating the solvent. It has been seen that the forward bias current–voltage (I–V) characteristics of polyaniline–poly-3-methyl thiophene blend/p-Si/Al with a barrier height value of 0.60 eV and an ideality factor value of 3.37 showed rectifying behaviour at room temperature. The polyaniline–poly-3-methyl thiophene blend/p-Si/Al Schottky barrier diode showed non-ideal I–V behaviour with the value of ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. Furthermore, Cheung's functions and modified Norde's function were used to extract the diode parameters including ideality factor, barrier height and series resistance. It has been seen that there is a good agreement between the barrier height values from all methods. However, the values of series resistance obtained from Cheung's functions is higher than the values obtained from Norde's functions. The energy distribution of interface states density, determined from forward bias current–voltage (I–V) characteristic technique at room temperature, increases exponentially with bias from 2.81 × 10¹⁶ cm^?2 eV^?1 in (0.73–E_v) eV to 1.14 × 10¹⁷ cm^?2 eV^?1 in (0.48–E_v) eV.     

MoS2 nanorods with inner caves through synchronous encapsulation of sulfur for high performance Li–S cathodes

Lithium–sulfur(Li–S)batteries have become one of the most promising candidates for next-generation batteries owing to their high specific capacity,low cost,and environment-friendliness.Many efforts have been made to mitigate the"shuttle effect"through physical adsorption and chemical bonding.MoS2 has been proposed as a cathode material to provide effective anchoring sites for lithium polysulfides(Li PSs),but is still limited by its layer structure.Herein,we designed novel MoS2 nanorods with inner caves based on our previous work,and performed synchronous encapsulation of sulfur during the synthesis process.The outer MoS2 tubular shells physically inhibit the outward diffusion of polysulfide species while the inner particles chemically anchor the polysulfides to prevent shuttling.As the cathode matrix in Li–S batteries,the electrochemical results deliver a high initial discharge capacity of 1213 mAhg^-1 for sulfur at 0.1 C.After cycling at 1 C for 300 cycles,the cells exhibit a capacity decay of only 0.076%per cycle and high average coulombic efficiency over 95%.The tubular MoS2 structure is an innovative and appealing design,which could be regarded as a prospective substrate for the improved performance of Li–S batteries.     

Sol–gel synthesized high anisotropy magnetic nanoparticles of NiCr x Fe2−x O4

The nanoparticles of NiCr _x Fe_2?x O₄ were synthesized through sol–gel reactions involving nitrates of Ni, Cr and Fe in an aqueous medium containing citric acid. The cubic spinel structure in single phase with nanometric crystallite size of ~5 nm, the spherical morphology and magnetic relaxations were examined through XRD, TEM and Mössbauer techniques. The abnormal occurrence of finite remanance (M _r ) and coercivity (H _c ) resulted in the room temperature dc magnetization measurements for the small particles authenticate the ferrimagnetic regime, as proposed by the room temperature Mössbauer results of the samples, with a proximate superparamagnetic regime still at lower particle volumes. This could be attributed to the antiferromagnetic spin interactions of chromium ions at octahedral sites and subsequently the over-occupancy of the rest of the cations at tetrahedral sites. In justification to this, the magnetocrystalline anisotropy constant, K, is estimated to have value relatively high of the order of 10⁷ erg/cm³ at room temperature for all studied concentrations.     

Fabrication and characterization of calix[4]arene Langmuir–Blodgett thin film for gas sensing applications

Microwave irradiation has been found to be a highly efficient method for etherification of p-tert-butylcalix[4]arene with alkyl bromides or ditosylate. The corresponding products were obtained as a pure form in modest yield within short reaction time when the reactions were performed under microwave irradiation.     

Physical–chemical and catalytic properties of deposited MoO3 and V2O5

The deposition of molybdenum and vanadium oxides onto fumed silica, titania, and alumina as supports through dry milling has been carried out. The structure of prepared compositions has been investigated by means of XRD, DTA?CTG, FTIR, and UV?CVis spectroscopy, nitrogen adsorption. The deposited crystal phases are sufficiently uniformly distributed on support surface. The supported oxides are subjected to dispersion in process of milling to the state of oligomeric or isolated species. Milled bulk and deposited MoO₃ (first of all, on alumina) possesses improved catalytic performance in process of epoxidation of 1-octene. Vanadium pentoxide also has higher activity in this process.     

Synthesis,characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt,Pt–Rh,Pt–SnO2 and Pt–Rh–SnO2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO₂ and Pt–Rh–SnO₂ were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO₂/C catalyst: solid solution of Rh in Pt and SnO₂. The activity of Pt–Rh–SnO₂/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO₂/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H₂SO₄ concentrations (0.02–0.5 M) showed that Pt–Rh–SnO₂/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.     

Pt||ZrO2 nanoelectrode array synthesized through the sol–gel process: evaluation of their sensing capability

Homogeneous, circular Pt||ZrO₂ nanoelectrodes have been synthesized through the sol–gel chemistry and the dip-coating process. These nanoelectrode arrays have been evaluated as a platform for electropolymerization of phenol, as model. We have shown that the microstructure of the polymer depends on the confined environment of the electrode and on the position of the –OH group of the monomer. Additionally, these nanoelectrodes have been tested as an electrochemical sensor for dihydroxybenzene isomers in aqueous medium. These Pt||ZrO ₂ nanoelectrodes exhibit a detection limit of 2?×?10^?7?M for resorcinol and 1?×?10^?6?M for catechol.     

Asymmetric synthesis of planar-chiral paracyclophanes by double C–S bond formation: comparison of catalytic activity and enantioselectivity of Pd and Rh catalysts

We have determined that a cationic palladium(II)/(R)-BINAP complex is able to catalyze enantioselective double C–S bond-forming reactions between dithiols and dibenzyl dibromides leading to planar-chiral dithiaparacyclophanes. Although the yields and ee values of the palladium(II)-catalyzed syntheses of dithiaparacyclophanes did not exceed our previously reported cationic rhodium(I)/(S)-BINAPHANE complex-catalyzed ones, the palladium(II)-catalyzed reactions allowed the use of commercially available and inexpensive (R)-BINAP as a ligand. On the other hand, an almost racemic product was obtained by using a cationic rhodium(I)/(R)-BINAP complex as a catalyst.     

Conductivity and Morphology of Composite Solid Electrolytes SnO2· nH2O–Heteropolycompounds

The structure and surface characteristics of SnO₂ · 1.5H₂O and composite materials with heteropolycompounds (HPC) formulated as SnO₂ · 1.5H₂O–HPC (where HPC = (NH₄)₃PW₁₂O₄₀ · nH₂O, (NH₄)₂HPW₁₂O₄₀ · nH₂O, and H₃PW₁₂O₄₀ · nH₂O) are studied by scanning tunneling microscopy. Hydrated tin oxide is characterized by a globular structure which differs substantially from the morphology of composite materials. The conductivity is studied as a function of both the temperature and humidity of environment and the composition of composite materials. For composite materials containing ((NH₄)₂HPW₁₂O₄₀ · nH₂O, the conductivity is shown to vary monotonously with the composition and obey the mixture rule. Introduction of (NH₄)₃PW₁₂O₄₀ · nH₂O to a composite is found to cause an extremely fast conductivity decay, whereas addition of H₃PW₁₂O₄₀ · nH₂O results in the appearance of a plateau on the conductivity vs. composition curve. The explanation given to the phenomena observed is based on the mechanism of protonic transport in heteropolycompounds.     

Pore structure and acid properties of high-silica zeolites synthesized with different templates and their catalytic performance in conversion of the propane–butane fraction

The effect of the template on the physicochemical properties of zeolitic catalysts and on the yield and selectivity of formation of aromatic hydrocarbons in conversion of the propane–butane fraction was examined. The zeolitic catalyst sample synthesized with an alcohol fraction as template is characterized by the highest values of the acid site concentration, adsorption capacity, micropore volume, and specific surface area. Therefore, this catalyst ensures the highest, compared to the other samples, conversion of the propane–butane fraction and yield of aromatic hydrocarbons.     

Cooperative effect of Fe and Ti species over Fe–Ti–Ox catalysts on the catalytic hydrolysis performance of hydrogen cyanide

FeO_x, TiO₂, and Fe–Ti–O_x catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–O_x catalyst. TiO₂ rutile was detected over TiO₂, but not over Fe–Ti–O_x, which suggested that the interaction between Fe and Ti species could inhibit the TiO₂ phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–O_x could promote the selectivity of NH₃ and CO. The mechanism of hydrolysis of HCN over FeO_x, TiO₂, and Fe–Ti–O_x can be given as follows: HCN + H₂O → methanamide → ammonium formate → formic acid → H₂O + CO.     

Solid-State Synthesis of SnO2–Zn2SnO4 Nanocomposite and Its Application for Electrochemical Detection of Cabergoline as Dopamine Receptor Antagonists

Russian Journal of Electrochemistry - In the present work, the synthesis of SnO2–Zn2SnO4 nanocomposite was fulfilled according to solid-state technique followed by calcination. The...     

Structure and properties of glasses in the system Li2O–SnO–B2O3

Glasses in the system Li₂O–SnO–B₂O₃ system were prepared by a melt-quenching method. Thermal and viscous properties and local structure of these glasses were investigated. The SnO–B₂O₃ glasses exhibited relatively low glass-transition temperatures (T_g) around 350 °C and excellent thermal stability against crystallization. Viscosity measurements in the vicinity of T_g indicated that the glasses were considerably fragile compared to alkali borate glasses. Fraction of four-coordinated boron was maximized at the composition with 50 mol% SnO and that of nonbridging oxygen, which is not purely ionic in alkali borate systems but partially covalent, augmented with an increase in the SnO content. Correlation between glass properties and structure was discussed in the SnO–B₂O₃ binary system.     

Synthesis and Activity of Nanodispersed SnO2–CeO2 Catalyst in the Oxidation Reactions of Carbon Monoxide and Methane

Kinetics and Catalysis - Nanodispersed SnO2–CeO2 catalysts for the oxidation of CO and СН4 were synthesized by coprecipitation in a water–isopropanol solution followed by...