An easy access to nanocrystalline alkaline earth metal fluorides – just by shaking

High energy ball milling as fast, direct and solvent free method allows an easy access to nanocrystalline alkaline earth metal fluorides MF₂ (M: Mg, Ca, Sr, Ba). Comparable metal sources (acetates, carbonates, hydroxides, alkoxides) were used for the reaction with NH₄F as fluorinating agent. Even very simple manual shaking experiments between NH₄F and the corresponding hydroxides in the stoichiometric ratio (M:F = 1:2, M: Ca, Sr, Ba) give phase pure fluorides. Moreover, comparable classical thermal reactions in closed crucibles at higher temperatures provide phase pure crystalline fluorides in nearly all cases as well.     

A novel multicomponent approach to the synthesis of 1,3-thiazolidine-2-thiones

An easy, efficient, and simple one-pot approach for the synthesis of 1,3-thiazolidine-2-thiones via multicomponent reaction is reported. The reaction of a primary amine with carbon disulfide in the presence of dibenzoylacetylene or bis(4-methyl-1-benzoyl)acetylene in a mixture of CH₂Cl₂ and H₂O after 5 h, afforded the title compound as alkene diastereomers.     

Theoretical investigation of the formic acid decomposition kinetics

Decomposition of formic acid (HCO₂H) proceeds via three unimolecular channels: dehydration, decarboxylation, and dissociation, the latter expected to be of minor contribution to the overall kinetics. In addition, despite the similar values reported for the individual activation energies for the dehydration and decarboxylation reactions, experimental works have shown that the former is dominant in the reaction mechanism. These reactions show pressure-dependent rate coefficients, and the high-pressure condition is not yet verified at atmospheric pressure. This work aims to investigate the influence of temperature and pressure on the rate coefficients. Hence, theoretical calculations at the CCSD(T)/CBS level have been performed to accurately describe the unimolecular reaction and Rice-Ramsperger-Kassel-Marcus (RRKM) rate coefficients have been calculated and integrated for the prediction of k(T,P) rate coefficients, adopting both strong and weak collision models, over the intervals 0.5-10 atm and 298-2200 K. Our results suggest that the isomerization path is important and explains the preference for the (CO + H₂O) channel. Rate coefficients for the (CO₂ + H₂) and (CO + H₂O) formations are given, in s⁻¹, as exp(−34404/T) and exp(−33785/T), respectively. The dissociation limit of 107.29 kcal mol^–1, with respect the Z-HCO₂H conformer, leading to OH + HCO, via a barrierless potential curve, with rate coefficients, in s⁻¹, expressed as k_HCO+OH(T) = 1.68 × 10¹⁷ exp(−56018/T). Temperature and pressure dependence for the HCO + OH → CO₂ + H₂ and HCO + OH → CO + H₂O reactions have also been estimated.     

A new solution route for the synthesis of silicon nanoparticles presenting different surface substituents

This paper describes a new solution route for the preparation of silicon nanoparticles functionalized at the surface using potassium incorporated in graphite (C₈K) as reducing agent of silicon tetrachloride (SiCl₄). In a first step, chloride,capped silicon nanoparticles were obtained. They allowed an easy access, in a second step, to a range of surface functionalities by simple nucleophilic substitutions: hydroxy, alkyl, alkoxy or amino groups. They were characterized by FTIR, ¹H, ¹³C and ²⁹Si NMR. A mean diameter of 13 nm was found for these particles.     

Highly active PtRuFe/C catalyst for methanol electro-oxidation

High methanol electro-oxidation activity was obtained on novel PtRuFe/C (2:1:1 at.%) catalyst. Mass and specific activities were 5.67 A  g⁻¹ catal. and 177 mA m⁻² for the PtRuFe/C catalyst while those of the commercial PtRu/C catalyst were 2.28 A g⁻¹ catal. and 87.7 mA m⁻², respectively. CO stripping results showed that on-set voltage for CO electro-oxidation was lowered by incorporation of Fe. XRD and XPS results revealed that Fe₂O₃ was formed instead of Fe(0), which resulted in large electron deficiency in Pt and easy CO electro-oxidation. The electron deficiency of Pt was proved by XPS results of Pt4f peaks, which moved to higher binding energies in PtRuFe/C than PtRu/C.     

LiTFSI as a plastic salt in the quasi-solid state polymer electrolyte for dye-sensitized solar cells

Ionic conductivity and the type of ions are important for the composite polymer electrolyte (CPE) of the dye-sensitized solar cells (DSSCs). Lithium bis(trifluoromethane sulphone)imide (LiTFSI for short) which is easy to dissociate, is added in the composite polymer electrolyte(CPE) as a plasticizer. The LiTFSI acts differently from the conventional LiClO₄. LiTFSI changes the conformation of the polymer chain and shows higher ionic conductivity than LiClO₄. That contributes to the improvement of the short current density of the DSSC. Furthermore, the DSSCs with LiTFSI modification show higher photovoltage than the LiClO₄. The anions of TFSI^? prohibit the interface recombination more effectively compared with the LiClO₄ as the electrochemical impedance spectroscopy indicated. With the LiTFSI modified electrolyte, the performances of the DSSCs under 1 Sun, AM1.5 are improved and reaches the highest of 4.82% at the LiTFSI:LiI = 0.116:1, much better than the original DSSC(3.6%) and the LiClO₄ modified CPE electrolyte DSSC(4.32%).     

Effect of fluorinated/non‐fluorinated β‐diketones and side‐chain branching of N‐protected amino acids on the antibacterial potential of new heptacoordinated monobutyltin(IV) complexes

The effect of fluorinated/non‐fluorinated β‐diketones and side‐chain branching of N‐protected amino acids on the antibacterial potential of new heptacoordinated monobutyltin(IV) complexes was investigated. New heptacoordinated monobutyltin(IV) complexes having the general formulae BuSn(A)₂B and BuSnA(B)₂ [where AH = (1,3‐dihydro‐1,3‐dioxo‐α‐(substituted)‐2H ‐isoindole‐2‐acetic acids, N‐protected amino acids), R =  CH(CH₃)CH₂CH₃: A₁H; R =  CH(CH₃)₂: A₂H; and BH = R'COCH₂COR″ (β‐diketones), R′ = R″ =  CH₃: B₁H; R′ =  CH₃, R″ =  C₆H₅: B₂H; R′ =  CF₃, R″ =  C₆H₅: B₃H] were synthesized. Complexes BuSn(A)₂B and BuSnA(B)₂ were generated by the reaction of sodium salts of the ligands AH and BH with BuSnCl₃ in 2:1:1 and 1:2:1 molar ratios, respectively. These newly generated complexes were characterized in physicochemical and spectroscopic studies. These complexes contain heptacoordinated tin centres as revealed by ¹¹⁹Sn NMR chemical shift values. Some of the newly generated complexes and their corresponding ligands were screened for their antibacterial activity to study the structure–activity relationship.     

EPR spectroscopy of multicomponent,multispin molecular system obtained by the photolysis of 2,4,6-triazido-3-cyano-5-fluoropyridine in solid argon

Complex multicomponent, multispin molecular system, consisting of a septet trinitrene, two quintet dinitrenes, and three triplet mononitrenes, was obtained by the photolysis of 2,4,6-triazido-3-cyano-5-fluoropyridine in solid argon. To identify these paramagnetic products, electron paramagnetic resonance spectroscopy in combination with line-shape spectral simulations and density functional theory calculations was used. The products of the photolysis was found to be triplet 2,4-diazido-3-cyano-5-fluoropyridyl-6-nitrene (D_T = 1.000 cm⁻¹, E_T = 0), triplet 2,4-diazido-3-cyano-5-fluoropyridyl-2-nitrene (D_T = 1.043 cm⁻¹, E_T = 0), triplet 2,6-diazido-3-cyano-5-fluoropyridyl-4-nitrene (D_T = 1.128 cm⁻¹, E_T = 0 cm⁻¹), quintet 4-azido-3-cyano-5-fluoropyridyl-2,6-dinitrene (D_Q = 0.211 cm⁻¹, E_Q = 0.0532 cm⁻¹), quintet 2-azido-3-cyano-5-fluoropyridyl-4,6-dinitrene (D_Q = 0.208 cm⁻¹, E_Q = 0.0386 cm⁻¹), and septet 3-cyano-5-fluoropyridyl-2,4,6-trinitrene (D_S = −0.1017 cm⁻¹, E_S = −0.0042 cm⁻¹) in a 38:4:7:22:14:4 ratio, respectively.     

Rate constants of the reactions of O(3P) atoms with Br2 and NO2 over the temperature range 220-950 K

The kinetics of the reactions of Br₂ and NO₂ with ground state oxygen atoms have been studied over a wide temperature range, T = 220-950 K, using a low-pressure flow tube reactor coupled with a quadrupole mass spectrometer: O + NO₂ → NO + O₂ (1) and O + Br₂ → Br + BrO (2). The rate constant of reaction (1) was determined under pseudo–first-order conditions, either monitoring the kinetics of O-atom or NO₂ consumption in excess of NO₂ or of the oxygen atoms, respectively: k₁ = (6.1 ± 0.4) × 10⁻¹² exp((155 ± 18)/T) cm³ molecule⁻¹ s⁻¹ (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k₁ being 15% at all temperatures). The temperature dependence of k₁, found to be in excellent agreement with multiple previous low-temperature data, was extended to 950 K. The rate constant of reaction (2) determined under pseudo–first-order conditions, monitoring the kinetics of Br₂ consumption in excess of O-atoms, showed upward curvature at low and high temperatures of the study and was fitted with the following three-parameter expression: k₂ = 9.85 × 10⁻¹⁶ T^1.41 exp(543/T) cm³ molecule⁻¹ s⁻¹ at T = (220-950) K, which is recommended from the present study with an independent of temperature conservative uncertainty of 15% on k₂.     

Application of chloroaluminate ionic liquid as catalyst and medium for the dealkylation of esters

Abstract  

Dealkylation of esters to carboxylic acids was performed using chloroaluminate ionic liquids (PyHBr/AlCl₃, PyHCl/AlCl₃, Me₃NHCl/AlCl₃, Et₃NHCl/AlCl₃) as catalyst and medium. The catalytic activity of PyHBr/AlCl₃ (X(AlCl₃) = 0.67) proved to be superior to the other three ionic liquids for the dealkylation of methyl benzoate with a conversion of 97% after 3 h at 140 °C. After easy separation from the products the ionic liquid PyHBr/AlCl₃ could be reused six times without loss of its activity.     

Phase behaviour of binary and ternary mixtures for the poly(methyl methacrylate-co-hexafluorobutyl methacrylate) [P(MMA-co-HFBMA)] in supercritical fluorine solvents

In this study, the poly(methyl methacrylate-co-2,2,3,4,4,4-hexafluorobutyl methacrylate) [P(MMA-co-HFBMA)] as a fluoric copolymer was prepared using dispersion polymerization in supercritical carbon dioxide. The characterization for the prepared P(MMA-co-HFBMA) was investigated with varied ratios of MMA vs HFBMA (30:1, 25:1, 22:1 and 20:1), 2,2′-azobisisobutyronitrile (AIBN) amounts (1.0, 2.0, 3.0, and 4.0) wt% and the weight average molar mass (M_w).Experimental cloud-point data at temperatures to 454 K and pressures up to 184 MPa are reported for binary and ternary mixtures of P(MMA-co-HFBMA) in supercritical CH₂F₂, CHF₃ and CHClF₂. Experiments are performed in order to determine phase behaviour of binary system for the P(MMA-co-HFBMA) (mole ratio: 25:1, AIBN: (1.0, 2.0, 3.0 and 4.0) wt%) + supercritical solvents (CH₂F₂, CHF₃ and CHClF₂) mixtures at temperature range from (333 to 454) K and pressure up to 184 MPa. It appears that the {P(MMA-co-HFBMA) + CH₂F₂} mixtures show the upper critical solution temperature (UCST) type behaviour with negative slope, while the {P(MMA-co-HFBMA) + CHF₃} and {P(MMA-co-HFBMA) + CHClF₂} mixtures show lower critical solution temperature (LCST) type curve with positive slope. Cloud-point curves for the P(MMA-co-HFBMA) [mole ratio: 30:1 (M_w = 186,000 g · mol⁻¹), 25:1 (M_w = 176,000 g · mol⁻¹), 22:1 (M_w = 158,000 g · mol⁻¹) and 20:1 (M_w = 126,000 g · mol⁻¹); AIBN: 1.0 wt%) + supercritical (CH₂F₂, CHF₃ and CHClF₂) mixtures show a negative slope for the {P(MMA-co-HFBMA) + CH₂F₂}, and a positive slope for the {P(MMA-co-HFBMA) + CHF₃} and {P(MMA-co-HFBMA) + CHClF₂} mixtures at temperatures to 454 K and pressure up to 184 MPa. Also, the impact of MMA on phase behaviour for the {P(MMA-co-HFBMA) (mole ratio: 25:1; AIBN: (1.0 and 2.0) wt%) + CH₂F₂} mixtures are measured in changes of the (pressure + temperature) slope from UCST behaviour to LCST behaviour, and with MMA co-solvent concentrations of (0.0 to 40.1) wt%.     

An FT-IR study of the isomerization of 1-butoxy radicals under atmospheric conditions

Relative rate-studies of the reactions of 1-butoxy radicals have been carried out using a 47 L static reactor with detection of end products by FT-IR spectroscopy. Experiments were performed at 700 torr total pressure and over the temperature range 253–295 K. The chemistry of 1-butoxy is characterized by a competition between reaction with oxygen CH₃CH₂CH₂CH₂O + O₂ → n-C₃H₇CHO + HO₂ (R2), which yields butanal and isomerization CH₃CH₂CH₂CH₂O → CH₂CH₂CH₂CH₂OH (R3), to form a hydroxylated carbonyl-product. A reference spectrum attributed to the product of 1-butoxy isomerization was obtained and used to determine the competition between 1-butoxy isomerization versus reaction with oxygen. The results indicate that isomerization is the dominant fate of 1-butoxy radicals at ambient temperature and pressure and that its importance decreases with decreasing temperature. The rate-coefficient ratio k₃/k₂ (molecule cm⁻³) = 5.5 × 10²³ exp[(−25.1 ± 0.9 kJmol⁻¹)/RT] was obtained. This agrees with other estimates based on methods without monitoring of the isomerization product.     

Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

With MnSO₄, NaOH and K₂S₂O₈ as the raw materials, the amorphous and δ-type manganese dioxide (MnO₂) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge–discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO₂ reaches to 301.2 F g⁻¹ at a current density of 200 mA g⁻¹ and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g⁻¹ and 71% of the δ-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO₂ should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi₂O₃ is coated on the amorphous MnO₂, its specific capacitance increases to 352.8 F g⁻¹ and the capacitance retention rate is 90% after 2000 cycles.     

A study of some kinetic aspects of the CCl4 interaction with oxide ions in KCl-SrCl2 melts with different content of SrCl2

A comparative investigation of a complex process of the interaction between CCl₄ vapor and oxide ions O^2– (carbochlorination) in K₂SrCl₄ and KSr₂Cl₅ melts at 973 K was performed by the potentiometric method using Pt(O₂)|ZrO₂(Y₂O₃) membrane oxygen electrode as reversible to oxide ion. The analysis of the limiting stages of this process was made on the basis of van't Hoff diagrams. The entire process can be divided into three stages with corresponding limiting processes: the rate of CCl₄ dissolution in the melts for stage 1, the chemical reaction in the melts for stage 2, and the rate of the contamination of the melts with oxygen-containing admixtures for the stage 3. The rate constants of the carbochlorination process in both melts at 973 K were calculated using the data corresponding to stage 2 as (4.4 ± 0.25) × 10⁵ kg mol⁻¹ min⁻¹ for K₂SrCl₄ and (1.83 ± 0.5) × 10⁵ kg mol⁻¹ min⁻¹ for KSr₂Cl₅. The final concentration of oxide ions after the treatment is higher ( = (1.6 ± 0.7) × 10⁻⁷ mol kg⁻¹ for KSr₂Cl₅ and  = (2.5 ± 1.3) × 10⁻⁸ mol kg⁻¹ for K₂SrCl₄ melt, respectively). This corresponds to the difference in the oxoacidic properties of the studied melts.     

Influence of polycrystalline MoS2 nanoflowers on mouse breast cancer cell proliferation via molten salt sintering

In this paper, polycrystalline molybdenum disulfide (MoS₂) nanoflowers were prepared by mixing ammonium molybdate tetrahydrate [(NH₄)₆Mo₇O₂₄·4H₂O] and potassium thiocyanate (KSCN) at 300 °C for 2 h via molten salt sintering method. Under scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), MoS₂ showed popcorn-like shape, which surface distribution defects were easy to be further modified. MoS₂ as a nano-enzyme was used to inhibit the proliferation of mouse breast cancer cells (4 T1), which had 69.8 % inhibitory effect on 4 T1 cell proliferation. Electron spin resonance (ESR) analysis showed that MoS₂ could produce a large number of stable hydroxyl radicals (–OH). The disulfide bond in MoS₂ was highly sensitive to reactive oxygen species (ROS). High ROS level leads to the death of cancer cells under oxidative stress and inhibits the proliferation of 4 T1. This work demonstrates that MoS₂ is a potential anticancer drug or carrier for cancer treatment.     

FeNH4(SO4)2·12H2O (alum)-catalyzed preparation of 1,4-dihydropyridines: improved conditions for the Hantzsch reaction

Abstract  

FeNH₄(SO₄)₂·12H₂O (alum) efficiently catalyzes the one-pot three-component reaction of dimedone, aldehydes, and 3-aminocrotonate to afford 1,4-dihydropyridines. The work-up is easy, and the products are obtained in good to excellent yields and high purity.     

Experimental determination of the rate constants of the reactions of HO2 + DO2 and DO2 + DO2

The rate constants of the reactions of DO₂ + HO₂ (R1) and DO₂ + DO₂ (R2) have been determined by the simultaneous, selective, and quantitative measurement of HO₂ and DO₂ by continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near infrared, coupled to a radical generation by laser photolysis. HO₂ was generated by photolyzing Cl₂ in the presence of CH₃OH and O₂. Low concentrations of DO₂ were generated simultaneously by adding low concentrations of D₂O to the reaction mixture, leading through isotopic exchange on tubing and reactor walls to formation of low concentrations of CH₃OD and thus formation of DO₂. Excess DO₂ was generated by photolyzing Cl₂ in the presence of CD₃OD and O₂, small concentrations of HO₂ were always generated simultaneously by isotopic exchange between CD₃OD and residual H₂O. The rate constant k₁ at 295 K was found to be pressure independent in the range 25–200 Torr helium, but increased with increasing D₂O concentration k₁ = (1.67 ± 0.03) × 10⁻¹² × (1 + (8.2 ± 1.6) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The rate constant for the DO₂ self-reaction k₂ has been measured under excess DO₂ concentration, and the DO₂ concentration has been determined by fitting the HO₂ decays, now governed by their reaction with DO₂, to the rate constant k₁. A rate constant with insignificant pressure dependence was found: k₂ = (4.1 ± 0.6) × 10⁻¹³ (1 + (2 ± 2) × 10⁻²⁰ cm³ × [He] cm⁻³) cm³ s⁻¹ as well as an increase of k₂ with increasing D₂O concentration was observed: k₂ = (4.14 ± 0.02) × 10⁻¹³ × (1 + (6.5 ± 1.3) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The result for k₂ is in excellent agreement with literature values, whereas this is the first determination of k₁.     

Formation of phenanthrene via H-assisted isomerization of 2-ethynylbiphenyl produced in the reaction of phenyl with phenylacetylene

Model chemistry G3(MP2,CC)//B3LYP/6-311G(d,p) calculations of the potential energy surface for the reaction of phenyl radical (C₆H₅) with phenylacetylene (C₈H₆) have been carried out and combined with Rice-Ramsperger-Kassel-Marcus/Master Equation calculations of temperature- and pressure-dependent rate constants. The results showed that the reaction can serve as a viable source for the formation of phenanthrene via an indirect route involving a primary reaction of phenyl addition to the ortho carbon in the ring of phenylacetylene and H elimination producing 2-ethynylbiphenyl followed by secondary H-assisted isomerization of 2-ethynylbiphenyl to phenanthrene. In the secondary reaction, the H atom adds to the α carbon of the ethynyl side chain, then a six-member ring closure takes place followed by aromatization via an H loss. The channel of H addition to the side chain of 2-ethynylbiphenyl appears to be much faster than H addition to the ortho carbon in the ethynyl-substituted ring leading back to the initial C₆H₅ + C₈H₆ reactants. Rate constants for the primary C₆H₅ + C₈H₆2-ethynylbiphenyl ( p1 ) + H and secondary p1  + Hphenanthrene ( p2 ) + H reactions have been computed in the temperature range of 500-2500 K at pressures of 30 Torr, 1, 10, and 100 atm and fitted to modified Arrhenius expressions. The suggested kinetic scheme and rate constants are proposed as a prototype for the modeling of the growth of polycyclic aromatic hydrocarbons via the phenyl addition-dehydrocyclization (PAC) mechanism involving an addition of a PAH radical to an ethynyl-substituted PAH molecule.     

Effect of Lorentz force on the electrochemical performance of lithium-ion batteries

Lorentz force theory demonstrates that electric current density and magnetic force are proportional, indicating that they compensate each other. In a battery operated at high magnetic forces, the electrons in the active material move fast in a specific magnetic field. γ-Fe₂O₃, a highly magnetic material, is used to prepare LiFePO₄ electrodes to study the effect of the Lorentz force on lithium-ion battery performance. The magnetic field created by γ-Fe₂O₃ induces magnetic forces on the charged LiFePO₄ particles, accelerating electron movement. Superconducting quantum interference measurements reveal that saturation magnetization and remanence are prominent when γ-Fe₂O₃ is added to the LiFePO₄ electrodes. The LiFePO₄ electrode containing 15 wt% γ-Fe₂O₃ led to superior battery capacity (69.8 mAh g^− 1 at 10C) compared with the pure LiFePO₄ electrode (1.8 mAh g^− 1 at 10C). In this study, Lorentz force theory is applied to improve the specific capacity and cycle life at high current rates of a battery containing LiFePO₄ cathode materials, suggesting that incorporating γ-Fe₂O₃ into the cathode is an easy and cheap strategy for increasing the power density and cycle life of lithium-ion batteries.     

Additive free electrodeposition of nanocrystalline aluminium in a water and air stable ionic liquid

This paper shows for the first time that nanocrystalline aluminium can be electrodeposited without any additives in the ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide saturated with AlCl₃. The advantages of this ionic liquid compared to chloroaluminate ionic liquids, which were intensively investigated in the past, are that it is water and air stable, easy to purify as well as it is easy to dry to water contents below 1 ppm. Interestingly, this ionic liquid shows biphasic behaviour above a concentration of AlCl₃ of 1.6 mol/L. A significant current loop attributed to nucleation was found for bulk deposition of aluminium at room temperature on gold, whereas at 100 °C there is no nucleation loop. The deposits obtained are generally uniform, dense, shining and adherent to the substrate with crystallites in the nanosize regime. At 100 °C, the quality of the deposit is even better with an average size of the crystallites of 34 nm.