Quantitative Study on the Influence of Bromide Ions toward the Reduction Kinetics for Size-Tunable Palladium Nanocubes

During the preparation of nanocrystals, regulating the dosage of key additives in the reaction system and the reaction temperature commonly affects the sizes and morphologies of the products. Despite the fact that bromide ions play a pivotal role in the synthesis of palladium nanocubes (Pd NCs), there is still a lack of quantitative and in-depth research on how the ions affect the reduction kinetics of Pd precursors and further on products. In this work, Pd NCs with different sizes have been prepared under various reaction conditions coupled to a systematic mechanism study. Quantitative measurements demonstrate that the reduction processes could be considered quasi-first-order reactions, and the corresponding kinetic parameters have been obtained. Furthermore, a linear relationship is discovered between k and the average size (d) of Pd NCs. The investigation on the growth patterns of four chosen systems reveals that given reaction conditions lead to certain results with unique growth patterns

Systematic Study on the Precursor Reduction Kinetics and Growth Pattern for Size-Tunable Palladium Nanocubes

Unveiling the underlying chemistry during the growth of well-defined nanocrystals is a fundamental but challenging task in materials chemistry. Herein, Pd NCs with tunable sizes ranging from 4.5 to 23.5 nm have been synthesized in the presence of potassium acetate (KOAc). The Pd precursor variation trends of these preparation systems along with reaction time have been determined using a UV–vis spectrometer, and corresponding reduction kinetic parameters, including the apparent reduction rate constant (k) and activation energy (Ea), are calculated by regarding the reduction processes as quasi-first-order reactions. It is confirmed that the introduction of KOAc does not affect the value of the Ea of different reaction systems. The interrelationship of k, product size (d), and reaction temperature (T) is discussed in depth. Results indicate that the three parameters are closely related, and for given reaction systems, they are specified. With the careful investigation of six specific systems (reaction systems with 10 mM, 20 mM KOAc at 55 °C, with 5 mM, 10 mM KOAc at 65 °C, without KOAc at 75 °C, and with 5 mM KOAc at 85 °C), the growth pattern of Pd NCs is described with an empirical expression and is further confirmed as a synergistic result of k and T

Thermal Stability and Decomposition Kinetics of 1,3-Dimethyladamantane

For a comprehensive understanding of the properties of 1,3-dimethyladamantane (1,3-DMA) as a candidate of high energy-density hydrocarbon fuels, thermal stability of 1,3-DMA under different conditions is investigated. The thermal decomposition kinetics in the batch reactor between 693 and 743 K has been determined, with the rate constants ranging from 4.00 × 10^–7 s^–1 at 693 K to 35.19 × 10^–7 s^–1 at 743 K, along with the Arrhenius parameters of <i>A</i> = 2.39 × 10⁷ s^–1 and activation energy <i>E</i>_a = 183 kJ·mol^–1. The rate constants for the thermal decomposition of 1,3-DMA are observed to be smaller than those of some typical model fuels, decalin, propylcyclohexane, butylcylohexane, and <i>n</i>-dodecane, demonstrating that the thermal stability of 1,3-DMA is satisfactory. The thermal decomposition of 1,3-DMA in the flowing reactor at temperatures from 873 to 973 K and pressures from 0.1 to 5.0 MPa is further performed. It can be observed that the conversion of 1,3-DMA and the yield of gaseous products increase clearly with the rise of temperature or pressure. The residence time is the main factor for the change of decomposition depth. Methane and hydrogen are the major gaseous products that are produced through demethylation and dehydrogenation. In the liquid residues, toluene and xylene are observed and quantified by GC-MS, HPLC, and NMR as the main aromatics produced. On the basis of component analysis, a hypothetical mechanism of thermal decomposition of 1,3-DMA is proposed to explain the product distribution. It is shown that the different products are mainly obtained through a combination of isomerization, hydrogen transfer, β-scission, and dehydrogenation. The results are expected to provide experimental information for the search of new high energy-density hydrocarbon fuels

Micellization Parameters of Six Gemini Quaternary Ammonium Surfactants from Measurements of Conductivity and Surface Tension

The micellization of six Gemini quaternary ammonium surfactants aqueous solutions has been investigated from measurements on specific conductivity as a function of surfactant concentration at different temperatures from (298.15 to 323.15) K. The micellization parameters such as the critical micellar concentration (CMC) and the degree of counterion dissociation (β), Gibbs free energy (Δ<i>G</i>_mic), enthalpy (Δ<i>H</i>_mic), and entropy (Δ<i>S</i>_mic) of micellization are then obtained. It is shown that the conductometry measurements provide agreement of the CMC values at 298.15 K with the surface tension studies. With the rise of temperature, the values of CMC and β increase, while Δ<i>G</i>_mic changes little. The linear plots of <i>T</i>Δ<i>S</i>_mic versus Δ<i>H</i>_mic show the effects of enthalpy–entropy compensation. The length of alkyl chain and the spacer group of the Gemini surfactant have significant influences on micellization parameters

Influence of Reduction Kinetics on the Preparation of Well-Defined Cubic Palladium Nanocrystals

A facile synthesis strategy has been developed to synthesize palladium nanocubes with tunable size and well-controlled morphology. Through adjusting the dosages of acetate species (KOAc, NH₄OAc, and HOAc), the sizes of well-defined Pd nanocubes are tuned. The reduction of Pd precursors, a first-order reaction, is influenceable by acetate species, and a quantitative relationship between cubic width and apparent reduction rate constant, which has been found to be an effective parameter to describe the growth process of Pd nanocubes, has been uncovered. The effect of apparent reduction rate constant on the growth of Pd nanocubes has been discussed, and the growth kinetics of Pd nanocubes is quantitatively depicted

Densities and Viscosities for the Ternary System of Decalin + Methylcyclohexane + Cyclopentanol and Corresponding Binaries at <i>T</i> = 293.15 to 343.15 K

Densities (ρ) and viscosities (η) for the ternary system of decalin (1) + methylcyclohexane (2) + cyclopentanol (3) and three corresponding binary systems have been measured over the whole composition range at 11 temperature points from 293.15 K to 343.15 K under atmospheric pressure (0.1 MPa). The excess molar volumes (VmE) and viscosity deviations (Δη) of binary systems have been calculated and further fitted with the Redlich–Kister equation, while corresponding physical data of the ternary system have been correlated via the Clibuka, Singh, Nagata-Tamura, and Redlich–Kister equations. The VmE values are negative for the binary system of decalin (1) + methylcyclohexane (2) with a minimum when the moles of the two components are similar. For the system of decalin (1) + cyclopentanol (2), the VmE values are always positive with a maximun at about x1 = 0.6. At the same time, a sigmoid curve can be observed for the system of methylcyclohexane (1) + cyclopentanol (2). The minimum and maximum appear around x1 = 0.2 and x1 = 0.9, respectively. The Δη values of the three binary systems are all negative and the absolute values decrease with increase in temperature. For the ternary system, the VmE values are partially negative and the Δη values are negative over the entire concentration range. The nonideal behaviors of the mixtures are discussed in the perspective of intermolecular interaction and structural effect

Novel Guanidinium<b>-</b>Based Ionic Liquids for Highly Efficient SO₂ Capture

The application of ionic liquids (ILs) for acidic gas absorption has long been an interesting and challenging issue. In this work, the ethyl sulfate ([C₂OSO₃]⁻) anion has been introduced into the structure of guanidinium-based ILs to form two novel low-cost ethyl sulfate ILs, namely 2-ethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([C₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate ([(C₂)₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃]). The ethyl sulfate ILs, together with 2-ethyl-1,1,3,3-tetramethylguanidinium bis­(trifluoromethylsulfonyl)­imide ([C₂²(C₁)₂(C₁)₂³gu]­[NTf₂]) and 2,2-diethyl-1,1,3,3-tetramethylguanidinium bis­(trifluoromethylsulfonyl)­imide ([(C₂)₂²(C₁)₂(C₁)₂³gu]­[NTf₂]), are employed to evaluate the SO₂ absorption and desorption performance. The recyclable ethyl sulfate ILs demonstrate high absorption capacities of SO₂. At a low pressure of 0.1 bar and at 20 °C, 0.71 and 1.08 mol SO₂ per mole of IL can be captured by [C₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃] and [(C₂)₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃], respectively. The absorption enthalpy for SO₂ absorption with [C₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃] and [(C₂)₂²(C₁)₂(C₁)₂³gu]­[C₂OSO₃] are −3.98 and −3.43 kcal mol^–1, respectively. While those by [C₂²(C₁)₂(C₁)₂³gu]­[NTf₂] and [(C₂)₂²(C₁)₂(C₁)₂³gu]­[NTf₂] turn out to be only 0.17 and 0.24 mol SO₂ per mole of IL under the same conditions. It can be concluded that the guanidinium ethyl sulfate ILs show good performance for SO₂ capture. Quantum chemistry calculations reveal nonbonded weak interactions between the ILs and SO₂. The anionic moieties of the ILs play an important role in SO₂ capture on the basis of the consistently experimental and computational results

Paraffin-Coated Hydrophobic Hemostatic Zeolite Gauze for Rapid Coagulation with Minimal Adhesion

To solve the problem of strong adhesion and excessive blood loss caused by the use of hydrophilic zeolite gauze (Z-Gauze) in uncontrollable bleeding, we have modified the surface of commercial Z-Gauze with a paraffin coating and prepared a hydrophobic dressing PZ-Gauze. After paraffin coating, the adhesion of Z-Gauze was reduced without an obvious decrease in coagulation activity. The clotting time of the hydrophobic PZ-Gauze was reduced from 378.3 to 154.6 s compared with that of cotton gauze, and the peeling force was decreased from 348.8 to 84.7 mN compared with that of Z-Gauze. Besides, PZ-Gauze can efficiently cut down the blood loss during treatment. On the basis of in vitro and in vivo experiments, it is confirmed that surface hydrophobic modification does not change the procoagulant performance because of the maintained cation exchange capacity of zeolites, and the reduced blood loss as well as enhanced difficulty for fibrin adhesion is attributed to its hydrophobicity. This is different from the traditional gauze procoagulant theories, where gauze hydrophilicity and procoagulant performance are always positively correlated

Density, Viscosity, and Freezing Point for Four Binary Systems of <i>n</i>‑Dodecane or Methylcyclohexane Mixed with 1‑Heptanol or Cyclohexylmethanol

Measurements on density and viscosity at <i>T</i> = (293.15, 298.15, 303.15, 308.15 313.15, 318.15, 323.15, 328.15, and 333.15) K and the pressure <i>P</i> = 0.1 MPa for binary mixtures of <i>n</i>-dodecane or methylcyclohexane with 1-heptanol or cyclohexylmethanol have been carried out over the whole composition range. Densities were measured with a vibrating-tube densimeter. Viscosities were determined by an automatic microviscometer based on the rolling-ball principle. The excess molar volumes (<i>V</i>_m^E) and viscosity deviations (Δη) were calculated with experimental data and fitted to the Redlich–Kister equation. The results of these excess or deviation functions are explained by molecular interactions and structural effects. Freezing points were measured with a differential scanning calorimeter. The fundamental data, <i>V</i>_m^E and Δη can be used to study the nature of mixing behaviors between new hydrocarbon fuels

Paraffin-Coated Hydrophobic Hemostatic Zeolite Gauze for Rapid Coagulation with Minimal Adhesion

To solve the problem of strong adhesion and excessive blood loss caused by the use of hydrophilic zeolite gauze (Z-Gauze) in uncontrollable bleeding, we have modified the surface of commercial Z-Gauze with a paraffin coating and prepared a hydrophobic dressing PZ-Gauze. After paraffin coating, the adhesion of Z-Gauze was reduced without an obvious decrease in coagulation activity. The clotting time of the hydrophobic PZ-Gauze was reduced from 378.3 to 154.6 s compared with that of cotton gauze, and the peeling force was decreased from 348.8 to 84.7 mN compared with that of Z-Gauze. Besides, PZ-Gauze can efficiently cut down the blood loss during treatment. On the basis of in vitro and in vivo experiments, it is confirmed that surface hydrophobic modification does not change the procoagulant performance because of the maintained cation exchange capacity of zeolites, and the reduced blood loss as well as enhanced difficulty for fibrin adhesion is attributed to its hydrophobicity. This is different from the traditional gauze procoagulant theories, where gauze hydrophilicity and procoagulant performance are always positively correlated