Gas-phase Method Research Articles

DFT study about the effects of BX3 (X = H, F, Cl and Br) derivatives on the C–H acidity enhancement

A computational study about the effect of BX3 (X = H, F, Cl and Br) interaction in C–H acidity enhancement of some aldehyde, ketone and imine molecules is performed by B3LYP/6- 311++G(d,p) method in gas phase. The boron derivatives of model molecules show more acidity in comparison with their pure forms. This acidity improvement is attributed to the effective interaction of the C = O/C = N group with the B atom of BX3. The acidity enhancement is according to the BBr3 > BCl3 > BF3 > BH3 order which shows that boron compounds with electron withdrawing groups and especially BBr3 can be used as an effective and promising C–H activator in various organic reactions.

Energy-saving Technology in Steady-state Simulation of Ethylene Acetate Production Process Using Aspen Plus

It is necessary to strengthen energy management in chemical and petrochemical industries because of the shortage of energy supply. Aspen Plus was used to simulate and optimize vinyl acetate production process via ethylene gas-phase method. The appropriate thermodynamic equations and unit modules were selected. The simulation and optimization results of vinyl acetate production were in accordance with the industrial production data. Based on steady-state simulation and optimization results, heat exchanger network synthesis and heat pump assisted distillation technology were proposed for energy conservation. For heat exchanger network synthesis technology, energy conservation can be achieved through the energy matching of cold and hot streams based on pinch theory. As a result, cold utilities, hot utilities, heat transfer area and the number of heat exchanger decreased by 25.52%, 59.52%, 70.60% and 30.77%, respectively. For heat pump assisted distillation technology, compared with the conventional distillation technology in the purification of acetic acid from aqueous acetic acid solution, 48.05% of cold energy consumption and 82.40% of heat energy consumption could be saved. Based on the simulation and optimization results, it can be found that heat exchanger network synthesis and optimization as well as heat pump assisted distillation technology can provide good ideas for the rational use of energy.

Environmentally friendly gas phase grafting of mesoporous silicas

Tumbling chemical vapour deposition (T-CVD) is presented as a novel methodology for the gas phase grafting (GPG) of a variety of alkoxy- and chloro-silanes on mesoporous silica. Compared to conventional solution grafting techniques, this method is sustainable, and cost- and time-effective. Although the method was successfully applied to a variety of silanes, application of the gas phase methodology to the preparation of propylamine-grafted CO2 adsorbents (AGA) is presented in depth, for illustration. A detailed comparative characterization of AGAs derived from GPG and solution grafting is discussed. Unprecedentedly high propylamine contents were achieved (up to 5.51 mmol/g), indicating enhanced accessibility of surface hydroxyl groups and more favorable packing of propylamine chains on the support surface, thereby enabling much higher surface density compared to traditional solution grafting procedures. The gas phase method achieves higher grafting efficiency, with less silane waste, necessitating recycling. Furthermore, not only higher CO2 uptake, but also higher amine efficiency (CO2/N) was obtained from GPG-derived adsorbents compared to those obtained by solution grafting. GPG was also found to be suitable for grafting granules and pellets with limited mechanical strength, which may otherwise be crushed while being stirred during grafting in solution.

Study of potential of Fe-Si76 as catalyst for CO2 reduction to CH3OH

In this study, mechanisms of reduction reaction of carbon dioxide on Iron doped silicon nanocage are investigated in gas phase and water. The metal catalysts have several fundamental problems such as slow kinetics, high over potential, low performance and insignificant selectivity. The reaction pathways of carbon dioxide conversion to methanol are examined by theoretical methods in gas phase and water. The acceptable reaction pathway is identified from thermodynamic view point in gas phase ad water. Results indicated that the in carbon dioxide conversion to methanol the reaction step of 4 is the rate-limiting step. Results indicated that the over potential (−0.825 V) of reaction steps in gas phase and water is lower than metal catalysts (−1.116 V). The Iron doped silicon nanocage with low barrier energies and low over potential is proposed as efficient catalyst in gas phase and water.

Does Symmetry Control Photocatalytic Activity of Titania-Based Photocatalysts?

Decahedral anatase particles (DAPs) have been prepared by the gas-phase method, characterized, and analyzed for property-governed photocatalytic activity. It has been found that depending on the reaction systems, different properties control the photocatalytic activity, that is, the particle aspect ratio, the density of electron traps and the morphology seem to be responsible for the efficiency of water oxidation, methanol dehydrogenation and oxidative decomposition of acetic acid, respectively. For the discussion on the dependence of the photocatalytic activity on the morphology and/or the symmetry other titania-based photocatalysts have also been analyzed, that is, octahedral anatase particles (OAP), commercial titania P25, inverse opal titania with and without incorporated gold NPs in void spaces and plasmonic photocatalysts (titania with deposits of gold). It has been concluded that though the morphology governs photocatalytic activity, the symmetry (despite its importance in many cases) rather does not control the photocatalytic performance.

Progress in Preparation of ZrB2 Nanopowders Based on Traditional Solid-State Synthesis.

ZrB2 is of particular interest among ultra-high temperature ceramics because it exhibits excellent thermal resistance at high temperature, as well as chemical stability, high hardness, low cost, and good electrical and thermal conductivity, which meet the requirements of high-temperature components of hyper-sonic aircraft in extreme environments. As raw materials and basic units of ultra-high temperature ceramics and their composites, ZrB2 powders provide an important way for researchers to improve material properties and explore new properties by way of synthesis design and innovation. In recent years, the development of ZrB2 powders’ synthesis method has broken through the classification of traditional solid-phase method, liquid-phase method, and gas-phase method, and there is a trend of integration of them. The present review covers the most important methods used in ZrB2 nanopowder synthesis, focusing on the solid-phase synthesis and its improved process, including modified self-propagating high-temperature synthesis, solution-derived precursor method, and plasma-enhanced exothermic reaction. Specific examples and strategies in synthesis of ZrB2 nano powders are introduced, followed by challenges and the perspectives on future directions. The integration of various synthesis methods, the combination of different material components, and the connection between synthesis and its subsequent application process is the trend of development in the future.

One-step fabrication of fiber optic SERS sensors via spark ablation

Spark ablation, a versatile, gas-phase physical nanoparticle synthesis method was employed to fabricate fiber-optic surface enhanced Raman scattering (SERS) sensors in a simple single-step process. We demonstrate that spark-generated silver nanoparticles can be simply deposited onto a fiber tip by means of a modified low-pressure inertial impactor, thus providing significant surface enhancement for fiber-based Raman measurements. The surface morphology of the produced sensors was characterized along with the estimation of the enhancement factor and the inter- and intra-experimental variation of the measured Raman spectrum as well as the investigation of the concentration dependence of the SERS signal. The electric field enhancement over the deposited silver nanostructure was simulated in order to facilitate the better understanding of the performance of the fabricated SERS sensors. A potential application in the continuous monitoring of a target molecule was demonstrated on a simple model system.

Ultrasonically modified P25-TiO2 /In2O3 heterostructured nanoparticles: An efficient dual- responsive photocatalyst for solution and gas phase reactions

BackgroundDesigning and fabricating an efficient heterostructured photocatalyst for degrading organic pollutants is a major concern for environmental remediation researchers. In that series we fabricated a P25-TiO2/In2O3 (PT/In) heterostructured nanocomposite via the facile ultrasonication and sol-gel synthesis method. MethodsIn both solution and gas-phase methods, the photocatalytic efficiency of the obtained PT/In nanocomposite was investigated. DRIFT-IR was measured at room temperature with the effect of adsorbed ethanol molecules, which would be used as a different approach to confirm the photocatalytic reaction mechanism. Significant FindingsUnder UV-Visible light illumination, the PT/In-4 nanocomposite was found to be an excellent photocatalyst for degrading Acid Blue (AB) dye. The calculated degradation rate constant (k) of PT/In-4 was 4.0 × 10−2 min−1, which was 13.3 and 5.7 times higher than that of PT-4 (0.3 × 10−2 min−1) and bare In2O3 (0.7 × 10−2 min−1) materials, respectively. The enhancement in photocatalytic performance is owing to the synergistic effect of the heterojunction between TiO2 and In2O3 and a reduction in the recombination rate. Furthermore, the PT/In-4 nanocomposite showed high stability even after five consecutive cycles. The photocatalytic mechanism was proposed based on experimental results obtained through the gas phase photocatalytic studies via DRIFT-IR technique.

Doped ZnO Nanostructured and their application as photocatalytic: as Review

There are two types of methods of synthesis of several different kinds of doped ZnO nanomaterials for photocatalytic applications, gas phase methods, include pulsed laser deposition and chemical vapor deposition and wet chemical methods such as sol–gel, electrospinning, hydrothermal, spray pyrolysis, thermomechanical .doping with metal ions is make local energies levels within the semiconductor energy gap, which results in prolongation of the light absorbance to the visible light region. Several studies have that metaldoped ZnO, such as N, S, and C, using Co, Fe, Cu, Eu, Ce, Ag, Mn, and Al and non-metal doping, ZnO to the reducing Energies and enhancement of photocatalytic behavior in the region of visible light.

Gas-Phase Structural Analysis of Supramolecular Assemblies.

Ion mobility spectrometry and gas-phase IR action spectroscopy are two structure-sensitive mass-spectrometric methods becoming more popular recently. While ion mobility spectrometry provides collision cross sections as a size and shape dependent parameter of an ion of interest, gas-phase spectroscopy identifies functional groups and is capable of distinguishing different isomers. Both methods have recently found application for the investigation of supramolecular assemblies. We here highlight several aspects.Starting with the characterization of switching states in azobenzene photoswitches as well as redox-switchable lasso-type pseudorotaxanes, structures of isomers can be distinguished and mechanistic details analyzed. Ion mobility mass spectrometry in combination with gas-phase H/D-exchange reactions unravels subtle structural details as described for the chiral recognition of crown ether amino acid complexes. Gas-phase IR spectroscopy allows identification of details of the binding patterns in dimeric amino acid clusters as well as the serine octamer. This research can be extended into the analysis of peptide assemblies that are of medical relevance, for example, in Alzheimer's disease, and into a general hydrophobicity scale for natural as well as synthetic amino acids. The development of ultracold gas-phase spectroscopy that for example makes use of ions trapped in liquid helium droplets provides access to very well resolved spectra. The combination of ion mobility separation of ions with subsequent spectroscopic analysis even permits separation of different isomers and studying them separately with respect to their structure. This represents a great advantage of these gas-phase methods over solution experiments, in which the supramolecular complexes under study typically equilibrate and thus prevent a separate investigation of different isomers. At the end of this overview, we will discuss larger and more complex supramolecules, among them giant halogen-bonded cages and complex intertwined topologies such as molecular knots and Solomon links.

Gas-phase studies of chemically synthesized Au and Ag clusters.

Atomically precise Au and Ag clusters protected by monolayers of organic ligands have attracted growing interests as promising building units of functional materials and ideal platforms to study size-dependent evolution of structures and physicochemical properties. The use of gas-phase methods including mass spectrometry, ion mobility mass spectrometry, collision-induced dissociation mass spectrometry, photoelectron spectroscopy, and photodissociation spectroscopy will reveal novel and complementary information on their intrinsic geometric and electronic structures that cannot be obtained by conventional characterization methods. This Perspective surveys the recent progress and outlook of gas-phase studies on chemically synthesized Au/Ag clusters.

Ionic Transport in CsNO2-Based Nanocomposites with Inclusions of Surface Functionalized Nanodiamonds.

Composite solid electrolytes (1 − x)CsNO2-xND, where ND are nanodiamonds, including those after liquid-phase and gas-phase oxidation and reduction functionalization, were prepared, and their properties investigated by XRD, analysis of BET nitrogen adsorption isotherms, IR spectroscopy and impedance spectroscopy. The electrical conductivity of composites (1 − x)CsNO2-xND obeys the Arrhenius dependence and has a maximum at x = 0.95 regardless of the ND pretreatment. It was found that the conductivity depends on the mode of functionalization of the ND surface, as well as on the processing time. The electrical conductivity of composites with ND, processed by the gas-phase method, is 1.5–2.6 times higher than that of composites with initial ND, in which the conductivity is 2 orders of magnitude higher than that of pure cesium nitrate. Thus, the possibility of using ND as an effective heterogeneous additive for the preparation of composite solid electrolytes, including cesium nitrite, has been demonstrated for the first time.

Fabrication and application of ZnO-Ag nanocomposite materials prepared by gas-phase methods

Zinc oxide nanoparticles have been used in various applications because of its unique physical and chemical properties. Unfortunately, the performance of pristine ZnO is inhibited by electron-hole recombination. The zinc oxide performance can be improved by metal doping to enhance its properties. This review paper provides summary of the synthesis and application of zinc oxide doped by silver (Ag) using different synthesis via gas-phase methods. From this review, synthesis parameters that will affect the ZnO-Ag nanoparticle and its application will be concluded. The gas-phase synthesis methods include flame spray pyrolysis, spray pyrolysis, sputtering, plasma enhanced chemical vapor deposition, electron beam evaporation, atomic layer deposition and electrospinning. It is clearly observed that the morphology, crystallinity, and performance of ZnO-Ag nanocomposite is significantly affected by the fabrication method. The precursors used, spray rate, deposition rate, precursor concentration, deposition time, morphology of the nanoparticle and deposition or annealing temperature affect the performance capability of ZnO-Ag. We believe that this review paper will provide valuable information and new insights into possible fabrication methods of ZnO-Ag nanocomposite materials in the gas-phase, which can be used for many applications as photocatalyst, anti-microbial applications, catalyst for hydrogen production as well as in dye-sensitized solar cells and gas sensors.

Прогнозирование условий хлоридно-гидридной эпитаксии слоев Ga1–yInyAs1–xPx, изопериодных с GaAs и GaAs1–xPx

Multicomponent solid solutions of AIIIBV are increasingly used in optoelectronics, photonics, and other fields of science and technology. These are AlGaInN-based emitters, InGaAsP-based receivers, etc. In addition, these materials are widely used as buffer and isomorphic layers in general-purpose nanoheterostructures. The main methods of their production are gas-phase methods, such as chloride-hydride, MOS-hydride epitaxy, MBE. The development of optimal technological modes of multicomponent layers and structures, as a rule, takes a lot of time and is quite expensive. In this paper, the author proposed a method for modeling processes based on the basic physical and chemical laws of the crystallization processes of materials and the properties of AIIIBV compounds. The analysis and prediction of the processes of obtaining four-component solid solutions In1–yGayAs1–xPx, isoperiodic with GaAs, three-component solid solutions GaAs0,8P0,2 and GaAs0,6P0,4 were performed. The calculated modes have been experimentally implemented and the materials corresponding to the current level of quality have been obtained.

Structural and electronic switching of a single crystal 2D metal-organic framework prepared by chemical vapor deposition

The incorporation of metal-organic frameworks into advanced devices remains a desirable goal, but progress is hindered by difficulties in preparing large crystalline metal-organic framework films with suitable electronic performance. We demonstrate the direct growth of large-area, high quality, and phase pure single metal-organic framework crystals through chemical vapor deposition of a dimolybdenum paddlewheel precursor, Mo2(INA)4. These exceptionally uniform, high quality crystals cover areas up to 8600 µm2 and can be grown down to thicknesses of 30 nm. Moreover, scanning tunneling microscopy indicates that the Mo2(INA)4 clusters assemble into a two-dimensional, single-layer framework. Devices are readily fabricated from single vapor-phase grown crystals and exhibit reversible 8-fold changes in conductivity upon illumination at modest powers. Moreover, we identify vapor-induced single crystal transitions that are reversible and responsible for 30-fold changes in conductivity of the metal-organic framework as monitored by in situ device measurements. Gas-phase methods, including chemical vapor deposition, show broader promise for the preparation of high-quality molecular frameworks, and may enable their integration into devices, including detectors and actuators.

Theoretical Investigation of New Organic Compounds (D-π-A) Based on Triphenylamine as Photosensitizer for Dyesensitized Solar Cells

The current work involved suggestion of a new material “D-π-A system” for use in solar cells as organic dyes sensitized. The ground state estimations are done by utilizing the hybrid functional “B3LYP” with 6-311G(d, p) basis set on density functional theory (DFT) method in gas phase. Besides, the TD-DFT was selected with same functional to modulate the electronic absorption spectra and charge-transfer capabilities of the dyes analyzed in this study. The effects of introducing different groups as π-bridge on the properties of these materials were examined with intending to confirm the connection between compounds structure and its properties. In addition, various electronic, optical, chemical reactivity and optical parameters were determined from the fully optimized structures. The results demonstrate these materials can be utilized as organic sensitizers for solar cell because of its properties and probability of the electron injection process from each studied molecule to the ECB “conduction band” of TiO2 and PCBM and the subsequent regeneration are possible, finally the electrons transfer will be simple from the examined dyes to TiO2 or PCBM.

Acidity enhancement of sulfonic acid derivatives by hydrogen bond networks

New Brønsted acids with a wide range of acidity were designed using substitution of –CH3 group of methanesulfonic acid by –CH2OH, –CH(OH)CH2OH, and –CH(OH)CH(OH)CH2OH chains (compounds 1–3). The conjugate bases of the proposed acids are stabilized by formation of a hydrogen bond network including OH…OH and OH…OS interactions. To extend the hydrogen bond network, hydrogen atoms of –CH3 group of methanesulfonic acid were substituted by three CH2OH3, –CH(OH)CH2OH, and –CH(OH)CH(OH)CH2OH chains (compounds 4–6). The acidity of these acids was assessed using B3LYP/6-311++G(d,p) method in gas phase. It was found that compounds 4–6 with three, six, and nine hydrogen bonds are stronger acids than CH3SO3H by about 21, 35, and 42 kcal mol−1, respectively. Perfluorination of the polyol chains led to 10–20 kcal mol−1 acidity enhancement. Effect of electron delocalization on the acidity of the proposed acids was also investigated.

Morphology, Sizes and Oxidation of Composite Copper Nanopowders, Obtained by an Electron Beam with Different Energies

Copper nanopowders were obtained by the gas-phase method under the influence of an electron beam of different powers. Thermodynamic modeling of the phase equilibrium state of the Cu-O2-C system during heating in argon and atmospheric pressure was carried out using the TERRA software package. The obtained nanopowders of copper were studied by X-ray phase analysis and transmission electron microscopy. The morphology, structure, size distribution, and average size of copper nanoparticles are determined. The dependence of the content of copper oxides in a copper-containing nanopowder on the electron beam power has been established. It is shown that copper nanopowders obtained at high power are not oxidized.

Interfacial phenomena and molecular dynamics in core-shell-type nanocomposites based on polydimethylsiloxane and fumed silica: Comparison between impregnation and the new mechano-sorption modification as preparation methods

In this study, we investigate interfacial phenomena in nanocomposites of the ‘core-shell’ type based on fumed silica nanoparticles (core) and linear polydimethylsiloxane, PDMS, (shell) of low molecular weight (~3 kg/mol). In particular, we study the interfacial polymer in terms of the amount and dynamics and compare between two methods of nanocomposite preparation, the simple impregnation (liquid phase method) and the relatively new and environmentally more friendly mechano-sorption modification, MSM (gas phase method). To that aim, we employ differential scanning calorimetry, DSC, and broadband dielectric spectroscopy, BDS, as the main investigation tools, supplemented by scanning electron microscopy, SEM, and Fourier transform infrared spectroscopy, FTIR. The silica-PDMS interactions result in constraints on the polymer diffusion/mobility and, subsequently, on the formation of an interfacial polymer fraction being rigid in DSC or exhibiting retarded dynamics in BDS. In qualitative agreement between the two techniques, the amount of interfacial polymer was found systematically larger for MSM as compared to impregnation, confirming actually the scope of employing MSM. The latter is shown here for the first time in silica nanocomposites employing the said experimental methodology. From the basic research point of view, the bulk-like dynamics (glass transition and α/αc relaxations) is mainly similar between the nanocomposites and neat PDMS, with the larger interfacial amounts imposing a slight increase of the Tg. Owing to the high resolving power of BDS, the interfacial polymer dynamics is recorded individually via the αint relaxation next to the bulk-like α/αc in the nanocomposites. αint exhibits a non-cooperative character and relatively high strength, which, comparing to previous work on similar and systems, suggests the existence of many PDMS tails distributed on the silica surfaces, with the interfacial chains packing being possibly more dense in the case of MSM as compared to impregnation.

Charge-switch derivatization of fatty acid esters of hydroxy fatty acids via gas-phase ion/ion reactions

Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are a recently discovered class of endogenous bioactive lipids with anti-diabetic and anti-inflammatory effects. Identification of FAHFAs is challenging due to both the relatively low abundance of these metabolites in most biological samples and the significant structural diversity arising from the co-occurrence of numerous regioisomers. Ultimately, development of sensitive analytical techniques that enable rapid and unambiguous identification of FAHFAs is integral to understanding their diverse physiological functions in health and disease. While a battery of mass spectrometry (MS) based methods for complex lipid analysis has been developed, FAHFA identification presents specific challenges to conventional approaches. Notably, while the MS2 product ion spectra of [FAHFA – H]¯ anions afford the assignment of fatty acid (FA) and hydroxy fatty acid (HFA) constituents, FAHFA regioisomers are usually indistinguishable by this approach. Here, we report the development of a novel MS-based technique employing charge inversion ion/ion reactions with tris-phenanthroline magnesium complex dications, Mg(Phen)32+, to selectively and efficiently derivatize [FAHFA – H]¯ anions in the gas phase, yielding fixed-charge cations. Subsequent activation of [FAHFA – H + MgPhen2]+ cations yield product ions that facilitate the assignment of FA and HFA constituents, pinpoints unsaturation sites within the FA moiety, and elucidates ester linkage regiochemistry. Collectively, the presented approach represents a rapid, entirely gas-phase method for near-complete FAHFA structural elucidation and confident isomer discrimination without the requirement for authentic FAHFA standards.