Gas-phase Method Research Articles

Status and demand of research to bring laser generation of nanoparticles in liquids to maturity

Abstract Nanoparticles are already implemented as functional elements on surfaces and into volume, but also in hybrid nanostructures. Each application requires specific features regarding size, morphology, surface chemistry, purity, colloidal stability, defects, or doping. However, integration of the “nano-function” into products is still limited due to drawbacks of gas phase and chemical synthesis methods regarding particle aggregation and contamination by adsorbates causing deactivation of their surfaces. In addition, thermodynamically-controlled synthesis methods naturally face limited access to alloy nanoparticle systems with miscibility gaps. The development of new synthesis methods which can be reliably scaled up to industrial levels of production is mandatory to overcome these limitations and then widen the application prospectives of nanomaterials. Since the nineties, Laser Ablation in Liquids (LAL) has proven its reliability and its versatility to synthesize colloidal nanoparticles. More generally, laser/matter interaction in liquids offers several synthesis routes for nanoparticle generation. In addition to LAL, Laser Melting in Liquids (LML), Laser Fragmentation in Liquids (LFL), as well as pulsed Laser Photoreduction/oxidation in Liquids (LPL), offer different routes to obtain colloids with controled nanoparticle sizes. We will present a digest of the breakthroughs achieved in the last years not only on the synthesis control, but also on the understanding of the basics. These achievements suggest that laser generation of nanoparticles in liquids is mature enough for industrial outlets of colloid production, with series products likely to approach the real world in the near future.

Theoretical study on the efficacy of DBN/LiBr system as a catalyst for fixation of CO2 with propylene oxide: Solvent effects on activation barriers

The fixation of carbon dioxide with propylene oxide (PO) catalyzed by DBN/ LiBr system to produce a five-membered cyclic carbonate, has been extensively studied employing DFT method in gas phase and in solvents. The solvent effects were considered by means of a PCM model. The title reaction was investigated in the absence of catalyst, in the presence of LiBr alone and DBN/LiBr mediated pathways. Two hypothetical reaction pathways were proposed for DBN/LiBr catalyzed reaction and their corresponding energetics are explored to demonstrate the favorable route. DFT results indicated that mechanism I is more favorable pathway kinetically and thermodynamically than mechanism II. The more favorable pathway comprises three main steps: ring-opening of the epoxide by Br- anion, carbon dioxide insertion, and ring-closure process. The free energy of activation computed at the B3LYP/6-311++G(d,p)//B3LYP/6-31+G(d,p) level reveals that the rate-determining step is the ring-opening of epoxide; which demanded 34.95, 22.55, 19.83 and 19.75 kcal/mol in gas phase, diethyle ether, ethanol and water, respectively. The carbon dioxide insertion step was determined to be barrierless. Although the ring opening step is endothermic, the overall reaction is exothermic. Finally, the catalytic activity of other catalysts reported for the title reaction somewhere else was compared with the activity of DBN/LiBr system.

FUNCTIONAL MODELING OF CARBON SORBENTS SYNTHESIS CONTROL

The formalized model of carbon sorbent synthesis control based on the methodology for functional modeling is constructed. The correlations between the directions of use and the properties of carbon sorbents are revealed. The characteristics that are essential regardless of the direction of use of the sorbent, in particular, sorption properties and strength are identified. The technologies based on the gas-phase method of obtaining carbon material are considered, the analysis of individual stages of the process of obtaining carbon sorbents is carried out. The analysis of the influence of the technological parameters of the synthesis on the properties of sorbents is carried out. On the basis of the established relationships, a functional model has been built that provides a hierarchically ordered, structured, visual description of the management of carbon sorbent synthesis. The simulation is performed “from top to bottom” from the most general description to the detail. The resulting model is a set of interrelated graphical diagrams. At the initial stage, the synthesis of carbon sorbent is considered as a single process, the input parameters of which are hydrocarbon gas, the activating agent and the material form factor, the output - carbon sorbent, and the control parameters are the requirements for strength and sorption properties. Then the synthesis process is decomposed. The control processes (analysis of raw material properties and matrix selection), technological processes (raw material preparation) and mixed processes are distinguished as a result of decomposition. The model includes a consistent description of the technological parameters selection (temperature, gas flow and time) for both stages of the synthesis process. The model is the base for information support providing for the production of carbon sorbents with the required properties.

Self-formed porous Ni(OH)2 on Ni3S2/Ni foam during electrochemical cycling for high performance supercapacitor with ultrahigh areal capacitance

In this work, Ni3S2/Ni foam was successfully synthesized using a facile gas-phase method of annealing Ni foam in H2S atmosphere. It was used as a binder free electrode for high-performance supercapacitors. The areal capacitance increases rapidly in the initial charge-discharge cycling and then reaches a stable stage. An ultrahigh areal capacitance of 9.88 F cm−2 at the current density of 10 mA cm−2 is achieved in the stable charge-discharge stage, which is around 88 times of initial capacitance (112.5 mF cm−2). Further studies reveal that surface Ni3S2 transforms into porous Ni(OH)2 during charge-discharge process, and surface area increases more than 100 times. The soaring specific surface area is the dominant factor contributing to the increased areal capacitance. More importantly, this self-formed porous structure exhibits ultra-stable long-time cycling ability, as no capacity fading is observed even after 60000 cycles of charge-discharge at high current density (150 mA cm−2). These results indicate that self-formed porous Ni(OH)2 structure during electrochemical cycling maybe a promising electrode for high performance supercapacitor applications.

Quantum mechanical, spectroscopic and molecular docking studies of N-[4-cyano-3-(trifluoromethyl) phenyl]-3-[(4-fluorophenyl)sulfonyl]-2-hydroxy-2-methylpropanamide

Abstract The title compound N-[4-cyano-3-(trifluoromethyl) phenyl]-3-[(4-fluorophenyl)sulfonyl]-2-hydroxy-2-methylpropanamide was characterized by FT-IR, FT-RAMAN, UV, 1H NMR and 13C NMR spectral analysis. The common name of the compound is Bicalutamide. The optimized molecular geometry, the vibrational wave numbers, the infrared intensities and the Raman scattering data were calculated by using density functional theory (DFT)B3LYP method 6-311++G(d,p) basis set. From the UV–Visible spectrum the electronic properties were evaluated by TD-DFT in DMSO solution and gas phase method using B3LYP/6-311++G(d,p). The calculated HOMO-LUMO band gap energy shows that charge transfer takes place within the molecule. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by Gauge Independent Atomic Orbital (GIAO) method. NBO analysis was carried out to find out the intra molecular electronic interactions and their stabilization energy. To study the biological activity of the molecule, molecular docking was done to identify the hydrogen bond lengths and binding energy with prostate cancer protein.

Introducing the concept of pulsed vapor phase copper-free surface click-chemistry using the ALD technique.

We report for the first time on a pulsed vapor phase copper-free azide-alkyne click reaction on ZnO by using the atomic layer deposition (ALD) process technology. This reproducible and fast method is based on an in situ two-step reaction consisting of sequential exposures of ZnO to propiolic acid and benzyl azide.

From a volatile molecular precursor to twin-free single crystals of bismuth.

A highly volatile molecular precursor, dibismuth(ii) (tetra)trifluoroacetate, was successfully utilized for the gas phase growth of twin-free single crystals of bismuth. This allowed high-quality single-crystal X-ray diffraction data to be collected, providing accurate structural parameters for elemental bismuth under ambient conditions.

Characterization of chemically modified gold and silver clusters in gas phase.

Atomically precise Au and Ag clusters protected by organic ligands can be viewed as chemically modified Au/Ag superatoms and have attracted interest as promising building units of functional materials and ideal platforms for studying the size-dependent evolution of structures and properties. Their structures, stability, and physicochemical properties have been characterized in solution and solid (or crystalline) phases by various methods conventionally used in materials science. However, novel and complementary information on their intrinsic stability and structures can be obtained by applying a variety of gas-phase methods, including mass spectrometry, ion mobility mass spectrometry, collision- or surface-induced dissociation mass spectrometry, photoelectron spectroscopy, and photodissociation mass spectrometry, to the chemically modified Au/Ag superatoms isolated in the gas phase. This perspective describes our recent efforts in the gas-phase studies on chemically synthesized Au/Ag superatoms.

Facile and Efficient Gas-Phase Pressure-Controlled Thermal Functionalization of Nanocrystalline Porous Silicon with 1-Hexene

Substitution of hydrogen at porous silicon (PSi) surface by organic groups can be done via thermally activated hydrosilylation reactions in which PSi is left for several hours into liquid alkenes at temperatures typically over 100°C. For alkenes whose boiling points are below 100°C (e.g. 1-heptene and shorter molecules), the process suffers from high reagent boiling and evaporation. Gas-phase hydrosilylation is an alternative when using short molecules. It has not been as extensively studied, and was mainly done in plasma reactors with silicon nanocrystals. Here we present a new method for facile gas-phase thermally-activated hydrosilylation in PSi, but using liquid solutions as reagent (1-hexene was used here). PSi and liquid alkene are loaded at room temperature into a chamber which is then closed and heated up to a temperature greater than the alkene boiling point. The effects of process temperature, time and pressure were investigated by means of Fourier transform infrared spectroscopy. The maximum theoretical derivatization efficiency was achieved with optimized parameters. The derivatization was uniform across the PSi layer depth. PSi luminescence was effectively stabilized by the process. The new gas-phase method presented here is facile, requires very small amount of liquid reagent, and is useful for attachment of short molecules to PSi or other materials surface.

In English

As an one of the most promising materials of green energy as a photocatalyst for the production of hydrogen from renewable, natural sources (water, greenhouse gas) and environmental remediation through the degradation of toxic organic pollutants, graphite-like carbon nitride (characterized as a non-toxic and chemically highly resistant material) and its nanostructured and doped (especially by oxygen atoms) derivatives attract special attention. The actual task for expanding the scope of application of g-C 3 N 4 is to improve and optimize its catalytic, electronic and optical properties by increasing both the surface area of graphitic carbon nitride and the number of active centers of the carbon nitride network due to doping of carbon nitride. The use of a mixture of two different precursors ensures the creation of heterojunctions, and as a result, an improvement the photocatalytic characteristics of g-C 3 N 4 . The oxygen-doped carbon nitride (O-g-C 3 N 4 ) and water-soluble carbon nitride oxide (g-C 3 N 4 )O was simultaneously synthesized by the gas phase method under special reaction conditions of pyrolysis of cyanuric acid and urea mixture. Reduction by the hydroquinone of carbon nitride oxide (g-C 3 N 4 )O yields nanostructured reduced carbon nitride (or reduced multilayer azagraphene). Obtained products were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), chemical and X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM). According to the results of XPS and IR spectrometry the chemical bonds between atoms in a heteroatomic plane of reduced carbon nitride (RCN) correspond to the bonds in a synthesized carbon nitride (SCN). However, according to XRD results, reduced carbon nitride (RCN) probably consists of poorly connected heteroatomic azagraphene layers, because it has a significantly larger (on 0.09 nm) interplanar distance between the adjacent nitrogen-carbon layers than interplanar distance between the layers of synthesized carbon nitride (SCN). By SEM characterization it was found that the pyrolysis of a mixture of various precursors (cyanuric acid and urea) yielded a product with smaller crystalline domains (which can improve photocatalytic characteristics) than the pyrolysis of a single precursor (urea only).

Ion mobility–mass spectrometry of supramolecular complexes and assemblies

Despite their structural and functional differences, synthetic supramolecular assemblies share many similarities with biological assemblies, especially enzymes. The assemblies can be on the same length scale, and their structures and guest binding are typically governed by non-covalent interactions. Thus, only relatively weak interactions define the shape of a synthetic supramolecule or the secondary and tertiary structure of a protein, such that the resulting dynamism makes structure elucidation challenging. For biomolecules such as peptides, proteins, glycans and lipids this has often been tackled using ion mobility–mass spectrometry (IM-MS), whereby analyte ions are separated according to their gas-phase mobility and their mass-to-charge ratio. IM-MS is an established method in omics, separation sciences and small-molecule structural chemistry, but has only recently grown in popularity for the study of synthetic supramolecular assemblies in the gas phase. This Review describes IM-MS techniques and how they can help us understand the structures of molecular self-assemblies, host–guest complexes and metallosupramolecular complexes. Ion mobility–mass spectrometry (IM-MS) is a gas-phase method for structural characterization — a tool prevalent in biology but only recently finding applications in supramolecular chemistry. This Perspective describes how IM-MS techniques give us information about the structures of molecular self-assemblies, host–guest complexes and metallosupramolecular systems.

Molar activity – The keystone in 11C-radiochemistry: An explorative study using the gas phase method

IntroductionRadiochemists/radiopharmacists, involved in the preparation of radiopharmaceuticals are regularly confronted with the requirement of continuous high quality productions in their day-to-day business. One of these requirements is high specific or molar activity of the radiotracer in order to avoid e.g. receptor saturation and pharmacological or even toxic effects of the applied tracer for positron emission tomography. In the case of 11C-labeled radiotracers, the reasons for low molar activity are manifold and often the search for potential 12C-contaminations is time-consuming. MethodsIn this study, diverse 12C-contaminations were analyzed and quantified, which occurred during >450 syntheses of six PET tracers using [11C]CO2 or [11C]CH3I generated via the gas phase method in a commercially available synthesizer. Additionally, non-radioactive syntheses were performed in order to identify the origins of carbon-12. ResultsThe manifold contributions to low molar activity can be attributed to three main categories, namely technical parameters (e.g. quality of target gases, reagents or tubings), inter/intralaboratory parameters (e.g. maintenance interval, burden of the module, etc.) and interoperator parameters (e.g. handling of the module). ConclusionOur study provides a better understanding of different factors contributing to the overall carbon load of a synthesis module, which facilitates maintenance of high molar activity of carbon-11-labeled radiopharmaceuticals.

Diastereomeric discrimination by achiral substances: the effect of diverse ions in the stability of amphi-ionophore cystine-based cyclopeptide stereoisomers

ABSTRACTCyclic peptides are a large class of natural compounds which attracted a great deal of attention, especially as potential amphi-ionophores. Herein, a theoretical study on the stability of new cystine-based tricyclopeptide (TCP) stereoisomers in achiral media in the presence of Li+, Na+, K+, F−, Cl−, and Br− ions was performed at the M06-2X/6-311++G(d,p) level of theory in both gas and aqueous phases. The nature of the intermolecular interaction between TCPs and ions were studied by natural bond orbital analysis (NBO) and the quantum theory of atoms in molecules (QTAIM) methods in gas phase. According to the size of the ions and configuration of TCPs, the location of ions (within or above the TCPs) and the types of formed intermolecular interactions are different. The results revealed that the free TCP7 and TCP8 enantiomers in gas phase and also TCP1 and TCP2 enantiomers in aqueous phase are the most stable structures among all TCPs. Moreover, the calculated energies of the optimised complexes containing the same ion show different stability order as compared to the free TCPs.

Temperature Difference Triggering Controlled Growth of All-Inorganic Perovskite Nanowire Arrays in Air.

All-inorganic perovskites have attracted increasing worldwide interest due to its significantly improved stability in atmospheric environment compared to organic-inorganic hybrid perovskites, which renders it infinitely applicable in many fields such as electronics, optoelectronics, and energy storage. However, all-inorganic perovskites have to confront the challenges from fabrication before their wide utilization in the aforementioned applications. Liquid-phase synthesis holds the advantage of mass production and easy modulation of composition but with the deficiencies of relatively low crystallinity and disordered products. Interestingly, gas-phase growth has complementary characteristics compared to the liquid-phase method. In this work, it is proposed that a novel temperature difference triggers growth strategy to integrate the merits of the liquid- and gas-phase methods, and the feasibility of this strategy via a simple lab-use hot plate is demonstrated. High quality all-inorganic perovskites, cesium lead halide (CsPbX3 ) nanowire arrays, can be epitaxially grown as in a gas-phase method, but at the same time, the composition of products can be easily modulated by predesigning the recipe of precursors as in the liquid-phase method on a large scale. Notably, the as-fabricated CsPbX3 perovskite nanowire arrays demonstrate excellent stability and good optoelectronic properties in air. It is believed that this novel strategy can strikingly prompt the development of perovskites fabrication and applications in future.

Gas-phase method makes membranes selective

Permeable membranes could potentially lower the cost of industrial gas separations traditionally done via the energy-intensive process of cryogenic distillation. A number of metal-organic framework compounds known as ZIFs—zeolite-type structures consisting of transition metals connected by imidazolate linkers—show promise for this application, but the solution-based methods used to make them are tough to scale up reliably. So Xiaoli Ma, Michael Tsapatsis, and coworkers at the University of Minnesota came up with a simple vapor-phase ZIF-preparation method based on atomic layer deposition (ALD), a well-known film-growth technique. The group showed that the ZIF membranes they produced efficiently separate the gases propane and propylene (Science 2018, DOI: 10.1126/science.aat4123). The researchers started with a common substrate made by sandwiching two types of alumina. That material is gas permeable but does not separate propane from propylene. Using ALD, they deposited zinc oxide on the alumina, plugging ...

Alignment of liquid crystal molecules on self-assembled monolayer with fluorinated alkyl chain at different deposition time

We demonstrated a homeotropic liquid crystal (LC) alignment state on fluorinated self-assembled monolayers (FSAMs) deposited by gas-phase method as a function of deposition time. The gas-phase method to deposit FSAMs was simple process and cost-effective. Contact angle data and surface energy analyses of the FSAMs showed that film formation occurs, and showed a correlation with the homeotropic alignment of LC molecules on the FSAMs. Stable LC alignments on FSAMs were achieved at deposition time over 60 min. In addition, high transparency and thermal stability of FSAM further enhanced its possibility as a LC alignment layer.

Mass Production of Large-Sized, Nonlayered 2D Nanosheets: Their Directed Synthesis by a Rapid "Gel-Blowing" Strategy, and Applications in Li/Na Storage and Catalysis.

2D nanomaterials are well suited for energy conversion and storage because of their thickness-dependent physical and chemical properties. However, current synthetic methods for translating 2D materials from the laboratory to industry cannot integrate both advantages of liquid-phase method (i.e., solution processibility, homogeneity, and massive production), and gas-phase method (i.e., high quality and large lateral size). Here, inspired by Chinese Sugar Figure Blowing Art, a rapid "gel-blowing" strategy is proposed for the mass production of 2D nonlayered nanosheets by thermally expanding the viscous gel precursors within a short time (≈1 min). A wide variety of 2D nanosheets including oxides, carbon, oxides/carbon and metal/carbon composites are synthesized on a large scale and with no impurities. Importantly, this method unifies the merits of both liquid-phase and gas-phase syntheses, giving rise to 2D products with high uniformity, nanometer thickness, and large lateral sizes (up to hundreds of micrometers) simultaneously. The success of this strategy highly relies on the speed of "blowing" and control of the amount of reactants. The as-synthesized nanosheet electrodes manifest excellent electrochemical performance for alkali-ion batteries and electrocatalysis. This method opens up a new avenue for economical and massive preparation of good-quality nonlayered 2D nanosheets for energy-related applications and beyond.

Synthesis of high-specific volume carbon nanotube structures for gas-phase applications

A novel and efficient gas-phase method has been developed for synthesizing carbon nanotube (CNT) structures with very high specific volume, high surface area and high porosity. The resulting material has potential application as a catalyst and adsorbent support for gas-phase chemical processes and has several advantages over the conventional liquid-phase approach that involves multiple steps and takes many hours to days resulting in a dense mat of CNTs. Multi-walled CNTs were initially nucleated and grown on alumina nanoparticles using a liquid precursor of ferrocene dissolved in xylene. The CNT seeds were extended using ethylene as the gas precursor. Forces generated by CNT growth separated the alumina support clusters to result in a porous entangled structure with a 60 times gain in weight and a 1300 times gain in volume, compared to the original alumina particles. Effects of ferrocene injection rate, alumina particle sizes, and CNT growth parameters on the volume of the structure were analyzed and it was determined that high ferrocene input, moderate temperatures, and small alumina particles all favor the synthesis of high-volume CNT structures.

Synthesis of CuInS2 Compound Solar Cell Nanoparticles in an Aqueous Solution By Controlling the Concentration of Metal Complexes

CuInS2(CIS) is one of the most effective photovoltaic devices for developing high stability and low cost solar cell. Bandgap of CIS is 1.5eV while ideal band gap for solar cell is 1.4eV, so CIS is suitable as solar cell materials. Moreover, unlike Cu(In,Ga)Se2(CIGS), it does not contain toxic materials, such as Se [1]. Until now, CIS solar cells have been synthesized by utilizing gas phase method. However, the gas phase evaporation process needs high energy consumption, high initial cost, and large amount loss of resources. For spreading the solar cells greatly, it is required to develop a method which can resolve the above problems, so it is necessary to synthesize CIS solar cells in liquid method. Here, we have already developed a synthesizing method of single phase and homogeneous Copper-Indium (CI) alloy nanoparticles in an aqueous solution. In this method, the concentration ratio of the metal complexes in the solution are calculated by using the critical stability constants, and the reduction reaction rate is also controlled. Synthesized CI nanoparticles were spin coated onto substrate and selenized, consequently it shows the photo voltaic effect. Thus, printable solar cell can be formed by using this method. However, CIS2 nanoparticles were not synthesized until now, because of ligand exchange reaction between the complexing agents and Cu and In. Therefore, in this study, to prevent these undesirable reaction, we tried to control the condition of Cu-In-complexing reagent(s) system precisely by using the calculation. By using these calculation results, CIS2 particles were tried to synthesized in an aqueous solution Results of calculation indicated that iminodiacetic acid (IDA) was appropriate complexing reagent. In the ternary system of Cu-In-IDA, it was calculated that the Copper comlexes and Indium complexes can be restricted to homogenized species, [(Cu2+)(IDA)] (pH3) and [(In3+)(IDA)2] (pH3) under the condition that the total molar concentration of Copper and Indium ions were 5 mM, respectively. Based on this calculation, a solution under the above condition was prepared, and both metal complexes were tried to co-sulfurize. As a results, particles with amorphous like morphology were obtained. Therefore, in order to improve the crystallinity, the particles were heated for 30 min at 500 °C under N2 atmosphere. XRD results of heat treated samples indicated that several peaks with a dominant CIS2 peak were observed. Thus, it can be said that CIS2 nanoparticles were successfully synthesized in an aqueous solution, without undesirable ligand exchange reaction during reaction. These results indicated that homogenize metal complexes system of Cu-In-IDA are essential for the synthesis of CIS2 particles. In our presentation, detailed and another results will be introduced. [1]Recent Development of Thin Film Compound Semiconductor Photovoltaic Cells, Wada, Publication of CMC, 2007

Homeotropic alignment behavior of liquid crystal molecules on self-assembled monolayers with fluorinated alkyl chain

This study demonstrates the orientation characteristics of liquid crystals (LCs) on fluorinated self-assembled monolayers (FSAMs) deposited using the gas phase method. The authors confirmed that the FSAMs were properly deposited on indium-doped tin oxide glass substrates using x-ray photoelectron spectroscopy and atomic force microscopy. Compared with conventional polyimide (PI) layers, the authors confirmed that the FSAM is an alternative to the conventional PI layer. Regardless of the positive and negative LC characteristics, the LC molecules were vertically aligned on the FSAMs, with hydrophobic properties. In addition, an LC cell using an FSAM showed faster response times than that with a conventional PI layer when the electro-optical characteristics were examined. Therefore, these results indicate that FSAMs are suitable for LC applications as homeotropic LC alignment layers.