Vapor-phase Synthesis Research Articles

Vapor-phase reduction synthesis of N, S co-doped graphene/MWCNT hybrid membrane for all-solid-state supercapacitors and adsorption of organic pollutants

Owing to the limited reserves of fossil fuels, many researchers are focused on seeking advanced materials to relieve the drawbacks caused by the imbalance between the supply and demand of fossil fuels. In this study, a N, S co-doped graphene/multi-walled carbon nanotubes hybrid membrane (GMHE) was synthesized by flow-directed assembly followed by vapor-phase reduction. The resulting hybrid membrane not only exhibited excellent capacitance performance, but also good adsorption capacity for organic pollutants owing to its high electrochemical activity, well-developed pore structure, and rich surface state. The assembled GMHE all-solid-state symmetric supercapacitor delivered a high power density of 6000 W·kg−1 at an energy density of 16.0 W·h·kg−1 and superior capacitance stability (retaining 97.2 % of its initial capacitance value at 3 A·g−1). The adsorption capacity of the GMHE for organic pollutants was 50 times (chlorobenzene) its own mass. In addition, the hybrid membrane exhibited remarkable reusability over in adsorption–combustion cycles. The judiciously designed bifunctional membrane material developed herein can be directly applied in energy storage and oil pollution cleanup, supporting sustainable economic development.

Boosting Monolayer Transition Metal Dichalcogenides Growth by Hydrogen-Free Ramping during Chemical Vapor Deposition.

The controlled vapor-phase synthesis of two-dimensional (2D) transition metal dichalcogenides (TMDs) is essential for functional applications. While chemical vapor deposition (CVD) techniques have been successful for transition metal sulfides, extending these methods to selenides and tellurides often faces challenges due to uncertain roles of hydrogen (H2) in their synthesis. Using CVD growth of MoSe2 as an example, this study illustrates the role of a H2-free environment during temperature ramping in suppressing the reduction of MoO3, which promotes effective vaporization and selenization of the Mo precursor to form MoSe2 monolayers with excellent crystal quality. As-synthesized MoSe2 monolayer-based field-effect transistors show excellent carrier mobility of up to 20.9 cm2/(V·s) with an on-off ratio of 7 × 107. This approach can be extended to other TMDs, such as WSe2, MoTe2, and MoSe2/WSe2 in-plane heterostructures. Our work provides a rational and facile approach to reproducibly synthesize high-quality TMD monolayers, facilitating their translation from laboratory to manufacturing.

Unraveling nanosprings: morphology control and mechanical characterization.

Nanosprings demonstrate promising mechanical characteristics, positioning them as pivotal components in a diverse array of potential nanoengineering applications. To unlock the full potential of these nanosprings, ongoing research is concentrated on emulating springs at the nanoscale in terms of both morphology and function. This review underscores recent advancements in the field and provides a comprehensive overview of the diverse methods employed for nanospring preparation. Understanding the general mechanism behind nanospring formation lays the groundwork for the informed design of nanosprings. The synthesis section delineates four prominent methods employed for nanospring fabrication: vapor phase synthesis, templating methods, post-treatment techniques, and molecular engineering. Each method is critically analyzed, highlighting its strengths, limitations, and potential for scalability. Mechanical properties of nanosprings are explored in depth, discussing their response to external stimuli and their potential applications in various fields such as sensing, energy storage, and biomedical engineering. The interplay between nanospring morphology and mechanical behavior is elucidated, providing insights into the design principles for tailored functionality. Additionally, we anticipate that the evolution of state-of-the-art characterization tools, such as in situ transmission electron microscopy, 3D electron tomography, and machine learning, will significantly contribute to both the study of nanospring mechanisms and their applications.

Vapor phase synthesis of metal–organic frameworks on a nanofibrous aerogel creates enhanced functionality

Vapor-phase synthesis of metal–organic frameworks (MOFs) on nanofibrous aerogels provides a hierarchically porous and mechanically robust material platform for use in a multitude of applications, from carbon dioxide capture to heavy metal removal.

Vapor-Phase Synthesis of Electrocatalytic Covalent Organic Frameworks.

The inability to process many covalent organic frameworks (COFs) as thin films plagues their widespread utilization. Herein, a vapor-phase pathway for the bottom-up synthesis of a class of porphyrin-based COFs is presented. This approach allows integrating electrocatalysts made of metal-ion-containing COFs into the electrodes' architectures in a single-step synthesis and deposition. By precisely controlling the metal sites at the atomic level, remarkable electrocatalytic performance is achieved, resulting in unprecedentedly high mass activity values. How the choice of metal atoms, i.e., cobalt and copper, can determine the catalytic activities of POR-COFs is demonstrated. The theoretical data proves that the Cu site is highly active for nitrate conversion to ammonia on the synthesized COFs.

Crystal grain size effects and crystallinity dynamics during supersonic particle impacts

We examine the effect of crystal grain size on particle impacts with substrates at supersonic speeds, which are commonly used in producing metal and ceramic coatings. Large-scale atomistic simulations are utilized to examine the impact outcomes of 60 nm nickel particle impacts on nickel substrates, with mean crystal grain sizes varied from 5 nm to 30 nm, representing nanoparticles commonly formed in vapor phase synthesis processes. We observe that smaller grain particles have higher critical strains and lower Young’s moduli than their larger grain counterparts due to having a larger fraction of grain boundaries. Smaller grain particles also experience a greater degree of heating and amorphization during higher speed impacts, while defect formation and propagation are hindered. We also provide insight into experimentally observed losses in crystallinity during high-speed deposition processes; in all cases a rapid loss of crystallinity occurs at impact, followed by recrystallization, with the net result being a decrease in crystal grain sizes.

Surface Conversion of ZnO Tetrapods Produces Pinhole-Free ZIF-8 Layers for Selective and Sensitive H2 Sensing Even in Pure Methane.

As the necessary transition to a supply of renewable energy moves forward rapidly, hydrogen (H2) becomes increasingly important as a green chemical energy carrier. The manifold applications associated with the use of hydrogen in the energy sector require sensor materials that can efficiently detect H2 in small quantities and in gas mixtures. As a possible candidate, we here present a metal-organic framework (MOF, namely ZIF-8) functionalized metal-oxide gas sensor (MOS, namely ZnO). The gas sensor is based on single-crystalline tetrapodal ZnO (t-ZnO) microparticles, which are coated with a thin layer of ZIF-8 ([Zn(C4H5N2)2]) by a ZnO conversion reaction to obtain t-ZnO@ZIF-8 (core@shell) composites. The vapor-phase synthesis enables ZIF-8 thickness control as shown by powder X-ray diffraction, thermogravimetric analysis, and N2 sorption measurements. Gas-sensing measurements of a single microrod of t-ZnO@ZIF-8 composite demonstrate the synergistic benefits of both MOS sensors and MOFs, resulting in an outstanding high selectivity, sensitivity (S ≅ 546), and response times (1-2 s) to 100 ppm H2 in the air at a low operation temperature of 100 °C. Under these conditions, no response to acetone, n-butanol, methane, ethanol, ammonia, 2-propanol, and carbon dioxide was observed. Thereby, the sensor is able to reliably detect H2 in mixtures with air and even methane, with the latter being highly important for determining the H2 dilution level in natural gas pipelines, which is of great importance to the energy sector.

Nanostructured Vanadium Dioxide Materials for Optical Sensing Applications.

Vanadium dioxide (VO2) is one of the strongly correlated materials exhibiting a reversible insulator-metal phase transition accompanied by a structural transition from a low-temperature monoclinic phase to high-temperature rutile phase near room temperature. Due to the dramatic change in electrical resistance and optical transmittance of VO2, it has attracted considerable attention towards the electronic and optical device applications, such as switching devices, memory devices, memristors, smart windows, sensors, actuators, etc. The present review provides an overview of several methods for the synthesis of nanostructured VO2, such as solution-based chemical approaches (sol-gel process and hydrothermal synthesis) and gas or vapor phase synthesis techniques (pulsed laser deposition, sputtering method, and chemical vapor deposition). This review also presents stoichiometry, strain, and doping engineering as modulation strategies of physical properties for nanostructured VO2. In particular, this review describes ultraviolet-visible-near infrared photodetectors, optical switches, and color modulators as optical sensing applications associated with nanostructured VO2 materials. Finally, current research trends and perspectives are also discussed.

Understanding the unique optical and vibrational signatures of sequential infiltration synthesis derived indium oxyhydroxide clusters for CO2 absorption

Sequential infiltration synthesis (SIS) is a vapor phase synthesis technique with potential to exert precise control over metal oxyhydroxide incorporation into polymer scaffolds. We observe strong size-dependent properties of InOx(OH)y few-atom clusters deposited with variable SIS cycle numbers within a polymethylmethacrylate (PMMA) matrix. Infrared spectroscopy and ultraviolet-visible absorption spectroscopy reveal that the metal atom coordination and optical properties of the clusters depend on the number of SIS cycles performed as well as the choice of processing parameters. The incorporation of indium oxyhydroxide in PMMA via SIS presents an opportunity to improve the CO2 absorption capacity and gas selectivity of inexpensive polymers.

Vapor-Phase Synthesis of Molecularly Imprinted Polymers on Nanostructured Materials at Room-Temperature.

Molecularly imprinted polymers (MIPs) have recently emerged as robust and versatile artificial receptors. MIP synthesis is carried out in liquid phase and optimized on planar surfaces. Application of MIPs to nanostructured materials is challenging due to diffusion-limited transport of monomers within the nanomaterial recesses, especially when the aspect ratio is >10. Here, the room temperature vapor-phase synthesis of MIPs in nanostructured materials is reported. The vapor phase synthesis leverages a >1000-fold increase in the diffusion coefficient of monomers in vapor phase, compared to liquid phase, to relax diffusion-limited transport and enablethe controlled synthesis of MIPs also in nanostructures with high aspect ratio. As proof-of-concept application, pyrrole is used as the functional monomer thanks to its large exploitation in MIP preparation; nanostructured porous silicon oxide (PSiO2 ) is chosen to assess the vapor-phase deposition of PPy-based MIP in nanostructures with aspect ratio >100; human hemoglobin (HHb) is selected as the target molecule for the preparation of a MIP-based PSiO2 optical sensor. High sensitivityand selectivity, low detection limit, high stability and reusability are achieved in label-free optical detection of HHb, also in human plasma and artificial serum. The proposed vapor-phase synthesis of MIPs is immediately transferable to other nanomaterials, transducers, and proteins.

Morphological and structural modification of CaGe2 by annealing with MgCl2/Mg

Ge-based nanosheets and GeH phases were synthesized in the vapor phase using CaGe2 crystals as templates. Ge-based nanosheets have been synthesized in the liquid-phase, but not in the vapor-phase. Compared with liquid-phase synthesis, vapor-phase synthesis is more useful for nanostructure control and impurity addition technologies. These technologies will increase the future popularity of nanosheets. And it is important to apply these technologies after clarifying the effects of certain parameters, such as annealing temperature and changes in the mole fractions. As an introduction to the future development of vapor-phase synthesized Ge-based nanosheets, this study proposes the thermal annealing of CaGe2 powders with MgCl2. Furthermore, the effects of changing the molar fraction containing Mg atoms and the behavior of HCl were investigated from 100 °C–600 °C.

Layer-Structured Anisotropic Metal Chalcogenides: Recent Advances in Synthesis, Modulation, and Applications.

The unique electronic and catalytic properties emerging from low symmetry anisotropic (1D and 2D) metal chalcogenides (MCs) have generated tremendous interest for use in next generation electronics, optoelectronics, electrochemical energy storage devices, and chemical sensing devices. Despite many proof-of-concept demonstrations so far, the full potential of anisotropic chalcogenides has yet to be investigated. This article provides a comprehensive overview of the recent progress made in the synthesis, mechanistic understanding, property modulation strategies, and applications of the anisotropic chalcogenides. It begins with an introduction to the basic crystal structures, and then the unique physical and chemical properties of 1D and 2D MCs. Controlled synthetic routes for anisotropic MC crystals are summarized with example advances in the solution-phase synthesis, vapor-phase synthesis, and exfoliation. Several important approaches to modulate dimensions, phases, compositions, defects, and heterostructures of anisotropic MCs are discussed. Recent significant advances in applications are highlighted for electronics, optoelectronic devices, catalysts, batteries, supercapacitors, sensing platforms, and thermoelectric devices. The article ends with prospects for future opportunities and challenges to be addressed in the academic research and practical engineering of anisotropic MCs.

Surface steered aligned gradient inorganic lead halide perovskite CsPbBrxI3−x nanowires for use in photodetectors

Explicit control over the orientation and yield of aligned planar nanowires (NWs) offers a unique blueprint for the facile integration of sophisticated functional devices with ultra-high compactness. In this report, vapor-phase synthesis produces a massive parallel assembly of nanowires owing to the graphoepitaxial effect exhibited by the annealed M-plane sapphire surface. The nanochannels on the substrate surface serve as natural templates and define the position, growth direction, and length of NWs. Microstructure characterizations and strong band-edge photoluminescence (PL) reveal the superior quality crystal structure of CsPbBrxI3-x NWs. The NW's axially asynchronous bromide-iodide composition provides a graded bandgap with two advantages: broad gamut absorption and a dominant unidirectional built-in electric field. The electric field promotes charge carrier transportation via an energy-funneling process, as demonstrated by the outstanding performance of the CsPbBrxI3-x NW photodetector, which has a responsivity of 370 A/W and a brisk photoresponse time of about 4 ms. Bright PL observation even after 100 days of storage at room temperature (RT) and 25 % relative humidity (RH) conditions indicates a boost in monoclinic phase stability and improved environmental degradation resistance. This work presents the feasibility of massive-scale synthesis of parallel NWs and their direct integration into circuits and functional systems for smart and efficient spectrometers, image sensors, optical communication, chemical or biological detection, and other optoelectronic applications.

Vapor-phase synthesis of a robust polysulfide film for transparent, biocompatible, and long-term stable anti-biofilm coating

Vapor-phase synthesis of a robust polysulfide film for transparent, biocompatible, and long-term stable anti-biofilm coating

Nanostructured Poly(3,4-ethylenedioxythiophene) Coatings on Functionalized Glass for Energy Storage

Conducting polymers rise among some of the most promising transparent supercapacitor electrode materials due to high conductivity, environmental stability, light weight, and ease of synthesis. A major challenge for depositing conducting polymers on a glass substrate is the lack of molecular interactions between organic and inorganic moieties resulting in poor adhesion and low cycling stability of the electrode. We present a synthetic approach by covalently linking poly(3,4-ethylyenedioxythiophene) (PEDOT) and glass through Friedel-Crafts alkylation on a self-assembled diphenyldimethoxysilane monolayer. This method obviates the need for a conductive FTO or ITO coating, enabling the fabrication of current collector-free planar supercapacitor electrodes on any glass surface. The electrode produced from our vapor-phase synthesis is coated with a highly conductive nanofibrillar PEDOT film (sheet resistance 2.1 Ω/□) possessing a gravimetric capacitance of ∼200 F/g. Our PEDOT planar supercapacitor possesses outstanding stability (86% capacitance retention after 50,000 cycles). We also fabricate a proof-of-concept transparent tandem supercapacitor on PEDOT-coated glass using 3D-printed frames that supplies enough voltage and current to light up a blue light-emitting diode (LED).

Investigating the vapour phase synthesis of copper terephthalate metal organic framework thin films by atomic/molecular layer deposition.

Solventless synthesis and processing of Metal Organic Frameworks (MOFs) is critical to implement these materials in applied technologies. Vapour phase synthesis of MOF thin films is particularly suitable for such applications, but challenging compared to the conventional solution based methods. It is therefore compelling to advance and widen the vapour phase synthesis of MOF thin films. Crystalline copper terephthalate MOF thin films are grown in the vapour phase by means of atomic and molecular layer deposition (ALD/MLD) on different kinds of substrates. Expanding from the pioneering work, the formation of the 3D phase is clearly evidenced for the first time and the adaptability of the process to several kinds of substrates is revealed. A directional film growth is observed at the early stage of the ALD/MLD process leading to oriented MOF crystallites on a surface, when isotropical growth proceeds with the increasing number of ALD/MLD cycles. Notably, this study primarily demonstrates a heteroepitaxial growth achievable in the vapour phase by using DMOF-1 single crystals as the starting surface with a lattice matching topology. Such an approach offers an appealing pathway to develop MOF on MOF superlattice materials in the vapour phase.

Vapor-phase synthesis of low-valent metal–organic frameworks from metal carbonyl synthons

We demonstrate the facile vapor-phase synthesis of a novel, porous zero-valent metal–organic framework from the reaction between volatile M(CO)6 (M = Mo, W) and 4,4'-bipyridine precursors.

Nanostructuring Pt‐Pd Bimetallic Electrocatalysts for CO2 Reduction Using Atmospheric Pressure Atomic Layer Deposition

AbstractPreparing supported nanoparticles with a well‐defined structure, uniform particle size, and composition using conventional catalyst synthesis methods, such as impregnation, precipitation, and deposition‐precipitation is challenging. Furthermore, these liquid phase methods require significant solvent consumption, which has sustainable issues and requires complex purification processes, usually leaving impurities on the catalyst, affecting its selectivity and activity. In this work, we employed atomic layer deposition (ALD, a vapor phase synthesis method) to synthesize electrocatalysts with well‐controlled core‐shell and alloy structures for CO2 reduction to formic acid. With this approach, the structural control of the catalysts is down to the atomic scale, and the effect of core‐shell and alloy structure on Pt−Pd bimetallic catalysts has been investigated. It is shown that the Pt−Pd alloy catalyst displays a 46 % faradaic efficiency toward formic acid, outperforming Pt@Pd and Pd@Pt core‐shell structures that show faradaic efficiencies of 22 % and 11 %, respectively. Moreover, both core‐shell bimetallic catalysts (Pd@Pt and Pt@Pd) are not stable under electroreduction conditions. These catalysts restructure to more thermodynamically stable structures, such as segregated clusters or alloy particles, during the electrochemical reduction reaction, altering the catalytic selectivity.

Investigation of electron-phonon interaction in Pure and Indium doped MoS2 using temperature dependent Raman Spectra

Direct vapor phase synthesis technique was used to grow the bulk InxMo1-xS2 (x = 0, 0.05, 0.1). The grown material has hexagonal structure with P63/mmc space group. Electron-Phonon interaction in bulk InxMo1-xS2 (x = 0, 0.05, 0.1) were studied using Raman spectroscopy. First order mode i.e. A1g and E2g and second order mode i.e. b-mode were observed in bulk InxMo1-xS2 (x = 0, 0.05, 0.1) crystals. Temperature dependent Raman spectroscopy over the temperature range -180 °C to 240 °C shows the peak shifting. The higher sulfur void in bulk MoS2 as corelate to that of indium doped MoS2was responsible for excessive electron concentration. This study was supported by Energy Dispersive Analysis of X-ray (EDAX) and powder X-ray Diffraction (XRD) on bulk InxMo1-xS2 (x = 0, 0.05, 0.1).

Magnetic-atom strategy enables unilamellar MoS2-C interoverlapped superstructure with ultrahigh capacity and ultrafast ion transfer capability in Li/Na/K-ion batteries

Constructing a unilamellar MoS2-C interoverlapped superstructure (UIS) is the most promising way to improve electrical conductivity and alleviate volume expansion of MoS2 electrodes during Li+/Na+/K+ storage due to the maximized atomic interface contact. However, the interlayer distance of ∼ 0.48 nm between MoS2 and C (lower than 0.62 nm of pristine MoS2), the unconspicuous enhancement of intrinsic conductivity of MoS2, and the inevitable decrease in capacity due to the introduced low-capacity C undoubtedly hamper ion transport and storage, thus resulting in limited enhancement of capacity and fast-charging performances of UIS. Herein, we propose a magnetic-atom strategy for UIS via a one-step high-pressure vapor-phase synthesis method, during which the interlayer electrostatic repulsion is in-situ constructed by magnetic-atom Fe and/or Co doping to adjust the interlayer distance from 0.48 to 0.64 nm. In addition, the doped magnetic atom can regulate the electronic structure of UIS to obtain the bandgap of 0 eV to enhance electron transfer. Importantly, the doped magnetic atom can be reduced to superparamagnetic metallic nanoparticles during conversion reactions, which can store abundant spin-polarized electrons to induce strong surface-capacitance effects, thus boosting ion transport and storage. Consequently, the magnetic-atom strategy endows the UIS with ultrahigh reversible capacities of 1572.1/738.5/542.3 mAh/g at 0.1C, 971.2/383.5/209.8 mAh/g at 5C after 3000 cycles, and 761.5/340.8/204.5 mAh/g at 20C as Li/Na/K-ion-battery anodes, respectively. This work verifies the efficiency of magnetic-atom strategy and paves a way for the design of other transition metal dichalcogenides for electrochemical energy storage.