One-step Chemical Vapor Deposition Research Articles

Effects of CaCO3/MgO on Fe-Co-Mo catalyst in the reprocessing of recycled polypropylene to carbon nanotubes

In recent times, there has been a global discourse on the menace of plastic waste (PW) materials on the ecosystem and ways for effective management of PW. This has resulted in the utilization of PW in the research arena in the synthesis of smart nanomaterials of high value as a sustainable solution. In this study, the catalytic-pyrolysis procedure was used to develop carbon nanotubes (CNTs) from recycled polypropylene (PP) plastic in a one-step chemical vapour deposition (CVD) reactor. The impacts of CaCO3 and MgO as supports for Fe-Co-Mo catalysts in the production of CNTs were studied. Kinetic and thermodynamic parameters were determined from the thermal profile of the catalysts to establish the nature of the reaction in CNTs synthesis. Transmission electron microscopy (TEM), energy Dispersive X-ray (EDX), selected area electron diffraction pattern, particle size distribution (PSD), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier transforms infrared (FTIR) and X-ray diffraction (XRD) were employed to characterize the catalysts and CNTs. The results obtained showed the impact of the supports on the yield, quality, and morphology of the synthesized CNTs. The CNTs yield from catalysts supported with CaCO3 and MgO were 35.12 % and 37.24% respectively. The average outer diameters of CNTs produced over the catalyst with CaCO3 and MgO supports were 36 and 29 nm respectively. The ID/IG ratio for CaCO3 and MgO supports were 0.6724 and 0.8401 respectively. The change in entropy for all phases were −274.41 and −1032.97 J/mol/K and −213.0, −318.48 and −1022.13 J/mol/K for CaCO3 and MgO supported catalyst respectively which confirmed non-spontaneous endothermic reaction. It was observed that MgO support showed better catalytic activity toward CNTs growth in terms of yield while those with CaCO3 support showed higher graphitization.

Anti-fouling underwater superoleophobic membranes based on hierarchical double networks for high efficiency oil–water separation

Oil fouling is a key problem of superwettable oil–water separation membranes because the membranes are inevitably susceptible to varying degrees of oil contamination during the ongoing separation processes, which usually results in a severe impact on separation performance. Consequently, it is a great challenge to construct oil-removal membranes with superior resistance to oil contamination. Herein, we fabricated hierarchical double networks (HDT)-modified porous glass membrane with superhydrophilicity/underwater superhydrophobicity. Firstly, a layer of silicone nanofilament (SNF) network bearing tremendous C = C double bonds were fabricated on a porous glass membrane surface by one-step chemical vapor deposition (CVD) using vinyltrichlorosilane (VTCS) as a precursor. Subsequently, the second network layer was constructed by copolymerization of the C = C double bonds on the SNF network and those in sulfobetaine-derived monomer (sulfobetaine methacrylate, SBMA), using N,N′-methylenebisacrylamide (MBA) as the cross-linkering agent. It was observed that the obtained HDT-modified glass membranes displayed excellent superhydrophilicity/underwater superhydrophobicity accompanied with superior self-cleaning performance and oil-resistance properties. As a result, the HDT-modified membranes showed high separation flux and high efficiency for both oil/water mixtures (7500 L m−2h−1, above 99.98 %) and surfactant-stabilized oil-in-water emulsions (1100 L m−2h−1, above 99.96 %) with excellent cyclability. The outstanding advantages with characteristics of excellent oil resistance and superior separation performance enable the HDT-modified glass membrane promising applications in a wide range of industries related to oil–water separations.

Two-dimensional GeS synthesized by one-step space-confined APCVD and its self-powered photodetector

Germanium sulfide (GeS) is a notable two-dimensional (2D) layered material that has gained attention across various research domains. However, challenges remain in realizing large areas of high-quality 2D GeS, despite the efforts made. Recently, we have successfully synthesized rectangular 2D single-crystal GeS flakes with a thickness of about 52 nm and a lateral length of 100 μm by one-step space-confined atmospheric pressure chemical vapor deposition (APCVD) using sulfur and germanium powders as raw materials. There is a direct relationship between the area size and the growth time. The further prepared GeS device has good photoresponsivity in the visible range. At 532 nm, it includes a responsivity of 40 mA/W, a detectivity of 8 × 108 Jones and a fast response time of 199 ms. In addition, the GeS device exhibits p-type conductive behavior and a unique self-powered effect. After prolonged storage, the GeS photodetector still exhibits good and stable photoswitching characteristics.

Band Gap Engineering of MoxW1-xS2 Alloy Monolayers with Wafer-Scale Uniformity.

Modulating the band gap of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is critical for their application in a wider spectral range. Alloying has been demonstrated as an effective method for regulating the band gap of 2D TMDC semiconductors. The fabrication of large-area 2D TMDC alloy films with centimeter-scale uniformity is fundamental to the application of integrated devices. Herein, we report a liquid-phase precursor one-step chemical vapor deposition (CVD) method for fabricating a MoxW1-xS2 alloy monolayer with a large size and an adjustable band gap. Good crystalline quality and high uniformity on a wafer scale enable the continuous adjustment of its band gap in the range of 1.8-2.0 eV. Density functional theory calculations provided a deep understanding of the Raman-active vibration modes of the MoxW1-xS2 alloy monolayer and the change in the conductivity of the alloy with photon energy. The synthesis of large-area MoxW1-xS2 alloy monolayers is a critical step toward the application of 2D layered semiconductors in practical optoelectronic devices.

Lead-free CsCu2I3 thin films prepared by one-step chemical vapor deposition method for ultraviolet photodetector

Lead-free CsCu2I3 thin films prepared by one-step chemical vapor deposition method for ultraviolet photodetector

Controllable Synthesis of Transferable Ultrathin Bi2Ge(Si)O5 Dielectric Alloys with Composition-Tunable High-κ Properties.

Two-dimensional (2D) alloys hold great promise to serve as important components of 2D transistors, since their properties allow continuous regulation by varying their compositions. However, previous studies are mainly limited to the metallic/semiconducting ones as contact/channel materials, but very few are related to the insulating dielectrics. Here, we use a facile one-step chemical vapor deposition (CVD) method to synthesize ultrathin Bi2SixGe1-xO5 dielectric alloys, whose composition is tunable over the full range of x just by changing the relative ratios of the GeO2/SiO2 precursors. Moreover, their dielectric properties are highly composition-tunable, showing a record-high dielectric constant of >40 among CVD-grown 2D insulators. The vertically grown nature of Bi2GeO5 and Bi2SixGe1-xO5 enables polymer-free transfer and subsequent clean van der Waals integration as the high-κ encapsulation layer to enhance the mobility of 2D semiconductors. Besides, the MoS2 transistors using Bi2SixGe1-xO5 alloy as gate dielectrics exhibit a large Ion/Ioff (>108), ideal subthreshold swing of ∼61 mV/decade, and a small gate hysteresis (∼5 mV). Our work not only gives very few examples on controlled CVD growth of insulating dielectric alloys but also expands the family of 2D single-crystalline high-κ dielectrics.

Compositional design of C-coated multi-elemental alloy nanoparticles for superior microwave absorption

Exploring improved electromagnetic wave absorption performance in magnetic components involves capitalizing on dual dielectric relaxation and multiple magnetic resonances, ultimately giving rise to a dielectric-magnetic matching effect. Herein, a one-step Metal-organic Chemical Vapor Deposition (MOCVD) method has been utilized to fabricate C-coated ternary and quaternary alloy nanoparticles (FeCoNi, FeCoNiCu, FeCoNiMg, and FeCoNiMn) with tunable magnetization. The results affirm that the capabilities of impedance matching and electromagnetic wave attenuation can be significantly regulated by compositing nanoparticles with different elements. The optimized C-coated FeCoNiMg nanoparticles demonstrate an exceptional capacity for electromagnetic wave attenuation, achieving a reflection loss value of −51.8 dB at a matched thickness of 2.9 mm. Moreover, the absorption bandwidth significantly broadens to 7.60 GHz (10.4 – 18.0 GHz) with a thickness of 2.7 mm. The exceptional performance in electromagnetic attenuation is credited to the dielectric loss and improved impedance matching characteristics induced by the C-coated FeCoNiMg nanoparticles. The findings from this study will be beneficial in the development of lightweight and highly effective electromagnetic wave absorbers using magnetic alloy nanoparticles.

Core-shell designed high entropy alloy CoNiFeCuV-C nanoparticles for enhanced microwave absorption

The widespread interest in high entropy alloy nanostructures stems from their potential utilization in a variety of technological and scientific fields. This study presents an innovative approach employing a one-step metal organic chemical vapor deposition to synthesize quinary high entropy alloy (CoNiFeCuV-C) core-shell nanoparticles designed for microwave absorption applications. Superior microwave absorption performance is attained through the optimization of conduction loss via thermal treatment, coupled with the interfacial polarization across the interfaces between CoNiFeCuV cores and C shell. The paraffin composite filled with an optimal 20% content of CoNiFeCuV-C core-shell nanoparticles demonstrates a minimal reflection loss (RLmin) of −51.8 dB at 13.76 GHz, achieving this performance with a thickness of 2.2 mm. Moreover, the absorbing bandwidth spans 7.44 GHz at a thickness of 2.4 mm. The outstanding accomplishments underscore the potential of utilizing CoNiFeCuV-C core-shell nanoparticles as a promising choice for lightweight, effective microwave absorber material.

Thermal transport and optical anisotropy in CVD grown large area few-layer MoS2 over an FTO substrate

Atomically thin MoS2 is a promising candidate for its integration into devices due to its strikingly unique electronic, optical, and thermal properties. Here, we report the fabrication of a few-layer MoS2 thin film over a conducting fluorine-doped tin oxide-coated glass substrate via a one-step chemical vapor deposition method. We have quantitatively analyzed the nonlinear temperature-dependent Raman shift using a physical model that includes thermal expansion and three- and four-phonon anharmonic effects, which exhibits that the main origin of nonlinearity in both the phonon modes primarily arises from the three-phonon anharmonic process. We have also measured the interfacial thermal conductance (g) and thermal conductivity (ks) of the synthesized film using the optothermal Raman spectroscopy technique. The obtained values of g and ks are ∼7.218 ± 0.023 MW m−2 K−1 and ∼40 ± 2 W m−1 K−1, respectively, suggesting the suitability of thermal dissipation in MoS2 based electronic and optoelectronic devices. Furthermore, we performed a polarization study using the angle resolved polarized Raman spectroscopy technique under non-resonance and resonance excitations to reveal the electron–photon–phonon interaction in the prepared MoS2, based on the semi-classical theory that includes deformation potential and Fröhlich interaction. Our study provides much needed experimental information about thermal conductivity and polarization response in a few-layer MoS2 grown over the conducting substrate, which is relevant for applications in low power thermoelectric and optoelectronic devices.

One-step chemical vapor deposition synthesis of Si NWs@C core/shell anodes without additional catalysts by the oxide-assisted growth mechanism for lithium-ion batteries.

Si NWs@C core/shell anodes for lithium-ion batteries were synthesized via a one-step environmental-pressure chemical vapor deposition (CVD) process utilizing nano-silicon and methane as raw materials. In this structure, the silicon nanowire core is obtained by controlling the temperature above 900 °C to catalyze the growth of nano-silicon particles coated with a natural oxide layer according to the oxide-assisted growth (OAG) mechanism, while the carbon as a protective coating shell is derived from methane cracking. In contrast to the conventional nanowire catalytic approach, this method obviates the addition of metal catalysts while ensuring a straightforward and scalable process. This Si NWs@C electrode displayed excellent electrochemical performance, exhibiting high reversible capacity (745.8 mA h g-1) and excellent cycling stability (91.3% after 100 cycles at 0.5 A g-1).

One-step synthesis of single-crystal Si3N4 nanowires-amorphous SiO2 beads nanochains by chemical vapor deposition

One-dimensional (1D) nanochain heterojunctions have attracted wide attention due to their unique optical and electrical properties, while efficient and controllable synthesis of nanochains is still difficult. Herein, Si3N4/SiO2 nanochain heterojunctions (Si3N4 single-crystal nanowires and amorphous SiO2 beads) were successfully synthesized by a one-step chemical vapor deposition (CVD) process without using any templates and catalysts. A two-stage growth mode was proposed to explain the formation mechanism of the special nanochain. We found that carbon vapor induced the formation of Si3N4 nanowires and suppressed the formation of Si2N2O. The Si3N4/SiO2 nanochains can only be synthesized within a suitable concentration range of carbon vapor. The as-synthesized fascinating nanochain exhibits an extra strong emission at about 3.02 eV, showing great promise for optoelectronic nanodevices.

Preparation of a Cu/CuO-vertical graphene microelectrode for the simultaneous determination of epinephrine and 2-aminoadenosine

The correlation between neurotransmitters, drugs, and neurotoxicity is important for disease diagnosis. Herein, a flexible Cu/CuO-vertical graphene (VG) microelectrode-based electrochemical sensor was developed for the detection of epinephrine (Ep) and 2-aminoadenosine (AAD). A Cu/CuO-VG microelectrode with a diameter of 200 μm was prepared by optimizing the Cu/CuO nanoparticle distribution and VG film thickness using one-step chemical vapor deposition. Under the synergistic electrocatalytic effect of Cu/CuO nanoparticles and graphene nanosheets, as well as the coordination of the VG film for bulk ion adsorption and long-range electron transport, the optimized Cu/CuO-VG microelectrode responded sensitively to Ep and AAD. Quantitative detection of Ep and AAD was achieved over a wide pH range of 5.0–9.0 and concentrations of 0.5–100 μM, with limits of detection reaching 0.13–0.18 and 0.13–0.19 μM, respectively. The microelectrode exhibited high selectivity, repeatability, and long-term stability for the detection of Ep and AAD. This method was successfully applied for the simultaneous detection of Ep and AAD in human blood and urine samples, with excellent recoveries of 92.9%–109.3% and 90.6%–107.6%, respectively.

Controllable Synthesis of 2H-1T' Mox Re(1- x ) S2 Lateral Heterostructures and Their Tunable Optoelectronic Properties.

Constructing heterostructures and doping are valid ways to improve the optoelectronic properties of transition metal dichalcogenides (TMDs) and optimize the performance of TMDs-based photodetectors. Compared with transfer techniques, chemical vapor deposition (CVD) has higher efficiency in preparing heterostructures. As for the one-step CVD growth of heterostructures, cross-contamination between the two materials may occur during the growth process, which may provide the possibility of one-step simultaneous realization of controllable doping and formation of alloy-based heterostructures by finely tuning the growth dynamics. Here, 2H-1T' Mox Re(1- x ) S2 alloy-to-alloy lateral heterostructures are synthesized through this one-step CVD growth method, utilizing the cross-contamination and different growth temperatures of the two alloys. Due to the doping of a small amount of Re atoms in 2H MoS2 , 2H Mox Re(1- x ) S2 has a high response rejection ratio in the solar-blind ultraviolet (SBUV) region and exhibits a positive photoconductive (PPC) effect. While the 1T' Mox Re(1- x ) S2 formed by heavily doping Mo atoms into 1T' ReS2 will produce a negative photoconductivity (NPC) effect under ultraviolet (UV) laser irradiation. The optoelectronic property of 2H-1T' Mox Re(1- x ) S2 -based heterostructures can be modulated by gate voltage. These findings are expected to expand the functionality of traditional optoelectronic devices and have potential applications in optoelectronic logic devices. This article is protected by copyright. All rights reserved.

Room-Temperature Ferromagnetism in Layered Mn-Substituted MoS2

Intrinsically two-dimensional (2D) ferromagnetic materials normally exhibit a low transition temperature, above which they would lose their magnetic properties. This makes it difficult to develop them for practical applications. Substituting transition metal atoms into 2D systems provides a straightforward way for achieving room-temperature ferromagnetism. Here, we propose a one-step chemical vapor deposition method to prepare Mn-substituted MoS2 monolayers, which exhibit robust magnetism, as confirmed by a combined study of physical property measurement systems and magneto-optical measurements. High-resolution transmission electron microscopy, Raman signals, and X-ray photoelectron spectroscopy analysis have all shown that the manganese atoms in MoS2 act as a substitute for the molybdenum sites. The microscopic origin of magnetism in Mn-MoS2 is further revealed on the basis of first-principles calculations, which corroborate the experimental results obtained. Our study demonstrates a simple route to creating 2D ferroelectric materials with broad prospects in spintronic devices and next-generation memory components.

Synergistic degradation of tetracycline from Mo2C/MoOx films mediated peroxymonosulfate activation and visible-light triggered photocatalysis

Advanced oxidation processes (AOPs) based on photocatalysis and peroxymonosulfate (PMS) activation have shown potential in antibiotics degradation by generating series of reactive oxygen species (ROS). However, construction of AOP materials with easy preparation and high reusability is still a challenge. Herein, we prepared a Mo2C/MoOx thin film through one-step chemical vapor deposition (CVD), and this film could synergistically promote PMS activation and visible-light photocatalysis due to the redox cycles of multiple Mo valence states and staggered bandgap structures of Mo-based components in the film. The generated oxygen species (mainly 1O2 radical, accompanying by other ones involving OH, SO4− and O2− radicals) could efficiently degrade the uneasily degradable antibiotics, tetracycline (TC), with a removal efficiency of 91.7 % within 60 min. Meanwhile, the film could maintain the TC degradation capability for at least 10 cycles, exhibiting promising reusability. The work could provide feasible approaches to develop easily prepared AOP thin film materials for antibiotic pollutant degradation.

Blue perovskite single-mode lasing in a rubidium lead bromide microcubic cavity

Lead halide perovskite microlasers have shown impressive performance in the green and red wavebands. However, there has been limited progress in achieving blue-emitting perovskite microlasers. Here, blue-emitting perovskite-phase rubidium lead bromide (RbPbBr3) microcubes were successfully prepared by using a one-step chemical vapor deposition process, which can be utilized to construct optically pumped whispering gallery mode microlasers. By regulating the growth temperature, we found that a high-temperature environment can facilitate the formation of the perovskite phase and microcubic morphology of RbPbBr3. Notably, blue single-mode lasing in a RbPbBr3 microcubic cavity with a narrow linewidth of 0.21 nm and a high-quality factor (∼2200) was achieved. The obtained lasing from RbPbBr3 microlasers also exhibited an excellent polarization state factor (∼0.77). By modulating the mixed-monovalent cation composition, the wavelength of the microlaser could be tuned from green (536 nm) to pure blue (468 nm). Additionally, the heat stability of the mix-cation perovskite was better than that of conventional CsPbBr3. The stable and high-performance blue single-mode microlasers may thus facilitate the application of perovskite lasers in blue laser fields.

Synthesis of non-planar graphene-wrapped copper nanoparticles with iron(III) oxide decoration for high performance supercapacitors

The performance of supercapacitors strongly depends on the electrochemical characterizations of electrode materials. Herein, a composite material consisted of iron(III) oxide (Fe2O3) and multilayer graphene-wrapped copper nanoparticles (Fe2O3/MLG-Cu NPs) is fabricated on a flexible carbon cloth (CC) substrate via two-step synthesis process for supercapacitor application. Where, MLG-Cu NPs are prepared on CC by one-step chemical vapor deposition synthesis approach; thereafter, the Fe2O3 is further deposited on the MLG-Cu NPs/CC via successive ionic layer adsorption and reaction method. The related material characterizations of Fe2O3/MLG-Cu NPs are well investigated by scanning electron microscopic, high resolution transmission electron microscopy), Raman spectrometer and X-ray photoelectron spectroscopy; the electrochemical behaviors of the pertinent electrodes are studied by cyclic voltammogram, galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy measurements. The flexible electrode with Fe2O3/MLG-Cu NPs composites exhibits the best specific capacitance of 1092.6 mF cm−2 at 1 A g−1, which is much higher than those of electrodes with Fe2O3 (863.7 mF cm−2), MLG-Cu NPs (257.4 mF cm−2), multilayer graphene hollow balls (MLGHBs, 14.4 mF cm−2) and Fe2O3/MLGHBs (287.2 mF cm−2). Fe2O3/MLG-Cu NPs electrode also exhibits an excellent GCD durability, and its capacitance remains 88% of its original value after 5000 cycles of the GCD process. Finally, a supercapacitor system consisted of four Fe2O3/MLG-Cu NPs/CC electrodes can efficiently power various light-emitting diodes (i.e. red, yellow, green, and blue lights), demonstrating the practical application of Fe2O3/MLG-Cu NPs/CC electrode.

Versatile graphene-alumina nanofibers for microwave absorption and EMI shielding

Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer structure with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 ± 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 °C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the obtained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of −25 dB at ∼11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption characteristics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.

Continuous Growth of Carbon Nanotubes on Carbon Fiber Surface by Chemical Vapor Deposition Catalyzed by Cobalt with Thiourea

The continuous preparation of carbon nanotubes (CNTs)/carbon fiber (CF) multiscale reinforcements was realized via one-step chemical vapor deposition (CVD) method. In order to alleviate the damage of CF caused by catalyst etching at high temperature, catalytic promoter was adopted to improve the activity of the catalyst, thus reducing the CVD temperature. By adjusting the cobalt-based catalyst system, the effects of thiourea concentration on the morphology, microstructure and tensile strength of CNTs/CF samples were systematically investigated. It was found that the length and quantity of CNTs were added as the thiourea concentration increased, and the graphitization degree of the sample increased at first because of the well-grown CNTs, and then decreased due to the formation of amorphous carbon. Moreover, the tensile strength of CNTs/CF multiscale reinforcements was improved, which derived from the enhanced defect repair function of synthesized CNTs. Remarkably, CNTs/CF-0.02 exhibited a high single-filament tensile strength value (up to 4.51 GPa), which was about 6.6% higher than that of Desized cf Besides, the crystal structure and composition of reduced catalysts were analyzed, confirming the successful sulfur doping into cobalt particles. Therefore, the work offers a facile, economical, and efficient route for manufacturing CNTs/CF multi-scale reinforcements at comparatively low temperature.

In-plane anisotropy in van der Waals epitaxial MoS2 on MoO2(010)

Transition metal dichalcogenide based 2D/2D or 2D/3D van der Waals heterostructures exhibit superior properties for high-performance electronics, tunneling transistors, and catalysts. Here, we report on the fabrication of high quality 2D/3D MoS2/MoO2 heterostructures with an atomic clean interface by one-step chemical vapor deposition. Optical microscopy, atomic force microscopy, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy measurements reveal the high-quality of as-grown samples and the specific epitaxial relationship between MoS2 and MoO2: MoS2[1¯1¯20]//MoO2[001] and MoS2[1¯100]//MoO2[201]. Photoluminescence and Kelvin probe force microscopy measurements combined with density functional theory calculations confirm the interfacial charge transfer from MoS2 to the underlying MoO2. Furthermore, MoO2 induced in-plane anisotropy in MoS2 was revealed using angle-resolved polarized Raman and photoluminescence spectroscopy with anisotropic ratios of 1.27 (Raman) and 1.29 (photoluminescence), respectively, which is most possibly attributed to anisotropic interfacial charge interactions. Our findings provide an excellent platform for the investigation on interfacial effects. Moreover, the in-plane anisotropy in MoS2 induced by MoO2 has expanded the application of isotropic MoS2 in the polarization-dependent fields.