Simple Chemical Vapor Deposition Research Articles

Red Phosphorus Nanodot-Decorated Polymeric Carbon Nitride Nanotubes for Visible-Light-Driven Photocatalytic Bacterial Inactivation

Pathogenic microorganisms related to infectious diseases severely threaten human health, and visible-light-driven (VLD) photocatalysis is a promising strategy for mitigating microbial-induced health crises. In this work, a superior and effective VLD photocatalyst comprising a red phosphorus nanodot-modified one-dimensional carbon nitride nanotube (RP-CN) heterostructure was synthesized with a simple chemical vapor deposition method and used for bacterial inactivation. The optimized RP (40)-CN rapidly and completely destroyed Escherichia coli and Staphylococcus aureus (107 CFU mL–1) within 25 and 30 min under irradiation with a white LED, respectively. The efficient photocatalytic activity was attributed to the fact that the matching work function in the CN-RP heterojunction promotes the charge migration/separation that occurs at the CN and RP interface and the broad absorption spectra by RP loading. Additional unpaired photoelectrons reacted with water to generate •O2– radicals and H2O2 for efficient bacterial cell inactivation. The present study highlights the design of nanostructured photocatalysts with wide spectral responses for efficient energy conversion and wide antibacterial scope.

Coir fiber-reinforced PVA aerogels for oil adsorption

Mechanically and thermally stable hydrophobic aerogels were prepared by simple boric acid condensation, freeze-drying, and chemical vapor deposition for the treatment of oily wastewater.

Heterogeneous Interface-Derived Engineered Electronic Structure of SiO with Enhanced Lithium Storage

Constructing a heterogenous structure has always been one of the effective strategies to improve the electrochemical performance of anode materials for lithium-ion batteries (LIBs). As a semiconductor material, wide band gaps and high charge transfer resistance of SiO greatly affect the electron conduction and ion diffusion during lithium storage. Unfortunately, few studies have focused on SiO-based heterogenous interface engineering to improve its battery performance. In this work, a simple chemical vapor deposition strategy is utilized to fabricate Se-coated m-SiO (m-SiO@Se) as an anode for LIBs. Combining first-principles calculations and experimental results, it is revealed that the heterogenous interface formed between SiO and Se is highly functional in optimizing the energy band structure and promoting the Li+ diffusion kinetics, which boost electron and ion conduction of SiO with enhanced lithium storage. This research provides a reliable direction and theoretical support for the future development of interface engineering in electrochemical energy storage.

Achieving Short‐Wavelength Phase‐Matching Second Harmonic Generation in Boron‐Rich Borosulfate with Planar [BO3] Units

AbstractUltraviolet (UV) nonlinear optical (NLO) crystals which can produce short‐wavelength lasers via a direct second harmonic generation (SHG) process are of great importance in modern laser technology. Currently, the exploration of UV NLO crystals in borosulfates is nearly stagnant since the non‐phase matching (PM) property lies on the small birefringence induced by the intrinsically small optical anisotropy of the tetrahedral groups. Herein, for the first time, the planar [BO3] units were introduced into borosulfates leading to a boron‐rich borosulfate (NH4)2B4SO10 with unprecedented [B4SO10]∞ layers and evidently enhanced birefringence. To the best of our knowledge, it achieves the shortest SHG PM wavelength of 252 nm in all reported borosulfates with deep UV cutoff edge (184 nm), large SHG response (1.1×KDP at 1064 nm and 0.15×β‐BBO at 532 nm) and large birefringence (0.053 at 1064 nm) and is easy to grow single crystals via simple chemical vapor deposition method. These results confirm the feasibility of utilizing planar [BO3] units to optimize birefringence of borosulfates, and also open up broad prospects for UV NLO crystals in boron‐rich borosulfates.

Achieving Short-Wavelength Phase-Matching Second Harmonic Generation in Boron-Rich Borosulfate with Planar [BO3 ] Units.

Ultraviolet (UV) nonlinear optical (NLO) crystals which can produce short-wavelength lasers via a direct second harmonic generation (SHG) process are of great importance in modern laser technology. Currently, the exploration of UV NLO crystals in borosulfates is nearly stagnant since the non-phase matching (PM) property lies on the small birefringence induced by the intrinsically small optical anisotropy of the tetrahedral groups. Herein, for the first time, the planar [BO3 ] units were introduced into borosulfates leading to a boron-rich borosulfate (NH4 )2 B4 SO10 with unprecedented [B4 SO10 ]∞ layers and evidently enhanced birefringence. To the best of our knowledge, it achieves the shortest SHG PM wavelength of 252 nm in all reported borosulfates with deep UV cutoff edge (184 nm), large SHG response (1.1×KDP at 1064 nm and 0.15×β-BBO at 532 nm) and large birefringence (0.053 at 1064 nm) and is easy to grow single crystals via simple chemical vapor deposition method. These results confirm the feasibility of utilizing planar [BO3 ] units to optimize birefringence of borosulfates, and also open up broad prospects for UV NLO crystals in boron-rich borosulfates.

CVD Diamond Coated Tungsten Carbide (WC) Tool Inserts

In this paper a self-developed polycrystalline diamond coating was done on tungsten carbide (WC) tool insets by using simple thermal chemical vapor deposition technique. The growth of these diamond films has been carried out at ~900 ºC temperature. The as-grown polycrystalline diamond films on the surface of tungsten carbide tool inserts have been characterized using Raman spectrometer and scanning electron microscope (SEM). The morphological studies reveal that the as-grown diamond films are of high crystalline quality. The as-grown diamond films possess compressive stress. The micro-hardness indentation test of the as-grown diamond films on WC tool inserts and bare have also been done and it has been found that the Vicker’s hardness of the as-grown diamond WC tool inserts is found to be 1423.32 HV which is 29% better than the un-coated tools.

Adsorbent/catalyst bi-functional Fe-ZSM-5 prepared by a simple CVD process for exhaust gas treatment

In exhaust gas purification systems, the use of an inorganic porous ‘pre-filter’ in combination with a conventional catalytic converter with Pt-group metal nanoparticles is considered to be effective for reducing cold-start emissions. Organic compounds that are difficult to catalytically oxidize at low temperatures can be captured to this ‘pre-filter’ until the Pt-group catalyst has reached its operating temperature. In the present work, a simple chemical vapor deposition (CVD) method was applied to load catalytically active Fe species (Fe(III) ions, Fe(III)xOy clusters, and Fe2O3 nanoparticles) on a commercial MFI type H-ZSM-5 zeolite. The CVD could maintain the adsorption performance of H-ZSM-5 zeolite, but more importantly enhance the catalytic oxidation activity of acetaldehyde. The adsorbed acetaldehyde was oxidized with high efficiency on Fe ion & oxide loaded H-ZSM-5 (Fe-ZSM-5), which eventually can reduce cold-start emissions and improve the catalytic conversion efficiency of exhaust purification systems. Furthermore, based on in-situ DRIFTS analyses, surface poisoning of H-ZSM-5 that was induced by accumulation of coke could be eliminated by CVD of Fe ion & oxide.

Hydrophobic and self-recoverable cellulose nanofibrils/N-alkylated chitosan/poly(vinyl alcohol) sponge for selective and versatile oil/water separation

A highly hydrophobic and self-recoverable sponge was prepared with cellulose nanofibrils (CNFs), N-alkylated chitosan (NCS), and poly (vinyl alcohol) (PVA), which was then endowed with hydrophobic properties via simple thermal chemical vapor deposition (CVD). The three-dimensional (3D) interconnected microstructure of the prepared CNF/NCS/PVA sponge was found to have 96% porosity, ultra-low density (16.61–50.91 mg/cm3) and high hydrophobicity (water contact angle of 147°), which can absorb various organic solvents with an absorption capacity of 19.05–51.08 times of its original weight. Besides, the sponge could bear 80% strain and be cyclically compressed 50 times under the strain of 50%. The sponge can effectively separate oil/water mixtures and water-in-oil emulsions with high separation efficiency and fluxes. Moreover, the sponge could keep its good stability in various acidic, saline and mechanical abrasion conditions. The green preparation and good separation efficiency suggest a potential application of recyclable and versatile CNF/NCS/PVA sponges in oil/water separation.

Core-shell structured nanocomposites formed by silicon coated carbon nanotubes with anti-oxidation and electromagnetic wave absorption

The silicon coated Carbon nanotubes (CNTs) nanocomposite (CNTs@Si) with a shell structure was successfully synthesized by a simple chemical vapor deposition (CVD) method. In this work, the CNTs@Si is not only introduced as a structural material providing oxidation performance, but also as an extremely effective electromagnetic wave (EMW) absorption nanocomposite. Dielectric characteristics EMW absorption properties within the frequency range of 2–18 GHz of CNTs@Si were studied, and the oxidation resistance of CNTs@Si was characterized. Due to the dense space conductive network formed by CNTs, the EMW absorbing properties of CNTs@Si nanocomposite features excellent electromagnetic wave absorption capacity at a filling amount of 1%. The maximum reflection loss (RL) reaches −61.57 dB at the thickness of 1.8 mm, and a wide effective absorption bandwidth (EAB, RL < −10 dB) of 2.88 GHz is achieved. The obtained CNTs@Si core-shell nanocomposites exhibit excellent antioxidant performance and absorbing performance due to silicon bridging. Efficient electromagnetic wave absorption and excellent oxidation resistance of CNTs@Si can be regarded as a brand-new competitive candidate for EMW absorption materials in harsh environment.

Chemical Vapor Deposition of Highly Conjugated, Transparent Boron Carbon Nitride Thin Films.

Ternary materials made up only from the lightweight elements boron, carbon, and nitrogen are very attractive due to their tunable properties that can be obtained by changing the relative elemental composition. However, most of the times, the synthesis requires to use up to three different precursor and very high temperatures for the synthesis. Moreover, the low reciprocal solubility of boron nitride and graphene often leads to BN‐C composite materials due to phase segregation. Herein, an innovative method is presented to prepare BCN thin films by chemical vapor deposition from a single source precursor, melamine diborate. The deposition occurs homogenously at relatively low temperatures generating very high degree of sp2 conjugation. The as‐prepared thin films possess high transparency and refractive index values in the visible range that are of interest for reflective mirrors and lenses. Furthermore, they are wide‐bandgap semiconductor with very positive valence band, making these materials very stable against oxidation of interest as protective coating and charge transport layer for solar cells. The simple chemical vapor deposition method that relies on commonly available and low‐hazard precursor can open the way for application of BCN thin films in optics, optoelectronics, and beyond.

Construction of MnO-skeleton cross-linked by carbon nanotubes networks for efficient microwave absorption

Constructing nanostructures with abundant heterogeneous interfaces is highly efficient in improving microwave absorbing properties. Herein, a simple chemical vapor deposition (CVD) route for the in-situ growth of carbon nanotubes (CNTs) in the voids of MnO particles clusters skeleton has been developed to fabricate MnO/CNTs heterostructure composites with tunable dielectric properties. The optimized MnO/CNTs-1 composite with 45 wt% CNTs content exhibits comprehensive enhanced microwave absorption performance, with the minimum reflection loss (RLmin) can reach −50.6 dB (20 wt% in paraffin composite). The effective absorption bandwidth (RL < −10 dB, 90% absorption) up to 13.7 GHz was achieved by adjusting the thickness from 2 to 5 mm, covering the entire C, X and Ku bands. Herein, the MnO particles and CNTs networks act as skeleton and crosslinker, respectively. The MnO particles attached throughout the CNTs networks can provide multiple interfacial polarization and multiple scattering/reflection. Our works provide new insights for the facile designing lightweight nanostructure to enhance the microwave absorption performance of the CNTs.

Verification of electrolyte decomposition in lithium-ion batteries: Based on the unique bowling-like Sn@C/EG-S composite

The practical application of alloy materials has been limited due to the huge volume expansion during the lithiation/delithiation process. Designing reasonable structure is an effective method to alleviate volume expansion. Therefore, various structures are synthesized, for example, 1D nanorods, 2D nanosheets, 3D nanospheres, and so on. However, the synthesis of special structures usually has to go through a complex process and expensive, which is not conducive to large-scale application. Herein, the S-doped expanded graphite, Sn and carbon composite anode material with bowling-like structure for lithium ion battery is synthesized by a simple chemical vapor deposition (CVD) method. The unique cavity provides usable space for the volume expansion. The Sn particles are avoided contacting with the electrolyte directly under the protection of the carbon shell so that the side reactions are suppressed. Expanded graphite also improves the conductivity and provides secondary protection for the agglomeration of crushed Sn particles. Benefiting from the unique structure, the sample exhibits excellent electrochemical performance. A high specific capacity of 733 mAh g−1 is remained after 200 cycles at 500 mA g−1. Especially, at a high current density of 5000 mA g−1, the specific capacity of 428 mAh g−1 is obtained after 400 cycles. In addition, the contribution of electrolyte decomposition was also analysed by accurately controlling the volume of electrolyte. With the volume increasing of electrolyte to a certain extent, the trend of capacity upward is more distinct until the electrolyte is ran out. The phenomenon is intuitively verified that the electrolyte is decomposed continually under the condition of excessive, which result in the capacity increment. Therefore, the influence of electrolyte decomposition on cycle performance is verified quantitatively.

Unraveling the synergistic effect of defects and interfacial electronic structure modulation of pealike CoFe@Fe3N to achieve superior oxygen reduction performance

Engineering of defect and interface are two effective strategies to regulate the electronic structure and electrocatalytic activities. However, integrated the synergistic effect of carbon/oxygen defects and interfacial effects into spinel derivatives to dramatically improve the electrocatalytic property has not been studied up till now. Herein, a CoFe@Fe3N hybrid embedded into N-doped carbon nanotube has been prepared by heat-treatment of CoFe2O4 using a simple chemical vapor deposition method. Impressively, the as-prepared CoFe@Fe3N-CNT catalyst manifests a prominent stability and catalytic performance towards the oxygen reduction reaction (ORR), as demonstrated by an ultrahigh half-wave potential (E1/2) of 0.936 V, which is the best ORR spinel-based catalysts. Furthermore, it was assembled into a rechargeable ZAB, which showed a high-power density of 173.6 mW cm−2 and an open circuit voltage of 1.534 V. The enhanced electrochemical performances are primarily due to the synergistic effect of carbon-oxygen double defects and interfacial electronic structure modulation.

In Situ Growth of GeS Nanowires with Sulfur-Rich Shell for Featured Negative Photoconductivity.

The negative photoconductivity (NPC) effect originating from the surface shell layer has been considered as an efficient approach to improve the performance of optoelectronic nanodevices. However, a scientific design and precise growth of NPC-effect-caused shell during nanowire (NW) growth process for achieving high-performance photodetectors are still lacking. In this work, GeS NWs with a controlled sulfur-rich shell, diameter, and length are successfully prepared by a simple chemical vapor deposition method. As checked by transmission electron microscopy, the thickness of the sulfur-rich shell ranges from 10.5 ± 1.5 to 13.4 ± 2.5 nm by controlling the NW growth time. The composition of the sulfur-rich shell is studied by X-ray photoelectron spectroscopy, showing the decrease of S in the GeSx shell from the surface to core. When configured into the well-known phototransistor, a featured NPC effect is observed, benefiting the high-performance photodetector with high responsivity of 105 A·W-1 and detectivity of 1012 Jones for λ = 405 nm with ultralow intensity of 0.04 mW·cm-2. However, the thicker-shell NW phototransistor shows an unstable photodetector behavior with smaller negative photocurrent because of more hole-trapping states in the thicker shell. All results suggest a careful design and controlled growth of an NPC-effect-caused shell for future optoelectronic applications.

Spontaneous Folding Growth of Graphene on h-BN.

Graphene has been the subject of much research, with structural engineering frequently used to harness its various properties. In particular, the concepts of graphene origami and kirigami have inspired the design of quasi-three-dimensional graphene structures, which possess intriguing mechanical, electronic, and optical properties. However, accurate controlling the folding process remains a big challenge. Here, we report the discovery of spontaneous folding growth of graphene on the h-BN substrate via adopting a simple chemical vapor deposition method. Folded edges are formed when two stacked graphene layers share a joint edge at a growth temperature up to 1300 °C. Using first-principles density functional theory calculations, the bilayer graphene with folded edges is demonstrated to be more stable than that with open edges. Utilizing this novel growth mode, hexagram bilayer graphene containing entirely sealed edges is eventually realized. Our findings provide a route for designing graphene devices with a new folding dimension.

S/Mo ratio and petal size controlled MoS2 nanoflowers with low temperature metal organic chemical vapor deposition and their application in solar cells

Vertically aligned two-dimensional (2D) molybdenum disulfide nanoflowers (MoS2 NFs) have drawn considerable attention as a novel functional material with potential for next-generation applications owing to their inherently distinctive structure and extraordinary properties. We report a simple metal organic chemical vapor deposition (MOCVD) method that can grow high crystal quality, large-scale and highly homogeneous MoS2 NFs through precisely controlling the partial pressure ratio of H2S reaction gas, P SR, to Mo(CO)6 precursor, P MoP, at a substrate temperature of 250 °C. We investigate microscopically and spectroscopically that the S/Mo ratio, optical properties and orientation of the grown MoS2 NFs can be controlled by adjusting the partial pressure ratio, P SR/P MoP. It is also shown that the low temperature MOCVD (LT-MOCVD) growth method can regulate the petal size of MoS2 NFs through the growth time, thereby controlling photoluminescence intensity. More importantly, the MoS2 NFs/GaAs heterojunction flexible solar cell exhibiting a power conversion efficiency of ∼1.3% under air mass 1.5 G illumination demonstrates the utility of the LT-MOCVD method that enables the direct growth of MoS2 NFs on the flexible devices. Our work can pave the way for practical, easy-to-fabricate 2D materials integrated flexible devices in optical and photonic applications.

Lateral growth of indium(III) selenide nanoribbons and their optoelectronic performance for weak signal detection

Two-dimensional indium(III) selenide (In2Se3) is attractive because of its multiple phases and the unique properties associated with each phase, which make it promising for future flexible multifunctional applications. Here, the direct growth of lateral β’-phase In2Se3 nanoribbons using a simple atmospheric chemical vapor deposition method is demonstrated. Field-effect transistors based on the β’-phase In2Se3 nanoribbons exhibited n-type semiconducting behavior with an on/off ratio of about 104. The In2Se3 nanoribbons possessed a high external quantum efficiency (8.1 × 103%) and ultrahigh specific detectivity (7 × 1012 Jones). In addition, the In2Se3 nanoribbons were sensitive to low illumination intensity (down to 1.5 μW/cm2). This work suggests that In2Se3 nanoribbons can potentially be used in optoelectronic devices for weak signal detection.

Synthesis, thermal stability, magnetic properties, and microwave absorption applications of CoNi-C core-shell nanoparticles with tunable Co/Ni molar ratio

Magnetic alloy-C core-shell nanoparticles with tunable elemental components are highly expected for their controllable magnetic, catalytic, and electromagnetic properties, and high air stability. Here we present a simple one-step metal organic chemical vapor deposition for the synthesis of CoNi-C core-shell nanoparticles with tunable Co/Ni molar ratio. The as-synthesized nanoparticles have core sizes of 5–50 nm, shell thicknesses of ~5 nm, and tunable Co/Ni molar ratio determined by the molar ratio of Co(acac)3/Ni(acac)2 used in the precursor. The core-shell nanoparticles are very stable in ambient atmosphere at the temperature below 200 °C, and exhibit a slight oxidation in the temperature range of 200–400 °C. The core-shell nanoparticles with Co/Ni molar ratios of 1.27:1, 0.64:1, and 0.30:1 exhibit saturation magnetization values of 41, 31, and 24 emu/g, and coercivity values of 483, 346, and 362 Oe, respectively. It is demonstrated that the microwave absorption parameters of the as-synthesized nanoparticles can be tuned by the Co/Ni molar ratio, which provides a practical strategy to regulate the microwave absorption properties of nanostructured absorbers.

High-capacity CVD-grown Ge nanowire anodes for lithium-ion batteries: simple chemical etching approach for oxide removal

We demonstrated high-performance Ge nanowire (NWs) anodes for rechargeable lithium-ion batteries with high-capacity and high coulombic efficiency. The NWs were prepared using a simple chemical vapor deposition (CVD) method, which is favorable for the mass production of electrodes. The unstable oxides of Ge deteriorate the electrochemical characteristics of the batteries made from Ge-based anodes. To resolve the issue of the oxides and enhance the electrochemical performance, the oxides of the NWs were removed efficiently by a simple wet chemical etching method via a 10% HCl (aq) treatment. Transmission electron microscopy and energy-dispersive X-ray spectroscopy elemental mapping verified the removal of oxides. Charge and discharge capacity of the pristine NWs were 833.803 mAhg−1 and 650.63 mAhg−1 at first cycle. In comparison, the charge and discharge capacities after oxide removal were 1064.1 mAhg−1 and 905.6 mAhg−1 under the same conditions. The discharge capacity and coulombic efficiency of the oxide-removed NWs were 39.2% and 7.1% higher than those achieved without oxide removal. The coulombic efficiency of the oxide-removed NWs was higher than that of the pristine NWs (7.1% increase). The NWs were stable over 25 cycles at different C-rates. This approach provides an efficient and practical way to resolve the oxide issue of Ge-based anodes, and high-performance lithium-ion batteries were demonstrated using the oxide-removed NW anodes. This study presents an advance towards the realization of the commercial batteries based on Ge as an active electrode material.

Growth of GaN on monolayer hexagonal boron nitride by chemical vapor deposition for ultraviolet photodetectors

Chemical vapor deposition (CVD) technology is a simple and flexible method used to prepare high-quality crystalline materials. Traditional CVD technology, based on pre-deposited thin catalyst metal, usually produces nanostructures instead of continuous films. In this work, a continuous GaN film on a monolayer boron nitride (h-BN) insertion layer is demonstrated using CVD technology. The experimental results and theoretical calculations indicate that abundant GaN nanocrystallites are firstly formed at the edges or grain boundaries of the monolayer h-BN by quasi-van der Waals epitaxy. Then, the vapor-solid mechanism will control further growth of the GaN nanocrystallites, causing them to merge into a continuous GaN film. Meanwhile, the CVD-grown GaN ultraviolet detector exhibits a relatively high responsivity with a value of 0.57 A W−1 at 2 V. In this paper, a simple low-cost CVD method is proposed for preparing continuous films on two-dimensional materials for electronic and optoelectronic devices.