Ethanol Chemical Vapor Deposition Research Articles

Nanocrystalline graphene for ultrasensitive surface-enhanced Raman spectroscopy

The development of ultrasensitive and biocompatible Surface-Enhanced Raman Spectroscopy (SERS) substrates, able to provide uniform and reproducible signals, has become a focus of study in the last decade. Graphene, with his advantageous properties, such as photoluminescence quenching of fluorescent dyes, chemical inertness and biocompatibility, allows to overcome many important limitations of conventional metal SERS substrates. In this work, we develop ultrasensitive graphene substrates by ethanol Chemical Vapor Deposition (CVD). Large-area thin films composed of nanosized sp2 grains surrounded by disordered regions are obtained by lowering the growth temperature from the standard 1070 °C to 700 °C. Our substrates are able to detect trace amounts of molecules, down to 6·10−11 M, which is the lowest concentration that has been achieved in Graphene-Enhanced Raman Spectroscopy (GERS) with rhodamine 6G (R6G) as probe molecule. This outstanding result is attributable to two main features: i) more efficient charge transfer due to the energy level matching between R6G and the nanocrystalline graphene film; ii) large number of grain boundaries acting as “trapping sites” for the molecules.

Scanning probe analysis of twisted graphene grown on a graphene/silicon carbide template

Overlayer growth of graphene on an epitaxial graphene/silicon carbide (SiC) as a solid template by ethanol chemical vapor deposition is performed over a wide growth temperature range from 900 °C to 1450 °C. Structural analysis using atomic force and scanning tunneling microscopies reveal that graphene islands grown at 1300 °C form hexagonal twisted bilayer graphene as a single crystal. When the growth temperature exceeds 1400 °C, the grown graphene islands show a circular shape. Moreover, moiré patterns with different periods are observed in a single graphene island. This means that the graphene islands grown at high temperature are composed of several graphene domains with different twist angles. From these results, we conclude that graphene overlayer growth on the epitaxial graphene/SiC solid at 1300 °C effectively synthesizes the twisted few-layer graphene with a high crystallinity.

Iron induced porosity of the templated carbon for enhancement of electrochemical capacitance

Porous carbon (PC) materials with a large specific surface area and high volume of mesopores were produced using iron-doped calcium tartrate (CaTr) as a template precursor and ethanol as a carbon source. The iron doping concentration was varied from 0.2 to 1.6 at%. Template precursor was decomposed in argon at 800 °C, the formed template nanoparticles were immediately used for chemical vapor deposition (CVD) of ethanol, and after the synthesis, they were removed by HCl treatment. It was shown that the template consisted of CaO nanoparticles 5–20 nm in size with oxidized carbon layers on the surface. The incorporation of iron into CaTr promoted graphitization of the carbon layers and led to formation of iron oxide nanoparticles 3–4 nm in size. These nanoparticles served as a replica for small mesopores in the graphitic layers obtained in the ethanol CVD process. PC materials grown on the templates with an iron doping 0.2–0.4 at% were enriched with small mesopores, and due to this, they had a surface area of 907–931 m2 g−1 and pore volume of 3.3 cm3 g−1. These materials showed the highest specific capacitances of 280–230 F g−1 at 2 mV s−1 in 1 M H2SO4 electrolyte and a good rate capability.

Graphene-like carbon nanosheets grown over alkali-earth metal oxides: Effects of chemical composition and physico-chemical properties

Catalytic effects of alkali-earth metal oxides (MgO, CaO, SrO and BaO) on the growth of graphene-like carbon nanosheets via catalytic chemical vapor deposition of ethanol at 950 °C under atmospheric pressure were investigated. Both commercially available alkali-earth metal oxides as well as three synthetic MgO catalysts were used in this study. Chemical composition and physico-chemical properties, such as morphology, crystal surface geometry and porosity of catalysts were demonstrated to influence the yield and quality of graphene-like carbon nanosheets. Among investigated oxides, the MgO, CaO and SrO displayed different catalytic ability towards the growth of graphene-like carbon nanosheets determined by chemical compositions. The effect of physico-chemical properties was suggested by different properties of carbon products over synthetic MgO. MgO catalysts synthesized with ammonia produced the lowest defect level (ID/IG = 0.26) while MgO synthesized with urea and ethylene glycol produced the highest yield (12.1% per catalyst mass) of graphene-like carbon nanosheets compared to the other catalysts. The lower defect level and higher graphitization degree were attributed to well-defined morphology with uniform oxide crystal particle size and improvement of crystal orientation along (200) lattice plane in the catalyst. The higher yield was related to the higher porosity of catalysts.

Pit formation with graphene growth on copper foils by ethanol chemical vapor deposition

Long-time chemical vapor deposition (CVD) with ethanol was carried out for the growth of graphene films on copper (Cu) foils. Multilayer graphene like graphite is formed on Cu surface. Interestingly, some pits with unique shapes are produced at defective parts such as nucleation sites and grain boundaries of grown multilayer graphene, and single-layer graphene is formed only on the pit bottom with the square shape. The pits are produced by the oxidation and reduction of Cu surface due to the long-time reaction with ethanol and vacuum process in the CVD. The square shape of the pit bottom is related to the symmetry of (100) crystallographic plane of Cu underneath the oxidation layer. The clean (100) surface of Cu appears on the pit bottom after the reduction, and single-layer graphene is formed on the clean surface. The pit formation accompanied by graphene growth occurs in the ethanol CVD process. Such synthesis process by the ethanol CVD can provide an insight for the growth control and patterning for graphene.

Diameter-Selective Synthesis of Single-Walled Carbon Nanotubes on Supported Cobalt Catalysts

Supported Co catalysts were prepared by impregnating the support (MgO, SiO2 and Al2O[Formula: see text] with Co(acac)2 solution, and diameter-selective growth of single-walled carbon nanotubes (SWCNTs) by ethanol chemical vapor deposition has been assessed on these Co catalysts. In contrast to Co/SiO2 and Co/Al2O3 catalysts with relatively high surface areas, Co/MgO catalyst with a low surface area demonstrates the best performances in the diameter-selective growth of SWCNTs under an optimal growth condition. Multiple characterizations on catalysts and SWCNTs revealed that Co(acac)2 was absorbed on MgO by ligand exchange and anhydrous solvent CH2Cl2 strengthened the anchoring of Co(acac)2 on the MgO surface, which resulted in well-dispersed Co species upon calcination in air. Under a modest reduction temperature, the reduction of Co oxides provided Co clusters, which were anchored by the unreacted Co ions in the interior of MgO support, leading to the synthesis of SWCNTs with a narrow diameter distribution.

Selective growth of semiconducting single-wall carbon nanotubes using SiC as a catalyst

Semiconducting single-wall carbon nanotubes (s-SWCNTs) without metal impurities are highly desired for use in high-performance field effect transistors as a channel material. Here we use SiC nanoparticles as a catalyst to selectively grow s-SWCNTs. The Si atoms on the surface of the SiC nanoparticles are found to be depleted during thermal treatment, and carbon atoms are exposed, which leads to the formation of carbon nanocaps on the SiC nanoparticles. Under a hydrogen atmosphere, the chemically active metallic carbon caps are preferentially etched away so that high purity s-SWCNTs with a content of ∼95% without any residue metal impurities are obtained by the chemical vapor deposition of ethanol and can be used to fabricate high-performance thin film transistors.

Selective Growth of Metal-Free Metallic and Semiconducting Single-Wall Carbon Nanotubes.

A major obstacle for the use of single-wall carbon nanotubes (SWCNTs) in electronic devices is their mixture of different types of electrical conductivity that strongly depends on their helical structure. The existence of metal impurities as a residue of a metallic growth catalyst may also lower the performance of SWCNT-based devices. Here, it is shown that by using silicon oxide (SiOx ) nanoparticles as a catalyst, metal-free semiconducting and metallic SWCNTs can be selectively synthesized by the chemical vapor deposition of ethanol. It is found that control over the nanoparticle size and the content of oxygen in the SiOx catalyst plays a key role in the selective growth of SWCNTs. Furthermore, by using the as-grown semiconducting and metallic SWCNTs as the channel material and source/drain electrodes, respectively, all-SWCNT thin-film transistors are fabricated to demonstrate the remarkable potential of these SWCNTs for electronic devices.

Residue-based iron catalyst for the degradation of textile dye via heterogeneous photo-Fenton

In this work, the use of a residue-based catalyst for heterogeneous photo-Fenton of Reactive black 5 (RB5) textile dye was evaluated. The catalyst was prepared by chemical vapor deposition of ethanol on a red mud residue, an important waste of the aluminum industry rich in iron oxide. The catalyst was characterized by different techniques, i.e., Mössbauer spectroscopy, Raman spectroscopy, CHN elemental analysis, BET surface area, and scanning and transmission electron microscopies. Results showed that the iron phases present in the red mud are reduced and a carbon coating is formed, protecting the catalyst from excessive iron leaching. The photo-Fenton experiments were carried out by varying pH, H2O2 concentration and radiation power and assessing dye conversion as the response variable. Studies on textile dye degradation showed that low pH favors the reaction and 100% photo-degradation efficiency was obtained, reducing the toxicity of the dye. The best operational condition was achieved at pH 3 and H2O2 initial concentration of 11mM, after 60min of reaction. Kinetic data related to RB5 dye degradation were well fitted to the Langmuir–Hinshelwood model in the range of 20–50mgL−1 of RB5 initial concentration with obtained initial rate constant of 9.4×10−8molL−1min−1. A reaction pathway was proposed in which the H2O2 is activated by surface Fe2+ sites on RM based catalyst, especially in the presence of light, producing OH radicals in a heterogeneous photo-Fenton-like mechanism to oxidize the organic pollutant Reactive black 5 dye.

Control of Cobalt Catalyst Thin Film Thickness by Varying Spin Speed in Spin Coating towards Carbon Nanotube Growth

Cobalt (Co) catalyst thin film is an active metal catalyst that can be very helpful to grow carbon nanotubes (CNTs). The catalyst thin films were prepared on silicon wafers by spin coating the solution of cobalt acetate tetrahydrate and ethanol. The effects of different spin speed parameter during the spin coating process were investigated. The findings showed that the optimum thickness of the Co catalyst thin films, i.e., 12.1 nm, was obtained at the highest spin speed of 8000 rpm. The uniformity of the thin films was also found to increase with increasing spin speed. The study also demonstrated that single-walled carbon nanotubes could be grown from Co catalyst particles after the catalytic chemical vapor deposition of ethanol. The particle and thickness analysis, as performed by means of FESEM while the existence of CNTs, was performed by Raman spectroscopy.

Surface phase transition on silicon crystals (100) with low-temperature microwave plasma chemical vapor deposition

Using the Langmuir model of adsorption from the precursor state, the phenomenon of self-organization of nanosized domains with low-pressure ethanol chemical vapor deposition of submonolayer carbonaceous coatings on the atomically-clean surface of silicon crystals (100) is investigated. The dependence of the substrate temperature and the electrical bias on the kinetics and the mechanism of the domain structuring, which is the phase transition on the silicon surface (100), is analyzed. It is shown that, in some chemically-active gaseous environments, the high etching selectivity of silicon and carbon makes it possible to use carbon islands being formed as nonlithographic masks to create nanosized integrated column structures in silicon crystals (100) by means of high-resolution plasma-chemical etching.

Sulfur-induced chirality changes in single-walled carbon nanotube synthesis by ethanol chemical vapor deposition on a Co/SiO2catalyst

Sulfur-containing compounds can be used as additives to significantly change the chiral selectivity and carbon yield in single-walled carbon nanotube synthesis.

Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol

The growth of graphene by chemical vapor deposition on metal foils is a promising technique to deliver large-area films with high electron mobility. Nowadays, the chemical vapor deposition of hydrocarbons on copper is the most investigated synthesis method, although many other carbon precursors and metal substrates are used too. Among these, ethanol is a safe and inexpensive precursor that seems to offer favorable synthesis kinetics. We explored the growth of graphene on copper from ethanol, focusing on processes of short duration (up to one min). We investigated the produced films by electron microscopy, Raman and X-ray photoemission spectroscopy. A graphene film with high crystalline quality was found to cover the entire copper catalyst substrate in just 20s, making ethanol appear as a more efficient carbon feedstock than methane and other commonly used precursors.

Multi-layer graphene on Co(0001) by ethanol chemical vapor deposition

N layer (1 ⩽ N ⩽ 10) monolayer films of graphene were formed by the chemical vapor deposition of ethanol on either clean or oxidized Co(0001) substrates at 1000 K, with no evidence of either interfacial oxide formation or graphene/substrate charge transfer. Low energy electron diffraction data indicate that the graphene layers or domains are azimuthally rotated, but otherwise show the characteristics of graphene with a Raman spectra D/G intensity ratio of 0.25 or less, and a C 1s binding energy of 284.5 eV with an observable π → π* transition. Magneto optic Kerr effect spectra indicate only the ferromagnetic hysteresis with high remanence, with no evidence of Co/graphene exchange bias. This is very different from the negligible remanent magnetization of graphene/Co3O4/Co trilayer structures.

Complete coverage of reduced graphene oxide on silicon dioxide substrates

Reduced graphene oxide (RGO) has the advantage of an aqueous and industrial-scale production route. No other approaches can rival the RGO field effect transistor platform in terms of cost (<US$1) and portability (millimetre scale). However the large deviations in the electrical resistivity of this fabricated material prevent it from being used widely. After an ethanol chemical vapor deposition (CVD) post-treatment to graphene oxide with ethanol, carbon islets are deposited preferentially at the edges of existing flakes. With a 2-h treatment, the standard deviation in electrical resistance of the treated chips can be reduced by 99.95%. Thus this process could enable RGO to be used in practical electronic devices.

Stable cyclic performance of nickel oxide–carbon composite anode for lithium-ion batteries

Nickel oxide (NiO) directly grown on nickel foam is regarded as a promising lithium ion battery anode material which shows good cyclic and rate performances with a theoretical specific capacity of 718mAhg−1. In this study, we demonstrated a carbon-incorporated NiO anode (NiO–C) with a capacity per unit area of 2.11mAhcm−2 and 1.76mAhcm−2 at 0.2C and 0.5C rates, respectively, fabricated by thermal oxidation of carbon coated nickel foam. The specific capacity of our NiO–C composite samples at 0.5C rate is found to be typically 389.16mAhg−1, with a stable cyclic performance up to more than 100cycles. This remarkable performance is apparently superior to the control samples of pure NiO samples. The improved performance is contributed to carbon incorporation which serves as a fluent channel for electrons and a flexible network preventing NiO nanostructures from structural deformation during charge and discharge processes. The advantage of using our approach is the easy preparation of the NiO–C composite using a simple two-step process: chemical vapor deposition of ethanol and annealing in air.

High-Temperature Growth of Graphene Films on Copper Foils by Ethanol Chemical Vapor Deposition

Chemical vapor deposition (CVD) is widely utilized to synthesize graphene with controlled properties for many applications, especially when continuous films over large areas are required. Although hydrocarbons such as methane are quite efficient precursors for CVD at high temperature (∼1000 °C), finding less explosive and safer carbon sources is considered beneficial for the transition to large-scale production. In this work, we investigated the CVD growth of graphene using ethanol, which is a harmless and readily processable carbon feedstock that is expected to provide favorable kinetics. We tested a wide range of synthesis conditions (i.e., temperature, time, gas ratios), and on the basis of systematic analysis by Raman spectroscopy, we identified the optimal parameters for producing highly crystalline graphene with different numbers of layers. Our results demonstrate the importance of high temperature (1070 °C) for ethanol CVD and emphasize the significant effects that hydrogen and water vapor, coming ...

Adsorption of sulfur and nitrogen compounds on hydrophobic bentonite

The successful synthesis of hydrophobic magnetic composites formed by carbon filaments on bentonite surface has been obtained via chemical vapor deposition of ethanol and studied by electron microscopy, XRD, Mössbauer spectroscopy, Raman, and thermal analysis measurements. Bentonite clay was impregnated with different concentrations of iron salt and subjected to a chemical vapor deposition using ethanol as carbon source. The results suggest the reaction of iron on the surface of bentonite with ethanol leading to the formation of reduced iron phases and carbon. The carbon deposited is present as graphite, amorphous and filaments and the resulting materials show hydrophobic behavior besides magnetic properties conferred by the iron phases. This magnetic property is very interesting and allows the materials to be easily removed from the system. The hydrophobic bentonite was used as adsorbent of sulfur and nitrogen compounds, important contaminants in fuels, showing adsorption capacity of 38.7mgg−1 and 54.5mgg−1 for nitrogen and sulfur compounds respectively, a very high adsorption capacity compared with other materials with carbon presented in the literature.

The extended growth of graphene oxide flakes using ethanol CVD

We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of <5 layers. This newly grown RGO possesses lower defect density with larger and increased distribution of sp(2) domains than chemically reduced RGO. Furthermore this method without optimization reduces the relative standard deviation of electrical conductivity between chips, from 80.5% to 16.5%, enabling RGO to be used in practical electronic devices.

Novel Biosensor for InterLeukin-6 Detection

Interleukin-6 (IL-6) is a pleiotropic cytokine with an important role in both immune regulation and exercise metabolism. During exercise, IL-6 is predominantly produced within, and released from, the working skeletal muscle, with the magnitude of IL-6 release related to the duration and intensity of the exercise bout. IL-6 (a) is the first cytokine to appear in circulation following initiation of exercise and (b) undergoes the most pronounced increase as compared to any cytokine in response to exercise. In the last decade, studies have suggested a role for IL-6 as a muscle energy sensor, pointing to its potential role as a biomarker of overtraining. Currently, ELISA and western blot is the staple detection technique for IL-6. However, they require substantial time, cost, machinery and specialist training. On the other hand, a Graphene Oxide-based amperometric sensor can provide real-time, low-cost yet sensitive protein detection. But, the coverage of mono-layered Graphene Oxide (GO) flake on SiO2 substrate is limited due to rinsing and unwanted crosslinking of the 3-AminoPropylTriEthoxy Silane (APTES) adhesion layer, thus leading to low available GO surface area, high variability of electrical conductivity between chips and low sheet transconductance that limits sensitivity of the sensor. This work had overcome this limitation by depositing carbon on the edges of GO flakes using an ethanol chemical vapor deposition (CVD). Then, the post-treated GO is fabricated into a liquid-gated biosensor and the detection window for IL-6 is presented. Our work yielded a highly conductive and electrically homogeneous carbon-based transducer to enable low-cost, facile, real-time yet sensitive amperometric sensors for IL-6.