Nanocarbon Film Research Articles

Nanocarbon film electrodes for electro-analysis and electrochemical sensors

Carbon films fabricated by sputtering and a related vacuum technique have unique features as regards electrochemical performance including relatively high electrochemical activity, and a wide potential window with low noise, in addition to low cost and the capacity for fabrication with any shape and size. Various applications for detecting environmental and biochemical molecules have been reported in recent years. This review focuses on the fabrication, structure, and electrochemical properties of carbon film electrodes. The review also introduces applications of carbon, heteroatom doped and surface terminated carbon film electrodes for heavy metal detection, biomolecular sensing, and DNA methylation level quantitative analysis. • Sputtered carbon films are introduced including their structure, electrochemical performance, and application. • The potential window of the carbon films increases by increasing sp 3 concentrations. • The electrochemical activity of carbon films depends on the nanocrystalline structure and surface functional groups. • A variety of the applications are introduced including detection of small biochemicals, DNAs and environmental pollutants.

Superhydrophobic Graphene-Like Nanocarbon Film Formation on Arbitrary Surfaces through MgO Nanoparticle Catalysis: Advanced Coatings for Energy Storage and Nanocomposites

Superhydrophobic Graphene-Like Nanocarbon Film Formation on Arbitrary Surfaces through MgO Nanoparticle Catalysis: Advanced Coatings for Energy Storage and Nanocomposites

A Substrate-Induced Fabrication of Active Free-Standing Nanocarbon Film as Air Cathode in Rechargeable Zinc-Air Batteries.

Designing cost-effective and high-efficiency bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurred at air electrodes is vitallysignificant yet challenging for Zn-air batteries (ZABs). In this work, a zinc substrate induced fabrication is reported of free-standing nanocarbon hybrid film which shows good bifunctional activity and can be directly used as the air electrode in the rechargeable ZABs. The designed nanocarbon film in Zn-air battery provides a satisfactory power density of 185mW cm-2 and cycling stability for 1200 h under the current density of 10mA cm-2 . This hybrid film also gives a solid-state ZAB excellent flexibility with a power density of 160mW cm-2 . The free-standing hybrid with abundant cobalt-nitrogen-carbon species coupled with porous architecture would be the original factor for its satisfactory performance of rechargeable ZABs. This work would pave an ideal way to design integrated electrode with high electrocatalytic performance towards electrochemical energy technologies.

Lipophilic Vitamin E Diffusion through Bicontinuous Microemulsions.

We studied the diffusion properties of lipophilic vitamin E (VE) through bicontinuous microemulsions (BME) using both electrochemical and fluorescence correlation spectroscopy (FCS) measurements. We investigated the effect of different composition ratios of micro-water and micro-oil phases in BMEs (W/OBME). When we employed the BME with a lower W/OBME value of 40/60 (oil-rich BME) as an electrolyte solution, we obtained a larger current response from VE at a fluorinated nanocarbon film electrode. Further voltammetric studies revealed that a higher VE diffusion coefficient was observed in the oil-rich BME. The FCS results also exhibited faster diffusion through the oil-rich BME, which played a significant role in accelerating the VE diffusion probably due to the widening of the micro-oil phase pathway in the BME. Moreover, the effect of increasing the VE diffusion was pronounced at the interface between the electrode surface and the BME solution. These results indicate that controlling the conditions of the BME as the measurement electrolyte is very effective for achieving superior electrochemical measurements in a BME.

Electrochemical Detection of Tryptophan Metabolites via Kynurenine Pathway by Using Nanocarbon Films

AbstractWe studied nanocarbon film electrodes with the aim of detecting tryptophan metabolites via the kynurenine pathway. The nanocarbon films were formed by using unbalanced magnetron sputtering, and they exhibited superior electrode properties including a wide potential window and a low background current as a result of the sp3‐containing structure and ultraflat surface. These properties allowed us to detect certain tryptophan metabolites such as kynurenic acid (KYNA), which has a relatively high oxidation potential. We also investigated the effect of the sp2/sp3 ratio of the nanocarbon film as regards the electrode activity in relation to target molecules. We found that the sp2/sp3 ratio played important roles in both widening the potential window and obtaining superior electrode performance for the metabolites. The nanocarbon film with a high sp3 content was beneficial as regards the electrode performance with respect to the detection limit and sensitivity. Compared with conventional carbon‐based electrodes, the nanocarbon film electrode with a high sp3 content exhibited higher electrode activity against KYNA while maintaining a low background current. Computational experiments revealed that the theoretical oxidation potential (Eox) value for some targets coincided with that obtained in electrochemical experiments using our nanocarbon film electrode.

Electrochemical measurements with nanocarbon film electrodes

Electrochemical measurements with nanocarbon film electrodes

DRIE Si Nanowire Arrays Supported Nano-Carbon Film for Deriving High Specific Energy Supercapacitors On-Chip

Supercapacitor is a promising solution to storage of pulsed energy generated by MEMS energy harvesting systems, relying on its faster charging/discharging capability than secondary battery. To improve the energy density of on-chip supercapacitor which shows potential for integration with MEMS devices, in this paper we first present a successful electrode design for high specific energy pseudo-supercapacitors on the basis of deep reactive ion etched Si nanowire array supported nano-carbon matrix. Widely used pseudo-capacitive manganese oxide active material is facilely deposited into the conductive nano-carbon matrix by a chemical bath deposition. The derived electrode exhibits a remarkable capacitance increase (around 4.5x enhancement) compared with the nano-carbon matrix benefiting from the contribution of pseudo-capacitive manganese oxide. Assembled sandwich prototype on-chip supercapacitors with a symmetric configuration offer a high specific capacitance of 741.6 mF cm−2 when discharged at 1 mA cm−2, and the energy density can attain as high as 51.5 μWh cm−2. The achieved high specific energy makes such on-chip supercapacitors attractive in the field of energy collection when cooperated with micro-or nano-energy generators.

Suppression of Surface Oxygen on Nanocarbon Film Electrodes for Maintaining Electrode Activity.

We investigated sputtered nanocarbon films with respect to the effect of suppressing surface oxygen on their electrochemical properties. The nanocarbon film consisted of nanocrystallites with mixed sp2 and sp3 bonds formed by unbalanced magnetron sputtering. Ultraviolet/ozone (UV/O3) irradiation and electrochemical pretreatment (ECP) were conducted to change the surface oxygen concentration of nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of the surface roughness (Ra) at the angstrom level after treatments, owing to a stable structure containing 40% of sp3 bonds. The electrode characteristics, including the potential window and electrochemical properties for some redox species, such as Ru(NH3)63+/2+, were investigated. Some electrochemical measurements of zinc ions (Zn2+) and hydrogen peroxide (H2O2) showed that the electrochemical reaction was improved by suppressing the surface oxygen. These results clearly indicated that the low surface oxygen concentration plays an important role in these electrochemical reactions.

Plasma-Treated Sputtered Nanocarbon Film Electrodes for Suppressing Electrochemical Fouling by Serotonin

Plasma-Treated Sputtered Nanocarbon Film Electrodes for Suppressing Electrochemical Fouling by Serotonin

Controlling Surface Oxygen Concentration of a Nanocarbon Film Electrode for Improvement of Target Analytes.

A nanocarbon film consisting of nanocrystallites with mixed sp2 and sp3 bonds formed by unbalanced magnetron sputtering, was studied with respect to changes in the characteristics caused by the surface oxygen concentration. An electrochemical pretreatment (ECP) was conducted to change the surface oxygen concentration of the nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of surface roughness (Ra) at the angstrom level after ECP, owing to a stable structure containing 40% of sp3 bonds. The electrode characteristics, including the potential window, and electrochemical properties for some redox species, such as Ru(NH3)63+/2+, Fe(CN)63-/4- and some biomolecules, were investigated. The anodic potential limit became wider and ΔEp of Fe(CN)63-/4- became smaller at the treated nanocarbon film electrode than those of the as-deposited nanocarbon film electrode. Based on these results, we realized to measure uridylic acid (UMP) and inosine triphosphate (ITP) with a high oxidation potential by direct oxidation, which was difficult to measure at the as-deposited nanocarbon film electrode.

Oxidation potential-dependent selective detection of epigenetic 5-hydroxymethylcytosine using nanocarbon film

We developed and used the nanocarbon film electrode to successfully detect epigenetic mark 5-hydroxymethylcytosine (5hmC) through direct oxidation after digesting genomic DNA (gDNA) with nuclease P1. The film showed superior key film properties including a very chemically stable structure and an ultraflat surface (Ra = 0.21 nm) that resulted in better electrode properties such as a wider potential window and lower background current than the widely used carbon electrode. Computational experiments revealed that the theoretical oxidation potential (Eox) value for 5hmC coincided with that obtained in electrochemical experiments using our nanocarbon film electrode. We successfully detected 5hmC by using this film electrode in combination with HPLC. Due to the difference of each oxidation potential, we achieved the oxidation potential-dependent selective detection of 5hmC in gDNA from excess amounts of unmethylated cytosine with a similar polarity to 5hmC.

Influence of external impact on secondary emission characteristics of anti-multipactor nanocarbon

This work demonstrates that a thin nanocarbon film applied to a metal surface is capable of decreasing the coefficient of secondary emission down to the value of 1 ÷ 1.5. Thereby, eliminating the possibility of a multipactor discharge. In this paper we describe a method of making an anti-multipactor coating from a colloid solution of nanocarbon. The colloid solution of nanocarbon is made by creating a multi-spark high voltage pulse discharge in ethanol where argon is injected into the inter electrode space. Thermal, climate and tear-off tests have shown that emission properties of the surface are retained.

Silicon Anode Confined in Carbon Nano-Spaces for Efficient Lithium Storage

Commercial Li-ion batteries employ graphite and other carbonaceous materials as anodes, which has excellent stability and low cost, but has a theoretical capacity limit at 372 mAh/g by forming a fully intercalated LiC6 compound. For anode materials, silicon is also known to have the highest theoretical specific capacity (4200 mAh/g), and is considered to be the active materials for the next generation lithium ion batteries. However it has the large volume change (>400%) during lithiation and delithiation causes pulverization, resulting in capacity loss in a high number of cycles. Here, this study reports the use of engineering nanocarbon film with confined silicon nanoparticles as an anode material for lithium-ion batteries. The unique “concave” graphitic nanostructure, prepared in porous templates with morphology of interconnected arrays, makes nanocarbon electrodes a good lithium-ion intercalation medium and, more importantly, robust nanocontainers to effectively confine high-capacity silicon nanoparticles for lithium-ion storage. Our unique anode, which is based the concave graphitic film and silicon particles confined in its nanospace, have three notable features for the use as the effective electrode material in a lithium-ion battery. First, Li ion diffusion into the interior of the nanocarbons through the opened structures can shorten the diffusion length of the redox couple and provide rapid charge transport. Second, the exposed silicon active materials in the direction of Li ion diffusion increase the accessibility of the electrode interior to the electrolyte, which ensures a high charge/discharge capacity. Finally, the nanoconfined silicon system inside the carbon nanospace improves the cycle life by preventing volume expansion during electrochemical Li insertion/extraction. As a result, high performance Li storage with a mass-specific capacity of 2500 mAh/g was obtained at 0.5A/g. The discharge capacity was retained constantly during 200 cycles with coulombic efficiency of above 98%. These results suggest that the novel structure can lead to high storage capacities and rate capability as anode material in future high performance Li-ion batteries.

Gas-phase Treatment Methods for Chemical Termination of Sputtered Nanocarbon Film Electrodes to Suppress Surface Fouling by Proteins

Gas-phase Treatment Methods for Chemical Termination of Sputtered Nanocarbon Film Electrodes to Suppress Surface Fouling by Proteins

Low-temperature fabrication of nanographene on a copper substrate using pentacene

We developed a low-temperature fabrication method for nanographene on a copper (Cu) substrate. This process is called hot-mesh deposition (HMD) and uses pentacene, H2, and a tungsten (W) mesh. In HMD, pentacene and H2 molecules decompose on a heated W mesh placed between a pentacene source in a molybdenum boat and a Cu substrate. A clean surface was obtained using atomic hydrogen treatment prior to nanocarbon film formation. The nanocarbon films consisted of nanographenes, which formed on the cleaned Cu substrate. The peaks due to the D and D' bands of nanographene were observed in the Raman spectrum. It was found that nanographene could be produced by HMD even at temperatures as low as 250 °C. It is considered that the key factors for the low-temperature formation of nanographene are a clean Cu surface, and the reaction of pentacene with the 6,13-dihydropentacene generated on the heated W mesh.

Increased electrode activity during geosmin oxidation provided by Pt nanoparticle-embedded nanocarbon film.

The musty odor compound geosmin was electrochemically detected by using Pt nanoparticle (PtNP)-embedded nanocarbon (Pt-C) films formed with unbalanced magnetron (UBM) co-sputtering. The sputtered Pt components formed NPs (typically 1.53-4.75 nm in diameter) spontaneously in the carbon films, owing to the poor intermiscibility of Pt with carbon. The surface concentrations of PtNPs embedded in the nanocarbon film were widely controllable (Pt = 4.8-35.9 at%) by regulating the target powers of the Pt and carbon individually. The obtained film had a flat surface (Ra = 0.17-0.18 nm) despite the fact the PtNPs were partially exposed at the surface. Compared with a Pt film electrode, some Pt-C films exhibited higher electrode activity against geosmin although the surface Pt concentrations of these Pt-C films were much lower than that of the Pt film electrode, thanks to the wider potential window and lower background current that resulted from the ultraflat and stable carbon-based film prepared by UBM co-sputtering. Computational experiments revealed that the theoretical oxidation potential (Eox) value for geosmin was relatively similar to that obtained in electrochemical experiments using our Pt-C film electrode. Moreover, we also theoretically estimated the possible oxidation site of geosmin molecules and the advantage of the NP shape of the electroactive Pt parts as regards the electrochemical oxidation of geosmin. We successfully used the Pt-C film (10.6 at%) electrode to detect geosmin in combination with HPLC at a low detection limit of 100 ng L-1.

Electrochemical performance at sputter-deposited nanocarbon film with different surface nitrogen-containing groups.

Carbon materials containing nitrogen have been extensively studied as electrode materials for use in non-platinum cathodes of fuel cells due to their high electrocatalytic activity for oxygen reduction. The activity is strongly dependent on the structure of surface nitrogen-containing functional groups. Carbon film containing nitrogen is also suitable for analytical applications because of its low background noise and its electrocatalytic activity, which is superior to that of pure carbon film. Here, we fabricated sputter-deposited nanocarbon film with a nitrogen-containing group and estimated the efficacy of a surface nitrogen-containing group for detecting biomolecules. Two types of carbon films, one rich in graphite-like nitrogen-containing bonds and the other rich in pyridine-like bonds, were successfully fabricated without changing their nitrogen concentration, sp2/sp3 ratio or surface flatness. The carbon film rich in pyridine-like bonds shows a positive oxygen reduction peak of about 250 mV compared with pure carbon film and is also 200 mV more positive compared with film with graphite-like nitrogen-containing bonds. This indicates that pyridine-like bonds contribute more effectively to electrocatalytic activity than graphite-like nitrogen-containing bonds. For detecting biomolecules, carbon film rich in pyridine-like bonds also exhibits more negative peak potentials for the oxidation of NADH and l-ascorbic acid, suggesting that carbon film rich in pyridine-like bonds will show improved performance for detecting electroactive biomolecules.

Amplified Zinc Signal at a Nanocarbon Film Electrode for Lipopolysaccharide Detection

We report an electrochemical method for detecting low concentrations of lipopolysaccharide (LPS), based on amplified zinc (Zn) signals on a sputtered nanocarbon film electrode. The nanocarbon film ...

Watervoltaic materials and energy conversion device based on carbon nanomaterials

Harvesting renewable energy and realizing its transformation into electricity is one of the effective ways to solve energy crisis and environmental problems. Hydroenergy has been considered as a promising energy with enormous development potential and application value because of its great advantages of large reserves, wide distribution, and environmentally friendly. Nowadays, the development and utilization of hydropower resources mainly rely on dams, generators and other steel facilities to convert mechanical energy to electricity, with inherent defects of inefficiency and damage to the ecological environment. Therefore, developing new types of watervoltaic materials and devices with diverse application environments, high energy conversion efficiency and low power generation costs is an effective improvement and complement to current water energy utilization condition. Carbon nanotube flow sensor reported by Shankar Ghosh in 2003 first proved the property of carbon nanotube that it can generate electricity in floating water, promoting the research of carbon nanomaterials for power generation in fluids. In the following years, several kind of carbon nanomaterials with different dimensions including carbon nanotube, graphene, et al. were successively confirmed that they have similar character to convert hydroenergy to electricity. Various theories including phonon dragging were proposed to explain this phenomenon as well as the form of electric double layer (EDL) and electrokinetic theory fit it reasonably both in charge transfer and electrical output. Related devices were also designed and assembled to convert energy in liquid water, such as ion water drops, saline solution, et al., to electricity, increasing electrical output from initial a few millivolts to a few volts with a small number of devices in series, which is enough to drive small loads. Subsequently, carbon nanomaterials/polymer conducting composite film was designed to harvest energy from real raindrops and seawater waves, making a great progress of watervoltaic materials and devices in practical application. In addition to converting energy in liquid water, devices based on carbon nanomaterials with different dimensions including quantum dots, nano-carbon film and graphene oxide can harvest energy in water vapor and water evaporation, making it possible to collect and convert energy in gaseous water in nature. Unique structures of holes, elemental concentration gradient, et al. were considered to make contributions to capture water molecule and transfer charges, resulting of the electrical output between electrodes. The combination of nano-carbon electrode and all inorganic perovskite solar cells realizes simultaneous collection of water vapor energy and solar energy, making great significance for implementing multi-energy integration of devices. Since carbon nanomaterials were confirmed to be able to convert extensive water energy in natural into electrical energy, different materials and devices were designed and manufactured to increase the electrical output, improve stability and reduce power generation costs. However, there are also challenges including unclear working mechanism, high environmentally demanding and difficulty to integrate devices on a large scale need to be overcomed in the future. Despite this, watervoltaic materials and energy conversion devices have become promising green energy capture technologies due to their high conversion efficiency, wide application environment, and simple device structure. Improving usability is one of the directions of watervoltaic devices development.

Efficient lithium storage of concave graphitic anode embedded with nanoconfined silicon

This study reports the use of engineering nanocarbon film with confined silicon nanoparticles as an anode material for lithium-ion batteries. The unique “concave” graphitic nanostructure, prepared in porous templates with morphology of interconnected arrays, makes nanocarbon electrodes a good lithium-ion intercalation medium and, more importantly, robust nanocontainers to effectively confine high-capacity silicon nanoparticles for lithium-ion storage. Open structures of the concave nanocarbon increase the accessibility of Li ions, and allow Li ions to diffuse active materials. In addition, the highly textured concave pores allow the volume expansion of the silicon nanoparticles to be confined to the nanospace during lithium-ion insertion/extraction. The specific capacity of the nanoconfined silicon/nanocarbon anode reaches up to 2500 mAh/g at 0.5 A/g. After long cycling, the anode materials becomes even more stable, showing the invariant lithium-ion storage capacity as the charge-discharge rate is increased by 10 times from 2–20 A/g. The capacity is retained constantly after 200 charge-discharge cycles.