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Methods for effectively utilizing lignin are necessary for the realization of a sustainable society. Herein, we report a method for directly converting lignin to graphene-based materials. Fe-supported lignin is prepared by dissolving lignin in an aqueous FeCl2 solution, followed by freeze drying. Graphene is then produced by catalytically carbonizing this Fe-supported lignin at 1200 °C. The characteristics of both the Fe catalyst and lignin are crucial for the production of high-quality graphene. Specifically, the lignin should disperse well in water, freeze dry, and carbonize via solid-state carbonization. The obtained graphene-based material is highly resistant to electrochemical oxidation, as observed in other graphene-based materials. The direct conversion of lignin to graphene described herein is an unprecedented method for synthesizing large amounts of graphene-based material at low cost, as well as being an excellent use for lignin.

A deuterium-labeled temperature-programmed desorption (TPD) technique was developed to accurately characterize functional groups on the surface of carbon-based materials. After the protic hydrogen of the functional groups on activated carbons was substituted by deuterium, TPD analysis revealed the desorption of deuterium compounds (D2O, DHO, D2, DH). The functional groups were estimated from the predicted desorption mechanisms of these deuterium compounds, which can be distinguished according to the functional groups and their surrounding chemical structures. Thus, this technique provides information on not only the type of functional groups but also the extensive chemical structure around them. The phenolic group, ether, and edge hydrogen formed on the activated carbons were separately quantified, and the functional groups were further classified into 12 types by the nearby chemical structures. Comparison with IR spectra indicated that the deuterium-labeled TPD gave qualitatively reasonable results. This technique is useful for obtaining a deeper understanding of the surface chemical structure of carbon-based materials.

Methods for effectively utilizing lignin are necessary for the realization of a sustainable society. Herein, we report a method for directly converting lignin to graphene-based materials. Fe-supported lignin is prepared by dissolving lignin in an aqueous FeCl

We simulate the inter-firm trading network which consists of approximately 1 million nodes, and we estimate the firm sales in Japan. We apply the gravity interaction model to the real Japanese inter-firm trading network to calculate the money transport between firms. Sales of each firm are evaluated through the scaling relation between the money flow and the sales, and then the total sales are calculated as an economic indicator. This calculation method is applicable to other situations. As an example, we present an estimation of sales decrease caused by the blackout due to the Hokkaido earthquake in September 6, 2018. The total sales are calculated in both cases: before and just after the earthquake. The total loss of sales is estimated as 35 billion yen per day for direct decrease in the firm sales in Hokkaido, while as 90 billion yen per day for indirect decrease in the other areas. The indirect sales decrease is about 2.6 times as well as the direct sales decrease.

A modeled Japanese inter-firm trading network is simulated to investigate phase transition structure in money transport. First, the network structure is calculated as a steady state in a stochastic process. Second, the money transport between the firms is estimated in terms of the gravity interaction model. A linear stability analysis is performed to detect the phase transition in the transport. Some of the phase transitions are accompanied by the significant changes in the sales of the several top firms.

A catalyst support can improve the catalytic activity of metal catalysts, and this phenomenon is well known as the support effect. The effective use of this support effect is considered important for improving catalytic activity. However, the factors affecting this phenomenon are complex. It is, therefore, important to understand the interaction between the support and metal catalyst as well as the surface characteristics of the support for elucidating this phenomenon. Carbon is a useful support material because of its high chemical and thermal stability and electroconductivity. Moreover, its surface properties can be controlled by doping the carbon structure with heteroatoms. In this study, the catalytic activity of metal particles supported on heteroatom-doped carbon materials was evaluated to investigate the support effect of the doped carbon. The catalytic activity of carbon-supported Ni particles in benzene hydrogenation was improved by introducing N and B into the carbon support. In particular, Ni supported on N-doped carbon showed a two-fold improvement in activity compared to that supported on undoped carbon. A compensation effect was confirmed for the catalytic activity of Ni particles. The results suggest that the introduction of heteroatoms into the carbon support changed the adsorption energy of the reactant on Ni, thereby improving the Ni catalytic activity.

Trace amounts of edge sites in natural graphite, synthetic graphite and high-temperature treated coke are quantitatively analyzed from the numbers of hydrogen atoms and oxygen-containing functional groups at carbon edge sites. For the analysis of hydrogen content, a new analytical technique is developed. The oxygen-containing functional groups are analyzed with a highly sensitive temperature-programmed desorption (TPD) technique. These techniques allow us to estimate the trace amounts of edge sites in the range of 1–10 × 10−4 at.% with extremely high accuracy and reveal that the concentration and the type of edges sites differ depending on the type and the particle size of these graphitized carbons. Moreover, the average sizes of graphene sheets in these carbons are estimated from the total number of edge sites. The graphene sheet size thus obtained is compared with the crystallite sizes, La, and the average particle size, and such comparison provides deep insight into the understanding of carbon molecular structure in the graphitized carbons.

The use of carbon cathode catalysts in polymer electrolyte fuel cells instead of the current platinum catalysts is attracting increasing attention. We claim that two factors are important for enhancing the activity of carbon cathode catalysts in the oxygen reduction reaction (ORR): the formation of a nanoshell structure and co-doping with boron and nitrogen. Herein, we investigate the preparation and characterization of active ORR carbon catalysts that combine the above factors. Boron and nitrogen (BN)-doped nanoshell-containing carbon (BN-NSCC) was prepared by carbonizing a mixture of poly(furfuryl alcohol), cobalt phthalocyanine, melamine, and a trifluoroborane–methanol complex at 1000 °C. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed the formation of nanoshell structures with distorted graphitic layers and the introduction of boron and nitrogen atoms, respectively. The ORR activity was evaluated in oxygen-saturated 0.5 mol dm−3 H2SO4 using Koutecky–Levich analysis. The BN-NSCC showed an eight to ten times higher ORR activity than undoped NSCC, with an increased number of electrons participating in the reaction. Tafel analysis revealed a change in the rate-determining step caused by BN-doping. Thus, the combination of a nanoshell structure and co-doping with boron and nitrogen was found to improve the ORR activity of carbon catalysts.

This study reports the synergistic improvement of the oxygen reduction reaction (ORR) activity of a carbon catalyst prepared from a phenol–formaldehyde resin by simultaneous incorporation of Cu and Fe phthalocyanines. This carbon catalyst exhibited higher ORR activities than those prepared with either Cu or Fe phthalocyanines, with an approx. 28-fold maximum ORR current enhancement observed when Cu/Fe = 75:25 was incorporated into the carbon precursor. Surface and structural characterizations of these catalysts suggested that the incorporated Cu played a role in suppressing the catalytic activity of Fe, forming the reported nanoshell structure, and in keeping more nitrogen atoms attached to carbons. The incorporation of Cu in the carbon catalyst provided a doping effect for nitrogen into the carbon structure and inhibited catalytic graphitization caused by Fe species. These effects resulted in a distinctive carbon structure in the nanoshell. These multiple effects of Cu incorporation were considered key factors in the enhancement of ORR activity caused by Fe and Cu incorporation.

The activity of non-precious metal catalysts (NPMCs) has now reached a stage at which they can be considered as possible alternatives to Pt for some proton exchange membrane fuel cell (PEMFC) applications. However, despite significant efforts over the past 50 years on catalyst development, only limited studies have been performed on NPMC-based cathode catalyst layer (CCL) designs. In this work, an extensive ionomer study is performed to investigate the impact of ionomer equivalent weight on performance, which has uncovered two crucial findings. Firstly, it is demonstrated that beyond a critical CCL conductance, no further improvement in performance is observed. The procedure used to determine this critical conductance can be used by other researchers in this field to aid in their design of high performing NPMC-based CCLs. Secondly, it is shown that the stability of NPMC-based CCLs can be improved through the use of low equivalent weight ionomers. This represents a completely unexplored pathway for further stability improvements, and also provides new insights into the possible degradation mechanisms occurring in NPMC-based CCLs. These findings have broad implications on all future NPMC-based CCL designs.

The risk on which the whole economic system is exposed is called “systemic risk”, a topic that has received a great of attention from researchers, recently. As one of the studies, we studied effcts of the interaction between banks and firms on the whole systems. In particular, we focused on investments from banks to firms and researched the number of bankrupt banks and firms varying two parameters: 1. Lending threshold of banks; 2. Lending sensibility to a firm’s growth rate. As results, we got two results: 1. As banks have a lower lending threshold, the average number of bankrupt of banks and firms rises; 2. The lending threshold of banks and lending sensibility to firms’ growth rate increases the disparity between firms. These results suggest that greater investment have negative effects on both banks and firms and biased investment enlarge the disparity between firms.

Zeolite template carbon (ZTC) is a carbon material composed of a three-dimensional network of graphene nanoribbons (GNR), and thus, is expected to exhibit electronic characteristics identical to those of GNR. ZTC is capable of doping heteroatoms in its structure, which offers the advantage of controlling its electronic properties by the presence of the heteroatoms. In this study, we prepared heteroatom-doped ZTCs and applied them to an ion-sensitive field effect transistor (ISFET), for investigating the effect of heteroatom doping on its electronic properties. The ISFET characteristics of un-doped ZTC include bipolarity, whereas oxygen-doped ZTC shows p-type semiconductor characteristics, and nitrogen-doped ZTC shows n-type characteristics. Furthermore, copper and nitrogen co-doped ZTC exhibits high sensor sensitivity (the change of electric conductivity reaches up to 50%) as a carbon-based ISFET. As a result of the analytical evaluation, a copper-nitrogen complex is formed in the co-doped ZTC, and the electronic interaction between copper and nitrogen atoms is able to change electrochemically. Owing to the presence of the copper-nitrogen complex, the co-doped ZTC shows specific ISFET characteristics.

A novel, one-step protocol for the selective synthesis of W2C nanoparticles from phosphotungstic acid (H3PW12O40), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1–50 nm and were dispersed on a carbon substrate. The W2C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H3PW12O40 followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W2C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H2WO4. Stable W2C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W2C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W2C nanoparticles, leading to the formation of WC. The W2C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade. The HER catalytic activity was notably high, being comparable to that of MoS2, which is a promising alternative to Pt. The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the HER.

Improving the specific oxygen reduction reaction (ORR) activity (SOA) of platinum catalysts is a promising way to reduce the amount of platinum required for the cathode in polymer electrolyte fuel cells. In this study, we compared the SOA of Pt catalysts loaded on two types of Ketjen Black: pristine (KB) and a sample heat treated at 1500 °C (KB1500). In addition, we characterized the platinum deposited on the carbon and compared the durability of these catalysts against potential cycling. The platinum catalyst loaded on KB1500 (Pt/KB1500) showed doublet hydrogen adsorption peaks at 0.12 V vs. RHE, observed by cyclic voltammetry, and the formation of atomically disperse platinum catalysts, which formed a cloud-like distribution with platinum atoms. Such a cloud-like distribution has not been observed for Pt/KB previously, and the higher SOA of the Pt/KB1500 catalyst was due to the presence of the finely dispersed cloud-like platinum species. The differences in the surface structure of the carbon supports were investigated using X-ray diffraction, Raman scattering, electron spin resonance, and temperature-programmed desorption. The characterization revealed that KB1500 has continuous larger graphitic layers with point defects and holes, whereas KB has smaller graphitic layers whose edge sites are decorated with oxygen functional groups and hydrogen atoms. The durability of Pt/KB1500 in potential cycling tests was determined by cyclic voltammetry between 0.6 and 1.0 V vs. RHE for 10,000 cycles. These measurements revealed the high SOA and survival of the characteristic hydrogen adsorption peak at 0.12 V vs. RHE.

Hard carbons emerge as one of the most promising candidate for an anode of Na-ion batteries. This research focuses on the carbon monolith derived from resorcinol-formaldehyde (RF) gels as a model hard carbon electrode. A series of binder-free monolithic carbon electrodes heat-treated at varied temperatures allow the comparative investigation of the correlation between carbon nanotexture and electrochemical Na + -ion storage. The increase in carbonization temperature exerts a favorable influence on electrode performance, especially in the range between 1600 °C and 2500 °C. The comparison between Li + - and Na + -storage behaviors in the carbon electrodes discloses that the Na + -trapping in nanovoids is negligible when the carbonization temperature is higher than 1600 °C. On the other hand, the high-temperature sintering at 2500–3000 °C enlarges the resistance for Na + -insertion into interlayer spacing as well as Na + -filling into nanovoids. In addition, the study on the effect of pore size clearly demonstrates that not the BET surface area but the surface area related to meso- and macropores is a predominant factor for the initial irreversible capacity. The outcomes of this work are expected to become a benchmark for other hard carbon electrodes prepared from various precursors.

Hard carbons have immense potential as anode materials for Na-ion batteries, because the expanded graphene interlayers and nanovoids between randomly stacked aromatic fragments can accommodate a substantial amount of sodium. However, the large irreversible capacity in the first cycle still remains as a significant issue in terms of a practicable battery technology. Here, we show that hard carbon electrodes derived from a common phenol resin deliver a high reversible capacity within the narrow potential range of 0.1–0.005 V (vs. Na+/Na) and an excellent initial coulombic efficiency up to 95 %. The former allows the sustainable high voltage, whereas the latter minimizes the amount of unavailable Na+ in a closed cell. The findings in this work put forward a guideline for manufacturing hard carbon electrodes, which goes against the current trend of nanostructuring and downsizing.

A major hurdle to the widespread commercialization of proton exchange membrane fuel cells (PEMFCs) is the high loading of noble metal (Pt/Pt-alloy) catalyst at the cathode, which is necessary to facilitate the inherently sluggish oxygen reduction reaction (ORR). To eliminate the use of Pt/Pt-alloy catalysts at the cathode of PEMFCs and thus significantly reduce the cost, extensive research on non-precious metal catalysts (NPMCs) has been carried out over the past decade. Major advances in improving the ORR activity of NPMCs, particularly Fe- and Co-based NPMCs, have elevated these materials to a level at which they can start to be considered as potential alternatives to Pt/Pt-alloy catalysts. Unfortunately, the stability (performance loss following galvanostatic experiments) of these materials is currently unacceptably low and the durability (performance loss following voltage cycling) remains uncertain. The three primary mechanisms of instability are: (a) Leaching of the metal site, (b) Oxidative attack by H2O2, and (c) Protonation followed by possible anion adsorption of the active site. While (a) has largely been solved, further work is required to understand and prevent losses from (b) and/or (c). Thus, this review is focused on historical progress in (and possible future strategies for) improving the stability/durability of NPMCs.

Onion-like carbon (OLC) is known to form as an intermediate structure when nanodiamond (ND) is heat treated at 1100–1500 °C. In this letter, we report on the electrochemical activity of its oxygen reduction reaction (ORR) when prepared at temperatures from 1000 to 2000 °C. The ORR activity is found to exhibit excellent correlation with the degree of defects, with OLC prepared at 1400 °C found to have the highest activity. This is attributed to the formation of curved graphitic layers containing edges during ND-OLC transformation, which function as active sites for the adsorption and subsequent reduction of oxygen.

Using hydrogen as an energy source is the most promising option to construct a society with low carbon dioxide emission. We are dreaming to establish such a world by using carbon materials to produce, store and use hydrogen. The present paper provides an explanation of the carbon alloy cathode catalysts for polymer electrolyte fuel cells, which we have discovered and nurtured to the level of platinum catalysts. The paper explains the necessity of developing non-platinum cathode catalysts and our ideas for carbon alloy cathode catalysts, to meet the demand. It then gives our research results on the active sites for oxygen reduction reaction (ORR) of the carbon alloy catalysts by comparing them with results from other researchers on non-platinum cathode catalysts. The paper concludes that the ORR active sites of our catalysts are disordered carbon structures formed on the carbon alloy catalysts. Lastly, the paper describes our efforts to improve the catalytic activity, where our latest carbon alloy catalysts with the highest cell performance are presented. [TANSO 2014 (No. 265) 204–212.]

Crystalline mesoporous carbon was prepared from nanoshell-containing carbon (NSCC) by a sculpturing technique, i.e., the selective oxidation of amorphous carbon moieties (ACM) in NSCC using hydrogen peroxide (H2O2) treatment. The carbon structures of the NSCC and the H2O2-treated NSCC were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) measurement and N2 adsorption–desorption. Multiple repetitions of the treatment resulted in an increase of nanoshell fraction by the selective oxidation of the ACM intrinsically included in NSCC. This was confirmed by TEM, SEM and XRD measurements. N2 adsorption–desorption measurement showed that the treatment caused remarkable increases in mesopore volumes and the mesopore ratios. In particular, when the treatment was repeated five times the highest mesopore ratio of approximately unity was observed.

Recently carbon-based catalysts have attracted much attention for its high ability to catalyze oxygen reduction reaction (ORR) in a cathode for polymer electrolyte fuel cells. Among active site models of the catalyst, edge region of sp2 carbon network is expected to demonstrate high ORR activity comparable to platinum catalysts. However, it is difficult to directly identify the chemical structure of the edge sites by applying conventional structural or electronic probes to actual catalysts. Here, we used C 1s X-ray absorption spectroscopy to observe electronic structure of carbon in iron phthalocyanine-based catalysts, and found a signature of edge exposure below the π* edge, whose intensity is well correlated with the ORR activity. Combined with information about the chemical structure of nitrogen, ORR activity of the catalyst is characterized in terms of the edge exposure.

Nanoshell-containing carbon (NSCC) is one of the Pt-surrogate catalysts for proton exchange membrane fuel cell (PEMFC) invented by us to promote oxygen reduction reaction (ORR), the cathode reaction of the cell. In the present study, we selected one of renewable resources, lignin from herbaceous plants as the carbon precursor for NSCC. The lignin was admixed with cobalt phthalocyanine (CoPc), the nanoshell (NS) forming catalyst, and then carbonized at 1000℃. Transmission electron microscopy and X-ray diffraction studies confirmed the formation of NS structure. The ORR activity of the prepared NSCC increased with the amount of CoPc, and the activity of lignin-based NSCC was higher than that of phenol-formaldehyde resin-based NSCC with the same amount of CoPc added. Surface analysis by X-ray photoelectron spectroscopy revealed no metal species on the NSCC but higher N/C ratio for the lignin-based NSCC by two folds. This study shows the possibility of lignin as a precursor of NSCC cathode catalyst for PEMFC.

The influences of the heat-treatment of Ketjen Black EC300J in the temperature range 1000–2000 °C on the catalytic activity of loaded Pt for oxygen reduction reaction (ORR) were studied. A maximum enhancement in the specific ORR activities (SOA) was observed for the carbon heat-treatment at 1500 °C. The heat-treatment of carbon induced decreases in porosity and the development of graphitic structures; however, no direct correlations were observed between these properties and the SOA. Transmission electron microscopy and X-ray photoelectron spectroscopy, respectively, showed enhancements in the uniformity of the Pt particle size distribution and of the extent of surface reduction of Pt with increasing heat-treatment temperature (HTT). Cyclic voltammetry in 0.5 M H2SO4 aqueous solution detected changes in the hydrogen adsorption at 0.12 V vs. a reversible hydrogen electrode, depending on the HTT of the carbon support, and this was ascribed to hydrogen adsorption on the Pt(110) surface, the most active crystal face of Pt for ORR. The fraction of Pt atoms belonging to the (110) surface out of the total surface Pt atoms showed an excellent correlation with the SOA. Heat-treatment of the carbon support was therefore concluded to be an effective treatment for enhancing the SOA of Pt.

C 6 -hydrocarbons, namely, n-hexane, 1-hexene, cyclohexane, and benzene, were selected as surrogate tar in low-temperature gasification (LTG) of biomass in the study of carbon deposition of organic compounds on a Ni/Al 2 O 3 catalyst. All the compounds showed a two-stage weight increase due to carbon deposition; the two stages were the low-temperature stage (LTS: 300–650 °C) and high-temperature stage (HTS: above 650 °C). The LTS is the focus of this study. The susceptibility of the catalyst to carbon deposition was measured by the temperature ( T max ) giving maximum rate of weight increase ( r max ). 1-hexene was found to be the most influential compound with the lowest T max and the highest r max , followed by benzene. The saturated hydrocarbons, n-hexane and cyclohexane, were the least influential compounds for carbon deposition. The morphology of the deposits was found to be mainly herringbone-type carbon nanofibers, determined by transmission electron microscopy. Thermodynamic calculation revealed that 1-hexene was the most reactive compound for carbon deposition, while benzene was the most stable compound. The factors determining the carbon deposition of hydrocarbon compounds were explained in terms of both thermodynamic and adsorptive properties of the compounds.

A technique to determine a trace amount of hydrogen in carbon materials heat-treated above 1000 °C was developed. Three types of carbons prepared from poly(furfulyl alcohol), poly(vinyl chloride) and mesophase carbon microbeads were heat-treated at various temperatures ranging from 1000 to 1800 °C. Then they were gasified by O2 in a fixed bed flow reactor, and the H2O gases formed during the gasification processes were carefully monitored with a Karl Fischer moisture analyzer. As a result, this method makes it possible to determine the hydrogen contents in the carbons down to three places of decimals as a weight percent and can detect even a trace amount of hydrogen as low as 0.002 wt.%. A possible chemical structure of carbon edge sites was also discussed based on the experimentally determined hydrogen contents.

To obtain uniformly and finely dispersed nanoshell structures in nanoshell carbons (NSCs), we synthesized three oxine–polymer (OFR)/cobalt complexes with different ligand/metal ratios (L/M) ( x OFR(Co), x = L/M = 1, 2, and 3) as the starting materials of NSCs by polycondensation of 8-hydroxyquinoline (oxine) and formaldehyde. The formation of polymeric structures and coordination bonds was confirmed by infrared spectroscopy. Thermogravimetry revealed that the thermal decomposition temperature increased with the L/M ratio. Carbonization of x OFR(Co) ( x = 2 and 3) at 1000 °C resulted in the uniform formation of nanoshells with diameters of 30 nm, while carbonization of 1OFR(Co) resulted in the formation of nanoshells with a broader size distribution including some with diameters over several hundred nm. The results indicate that the fixation of metal atoms in the starting polymers is an effective method for the preparation of uniformly and finely dispersed nanoshells in NSCs. The carbon from 3OFR(Co), i.e., 3OFR(Co)/C, showed the highest electrocatalytic activity for the oxygen reduction reaction (ORR). The linear shape of the voltammograms were understood in terms of the distribution of active sites for ORR with different activation energies.

The electronic structure of the residual metal atoms in Fe phthalocyanine (FePc)-based carbon catalysts, prepared by pyrolyzing a mixture of FePc and phenolic resin polymer at 800 °C, before and after acid washing have been investigated using X-ray absorption fine structure (XAFS) spectroscopy to clarify the role of Fe in the oxygen reduction reaction (ORR) activity. The Fe K X-ray emission intensity suggests that the acid washing process reduces 36% of the total amount of residual Fe in the FePc-based catalysts. The decomposition analyses for the XAFS spectra reveal that the composition ratio of each Fe component is unaltered by the acid washing, indicating that the residual Fe components were removed by the acid washing irrespective of their chemical states. Because the oxygen reduction potential was approximately unchanged by the acid washing, the residual Fe itself does not seem to contribute directly to the ORR activity of the samples. The residual Fe is composed mainly of metallic Fe components (Fe metal and iron carbide Fe3C), which can act as a catalyst to accelerate the growth of the sp2 carbon network during pyrolysis. The results imply that light elements such as C and N are components of the ORR active sites in the FePc-based carbon catalysts pyrolyzed at high temperatures where the metal-N4 structures in the macrocycles are mostly decomposed.

Nanoshell carbon (NS) have properties such as hollow shell like structure, size range of primary particle (20–50 nm in diameter), high rate of electron transfer and excellent dispersivity in aqueous solutions without surface modification. Investigation of cytochrome c (cyt c ) adsorption was performed against NSs prepared by varying carbonization catalysts (Co, Fe) and temperatures (800, 1000 °C). Higher carbonization temperature and the selection of Fe as the carbonization catalyst seemed to lead to better adsorptive abilities of carbons toward cyt c . Quinone groups on NS surface might play an important role on the adsorption of cyt c . The results obtained in this study suggest that NSs have the potential for use as novel electrode materials for immobilization of cyt c .