minh hai Tran | Daegu University (original) (raw)

Papers by minh hai Tran

ACS omega, Nov 23, 2022

An economical and facile method to synthesize a precursor for carbon films and materials has been... more An economical and facile method to synthesize a precursor for carbon films and materials has been developed. This precursor can be easily coated onto substrates without binder reagents and then converted into a graphitic-like structure after mild thermal treatment. This approach potentially allows the coating of glass surfaces of different shapes and forms, such as the inside of a glass tube, for instance. The precursor consists of tetrahedral halocarbyne units which randomly combine through single electron transfer with organometallic compounds to create a poly(carbyne)-like polymeric material. Advanced characterization tools reveal that the synthesized product (poly(halocarbyne) or PXC, where X indicate the presence of halogens, is composed mostly of carbon, hydrogen, and a variable percentage of residual halocarbon groups. Therefore, it possesses good solubility in organic solvents and can be coated on any complex substrate. The coated PXC material produced here was annealed under mild conditions, leading to the production of a graphitic-like film on a glass substrate. The chemical homogeneity of the carbon material of the film was confirmed by Raman spectroscopy.

Journal of Materials Science: Materials in Electronics, 2017

for EDLC electrodes, and several allotropic forms such as diamond, graphite, carbon nanotubes, gr... more for EDLC electrodes, and several allotropic forms such as diamond, graphite, carbon nanotubes, graphene, and amorphous carbon exist. Both graphite and amorphous carbon are inexpensive and particularly easy to fabricate for use in electrodes, and so they are commonly used for energy storage devices [2-6]. Among the types of amorphous carbon, activated carbon has a very high surface area (more than 2000 m 2 g −1) due to its microporous surface [6], and graphene also has a very large surface area (2630 m 2 g −1) with precious properties such as high electrical conductivity (200,000 cm 2 V −1 s −1) and high thermal conductivity (5000 Wm −1 K −1) [7]. Therefore, activated carbon and graphene have attracted attention as energy storage materials [2-6]. In this study, we synthesize ruthenium oxide composite with activated carbon or graphene and compare their electrochemical performance for use in supercapacitor applications. Ruthenium oxide (RuO 2) is a typical material for pseudo-capacitors and is used to increase energy density by the faradaic process in which Ru 4+ is reduced to various oxidation states [1]. Ruthenium dioxide exists in two forms in electrodes [8-10]: anhydrous structure (RuO 2) and hydrous structure (RuO 2 •H 2 O). Hydrous ruthenium oxide has a more than three times higher specific capacitance compared to anhydrous ruthenium oxide due to mixed protonic-electronic conductivity [8-10]. Hydrous regions of hydrous ruthenium oxide allow facile proton permeation into the bulk, resulting in good protonic conductivity. The water bonded to ruthenium oxide provides a pathway for H + throughout the bulk [9] but too much water could lessen the electronic conducting pathway in ruthenium oxide [8]. Thus, both the protonic and electronic conductivity of ruthenium oxide must be optimized by mixing anhydrous and hydrous structure for better electrochemical performance [8-10].

New Physics: Sae Mulli, 2015

Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future ene... more Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future energy-storage devices are investigated. The chemical reduction followed by the thermal reduction provides better reduction of graphene oxide than the chemical or the thermal reduction only, but the effective surface area after both processes is smaller than that after only the thermal reduction process. The smaller surface area has negative effects on the performance of the electrochemical capacitors. We, therefore, conclude that the reduction level, the graphene structure, and the effective surface area should be concerns for future energy-storage applications.

New Physics: Sae Mulli, 2013

Graphene is a single sheet of graphite and becomes a widely researched material due to its extrao... more Graphene is a single sheet of graphite and becomes a widely researched material due to its extraordinary electrical, magnetic, thermal, and mechanical properties [1– 4]. An established route for the large scale production of graphene at low cost is through the graphite oxide (GO) by chemical methods [5]. It is, therefore, important to understand effects of the grain size and type of the precursor graphite on the synthesis of graphite oxide and graphene oxide for the future graphene applications. Two types of graphite, natural and synthetic, exist generally and are distinguished by physical characteristics that are the result of major differences in a geologic origin and occurrence [6,7]. In this paper we considered the influence of the grain size and type of precursor graphite on making graphite oxide. It was found that the smaller size graphite was more oxidized in a same condition and then easily dispersed in the distilled water, indicating that it could produce the single layer of graphene oxide simply. The large size graphite oxides showed higher crystallinity and uniformity after additional sonication treatment. The oxi-

Journal of Materials Science, 2017

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions... more Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultravioletvisible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.

Journal of Physics and Chemistry of Solids, 2018

A solution plasma approach for modification of phase and morphology of titanium dioxide is explor... more A solution plasma approach for modification of phase and morphology of titanium dioxide is explored as complementary to the standard sol-gel method. Titanium dioxide powders with different proportions of anatase and rutile phases were successfully synthesized by solution plasma treatment and the photocatalytic activities investigated by solar irradiation of methylene blue. The plasma can facilitate not only the phase transition from anatase to rutile structure but also decrease of particle size significantly through a thermal shocking effect, resulting in shifting of energy bandgap from 3.2 to 3.0 eV. Degradation of methylene blue in the titanium dioxide is evident and amounts up to 50% drop in

Journal of Materials Science: Materials in Electronics, 2017

Journal of Materials Science, 2017

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions... more Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultravioletvisible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.

Journal of Physics and Chemistry of Solids, 2018

A solution plasma approach for modification of phase and morphology of titanium dioxide is explor... more A solution plasma approach for modification of phase and morphology of titanium dioxide is explored as complementary to the standard sol-gel method. Titanium dioxide powders with different proportions of anatase and rutile phases were successfully synthesized by solution plasma treatment and the photocatalytic activities investigated by solar irradiation of methylene blue. The plasma can facilitate not only the phase transition from anatase to rutile structure but also decrease of particle size significantly through a thermal shocking effect, resulting in shifting of energy bandgap from 3.2 to 3.0 eV. Degradation of methylene blue in the titanium dioxide is evident and amounts up to 50% drop in

Chemical Physics Letters, 2017

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1,933 m 2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

Chemical Physics Letters, 2017

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1,933 m 2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

Electrochimica Acta, 2016

Abstract A novel approach to reduce poly (sodium 4-styrene sulfonate) graphite oxide (PSSGO) film... more Abstract A novel approach to reduce poly (sodium 4-styrene sulfonate) graphite oxide (PSSGO) film by ambient plasma is introduced. The film after the plasma treatment shows a significant change in morphology with many pores, leading to increased surface area. Oxygen functional groups existing in the film are removed, resulting in higher electric conductivity after the plasma treatment. The enhancement of the surface area and conductivity of the film results in better electrochemical performance for supercapacitor applications. The ambient plasma method is effective, easy, economical, and non-toxic when applied to the effective reduction of films.

Electrochimica Acta, 2015

Abstract Reduced graphene oxide (RGO) is functionalized with glucose and nickel oxide for the sup... more Abstract Reduced graphene oxide (RGO) is functionalized with glucose and nickel oxide for the supercapacitor application. The RGO layers intercalated by glucose create microspores inside the composite after thermal treatment at 500 °C, and the addition of nickel oxide reduces impedance of the composite, resulting in synergetic effects on the supercapacitor performance. That is, the specific capacitance of the composite is about five times higher than that of the RGO which has no glucose nor nickel oxide. The ternary composite also exhibits high performance of electric double layer capacitor (EDLC) and maintains the same specific capacitances up to 5,000 cycles, providing excellent cyclic stability. The ternary composite of the high EDLC performance, therefore, could be a good candidate of the supercapacitor electrodes.

Proceedings of the 6th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2009

In ubiquitous computing environments, certain entities (or actors) often need to interact with ea... more In ubiquitous computing environments, certain entities (or actors) often need to interact with each other in achieving a joint goal in a dynamically changing context. To perform such interactions in a seamless manner, the actors need to be aware of not only their physical context (e.g. location) but also their changing relationships with respect to the particular task or goal. The latter interaction-oriented context, which we refer to as social context, has significant impacts on the way actors manage their adaptive behavior. However, very little research has focused on supporting such social context in ubiquitous environments. This paper presents our novel approach to modeling and realizing social context. Social context is modeled as a managed composition of loosely-coupled roles with their interaction relationships expressed as contracts. In addition, it is modeled from an individual actor's perspective to allow for possible differences in the actors' perception of the relationships. The social contexts of an actor are externalized from the actor itself to achieve easy management of the actors' adaptive behavior concerning interaction. A layered system architecture is introduced to realize the approach and demonstrate the development of automotive telematics systems that are physically and socially context-aware.

Lecture Notes in Computer Science, 2008

Making justifiable decisions is a critical aspect of software architecture design. However, there... more Making justifiable decisions is a critical aspect of software architecture design. However, there has been limited empirical research on the effects of design reasoning on the quality of software design. The goal of this work is to investigate if there is any quality improvement to software design when design reasoning is applied. We conducted an empirical study involving twenty designers, the designers were asked to design a user interface and their designs were scored and compared. The results showed that the test group that was equipped with design reasoning produced a higher quality design than the control group, especially for inexperienced designers.

Current Applied Physics, 2014

Submitted for the MAR14 Meeting of The American Physical Society Influence of Graphite Size on th... more Submitted for the MAR14 Meeting of The American Physical Society Influence of Graphite Size on the Synthesis and Reduction of Graphite Oxides HAE KYUNG JEONG, Daegu University-We investigated the influence of the precursor, graphite, size on the synthesis and reduction of graphite oxide. Three precursors of graphite with different size were used to synthesize the graphite oxide which was consecutively reduced by hydrazine of different concentration ratios. Size dependent effect on the reduction of the graphite oxide was found, and the graphite oxide of the smallest size provided the best reduction result. Electrochemical properties of the reduced graphene oxide were investigated in both of the base and acid electrolytes, finding the reduced graphene oxide of the smallest size gives the best electrochemical performance due to the high reduction. Therefore, the precursor size is a very important factor in the synthesis and reduction of graphite oxide, affecting the electrochemical performance considerably for the energy storage applications.

Analytical Biochemistry, 2014

In this article, we report the intrinsic catalytic activity of graphene oxide (GO) for the nonspe... more In this article, we report the intrinsic catalytic activity of graphene oxide (GO) for the nonspecific cleavage of proteins. We used bovine serum albumin (BSA) and a recombinant esterase (rEstKp) from the coldadapted bacterium Pseudomonas mandelii as test proteins. Cleavage of BSA and rEstKp was nonspecific regarding amino acid sequence, but it exhibited dependence on temperature, time, and the amount of GO. However, cleavage of the proteins did not result in complete hydrolysis into their constituent amino acids. GO also invoked hydrolysis of p-nitrophenyl esters at moderate temperatures lower than those required for peptide hydrolysis regardless of chain length of the fatty acyl esters. Based on the results, the functional groups of GO, including alcohols, phenols, and carboxylates, can be considered as crucial roles in the GO-mediated hydrolysis of peptides and esters via general acid-base catalysis. Our findings provide novel insights into the role of GO as a carbocatalyst with nonspecific endopeptidase activity in biochemical reactions.

Chemical Physics Letters, 2015

A single residue, dipeptide, or tripeptide of alanine or histidine is covalently attached to grap... more A single residue, dipeptide, or tripeptide of alanine or histidine is covalently attached to graphene oxide (GO), and the effect of the amino acid immobilization on the impedance of GO is investigated using the impedance spectroscopy. The histidine of a tripeptide exhibits the lowest resistance compared to the single or dipeptide histidine in the KCl electrolyte, and the single alanine residue shows the lowest resistance in an acidic electrolyte compared to the dipeptide or tripeptide alanine. The peculiar behavior of the impedance could be explained by different net charges of the amino acids, chain length, andstacking interaction.

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1933 m 2 g À1 and low equivalent series resistance of 2 X, demonstrating that it improve the electrochemical performance for supercapac-itor applications.

Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future ene... more Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future energy-storage devices are investigated. The chemical reduction followed by the thermal reduction provides better reduction of graphene oxide than the chemical or the thermal reduction only, but the effective surface area after both processes is smaller than that after only the thermal reduction process. The smaller surface area has negative effects on the performance of the electrochemical ca-pacitors. We, therefore, conclude that the reduction level, the graphene structure, and the effective surface area should be concerns for future energy-storage applications.

ACS omega, Nov 23, 2022

An economical and facile method to synthesize a precursor for carbon films and materials has been... more An economical and facile method to synthesize a precursor for carbon films and materials has been developed. This precursor can be easily coated onto substrates without binder reagents and then converted into a graphitic-like structure after mild thermal treatment. This approach potentially allows the coating of glass surfaces of different shapes and forms, such as the inside of a glass tube, for instance. The precursor consists of tetrahedral halocarbyne units which randomly combine through single electron transfer with organometallic compounds to create a poly(carbyne)-like polymeric material. Advanced characterization tools reveal that the synthesized product (poly(halocarbyne) or PXC, where X indicate the presence of halogens, is composed mostly of carbon, hydrogen, and a variable percentage of residual halocarbon groups. Therefore, it possesses good solubility in organic solvents and can be coated on any complex substrate. The coated PXC material produced here was annealed under mild conditions, leading to the production of a graphitic-like film on a glass substrate. The chemical homogeneity of the carbon material of the film was confirmed by Raman spectroscopy.

Journal of Materials Science: Materials in Electronics, 2017

for EDLC electrodes, and several allotropic forms such as diamond, graphite, carbon nanotubes, gr... more for EDLC electrodes, and several allotropic forms such as diamond, graphite, carbon nanotubes, graphene, and amorphous carbon exist. Both graphite and amorphous carbon are inexpensive and particularly easy to fabricate for use in electrodes, and so they are commonly used for energy storage devices [2-6]. Among the types of amorphous carbon, activated carbon has a very high surface area (more than 2000 m 2 g −1) due to its microporous surface [6], and graphene also has a very large surface area (2630 m 2 g −1) with precious properties such as high electrical conductivity (200,000 cm 2 V −1 s −1) and high thermal conductivity (5000 Wm −1 K −1) [7]. Therefore, activated carbon and graphene have attracted attention as energy storage materials [2-6]. In this study, we synthesize ruthenium oxide composite with activated carbon or graphene and compare their electrochemical performance for use in supercapacitor applications. Ruthenium oxide (RuO 2) is a typical material for pseudo-capacitors and is used to increase energy density by the faradaic process in which Ru 4+ is reduced to various oxidation states [1]. Ruthenium dioxide exists in two forms in electrodes [8-10]: anhydrous structure (RuO 2) and hydrous structure (RuO 2 •H 2 O). Hydrous ruthenium oxide has a more than three times higher specific capacitance compared to anhydrous ruthenium oxide due to mixed protonic-electronic conductivity [8-10]. Hydrous regions of hydrous ruthenium oxide allow facile proton permeation into the bulk, resulting in good protonic conductivity. The water bonded to ruthenium oxide provides a pathway for H + throughout the bulk [9] but too much water could lessen the electronic conducting pathway in ruthenium oxide [8]. Thus, both the protonic and electronic conductivity of ruthenium oxide must be optimized by mixing anhydrous and hydrous structure for better electrochemical performance [8-10].

New Physics: Sae Mulli, 2015

Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future ene... more Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future energy-storage devices are investigated. The chemical reduction followed by the thermal reduction provides better reduction of graphene oxide than the chemical or the thermal reduction only, but the effective surface area after both processes is smaller than that after only the thermal reduction process. The smaller surface area has negative effects on the performance of the electrochemical capacitors. We, therefore, conclude that the reduction level, the graphene structure, and the effective surface area should be concerns for future energy-storage applications.

New Physics: Sae Mulli, 2013

Graphene is a single sheet of graphite and becomes a widely researched material due to its extrao... more Graphene is a single sheet of graphite and becomes a widely researched material due to its extraordinary electrical, magnetic, thermal, and mechanical properties [1– 4]. An established route for the large scale production of graphene at low cost is through the graphite oxide (GO) by chemical methods [5]. It is, therefore, important to understand effects of the grain size and type of the precursor graphite on the synthesis of graphite oxide and graphene oxide for the future graphene applications. Two types of graphite, natural and synthetic, exist generally and are distinguished by physical characteristics that are the result of major differences in a geologic origin and occurrence [6,7]. In this paper we considered the influence of the grain size and type of precursor graphite on making graphite oxide. It was found that the smaller size graphite was more oxidized in a same condition and then easily dispersed in the distilled water, indicating that it could produce the single layer of graphene oxide simply. The large size graphite oxides showed higher crystallinity and uniformity after additional sonication treatment. The oxi-

Journal of Materials Science, 2017

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions... more Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultravioletvisible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.

Journal of Physics and Chemistry of Solids, 2018

A solution plasma approach for modification of phase and morphology of titanium dioxide is explor... more A solution plasma approach for modification of phase and morphology of titanium dioxide is explored as complementary to the standard sol-gel method. Titanium dioxide powders with different proportions of anatase and rutile phases were successfully synthesized by solution plasma treatment and the photocatalytic activities investigated by solar irradiation of methylene blue. The plasma can facilitate not only the phase transition from anatase to rutile structure but also decrease of particle size significantly through a thermal shocking effect, resulting in shifting of energy bandgap from 3.2 to 3.0 eV. Degradation of methylene blue in the titanium dioxide is evident and amounts up to 50% drop in

Journal of Materials Science: Materials in Electronics, 2017

Journal of Materials Science, 2017

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions... more Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultravioletvisible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.

Journal of Physics and Chemistry of Solids, 2018

A solution plasma approach for modification of phase and morphology of titanium dioxide is explor... more A solution plasma approach for modification of phase and morphology of titanium dioxide is explored as complementary to the standard sol-gel method. Titanium dioxide powders with different proportions of anatase and rutile phases were successfully synthesized by solution plasma treatment and the photocatalytic activities investigated by solar irradiation of methylene blue. The plasma can facilitate not only the phase transition from anatase to rutile structure but also decrease of particle size significantly through a thermal shocking effect, resulting in shifting of energy bandgap from 3.2 to 3.0 eV. Degradation of methylene blue in the titanium dioxide is evident and amounts up to 50% drop in

Chemical Physics Letters, 2017

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1,933 m 2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

Chemical Physics Letters, 2017

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1,933 m 2 g-1 and low equivalent series resistance of 2 Ω, demonstrating that it improve the electrochemical performance for supercapacitor applications.

Electrochimica Acta, 2016

Abstract A novel approach to reduce poly (sodium 4-styrene sulfonate) graphite oxide (PSSGO) film... more Abstract A novel approach to reduce poly (sodium 4-styrene sulfonate) graphite oxide (PSSGO) film by ambient plasma is introduced. The film after the plasma treatment shows a significant change in morphology with many pores, leading to increased surface area. Oxygen functional groups existing in the film are removed, resulting in higher electric conductivity after the plasma treatment. The enhancement of the surface area and conductivity of the film results in better electrochemical performance for supercapacitor applications. The ambient plasma method is effective, easy, economical, and non-toxic when applied to the effective reduction of films.

Electrochimica Acta, 2015

Abstract Reduced graphene oxide (RGO) is functionalized with glucose and nickel oxide for the sup... more Abstract Reduced graphene oxide (RGO) is functionalized with glucose and nickel oxide for the supercapacitor application. The RGO layers intercalated by glucose create microspores inside the composite after thermal treatment at 500 °C, and the addition of nickel oxide reduces impedance of the composite, resulting in synergetic effects on the supercapacitor performance. That is, the specific capacitance of the composite is about five times higher than that of the RGO which has no glucose nor nickel oxide. The ternary composite also exhibits high performance of electric double layer capacitor (EDLC) and maintains the same specific capacitances up to 5,000 cycles, providing excellent cyclic stability. The ternary composite of the high EDLC performance, therefore, could be a good candidate of the supercapacitor electrodes.

Proceedings of the 6th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2009

In ubiquitous computing environments, certain entities (or actors) often need to interact with ea... more In ubiquitous computing environments, certain entities (or actors) often need to interact with each other in achieving a joint goal in a dynamically changing context. To perform such interactions in a seamless manner, the actors need to be aware of not only their physical context (e.g. location) but also their changing relationships with respect to the particular task or goal. The latter interaction-oriented context, which we refer to as social context, has significant impacts on the way actors manage their adaptive behavior. However, very little research has focused on supporting such social context in ubiquitous environments. This paper presents our novel approach to modeling and realizing social context. Social context is modeled as a managed composition of loosely-coupled roles with their interaction relationships expressed as contracts. In addition, it is modeled from an individual actor's perspective to allow for possible differences in the actors' perception of the relationships. The social contexts of an actor are externalized from the actor itself to achieve easy management of the actors' adaptive behavior concerning interaction. A layered system architecture is introduced to realize the approach and demonstrate the development of automotive telematics systems that are physically and socially context-aware.

Lecture Notes in Computer Science, 2008

Making justifiable decisions is a critical aspect of software architecture design. However, there... more Making justifiable decisions is a critical aspect of software architecture design. However, there has been limited empirical research on the effects of design reasoning on the quality of software design. The goal of this work is to investigate if there is any quality improvement to software design when design reasoning is applied. We conducted an empirical study involving twenty designers, the designers were asked to design a user interface and their designs were scored and compared. The results showed that the test group that was equipped with design reasoning produced a higher quality design than the control group, especially for inexperienced designers.

Current Applied Physics, 2014

Submitted for the MAR14 Meeting of The American Physical Society Influence of Graphite Size on th... more Submitted for the MAR14 Meeting of The American Physical Society Influence of Graphite Size on the Synthesis and Reduction of Graphite Oxides HAE KYUNG JEONG, Daegu University-We investigated the influence of the precursor, graphite, size on the synthesis and reduction of graphite oxide. Three precursors of graphite with different size were used to synthesize the graphite oxide which was consecutively reduced by hydrazine of different concentration ratios. Size dependent effect on the reduction of the graphite oxide was found, and the graphite oxide of the smallest size provided the best reduction result. Electrochemical properties of the reduced graphene oxide were investigated in both of the base and acid electrolytes, finding the reduced graphene oxide of the smallest size gives the best electrochemical performance due to the high reduction. Therefore, the precursor size is a very important factor in the synthesis and reduction of graphite oxide, affecting the electrochemical performance considerably for the energy storage applications.

Analytical Biochemistry, 2014

In this article, we report the intrinsic catalytic activity of graphene oxide (GO) for the nonspe... more In this article, we report the intrinsic catalytic activity of graphene oxide (GO) for the nonspecific cleavage of proteins. We used bovine serum albumin (BSA) and a recombinant esterase (rEstKp) from the coldadapted bacterium Pseudomonas mandelii as test proteins. Cleavage of BSA and rEstKp was nonspecific regarding amino acid sequence, but it exhibited dependence on temperature, time, and the amount of GO. However, cleavage of the proteins did not result in complete hydrolysis into their constituent amino acids. GO also invoked hydrolysis of p-nitrophenyl esters at moderate temperatures lower than those required for peptide hydrolysis regardless of chain length of the fatty acyl esters. Based on the results, the functional groups of GO, including alcohols, phenols, and carboxylates, can be considered as crucial roles in the GO-mediated hydrolysis of peptides and esters via general acid-base catalysis. Our findings provide novel insights into the role of GO as a carbocatalyst with nonspecific endopeptidase activity in biochemical reactions.

Chemical Physics Letters, 2015

A single residue, dipeptide, or tripeptide of alanine or histidine is covalently attached to grap... more A single residue, dipeptide, or tripeptide of alanine or histidine is covalently attached to graphene oxide (GO), and the effect of the amino acid immobilization on the impedance of GO is investigated using the impedance spectroscopy. The histidine of a tripeptide exhibits the lowest resistance compared to the single or dipeptide histidine in the KCl electrolyte, and the single alanine residue shows the lowest resistance in an acidic electrolyte compared to the dipeptide or tripeptide alanine. The peculiar behavior of the impedance could be explained by different net charges of the amino acids, chain length, andstacking interaction.

A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modific... more A simple, binder-free, method of making supercapacitor electrodes is introduced, based on modification of activated carbon with graphite oxide and carbon nanotubes. The three carbon precursors of different morphologies support each other to provide outstanding electrochemical performance, such as high capacitance and high energy density. The ternary carbon composite shows six times higher specific capacitance compared to that of activated carbon itself with high retention. The excellent electrochemical properties of the ternary composite attribute to the high surface area of 1933 m 2 g À1 and low equivalent series resistance of 2 X, demonstrating that it improve the electrochemical performance for supercapac-itor applications.

Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future ene... more Three kinds of reduction processes (chemical, thermal, and both) of graphene oxide for future energy-storage devices are investigated. The chemical reduction followed by the thermal reduction provides better reduction of graphene oxide than the chemical or the thermal reduction only, but the effective surface area after both processes is smaller than that after only the thermal reduction process. The smaller surface area has negative effects on the performance of the electrochemical ca-pacitors. We, therefore, conclude that the reduction level, the graphene structure, and the effective surface area should be concerns for future energy-storage applications.