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Joong Hee Lee - One of the best experts on this subject based on the ideXlab platform.
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effects of various surfactants on the Dispersion Stability and electrical conductivity of surface modified graphene
Journal of Alloys and Compounds, 2013Co-Authors: Md Elias Uddin, Nam Hoon Kim, Tapas Kuila, Ganesh Chandra Nayak, Joong Hee LeeAbstract:Abstract Ionic and non-ionic surfactant functionalized, water dispersible graphene were prepared to investigate the effects on the Dispersion Stability and electrical conductivity of graphene. In this study, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate and 4-(1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol (Triton X-100) were used as ionic and non-ionic surfactants. The effects of surfactant concentrations on the dispersibility and electrical conductivity of the surface modified graphene were investigated. The Dispersion Stability of SDBS functionalized graphene (SDBS-G) was found to be best in water at 1.5 mg ml −1 . X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis indicate that the presence of surfactants does not prevent the reduction of graphene oxide (GO). These measurements also demonstrated that the surfactants were present on the surface of graphene, resulting in the formation of functionalized graphene. The thickness of different functionalized graphene was measured by Atomic force microscopy and varied significantly with different surfactants. The thermal properties of the functionalized graphene were also found to be dependent on the nature of the surfactants. The electrical conductivity of SDBS-G (108 S m −1 ) was comparatively higher than SDS and Triton X-100 functionalized graphene.
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Effect of surface treatment with potassium persulfate on Dispersion Stability of multi-walled carbon nanotubes
Materials Letters, 2010Co-Authors: Ok-kyung Park, Nam Hoon Kim, Kin-tak Lau, Joong Hee LeeAbstract:Muti-walled carbon nanotubes (MWCNTs) were treated with different concentrations of potassium persulfate (KPS; K2S2O8) to improve their Dispersion Stability, which were characterized by thermal gravimetric analysis, ultraviolet/visible spectroscopy, field emission scanning electron microscopy and field emission transmission electron microscopy. The amount of sulfate groups on the MWCNTs increased with increasing KPS concentration, which enhanced the hydrophilicity, but deteriorated the Dispersion Stability. The optimal KPS concentration for the best Dispersion Stability of the KPS-treated MWCNTs was 0.01 M.
Dongmao Zhang - One of the best experts on this subject based on the ideXlab platform.
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Dispersion Stability, Ligand Structure and Conformation, and SERS Activities of 1-Alkanethiol Functionalized Gold and Silver Nanoparticles
Journal of Physical Chemistry C, 2014Co-Authors: Siyam M. Ansar, Manuel Gadogbe, Kumudu Siriwardana, Jane Y. Howe, Stas Dogel, Hooman Hosseinkhannazer, Willard E. Collier, José A. Rodriguez, Dongmao ZhangAbstract:Dispersion Stability, ligand structure and conformation, and SERS activities of 1-alkanethiol (CnH2n+1SH, n = 2–14) functionalized gold and silver nanoparticles (AuNPs and AgNPs) were studied as a function of alkanethiol carbon chain length and nanoparticle (NP) type and size. The Dispersion Stability of alkanethiol functionalized NPs in water increases with increasing alkanethiol chain length and NP size, and the stabilities of the alkanethiol-containing AuNPs are higher than their AgNP counterparts. C3H7SH and longer alkanethiols are highly ordered on AgNPs but disordered on AuNPs. The SERS intensity of the C–S stretch band for the model alkanethiols on AgNPs and AuNPs decays exponentially (I = I0 exp(−Nc/N0)) with increasing number of carbon atoms (Nc). The empirical decay length N0, in terms of the number of the carbon atoms, is 1.29, 0.53, and 0.10 for AgNPs with diameters of 50, 30, and 10 nm, respectively. This decay length is less than 1 for AuNPs of difference sizes. These results show that chang...
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Dispersion Stability, Ligand Structure and Conformation, and SERS Activities of 1-Alkanethiol Functionalized Gold and Silver Nanoparticles
Journal of Physical Chemistry C, 2014Co-Authors: Siyam M. Ansar, Manuel Gadogbe, Kumudu Siriwardana, Jane Y. Howe, Stas Dogel, Hooman Hosseinkhannazer, Willard E. Collier, José A. Rodriguez, Dongmao ZhangAbstract:Dispersion Stability, ligand structure and conformation, and SERS activities of 1-alkanethiol (CnH2n+1SH, n = 2–14) functionalized gold and silver nanoparticles (AuNPs and AgNPs) were studied as a function of alkanethiol carbon chain length and nanoparticle (NP) type and size. The Dispersion Stability of alkanethiol functionalized NPs in water increases with increasing alkanethiol chain length and NP size, and the stabilities of the alkanethiol-containing AuNPs are higher than their AgNP counterparts. C3H7SH and longer alkanethiols are highly ordered on AgNPs but disordered on AuNPs. The SERS intensity of the C–S stretch band for the model alkanethiols on AgNPs and AuNPs decays exponentially (I = I0 exp(−Nc/N0)) with increasing number of carbon atoms (Nc). The empirical decay length N0, in terms of the number of the carbon atoms, is 1.29, 0.53, and 0.10 for AgNPs with diameters of 50, 30, and 10 nm, respectively. This decay length is less than 1 for AuNPs of difference sizes. These results show that chang...
Zhengguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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preparation and photo thermal conversion performance of modified graphene ionic liquid nanofluids with excellent Dispersion Stability
Solar Energy Materials and Solar Cells, 2017Co-Authors: Jian Liu, Leilei Chen, Xiaoming Fang, Zhengguo ZhangAbstract:Abstract Dispersion Stability has been long considered as a critical issue for applying nanofluids in various fields, especially for the applications at elevated temperatures. Herein a novel route is explored to improve the Dispersion Stability of graphene (GE)/ionic liquid (IL) nanofluids for use as working fluids in medium- and high-temperature direct absorption solar collectors (DASCs), which involves modifying GE according to the molecular structure of the IL. Specifically, GE was modified using the reagents and process for synthesizing [HMIM]BF 4 , followed by dispersing the modified GE (MGE) into [HMIM]BF 4. It is verified that the molecular chains similar to [HMIM]BF 4 have been grafted on the nanosheets of GE, and the MGE/[HMIM]BF 4 nanofluids exhibit much better Dispersion Stability than the one containing the unmodified GE, even at elevated temperatures. Moreover, the temperature profiles of the nanofluids containing MGE and GE were obtained both from the experimental measurement and the theoretical prediction using a one-dimensional transient heat transfer model. It is shown that the experimental data are in good agreement with the numerical ones for the MGE nanofluids, while a large deviation between them is found for the one containing the unmodified GE. And the MGE nanofluid shows enhanced receiver efficiency as compared to the GE one due to its much improved Dispersion Stability. Further, the transient model was used to predict the performance of the MGE nanofluid based DASCs under high solar concentrations. And by integrating the MGE concentration and the receiver height into a parameter, namely optical thickness, the optimization of the MGE nanofluid based DASC was carried out varying solar concentration, MGE concentration, nanofluid height and exposure time. It is revealed that the photo-thermal conversion performance of nanofluids greatly depends on its Dispersion Stability at elevated temperatures, and the MGE/[HMIM]BF 4 nanofluids possess excellent Dispersion Stability and show great potentials for use as the working fluids in DASCs. This work sheds light on effective routes for improving Dispersion Stability of nanofluids as well as numerical investigations on nanofluid based DASCs.
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Preparation and photo-thermal conversion performance of modified graphene/ionic liquid nanofluids with excellent Dispersion Stability
Solar Energy Materials and Solar Cells, 2017Co-Authors: Jian Liu, Leilei Chen, Xiaoming Fang, Zhengguo ZhangAbstract:Abstract Dispersion Stability has been long considered as a critical issue for applying nanofluids in various fields, especially for the applications at elevated temperatures. Herein a novel route is explored to improve the Dispersion Stability of graphene (GE)/ionic liquid (IL) nanofluids for use as working fluids in medium- and high-temperature direct absorption solar collectors (DASCs), which involves modifying GE according to the molecular structure of the IL. Specifically, GE was modified using the reagents and process for synthesizing [HMIM]BF 4 , followed by dispersing the modified GE (MGE) into [HMIM]BF 4. It is verified that the molecular chains similar to [HMIM]BF 4 have been grafted on the nanosheets of GE, and the MGE/[HMIM]BF 4 nanofluids exhibit much better Dispersion Stability than the one containing the unmodified GE, even at elevated temperatures. Moreover, the temperature profiles of the nanofluids containing MGE and GE were obtained both from the experimental measurement and the theoretical prediction using a one-dimensional transient heat transfer model. It is shown that the experimental data are in good agreement with the numerical ones for the MGE nanofluids, while a large deviation between them is found for the one containing the unmodified GE. And the MGE nanofluid shows enhanced receiver efficiency as compared to the GE one due to its much improved Dispersion Stability. Further, the transient model was used to predict the performance of the MGE nanofluid based DASCs under high solar concentrations. And by integrating the MGE concentration and the receiver height into a parameter, namely optical thickness, the optimization of the MGE nanofluid based DASC was carried out varying solar concentration, MGE concentration, nanofluid height and exposure time. It is revealed that the photo-thermal conversion performance of nanofluids greatly depends on its Dispersion Stability at elevated temperatures, and the MGE/[HMIM]BF 4 nanofluids possess excellent Dispersion Stability and show great potentials for use as the working fluids in DASCs. This work sheds light on effective routes for improving Dispersion Stability of nanofluids as well as numerical investigations on nanofluid based DASCs.
Siyam M. Ansar - One of the best experts on this subject based on the ideXlab platform.
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Dispersion Stability, Ligand Structure and Conformation, and SERS Activities of 1-Alkanethiol Functionalized Gold and Silver Nanoparticles
Journal of Physical Chemistry C, 2014Co-Authors: Siyam M. Ansar, Manuel Gadogbe, Kumudu Siriwardana, Jane Y. Howe, Stas Dogel, Hooman Hosseinkhannazer, Willard E. Collier, José A. Rodriguez, Dongmao ZhangAbstract:Dispersion Stability, ligand structure and conformation, and SERS activities of 1-alkanethiol (CnH2n+1SH, n = 2–14) functionalized gold and silver nanoparticles (AuNPs and AgNPs) were studied as a function of alkanethiol carbon chain length and nanoparticle (NP) type and size. The Dispersion Stability of alkanethiol functionalized NPs in water increases with increasing alkanethiol chain length and NP size, and the stabilities of the alkanethiol-containing AuNPs are higher than their AgNP counterparts. C3H7SH and longer alkanethiols are highly ordered on AgNPs but disordered on AuNPs. The SERS intensity of the C–S stretch band for the model alkanethiols on AgNPs and AuNPs decays exponentially (I = I0 exp(−Nc/N0)) with increasing number of carbon atoms (Nc). The empirical decay length N0, in terms of the number of the carbon atoms, is 1.29, 0.53, and 0.10 for AgNPs with diameters of 50, 30, and 10 nm, respectively. This decay length is less than 1 for AuNPs of difference sizes. These results show that chang...
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Dispersion Stability, Ligand Structure and Conformation, and SERS Activities of 1-Alkanethiol Functionalized Gold and Silver Nanoparticles
Journal of Physical Chemistry C, 2014Co-Authors: Siyam M. Ansar, Manuel Gadogbe, Kumudu Siriwardana, Jane Y. Howe, Stas Dogel, Hooman Hosseinkhannazer, Willard E. Collier, José A. Rodriguez, Dongmao ZhangAbstract:Dispersion Stability, ligand structure and conformation, and SERS activities of 1-alkanethiol (CnH2n+1SH, n = 2–14) functionalized gold and silver nanoparticles (AuNPs and AgNPs) were studied as a function of alkanethiol carbon chain length and nanoparticle (NP) type and size. The Dispersion Stability of alkanethiol functionalized NPs in water increases with increasing alkanethiol chain length and NP size, and the stabilities of the alkanethiol-containing AuNPs are higher than their AgNP counterparts. C3H7SH and longer alkanethiols are highly ordered on AgNPs but disordered on AuNPs. The SERS intensity of the C–S stretch band for the model alkanethiols on AgNPs and AuNPs decays exponentially (I = I0 exp(−Nc/N0)) with increasing number of carbon atoms (Nc). The empirical decay length N0, in terms of the number of the carbon atoms, is 1.29, 0.53, and 0.10 for AgNPs with diameters of 50, 30, and 10 nm, respectively. This decay length is less than 1 for AuNPs of difference sizes. These results show that chang...
Tatsuo Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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unique coexistence of Dispersion Stability and nanoparticle chemisorption in alkylamine alkylacid encapsulated silver nanocolloids
Scientific Reports, 2018Co-Authors: Keisuke Aoshima, Yuya Hirakawa, Takanari Togashi, Masato Kurihara, Shunto Arai, Tatsuo HasegawaAbstract:Surface encapsulation of metal nanoparticles (NPs) is fundamental to achieve sufficient Dispersion Stability of metal nanocolloids, or metal nanoink. However, the feature is incompatible with surface reactive nature of the metal NPs, although these features are both essential to realizing the functional applications into printed electronics technologies. Here we show that two different kinds of encapsulation for silver NPs (AgNPs) by alkylamine and alkylacid together are the key to achieve unique compatibility between the high Dispersion Stability as dense nanoclolloids and the AgNP chemisorption printing on activated patterned polymer surfaces. Advanced confocal dynamic light scattering study reveals that an additive trace amount of oleic acid is the critical parameter for controlling the Dispersion and coagulative (or surface-reactive) characteristics of the silver nanocolloids. The composition of the disperse media is also important for obtaining highly concentrated but low-viscosity silver nanocolloids that show very stable Dispersion. The results demonstrate that the high-resolution AgNP chemisorption printing is possible only by using unique silver nanocolloids composed of an exceptional balance of ligand formulation and dispersant composition.
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Unique coexistence of Dispersion Stability and nanoparticle chemisorption in alkylamine/alkylacid encapsulated silver nanocolloids
Scientific reports, 2018Co-Authors: Keisuke Aoshima, Yuya Hirakawa, Takanari Togashi, Masato Kurihara, Shunto Arai, Tatsuo HasegawaAbstract:Surface encapsulation of metal nanoparticles (NPs) is fundamental to achieve sufficient Dispersion Stability of metal nanocolloids, or metal nanoink. However, the feature is incompatible with surface reactive nature of the metal NPs, although these features are both essential to realizing the functional applications into printed electronics technologies. Here we show that two different kinds of encapsulation for silver NPs (AgNPs) by alkylamine and alkylacid together are the key to achieve unique compatibility between the high Dispersion Stability as dense nanoclolloids and the AgNP chemisorption printing on activated patterned polymer surfaces. Advanced confocal dynamic light scattering study reveals that an additive trace amount of oleic acid is the critical parameter for controlling the Dispersion and coagulative (or surface-reactive) characteristics of the silver nanocolloids. The composition of the disperse media is also important for obtaining highly concentrated but low-viscosity silver nanocolloids that show very stable Dispersion. The results demonstrate that the high-resolution AgNP chemisorption printing is possible only by using unique silver nanocolloids composed of an exceptional balance of ligand formulation and dispersant composition.