Binh Duong - Academia.edu (original) (raw)

Papers by Binh Duong

Carbon, Sep 1, 2011

The effects of growth conditions, such as methane flow rates and type of substrate on the distrib... more The effects of growth conditions, such as methane flow rates and type of substrate on the distribution, structure and properties of nanotubes were examined. A scanning electron microscope equipped with a Raman spectrometer enabled us to obtain critical information about the structure and electrical properties of the nanotubes simultaneously, and it was shown that these were highly dependent on the methane flow rate. At a methane flow rate of 600 cc/min, we primarily obtained double-walled carbon nanotubes having predominantly semiconducting properties. At a higher methane flow rate (700 cc/min), a mixture of single-walled and double-walled carbon nanotubes was created, most of which were semiconducting. At low methane flow rates (300 and 500 cc/min), metallic multi-walled carbon nanotubes were predominated. Carbon nanotubes grown on a quartz substrate were between 4-10 lm in length, whereas those grown on silicon were longer ($15-20 lm). The primary growth mechanism observed was base growth, although some cap growth did occur. Based on the results of this study, it is now possible to carefully control the synthesis conditions to produce carbon nanotubes that possess specific electrical properties that suit the desired application.

This article presents the synthesis and characterization of carbon nanotubes (CNTs) on silicon su... more This article presents the synthesis and characterization of carbon nanotubes (CNTs) on silicon substrates by chemical vapor deposition (CVD) at 900ºC using methane and hydrogen flow rates. The variation of H 2 gas concentration and a set growth time of 15 minutes have a significant effect on distribution, morphology, internal structure, and electronic properties of the nanotubes. The transmission electron microscope (TEM) and state-of-the-art scanning electron microscope (SEM), equipped with Raman spectrometer, allowed us to obtain critical information on the morphology and chemical and electronic structures of the CNTs. The results revealed substantial quantity trends as hydrogen flow rate increased from 100 to 700 standard cubic centimeter per minute (sccm). At a constant CH 4 flow rate of 700 sccm and varied H 2 of 100 and 200 sccm, we observed that few CNTs were produced. Between H 2 flow rates of 300 and 400 Journal of Undergraduate Research in Physics August 27, 2010

physica status solidi (a), 2013

In thin film devices such as light-emitting diodes, photovoltaic cells and field-effect transisto... more In thin film devices such as light-emitting diodes, photovoltaic cells and field-effect transistors, the processes of charge injection, charge transport, charge recombination, separation and collection are critical to performance. Most of these processes are relevant to nanoscale metal and metal oxide electrode-organic material interfacial phenomena. In this report we present a unique method for creating tailored onedimensional nanostructured silver, tin and/or zinc substituted indium oxide electrode structures over large areas. The method allows production of high aspect ratio nanoscale structures with feature sizes below 100 nm and a large range of dimensional tunability. We observed that both the electronic and optical properties of these electrodes are closely correlated to the nanostructure dimensions and can be easily tuned by control of the feature size. Surface area enhancement accurately describes the conductivity studies, while nanostructure dependent optical properties highlight the quasi-plasmonic nature of the electrodes. Optimization of the nanostructured electrode transparency and conductivity for specific opto-electronic systems is expected to provide improvement in device performance.

Advanced Materials Interfaces, 2013

ACS Applied Materials & Interfaces, 2014

There is an urgent need to develop taggants that can be used to identify objects, prevent fraud, ... more There is an urgent need to develop taggants that can be used to identify objects, prevent fraud, and deter counterfeiting with high reliability, high capacity, and minimal effort. This paper describes a new multilayer covert taggant based on phase change nanoparticles (metals and eutectic alloys). A panel of selected nanoparticles with different melting temperatures have been added in matrix materials together with fluorescent dye and printed on substrates to form micro-/macrofeatures that contain thermal, fluorescence signature, and structural components. The multilayer taggants can greatly enhance security level for many commercial and forensic applications by their extremely large labeling capacity, coding readiness, and covertness.

Scientific Reports, 2014

An unmet need is to develop covert barcodes that can be used to track-trace objects, and authenti... more An unmet need is to develop covert barcodes that can be used to track-trace objects, and authenticate documents. This paper describes a new nanoparticle-based covert barcode system, in which a selected panel of solid-to-liquid phase change nanoparticles with discrete and sharp melting peaks is added in a variety of objects such as explosive derivative, drug, polymer, and ink. This method has high labeling capacity owing to the small sizes of nanoparticles, sharp melting peaks, and large scan range of thermal analysis. The thermal barcode can enhance forensic investigation by its technical readiness, structural covertness, and robustness.

Renewable Energy and the Environment Optics and Photonics Congress, 2012

An integrating sphere is used to measure the absorptance of P3HT:PCBM layers with 700 nm period g... more An integrating sphere is used to measure the absorptance of P3HT:PCBM layers with 700 nm period gratings on the reverse side of the substrate. Gratings that do not exploit TIR adversely affect the absorptance.

Microscopy and Microanalysis, 2008

Ferrites (AFe 2 O 4 , A = Mn, Co, Ni, Cu, Zn), particularly nanoparticles, have high potential fo... more Ferrites (AFe 2 O 4 , A = Mn, Co, Ni, Cu, Zn), particularly nanoparticles, have high potential for many new technological applications, e.g. magnetic recording media and storage, MRI enhancement, magnetically guided drug delivery, and waste water treatment. Spinel zinc ferrite (ZnFe 2 O 4 ) is paramagnetic and exhibits antiferromagnetism with the Neel temperature (T N ) of about 10K [1]. On the other hand, nickel ferrite (Ni Fe 2 O 4 ) has an inverse spinel structure showing ferri-magnetism that originates from magnetic moment of anti-parrallel spins between Fe 3+ ions at tetrahedral sites and Ni 2+ ions at octahedral sites . It was suggested recently that some Zn, Ni and Cu ferrites offer superior magnetic properties depending on certain concentration of Ni, Cu, Zn in the ferrites . The present study reports on the effects of Zn, Ni, and Cu concentrations on the structural and magnetic properties of the ferrites prepared by simple, cost-effective, non-toxic sol-gel methods.

Microscopy and Microanalysis, 2008

Carbon nanotubes (CNTs) are allotropes of carbon with a few nanometers in diameter and several mi... more Carbon nanotubes (CNTs) are allotropes of carbon with a few nanometers in diameter and several micrometers in length. Numerous studies reported on various methods to grow CNTs including electric arc discharge, laser vaporization, and chemical vapor deposition (CVD). There are strong correlations between the synthesis, structure, and properties of the CNTs [1]. In this work, we used CVD method to grow CNTs on two types of substrates-quartz and Si/SiO 2 in order to investigate their properties in the microwave range for electronic devices. Several sets of samples with different catalysts, growth temperature, time, and gas flow rate were studied.

Journal of Power Sources, 2012

The effect of the microporous layer (MPL) and wet proofing on the MacMullin number has been evalu... more The effect of the microporous layer (MPL) and wet proofing on the MacMullin number has been evaluated for a custom series of Toray TGP-H-060 carbon paper gas diffusion layer (GDL). Complementary characterizations for these GDLs were performed by using scanning electron microscopy (SEM) images, pore size distribution (PSD) and fuel cell performance. The GDLs were customized by the addition of a microporous layer (MPL) and the treatment of, either or both, the substrate and MPL with 10% and 40% hydrophobic agent. SEM images correlated very well with the data shown for PSD. Distinction between the substrate layer and the MPL were clearly shown as two different slopes in the integral distribution and two different peaks in the differential distribution. The MacMullin number increased with increase in wet proofing but decreased with the addition of the MPL. The MacMullin number is a key parameter that contains the missing information for the path length in GDLs, which is generally approximated with the Bruggeman expression. The results provided an overview for the interpretation of the combined effect of the substrate and MPL properties as well as the cell operating conditions.

Journal of Power Sources, 2012

A gas diffusion layer (GDL) in a proton exchange membrane fuel cell may consist of several, mater... more A gas diffusion layer (GDL) in a proton exchange membrane fuel cell may consist of several, materials of different porosities, with each material serving a specific set of functions. For example, samples analyzed in this work consisted of a macro porous carbon paper substrate treated with a, hydrophobic wet proofing material in differing amounts, which was then coupled to a micro porous, layer. The porosities of four such GDLs were determined by using 2D scanning electron microscope (SEM) images to mathematically model the volumes filled by each solid in the 3D structures. Results, were then compared with mercury intrusion porosimetry (MIP) measurements to verify the accuracy, of the method. It was found that the use of SEM not only allowed for detailed porosity analysis of, separate porous materials within the GDL, but also porosity for the entire GDL could be calculated for, the seemingly complex structures with reasonable accuracy. With some basic geometric assumptions, and use of the superposition principle, the calculated results were accurate to less than a 2% absolute, difference of the porosity measured by MIP for each of the four samples analyzed.

Carbon, 2011

The effects of growth conditions, such as methane flow rates and type of substrate on the distrib... more The effects of growth conditions, such as methane flow rates and type of substrate on the distribution, structure and properties of nanotubes were examined. A scanning electron microscope equipped with a Raman spectrometer enabled us to obtain critical information about the structure and electrical properties of the nanotubes simultaneously, and it was shown that these were highly dependent on the methane flow rate. At a methane flow rate of 600 cc/min, we primarily obtained double-walled carbon nanotubes having predominantly semiconducting properties. At a higher methane flow rate (700 cc/min), a mixture of single-walled and double-walled carbon nanotubes was created, most of which were semiconducting. At low methane flow rates (300 and 500 cc/min), metallic multi-walled carbon nanotubes were predominated. Carbon nanotubes grown on a quartz substrate were between 4-10 lm in length, whereas those grown on silicon were longer ($15-20 lm). The primary growth mechanism observed was base growth, although some cap growth did occur. Based on the results of this study, it is now possible to carefully control the synthesis conditions to produce carbon nanotubes that possess specific electrical properties that suit the desired application.

Carbon, Sep 1, 2011

The effects of growth conditions, such as methane flow rates and type of substrate on the distrib... more The effects of growth conditions, such as methane flow rates and type of substrate on the distribution, structure and properties of nanotubes were examined. A scanning electron microscope equipped with a Raman spectrometer enabled us to obtain critical information about the structure and electrical properties of the nanotubes simultaneously, and it was shown that these were highly dependent on the methane flow rate. At a methane flow rate of 600 cc/min, we primarily obtained double-walled carbon nanotubes having predominantly semiconducting properties. At a higher methane flow rate (700 cc/min), a mixture of single-walled and double-walled carbon nanotubes was created, most of which were semiconducting. At low methane flow rates (300 and 500 cc/min), metallic multi-walled carbon nanotubes were predominated. Carbon nanotubes grown on a quartz substrate were between 4-10 lm in length, whereas those grown on silicon were longer ($15-20 lm). The primary growth mechanism observed was base growth, although some cap growth did occur. Based on the results of this study, it is now possible to carefully control the synthesis conditions to produce carbon nanotubes that possess specific electrical properties that suit the desired application.

This article presents the synthesis and characterization of carbon nanotubes (CNTs) on silicon su... more This article presents the synthesis and characterization of carbon nanotubes (CNTs) on silicon substrates by chemical vapor deposition (CVD) at 900ºC using methane and hydrogen flow rates. The variation of H 2 gas concentration and a set growth time of 15 minutes have a significant effect on distribution, morphology, internal structure, and electronic properties of the nanotubes. The transmission electron microscope (TEM) and state-of-the-art scanning electron microscope (SEM), equipped with Raman spectrometer, allowed us to obtain critical information on the morphology and chemical and electronic structures of the CNTs. The results revealed substantial quantity trends as hydrogen flow rate increased from 100 to 700 standard cubic centimeter per minute (sccm). At a constant CH 4 flow rate of 700 sccm and varied H 2 of 100 and 200 sccm, we observed that few CNTs were produced. Between H 2 flow rates of 300 and 400 Journal of Undergraduate Research in Physics August 27, 2010

physica status solidi (a), 2013

In thin film devices such as light-emitting diodes, photovoltaic cells and field-effect transisto... more In thin film devices such as light-emitting diodes, photovoltaic cells and field-effect transistors, the processes of charge injection, charge transport, charge recombination, separation and collection are critical to performance. Most of these processes are relevant to nanoscale metal and metal oxide electrode-organic material interfacial phenomena. In this report we present a unique method for creating tailored onedimensional nanostructured silver, tin and/or zinc substituted indium oxide electrode structures over large areas. The method allows production of high aspect ratio nanoscale structures with feature sizes below 100 nm and a large range of dimensional tunability. We observed that both the electronic and optical properties of these electrodes are closely correlated to the nanostructure dimensions and can be easily tuned by control of the feature size. Surface area enhancement accurately describes the conductivity studies, while nanostructure dependent optical properties highlight the quasi-plasmonic nature of the electrodes. Optimization of the nanostructured electrode transparency and conductivity for specific opto-electronic systems is expected to provide improvement in device performance.

Advanced Materials Interfaces, 2013

ACS Applied Materials & Interfaces, 2014

There is an urgent need to develop taggants that can be used to identify objects, prevent fraud, ... more There is an urgent need to develop taggants that can be used to identify objects, prevent fraud, and deter counterfeiting with high reliability, high capacity, and minimal effort. This paper describes a new multilayer covert taggant based on phase change nanoparticles (metals and eutectic alloys). A panel of selected nanoparticles with different melting temperatures have been added in matrix materials together with fluorescent dye and printed on substrates to form micro-/macrofeatures that contain thermal, fluorescence signature, and structural components. The multilayer taggants can greatly enhance security level for many commercial and forensic applications by their extremely large labeling capacity, coding readiness, and covertness.

Scientific Reports, 2014

An unmet need is to develop covert barcodes that can be used to track-trace objects, and authenti... more An unmet need is to develop covert barcodes that can be used to track-trace objects, and authenticate documents. This paper describes a new nanoparticle-based covert barcode system, in which a selected panel of solid-to-liquid phase change nanoparticles with discrete and sharp melting peaks is added in a variety of objects such as explosive derivative, drug, polymer, and ink. This method has high labeling capacity owing to the small sizes of nanoparticles, sharp melting peaks, and large scan range of thermal analysis. The thermal barcode can enhance forensic investigation by its technical readiness, structural covertness, and robustness.

Renewable Energy and the Environment Optics and Photonics Congress, 2012

An integrating sphere is used to measure the absorptance of P3HT:PCBM layers with 700 nm period g... more An integrating sphere is used to measure the absorptance of P3HT:PCBM layers with 700 nm period gratings on the reverse side of the substrate. Gratings that do not exploit TIR adversely affect the absorptance.

Microscopy and Microanalysis, 2008

Ferrites (AFe 2 O 4 , A = Mn, Co, Ni, Cu, Zn), particularly nanoparticles, have high potential fo... more Ferrites (AFe 2 O 4 , A = Mn, Co, Ni, Cu, Zn), particularly nanoparticles, have high potential for many new technological applications, e.g. magnetic recording media and storage, MRI enhancement, magnetically guided drug delivery, and waste water treatment. Spinel zinc ferrite (ZnFe 2 O 4 ) is paramagnetic and exhibits antiferromagnetism with the Neel temperature (T N ) of about 10K [1]. On the other hand, nickel ferrite (Ni Fe 2 O 4 ) has an inverse spinel structure showing ferri-magnetism that originates from magnetic moment of anti-parrallel spins between Fe 3+ ions at tetrahedral sites and Ni 2+ ions at octahedral sites . It was suggested recently that some Zn, Ni and Cu ferrites offer superior magnetic properties depending on certain concentration of Ni, Cu, Zn in the ferrites . The present study reports on the effects of Zn, Ni, and Cu concentrations on the structural and magnetic properties of the ferrites prepared by simple, cost-effective, non-toxic sol-gel methods.

Microscopy and Microanalysis, 2008

Carbon nanotubes (CNTs) are allotropes of carbon with a few nanometers in diameter and several mi... more Carbon nanotubes (CNTs) are allotropes of carbon with a few nanometers in diameter and several micrometers in length. Numerous studies reported on various methods to grow CNTs including electric arc discharge, laser vaporization, and chemical vapor deposition (CVD). There are strong correlations between the synthesis, structure, and properties of the CNTs [1]. In this work, we used CVD method to grow CNTs on two types of substrates-quartz and Si/SiO 2 in order to investigate their properties in the microwave range for electronic devices. Several sets of samples with different catalysts, growth temperature, time, and gas flow rate were studied.

Journal of Power Sources, 2012

The effect of the microporous layer (MPL) and wet proofing on the MacMullin number has been evalu... more The effect of the microporous layer (MPL) and wet proofing on the MacMullin number has been evaluated for a custom series of Toray TGP-H-060 carbon paper gas diffusion layer (GDL). Complementary characterizations for these GDLs were performed by using scanning electron microscopy (SEM) images, pore size distribution (PSD) and fuel cell performance. The GDLs were customized by the addition of a microporous layer (MPL) and the treatment of, either or both, the substrate and MPL with 10% and 40% hydrophobic agent. SEM images correlated very well with the data shown for PSD. Distinction between the substrate layer and the MPL were clearly shown as two different slopes in the integral distribution and two different peaks in the differential distribution. The MacMullin number increased with increase in wet proofing but decreased with the addition of the MPL. The MacMullin number is a key parameter that contains the missing information for the path length in GDLs, which is generally approximated with the Bruggeman expression. The results provided an overview for the interpretation of the combined effect of the substrate and MPL properties as well as the cell operating conditions.

Journal of Power Sources, 2012

A gas diffusion layer (GDL) in a proton exchange membrane fuel cell may consist of several, mater... more A gas diffusion layer (GDL) in a proton exchange membrane fuel cell may consist of several, materials of different porosities, with each material serving a specific set of functions. For example, samples analyzed in this work consisted of a macro porous carbon paper substrate treated with a, hydrophobic wet proofing material in differing amounts, which was then coupled to a micro porous, layer. The porosities of four such GDLs were determined by using 2D scanning electron microscope (SEM) images to mathematically model the volumes filled by each solid in the 3D structures. Results, were then compared with mercury intrusion porosimetry (MIP) measurements to verify the accuracy, of the method. It was found that the use of SEM not only allowed for detailed porosity analysis of, separate porous materials within the GDL, but also porosity for the entire GDL could be calculated for, the seemingly complex structures with reasonable accuracy. With some basic geometric assumptions, and use of the superposition principle, the calculated results were accurate to less than a 2% absolute, difference of the porosity measured by MIP for each of the four samples analyzed.

Carbon, 2011

The effects of growth conditions, such as methane flow rates and type of substrate on the distrib... more The effects of growth conditions, such as methane flow rates and type of substrate on the distribution, structure and properties of nanotubes were examined. A scanning electron microscope equipped with a Raman spectrometer enabled us to obtain critical information about the structure and electrical properties of the nanotubes simultaneously, and it was shown that these were highly dependent on the methane flow rate. At a methane flow rate of 600 cc/min, we primarily obtained double-walled carbon nanotubes having predominantly semiconducting properties. At a higher methane flow rate (700 cc/min), a mixture of single-walled and double-walled carbon nanotubes was created, most of which were semiconducting. At low methane flow rates (300 and 500 cc/min), metallic multi-walled carbon nanotubes were predominated. Carbon nanotubes grown on a quartz substrate were between 4-10 lm in length, whereas those grown on silicon were longer ($15-20 lm). The primary growth mechanism observed was base growth, although some cap growth did occur. Based on the results of this study, it is now possible to carefully control the synthesis conditions to produce carbon nanotubes that possess specific electrical properties that suit the desired application.