Synthesis, Characterization and Chemical Functionalization of Nitrogen Doped Carbon Nanotubes for the Application in Gas- and Bio-Sensors

In this work, a chemiresistor-type sensing platform based on aligned arrays of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) was developed. Our N-MWCNT based sensors can be made on both rigid and flexible substrates; they are small, have low power consumption and are suitable for highly efficient and reliable detection of different biomolecules and gases, at room temperature. The performance of these sensors was demonstrated for avian influenza virus (AIV) subtype H5N1 DNA sequences and toxic gases NO and NH3 at low concentrations. In our study, chemical vapor deposition (CVD) method was applied to synthesize vertically aligned nitrogen doped carbon nanotube arrays on a large area (> 1 cm2) on Si/SiO2 substrate using Fe/Al2O3 layer as a catalyst and a mixture of ethanol and acetonitrile as a C/N source. Especially, the diameter, length, nitrogen-doping concentration and morphology of the nanotubes were controllably tailored by adjusting the thickness of catalyst film, reaction duration and temperature as well as the amount of nitrogen-containing precursor. For integrating N-MWCNTs into chemiresistor devices, we developed a direct contact printing method for a dry, controllable and uniform transferring and positioning of the CVD-grown vertical nanotubes onto well-defined areas of various rigid and flexible substrates. After horizontally aligned N-MWCNT arrays were formed on a target substrate, interdigitated metallic microelectrodes with an interspacing of 3 µm were deposited perpendicular to the nanotube alignment direction to fabricate chemiresistor devices for biomolecule and gas sensing. This way, well-aligned nanotubes were laid across the Au/Cr interdigitated electrode fingers, had a strong adhesion with the electrodes and served as conducting channels bridging the electrodes. The N-MWCNT based chemiresistor device was applied as a label-free DNA sensor for a highly sensitive and fast detection of AIV subtype H5N1 DNA sequences. For this, the nanotubes were functionalized with probe DNA, which was non-covalently attached to sidewalls of the N-MWCNTs via π-π interaction. Such functionalized sensors were applied to quantitatively detect complementary DNA target with concentration ranging from 20 pM to 2 nM after 15 min incubation at room temperature. The sensors showed no response to non-complementary DNA target for concentrations up to 2 µM showing an excellent selectivity. Investigations on the efficient gas sensing of N-MWCNT-based chemiresistor of reducing/ oxidizing gases NH3 and NO were also reported in this work. The aim was to assess the possibility for N-MWCNTs to be applied as innovative sensing materials for room temperature gas sensing. N-MWCNTs with varying doping levels (N/C ratio of 5.6 to 9.3at%) were used as sensing materials and exposed to NH3 (1.5-1000 ppm) and NO (50-1000 ppm) for exploring and comparing their sensing performance. This study offered an effective route for further modification of CNTs according to various sensing application. Finally, our investigations showed a high potential of the developed N-MWCNT-based sensing platform for various applications ranging from environmental monitoring to point-of-care medical diagnostics

Synthesis, Characterization and Chemical Functionalization of Nitrogen Doped Carbon Nanotubes for the Application in Gas- and Bio-Sensors

In this work, a chemiresistor-type sensing platform based on aligned arrays of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) was developed. Our N-MWCNT based sensors can be made on both rigid and flexible substrates; they are small, have low power consumption and are suitable for highly efficient and reliable detection of different biomolecules and gases, at room temperature. The performance of these sensors was demonstrated for avian influenza virus (AIV) subtype H5N1 DNA sequences and toxic gases NO and NH3 at low concentrations. In our study, chemical vapor deposition (CVD) method was applied to synthesize vertically aligned nitrogen doped carbon nanotube arrays on a large area (> 1 cm2) on Si/SiO2 substrate using Fe/Al2O3 layer as a catalyst and a mixture of ethanol and acetonitrile as a C/N source. Especially, the diameter, length, nitrogen-doping concentration and morphology of the nanotubes were controllably tailored by adjusting the thickness of catalyst film, reaction duration and temperature as well as the amount of nitrogen-containing precursor. For integrating N-MWCNTs into chemiresistor devices, we developed a direct contact printing method for a dry, controllable and uniform transferring and positioning of the CVD-grown vertical nanotubes onto well-defined areas of various rigid and flexible substrates. After horizontally aligned N-MWCNT arrays were formed on a target substrate, interdigitated metallic microelectrodes with an interspacing of 3 µm were deposited perpendicular to the nanotube alignment direction to fabricate chemiresistor devices for biomolecule and gas sensing. This way, well-aligned nanotubes were laid across the Au/Cr interdigitated electrode fingers, had a strong adhesion with the electrodes and served as conducting channels bridging the electrodes. The N-MWCNT based chemiresistor device was applied as a label-free DNA sensor for a highly sensitive and fast detection of AIV subtype H5N1 DNA sequences. For this, the nanotubes were functionalized with probe DNA, which was non-covalently attached to sidewalls of the N-MWCNTs via π-π interaction. Such functionalized sensors were applied to quantitatively detect complementary DNA target with concentration ranging from 20 pM to 2 nM after 15 min incubation at room temperature. The sensors showed no response to non-complementary DNA target for concentrations up to 2 µM showing an excellent selectivity. Investigations on the efficient gas sensing of N-MWCNT-based chemiresistor of reducing/ oxidizing gases NH3 and NO were also reported in this work. The aim was to assess the possibility for N-MWCNTs to be applied as innovative sensing materials for room temperature gas sensing. N-MWCNTs with varying doping levels (N/C ratio of 5.6 to 9.3at%) were used as sensing materials and exposed to NH3 (1.5-1000 ppm) and NO (50-1000 ppm) for exploring and comparing their sensing performance. This study offered an effective route for further modification of CNTs according to various sensing application. Finally, our investigations showed a high potential of the developed N-MWCNT-based sensing platform for various applications ranging from environmental monitoring to point-of-care medical diagnostics

Water-Shed: Architectural Opportunity in Infrastructure

The current systems of infrastructure that comprise water supply are incapable of recognising value in water's urban place in anything other than in empirical terms. The 'Water-Shed' scheme transforms this utility into a rarely considered design opportunity that reinvigorates the relationship between the borough of Petone and its water supply at Waiwhetu aquifer. With a framework compiled from history, art, landscape and architecture practice, it entails the re-appropriation of the systems and technologies of contemporary water extraction. The outcome is an architecture that recovers meaning within this amenity and re-confirms waters central value to life. Light in conjunction with material manipulation are used directly and incidentally to reveal water's character. The scheme also conceives of nature in constructed terms, opening the possibility for infrastructures like Water-Shed to negotiate non-oppositional relationships between city and environment. The result is the maturation of industrial landscape the reinforcement of the hydrological and civic identities of Petone. No longer is water amenity simply reduced to productive issues of cost, efficiency and reliability. Debate regarding the access and availability of drinking water will be one of the defining issues of the 21st century. Water-Shed contributes to this discussion by asking how we can re-think the buildings and sites that form parts of the city's water distribution network

Kichwa-English-Spanish Dictionary

This dictionary is written for Kichwa speakers and non-Kichwa speakers. Whoever wants to learn the language of the Inkas should find it useful. A native English speaker does not have to know Spanish in order to learn Kichwa. We hope this dictionary will also be useful for translators of academic works, school teachers, radio and television producers, and travelers who want to communicate with Kichwa speakers throughout the Andes. I want more people to be exposed to Kichwa, learn it, and support its preservation

Sustainability in design: now! Challenges and opportunities for design research, education and practice in the XXI century

Copyright @ 2010 Greenleaf PublicationsLeNS project funded by the Asia Link Programme, EuropeAid, European Commission

Directing Koreanness: Directors and Playwrights Under the National Flag, 1970-2000.

In this dissertation, I venture to explicate the social and political significance of the Korean nationalist theatre performance. The Korean nationalist theatre utilizes elements of indigenous cultures and searches for the Korean ethnic archetype as the ideal Korean type or genuine Koreanness for the reconstruction of the Korean ethnic community. In this context, this dissertation thematically approaches rethinking the issue of rhetorical representation. As a methodological tool, I adopt feminist deconstruction to unfold the epistemological contradictions of the essentialist idea embedded in the notion of the Korean archetype, problematizing the ethnocentric and phallocentric nature of the representation. This dissertation interrogates the major task of the Korean nationalist theatre, which ideologically promulgates the idea of ethnocentric patriarchy supported by the traditional notion of community, inquiring if this type of theatre can provide useful and practical prospects for imagining a more democratic and plural civilian society in Korea today, when the interaction of globalization, nationalism, regionalism, and localism simultaneously impact our everyday life and cultural identification. In this dissertation, I explore genealogical trajectories of the Korean nationalist theatre contesting with other theatrical performances for nation building, cultural identification, and national unity. Paying close attention to changing social and political situations and conditions, I trace the routes, not roots, of the Korean nationalist theatre, and observe how its theorists and the practitioners were able or unable to come to terms with shifting situations and conditions. I have selected works mainly from the 1970s to the 1990s since the works provide grounding images, symbols, metaphors, and allegories pertinent to discussing how the Korean ethnic community has been narrativized through the performances of the Korean nationalist theatre during the turbulent epoch. Reflecting on the limits, accomplishments, and insights of the preceding researchers, I hope that this dissertation presents the Korean nationalist theatre with fully contoured critical views and ideas. This dissertation takes a small step towards a genealogy of the Korean nationalist theatre, and hopes to opens up a space for a dialogue among troubled artists and activists confronting globalization as a shared issue