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Auburn, AL, United States

Kim G.-Y.,Korea Atomic Energy Research Institute | Wang X.,Auburn University | Ahn H.,Materials Research and Education Center | Son A.,Auburn University
Environmental Science and Technology | Year: 2011

NanoGene assay is a magnetic bead and quantum dot nanoparticles based gene quantification assay. It relies on a set of probe and signaling probe DNAs to capture the target DNA via hybridization. We have demonstrated the inhibition resistance of the NanoGene assay using humic acids laden genomic DNA (gDNA). At 1 μg of humic acid per mL, quantitiative PCR (qPCR) was inhibited to 0% of its quantification capability whereas NanoGene assay was able to maintain more than 60% of its quantification capability. To further increase the inhibition resistance of NanoGene assay at high concentration of humic acids, we have identified the specific mechanisms that are responsible for the inhibition. We examined five potential mechanisms with which the humic acids can partially inhibit our NanoGene assay. The mechanisms examined were (1) adsorption of humic acids on the particle surface; (2) particle aggregation induced by humic acids; (3) fluorescence quenching of quantum dots by humic acids during hybridization; (4) humic acids mimicking of target DNA; and (5) nonspecific binding between humic acids and target gDNA. The investigation showed that no adsorption of humic acids onto the particles' surface was observed for the humic acids' concentration. Particle aggregation and fluorescence quenching were also negligible. Humic acids also did not mimic the target gDNA except 1000 μg of humic acids per mL and hence should not contribute to the partial inhibition. Four of the above mechanisms were not related to the inhibition effect of humic acids particularly at the environmentally relevant concentrations (<100 μg/mL). However, a substantial amount of nonspecific binding was observed between the humic acids and target gDNA. This possibly results in lesser amount of target gDNA being captured by the probe and signaling DNA. © 2011 American Chemical Society. Source

Kim D.-J.,Materials Research and Education Center | Park J.-H.,Materials Research and Education Center
Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010 | Year: 2010

With higher integration, smaller size, and automated processes, sensors and wireless devices have seen dramatic enhancements to their quality, robustness, and reliability. Recent efforts have been made toward developing autonomous, self-powered remote sensor systems that can offer enhanced applicability and performance with cost savings. With the decrease in power requirements for wireless sensors, the application of piezoelectricity to energy harvesting has become viable. The technological challenge of realizing such a system lies in the construction and fabrication of a miniaturized vibration energy harvester. The current design of MEMS-scale devices comprises a seismic mass made of silicon connected to the substrate by a thin PZT cantilever beam. Factors relating to power improvement and reliability of the device are discussed by addressing the shape of the cantilever beam, piezoelectric mode, MEMS process, and environmental temperature. © 2010 Society for Experimental Mechanics Inc. Source

Ahn H.,Materials Research and Education Center | Wikle III H.C.,Materials Research and Education Center | Kim S.-B.,Materials Research and Education Center | Liu D.,Materials Research and Education Center | And 3 more authors.
Journal of the Electrochemical Society | Year: 2012

ZnO nanorods were grown on ZnO seed layers, i.e. thin films deposited on flexible polyimide substrates. The ZnO seed layers were prepared by rf sputter deposition and the ZnO nanorods were prepared by a thermolysis assisted aqueous solution method. Structural characterizations show that the seed layer thickness, less than 200 nm, does not affect the growth behavior or the crystalline phase of ZnO nanorods. The sensitivity of both ZnO thin film and nanorods sensors to ethanol were compared as a function of the thin film (seed layer) thickness. The highest sensitivity for the ZnO thin film sensors was observed at a film thickness of 40 nm but no effect was seen from the film (seed) thickness on the ZnO nanorod sensor sensitivity. The nanorod dimensions obviously played an important role in determining the sensitivities. These results indicate that the charge carrier density within the ZnO nanorods and transport through the nanorods are primarily responsible for the gas sensing properties. A quantitative equation was derived to explain why control of the ZnO nanorod dimensions is more effective than control of the seed layers thickness regarding better gas sensitivity. © 2011 The Electrochemical Society. Source

Ahn H.,Korea Institute of Construction Technology | Ahn H.,Materials Research and Education Center | Park H.,Materials Research and Education Center | Joo J.-C.,Korea Institute of Construction Technology | Kim D.-J.,Materials Research and Education Center
ECS Solid State Letters | Year: 2013

Compositionally gradient tin oxide thin films were prepared by co-sputtering from tin and tin oxides targets. After annealing at 450°C, gradient crystalline phases of SnO and SnO2 were fabricated on a single sensor. Acetone, ethanol, and ethylene were utilized to investigate sensing properties of the gradient tin oxide sensor. Coexisting p-type SnO and n-type SnO2 affect the direction of electrical resistance and the response during gas reaction and recovery. Construction of gradient tin oxide film in terms of composition and crystalline phase demonstrates the design of a gas sensor for the selective gas detection via the combinatorial approach. © 2012 The Electrochemical Society. Source

Ahn H.,Materials Research and Education Center | Noh J.H.,Materials Research and Education Center | Kim S.-B.,Materials Research and Education Center | Overfelt R.A.,Materials Research and Education Center | And 2 more authors.
Materials Chemistry and Physics | Year: 2010

SnO2 thin films were deposited on alumina substrates by R.F. magnetron sputtering to fabricate a sensor for ethylene gas detection. Two deposition parameters, the argon-to-oxygen ratio in sputter gas and post-annealing, were controlled to investigate the effects on the structural and gas sensing properties of SnO2 thin films. Argon-to-oxygen ratios ranging from 15:15 to 27.3:2.7 and post-annealing was performed at 650 °C in air. The microstructure and crystalline phase of sputtered tin oxide are more influenced by post-annealing than the argon-to-oxygen ratio. In ethylene gas detection, post-annealed SnO2 films showed more highly improved sensitivity than as-deposited films, but the effect of the argon-to-oxygen ratio during SnO2 sputter deposition on ethylene gas sensing was not evident. © 2010 Elsevier B.V. All rights reserved. Source

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