No abstract

The potential of hysteresis loop-based methods for the characterization of granular magnetic materials is investigated in the presence of thermal relaxation effects. Specifically, we study the reliability of the ⌬H͑M,⌬M͒-method to recover the intrinsic switching field distribution in the presence of thermal relaxation. As input data, we use the computational results obtained from kinetic Monte Carlo simulations of interacting Stoner-Wohlfarth particle arrays including the anisotropy field and grain size distributions, and then analyze them using the hysteron-based ⌬H͑M,⌬M͒-method to identify the accuracy limits of this methodology. It is found that the accuracy of the ⌬H͑M,⌬M͒-method is not substantially changed by the presence of thermal relaxation.

Gas sensing characteristics of single-walled carbon nanotube (SWNT) devices decorated with single-stranded RNA (ss-RNA) were studied. Our results showed that RNA decoration could significantly improve the magnitude of SWNTs' response to methanol and IPA vapors. Furthermore, the sensing characteristics of various RNA functionalized SWNT devices were highly sequence dependent. Specifically, for homo RNA decorated SWNTs, the sensing response followed the trend: C > G > U > A for methanol and G > C > U > A for IPA. For repeated RNA base coated SWNTs, the sensing response trend was: GU > AG > AC > CU for methanol and GU > AC > AG > CU for IPA. These findings provided insight to the binding affinities of RNA oligomers on SWNTs and further paved the way to control the sensing specificity of RNA functionalized SWNT sensors for chemical and biological applications.

In this paper, we present a single chip nanosensor composed of Single-Walled Carbon Nanotubes (SWNTs) integrated on complementary metal oxide semiconductor (CMOS) circuitry with custom designed on-chip amplifiers for chemical agent detection. The SWNTs were integrated on CMOS circuitry utilizing a low temperature and low voltage Dielectrophoretic (DEP) assembly process. Furthermore, we incorporated different sequences of single-stranded DNA (ss-DNA) on to SWNTs which improved their response to two toxic and explosive gases, namely Dimethyl methylphosphonate (DMMP) (an analog of nerve agent sarin [1]) by 9 times and Dinitrotoluene (DNT) (a byproduct of TNT [2]) by 12 times. In addition, the change in resistance (ΔR/R) of SWNT sensors increased from 12% to 24% when the concentration of DMMP vapor was increased from 8 ppm to 72 ppm; While ΔR/R increased from 7% to 23% when the concentration of DNT was increased from 9 ppm to 46 ppm. The SWNTs coupled with ss-DNA integrated onto CMOS circuitry shows great promise for monitoring low concentrations of toxic and explosive gases and potentially can be used to realize ultra-sensitive nanosensors.