50 research outputs found
Label-free as-grown double wall carbon nanotubes bundles for Salmonella typhimurium immunoassay
Background:
A label-free immunosensor from as-grown double wall carbon nanotubes (DW) bundles was
developed for detecting Salmonella typhimurium. The immunosensor was fabricated by using
the as-grown DW bundles as an electrode material with an anti-Salmonella impregnated on
the surface. The immunosensor was electrochemically characterized by cyclic voltammetry.
The working potential (100, 200, 300 and 400 mV vs. Ag/AgCl) and the anti-Salmonella
concentration (10, 25, 50, 75, and 100 μg/mL) at the electrode were subsequently optimized.
Then, chronoamperometry was used with the optimum potential of 100 mV vs. Ag/AgCl) and
the optimum impregnated anti-Salmonella of 10 μg/mL to detect S. typhimurium cells (0-109
CFU/mL).
Results:
The DW immunosensor exhibited a detection range of 102 to 107 CFU/mL for the bacteria
with a limit of detection of 8.9 CFU/mL according to the IUPAC recommendation. The
electrode also showed specificity to S. typhimurium but no current response to Escherichia
coli. Conclusions:
These findings suggest that the use of a label-free DW immunosensor is promising for
detecting S. typhimurium
Magnetic field dependence of the martensitic transition and magnetocaloric effects in Ni49BiMn35In15
The structural, magnetic, and magnetocaloric properties of the Bi-doped Heusler alloy Ni49BiMn35In15 have been investigated using room temperature X-ray diffraction (XRD) and magnetization measurements in a temperature interval of 5-400 K. The alloy at room temperature was found to be in a mixture of a high temperature austenite phase (AP) and a low temperature martensite phase (MP). A drastic shift in the martensitic transition temperature at the rate of 16 K/T from 197 K to lower temperatures was observed. A kinetic arrest phenomenon of the AP was observed in the magnetization and electrical resistivity measurements during field-cooled (FC) measurements at 5T. A metamagnetic behavior characterized by a jump in magnetization in the isothermal M(H) curves near TM was observed. The maximum value of the magnetic entropy change and refrigerant capacity at Curie temperature were found to be 5.5 Jkg-1K-1 and 312 Jkg-1 for μoΔH = 5T, respectively. A large magnetoresistance value of -56% was found near the martensitic transition
Magnetic Properties and Phase Transitions of Gadolinium-infused Carbon Nanotubes
Carbon nanotube (CNT)/metal-cluster-based composites are envisioned as new materials that possess unique electronic properties which may be utilized in a variety of future applications. Superparamagnetic behavior was reported for CNTs with Gd ions introduced into the CNT openings by internal loading with an aqueous GdCl3 chemical process. In the current work, the magnetic properties of the CNT/Gd composites were obtained by the joining and annealing of Gd metal and CNTs at 850 degrees C for 48 h. Energy dispersive X-ray analysis shows the presence of Gd intermingled with the CNT walls with maximum and average Gd concentrations of about 20% and 4% (by weight), respectively. The Gd clusters have a non-uniform distribution and are mostly concentrated at the ends of the CNTs. A ferromagnetic-type transition at TC ~ to 320K, accompanied by jump like change in magnetization and temperature hysteresis typical for the temperature induced first order phase transitions has been observed by magnetization measurements. It was found that Gd infused into the CNTs by the annealing results in a first order paramagnetic-ferromagnetic transition at TC = 320K
Growth of carbon nanotubes on quasicrystalline alloys
We report on the synthesis of carbon nanotubes on quasicrystalline alloys.
Aligned multiwalled carbon nanotubes (MWNTs) on the conducting faces of
decagonal quasicrystals were synthesized using floating catalyst chemical vapor
deposition. The alignment of the nanotubes was found perpendicular to the
decagonal faces of the quasicrystals. A comparison between the growth and tube
quality has also been made between tubes grown on various quasicrystalline and
SiO2 substrates. While a significant MWNT growth was observed on decagonal
quasicrystalline substrate, there was no significant growth observed on
icosahedral quasicrystalline substrate. Raman spectroscopy and high resolution
transmission electron microscopy (HRTEM) results show high crystalline nature
of the nanotubes. Presence of continuous iron filled core in the nanotubes
grown on these substrates was also observed, which is typically not seen in
MWNTs grown using similar process on silicon and/or silicon dioxide substrates.
The study has important implications for understanding the growth mechanism of
MWNTs on conducting substrates which have potential applications as heat sinks
Effects of magnetic and structural phase transitions on the normal and anomalous Hall effects in Ni-Mn-In-B Heusler alloys
Magnetization, electrical resistivity, magnetoresistance, and Hall resistivity of Ni50Mn35In14.25B0.75 and Ni50Mn35In14.5B0.5 Heusler alloys were studied in a temperature range T=80-400K in magnetic fields up to 20 kOe. Both alloys exhibit a martensitic transformation from a higherature ferromagnetic austenite phase to a lowerature, low-magnetization martensitic phase. The electrical resistivity nearly doubles as a result of the martensitic transformation, reaching 180 and 100 μ cm in the martensitic states of Ni50Mn35In14.25B0.75 and Ni50Mn35In14.5B0.5, respectively. The temperature dependence of the electrical resistivity does not corresponded with the Mooij correlation. The magnetoresistance is negative with a narrow negative peak at the martensitic transition. Normal and anomalous Hall effect coefficients were determined by fitting the field dependences of the Hall resistivity using magnetization data. The coefficients of the normal Hall effect for both compositions were found to decrease with temperature from positive values in the austenite to negative values in the martensite phase. None of the known correlations between the anomalous Hall effect coefficient and resistivity were satisfied. Significant changes in the values of the anomalous Hall coefficients during the martensitic transformation are explained by the difference in spin-up and spin-down state occupations in the martensite and austenite phases. First-principles calculations of the electronic structures confirm this explanation