Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic defor...
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Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic deformation of the nematic and anisotropic surface forces. The balance of these forces dictates that tactoids must display a continuous variation in aspect ratio and director-field configuration. Yet, such continuous transition has eluded observation for decades: tactoids have displayed either a bipolar configuration with particles aligned parallel to the droplet interface or a homogeneous configuration with particles aligned parallel to the long axis of the tactoid. Here, we report the first observation of the continuous transition in shape and director-field configuration of tactoids in true solutions of carbon nanotubes in chlorosulfonic acid. This observation is possible because the exceptional length of carbon nanotubes shifts the transition to a size range that can be visualized by optical microscopy. Polarization micrographs yield the interfacial and elastic properties of the system. Absorbance anisotropy measurements provide the highest nematic order parameter (S=0.79) measured to date for a nematic phase of carbon nanotubes at coexistence with its isotropic phase.
Two methods have been employed to synthesize zinc ferrite materials using metal precursors (nitrates) and various carbonaceous fuels (sucrose, urea, or ethylenediaminetetraacetic acid (EDTA)) dissolved in de-ionized w...
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Two methods have been employed to synthesize zinc ferrite materials using metal precursors (nitrates) and various carbonaceous fuels (sucrose, urea, or ethylenediaminetetraacetic acid (EDTA)) dissolved in de-ionized water. In the first method, preheating of the metal precursor-fuel solution was conducted on a hot plate at 300°C or in a microwave furnace depending on the nature of the precursors. This heating technique provided fast vaporization of water followed by self-ignition of reactants. In the second method, the metal precursor-fuel solution was slowly evaporated at 50°C and later heated in a muffle furnace up to 650°C in air at a rate of 20 °C/min for nitrate decomposition in the presence of a carbonaceous fuel. While the former method resulted in amorphous oxide materials or multiple phases, the latter method led to the formation of a crystalline material in the form of nano-particles consisting mainly of a desired spinel ZnFe2O4 phase. Average crystallite sizes of synthesized ferrites calculated by the Scherrer's equation from X-ray diffraction (XRD) peaks were in the range of 14-32nm, which agreed with transmission electron microscope (TEM) observations. Scanning electron microscope (SEM) images of doped ferrites revealed that these nanocrystals are in the form of agglomerates. The specific surface area of the doped ferrites was found to be dependent on the synthesis method and a type of fuel used.
The use of near-infrared plasmon resonance of gold nanorods (NR) to offer an integrated platform for multiplexed Raman detection and remote-controlled photothermal heating is analyzed. Surface enhanced Raman scatterin...
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The use of near-infrared plasmon resonance of gold nanorods (NR) to offer an integrated platform for multiplexed Raman detection and remote-controlled photothermal heating is analyzed. Surface enhanced Raman scattering (SERS)-coded NRs were efficiently detected following subcutaneous or intratumoral injection and enabled remote photothermal tumor heating to ablative temperatures. Cetyltrimethylammonium bromide (CTAB)-coated gold NRs were bought from Nanopartz with a peak plasmon resonance at 790 nm. NRs were purified further with multiple rounds of centrifugation using molecular weight cutoff centrifugal filters and stored at 200 pm at 4C. The SERS intensities of NRs coated with different dyes were compared using ethanol as an internal standard. The best NRs were selected by comparing the peak height ratio of the dye's most intense SERS peak to the peak height of the ethanol vibration at 879 cm-1 used as an internal standard.
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