By selective placement of fluorescent dyes, we have measured the glass transition temperature (T g ) of individual layers within supported bilayer films of different polymers to determine the extent to which strong free-surface effects and substrate interactions are mediated by a narrow interface between immiscible polymers. We have discovered that the impact a free surface has on T g within an ultrathin PS layer is extremely sensitive to the polymer species used in the underlayer. The large T g reduction of ∼32 K relative to bulk T g observed for a 14 nm thick surface layer of polystyrene (PS) supported on bulk PS is virtually eliminated when a 14 nm thick surface layer of PS is placed on an underlayer of poly(methyl methacrylate) or poly(2-vinylpyridine) (P2VP), even of bulk thickness. Thus, the cooperative segmental mobility associated with the T g of the PS freesurface layer is greatly hindered by the narrow, several-nanometer-wide interfacial region formed with the dissimilar polymer underlayer. This indicates that the dynamics of nanoscale layers can be strongly modified by adjacent layers or domains of unlike polymers via propagation of effects across an interfacial layer of cooperatively rearranging regions containing segments of the two immiscible polymers, which has important implications for multilayer films and nanostructured blends. Conversely, the T g of an ultrathin P2VP film is unaffected by the presence of a PS capping layer, indicating that strong attractive interactions of P2VP with hydroxyl groups on the surface of the silica substrate dominate over a much weaker free-surface effect in P2VP.

The semiconductors Li(2)CdGeS(4) and Li(2)CdSnS(4), which are of interest for their nonlinear optical properties, were synthesized using high-temperature solid-state and polychalcogenide flux syntheses. Both compounds were found to crystallize in Pmn2(1), with R1 (for all data) = 1.93% and 1.86% for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively. The structures of both compounds are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in the structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds. Li(2)CdGeS(4) displayed a type I phase-matchable response of approximately 70x alpha-quartz, while Li(2)CdSnS(4) displayed a type I non-phase-matchable response of approximately 100x alpha-quartz. Diffuse-reflectance spectroscopy was used to determine band gaps of 3.10 and 3.26 eV for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively.

Purpose This paper describes a preclinical investigation of the feasibility of thermotherapy treatment of bladder cancer with Magnetic Fluid Hyperthermia (MFH), performed by analyzing the thermal dosimetry of nanoparticle heating in a rat bladder model. Materials and Methods The bladders of twenty-five female rats were instilled with magnetite-based nanoparticles, and hyperthermia was induced using a novel small animal magnetic field applicator (Actium Biosystems, Boulder, CO). We aimed to increase the bladder lumen temperature to 42°C in <10 min and maintain that temperature for 60 min. Temperatures were measured within the bladder lumen and throughout the rat with seven fiberoptic probes (OpSens Technologies, Quebec, Canada). An MRI analysis was used to confirm the effectiveness of the catheterization method to deliver and maintain various nanoparticle volumes within the bladder. Thermal dosimetry measurements recorded the temperature rise of rat tissues for a variety of nanoparticle exposure conditions. Results Thermal dosimetry data demonstrated our ability to raise and control the temperature of rat bladder lumen ≥1°C/min to a steady-state of 42°C with minimal heating of surrounding normal tissues. MRI scans confirmed the homogenous nanoparticle distribution throughout the bladder. Conclusion These data demonstrate that our MFH system with magnetite-based nanoparticles provide well-localized heating of rat bladder lumen with effective control of temperature in the bladder and minimal heating of surrounding tissues.

Magnetic nanoparticles (MNPs) possessing low Curie temperatures (TC’s) offer the possibility for self-regulated heating of cancer cells, where the TC acts as an upper limit to heating to prevent damage to neighboring healthy tissue. We report the synthesis of monodisperse metastable fcc γ-phase Fe–Ni MNPs possessing tunable TC’s, whose stoichiometries have been predicted from metastable extensions to an equilibrium Fe–Ni phase diagram. Metastable alloys have been predicted within the constructs of the T0 construction in the Fe–Ni eutectoid phase diagram. Fe–Ni MNPs have been synthesized via chemical reduction in Fe- and Ni-precursors with stoichiometries ranging from Fe90Ni10 to Fe70Ni30. Mn-precursors have been added to further reduce the alloy’s TC. MNP morphology and structure have been confirmed by x-ray diffraction and transmission electron microscopy while magnetic properties were investigated using vibrating sample magnetometry. Fe70Ni30 MNPs were found to have a TC of 82 °C and specific magnetization of 66 emu/g. Addition of 1 wt % Mn to Fe75Ni25 reduced the TC to 78 °C, which is the lowest reported for fcc Fe–Ni alloys. We also report a model for radio frequency self-regulated heating, in which the maximum achievable temperature of water-MNP suspensions (TC&lt;100 °C) or octyl ether-MNP suspensions (TC&gt;100 °C) is approximately the TC of the MNPs suspended in the solution.