Magnetic field control of fluorescent polymer nanorods.

Nanoscale objects that combine high luminescence output with a magnetic response may be useful for probing local environments or manipulating objects on small scales. Ideally, these two properties would not interfere with each other. In this paper, we show that a fluorescent polymer host material can be doped with high concentrations of 20-30 nm diameter magnetic γ-Fe2O3 particles and then formed into 200 nm diameter nanorods using porous anodic alumina oxide templates. Two different polymer hosts are used: the conjugated polymer polydioctylfluorene and also polystyrene doped with the fluorescent dye Lumogen Red. Fluorescence decay measurements show that 14% by weight loading of the γ-Fe2O3 nanoparticles quenches the fluorescence of the polydioctylfluorene by approximately 33%, but the polystyrene/Lumogen Red fluorescence is almost unaffected. The three-dimensional orientation of both types of nanorods can be precisely controlled by the application of a moderate strength (∼0.1 T) external field with sub-second response times. Transmission electron microscope images reveal that the nanoparticles cluster in the polymer matrix, and these clusters may serve both to prevent fluorescence quenching and to generate the magnetic moment that rotates in response to the applied magnetic field.

Dielectric properties of fully hydrated nucleotides in the terahertz frequency range.

We use terahertz time domain spectroscopy (THz-TDS) to determine the complex frequency-dependent dielectric response of all four nucleotides at different dilute concentrations. In addition, the suspension model's ability to extract the dielectric response of just the nucleotide with the hydration shell epsilon(b) excluding the dielectric information relating to the bulk will be verified. The suspension model enables us to make the determination that the nucleotides have influences on the water molecules out to the fourth hydration shell. We use a two Debye relaxation fit model for water, all concentrations and all epsilon(b) values. We observed how the nucleotides affect the relaxation parameters in relation to that of pure bulk water. With this information, we notice a transition between purines and pyrimidines, where one is a hydrogen-bond network structure building type material with a low concentration increment and the other is a structure breaking type material with a low concentration decrement. Due to conductivity measurements, we determine that kinetic depolarization is a negligible affect compared to that of dielectric saturation, which we find to dominate where a decrement is found.

Metal-complex-decorated homochiral heterobimetallic telluride single-stranded helix.

Solvothermal reaction of a mixture of Sn, Mn, and Te at 200 degrees C using teta as the solvent yields a novel inorganic-organic hybrid solid [Mn(teta)(en)].[Mn(teta)][Mn(SnTe4)2.Mn(teta)] (teta=triethylenetetramine and en=ethylenediamine; 1), which has a homochiral single-stranded helical structure. The material is a semiconductor with a band gap of 0.88 eV and shows paramagnetic behavior between 2 and 300 K.