Based on a first-principles approach, we exploit a class of shaped graded materials in which thermal energy is apparently controlled to transfer from a region of lower temperature to a region of higher temperature. This phenomenon, which is in contrast to our common intuition, is indicative of an apparent negative thermal conductivity (ANTC). Further analysis shows that the ANTC is related to a symmetric oscillation of paired thermal conductivities with specific gradation profiles, which are shown to satisfy a sum rule. Such shaped graded materials can serve as good candidates for thermal rectification.

Resonance Raman spectroscopic imaging is introduced as a physical probe to identify and spatially map morphology-dependent variations of intra- and interchain interactions and order in poly-3-hexylthiophene (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) photovoltaic blend thin films. Absorption spectra and C=C symmetric stretching Raman modes of P3HT/PCBM blend films show contributions from two distinct species that are assigned as aggregated and unaggregated P3HT chains with characteristic Raman frequencies of approximately 1450 (I(C=C)(agg)) and approximately 1470 cm(-1) (I(C=C)(un)), respectively. Upon thermal annealing of blend films, the relative concentrations of I(C=C)(agg) and I(C=C)(un) species (R = I(C=C)(agg)/I(C=C)(un)) changes on average from 0.79 +/- 0.20 (as-cast) to 2.45 +/- 0.77 (annealed). It is proposed that R values report on the relative densities of states (DOS) of aggregated and unaggregated species, and resonance Raman imaging is then used to spatially map morphology-dependent variations of R values and uncover subclassifications of these species. From both R and frequency dispersion resonance Raman images of I(C=C)(agg) and I(C=C)(un) species, four distinct types of P3HT chains are identified and mapped in annealed P3HT/PCBM blend thin films: (i) highly aggregated/crystalline, (ii) partially aggregated, (iii) interfacial, and (iv) unaggregated/PCBM rich. The change in aggregation upon annealing is attributed to an increase in planarity of the P3HT chains that is determined from the ratios of C=C/C-C symmetric stretching mode intensities.

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High yield hausmannite (Mn3O4) nanorods with diameters of about 100 nm and lengths up to 15–20 µm have been prepared by vacuum calcining of the precursor (Mn3O4+MnOOH), which was hydrothermally prepared by the reaction of PEG-20000 and KMnO4 at 180 °C for 20 h. Transmission electron microscopy and the selected-area electron diffraction pattern reveal that these Mn3O4 nanorods show single-crystal growth along the [100] direction. The PEG-20000 and the calcination conditions have key effects on the morphology and phase purity of the product. Magnetism measurements show that the blocking temperature for these Mn3O4 nanorods is 41 K, which agrees with the bulk material value, whereas the remnant magnetization and coercivity are 0.89 μB and 6177 Oe respectively.

A large number of one‐dimensional bundles of ZnSe nanowires with diameters ranging from 15–20 nm and lengths of up to tens of micrometers have been prepared via the thermal treatment of a ribbon‐like precursor (ZnSe·3ethylenediamine), which has been synthesized by a mixed solvothermal route, in an argon atmosphere. The as‐obtained precursor has been characterized by powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), IR spectroscopy, thermogravimetric analysis, and elemental analysis. XRD and high‐resolution TEM characterization reveal that the as‐synthesized ZnSe nanowires have the single‐crystal hexagonal wurtzite structure with the [001] growth direction. The surface chemical composition of ZnSe nanowires has been studied by X‐ray photoelectron spectroscopy. The cooperative action of the mixed solvents may be responsible for the formation of the morphology of the resulting products. Room‐temperature photoluminescence measurements indicate the as‐grown ZnSe nanostructures have a strong emission peak centered at 587 nm and two weak emission peaks centered at 435 and 462 nm. The strong emission from the ZnSe nanostructures reveals their potential as building blocks for optoelectronic devices.