We measured the molecular order of poly(3-alkylthiophene) chains in thin films before and after melting through the combination of several polarized photon spectroscopies: infrared (IR) absorption, variable angle spectroscopic ellipsometry (SE), and near-edge X-ray absorption fine structure (NEXAFS). The data from the various techniques can be uniformly treated in the context of the dielectric constant tensor epsilon for the film. The combined spectroscopies allow determination of the orientation distribution of the main-chain axis (SE and IR), the conjugated pi system normal (NEXAFS), and the side-chain axis (IR). We find significant improvement in the backbone order of the films after recrystallization of the material at temperatures just below the melting temperature. Less aggressive thermal treatments are less effective. IR studies show that the changes in backbone structure occur without significant alteration of the structure of the alkyl side chains. The data indicate that the side chains exhibit significant disorder for all films regardless of the thermal history of the sample.

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Synchrotron-based high-resolution photoemission and X-ray absorption near-edge spectroscopy (XANES) have been used to study the interaction of NO2 with polycrystalline surfaces of metallic zinc and zinc oxide. NO2 exhibits a complex chemistry on metallic zinc. After adsorbing nitrogen dioxide, N, O, NO, NO2, and NO3 are present on the surface of the metal. At room temperature the NO2 molecule mainly dissociates into O adatoms and gaseous NO, whereas at low temperatures (<250 K) chemisorbed NO2 and NO3 dominate on the surface. NO2 is a very good oxidizing agent for preparing ZnO from metallic zinc. Zn reacts more vigorously with NO2 than metals, such as Rh, Pd, or Pt which are typical catalysts for the removal of NO x molecules (DeNO x process). At 300 K, the main product of the reaction of NO2 with polycrystalline ZnO is adsorbed NO3 with little NO2 or NO present on the surface of the oxide. No evidence was found for the full decomposition of the NO2 molecule (i.e., no NO2 → N + 2O). The results of density functional (DF-GGA) calculations for the adsorption of NO2 on a six-layer slab of ZnO, or INDO/S calculations for NO2 on a Zn37O37 cluster, show stronger chemisorption bonds on (0001) Zn-terminated terraces than on (0001̄) O-terminated terraces. The Zn ↔ NO2 interactions on ZnO are strong and the Zn sites probably get oxidized and nitrated as a result of them. It appears that NO2 is very efficient for fully oxidizing metal centers that are missing O neighbors in oxide surfaces. On zinc oxide, the nitrate species are stable up to temperatures near 700 K. ZnO can be useful as a sorbent in DeNO x operations.

The surface molecular orientation of a liquid crystalline (LC) layer made up of semifluorinated (SF) single side groups [−CO−(CH2) x - 1−(CF2) y F] (single SF groups) attached to polyisoprene homopolymer or the isoprene block of a styrene−isoprene diblock copolymer was determined by analyzing the partial electron yield C-edge NEXAFS signal. The results show that the surfaces of thin SF polymer films are covered with a uniform layer, consisting of the SF−LC groups whose average −CF2− tilt angle with the surface normal lies in the range 29−46°. This is in direct contrast to the bulk, where the directors of the SF−LC mesogens are aligned parallel to the polystyrene/SF−polyisoprene interface of the block copolymers. This average tilt angle increases with increasing the length of the −(CH2) x - 1− group (x increases) but decreases with increasing the length of the −(CF2) y − part of the molecule (y increases) at constant x.