Scott A. Speakman

Growth of Metal−Organic Frameworks on Polymer Surfaces

Polymer substrates have been functionalized with a MOF material (MIL-47) synthesized directly on polyacrylonitrile using in situ microwave irradiation. The growth of MIL-47 on these substrates was studied as a function of microwave irradiation time using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The conversion of nitrile to carboxylic acid groups on the PAN surface was necessary for the growth of MIL-47 on the substrate. MIL-47 crystals grew over time at the expense of a related disordered precursor phase, which lacks the long-range order of MIL-47. This work paves the way for the development of a new class of hybrid MOF-polymer materials that will extend the applications of MOFs to fields such as membrane separations, filtration, and protective textiles.

Facile Synthesis of Vanadium Metal–Organic Frameworks and their Magnetic Properties

Metal–organic frameworks (MOFs) are materials obtained by the assembly of small inorganic clusters and organic linkers to form one-, two-, or three-dimensional (3D) crystalline networks. The synthesis of 3D porous MOFs with large surface area and pore volume and chemical stability, coupled with the ability to tailor pore sizes and functionality during the synthesis step, makes these materials promising in hydrogen storage, separation, sequestration of carbon dioxide or harmful gases, and catalysis. When transition metal ions are incorporated in the MOF structures, these materials show interesting optical, ionic conductivity, and magnetic properties that, combined with their exceptional porous characteristics, provide the opportunity to develop new low-density multifunctional materials. In this Communication, we present the facile and fast microwave synthesis of MIL-47, one of the most studied MOF materials, and 6 new vanadium MOFs obtained under similar conditions using different organic building blocks. We show that these different organic building blocks affect the interactions between V ions, and, consequently, the magnetic properties of the MOF. Furthermore, we studied the effect on the magnetic properties when guest molecules were removed from the MIL-47 pores. It was suggested that changes in the magnetic properties upon guest-molecule desorption are due to a change in the vanadium oxidation state from V3þ to V4þ. In this Communication, we will show that the changes in the material magnetic properties are due to

Structural, magnetic, and magneto-optical properties of Co-doped CeO2−δ films

Magnetically doped CeO2 is a promising dilute magnetic semiconductor and may also be useful in magneto-optical applications. Ce1−xCoxO2−δ (x=0, 0.02, 0.06, 0.15, and 0.25) films were deposited by pulsed laser deposition on MgO(100) substrates and their structural, magnetic, and magneto-optical properties were characterized. The films show a textured ceria single phase with (111) preferred orientation. All the Co-doped samples show room temperature ferromagnetism and large magnetic anisotropy with an out-of-plane easy axis. Magneto-optical measurements indicate that the Co-doped films also have high saturation Faraday rotation ranging from 230to6000deg∕cm depending on the Co concentration, and their refractive index and extinction coefficient also increase with Co concentration.

Fiber Field‐Effect Device Via In Situ Channel Crystallization

The in situ crystallization of the incorporated amorphous semiconductor within the multimaterial fiber device yields a large decrease in defect density and a concomitant five-order-of-magnitude decrease in resistivity of the novel metal-insulator-crystalline semiconductor structure. Using a post-drawing crystallization process, the first tens-of-meters-long single-fiber field-effect device is demonstrated. This work opens significant opportunities for incorporating higher functionality in functional fibers and fabrics.

Formation of High-Aspect-Ratio Helical Nanorods via Chiral Self-Assembly of Fullerodendrimers

Two novel, asymmetric methanofullerenes are presented, which self-assemble in cyclohexane upon thermal cycling to 80 °C. We show that, through the introduction of a dipeptide sequence to one terminus of the dendritic methanofullerene, it is possible to transform the assembly behavior of these molecules from poorly formed aggregates to high-aspect-ratio nanorods. These nanorods have diameters of 3.76 ± 0.52 nm and appear to be composed of interwoven helices of dendritic fullerenes. As evidenced by circular dichroism, the helicity is characterized by a preferential handedness of assembly, which is imparted by the dipeptide moiety.

Materials and Techniques of Thai Painting

The materials and techniques employed in 18 th to 20 th century art works from Thailand have received little attention compared to those of other Asian countries, most notably China and Japan. A multi-disciplinary study of Thai manuscripts and banner paintings aims to characterize the materials used, inorganic and organic pigments and binders, and the painting techniques employed. Samples from these works have been analyzed by a range of techniques, including x-ray flourescence (XRF), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive microanalysis (SEM-EDS). The results suggest a change in palette from the 18 th to 20 th century due to the introduction of imported pigments, most notably emerald green, Prussian blue and chrome yellow, during the 19 th and early 20 th century. The analyses show that the green pigment used on most 18 th century manuscripts is an organic copper salt, a hydrated copper citrate, which has not previously been identified on art works. The occurrence of this on a number of different art works suggests deliberate manufacture of this unusual pigment. The color of the copper citrates differs depending on their hydration state and they are easily dehydrated and re-hydrated. This suggests some alteration of the original manuscript pigments might be expected, raising questions as to the original color of the pigment and whether the visual appearance has altered with time. In order to assess this, the pigments found on the art works must be fully characterized and any variations identified. The study includes laboratory based sythesis with pure reagents and synthesis following a recipe for refinement of verdigris given in a 17 th century Venetian manuscript.