Scott J. Kirkby

Bio: Scott J. Kirkby is an academic researcher from East Tennessee State University. The author has contributed to research in topics: Raman spectroscopy & Normal mode. The author has an hindex of 11, co-authored 19 publications receiving 424 citations. Previous affiliations of Scott J. Kirkby include University of Missouri & Missouri University of Science and Technology.

Dimetal Linked Open Frameworks: [(CH3)4N]2(Ag2,Cu2)Ge4S10

Abstract: Synthetic and X-ray structural details, optical and vibrational spectroscopic, and thermal properties of the materials [(CH3)4N]2M2Ge4S10 (where M = Cu, Ag), are described for the first time. Rietveld PXRD full-profile structure refinements of [(CH3)4N]2M2Ge4S10 reveal a novel open-framework architecture in which dimetal M22+ and adamantanoid Ge4S104- building blocks are alternately substituted into the tetrahedral Zn2+ and S2- sites of a zinc blende lattice, all linked together by [Ge(μ-S)]2M−M[(μ-S)Ge]2 metal−metal bonded bridging units. The metal−metal distances in the S2M−MS2 “twisted I” dihedral unit are 2.761 A (Ag) and 2.409 A (Cu). These internuclear separations are shorter than the bulk metals themselves (2.89 A, Ag; 2.54 A, Cu). This implies that the adamantanoid Ge4S104--based open-framework structure is held together by d10−d10 M+−M+ metal−metal bonds. FT-Raman provides a direct probe of this interaction. Dimetal-framework breathing vibrational modes are observed around 38 cm-1 for M = Ag and ...

Raman Spectra of the Unidimensional Aluminophosphate Molecular Sieves AlPO4-11, AlPO4-5, AlPO4-8, and VPI-5

Abstract: Laser Raman scattering spectra of the unidimensional molecular sieves AlPO 4 -11, AlPO 4 -5 (with and without Pr 3 N template), AlPO 4 -8, and VPI-5 are reported. The lattice deformation region, ca. 300-500 cm -1 , was observed to some increasingly complex as the contents of the Bravais cell increased and the factor group symmetry was reduced. Bands at ca. 400 and ca. 500 cm -1 , absent in the Raman spectrum of α-AlPO 4 (berlinite), were attributed to the presence of four T-atom rings in the above molecular sieve structures. Bands at ca. 260-310 cm -1 were ascribed to «pore-breathing» framework vibrational modes

Cloverite: Exploring the 30 A Supercage for Advanced Materials Science Applications

Abstract: The cubic network of 30 A diameter supercages in the novel gallophosphate molecular sieve cloverite receives attention in this work because of its potential as a host in innovative host-guest nanochemistry aimed at advanced materials applications. A multiprong analytical approach (PXRD, TGA/DSC/TMA/MS, 'H, I3C, 3'P, "Ga, '29Xe NMR, UV-Vis, FT-IR, Raman, physical adsorption) is employed to begin the exploration of the thermal and chemical properties of cloverite, as-synthesized with the quinuclidine template and following various post-synthesis treatments. The freezing out of guest motions (template/water) and/or a change in the space group of as-synthesized cloverite occurs around -57 OC. Removal of extraframework H20 occurs in two barely resolved stages at 90 "C and 110 'C. At this stage the quinuclidine template exists predominantly in the protonated form. The dehydration event is reversible and has very little effect on the integrity of the cloverite framework. Acid-base titrations of dehydrated cloverite with anhydrous NH, and HCI at room temperature reveal the essentially neutral nature of both the P(0H) and Ga(0H) hydroxyl groups of the interrupted framework of cloverite. This is to be contrasted with defect hydroxides in cloverite which behave as Brinsted acid sites. However, all P(0H) and Ga(0H) groups can be selectively deuterated with D2 at 240 "C and D20 at room temperature, leaving the hydrogens on the quinuclidinium template effectively untouched. Xe gas can access the larger, but not the smaller, channel of cloverite, both as-synthesized and after dehydration at 150 OC. Three thermal events occur around 350 "C, 450 "C, and 550 "C in which the occluded template (25%, 70%, 100%) and framework hydroxyls (4076, 90%, 100%) are systematically depleted from cloverite, simultaneously with the evolution of quinuclidine cracking products, framework HF, and H20. At each of these stages, Xe gas can only gain acceSS to the supercages, being excluded from the LTA/RPA channel system of cloverite. The proton on the quinuclidinium housed in the interrupted framework of cloverite appears to play a key role in the production of dehydroxylated-dehydrofluorinated and/or partially fragmented double four-rings, through the thermally induced loss of framework HF and H20 over this temperature range. However, up until about 450-500 "C, the disruption of double four-rings appears to be localized and short-range in nature. It does not appear to significantly reduce the crystallinity of cloverite at the unit cell level or the framework microporosity of the material, the latter with respect to O2 and n-hexane adsorption. This process continues up to 800 "C, with the unit cell maintained essentially intact, at which point one observes catastrophic breakdown of the cloverite structure. The collapsed material at this stage is X-ray amorphous, but around 850 OC it recrystallizes predominantly into the dense phase tridymite form of GaP04. Between 850 and 1050 "C the evolution of CO is observed, which is considered to arise from a carbothermal reduction of the gallophosphate by residual carbon. A transformation of GaPO&idymite into predominantly GaPO,sristobalite occurs around 1000 "C. A sintering transition begins around 1090 OC. Clearly the unit cell of cloverite remains essentially intact up until around 800 "C, although some short range disorder is introduced into the system up to this stage, most likely originating from the random production of disrupted double four-rings. ~~~ ~~ ~ ~~~

Nanocomposite Materials for Optical Applications

Abstract: A substantial amount of work has been carried out in the area of nanocomposite materials for optical applications. Composites are typically constructed by embedding an optically functional phase into a processable, transparent matrix material. By doing so, the optical properties can be utilized in more technologically important forms such as films and fibers. This review covers many areas of optical composite research to date. Composites with second- and third-order nonlinearities and laser amplification properties are discussed with examples from the recent literature. Other composites, including transparent magnets, may be made using similar structures. The principles used to construct these composites may have important technological applications soon and are therefore summarized in this review.

The Interface Chemistry between Chalcogenide Clusters and Open Framework Chalcogenides

Abstract: One of the most exciting recent developments concerning molecular architectures is the emerging field of crystalline chalcogenide superlattices that bridges two traditional but distinct areas of research: chalcogenide clusters and porous materials. By combining synthetic and structural concepts in these two areas, many crystalline solids containing spatially organized chalcogenide clusters have been created that exhibit varied properties ranging from microporosity, fast ion conductivity, and photoluminescence to narrow and tunable electronic band gaps. The potential applications of these materials extend beyond traditional areas such as acid catalysis or adsorption-based separation to include shape- or size-selective photocatalysis, solid-state ionics, and electrochemistry.

Microporous and Photoluminescent Chalcogenide Zeolite Analogs

Abstract: Crystalline semiconducting sulfide and selenide zeolite analogs were synthesized that possess four-connected, three-dimensional tetrahedral networks built from tetravalent (M 4+ = Ge 4+ or Sn 4+ , where M = meta) and trivalent (M 3+ = Ga 3+ or In 3+ ) cations. Microporous materials were obtained in all four combinations of M 4+ and M 3+ , and some of them were thermally stable up to at least 380°C. These materials exhibit framework topologies with pore size ranging from 12 to 24 tetrahedral atoms, high surface area, high framework charge density and ion exchange capacity, and tunable electronic and optical properties.