M. Curry

Thin Metal Films Deposited on Dendrimer Monolayers

Chemical interactions and the evolution of surface morphology resulting from deposition of Cr and Co onto dendrimer monolayers have been investigated by XPS, RAIRS, and AFM. Evidence is presented for formation of metal nitrides and mediation of film morphology as a function of the metal and generation number of the dendrimer comprising the monolayer.

Kinetic energy influences on the growth mode of metal overlayers on dendrimer mediated substrates

Evidence is presented here for kinetic energy influences on the growth mode and chemical interactions of Cr, Co, and Cu deposited by sputtering and evaporative methods on self-assembled monolayers of amine-terminated poly(amidoamine) (PAMAM) dendrimers on SiOx. X-ray photoelectron spectroscopy (XPS) measurements show that metal nitrides are formed upon deposition of the more reactive metals and the extent of reaction increases with increasing kinetic energy of the deposited species. A peak observed at 398.5 eV in the N 1s spectrum following Cu deposition apparently indicates bond breaking in the internal amido branches of the dendrimer structure but not formation of the metal nitride. Atomic force microscopy (AFM) reveals obvious changes in the surface topography due to the dendrimer adlayer, particularly for the less reactive Cu.Evidence is presented here for kinetic energy influences on the growth mode and chemical interactions of Cr, Co, and Cu deposited by sputtering and evaporative methods on self-assembled monolayers of amine-terminated poly(amidoamine) (PAMAM) dendrimers on SiOx. X-ray photoelectron spectroscopy (XPS) measurements show that metal nitrides are formed upon deposition of the more reactive metals and the extent of reaction increases with increasing kinetic energy of the deposited species. A peak observed at 398.5 eV in the N 1s spectrum following Cu deposition apparently indicates bond breaking in the internal amido branches of the dendrimer structure but not formation of the metal nitride. Atomic force microscopy (AFM) reveals obvious changes in the surface topography due to the dendrimer adlayer, particularly for the less reactive Cu.

Influence of Strong Acid Hydrolysis Processing on the Thermal Stability and Crystallinity of Cellulose Isolated from Wheat Straw

Cellulose extractions from wheat straw via hydrochloric, nitric, and sulfuric acid hydrolysis methods were carried out. X-ray diffraction spectral analyses reveal that depending on the acid conditions used the structure of the cellulose exhibited a mixture of polymorphs (i.e., CI and CIII cellulose phases). In addition, the percent crystallinity, diameter, and length of the cellulose fibers varied tremendously as determined by X-ray diffraction and scanning electron microscopy. Thermal gravimetric analysis measurements revealed that the thermal stability of the extracted cellulose varied as a function of the acid strength and conditions used. Scanning electron microscopy analysis revealed that the aggregation of cellulose fibers during the drying process is strongly dependent upon the drying process and strength of the acids used.

Chemical Functionalization and Characterization of Cellulose Extracted from Wheat Straw Using Acid Hydrolysis Methodologies

The nonuniform distribution of cellulose into many composite materials is attributed to the hydrogen bonding observed by the three hydroxyl groups located on each glucose monomer. As an alternative, chemical functionalization is performed to disrupt the strong hydrogen bonding behavior without significant altering of the chemical structure or lowering of the thermal stability. In this report, we use wheat straw as the biomass source for the extraction of cellulose and, subsequently, chemical modification via the Albright-Goldman and Jones oxidation reactions. X-ray diffraction analyses reveal that upon oxidation a slight change in the cellulose polymorphic structure (CI to CII) can be observed when compared to its unmodified counterpart. Scanning electron microscopy analyses show that the oxidized cellulose structure exhibits fiber-like crystals with lengths and diameters on the micrometer scale. Thermal analyses (differential scanning calorimetry and thermogravimetric analysis) show an increase in the thermal stability for the modified cellulose at extremely high temperatures (>300°C).

Electrodeposition of cobalt nanowires on H-terminated conductive Si(111) surfaces using coblock polymer templating

The authors have investigated the formation of block copolymer nanocavities on H-terminated conducting Si(111) surfaces as templates for the electrochemical growth of perpendicular metallic nanowire arrays. Poly(styrene)-block-poly(methyl methacrylate) block copolymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio were used to create a self-assembled array of perpendicular nanocavities in which the PS majority phase is continuous and surrounds cylinders of the minority PMMA phase. Here, we report that H-terminated conducting Si(111) surfaces are also capable of inducing a perpendicular orientation in block copolymers, which—in all likelihood—is a direct result of the H-termination (i.e., removal of the oxide layer). Atomic force microscopy reveals that an acetic acid wash of the annealed block copolymer causes the minority PMMA component to be rearranged, giving rise to cavities that are perpendicular to the conducting Si substrate. Subsequently, scanning electron microscopy reveals that el...

Influence of Cellulose on the Mechanical and Thermal Stability of ABS Plastic Composites

Microcrystalline cellulose was explored as possible biodegradable fillers in the fabrication of ABS plastic composites. TGA indicates that upon inclusion of cellulose microcrystals the thermal stability of the ABS plastics was improved significantly when compared to the neat ABS plastic counterparts. Furthermore, inclusion of extracted cellulose from plant biomass showed a higher thermal stability with maximum decomposition temperatures around 131.95°C and 124.19°C for cellulose from cotton and Hibiscus sabdariffa, respectively, when compared to that of the purchased cellulose. In addition, TMA revealed that the average CTE value for the neat ABS and 1 : 1 ratio of cellulose to ABS fabricated in this study was significantly lower than the reported CTE (ca. 73.8 μm/m°C).

Development of Block Co-Polymers as Self-Assembling Templates for Patterned Media

Block copolymers that self-organize are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. Poly(styrene)-Poly(methylmethacrylate) block co-polymers (PS- b -PMMA) of appropriate block length and PS to PMMA ratio self-assemble into a 2-D hexagonal phase in which the PS majority phase is continuous and surrounds cylinders of the minority, PMMA phase. For application of this phase to patterned media it is necessary that the cylinders of the minority phase be oriented perpendicular to the substrate surface. This can be achieved by a number of methods, including appropriate choice of substrate and use of a random co-polymer underlayer. Appropriate substrates include H-terminated silicon, some carbon coatings and some ITO glasses. Use of an acetic acid wash causes the minority PMMA component can be induced to be rearranged, giving rise to pores perpendicular to the substrate. Electrodeposition of a metal into the pores produces a hardmask which can be used with ion-milling to transfer the block co-polymer pattern onto a magnetic thin film.

Heterogeneous Catalysis of C–O Bond Cleavage for Cellulose Deconstruction: A Potential Pathway for Ethanol Production

Due to difficulty deconstructing the linkages between lignin, hemicellulose and cellulose during the conversion of cellulose to sugar, the commercial production of cellulosic ethanol is limited. This can be overcome by using a high surface-area metal catalyst. In this study, high surface-area metal NPs were synthesized using 20 mM of chloroplatinic acid and cobalt chloride prepared in THF with 0.1 mM of generation four poly(amido)amine (PAMAM) terminated dendrimer (G4-NH2) prepared in methanol and stirred for 2 hours under nitrogen. Subsequently, Pt