G.E. Buono-Core

PHOTOCHEMICAL DEPOSITION OF Pd-LOADED AND Pt-LOADED TIN OXIDE THIN FILMS

Pd and Pt loaded tin oxide thin films have been successfully prepared by direct UV irradiation of amorphous films of β-diketonate complexes on Si(100) substrates. Tin oxide films loaded with 10, 30 and 50% Pd and Pt, were characterized by Auger electron spectroscopy (AES). The Auger peak intensity ratios of O KL 23 L 23 to Sn M 4 N 45 N 45 showed that as-deposited films consist of mixed tin oxide phases whereas annealed films consist mainly of single phase SnO 2 . The results showed that the stoichiometry of the resulting films is in relative agreement with the composition of the precursor films. The surface characterization of these thin films was performed using Atomic Force Microscopy (AFM). This analysis revealed that loaded tin oxide films have a much rougher surface than unloaded films, with rms roughness values ranging from 28-54 nm for as-deposited Pd-SnO X films to 3.6-20 nm for as-deposited Pt-SnO X films. It was also found that Pt-loaded tin oxide films present a better particle size distribution and uniformity when compared to Pd-loaded tin oxide films. These results demonstrate the potential use of these deposited films in the manufacture of gas-sensing devices.

MOLYBDENUM TRIOXIDE THIN FILMS DOPED WITH GOLD NANOPARTICLES GROWN BY A SEQUENTIAL METHODOLOGY: PHOTOCHEMICAL METAL-ORGANIC DEPOSITION (PMOD) AND DC-MAGNETRON SPUTTERING

Gold nanoparticles (AuNPs) were deposited by DC-magnetron sputtering onto molybdenum trioxide (MoO3) thin films grown by Photochemical Metal- Organic Deposition (PMOD) on Si(100) and borosilicate glass substrates. The chemical, optical and morphology properties of the films were studied by UV/ Vis Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and X-Ray Diffraction (XRD). SEM revealed that AuNPs formed after 5 s of sputtering. AuNPs are spherical and have both an average diameter of 18 nm and a relatively narrow size distribution. As the deposition time increases, larger structures are formed by an aggregation of AuNPs. XPS studies of the AuNP/MoO3 films on Si(100) showed the presence of Mo(VI) and Mo(V), which indicated that the films were primarily non-stoichiometric molybdenum oxides. The occurrence of oxygen vacancies in the substrate play an important role to stabilize the AuNPs.

STRUCTURAL ELUCIDATION OF BIOACTIVE PRINCIPLES IN FLORAL EXTRACTS OF GERMAN CHAMOMILLE (MATRICARIA RECUTITA L.)

In this work, bioactive compounds present in flower heads of German Chamomille, were extracted and isolated in pure forms by chromatographic techniques. These compounds, spiroketal enol ethers, present in both isomeric forms Z and E, were characterized and unequivocally identified by spectroscopic techniques. One- (1H, 13C) and two-dimensional (1H-1H-COSY, 1H-1H-NOESY, HMQC and HMBC) NMR were used to assign the configuration of each isomeric compound. It was also found that irradiation of the extracts with UV light induced the photoisomerization of the en-yn-dicycloethers favoring the formation of the more stable E isomer.

EVALUATION OF b-DIKETONATE TIN AND INDIUM COMPLEXES AS PRECURSORS FOR THE PHOTODEPOSITION OF SnO2 AND In2O3 THIN FILMS

SnO2 and In2O3 thin films have been succesfully prepared by direct UV irradiation of amorphous films of b-diketonate complexes on Si(100) substrates. The as-deposited films were analyzed by Auger electron spectroscopy (AES), whereas annealing was required in order to get X-ray diffraction spectra, indicating the amorphous nature of the films. The surface morphology of the films examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) revealed that In2O3 films are much smoother than SnO2 films, with average surface roughness (Ra) of 3 nm and 11 nm respectively. The low resistivity values determined for these metal oxide films (3-4 x 10-4 W cm) demonstrate the potential use of these deposited films in gas-sensing devices for detection of environmentally significant concentrations of oxidizing species such as NO2 and O3

EFFECT OF SOME NATURAL UV-ABSORBERS ON THE PHOTOSTABILIZATION OF ACTIVE INGREDIENTS IN GERMAN CHAMOMILLE FLORAL EXTRACTS: PART I

The effect of some natural UV absorbers on the photostabilization of spiroketal enol ethers (en-yn-dicycloethers) present in German Chamomille extracts precoated on glass plates (solid phase) was examined. Plates were exposed to sunlight radiation from a UV-sun radiation lamp, in the presence and absence of gallic acid, cinnamic acid, caffeic acid, ferulic acid and aloin, all natural UV absorbers. At particular intervals the remaining concentration of the en-yn-dicycloethers was analyzed by HPLC. Using first-order kinetic equation, the dissipation half-life values (DT 50 ) for the degradation of the en-yn-dicycloethers under UV-sun radiation were obtained. The results showed that the addition of cumaric acid and caffeic acid provided moderate degree of photostabilization of the en-yndicycloethers and that addition of ferulic acid provided the best photostabilization among the UV absorbers studied. Photostabilization effect appears to be due to a competitive energy absorption of UV photons by the absorber molecules.

η²-COORDINATION OF CHLOROBENZENES TO RHENIUM FRAGMENT Cp*Re(CO)2: CHEMICAL AND PHOTOCHEMICAL SYNTHESES OF Cp*Re(CO)2(η²-C6H6-nCl n)

ABSTRACT The complexes Cp*Re(CO) 2 (h 2 -C 6 H 6-n Cl n ), n = 4, (5,6-h-1,2,3,4-C 6 H 2 Cl 4 ) 2a ; n = 3, (5,6-h 2 -1,2,4-C 6 H 3 Cl 3 ) 2b ; n = 2, (2,3-h 2 -1,4-C 6 H 4 Cl 2 ) 2c and (4,5-h 2 -1,3-C 6 H 4 Cl 2 ) 2d , have been conveniently prepared by two alternative procedures: Directly, by the photochemical reaction of Cp*Re(CO) 2 (N 2 ) in neat or saturated hexane solution of the corresponding partially chlorinated benzene or stepwise, by the reaction of the appropriate trans-Cp*Re(CO) 2 (Ar Cl )X, X = Cl, Br ( 1a-d ) with LiBHEt 3 followed by protonation with HCl to form the hydrido complexes trans-Cp*Re(CO) 2 (Ar Cl )H which resulted thermally unstable in solution and convert to h 2 -coordination complexes 2a-d . Due to their low stability as solids and in solution, the new complexes were only characterized by IR and 1 H and 13 C NMR spectroscopy. The 1 H NMR spectra of the two derivatives containing dichlorobenzene ( 2c and 2d ) indicate that a rapid exchange occurs between the hydrogen atoms on the coordinated carbons and those on the non-coordinated carbons.e-mail: fernando.godoy@usach.cl

Identification and synthesis of some fatty acid derivatives from larvae of Chilecomadia valdiviana (Lepidoptera: Cossidae)

Larvae of Chilecomadia valdiviana (Lepidoptera: Cossidae) were extracted and the extract was fractionated by chromatography on silica. As shown by gas chromatography–mass spectrometry, the major fraction contained saturated and unsaturated straight-chain acetates, with (Z )-5,13-tetradecadienyl acetate and dodecyl acetate as the main components, while in a minor fraction the corresponding alcohols were detected. The identification of the compounds and the synthesis of some reference material are presented.

SOLID STATE PHOTOCHEMISTRY OF Cu(II) ALKYLTROPOLONATE COMPLEXES IN THIN FILMS: THE PHOTOCHEMICAL FORMATION OF HIGH QUALITY FILMS OF COPPER(I) OXIDE

In this paper we report the utilization of a series of alkyltropolonate Cu(II) complexes as precursors for the direct photodeposition of amorphous thin films of Cu(I) oxide. Linear and branched alkyl substituents in the tropolone ligands were used to diminish the intermolecular interactions and in this way improve the quality of the films. Spin-coating techniques were used for the deposition of precursor films which were evaluated by optical microscopy, prior to irradiation with 254 nm UV light. Characterization of the photodeposited films by XRD and Auger spectroscopy showed the formation of Cu2O. The photochemical deposition of patterns of copper oxide was shown to be compatible with standard lithographic techniques by the lithography of 2 x 100 µm lines. This results demonstrate the potential use of Cu(II)alkyltropolonates as precursors for the photodeposition of metal and metal oxides thin films