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This article reports the valence-band x-ray photoelectron spectroscopy (XPS) of various forms of sodium phosphate. Valence-band spectra are compared to spectra generated from cluster and band-structure calculations. Five different forms of sodium phosphate are studied as follows, Na4P2O7, Na5P3O10, Na4P4O12, Na2H2P2O7, and NaH2PO2. Core-level XPS studies are of little use for differentiating between such similar compounds while valence band photoemission has been found to be particularly effective at identifying subtle differences in surface chemistry. The results indicate that the valence-band region clearly distinguishes between these different phosphates and that these differences can be predicted by spectra generated from both cluster and band-structure calculations.

Oleic acid capped lead sulfide (PbS) and lead selenide (PbSe) were synthesized, then subjected to a postsynthesis washing in a 1:1 ethanol/hexane solution. The relationship of third order nonlinear optical properties to nanocrystal surface chemistry as affected by washing was analyzed using nanosecond 532 nm Z-scan and measurement of near-IR radiative emission. The results indicated a significant change in optical nonlinearities which emerged only after the nanocrystals were washed in the ethanol/hexane mixture. Transmission electron microscopy of the oleic acid capped PbSe and PbS nanocrystals showed a cubic shape, narrow size distribution and an average size of ∼10 nm. Neither size nor shape of the nanocrystals were modified by the washing process, indicating that all optical differences were related to changes in surface chemistry and the formation of deep trap states. The “as grown” nanocrystals showed high emission efficiency, weak saturable absorption, and a self-defocusing refractive index, n2, det...

A series of lead sulfide (PbS) nanocrystals grown in oleic acid (OA), poly(1-decene) (PD), poly(1-butene) (PB), and poly(vinyl alcohol) (PVA) were synthesized. The relationship between nonlinear optical properties and surface properties of PbS nanocrystals were analyzed using 532 and 1064 nm nanosecond open-aperture Z-scan measurements and femtosecond pump−probe experiments with a 390 nm pump and a 450−700 nm probe. The results indicated a clear difference in nonlinear optical properties between the OA and PVA composites in comparison to PB and PD. The materials with strong covalent bonding between the nanocrystal surface and organic phase, PVA and OA, did not show nonlinear absorption behavior in Z-scan measurements at 532 or 1064 nm. The PB and PD composites did, however, show strong reverse saturable absorption in Z-scans recorded at these wavelengths. The transient absorption measurements further separated the PVA and OA composites from the PD and PB samples. The decays for each of the samples indicat...

Lead sulfide nanocrystals were grown in toluene solutions of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene, polyethylene, poly(1-butene), poly(1-decene), and polystyrene. The PbS nanocrystal diameter was controlled by the polymer used for synthesis and ranged from 4 to 9 nm. Strong nonlinear absorption was observed in open aperture Z-scan measurements of solutions containing the synthesized nanocomposites. The best fit to the experimental data gave high values for βeff in the range of 100−200 cm/GW. The nonlinear absorption of these polymer grown nanocrystals was not observed in nanocrystals grown in polyvinyl alcohol or with oleic acid capping. These differences in nonlinear optical absorption were due to surface chemistry, as the polymer synthesized nanocrystals were free of strongly bonding groups such as surfactant capping or hydroxyl groups. The βeff values in these materials also showed no dependence on nanocrystal size.

Valence band and core level X-ray photoelectron spectroscopy (XPS) were used to probe lead sulfide (PbS) nanoparticle–polymer nanocomposites. Composite materials were prepared by trapping commercially available monodisperse 3 and 10 nm PbS nanoparticles in two polymers, the non-conducting polymer, polystyrene, and the conjugated polymer, poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene (referred to below as MEH-PPV). The nanocomposites prepared from commercial nanoparticles underwent oxidation, mainly to form lead sulfate. However, the narrow size distributions of the commercial nanoparticles allowed observation of distinct changes in the valence band from the 3 to 10 nm nanoparticles. Nanocomposites of 2–5 and 4–7 nm PbS nanoparticles were synthesized by growing the particles in poly(vinyl alcohol) (referred to below as PVA) and MEH-PPV, respectively. These composites both indicated the formation of lead sulfide nanoparticles. Furthermore, the XP spectra for the PVA/PbS composite displayed bonding between the PbS nanoparticles and the polymer while MEH-PPV showed no PbS–polymer bonding. The nanoparticles synthesized in MEH-PPV did not undergo oxidation. The particle size distributions of the synthesized nanoparticles were too broad to display size-dependent changes in the valence band.

This article continues a series of papers that shows how thin (10nm or less) oxide-free phosphate films can be formed on a number of metals. The films formed have potential as corrosion resistant films. Previous papers have shown that it is possible to extend the range of the surface coatings that can be formed by placing a thin polymer layer over the phosphate layer. In this work it is shown how the water insoluble polymer poly(ether ketone ketone) (PEKK) can be placed over a thin oxide-free phosphate film on aluminum metal. The surface and the interfaces involved were studied by valence band and core level x-ray photoelectron spectroscopy. Difference spectra in the valence band region were used to show that there is a chemical interaction between the PEKK and phosphate thin films on the aluminum metal. Three different phosphate film compositions were studied using different phosphorous containing acids, H3PO4, H3PO3, and H3PO2. This type of interaction illustrates the potential of phosphates to act as a...

This article reports the preparation of thin (less than 100A) oxide-free phosphate films of various compositions on vanadium metal. These films are interesting because of their potential for corrosion inhibition, adhesion promotion, and biocompatibility. Valence and core-level x-ray photoelectron spectroscopy (XPS) were used to characterize the films. The valence band spectra obtained were compared with spectra generated from band structure calculations for various vanadium phosphates and from previously reported spectra of vanadium phosphates. Vanadium phosphate coatings were created by the reaction of vanadium metal and different phosphorus-oxygen containing acids: H3PO4, H3PO3, H3PO2, and H2P2O7. This article focuses upon the valence band region which shows significant differences between the four vanadium phosphate films formed as well as clear differences between the these phosphates and vanadium oxides. The valence band spectra are effectively interpreted by band structure calculations.

The valence-band and core-level x-ray photoelectron spectroscopy (XPS) of vanadium phosphates are reported, and the valence-band spectra interpreted by various calculation models. The spectral interpretation of the vanadium phosphates is used to show that an oxide-free vanadium phosphate film corresponding to VO(H2PO4)2 can be prepared on vanadium metal. Three types of vanadium phosphate were investigated to provide an understanding of the XPS data for vanadium phosphates, and to demonstrate the differences between these phosphates and vanadium oxides. The three phosphates formed, VO(H2PO4)2, VOHPO4.0.5H2O, and VOPO4⋅2H2O were prepared by reaction of vanadium with phosphoric acid under a variety of conditions. The article focuses upon the valence-band region which shows significant differences between different types of vanadium phosphates as well as clear differences between the phosphates on the one hand and oxides on the other hand. The valence-band spectra are effectively interpreted by the multiple s...

The XPS spectra of vanadyl hydrogen phosphate were collected with a VSW HA150 using monochromatic Al Kα x-radiation. The valence band region is determined by the features of the HPO42− ion which shows subtle but significant differences from the valence band region of the orthophosphate ion (PO43−). The valence band, survey, V 2p, V 3p, O 1s, P 2p, P 2s, and C 1s are reported.

We report the XPS spectra of sodium polyphosphate. XPS spectra were collected with a VSW HA150 x-ray photoelectron spectrometer using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band of sodium polyphosphate due to the absence of interfering x-ray satellites from the intense O 2s region. The features seen in the valence band are unique to the (P4O12)4− ion and therefore provide a means for distinguishing this compound from chemically similar compounds such as other phosphates. The valence band, survey, Na 1s, O 1s, C 1s, P 2s, P 2p, and Na 2s levels are reported.

We report the XPS spectra of sodium dihydrogenpyrophosphate. XPS spectra were collected with a VSW HA150 x-ray photoelectron spectrometer using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band of sodium dihydrogenpyrophosphate due to the absence of interfering x-ray satellites from the intense O 2s region. The features seen in the valence band are unique to the (H2P2O7)2− ion which shows small but significant differences from the (P2O7)4− ion. The valence band, survey, Na 1s, O 1s, C 1s, P 2s, P 2p, and Na 2s levels are reported.

We report the XPS spectra of sodium pyrophosphate. XPS spectra were collected with a VSW HA150 x-ray photoelectron spectrometer using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band of sodium pyrophosphate due to the absence of interfering x-ray satellites from the intense O 2s region. The features seen in the valence band are unique to the (P2O7)4− ion and therefore provide a means for distinguishing this compound from chemically similar compounds such as other phosphates. The valence band, survey, Na 1s, O 1s, C 1s, P 2s, P 2p, and Na 2s levels are reported.

The XPS spectra of vanadyl dihydrogenphosphate were collected with a VSW HA150 using monochromatic Al Kα x-radiation. The valence band region is determined by the features of the HPO4− ion which shows subtle but significant differences from the valence band region of the orthophosphate ion (PO43−). The valence band, survey, V 2p, V 3p, O 1s, P 2p, P 2s, and C 1s are reported.

The XPS spectra of ferrous phosphate were collected with a VSW HA150 using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band of ferrous phosphate due to the absence of interfering x-ray satellites from the intense O 2s region. The valence band, survey, and the P 2s, P 2p, Fe 2p, Fe 3p, O 1s, and C 1s core levels are reported.

We report the XPS spectra of sodium tripolyphosphate. XPS spectra were collected with a VSW HA150 x-ray photoelectron spectrometer using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the rich peak structure in the valence band of sodium tripolyphosphate due to the absence of interfering x-ray satellites from the intense O 2s region. The features seen in the valence band are unique to the (P3O10)5− ion and therefore provide a means for distinguishing this compound from chemically similar compounds such as other phosphates. The valence band, survey, Na 1s, O 1s, C 1s, P 2s, P 2p, and Na 2s levels are reported.

The XPS spectra of vanadyl orthophosphate dihydrate were collected with a VSW HA150 using monochromatic Al Kα x-radiation. The valence band region is determined by the features of the orthophosphate ion. The valence band region is typical of that of an orthophosphate compound.

The electron injection dynamics of RuII(4,4‘-dicarboxy-2,2‘-bipyridine)2cis(NCS)2 (N3 dye) adsorbed on MoS2 nanoclusters have been studied using static and time-resolved optical spectroscopy. Static spectroscopy and the comparison with RuII(2,2‘-bipyridine)2cis(NCS)2 indicate that the N3 is bound to the MoS2 nanoclusters and that the binding occurs through the carboxylates. The static absorption spectrum of adsorbed N3/MoS2 is red shifted about 1.2 nm compared to N3 in an equivalent acetonitrile/hexanol/tridodecylmethylammonium iodide solution. The extent of the spectral shift indicates that the coupling is comparable to that in the N3/TiO2 case. The time-resolved results indicate that about 35% of the adsorbed dyes inject electrons into the MoS2 conduction band on the 250 ps time scale, and about 65% do not inject. These results indicate that electron injection is comparatively slow in these systems (250 ps compared to

Surface polymerization by ion-assisted deposition was used to grow phenylene vinylene films (SPIAD-PPV) using the evaporation of 2methoxy-5-(2'-ethylhexyloxy)-1,4-bis((4',4 ''-bisstyryl) benzene) (MEH-OPV5) and the simultaneous deposition of non-mass-selected 10-200 eV thiophene or acetylene ions. Images recorded by scanning electron microscopy showed differences in SPIAD-PPV film morphology versus evaporated MEH-OPV5 that indicated changes in the underlying chemical structure. Spectroscopic differences between MEH-OPV5 and SPIAD-PPV films suggested preferential attack of vinylene groups and/or hydrocarbon side chains. A possible explanation for the changes in morphology and electronic structure was cross-linking at vinylene sites of adjacent MEH-OPV5 molecules which could lead to changes in molecular packing. Although morphological and electronic differences were seen for SPIAD-PPV films, these films still showed valence bands characteristic of phenylene vinylenes. (c) 2008 Elsevier B.V. All rights reserved.