A method to produce hybrid systems of cellulose ultrathin films containing immobilized silver nanoparticles (Ag NPs) generated and grown at the surface is presented. Ag NPs were produced via a mild wet chemistry technique on cellulose ultrathin films spin-coated on GaAs substrates and on modified films after grafting of diaminoalkanes activated by N,N 0 -carbonyldiimidazole. Appended amine groups operate as anchoring centers of the silver NPs enabling selective generation and immobilization of Ag NPs. The different phases of the modification process were followed by Fourier transform infrared spectroscopy (FTIRS) in attenuated total reflection in multiple internal reflections (ATR/MIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The generation of NPs is observed even on untreated cellulose surfaces with sizes ranging from 7 to 30 nm but not specifically at the surface. For modified surfaces with diaminoalkanes, higher NP density regions including extensive plates are obtained, which are specifically located at the film extreme surface. The highest NP density is achieved when the NP generation is performed on these modified surfaces in the presence of a carboxylic salt.

High resolution electron energy loss spectroscopy (HREELS) was used to study vibrational and electronic excitations induced by electrons in polystyrene thin films cast on silicon substrates. In order to deduce the nature of the interaction mechanisms involved, differential cross-sections of vibrational and electronic excitations were measured as a function of the incident electron energy and of the geometrical configuration of the experiment. Vibrational excitations were compared with the very strong bands of infrared and Raman spectra. Losses produced by impact interaction correspond mostly to Raman active modes; those produced by dipole interaction correspond mostly to infrared active modes. Electronic excitations leading to triplet or singlet excited states and having constant widths around 0.7 eV were detected. In this case, pronounced resonance mechanisms are involved, mainly in geometrical configurations far from specular conditions, showing the existence of transient negative ions centred at the maxima found for the excitation functions. The resonant mechanisms decline as specular conditions are reached. Losses having widths increasing with incident energy are assigned to interband transitions. Finally, structures at fixed kinetic energies, appearing in all spectra, are associated with the relaxation of slow electrons occupying conduction band levels with high density of states before escaping to the vacuum. ᭧ 1997 Elsevier Science B.V.

Ultrathin films of cellulose were functionalized with iron protoporphyrin IX (FePP). Spin-coating allows the production of silylated cellulose films in a controlled way. Cellulose regeneration is achieved through the hydrolyzation of the silane groups, exposing the film to acidic vapors. To enhance the reactivity of the cellulose surface to the protoporphyrin, carbonyldiimidazole (CDI) was used as an activator. The effect of different spacers on the porphyrin grafting such as 1,8-diaminooctane and 1,4-phenylenediamine was studied. The highest level of cellulose functionalization with FePP was achieved when both the cellulose film and FePP were activated by CDI and a diaminoalkane was used as a spacer between the surface and the FePP. ATR/MIR (attenuated total reflection in multiple internal reflections) was performed in situ to follow the kinetics of the different chemical reactions with the cellulose surface. ATR/MIR proved again to be a powerful tool for probing the surface reaction. X-ray photoelectron spectroscopy permitted the elemental analysis of the cellulose surface after the chemical modification.

High-resolution electron energy loss spectroscopy (HREELS) is applied to study film surfaces of two silicon-based polymers having methyl and/or phenyl rings as pendant groups: poly(diphenylsiloxane) and poly(methylphenylsilane). These spectra are compared with those obtained by infrared absorption, Raman scattering, and UV/vis absorption spectroscopy for the polymer bulk. Both vibrational and electronic spectra of these two polymers exhibit common features corresponding to the phenyl pendant group excitations. Positions of peaks appearing in HREELS vibrational spectra correspond well to infraredand Raman-active modes of the polymer bulk. Electronic losses also correspond to the electronic excited states of phenyl groups cited in the literature. Differences related to secondary emission and accumulation of relaxed electrons are assigned to the electronic structure of the film. The absence of a loss corresponding to the excitation of polysilane chain is related to a trapping mechanism.

We present results from high-resolution electron energy loss spectroscopy (HREELS) and XPS studies of self-assembled monolayers of DNA. The monolayers are well-organized and display sharp vibrational peaks in the HREEL spectra. The electrons interact mainly with the backbone of the DNA. The XPS results indicate that, in most of the samples studied, the phosphates on the DNA are not charged.

Transparent and conductive/semiconductive undoped indium oxide (InOx) thin films were deposited at room temperature. The deposition
technique used is the radio frequency (rf) plasma enhanced reactive thermal evaporation (rf-PERTE) of indium (In) in the presence
of oxygen. The influence of oxygen partial pressure on the properties of these films is presented. The oxygen partial pressure varied
between 3 · 102 and 1.3 · 101 Pa. Undoped InOx films, 100 nm thick, deposited at the oxygen partial pressure of 6 · 102 Pa show a
conductive behaviour, exhibit an average visible transmittance of 81%, a band gap around 2.7 eV and an electrical conductivity of about
1100 (X cm)1. For oxygen pressures greater than 6 · 102 Pa, semiconductive films are obtained, maintaining the visible transmittance.
Films deposited at lower pressures are conductive but dark. From XPS data, films deposited at an oxygen partial pressure of 6 · 102 Pa
show the highest amount of oxygen in the film surface and the lowest ratio between oxygen in the oxide crystalline and amorphous phases.

The effect of different mild post-annealing treatments in air, at 270 ◦C, for 4–6 min, on the optical, electrical,
structural and chemical properties of copper sulphide (CuxS) thin films deposited atroomtemperature
are investigated. CuxS films, 70nm thick, are deposited on glass substrates by vacuum thermal evaporation
from a Cu2S:S (50:50 wt.%) sulphur rich powder mixture. The as-deposited highly conductive
crystalline CuS (covellite) films show high carrier concentration (∼1022 cm−3), low electrical resistivity
(∼10−4 cm) and inconclusive p-type conduction. After the mild post-annealing, these films display
increasing values of resistivity (∼10−3 to ∼10−2 cm) with annealing time and exhibit conclusive p-type
conduction. An increase of copper content in CuxS phases towards the semiconductive Cu2S (chalcocite)
compound with annealing time is reported, due to re-evaporation of sulphur from the films. However,
the latter stoichiometry was not obtained, which indicates the presence of vacancies in the Cu lattice.
In the most resistive films a Cu2O phase is also observed, diminishing the amount of available copper
to combine with sulphur, and therefore the highest values of optical transmittance are reached (65%).
The appearance on the surface of amorphous sulphates with annealing time increase is also detected as a
consequence of sulphur oxidation and replacement of sulphur with oxygen. All annealed films are copper
deficient in regards to the stoichiometric Cu2S and exhibit stable p-type conductivity.

ZnO is a natural n-type widespread semiconductor with wide direct bandgap of 3.37 eV, large exciton bending energy (60 meV) and high optical gain (300 cm −1 ). One dimensional ZnO nanomaterials such as nanowires or nanorods have focused much attention due to their multifunctionality in optoelectronic devices, gas sensing, piezoelectricity and thin film transistors for transparent and flexible electronics. Solution-phase chemical synthesis of nanomaterials has several important advantages, as low temperatures, high versatility, low cost, simple equipments and handling.

Films and fibres of cellulose were functionalised with silver and gold nanoparticles directly generated on the surface. The present method lays on the cellulose surface pre-modification, replacing some of the hydroxyl groups by amino functions, which selectively act as the seed coordination sites. Nanoparticles can then grow through the interaction with aqueous dilute solutions of AgNO 3 or NaAuCl 4 at room temperature, without adding any reducing agent. The procedure offers the advantage of limiting the generation of nanoparticles to the cellulose surface, leaving the dispersion medium completely exempt of them. The cellulose pre-modification also ensures chemical anchoring of the nanoparticles to the surface, avoiding any risk of particle desorption and extending the lifetime of the resulting hybrid materials. Evidence of the formation of the NPs on the cellulose surfaces was supported by FE-SEM, AFM, XPS and XRD. The method is simple and reproducible.

A method to produce hybrid systems of cellulose ultrathin films containing immobilized silver nanoparticles (Ag NPs) generated and grown at the surface is presented. Ag NPs were produced via a mild wet chemistry technique on cellulose ultrathin films spin-coated on GaAs substrates and on modified films after grafting of diaminoalkanes activated by N,N 0 -carbonyldiimidazole. Appended amine groups operate as anchoring centers of the silver NPs enabling selective generation and immobilization of Ag NPs. The different phases of the modification process were followed by Fourier transform infrared spectroscopy (FTIRS) in attenuated total reflection in multiple internal reflections (ATR/MIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The generation of NPs is observed even on untreated cellulose surfaces with sizes ranging from 7 to 30 nm but not specifically at the surface. For modified surfaces with diaminoalkanes, higher NP density regions including extensive plates are obtained, which are specifically located at the film extreme surface. The highest NP density is achieved when the NP generation is performed on these modified surfaces in the presence of a carboxylic salt.

High resolution electron energy loss spectroscopy (HREELS) was used to study vibrational and electronic excitations induced by electrons in polystyrene thin films cast on silicon substrates. In order to deduce the nature of the interaction mechanisms involved, differential cross-sections of vibrational and electronic excitations were measured as a function of the incident electron energy and of the geometrical configuration of the experiment. Vibrational excitations were compared with the very strong bands of infrared and Raman spectra. Losses produced by impact interaction correspond mostly to Raman active modes; those produced by dipole interaction correspond mostly to infrared active modes. Electronic excitations leading to triplet or singlet excited states and having constant widths around 0.7 eV were detected. In this case, pronounced resonance mechanisms are involved, mainly in geometrical configurations far from specular conditions, showing the existence of transient negative ions centred at the maxima found for the excitation functions. The resonant mechanisms decline as specular conditions are reached. Losses having widths increasing with incident energy are assigned to interband transitions. Finally, structures at fixed kinetic energies, appearing in all spectra, are associated with the relaxation of slow electrons occupying conduction band levels with high density of states before escaping to the vacuum. ᭧ 1997 Elsevier Science B.V.