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The effect of (60)Co gamma rays irradiation on the polymetallayne [-Pt(PBu(3))-C≡C-C(6)H(4)-C(6)H(4)-C≡C-](n) (Pt-DEBP) of defined chain length corresponding to 10 repeat units, has been studied in detail. The UV-vis absorption spectra of Pt-DEBP have been recorded in solution upon exposure of the polymetallayne at increasing radiation doses in the range up to 90 Gy, with special care to the features related to low doses. Complex modifications of the chemical structure of Pt-DEBP could be accessed through NMR, FTIR, GPC, and XPS characterizations, which support the attack of Cl and H radicals coming from the radiolysis of the solvent, CHCl(3), to the triple C≡C bonds of the backbone, leading to the formation of chlorinated double and single C-C bonds, with a concomitant increase of the molecular weight due to a recombinant effect of oligomer fragments upon irradiation. The presence of vinyl and single chlorinated moieties has been sustained from the simulation of the UV-vis spectra based on theoretical calculations.

Self assembling monolayers (SAMs) of organometallic thiols trans-[HS–Pd(PBu3)2–SH], trans-[HS–Pd(PBu3)2(–C C–C6H5)] and trans,trans-[HS–Pd(PBu3)2(–C C–C6H4–C6H4–C C–Pd(PBu3)2–SH] on gold were obtained from the corresponding multilayers through thermally induced desorption. Temperature-dependent synchrotron radiation-induced X-ray photoelectron spectroscopy (SR-XPS) measurements were carried out on the heated multilayers during the annealing process, in order to investigate the thermal and chemical stability of the systems. SAMs of the same organometallic thiols were also obtained by rinsing the thick films with appropriate solvents. SR-XPS was used to ascertain that the molecular and electronic structure of the two series of SAMs are not influenced by the rinsing or thermal desorption process, i.e. both strategies allow for obtaining well ordered monolayers of organometallic thiols.

The influence of the transition metals on the molecular orientation and molecule-substrate interaction has been investigated by angular dependent NEXAFS spectroscopy for the recently synthesised dialkynyl bridged complexes M-2-DEBP (Cl(PBu3)(2)M-C equivalent to C-C6H4[4 C6H4-C equivalent to CM(PBu3)(2)Cl, M = Pt, Pd; DEBP = diethynyl-biphenyl, i.e. C equivalent to C-C6H4-C6H4-C equivalent to C-). Thin films of both samples have been deposited on Au/Si(111), and the angular dependent analysis of the main pi* feature deriving by the superimposition of the resonances due to benzene and acetylene carbon orbitals showed a polarisation effect for Pd-2-DEBP only. A tendency to a preferential molecular orientation at nearly 50 degrees to the surface was calculated. Furthermore, for Pd2-DEBP, the two pi* resonances already assigned to benzene and acetylene carbon atoms showed different angular effects; a likely explanation for this behaviour bear in mind the interaction between sp and sp 2 carbons of the organic DEBP moieties with Pd centres of neighbouring macromolecules, giving rise to interchain interactions then leading to an enhancement of the already assessed self-assembling properties.

In this paper, we focus our attention on the morphological and optical characterisation of self-assembled Zn-porphyrin-based/fullerene systems. Diethynyl-Zn-porphyrin (ZnDEP) and bimetallic σ-bonded arrays of diethynyl-Zn-porphyrin with Pd(II) and Pt(II) square planar complexes, namely, ZnDEP, Pd–ZnDEP and Pt–ZnDEP, have been synthesised, and these compounds were studied in the self-assembly behaviour with fullerene, giving rise to the molecular composites ZnDEP/C 60 , Pd–ZnDEP/C 60 and Pt–ZnDEP/C 60 . Thick films of the materials were deposited by slow evaporation on glass substrates, in order to be morphologically characterised by scanning electron microscopy (SEM) technique. The surface analysis showed a peculiar nanometric structure of the composites. The optical (UV–Vis absorption and emission) characterisation of toluene solutions and a preliminary study on the molecular oxygen luminescence quenching of diethynyl-Zn-porphyrin, diethynyl-Zn-porphyrin/fullerene and platinum or palladium-containing homologues have been performed and will be here discussed. A luminescence response towards molecular oxygen was observed in the case of ZnDEP and ZnDEP/C 60 samples with a lowering of the intensity of the emission, suggesting promising applications in optical sensors.

""Poly(phenylacetylene) (PPA) and poly(phenylacetylene-co-acrylic acid) (P(PA-co-AA)), nanoparticles bioconjugated with dexamethasone (DXM) during the synthesis, named PPA@DXM and P(PA-co-AA)@DXM, were prepared by a modified surfactant free emulsion method. The loading was studied as a function of different functionality grades of the copolymer and different amounts of drug, obtaining up to 90% of drug loading for P(PA-co-AA)@DXM with 8\\\/1 PA\\\/AA monomer ratio. The SEM images and DLS measurements showed spheres with average diameters in the range 190-500 nm, depending on the content of acrylic acid monomer units in the copolymer and of DXM loading. ζ-potential and surface charge density of DXM loaded nanoparticles were also investigated and confirm the charge density modulation in the range 0.62-2.68σ (μC\\\/m(2)). The results highlight the enhanced capability of our copolymer of hosting DXM, with the advantage of a control of size, surface functionality, charge and release. Moreover we demonstrate for the first time the ability of P(PA-co-AA) DXM loaded nanoparticles to be used in the apoptosis inhibition of human tumor cells (HeLa). On the basis of the results obtained by comparing the effects elicited in HeLa cells by free DXM versus DXM loaded nanoparticles we confirmed the biological efficacy of our preparation.. . ""

"The local atomic structure and chemical nature. of newly synthesized silver nanoparticles (AgNPs) functionalized. with the organic thiol allylmercaptane (AM) have been. probed combining synchrotron radiation-based techniques: Xray. photoelectron spectroscopy (XPS) and X-ray absorption. fine structure spectroscopy (XAFS). Complementary information. about the chemical and electronic structure is obtained. combining XAFS and XPS data. These results coherently. suggest a core shell morphology of the NPs resulting in. metallic Ag cores surrounded by Ag2S-like phase. The external. layer of AM molecules is grafted to the NPs surface through. Ag−S chemical bonds. NP size and composition were found as. a function of the chemical synthetic route (i.e., Ag\\\/AM molar ratio). It was observed that by increasing the Ag\\\/AM ratio, larger. AgNPs were obtained. It was found that a higher Ag\\\/AM molar ratio leads to an increasing of the Ag2S layer thickness, while the. external AM layer remains unvaried. TEM analysis showed well-separated and dispersed nanoparticles, and ED pattern allowed. one to identify two different phases of single crystal corresponding to the presence of Ag face-center-cubic single-crystal. symmetry, together with weak diffraction spots in agreement with Ag2S cubic symmetry in Im3m space groups.""

A new surface acoustic wave humidity sensor has been developed and tested. It is based on the use of a polyphenylacetylene (PPA) membrane which has already been utilized in the I 2 -doped form for the study of humidity sensors based on electrical conductivity responses. PPA shows physical properties which make it an almost ideal membrane for acoustic wave type sensors. Measurements performed on both Rayleigh and surface transverse waves have shown a high sensitivity of the device over a wide range of relative humidity values, a reversible behaviour together with a fairly fast response time.

The electrical properties of iodine-doped poly(phenylacetylene) [PPA] solutions have been studied by means of low-frequency electrical conductivity and dielectric measurements in the frequency range 1 MHz-1 GHz. These data show that, in these systems, the conducting mechanism is different and more complicated than the typical additive behaviour of diluted ionic solutions. The high-frequency dielectric measurements display a pronounced dielectric dispersion characterized by a single Debye-type relaxation process. This dielectric behaviour can be attributed to the dipolar character of PPA, enhanced when the polymer interacts with the iodine doping species.

The interaction of small molecules (H2O, O2 and CO2) with polyphenylacetylene (PPA) thin films has been studied. The air-exposed PPA interacts with the atmosphere water vapour, leading to covalently bonded OH groups on the basis of X-ray photoelectron spectroscopy (XPS) core-level spectra of C 1s and O 1s. The surface-depth layer involved in the reaction is about 15 angstrom, as determined by Ar ion-sputtering measurements. The ion sputtering allows one also to obtain an oxygen-free PPA surface which in turn is exposed to H2O, O2 and CO2. The required gas pressure, in order to reach a detectable interaction, is greater-than-or-equal-to 760 Torr. Water vapour undergoes a dissociation reaction which gives OH moieties bonded to the polymer carbon atoms. O2 is only physisorbed at the PPA surface, while CO2 gives a chemical reaction which leads to the formation of weakly bonded C = O groups.

A joint X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) investigation of the adsorption of phenylacetylene (PA, C 6 H 5 C CH) on the surface of Rh(1 0 0) single crystal was carried out by evaporating PA on the clean metal surface in the monolayer and multilayer regimes. The experimental results indicate that the interaction of the PA molecule with the Rh(1 0 0) surface involves mainly the two carbon atoms of the alkyne moiety; the binding of the alkyne group to the metal surface produces the opening of the triple bond. A comparison with the results obtained for PA adsorption on the surface of Pt (1 1 1) and Cu (1 0 0) is also discussed.

Macromolecular arrays containing Zn-diethynylporphyrin coordinated to platinum tethers were studied using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the N K-edge. Porphin (Pf), 2,8,12,18-tetraethyl-5,15-diethynyl-3,7,13,17-tetramethylporphyrin (PfNH) and 2,8,12,18-tetraethyl-5,15-diethynyl-3,7,13,17-tetramethylporphyrinatozinc(II) (Zn-Pf2), have been taken as experimental models. The resonances assignment is supported by static-exchange (STEX) calculations for the porphin (Pf) and Zn-porphin (Zn-Pf1) molecules. By calculation, four π* resonances occur for porphin (Pf) and two for Zn-Pf1. Experimentally we detect four resonances for porphin and PfNH, and two for the Zn-complexed ones. They can be assigned to core excitations to a couple of energy split π* orbitals for each not equivalent N atom. Our calculations justify the observed low π* intensity as due to an extended delocalization of the π* orbitals. The NEXAFS investigations on platinum complex/Zn-porphyrinato assembled macrosystems (i.e. Pt-ZnPf1, Pt-ZnPf2 and Pt-ZnPf3) show the influence of the Pt tethers bound to the porphyrin through the ethynyl moiety on the electronic structure of the tetrapyrrolic cycle.

The adsorption dynamics and geometry of phenylacetylene (PA) on Cu(100) was investigated by means of X-ray photoemission (XPS), near edge X-ray absorption (NEXAFS) spectroscopies and by quantum chemical calculations. The clean metal surface was exposed to PA vapors and the C1s core level spectrum evolution was monitored by means of time-resolved XPS measurements. Photoemission (C1s) and absorption (C K-edge) spectra were recorded both in monolayer and multilayer regimes; polarization-dependent NEXAFS investigations were carried out on the PA monolayer at room temperature (RT). The experimental results have been interpreted with the help of quantum chemical calculations: DFT (Density Functional Theory) plane-wave based calculations for the optimization of the interaction geometry of PA on a two layered (100)-slab of Cu atoms using periodic boundary conditions and ab-initio simulation of the XPS spectrum for a small cluster including PA in the optimized adsorbate geometry and the 2 Cu atoms more directly involved in the adsorption. Comparison between NEXAFS spectra of PA monolayer, adsorbed at room temperature and of PA multilayer condensed at 130 K, evidences a strong interaction taking place between the PA molecule and the Cu(100) surface. The modifications observed in the C1s->pi* region of the NEXAFS spectrum suggest, with the support of the theoretical results, the partial opening of the CC triple bond of the alkyn group, leading to a di-sigma-bond interaction with the metal substrate, while the structure of the benzene ring appears unaffected but undergoes torsion. The polarization dependence analysis of the pi* resonances intensity for PA monolayer, indicates that the normal to the benzene ring is tilted about 55 degrees with respect to the normal to the surface.

A near-edge x-ray absorption fine structure (NEXAFS) spectroscopy investigation on the electronic structure of some novel pi-conjugated organometallic polymers is presented. The investigated materials consist of Pt and Pd(II) complex units linked together through sigma-bonded organic spacers of ethynyl-thiophene type in a polymeric array. The C K-edge NEXAFS spectra were interpreted by comparison with literature data and with the spectra of reference samples. The linking between the thiophene rings and alkyne groups produces a splitting of the C1s --> pi* peak observed in the spectra of the thiophene systems. Angle-dependent measurements, performed at normal and grazing incidence of the linearly polarized photons, evidenced a preferential orientation of the polymer chains with an average tilt angle of 45 degrees for the thiophene moieties

The structure of some novel oligomeric thiophene-containing pi-conjugated Pd(II) complexes, recently prepared in our laboratory, Cl-Pd(PBu3)(2)-C=C-C4H2S-C=C-C4H2S-C=C-C4H2S-C=C-Pd(PBu3)(2)Cl or Pd-TRI and Cl[-Pd(PBu3)(2)-C=C-C4H2S-C=C-](3)-Pd(PBu3)(2)Cl Or Pd-DET, were studied by means of x-ray photoelectron spectroscopy. The interface formation between chromium and the organometallic rr-conjugated polymer films was also investigated. Chromium was evaporated stepwise in situ onto the surface of the polymer films and the XPS core-level spectra of the polymer and of the metal overlayer were studied as a function of Cr coverage. A charge-transfer reaction from the deposited metal atoms to the substrate material was evidenced by the modifications taking place in the polymer spectra upon Cr deposition. A comparison with the surface reactivity towards chromium of [-Pd(PBu3)(2)-C=C-C6H4-C6H4-C=C-](n), Pd-DEBP, a related polymer where benzene groups replace thiophene in the organic conjugated moiety, will be discussed.

X-ray photoelectron spectroscopy was used in order to investigate the interface formation between chromium and thin films of a newly synthesised π-conjugated polymer P(PA- p NO 2 PA); the investigated material is a block copolymer consisting of phenylacetylene (PA) and para -nitro phenylacetylene ( p NO 2 PA) units {[–(CHC–R) n –(CHC–R′) m –] N ; RC 6 H 5 , R′C 6 H 4 NO 2 }. Chromium was evaporated stepwise in situ onto the polymer surface and the XPS spectra of the substrate polymer and of the metal overlayer were studied as a function of increasing chromium thickness. In the early stages of the interface formation, chromium was found to interact mainly with the nitrogen atoms of the –NO 2 groups, that are reduced to nitride-like species; the N–O bond is broken, as evidenced by the modifications occurring in the N1s and O1s spectra. The changes in the C1s spectra upon increasing metal deposition suggest the formation of a chromium–arene π-complex at low chromium coverage and of carbide-like species at higher chromium thickness.

Gas phase near-edge X-ray absorption fine structure spectra of phenylacetylene (PA, C 6 H 5 –CCH) have been recorded at the carbon K-edge. The experimental data have been interpreted with the help of ab initio calculations: both the ionisation potentials for the C1s electrons and the theoretical C K-edge absorption spectra have been calculated for all the six inequivalent carbon atoms of PA. A good agreement is observed between experimental and theoretical data, allowing a detailed attribution of the various features in the measured spectrum.

New features of the interface between chromium and Pd-DEBP, [–Pd(PBu 3 ) 2 –CC–C 6 H 4 –C 6 H 4 –CC–] n , a π-conjugated organometallic polymer, were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Analysis of the C1s peak structure at increasing Cr coverage reveals that chromium reacts preferentially with the conjugated DEBP moiety to form carbide-like species; phosphide-like species are also produced, involving mainly the P–C bond. Investigations of the XPS signals intensity variations upon Cr coverage and AFM measurements indicate a cluster growth of chromium on the Pd-DEBP surface; the interdiffusion between the deposited metal and the polymer film and the surface localisation of the phosphide and carbide species were also evidenced.

Synchrotron radiation excited photoemission was used to investigate the chemical reactions occurring at a metal/polymer interface. Chromium was evaporated onto the surface of a Pd-DEBP [Pd(PBu(3))(2)-C equivalent to drop C-C6H4-C6H4-C=C-](n) film, a pi-conjugated palladium-intercalated polymer. The evolution of the core level spectra of the polymer film and the evaporated metal were followed to a nominal thickness of 25 Angstrom of the metal overlayer. The disappearance of the shake-up satellite in the C1s spectra suggests a strong initial interaction between the chromium atoms and the pi-system of the DEEP moiety. A new carbide-like C1s signal appears upon increasing the chromium deposition, indicating a charge-transfer reaction from the metal overlayer to the DEEP carbons. An initial formation of a chromium arene pi-complex is found; the reactivity of chromium upon further metal deposition leads to a sigma-bonded chromium carbide. Moreover, chromium reacts with phosphorus atoms, leading to the formation of phosphide-like species, suggested by the presence of a low BE signal in the P2p spectra.

The electrical conductivity of poly(phenylacetylene)-iodine in tetrahydrofuran solution has been measured at the frequency of 10 kHz, in the temperature range from −15 to 40 °C as a function of iodine concentration. The data have been analysed on the basis of the counterion fluctuation model developed for highly charged polyelectrolyte aqueous solutions. The dependence of the electrical conductivity on the iodine concentration suggests that the conduction mechanism is governed by the interaction of the polymer with iodine molecules, resulting in a charge-transfer complex in solution, the effectiveness of which is maximum at some well-defined concentrations corresponding to six polymer units for each I5− ion.

The electrical conductivity of poly(phenylacetylene)-iodine in tetrahydrofuran solutions has been measured at the frequency of 10 kHz, in the temperature range from − 15 to 40 °C. The data have been analysed in the light of current theories of polyelectrolyte solutions, considering the effect of counterions along the charged polymer chain. Our results show a linear dependence of electrical conductivity on the polymer concentration at an I 2 doping concentration of 10 mg/ml. These data can be accounted for by considering an electronic charge distributed over, on average, a polymer segment containing six monomers.

A device for surface acoustic wave (SAW) measurements, based on a polymeric sensitive membrane, that is polyethynylfluorenol (PEFl), has been realized. The SAW/PEFl sensor shows relatively fast and highly sensitive responses in the range of relative humidity 0–60%. The enhanced sensitivity of the SAW/PEFl device, in comparison with that of a SAW sensor which utilized a polyphenylacetylene film, may be attributed to the presence of OH groups belonging to the polymer repeat unit.

A coverage-dependent XPS investigation of the early stages of interaction between evaporated Cu and polyphenylacetylene (PPA) has been carried out. Copper films have been deposited at 300 K to a final thickness of about 5 monolayers. Overlayer and substrate core-level emission behaviour indicates the layer-by-layer growth of Cu on the PPA surface without interdiffusion. At low copper coverages a chemical interaction between the Cu adatoms and the substrate is observed by monitoring the changes occurring at the pi --> pi * satellite feature of the C1s core-level line. We observe a decrease of intensity for this satellite as the copper coverage increases, interpreted in terms of the formation of a Cu-pi complex with the phenyl ring. The Cu Auger spectra demonstrate the presence of positively charged metal atoms up to a coverage of approximately 5 angstrom. In the submonolayer region the occurrence of broadening of the C1s core level on the low binding energy side is observed together with a positive shift for the Cu2p3/2 emission. Upon completion of the first copper monolayer these phenomena are removed. The observed behaviour can be accounted for in terms of differential charging with injection and trapping of charge into the PPA film from the Cu atoms that have not yet completed the first monolayer.

The morphological evolution of as-grown poly(phenylacetylene) (PPA) free standing films has been studied. Investigations performed by scanning electron microscopy show that the freshly prepared PPA films exhibit a glass-like morphology which subsequently evolves into a microsphere structure. After ageing for 3 months at room temperature, PPA films reach a stable enamel-like phase. The chemical structure of the Rh(I) catalysts does not appear to influence the morphology of PPA. However, different catalysts yield different rates of morphological evolution.

XPS investigation of the early stages of Cu/PPA interface formation has been performed in the range of coverage 0.5 A 13 A Cu . Copper is found to grow in a layer-by-layer mode without interdiffusion with the substrate. Weak chemical interaction between Cu and the π ring electrons of the phenyl groups is evidenced by monitoring the changes occuring at the C 1s secondary structure π→π ∗ shake up transition.

A new dinuclear rhodium(I) complex [Rh2(cod)2(imH)2im]PF6 (I) has been synthesized and characterized. The complex is unstable in solution where it undergoes modifications leading to insoluble oligomers. However, it exhibits high catalytic activity towards polymerization of phenylacetylene as compared with other rhodium-imidazole complexes. Free-standing polylphenylacetylene (PPA) films can be obtained under mild reaction conditions. As-grown PPA films are stable and soluble. Two different types of morphologies were found: one exhibits a cell-like structure with microfibrils inside the cell and the other a dense enamel-like smooth surfac

A humidity sensor has been fabricated by using thin films of iodine-doped polyphenylacetylene. The electrical response of the sensor towards relative humidity variations is fast and reversible during long working periods. The investigated sensor is also sensitive to the vapours of other chemical substances.

The polymerization reactions of ethynylfluorenol (EFl) in the presence of Rh(I), Pt(II), Pd(II) and WCl6 catalysts have been investigated. The polymer (PEFl) is air stable and soluble; in solution PEFl slowly releases some of the pendent groups which are converted into 9-fluorenone. Upon doping, enhancement of the conductivity up to about 10 orders of magnitude can be achieved. X.p.s. measurements performed on I2-doped PEFl suggest that I−5 is the major doping species. An interesting reversible response to relative humidity variations is found for FeCl3-doped samples.

A new material, polyethynylfluorenol (PEFl), has been prepared and characterized, either undoped or homogeneously doped with SnCl 2 . We have chosen as basic device for the sensor a simple humistor (humidity sensor resistor) since we have observed that the PEFl conductivity varies with the environmental relative humidity (r.h.). This behaviour is completely reversible without any noticeable 'memory effect'. PEFl can be considered a promising material for the fabrication of humidity sensors.