The possibility of using novel architectures based on carbon nanotubes (CNTs) for a realistic monitoring the air quality in an urban environment requires capability to monitor concentrations polluting gases low-ppb range. This limit has been so far virtually neglected, as most testing new ammonia gas sensor devices CNTs is carried out above ppm limit. In this paper, we present single-wall nanotube (SWCNT) chemiresistor sensors operating at room temperature, displaying enhanced sensitivity...

Increasingly high hopes are being placed on organic semiconductors for a variety of applications. Progress along these lines, however, requires the design and growth increasingly complex systems with well-defined structural electronic properties. These issues have been studied reviewed extensively in single-component layers, but focus is gradually shifting towards more functional multi-component assemblies such as donor-acceptor networks. blends show different properties from those...

The molecule/metal interface is the key element in charge injection devices. It can be generally defined by a monolayer-thick blend of donor and/or acceptor molecules contact with metal surface. Energy barriers for electron and hole are determined offset from HOMO (highest occupied) LUMO (lowest unoccupied) molecular levels this layer respect to Fermi level electrode. However, alignment not easy elucidate complex multicomponent, systems. We demonstrate that core-level photoemission...

In-situ metalation of porphyrin molecules in ultrahigh vacuum (UHV) is great interest for the characterization pure species a controlled environment. Here, we report electronic states and molecules' geometrical adaptation during formation 2H-5,10,15,20-tetraphenylporphyrin (2H-TPP) Fe- tetraphenylporphyrin (Fe-TPP) layers on Ag(111) single crystal. Core level absorption spectra indicate flat conformation monolayer suggesting an adatom hopping instead surface mediated dopant diffusion...

The nature of defects in ZnO smoke was studied at different stages the material’s history by combining photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy.

Ultrapure ZnO nanopowders were synthesized via vapor-phase-based methods under oxygen-deficient conditions. The type and relative proportions of intrinsic point defects studied by photoluminescence (PL) EPR spectroscopies performed strictly controlled Besides coupled PL/EPR signals recently assigned to Zni+ (2.80 eV, g = 1.96), two green emissions systematically detected at 2.50 2.22 eV without counterparts, whereas their contributions observed depend on the synthesis oxygen partial pressure...

Scratching the surface: Formation of a monolayer 2H-tetraphenylporphyrins (2H-TPP) on Ag(111), either by sublimation multilayer in range 525-600 K or annealing (at same temperature) deposited at room temperature, induces chemical modification molecules. Rotation phenyl rings into flat conformation is observed and tentatively explained, using DFT calculations, as peculiar reaction due to molecular dehydrogenation.

Experimental evidence of differences in the electronic properties an insulating and a conducting SrTiO3/LaAlO3 interface is provided by soft x-ray spectroscopies. While core level photoemission measurements show that only at Ti ions with 3+ ionization state are present, using resonant absorption spectroscopies, it shown both samples in-gap states 3d character but their density higher interface.

The electronic character of a π-conjugated molecular overlayer on metal surface can change from semiconducting to metallic, depending how orbitals arrange with respect the electrode's Fermi level. Molecular level alignment is thus key property that strongly influences performance organic-based devices. In this work, we report copper phthalocyanines surfaces be tailored by controlling substrate work function. We even show way finely tune it for one fixed phthalocyanine-metal combination...

Codeposition of two molecular species [copper phtalocyanine (CuPc, donor) and perfluoropentacene (PFP, acceptor)] on noble metal (111) surfaces leads to the self-assembly an ordered mixed layer with a maximized donor-acceptor contact area. The main driving force behind this arrangement is assumed be intermolecular $\mathrm{C}\text{\ensuremath{-}}\mathrm{H}\ensuremath{\cdots}\mathrm{F}$ hydrogen-bond interactions. Such interactions would for coplanar arrangement. However, precise measurement...

The present study is focused on the implementation of a novel, low cost, urban grid nanostructured chemresistor gas sensors for ammonia concentration ([NH(3)]) monitoring, with NH(3) being one main precursors secondary fine particulate. Low-cost based carbon nanotubes have been developed, their response to [NH(3)] in 0.17-5.0 ppm range has tested, and devices properly calibrated under different relative humidity conditions 33-63% range. In order improve selectivity towards [NH(3)], an Expert...

Model donor–acceptor assemblies at metal–organic interfaces, namely, fluorinated copper-phthalocyanines (F16CuPC) and pentacene (PEN) on the Au(111) surface, have been focus of present study. A full picture crystallographic electronic structure PEN F16CuPC monolayers as well their 1:1 binary mixture surface has explored by means a variety surface-sensitive techniques, providing important information intermolecular molecule–substrate interactions governing self-assembly process. long-range...

Abstract In molecular devices, the importance of interfaces cannot be neglected as they determine charge injection and flow and, therefore, device performance. Herein we report on interaction one single layer Zn‐tetraphenyl‐porphyrin with Ag(110) Si(111). Photoemission, near‐edge X‐ray absorption, resonant photoemission are used to study bonding nature, adsorption geometry well dynamics electron transfer between molecules metal or semiconductor surfaces. Molecule–substrate is driven by...

Due to the growing interest in ferromagnetic properties of Fe-octaethylporphyrins (Fe-OEP) for applications spintronics, methods produce stable Fe-porphyrins with no Cl atoms are highly demanded. Here, we demonstrate formation Fe-OEP layers on Ag(111) single crystal by ultra high vacuum situ metalation free-base 2H-2,3,7,8,12,13,17,18-octaethylporphyrin (2H-OEP) molecules. The proceeds exactly as case 2H-5,10,15,20-tetraphenylporphyrin (2H-TPP) same substrate. An extensive surface...

We present a combined experimental and theoretical study of the ultrathin film Co-octaethylporphyrin (Co-OEP) molecules deposited on Ag(110) surface. The morphological electronic properties this heterogeneous metallorganic interface were studied by means scanning tunneling microscopy (STM), near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, ultraviolet photoemission spectroscopy (UPS), density functional theory calculations (DFT). long-range self-ordered single layer Co-OEP was...

We present single-wall carbon nanotube (SWCNT) chemiresistor gas sensor (CGS) operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in the full range of average [NH3] a urban environment have been measured, and detection limit 3 ppb is demonstrated, which well below sensitivities so far reported for non- functionalized SWCNTs temperature. Different materials were tested as substrates, including cheap plastic flexible substrates. In addition careful...

One of the most viable ways to grow nanostructures is electro deposition. However, electrodeposited samples are obtained by three-electrode electrochemical cell. We successfully use a much simpler two-electrode cell different ZnO from common chemical reagents. Concentration, pH electrolytes and growth parameters like potentials at electrodes, tailored allow fast without complexity. Morphology surface roughness investigated Scanning Electron Air Force Microscopy (SEM AFM) respectively,...

We investigate the scattering of electrons belonging to Shockley states (111)-oriented noble metal surfaces using angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). Both ARPES STM indicate that monatomic steps on a surface may act either as strongly repulsive or highly transmissive barriers for electrons, depending coherence step lattice, irrespectively average spacing. By measuring curved crystal with terrace length ranging from 30 180 \AA{}, we show vicinal Au Ag...

The electronic structure of eumelanin thin films has been investigated by means x-ray absorption and photoemission spectroscopies. main features the experimental data are interpreted on basis density-functional calculations for isolated monomers participating to macromolecule. In order single out polymerization effects, we followed a bottom-up scaling approach establish minimum supramolecular level organization that can provide consistent spectroscopical picture an altogether complex highly...

The role of potassium in the formation synthetic eumelanin aggregates is investigated by atomic force microscopy and soft-X-ray spectroscopy. Control over thin film granularity achieved using K salts, both drop casting electrodeposition films. Further control orientation made possible a suitable choice substrate: evidence self-assembly found for films deposited on gold. Finally, it shown that content affects not only samples morphology, but also low-lying states valence band, where transfer...

The wealth of properties titanium dioxide relies on its various polymorphs and their mixtures coupled with a sensitivity to crystallographic orientations. It is therefore pivotal set out methods that allow surface structural identification. We demonstrate herein the ability photoemission spectroscopy provide Ti LMV (V = valence) Auger templates quantitatively analyze TiO2 polymorphs. decay reflects 4sp-O 2p hybridizations are intrinsic phases collected rutile (110), anatase (101), (100)...

Near Edge X-ray Absorption, Valence and Core-level Photoemission Density Functional Theory calculations are used to study molecular levels of tetracyano-2,3,5,6-tetrafluoroquinodimethane (F$_4$TCNQ) deposited on Ag(111) BiAg$_2$/Ag(111). The high electron affinity F$_4$TCNQ triggers a large static charge transfer from the substrate, and, more interestingly, hybridization with substrate leads radical change symmetry, shape energy frontier orbitals. Lowest Unoccupied Molecular Orbital (LUMO)...

Molecular bilayers made up of a donor–acceptor blend in contact with the metal and capped single-component layer show tunable energy level alignment at both metal–organic organic–organic interfaces. To ensure sharp heteromolecular interfaces, is formed by stable pentacene (PEN) perfluorinated copper phthalocyanine (F16CuPc) on Au(111) Ag(111) perfluoropentacene (PFP) (CuPc) Ag(111). Core-level valence band photoemission reveal that, upon capping pure F16CuPc, CuPc, PEN, electronic states...

The photoemission cross-section of the Shockley surface state Au(111) is studied over a wide range photon energies both experimentally and theoretically. measurements are fully understood based on theoretical analysis within one-step ab initio theory photoemission. constant initial spectrum shown to be very sensitive structure topmost atomic layer. A maximum in at 60 eV identified as fingerprint reconstruction.