Spin-polarized electrons confined in low-dimensional structures are of high interest for spintronics applications. Here, we investigate the electronic structure of an ordered array of Bi monomer and dimer chains on the Ag(110) surface. By means of spin-resolved photoemission spectroscopy, we find Rashba-Bychkov split bands crossing the Fermi level with one-dimensional constant energy contours. These bands are up-spin polarized for positive wave vectors and down-spin polarized for negative wave vectors, at variance with the Rashba-Bychkov model that predicts a pair of states with opposite spin in each half of the surface Brillouin zone. Density functional theory shows that spin-selective hybridization with the Ag bulk bands originates this unconventional spin texture.

Metal monochalcogenides (MX) have recently been rediscovered as two-dimensional materials with electronic properties highly dependent on the number of layers. Although some intriguing properties appear in the few-layer regime, the carrier mobility of MX compounds increases with the number of layers, motivating the interest in multilayered heterostructures or bulk materials. By means of angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory calculations, we compare the electronic band structure of bulk ?-GaSe and ?-InSe semiconductors. We focus our attention on the top valence band of the two compounds along main symmetry directions, discussing the effect of spin-orbit coupling and contributions from post-transition-metal (Ga or In) and Se atoms. Our results show that the top valence band at ? point is dominated by Se pz states, while the main effect of Ga or In appears more deeply in binding energy, at the Brillouin zone corners, and in the conduction band. These findings explain also the experimental observation of a hole effective mass rather insensitive to the post-transition metal. Finally, by means of spin-resolved ARPES and surface band structure calculations we describe Rashba-Bychkov spin splitting of surface states in ?-InSe.

Two-dimensional materials with high charge carrier mobility and tunable band gaps have attracted intense research effort for their potential use in nanoelectronics. Two-dimensional ?-conjugated polymers constitute a promising subclass because the band structure can be manipulated by varying the molecular building blocks while preserving key features such as Dirac cones and high charge mobility. The major barriers to the application of two-dimensional ?-conjugated polymers have been the small domain size and high defect density attained in the syntheses explored so far. Here, we demonstrate the fabrication of mesoscale ordered two-dimensional ?-conjugated polymer kagome lattices with semiconducting properties, Dirac cone structures and flat bands on Au(111). This material has been obtained by combining a rigid azatriangulene precursor and a hot dosing approach, which favours molecular diffusion and eliminates voids in the network. These results open opportunities for the synthesis of two-dimensional ?-conjugated polymer Dirac cone materials and their integration into devices.

The study of transitionmetal coordination complexes has played a key role in establishing quantum chemistry concepts such as that of ligand field theory. Furthermore, the study of the dynamics of their excited states is of primary importance in determining the de-excitation path of electrons to tailor the electronic properties required for important technological applications. This work focuses on femtosecond transient absorption spectroscopy of Cobalt tris(acetylacetonate) (Co(AcAc)(3)) in solution. The fast transient absorption spectroscopy has been employed to study the excited state dynamics after optical excitation. Density functional theory coupled with the polarizable continuum model has been used to characterize the geometries and the electronic states of the solvated ion. The excited states have been calculated using the time dependent density functional theory formalism. The time resolved dynamics of the ligand to metal charge transfer excitation revealed a biphasic behavior with an ultrafast rise time of 0.07 +/- 0.04 ps and a decay time of 1.5 +/- 0.3 ps, while the ligand field excitations dynamics is characterized by a rise time of 0.07 +/- 0.04 ps and a decay time of 1.8 +/- 0.3 ps. Time dependent density functional theory calculations of the spin-orbit coupling suggest that the ultrafast rise time can be related to the intersystem crossing from the originally photoexcited state. The picosecond decay is faster than that of similar cobalt coordination complexes and is mainly assigned to internal conversion within the triplet state manifold. The lack of detectable long living states (>5 ps) suggests that non-radiative decay plays an important role in the dynamics of these molecules.

We examine the electronic structure of Ag deposits intercalated between graphene and Co(0001). Angle-resolved photoemission spectroscopy measurements reveal the formation of Ag sp-derived quantum well states due to finite electron reflectivity across the buried metal/metal interface. This observation provides evidence of flat Ag(111) film growth underneath graphene, in analogy with the layer-by-layer growth of Ag on the corresponding graphene-free surfaces. Band dispersion and spectral properties of the quantum well states reflect primarily the interaction with the supporting substrate. Signatures of the coupling between graphene and the underlying films are the shift of the Ag(111) surface state, the hybridization gap opening of the ? state crossing the Ag 4d states, the downward shift of the Dirac point (n-type doping), and the gap between ? and ?* Dirac cones. Similar observations are reported for Ag(111) films intercalated between Gr and Pt(111). These systems can be considered as prototypes of graphene-protected thin metal films displaying electron confinement effects.

There has been a strong interest in methods of creating nanometer scale structures and in particular forming one- and two-dimensional electron confinement structures. Self-organisation has been recognised as a promising way for growing large nanostructure domains with sufficiently regular size and spacing as required for the observation of quantum well states. We investigated the electronic properties and the morphology of Ag nano-structures on c(2 × 2)-N/Cu(001) surface. This system is an example of epitaxial growth confined on nanoscale regions due to the occurrence of an adsorbate induced reconstruction. Using a combination of Scanning Tunneling Microscopy and Angle Resolved Photoemission Spectroscopy techniques we were able to determine the morphology and the growth mode of Ag on N-modified Cu(001) surface and the occurrence of quantum size effects in the electron properties of Ag nanostripes and nanoislands, evidenced in the observation of quantum well states.

Spin-and angle-resolved photoemission spectroscopy of thin Ag(111) films on ferromagnetic Fe(110) shows a series of spin-polarized peaks. These features derive from Ag sp-bands, which form quantum well states and resonances due to confinement by a spin-dependent interface potential barrier. The spin-up states are broader and located at higher binding energy than the corresponding spin-down states at (Gamma) over bar, although the differences attenuate near the Fermi level. The spin-down states display multiple gap openings, which interrupt their parabolic-like dispersion. First-principles calculations attribute these findings to the symmetry- and spin-selective hybridization of the Ag states with the exchange-split bands of the substrate.

We study the magnetic coupling between different ferromagnetic metals (FMs) across a graphene (G) layer, and the role of graphene as a thin covalent spacer. Starting with G grown on a FM substrate (Ni or Co), we deposited on top at room temperature several FM metals (Fe, Ni, Co). By measuring the dichroic effect of 3p photoemission lines we detect the magnetization of the substrate and the sign of the exchange coupling in FM overlayer at room temperature. We show that the G layer magnetically decouples the FM metals.

The joint effect of exchange and Rashba spin-orbit interactions is examined on the surface and quantum well states of Ag2Bi-terminated Ag films grown on ferromagnetic Fe(110). The system displays a particular combination of time-reversal and translational symmetry breaking that strongly influences its electronic structure. Angle-resolved photoemission reveals asymmetric band-gap openings, due to spin-selective hybridization between Rashba-split surface states and exchange-split quantum well states. This results in an unequal number of states along positive and negative reciprocal space directions. We suggest that the peculiar asymmetry of the discovered electronic structure can have significant influence on spin-polarized transport properties.

The quantum well states of a film can be used to sample the electronic structure of the parent bulk material and determine its band parameters. We highlight the benefits of two-dimensional film band mapping, with respect to complex bulk analysis, in an angle-resolved photoemission spectroscopy study of the 5d states of Au(111). Discrete 5d-derived quantum well states of various orbital characters form in Au(111) films and span the width of the corresponding bulk bands. For sufficiently thick films, the dispersion of these states samples the bulk band edges, as confirmed by first-principles calculations, thus providing the positions of the critical points of bulk Au in agreement with previously determined values. In turn, this analysis identifies several d-like surface states and resonances with large spin splittings that originate from the strong spin-orbit coupling of the Au 5d atomic levels.

FULL ARTICLE Label-free and non-invasive discrimination of HaCaT and melanoma cells in a co-culture model by hyperspectral confocal reflectance microscopy Francesca R. Bertani 1 , Elisabetta Botti 2 , Luisa Ferrari 1 , Valentina Mussi 1 , Antonio Costanzo 2 , Marco D ' Alessandro 1 , Francesco Cilloco 1 , and Stefano Selci * ,1 1 CNR-ISC Istituto del Sistemi Complessi, Consiglio Nazionale delle Ricerche, Via fosso del Cavaliere, 100 00133 Rome, Italy 2 Dermatology Unit, NESMOS Department, Sapienza University of Rome, via di Grottarossa 1035, 00189 Rome, Italy Received 5 March 2015, revised 8 July 2015, accepted 5 August 2015 Published online 17 September 2015 Key words: hyperspectral microscopy, multivariate analysis, melanoma cells HaCaT cells co-culture. 1. Introduction The possibility of discriminating single cell and tissue properties without perturbation of their metabolic or differentiation status has enormous potential impact in diagnostic [1] and therapeutic fields [2]. The chance of gaining information from cells living and evolving in their environment opens a new way for cell therapy, regenerative medicine, personalized im- munotherapy and cancer treatment [3]. The defini- tion of methods for label free and non-invasive high resolution imaging represents one of the principal goals of several methodological and instrumental ap- proaches. In recent years, we are experiencing a sort of change of paradigm in imaging methods, similarly to what happened in life sciences. There, the change in genomic paradigm has meant the transition from the strict correspondence of one protein to only one function, to a more complex view of genetic and epi- genetic world. As regards the imaging methods we are going toward the " global analysis " of cell fea- * Corresponding author: e-mail: stefano.selci@isc.cnr.it , Phone: +39 06 4993 4167, Fax: +39 06 4548 8043 A novel hyperspectral confocal microscopy method to se- parate different cell populations in a co-culture model is presented here. The described methodological and instru- mental approach allows discrimination of different cell types using a non-invasive, label free method with good accuracy with a single cell resolution. In particular, mela- noma cells are discriminated from HaCaT cells by hyper- spectral confocal imaging, principal component analysis and optical frequencies signing, as confirmed by fluores- cence labelling cross check. The identification seems to be quite robust to be insensitive to the cellular shape within the studied samples, enabling to separate cells according to their cytotype down to a single cell sensitivity.

We report on an angle-resolved photoemission investigation of the valence states and chiral properties of a nonchirally oriented phase of tartaric acid deposited on a Cu(110) surface, observed with circularly polarized light. The two optical enantiomers R,R and S,S of tartaric acid, separately deposited, produce (40,23) overlayers which show a large dichroic effect and enantiomeric behavior all over the valence energies. The dichroic effects are displayed by native chiral molecular states and molecule-copper interface states. Density-functional theory calculations of the site-resolved density of states analyze the formation of hybrid states at the tartaric acid-copper interface and suggest that an observed interface state acquires chirality on binding.

Photoemission, from core levels and valence band, and low-energy electron diffraction (LEED) have been employed to investigate the electronic and structural properties of graphene-ferromagnetic (G-FM) systems, obtained by intercalation of one monolayer (1 ML) and several layers (4 ML) of Co on G grown on Ir(111). Upon intercalation of 1 ML of Co, the Co lattice is resized to match the Ir-Ir lattice parameter, resulting in a mismatched G/Co/Ir(111) system. The intercalation of further Co layers leads to a relaxation of the Co lattice and a progressive formation of a commensurate G layer lying on top. We show the C 1s line shape and the band structure of G in the two artificial phases, mismatched and commensurate G/Co, through a comparison with the electronic structure of G grown directly on a Co thick film. Our results show that while the G valence band mainly reflects the hybridization with the d states of Co, regardless of the structural phase, the C 1s line shape is very sensitive to the rumpling of the G layer and the coordination of carbon atoms with the underlying Co. Even in the commensurate (1×1) G/Co phase, where graphene is in register with the Co film, from the angular dependence of the C 1s core level we infer the presence of more than a single component, due to inequivalent adsorption sites of carbon sublattices.

Among the optical techniques used for exploring the properties of cells and tissues, those based on hyperspectral label-free analysis are particularly interesting due to their non-invasive character and their ability to fast collect a huge number of information on the different sample constituents and their spatial distribution. Here we present results obtained with a novel hyperspectral reflectance confocal microscope of label-free discrimination of cells undergoing apoptosis. Our data, analyzed by means of a powerful statistical method, enable to obtain information on the biological status at a single cell level through the local measurement of reflectivity. Furthermore, an optical model of the local dielectric response gives an additional insight of the parameters linking the optical responsivity to the biological status.

A broad range hyper-spectroscopic microscope fed by a supercontinuum laser source and equipped with an almost achromatic optical layout is illustrated with detailed explanations of the design, implementation and data. The real novelty of this instrument, a confocal spectroscopic microscope capable of recording high resolution reflectance data in the VIS-IR spectral range from about 500 nm to 2.5 ?m wavelengths, is the possibility of acquiring spectral data at every physical point as defined by lateral coordinates, X and Y, as well as at a depth coordinate, Z, as obtained by the confocal optical sectioning advantage. With this apparatus we collect each single scanning point as a whole spectrum by combining two linear spectral detector arrays, one CCD for the visible range, and one InGaAs infrared array, simultaneously available at the sensor output channel of the home made instrument. This microscope has been developed for biomedical analysis of human skin and other similar applications. Results are shown illustrating the technical performances of the instrument and the capability in extracting information about the composition and the structure of different parts or compartments in biological samples as well as in solid statematter. A complete spectroscopic fingerprinting of samples at microscopic level is shown possible by using statistical analysis on raw data or analytical reflectance models based on Abelés matrix transfer methods.

Newly synthesized fluorescent nanoparticles of 2-amino-6-ethoxy-4-[4-(4-morpholinyl)phenyl]-3, 5-pyridinedicarbonitrile have been developed and characterized for possible applications as security marker in paper documents. Nanoparticles have been prepared by reprecipitation in water under sonication. The size and the shape of these nanoparticles, characterized by light scattering and atomic force microscopy, have been found to be highly dependent on sonication power. Typical sizes range from tens to hundreds of nanometers. Furthermore, a remarkable increase in the fluorescence yield has been observed as nanoparticles sizes decrease. Finally, all of the above features, together with the striking stability of optical and mechanical properties over the course of months, allow for straightforward applications that rely on strong and stable fluorescence such as marking important or valuable documents.

We examined by low-energy electron diffraction and scanning tunneling microscopy the surface of thin Cu films on Pt(111). The Cu/Pt lattice mismatch induces a moiré modulation for films from 3 to about 10 ML thickness. We used angle-resolved photoemission spectroscopy to examine the effects of this structural modulation on the electronic states of the system. A series of hexagonal- and trigonal-like constant energy contours is found in the proximity of the Cu(111) zone boundaries. These electronic patterns are generated by Cu sp-quantum well state replicas, originating from multiple points of the reciprocal lattice associated with the moiré superstructure. Layer-dependent strain relaxation and hybridization with the substrate bands concur to determine the dispersion and energy position of the Cu Shockley surface state.

We report the design and implementation of a new reflectance laser scanning confocal system with spectroscopy imaging capabilities. Confocal spectroscopy is achieved by using a very broad spectral range supercontinuum source capable of high precision reflectance data in the VIS-IR spectral range thanks to an almost achromatic optical layout.With this apparatus we collect each single scanning point as a whole spectrum in a continuous range, associated with the optical section imaging possibilities typical of a confocal set up. While such a microscope has been developed for bio medical analysis of human skin and other similar applications, first test results on solid samples produce spectroscopic results that, compared to analytical models based on theAbel´es matrix transfer methods, show a very good agreement, opening new possibilities of a complete spectroscopic fingerprinting of samples with microscopic details.