Albano Cossaro

University of Trieste | UNITS · Department of Chemical and Pharmaceutical Sciences

We present our findings on the on‐surface synthesis of polyboroxine molecules derived from boroxine molecules precursors. This process is promoted by oxygen species present on the Au(111) surface: oxygen atoms facilitate the detachment of naphthalene units of trinaphthyl‐boroxine molecules and bridge two unsaturated boroxine centers to form a borox...

On-surface synthesis often proceeds under kinetic control due to the irreversibility of key reaction steps, rendering kinetic studies pivotal. The accurate quantification of reaction rates also bears potential for unveiling...

Coordination polymers may be synthesized by linear bridging ligands to metal ions with conventional chemistry methods (e.g. in solution). Such complexes can be hardly brought onto a substrate with the...

The control of molecular structures at the nanoscale plays a critical role in the development of materials and applications. The adsorption of a polyheteroaromatic molecule with hydrogen bond donor and acceptor sites integrated in the conjugated structure itself, namely, benzodi-7-azaindole (BDAI), has been studied on Au(111). Intermolecular hydrog...

In this paper we performed the deposition and self-assembly of a Pd-cyclometallated compound on Ag(1 1 0) surface for the first time. The system is investigated from the morphological and chemical point of view by scanning tunneling microscopy and x-ray photoemission spectroscopy, respectively, and the results are validated by ab-initio calculation...

The Pd cyclometallated complex [(5-bromo-2-phenylpyridine)Pd(μ-Cl)]2 is deposited on Ag(1 1 0) at room temperature by sublimation in ultra-high vacuum. The thermal evolution of the system is followed by scanning tunnelling microscopy and X-ray photoemission spectroscopy, while the initial and final configurations are validated by ab-initio calculat...

The electronic characterization of the cyanuric acid both in gas phase and when embedded within an H-bonded scheme forming a monolayer on the Au(111) surface has been performed by means of X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The experimental spectra at the N, O, and C K-edges h...

Chemoselective reduction of nitro groups in multifunctional nitroaromatics is a challenging catalytic process with high interest due to the importance of the resulting anilines for the chemical industry. Molecular-level understanding...

The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework obtained experimentally, as supported by the Au(1...

Due to its biocompatibility, TiO2 is a relevant material for the study of bio-interfaces. Its electronic and chemical properties are influenced by defects, which mainly consist of oxygen vacancies or adsorbed OH groups and which affect, consequently, also the interaction with biological molecules. Here we report on an X-ray photoemission spectrosco...

Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F430 and P450nor co‐factors, with their reduced NiI‐ and FeIII‐containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, using...

Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F430 and P450nor co‐factors, with their reduced Ni(I)‐ and Fe(III)‐containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, u...

In this article, we analyze the electronic structure modifications of triphenylamine (TPA), a well-known electron donor molecule widely used in photovoltaics and optoelectronics, upon deposition on Au(111) at a monolayer coverage. A detailed study was carried out by synchrotron radiation-based photoelectron spectroscopy, near-edge X-ray absorption...

The on-surface synthesis of boroxine-containing molecules can be a convenient method of introducing specific functionalities. Here, we show the validity of a previously described synthesis protocol on the Au (111) surface by applying it to a different molecular precursor. We study in detail the assembly of the precursor, highlighting possible inter...

The electronic properties of a diboron molecule, namely bis(catecholato)diboron (2-(1,3,2-benzodioxaborol-2-yl)-1,3,2-benzodioxaborole) (B2Cat2), have been studied by comparing the results of photoemission (XPS) and near edge X-ray absorption spectroscopy (NEXAFS) experiments with the outcome of DFT calculations. The B 1s, C 1s and O 1s K-edges hav...

Molecular interfaces formed between metals and molecular compounds offer a great potential as building blocks for future opto‐electronics and spintronics devices. Here, a combined theoretical and experimental spectro‐microscopy approach is used to show that the charge transfer occurring at the interface between nickel tetraphenyl porphyrins and cop...

The incorporation of singlet fission (SF) chromophores in solar cells is expected to bring significant increases in the power conversion efficiency thanks to multiexciton generation. However, efficient charge generation in the device is determined by the energy level alignment (ELA) between the active materials, which should favor exciton transport...

Organic photovoltaics (OPVs) technology now offers power conversion efficiency (PCE) of over 18% and is one of the main emerging photovoltaic technologies. In such devices, titanium dioxide (TiO x ) has been vastly used as an electron extraction layer, typically showing unwanted charge-extraction barriers and the need for light-soaking. In the pres...

The water-splitting photo-catalysis by carbon nitride heterocycles has been the subject of recent theoretical investigations, revealing a proton-coupled electron transfer (PCET) reaction from the H-bonded water molecule to the CN-heterocycle. In this context, a detailed characterization of the water-catalyst binding configuration becomes mandatory...

By means of Mn-Cu transmetalation, we incorporated Mn atoms in an array of TCNQ (7,7,8,8-tetracyanoquinodimethane) grown on Cu(100), forming a long range ordered and commensurate metal-organic coordination network (MOCN). Preliminary Sn alloying of the Cu(100) surface allowed us to control the degree of substrate reactivity, thus preventing the che...

Due to its unique magnetic properties offered by the open‐shell electronic structure of the central metal ion, and for being an effective catalyst in a wide variety of reactions, iron phthalocyanine has drawn significant interest from the scientific community. Nevertheless, upon surface deposition, the magnetic properties of the molecular layer can...

Catechols are ubiquitous substances often acting as antioxidants, thus of importance in a variety of biological processes. The Fenton and Haber-Weiss processes are thought to transform these molecules into aggressive reactive oxygen species (ROS), a source of oxidative stress and possibly inducing degenerative diseases. Here, using model conditions...

The VO 2 is a 3d 1 electron system that undergoes a reversible metal-insulator transition (MIT) triggered by temperature and characterized by an interplay between orbital, charge and lattice degrees of freedom. The characterization of the MIT features are therefore extremely challenging and powerful investigation tools are required. In this work, w...

The Metal-Insulator transition (MIT) in VO2 is characterized by the complex interplay among lattice, electronic and orbital degrees of freedom. In this contribution we investigated the strain-modulation of the orbital hierarchy and the influence over macroscopic properties of the metallic phase of VO2 such as Fermi Level (FL) population and metalli...

The thermal treatment of a monolayer of 1-naphthylmethylamine (NMA) on Ni(1 1 1) surface reveals a complex chemistry promoted by the high surface reactivity. Both the amino-terminated functional group and the naphthalene body of NMA undergo a progressive dehydrogenation, which eventually leads to the coalescence of the molecules. As a result, 2D st...

We present a comparative study of the room-temperature adsorption of p-aminophenol (p-AP) molecules on three metal surfaces, namely Cu(110), Cu(111) and Pt(111). We show that the chemical nature and the structural symmetry of the substrate control the activation of the terminal molecular groups, which result in different arrangements of the interfa...

Surface alloying of Cu(001) by Sn deposition is a finely controllable method of tuning the degree of copper reactivity in order to drive the on-surface assembly and synthesis of metal-organic coordination networks. In this work we show that the (3√2 × √2)R45° reconstruction of the Sn/Cu(001) surface alloy acts as a weakly-interacting substrate idea...

VO2 is a strongly correlated material, which undergoes a reversible metal insulator transition (MIT) coupled to a structural phase transition upon heating (T = 67 °C). Since its discovery, the nature of the insulating state has long been debated and different solid-state mechanisms have been proposed to explain its nature: Mott-Hubbard correlation,...

Atomically-defined graphene nanoribbons (GNRs), which are narrow strips of graphene that feature a quantum confinement-induced bandgap, have shown great promise for applications in the next-generation semiconductor devices. Within this context, although numerous studies have demonstrated the bottom-up synthesis of all-carbon GNRs, a comparatively l...

Many applications of molecular layers deposited on metal surfaces, ranging from single-atom catalysis to on-surface magnetochemistry and biosensing, rely on the use of thermal cycles to regenerate the pristine properties of the system. Thus, understanding the microscopic origin behind the thermal stability of organic/metal interfaces is fundamental...

The Metal-Insulator transition (MIT) in VO2 is characterized by the complex interplay among lattice, electronic and orbital degrees of freedom. In this contribution we investigated the strain-modulation of the orbital hierarchy and the influence over macroscopic properties of the metallic phase of VO2 such as Fermi Level (FL) population and metalli...

Many applications of molecular layers deposited on metal surfaces, ranging from single-atom catalysis to on-surface magnetochemistry and biosensing, rely on the use of thermal cycles to regenerate the pristine properties of the system. Thus, understanding the microscopic origin behind the thermal stability of organic/metal interfaces is fundamental...

Since its discovery, the environmental instability of exfoliated black phosphorus (2D bP) has emerged as a challenge that hampers its wide application in chemistry, physics, and materials science. Many studies have been carried out to overcome this drawback. Here we show a relevant enhancement of ambient stability in few-layer bP decorated with nic...

The self-assembly of Leucoquinizarin molecule on Au(111) surface is shown to be characterized by the molecules mostly in their keto-enolic tautomeric form, with evidences of their temporary switching to other tautomeric forms. This reveals a metastable chemistry of the assembled molecules, to be considered for their possible employment in the forma...

A 2D self-assembly of Ni-containing tetrapyrroles on Cu(100) allows the control of the Ni atoms oxidation state, yielding inactive Ni(II) or active Ni(I) upon modification of the molecule–substrate interaction, resembling the behavior of the biochemical counterpart. Ni(I) is indeed the active site of methanogenic bacteria in the tetrahydrocorphin o...

The self-assembly of Leucoquinizarin molecule on Au(111) surface is shown to be characterized by the molecules mostly in their keto-enolic tautomeric form, with evidences of their temporary switching to other...

VO2 is a strongly correlated material, which undergoes a reversible metal insulator transition (MIT) coupled to a structural phase transition upon heating (T= 67° C). Since its discovery the nature of the insulating state has long been debated and different solid-state mechanisms have been proposed to explain its nature: Mott-Hubbard correlation, P...

VO2 is a strongly correlated material, which undergoes a reversible metal insulator transition (MIT) coupled to a structural phase transition upon heating (T= 67{\deg} C). Since its discovery the nature of the insulating state has long been debated and different solid-state mechanisms have been proposed to explain its nature: Mott-Hubbard correlati...

Fundamental understanding of the correlation between the structure and reactivity of chemically-addressable N-Heterocyclic Carbene molecules (NHCs) is essential for the design of functional NHC-based self-assembled monolayers (SAMs). In this work we identified the ways by which the deposition of chemically-addressable OH-NHCs on Au (111) or Pt (111...

Thin molecular films under model conditions are often exploited as benchmarks and case studies to investigate the electronic and structural changes occurring on the surface of metallic electrodes. Here we show that the modification of a metallic surface induced by oxygen adsorption allows the preservation of the geometry of a molecular adlayer, giv...

We perform on-surface synthesis of single-ion molecular magnets on an Ag(111) surface and characterize their morphology, chemistry, and magnetism. The first molecule we synthesize is TbPc2 to enable comparison with chemically synthesized and subsequently surface adsorbed species. We demonstrate the formation of TbPc2 with a yield close to 100% and...

The formation of flexible self‐assembled monolayers (SAMs) in which an external trigger modifies the geometry of surface‐anchored molecules is essential for the development of functional materials with tunable properties. In this work, it is demonstrated that NO2‐functionalized N‐heterocyclic carbene molecules (NHCs), which were anchored on Au (111...

Invited for the cover of this issue are Elad Gross, F. Dean Toste, and co‐workers at The Hebrew University and UC Berkeley. The image depicts the flexible anchoring geometry of addressable carbene molecules on Au surface, which upon exposure to reducing conditions changed their orientation from a standing into a flat‐lying position. Read the full t...

We performed a theoretical investigation on the influence of electronic correlation effects on the B1s NEXAFS spectrum of boronic acid derivatives, namely, boric acid [B(OH)3], phenyl boronic acid (PBA), and 1,4-phenyl diboronic acid (PDBA), employing different computational schemes of increasing complexity, ranging from the purely one-electron sch...

Flexible monolayers of NO2‐functionlized N‐heterocyclic carbene molecules were assembled on Au surfaces. The reorientation of the surface‐anchored molecules from tilted into flat‐lying position was triggered by exposure of the sample to reducing conditions that facilitated reduction of the chemically active nitro groups. More information can be fou...

Thin molecular films under model conditions are often exploited as benchmarks and case studies to investigate the electronic and structural changes occurring on the surface of metallic electrodes. Here we show that the modification of a metallic surface induced by oxygen adsorption allows the preservation of the geometry of a molecular adlayer, giv...

The properties of atomically thin materials essentially depend on their structures, including impurities, defects and interfaces with underlying substrates. Thus, the detailed structural information is relevant for creation of 2D materials with desired properties. Here, we explore the capabilities of photoelectron diffraction and holography for str...

The development of chemically-addressable N-heterocyclic carbene (NHC) based self-assembled monolayers (SAMs) requires in-depth understanding of the influence of NHCs anchoring geometry on its chemical functionality. Herein, it is demonstrated that the chemical reactivity of surface anchored NO2-functionalized NHCs (NO2-NHCs) can be tuned by modify...

Since its discovery, the environmental instability of exfoliated black phosphorus (2D bP) has emerged as a challenge that hampers its wide application in chemistry, physics, and materials science. Many studies have been carried out to overcome this drawback. Here we show a relevant enhancement of ambient stability in few-layer bP decorated with nic...

Singlet fission is a photophysical process in which an optically excited singlet exciton is converted into two triplet excitons. Singlet fission sensitized solar cells are expected to display a greatly enhanced power conversion efficiency compared to conventional single-junction cells, but the efficient design of such devices relies on the selectio...

Crown ethers, assembled into a regular 2D array via a chemical guest-host recognition process, have been successfully employed to trap sodium atoms on a surface, under ultra-high vacuum conditions.

Metal-containing enzyme cofactors achieve their unusual seactivity by stabilizing uncommon metal oxidation states with structurally complex ligands. In particular, the specific cofactor promoting both methanogenesis and anaerobic methane oxidation is a porphynoid chelated to a nickel (I) atom via a multi-step biosynthetic path, where the nickel red...

In this report we illustrate the instrumental developments involving the branchline of the ALOISA beamline at the Elettra synchrotron, with the setup of the ANCHOR-SUNDYN endstation. The ANCHOR experimental chamber is designed for the study of in-situ prepared organo-metallic hybrid interfaces, by means of synchrotron based soft x-ray spectroscopic...

Catalytic nanoparticles are heterogeneous in their nature and even within the simplest particle various surface sites exist and influence the catalytic reactivity. Thus, detailed chemical information at the nanoscale is essential for understanding how surface properties and reaction conditions direct the reactivity of different surface sites of cat...

On‐surface synthesis is an emerging approach to obtain, in a single step, precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. A facile on‐surface chemistry route has now been u...

On-surface synthesis is an emerging approach to obtain in a single step precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. We present a facile on surface chemistry route to sy...

We compare the ultrafast charge transfer dynamics from molecules on epitaxial graphene and bi-layer graphene grown on Ni(111) interfaces through first principle calculations and x-ray resonant photoemission spectroscopy. We use 4,4 0 -bipyridine as the prototypical molecule for these explorations as the energy level alignment of core-excited molecu...

The synthesis and preliminary characterization of a boroxine framework are presented. The peculiar electronic and morphologic properties of this compound, together with its facile formation process, open to its possible...

We performed an exhaustive study of terephthalic acid (TPA) self-assembly on the Cu(100) surface, where first-layer molecules display two sequential phase transitions in the 200 - 400 K temperature range, corresponding to different stages of molecular deprotonation. We followed the chemical and structural changes by means of high-resolution X-ray p...

A regular 2D array of crown molecules, which would spontaneously self-assemble into disordered molecular clusters, is obtained by exploiting a guest-host process, based on the chemical affinity between amino and carboxylic groups on a gold surface. First a carboxylic organic template is formed, which then serves as a host for amino-functionalized c...

Among transition metal oxides, VO2 is a particularly interesting and challenging correlated electron material where an insulator to metal transition (MIT) occurs near room temperature. Here we investigate a 16 nm thick strained vanadium dioxide film, trying to clarify the dynamic behavior of the insulator/metal transition. We measured (resonant) ph...

The occupied and unoccupied electronic structure of three high spin TM(acac) 3 (TM = Cr, Mn, and Fe) complexes ( I , II , and III , respectively) has been studied by revisiting their literature...

2,2’,6,6’-tetraphenyl-4,4’-dipyranylidene (DIPO-Ph4) was grown by vacuum-deposition on an indium tin oxide (ITO) substrate. The films were characterized by atomic force microscopy and synchrotron radiation UV and X-ray photoelectron spectroscopy to gain an insight into the material growth and to better understand the electronic properties of the DI...

New nanoarchitectures can be built from polycyclic aromatic hydrocarbons (PAHs) by exploiting the capability of some metal surfaces of inducing cyclodehydrogenation reactions. This bottom-up approach allows the formation of nanostructures with different dimensionality from the same precursor as a consequence of the diffusion and coupling of the PAH...

The knowledge of the picosecond dynamics of the energy level alignment between donor and acceptor materials in organic photovoltaic devices under working conditions is a challenge for fundamental material research. We measured by means of time-resolved Resonant X-ray Photoemission Spectroscopy (RPES) the energy level alignment in ZnPc/C60 films. We...

We performed a combined experimental and theoretical study of the assembly of phenylboronic acid on the Au(111) surface, which is found to lead to the formation of triphenylboroxines by spontaneous condensation of trimers of molecules. The interface between the boroxine group and the gold surface has been characterized in terms of its electronic pr...

The performance of devices from organic semiconductors is often governed by charge transfer phenomena at structurally and electronically complex interfaces, which remain challenging to access and study with excellent chemical and temporal resolution. Herein, we report the preparation and X-ray spectroscopic characterization of well-defined model or...

A number of studies have investigated the properties of monomeric and double-decker phthalocyanines (Pcs) adsorbed on metal surfaces, in view of applications in spintronics devices. In a combined experimental and theoretical study, we consider here a different member of the Pcs family, the (RuPc)2 dimer, whose structure is characterized by two pair...

Surface-confined polymerization via Ullmann coupling is a promising route to create one- and two-dimensional covalent π-conjugated structures, including the bottom-up growth of graphene nanoribbons. Understanding the mechanism of the Ullmann reaction is needed to provide a platform for rationally controlling the formation of these materials. We use...

Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and el...

Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and el...

Charge transfer rates at metal/organic interfaces affect the efficiencies of devices for organic based electronics and photovoltaics. A quantitative study of electron transfer rates, which take place on the femtosecond timescale, is often difficult, especially since in most systems the molecular adsorption geometry is unknown. Here, we use X-ray re...

Molecular bilayers made up of a donor-acceptor blend in contact with the metal and capped with a single-component layer show a tunable energy level alignment at both metal-organic and organic-organic interfaces. To ensure sharp heteromolecular interfaces, a contact layer is formed by a stable blend of pentacene (PEN) and perfluorinated copper phtha...

The self-assembly of the naphthylmethylamine molecules (NMA) on the Au(111) surface is investigated by a combined experimental and theoretical approach. Three well-defined phases are observed upon different thermal treatments at the monolayer stage. The role played by the methylamine termination is evidenced in both the molecule–molecule and molecu...

Charge transport properties of a vertically stacked organic hetero-junction, based on the amino-carboxylic (A-C) hydrogen bond coupling scheme, are investigated by means of X-ray Resonant Photoemission and the Core-Hole Clock method. We demonstrate that hydrogen bonding in molecular bi-layers of benzoic acid/cysteamine (BA/CA) with an A-C coupling...

We report the interface energetics of decacyclene-tri-anhydride (DTA) monolayers on top of two distinct model surfaces, namely Au(111) and Ag(111). On the latter, combined valence band photoemission and X-ray absorption measurements that access the occupied and unoccupied molecular orbitals, respectively, reveal that electron transfer from substrat...

We investigate bidirectional femtosecond charge transfer dynamics using the core-hole clock implementation of resonant photoemission spectroscopy from 4,4'-bipyridine molecular layers on three different surfaces: Au(111), epitaxial graphene and graphene nanoribbons. We show that the lowest unoccupied molecular orbital (LUMO) of the molecule drops p...

In this paper we investigate the local adsorption geometry of CoPc films adsorbed on a Ag(100) surface and its effect on the molecule–substrate interactions. Using high-resolution electron energy loss spectroscopy we demonstrate that the charge-transfer mechanism at the organic–metal interface depends on the structural properties of the CoPc film....

We report the formation of Dimethyl Sulfoxide (DMSO) molecular complexes on Au(111) enabled by native gold adatoms unusually linking the molecules via a bonding of ionic nature, yielding a mutual stabilization between molecules and adatom(s). DMSO is a widely used polar, aprotic solvent whose interaction with metal surfaces is not fully understood....

Keywords: Density functional calculations / Ligand effects / NEXAFS spectroscopy / X-ray absorption spectroscopy / Copper The low-lying empty orbitals of bis(acetylacetonato)copper have been probed by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Cu L 2,3 edges and time-dependent density functional theory (TDDFT) calculatio...

An amino-carboxylic motif is identified as a novel synthon in the formation of 2D hetero-organic architectures at surfaces. The well-defined interacting scheme we describe herein represents an ideal prototypical system for further investigation of the interaction at surfaces of the two functional groups.

Primary amines can interact with neighbor molecules or with a metal substrate via weak bonds involving the electron lone pair of their amino functional group. Near edge X-ray absorption spectra (NEXAFS) on the N 1s edge show that the structure of the empty molecular orbitals localized on the nitrogen atom is very sensitive to these interactions. He...