ultrafast electron injection into photo excited organic molecules

State-of-the-art X-ray spectroscopy allows femtosecond gating of energy levels of photo-excited molecules on a metal substrate enabling ultrafast and bi-directional charge transfer across the interface with controllable dependence on the molecular adsorption geometry

Length-Independent Charge Transport in Chimeric Molecular Wires

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 electrochemical interrogation of DNA-like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high-performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors

Electronic properties of the boroxine–gold interface: evidence of ultra-fast charge delocalization

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 properties, revealing the existence of an ultra-fast charge delocalization channel in the proximity of the oxygen atoms of the heterocyclic group. More specifically, the DFT calculations show the presence of an unoccupied electronic state localized on both the oxygen atoms of the adsorbed triphenylboroxine and the gold atoms of the topmost layer. By means of resonant Auger electron spectroscopy, we demonstrate that this interface state represents an ultra-fast charge delocalization channel. Boroxine groups are among the most widely adopted building blocks in the synthesis of covalent organic frameworks on surfaces. Our findings indicate that such systems, typically employed as templates for the growth of organic films, can also act as active interlayers that provide an efficient electronic transport channel bridging the inorganic substrate and organic overlayer

Percepcija in produkcija standardnih britanskih /ɪə/, /eə/ in /ʊə/ pri slovenskih govorcih angleščine

In this thesis, we asked ourselves how well Slovene speakers of English perform at perceiving the General British centring diphthongs /ɪə/, /eə/ and /ʊə/, whether and how often they reproduce them, and if so, to what extent of precision. These three phonemes have been chosen because they are expected to present difficulty in perception and production, because Standard Slovene does not feature similar phonemes (or combinations of phonemes), because they are being increasingly monophthongized in General British English, and because they do not appear in General American English. We have conducted two tests, one for perception and one for production, on first-year students of English. We have discovered that both perception and production of centring diphthongs is problematic, the latter more so than the former, with the majority of participants preferring a pronunciation closer to General American English rather than General British English. Those who reproduce centring diphthongs consistently exhibit more precision in pronunciation than those those who reproduce them sporadically. Finally, there is a slight, but varied, correlation between strong performers in perception and strong performers in production.V tej nalogi se sprašujemo, kako se slovenski govorci angleščine odrežejo pri percepciji standardnih britanskih (General British) centričnih diftongov /ɪə/, /eə/ in /ʊə/, če in kako pogosto jih reproducirajo, in če jih, s kakšno natančnostjo. Te tri foneme smo izbrali, ker se pričakuje, da bodo predstavljali težave pri percepciji in produkciji, saj knjižna slovenščina podobnih fonemov ne vključuje (niti ne v kombinaciji fonemov), ker se v standardni britanski angleščini vse bolj pogosto monoftongizirajo in ker se ne pojavljajo v standardni ameriški angleščini (General American). Izvedli smo dva testa, enega za percepcijo in enega za produkcijo, na študentih Anglistike, ki obiskujejo prvi letnik. Ugotovili smo, da percepcija in produkcija centričnih diftongov predstavljata težave, pri čemer jih produkcija predstavlja več, saj se večina udeležencev nagiba k izgovorjavi, ki je bližja standardni ameriški angleščini kot standardni britanski angleščini. Ti, ki konsistentno reproducirajo centrične diftonge, so bolj natančni v izgovorjavi, kot ti, ki jih reproducirajo občasno. Ugotovili smo, da se kaže delna, a razgibna, korelacija med uspešnimi udeleženci pri percepciji in uspešnimi udeleženci pri produkciji

Determination of the valence band edge of Fe oxide nanoparticles dispersed in aqueous solution through resonant photoelectron spectroscopy from a liquid microjet

We use X-ray photoemission and a near ambient pressure with a liquid microjet setup to investigate the electronic structure of FeOOH nanoparticles dispersed in aqueous solution. In particular, we show that by using X-ray resonant photoemission in dilute solutions, we can overcome the limits of conventional photoemission such as low nanoparticle-to-solvent signal ratio, and local nanoparticle charging and measure the valence band structure of FeOOH nanoparticles in aqueous solution with chemical specificity. The resonant photoemission signal across the Fe 2p3/2 absorption edge is measured for 2 wt% aqueous solutions of FeOOH nanoparticles (NPs) and the valence band maximum (VBM) of the hydrated FeOOH nanoparticles is determined. We compare the obtained VBM value in aqueous solution to that of FeOOH NPs in the dry phase. We show that the valence band edge position of NPs in the liquid phase can be accurately predicted from the values obtained in the dry phase provided that a simple potential shift due to solution chemistry is applied. Our results demonstrate the suitability of resonant photoemission in measuring the electronic structure of strongly diluted nanosystems where the conventional non-resonant photoemission technique fails.ISSN:2516-023

Ultrafast Bidirectional Charge Transport and Electron Decoherence at Molecule/Surface Interfaces: A Comparison of Gold, Graphene, and Graphene Nanoribbon Surfaces

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 on Ni(111), and graphene nanoribbons. We show that the lowest unoccupied molecular orbital (LUMO) of the molecule drops partially below the Fermi level upon core-hole creation in all systems, opening an additional decay channel for the core-hole, involving electron donation from substrate to the molecule. Furthermore, using the core-hole clock method, we find that the bidirectional charge transfer time between the substrate and the molecule is fastest on Au(111), with a 2 fs time, then around 4 fs for epitaxial graphene and slowest with graphene nanoribbon surface, taking around 10 fs. Finally, we provide evidence for fast phase decoherence of the core-excited LUMO* electron through an interaction with the substrate providing the first observation of such a fast bidirectional charge transfer across an organic/graphene interface