Dynamical evolution of the Schottky barrier as a determinant contribution to electron-hole pair stabilization and photocatalysis of plasmon-induced hot carriers.

The harnessing of plasmon-induced hot carriers promises to open new avenues for the development of clean energies and chemical catalysis. The extraction of carriers before thermalization and recombination is of fundamental importance to obtain appealing conversion yields. Here, hot carrier injection in the paradigmatic Au-TiO system is studied by means of electronic and electron-ion dynamics.

Spin-Polarized Tunable Photocurrents.

Harnessing the unique features of topological materials for the development of a new generation of topological based devices is a challenge of paramount importance. Using Floquet scattering theory combined with atomistic models we study the interplay among laser illumination, spin, and topology in a two-dimensional material with spin-orbit coupling. Starting from a topological phase, we show how laser illumination can selectively disrupt the topological edge states depending on their spin.

Plasmon-induced hot-carrier generation differences in gold and silver nanoclusters.

In the last thirty years, the study of plasmonic properties of noble metal nanostructures has become a very dynamic research area. The design and manipulation of matter in the nanometric scale demands a deep understanding of the underlying physico-chemical processes that operate in this size regimen. Here, a fully atomistic study of the spectroscopic and photodynamic properties of different icosahedral silver and gold nanoclusters has been carried out by using a Time-Dependent Density Functional Tight-Binding (TD-DFTB) model.

Solvation of barium atoms and singly charged cations in acetonitrile clusters.

The size distributions of neutral and cationic Ba (CHCN) ( = 0, +1; ≤ 7) clusters, as produced by a standard laser vaporization-supersonic expansion pick-up source, were determined from molecular beam experiments. The size distribution for cations is in the range of = 1-7, whereas only the = 1 complex is observed for neutral clusters, and these two features are unaffected by the variables controlling the performance of the cluster source. The distinct behavior is compatible with the expected charge-dipole interactions in the ionic species, which are stronger than the dipole induced-dipole interactions at play in neutral clusters, and it is corroborated by the relative magnitude of the theoretical successive binding energies (SBEs) for the lowest-lying isomers of cationic and neutral clusters with = 1-5, as computed at the density functional theory level.

Optical properties and charge distribution in rod-shape DNA-silver cluster emitters.

While the atomic structure of DNA_Agn clusters remains unknown many efforts have been made to understand the photophysical properties of this type of systems. It is known that partial oxidation of the silver cluster is necessary for generation of fluorescent emitters. In this sense, the rod-shape model proposed by Gwinn and coworkers (D.

Fingerprints of Both Watson-Crick and Hoogsteen Isomers of the Isolated (Cytosine-Guanine)H Pair.

 Gas phase protonated guanine-cytosine (CGH) pair was generated using an electrospray ionization source from solutions at two different pH (5.8 and 3.2).

DNA-protected silver emitters: charge dependent switching of fluorescence.

The relationship between the state of charge and spectroscopy of DNA-protected silver emitters is not yet well understood. This remains one of the major issues to unveil in order to fully disentangle the spectroscopic features of these novel systems. It is a well known fact that a fluorescence response arises upon chemical reduction of silver cations attached to DNA, leading to neutral (or partially oxidized) "bright" clusters.

Analysis of illicit drugs by direct ablation of solid samples.

Analysis of illicit drugs arises as an important field of work given the high social impacts presented by drugs in the modern society. Direct laser ablation of solid compounds allows their analysis without sampling or preparation procedures. For that purpose, an experimental set-up that combines laser ablation with time-of- flight mass spectrometry has been constructed very recently to perform studies on the mass spectra of such drugs as 3,4-methylenedioxy-N-methylamphetamine, commonly known as MDMA or ecstasy.

Effect of Ag(+) on the Excited-State Properties of a Gas-Phase (Cytosine)2Ag(+) Complex: Electronic Transition and Estimated Lifetime.

Recently, DNA molecules have received great attention because of their potential applications in material science. One interesting example is the production of highly fluorescent and tunable DNA-Agn clusters with cytosine (C)-rich DNA strands. Here, we report the UV photofragmentation spectra of gas-phase cytosine···Ag(+)···cytosine (C2Ag(+)) and cytosine···H(+)···cytosine (C2H(+)) complexes together with theoretical calculations.

Communication: UV photoionization of cytosine catalyzed by Ag(+).

The photo-induced damages of DNA in interaction with metal cations, which are found in various environments, still remain to be characterized. In this paper, we show how the complexation of a DNA base (cytosine (Cyt)) with a metal cation (Ag(+)) changes its electronic properties. By means of UV photofragment spectroscopy of cold ions, it was found that the photoexcitation of the CytAg(+) complex at low energy (315-282) nm efficiently leads to ionized cytosine (Cyt(+)) as the single product.

On the Ag(+)-cytosine interaction: the effect of microhydration probed by IR optical spectroscopy and density functional theory.

The gas-phase structures of cytosine-Ag(+) [CAg](+) and cytosine-Ag(+)-H2O [CAg-H2O](+) complexes have been studied by mass-selected infrared multiphoton dissociation (IRMPD) spectroscopy in the 900-1800 cm(-1) spectral region using the Free Electron Laser facility in Orsay (CLIO). The IRMPD experimental spectra have been compared with the calculated IR absorption spectra of the different low-lying isomers (computed at the DFT level using the B3LYP functional and the 6-311G++(d,p) basis set for C, H, N and O atoms and the Stuttgart effective core potential for Ag). For the [CAg](+) complex, only one isomer with cytosine in the keto-amino (KA) tautomeric form and Ag(+) interacting simultaneously with the C(2)[double bond, length as m-dash]O(7) group and N(3) of cytosine was observed.

The shape of D-glucosamine.

The bioactive amino monosaccharide D-glucosamine has been generated in the gas phase via laser ablation of D-glucosamine hydrochloride. Three cyclic α-(4)C1 pyranose forms have been identified using Fourier transform microwave techniques. Stereoelectronic hyperconjugative forces - essentially linked with the anomeric or gauche effect - and cooperative OH···O, OH···N and NH···O chains, extended along the entire molecule, are found to be the main factors driving the conformational behavior.

Excited states of proton-bound DNA/RNA base homodimers: pyrimidines.

We are presenting the electronic photofragment spectra of the protonated pyrimidine DNA base homodimers. Only the thymine dimer exhibits a well structured vibrational progression, while the protonated monomer shows broad vibrational bands. This shows that proton bonding can block some nonradiative processes present in the monomer.

Gas Phase Structure of Metal Mediated (Cytosine)Ag Mimics the Hemiprotonated (Cytosine)H Dimer in i-Motif Folding.

The study of metal ion-DNA interaction aiming to understand the stabilization of artificial base pairing and a number of noncanonical motifs is of current interest, due to their potential exploitation in developing new technological devices and expanding the genetic code. A successful strategy has been the synthesis of metal-mediated base pairs, in which a coordinative bond to a central metal cation replaces a H-bond in a natural pair. In this work, we characterized, for the first time, the gas phase structure of the cytosine···Ag···cytosine (C-Ag-C) complex by means of InfraRed-MultiPhoton-Dissociation (IR-MPD) spectroscopy and theoretical calculation.

Excited states of protonated DNA/RNA bases.

The very fast relaxation of the excited states to the ground state in DNA/RNA bases is a necessary process to ensure the photostability of DNA and its rate is highly sensitive to the tautomeric form of the bases. Protonation of the bases plays a crucial role in many biochemical and mutagenic processes and it can result in alternative tautomeric structures, thus making important the knowledge of the properties of protonated DNA/RNA bases. We report here the photofragmentation spectra of the five protonated DNA/RNA bases.