Coherent ultrafast lattice-directed reaction dynamics of triiodide anion photodissociation

Solid-state reactions are influenced by the spatial arrangement of the reactants and the electrostatic environment of the lattice, which may enable lattice-directed chemical dynamics. Unlike the caging imposed by an inert matrix, an active lattice participates in the reaction, however, little evidence of such lattice participation has been gathered on ultrafast timescales due to the irreversibility of solid-state chemical systems. Here, by lowering the temperature to 80 K, we have been able to study the dissociative photochemistry of the triiodide anion (I₃−) in single-crystal tetra-n-butylammonium triiodide using broadband transient absorption spectroscopy. We identified the coherently formed tetraiodide radical anion (I₄•−) as a reaction intermediate. Its delayed appearance after that of the primary photoproduct, diiodide radical I₂•−, indicates that I₄•− was formed via a secondary reaction between a dissociated iodine radical (I^•) and an adjacent I₃−. This chemistry occurs as a result of the intermolecular interaction determined by the crystalline arrangement and is in stark contrast with previous solution studies

Synchronised photoreversion of spirooxazine ring opening in thin crystals to uncover ultrafast dynamics

Reversibility is an important issue that prevents ultrafast studies of chemical reactions in solid state due to product accumulation. Here we present an approach that makes use of spectrally-selected, post-excitation, ultrashort laser pulses to minimise photoproduct build-up, i.e. recover before destroy. We demonstrate that this method enabled us to probe the ultrafast dynamics of the ring opening reaction of spironaphthooxazine thin crystals by means of transient absorption spectroscopy. By extension, this approach should be amenable to other photochromic systems and use with structural probes

Towards Atomically-Resolved Structural Changes during a Solid State Geminate Recombination Reaction

Joint investigation of the photo-initiated geminate recombination of triiodide in solid state using transient absorption spectroscopy and ultrafast electron diffraction provides evidence of the atomic origins of the coherent modes driven by the reaction

Observation of the photoinduced phase transition in Me4P[Pt(dmit)2]2 by femtosecond electron diffraction

Femtosecond electron diffraction has been used to probe the photoinduced phase transition in the strongly-correlated system, Me4P[Pt(dmit)2]2, revealing molecular motions involved in this process and breaking new ground in terms of chemical complexity

Direct observation of collective modes coupled to molecular orbital–driven charge transfer

Correlated electron systems can undergo ultrafast photoinduced phase transitions involving concerted transformations of electronic and lattice structure. Understanding these phenomena requires identifying the key structural modes that couple to the electronic states. We report the ultrafast photoresponse of the molecular crystal Me4P[Pt(dmit)2]2, which exhibits a photoinduced charge transfer similar to transitions between thermally accessible states, and demonstrate how femtosecond electron diffraction can be applied to directly observe the associated molecular motions. Even for such a complex system, the key large-amplitude modes can be identified by eye and involve a dimer expansion and a librational mode. The dynamics are consistent with the time-resolved optical study, revealing how the electronic, molecular, and lattice structures together facilitate ultrafast switching of the state

Understanding the surface chemistry of thiolate-protected metallic nanoparticles

Metallic nanoparticles (NPs) appear as promising materials to be used in biomedicine, as efficient catalysts and electrocatalysts, and as active elements in electronic and sensing devices. The most common strategy to protect these NPs is by using thiolate self-assembled monolayers (SAMs), a strategy that has proved to be useful to control the physical and chemical properties of extended solid surfaces. However, the knowledge of the structure and chemistry of thiol−metal interfaces yet remains elusive, although it is crucial for understanding how NPs interact with molecules, biomolecules, and living cells and also for a better design of NP-based devices. This Perspective strives to show the complexity of the thiol−metal NP interface chemistry and how this changes with the nature of the metallic core.Fil: Azcárate, Julio César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Corthey, Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Pensa, Evangelina Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Vericat, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Fonticelli, Mariano Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Carro, Pilar. Universidad de la Laguna; Españ

New Insights into the Chemistry of Thiolate-Protected Palladium Nanoparticles

This paper establishes the chemical nature of Pd nanoparticles protected by alkanethiolates that were prepared through a ligand place-exchange approach and the two-phase method, first developed for Au nanoparticles by Brust and Schiffrin. After 10 years since the first study on this kind of Pd nanoparticles was published, the surface composition of the particles is a matter of debate in the literature and it has not been unambiguously assessed. The nanoparticles were studied by means of several techniques: UV–visible spectroscopy, scanning transmission electron microscopy, Fourier-transform infrared spectroscopy, extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy. The experimental data, obtained for the 3 nm diameter Pd particles, prepared by both synthetic routes, are consistent with nanoparticles composed by Pd(0) cores surrounded by a submonolayer of sulfide species, which are protected by alkanethiolates. Also, we unambiguously demonstrate that the chemical nature of these particles is very similar to that experimentally found for alkanethiolate-modified bulk Pd. The results from this paper are important not only for handling thiolate-protected Pd nanoparticles in catalysis and sensing, but also for the basic comprehension of metallic nanoparticles and the relation of their surface structure with the synthesis method