Overcoming the Exciton Binding Energy in Two-Dimensional Perovskite Nanoplatelets by Attachment of Conjugated Organic Chromophores

In this work we demonstrate a novel approach to achieve efficient charge separation in dimensionally and dielectrically confined two-dimensional perovskite materials. Two-dimensional perovskites generally exhibit large exciton binding energies that limit their application in optoelectronic devices that require charge separation such as solar cells, photo-detectors and in photo-catalysis. Here, we show that by incorporating a strongly electron accepting moiety, perylene diimide organic chromophores, on the surface of the two-dimensional perovskite nanoplatelets it is possible to achieve efficient formation of mobile free charge carriers. These free charge carriers are generated with ten times higher yield and lifetimes of tens of microseconds, which is two orders of magnitude longer than without the peryline diimide acceptor. This opens a novel synergistic approach, where the inorganic perovskite layers are combined with functional organic chromophores in the same material to tune the properties for specific applications. Functionalizing two-dimensional (2D) hybrid perovskites with organic chromophores is a novel approach to tune their optoelectronic properties. Here, the authors report efficient charge separation and conduction in 2D hybrid perovskite nanoplatelets by incorporating an electron acceptor chromophoreThis work has received funding from the European Research Council Horizon 2020 ERC Grant Agreement No. 648433

Quantified epistemic logics for reasoning about knowledge in multi-agent systems

AbstractWe introduce quantified interpreted systems, a semantics to reason about knowledge in multi-agent systems in a first-order setting. Quantified interpreted systems may be used to interpret a variety of first-order modal epistemic languages with global and local terms, quantifiers, and individual and distributed knowledge operators for the agents in the system. We define first-order modal axiomatisations for different settings, and show that they are sound and complete with respect to the corresponding semantical classes.The expressibility potential of the formalism is explored by analysing two MAS scenarios: an infinite version of the muddy children problem, a typical epistemic puzzle, and a version of the battlefield game. Furthermore, we apply the theoretical results here presented to the analysis of message passing systems [R. Fagin, J. Halpern, Y. Moses, M. Vardi, Reasoning about Knowledge, MIT Press, 1995; L. Lamport, Time, clocks, and the ordering of events in a distributed system, Communication of the ACM 21 (7) (1978) 558–565], and compare the results obtained to their propositional counterparts. By doing so we find that key known meta-theorems of the propositional case can be expressed as validities on the corresponding class of quantified interpreted systems

Sterically Overcrowded Alkenes; a Stereospecific Photochemical and Thermal Isomerization of a Benzoannulated Bithioxanthylidene

Enantiomerically pure sterically overcrowded 12H-benzo[a]thioxanthenyl-12-(2'-methyl-9'H-thioxanthene-9'-ylidene) shows a stereospecific photochemical and thermal isomerization of the P-trans into the M-cis isomer (and vice versa), with a large thermal isomerization barrier (ΔG‡ = 28.6 kcal mol–1) (1 cal = 4.184 J), making this type of molecule especially suitable as the key structural unit for applications as chiroptical molecular switches.