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An efficient and accurate theoretical description of the structural hydration of biological macromolecules is presented. The hydration of molecules of almost arbitrary size (tRNA, antibody–antigen complexes, photosynthetic reaction centre) can be studied in solution and in the crystalline environment. The biomolecular structure obtained from X-ray crystallography, NMR or modelling is required as input information. The structural arrangement of water molecules near a biomolecular surface is represented by the local water density, analogous to the corresponding electron density in an X-ray diffraction experiment. The water-density distribution is approximated in terms of two- and three-particle correlation functions of solute atoms with water using a potentials-of-mean-force expansion.

In this work we report on the ultrafast photodynamics of the photosensitizer zinc phthalocyanine (ZnPc) and manipulation thereof. Two approaches are followed: active control via pulse shaping and passive control via strategic manipulation in the periphery of the molecular structure. The objective of both of these control experiments is the same: to enhance the yield of the functional pathway and to minimize loss channels. The aim of the active control experiments is to increase the intersystem crossing yield in ZnPc, which is important for application in photodynamic therapy (PDT). Pulse shaping allowed an improvement in triplet to singlet ratio of 15% as compared to a transform-limited pulse. This effect is ascribed to a control mechanism that utilizes multiphoton pathways to higher-lying states from where intersystem crossing is more likely to occur. The passive control experiments are performed on ZnPc derivatives deposited onto TiO 2 , serving as a model system of a dye -sensitized solar cell (DSSC). Modification of the anchoring ligand of the molecular structure resulted in an increased rate for electron injection into TiO 2 and slower back electron transfer , improving the DSSC efficiency.

Recent developments in the growth of ultra-thin epitaxial layers of oxides and the fabrication of a diversity of nanostructures has led to current interest in, and much speculation about, the properties of low dimensional systems. In this paper we report recent calculations for low dimensional NiO on MgO(100) surfaces both from first principles electronic structure calculations and free energy calculations based on surface lattice dynamics. The results include surface structures and dynamics at a range of temperatures and electronic structures of ground, excited, ionised, d→d and charge–transfer excitonic states in different spin alignments.

The reaction of the rhodium( I ) complexes [Rh(E)(PEt 3 ) 3 ] (E = GePh 3 ( 1 ), Si(OEt) 3 ( 5 )) with HFO-1234yf (2,3,3,3-tetrafluoropropene) afforded [Rh(F)(PEt 3 ) 3 ] ( 2 ) and the functionalized olefins Z -CF 3 CH CH(E) (E = GePh 3 ( 4a ), Si(OEt) 3 ( 7 )). Conceivable reaction pathways were assessed using DFT calculations. Reactions of [Rh(E)(PEt 3 ) 3 ] with HFO-1234ze ( E -1,3,3,3-tetrafluoropropene) yielded the rhodium fluorido complex 2 and [Rh{( E )-CH CH(CF 3 )}(PEt 3 ) 3 ] ( 9 ) via two different reaction pathways. Using complexes 1 and 5 as catalysts, functionalized building blocks were obtained.

There is increasing evidence that the direct absorption of photons with energies that are lower than the ionization potential of nucleobases may result in oxidative damage to DNA. The present work, which combines nanosecond transient absorption spectroscopy and quantum mechanical calculations, studies this process in alternating adenine–thymine duplexes (AT) n . We show that the one-photon ionization quantum yield of (AT) 10 at 266 nm (4.66 eV) is (1.5 ± 0.3) × 10 ?3 . According to our PCM/TD-DFT calculations carried out on model duplexes composed of two base pairs, (AT) 1 and (TA) 1 , simultaneous base pairing and stacking does not induce important changes in the absorption spectra of the adenine radical cation and deprotonated radical. The adenine radicals, thus identified in the time-resolved spectra, disappear with a lifetime of 2.5 ms, giving rise to a reaction product that absorbs at 350 nm. In parallel, the fingerprint of reaction intermediates other than radicals, formed directly from singlet excited states and assigned to AT/TA dimers, is detected at shorter wavelengths. PCM/TD-DFT calculations are carried out to map the pathways leading to such species and to characterize their absorption spectra; we find that, in addition to the path leading to the well-known TA* photoproduct, an AT photo-dimerization path may be operative in duplexes.

Amphoteric water was mixed with equimolar amounts of a super-strong acid, trifluoromethanesulfonic acid (TfOH), and a super-strong base, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU). Bulk physicochemical and electrochemical properties of the mixtures were compared with those of the best ever reported protic ionic liquid (PIL), diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), which has excellent physicochemical properties as a fuel cell electrolyte. The acidic mixture ([H 3 O][TfO]) behaved as a protic ionic liquid, while the basic mixture ([DBU]OH) showed incomplete proton transfer. The Walden plot indicated that [H 3 O][TfO] behaves as a good PIL, similar to [dema][TfO], whereas [DBU]OH behaves as a poor PIL. [H 3 O][TfO] showed excellent H 2 /O 2 fuel cell performance at 80 °C; however, the performance deteriorated as the bulk water content increased, because of the retardation of the electrode kinetics due to the oxidation of Pt in the presence of bulk water. On the other hand, [DBU]OH exhibited very poor performance possibly because of the existence of neutral species in the system.

A thermodynamic equilibrium sensor is proposed that measures the ratio of the number of elementary charges z to the mass m of charged solutes such as charged colloids and nanoparticles. The sensor comprises a small, membrane-encapsulated salt solution volume that absorbs neutral salt molecules in response to the release of mobile counter-ions by charge carriers in the surrounding suspension. The sensor state emerges as a limiting case of the equilibrium salt imbalance, and the ensuing osmotic pressure difference, between arbitrary salt and suspension volumes. A weight concentration of charge carriers c is predicted to significantly increase the sensor's salt number density from its initial value ρ s,0 to ρ R s , according to the relation ( ρ R s / ρ s,0 ) 2 ? 1 = zc / mρ s,0 , under the assumption that the mobile ions involved in the thermodynamic sensor-suspension equilibrium are ideal and homogeneously distributed.

Crystal growth by non-classical mechanisms, such as oriented aggregation, frequently involves an aggregation step. The aggregation of nanoparticles is sensitive to solution variables like ionic strength and pH, as well as the presence and concentration of other chemical species. Aggregation is a critical first step during the early stages of oriented aggregation. Time-resolved, cryogenic transmission electron microscopy was employed to characterize the degree of aggregation, the reversibility of aggregation, and the influence of additives on aggregation in aqueous suspensions. In this work, freshly synthesized ferrihydrite nanoparticles in aqueous suspension were employed as the model system. These nanoparticles are largely aggregated even with a solution pH several pH units away from the point of zero net proton charge (PZNPC) and a very low ionic strength ( 10 ?4 M). Reversibility of aggregation was observed to be time-dependent. Finally, chemical additives dramatically change the evolution of aggregation state with strongly coordinating ligands strongly suppressing aggregation, even after aging at an elevated temperature.

This article presents the Closing Remarks of the Faraday Discussion on aggregation induced emission (AIE) held in Guangzhou, China in November 2016. The history of the AIE phenomenon is summarized, from its discovery and mechanistic studies to real-life applications in optoelectronics, environmental monitoring and biomedical research. The paper concludes with comments on the future perspectives of the field.

Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T , and solution water activity, a w , which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, J het , to be uniquely expressed by T and a w , a result we term the a w based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, J het , frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A , and cooling rates, r , of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log 10 ( J het ) values for the various IN types derived exclusively by T and a w , provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T , RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Lastly, we demonstrate that ABIFM can be used to derive frozen fractions of droplets and ice particle production for atmospheric models of cirrus and mixed phase cloud conditions.