Katrin R. Siefermann

The Hydrated Electron: A Seemingly Familiar Chemical and Biological Transient

Since the discovery of the hydrated electron in bulk water in 1962, the species has been the subject of intense research and speculation. For many decades even the basic features of the simplest of all chemical and biological transients and reactants--such as its structure, binding motifs, lifetimes, and binding energies--remained elusive. Recently, another milestone in the research of the hydrated electron was the determination of its vertical binding energy (VBE). Also a long-lived hydrated electron near the surface of liquid water has been discovered. The present Minireview discusses the implications and consequences of this and other new findings in addition to the emerging complex picture of a solvated electron in water.

Ion Chemistry Mediated by Water Networks

The reaction of ions such as NO+ with networks of only a few water molecules has implications for understanding chemistry in the ionosphere. The remarkable properties of liquid water derive largely from its ability to form fluctuating networks of hydrogen bonds. However, even in the gas phase, where clusters of only a few water molecules may form, their sparse hydrogen-bonded networks may still absorb energy and stabilize reactants and products (1–3), stabilize intermediates as catalysts (1), or act as reaction partners. In the D region of the ionosphere (70 to 85 km above Earth), the positively charged ions that form there, such as NO+, can formally transfer charge to one water molecule and add an OH− group to form a neutral species (such as HONO). The resulting protonated water networks (4–7) are regarded as the major positive-charge carrier in the D region, which is the lowest ionospheric layer that affects radio communications. On page 308 of this issue, Relph et al. (8) report on a combined experimental and theoretical study that tries to unravel the relation between the hydrogen-bonding arrangement of a set of water molecules around an NO+ ion and the chemical activity of this ensemble. Their results bear on a key open question: Are there particular water clusters that account for most of the reactivity?

Efficient synthesis of triarylamine-based dyes for p -type dye-sensitized solar cells

The class of triarylamine-based dyes has proven great potential as efficient light absorbers in inverse (p-type) dye sensitized solar cells (DSSCs). However, detailed investigation and further improvement of p-type DSSCs is strongly hindered by the fact that available synthesis routes of triarylamine-based dyes are inefficient and particularly demanding with regard to time and costs. Here, we report on an efficient synthesis strategy for triarylamine-based dyes for p-type DSSCs. A protocol for the synthesis of the dye-precursor (4-(bis(4-bromophenyl)amino)benzoic acid) is presented along with its X-ray crystal structure. The dye precursor is obtained from the commercially available 4(diphenylamino)benzaldehyde in a yield of 87% and serves as a starting point for the synthesis of various triarylamine-based dyes. Starting from the precursor we further describe a synthesis protocol for the dye 4-{bis[4′-(2,2-dicyanovinyl)-[1,1′-biphenyl]-4-yl]amino}benzoic acid (also known as dye P4) in a yield of 74%. All synthesis steps are characterized by high yields and high purities without the need for laborious purification steps and thus fulfill essential requirements for scale-up.

Imaging Nanoscale Morphology of Semiconducting Polymer Films with Photoemission Electron Microscopy

Photoemission electron microscopy in combination with polarized laser light is presented as a tool permitting direct imaging of polymer-chain orientation and local degree of order in semicrystalline samples of semiconducting polymers, a promising class of materials for future electronics. The key advantages of this imaging tool are its nondestructive and fast measurements, straightforward data analysis, the low complexity of sample preparation, and the possibility of performing measurements on a broad variety of technologically relevant substrates. The high spatial resolution of the microscope provides insights into the nanoscale morphology, which is relevant for the materials performance in electronic devices.

Nanostructure-enhanced Atomic Line Emission from Noble Gases driven by Low-Energy, Few-Cycle Laser Pulses

We present extreme ultraviolet emission from noble gases driven by low-energy, few-cycle light pulses enhanced in plasmonic nanostructures. The origin of the emission is atomic fluorescence, and we find no sign of high harmonic radiation.