Volume 83, Issue 12

<div>IUPAC’s vision statement declares that the Union advances the worldwide role of chemistry for the benefit of Mankind. And one of its long-range goals states “IUPAC will utilize its global perspective and network to contribute to the enhancement of chemistry education, the career development of young chemical scientists, and the public appreciation of chemistry”. In pursuit of this spirit, the Union established in 2000 the IUPAC Prize for Young Chemists and has been honoring since then outstanding young research chemists at the beginning of their careers by making annual awards.<br /><br />The prizes are given for the most outstanding Ph.D. theses in the area of the chemical sciences, as described in 1000-word essays. For details, please refer to <http://www.iupac.org/news/prize.html> (IUPAC Prizes for Young Chemists). IUPAC awards up to five prizes annually, each comprising USD 1000 and travel expenses to the next IUPAC Congress.<br /><br />As immediate Past President of IUPAC, I was honored to chair the prize selection committee of eminent chemists, who enjoyed reading essays of 47 applicants from 19 countries. The committee was extremely pleased to note the increase in the number of applicants to 47 from 29 last year. This increase is in excellent accord with IUPAC’s worldwide celebration of the International Year of Chemistry throughout this year. After critical evaluation of the originality and excellence of the essays and research results, the committee decided unanimously to award 2011 Prizes to the following six chemists:<br /><br /><b>Rubén D. Costa</b>, University of Valencia, Valencia, Spain: “Theoretical and experimental study of light-emitting electrochemical cells based on ionic transition-metal complexes: From the molecule to the device”<br /><br /><b>William Donald</b>, University of California, Berkeley, CA, USA: “Ion nanocalorimetry: Measuring absolute reduction potentials and investigating effects of water on electron solvation and ion fluorescence”<br /><br /><b>Matthew Macauley</b>, Simon Fraser University, Burnaby, BC, Canada: “Insight into O-GlcNAc protein modification using chemical and biochemical tools”<br /><br /><b>Bozhi Tian</b>, Harvard University, Cambridge, MA, USA: “Design, synthesis, and characterization of novel nanowire structures for photovoltaics and intracellular probes”<br /><br /><b>Sheng Xu</b>, Georgia Institute of Technology, Atlanta, GA, USA: “Oxide nanowire arrays for energy sciences”<br /><br /><b>Chengqi Yi</b>, University of Chicago, Chicago, IL, USA: “Probing the AlkB family DNA/RNA repair enzymes with a chemical disulphide cross-linking approach”<br /><br />All the awardees were invited to present posters on their research at the 43rd IUPAC World Chemistry Congress, San Juan, Puerto Rico, 30 July-6 August 2011. Upon IUPAC’s invitation, five of the six winners offered review papers on their research topics for consideration as publications in <i>Pure and Applied Chemistry (PAC)</i>. And the five refereed articles appear in this issue of <i>PAC</i>.<br /><br />Finally, it is an honor and a pleasure to congratulate each of the winners and their supervisors for winning the 2011 IUPAC Prize for Young Chemists. It is hoped that each of them will continue to contribute to a bright future for chemical sciences and technologies and to take active roles in IUPAC bodies in the future.<br /><br /><b>Jung-Il Jin</b><br />IUPAC Immediate Past President and Chair of the IUPAC Prize Selection Committee<br /><br /></div>

Light-emitting electrochemical cells (LECs) are solution-processable thin-film electroluminescent devices consisting of a luminescent material in an ionic environment. The simplest type of LEC is based on only one material, ionic transition-metal complexes (iTMCs). These materials are of interest for different scientific fields such as chemistry, physics, and technology as selected chemical modifications of iTMCs resulted in crucial breakthroughs for the performance of LECs. This short review highlights the different strategies used to design these compounds with the aim to enhance the performances of LECs.

In solution, half-cell potentials and ion solvation energies (or enthalpies) are measured relative to other values, thus establishing ladders of thermochemical values that are referenced to the potential of the standard hydrogen electrode (SHE) and the proton hydration energy (or enthalpy), respectively, which are both arbitrarily assigned a value of 0. In this focused review article, we describe three routes for obtaining absolute solution-phase half-cell potentials using ion nanocalorimetry, in which the energy resulting from electron capture (EC) by large hydrated ions in the gas phase are obtained from the number of water molecules lost from the reduced precursor cluster, which was developed by the Williams group at the University of California, Berkeley. Recent ion nanocalorimetry methods for investigating ion and electron hydration and for obtaining the absolute hydration enthalpy of the electron are discussed. From these methods, an absolute electrochemical scale and ion solvation scale can be established from experimental measurements without any models.

Semiconductor nanowires (NWs) represent a unique system for exploring phenomena at the nanoscale and are expected to play a critical role in future electronic, optoelectronic, and miniaturized biomedical devices. Modulation of the composition and geometry of nanostructures during growth could encode information or function, and realize novel applications beyond the conventional lithographical limits. This review focuses on the fundamental science aspects of the bottom-up paradigm, which are synthesis and physical property characterization of semiconductor NWs and NW heterostructures, as well as proof-of-concept device concept demonstrations, including solar energy conversion and intracellular probes. A new NW materials synthesis is discussed and, in particular, a new “nano-tectonic” approach is introduced that provides iterative control over the NW nucleation and growth for constructing 2D kinked NW superstructures. The use of radial and axial p -type/intrinsic/ n -type ( p - i - n ) silicon NW (Si-NW) building blocks for solar cells and nanoscale power source applications is then discussed. The critical benefits of such structures and recent results are described and critically analyzed, together with some of the diverse challenges and opportunities in the near future. Finally, results are presented on several new directions, which have recently been exploited in interfacing biological systems with NW devices.

As an outstanding member in the oxide nanowire family, ZnO nanowire is widely studied for its optical, semiconductive, and piezoelectric properties. PbZr x Ti 1– x O 3 (PZT), usually in the form of polycrystalline thin films, is known for its high piezoelectric coefficient and is an ideal material as actuator. In this review, we first briefly introduce the rational growth of ZnO and PZT nanowire arrays by seedless wet chemical methods. Utilizing the ordered ZnO nanowires grown on p -type substrates, we next present an array of single ZnO nanowire-based blue/near-UV light-emitting diodes (LEDs), including their fabrication process, electroluminescence (EL) spectra, and external quantum efficiency. Finally, we discuss the piezoelectric ZnO and PZT nanowire-enabled three-dimensionally integrated direct- and alternating-current nanogenerators, and their primary roles in self-powered nanosystems and for powering personal microelectronics.

Reaction intermediates define the chemical steps of transformation from substrates to products, and capture of intermediates along catalytic pathways remains one focal point in the studies of enzymatic mechanisms. Performing enzymatic reactions in protein single crystals has been shown to be very effective in trapping and identifying unstable intermediates. In this critical review, we provide several examples of in crystallo approaches to trap reactive oxidation intermediates, thereby allowing the studies of enzymatic oxidation mechanisms.

The use of standards for the measurement of photoluminescence quantum yields (QYs) in dilute solutions is reviewed. Only three standards can be considered well established. Another group of six standards has been investigated by several independent researchers. A large group of standards is frequently used in recent literature, but the validity of these is less certain. The needs for future development comprise: (i) confirmation of the validity of the QY values of many commonly used standard materials, preferably in the form of SI traceable standards; (ii) extension of the set of standard materials to the UV and near-IR spectral ranges; and (iii) good standards or robust protocols for the measurements of low QYs.

A large group of industrially important polymerization processes is carried out in dispersed systems. These processes differ with respect to their physical nature, mechanism of particle formation, particle morphology, size, charge, types of interparticle interactions, and many other aspects. Polymer dispersions, and polymers derived from polymerization in dispersed systems, are used in diverse areas such as paints, adhesives, microelectronics, medicine, cosmetics, biotechnology, and others. Frequently, the same names are used for different processes and products or different names are used for the same processes and products. The document contains a list of recommended terms and definitions necessary for the unambiguous description of processes, products, parameters, and characteristic features relevant to polymers in dispersed systems.