Volume 76, Issue 12

Semiconductor nanowires (NWs)represent an ideal system for investigating low-dimensional physics and are expected to play an important role as both interconnects and functional device elements in nanoscale electronic and optoelectronic devices. Here we review a series of key advances defining a new paradigm of bottom-up assembling integrated nanosystems using semiconductor NW building blocks. We first introduce a general approach for the synthesis of a broad range of semiconductor NWs with precisely controlled chemical composition, physical dimension, and electronic, optical properties using a metal cluster-catalyzed vapor-liquid-solid growth mechanism. Subsequently, we describe rational strategies for the hierarchical assembly of NW building blocks into functional devices and complex architectures based on electric field or micro-fluidic flow. Next, we discuss a variety of new nanoscale electronic device concepts including crossed NW p-n diode and crossed NW field effect transistors (FETs). Reproducible assembly of these scalable crossed NW device elements enables a catalog of integrated structures, including logic gates and computational circuits. Lastly, we describe a wide range of photonic and optoelectronic devices, including nanoscale light-emitting diodes (nanoLEDs), multicolor LED arrays, integrated nanoLED-nanoFET arrays, single nanowire waveguide, and single nanowire nanolaser. The potential application of these nanoscale light sources for chemical and biological analyses is discussed.

The last decade has seen rapid expansion and development in the field of density functional theory (DFT) simulation on the complex chemical processes that occur at surfaces and interfaces. The understanding of the phenomena in surface science and heterogeneous catalysis has benefited tremendously from these quantum mechanic calculations. This article reviews current progress in the theory of reactions on surfaces, in particular, those relevant to the barrier and the active site of surface reactions. Two representative reactions, namely, NO dissociation and CO oxidation, are selected to illustrate how these theoretical concepts are applied to understand catalytic reactions. Here, the pathways and energetics of these reactions under various catalytic conditions are described in detail, and the understanding of the reactions is generalized. It is concluded that DFT-based methods can be well applied to catalysis to understand the electronic structure of chemical processes and to elucidate mechanisms of complex surface reactions.

The theory that RNA molecules played a pivotal role in the early evolution of life is now widely accepted. Studies related to this hypothetical “RNA world” include three major areas: the formation of precursors for the first RNA molecules, the polymerization process, and the potential of RNA to catalyze chemical and biochemical reactions. Several chemical and biochemical studies performed under simulated prebiotic conditions support the role of RNA as both genetic as well as catalytic material. However, owing to the lack of credible mechanism for de novo nucleic acid synthesis and the hydrolytic instability of RNA molecules, there has been some serious discussion of whether biopolymers that closely resembled nucleic acid preceded the “RNA world”. In this context, an overview of prebiotic chemistry, the role of mineral surface, and the significance of studies related to RNA-like polymers in the origin of life are presented here.

A joint IUPAC-IUPAP Working Party (JWP) confirmed the discovery of element number 111. In accord with IUPAC procedures, the discoverers proposed a name and symbol for the element. The Inorganic Chemistry Division recommended this proposal for acceptance, and it was adopted by IUPAC on 1 November 2004. The recommended name is roentgenium with symbol Rg.

This document updates the first version of the IUPAC technical report on “Chemical actinometers” published in Pure Appl. Chem . 61 ,187-210 (1989). Since then, some methods have been improved, procedures have been modified, and new substances have been proposed as chemical actinometers. An actinometer is a chemical system or a physical device by which the number of photons in a beam absorbed into the defined space of a chemical reactor can be determined integrally or per time. This compilation includes chemical actinometers for the gas, solid, microheterogeneous, and liquid phases, as well as for the use with pulsed lasers for the measurement of transient absorbances, including the quantum yield of phototransformation, as well as the literature for each of the actinometers. The actinometers listed are for the use in the wavelength range from the UV to the red region of the spectrum. A set of recommended standard procedures is also given. Advantages and disadvantages are discussed regarding the use of chemical actinometers vs. electronic devices for the measurement of the number of photons absorbed. Procedures for the absolute measurement of incident photon flux by means of photodiodes are also discussed.

This document provides an inventory of theoretical and methodological concepts in electrochemistry at the interface between two immiscible electrolyte solutions (ITIES). Definitions of basic relationships are given, together with recommendations for the preferred symbols, terminology, and nomenclature. Methods of study of ITIES are briefly described, current experimental problems are indicated, and representative experimental data are shown. The practical applications of electrochemistry at ITIES are summarized.