Physical Chemistry

Physical Chemistry

Gold has been treasured throughout history partly because of its great chemical stability. Resistant to attack by oxygen, which rusts or tarnishes other metals, gold remains bright and beautiful under ordinary environmental conditions for centuries. Gold, however, does oxidize, forming Au2O3, when exposed to environments containing a highly reactive form of oxygen—e.g., atomic oxygen or ozone. Hans-Gerd Boyen of the University of Ulm, Ger., led a German-Swiss team that announced the discovery of a more oxidation-resistant form of gold. The material, called Au55, consists of gold nanoparticles; each nanoparticle is a tiny cluster comprising exactly 55 gold atoms and measuring about 1.4 nm (nanometres). Boyen's group reported that Au55 resisted corrosion under conditions that corroded bulk gold and gold nanoparticles consisting of either larger or smaller numbers of atoms. The researchers speculated that the chemical stability is conferred by special properties of the cluster's 55-atom structure and that Au55 may be useful as a catalyst for reactions that convert carbon monoxide to carbon dioxide.

 

Incandescent tungsten-filament light bulbs, the world's main source of artificial light, are noted for inefficiency. About 95% of the electricity flowing through an incandescent bulb is transformed into unwanted heat rather than the desired entity, light. In some homes and large offices illuminated by many lights, the energy waste multiplies when additional electricity must be used for air conditioning to remove the unwanted heat from electric lighting.

Shawn Lin and Jim Fleming of Sandia National Laboratories, Albuquerque, N.M., developed a microscopic tungsten structure that, if it could be incorporated into a filament, might improve a lightbulb's efficiency. The new material consists of tungsten fabricated to have an artificial micrometer-scale crystalline pattern, called a photonic lattice, that traps infrared energy—radiant heat—emitted by the electrically excited tungsten atoms and converts it into frequencies of visible light, to which the lattice is transparent. The artificial lattice, in effect, repartitions the excitation energy between heat and visible light, favouring the latter. Lin and Fleming believed that the tungsten material could eventually raise the efficiency of incandescent bulbs to more than 60%.