Thursday, June 6, 2013

Silicene: a honeycombed, atom-thick sheet of silicon named to recall similarly structured graphene

Silicene sheets can be epitaxially grown on a close-packed silver surface, Ag(111), via silicon atomic flux under ultrahigh vacuum conditions [1]. The condensed atoms arrange themselves within a two-dimensional honycomb lattice, geometrically resembling the structure of carbon atoms in graphene sheets. Chemists like to indicate structural and functional similarity of compounds in the ending of their names:  hence, the name silicene, which rhymes with graphene.

Equal or similar topology, however, does not necessarily imply property similarity. So far, many silicene properties have been predicted rather than measured, since the graphen-like form of silicon proves hard to handle [2].  Whereas graphene is very stable, silicene is reacting with other molecules and materials in its neighborhood. Silicene sheets also show a tendency to crinkle. Yet, the interest in silicene, its properties and potential applications is rapidly growing [3-5].

And to continue with the analogy of chemical elements of the carbon group (Group IV or Group 14), germanene—the planar, hexagonal germanium allotrope—could then be the next thin sheet.   

The CurlySMILES notation for silicene is [Si]{alall=silicene}, in which the square bracket code (SQC) for silicon is annotated with al for atomic layer and all for allotrope. The analogous linear notation for graphene and germanene are [C]{alall=graphene} and [Ge]{alall=germanene}, respectively.

Keywords: inorganic chemistry, material science, nanotechnology, epitaxy, spontaneous organization, honeycomb lattice, allotropes.

References and more to explore
[1] B. Lalmi et al.: Epitaxial growth of a silicene sheet. Appl. Phys. Lett. 2010, 97, pp. 223109-223110. doi: 10.1063/1.3524215.
[2] G. Brumfiel: Sticky problems snares wonder material. Nature March 14, 2013, 495, pp. 152-153. doi: 10.1038/495152a.
[3] B. Feng et al.: Evidence of Silicene in Honeycomb Structures of Silicon on Ag(111). Nano Lett. 2012, 12 (3), pp. 3507-3511. doi: 10.1021/nl301047g.
[4] Z. Ni et al.: Tunable Bandgap in Silicene and Germanene. Nano Lett. 2012, 12 (1), pp. 113-118. doi:
[5] Foresight Institute: Silicene: silicon's answer to graphene [].

Saturday, June 1, 2013

Translating the names of chemical compounds and compound classes

Chemists are typically not trained as translators. The latter, on the other hand, often do not have a background in chemistry and materials science. The translation of chemical compound and class names can easily turn into a non-trivial task.

In some cases translation is a simple matter of dictionary knowledge and look-up. For example, the names of the so-called “standard amino acids, ” a set of  α-amino acids, display overall name consistency across languages (one-word names with the exceptions of aspartic acid and glutamic acid [1]): for a given molecular structure the linguistic root of an amino acid name is recognizable—language-specific names are just spelled differently based on language character. As “trivial names ” they have not been derived by employment of a nomenclature scheme.

Generally, for complex chemical structures and nanoscale architectures, it can be a challenge to correctly translate a chemical compound name or chemical class name, which commonly is constructed from prefixes, suffixes, locants and (sub)structure (functional group) names. Bernardo Herold emphasizes a basic two-step approach, to which one should adhere, when translating a chemical term from English into a target language (or vice versa) [2]:
  1. Establish the required rules of nomenclature in the target language.
  2. Translate a name based on the vocabulary and rules of the target language.
Language-specific spelling is the main reason why composed chemical names cannot always be translated successively name-part by name-part. In particular, the spelling of the names of certain chemical groups varies between languages, giving rise to different alphabetical ordering—for example, phenyl in English and German becomes phényle in French, fenyl in Dutch and fenil in Italian, Portuguese and Spanish. Herold demonstrates how the English-language name 3-methyl-5-phenylpyridine is correctly translated—according to IUPAC rules—into the Romanic-language name 3-fenil-5-metilpiridina [2].

In addition to language-adjusted nomenclature application, the understanding of the language-specific grammar is important. It determines features such as word order and word concatenation: potassium bromide in English is Kaliumbromid (one word) in German and  bromuro de potasio  (change of word order and insertion of preposition) in Spanish.  

Chemical nomenclature books are available in several languages [3].

Keywords: multilingual collaboration, linguistics, chemical terminology, IUPAC naming, disambiguation.

References and more to explore
[1] Latintos: Amino acids in English, French, German, Italian, Portuguese and Spanish [].
[2] Bernardo Herold: Why Translate Nomenclature? Chemistry International May-June 2013, 35 (3), pp. 12-15 [].
[3] International Union of Pure and Applied Chemistry - Nomenclature Books: