IUPAC conventions

The average pore size of PS structures covers four orders of magnitude, from nanometers to tens of micrometers. The pore size, or more precisely the pore width d, is defined as the distance between two opposite walls of the pore. It so happens that the different size regimes of PS characterized by different pore morphologies and different formation mechanisms closely match the classification of porous media, as laid down in the IUPAC convention [Iu2]. Therefore the PS structures discussed in the next three chapters will be ordered according to the pore diameters as mostly microporous (d<2 nm), mostly mesoporous (2 nm50 rim). Note that the term nanoporous is sometimes used in the literature for the microporous size regime. 

The smallest pores that can be formed electrochemically in silicon have radii of < 1 nm and are therefore truly microporous. However, confinement effects proposed to be responsible for micropore formation extend well into the lower mesoporous regime and in addition are largely determined by skeleton size, not by pore size. Therefore the IUPAC convention of pore size will not be applied strictly and all PS properties that are dominated by quantum size effects, for example the optical properties, will be discussed in Chapter 7, independently of actual pore size. Furthermore, it is useful in some cases to compare the properties of different pore size regimes. Meso PS, for example, has roughly the same internal surface area as micro PS but shows only negligible confinement effects. It is therefore perfectly standard to decide whether observations at micro PS samples are surface-related or QC-related. As a result, a few properties of microporous silicon will be discussed in the section about mesoporous materials, and vice versa. Properties of PS common to all size regimes, e.g. growth rate, porosity or dissolution valence, will be discussed in this chapter. 

The potential/current signs in the IUPAC convention follows the criterium positive currents for processes occurring at positive potentials , and vice versa. The American convention still adopts the opposite criterium positive currents for processes occurring at negative potentials , and vice versa. Even if the present theoretical treatment follows the American convention (positive sign to reduction processes), in presenting cyclic voltammetric profiles the IUPAC recommendation will be adopted. 

Fig. 7.175. The IUPAC convention ascribes to the standard electrode potential the same sign as that experimentally observed when the electrode in question is connected to a cell with the SHE.

Figure 18.2—Measurement of pH. The concentration of H+ ions can be determined from the potential difference between the reference electrode and the glass electrode. Details of the membrane, which is permeable to the H1 ion, are shown. When an H+ ion forms a silanol bond, a sodium ion moves into the solution to preserve electroneutrality. A cross-section of the membrane showing this exchange reaction is presented (IUPAC conventions are not followed to improve clarity in the diagram). Prior to its use, the pH meter is calibrated with a buffer solution of known pH.

This is the usual convention in electroanalytical chemistry, though it is at variance with the more logical IUPAC convention [8],... 

Dienes and trienes are named according to the IUPAC convention by replacing the -ane ending of the alkane with -adiene or -atriene and locating the positions of the double bonds by number. The stereoisomers are identified as E or Z according to the rules established in Chapter 5. 

According to the latest IUPAC Convention the names of ligands surrounding the central metal atom are written in alphabetical order of preference irrespective of whether they are negative or neutral. For example, in the complex [Co(NH3)4 C1(N02)], the ligands are named in the order ammine, chloro and... 

Contrary to IUPAC conventions, chemical shifts 5 in this book are scaled in ppm in the spectra, thus enabling the reader to differentiate at all times between shift values (ppm) and coupling constants (Hz) ppm (parts per million) is in this case the ratio of two frequencies of different orders of magnitude, Hz / MHz = 1 106 without physical dimension... 

A double bond between two carbon atoms indicates the site, and possibly type, of hydrogen unsaturation. When double bonds are present, the suffix anoic is changed to enoic, dienoic, or trienoic to indicate the number of bonds. The location of the first carbon in the double bond is indicated by a number preceding the systemic name. Under International Union of Pure and Applied Chemistry (IUPAC) convention, stearic, oleic, linoleic, and linolenic acids are called octadecanoic, 9-octadecenoic, 9,12-octadecadienoic, and 9,12,15-octadecatrienoic acids, respectively. 

Figure 11. Charts of indan (8), tetralin (9) and o-dimethylbenzene (10) and numbering of heavy atoms (not using the IUPAC convention).

Consensus on nomenclature had been reached by the 1890s. Aniline was the parent of its derivatives, though sulfonic acids were considered derivatives of benzene, such as aminobenzenesulfonic acid. The prefix amino- was added to naphthalene and its derivatives. Many trivial names came into use, particularly for aminonaphthalenesulfonic acids, found in both academic and industrial research laboratories. Though IUPAC convention now numbers amino aryl compounds according to the parent hydrocarbon, the earlier system of numbering has often been retained, since some names include the positions of substituents at carbon atoms numbered according to the older systems. 

If the oxygen electrode is placed on the right and the hydrogen electrode on the left in Fig. 3, according to IUPAC convention, the electrode reactions must be written... 

Fig. 3 Electrochemical cell for the definition of cell voltage measurement according to the IUPAC convention [51].

To avoid the crowding of subsequent formulae by factors of 2, we define the self termination rates here by, for example, d[R]/ dt = —itR[R]2, deviating from the IUPAC convention. 

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