Species at Ag Electrodes

Cationic species which have been observed with SERS are listed in Table VIII. Early references for SERS investigations of pyridinium, tetraalkylam- 

TABLE VII. Anions Whose SERS Has Been Observed on Ag Electrodes  

Tetramethylammonium, tetraethylammonium, and tetrabutylammonium N- Methylpy ridinium Cetylpyridinium i so, 151) 

In the pyridinium/pyridine system, we have found that a ratio of band intensities for bands characteristic of the conjugate acid and base can be used to estimate changes in pH at the surface (assumed to be the outer Helmholtz plane). The SERS results show that, as expected, increased specific adsorption of Cr lowers the pH in the double layer. Surfactants with pyridinium and other cationic head groups have also been observed to give SERS. The SERS of cetylpyridinium (C16H33 alkyl chain) and cetylquinolinium ions on Ag and Au colloids and of cetylpyridinium and cetyltrimethylammonium on an Ag electrode have been observed.  

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