Hydrophobic aliphatic thiols

Thiol-derivatized gold clusters are materials stable for months in air at room temperature which can be handled like simple chemical compounds. They have a hydrophobic nature and consequently are very soluble in aliphatic and aromatic hydrocarbons (e.g., heptane, cyclohexane, benzene), chlorine solvents (e.g., chloroform, carbon tetrachloride, dichloroethane), and ethers (e.g., diethyl... 

Sudan 1 dye was extracted from chilli powder and detected using Au NPs in concentration as low as 48 ng in 1 g of powder (Cheung et al. 2010). Recently, Jahn and co-workers employed enzymatically generated Ag NPs prepared by a bottom-up and self-organizing procedure (see Sect. 3.4.2.1), in combination with a lipophilic sensor layer for the detection of water-insoluble azo-dye Sudan III in real food matrix, paprika products (Jahn et al. 2015). The surface modification consisted of self-assembled aliphatic hydrocarbons with a thiol moiety forming hydrophobic monolayer on the SERS substrate. The resulting layer repelled unwanted water-soluble analytes from the surface whereas water-insoluble ones were adsorbed and detected by SERS. The riboflavin was introduced as a water-soluble competitor, which is part of the relevant food matrices. Sudan 111 dye was detected down to 9 pmol 1 concentration from paprika powder extract in the methanol. Beside this, lipophilic sensor layer can also be applied for further analytical tasks for which it is beneficial to discriminate water-soluble from insoluble substances. 

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