Currently the detection of toxic ions in wastewater streams is carried out using bulky and expensive techniques, which require long periods to acquire test results and are unable to be adapted to produce an in situ and portable sensor for field application.
This project involves the development of an in situ sensor, which uses calix[ 4]arene derivatives within a supported liquid membrane to detect a range of metals ions found in wastewater streams.
Calix[ 4]arene derivatives with functionalities were synthesised via dialkylation
of p-tert-butylcalix[ 4]arene, to investigate their ability to carry out facilitated transfer of metal ions (e.g. Cu2 + and Ag+) and anions (e.g. phosphates) from an aqueous to an organic phase.
Analysis of the attempted transfer using UVNis spectroscopy showed that
calix[ 4]arenes without any functionality were only able to transfer alkali metal ions. Of the calix[4]arene derivatives, bipyridyl showed complexation of Cu2
+ ions. Liquid /liquid cyclic voltammetry studies showed that of all the calix[ 4]arene derivatives, only the p-tert-butyl calix[ 4 ]arene thioether 39 was able to carry out a facilitated transfer and this was for the Ag+ ion.
Calix[ 4]arenes bearing p-thioalkyl groups (butyl, hexyl and undecyl) were also
synthesised by direct acylation of the para position with bromoalkyl groups followed by silane reduction and conversion of the bromines to thiols or thioacetates, to study as self assembled monolayers on a gold surface.
Cyclic voltammetry, QCM and SNIFTIRS were used to study the formation of
self assembled monolayers on polycrystalline gold, and their interaction with Ag+ and Cu2+ ions.
Evidence for the loss of the monolayers and formation of calixarene micelles in
the presence of Ag+ was also believed to occur. Reductive desorption studies, indicated the stability of Cu2+/Calix monolayers, whereas the presence of Ag+ ions results in the cleavage of the S-Au bonds.
SNIFTIRS analysis of the calix[4]arene monolayers also indicated that in the
presence of Ag+ ions the monolayers, with the hydrated shell around the Ag+ ion initially masking the hydroxyl groups before being expelled from the monolayer structure as the potential was increased.