Multichannel Sensors Based on Biphenyl and Cyclohexane Conformational Changes - Designing Receptors for the Next Generation of Biosensors - page 8

Fig. 6 (From left to right )
CVs of a 2.0 mM 4 + 4 times
excess of Zn 2+ solution in
0.10 M Bu 4 NPF 6 /MeCN.
A 2.0 mM 4 + 4 times excess
of Cd solution in 0.10 M
Bu 4 NPF 6 /MeCN. A 2.0 mM
5 + 4 times excess of Zn 2+
solution in 0.10 M Bu 4 NPF 6 /
MeCN. A 2.0 mM 5 +4
times excess of Cd 2+ solution
in 0.10 M Bu 4 NPF 6 /MeCN.
Potential scan rate of
100 mV/s
ionic mercury salts, such as Hg(ClO 4 ) 2 , give rise to fluorescence quenching,
whereas covalent derivatives, such as Hg(CN) 2 , enhance fluorescence (Fig. 8 ).
These results are related to the different types of interactions between host and
guest. Hence, ionic salts place their cations inside the crown cavity, whereas covalent
mercury compounds probably interact with the external diamine groups [ 21 ].
Compounds 8 and 9, with related structures yet of different sizes and binding
atoms, behave as double channel sensors for some transition metal cations (Zn 2+ and
Cd 2+ ). Thus, these compounds give rise to fluorescence quenching in the presence of
transition metal cations due to their coordination inside the coronand cavity.