Chemistry Reference
In-Depth Information
Fig. 4.5 Readouts for the porphyrin-functionalised holographic metal ion sensor. a, b The
shrinkage of the pHEMA-co-TACPP matrix due to Donnan osmotic pressure (dominant) and the
chelation effect at 24
°
C in citric acid-Na
2
HPO
4
buffers. c Blue Bragg shifts due to metal cation
chelation. The sensor displays a higher blue Bragg shifts for Cu
2+
and Fe
2+
cations than
monovalent and other divalent cations at 1.0 M. d Blue Bragg shifts as a function of Cu
2+
and Fe
2+
cation concentrations. Reproduced from Ref. [
1
] with permission from The Royal Society of
Chemistry
s response to Cu
2+
and Fe
2+
ions with 200 mM increments was mea-
sured over three trials (Fig.
4.5
d). The stability constant of the cavity of TACPP
with cations depends on the chelate effect (entropy) [
22
], macrocyclic effect [
23
],
geometrical factors [
24
], classi
The sensor
'
cation of donor atoms [
25
] and ionic radius [
26
].
For example, Cu
2+
ions have a greater capacity to bind to the cavity of TACPP than
other cations [
26
]. In terms of response time, for example, a variation in Cu
2+
ion
concentration from 0 to 200 mM, followed by the rinsing step, required
30 s to
*
equilibrate (
±
sub nm). The sensor response was reversible without hysteresis.
