Chemistry Reference
In-Depth Information
swelling behaviour as a function of complexation in the presence of
≤
30 mM metal
ions exhibiting
200 nm of Bragg peak shift within 30 s, showing its potential to be
used in the quanti
≤
cation of electrolytes in biological samples. However, the
selectivity of the other crown ether derivatives was shown to be limited. Another
study demonstrated that a holographic sensor based on copolymers of acrylamide
with ionogen comonomers was sensitive to Pb
2+
and Co
2+
ions (10
−
5
M), whereas
the sensor
s sensitivity to Mn
2+
and Sr
2+
ions was two orders of magnitude lower
[
8
]. Additionally, the response to alkali metal ions (Na
+
,K
+
) was an order of
magnitude lower than Pb
2+
ions. Further studies in holographic sensing with
chelating agents investigated incorporation of a methacrylated analogue of imino-
diacetic acid (IDA), which was copolymerised with 2-hydroxyethyl methacrylate
(HEMA) to form a sensor for the detection of divalent metal ions such as Ca
2+
,
Mg
2+
,Ni
2+
,Co
2+
and Zn
2+
[
9
]. Sensors containing >10 mol% chelating monomer
and 6 mol% crosslinker shifted the Bragg peak by 46.3 nm within 30 s at an ion
concentration of 0
'
40 mM. The relative selectivity of the holograms had a hier-
archy of Ni
2+
>Zn
2+
>Co
2+
>Ca
2+
>Mg
2+
ions. The real-time reversible response
of the sensor was demonstrated in monitoring Ca
+
ion ef
−
fl
ux during the early stages
of germination of Bacillus megaterium spores [
9
].
4.1 Fabrication of Holographic Metal Ion Sensors
via Photopolymerisation
Porphyrins have a versatile nature in coordination with the analytes and synthetic
modularity [
10
]. They have been used in organic solar cells [
11
], non-linear optics
[
12
], catalysis [
13
] and odour visualisation [
14
]. In the present study, a porphyrin
derivative was used as a dye pigment in the fabrication of the holographic sensor. To
achieve homogenous solubility, these molecules have been further modi
ed with
acrylate groups to serve as a crosslinker as well as laser-light interactive pigments.
Tetra carboxyphenyl porphyrin (TACPP) 1 was synthesised as reported previously
[
15
], and it was further condensed with 3-(4-hydroxy-phenoxy)propyl acrylate to
obtain the desired product (Fig.
4.1
). p-Carboxybenzaldehyde (4.00 g, 26.5 mmol)
was mixed in propanoic acid (
200 mL) in a round-bottom
fl
ask
fitted with a
*
condenser. The reaction mixture was heated under re
ux for 1 h followed by the
successive dropwise addition of pyrrole (1.9 mL, 26.5 mmol) via a syringe. The
resultant dark mixture was re
fl
fl
uxed with continued stirring for
∼
3 h under a constant
fl
filtration and
washed with warm dichloromethane (DCM) followed by a small amount of cold
methanol. The
flow of air. The product was separated from the reaction mixture by hot
ed by recrystal-
lisation frommethanol/DCM (50:50, v/v), desired product 1 was obtained as a purple
solid (Fig.
4.1
). Yield: 1.5 g, 28 %.
1
HNMR (500 MHz, DMSO):
filtrate was collected, dried under vacuum and puri
ʴ
-2.94 (s, 2H, NH),
7.30
-CH), and
13.32 (s, 4H, COOH). FT-IR (cm
−
1
): 3435, 3061, 1685, 1600, 1285, 782. TACPP 1
−
7.32(m, 8H, ArH). 8.37
−
8.41 (m, 8H, ArH), 8.65 (s, 8H, pyrrolic-
ʲ
