Chemistry Reference
In-Depth Information
Fig. 3.1 Fabrication of holographic sensors through silver halide chemistry. a A glass slide was
functionalised with silane chemistry. b The monomer mixture was polymerised on the glass slide.
c The resulting system was rinsed with ethanol. d AgClO
4
solution was allowed to diffuse into the
pHEMA matrix. e The excess AgClO
4
solution was removed and the pHEMA matrix was dried.
f AgBr nanocrystals were formed in the pHEMA matrix. g The matrix was rinsed with DI water.
h The pHEMA matrix was exposed to a single pulse of a laser light at 5
. i The latent image sites
were developed to silver metal (Ag
0
). j The pHEMA matrix was neutralised. k Undeveloped AgBr
grains were removed from the pHEMA matrix using hypo. l The pHEMA matrix was rinsed with
ethanol solution in order to remove the cyanine dye from the matrix. Adapted from Ref. [
17
] with
permission from The Royal Society of Chemistry
°
3.2 Fabrication of Holographic pH Sensors Through
in Situ Size Reduction of Ag
0
NPs
Depending on its manufacturing technique, polymethyl (methacrylate) (PMMA)
may have comparable optical properties to glass [
22
,
23
]. PMMA was adapted as a
substrate to fabricate holographic sensors. PMMA manufactured through casting
was used since these substrates did not have birefringence and this was a
requirement in Denisyuk re
ection holography. Using an O
2
plasma cleaner, the
substrates were treated under a vacuum of 1 torr for 3 min to render the PMMA
surface hydrophilic. On these substrates, pHEMA matrices were synthesised by free
radical polymerisation (Fig.
3.2
a). AgNO
3
(1 M, 200
fl
l) dissolved in DI water was
pipetted as an elongated blob onto a glass sheet. pHEMA matrix side down, the
slide was placed on the elongated blob and the slide was incubated in situ for 3 min
to allow diffusion of AgNO
3
into the pHEMA matrix (Fig.
3.2
b). The sample was
dried under a tepid air current for 10 s. The pHEMA matrix was immersed in a
µ
