2.2. ENR coating
A 10% wt/v ENR solution (LENR) was prepared by stirring
the ENR-50 (supplied by Zarm Scientific & Supplies (M)
Sdn. Bhd.) in toluene (purchased from Sigma Aldrich (M)
Sdn. Bhd.) until the ENR-50 was fully dissolved. The raw
OPA particles were mixed and stirred using a mechanical
stirrer for one hour at room temperature and then transferred
to an Elma ultrasonic vibrator (model Transsonic
Digital S) for another 30 minutes to ensure that the OPA
particles were optimally coated by ENR. The LENR-coated
OPA was filtered and dried in an oven at 60 C until constant
weight was obtained.
2.3. Characterization of LENR-coated OPA
Fourier Transform Infrared spectroscopy (FTIR) was
used to obtain qualitative information on the functional
groups and chemical characteristics of the raw OPA and
the LENR-coated OPA. Before being subjected to FTIR,
potassium bromide (KBr) and OPA were ground to form a
pellet, which was then used to obtain the infrared spectra
of OPA; where KBr is an inert, infrared transparent material,
and acts as a support for the OPA. FTIR spectra were
obtained and recorded in transmission mode using a
Perkin Elmer Spectrometer (Massachusetts, USA) in the
range of 450 cm1 to 4000 cm1 at a resolution of 4 cm1.
For each spectrum, 16 scans were co-added. The LENRcoated
OPA was characterised in the same manner as the
raw OPA.