2.4. Characterization
TEM images were obtained using a JEOL 2010 equipped with an
analytical pole piece. The images were acquired at an accelerating voltage
of 200 kV and captured using a Gatan Image Filter, model 678. The
images acquired were “zero loss” images using a10 eV energy slit.
Samples were ultra - sonicated in absolute ethanol for 20 minutes and
then disper sed on 100 mesh copper grids with continuous carbon
suppor t films. Measurement s were carried out on the images using the
MeasureIT v5.0 software package (Olympus Soft Imaging Solutions). The
EDX spectra on the TEM were obtained using a Noran Instrument s,
Pioneer SiLi 30 mm 2 detector with a Moxtek ultra - thin window.
Infrared spectra were recorded using a Matson Polaris FTIR
spectrophotome te r equipped with room temperature DTGS detector and
running WinFirst spectroscopy software. IR spectra of nano- particles
were collected in transmis sion mode by pressing the particle sample with
KBr or KI powder to form pellets. A resolution of 2 cm - 1 and a total of 96
scans were collected for each IR spectrum .
TGA curves were collected with a Mettler Toledo TGA/SDTA851e
thermal analysis system with a temperature ramp of 5 oC per minute. The system was purged with nitrogen using a flow rate of 50 mL per minute.
Raman spectra were obtained using an inVia confocal microscope
system (Renishaw, Gloucester shire, UK) with 785nm excitation from a
diode laser through a x20 (0.4 NA) objective. To avoid the effect of high
laser power, all the Raman spectra were collected using 0.35 mW of laser
power. Laser powers between 0.35 and 8.85 mW were used to study the
effect of irradiation of the MNPs. All laser powers were measured at the
sample using a NOVA (Ophir Optronics, Israel) laser power meter fitted
with a PD300- 3W head. The ND filter was removed for low power
measurement s A coaxial backscatter geomet ry was employed for signal
collection. Samples were compacted into a 1mm cavity held on an
anodized aluminum plate. Spectra were collected over the range 3200 to
100 cm- 1 and averaged over 10 scans, each with an exposure time of 10
seconds. Five spectra were co- added to further reduce noise. The Raman
shifts were calibrated using the 520 cm - 1 line of a silicon wafer. The
spectral resolution was ~1 cm - 1. Data manipulation was carried out
using Grams AI software.