2.5 Field Emission Scanning Electron Microscopy
Field emission scanning electron microscopy (FESEM) analysis was performed
with a HITACHI S-4800 instrument in a cryo-mode with secondary electron image
resolution of 1.0–1.4 nm at voltages of 1–15 kV. For all measurements, aqueous
solutions of nanogels with a concentration of 5 mg/mL were rapidly vitrified in
liquid propane and transferred to the high vacuum Balzers BF freeze-etching
chamber. Fracture surfaces were prepared by means of a lever and etched by
sublimation of the vitrified water for 5–15 min.
2.6 UV–Visible Spectrophotometer
UV–visible spectra were determined using a Varian Cary 100 Bio-UV-Visible splitbeam spectrophotometer running with Cary WinUV scan application with a capacity of measuring six samples at a time. Samples were scanned at 500 nm. A highintensity Xe flash lamp was used as the source for UV light, which permits taking
80 data per second.
2.7 Zeta Potential Measurements
Measurements were performed at 20
C as a function of pH in the range of 3–10 by
addition of 0.01 M HCl or 0.01 M NaOH using a Malvern Zetasizer Nano
ZS. Microgel solutions with a concentration of 5 mg/mL were dialyzed in standard
1 mM KCl solution and measured in disposable polystyrene cuvettes. One hundred
scans were made for each sample and the zeta potential was calculated using
Henry’s equation. Expert System software was used for data interpretation.
2.8 Dynamic Light Scattering
Microgel solutions of about 1 mg/mL in double-distilled water were passed through
a 5-μm poly(tetrafluoroethylene) membrane filter. The particle sizes were measured
by photon correlation spectroscopy performed at an angle θ ¼ 90
with a setup
consisting of an ALV-SP8 goniometer, an ALV-SIPC photomultiplier, a multiple τ
digital real-time ALV-7004 correlator, and a solid state laser (Koheras) with a
wavelength of 473 nm as the light source. Sample cuvettes were immersed in a
toluene bath and thermostatted within an error of Æ0.1
C. Autocorrelation functions (ACF) of intensity fluctuations g 2 (q, t) in the self-beating mode were
measured and expressed by the Siegert relation:
420
S. Singh et al.
Field emission scanning electron microscopy (FESEM) analysis was performed
with a HITACHI S-4800 instrument in a cryo-mode with secondary electron image
resolution of 1.0–1.4 nm at voltages of 1–15 kV. For all measurements, aqueous
solutions of nanogels with a concentration of 5 mg/mL were rapidly vitrified in
liquid propane and transferred to the high vacuum Balzers BF freeze-etching
chamber. Fracture surfaces were prepared by means of a lever and etched by
sublimation of the vitrified water for 5–15 min.
2.6 UV–Visible Spectrophotometer
UV–visible spectra were determined using a Varian Cary 100 Bio-UV-Visible splitbeam spectrophotometer running with Cary WinUV scan application with a capacity of measuring six samples at a time. Samples were scanned at 500 nm. A highintensity Xe flash lamp was used as the source for UV light, which permits taking
80 data per second.
2.7 Zeta Potential Measurements
Measurements were performed at 20
C as a function of pH in the range of 3–10 by
addition of 0.01 M HCl or 0.01 M NaOH using a Malvern Zetasizer Nano
ZS. Microgel solutions with a concentration of 5 mg/mL were dialyzed in standard
1 mM KCl solution and measured in disposable polystyrene cuvettes. One hundred
scans were made for each sample and the zeta potential was calculated using
Henry’s equation. Expert System software was used for data interpretation.
2.8 Dynamic Light Scattering
Microgel solutions of about 1 mg/mL in double-distilled water were passed through
a 5-μm poly(tetrafluoroethylene) membrane filter. The particle sizes were measured
by photon correlation spectroscopy performed at an angle θ ¼ 90
with a setup
consisting of an ALV-SP8 goniometer, an ALV-SIPC photomultiplier, a multiple τ
digital real-time ALV-7004 correlator, and a solid state laser (Koheras) with a
wavelength of 473 nm as the light source. Sample cuvettes were immersed in a
toluene bath and thermostatted within an error of Æ0.1
C. Autocorrelation functions (ACF) of intensity fluctuations g 2 (q, t) in the self-beating mode were
measured and expressed by the Siegert relation:
420
S. Singh et al.