Pixis 100 ccd

Optical density measurements were collected from the above solutions
using a UV-2700 Shimadzu spectrometer. Spectra were collected over
the 300–800 nm wavelength range in 1.0 nm increments. All spectra
were measured with a 1 mm path length quartz cuvette. Photoluminscence
(PL) and PL excitation (PLE) spectra were collected using a Horiba
Fluoromax-4 spectrometer in a right-angle geometry. In PL measurements,
the excitation wavelength was set to 375 nm, and the PL intensity
was collected in the 350–800 nm range in 1 nm increments, with
excitation and emission slit widths set to 1 nm bandpass. For PLE
measurements, the fixed emission wavelength was set to 680 nm, and
the excitation wavelength was scanned from 300 to 800 nm in 1 nm increments,
with excitation and emission slit widths set to 2 nm bandpass. For
quantitative quenching measurements, samples were excited with a 375
nm pulsed picosecond diode laser (BDS-SM series, Becker & Hickl,
GmbH), and PL spectra were collected using a Pixis 100 CCD (Princeton
Instruments) mounted on a monochromator (Acton Spectra Pro 2300, Princeton
Instruments).

To collect UV–vis
and PL spectra, a small portion of the hydrogel was sandwiched between
standard microscope slides, with the edges sealed by Kapton tape.
UV–vis spectra were collected with a 1 nm bandpass with a wavelength
increment of 1 nm. PL spectra were collected in front-face detection
under laser excitaiton (NKT). PL signal was collected using a Pixis
100 CCD (Princeton Instruments) mounted on a monochromator (Princeton
Instruments).
TRPL and time-resolved anisotropy measurements
were collected using time-correlated single photon counting on a home-built
instrument which has been described previously.^{18 (link)} Samples were prepared as described above for steady-state
measurements. TRPL measurements were taken at 5 different locations
on the sample. For each sample, measurement time was varied to achieve
∼10,000 counts in the main channel. At each position, 10 measurements
were collected and averaged. All samples were excited at 450 nm, with
emission collected at 675 nm. Deconvolution and fluorescence lifetime
analysis were performed in MATLAB using the DecayFit toolbox.