Q vib B Band
2. Experimental 1 Materials
2.2 Instrumentation
1. UV–Vis absorption spectra were measured at room temperature on a Shimadzu UV-2550 spectrophotometer using a 1 cm pathlength cuvette in solution. A Perkin Elmer Lambda 950 UV-vis spectrophotometer was used for solid state spectra of the functionalised fibers.
2. Fluorescence emission and excitation spectra were obtained on a Varian Eclipse spectrofluorometer using a 1 cm pathlength quartz cuvette.
3. Fluorescence lifetimes were measured using a time correlated single photon counting (TCSPC) setup (FluoTime 300, Picoquant GmbH), Figure 2.1. The excitation source was a diode laser (LDH-P-670 driven by PDL 800-B, 670 nm, 20 MHz repetition rate, 44 ps pulse width, Pico quant GmbH). Fluorescence was detected under the magic angle with a peltier cooled photomultiplier tube (PMT) (PMA-C 192-N-M, Picoquant GmbH) and integrated electronics (PicoHarp 300E, Picoquant GmbH). A monochromator with a spectral width of 4 nm was used to select the required emission wavelength. The response function of the system, which was measured with a scattering Ludox solution (DuPont), had a full width at half-maximum (FWHM) of about 300 ns. The ratio of stop to start pulses was kept low (below 0.05) to ensure good statistics. The luminescence decay curve was measured at the maximum of the emission peak. The data was analyzed with the FluoFit Software program (Picoquant GmbH, Germany). The support plane approach was used to estimate the errors of the decay times.
32 Figure 2.1: Schematic diagram of a TCSPC setup.
(MCP)-PMT= (Multichannel plate detector)-Photomultiplier tube, PC= Personal computer
4. Elemental Analyses (CHNS) were done using a Vario-Elementar Microcube ELIII Series.
5. Energy dispersive X-ray spectroscopy (EDX) was done on an INCA PENTA FET coupled to the VAGA TESCAM using 20 kV accelerating voltage.
6. Dynamic light scattering (DLS) experiments were done on a Malvern Zetasizer Nanoseries, Nano-ZS90.
7. Mass spectral data were collected with a Bruker AutoFLEX III Smartbeam TOF/TOF Mass spectrometer operated in the positive mode using α-cyano-4-hydroxycinnamic acid as the MALDI matrix.
8. Transmission electron microscopy (TEM) images for the MNPs were obtained using a ZEISS LIBRA® TEM.
33 9. Scanning electron microscopy (SEM) images of the electrospun nanofibers were examined using a scanning electron microscope (JOEL JSM 840 scanning electron microscope) at an accelerating voltage of 20 kV.
10. Perkin Elmer TGA 7 Thermogravimetric analyser was used to study the thermal properties of the electrospun fibers under an inert nitrogen atmosphere flowing at 20 mL-1 heating at a rate of 10 oC min-1.
11. Nitrogen adsorption/desorption isotherms were carried out at 77 K using a Micrometrics ASAP 2020 Surface Area and Porosity Analyzer. Prior to each measurement, degasing was carried at 50 0C for 48 h per sample. The Brunauer–Emmett–Teller (BET) method was employed to determine surface area and porosity. The BET surface area and total pore volume were calculated from the isotherms obtained.
12. A Metrohm Swiss 827 pH meter was used for all pH measurements.
13. X-ray powder diffraction patterns were recorded on a Bruker D8 Discover equipped with a LynxEye detector, using CuKa radiation (A = 1.5405 A, nickel filter). Data were collected in the range from 20 = 5° to 100°, scanning at 1° min-1 with a filter time-constant of 2.5 s per step and a slit width of 6.0 mm. Samples were placed on a zero background silicon wafer slide. The X-ray diffraction data were treated using Eva (evaluation curve fitting) software.
Baseline correction was performed on each diffraction pattern.
14. Triplet quantum yields were determined using a laser flash photolysis system (Figure 2.2). EKSPLA NT342N-20-AW tunable wavelength laser with excitation pulses (3-5 ns) was used as the laser. The analysing beam source was from a Thermo Oriel Xenon arc lamp, and photomultiplier tube (a Kratos Lis Projekte MLIS-X3) was used as a detector. Signals were
34 recorded with a two-channel 300 MHz digital real time oscilloscope (Tektronix TDS 3032C) and the kinetic curves were averaged over 256 laser pulses.
Figure 2.2: Laser flash photolysis setup.
15. X-ray photoelectron spectroscopy (XPS) analysis was done using an AXIS Ultra DLD, with Al (monochromatic) anode equipped with a charge neutraliser, supplied by Kratos Analytical. The following parameters were used: the emission was 10 mA, the anode (HT) was 15 kV and the operating pressure below 5 x 10-9 torr. A hybrid lens was used and resolution to acquire scans was at 160 eV pass energy in slot mode. The centre used for the scans was at 520 eV with a width of 1205 eV, with steps at 1 eV and dwell time at 100 ms as reported before [134]. The high resolution scans were acquires using 80 eV pass energy in slot mode.
Monochromator Oscilloscope
Photomultiplier Tube (PMT) Ekspla Laser
Sample Xenon Lamp
35 16. The electrospun fibers were obtained from an electrospinning setup consisting of a high voltage source (Glassman High Voltage. Inc.m series, 0-40 kV), a pump (Kd Scientific, KDS-100-CE) and a plastic syringe equipped with a steel needle with diameter of a 0.60 mm, Figure 2.3. An aluminium foil was as a ground collector for the fibers.
Figure 2.3: Electrospinning setup.
17. Irradiations for singlet oxygen determination were conducted using a general electric quartz lamp (300W), 600 nm glass (Schott) and water filters were used to filter off ultraviolet and far infrared radiations respectively, Figure 2.4. An interference filter of 670 nm with a band of 40 nm was placed in the light path just before the cell containing the sample. The intensity of the light reaching the cell was measured with a POWER MAX 5100 (Molelectron Detector Incorporated) power meter.
Collector
High Voltage Source Plastic syringe equipped with steel needle
36 Figure 2.4: Schematic diagram of photochemical setup.
18. 1H nuclear magnetic resonance spectra were recorded on a Bruker AMX 400 MHz NMR spectrometer.
19. IR spectra were recorded on a Perkin-Rlmer Spectrum 100 ATR FT-IR spectrometer.
20. Photocatalysis of pollutants was carried out using the Modulight® Medical Laser system (ML) 7710-680 with cylindrical output channels, aiming beam, integrated calibration module, foot/hand switch pedal, fiber sensors (subminiature version A) connectors and safety interlocks. The system was equipped with a magnetic stirrer and using a sample holder with spot diameter of 5.5 cm. The instrument setup is shown in Figure 2.5.
37 Figure 2.5: Photodegradation laser setup.