5 5 dimethyl 1 pyrroline

Water dispersions (1 mg/mL) of micro- and nanoparticles were obtained by either dissolving the microsized powders in water or by redispersing in water the nanoparticles at the right concentration after repeated centrifugation and washing steps to eliminate any EtOH content. Then the water suspensions were sonicated for 10 min to obtain a good dispersion. 100 μL of as prepared dispersion were mixed with 100 μL of 50 mM of DMPO (5,5-Dimethyl-1-pyrroline, Sigma Aldrich) in water and 1 μL of DTPA (Diethylenetriaminepentaacetic acid, Sigma Aldrich). The aqueous suspension was placed in an ultrasound bath and the ultrasonic irradiation (Frequency of 59 kHz, total intensity of about 1W m⁻²) was performed for 30 min, as described above. The temperature of the ultrasound bath was maintained at 20 °C. Further experiments were carried out by UV–vis light irradiation, as explained above in details. After the reaction time, 50 μL of the solution was transferred in a quartz capillary tube and the latter was placed in the Electron Paramagnetic Resonance (EPR) cavity of the spectrometer (EMX-Nano, Bruker). The magnetic field was set to a center field of 3423 G, sweep width of 100 G, sweep time of 160 s. The signal channel was set with a receiver gain of 60 dB, Mod. Amp. of 1 G and 15 number of scans.