F 4700

Fluorescent and water-dispersible polymer nanospheres with uniform diameters can be used as probes to determine the effective pore size of membranes [47 (link)]. Monodispersed fluorescent PS microspheres are commercially available and the method to measure pore size using these microspheres has been established [48 ]. Standard PS fluorescent microspheres with a certain nominal diameter were diluted to 1 μg/mL with deionized water and thoroughly sonicated, and then filtered through the membrane. Subsequently, the fluorescence spectrum of the filtrate was obtained with a fluorescence spectrophotometer (Hitachi F-4700, Tokyo, Japan), and the peak intensity at the corresponding emission wavelength was used to quantify PS microspheres in solution. At a low concentration, the concentration of PS microspheres is directly proportional to the peak intensity at the emission wavelength. The observed solute retention rate (R) can be calculated using the following equation: $$R\left(\%\right)=\left(1-\frac{C_{\mathrm{p}}}{C_{\mathrm{f}}}\right)\times 100\%$$
where C_f and C_p are the concentrations of PS microspheres in feed and permeate, respectively.
All retention tests were conducted at room temperature and the feed solution has a pH of 7.0 ± 0.2. The results presented were average data from at least three samples of each membrane.

Fluorescence experiments were carried out by a spectrophotometer (F-4700, HITACHI, Japan) equipped with a quartz cuvette of 1 cm light path length. The excitation wavelength was 280 nm, while the emission wavelength was recorded from 290 to 490 nm. The slit widths of both excitation and emission were set at 5 nm, and the voltage was 360 V with the scan speed set at 12,000 nm/min [5 (link)].