U 5100 uv visible spectrophotometer

A crystal violet colorimetry method was used [24 (link)]. Briefly, cells were rinsed with PBS (Ca²⁺ Mg²⁺). Each well containing cells was covered with 400 µL of 0.1% (m/v) crystal violet diluted in pulsation buffer and incubated for 15 min under mild agitation. Subsequently, the cells were rinsed three times with PBS (Ca²⁺ Mg²⁺). Finally, the cells were incubated with 400 µL of 10% acetic acid diluted in water to obtain cell lysates. Fifty µL of cell lysate of each pulsation condition were diluted with 950 µL of water, and the optical density (OD) at 595 nm was measured by spectrophotometry (Hitachi’s U-5100 UV-Visible Spectrophotometer, Santa Clara, CA, USA). OD is proportional to the number of cells. Cell viability, expressed in percentage (%V), is given by the following formula: % V = (OD)/(OD _{(0 Volt)}) × 100.

Chlorophyll was extracted in 95% ethanol. Four leaf discs were punched with a 6 mm diameter puncher (having a total surface of 1.12 cm²) and placed in a vial with 5 mL ethanol. Vials were kept in the dark at 4°C in a refrigerator for 20 hours with occasional shaking. The amounts of Chl (a + b) and carotenoid were measured spectrophotometrically [16 ]. Another four leaf discs were extracted with 1% (w/v) HCl in methanol, and the anthocyanin contents were assayed spectrophotometrically. The relative amounts of anthocyanin were expressed by A₅₃₀ − 0.25A₆₅₇ [17 (link)]. Absorbance was measured with a Hitachi U-5100 UV-visible spectrophotometer.

The fluorescent intensity of PAH-Cu NCs was measured by using a Hitachi F-4500 Fluorescence spectrometer (Tokyo, Japan). The excitation and emission wavelengths were set at 360 and 450 nm, respectively. The slits were set at 10 nm. The UV-visible spectra of each material were measured using a Hitachi U-5100 UV-Visible spectrophotometer (Tokyo, Japan). The pH value of buffer was adjusted using a DKK-TOA pH meter HM-25R (Tokyo, Japan). The X-ray photoelectron spectroscopy (XPS) was determined by ULVAC-PHI PHI 5000 VersaProbe. The transmission electron microscopy (TEM) images of PAH-Cu NCs were obtained by using a JEOL JEM-2100 transmission electron microscopy at a voltage of 200 kV. Fourier transform infrared spectroscopy (FT-IR) spectra of PAH-Cu NCs were measured using a Perkin-Elmer system 2000.