Uv 2450 2550

CS, GA-CS and GA-g-CS powder were dissolved in acetic acid solution (1%, v/v) at a concentration of 1 mg/mL individually. Then, the samples were subjected to full-wavelength scanning from 200 to 600 nm using a UV-visible (UV-Vis) spectrophotometer (UV-2450/2550, Shimadzu, Kyoto, Japan).
The powdered samples were subjected to Fourier transform infrared spectroscopy (FT-IR) (Nicolet iS50, Madison, WI) (128 scans, 10 kHz, 500–4000 cm⁻¹⁾. The ambient gas was air. The grafting situation of GA and CS was determined by bond analysis.

The characteristic absorption peaks of 7-HT are at 330 and 392 nm in the medium and that of pyoverdine is 405 nm in liquid MKB. The characteristic peaks of the siderophores were identified according to their UV/visible spectra (UV-2450/2550; Shimadzu; Kyoto, Japanese), measuring the absorption spectra of the filtered supernatants of 24 h MKB cultures (normalized to an OD₆₀₀ = 0.5) every 0.5 nm.
The siderophore yield was determined using the following method. Siderophores secreted by bacteria were detected semi-quantitatively using CAS detection solution. A 24 h MKB culture (optical density at 600 nm (OD₆₀₀) adjusted to 1.0) was compared with double-distilled water (ddH₂O), and the appropriately diluted supernatant was mixed with an equal volume of CAS assay solution. The absorbances at 630 nm of the sample (As) and blank control (Ar) were determined after 1 h of light-proof reaction. The siderophore unit was calculated according to the formula (Ar − As) × 100/Ar% iron content unit [38 (link)]. Estimation of pyoverdine production in liquid MKB medium (emitted at 460 nm after 405 nm excitation) was carried out using a fluorescence spectrometer [56 (link)].

Ten milligrams of graphene oxide was dispersed into ten millilitres of water by sonication for 1 h to achieve a uniform graphene oxide solution. Then, 50 mg of hemin, 10 mL of water, 500 µL of ammonia hydroxide, and 30 µL of hydrazine hydrate were added to the system. The mixture was vortexed for 10 min before incubation at 60 °C for 4 h, which was followed by centrifugation at 16,000× g for 45 min. The supernatant was removed, and the pellet was washed twice, each time with 20 mL of water. The product was resuspended into 10 mL of water and stored in the dark at 4 °C. The conjugation of hemin onto the reduced graphene oxide was confirmed by atomic force microscopy (AFM, Agilent 5500), ultraviolet (UV-2450/2550, Shimadzu, Japan), and infrared (FT-IR, PerkinElmer Spectrum Two, Wellesley, MA, United States) absorption spectroscopy, as well as X-ray photoelectron spectroscopy (XPS, ESCALAB 250Xi spectrometer).