Iraffinity 1s ftir

A small volume of the gold nanoparticles suspension was lyophilized to remove the water from the sample. The dry powder was mixed with KCl (Sigma-Aldrich) and homogenized with a mortar and pestle. A very fine powder was used for the measurement. The analysis was performed using a Shimadzu Corp IRAffinity-1S FTIR with a frequency range of 4000–400 cm⁻¹ with 100 scans and a resolution of 4 cm⁻¹.

The electronic (UV–Vis) spectra of the neutral Mo₂ dimers [EE′–(ph)_n–EE′] were recorded on Shimadzu UV-3600 (UV–VIS–NIR) or Cary 600 spectrometer in the range of 300–800 nm. For the MV complexes [EE′–(ph)_n–EE′]⁺, to record the low-energy IVCT absorption, a Shimadzu IRAffinity-1s FTIR or Nicolet 6700 FTIR spectrophotometer was used. For those having the main part of the IVCT band extending to the IR region, the spectra were generated by combing the data obtained from the two instruments. All the spectroscopic measurements were conducted in DCM solution (5 × 10⁻⁴ mol L⁻¹) using quartz cell with light path length of 2 mm.

To identify the chemical bonds present in the material, Fourier-transform infrared spectroscopy (IRAffinity-1S-FTIR Shimadzu spectrophotometer, São Paulo, Brazil) was used. The specters were obtained in the range of 4000–400 cm⁻¹, with a resolution of 4 cm¹ (n = 3).

The free bromelain and bacterial cellulose membrane with and without bromelain were analysed using Fourier Transform Infrared Spectroscopy (FTIR) (Shimadzu, FTIR IRAffinity-1S, Kyoto, Japan) using transmittance modes. Membranes were kept in an oven at 30 °C, after drying they were ground. Approximately 2 mg of the sample was mixed with 300 mg of KBr to form the pellet. Spectra were obtained in the 4000 to 400 cm⁻¹ wavelength range after 64 scans, with a resolution of 4 cm⁻¹. The spectra were normalized and the vibration bands were associated with the main chemical groups.

The fluorescence measurements were performed on a Shimadzu RF-5301 PC fluorophotometer (Kyoto, Japan) and Microplate reader (BioTek, Winooski, VT, USA). A 1 cm path length quartz cuvette and 96-well microplates were used in the experiments. The widths of the excitation and emission slits of the fluorophotometer were set to 3.0 and 3.0 nm, respectively. The Fourier-transform infrared (FTIR) spectrum was recorded in the range of 400–4000 cm⁻¹ on KBr (FTIR IRAffinity-1s, Shimadzu, Japan). The pH measurements were performed by a PHS-25 pH meter (Shanghai INESA Scientific Instrument Co. Ltd., Shanghai, China). The UV–vis spectrum was recorded in the range of 200–1100 nm on a UV–vis spectrophotometer (Puxi Inc., Beijing, China). Zeta potential was measured by photon correlation spectroscopy using a Zetasizer (Nano-ZS90). A scanning electron microscopy (SEM) image was characterized by a Zeiss Merlin at 1.0 kV. The purified water was obtained from a SMART-N Heal Force Water Purification System (Shanghai Canrex Analytic Instrument Co., Ltd., Pudong, Shanghai, China). The nanoparticle surface charge was determined with a Malvern Zetasizer. The P element was determined by an inductively coupled plasma mass spectrometer (ELAN DRC-e, PerkinElmer, Concord, Ontario, Canada).