Quartz cell

In this work, the UV–VIS absorption spectra of the synthesized Cu@Pt nanoparticles were obtained from a spectrophotometer Cary E 5000 in the range of 300–800 nm using a quartz cell with 10 mm of optical path length (Agilent, USA). FTIR spectra of the samples were measured using Perkin-Elmer Spectrum 1000, in attenuated total reflection mode, and using the spectral range of 4000–380 cm⁻¹. The study also used one instrument in the diffuse reflectance mode at the resolution of 4 cm⁻¹ in KBr pellets (Perkin Elmer, USA). The obtained Cu@Pt nanoparticles were characterized using an Atomic Force Microscope (Agilent, USA). The size and morphology of the synthesized Cu@Pt nanoparticles were characterized using a Transmission Electron Microscope JEOL JEM 1200 EXII, operating at 200 kV. Moreover, we used a Scanning Electron Microscope (HR SEM) Helios NanoLab 660 (FEI). SEM imaging was performed in the immersion mode (Thermo Fisher Scientific, USA).

About 2 mL of liquid sample was withdrawn hourly using a disposable hypodermic
needle (25G × 1”, Terumo Corporation, USA) attached to a sterile disposable
syringe (3 mL, Nipro Medical Corporation, USA) and deposited in a quartz cell
(Agilent Technologies, USA). The optical densities of the samples were measured
at 600 nm using a double-beam UV/Vis spectrophotometer (Agilent Technologies,
Carry, USA). The concentration of acetate in the liquid sample was determined by
a high-performance liquid chromatography (HPLC) (1260 Infinity I, Agilent
Technologies, USA) equipped with Aminex HPX-87 H column and G7165A multiple
wavelength detector (190-240 nm). About 5 mM of H₂SO₄solution at 0.5 mL/min was used as the mobile phase. The column oven was set at
60°C. The liquid samples were centrifuged at 20 g for 5 minutes before analysis.
Acetate was calibrated using standard solutions at 0.01, 0.05, 0.1, 0.25, 0.5,
and 0.75 mM. Two additional methods were used to confirm the presence of
acetate: gas chromatography (GC) (PerkinElmer Clarus 580, USA) and 500 MHz
proton nuclear magnetic resonance (NMR) spectroscopy (Bruker, USA). A control
sample with minimal medium and no inoculum was also tested with all 3 methods to
confirm our detection and measurement of acetate.