T70 t80 series uv vis spectrophotometer

UV–Visible
spectroscopy measurements were conducted via a double-beam
spectrophotometer (T70/T80 series UV/Vis spectrophotometer, PG instruments
Ltd, U.K.), in the scanning range 200–800 nm. TEM measurements
were performed on a JEOL, JEM-2100F, Japan, operated at an accelerating
voltage of 200 kV. FTIR measurements were conducted on a JASCO spectrometer
in the range 4000–600 cm^–1. ζ potential
was examined in a ζ potential analyzer (Zetasizer Nano ZS Malvern).
XRD was conducted on an X-ray diffractometer (X’Pert PRO, The
Netherlands) operated at a voltage of 45 kV and a current of 40 mA
with Cu Kα1 radiation (λ = 1.54056 Å) in the 2θ
range from 20 to 80°. Energy-dispersive X-ray spectroscopy (EDX)
was performed by a JEOL model JSM-IT100. Raman spectroscopy was performed
on the dried sample at room temperature using a SENTERRA Raman spectrometer,
Bruker, Germany, with a 514.5 nm excitation wavelength to determine
the extent of graphitic disorder within the prepared material.

Briefly,
0.1 mL of AuNPs and rGO-AuNPs were added separately to
10 mL of various aqueous solutions of MB with concentrations ranging
from 10 to 20 ppm (10, 15, and 20 ppm). Then, 0.1 mL of freshly prepared
aqueous NaBH₄ solution (0.058 M) was added to these solutions.
Progress of the reaction was monitored by recording the time-dependent
UV–vis absorption spectra of these mixtures at 664 nm in a
quartz cuvette (path length 1 cm) using UV–vis spectroscopy
(T70/T80 series UV/vis spectrophotometer, PG instruments Ltd, U.K.).
Control experiments were conducted under the same experimental conditions
yet without AuNPs, rGO-AuNPs, or NaBH₄. Scanning was performed
in the range 200–800 nm at ambient room temperature (25 °C),
and the efficacy was measured by the following equation^{80 (link),108 (link)} where A₀ represents
the initial absorbance and A refers to the final
absorbance.

The photocatalytic
activity of the green synthesized Ag@biochar nanocomposite against
MB dye was evaluated. 5 mg of the Ag@biochar nanocomposite was added
to 10 mL of three different concentrations of MB solution (10, 25,
and 50 ppm). The control experiment was carried out using 5 mg of
biochar with an MB solution of a concentration of 25 ppm. Both test
and control solutions were mixed for 30 min under dark conditions
for adsorption/desorption equilibration. Then, the solutions were
stirred under a xenon lamp as a visible-light source (λ >420
nm) and monitored. Next, 2 mL aliquots were removed and centrifuged
at 17,000 rpm for 2 min to separate the solid nanocatalyst. The absorbance
of the resultant supernatant of MB dye of both control and test solutions
was measured at 664 nm wavelength in a quartz cuvette (path length
of 1 cm) using UV–vis spectroscopy (T70/T80 series UV/vis spectrophotometer,
PG Instruments Ltd., UK); scanning was done in the range of 200–800
nm. The percentage of MB dye degradation was calculated by the following
formula^{83 (link)} Concerning the regeneration process, Ag@biochar
was first removed from the solution via centrifugation
at 17,000 rpm for 1 min, and then it was thoroughly washed with DW
and eventually dried overnight in an oven.