Model no uv 1800

Amylase activity was determined using soluble starch (1% w/v) as substrate dissolved in 0.05 M sodium phosphate buffer (pH 6.5) as described previously by Gomes et al. [20] . The final reaction mixture, prepared by adding 1.8 mL starch solution and 0.2 mL enzyme solution, was incubated at 50 °C for 10 min. The reaction was stopped by adding 3 mL dinitrosalicylic acid (DNS). The amount of reducing sugar released was determined by taking absorbance at 540 nm with a UV–visible spectrophotometer (Model no. UV-1800; Shimadzu Corporation, Japan) as described by Miller [17] , [21] . One unit of amylase activity denotes the amount of enzyme required for releasing 1 μg of reducing sugar (maltose) per minute under assay conditions. The activity of the enzyme was calculated by using following formula [17] . $\text{Amylase activity}(\text{U}/\text{ml}/\text{min})=\frac{\text{Maltose released}(\mathrm{\mu }\text{g})\times \text{Total volume of reactive media}(\text{mL})\times \text{Dilution factor}(\text{DF})}{\text{Molecular weight of maltose}\times \text{Enzyme used}(\text{mL})\times \text{Time of incubation}(\text{min})}$

The crystalline
structures of the synthesized graphene samples were elucidated by
an X-ray diffractometer [Bruker, D8 Advance powder XRD] with Cu Kα
radiation (40 kV and 40 mA). A scanning electron microscope [Hitachi,
S-4800 FESEM] coupled with energy-dispersive spectroscopy (EDS) was
utilized to observe the microstructures and elemental composition
of the samples. Fourier transform-infrared (FTIR) spectra analysis
was performed on a Nicolet 5700 FT-IR spectrometer [Thermo Fisher]
with the standard KBr pellet method. UV–vis spectroscopy [Shimadzu,
model no-UV 1800] was used to detect the optical properties of the
synthesized graphene, while thermogravimetric analysis (TGA) was conducted
by a TGA/DSC 2 instrument [Mettler Toledo] with a flow rate of 60
mL/min and heating rate at 10 °C/min. Zeta potential was conducted
on triplicates using Zetasizer Nano ZS [Malvern Panalytical]. Raman
spectroscopy analysis was performed on a SENTERRA Raman spectrometer
[Bruker-Germany] with a 514.5 nm excitation wavelength and power output
of 10 mW at room temperature.