**5. Conclusion**

*Novel Nanomaterials*

**38**

bonds [31].

**Figure 13.**

bondings of the C-C aromatic rings.

Concisely, with the help of the Beer–Lambert law, absorption coefficient (A = αcl) of graphene could be found by using dispersion at specific concentrations [29, 32–35]. UV–Vis absorbance spectroscopy was conducted at fixed wavenumbers of 253 nm for graphene. A piercing peak at 210 nm can be noticed and one more peak around 226 nm with a little bit less intensity of absorption peak is also observed due to Π-Π\*

The obtained graphene samples, which are labeled as US-G-DMSO, US-G-

C=C

DMF and US-G-PA, show peak at 265 nm wavelength that referring sp2

*Lateral size results of synthesized samples, (a) US-G-DMSO, (b) US-G-DMF, (c) US-G-PA.*

Microwave (MW)-assisted method was developed. Although many solvents have been studied, carbon product, which was synthesized in DMF, showed the highest electrical conductivity. Electrical conductivities of MW-assisted graphene products were higher when the used solvents have 2–4 Debye (D) dipole moments. These results are compatible with the dielectric constants and surface tensions of the used chemicals. Layer numbers show distribution between 10 and 16. EG has minimum layer number with the value of 5.5. Solvents that have surface tension bigger than 40 mN/m show better layer number results. When the dielectric constants (ε) get larger, electrical conductivity values of synthesized products increased. As the surface tensions increased, layer numbers decreased. PA showed the optimum electrical conductivity and layer number values for the MW-assisted graphene synthesis. According to the UV–vis spectrums of MW assisted graphene samples. The obtained graphene samples, which were labeled as MW-G-PA, MW-G-NaOH, MW-G-n-Hexa, MW-G-ED, MW-G-DMSO, and MW-G-OCTA showed peak at 265 nm wavelength that referring sp2 C=C bonds.

Ultrasound (US)-assisted method was studied. Graphene samples were easily synthesized via solution-based process. According to the UV–vis spectrums, all graphene products gave peak at 265 nm wavelengths, which may be caused by the ultrasonication required for proper suspension using the solution-based process. Also, as a result of AFM analyses, US-G-DMSO has four layers, US-G-DMF has five layers and US-G-PA has thirty-one layers. It can be understood that DMSO shows better solvent effect on graphite exfoliation by sonication process. Z-average hydrodynamic radius (Rh) of US-G-DMF is 3846 nm, Rh of US-G-DMSO is 6930 nm, and Rh of US-G-PA is 7137 nm. It can be concluded that, DMF provides graphene products with smallest lateral size.
