Ultrasonication induced sp3 hybridization defects in Langmuir-Schaefer layers of turbostratic graphene

Karol Rytel, Małgorzata Widelicka, Damian Łukawski, Filip Lisiecki, Kamil Kedzierski, Danuta Wróbel

Index: 10.1039/C8CP01363B

Full Text: HTML

Abstract

Ultrasonic homogenization is the method of choice for producing and dispersing graphene. In this paper we show that sp3 hybridization defects introduced by long high-power sonication cause a significant decrease in electrical conductivity. In order to show this two turbostratic graphene (TG) dispersions were sonicated at two power settings of tip sonifier at 20 W and 60 W, and for different periods varied from 1 min to 180 min. Afterwards, TG thin films were prepared by Langmuir technique and transferred onto quartz substrate by the Langmuir-Schaffer method. The thin films were investigated by electrical conductivity measurement, UV-VIS, Raman spectroscopy and scanning electron microscopy. We found that the relative performance of the TG films in terms of transparency and sheet resistance obtained for TG thin films was higher than that for similarly prepared pristine graphene flakes, reported in our previous works. Moreover, despite the increase in transmittance, the electrical conductance significantly decreases with the time of sonication, especially for the 60 W of sonication power. The results of Raman spectroscopy indicate that this particular behavior was explained by introducing sp3 hybridization defects to TG flakes during high power sonication.