**1. Introduction**

Graphene is the wonder nanomaterial discovered in 2004, most widely investigated because of its excellent electrical, mechanical, optical, chemical properties [1, 2]. The main properties are it is 97.7% transparent and is used for making transparent conducting electrodes. Its high carrier mobility (200,000 cm2 v −1 s−1), Young's modulus of 1.0 TPa is another important properties of graphene. It is considered 200 times more conductive than copper and 100 times stronger than steel [3–7]. In addition to this it is very flexible in nature as it can be stretched to 20% of its original length. These exceptional properties of graphene are highly suitable for the fabrication of various modern electronics device applications such as energy storage devices and sensors etc. However, for the efficient use of graphene in these modern devices, the colloidal dispersion of graphene has to be prepared for using in solution phase. The colloidal solution of graphene has some advantages in comparison to the other forms of graphene to be utilized for the formation of various devices.

Nowadays the modern electronics devices are being fabricated using printable electronics process. For the fabrication of the electronics devices such as sensors, energy storage devices using printable electronics the graphene has to be available in the colloidal solution form so that it will be easy to fabricate these graphene based flexible electronics devices using spray coating, brush coating, screen printing techniques [8]. Therefore, it is absolutely necessary to produce the colloidal solution of graphene.
