# Graphene Deposition on Glass Fibers by Triboelectrification
## 2 Experimental Part
### Samples Preparation  
A schematic description of the lab-made setup for the TE of glass fibers is represented in Figure 1. The system is composed of two fibers winding systems, the first containing the wounded fibers (W1), while the second drew the fibers with the help of an electrical motor (W2). The device is composed of a vertical insulating wood panel containing two grounded steel electrodes (E1), two PTFE wheels (P1 and P2) mounted in the center, and two other steel electrodes (E2) connected to a Keithhey 6517A electrometer/high resistance meter (Tektronix Inc., Beaverton, OR, USA). The electrometer was controlled with a MATLAB program for real-time acquisition of the surface charge on GFs as a function of the fibers scrolling time. All the system (except the electrometer) was placed inside a grounded Faraday's cage. Initially, the TE process of GF involved the scrolling of fibers from W1 to E1. The placement of the two electrodes in E1 allowed both sides of the fibers to touch the electrodes to discharge the as-received fibers from any pre-existing electrification. Then, for the analysis of the TE process, the discharged fibers followed three different paths. For the analysis of discharged fibers only (0T), the fibers passed over E2 electrodes for charge measurement, while for the TE of fibers by one PTFE (1T), GF passed over P1 only and then passed over E2 electrodes for charge measurement. For the CE by two PTFE (2T), GF passed over P2 and P1 before passing over E2 electrodes for charge measurement.  
The 0T path was useful to evaluate pre-existing electrification phenomena on the fibers. The 1T path was used to evaluate the contact electrification effect on fibers using one PTFE contact, while the 2T path was useful to understand if there is an effect on the electrification level by an increased number of contact points between fibers and PTFE. The temperature and humidity values inside the cage were registered during the tests since they can influence the charge measurement. In literature, it is reported that, for having a reliable charge measurement, the recommended temperature should be around 23 \({}^{\circ}\)C with an optimal humidity between 20% to 25% [42]. The whole TE process was performed at three different scrolling velocities (0.61 cm/s, 1.19 cm/s, and 4.05 cm/s) to evaluate their effect on the surface charge development.  
For the TE based deposition of GO, the same setup was used, with the difference being that the fibers did not pass over the second set of electrodes, E2, but they passed through a graphene oxide bath after following paths 1T or 2T, as reported in Figure 2. Electrified coated fibers were then compared with non-electrified fibers (NEF), whose GO coating was obtained by manually dipping the discharged fibers in a GO bath. After the deposition, all the coated fibers were dried in an oven for at least 12 h at 50 \({}^{\circ}\)C under vacuum. The chemical reduction of GO-coated glass fibers was performed by exposing them at 100 \({}^{\circ}\)C in a hydrazine hydrate-rich environment for 24 h [28].  
The list of the produced GO and rGO coated glass fibers, together with their designation, is reported in Table 1. The first number represents the initial graphene oxide concentration, then the coating type (GO or rGO) and the electrification process is reported.  
Figure 1: Schematic representation of lab-made setup for the triboelectrification of glass fibers and charge measurements tests.  
Figure 2: Schematic representation of the triboelectrification deposition process of graphene oxide on glass fibers.