Electrically Conductive, Reduced Graphene Oxide Structures Fabricated by Inkjet Printing and Low Temperature Plasma Reduction

Abstract

Here, an environmentally‐friendly and scalable process is reported to synthesize reduced graphene oxide (RGO) thin films for printed electronics applications. The films are produced by inkjet printing GO flakes dispersed binder‐free in aqueous solutions followed by treatment with a nonthermal, radio‐frequency (RF) plasma containing only argon (Ar) gas. The plasma process is found to heat the substrate to temperatures no greater than 138 °C, enabling RGO to be printed directly on a wide range of temperature‐sensitive substrate materials including photo paper. Unlike other low‐temperature methods such as electrochemical reduction, plasma reduction is friendly to moisture absorbent materials. Moreover, the plasma treatment can be performed on nonconducting substrates, eliminating the need for film transfer. From an applications perspective, the printed, plasma‐reduced RGO exhibits excellent electrical, mechanical, and electrochemical properties. As a technology demonstrator, the working electrodes of hydrogen peroxide (H2O2) sensors fabricated from plasma‐reduced GO show a sensitivity of 277 ± 80 µA mm−1 cm−2, which is comparable to RGO working electrodes made by electrochemical reduction.

Plasmas for additive manufacturing

“…Recently, a low‐pressure plasma with only Ar gas was shown to be capable of reducing inkjet‐printed GO and yielded a sheet resistance as low as 2 kΩ/sq. [ 129 ] A hydrogen peroxide (H 2 O 2 ) sensor fabricated with the plasma‐reduced GO showed comparable sensitivity to electrochemical reduction, with the advantage of being a dry process, which enables printing rGO on absorbent substrates that disintegrate or swell in liquid such as paper.…”

“…In particular, the choice of gas and desired gas chemistry is nontrivial. For example, to reduce printed GO films, H 2 , [ 126 ] NH 3 , [ 127 ] CH 4 [ 128 ] and Ar, [ 129 ] have all been successfully demonstrated. Very often, the gas is selected based on other issues such as cost, ease of availability, and safety.…”

Plasma Assisted Reduction of Graphene Oxide Films

“…Fourier-transform infrared spectroscopy (FTIR) is also a useful tool to investigate the effectiveness of GO-reduction. The presence of various oxygen-containing groups can be recognized in GO/rGO, and thus their removal can be examined [ 161 , 162 ]. The configurations that can be identified with FTIR are [ 163 ]: epoxide (C-O-C): 1230–1320 cm −1 , asymmetric stretching; ~850 cm −1 bending motion, sp 2 -hybridized C=C: 1500–1600 cm −1 , in-plane vibrations, carboxyl (COOH): 1650–1750 cm −1 (including C-OH vibrations at 3530 and 1080 cm −1 ), ketonic species (C=O): 1600–1650 and 1750–1850cm −1 , and hydroxyl (namely phenol, C-OH): 3050–3800 and 1070 cm −1 ) with all C-OH vibrations from COOH and H 2 O.…”

“…Since then, in the last 13 years, several kinds of plasma-assisted reduction processes were developed. To name some ways plasma generation is utilized: radio-frequency (RF) plasma [ 150 , 162 , 178 , 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 , 195 , 196 , 197 ], low-pressure direct current (DC) plasma [ 198 , 199 , 200 , 201 ], micro-DC plasma [ 202 ], atmospheric pressure glow discharge (AGD) plasma [ 56 ], electron beam (EB) plasma [ 203 ], active screen (AS) plasma [ 204 ], atmospheric pressure plasma jet (APPJ) [ 205 ] and μ-APPJ [ 206 ], and dielectric barrier discharge (DBD) plasma [ 207 , 208 ]. In the following sections, the reduction processes classified according to the discharge gas will be discussed in detail.…”

Sensible graphene oxide differentiates macrophages and Leishmania: a bio-nano interplay in attenuating intracellular parasite

“…1D; black curve). 32,[35][36][37][38] In reference to GO, the G band in AGO showed a marginal shi from 1604 to 1597 cm À1 , which may be due to the electrondonating nature of EDA in AGO or restoration of the sp 2 domain ( Fig. 1D; red curve).…”