A Comparative Investigation of Chemically Reduced Graphene Oxide Thin Films Deposited via Spray Pyrolysis

Abstract

We present a comparative investigation between thin films of graphene oxide (GO) and chemically reduced graphene oxide (rGO) deposited onto glass substrates via spray pyrolysis. Two reduction techniques are investigated: (1) the exposition of a sprayed layer of GO to vapors of hydrazine hydrate to produce rGO V and (2) the addition of liquid hydrazine hydrate to a suspended GO solution, which is then sprayed onto a substrate to produce rGO L . Three different spectroscopy techniques, Raman, Fourier transform infrared, and UV–Vis–NIR, show that the two reduced samples have less lattice disorder in comparison to GO, with rGO L having the highest degree of reduction. Interestingly, topography characterization by atomic force microscopy reveals a morphological change occurring during the exposure to hydrazine hydrate vapors, resulting in a thickness of 110 nm for the rGO V film, which is a factor of 16 larger than rGO L and GO. Finally, I – V measurements show a significant decrease of the GO’s resistivity after the reduction process, where rGO L features a resistivity 90 times lower than rGO V , confirming that rGO L has the highest degree of reduction. Our results indicate that the reduction process for rGO V is susceptible to introducing intercalated water molecules in the material while the fabrication technique for rGO L is a suitable route to obtain a material with minimal lattice disorder and properties approaching those of graphene.

Photoluminescence and Fluorescence Quenching of Graphene Oxide: A Review

“…Bai et al summarized the electrochemical reduction of GO to change the band gap of GO, and some shortcomings of electrochemical reduction methods were also mentioned; for instance, the reduction reaction only occurs on the surface of the electrode, and the reduction capacity is restricted by multiple factors such as the electrode area [ 31 ]. Ménard et al prepared rGO using the spray pyrolysis deposition method, which also shows a high degree of reduction [ 32 ]. Figure 3 displays the schematic diagram of the partial reduction of GO.…”

Dynamics of reduced graphene oxide: synthesis and structural models

“…38 Since the most common oxygen-containing moieties on the surface of GO are OH, C–O–C, –COOH and CO, reduction minimises their content but retains surface polarity and exfoliation in aqueous-media. 3,39 The residual oxygen-containing functionalities on the sheets of RGO allow interaction with metal ligands, and thus allow chemical linkage of metal oxides in most composites. 40 The chemical composition of RGO is controlled by precise synthesis protocols and the C/O ratio in most reports is ∼12.…”

“…This is imperative because ultimate structural characteristics and film thickness of RGO influence optical band gap values. 39 In addition, the rich oxygen located on surfaces and edges (hydroxyl, carboxyl and epoxy), delocalized π–π electrons (due to restored aromaticity) and large surface of RGO enhance intercalation/adsorption of aromatic organic pollutants that can be photocatalytically degraded, particularly in composites with semiconductors. 10,82–85 Since oxidation is known to enhance the optical band gap energy (in GO relative to graphene), reduction towards a more graphene-like material (in RGO) infers a lower optical band gap energy.…”

“…In addition, the ultimate surface area and porosity traits of RGO were reported to increase with a rise in pyrolysis temperature, under inert atmospheric conditions, owing to generated oxygen vacancies that are available for nitrogen sorption. 19 The work by Bargaoui et al 39 has shown that OH moieties in H-bonds are preferentially pyrolyzed in hydrazine better than the C–O functionalities in epoxides. The same study has also hinted that the decline in OH groups after pyrolysis is a common oversight in most reports due to water contamination (intercalated water) owing to the hygroscopic nature of RGO.…”

Hybrid architectures for terahertz molecular polaritonics

“…Until now, the coupling of molecules with hybrid cavities has remained mostly unexplored, in part due to the complexity of fabricating a dense layer of organic material within a spatially confined electromagnetic mode volume. Using a spray coating technique 35 , we obtain a dense molecular layer in direct contact with the surface of the MS, allowing us to reach the strong light-matter coupling regime involving a resonant plasmonic and molecular vibrational mode. This system can then be inserted into the design of a planar resonator geometry to enable further hybridization with a photonic mode.…”