An electroconductive ink containing the reduced graphene oxide‒metal oxide‒carbon nanotube semiconductor applied to flexible electronic circuits

Abstract

We present an interesting low-cost, green, and scalable technique for direct ink writing for flexible electronic applications different from traditional fabrication techniques. In this work, a reduced graphene oxide (RGO)‒bismuth oxide (Bi₂O₃)/carbon nanotube (CNT) (RGBC) ternary conductive ink was prepared by an initial synthesis of RGO‒Bi₂O₃ (RGB) via a hydrothermal method. This was followed by the fabrication of conductive ink through homogenous mixing of the binary nanocomposite with CNTs in a mixture of ethanol, ethylene glycol, glycerol, and double-distilled water as the solvent. Electronic circuits were fabricated through directly writing the prepared ink on flexible nanocrystalline cellulose (NCC) thin film substrates. The nanocomposites consisted of rod-shaped nanoparticles that were grown on the surface of the nanographene sheet. The semiconductor nanocomposite exhibited excellent conductivity and further confirmed by applying it as an electrode in the electrical circuit to light a light-emitting diode (LED) bulb. The highest electrical conductivity achieved was 2.84 × 10³ S·m⁻¹ with a contact angle of 37°. The electronic circuit written using the conductive ink exhibited good homogeneity, uniformity, and adhesion. The LED experiment demonstrates the good conductivity of the electroconductive circuit and prepared ink. Hence, the NCC substrate and RGBC conductive ink showcase an excellent potential for flexible electronic applications.

Graphical abstract

Keywords

reduced graphene oxide / nanocrystalline cellulose / electroconductive ink / flexible electronic circuit / hydrothermal synthesis

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Declaration of competing interests

The authors declare no competing financial interests.

Acknowledgements

The authors are grateful for financial support from the University of KwaZulu-Natal (UKZN), Eskom Tertiary Education Support Programme (TESP), National Research Foundation of South Africa, and the UKZN Nanotechnology Platform. H.O.S. appreciates the support of the UKZN NanoChemistry Research Group members and colleagues. Appreciation is due to Dr. Edigar Muchuweni for proofreading the manuscript and Dr. Solomon Uriri for assisting with AFM imaging.

Online appendix

Electronic supplementary material (ESM) can be found in the online version at https://doi.org/10.1007/s11706-025-0712-5 and https://journal.hep.com.cn/foms/EN/10.1007/s11706-025-0712-5 that includes Figs. S1–S6 and Table S1.

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