Dr. Svetlana Jovanović Vučetić

In the last decade, scientific interest in and industrial needs for new electromagnetic (EM) shielding materials have significantly increased due to technological developments in the telecommunication and electronic sectors. The world market for shielding materials demands new, lightweight, flexible, and durable shielding materials. At the same time, ecological aspects in the production process must be considered. Priority will be given to materials produced in an eco-friendly and sustainable manner. Due to its light weight, flexibility, chemical stability, and electrical properties, graphene and its derivates are promising candidates for future EM shielding materials. The GrInShield project is focused on developing graphene-based composites able to block the propagation of electromagnetic waves from low (150 kHz) to high frequencies (8-12 GHz). The purpose of these materials will be the protection of electronic devices and sensitive instruments from secondary EM waves and wearable protection by developing textiles for professional clothes. Our research showed that graphene oxides in the form of free-standing films show very low EM shielding efficiency (~ 2 dB) while after chemical reduction, materials with the same thicknesses (13 ±0.32 μm) become more efficient (~ 6 dB). EM shielding efficiency was increased by including metal-based nanomaterials in graphene composites. Namely, adding 50 wt% silver nanowires (AgNWs) to graphene oxide free-standing films improved EM shielding efficiency to -12.1 dB, while 80 wt% of AgNWs led to -33.3 dB. When these materials were chemically reduced, the EM shielding effectiveness was -24.17 dB and -35.6 dB. Recently, as an answer to the high price of graphene and low production, new methods are developing for graphene-based nanomaterials production, where precursors are different biomasses. Precursor carbonization occurs during the process of heating in an oxygen-free atmosphere. These materials are known as biochar, and they were studied mainly as sorbents. GrInShield team produced biochars using fruit-processing biowastes. After mixing with the polymer sodium silicate resin, a flexible, 0.2 cm thin composite showed EM shielding effectiveness, blocking above 70 % of the incident waves. These results indicated the outstanding potential of biochars and graphene-metallic nanomaterials composites for their application in EM shielding. Acknowledgments This research was supported by the European Union’s Horizon Europe Coordination and Support Actions programme under grant agreement No 101079151 – GrInShield. Also, the authors are thankful to the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (grant number 451-03-136/2025-03/ 200017).

Keywords: graphene, graphene oxide, shielding, composites