2D material offers alternative to lead X-ray shielding

Researchers at the University of Adelaide, Royal Adelaide Hospital, and Griffith University in Australia, together with colleagues at the University of Campinas in Brazil, have come up with a new concept for a lead-free X-ray shielding material [Nine et al., Applied Materials Today 29 (2022) 101566, https://doi.org/10.1016/j.apmt.2022.101566 ].

Ionizing radiation sources are widely used in medical imaging and therapy, airport security, engineering, and the nuclear and space industries, but protection is required to mitigate adverse health effects. Personnel and patients frequently exposed to ionizing radiation typically resort to lead (Pb) aprons, which while offering protection are heavy, inflexible, toxic, and of limited durability. There is great interest, therefore, in alternatives to Pb offering efficient radiation protection and many potential candidate materials have been investigated.

Now a team led by Dusan Losic have devised a new protective material based on a laminated structure of the two-dimensional material antimonene as an alternative to conventional Pb-free blend-and-mix composites.

“[Our] work addresses several key issues in conventional radiation-shielding composites such as agglomeration, random distribution of shielding particles, large-interparticle gaps, low density, micro-cracks etc. that can result in poor X-ray attenuation,” explains first author of the study Md J. Nine.

Exfoliation of bulk antimony produces crystalline, single-layer nanoflakes of antimonene that self-assemble into dense films with minimal interparticle gaps on cotton layers, which are sandwiched together in an elastomer (PDMS) to form a flexible shielding material.

“The laminated structure based on antimonene demonstrates effective X-ray attenuation with an enhancement of 45% compared with its conventional form as a composite, despite having an identical composition,” points out Nine.

Laminated two-dimensional materials offer a new concept in X-ray radiation shielding, believe the researchers, with their unique nanolayered structures scattering and reflecting photons between the layers and their interfaces. The layered two-dimensional material offers improved shielding compared with conventional composites of the same composition and avoids issues such as microcracking and inflexibility.

“Applications include areas where we need protection from ionizing radiation such as in medical imaging, radiation therapy, airport security, nuclear fuel imaging, diagnosis of structural faults, defense and space industries,” says Nine.

Moreover, the approach lends itself to the inclusion of different two-dimensional materials such as MoS₂ and MXenes to create multi-layered sandwich structures, which could be effective in attenuating broad-band ionizing radiation. The researchers now plan to create lightweight prototype protective garments and explore the approach for high energy gamma radiation.

This research is supported by ARC Research Hub for Graphene Enabled Industry Transformation, funded by the Australian Research Council.