Defect-rich single-layer MoS2 nanosheets with high dielectric-loss for contrast-enhanced thermoacoustic imaging of breast tumor

Abstract

Microwave induced thermoacoustic imaging (MTAI), combining high contrast of tissue dielectric absorption and high resolution of ultrasonography, is a potential nonionizing candidate for breast tumor detection. In this work, defect-rich single-layer molybdenum disulfide (S-MoS2) nanosheets with high dielectric-loss were developed for enhancement of thermoacoustic (TA) contrast. The underlying mechanism involves a large number of Mo and S atom vacancies on the prepared S-MoS2 nanosheets. The distribution of electron clouds around the vacancies is uneven, thus creating a defect electric dipole. With pulsed microwaves, the defect electric dipoles were repeatedly polarized at gigahertz. This results in a transient heating and thermoelastic expansion yielding a TA wave. The results confirm that the defect-rich S-MoS2 nanosheets can produce a stronger TA signal with significantly enhanced contrast than the commonly used TA probes on a per mass basis. The feasibility of the MoS2 nanosheets was evaluated with a model of breast tumor. The results demonstrate that defect-rich S-MoS2 nanosheets are promising candidates for breast tumor imaging.