One-Step Laser Synthesis of Hemispherical MoS₂ for Self-Powered Image Sensor

Molybdenum disulfide (MoS₂) has recently gained a significant attention in triboelectric nanogenerators (TENGs) due to its negative potential nature against polymeric layers, combined with its transparency and flexibility. However, MoS₂-based TENGs face challenges in the contact-separation mode, leading to physical wear and limited triboelectric enhancement within two-dimensional (2D) geometries. In this study, we present a one-step laser synthesis method to produce hemispheres MoS₂ using laser-assisted nucleation growth of MoS₂ precursor seeds. The resulting hemispheres MoS₂, synthesized with optimized precursor concentrations (0.32 M), exhibit average diameters of 234.4 nm with a standard deviation of 30.4 nm on a wafer-scale. These hemispherical MoS₂ significantly enhance the electric field concentration and make them suitable for non-contact mode TENG (NC-TENG) devices. Compared to thin film MoS₂-based NC-TENG, the hemispherical MoS₂-based NC-TENG shows a 22-fold increase in average capacitance (~ 112 pF, D = 2 mm) and a 8-fold increase in open circuit voltage (OCV) (~ 2.50 V, D = 2 mm) with an extended operational distance (D ≥ 20 mm). This advanced hemispherical MoS₂ is further applied to fabricate a self-powered image sensor array, where a spherical object is successfully detected under the dynamically moving conditions. Considering the simple synthesis process and extraordinary triboelectric/optical performance of the hemispherical MoS₂, it is expected to expand the potential of MoS₂ for advanced sensing applications.