[PDF] from wiley.com GetIt!@UWaterloo Femtosecond Laser Carburization of WS2 Flakes to W2C for Enhanced Photothermal Conversion Efficiency

Photothermal therapy is a new, promising approach for treating cancer in a non‐invasive way. In this work, we synthesized a photothermally efficient nanomaterial, by exposing bulk WS₂ powder, dispersed in carbon‐rich acetonitrile, to high‐intensity femtosecond laser pulses. The photothermal measurements showed a significantly higher rise in temperature and enhanced photothermal efficiency for the laser‐treated material. We attribute the enhancement to the formation of tungsten semi‐carbide (W₂C), which we verified by morphological and structural characterization. The tungsten semi‐carbide was formed by laser‐induced carburization; intense laser pulses knock S atoms out of the WS₂ lattice and dissociate the acetonitrile molecules, resulting in the formation of W₂C. Interestingly, the hexagonal W₂C had a two‐dimensional (2D) layered morphology like that of the WS₂, suggesting its morphology is not