  Surface charges play a fundamental role in physics and chemistry,
particularly in shaping the catalytic properties of nanomaterials. Tracking
nanoscale surface charge dynamics remains challenging due to the involved
length and time scales. Here, we demonstrate real-time access to the nanoscale
charge dynamics on dielectric nanoparticles employing reaction nanoscopy. We
present a four-dimensional visualization of the non-linear charge dynamics on
strong-field irradiated single SiO$_2$ nanoparticles with femtosecond-nanometer
resolution and reveal how surface charges affect surface molecular bonding with
quantum dynamical simulations. We performed semi-classical simulations to
uncover the roles of diffusion and charge loss in the surface charge
redistribution process. Understanding nanoscale surface charge dynamics and its
influence on chemical bonding on a single nanoparticle level unlocks an
increased ability to address global needs in renewable energy and advanced
healthcare.
