Laser-Induced Stress-Driven Nanoplate Jumping Visualized by Ultrafast Electron Microscopy.

Understanding laser-induced jumping has attracted great interest in nanomaterial launching and transfer but requires a high spatiotemporal resolution visualization. Here, we report a jumping dynamics of nanoplate driven by ultrafast laser-induced stress using time-resolved transmission electron microscopy. Single-shot imaging reveals a nondestructive launching of gold nanoplates in several nanoseconds after the pulsed femtosecond laser excitation. The temperature rise and acoustic vibration, derived from ultrafast electron crystallography with a picosecond time resolution, confirm the existence of a laser-induced elastic stress wave. The generation, propagation, and reflection of thermal stress waves are further clarified by atomic simulation. The nonequilibrium ultrafast laser heating produces a compressive stress wave within several picoseconds, constrained by the supporting substrate under nanoplate to provide thrust force. This compressive stress is subsequently reflected into tensile stress by the substrate, promoting the nanoplate to jump off the substrate. Furthermore, the uneven interface adhesion results in the jumping flip of nanoplates, as well as, diminished their jumping speed. This study unveils the jumping regime driven by impulsive laser-excited stress and offers understanding of light-matter interaction.

Direct Nanosecond Multiframe Imaging of Irreversible Dynamics in 4D Electron Microscopy.

Irreversible ultrafast events are prevalent in nature, yet their capture in real time poses significant challenges. Traditional single-shot imaging technologies, which utilize a single optical pump and single delayed electron probe, offer high spatiotemporal resolution but fail to capture the entire dynamic evolutions. Here, we introduce a novel imaging method employing a single optical pump and delayed multiple electron probes. This approach, facilitated by an innovative deflector in ultrafast electron microscopy, enables the acquisition of nine frames per exposure, paving the way for statistical and quantitative analyses. We have developed an algorithm that corrects frame-by-frame distortions, realizing a cross-correlation enhancement of ∼26%. Achieving ∼12 nm and 20 ns resolution, our method allows for the comprehensive visualization of laser-induced behaviors in Au nanoparticles, including merging, jumping, and collision processes. Our results demonstrate the capability of this multiframe imaging technique to document irreversible processes across materials science and biology with unprecedented nanometer-nanosecond precision.

Visualizing the Redox Reaction Dynamics of Perovskite Nanocrystals in Real and Reciprocal Space.

Redox reaction, involving the gain and loss of electrons between reactants, is one type of common chemical reaction governing fundamental energy issues in nature. However, reports of vividly visualizing such key processes with simultaneous structural determination of new phases that are involved are rare. Here, by achieving simultaneous recording in both real and reciprocal space, we demonstrate in situ imaging of the redox reaction dynamics in perovskite nanocrystals. The thorough atomic-scale movies enable an in-depth understanding of the reaction-induced nucleation and growth mechanism of clusters with the aid of carbon, and a simple way of using SiN films at room temperature to fully prevent the irradiation-induced degradation in perovskites is proposed, in contrast to the costly low-temperature strategy. Real-time atomic-scale imaging in both real and reciprocal space paves the way for revealing various chemical and physical events at targeted nanoscale positions with complementary structural information.