Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young's modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young's modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.

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Visualizing deep-brain vasculature and hemodynamics is key to understanding brain physiology and pathology. Among the various adopted imaging modalities, multiphoton microscopy (MPM) is well-known for its deep-brain structural and hemodynamic imaging capability. However, the largest imaging depth in MPM is limited by signal depletion in the deep brain. Here we demonstrate that quantum dots are an enabling material for significantly deeper structural and hemodynamic MPM in mouse brain in vivo. We characterized both three-photon excitation and emission parameters for quantum dots: the measured three-photon cross sections of quantum dots are 4–5 orders of magnitude larger than those of conventional fluorescent dyes excited at the 1700 nm window, while the three-photon emission spectrum measured in the circulating blood in vivo shows a slight red shift and broadening compared with ex vivo measurement. On the basis of these measured results, we further demonstrate both structural and hemodynamic three-photon microscopy in the mouse brain in vivo labeled by quantum dots, at record depths among all MPM modalities at all demonstrated excitation wavelengths.

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A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM. The SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.

Fluorogens with aggregation-induced emission (AIEgens) are promising optical agents for cellular and vascular imaging. AIEgens with bright emission in the far-red and near-infrared (NIR) regions are highly desirable, but the traditional strategies, i.e., introducing donor–acceptor (D–A) structures into AIEgens, generally lead to fluorogens with photoluminescence that is vulnerable to the polarity of the surrounding environment. In addition, because of the intrinsic rotor structure, AIEgens usually show absorption in the short-wavelength region, which is not optimized for imaging applications. In this contribution, we report binary organic nanoparticles (NPs) with tunable emission and high quantum efficiency in the red and far-red regions. By increasing the intermolecular distance, the obtained NPs offered enhanced luminescence quantum yields from 0.01 to 0.23 and increased three-photon excitation (3PE) cross sections, enabling high-quality and deep brain vascular imaging on an 8-week-old BALB/C mouse with up to 1.68 mm upon excitation at 1610 nm.