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We compare the electron dynamics at monocrystalline Cu(111), Au(100) and Pd(111) precursor substrates with vicinal nanosteps. The unoccupied bands of a surface superlattice are populated via the resonant charge transfer (RCT) between the surface and a H − ion that flies by at grazing angles. A quantum mechanical wave packet propagation approach is used to simulate the motion of the active electron, and time-evolved wave packet densities are used to visualize the dynamics through the superlattice. The survived ion fraction in the reflected beam generally exhibits modulations as a function of the vicinal terrace size and shows peaks at those energies that access the image state subband dispersions. Differences in magnitudes of the ion-survival as a function of the particular substrate selection and the ion-surface interaction time, based on the choice of two ion-trajectories, are examined. A square well model, producing standing waves between the steps on the surface, explains the energies of the maxima in the ion survival probability for all the metals considered. This indicates that the primary process of confinement induced subband formation is robust. The work may motivate measurements and applications of shallow-angle ion-scattering spectroscopy to access electronic substructures in periodically nanostructured surfaces. 

Nondestructive neurotransmitter detection and real‐time monitoring of stem cell differentiation are both of great significance in the field of neurodegenerative disease and regenerative medicine. Although luminescent biosensing nanoprobes have been developed to address this need, they have intrinsic limitations such as autofluorescence, scattering, and phototoxicity. Upconversion nanoparticles (UCNPs) have gained increasing attention for various biomedical applications due to their high photostability, low auto‐fluorescent background, and deep tissue penetration; however, UCNPs also suffer from low emission intensities due to undesirable energy migration pathways. To address the aforementioned issue, a single‐crystal core–shell–shell “sandwich” structured UCNP is developed that is designed to minimize deleterious energy back‐transfer to yield bright visible emissions using low power density excitations. These UCNPs show a remarkable enhancement of luminescent output relative to conventional β‐NaYF4:Yb,Er codoped UCNPs and β‐NaYF4:Yb,Er@NaYF4:Yb “active shell” alike. Moreover, this advanced core–shell–shell UCNP is subsequently used to develop a highly sensitive biosensor for the ultrasensitive detection of dopamine released from stem cell‐derived dopaminergic‐neurons. Given the challenges of in situ detection of neurotransmitters, the developed NIR‐based biosensing of neurotransmitters in stem cell‐derived neural interfaces present a unique tool for investigating single‐cell mechanisms associated with dopamine, or other neurotransmitters, and their roles in neurological processes.