A new type of nano-sized silicon/carbon composite electrode for reversible lithium insertion

A new type of nano-sized silicon/carbon composite was developed. It shows superior electrochemical cycling properties as negative electrode material for possible use in lithium-ion batteries with respect to high reversible and low irreversible capacity, and low fading.     

Fast quantification of water in single living cells by near-infrared microscopy

We have set up a near-infrared microscope using a tuneable diode laser in the range from 1530 to 1570 nm. This spectral range is close to the peak of the water overtone absorption. We used this new microscope to study liver cells, hepatocytes, showing that quantitative information of the intracellular water concentration in living cells can be extracted.     

Functionalization of silicon nanoparticles via hydrosilylation with 1-alkenes

Studies focusing on the functionalization of the surface of free silicon nanoparticles are presented. This functionalization is applied to hydrogen-terminated silicon nanoparticles to evaluate how far the well-known solution-phase chemistry of thermal-, radical-, Lewis acid- and UV light-mediated hydrosilylation can be applied to the surface chemistry of silicon nanoparticles. The efficiencies of hydrosilylation for thermal-, radical- and Lewis acid-mediated reactions on silicon nanoparticles surfaces, deduced from the intensity of the ν(Si–H) absorption, are found to be comparable.     

A New Method and a New Scaling for Deriving Fermionic Mean-Field Dynamics

We introduce a new method for deriving the time-dependent Hartree or Hartree-Fock equations as an effective mean-field dynamics from the microscopic Schrödinger equation for fermionic many-particle systems in quantum mechanics. The method is an adaption of the method used in Pickl (Lett. Math. Phys. 97 (2) 151–164 2011) for bosonic systems to fermionic systems. It is based on a Gronwall type estimate for a suitable measure of distance between the microscopic solution and an antisymmetrized product state. We use this method to treat a new mean-field limit for fermions with long-range interactions in a large volume. Some of our results hold for singular attractive or repulsive interactions. We can also treat Coulomb interaction assuming either a mild singularity cutoff or certain regularity conditions on the solutions to the Hartree(-Fock) equations. In the considered limit, the kinetic and interaction energy are of the same order, while the average force is subleading. For some interactions, we prove that the Hartree(-Fock) dynamics is a more accurate approximation than a simpler dynamics that one would expect from the subleading force. With our method we also treat the mean-field limit coupled to a semiclassical limit, which was discussed in the literature before, and we recover some of the previous results. All results hold for initial data close (but not necessarily equal) to antisymmetrized product states and we always provide explicit rates of convergence.     

Electrical properties of surface functionalized silicon nanoparticles

The present study relates to the applicability of silicon nanoparticles as basic component in printing inks for the fabrication of printable electronic devices. It is systematically investigated, how the surface functionalization of silicon nanoparticles with 1-alkenes affects the electrical properties of thin films made of them. Therefore, films of as-prepared silicon nanoparticles with a size of 42 nm as well as freshly etched ones, both terminated with hydrogen, are compared with films of silicon nanoparticles functionalized with n-octene, n-dodecene, allylmercaptan, and allylamine, respectively. It is found, that the activation energy of the electron transport through the films is in the range of 0.5 eV and scales with the polarity of the functionalization.     

Multi-Time Wave Functions Versus Multiple Timelike Dimensions

Multi-time wave functions are wave functions for multi-particle quantum systems that involve several time variables (one per particle). In this paper we contrast them with solutions of wave equations on a space–time with multiple timelike dimensions, i.e., on a pseudo-Riemannian manifold whose metric has signature such as \({+}{+}{-}{-}\) or \({+}{+}{-}{-}{-}{-}{-}{-}\), instead of \({+}{-}{-}{-}\). Despite the superficial similarity, the two behave very differently: whereas wave equations in multiple timelike dimensions are typically mathematically ill-posed and presumably unphysical, relevant Schrödinger equations for multi-time wave functions possess for every initial datum a unique solution on the spacelike configurations and form a natural covariant representation of quantum states.