1,153 research outputs found
Reversible Transient Nucleation in Ionic Solutions as the Precursor of Ion Crystallization
Molecular dynamics simulations for aqueous sodium chloride solutions were
carried out at various concentrations. Supplementary to the Debye-H\"uckel
theory, reversible transient nucleation of ions was observed even in dilute
solutions. The average size of formed ion clusters and the lifetime of ion
pairs increase with concentration until the saturation point, when ion clusters
become stable and individual ions adjust their positions to form ordered
lattice structures, leading to irreversible ion crystallization, which is
beyond the description of the classical nucleation theory.Comment: 4 pages, 5 figures, and 46 reference
One-step hydrothermal synthesis of fluorescence carbon quantum dots with high product yield and quantum yield
A one-step hydrothermal synthesis of nitrogen and silicon co-doped fluorescence carbon quantum dots (N,Si-CQDs), from citric acid monohydrate and silane coupling agent KH-792 with a high product yield (PY) of 52.56% and high quantum yield (QY) of 97.32%, was developed. This greatly improves both the PY and QY of CQDs and provides a new approach for a large-scale production of high-quality CQDs. Furthermore, N,Si-CQDs were employed as phosphors without dispersants to fabricate white light-emitting diodes (WLEDs) with the color coordinates at (0.29, 0.32). It is suggested that N,Si-CQDs have great potential as promising fluorescent materials to be applied in WLEDs.Peer reviewe
Microscopic structure and dynamics of air/water interface by computer simulations-comparison with sum-frequency generation experiments
The air/water interface was simulated and the mode amplitudes and their ratios of the effective nonlinear sum-frequency generation (SFG) susceptibilities (A_(eff)'s) were calculated for the ssp, ppp, and sps polarization combinations and compared with experiments. By designating “surface-sensitive” free OH bonds on the water surface, many aspects of the SFG measurements were calculated and compared with those inferred from experiment. We calculate an average tilt angle close to the SFG observed value of 35, an average surface density of free OH bonds close to the experimental value of about 2.8 × 10^(18) m^(−2), computed ratios of A_(eff)'s that are very similar to those from the SFG experiment, and their absolute values that are in reasonable agreement with experiment. A one-parameter model was used to calculate these properties. The method utilizes results available from independent IR and Raman experiments to obtain some of the needed quantities, rather than calculating them ab initio. The present results provide microscopic information on water structure useful to applications such as in our recent theory of on-water heterogeneous catalysis
The -index of graphs without intersecting triangles/quadrangles as a minor
The -matrix of a graph is the convex linear combination of
the adjacency matrix and the diagonal matrix of vertex degrees ,
i.e., , where . The -index of is the largest eigenvalue of .
Particularly, the matrix (resp. ) is exactly the
adjacency matrix (resp. signless Laplacian matrix) of . He, Li and Feng
[arXiv:2301.06008 (2023)] determined the extremal graphs with maximum adjacency
spectral radius among all graphs of sufficiently large order without
intersecting triangles and quadrangles as a minor, respectively. Motivated by
the above results of He, Li and Feng, in this paper we characterize the
extremal graphs with maximum -index among all graphs of sufficiently
large order without intersecting triangles and quadrangles as a minor for any
, respectively. As by-products, we determine the extremal graphs
with maximum signless Laplacian radius among all graphs of sufficiently large
order without intersecting triangles and quadrangles as a minor, respectively.Comment: 15 page
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