Using molecular dynamics simulations, we study collisions between amorphous silica nanoparticles. Our silica model contains uncontaminated surfaces, that is, the effect of surface hydroxylation or of adsorbed water layers is excluded. For central collisions, we characterize the boundary between sticking and bouncing collisions as a function of impact velocity and particle size and quantify the coefficient of restitution. We show that the traditional Johnson-Kendall-Roberts (JKR) model provides a valid description of the ingoing trajectory of two grains up to the moment of maximum compression. The distance of closest approach is slightly underestimated by the JKR model, due to the appearance of plasticity in the grains, which shows up in the form of localized shear transformation zones. The JKR model strongly underestimates the contact radius and the collision duration during the outgoing trajectory, evidencing that the breaking of covalent bonds during grain separation is not well described by this model. The adhesive neck formed between the two grains finally collapses while creating narrow filaments joining the grains, which eventually tear.

Ripple patterns forming on Pt͑111͒ due to 5 keV Ar + grazing-incidence ion bombardment were investigated by scanning tunneling microscopy in a broad temperature range from 100 to 720 K and for ion fluences up to 3 ϫ 10 20 ions/ m 2 . A detailed morphological analysis together with molecular dynamics simulations of single ion impacts allow us to develop atomic scale models for the formation of these patterns. The large difference in step edge versus terrace damage is shown to be crucial for ripple formation under grazing incidence. The importance of distinct diffusion processes-step adatom generation at kinks and adatom lattice gas formation-for temperature dependent transitions in the surface morphology is highlighted. Surprisingly, ion bombardment effects like thermal spike induced adatom production and planar subsurface channeling are important for pattern ordering.

The onset of pattern formation through exposure of Pt(111) with 5 keV Ar(+) ions at grazing incidence has been studied at 550 K by scanning tunneling microscopy and is supplemented by molecular-dynamics simulations of single ion impacts. A consistent description of pattern formation in terms of atomic scale mechanisms is given. Most surprisingly, pattern formation depends crucially on the angle of incidence of the ions. As soon as this angle allows subsurface channeling of the ions, pattern regularity and alignment with respect to the ion beam greatly improves. These effects are traced back to the positionally aligned formation of vacancy islands through the damage created by the ions at dechanneling locations.

Molecularly imprinted polymer (MIP) computational design is expected to become a routine technique prior to synthesis to produce polymers with high affinity and selectivity towards target molecules. Furthermore, using these simulations reduces the cost of optimizing polymerization composition. There are several computational methods used in MIP fabrication and each requires a comprehensive study in order to select a process with results that are most similar to properties exhibited by polymers synthesized through laboratory experiments. Until now, no review has linked computational strategies with experimental results, which are needed to determine the method that is most appropriate for use in designing MIP with high molecular recognition. This review will present an update of the computational approaches started from 2016 until now on quantum mechanics, molecular mechanics and molecular dynamics that have been widely used. It will also discuss the linear correlation between computational results and the polymer performance tests through laboratory experiments to examine to what extent these methods can be relied upon to obtain polymers with high molecular recognition. Based on the literature search, density functional theory (DFT) with various hybrid functions and basis sets is most often used as a theoretical method to provide a shorter MIP manufacturing process as well as good analytical performance as recognition material.

Scanning tunneling microscopy is used to quantify step-edge sputtering of Pt͑111͒ at 550 K by grazing incidence ion bombardment with 5 keV Ar + ions. For bombardment conditions causing negligible erosion on terraces, damage features associated with step bombardment allow us to visualize step retraction and thus to quantify the step-edge sputtering yield. An alternative method for step-edge yield determination, which is applicable under more general conditions, is the analysis of the concentration of ascending steps together with the removed amount as a function of ion fluence. Interestingly, the azimuthal direction of the impinging ions with respect to the surface significantly changes the sputtering yield at step edges. This change is attributed to the orientation dependence of subsurface channeling. Atomistic insight into step-edge sputtering and its azimuthal dependence is given by molecular dynamics simulations of ion impacts at 0 and 550 K. The simulations also demonstrate a strong dependence of the step-edge sputtering yield on temperature.

A molecular imprinted polymer (MIP) was computationally designed and synthesized for the selective extraction of salmeterol xinafoate (SLX) from human serum. In this study, semi-empirical PM3 calculations were used to find a suitable functional monomer (FM), the ratio of template (T) to FM, and types of crosslinkers. MIPs were synthesized with 2-hydroxyethyl methacrylate (HEMA) with T:FM mol ratios of 1:6 and 1:4 and ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TRIM) as a crosslinker. On the basis of computational and experimental results, HEMA and TRIM in the mol ratio 1:6 of T-FM (MIP3) were found to be the best choices of FM and crosslinker, respectively. These polymers were then used as a selective sorbent to develop a molecularly imprinted solid-phase extraction procedure followed by high performance liquid chromatography with UV detection for the determination of SLX in serum. The extraction ability of MIP3 was excellent with a recovery of 92.17% ± 2.66% of SLX in spiked serum, and 91.15% ± 1.12% when SLX was spiked as a mixture with another analogous structure. By comparing the performance of the synthesized sorbent with a C-18 cartridge with a recovery of 79.11% ± 2.96%, it was determined that MIP had better performance over the latter. On the basis of these results, the imprinted receptor MIPs, especially MIP 3, can be applied for the direct extraction of SLX in clinical analysis.

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The structural dynamics of short-pulse laser irradiated surfaces and nano-structures has been studied with nm spatial and ultrafast temporal resolution by means of single-shot coherent XUV-scattering techniques. The experiments allowed us to time-resolve the formation of laser-induced periodic surface structures, and to follow the expansion and disintegration of nano-objects during laser ablation.