Lateral migration of dual droplet trains in a double spiral microchannel

Microfluidic droplets have emerged as novel platforms for chemical and biological applications. Manipulation of droplets has thus attracted increasing attention. Different from solid particles, deformable droplets cannot be efficiently controlled by inertia-driven approaches. Here, we report a study on the lateral migration of dual droplet trains in a double spiral microchannel at low Reynolds numbers. The dominant driving mechanism is elucidated as wall effect originated from the droplet deformation. Three types of migration modes are observed with varying Reynolds numbers and the size-dependent mode is intensively investigated. We obtain empirical formulas by relating the migration to Reynolds numbers and droplet sizes. The effect of droplet deformability on the migration and the detailed migration behavior along the double spiral channel are discussed. Numerical simulations are also performed and yielded in qualitative agreement with the experiments. This proposed low Re approach based on lateral migration could be a promising alternative to existing inertia-driven approaches especially concerning deformable entities and susceptible bio-particles.     

Effect of Mie resonance on photocatalytic hydrogen evolution over dye-sensitized hollow C-TiO_2 nanoshells under visible light irradiation

Light utilization is one of the key factors for the improvement of photocatalytic perfo rmance.He rein,we design C-TiO_2 hollow nanoshells with strong Mie resonance for enhanced photocatalytic hydrogen evolution in a dye-sensitized system under visible light irradiation(λ≥420 nm).By tuning the inner diameters of hollow nanoshells,the Mie resonance in hollow nanoshells is adjusted for better excitation of dye molecules,which thus greatly enhances the light utilization in visible light region.This work shows the potential of Mie resonance in nanoshells can be an alternative strategy to increase the light utilization for photocatalysis.     

Superhydrophobic nickel films fabricated by electro and electroless deposition

In this work, a superhydrophobic nickel surface is fabricated by coupling electro and electroless deposition without chemical modification. SEM study reveals that electrodeposited nickel surface is characterized by nanocone arrays and has a contact angle of about 135°. After adding electroless deposition, as the second step, hemispherically topped nickel nanocone arrays are formed which leads to a high contact angle of 153.6°. That is, nickel surface has successfully transformed from hydrophobic to superhydrophobic. This transition is investigated both from the aspects of chemical composition and surface structure and proves the latter is the dominant factor. The present study inspires us to do more research about the creation of rough surfaces and enriches our comprehension about superhydrophobicity.     

A computational DFT analysis of OH chemisorption on catalytic Pt(111) nanoparticles

In this article, various energies and geometries of pure platinum nanoparticles and those of platinum nanoparticles with adsorbed OH were investigated. Fourteen different platinum clusters of 3–40 atoms were studied using spin-unrestricted density functional theory (DFT) with a double numerical plus polarization basis set. This range of sizes gave enough information for establishing the general trends that were the primary goal of the study. Three different shapes of platinum clusters were presented, and the effect of cluster size on binding energy, total energy, and HOMO–LUMO energy gap was investigated. Subsequently, same calculations were performed for those selected Pt clusters with OH adsorbate on the surface. The results show that the stability of both the pure clusters and the clusters with adsorbed OH molecule increases with an increase of cluster size. This fact indicates that direct influence of the size of Pt cluster on the reaction rate is possible, and the understanding of how cluster size would affect binding energy is important. As expected, the effect of cluster size on total energy of molecule was shown to be a linear function independent of cluster type. We also found that optimized (stable) Pt clusters were bigger in size than that of the initial clusters, or clusters with bulk geometry.