Self-assembly of noble metal nanoparticles into sub-100 nm colloidosomes with collective optical and catalytic properties.

Self-assembly at the nanoscale represents a powerful tool for creating materials with new structures and intriguing collective properties. Here, we report a novel strategy to synthesize nanoscale colloidosomes of noble metals by assembling primary metal nanoparticles at the interface of emulsion droplets formed by their capping agent. This strategy produces noble metal colloidosomes of unprecedentedly small sizes (<100 nm) in high yield and uniformity, which is highly desirable for practical applications. In addition, it enables the high tunability of the composition, producing a diversity of monometallic and bimetallic alloy colloidosomes. The colloidosomes exhibit interesting collective properties that are different from those of individual colloidal nanoparticles. Specifically, we demonstrate Au colloidosomes with well-controlled interparticle plasmon coupling and Au-Pd alloy colloidosomes with superior electrocatalytic performance, both thanks to the special structural features that arise from the assembly. We believe this strategy provides a general platform for producing a rich class of miniature colloidosomes that may have fascinating collective properties for a broad range of applications

Determining Singularity-Free Inner Workspace through Offline Conversion of Assembly Modes for a 3-RRR PPM

The existing singularity avoidance methods have deficiencies, such as the conditionality of the online conversion of the assembly modes (AMs) and the kinematically redundant manipulator with the predicament of the prototype design and added complexity of the mechanism. To address these issues, a method to determine a singularity-free inner workspace through offline conversion of the AMs of the 3-RRR planar parallel manipulator (PPM) is presented. Based on the geometric relations among rods of the manipulator during the occurrence of singularity, and the singular points at or near the boundary of the workspace are permitted, the AMs and ranges of the orientation angle of the moving platform corresponding to the inner singularity-free workspace are determined through a three-dimensional search method. The simulation and experimental comparisons indicate that singular-free paths related to the constant or variable orientation angle of the moving platform can be planned on the singularity-free inner workspace

Measurement to radius of Newton’s ring fringes using polar coordinate transform

Background: Newton’s ring method is often used to measure many physical parameters. And some measured physical quantity can be extracted by calculating the radius parameter of circular fringes from Newton's ring configuration. Methods: The paper presents a new measuring method for radius of circular fringes, which includes three main steps, i.e., determination of center coordinates of circular fringes, polar coordinates transformation of circular fringes, and gray projection of the transformed result which along the horizontal direction. Then the radius values of each order ring are calculated. Results: The simulated results indicate that the measuring accuracy of the radius under the effect of random noise can keep the degree of less than 0.5 pixels. Conclusions: The proposed method can obtain the radius data of each order closed circular fringes. Also, it has several other advantages, including ability of good anti-noise, sub-pixel accuracy and high reliability, and easy to in-situ use

2-Hydr­oxy-6,6-dimethyl­bicyclo­[3.1.1]heptane-2-carboxylic acid

The title compound, C10H16O3, with a bicyclo­[3.1.1]heptane unit, was obtained by oxidation of β-pinene. The asymmetric unit contains two independent mol­ecules with similar geometry: the six-membered rings in both mol­ecules adopt envelope conformations. In the crystal, the independent mol­ecules exist as O—H⋯O hydrogen-bonded dimers. The dimers are linked into helical chains along the b axis by O—H⋯O hydrogen bonds

2-(4-Isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)-5-methyl­nicotinic acid

In the title herbicideh/phytocide, known as imaza­pic, C14H17N3O3, the pyridine and imidazole rings are almost coplanar [dihedral angle = 3.08 (5)°]. An intra­molecular O—H⋯N hydrogen bond occurs. In the crystal, an N—H⋯O hydrogen bond links mol­ecules into a chain parallel to [010]

Sound absorption properties of polyurethane-based warp-knitted spacer fabric composites

Sound absorption properties of polyurethane-based warp-knitted spacer fabric composites (PWSF) have been studied. The warp-knitted spacer fabrics (WSF) are produced on a double-needle bar warp knitting machine using different structural parameters including inclination angle of spacer yarn, thickness, spacer yarn’s diameter and surface layer structure. The composites are fabricated based on a flexible polyurethane foam. Accordingly, the acoustical behaviors of composites are evaluated properly by using two-microphone transfer function techniques in impedance tube. The findings reveal that the composites possess excellent sound absorption properties and their sound absorbability can be tailored to meet the specificend-use requirements by varying the fabric structural parameters

1-(3,4-Dihydroxy­phen­yl)-2-(4-hydroxy­phen­yl)ethanone

The title compound, C14H12O4, is a deoxy­benzoin derivative in which the dihedral between the carbonyl group and the catechol unit is 5.99 (3)°. The dihedral angle between the two benzene rings is 60.26 (13)°. In the crystal structure, inter­molecular O—H⋯O hydrogen bonds connect mol­ecules, forming a two-dimensional network. In addition, weak inter­molecular C—H⋯O hydrogen bonds and C—H⋯π contacts further stabilize the crystal structure

Topological Dirac states beyond π\pi orbitals for silicene on SiC(0001) surface

The discovery of intriguing properties related to the Dirac states in graphene has spurred huge interest in exploring its two-dimensional group-IV counterparts, such as silicene, germanene, and stanene. However, these materials have to be obtained via synthesizing on substrates with strong interfacial interactions, which usually destroy their intrinsic $\pi$($p_z$)-orbital Dirac states. Here we report a theoretical study on the existence of Dirac states arising from the $p_{x,y}$ orbitals instead of $p_z$ orbitals in silicene on 4H-SiC(0001), which survive in spite of the strong interfacial interactions. We also show that the exchange field together with the spin-orbital coupling give rise to a detectable band gap of 1.3 meV. Berry curvature calculations demonstrate the nontrivial topological nature of such Dirac states with a Chern number $C = 2$, presenting the potential of realizing quantum anomalous Hall effect for silicene on SiC(0001). Finally, we construct a minimal effective model to capture the low-energy physics of this system. This finding is expected to be also applicable to germanene and stanene, and imply great application potentials in nanoelectronics.Comment: 6 Figures , Accepted by Nano Letter

Imidazolium trans-bis­(imino­diacetato-κ3 O,N,O′)cobaltate(III)

In the title compound, (C3H5N2)[Co(C4H5NO4)2], the cation and anion are located on a twofold rotation axis and inversion center, respectively. Inter­molecular N—H⋯O hydrogen bonds link the cations and anions into layers parallel to the ab plane. The crystal packing also exhibits weak C—H⋯O hydrogen bonds, including bifurcated hydrogen bonds, and C=O⋯π inter­actions