3D‐Printed Microfluidics

The advent of soft lithography allowed for an unprecedented expansion in the field of microfluidics. However, the vast majority of PDMS microfluidic devices are still made with extensive manual labor, are tethered to bulky control systems, and have cumbersome user interfaces, which all render commercialization difficult. On the other hand, 3D printing has begun to embrace the range of sizes and materials that appeal to the developers of microfluidic devices. Prior to fabrication, a design is digitally built as a detailed 3D CAD file. The design can be assembled in modules by remotely collaborating teams, and its mechanical and fluidic behavior can be simulated using finite‐element modeling. As structures are created by adding materials without the need for etching or dissolution, processing is environmentally friendly and economically efficient. We predict that in the next few years, 3D printing will replace most PDMS and plastic molding techniques in academia.     

Highly ortho‐Selective Chlorination of Anilines Using a Secondary Ammonium Salt Organocatalyst

An organocatalytic, highly facile, efficient, and regioselective ortho‐chlorination of anilines is described. A secondary ammonium chloride salt has been employed as the catalyst and the reaction can be conducted at room temperature without protection from air and moisture. In addition, the reaction is readily scalable and the catalyst can be recycled and reused. This catalytic protocol has been applied to the efficient synthesis of a highly potent c‐Met kinase inhibitor. Mechanistic studies revealed that unique structural features of the secondary ammonium chloride salt are important for both the catalysis and regioselectivity of the electrophilic ortho‐chlorination.     

Novel coassembly route to Cu-SiO2 MCM-41-like mesoporous materials

A series of mesostructured Cu-SiO2 composites have been synthesized with sodium metasilicate (Na2SiO3) and cuprammonia nitrate (Cu(NH3)4(NO3)2) respectively used as Si and Cu sources. The synthetic procedures were conducted at room temperature, and cetyltrimethylammonia bromide was used as a template. Under our experimental conditions, ordered mesoporous Cu-SiO2 composites could be obtained with a copper content up to 16.8 wt %. Average pore diameters (2.80-3.15 nm), wall thickness (1.30-2.20 nm), and specific surface area (1020-690 m2/g) are found to vary linearly with copper content (0-16.8 wt %). Results of thermal gravimetry-differential thermal analysis reveal the collapse temperature of the order structure starts at approximately 1250 K for mesoporous Cu-SiO2 with 16.8 wt % copper content. As indicated by the outcomes of inductively coupled plasma and X-ray photoelectron spectroscopy studies, copper is mainly incorporated inside the pore wall rather than embedded on the wall surface. Copper species strongly interact with silica, and calcination at high temperatures cannot cause phase separation between silica and copper oxide. Cu status in mesoporous Cu-SiO2 composites is similar to that in copper silicate in neighboring structures. Based on the results, a S+ I- I+ I- mechanism is proposed in which copper entities are surrounded by silicon species during synthesis of the mesostructured composite.     

Increased selectivity for electrochromatography by dynamic ion exchange

The separation of compounds with similar mobilities is expect to be difficult with capillary zone electrophoresis. Increased selectivity is shown for compounds of this type when other modes of separation are added to the system. A capillary coated with a hydrophobic stationary phase is shown to be a dynamic ion exchanger when a quaternary ammonium compound is added to the running buffer. Compounds are shown to have a decrease in retention when the concentration of the buffer ions is increased. The effect of adding an organic modifier and the influence of the concentration of the surface active reagent are also studied.     

Applications of fabry—pérot interferometry in multi-element flame emission analysis

A system for multi-element flame emission analysis based on a scanning Fabry–Pérot interferometer is described and evaluated. Detection limits and linearity of response for ten elements commonly determined by flame photometry compare well with conventional single-element methods. Analyses for several elements in tap water, serum, urine, standard orchard leaf and low-alloy steel demonstrate the good accuracy and precision of the technique; the resolution allows up to five elements to be determined simultaneously.     

Crystal structure of Ca2Ln3Sb3O14 (Ln=La, Pr, Nd and Y): A novel variant of weberite

The crystal structures of Ca₂Ln₃Sb₃O₁₄ (Ln=La, Pr, Nd and Y) and Ca₂Sb₂O₇ at room temperature were refined by the Rietveld method using combined X-ray and neutron powder diffraction data. Ca₂Sb₂O₇ adopts the weberite structure having the space group Imma. The structures of Ca₂Ln₃Sb₃O₁₄ are, however, neither the orthorhombic nor the tetragonal chiolite as has been suggested previously. They crystallize in the monoclinic space group I2/m11 belonging to a hitherto unknown type of deformation of the parent (orthorhombic) weberite structure.     

A Two-Level, Discrete-Particle Approach for Simulating Ordered Colloidal Structures

We devise a new, two-level discrete-particle model to simulate ordered colloidal structures with vastly different scales. We use the molecular dynamics paradigm with a Lennard-Jones-type potential to define colloidal particle system and dissipative particle dynamics (DPD) to model the solvent. The initially mixed, disordered particle ensemble undergoes a phase transition. We observe the spontaneous creation of spherical or rod-like micelles and their crystallization in stable hexagonal or worm-like structures, respectively. The ordered arrays obtained by using the particle model are similar to the two-dimensional colloidal crystals observed in laboratory experiments. The micelle shape depends on the ratio between the scaling factors of the colloid-colloid to colloid-solvent particle interactions. The properties of the DPD solvent, such as the strongly variable viscosity and partial pressure, determine the speed of crystallization. The intriguing features of colloidal arrays and their exotic symmetries, which persist also over two-dimensional domains, can be simulated numerically by using the two-level discrete-particle approach and are illustrated here. Copyright 2000 Academic Press.     

One‐Pot Process to Carborano‐Coumarin via Catalytic CascadeDehydrogenative Cross‐Coupling

Ir‐catalyzed cascade dehydrogenative CH/BH and BH/OH cross‐coupling of carboranyl carboxylic acid with readily available benzoic acid has been achieved, leading to the facile synthesis of previously unavailable carborano‐coumarin in a simple one‐pot process. Two cage B—H, one aryl C—H and one O—H bonds are activated to construct efficiently new B—C and B—O bonds. The cascade cyclization can stop at the first B—H/C—H cross‐coupling step by tuning the reaction conditions, resulting in a series of α‐carboranyl benzoic acid and aryl carborane derivatives. Control experiments indicate that B—H/C—H dehydrocoupling proceeds preferentially over B—H/O—H dehydrocoupling, and both directing groups and oxidants are crucial for this reaction. An iridium(V) intermediate is proposed to be involved in the catalytic cycle.     

Burntgas composition of the heliumoxygenacetylene flame

The burnt gas composition of a potentially important atom reservoir, the HeO₂C₂H₂ flame, is calculated. This flame, compared to the air—acetylene flame, provides a slightly more reducing and a much less quenching environment.