A Highly Ultrafine Core–Shell Ir–Cu Bimetallic Nanoparticles and Their Application in Catalytic Oxidation of Textile Dye,Congo Red,by Hexacyanoferrate(III) Ions: A Kinetic Approach

Kinetics and Catalysis - Bimetallic nanoparticles (BMNPs), a pioneer class of material research for catalysis, were intensively explored. We report a versatile catalyst, core–shell...     

Structure of short polymers at interfaces: a combined simulation and theoretical study

The structure of polymers confined between surfaces is studied using computer simulation and a density functional approach. The simple model system considers the polymer molecule as a pearl necklace of freely jointed hard spheres, having attractions among the beads, confined between attractive surfaces. This approach uses the universality of the free-energy functional to obtain the self-consistent field required in the single chain simulation. The second-order direct correlation function for the uniform bulk fluid required as input has been calculated from the reference interaction site model integral equation theory using mean spherical approximation. The theoretical results are shown to compare well with the Monte Carlo simulation results for varying densities, chain lengths, and with different attractive interaction parameters. The simulation results on the conformational properties give important indications regarding the behavior of chains as they approach the surfaces.     

Solution-Phase and Magnetic Approach towards Understanding Iron Gall Ink-like Nanoassemblies

Metal-containing tubes: The structures of several iron-containing C-methylpyrogallol[4]arene (PgC(1) ) nanoassemblies were studied in both the solid and solution phases. The nanoassemblies have a tubular architecture with the iron as part of the framework (see picture; gray C, red O, turquoise/blue Fe), and magnetic analysis suggests a canted or spiral arrangement of the iron centers.     

Fused deposition modeling-based additive manufacturing (3D printing): techniques for polymer material systems

While the developments of additive manufacturing (AM) techniques have been remarkable thus far, they are still significantly limited by the range of printable, functional material systems that meet the requirements of a broad range of industries; including the health care, manufacturing, packaging, aerospace, and automotive industries. Furthermore, with the rising demand for sustainable developments, this review broadly gives the reader a good overview of existing AM techniques; with more focus on the extrusion-based technologies (fused deposition modeling and direct ink writing) due to their scalability, cost efficiency and wider range of material processability. It then goes on to identify the innovative materials and recent research activities that may support the sustainable development of extrusion-based techniques for functional and multifunctional (4D printing) part and product fabrication.     

Surface modification of poly(dimethylsiloxane) with a perfluorinated alkoxysilane for selectivity toward fluorous tagged peptides

Poly(dimethylsiloxane) (PDMS) and similar polymers have proved to be of widespread interest for use in microfluidic and similar microanalytical devices. Surface modification of PDMS is required to extend the range of applications for devices made of this polymer, however. Here we report on the grafting of perfluorooctyltriethoxysilane via hydrolysis onto an oxidized PDMS substrate in order to form a fluorinated microchannel. Such a fluorinated device could be used for separating fluorous tagged proteins or peptides, similar to that which has been recently demonstrated in a capillary electrophoresis system or in an open tubular capillary column. The modified polymer is characterized using chemical force titrations, contact angle measurements, and X-ray photoelectron spectroscopy (XPS). We also report on a novel means of performing electroosmotic measurements on this material to determine the surface zeta potential. As might be expected, contact angle and chemical force titration measurements indicate the fluorinated surface to be highly hydrophobic. XPS indicates that fluorocarbon groups segregate to the surface of the polymer over a period of days following the initial surface modification, presumably driven by a lower surface free energy. One of the most interesting results is the zeta potential measurements, which show that significant surface charge can be maintained across a wide range of pH on this modified polymer, sufficient to promote electroosmotic flow in a microfluidic chip. Matrix-assisted time-of-flight mass spectrometry (MALDI-TOF MS) measurements show that a fluorous-tagged peptide will selectively adsorb on the fluorinated PDMS in aqueous solution, demonstrating that the fluorinated polymer could be used in devices designed for the enrichment or enhanced detection of fluorous-labeled proteins and peptides.     

Structural evolution and stability of hydrogenated Li(n) (n = 1-30) clusters: a density functional study

The structure and electronic and optical properties of hydrogenated lithium clusters Li(n)H(m) (n = 1-30, m ≤ n) have been investigated by density functional theory (DFT). The structural optimizations are performed with the Becke 3 Lee-Yang-Parr (B3LYP) exchange-correlation functional with 6-311G++(d, p) basis set. The reliability of the method employed has been established by excellent agreement with computational and experimental data, wherever available. The turn over from two- to three-dimensional geometry in Li(n)H(m) clusters is found to occur at size n = 4 and m = 3. Interestingly, a rock-salt-like face-centered cubic structure is seen in Li(13)H(14). The sequential addition of hydrogen to small-sized Li clusters predicted regions of regular lattice in saturated hydrogenated clusters. This led us to focus on large-sized saturated clusters rather than to increase the number of hydrogen atoms monotonically. The lattice constants of Li(9)H(9), Li(18)H(18), Li(20)H(20), and Li(30)H(30) calculated at their optimized geometry are found to gradually approach the corresponding bulk values of 4.083. The sequential addition of hydrogen stabilizes the cluster, irrespective of the cluster size. A significant increase in stability is seen in the case of completely hydrogenated clusters, i.e., when the number of hydrogen atoms equals Li atoms. The enhanced stability has been interpreted in terms of various electronic and optical properties like adiabatic and vertical ionization potential, HOMO-LUMO gap, and polarizability.     

Lanthanoid metal nitrates with hydrogen bonded hexamethylenetetramine

Cerium, praseodymium, and neodymium nitrate complexes with hydrogen bonded hexamethylenetetramine (HMTA) of the formula [Ce(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃, [Pr(NO₃)₂(H₂O)₆]₂[Pr(H₂O)₉](HMTA)₆(NO₃)₆(H₂O)₄ and [Nd(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃ have been prepared and characterized by X-ray crystallography. All the complexes belong to monoclinic crystal system. Ce and Nd complexes have P21/n space group, whereas Pr complex has C2/c. Thermal analyses of these complexes were carried out using TG, DSC, which showed their multi-step decomposition. Kinetics of thermolysis has been done by applying model fitting as well as model free isoconversional method. In order to see the response of rapid heating, ignition delay measurements were carried out. The thermal decomposition pathways have also been demonstrated. On the basis of thermal studies the thermal stability of the complexes was found in the order; Pr > Ce > Nd. In order to identify the end products of thermolyses, X-ray diffraction patterns of end product were carried out which showed the formation of corresponding metal oxides.     

Internal Structure Tailoring in 3D Nanoplasmonic Metasurface for Surface-Enhanced Raman Spectroscopy

Tunable nanoplasmonic metasurfaces have resulted in many versatile platforms for sensing applications including surface-enhanced Raman scattering (SERS)-based detection. However, to date, their fabrication still faces challenges in uniformity, repeatability, and controllability. Here, a novel large-area and hierarchical nanoplasmonic array with controlled internal structure and tunable plasmonic properties is reported, relying on controllably tailoring the single nanosphere on a uniform double-layered array into a well-defined nanoflower structure. The fabrication involves colloidal self-assembly, lithography, and plasmonic metal coating. First, a uniformly distributed double-layered colloidal array is fabricated via an ethanol-assisted self-assembly technique. Next, with the help of inductively coupled plasma dry etching, the lower layer is transformed to the nanoflower array with well-defined petal shape. Subsequently, a gold film with controlled thickness is deposited onto the nanoflower structured array, resulting in a tunable optical and SERS-active enhancement effect. Furthermore, 3D finite-difference time-domain simulation shows multiple enhancement sites inside the nanoflower array. Such a brand-new 3D structured array has the potential for varied applications, ranging from SERS sensors to light regulation.     

Anion‐ and Spacer‐Directed Host–Guest Complexes of Bipyridine with Pyrogallol[4]arene

New oval‐shaped capsular and bilayer‐type hydrogen‐bonded arrangements of C‐propyl‐ol‐pyrogallol[4]arene (PgC3‐OH) with bipyridine‐type spacer complexes are reported here. These complexes are engineered by virtue of derivatization of C‐alkyl tails of pyrogallol[4]arene and the use of divergent spacer ligands. Complexes of PgC3‐OH, PgC3‐OH with bpy (4,4′‐bipyridine) and PgC3‐OH with bpa (1,2‐bis(4‐pyridyl)acetylene) have bilayer type arrangements; however, the use of hydrogen chloride causes protonation of bpy molecule, which is then entrapped flat within an offset oval‐shaped dimeric hydrogen‐bonded PgC3‐OH nanocapsule. The presence of chloride anion in the crystal lattice controls the geometry of the resultant nanoassembly.