Elaborate Architectures Research Articles

Enhanced methanol oxidation performance on platinum with butterfly-scale architectures: toward structural design of efficient electrocatalysts

Enhanced methanol oxidation performance was achieved by combining elaborate butterfly-scale architectures into platinum electrocatalysts using an electroless deposition-detemplating method. The electrochemically active surface area and the forward peak current density for methanol oxidation were dramatically increased by 5 and 5.2 times, respectively, for lamellar-ridge architectured Pt compared to its unarchitectured counterpart. Excellent mass transport properties and efficient catalytic surface accessibility were further demonstrated by finite element simulation.

ChemInform Abstract: Elaborate Metallosupramolecular Architectures Through Desymmetrization Self‐Assembly of Symmetric Building Blocks

AbstractReview: <35 refs.

Butterflies: inspiration for solar cells and sunlight water-splitting catalysts

Solar cells and photocatalysts to yield hydrogen are two significant strategies for taking advantage of clean and sustainable solar energy, and their light manipulation and harvesting ability will play a dominant role in their conversion efficiencies. Butterflies demonstrate their brilliant colors due to their wonderful skills of light manipulation, originating intrinsically from their elaborate architectures. We review the inspiration of butterflies for solar cells and sunlight water-splitting catalysts, focusing on the nipple arrays in butterfly compound eyes, as well as ridge and hole arrays, and the photonic crystal structures in butterfly wing scales. After giving a brief introduction to the typical architectures, we reveal the physical principles lying behind antireflection of compound eyes and black scales and iridescence of wing scales, respective prototypes are extracted and highlighted for the design and fabrication of solar cells and sunlight water-splitting catalysts. We conclude by reviewing the prospects for the integration of these prototypes and the appropriate materials for solar energy, which is the product of an intimate conversation between humanity and nature, as well as close cooperation between scientists from diverse fields.

Non-Centrosymmetric Tetrameric Assemblies of Tetramethylammonium Halides with Uranyl Salophen Complexes in the Solid State

Ditopic salophen-UO(2) receptors 1-4 and 7 co-crystallize with tetramethylammonium (TMA) chloride and fluoride salts producing good quality crystals amenable for X-ray diffraction characterization. The arrangement of the receptor and salt units in the crystal lattice is such that tetrameric ball-shaped assemblies are formed, where an inner cluster of four TMA cations are surrounded by an outer shell of four UO(2)-bound anions. These elaborate architectures, which occur in all cases, regardless of a certain degree of structural modification on the receptors, lead to lattices that belong to non-centrosymmetric (NCS) space groups. Interestingly, the tetragonal symmetry of the tetrameric ball-shaped assemblies is either retained (I4̅) or lost (R3c and I4̅3d) at the lattice level, without compromising the NCS nature of the crystal lattices. The principal X-ray investigation on TMAX (X = Cl/F) co-crystals, that is, 1-(TMA)Cl, 2-(TMA)Cl, 3-(TMA)Cl, 4-(TMA)Cl, 7-(TMA)Cl, and 7-(TMA)F, is accompanied by NMR and electrospray ionization (ESI) mass spectrometry studies to gather additional insight on the modality of formation of the solid state structures observed. The important role of cation-π interactions in the receptor-salt recognition process is renewed and strengthened by comparison with NMR titration data with a novel reference compound, the salophen-UO(2) complex 8. Given the importance of NCS and polar crystalline solids in the development of functional materials, this study shows that this property can be introduced into elaborate host-guest systems, as those which assemble in the architectures described here, thus expanding its field of applicability.

A seamless software defined radio development flow for waveform and prototype debugging

With the increasing number of wireless communication standards flexibility has gained more and more importance which has lead to the software defined radio (SDR) concept. However, SDR development has to face many challenges, among them are the questions how SDR systems can be designed to achieve flexibility, architectural efficiency, energy efficiency and portability at the same time. These requirements result in very elaborate architectures and a highly increased design complexity. To cope with such complexity, we proposed an SDR development flow. During the development of such SDR, debugging becomes more efficient on a prototype hardware implementation than on a simulation model. However, error analysis on a prototype suffers from strong limitations like a reduced state visibility. In this paper, an extension to the SDR development flow is presented and successfully applied to an example SDR. It allows for an efficient error analysis with the SDR simulation model by the feedback of stimulus data from the prototype.

Discrete Supramolecular Assemblies of Porphyrins Mediated by Coordination Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Discrete Supramolecular Assemblies of Porphyrins Mediated by Coordination Compounds

AbstractMetal‐driven self‐assembly has emerged as a viable alternative to covalent synthesis in the construction of large and sophisticated multi‐porphyrin architectures, whose complexity and function begin to approach the properties of naturally occurring systems. The design and preparation of robust and shape‐persistent discrete assemblies, obtained by coordination of meso‐pyridylporphyrins to ruthenium, palladium and zinc centers, is comprehensively discussed in this microreview, that covers research in this field carried out by the authors at the University of Trieste in the last few years. NMR spectroscopy and X‐ray crystallography were used jointly for the unambiguous characterization of the new species in solution and solid state, respectively. Very often the adducts of nanoscopic dimensions, in which the number, position, relative distance and orientation of the chromophores is well defined, were obtained through hierarchical supramolecular self‐assembly: multi‐porphyrin components were used as building blocks for the metal‐mediated assembly of more elaborate architectures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Cover Picture: Discrete Supramolecular Assemblies of Porphyrins Mediated by Coordination Compounds (Eur. J. Inorg. Chem. 13/2003)

AbstractThe cover picture shows the X‐ray structure of an unprecedented supramolecular assembly comprising four porphyrins and six metal atoms (two Ru and four Zn); this very stable and symmetrical architecture was obtained by spontaneous self‐assembly through four 4′‐N(py)−Zn interactions of two equal bis(porphyrin)ruthenium self‐complementary building blocks. The design of this and other robust and shape‐persistent assemblies, obtained by coordination of meso‐pyridylporphyrins to ruthenium, palladium and zinc centers, is comprehensively discussed in the microreview by E. Alessio et al. on p. 2371 ff. NMR spectroscopy and X‐ray crystallography were used jointly for the unambiguous characterization of the new species in solution and solid state, respectively. Very often the adducts of nanoscopic dimensions, in which the number, position, relative distance and orientation of the chromophores is well defined, were obtained through hierarchical supramolecular self‐assembly: multi‐porphyrin components were used as building blocks for the metal‐mediated assembly of more elaborate architectures.

Synthesis and Excited-State Photodynamics of A Perylene-Monoimide-Oxochlorin Dyad. A Light-Harvesting Array

A perylene-oxochlorin dyad has been prepared and characterized for potential use as a new light-harvesting motif. The dyad (PMI−ZnO) consists of a perylene-monoimide dye (PMI) joined at the 5-position of a zinc oxochlorin (ZnO) via a diphenylethyne linker. The dyad and its subunits have been studied in both polar and nonpolar media using static and time-resolved optical spectroscopy and electrochemical techniques. Energy flows very rapidly from both unrelaxed (vibrationally, conformationally, or electronically) and relaxed forms of the excited perylene (PMI*) to the ground-state oxochlorin with an effective time constant of ∼4 ps and an efficiency of 99% in both toluene and benzonitrile. Subsequently, there is little or no quenching of the excited oxochlorin (ZnO*) in either solvent. These findings are consistent with the expectation that all charge-separated states such as PMI- ZnO+ lie energetically above both PMI* and ZnO* in both polar and nonpolar media. Furthermore, light absorption by the perylene and oxochlorin occurs in complementary regions, giving broad spectral coverage. Thus, the new perylene-oxochlorin dyad is an excellent light-harvesting unit that can be incorporated into more elaborate architectures for use in solar-energy and molecular-photonics applications.

Site-specific self-assembly of Si/SiO x nanoparticles on micropatterned poly(dimethylsiloxane) thin films

Recent efforts have focused on the design of 2D and 3D assemblies with the goal of creating highly ordered supramolecular structures. Ultrathin films patterned with topologically different surface chemical functionality may be used as a template for such elaborate architectures. Surface functionalization can be used to impose site-specific assembly and can further lead to the fabrication of highly ordered structures, which have a great importance in the microelectronic and optoelectronic industry. Recently, we have demonstrated the fabrication of surface modified Si/SiO x nanoparticles and their self-assembly on various surfaces. We presently report the specific self-assembly of Si/SiO x nanoparticles on poly(dimethylsiloxane) (PDMS) spin-cast films. The desire to create regions of SiO x , which coexist with silicones in a two-dimensional film, is motivated by the difference in surface energies and affinity contrast between SiO x and PDMS. As presently reported, the selectivity of the deposition of Si/SiO x nanoparticles on PDMS versus UV/O 3 converted SiO x offers a great opportunity for the fabrication of periodic structures with large modulation in refractive index.

Tin, lead, and tin-lead plating

Aqueous rechargeable batteries represent one promising candidate for new energy storage and conversion systems because of their good safety, low cost, high energy density based on Faradic reactions, and high power density originated from the high ionic conductivity of aqueous electrolyte. Herein, a novel aqueous rechargeable nickel-bismuth battery was developed with highly porous Bi2MoO6 microspheres as anode active materials and delicately designed binder-free Co0.5Ni0.5MoO4@NiCo-layered double hydroxide heterostructure nanoarrays as the cathode for the first time. The Bi2MoO6 anode active materials exhibit outstanding electrochemical performances (such as high capacity of 163.2 mAh/g at 1 A/g and superior rate capability of 79.6% at 15 A/g) owing to their porous structure. To obtain the improved cathode, substitution of Co for Ni species of CoXNi1-XMoO4 as ‘core’ materials and growing time of NiCo-layered double hydroxide onto the ‘core’ materials were optimized systematically. The optimal cathode (Co0.5Ni0.5MoO4@NCLDH-12) affords appreciably enhanced electrochemical performances with the high capacity of 386.7 mAh/g at 1 A/g and good rate capability of 64.9% at 15 A/g owing to its advantages in composition and architecture. Desirably, the nickel-bismuth battery can deliver the acceptable maximum energy density of 41.5 W h/kg and power density of 3896.2 W/kg, respectively. The excellent electrochemical performances can be put down to the elaborate architectures of electrodes and synergistic effect between active materials. This current research would enrich the chemistry systems of present aqueous rechargeable batteries and also pave the way to effectively construct promising electrode active materials for aqueous rechargeable nickel-bismuth batteries.

Novel monolabeled redox biomaterials: Amino-ended poly(ethylene oxide) ferrocenes and their biotin-conjugates

Treatment of ferrocenoyl chloride with symmetrical poly(oxyalkylene) diamine 1 in excess affords the monofonctionalized derivative 2 in moderate to good yields. This one-step procedure provides a convenient entry to novel monolabeled redox precursors such as the biotin derivative 3 for more elaborate architectures.