Light-harvesting hybrid assemblies

Light-harvesting hybrids have gained much importance as they are considered as potential mimics for photosynthetic systems. In this Concept article we introduce the design concepts involved in the building up of light-harvesting hybrids; these resemble the well-studied organic-based assemblies for energy transfer. We have structured this article into three parts based on the strategies adopted in the synthesis of hybrid assemblies, as covalent, semicovalent, and noncovalent procedures. Furthermore, the properties and structural features of the hybrids and analogous organic assemblies are compared. We also emphasize the challenges involved in the processability of these hybrid materials for device applications and present our views and results to address this issue through the design of soft-hybrids by a solution-state, noncovalent, self-assembly process.     

Structural,optical and secondary electron emission properties of diamond like carbon thin films deposited by pulsed-DC plasma CVD technique

Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp³ content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H₂ content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient (γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications.     

Oxovanadium (IV) complexes of bidentate [N,O] donor Schiff-base ligands: synthesis and mesomorphism

A series of new oxovanadium(IV) Schiff-base complexes of the type [VO(L)₂], [L?=?N-(4-n-alkoxysalicylaldimine)-4′-dodecyloxyaniline, n?=?6, 8, 16, and 18] have been synthesized. The compounds were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, UV-Vis, FAB-mass, and magnetic susceptibility measurements. The mesomorphic behavior of the compounds was studied by polarized optical microscopy and differential scanning calorimetry. The compounds are all highly thermally stable exhibiting smectic mesomorphism. Non-electrolytic nature of the complexes was ascertained by solution electrical conductance measurements. Cyclic voltammetry revealed a quasireversible single-electron response for VO(V)/VO(IV) couple. A ν_V=O stretching mode at ～970?cm^?1 indicates absence of any intermolecular V=O?···?V=O interactions. Density functional theory study was carried out using DMol3 at BLYP/DNP level to determine energy optimized structure revealed a distorted square pyramidal geometry for the vanadyl complexes.     

Orientational order parameter studies in two symmetric dimeric liquid crystals – an optical study

The optical technique developed by [W. Kuczynski, B. Zywucki, and J. Malecki, Determination of orientational order parameter in various liquid-crystalline phases, Mol. Cryst. Liq. Cryst. 381 (2002), pp. 1–19; B.J. Zywucki and W. Kuczynski, IEEE transactions on optical phenomena – The orientational order in nematic liquid crystals from birefringence measurements, Dielectr. Electr. Insul. 8 (2001), pp. 512–515] is fabricated and used to determine the orientational order parameter in two dimeric liquid crystalline compounds nematic and SmA phases of α,ω-bis(4-alkylanilinebenzylidene-4′-oxy)alkane (m.OnO.m) homologous series. The compounds studied are 5.O8O.5 and 5.O10O.5 which exhibit nematic and SmA, and nematic phases, respectively. The orientational order parameter in both the phases of nematic and SmA phases of the compound one and the nematic phase of the compound two are obtained using the principle of Newton's rings which gives directly the birefringence, δn of the liquid crystal dimer. The merits of the technique used are presented over the conventional techniques for the determination of orientational order parameter. The results for the two compounds are compared with those values estimated from n _e, n _o and density using the two internal field models due to Vuks and Neugebauer applicable to nematic phase.     

Phase transition and some physical properties of binary mixtures of two nematogenic compounds showing induced smectic phase

The binary mixtures of nematogenic compounds 4-n-pentyl phenyl 4-n′-hexyloxy benzoate (ME6O.5) and 4-cyanophenyl 4-pentyl benzoate (CPPB) show the presence of induced smectic phase. In this article, we report the phase diagram and the results of refractive index, density, static dielectric permittivity and X-ray diffraction measurements of different binary mixtures of (ME6O.5?+?CPPB) throughout the entire composition range. The density and refractive index values have been analysed to obtain orientational order parameters. The various physical properties of the system have been discussed on the basis of the phase diagram.     

Numerical modeling of interaction between surface radiation and natural convection of atmospheric aerosol in presence of transverse magnetic field

After the era of industrialization, technology is developing daily since the last century. Urbanization, communication, and transportation have grown rapidly and simultaneously deforestation and volcanic eruptions take place on a large scale. As result every moment tons of foreign particles like soot, dust, ash, and bio-fuel contaminants are released into the atmosphere. These contaminants mix with air and various green house gases, form a blanket structure in atmosphere. This mixture of ultrafine particle suspension with atmospheric air is known as aerosol. In the present study, numerical simulations of hydrodynamic single cell buoyant convection of atmospheric aerosol sample enclosed within a gray enclosure in the presence of a transverse magnetic field and surface radiation is addressed. Flow of the aerosol over deserts and industrial belts is a practical example of such a condition, where the thermal radiation emanating from the surface, affects the flow mechanism of the aerosol transport. The emphasis of the present study is only on carbon-black solid particles of a size in the nanometer range present in atmospheric air. The aerosol is treated as nanofluid for the numerical simulation. A comprehensive study on the controlling parameters that affect the flow and heat transfer characteristics are delineated. The governing equations are solved using modified MAC method and SIMPLER algorithm has been used to solve pressure velocity coupling employing relaxation technique. The transport equation for surface radiation is solved using the net radiation method. The cross string method is used to evaluate the view factor. The most striking result is that the heat transfer rate increases with increase in the volume fraction of the carbon-black particles, which has an adverse effect on both the climate and living creatures. The results are presented in tabular and graphical form. The heat transfer and flow characteristics are depicted in the form of isotherms and streamlines revealing the physics of this complex phenomenon.     

Selective terminal heck arylation of vinyl ethers with aryl chlorides: a combined experimental-computational approach including synthesis of betaxolol

Reaction conditions have been developed for palladium-catalyzed terminal (beta-) arylation of acyclic vinyl ethers with high regioselectivity using inexpensive aryl chlorides as starting materials and the P(t-Bu)3 releasing preligand [(t-Bu3)PH]BF4 as the key additive. This swift and straightforward protocol exploits non-inert conditions and controlled microwave heating to minimize handling and processing times and uses aqueous DMF or environmentally friendly PEG-200 as the reaction medium. The selectivity for linear beta-product in PEG-200 is slightly higher than in aqueous DMF. DFT calculations support a ligand-driven selectivity rationale, where the electronic and steric influence of bulky P(t-Bu)3 ligand provides improved beta-selectivity in the essential insertion step also with electron-rich aryl chlorides. A tentative computational rationalization of the improved selectivity in non-methylated PEG is discussed. Finally the synthetic methodology was used to provide efficient access to linear p-[2-(cyclopropylmethoxy)ethyl] phenol from p-nitrophenyl chloride, a key intermediate in the synthesis of the beta-adrenergic blocking agent Betaxolol.     

Retarded boson-fermion interaction in atomic systems

The retarded interaction between an electron and a spin-0 nucleus is derived from electrodynamical perturbation theory. The contribution of retardation at order v(2)c(2) mimics the Breit interaction [Phys. Rev. 34, 553 (1929); 36, 388 (1930); 39, 616 (1932)] with the Dirac matrix alpha(2) being replaced by p(2)m(2)c where p(2) is the linear momentum operator for the nucleus. An effective one-electron retardation operator is obtained in relative coordinates, and this can be used through all orders in perturbation theory without any problem of infinite degeneracy. A few steps of unitary transformation lead to the nonrelativistic limit. The leading terms in retardation corrections to energy are of order (m(e)m(n))alpha(2)Z(4)(alpha(2)m(e)c(2)). The implications for atomic systems are discussed.