Polarization Modulation in Ferroelectric Organic Field-Effect Transistors

The polarization modulation effect of the gate dielectric on the performance of metal-oxide-semiconductor field-effect transistors has been investigated for more than a decade. However, there are no comparable studies in the area of organic field-effect transistors (FETs) using polymer ferroelectric dielectrics, where the effect of polarization rotation by 90 is examined on the FET characteristics. We demonstrate the effect of polarization rotation in a relaxor ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene) (PVDF-TrFE), on the performance of small-molecule-based organic FETs. The subthreshold swing and other transistor parameters in organic FETs can be controlled in a reversible fashion by switching the polarization direction in the PVDF-TrFE layer. X-ray diffraction and electron microscopy images from PVDF-TrFE reveal changes in the ferroelectric phase and domain size, respectively, upon rotating the external electric field by 90. The structural changes corroborate density-functional-theoretical studies of an oligomer of the ferroelectric molecule in the presence of an applied electric field. The strategies enumerated here for polarization orientation of the polymer ferroelectric dielectric are applicable for a wide range of polymeric and organic transistors

Current advances in microalgae harvesting and lipid extraction processes for improved biodiesel production: A review

Microalgae have been considered as a potential feedstock for biodiesel production, since its cultivation uses less land than other traditional oil crops and has a higher growth rate. A great challenge is a choice of an effective approach for microalgae biomass recovery and lipid extraction, since the scheduling of these practices are critical and require an economical and environment friendly route. Flocculation has evolved as an efficient and economic approach for harvesting microalgae biomass. This review discussed the recent progress of chemical flocculants including organic and inorganic, bio-flocculants and nanomaterials-based processes for biomass recovery. In addition, the present review describes modifications made in conventional methods for lipid extraction. Several pre-treatment methods such as mechanical, chemical integrated with various solvents and nanoparticles are vastly investigated for lipid extraction. Use of green solvents namely, ionic liquids, supercritical fluids and switchable solvents are also reviewed, with the focus on cleaner biofuel synthesis. Furthermore, the article discusses policies implemented for the advancement in biofuel production, major challenges and considers future directions in microalgae harvesting and lipid recovery processes. This is the first study that extensively compares the recent approaches for biomass and lipid recovery. The present work intended to serve a long-term adaptation of the innovative techniques for copious economic benefit. Thus, this review emphasizes on advanced techniques that influence the microalgae biomass separation and cellular disruption for proficient lipid removal from microalgae, which deliberates towards the development of sustainable microalgae biofuel and heighten the bio-economy strategy

Orbital interactions and chemical reactivity of metal particles and metal surfaces

A review is presented with 101 refs. on chem. bonding to metal surfaces and small metal particles demonstrating the power of symmetry concepts to predict changes in chem. bonding. Ab-initio calcns. of chemisorption to small particles, as well as semiempirical extended Hueckel calcns. applied to the study of the reactivity of metal slabs are reviewed. On small metal particles, classical notions of electron promotion and hybridization are found to apply. The surroundings of a metal atom (ligands in complexes, other metal atoms at surfaces), affect bonding and reactivity through the prehybridization they induce. A factor specific for large particles and surfaces is the required localization of electrons on the atoms involved in the metal surface bond. At the surface, the bond energy is found to relate to the grou8p orbital local d. of states at the Fermi level. The use of this concept is extensively discussed and illustrated for chemisorption of CO and dissocn. of NO on metal surfaces. A discussion is given of the current decompn. schemes of bond energies and related concepts (exchange (Pauli)-repulsion, polarization, charge transfer). The role of non-orthogonality of fragment orbitals and of kinetic and potential energy for Pauli repulsion and (orbital) polarization is analyzed. Numerous examples are discussed to demonstrate the impact of those concepts on chem. bonding theor

[CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)

Four [CrIII8MII6]n+ (MII = Cu, Co) coordination cubes of formulae [Cr8Co6L24Cl12] (1), [Cr8Co6L24(SCN)12] (2), [Cr8Cu6L24(H2O)12](SO4)6 (3), and [Cr8Cu6L24Cl12] (4) (where HL is 1-(4-pyridyl)butane-1,3-dione), were synthesised using the [CrIIIL3] metalloligand in combination with a variety of MII salts. The metallic skeleton of each cage describes a cube in which the [CrIIIL3] moieties occupy the eight vertices and the MII ions lie at the centre of the six faces. The axial coordination sites of the MII cations are occupied by either H2O molecules or Cl?/SCN? anions originating from the MII salt used in the synthesis, resulting in neutral 1, 2 and 4 and the cage in 3 being a 12+ cation; the charge-balancing SO42? anions accommodated both inside and outside the cube. Magnetic susceptibility and magnetisation measurements reveal weak exchange between nearest neighbour metal ions, mediated via the L? ligands. The modular assembly of the cubes suggests that any combination of [MIIIL3] metalloligand and MII salt will work, potentially resulting in an enormous family of supramolecular assemblies. The charge of the cubes is controlled by the nature of the ligand occupying the axial sites on the MII ions, suggesting trivial ligand exchange may offer control over, amongst others, solubility, reactivity, post-synthetic modification and substrate specificity. The large internal cavities of the cubes also suggest host–guest chemistry may be a fruiful route to encapsulating magnetic and/or redox active guests which could be employed to control magnetic behaviour, and the construction of multifunctional materials

Interpenetrated Magnesium–Tricalcium Phosphate Composite: Manufacture, Characterization and In Vitro Degradation Test

Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test.Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test