Journal of Materials Chemistry Blog

Cholesteric liquid crystals (CLCs) show selective reflection due to their helical structures. They are formed by the introduction of chiral elements into liquid crystals molecules or by doping of nematic liquid crystals with chiral dopants. Photoresponsive chiral dopants are increasing being used to fabricate tuneable CLCs.

In this hot paper, Liu and colleagues use an imprinting method which used multiple UV-induced polymerisations. A helical polymer matrix was imprinted in the presence of a CLC. Desirable Bragg reflections were found, without any added liquid crystals or chiral compounds.

Fabrication and characterization of imprinted photonic crystalline polymer matrices via multiple UV polymerizations
J. Mater.  Chem., 2012, 22, 22446.  DOI: 10.1039/c2jm35151j (free to read for a short time)

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Combination of inorganic nanocrystals (NCs) and organic molecules into composites have shown a variety of novel optical and electronic properties. Many of these properties arise from the inter-phase energy transfer from the excited NCs to a semiconducting matrix.

In this hot paper, Nakanishi and co-workers report the fabrication of a composite material of CdSe NCs embedded in an alkylated room temperature liquid C₆₀ derivate. The photoelectrochemical and optical properties of the composite are investigated. It is found that the optical properties can be tuned by selection of the NC phase. Electronic band alignment between the NCs and the C₆₀ matrix enable inter-phase charge transfer, resulting in a long-lived charge transfer state. The composite shows potential for use in sensing applications and photoelectrochemical processes.

CdSe Nanocrystal/C₆₀-liquid composite material with enhanced photoelectrochemical performance
J. Mater. Chem., 2012, 22, 22370.  DOI: 10.1039/c2jm35294j (free to read for a short time)

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Fabrication of ZnO nanodisc arrays is reported using nanoimprint lithography (NIL) mold obtained sub-100 nm pattern resolution by Srinivasan, Krishnamoorthy and co-workers.

ZnO nanostructures have many applications such as use in LEDs, gas sensors and semiconducting devices. Controlling the densities, geometric attributes and batch to batch reproducibility of nanostructured ZnO can be a challenge. In this hot paper, a generic process is described, using block copolymer assisted NIL, to produce high-resolution NIL molds for the production of ZnO nanodiscs. The authors also investigate the charge storage properties of the produced ZnO nanodiscs.

Macroscopic high density nanodisc arrays of zinc oxide fabricated by block copolymer self-assembly assisted nanoimprint lithography
J. Mater. Chem., 2012, 22, 21871. DOI: 10.1039/c2jm33444e

(free to read for a short time)

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A thin film nanocomposite dielectric that can be prepared by deposition of Bi-doped BaTiO₃ nanocrystals on to a polymer is reported by O’Brien and colleagues.

In this hot paper, the authors use a novel approach to synthesise bismuth acceptor doped nanocrystals, Ba(Ti_xBi_1-x)O₃. The nanocrystals can be synthesised at low temperatures via a solvothermal method and are highly crystalline. The nanocomposite containing these nanocrystals, showed improved dielectric performance over BaTiO₃ and in particular highly desirable capacitor characteristics.

Comprehensive dielectric performance of bismuth acceptor doped BaTiO₃ based nanocrystal thin film capacitors
J. Mater. Chem., 2012, 22, 21862
DOI: 10.1039/c2jm34044e (free to read for a short time)

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Electronic structure engineering of lanthanide activated materials

This Highlight article by Pieter Dorenbos reviews new approaches to design novel lanthanide-based materials. He discusses methods and models to construct electron binding energy schemes which can be used to predict the properties, and therefore engineer, new materials.

J. Mater. Chem., 2012, DOI: 10.1039/C2JM34252A, Advance Article

Crystal structure of blue–white–yellow color-tunable Ca₄Si₂O₇F₂:Eu²⁺,Mn²⁺ phosphor and investigation of color tenability through energy transfer for single-phase white-light near-ultraviolet LEDs

Phosphor-converted LEDs that use a combination of blue InGaN chip and a yellow emitting Y₃Al₅O₁₂:Ce³⁺ phosphors have low color rendering indices and high correlated color temperatures which are disadvantageous. In this hot paper, Huang, Chen and co-workers, synthesis a series of single-composition Ca₄Si₂O₇F₂:Eu²⁺,Mn²⁺ phosphors and investigate their crystal structures and luminescence properties. They find that the phosphors generate white-light and are emission-tunable by using a sensitizer Eu³⁺. The critical distance between Eu²⁺ and Mn²⁺ is investigated in relation to the energy transfer mechanism. The phosphor has potential uses as a phosphor-converted white-light near-UV LED.

J. Mater. Chem., 2012, DOI: 10.1039/C2JM33160H, Advance Article

High rate performance of a Na₃V₂(PO₄)₃/C cathode prepared by pyro-synthesis for sodium-ion batteries

In this hot paper, Jaekook Kim’s group at Chonam National University, Korea report the synthesis of a Na-ion cathode as a high performing alternative to the Li-ion cathodes currently popular in the field. The carbon-coated Na₃V₂(PO₄)₃ cathode is synthesised via a polyol-assisted pyro-synthetic reaction which reduces the sintering time and temperature. The resulting nanoparticles showed greatly improved electrochemical performances in a Na-ion cell.

J. Mater. Chem., 2012, 22, 20857-20860

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