Hot articles: rainbow nanoparticles, atomic layer deposition and liquid crystals

Synthesis and characterization of tunable rainbow colored colloidal silver nanoparticles using single-nanoparticle plasmonic microscopy and spectroscopy

Synthesis and characterization of tunable rainbow colored colloidal silver nanoparticles using single-nanoparticle plasmonic microscopy and spectroscopy

Tao Huang and Xiao-Hong Nancy Xu*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01990A, Paper

Tao Huang and Xiao-Hong Nancy Xu have developed a rapid simple one-pot synthesis method to produce twelve representative colloidal Ag NPs that exhibit rainbow colors, ranging from violet to red (full visible range).  They characterized each colloid at single NP resolution and found that the colors of colloids were tunable by controlling the various amounts of sizes and shapes of single NPs. The colloids contained spherical, rod, triangular, and cookie shaped NPs.  These single NPs have the potential for use as multicolored optical probes for the study of dynamic events in solutions and living organisms at nm scale in real time.

Atomic layer deposition of CaB2O4 films using bis(tris(pyrazolyl)borate) calcium as a highly thermally stable boron and calcium source

 Atomic layer deposition of CaB2O4 films using bis(tris(pyrazolyl)borate)calcium as a highly thermally stable boron and calcium sourceMark J. Saly, Frans Munnik and Charles H. Winter*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02280B, Paper

Materials containing calcium ions have a wide range of applications. Few reports exist of calcium borate-based thin films and there are only a few deposition techniques.  Atomic layer deposition (ALD) is an emerging thin film deposition method in which gas phase precursors are introduced stepwise to the substrate and are separated by inert purges.  ALD leads to conformal and uniform films with precise thickness control and has been used to coat three dimensional substrates such as nanoparticles, nanotubes, and biotemplates. In this paper, Charles Winter and colleagues report the atomic layer deposition growth of CaB2O4 films using the gas phase precursors CaTp2 and water.

How much can an electric dipole stabilize a nematic phase? Polar and non-polar isosteric derivatives of [closo-1-CB9H10] and [closo-1,10-C2B8H10]

How much can an electric dipole stabilize a nematic phase? Polar and non-polar isosteric derivatives of [closo-1-CB9H10]− and [closo-1,10-C2B8H10]Bryan Ringstrand and Piotr Kaszynski*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02876B, Communication

Most liquid crystals of technological importance possess a dipole moment.  Typically, change of the molecular dipole moment is associated with alteration of the molecular geometry and conformational dynamics, which themselves affect phase behavior. Recently, Kaszynski and colleagues suggested that the N+–B fragment can serve as an isosteric polar replacement for the C–C fragment in liquid crystalline molecules, having negligible impact on molecular geometry and dynamics thus any change in phase properties being solely to the molecular dipole.  In this communication, Bryan Ringstrand and Piotr Kaszynski demonstrate for the first time, experimentally, that the replacement of a C–C fragment with a polar isosteric N+–B fragment leads to 5 pairs of non-polar/polar nematics.  Polar nematics, such these are of interest for LCD applications.

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