We report a bottom-up synthesis of a photochemically and thermally active azobenzene-based polyelectrolyte multilayer (PEM) planar defect embedded in a colloidal photonic crystal (CPC). Both photoisomerization and thermal cycling lead to a precise tuning of an intragap transmitting state induced by the PEM structural defect.

the second harmonic (527 nm) of a Nd:YLF laser operating at 100 MHz. The dye laser contained a single plate birefringent filter tuned to produce laser oscillation at 610 nm and a pulse width of approximately 1 ps full width at half maximum (FWHM). The dye laser was cavity-dumped at 1 MHz, and then frequency doubled using a potassium dihydrogen phosphate nonlinear crystal. Sample fluorescence was spectrally filtered with a monochromator (bandpass ∼ 10 nm) and detected with a cooled microchannel plate (PMT, Hamamatsu R2809U-11). Fluorescence transients were measured at the magic angle, 54.7° [24]. Temporal response function of the system was measured to a FWHM of ca. 50 ps.Construction of QD-Protein Conjugate Model: A model for the three-dimensional conformation of Cy3-maleimide was constructed using Chem-3D Ultra 8.0 (CambridgeSoft, Cambridge, MA). Using energy minimization MM2, low-energy conformers were located using the MM2 molecular dynamics module within Chem-3D Ultra. Conformer energies ranged from 17.9 to 23.0 kcal mol -1 . A low-energy conformer was selected, which had the maleimide oriented such that it could interact with a cysteine side chain on the protein to form a covalent bond. The Cy3-maleimide model was merged with the X-ray crystal structure of MBP using MidasPlus [16,25]. The preferred orientation of QD-surface-located MBP was previously investigated [16]. An optimal configuration of the QD-MBP-His assembly is assumed in the present analysis. Fitting of the open and closed forms of MBP was performed within MidasPlus by aligning six a carbons of residues in one of the two MBP lobes in the structure. Distance between the Cy3 fluorophore and the QD center was 73.7 Å corresponding to the previously ascertained value [16]. Photonic crystals (PCs) are characterized by a spatially periodic dielectric constant modulation, and can suppress, slow, or guide the flow of electromagnetic radiation in certain lattice directions when the periodicity is comparable to the radiation wavelength. [1,2] These attributes have made them promising candidates for a variety of optoelectronic devices COMMUNICATIONS

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Quantum-dot cellular automata (QCA) is a scheme for molecular electronics in which information is transmitted and processed through electrostatic interactions between charges in an array of quantum dots. QCA wires, majority gates, clocked cell operation, and (recently) true power gain between QCA cells has been demonstrated in a metal-dot prototype system at cryogenic temperatures. Molecular QCA offers very high device densities, low power dissipation, and ways to directly integrate sensors with QCA logic and memory elements. A group of faculty at Notre Dame has been working to implement QCA at the size scale of molecules, where room-temperature operation is theoretically predicted. This paper reviews QCA theory and the experimental measurements in metal-dot QCA systems, and describes progress toward making QCA molecules and working out surface attachment chemistry compatible with QCA operation.

The mechanical properties of colloidal nanocrystal superlattices can be tailored through exposure to low-pressure plasma. The elastic modulus and hardness of the ligand-free 3.7 nm ZrO superlattice are found to be similar to bulk yttria-stabilized tetragonal polycrystals of the same relative density but without any doping.