We describe the structural, optical, and electrical properties of high-quality films of PbSe nanocrystals fabricated by a layer-by-layer (LbL) dip-coating method that utilizes 1,2-ethanedithiol (EDT) as an insolubilizing agent. Comparative characterization of nanocrystal films made by spin-coating and by the LbL process shows that EDT quantitatively displaces oleic acid on the PbSe surface, causing a large volume loss that electronically couples the nanocrystals while severely degrading their positional and crystallographic order of the films. Field-effect transistors based on EDT-treated films are moderately conductive and ambipolar in the dark, becoming p-type and 30–60 times more conductive under 300 mW cm−2 broadband illumination. The nanocrystal films oxidize rapidly in air to yield, after short air exposures, highly conductive p-type solids. The LbL process described here is a general strategy for producing uniform, conductive nanocrystal films for applications in optoelectronics and solar energy co...

https://www.chem.uci.edu/~lawm/Structural,%20optical,%20and%20electrical%20properties%20of%20self-assembled%20films%20of%20PbSe%20nanocrystals%20treated%20with%201,2-ethanedithiol.pdf

Structural, Optical and Electrical Properties of Self-Assembled Films of PbSe Nanocrystals Treated with 1,2-Ethanedithiol

Ion-selective microelectrodes

Periodic mesoporous silicas (PMSs) give enormous stimulus to the field of nanostructured organic−inorganic composite materials, opening new horizons for selective organic transformations and material science. This article outlines advanced synthetic concepts of their intraporous surface organometallic chemistry involving alkyl, (silyl)amide, and alkoxide reagents. Conclusive methods of characterization, elaborating the importance of spectroscopic probe ligands and nitrogen physisorption, reinforce the excellent capacity of PMS materials as a model support of, for example, amorphous silica. Particular emphasis is placed on tailor-made hybrid materials, highlighting unexpected reaction behavior due to surface and pore confinement. Accordingly, surface silylation as an efficient method for designing the microenvironment is surveyed in detail.

SOMC@PMS. Surface Organometallic Chemistry at Periodic Mesoporous Silica†

Disilazane reagents of type HN(SiR1R22)2 carrying organic substituents R1,2 = H, Me, Ph, n-Bu, n-Oct, Vin (Vin = vinyl) of varying longitudinal and lateral extension are reacted with high quality MCM-41 samples of different pore sizes, i.e., effective pore diameters of 2.8 and 3.8 nm according to the BJH pore size analysis of the desorption branch. The reaction of the standard silylating reagent hexamethyldisilazane, HN(SiMe3)2, is shown to be controlled by the amount of added silylamine and the contact time, resulting in effective pore size engineering. Calculations from elemental analysis revealed that the degree of silylation (silylation efficiency) and hence the surface hydroxyl consumption depend on the steric bulk/shape of the groups R. The surface coverage varies from 0.74 to 1.85 silyl groups/nm2. The sterically least demanding tetramethyldisilazane, HN(SiHMe2)2, is the most efficient silylating reagent, while silyl groups with bulky phenyl substituents produce the lowest surface coverage featurin...

M. L. Hair

Papers

Reaction of hexamethyldisilazane with silica