A matrix addressable diode flat panel display has been fabricated using a carbon nanotube–epoxy composite as the electron emission source. Field-emission uniformity has been confirmed by measuring the I–V curves of pixels across the panel. This prototype display demonstrates well-lit pixels under ±150 V biasing signals. The “on” and “off” of the pixels are well controlled by the half voltage “off-pixel” method. Further improvement of this technology may lead to easy-to-make and inexpensive flat panel displays.

The photoluminescence of porous silicon can be quenched by adsorbates, and the degree of quenching can be tuned by chemical derivatization of the porous silicon surface. Thus, as-prepared porous silicon has a hydrophobic, hydrogen-terminated surface, and the photoluminescence is strongly quenched by ethanol and weakly quenched by water. Mild chemical oxidation (iodine followed by hydrolysis) produces a hydrophilic porous silicon surface. Photoluminescence from this hydrophilic material is quenched to a lesser extent by ethanol and to a greater extent by water, relative to the original surface. This demonstrates that the visible luminescence from porous silicon is highly surface-sensitive, and the surface interactions can be tuned by specific chemical transformations.

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A method using a hydrogen arc for synthesizing large quantities of carbon nanotubes filled with pure copper is reported. The interaction of small copper clusters with polycyclic aromatic hydrocarbons (PAHs) is shown to form carbon nanotubes and encapsulated copper nanowires. The effectiveness of this model is demonstrated by showing that no copper filled nanotubes are formed in a helium arc that does not generate PAHs. A direct proof of this model is demonstrated by using pyrene, a PAH molecule, to grow carbon nanotubes and encapsulated copper nanowires.

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Visible light emission from porous silicon can be stimulated by applying a positive bias to a formic acid/sodium formate liquid junction cell. The emission lasts for 45 min at +2.75 V applied potential (<5 mA/cm2, power conversion efficiency ≳10−2%) and is reliably generated from n- or p-type porous silicon. An applied voltage as low as 1.3 V is capable of generating the red (720 nm) emission, indicating that current-induced chemical reactions aid in the generation of charge carriers. A mechanism involving oxidation of formic acid followed by electron injection from a CO2− radical is proposed. Infrared spectra of the porous silicon surface taken after anodization show formation of a stable silyl-ester species that is thought to be responsible for the increase in radiative recombination efficiency through passivation of surface defects.

Interaction of the solvents tetrahydrofuran, diethyl ether, methylene chloride, toluene, o-xylene, benzene, and methanol with luminescent porous nSi (PS) results in reversible quenching of the luminescence associated with this material. The degree of quenching ranges from 99% -50%, and scales with solvent dipole moment. Reaction with gaseous C1 2 , Br2, or 12 results in irreversible quenching, associated with a surface reaction that removes Si-H bonds. Total luminescence quenching is observed on treatment of a PS wafer with a solution of the electron donor ferrocene in toluene, suggesting that charge transfer quenching may also be operative in this material. Luminescence is partially recovered by rinsing the PS in pure toluene. The data show that photoluminescence of PS is highly sensitive to surface adsorbates, suggesting that carrier trapping is easily induced in this material.

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