We report the realization of electrical coupling between neurons and depletion type floating gate (FG) p-channel MOS transistors. The devices were realized in a shortened 0.5 μm CMOS technology. Increased boron implant dose was used to form the depletion type devices. Post-CMOS processing steps were added to expose the devices sensing area. The neurons are coupled to the polycrystalline silicon (PS) FG through 420 Å thermal oxide in an area which is located over the thick field oxide away from the transistor. The combination of coupling area pad having a diameter of 10 or 15 μm and sensing transistor with W/L of 50/0.5 μm results in capacitive coupling ratio of the neuron signal of about 0.5 together with relatively large transistor transconductance. The combination of the FG structure with a depletion type device, leads to the following advantages. (a) No need for dc bias between the solution in which the neurons are cultured and the transistor with expected consequences to the neuron as well as the silicon die durability. (b) The sensing area of the neuron activity is separated from the active area of the transistor. Thus, it is possible to design the sensing area and the channel area separately. (c) The channel area, which is the most sensitive part of the transistor, can be insulated and shielded from the ionic solution in which the neurons are cultured. (d) There is an option to add a switching transistor to the FG and use the FG also for the neuron stimulation.

In the present contribution we report on a novel route to synthesize 2D-polyaniline (2DPAN) on sulfonated-poly(styrene) (SPS) templates by allowing first monomer assembly followed by chemical oxidation to achieve polymerization. We show that Aplysia neurons grown on 2D-PAN exhibit an unusual growth pattern and adhesion to this conducting substrate that is manifested by the formation of giant lamellipodia. The lamellipodial domains are characterized by small gap between the plasma membrane and the 2D-PAN substrate (ca. 30 nm) and actin rich skeleton resembling the skeleton of growth cones. This behavior is characteristic to uniform substrates containing only 2DPAN. However, in patterned substrates containing additionally poly(L-lysine) Aplysia neurons prefer to extend new neurites on the poly(L-lysine) domains.

Light-converting polyethylene film containing europium(III) complex with phenanthroline was manufactured under an extrusion process. The film was characterized first by means of time-of-flight secondary-ion-mass spectrometry (TOF-SIMS), ultraviolet-visible-infrared (UV-vis-IR) spectroscopy, then a study of excitation and luminescence spectra, quantum yield and lifetime of luminescence. The quantum yield of luminescence was measured as 5±2%, and the lifetime of luminescence was determined about 470 μsec. TOF-SIMS surface mapping showed the uniform distribution of europium(III) over the film. Visualization of strong picosecond UV laser beams through the use of the developed film has been demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.

We report on culturing of Aplysia neurons on porous silicon substrates. Good adhesion of the neurons to the porous silicon substrate and a formation of neuron-semiconductor contact have been accomplished. Cultured neurons survived for at least one week on porous silicon showing normal passive membrane properties and generation of action potentials. We have investigated the possibility of using the photoluminescence from porous silicon for transducing neuronal activity into photonic signals. We found that photoluminescence quenching occurs for cathodic current polarization using aqueous salt-based liquid solution contact. The quenching process is due to diffusion of electrons into the porous silicon, giving rise to Auger nonradiative recombination in the siliconnanocrystallites. The decay time of the photoluminescence was found to be relatively slow due to diffusive nature of the process.

The cyclo-octasulfur (S8) molecule is presented as the basis for conductive Au/S8 microcrystalline systems. Photolysis of 4,4‘-dithiodipyridine in pyridine/water solution was used for the production of S8 microcrystals. The mechanism of the photochemical reaction was verified by X-ray crystallography. The polymorphism of S8 can be used for shape-controlled crystallization.

A study of photoinduced processes in pyridine-based gels is presented. Poly(4-vinyl pyridine) dissolved in pyridine with water addition forms a photosensitive material. Under irradiation at the main absorption at 250 nm, a new intense absorption at 360 nm and an emission at 515 nm appeared. Upon continuation of radiation, together with an increase in the intensity of the new absorption, a prolonged tail through the whole visible range is observed. A new far red-shifted emission arises in correlation with the absorption spectrum changes. The presence of lower energy aggregates leads to polymer morphology changes. Short-range aggregates enhance polymer-polymer interactions. Long range aggregates have a tendency to crystallize. The photoinduced morphology changes was studied by transmission electron microscopy (TEM) of the polymer thin film and differential scanning calorimetry (DSC) of the gel. Phase separated species, micelles-like forms with domain size over 200 nm, and nanocrystals with average size 20-30 nm are demonstrated.