We report the real-time detection of protein using SWNT-FET-based biosensors comprising DNA aptamers as molecular recognition elements. Anti-thrombin aptamers that are highly specific to serine protein thrombin were immobilized on the sidewall of a SWNT-FET using CDI-Tween linking molecules. The binding of thrombin aptamers to SWNT-FETs causes a rightward shift of the threshold gate voltages, presumably due to the negatively charged backbone of the DNA aptamers. While the addition of thrombin solution causes an abrupt decrease in the conductance of the thrombin aptamer immobilized SWNT-FET, no noticeable change was observed with elastase.

Multiphase CuInSe 2 (CISe) nanoparticles including the CuSe phase are synthesized by the microwave-assisted solvothermal method. Without additional processing, multiphase CISe nanoparticles facilitate the solution-processed CISe absorber layer with a dense microstructure, large grains, high crystallinity, and composition controllability, which are essential for acceptable thin-film solar cell performance. The high performance, solution-processed CISe solar cell, with a conversion efficiency of 8.2%, is obtained through phase transformation, microstructural evolution, and composition adjustment by selenization (annealing under a Se atmosphere) at 530 C.

With the aim of inkjet printing highly conductive and well-defined Cu features on plastic substrates, aqueous based Cu ink is prepared for the first time using water-soluble Cu nanoparticles with a very thin surface oxide layer. Owing to the specific properties, high surface tension and low boiling point, of water, the aqueous based Cu ink endows a variety of advantages over conventional Cu inks based on organic solvents in printing narrow conductive patterns without irregular morphologies. It is demonstrated how the design of aqueous based ink affects the basic properties of printed conductive features such as surface morphology, microstructure, conductivity, and line width. The long-term stability of aqueous based Cu ink against oxidation is analyzed through an X-ray photoelectron spectroscopy (XPS) based investigation on the evolution of the surface oxide layer in the aqueous based ink.

We investigated the effect of humidity on the electrical transport properties of single-walled carbon nanotube field effect transistors (SWNT-FETs). Water molecules are found to behave as electron donors to the nanotube: Current through the p-type carbon nanotube device is found to decrease under a modest humidity, and starts to increase as the humidity increases over 65%, which is believed to be due to the opening of electron channels. Through first principles calculations based on the density functional theory, we found that water molecules can donate electrons to the carbon nanotube. Moreover, a hydrogen-bonded water monolayer will be formed around the nanotube at fully covered conditions. We suggest that this result could provide a systematic understanding of the humidity effect on SWNT-FETs, which has been believed to be essential in the development of nanotube-based sensors.

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CuInSe2 (CIS) absorber layer was formed by a direct nonvacuum coating and a subsequent selenization of precursor solutions of Cu(NO3)2 and InCl3 dissolved in methanol. The viscosity of precursor solutions was adjusted by adding ethyl-cellulose (EC) to be suitable for the doctor-blade coating. During the coating and drying process Cu2+ ions in the starting solution were reduced to Cu+, resulting in precursor films consisting of CuCl crystals and amorphous In compound embedded in EC matrix. Selenization of the precursor films with Se vapor at elevated temperature generated double-layered films with an upper layer of chalcopyrite CIS and a carbon residue bottom layer. Significant In loss was observed during the selenization, which was attributed to the evaporation of the In2Se binary phase, confirmed by investigating the change in the Cu/In ratio of the selenized film as a function of Se flux and substrate temperature. As a proof-of-concept, thin film solar cells were fabricated with the double-layered absorber film and the devices exhibited reproducible conversion efficiency as high as about 2%.

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Recently, various functional devices based on printing technologies have been of paramount interest, owing to their characteristic processing advantages along with excellent device performance. In particular, printable metallic electrodes have drawn attention in a variety of optoelectronic applications; however, research into printable metallic nanoparticles has been limited mainly to the case of an environmentally stable Ag phase. Despite its earth-abundance and highly conductive nature, the Cu phase, to date, has not been exploited as an ambient atmosphere-processable, printable material due to its critical oxidation problem in air. In this study, we demonstrate a facile route for generating highly conductive, flexible Cu electrodes in air by introducing the well-optimized photonic sintering at a time frame of 10(-3) s, at which the photon energy, rather than conventional thermal energy, is instantly provided. It is elucidated here how the surface oxide-free, printed Cu particulate films undergo chemical structural/microstructural evolution depending on the instantly irradiated photon energy, and a successful demonstration is provided of large-area, flexible, printed Cu conductors on various substrates, including polyimide (PI), polyethersulfone (PES), polyethylene terephthalate (PET), and paper. The applicability of the resulting printed Cu electrodes is evaluated via implementation into both flexible capacitor devices and indium-gallium-zinc oxide (IGZO) flexible thin-film transistors.