The exothermic reaction route of a self-heatable conductive ink for rapid processable printed electronics.

We report the exothermic reaction route and new capability of a self-heatable conductive ink (Ag2O and silver 2,2-dimethyloctanoate) in order to achieve both a low sintering temperature and electrical resistivity within a short sintering time for flexible printed electronics and display appliances. Unlike conventional conductive ink, which requires a costly external heating instrument for rapid sintering, self-heatable conductive ink by itself is capable of generating heat as high as 312 °C when its exothermic reaction is triggered at a temperature of 180 °C. This intensive exothermic reaction is found to result from the recursive reaction of the 2,2-dimethyloctanoate anion, which is thermally dissociated from silver 2,2-dimethyloctanoate, with silver oxide microparticles. Through this recursive reaction, a massive number of silver atoms are supplied from silver oxide microparticles, and the nucleation of silver atoms and the fusion of silver nanoparticles become the major source of heat. This exothermic reaction eventually realizes the electrical resistivity of self-heatable conductive ink as low as 27.5 µΩ cm within just 40 s by combining chemical annealing, which makes it suitable for the roll-to-roll printable electronics such as a flexible touch screen panel.

Rapid two-step metallization through physicochemical conversion of Ag2O for printed "black" transparent conductive films.

A rapid two-step metallization for fabrication of a "black" transparent conductive film on a flexible substrate for display applications is presented, using a mixture of silver oxide (Ag2O) and silver neodecanoate (C10H19AgO2), and its electrical conductivity and colour transition behaviours are investigated. Silver nanoparticles, which are physicochemically converted from silver oxide microparticles in the presence of silver neodecanoate in the course of the first metallization step at 150 °C for 10 min, are chemically annealed by immersing them in an acidic ferric chloride (FeCl3) solution at room temperature for 10 s. During this second metallization step, silver nanoparticles are found to be tightly packed through Ostwald ripening, which eventually leads to the dramatic enhancement of electrical conductivity by six orders of magnitude from 1.33 S m(-1) to 1.0 × 10(7) S m(-1), which corresponds to 15.9% of the electrical conductivity of bulk silver. In addition to the enhancement of electrical conductivity, the silver chloride (AgCl) layer formed on the surface of the silver layer due to ferric ions (Fe(3+)) enhances the blackness of the transparent conductive film by a factor of 1.69, from 36.29 B to 61.51 B. The sheet resistance and optical transparency of a roll-to-roll printed black transparent conductive film for a touch screen panel are found to be as low as 0.9 Ω□(-1) and 81%, respectively, after conducting the proposed two-step metallization.

Adsorption-stress relationship in drying of silica/PVA suspensions.

In this study, we investigated drying process of silica/PVA suspensions. After measuring the amount of polymer adsorption and the stress evolution of a film during drying process, we could find a quantitative relationship between polymer adsorption and stress development, for silica/PVA suspensions of different pH and mixing time. For all the suspensions of different pH, both the amount of polymer adsorption (Γ) and the plateau stress of dry film (σ(p)) could be scaled onto a single master curve as a function of mixing time (t(m)). The scaling of mixing time for both Γ and σ(p) could be performed by the same scale factor, which implies that there is a one to one correlation between adsorption and stress. This correlation implies that we can control the microstructure and performance of dry film by adjusting the amount of polymer adsorption. The origin of adsorption kinetics of silica/PVA suspension was also discussed in terms of saponification of acetate groups in PVA, which facilitates hydrogen bonding between silica and PVA.

Preparation and infrared/raman classification of 630 spectroscopically encoded styrene copolymers.

The barcoded resins (BCRs) were introduced recently as a platform for encoded combinatorial chemistry. One of the main challenges yet to be overcome is the demonstration that a large number of BCRs could be generated and classified with high confidence. Here, we describe the synthesis and classification of 630 polystyrene-based copolymers prepared from the combinatorial association of 15 spectroscopically active styrene monomers. Each of the 630 copolymers displayed a unique vibrational fingerprint (infrared and Raman), which was converted into a spectral vector. To each of the 630 copolymers, a vector of the known (reference) composition was assigned. Unknown (prediction) vectors were decoded using multivariate data analysis. From the inner product of the reference and prediction vectors, a correlation map comparing 396 900 copolymer pairs (630 x 630) was generated. In 100% of the cases, the highest correlation was obtained for polymer pairs in which the reference and prediction vectors correspond to copolymers prepared from identical styrene monomers, thus demonstrating the high reliability of this encoding strategy. We have also established that the spectroscopic barcodes generated from the Raman and infrared spectra are independent of the copolymers' morphology (beaded versus bulk polymers). Besides the demonstration of the generality of the polymer barcoding strategy, the analytical methods developed here could in principle be extended to the investigation of the composition and purity of any other synthetic polymer and biopolymer library, or even scaffold-based combinatorial libraries.

Characterization of the optical properties of silver nanoparticle films.

To understand the collective properties of nanoparticles, it is necessary to control the particle size, spacing and ordering. Here we describe the chemical synthesis of well-controlled silver nanoparticles, the wet coat preparation and the optical properties of its film. The light incidence angle and polarization dependency of the resonant spectra show distinctive surface plasmon resonance extinction peaks for isolated particles and the coupled modes of neighbouring particles. Furthermore, we discuss the thermal treatment and dielectric surrounding effects on the optical properties of silver nanoparticle film.

Classification of spectroscopically encoded resins by Raman mapping and infrared hyperspectral imaging.

Barcoded resins (BCRs) were recently introduced as a potential platform for pre-encoded multiplexed synthesis, screening, and biomedical diagnostics. A key step toward the development of this strategy is the ability to rapidly interrogate and classify the BCRs in a high-throughput, noninvasive manner. Here, we describe a one-step strategy based on Raman mapping and Fourier transform infrared imaging to classify and spatially resolve randomly distributed BCRs. To illustrate this methodology, mixtures of up to 25 different BCRs were imaged and classified with 100% confidence. This strategy can be readily extended to a larger pool of resins, provided each BCR features a unique vibrational fingerprint (spectroscopic barcode). We have also established that reliable single-bead Raman spectra can be recorded in 10 ms, thus confirming that Raman mapping, in particular, could be a very fast method to classify the BCRs.

Spectroscopically encoded resins for high throughput imaging time-of-flight secondary ion mass spectrometry.

Spectroscopic barcoding was recently introduced as a new pre-encoding strategy wherein the resin beads are not just carriers for solid phase synthesis, but are, in addition, the repository of the synthetic scheme to which they were subjected. To expand the repertoire of spectroscopically barcoded resins (BCRs), here we introduce a new family of halogenated polystyrene-based polymers designed for high-throughput combinatorial analysis using not only infrared and Raman spectroscopy but also imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS). In particular, we have established that (a) the halogen content of these new resins can be used as an encoding element in quantitative imaging ToF-SIMS and (b) the number of styrene monomers used to generate unique vibrational fingerprints can be significantly reduced by using monomers in different molar ratios. The combination of quantitative imaging ToF-SIMS and vibrational spectroscopy is anticipated to dramatically increase the repertoire of possible BCRs from a few hundreds to several thousands.

Highly selective Ba2+ separations with acyclic, lipophilic di-[N-(X)sulfonyl carbamoyl] polyethers.

New lipophilic acyclic polyethers with two N-(X)sulfonyl carbamoyl groups of "tunable" acidity exhibit remarkable selectivity for Ba2+ over other alkaline earth metal ions in competitive solvent extraction and transport across polymer inclusion membranes.

Preparation, physical properties, on-bead binding assay and spectroscopic reliability of 25 barcoded polystyrene-poly(ethylene glycol) graft copolymers.

Here we describe the preparation of 25 beaded polystyrene-poly(ethylene glycol) graft copolymers from six spectroscopically active styrene monomers: styrene, 2,5-dimethylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 4-tert-butylstyrene, and 3-methylstyrene. These polymers were thoroughly characterized by Raman, infrared, and (1)H/(13)C NMR spectroscopies, and differential scanning calorimetry. Determination of the swelling properties, peptide synthesis, and on-bead streptavidin-alkaline phosphatase (SAP) binding assay further established that their physical and chemical properties where not significantly altered by the diversity of their encoded polystyrene core. Each of the 25 resins displayed a unique Raman and infrared vibrational fingerprint, which was converted into a "spectroscopic barcode". The position of each bar matches the peak wavenumber in the corresponding spectrum but is independent of its intensity. From this simplified representation similarity maps comparing 35 000 resin pairs were generated to establish the spectroscopic barcoding as a reliable encoding methodology. In effect, in 99% of the cases, the highest similarity coefficients were obtained for resin pairs prepared from the same styrene derivatives even after SAP binding assay. We have also shown that a small but unique combination of a resin's vibrations (30-40%) is sufficient for its identification. However, in rare cases where a resin's vibrational signature has been severely compromised, both the Raman and infrared barcodes were synergistically and reliably utilized to unequivocally identify its chemical make up.