Detection and Sourcing of Gluten in Grain with Multiple Floating-Gate Transistor Biosensors

We report a chemically tunable electronic sensor for quantitation of gluten based on a floating-gate transistor (FGT) architecture. The FGTs are fabricated in parallel and each one is functionalized with a different chemical moiety designed to preferentially bind a specific grain source of gluten. The resulting set of FGT sensors can detect both wheat and barley gluten below the gluten-free limit of 20 ppm (w/w) while providing a source-dependent signature for improved accuracy. This label-free transduction method does not require any secondary binding events, resulting in a ca. 45 min reduction in analysis time relative to state-of-the-art ELISA kits with a simple and easily implemented workflow

Label-Free DNA Sensing Platform with Low-Voltage Electrolyte-Gated Transistors

We report a method to measure DNA hybridization potentiometrically in a manner conducive to portable or hand-held biosensors. An electrolyte-gated transistor (EGT) based on poly­(3-hexylthiophene) (P3HT) and an ion-gel serves as a transducer for surface hybridization of DNA. The key aspect of the design is the use of a floating-gate electrode functionalized with ssDNA whose potential is determined by both capacitive coupling with a primary, addressable gate electrode and the presence of adsorbed molecules. When DNA is hybridized at the floating gate, it offsets the primary gate voltage felt by the P3HT semiconductor; the offset is directly measurable and quantitatively related to the number density of dsDNA molecules. The presented sensing strategy can be readily adapted to other biomolecules of interest and integrated into a microfluidic system for field applications of biosensors

Interfacial Charge Contributions to Chemical Sensing by Electrolyte-Gated Transistors with Floating Gates

The floating gate, electrolyte-gated transistor (FGT) is a chemical sensing device utilizing a floating gate electrode to physically separate and electronically couple the active sensing area with the transistor. The FGT platform has yielded promising results for the detection of DNA and proteins, but questions remain regarding its fundamental operating mechanism. Using carboxylic acid-terminated self-assembled monolayers (SAMs) exposed to solutions of different pH, we create a charged surface and hence characterize the role that interfacial charge concentration plays relative to capacitance changes. The results agree with theoretical predictions from conventional double-layer theory, rationalizing nonlinear responses obtained at high analyte concentrations in previous work using the FGT architecture. Our study elucidates an important effect in the sensing mechanism of FGTs, expanding opportunities for the rational optimization of these devices for chemical and biochemical detection

An ADMET Route to Low-Band-Gap Poly(3-hexadecylthienylene vinylene): A Systematic Study of Molecular Weight on Photovoltaic Performance

The effect of molecular weight on organic photovoltaic device performance is investigated for a series of low-band-gap (ca. 1.65 eV) poly­(3-hexadecylthienylene vinylene)­s (C16-PTVs) prepared by acyclic diene metathesis (ADMET) polymerization. By utilizing monomers of varying cis:trans (<i>Z</i>:<i>E</i>) content, seven C16-PTVs were prepared with a number-average molecular weight range of 6–30 kg/mol. Polymers were characterized by size-exclusion chromatography, ¹H NMR spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, wide-angle X-ray scattering, and differential scanning calorimetry. C16-PTVs were integrated into bulk-heterojunction (BHJ) solar cells with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), and conversion efficiency was found to increase with increasing molecular weight. This observation is attributable to an increase in polymer aggregation in the solid state and a corresponding increase in hole mobility. Finally, phase behavior and morphology of the C16-PTV:PCBM active layers were investigated by differential scanning calorimetry and atomic force microscopy, respectively

Effects of Olefin Content and Alkyl Chain Placement on Optoelectronic and Morphological Properties in Poly(thienylene vinylenes)

The effects of olefin content and alkyl chain placement on the properties of two poly­(thienylene vinylene)- (PTV-) based polymer series were investigated. Polymers were prepared by ruthenium-catalyzed acyclic diene metathesis (ADMET) polymerization of four dipropenyl monomers. All polymers were thoroughly characterized with a variety of spectroscopic, thermal, and electronic techniques. Tuning the olefin content had direct impacts on optical and organic solar cell (OSC) behavior while systematic changes to alkyl substitution patterns manifested as differences in optical, thermal, and microstructural properties. Density functional theory (DFT) analysis provided support for the observed differences among all polymers. In addition, ¹³C NMR and IR analysis of selected polymers helped to confirm the stereochemistry of the PTV backbone