Multilayered Ag NP-PEDOT-Paper Composite Device for Human-Machine Interfacing.

Flexible pressure sensors have attracted increasing interest because of their potential applications on wearable sensing devices for human-machine interface connections, but challenges regarding material cost, fabrication robustness, signal transduction, sensitivity improvement, detection range, and operation convenience still need to be overcome. Herein, with a simple, low-cost, and scalable approach, a flexible and wearable pressure-sensing device fabricated by utilizing filter paper as the solid support, poly(3,4-ethylenedioxythiophene) to enhance conductivity, and silver nanoparticles to provide a rougher surface is introduced. Sandwiching and laminating composite material layers with two thermoplastic polypropylene films lead to robust integration of sensing devices, where assembling four layers of composite materials results in the best sensitivity toward applied pressure. This practical pressure-sensing device possessing properties such as high sensitivity of 0.119 kPa-1, high durability of 2000 operation cycles, and an ultralow energy consumption level of 10-5 W is a promising candidate for contriving point-of-care wearable electronic devices and applying it to human-machine interface connections.

Structure and Dynamics of a N-Methylfulleropyrrolidine-Mediated Gold Nanocomposite: A Spectroscopic Ruler.

A mechanistic understanding of the structure and dynamics of a chemically tunable N-methylfulleropyrrolidine (8-NMFP)-assisted gold nanocomposite and its aggregation via a controllable interparticle interaction is reported as a function of the molar ratio and pH of the medium. Electronic structure calculations adopting density functional theory methods implied electrostatic interactions to play a dominant role between 8-NMFP and citrate-capped gold nanoparticles. MM+ molecular mechanics force field computations revealed intermolecular gold-gold interactions, contributing toward the formation of spherical composite aggregates. Corroborating these, optical absorption spectra showed the usual surface plasmon band along with a higher-wavelength feature at ∼600-650 nm, indicative of the aggregated nanocomposite. pH-controlled reversible tuning of the plasmonic features in the composite was evident in a pH interval ∼5-6.8, revealing prevalent interparticle electrostatic interactions. In addition, photoluminescence (PL) and time-correlated single-photon counting studies revealed a strong nanocomposite interaction with a pure fluorescent dye, Rhodamine B, indicating excitation energy transfer from the dye to the composite. The dye upon interaction with the nanocomposite showed a significant quenching of its PL intensity and shortening of lifetime. Energy coupling between the metal nanoparticle composite and the emitting molecular dipole resulted in a long-range surface energy transfer (SET) from the donor dye to the surface plasmon modes of the nanoparticle following a donor-acceptor distance dependence of 1/r4. This molecular beacon with correlation between the nanoscale structure and the nonradiative nanometal SET can be used as a spectroscopic/molecular ruler in probing advanced functional materials.

Structure and dynamics of a dl-homocysteine functionalized fullerene-C60-gold nanocomposite: a femtomolar l-histidine sensor.

A functionalized fullerene-C60-thiol mediated gold nanocomposite was realized using dl-homocysteine as a bifunctional ligand. The nanocomposite was designed by following electronic structure calculations via the DFT formalism. The computed electrostatic potential profile and the electronic HOMO-LUMO energy gap implied enhanced electron transport across the nanocomposite skeleton. Accordingly, synthesis of the nanocomposite proceeded with the hydrophilic fullerene-C60 thiol derivative via in situ reduction of gold(iii), resulting in sterically full gold clusters bound to the fullerene-C60 core. Molecular dynamics simulations with the MM+ force field provided insight into the mode of interaction and direction of electron transfer in the nanocomposite-histidine ensemble. Subsequently, an electrochemical strategy for l-histidine sensing was proposed; the nanocomposite-modified glassy carbon electrode exhibited electrocatalytic activity towards l-histidine sensing, studied via cyclic and square wave voltammetry and impedance spectroscopy. A femtomolar l-histidine sensor, the first of its kind with orders of magnitude enhanced performance in its detection limit, linear range, sensitivity, stability and specificity, and free of interference, thus emerged.