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1. Long-Range Proton Transport in Films from a Reflectin-Derived Polypeptide

   https://doi.org/doi.org/10.1021/acsami.0c18929  

   Chengyi Xu, Nabin Kandel (May 2021, ACS applied materials interfaces)

   null (Ed.)

   Protein- and peptide-based proton conductors have been extensively studied because of their important roles in biological processes and established potential for bioelectronic device applications. However, despite much progress, the demonstration of long-range proton transport for such materials has remained relatively rare. Herein, we fabricate, electrically interrogate, and physically characterize films from a reflectin-derived polypeptide. The electrical measurements indicate that device-integrated films exhibit proton conductivities with values of ∼0.4 mS/cm and sustain proton transport over distances of ∼1 mm. The accompanying physical characterization indicates that the polypeptide possesses characteristics analogous to those of the parent protein class and furnishes insight into the relationship between the polypeptide’s electrical functionality and structure in the solid state. When considered together, our findings hold significance for the continued development and engineering of not only reflectin-based materials but also other bioinspired proton conductors. 

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2. Doping molecular organic semiconductors by diffusion from the vapor phase

   https://doi.org/10.1039/D0QM00442A  

   Peterson, Kelly A.; Patterson, Ashlea; Vega-Flick, Alejandro; Liao, Bolin; Chabinyc, Michael L. (January 2020, Materials Chemistry Frontiers)

   Thin films of amorphous small molecule semiconductors are widely used in organic light emitting displays and have promising applications in solar cells and thermoelectric devices. Adding dopants increases the conductivity of organic semiconductors, but high concentrations of dopants can disrupt their structural ordering, alter the shape of the electronic density of states in the material, and increase the effects of Coulomb interactions on charge transport. Electrical doping of the solution processable hole-transport material 2,2′,7,7′-tetrakis[ N , N -di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) was studied with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 TCNQ) as a p-type dopant. Infiltration of F 4 TCNQ from the vapor phase into films of spiro-OMeTAD provided a route to highly doped films with up to 39 ± 2 mol% doping. Structural characterization confirmed that the films remain amorphous even at the highest doping levels with no apparent phase separation. We quantitatively determined the carrier concentration using UV-Vis spectroscopy to interpret the evolution of the electrical conductivity. Over the range of carrier concentrations (10 19 –10 20 1 cm −3 ), the electrical conductivity increased no more than linearly with carrier concentration, while the thermopower had a small increase with carrier concentration. The trends in conductivity and thermopower were related to the unique electronic structure of spiro-OMeTAD, which is able to support two carriers per molecule. Temperature-dependent conductivity measurements were used to further analyze the transport mechanism. 

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3. Engineering inorganic interfaces using molecular nanolayers

   https://doi.org/10.1063/5.0146122  

   Ramanath, Ganpati; Rowe, Collin; Sharma, Geetu; Venkataramani, Venkat; Alauzun, Johan_G; Sundararaman, Ravishankar; Keblinski, Pawel; Sangiovanni, Davide_G; Eklund, Per; Pedersen, Henrik (June 2023, Applied Physics Letters)

   Advances in interface science over the last 20 years have demonstrated the use of molecular nanolayers (MNLs) at inorganic interfaces to access emergent phenomena and enhance a variety of interfacial properties. Here, we capture important aspects of how a MNL can induce multifold enhancements and tune multiple interfacial properties, including chemical stability, fracture energy, thermal and electrical transport, and electronic structure. Key challenges that need to be addressed for the maturation of this emerging field are described and discussed. MNL-induced interfacial engineering has opened up attractive opportunities for designing organic–inorganic hybrid nanomaterials with high interface fractions, where properties are determined predominantly by MNL-induced interfacial effects for applications. 

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4. Contact Resistance in Organic Field‐Effect Transistors: Conquering the Barrier

   https://doi.org/10.1002/adfm.201904576  

   Waldrip, Matthew; Jurchescu, Oana_D; Gundlach, David_J; Bittle, Emily_G (September 2019, Advanced Functional Materials)

   Abstract Organic semiconductors have sparked interest as flexible, solution processable, and chemically tunable electronic materials. Improvements in charge carrier mobility put organic semiconductors in a competitive position for incorporation in a variety of (opto‐)electronic applications. One example is the organic field‐effect transistor (OFET), which is the fundamental building block of many applications based on organic semiconductors. While the semiconductor performance improvements opened up the possibilities for applying organic materials as active components in fast switching electrical devices, the ability to make good electrical contact hinders further development of deployable electronics. Additionally, inefficient contacts represent serious bottlenecks in identifying new electronic materials by inhibiting access to their intrinsic properties or providing misleading information. Recent work focused on the relationships of contact resistance with device architecture, applied voltage, metal and dielectric interfaces, has led to a steady reduction in contact resistance in OFETs. While impressive progress was made, contact resistance is still above the limits necessary to drive devices at the speed required for many active electronic components. Here, the origins of contact resistance and recent improvement in organic transistors are presented, with emphasis on the electric field and geometric considerations of charge injection in OFETs. 

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5. Cell-Free Synthesis Goes Electric: Dual Optical and Electronic Biosensor via Direct Channel Integration into a Supported Membrane Electrode

   https://doi.org/10.1021/acssynbio.2c00531  

   Manzer, Zachary A.; Ghosh, Surajit; Roy, Arpita; Jacobs, Miranda L.; Carten, Juliana; Kamat, Neha P.; Daniel, Susan (February 2023, ACS Synthetic Biology)

   Assembling transmembrane proteins on organic electronic materials is one promising approach to couple biological functions to electrical readouts. A biosensing device produced in such a way would enable both the monitoring and regulation of physiological processes and the development of new analytical tools to identify drug targets and new protein functionalities. While transmembrane proteins can be interfaced with bioelectronics through supported lipid bilayers (SLBs), incorporating functional and oriented transmembrane proteins into these structures remains challenging. Here, we demonstrate that cell-free expression systems allow for the one-step integration of an ion channel into SLBs assembled on an organic conducting polymer, poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). Using the large conductance mechanosensitive channel (MscL) as a model ion channel, we demonstrate that MscL adopts the correct orientation, remains mobile in the SLB, and is active on the polyelectrolyte surface using optical and electrical readouts. This work serves as an important illustration of a rapidly assembled bioelectronic platform with a diverse array of downstream applications, including electrochemical sensing, physiological regulation, and screening of transmembrane protein modulators. 

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