Unconventional Materials: the mismatch between electronic charge centers and atomic positions

Relation Between Local Structure, Electric Dipole and Charge Carrier Dynamics in DHICA Melanin, a Model for Biocompatible Semiconductors

10.26434/chemrxiv.11323016 ◽

2019 ◽

Author(s):

Micaela Matta ◽

Alessandro Pezzella ◽

Alessandro Troisi

Keyword(s):

Electronic Structure ◽

Degrees Of Freedom ◽

Structural Model ◽

Computational Study ◽

Oxidative Polymerization ◽

Radical Scavenging ◽

Charge Carriers ◽

Electronic Charge ◽

Polymer Semiconductors ◽

Synthetic Pigments

<div><div><div><p>Eumelanins are a family of natural and synthetic pigments obtained by oxidative polymerization of their natural precursors: 5,6 dihydroxyindole and its 2-carboxy derivative (DHICA). The simultaneous presence of ionic and electronic charge carriers makes these pigments promising materials for applications in bioelectronics. In this computational study we build a structural model of DHICA melanin considering the interplay between its many degrees of freedom, then we examine the electronic structure of representative oligomers. We find that a non-vanishing dipole along the polymer chain sets this system apart from conventional polymer semiconductors, determining its electronic structure, reactivity toward oxidation and localization of the charge carriers. Our work sheds light on previously unnoticed features of DHICA melanin that not only fit well with its radical scavenging and photoprotective properties, but open new perspectives towards understanding and tuning charge transport in this class of materials.<br></p></div></div></div>

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Field Effect Modulation of Electrocatalytic Hydrogen Evolution at Back-Gated Two-Dimensional MoS2 Electrodes

10.26434/chemrxiv.8150660 ◽

2019 ◽

Author(s):

Yan Wang ◽

Sagar Udyavara ◽

Matthew Neurock ◽

C. Daniel Frisbie

Keyword(s):

Electric Field ◽

Hydrogen Evolution ◽

Active Sites ◽

Density Functional ◽

Electrode Materials ◽

Density Functional Theory Calculations ◽

Electronic Charge ◽

Back Side ◽

Gate Electrode ◽

Conventional Manner

<div> <div> <div> <p> </p><div> <div> <div> <p>Electrocatalytic activity for hydrogen evolution at monolayer MoS2 electrodes can be enhanced by the application of an electric field normal to the electrode plane. The electric field is produced by a gate electrode lying underneath the MoS2 and separated from it by a dielectric. Application of a voltage to the back-side gate electrode while sweeping the MoS2 electrochemical potential in a conventional manner in 0.5 M H2SO4 results in up to a 140-mV reduction in overpotential for hydrogen evolution at current densities of 50 mA/cm2. Tafel analysis indicates that the exchange current density is correspondingly improved by a factor of 4 to 0.1 mA/cm2 as gate voltage is increased. Density functional theory calculations support a mechanism in which the higher hydrogen evolution activity is caused by gate-induced electronic charge on Mo metal centers adjacent the S vacancies (the active sites), leading to enhanced Mo-H bond strengths. Overall, our findings indicate that the back-gated working electrode architecture is a convenient and versatile platform for investigating the connection between tunable electronic charge at active sites and overpotential for electrocatalytic processes on ultrathin electrode materials.</p></div></div></div><br><p></p></div></div></div>

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Electronic charge

Journal of the Franklin Institute ◽

10.1016/s0016-0032(12)90595-5 ◽

1912 ◽

Vol 173 (1) ◽

pp. 87

Keyword(s):

Electronic Charge

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Effects of a scattering center on the ground-state energy of quantum-dot lithium

Modern Physics Letters B ◽

10.1142/s0217984917500713 ◽

2017 ◽

Vol 31 (07) ◽

pp. 1750071

Author(s):

Z. D. Vatansever ◽

S. Sakiroglu ◽

I. Sokmen

Keyword(s):

Quantum Dot ◽

Ground State Energy ◽

Ground State ◽

State Energy ◽

Electronic Charge ◽

Strongly Correlated ◽

Configuration Interaction Method ◽

Charge Localization ◽

Scattering Center ◽

Spin Properties

In this paper, the effects of a repulsive scattering center on the ground-state energy and spin properties of a three-electron parabolic quantum dot are investigated theoretically by means of configuration interaction method. Phase transition from a weakly correlated regime to a strongly correlated regime is examined from several strengths and positions of Gaussian impurity. Numerical results reveal that the transition from spin-1/2 to spin-3/2 state depends strongly on the location of the impurity which accordingly states the controllability of the spin polarization. Moreover, broken circular symmetry results in more pronounced electronic charge localization.

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Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces

Advanced Materials ◽

10.1002/adma.202004132 ◽

2020 ◽

pp. 2004132

Author(s):

Marc‐André Rose ◽

Břetislav Šmíd ◽

Mykhailo Vorokhta ◽

Ivetta Slipukhina ◽

Michael Andrä ◽

...

Keyword(s):

Charge Transfer ◽

Electronic Charge ◽

Electronic Charge Transfer

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Interfacial Energy Alignment at the ITO/Ultra-Thin Electron Selective Dielectric Layer Interface and Its Effect on the Efficiency of Bulk-Heterojunction Organic Solar Cells

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2016.12277 ◽

2016 ◽

Vol 16 (4) ◽

pp. 3248-3253 ◽

Cited By ~ 1

Author(s):

Eiji Itoh ◽

Yoshinori Goto ◽

Yusuke Saka ◽

Katsutoshi Fukuda

Keyword(s):

Contact Resistance ◽

Active Layer ◽

Surface Potential ◽

Organic Solar Cells ◽

Indium Tin Oxide ◽

Bulk Heterojunction ◽

Electronic Charge ◽

Photovoltaic Properties ◽

Potential Measurement ◽

Layer Interface

We have investigated the photovoltaic properties of an inverted bulk heterojunction (BHJ) cell in a device with an indium-tin-oxide (ITO)/electron selective layer (ESL)/P3HT:PCBM active layer/MoOx/Ag multilayered structure. The insertion of only single layer of poly(diallyl-dimethylammonium chloride) (PDDA) cationic polymer film (or poly(ethyleneimine) (PEI) polymeric interfacial dipole layer) and titanium oxide nanosheet (TN) films as an ESL effectively improved cell performance. Abnormal S-shaped curves were observed in the inverted BHJ cells owing to the contact resistance across the ITO/active layer interface and the ITO/PDDA/TN/active layer interface. The series resistance across the ITO/ESL interface in the inverted BHJ cell was successfully reduced using an interfacial layer with a positively charged surface potential with respect to ITO base electrode. The positive dipole in PEI and the electronic charge phenomena at the electrophoretic deposited TN (ED-TN) films on ITO contributed to the reduction of the contact resistance at the electrode interface. The surface potential measurement revealed that the energy alignment by the transfer of electronic charges from the ED-TN to the base electrodes. The insertion of the ESL with a large positive surface potential reduced the potential barrier for the electron injection at ITO/TN interface and it improved the photovoltaic properties of the inverted cell with an ITO/TN/active layer/MoOx/Ag structure.

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