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Research Article Issue
Molecule-based vertical transistor via intermolecular charge transport through π-π stacking
Nano Research 2024, 17(5): 4573-4581
Published: 02 December 2023
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The π-π stacking is a well-recognized intermolecular interaction that is responsible for the construction of electron hopping channels in numerous conducting frameworks/aggregates. However, the exact role of π-to-π channels within typical single crystalline organic semiconductors remains unclear as the orientations of these molecules are diverse, and their control usually requires additional side chain groups that misrepresent the intrinsic properties of the original semiconducting molecules. Therefore, the construction of conduction channels with intrinsic π-π stacking in the molecule-based device is crucial for the utilization of their unique transport characteristics and understanding of the transport mechanism. To this end, we present a molecular intercalation strategy that integrates two-dimensional layered materials with functional organic semiconductor molecules for functional molecule-based electronics. Various organic semiconductor molecules can be effectively intercalated into the van der Waals gaps of semi-metallic TaS2 with π-π stacking configuration and controlled intercalant content. Our results show that the vertical charge transport in the stacking direction shows a tunneling-dominated mechanism that strongly depends on the molecular structures. Furthermore, we demonstrated a new type of molecule-based vertical transistor in which TaS2 and π-π stacked organic molecules function as the electrical contact and the active channel, respectively. On/off ratios as high as 447 are achieved under electrostatic modulation in ionic liquid, comparable to the current state-of-the-art molecular transistors. Our study provides an ideal platform for probing intrinsic charge transport across π-π stacked conjugated molecules and also a feasible approach for the construction of high-performance molecule-based electronic devices.

Open Access Review Issue
Recent Advances in Electrical Transport Spectroscopy for the in Situ Measurement of Electrochemical Interfaces
Journal of Electrochemistry 2022, 28(3): 2108491
Published: 10 January 2022
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Electrochemical/electrocatalytic technology has played a central role in achieving highly efficient energy conversion and storage. To date, the in-depth electrochemical research begins to require accurate and multi-dimensional information of electrochemical interfaces, which usually relies on the application of in situ characterizations. Electrical transport spectroscopy (ETS) is a newly developed measurement strategy based on chip-platform, and provides in situ information of electrochemical interfaces from a novel perspective due to a signal origin that is fundamentally different from typical spectroscopic and electrochemical techniques. In this tutorial review, the working principle and experimental setup of ETS are described in detail with the demonstration of several model electrocatalytic materials, including metal nanoparticle/nanowires, two-dimensional layered materials, nickel based hydroxide/oxyhydroxides and dissimilatory metal-reducing bacteria. The advantages of ETS are summarized, and the future challenges and opportunities that ETS faces are also prospected.

Research Article Issue
Intercalation and hybrid heterostructure integration of two- dimensional atomic crystals with functional organic semiconductor molecules
Nano Research 2020, 13(11): 2917-2924
Published: 27 July 2020
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Van der Waals (vdW) integration affords semiconductor heterostructures without constrains of lattice matching and opens up a new realm of functional devices by design. A particularly interesting approach is the electrochemical intercalation of two-dimensional (2D) atomic crystal and formation of superlattices, which can provide scalable production of novel vdW heterostructures. However, this approach has been limited to the use of organic cations with non-functional aliphatic chains, therefore failed to take the advantage of the vast potentials in molecular functionalities (electronic, photonic, magnetic, etc.). Here we report the integration of 2D crystal (MoS2, WS2, highly oriented pyrolytic graphite (HOPG), WSe2 as model systems) with electrochemically inert organic molecules that possess semiconducting characteristics (including perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), pentacene and fullerene), through on-chip electrochemical intercalation. An unprecedented long-range spatial feature of intercalation has been achieved, which allowed facile assembly of a vertical MoS2-PTCDA-Si junction. The intercalated heterostructure shows significant modulation of the lateral transport, and leads to a molecular tunneling characteristic at the vertical direction. The general intercalation of charge neutral and functional molecules defines a versatile platform of inorganic/organic hybrid vdW heterostructures with significantly extended molecular functional building blocks, holding great promise in future design of nano/quantum devices.

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