Molecular Electronics: Insights and Challenges

Dear Colleagues,

The prospect of constructing robust electronic devices from individual molecules opens a vast technological frontier. Single-molecule electronics promises molecular-scale systems capable of highly sensitive detection, chemical processing, and real-time electronic feedback, offering new paradigms for interfacing conventional electronics with chemistry, materials science, and biology. From organic molecules and polymers to biomolecules such as proteins and DNA, a wide range of systems exhibit intriguing charge transport phenomena at the nanoscale.

Evidence for long-range charge transport at the molecular level is compelling. Biological systems such as cable bacteria demonstrate electron transport over centimeter-scale distances, while synthetic molecular junctions routinely show conductance across nanometer gaps. Despite these advances, the field remains far from delivering practical and scalable technologies. The goal of this Special Issue is to bring together leading experimentalists and theorists working across the diverse landscape of single-molecule electronics to clarify fundamental mechanisms and define key challenges.

Significant theoretical questions remain unresolved. For example:

• Is charge transport quantum coherent, and if so, under what conditions can coherence persist despite environmental fluctuations?
• Is transport dominated by hopping mechanisms, and how can this be reconciled with large reorganization energies observed in many systems?
• What is the relative contribution of electrons versus ions? Do coupled processes, such as proton-coupled electron transfer, play a significant role?

The experimental landscape is equally complex. For instance:

• Scanning tunneling microscope (STM) studies often report conductances in the nS range over nanometer distances, while conducting atomic force microscopy (cAFM) measurements sometimes require large applied forces to observe comparable conductance.
• Reports of long-range transport in molecular assemblies and biological filaments vary significantly between laboratories, highlighting challenges in reproducibility and measurement consistency.
• Variability in electrode–molecule interfaces, molecular conformations, and environmental conditions continue to complicate the interpretation of experimental data.

The current state of single-molecule electronics is reminiscent of early surface science prior to the development of techniques enabling atomically clean and well-defined interfaces. Such advances ultimately enabled transformative technologies, including the field-effect transistor and modern CMOS electronics. Analogously, breakthroughs in controlling and reliably integrating single molecules into electronic circuits could lead to revolutionary developments, from ultra-sensitive sensors to massively parallel molecular-scale information processing systems.

Imagine, for example, electronic platforms where individual molecules—whether synthetic or biological—function as active circuit elements, enabling applications such as real-time biochemical analysis, nanoscale logic, or energy-efficient computation.

It is our hope that this Special Issue will help define the fundamental questions, experimental standards, and technological pathways that will shape the future of single-molecule electronics.

Prof. Dr. Stuart Lindsay
Guest Editor

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