Towards Supramolecular Electronics

Dr. S. S. Verma, Department of Physics, S.L.I.E.T., Longowal, Distt.-Sangrur (Punjab)-148106

2018-10-17 02:58:33



Since its origin electronics has grown faster than any other major engineering discipline. Different versions of electronics like organic electronics and spintronics are emerging with some constraints. Supramolecular organic electronics embodies one of the biggest promises made by supramolecular functional materials. Huge advancements have been made with regard to its theoretical and functional understanding over the past few decades. A supra-molecule in chemistry denotes those molecules that are held together by non-covalent bonding.

The most critically acclaimed carbon nano particles fall into this category, as well. The process of constructing electronic circuitry at nanoscales from these supra-molecules is underway. Sheets of electronic circuitry as thin as cellophane tapes will become a reality once this research turns out to be successful. Such circuits can be customized into cutting edge friction detection sensors and wrapped around the cricket ball without affecting its size, shape or texture. These sensors might further be programmed to transmit data in accordance with the amount of friction they experience. Various supramolecular aspects of domain control, monodispersity and control of dynamics of π-conjugated molecular assemblies can be looked into with most promising recent approaches in relevance to supramolecular electronics. Owing to their outstanding electrical, optical, chemical and thermal properties, two-dimensional (2D) materials, which consist of a single layer of atoms, hold great potential for technological applications such as electronic devices, sensors, catalysts, energy conversion and storage devices, among others. Thanks to their ultra-high surface sensitivity, 2D materials represent an ideal platform to study the interplay between nanoscale molecular assembly on surfaces and macroscopic electrical transport in devices.

Working principle

A molecular crystal, by itself, has an interspace and void. Molecular implantation is a novel technique that enables to store any functional molecules within the interspace. The designed organic hybrids realize new functionalities that are not accessible by a single component. This project will address how an electron can be controlled by a nano-scale molecule via interspace engineering on macromolecules, and will provide a new route of supramolecule electronics. Versatile approach of molecularly tailoring 2D materials is taking supramolecular electronics to a new level and closer to future applications. The work is groundbreaking for the realization of multifunctional hybrid components powered by nature's primary energy source - sunlight. In order to provide a unique light-responsivity to devices, the researchers have designed and synthesized a photoswitchable spiropyran building block, which is equipped with an anchoring group and which can be reversibly inter converted between two different forms by illumination with ultraviolet and visible light, respectively. On the surface of 2D materials, such as graphene or molybdenum disulfide (MoS2), the molecular photoswitches self-assemble into highly ordered ultrathin layers, thereby generating a hybrid, atomically precise superlattice. Upon illumination the system undergoes a collective structural rearrangement, which could be directly visualized and monitored with sub-nanometer resolution by scanning tunneling microscopy. This light-induced reorganization at the molecular level induces an optical modulation of the energetics of the underlying 2D material, which translates into a change in the electrical characteristics of the fabricated hybrid devices. In this regard, the collective nature of self-assembly allows to convert single-molecule events into a spatially homogeneous switching action, which generates a macroscopic electrical response in graphene and MoS2.


Development status

Organic electronics is of great fundamental interest in materials science and is also recognized as one of the most promising and competitive markets for industry. In particular, its expansion will be supported by the development of active components being easily processable, flexible, energy friendly, cheap, and compatible with their downscaling towards nano-devices. Researcher have now a strong fundamental understanding of supramolecular electronic systems, in terms of supramolecular properties and conduction mechanism, and are developing a number of systems based on this molecular core which shows its generality in terms of structuring properties and outstanding electronic performances. Recently, the so-called supramolecular electronics has been proposed as a promising intermediary-scale approach which rests on the design of electronic components at a length of 5-100 nm, that is comprised between plastic electronics (µm) and molecular electronics (Å). This is an essentially new class of materials that are engineered at a supramolecular level to achieve a greater control over the photo-physical and charge-carrying properties of the conjugated cores. The aim of the project is to investigate both the nature of the electronic process in the single supramolecular structures, and in large ensembles of them, which will be studied with the help of solid-state optoelectronic applications such as light-emitting diodes, LEDs, light-emitting electrochemical cells (LECs) and photovoltaic diodes, PVDs. The conditions required for supramolecular electronics, e.g. nano-sized optoelectronic devices, will be illustrated on the basis of the programmed self-assembly of pi-conjugated systems into individual nanosized wires. Using the supramolecular design rules nanowires can be created from almost any polymeric and oligomeric pi-conjugated system. In the case of oligomers it is even possible to construct individual wires having a uniform diameter of one molecule thickness. The construction of wires on a substrate is possible by self-assembly in solution or during the deposition. The transfer of the supramolecular stacks from solution to a solid support is a very delicate process. A comprehensive knowledge of all intermolecular interactions gives rise to controlled transfer of pi-conjugated assemblies to specific surfaces. There are a large number of very appealing targets that should be reached before supramolecular electronics can serve as an attractive alternative in between single molecule electronics and bulk devices. Nevertheless, the combination of exciting scientific results and intriguing technological challenges creates an interesting future for supramolecular electronics.