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One-dimensional organic molecular wires have emerged as idealized model systems for investigating charge transport mechanisms at 1-10 nm length scales, where the distinction between individual molecules and bulk materials begins to vanish. However, there are significant difficulties associated with the synthesis and electronic characterization of well-defined organic molecular wires. By drawing inspiration from oligonucleotide synthesis, we have developed a facile strategy for the assembly of perylene-based organic semiconductor building blocks in predetermined arrangements on a DNA-like backbone, resulting in molecular wires which have well-defined lengths, geometries, and sequence contexts. We self-assembled monolayers of these wires onto gold substrates and investigated their charge transport properties with both electrochemical and spectroscopic techniques. We found that as we increased the number of perylene building blocks, both the electron transfer and excited-state charge transfer dynamics show unexpected trends, which we rationalize with molecular dynamics and density-functional theory. Our findings hold significance both for fundamentally understanding nanoscale charge transport phenomena and for the development of new types of biological and molecular electronic devices.
Due to the rapid growth in the electronics industry for over the last century, the demand for more advanced materials has been raised. As a result of this, the number of the scientific studies to develop new type of electronic materials has increased and new fields of research such as molecular electronics and nanotechnology are now established. The trend in the advances in electronics follows the miniaturisation of the electrical components and therefore introducing single or a few molecules into electronic devices has become an important topic. In this work, a summary of the new aspects/developments in the field of single-molecule electronics is presented. Symmetrical tolane compounds with thiol (SH), amino (NH2), pyridyl (Py) and cyano (CN) anchoring groups were synthesised and single-molecule conductances of those molecules were systematically compared. With the help of density functional theory (DFT) calculations, single-molecular junction formation mechanism is also identified. Oligoyne molecular wires with different anchoring groups are also synthesised and their electron transport properties at the single-molecule level are studied. The stability of the functional diaryltetrayne compounds is discussed and X-ray molecular structures of the stable tetraynes are presented. The effects of the molecular length and the anchoring group are discussed in detail. Additionally, oligoynes with methyl shielding of the carbon backbone are synthesised and their stability is discussed. Finally, length-persistent, conjugated OPE and tolane analogues with different molecular lengths and amine anchors were synthesised and their transport properties were investigated in quantum dot sensitised solar cells.
Crucial to the progression of the field of molecular electronics is the intellectual conception, experimental fabrication and actual physical characterisation of molecular systems that function as electronic components. Future electronic devices could well incorporate such molecular systems in their manufacture, and expectations are high for the exploitation of molecular-scale properties. This thesis will report and discuss the stepwise construction of a variety of functional molecular wires embodied as self-assembled films on gold surfaces, providing evidence for their creation as well as characterisation of electrical properties. The growth of molecular wire systems were observed and monitored using the quartz crystal microbalance (QCM), with further physical and chemical characterisation being obtained from x-ray photoelectron (XPS) and infrared (IR) spectroscopic studies. These investigations demonstrated that amines compete with thiols for self-assembly on gold surfaces. This may have significant consequences for stepwise growth on gold supports when amino-thiols are used as initial building blocks. Electronic characterisation was achieved using the scanning tunnelling microscope (STM). Molecular wires self-assembled and grown on gold-coated surfaces were manipulated to exhibit rectifying behaviour, with current rectification ratios of ca. 55 at ±l V obtained for a D-x-A type functional molecular wire. The rectifying behaviour was found to conform to the Aviram and Ratner model. Investigations into the nature of 'current jump' events were also undertaken. These characteristic step changes in SlM tunnelling current have been employed in various studies to extract single molecule conductivities. However, the mechanism by which they occur has not been fully determined. Reported herein is evidence that suggests that current Jumps' most likely represent events whereby SlM probes make contact with Surface-bound molecules, as opposed to spontaneous molecular attachment. v.
As functional elements in opto-electronic devices approach the singlemolecule limit, conducting organic molecular wires are the appropriate interconnects that enable transport of charges and charge-like particles such as excitons within the device. Reproducible syntheses and a thorough understanding of the underlying principles are therefore indispensable for applications like even smaller transistors, molecular machines and light-harvesting materials. Bringing together experiment and theory to enable applications in real-life devices, this handbook and ready reference provides essential information on how to control and direct charge transport. Readers can therefore obtain a balanced view of charge and exciton transport, covering characterization techniques such as spectroscopy and current measurements together with quantitative models. Researchers are thus able to improve the performance of newly developed devices, while an additional overview of synthesis methods highlights ways of producing different organic wires. Written with the following market in mind: chemists, molecular physicists, materials scientists and electrical engineers.
This book addresses material growth, device fabrication, device application, and commercialization of energy-efficient white light-emitting diodes (LEDs), laser diodes, and power electronics devices. It begins with an overview on basics of semiconductor materials, physics, growth and characterization techniques, followed by detailed discussion of advantages, drawbacks, design issues, processing, applications, and key challenges for state of the art GaN-based devices. It includes state of the art material synthesis techniques with an overview on growth technologies for emerging bulk or free standing GaN and AlN substrates and their applications in electronics, detection, sensing, optoelectronics and photonics. Wengang (Wayne) Bi is Distinguished Chair Professor and Associate Dean in the College of Information and Electrical Engineering at Hebei University of Technology in Tianjin, China. Hao-chung (Henry) Kuo is Distinguished Professor and Associate Director of the Photonics Center at National Chiao-Tung University, Hsin-Tsu, Taiwan, China. Pei-Cheng Ku is an associate professor in the Department of Electrical Engineering & Computer Science at the University of Michigan, Ann Arbor, USA. Bo Shen is the Cheung Kong Professor at Peking University in China.
The ability to study and manipulate matter at the nanoscale is the defining feature of 21st-century science. The first edition of the standard-setting Handbook of Nanoscience, Engineering, and Technology saw the field through its infancy. Reassembling the preeminent team of leading scientists and researchers from all areas of nanoscience and nanote