Organic electrode materials are very attractive for electrochemical energy storage devices because they can be flexible, lightweight, low cost, benign to the environment, and used in a variety of ...device architectures. They are not mere alternatives to more traditional energy storage materials, rather, they have the potential to lead to disruptive technologies. Although organic electrode materials for energy storage have progressed in recent years, there are still significant challenges to overcome before reaching large-scale commercialization. This review provides an overview of energy storage systems as a whole, the metrics that are used to quantify the performance of electrodes, recent strategies that have been investigated to overcome the challenges associated with organic electrode materials, and the use of computational chemistry to design and study new materials and their properties. Design strategies are examined to overcome issues with capacity/capacitance, device voltage, rate capability, and cycling stability in order to guide future work in the area. The use of low cost materials is highlighted as a direction towards commercial realization.
We review organic electrode materials for energy storage devices and suggest directions for future work in this area.
Sulfur-containing compounds, particularly derivatives of thiophene, are well studied for organic optoelectronic applications. Incorporating selenium or tellurium in place of sulfur imparts different ...physical properties due to the fundamental differences of these atoms relative to their lighter analogues. This has a profound influence on the properties of molecules and materials that incorporate chalcogens that may ultimately lead to new opportunities and applications. This mini-review will focus on the quantitative and qualitative photophysical characteristics of organic materials containing selenium and tellurium as well as their emerging applications as molecular photoactive species, including light-emitting sensors, triplet sensitizers, and beyond.
Incorporating selenium or tellurium into photoactive species imparts new photophysical properties that may be exploited in materials applications.
Gold Nanoparticles for Biology and Medicine Giljohann, David A.; Seferos, Dwight S.; Daniel, Weston L. ...
Angewandte Chemie (International ed.),
April 26, 2010, Letnik:
49, Številka:
19
Journal Article
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Gold colloids have fascinated scientists for over a century and are now heavily utilized in chemistry, biology, engineering, and medicine. Today these materials can be synthesized reproducibly, ...modified with seemingly limitless chemical functional groups, and, in certain cases, characterized with atomic‐level precision. This Review highlights recent advances in the synthesis, bioconjugation, and cellular uses of gold nanoconjugates. There are now many examples of highly sensitive and selective assays based upon gold nanoconjugates. In recent years, focus has turned to therapeutic possibilities for such materials. Structures which behave as gene‐regulating agents, drug carriers, imaging agents, and photoresponsive therapeutics have been developed and studied in the context of cells and many debilitating diseases. These structures are not simply chosen as alternatives to molecule‐based systems, but rather for their new physical and chemical properties, which confer substantive advantages in cellular and medical applications.
Sitting on a gold mine: Gold nanoparticles have been developed and studied as gene‐regulating agents, drug carriers, photoresponsive therapeutics, and as imaging platforms (see the nanoflare, which allows detection of mRNA by fluorescence microscopy). These structures have new properties that are advantageous for biological applications. This Review highlights the synthesis of gold nanoparticles and their application from cell‐based assays to therapeutic materials.
The development of high-carbon-content polymers for optoelectronics is an area of intense research; however, carbon-rich materials have certain limitations that arise from their composition. Some of ...these limitations can be overcome by the judicious incorporation of heavier elements which do not significantly change the carbon content to a point where it adversely affects cost and processability. Here we examine the use of tellurium as a heavy atom in the design of optoelectronic polymers. Group 16 atom (O, S, Se, Te) substitution is a promising strategy for the development of high performance materials for organic electronic applications. The use of tellurium in place of selenium or sulfur in conjugated polymers lends new properties to these materials such as red-shifted optical absorption, high polarizability, high dielectric constant, and strong intermolecular interactions. These properties are favorable for organic photovoltaics (OPVs) and organic field effect transistors (OFETs). In particular, extending the absorption range to the near-IR allows for more efficient solar harvesting since low-energy photons are most abundant. Additionally, strong Te–Te interactions lead to enhanced interchain electronic coupling, which is expected to facilitate charge transport. The use of polymers containing tellurophene, the tellurium analogue of the well-studied thiophene, has only recently begun to emerge in the literature. New synthetic routes have been developed, and there now exist a handful of tellurophene-containing polymers that have been synthesized and used to fabricate OPVs and OFETs. Their performance in OPVs has not surpassed that of their lighter chalcogen analogues; however, the use of tellurophene-containing materials is a young field, and continued efforts in the development of new materials and device optimization should lead to improved performance. In this Perspective we discuss the current status of tellurium-containing polymers in terms of their synthesis, properties, and performance. We highlight the challenges that have been overcome thus far and emphasize those that should be the focus of future work. This includes overcoming synthetic challenges and developing an understanding of the current limitations in device performance with tellurium-containing polymers through studies of materials properties and excited state dynamics. We also suggest new applications and directions for tellurium-containing materials beyond OPVs and OFETs.
Conspectus Since the discovery of conductive poly(acetylene), the study of conjugated polymers has remained an active and interdisciplinary frontier between polymer chemistry, polymer physics, ...computation, and device engineering. One of the ultimate goals of polymer science is to reliably synthesize structures, similar to small molecule synthesis. Kumada catalyst-transfer polymerization (KCTP) is a powerful tool for synthesizing conjugated polymers with predictable molecular weights, narrow dispersities, specific end groups, and complex backbone architectures. However, expanding the monomer scope beyond the well-studied 3-alkylthiophenes to include electron-deficient and complex heterocycles has been difficult. Revisiting the successful applications of KCTP can help us gain new insight into the CTP mechanisms and thus inspire breakthroughs in the controlled polymerization of challenging π-conjugated monomers. In this Account, we highlight our efforts over the past decade to achieve controlled synthesis of homopolymers (p-type and n-type), copolymers (diblock and statistical), and monodisperse high oligomers. We first give a brief introduction of the mechanism and state-of-the-art of KCTP. Since the extent of polymerization control is determined by steric and electronic effects of both the catalyst and monomer, the polymerization can be optimized by modifying monomer and catalyst structures, as well as finding a well-matched monomer–catalyst system. We discuss the effects of side-chain steric hindrance and halogens in the context of heavy atom substituted monomers. By moving the side-chain branch point one carbon atom away from the heterocycle to alleviate steric crowding and stabilize the catalyst resting state, we were able to successfully control the polymerization of new tellurophene monomers. Inspired by innocent role of the sterically encumbered 2-transmetalated 3-alkylthiophene monomer, we introduce the treatment of hygroscopic monomers with a bulky Grignard compound as a water-scavenger for the improved synthesis of water-soluble conjugated polymers. For challenging electron-deficient monomers, we discuss the design of new Ni(II)diimine catalysts with electron-donating character which enhance the stability of the association complex between the catalyst and the growing polymer chain, resulting in the quasi-living synthesis of n-type polymers. Beyond n-type homopolymers, the Ni(II)diimine catalysts are also capable of producing electron-rich and electron-deficient diblock and statistical copolymers. We discuss how density functional theory (DFT) calculations elucidate the role of catalyst steric and electronic effects in controlling the synthesis of π-conjugated polymers. Moreover, we demonstrate the synthesis of monodisperse high oligomers by temperature cycling, which takes full advantage of the unique character of KCTP in that it proceeds through distinct intermediates that are not reactive. The insight we gained thus far leads to the first example of isolated living conjugated polymer chains prepared by a standard KCTP procedure, with general applicability to different monomers and catalytic systems. In summarizing a decade of innovation in KCTP, we hope this Account will inspire future development in the field to overcome key challenges including the controlled synthesis of electron-deficient heterocycles, complex and high-performance systems, and degradable and recyclable materials as well as cutting-edge catalyst design.
We have synthesized a series of cyclopentadithiophene–benzochalcogenodiazole donor–acceptor (D–A) copolymers, wherein a single atom in the benzochalcogenodiazole unit is varied from sulfur to ...selenium to tellurium, which allows us to explicitly study sulfur to selenium to tellurium substitution in D–A copolymers for the first time. The synthesis of S- and Se-containing polymers is straightforward; however, Te-containing polymers must be prepared by postpolymerization single atom substitution. All of the polymers have the representative dual-band optical absorption profile, consisting of both a low- and high-energy optical transition. Optical spectroscopy reveals that heavy atom substitution leads to a red-shift in the low-energy transition, while the high-energy band remains relatively constant in energy. The red-shift in the low-energy transition leads to optical band gap values of 1.59, 1.46, and 1.06 eV for the S-, Se-, and Te-containing polymers, respectively. Additionally, the strength of the low-energy band decreases, while the high-energy band remains constant. These trends cannot be explained by the present D and A theory where optical properties are governed exclusively by the strength of D and A units. A series of optical spectroscopy experiments, solvatochromism studies, density functional theory (DFT) calculations, and time-dependent DFT calculations are used to understand these trends. The red-shift in low-energy absorption is likely due to both a decrease in ionization potential and an increase in bond length and decrease in acceptor aromaticity. The loss of intensity of the low-energy band is likely the result of a loss of electronegativity and the acceptor unit’s ability to separate charge. Overall, in addition to the established theory that difference in electron density of the D and A units controls the band gap, single atom substitution at key positions can be used to control the band gap of D–A copolymers.
Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, ...polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, SuzukiMiyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.
This review systematically summarizes the history and recent progress in the synthesis, properties, and post-polymerization modifications of chalcogenophene-based homopolymers and copolymers.
Perfluoroaryl-substituted tellurophenes act as anion receptors through noncovalent chalcogen bonding interactions. Linking two tellurophenes through an ethynylene group results in a significant level ...of chelate cooperativity, thus demonstrating that chalcogen bonding can be used to achieve multidentate anion recognition.
We report the synthesis of three fully π-conjugated diblock copolymers containing selenophene- and thiophene-based repeating units. All of these diblock copolymers undergo phase separation, and by ...systematically changing the compatibility of the two blocks through side chain modification, we are able to access different thin film morphologies. Introducing a bulky 2-ethylhexyl side chain increases solubility while retaining crystallinity of the selenophene block. While poly(3-hexylselenophene)-b-poly(3-hexylthiophene) and poly(3-(2-ethylhexyl)selenophene-b-poly(3-(2-ethylhexyl)thiophene) form more disordered fibrillar structures, poly(3-hexylthiophene)-b-poly(3-(2-ethylhexyl)selenophene) forms long (1–2 μm) solid state fibrillar structures that are reminiscent of the lamellae that are formed by nonconjugated block copolymers. We further use electron energy loss spectroscopy to visualize thiophene- and selenophene-rich domains at the nanometer scale in each of these examples. By studying new polymer compositions and relating them to solid state structure, we further our understanding of heterocycle induced phase separation and phase separation in general.
Selenophene−thiophene block copolymers were synthesized and studied. The properties of these novel block copolymers are distinct from those of statistical copolymers prepared from the same monomers ...with a similar composition. Specifically, the block copolymers exhibit broad and red-shifted absorbance features and phase-separated domains in the solid state. Scanning transmission electron microscopy and topographic elemental mapping confirmed that the domains are either rich in selenophene or thiophene, indicating that the blocks of distinct heterocycles preferentially associate with one another in the solid state. This preference is surprising in view of the chemical similarities between repeat units. The overall results demonstrate a phase separation that is controlled by elemental differences. As a result of this phase separation, these novel conjugated block copolymers should find utility in a variety of studies and optoelectronics uses.
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