共查询到20条相似文献,搜索用时 38 毫秒
1.
Tracy Q. Ha Inco J. Planje Jhanelle R.G. White Albert C. Aragonès Ismael Díez-Pérez 《Current Opinion in Electrochemistry》2021
The emerging field of BioMolecular Electronics aims to unveil the charge transport characteristics of biomolecules with two primary outcomes envisioned. The first is to use nature's efficient charge transport mechanisms as an inspiration to build the next generation of hybrid bioelectronic devices towards a more sustainable, biocompatible and efficient technology. The second is to understand this ubiquitous physicochemical process in life, exploited in many fundamental biological processes such as cell signalling, respiration, photosynthesis or enzymatic catalysis, leading us to a better understanding of disease mechanisms connected to charge diffusion. Extracting electrical signatures from a protein requires optimised methods for tethering the molecules to an electrode surface, where it is advantageous to have precise electrochemical control over the energy levels of the hybrid protein–electrode interface. Here, we review recent progress towards understanding the charge transport mechanisms through protein–electrode–protein junctions, which has led to the rapid development of the new BioMolecular Electronics field. The field has brought a new vision into the molecular electronics realm, wherein complex supramolecular structures such as proteins can efficiently transport charge over long distances when placed in a hybrid bioelectronic device. Such anomalous long-range charge transport mechanisms acutely depend on specific chemical modifications of the supramolecular protein structure and on the precisely engineered protein–electrode chemical interactions. Key areas to explore in more detail are parameters such as protein stiffness (dynamics) and intrinsic electrostatic charge and how these influence the transport pathways and mechanisms in such hybrid devices. 相似文献
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Block Copolymer‐Derived Monolithic Polymer Films and Membranes Comprising Self‐Organized Cylindrical Nanopores for Chemical Sensing and Separations 下载免费PDF全文
Prof. Dr. Takashi Ito 《化学:亚洲杂志》2014,9(10):2708-2718
Microphase separation of block copolymers (BCPs) has been extensively studied because it leads to the self‐assembled formation of periodic structures controlled on the scale of tens of nanometers. In particular, BCP‐derived cylindrical microdomains have attracted considerable interest for various applications owing to their well‐defined shapes of uniform and tunable diameters. This focus review highlights recent efforts to apply BCP‐derived monolithic films/membranes comprising cylindrical nanopores for chemical sensing and separations. The nanopores provide confined molecular pathways that exhibit enhanced selectivity based on steric, electrostatic, and chemical interactions, and thus, enable us to design unique electrochemical sensors and highly efficient separation membranes. 相似文献
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Selective Carbon–Carbon Bond Cleavage for the Stereoselective Synthesis of Acyclic Systems 下载免费PDF全文
Prof. Dr. Ilan Marek Dr. Ahmad Masarwa Dr. Pierre‐Olivier Delaye Dr. Markus Leibeling 《Angewandte Chemie (International ed. in English)》2015,54(2):414-429
Most of the efforts of organic chemists have been directed to the development of creative strategies to build carbon–carbon and carbon–heteroatom bonds in a predictable and efficient manner. In this Review, we show an alternative approach where challenging molecular skeletons could be prepared through selective cleavage of carbon–carbon bonds. We demonstrate that it has the potential to be a general principle in organic synthesis for the regio‐, diastereo‐, and even enantioselective preparation of adducts despite the fact that C? C single bonds are among the least reactive functional groups. The development of such strategies may have an impact on synthesis design and can ultimately lead to new selective and efficient processes for the utilization of simple hydrocarbons. 相似文献
4.
Basem Moosa Lukman O. Alimi Aleksander Shkurenko Aliyah Fakim Prashant M. Bhatt Gengwu Zhang Mohamed Eddaoudi Niveen M. Khashab 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21551-21555
Developing the competence of molecular sorbents for energy-saving applications, such as C8 separations, requires efficient, stable, scalable, and easily recyclable materials that can readily transition to commercial implementation. Herein, we report an azobenzene-based cage for the selective separation of p-xylene isomer across a range of C8 isomers in both vapor and liquid states with selectivity that is higher than the reported all-organic sorbents. The crystal structure shows non-porous cages that are separated by p-xylene molecules through selective CH–π interactions between the azo bonds and the methyl hydrogen atoms of the xylene molecules. This cage is stable in solution and can be regenerated directly under vacuum to be used in multiple cycles. We envisage that this work will promote the investigation of the azo bond as well as guest-induced crystal-to-crystal phase transition in non-porous organic solids for energy-intensive separations. 相似文献
5.
Dongjie Zhang Miguel A. Soto Lev Lewis Wadood Y. Hamad Mark J. MacLachlan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4735-4740
Cellulose nanocrystals (CNCs) spontaneously assemble into gels when mixed with a polyionic organic or inorganic salt. Here, we have used this ion-induced gelation strategy to create functional CNC gels with a rigid tetracationic macrocycle, cyclobis(paraquat-p-phenylene) ( CBPQT 4+). Addition of [ CBPQT ]Cl4 to CNCs causes gelation and embeds an active host inside the material. The fabricated CNC gels can reversibly absorb guest molecules from solution then undergo molecular recognition processes that create colorful host–guest complexes. These materials have been implemented in gel chromatography (for guest exchange and separation), and as elements to encode 2- and 3-dimensional patterns. We anticipate that this concept might be extended to design a set of responsive and selective gel-like materials functioning as, for instance, water-pollutant scavengers, substrates for chiral separations, or molecular flasks. 相似文献
6.
Han X Yang K Yang J Fikes KN Cheng H Gross RW 《Journal of the American Society for Mass Spectrometry》2006,17(2):264-274
The external electric field induces a separation of cations from negative electrolyte ions in the infusate while differential ionization of molecular species that possess differential electrical propensities can be induced in either the positive- or negative-ion mode during the electrospray ionization process. These physical and electrical processes that occur in the electrospray ion source have been used to selectively ionize lipid classes possessing different electrical propensities that are now known as "intrasource separation and selective ionization". However, the chemical principles underlying charge-dependent alterations in ionization efficiencies responsible for the selective ionization of lipid classes are not known with certainty. Herein, we examined the multiple factors that contribute to intrasource separation and selective ionization of lipid classes under optimal instrumental conditions. We demonstrated that many different lipid classes could be selectively ionized in the ion source and that intrasource resolution of distinct molecular constituents was independent of lipid concentration, flow rate, and residual ions under most experimental conditions. Moreover, the presence of alkaline conditions facilitates the selective ionization of many lipid classes through a mechanism independent of the design of the ESI ion source. Collectively, this study provides an empirical foundation for understanding the chemical mechanisms underlying intrasource separation and selective ionization of lipid classes that can potentially be used for global analysis of cellular lipidomes without the need for chromatographic separation. 相似文献
7.
Issara Sereewatthanawut Andrew T. Boam Andrew G. Livingston 《Macromolecular Symposia》2008,264(1):184-188
The application of membrane technology, particularly water-based nanofiltration, as a separation process in the chemical industries has increased tremendously in recent years. However, the use of membranes capable of molecular separation in non-aqueous systems (e.g. nanofiltration) is a relatively new and growing application of membrane technology. The main challenge in applying polymeric nanofiltration membranes to non-aqueous systems is that the polymers developed for water-based applications are not suitable. Polyimide is a particularly interesting polymer as it has excellent chemical resistance, and membranes produced from it provide desirable separation properties – i.e. economically viable flux and good separation of nanoscale molecules. Various research works have shown that commercial polyimide organic solvent nanofiltration (OSN) membranes, trademark STARMEM™, 1 are robust and suitable for performing molecular separations. This work will discuss in detail the use of STARMEM™ in a pharmaceutical application. The EIC-OSN process was developed for separating the enantiomers of chiral compounds in pharmaceutical applications. High optical purity (94.9%) of (S)-phenylethanol from rac-phenylethanol was achieved through the use of STARMEM™122. Process simulation of the ideal eutomer-distomer system predicted that the highest theoretical resolvability from this process would be 99.2%. Other application areas of OSN are varied, including purification and fractionation in the natural products industry, homogeneous catalyst recovery, monomer separation from oligomers, etc. Currently, OSN is used in a small number of processes including a very large petrochemical application, but it has the potential to be applied to a wide range of separations across the full spectrum of the chemical industries. 相似文献
8.
Takahiro Muraoka Kazushi Kinbara 《Journal of Photochemistry and Photobiology, C: Photochemistry Reviews》2012,13(2):136-147
In the growing research area on molecular machinery, light is one of the attractive and useful stimuli source to operate synthetic molecular machines, since light allows selective operation of photoresponsive moieties without additives. We have proposed a new approach to design of photoresponsive molecular machines by interlocking mechanical motions between photoresponsive and movable units through covalent and non-covalent bonds. This approach is inspired by biological molecular machines consisting of multiple protein subunits, and potentially useful for construction of giant mechanical systems. In this review, we will introduce our concepts of the molecular design with several successful examples as well as their applications for controlling chemical events, and also glance at a semi-biological molecular machine controllable by light, which reveals a potential of biological systems for development of elaborate molecular devices. 相似文献
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Dongjie Zhang Miguel A. Soto Lev Lewis Wadood Y. Hamad Mark J. MacLachlan 《Angewandte Chemie (International ed. in English)》2020,59(12):4705-4710
Cellulose nanocrystals (CNCs) spontaneously assemble into gels when mixed with a polyionic organic or inorganic salt. Here, we have used this ion‐induced gelation strategy to create functional CNC gels with a rigid tetracationic macrocycle, cyclobis(paraquat‐p‐phenylene) ( CBPQT 4+). Addition of [ CBPQT ]Cl4 to CNCs causes gelation and embeds an active host inside the material. The fabricated CNC gels can reversibly absorb guest molecules from solution then undergo molecular recognition processes that create colorful host–guest complexes. These materials have been implemented in gel chromatography (for guest exchange and separation), and as elements to encode 2‐ and 3‐dimensional patterns. We anticipate that this concept might be extended to design a set of responsive and selective gel‐like materials functioning as, for instance, water‐pollutant scavengers, substrates for chiral separations, or molecular flasks. 相似文献
12.
The use of high temperatures (above 100 °C) in reversed-phase liquid chromatography (RP-HTLC) has opened up novel and enhanced
applications for this essential separation technique. Although the favourable effects of temperature on LC have been extensively
studied both theoretically and practically, its potential application to method development has barely been investigated.
These favourable effects include enhanced speed, efficiency, resolution and detectability, as well as changes in selectivity,
especially for polar and ionisable compounds, and the emergence of new options such as temperature programming and the concomitant
use of solvent and temperature gradients, green separations, and so on. The recent availability of silica-based columns that
routinely support high temperatures in addition to more conventional temperature-resistant columns (based on graphitised carbon,
polymers and zirconium oxide) and dedicated column ovens that allow accurate temperature control up to 200 °C makes it possible
to conceive of RP-HTLC as a routine separation technique in the modern analytical laboratory. On the other hand, the addition
of temperature as a new optimisable parameter to RPLC adds further complexity to method development. Thus, new computer-assisted
optimisation tools that extend the capabilities of current computer-assisted tools are being specifically developed for this
type of separation. A new specially developed computer-assisted method development (CAMD) tool is presented herein, and its
efficiency is demonstrated. This CAMD is based on the development of a rugged retention model for peaks, allowing the simulation
of any kind of RP-HTLC separation, including isocratic, linear, curved, multilinear and stepwise gradients of solvent composition
concomitant with constant, linear and multilinear temperature gradients. Both the retention models and the unattended optimisation
of separations are driven by evolutionary algorithms, thus providing negligible-cost, rapid, highly efficient, and user-friendly
optimisation processes. 相似文献
13.
There is a great potential for miniaturized analytical separation systems, e.g. in process control, environmental monitoring, or clinical chemistry. Particularly, miniaturized electro-driven systems open many new possibilities. Most efforts in this area have been focused on cylindrical capillary columns. In the present paper, thin rectangular conduits are considered and comparisons with cylindrical tubes are made on the basis of theoretical models. A critical and limiting factor in electro-driven separations is the generation of heat. For a given cross-section, heat dissipation is more efficient in rectangular columns. Silicon is proposed as column material. Apart from the better thermal conductivity, monocrystalline silicon can be machined with an extraordinary precision when selective chemical etching procedures are employed. This precision is of central importance in the development of miniaturized high performance systems. 相似文献
14.
《Separation & Purification Reviews》2013,42(2):233-245
The Arthur D. Little concept of unit operations embodied a number of different methods of separating mixtures and represented a major advance in chemical engineering. Over time, those and subsequent concepts have evolved into a unified field of separation processes. The ways in which this happened are traced. The more unified view of separations enables more coherent and powerful approaches for process selection and design, reducing energy requirements, for selecting separating agents, understanding the complex interactions of mass transfer and phase equilibria, and identifying new methods for separating complex mixtures. As such, separation processes provide one of the most effective vehicles for teaching and understanding the engineering of chemical processes. 相似文献
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After a long period of dormancy, membrane separation processes have begun to emerge as technically significant and commercially relevant unit operations. Prior to the mid-sixties, synthetic membranes were employed for those few specialized laboratory applications which could tolerate low permeability and poor selectivity or in electrochemical applications excluding, e. g., batteries, fuel cells, chloride-alkali electrolysis, where marginal chemical stability remained a severe limitation. Within the framework of a broad R & D program started in the US in the mid-fifties and devoted to the production of fresh water from brackish and seawater, developments of more suitable membranes arose out of the application of the principles of physical chemistry, modern polymer chemistry (especially surface or interfacial polymerization and polycondensation technology), and electron microscopy. In particular, it was learned that asymmetric membrane structures comprise a very thin consolidated barrier layer (5000 Å or less for membranes with economically practical filtration rates) supported by an integral but less dense substrate which does not participate in the transport process. Later and after much effort, composite membranes were developed in which the salt-rejecting skin (still only 5000 Å thick) was placed atop a supporting matrix formed from a more chemically and mechanically stable polymer.—The main desalination research effort led to several spin-off developments in related membrane fields, e.g. the successful preparation and commercialization of ultrafiltration technology in the automobile, food, and chemical industries. Also, ion-exchange membranes prepared from perfluorinated polymers offered the electrochemical industry much better chemical stability than the earlier phenolic-resin-based ion-exchange membranes.—Current efforts are aimed at the improved selectivity and stability required for very specific separation processes (e.g. separation of heavy metal salts from waste water or selective enrichment of gases). In the future, the mechanisms of biological processes will have to be exploited for successful development of synthetic membranes suitable for more sophisticated separations. 相似文献
17.
Recently, molecular imprinted polymers (MIPs) were extensively used for separation and identification of specific molecules, replacing expensive and unstable biological receptors. Nonetheless, their application in electrochemical sensors has not been sufficiently explored. Here we report the use of a MIP as a specific receptor in a new highly sensitive tributyltin (TBT) electrochemical sensor. The sensor combines the specificity, pre-concentration capability and robustness of molecular imprinted polymer attached onto magnetic nanoparticles with the quantitative outputs of impedimetric measurements. The proposed device detects TBT in a concentration range of 5 pM to 5 μM with a low limit of detection (5.37 pM), which is lower than the one recommended for TBT in sea water by the US Environmental Protection Agency (EPA). We believe that this new electrochemical sensor can play an important role in the monitoring of the quality of sea and fresh waters worldwide. 相似文献
18.
《The Journal of chemical thermodynamics》2003,35(1):21-39
As biotechnology sweeps the world, it is appropriate to remember that the great virtue of thermodynamics is its broad range of applicability. As a result, there is a growing literature describing how chemical thermodynamics can be used to inform processes for old and new biochemical products for industry and medicine. A particular application of molecular thermodynamics concerns separation of aqueous proteins by selective precipitation. For this purpose, we need phase diagrams; for constructing such diagrams, we need to understand not only the qualitative nature of phase equilibria of aqueous proteins but also the quantitative intermolecular forces between proteins in solution. Some examples are given to show how aqueous protein–protein forces can be calculated or measured to yield a potential of mean force and how that potential is then used along with a statistical thermodynamic model to establish liquid–liquid and liquid–crystal equilibria. Such equilibria are useful not only for separation processes but also for understanding diseases like Alzheimer’s, cataracts and sickle-cell anemia that appear to be caused by protein agglomeration. 相似文献
19.
Quantum tunneling effects play an important role in a variety of chemical reactions considerably affecting the reaction rates via opening the classically forbidden paths and emerging as highly efficient or selective processes. However, in the case of electrochemical reactions, quantum tunneling effects are less investigated due to complicated nature of chemical interactions at the electrified interfaces. In this review, we summarize the experimental/theoretical concept of electrochemical quantum proton tunneling (EQPT), which is a key element in microscopic electrode processes. First, we review the experimental observations of EQPT, and next, we discuss possible theoretical pictures of the process. This review shows that a combination of a wide spectrum of scientific efforts is required to understand microscopic mechanism of EQPT including development of the precise electrochemistry-oriented experimental techniques and methodologies, formulation of the appropriate theoretical models for specific systems, and performance of the advanced computational simulations. 相似文献
20.
M. Liezers S. A. Lehn K. B. Olsen O. T. FarmerIII Douglas C. Duckworth 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(1):299-304
Electrochemically modulated separations (EMS) are shown to be a rapid and selective means of extracting and concentrating
Pu from complex solutions prior to isotopic analysis by inductively coupled plasma mass spectrometry (ICP‐MS). This separation
is performed in a flow injection mode, on‐line with the ICP‐MS. A three‐electrode, flow‐by electrochemical cell is used to
accumulate Pu at an anodized glassy carbon electrode by redox conversion of Pu(III) to Pu (IV&VI). The entire process takes
place in 2% (v/v) (0.46 M) HNO3. No redox chemicals or acid concentration changes are required. Plutonium accumulation and release is redox dependent and
controlled by the applied cell potential. Large transient volumetric concentration enhancements can be achieved. Based on
more negative U(IV) potentials relative to Pu(IV), separation of Pu from uranium is efficient, thereby eliminating uranium
hydride interferences. EMS‐ICP‐MS isotope ratio measurement performance will be presented for femtogram to attogram level
plutonium isotope injections. 相似文献