Wongkaew, Nongnoot; Simsek, Marcel; Griesche, Christian; Baeumner, Antje J.(Chemical Reviews, American Chemical Society (ACS), 2018-09-24)[Article]
Electrochemical biosensors and associated lab-on-a-chip devices are the analytical system of choice when rapid and on-site results are needed in medical diagnostics and food safety, for environmental protection, process control, wastewater treatment, and life sciences discovery research among many others. A premier example is the glucose sensor used by diabetic patients. Current research focuses on developing sensors for specific analytes in these application fields and addresses challenges that need to be solved before viable commercial products can be designed. These challenges typically include the lowering of the limit of detection, the integration of sample preparation into the device and hence analysis directly within a sample matrix, finding strategies for long-term in vivo use, etc. Today, functional nanomaterials are synthesized, investigated, and applied in electrochemical biosensors and lab-on-a-chip devices to assist in this endeavor. This review answers many questions around the nanomaterials used, their inherent properties and the chemistries they offer that are of interest to the analytical systems, and their roles in analytical applications in the past 5 years (2013–2018), and it gives a quantitative assessment of their positive effects on the analyses. Furthermore, to facilitate an insightful understanding on how functional nanomaterials can be beneficial and effectively implemented into electrochemical biosensor-based lab-on-a-chip devices, seminal studies discussing important fundamental knowledge regarding device fabrication and nanomaterials are comprehensively included here. The review ultimately gives answers to the ultimate question: “Are they really needed or can bulk materials accomplish the same?” Finally, challenges and future directions are also discussed.
A neural electrode interface material is a key component for effective stimulation and recording of neural activity. The fundamental requirement of a neural electrode is for it to be able to deliver adequate charge to targeted neuronal population. Coating electrode surfaces with nanostructured material not only provides an increase in surface area, providing relatively more active sites for charge delivery than planar systems, but also allows for the reduction of electrode dimension to reduce invasiveness and increase selectivity. In this work, titanium nitride nanowires (TiN-NWs) synthesised by novel nitridation process in Plasma Enhanced Chemical Vapour Deposition (PECVD) is suggested as an enhanced coating material for neural electrodes. The synthesis involved the solution growth of crystalline titanium oxide nanorods (TiO2-NRs) from a sputtered TiN nucleation layer followed by nitridation. TiO2-NRs exhibited high aspect ratio of 23.1 and were converted into TiN after one hour of nitridation at 600°C. Evidence of conversion was studied by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). The nitridation temperature and time reported here are the lowest and shortest as compared to the literature. The near-stoichiometric TiN-NWs (x=0.49) achieved in this work were used subsequently for electrochemical characterisation through Cyclic Voltammetry (CV). The capacitance of relatively high aspect TiN-NWs was 3.78 mF/cm2, which was a 5-fold enhancement compared to thin film of TiN layer (0.7 mF/cm2). A stability test of the nanowires were performed in which the capacitance remained relatively unchanged.
Hybrid organic–inorganic perovskites exhibit strong spin–orbit coupling1, spin-dependent optical selection rules2,3 and large Rashba splitting4,5,6,7,8. These characteristics make them promising candidates for spintronic devices9 with photonic interfaces. Here we report that spin polarization in perovskites can be controlled through chemical design as well as by a magnetic field. We obtain both spin-polarized photon absorption and spin-polarized photoluminescence in reduced-dimensional chiral perovskites through combined strategies of chirality transfer and energy funnelling. A 3% spin-polarized photoluminescence is observed even in the absence of an applied external magnetic field owing to the different emission rates of σ+ and σ− polarized photoluminescence. Three-dimensional perovskites achieve a comparable degree of photoluminescence polarization only under an external magnetic field of 5 T. Our findings pave the way for chiral perovskites as powerful spintronic materials.
Exploiting novel devices for either collecting energy or self-powered sensors is vital for Internet of Things, sensor networks, and big data. Triboelectric nanogenerators (TENGs) have been proved as an effective solution for both energy harvesting and self-powered sensing. The traditional triboelectric nanogenerators are usually based on four modes: contact-separation mode, lateral sliding mode, single-electrode mode, and freestanding triboelectric-layer mode. Since the reciprocating displacement/force is necessary for all working modes, developing efficient elastic TENG is going to be important and urgent. Here, a kind of elastic-beam TENG with arc-stainless steel foil is developed, whose structure is quite simple, and its working states depend on the contact area and separating distance as proved by experiments and theoretical calculations. This structure is different from traditional structures, e.g., direct sliding or contact-separation structures, whose working states mainly depend on contact area or separating distance. This triboelectric nanogenerator shows advanced mechanical and electrical performance, such as high sensitivity, elasticity, and ultrahigh frequency response, which encourage applications as a force sensor, sensitivity scale, acceleration sensor, vibration sensor, and intelligent keyboard.
Since pioneering work done in the late 1990s, synthesis of functional hollow materials has experienced a rapid growth over the past two decades while their applications have been proven to be advantageous across many technological fields. In the field of heterogeneous catalysis, the development of micro- and nanoscale hollow materials as catalytic devices has also yielded promising results, because of their higher activity, stability, and selectivity. Herein, the architecture and preparation of these catalysts with tailorable composition and morphology are reviewed. First, synthesis of hollow materials is introduced according to the classification of template mediated, template free, and combined approaches. Second, different architectural designs of hollow catalytic devices, such as those without functionalization, with active components supported onto hollow materials, with active components incorporated within porous shells, and with active components confined within interior cavities, are evaluated respectively. The observed catalytic performances of this new class of catalysts are correlated to structural merits of individual configuration. Examples that demonstrate synthetic approaches and architected configurations are provided. Lastly, possible future directions are proposed to advance this type of hollow catalytic devices on the basis of our personal perspectives.
Natural gas production from shale formations has changed the energy landscape. Knowledge of adsorption in the subsurface shale formations improves resource assessment. The excess adsorption is directly measurable from experiments. Evaluation of fluid content in shale is based on the absolute adsorption. At high pressure relevant to subsurface conditions, the computation of absolute adsorption from excess adsorption has shortcomings when the conventional models are used. In this work, we first present the excess sorption data of light hydrocarbons and carbon dioxide in subsurface shale rock and in isolated kerogen. Gravimetric method was used in our measurements. The results show that, at high pressure, the excess adsorption of ethane and carbon dioxide decreases significantly as pressure increases. Excess adsorption of ethane at 60 °C for the shale sample investigated becomes negative at high pressure. The conventional models may provide a non-monotonic absolute adsorption and even magnify the unphysical negative adsorption. In addition to the proposed model based on adsorbed layer volume, we also account for effective sample volume due to the pore volume accessibility by different molecules, as well as the swelling of kerogen. The adsorption data from subsurface shale and the method for analysis presented in this work set the stage for prediction capability in hydrocarbon production from shale reservoirs.
Dussan, Karla; Won, Sang Hee; Ure, Andrew D.; Dryer, Frederick L.; Dooley, Stephen(Proceedings of the Combustion Institute, Elsevier BV, 2018-08-30)[Article]
The chemical functional group approach is investigated to verify the fundamental applicability of low-dimensional descriptors in the prediction of global combustion behavior, as described by homogeneous reflected shock ignition delay times. Three key chemical functional groups, CH2, CH3 and benzyl-type, are used to represent n-alkyl, iso-alkyl, and aromatic functionalities, respectively. To examine whether such descriptors can appropriately reflect the influences of these functionalities on ignition delay, Quantitative Structure-Property Relationship (QSPR) regression analysis is performed with the formulation of analytical models based on a fundamental Arrhenius-type description. The models are trained using literature measurements of reflected shock ignition delay times for stoichiometric fuel/air mixtures at 20 atm. Sensitivity analyses applied to the QSPR regression models show that the CH2 functional group dominates chemical kinetic behaviors at low temperature, while the chemical kinetic impacts of CH2, CH3, and benzyl-type functional groups all diminish as temperature increases. Further analyses of constant-volume adiabatic ignition delay predictions using detailed chemical kinetic models demonstrate influences of n-alkyl, iso-alkyl, and aromatic functionalities at both low and high temperature, consistent with those found for the QSPR regression models. Finally, 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy is used to directly quantify the chemical functional group compositions of both petroleum-derived and alternative jet fuels. Combining the QSPR model with NMR spectra interpretation, the applicability of current approach as an expeditious tool to accurately characterize the ignition propensity of real transportation fuels is demonstrated by comparison with experimental measurements.
Objective: Neural electrophysiology is often conducted with traditional, rigid depth probes. The mechanical mismatch between these probes and soft brain tissue is unfavorable for tissue interfacing. Making probes compliant can improve biocompatibility, but as a consequence, they become more difficult to insert into the brain. Therefore, new methods for inserting compliant neural probes must be developed.
\n Approach: Here, we present a new bioresorbable shuttle based on the hydrolytically degradable poly(vinyl alcohol) (PVA) and poly(lactic-co-glycolic acid) (PLGA). We show how to fabricate the PVA/PLGA shuttles on flexible and thin parylene probes. The method consists of PDMS molding used to fabricate a PVA shuttle aligned with the probe and to also impart a sharp tip necessary for piercing brain tissue. The PVA shuttle is then dip-coated with PLGA to create a bi-layered shuttle.
\n Main results: While single layered PVA shuttles are able to penetrate agarose brain models, only limited depths were achieved and repositioning was not possible due to the fast degradation. We demonstrate that a bilayered approach incorporating a slower dissolving PLGA layer prolongs degradation and enables facile insertion for at least several millimeters depth. Impedances of electrodes before and after shuttle preparation were characterized and showed that careful deposition of PLGA is required to maintain low impedance. Facilitated by the shuttles, compliant parylene probes were also successfully implanted into anaesthetized mice and enabled the recording of high quality local field potentials.
\n Significance: This work thereby presents a solution towards addressing a key challenge of implanting compliant neural probes using a two polymer system. PVA and PLGA are polymers with properties ideal for translation: commercially available, biocompatible with FDA-approved uses and bioresorbable. By presenting new ways to implant compliant neural probes, we can begin to fully evaluate their chronic biocompatibility and performance compared to traditional, rigid electronics.
Schroeder, Vera; Swager, Timothy M.(Journal of the American Chemical Society, American Chemical Society (ACS), 2018-08-14)[Article]
Activating molecules or functional groups with high chemoselectivity in complex environments is the central goal of transition-metal-based catalysis. Promoting strong interactions between a selected substrate and a catalytic system can also be used to create highly selective and customizable sensors, and these concepts are widely recognized for enzymatic processes. We demonstrate the successful translation of organometallic reactions to sensing capability. Specifically, we have developed single-walled carbon nanotube (SWCNT) chemiresistive sensors for the highly selective detection of acrylates using conditions for the aerobic oxidative Heck reaction. The sensors mirror the catalytic processes and selectively respond to electron-deficient alkenes by adapting a catalytic reaction system to modulate the doping levels in carbon nanotubes. The sensors readily detect acrylates at parts per million (ppm) levels in untreated air. The concepts presented here are generally applicable and can guide future sensor development based upon known catalytic processes.
Aryal, Dipak; Ganesan, Venkat(The Journal of Physical Chemistry B, American Chemical Society (ACS), 2018-08-14)[Article]
The dynamics of ions and solvent molecules in polyelectrolyte desalination membranes is key to water purification technologies in which selective transport of the different components is desired. Recent experimental and our computational results have shown that nontrivial mechanisms underlie the transport properties of salt ions and water in charged polymer membranes. Explicitly, in polymer electrolytes, we found a reversal in the salt concentration dependence of the mobilities of Na+, Cl– salt ions and water molecules when compared with aqueous solutions. Motivated by such results, in this study, we have used atomistic molecular dynamics simulations to probe whether the mechanisms deduced in our earlier work apply to other salt systems and to mixtures of salts. Specifically, we report results for the ion diffusivities in aqueous KCl, MgCl2, and a 1:1 mixture of NaCl and MgCl2 salt solutions at different concentrations (ranging from 0.06 to 1 M) and investigate, at the molecular level, the mechanisms underlying the behaviors of salt and water transport properties. Our results show that diffusion of salt ions and water in charged polymer membranes are in general influenced by their association with polymer charge groups and ion pairing effects. Divalent ions are more strongly coupled with the polymeric ionic groups than monovalent salt ions and exhibit diffusivity trends that are distinct relative to monovalent salts. Further, we demonstrate that the mobilities of water molecules are influenced by coordination of water with polymer charge groups and their ion pairing tendencies and also exhibit distinct trends in monovalent and divalent salt solutions.
The export option will allow you to export the current search results of the entered query to a file. Different
formats are available for download. To export the items, click on the button corresponding with the preferred download format.
By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.
For anonymous users the allowed maximum amount is 50 search results.
To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export.
The amount of items that can be exported at once is similarly restricted as the full export.
After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.