We report here the chemical modification of poly(methyl methacrylate) (PMMA) surfaces by their reaction with the monoanion of α,ω-diaminoalkanes (aminolysis reaction) to yield amine-terminated PMMA ...surfaces. It is found that the amine functionalities are tethered to the PMMA backbone through an alkane bridge to amide bonds formed during the aminolysis of the surface ester functionalities. The distribution of the amine termini is quite uniform as judged by fluorescence micrographs. It is found that the electroosmotic flow in aminated PMMA microchannels is reversed when compared to that in unmodified channels. In addition, it is demonstrated that enzymes can be immobilized onto the amine-terminated PMMA surfaces and are effective in the restriction digestion of dsDNAs. Finally, the availability of the surface amine groups is further demonstrated by their reaction with n-octadecane-1-isocyanate to form PMMA surfaces terminated with well-ordered and highly crystalline octadecane chains.
► Overview of materials-based H
2 storage for near-term markets. ► Discussion of operational issues of three main near-term markets in relation to materials-based H
2 storage. ► Highlights ...significant current developments in materials-based H
2 storage.
Although hydrogen is widely recognized as a promising energy carrier for the transportation sector, widespread adoption of hydrogen and fuel cell technologies depends critically on the ability to store hydrogen at adequate densities, as well as release hydrogen at sufficient rates (among other requirements) to meet PEM fuel cell power plant requirements. At present, no known material or storage means exists that satisfies all requirements to enable high-volume automotive application, however materials do exist that would satisfy requirements for near-term non-vehicular PEM fuel cell applications. The US DOE recognizes that non-vehicular early market applications are the most likely paths for the successful demonstration and application of material-based hydrogen storage technology. In this review, we provide a practical overview of the most probable near-term PEM fuel cell markets as identified through market reviews with an emphasis on the attributes of the relevant materials-based hydrogen storage for those near-term markets.
This work combines materials development with hydrogen storage technology advancements to address onboard hydrogen storage challenges in light-duty vehicle applications. These systems are comprised ...of the vehicle requirements design space, balance of plant requirements, storage system components, and materials engineering culminating in the development of an Adsorbent System Design Tool that serves as a preprocessor to the storage system and vehicle-level models created within the Hydrogen Storage Engineering Center of Excellence. Computational and experimental efforts were integrated to evaluate, design, analyze, and scale potential hydrogen storage systems and their supporting components against the Department of Energy 2020 and Ultimate Technical Targets for Hydrogen Storage Systems for Light Duty Vehicles. Ultimately, the Adsorbent System Design Tool was created to assist material developers in assessing initial design parameters that would be required to estimate the performance of the hydrogen storage system once integrated with the full fuel cell system.
Display omitted
•Model analysis of adsorption-based hydrogen system for fuel cell applications.•Evaluation of various engineering design options for tank and balance-of-plant.•Thermodynamic equations to predict charging/discharging of activated carbon and MOF-5.•Prototype validation and model sensitivity analysis for data comparison.•Full-vehicle level analysis compared to DOE standards to determine applicability.
Hydrogen has many positive attributes that make it a viable choice to augment the current portfolio of combustion-based fuels, especially when considering reducing pollution and greenhouse gas (GHG) ...emissions. However, conventional methods of storing H2 via high-pressure or liquid H2 do not provide long-term economic solutions for many applications, especially emerging applications such as man-portable or stationary power. Hydrogen storage in materials has the potential to meet the performance and cost demands, however, further developments are needed to address the thermodynamics and kinetics of H2 uptake and release. Therefore, the US Department of Energy (DOE) initiated three Centers of Excellence focused on developing H2 storage materials that could meet the stringent performance requirements for on-board vehicular applications. In this review, we have summarized the developments that occurred as a result of the efforts of the Metal Hydride and Chemical Hydrogen Storage Centers of Excellence on materials that bind hydrogen through ionic and covalent linkages and thus could provide moderate temperature, dense phase H2 storage options for a wide range of emerging Proton Exchange Membrane Fuel Cell (PEM FC) applications.
The free standing aluminum nanorods were grown on electrode and evaluated electrochemically as the anodes in the half-cell of Li-ion battery. The average diameter and length of the nanorods are 80
nm ...and 200
nm, respectively. The aligned nanorods demonstrated high capacity of 1243
mAh
g
−1 at rate of 0.5
C. A gradual decrease of the initial capacity was observed. The characterization of the anodes shows that the changes of the crystalline structure and morphology during cycling may be responsible for the capacity decay. The appropriate selection of the substrate can overcome the problems and lead the sustainable high capacity.
We are currently developing miniaturized, chip-based electrophoresis devices fabricated in plastics for the high-speed separation of oligonucleotides. One of the principal advantages associated with ...these devices is their small sample requirements, typically in the nanoliter to sub-nanoliter range. Unfortunately, most standard sample preparation protocols, especially for oligonucleotides, are done off-chip on a microliter-scale. Our work has focused on the development of capillary nanoreactors coupled to micro-separation platforms, such as micro-electrophoresis chips, for the preparation of sequencing ladders and also polymerase chain reactions (PCRs). These nanoreactors consist of fused-silica capillary tubes (10–20 cm×20–50 μm I.D.) with fluid pumping accomplished using the electroosmotic flow generated by the tubes. These reactors were situated in fast thermal cyclers to perform cycle sequencing or PCR amplification of the DNAs. The reactors could be interfaced to either a micro-electrophoresis chips via capillary connectors micromachined in polymethylmethacrylate (PMMA) using deep X-ray etching (width 50 μm; depth 50 μm) or conventional capillary gel tubes using zero-dead volume glass unions. For our chips, they also contained an injector, separation channel (length 6 cm; width 30 μm; depth 50 μm) and a dual fiber optic, near-infrared fluorescence detector. The sequencing nanoreactor used surface immobilized templates attached to the wall via a biotin–streptavidin–biotin linkage. Sequencing tracks could be directly injected into gel-filled capillary tubes with minimal degradation in the efficiency of the separation process. The nanoreactor could also be configured to perform PCR reactions by filling the capillary tube with the PCR reagents and template. After thermal cycling, the PCR cocktail could be pooled from multiple reactors and loaded onto a slab gel or injected into a capillary tube or microchip device for fractionation.
•Portable power and material handling equipment as early market technology pathways.•Engineering based system-level storage-materials requirements.•Application based targets.
The Hydrogen and Fuel ...Cells Technologies Office, carried out through the DOE Office of Energy Efficiency and Renewable Energy, maintains a broad portfolio of activities to enable the commercialization of fuel cells across a range of near, mid and long-term applications. Improved, advanced hydrogen storage technologies are seen as a critical need for successful implementation of hydrogen fuel cells in many of these applications. To guide and focus materials development efforts, the DOE develops system performance targets for the specific applications of interest, and carries out system engineering analyses to determine the system-level performance delivered when the materials are incorporated into a complete system. To meet the needs of applications, it is important to consider the system-level performance, not just the material-level properties. An overview of the DOE’s hydrogen storage efforts in developing application-specific performance targets and systems engineering to guide hydrogen storage materials identification and development is herein provided.
In this paper, we describe the application of micro-reversed-phase high-performance liquid chromatography (μ-RP-HPLC) for the separation and/or purification of polymerase chain reaction (PCR) ...products with detection accomplished using a miniaturized conductivity detector. The conductivity detector used two Pt wires and a bipolar waveform applied to the electrode pair from which the conductivity of the bulk solution could be measured. In the mobile phase used for the μ-RP-HPLC separation of the PCR product, the mass detection limit for herring sperm DNA using conductivity was found to be 11 ng. Efficient separation of the PCR amplicon from the other reagents present in the PCR cocktail was achieved in less than 4 min with a capacity factor of 2.5 and separation efficiency of 9.1·10
3 plates. The separation was carried out using reversed-phase ion-pair chromatography with a triethylammonium acetate ion-pairing agent.
As capillary electrophoresis continues to focus on miniaturization, either through reducing column dimensions or situating entire electrophoresis systems on planar chips, advances in detection become ...necessary to meet the challenges posed by these electrophoresis platforms. The challenges result from the fact that miniaturization requires smaller load volumes, demanding highly sensitive detection. In addition, many times multiple targets must be analyzed simultaneously (multiplexed applications), further complicating detection. Near‐infrared (NIR) fluorescence offers an attractive alternative to visible fluorescence for critical applications in capillary electrophoresis due to the impressive limits of detection that can be generated, in part resulting from the low background levels that are observed in the NIR. Advances in instrumentation and fluorogenic labels appropriate for NIR monitoring have led to a growing number of examples of the use of NIR fluorescence in capillary electrophoresis. In this review, we will cover instrumental components used to construct ultrasensitive NIR fluorescence detectors, including light sources and photon transducers. In addition, we will discuss various types of labeling dyes appropriate for NIR fluorescence and finally, we will present several applications that have used NIR fluorescence in capillary electrophoresis, especially for DNA sequencing and fragment analysis.
PDF
