비만아 부모의 돌봄 경험: q 방법론

Combining the electronic properties of graphene(1,2) and molybdenum disulphide (MoS2)(3-6) in hybrid heterostructures offers the possibility to create devices with various functionalities. Electronic logic and memory devices have already been constructed from graphene-MoS2 hybrids(7,8), but they do not make use of the photosensitivity of MoS2, which arises from its optical-range bandgap(9). Here, we demonstrate that graphene-on-MoS2 binary heterostructures display remarkable dual optoelectronic functionality, including highly sensitive photodetection and gate-tunable persistent photoconductivity. The responsivity of the hybrids was found to be nearly 1 x 10(10) A W-1 at 130 K and 5 x 10(8) A W-1 at room temperature, making them the most sensitive graphene-based photodetectors. When subjected to time-dependent photoillumination, the hybrids could also function as a rewritable optoelectronic switch or memory, where the persistent state shows almost no relaxation or decay within experimental timescales, indicating near-perfect charge retention. These effects can be quantitatively explained by gate-tunable charge exchange between the graphene and MoS2 layers, and may lead to new graphene-based optoelectronic devices that are naturally scalable for large-area applications at room temperature.

Graphene-MoS2 hybrid structures for multifunctional photoresponsive memory devices

2.3. Ionic Liquids (ILs) 5374 2.4. Complexation Reactions on Oxidized CNTs 5375 2.5. Halogenation 5376 2.6. Cycloaddition Reactions 5377 2.7. Radical Additions 5379 2.8. Nucleophilic Additions 5381 2.9. Electrophilic Additions 5381 2.10. Electrochemical Modifications 5381 2.11. Plasma-Activation 5381 2.12. Mechanochemical Functionalizations 5382 3. Noncovalent Interactions 5382 3.1. Polynuclear Aromatic Compounds 5382 3.2. Interactions with Other Substances 5384 3.3. Interactions with Biomolecules 5385 4. Endohedral Filling 5386 4.1. Encapsulation of Fullerenes 5386 4.2. Encapsulation of Organic Substances 5387 4.3. Encapsulation of Inorganic Substances 5387 5. Decoration of CNTs with Metal Nanoparticles 5388 5.1. Covalent Linkage 5388 5.2. Direct Formation on Defect Sites 5388 5.3. Electroless Deposition 5388 5.4. Electrodeposition 5389 5.5. Chemical Decoration 5390 5.6. Deposition of Nanoparticles onto CNTs 5391 5.7. π-π Stacking and Electrostatic Interactions 5391 6. Concluding Remarks 5392 7. Acknowledgments 5392 8. References 5392

Current progress on the chemical modification of carbon nanotubes.

Single-walled carbon nanotubes (SWNTs) are a family of molecules that have the same cylindrical shape but different chiralities. Many fundamental studies and technological applications of SWNTs require a population of tubes with identical chirality that current syntheses cannot provide. The SWNT sorting problem-that is, separation of a synthetic mixture of tubes into individual single-chirality components-has attracted considerable attention in recent years. Intense efforts so far have focused largely on, and resulted in solutions for, a weaker version of the sorting problem: metal/semiconductor separation. A systematic and general method to purify each and every single-chirality species of the same electronic type from the synthetic mixture of SWNTs is highly desirable, but the task has proven to be insurmountable to date. Here we report such a method, which allows purification of all 12 major single-chirality semiconducting species from a synthetic mixture, with sufficient yield for both fundamental studies and application development. We have designed an effective search of a DNA library of approximately 10(60) in size, and have identified more than 20 short DNA sequences, each of which recognizes and enables chromatographic purification of a particular nanotube species from the synthetic mixture. Recognition sequences exhibit a periodic purine-pyrimidines pattern, which can undergo hydrogen-bonding to form a two-dimensional sheet, and fold selectively on nanotubes into a well-ordered three-dimensional barrel. We propose that the ordered two-dimensional sheet and three-dimensional barrel provide the structural basis for the observed DNA recognition of SWNTs.

DNA sequence motifs for structure-specific recognition and separation of carbon nanotubes

Single-walled carbon nanotubes tend to be produced in polydisperse mixtures with different lengths, diameters and electronic properties. This review article surveys the various techniques that have been developed for producing monodisperse samples from these mixtures. Selective growth techniques are also covered.

Progress towards monodisperse single-walled carbon nanotubes

High purity of (7,5) SWNTs (∼79% of the semisonducting SWNT ensemble) can be obtained by polymer-assisted extraction from the narrow-diameter distributed SWNTs produced by the catalyst Co-MCM-41. The fluorene-based polymers are able to selectively wrap the single-walled carbon nanotubes (SWNTs) with certain chiral angles or diameters depending on their chemical structures. Poly(9,9-dioctyfluoreny1−2, 7-diyl) and poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(9,10-anthracene)] selectively wrap SWNTs with high chiral angles (>24.5°). By contrast, poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1‘-3}-thiadiazole)] preferentially wraps the SWNTs with certain diameter (1.02−1.06 nm).

Toward the extraction of single species of single-walled carbon nanotubes using fluorene-based polymers.

Seawater desalination is a leading method for tackling the challenge of global freshwater shortage. However, existing desalination technologies like capacitive deionization (CDI) have their own limits, including high energy consumption or low ion removal capacity, which is not sufficient for desalting high-concentration saline water with low cost. Herein, we present a concept of flow dual-ions electrochemical deionization technology, which consists of BiOCl for chloride ion Faradaic electrode on the negative side, sodium manganese oxide (Na0.44MnO2) as sodium ion Faradaic electrode on the positive side, and a flow salt feed as electrolyte. It utilizes a redox reaction to individually capture chloride ions and sodium ions concurrently. Under positive electric current operations, the two ions are released for NaCl water electrolyte to flow. On switching to negative electric current, the chloride ions are extracted into the negative electrode, and thus prevented from flowing into the NaCl solution while sodium ions are electrochemically captured into the positive electrode. The novel dual-ions in Faradaic deionization deliver a stable and reversible salt removal/release capacity of 68.5 mg g−1 when operated at a current density 100 mA g−1, which indicates an amount over twice the salt absorption amount of the previously reported best performance (31.2 mg g−1) obtained by a hybrid capacitive deionization system. The electric charge efficiency is up to 0.977 during salt desorption process and 0.958 during absorption process. Owing to the salt removal, energy will be released during discharge process; therefore, the current system is called “desalination generator”. Our research will supply a new method for desalination flow-through system.

Dual-ions electrochemical deionization: a desalination generator

Desalination is a sustainable process that removes sodium and chloride ions from seawater. Herein, we demonstrate a faradaic mechanism to promote the capacity of capacitive deionization in highly concentrated salt water via an electrochemical deionization device. In this system, ion removal is achieved by the faradaic mechanism via a constant current operation mode, which is improved based on the constant voltage operation mode used in the conventional CDI operation. Benefiting from the high capacity and excellent rate performance of Prussian blue as an active electrochemical reaction material, the designed unit has revealed a superior removal capacity with an ultrafast ion removal rate. A high removal capacity of 101.7 mg g−1 has been obtained with proper flow rate and current density. To further improve the performance of the EDI, a reduced graphene oxide with nanopores and Prussian blue composite has been synthesized. The PB@NPG has demonstrated a high salt removal capacity of 120.0 mg g−1 at 1 C with an energy consumption of 6.76 kT per ion removed, which is much lower than most CDI methods. A particularly high rate performance of 0.5430 mg g−1 s−1 has been achieved at 40 C. The faradaic mechanism promoted EDI has provided a new insight into the design and selection of host materials for highly concentrated salt water desalination.

A Prussian blue anode for high performance electrochemical deionization promoted by the faradaic mechanism

Novel desalination technologies with high ion removal capacity and low energy consumption are desirable to tackle the water shortage challenge. Herein, we report a dual-ion electrochemistry deionization (DEDI) system with silver chloride as the electrochemical chloride release/capture anode, sodium manganese oxide as the electrochemical sodium release/capture cathode, and flow salt solution as the electrolyte. Sodium and chloride ions are synergistically released to the flow electrolyte feed at an applied positive current. Under negative current conditions, the two ions are extracted from the flow electrolyte feed to their corresponding electrodes at the same time, which can cause a conductivity decrease indicating salt removal. The salt absorption/desorption capacity of the novel deionization system is stable and reversible, up to 57.4 mg g−1 for 100 cycles, which is much higher than that obtained by conventional or hybrid capacitive deionization devices. The charge efficiency is 0.979/0.956 during the salt desorption/absorption process. This research will be of great significance for high efficiency and low energy consumption seawater desalination.

A dual-ion electrochemistry deionization system based on AgCl-Na0.44MnO2 electrodes

Milled flake graphite/plasma nano-silicon@carbon composite with void sandwich structure for high performance as lithium ion battery anode at high temperature

Fuming Chen

Papers

Toward the extraction of single species of single-walled carbon nanotubes using fluorene-based polymers.

Dual-ions electrochemical deionization: a desalination generator

A Prussian blue anode for high performance electrochemical deionization promoted by the faradaic mechanism

A dual-ion electrochemistry deionization system based on AgCl-Na0.44MnO2 electrodes

Milled flake graphite/plasma nano-silicon@carbon composite with void sandwich structure for high performance as lithium ion battery anode at high temperature