ORCID Profile
0000-0003-2715-0618
Current Organisation
University of Technology Sydney
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Publisher: American Chemical Society (ACS)
Date: 18-02-2016
Publisher: American Chemical Society (ACS)
Date: 09-12-2021
Publisher: American Chemical Society (ACS)
Date: 14-09-2021
Publisher: arXiv
Date: 2012
Publisher: Elsevier BV
Date: 02-2023
Publisher: American Chemical Society (ACS)
Date: 15-08-2018
Publisher: Proceedings of the National Academy of Sciences
Date: 23-10-2017
Abstract: Magnetic field interactions with condensed matter can produce orientationally ordered states that are important for fundamental research and technological applications. Block copolymer (BCP) mesophases typically exhibit weak field coupling, requiring high-intensity fields generated by superconducting magnets to produce such states. This work advances a strategy for circumventing such field intensity limitations and creates highly aligned mesophases using fields an order of magnitude smaller than typically required and that can be produced by simple permanent magnets. We elucidate the roles of molecular mobility, grain size, and ordering kinetics on the mesophase field response. Low-intensity field-directed BCP ordering has potentially profound implications for processing functional materials and developing complex textures by field shaping.
Publisher: Springer Science and Business Media LLC
Date: 09-08-2021
DOI: 10.1186/S40580-021-00271-W
Abstract: Laser three-dimensional (3D) manufacturing technologies have gained substantial attention to fabricate 3D structured electrochemical rechargeable batteries. Laser 3D manufacturing techniques offer excellent 3D microstructure controllability, good design flexibility, process simplicity, and high energy and cost efficiencies, which are beneficial for rechargeable battery cell manufacturing. In this review, notable progress in development of the rechargeable battery cells via laser 3D manufacturing techniques is introduced and discussed. The basic concepts and remarkable achievements of four representative laser 3D manufacturing techniques such as selective laser sintering (or melting) techniques, direct laser writing for graphene-based electrodes, laser-induced forward transfer technique and laser ablation subtractive manufacturing are highlighted. Finally, major challenges and prospects of the laser 3D manufacturing technologies for battery cell manufacturing will be provided.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7ME00070G
Abstract: Phase behavior and dynamics of a LC block copolymer are manipulated by labile mesogens to enable alignment, photopatterning and nanopore orientation at low magnetic fields.
Publisher: American Chemical Society (ACS)
Date: 16-11-2015
Publisher: MDPI AG
Date: 27-10-2021
DOI: 10.3390/NANO11112867
Abstract: Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration.
Publisher: Elsevier BV
Date: 2023
DOI: 10.2139/SSRN.4343141
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SM00092H
Abstract: Microcapsules with high mechanical stability and elasticity are desirable in a variety of contexts. We report a single-step method to fabricate such microcapsules by microfluidic interfacial complexation between high stiffness cellulose nanofibrils (CNF) and an oil-soluble cationic random copolymer. Single-capsule compression measurements reveal an elastic modulus of 53 MPa for the CNF-based capsule shell with complete recovery of deformation from strains as large as 19%. We demonstrate the ability to manipulate the shell modulus by the use of polyacrylic acid (PAA) as a binder material, and observe a direct relationship between the shell modulus and the PAA concentration, with moduli as large as 0.5 GPa attained. These results demonstrate that CNF incorporation provides a facile route for producing strong yet flexible microcapsule shells.
Publisher: Wiley
Date: 27-09-2015
DOI: 10.1002/POLB.23913
Publisher: Wiley
Date: 15-05-2018
Publisher: American Chemical Society (ACS)
Date: 28-06-2016
Publisher: The Electrochemical Society
Date: 02-2022
Abstract: We investigate a polyacetal-based electrolyte, poly(1,3,6-trioxocane) (P(2EO-MO)) mixed with lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) salt, and report full electrochemical characterization of the transport parameters and a thermodynamic property in comparison to the previously reported poly(ethylene oxide) (PEO) electrolyte data [D. Gribble et al., J. Electrochem. Soc. , 166, A3228 (2019)]. While the steady-state current fraction ( ρ + ) of P(2EO-MO) electrolyte is greater than that of PEO electrolyte in the entire salt concentration window we explored, the rigorously defined transference number using Newman’s concentrated solution theory ( t + 0 ) appears to be similar to that of PEO electrolyte. On the basis of full electrochemical characterization, we calculate the salt concentration profile as a function of position in the cell and predict limiting current density ( i L L ) as a function of salt concentration. Experimental data were compared to the predicted values. The non-monotonic behaviors were observed both in prediction and experimental results with offset peak positions. We find that the limiting current density of P(2EO-MO) electrolyte is systematically lower than that of PEO electrolyte in most of the salt concentrations with the exception of r av = 0.05. It is noteworthy that even though one measure of electrolyte efficacy ( κρ + ) is superior in P(2EO-MO) electrolyte, the limiting current density, which is another metric of electrolyte efficacy at high currents, is not greater in P(2EO-MO).
Publisher: American Chemical Society (ACS)
Date: 30-07-2015
Abstract: In this study, we exploit the nitrogen-sulfur elemental contrast of thin-film composite (TFC) polyamide membranes and present, for the first time, the application of two elemental analysis techniques, scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDX) and X-ray photoelectron spectroscopy (XPS) C60+ ion-beam sputtering, to elucidate the nanoscale structure and chemical composition of the polyamide-polysulfone interface. Although STEM-EDX elemental mapping depicts the presence of a dense polyamide layer at the interface, it is incapable of resolving the elemental contrast at nanoscale resolution at the interfacial zone. Depth-resolved XPS C60+ ion-beam sputtering enabled nanoscale characterization of the polyamide-polysulfone interface and revealed the presence of a heterogeneous layer that contains both polyamide and polysulfone signatures. Our results have important implications for future studies to elucidate the structure-property-performance relationship of TFC membranes.
Publisher: American Chemical Society (ACS)
Date: 05-2014
DOI: 10.1021/MZ500161K
Abstract: We report on the development of a liquid crystalline block copolymer with brush-type architecture as a platform for creating functional materials by magnetic-field-directed self-assembly. Ring-opening metathesis of
Publisher: American Physical Society (APS)
Date: 13-02-2013
Publisher: Elsevier
Date: 2023
Publisher: Wiley
Date: 08-05-2015
Abstract: The fabrication of block copolymer (BCP) thin films is reported with vertically aligned cylindrical domains using continuous electrospray deposition onto bare wafer surfaces. The out-of-plane orientation of hexagonally packed styrene cylinders is achieved in the "fast-wet" deposition regime in which rapid evaporation of the solvent in deposited droplets of polymer solution drives the vertical alignment of the self-assembled structure. Thermally activated crosslinking of the polybutadiene matrix provides kinetic control of the morphology, freezing the vertical alignment and preventing relaxation of the system to its preferred parallel orientation on the nontreated substrate. Physically continuous vertically oriented domains can be achieved over several micrometers of film thickness. The ability of electrospray deposition to fabricate well-ordered and aligned BCP films on nontreated substrates, the low amount of material used relative to spin-coating, and the continuous nature of the deposition may open up new opportunities for BCP thin films.
Publisher: American Chemical Society (ACS)
Date: 24-09-2014
DOI: 10.1021/MA501597G
Publisher: Elsevier BV
Date: 06-2023
Publisher: American Chemical Society (ACS)
Date: 29-06-2021
Publisher: American Chemical Society (ACS)
Date: 26-04-2021
Publisher: Wiley
Date: 04-06-2014
Abstract: A scalable approach for developing large area polymer films, with stimuli responsive vertically aligned nanopores is reported. Magnetic fields are used to create highly aligned hexagonally packed block copolymer cylindrical microdomains with order parameters exceeding 0.95. Selective etch removal of material yields nanoporous films which demonstrate reversible pore closure on heating.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Chemical Society (ACS)
Date: 15-11-2017
DOI: 10.1021/ACS.LANGMUIR.7B03226
Abstract: Protein adsorption and assembly at interfaces provide a potentially versatile route to create useful constructs for fluid compartmentalization. In this context, we consider the interfacial assembly of a bacterial biofilm protein, BslA, at air-water and oil-water interfaces. Densely packed, high modulus monolayers form at air-water interfaces, leading to the formation of flattened sessile water drops. BslA forms elastic sheets at oil-water interfaces, leading to the production of stable monodisperse oil-in-water microcapsules. By contrast, water-in-oil microcapsules are unstable but display arrested rather than full coalescence on contact. The disparity in stability likely originates from a low areal density of BslA hydrophobic caps on the exterior surface of water-in-oil microcapsules, relative to the inverse case. In direct analogy with small molecule surfactants, the lack of stability of in idual water-in-oil microcapsules is consistent with the large value of the hydrophilic-lipophilic balance (HLB number) calculated based on the BslA crystal structure. The occurrence of arrested coalescence indicates that the surface activity of BslA is similar to that of colloidal particles that produce Pickering emulsions, with the stability of partially coalesced structures ensured by interfacial jamming. Micropipette aspiration and flow in tapered capillaries experiments reveal intriguing reversible and nonreversible modes of mechanical deformation, respectively. The mechanical robustness of the microcapsules and the ability to engineer their shape and to design highly specific binding responses through protein engineering suggest that these microcapsules may be useful for biomedical applications.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 26-02-2020
DOI: 10.1126/SCIROBOTICS.AAY3604
Abstract: An ethanol-based Pickering emulsion that spontaneously forms conductive composites is used to sustainably manufacture compliant strain sensors.
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Chemical Society (ACS)
Date: 06-11-2014
DOI: 10.1021/NN505037B
Abstract: There is long-standing interest in developing membranes possessing uniform pores with dimensions in the range of 1 nm and physical continuity in the macroscopic transport direction to meet the needs of challenging small molecule and ionic separations. Here we report facile, scalabe fabrication of polymer membranes with vertically (i.e., along the through-plane direction) aligned 1 nm pores by magnetic-field alignment and subsequent cross-linking of a liquid crystalline mesophase. We utilize a wedge-shaped hiphilic species as the building block of a thermotropic columnar mesophase with 1 nm ionic nanochannels, and leverage the magnetic anisotropy of the hiphile to control the alignment of these pores with a magnetic field. In situ X-ray scattering and subsequent optical microscopy reveal the formation of highly ordered nanostructured mesophases and cross-linked polymer films with orientational order parameters of ca. 0.95. High-resolution transmission electron microscopy (TEM) imaging provides direct visualization of long-range persistence of vertically aligned, hexagonally packed nanopores in unprecedented detail, demonstrating high-fidelity retention of structure and alignment after photo-cross-linking. Ionic conductivity measurements on the aligned membranes show a remarkable 85-fold enhancement of conductivity over nonaligned s les. These results provide a path to achieving the large area control of morphology and related enhancement of properties required for high-performance membranes and other applications.
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier BV
Date: 2022
DOI: 10.2139/SSRN.4144353
Publisher: Elsevier BV
Date: 2022
DOI: 10.2139/SSRN.4203035
Publisher: Wiley
Date: 15-05-2018
Abstract: The graft-through synthesis of Janus graft block copolymers (GBCPs) from branched macromonomers composed of various combinations of homopolymers is presented. Self-assembly of GBCPs resulted in ordered nanostructures with ultra-small domain sizes down to 2.8 nm (half-pitch). The grafted architecture introduces an additional parameter, the backbone length, which enables control over the thermomechanical properties and processability of the GBCPs independently of their self-assembled nanostructures. The simple synthetic route to GBCPs and the possibility of using a variety of polymer combinations contribute to the universality of this technique.
Publisher: American Chemical Society (ACS)
Date: 31-05-2018
Abstract: We demonstrate the fabrication of a loose, negatively charged nanofiltration (NF) membrane with tailored selectivity for the removal of perfluoroalkyl substances with reduced scaling potential. A selective polyamide layer was fabricated on top of a poly(ether sulfone) support via interfacial polymerization of trimesoyl chloride and a mixture of piperazine and bipiperidine. Incorporating high molecular weight bipiperidine during the interfacial polymerization enables the formation of a loose, nanoporous selective layer structure. The fabricated NF membrane possessed a negative surface charge and had a pore diameter of ∼1.2 nm, much larger than a widely used commercial NF membrane (i.e., NF270 with pore diameter of ∼0.8 nm). We evaluated the performance of the fabricated NF membrane for the rejection of different salts (i.e., NaCl, CaCl
Publisher: Wiley
Date: 12-12-2021
Abstract: The high theoretical specific energy of lithium/sulfur (Li/S) cells (2600 Wh/kg) has positioned the Li/S cell as one of the most promising candidates for the beyond lithium‐ion cell. Despite the evident advantages, there are remaining problems mainly associated with the unique solution‐based reaction chemistry involving lithium polysulfide (Li‐PS) that hinder the commercialization of the Li/S cells. Incorporating solid‐state electrolytes (SSEs) can avoid the Li‐PS shuttle problem while preserving the benefits of Li/S cells, but it introduces other challenges related to the electrode/electrolyte solid interfaces. This topical review summarizes the current status of solid‐state Li/S cells and their major challenges and discusses the recent efforts to improve cell performance and durability. Various solid‐state electrolytes, including oxides, sulfides, and solid polymer electrolytes, are briefly reviewed. In particular, we focus on the recent progress to improve the interfacial properties by two major approaches, morphological and chemical modifications of the electrode/electrolyte interfaces. The design strategy and implementation to overcome the prominent issues associated with sulfur electrodes are critically discussed. Also, several electrochemical and physicochemical characterization methods to examine the electron/ion transport at the interface are outlined. Given the superior theoretical physicochemical properties of the Li/S cells, we emphasize that the inappropriate interfacial design of the solid‐state Li/S cells is the major challenge to bring solid‐state Li/S cells to a commercially attractive level.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7NR06069F
Abstract: While kinetic aspects of self-assembly can hinder ordering, non-equilibirum effects can also be exploited to enforce a particular kind of order. We develop a pathway-engineering approach, using it to select a particular arrangement of a block copolymer cylinder phase.
Publisher: American Chemical Society (ACS)
Date: 10-07-2020
Publisher: Springer Science and Business Media LLC
Date: 21-12-2015
DOI: 10.1038/MICRONANO.2015.40
Abstract: Bulk metallic glasses (BMGs) have been developed as a means to achieve durable multiscale, nanotextured surfaces with desirable properties dictated by topography for a multitude of applications. One barrier to this achievement is the lack of a bridging technique between macroscale thermoplastic forming and nanoimprint lithography, which arises from the difficulty and cost of generating controlled nanostructures on complex geometries using conventional top-down approaches. This difficulty is compounded by the necessary destruction of any resulting reentrant structures during rigid demolding. We have developed a generalized method to overcome this limitation by sacrificial template imprinting using zinc oxide (ZnO) nanostructures. It is established that such structures can be grown inexpensively and quickly with tunable morphologies on a wide variety of substrates out of solution, which we exploit to generate the nanoscale portion of the multiscale pattern through this bottom-up approach. In this way, we achieve metallic structures that simultaneously demonstrate features from the macroscale down to the nanoscale, requiring only the top-down fabrication of macro/microstructured molds. Upon detachment of the formed part from the multiscale molds, the ZnO remains embedded in the surface and can be removed by etching in mild conditions to both regenerate the mold and render the surface of the BMGs nanoporous. The ability to pattern metallic surfaces in a single step on length scales from centimeters down to nanometers is a critical step toward fabricating devices with complex shapes that rely on multiscale topography for their intended functions, such as biomedical and electrochemical applications.
Location: United States of America
No related grants have been discovered for Youngwoo Choo.