Publications by authors named "Jong-Gun Lee"

This work focuses on the development of a responsive sponge made of an anionic cellulose nanocrystal (CNC) skeleton that is electrostatically crosslinked by a pH-responsive poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) polyelectrolyte complex (PEC). The results prove the formation of a global percolated network comprised of disordered CNC rods crosslinked by PEC clusters. The bulk density of the freeze-dried CNC-PEC sponges increases from 35 to 93 mg/cm with PEC concentration, while the compression modulus of dry specimens increases from 7 up to 62 kPa.

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In this study, we sought to describe a novel imaging apparatus that is lightweight, inexpensive, and highly effective for use in colorectal diagnostic and treatment settings. Typical probes for use in colorectal ultrasonic imaging applications are developed for surgeons to diagnose and stage rectal tumors and image the rectum and anus. Here we outline a new technique and use it for colorectal imaging in an animal.

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We have sequentially deposited layers of silver nanowires (AgNWs), silicon dioxide (SiO) nanoparticles, and polystyrene (PS) nanoparticles on uncoated glass by a rapid low-cost supersonic spraying method to create antifrosting, anticondensation, and self-cleaning glass. The conductive silver nanowire network embedded in the coating allows electrical heating of the glass surface. Supersonic spraying is a single-step coating technique that does not require vacuum.

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Controlling the thickness of quantum dot (QD) films is difficult using existing film formation techniques, which employ pre-ligand-exchanged PbS QD inks, because of several issues: 1) poor colloidal stability, 2) use of high-boiling-point solvents for QD dispersion, and 3) limitations associated with one-step deposition. Herein, we suggest a new protocol for QD film deposition using electrical double-layered PbS QD inks, prepared by solution-phase ligand exchange using methyl ammonium lead iodide (MAPbI). The films are deposited by the supersonic spraying technique, which facilitates the rapid evaporation of the solvent and the subsequent deposition of the PbS QD ink without requiring a post-deposition annealing treatment for solvent removal.

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We demonstrate production of nanotextured p-type cupric oxide (CuO) films via a low-cost scalable supersonic cold spray method in open air conditions. Simply sweeping the spray nozzle across a substrate produced a large-scale CuO film. When used as hydrogen evolution photocathodes, these films produced photocurrent densities (PCD) of up to 3.

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Water purification membranes, capable of purifying a few to tens of milliliters of aqueous methylene blue solution in a minute, were produced by supersonically blowing graphene flakes with a nylon-6 polymeric solution. The solution-blown nylon-6 nanofibers became entangled with graphene flakes thereby locking the graphene flakes within the frame of the bendable two-dimensional film structure. This method, which yielded a 5 × 7 cm(2)-sized membrane in less than 10 seconds, is commercially viable owing to fast fabrication and scalability.

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Multi-modality imaging is beneficial for both preclinical and clinical applications as it enables complementary information from each modality to be obtained in a single procedure. In this paper, we report the design, fabrication, and testing of a novel tri-modal in vivo imaging system to exploit molecular/functional information from fluorescence (FL) and photoacoustic (PA) imaging as well as anatomical information from ultrasound (US) imaging. The same ultrasound transducer was used for both US and PA imaging, bringing the pulsed laser light into a compact probe by fiberoptic bundles.

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Superhydrophilic and superhydrophobic surfaces enable self-cleaning phenomena, either forming a continuous water film or forming droplets that roll off the surface, respectively. TiO2 films are well-known for their extreme hydrophilicity and photocatalytic characteristics. Here, we describe nanostructured TiO2 thin films prepared by supersonic aerosol deposition, including a thorough study of the effects of the annealing temperature on the crystal structure, surface morphology, surface roughness, and wetting properties.

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A simple and rapid room-temperature aerosol deposition method was used to fabricate TiO(2) films for photokilling/photdegradation applications. TiO(2) particles were accelerated to supersonic speeds and fractured upon impacting a glass substrate to form a functional thin film, a process known as aerosol deposition. After deposition, the films were annealed at various temperatures, and their photokilling/photodegradation performances following ultraviolet (UV) exposure were evaluated by counting the number of surviving bacterial colonies, and by a methylene blue decolorization test.

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We have studied the polar structures in the binary mixtures of bent-core liquid crystals P-n-O-PIMB(n-2)*-(n-4)O showing the ferroelectric smectic- CAPF (Sm-CAPF) (n=8 and 10) and antiferroelectric Sm-CSPA (n=9) B2 phase. Although the polar structure of the one-to-one mixture is governed by the compound with longer end chains, it is much more complicated in the mixtures with slightly less fraction of compounds with longer end chains. Even if the mixtures show the antiferroelectric phase before field application, the ferroelectric domains remain once the field is applied and coexist with the antiferroelectric domains.

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Simple theoretical interpretation has been made on the previously reported odd-even behavior of the emergence of ferroelectricity and antiferroelectricity in homologous series of bent-core mesogens with the same chiral end chains (S,S) ; compounds with even and odd carbon numbers (including oxygen) exhibit ferroelectric and antiferroelectric B2 phases, respectively. The odd-even behavior was confirmed in newly synthesized racemic compounds with chiral end chains of R and S forms (R,S) together with (R,R) and (S,S) forms. According to our theoretical interpretation, ferroelectricity should be more stable in (R,S) compounds than in (S,S) compounds.

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Two chiral bent-core mesogens Pn-O-PIMB(n - 2)* (n = 9 and 10) and their oxygen analogues Pn-O-PIMB(n - 2)*-(n - 4)O (n = 8, 9, and 10) with omega-[(S)-amyloxy]alkoxy terminal groups were prepared, and their phase structures were investigated by means of electro-optic, polarization reversal current and second harmonic generation measurements in order to clarify the effect of the interlayer steric interaction on the emergence of polar orderings. The odd-even behavior for the alternative appearance of ferroelectricity and antiferroelectricity was observed in two homologous series; the bent-core mesogens P10-O-PIMB8*, P8-O-PIMB6*-4O, and P10-O-PIMB8*-6O in addition to the previously reported P6-O-PIMB4* and P8-O-PIMB6*, where the length of chains n is even, exhibited ferroelectric phases. On the contrary, the mesogens P7-O-PIMB5*, P9-O-PIMB7*, and P9-O-PIMB7*-5O, where n is odd, showed antiferroelectric phases.

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