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Chae, Inseok

Publications and source records attributed to Chae, Inseok.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Virus‐Based Pyroelectricity

Abstract The first observation of heat‐induced electrical potential generation on a virus and its detection through pyroelectricity are presented. Specifically, the authors investigate the pyroelectric properties of the M13 phage, which possesses inherent dipole structures derived from the noncentrosymmetric arrangement of the major coat protein (pVIII) with an α‐helical conformation. Unidirectional polarization of the phage is achieved through genetic engineering of the tail protein (pIII) and template‐assisted self‐assembly techniques. By modifying the pVIII proteins with varying numbers of glutamate residues, the structure‐dependent tunable pyroelectric properties of the phage are explored. The most polarized phage exhibits a pyroelectric coefficient of 0.13 µC m −2 °C −1 . Computational modeling and circular dichroism (CD) spectroscopy analysis confirm that the unfolding of α‐helices within the pVIII proteins leads to changes in phage polarization upon heating. Moreover, the phage is genetically modified to enable its pyroelectric function in diverse chemical environments. This phage‐based approach not only provides valuable insights into bio‐pyroelectricity but also opens up new opportunities for the detection of various viral particles. Furthermore, it holds great potential for the development of novel biomaterials for future applications in biosensors and bioelectric materials.

Kim, Han↗
DOE OSTI2023

Relaxation dynamics of water in the vicinity of cellulose nanocrystals

Water molecules near cellulose nanocrystals (CNCs; produced via the sulfuric acid-catalyzed hydrolysis of wood pulp) are believed to relax slower than those in the bulk liquid, which may result in unique properties of CNC aqueous dispersions. Herein this study analyzed the polarization behavior of water molecules in CNC aqueous dispersions and other reference samples using a dielectric relaxation spectroscopy (DRS) technique in the microwave frequency range (0.2–20 GHz). As the CNC concentration increases, two slow relaxation components become prominent. The comparison with DRS data of aqueous dispersions of nanoporous silica, polyvinyl alcohol (PVA), and hairy CNC (HCNC) with amorphous chains protruding from both ends suggested that these slow relaxation modes of water near CNC surfaces cannot be attributed to direct hydrogen bonding interactions with the hydroxyl (OH) groups exposed and immobilized at the solid surface. Instead, they are similar to the water molecules interacting with OH groups attached to flexible polymer chains. Molecular dynamics (MD) simulations of the polarization behavior of water near the (110) facet of cellulose Iβ crystals confirmed that the interactions of water molecules with the cellulose crystal surface do not cause slower relaxations in the frequency range studied via the DRS. These results indicated that the CNC surface cannot be depicted with the crystallographic facets of cellulose Iβ; instead, it resembles a polymer-brush surface on which the short glucan residues or fragments of the strong acid-catalyzed hydrolysis process are swollen and extended into the aqueous phase.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Anisotropic Optical and Frictional Properties of Langmuir–Blodgett Film Consisting of Uniaxially-Aligned Rod-Shaped Cellulose Nanocrystals

Langmuir–Blodgett (LB) film deposition gives an opportunity to control the packing density and orientation of anisotropic nanoparticles at a monolayer level, allowing accurate characterization of their anisotropic material properties. Additionally, the uniaxial deposition of rod-shaped cellulose nanocrystals (CNCs) over a macroscopically large area is achieved by aligning the long axis of CNCs on the LB trough with the direction of the maximum drag force within the meniscus during the vertical pulling of the substrate from the LB trough. On the uniaxially-aligned LB films, anisotropic linear and non-linear optical properties of CNCs are obtained using Mueller matrix spectroscopy and sum frequency generation spectroscopy, respectively, and explained with time-dependent density functional theory calculations. Also, the frictional anisotropy of the LB film is measured using atomic force microscopy and explained theoretically. The findings of this study will be valuable for preparation of anisotropic nanoparticle thin films with uniform arrangements and utilization of their anisotropic material properties.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Probing cellulose structures with vibrational spectroscopy

This paper reviews principles, data interpretations, and applications of vibrational spectroscopic methods used for analysis of cellulose in the isolated state and in plant cell walls or lignocellulose biomass. The paper begins with reviewing the crystalline structures of crystalline cellulose polymorphs and the principles of three different vibrational spectroscopy methods—infrared (IR), Raman, and sum frequency generation (SFG)—complemented with density functional theory calculations. Then, it discusses the vibrational modes of crystalline celluloses, how the chain orientation in crystalline domain is analyzed in each method, and how the concentration and spatial distribution of crystalline cellulose domains interspersed in amorphous matrices are manifested or analyzed differently in these three methods. Finally, the paper discusses examples of analyzing crystalline cellulose in plant cell walls or lignocellulose biomass with IR, Raman, and SFG including spectroscopic imaging. One review cannot cover all vibrational spectroscopy literatures on cellulose; this review aims at providing tutorial information, using selected literatures and experimental data, needed to interpret nano-, meso-, and micro-scale structures of cellulose in plant cell walls and lignocellulose biomass.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Vibrational Sum Frequency Generation (SFG) Analysis of Ferroelectric Response of PVDF-Based Copolymer and Terpolymer

In poly(vinylidene difluoride) (PVDF)-based polymers, the alignment of dipoles of the crystalline $β$ phase with alltrans conformations is responsible for ferroelectricity; however, there is a lack of direct spectroscopic evidence for this phenomenon. We report in situ monitoring of the molecular orientations associated with ferroelectric responses of PVDF-based polymers using vibrational sum frequency generation (SFG) spectroscopy. The orientation of CH 2 groups with respect to the -(CH 2 CF 2 ) n - chain axis of the poled $β$ domains in a PVDF copolymer was determined from the SFG dependence of an uniaxially aligned sample on the laser polarization and azimuthal angle. The relative intensities of CH 2 symmetric and asymmetric stretch modes as well as their total intensities revealed the transformation of the all-trans conformation domains during the electrical poling of PVDF based co- and terpolymer films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Nanowell-patterned TiO{sub 2} microcantilevers for calorimetric chemical sensing

A sensitive calorimetric sensor using a TiO{sub 2} microcantilever with nanowells patterned on one of its sides is described. This single material cantilever is sensitive to temperature change without relying on the metal deposition-based bimetallic effect. The thermomechanical sensitivity originates from the structure dependent variations in both the elastic modulus and thermal expansion coefficient due to the presence of ordered nanowells. These cantilever beams offer an alternate and efficient chemical sensing route for vapor phase analytes using photothermal spectroscopy. Selective and sensitive detection of organophosphorus compounds, as well as their photocatalytic decomposition under ultraviolet light exposure are demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Photothermal cantilever deflection spectroscopy of a photosensitive polymer

The mechanical and chemical information of a poly(methyl methacrylate) (PMMA) film on a microcantilever were simultaneously acquired by photothermal cantilever deflection spectroscopy as a function of ultraviolet (UV) irradiation time. Nanomechanical infrared (IR) spectra from the PMMA-coated microcantilever agreed well with the Fourier transform infrared spectroscopy (FTIR) spectra of PMMA on gold-coated silicon wafer. The decreasing intensities of nanomechanical IR peaks represent chemical as well as mechanical information of UV radiation-induced photodegradation processes in the PMMA which cannot be obtained by a conventional FTIR technique. The observed decrease in the resonance frequency of the microcantilever is related to the change in the Young's modulus of the PMMA under UV exposure.

36 MATERIALS SCIENCE↗