1
|
Choi WJ, Lee SH, Park BC, Kotov NA. Terahertz Circular Dichroism Spectroscopy of Molecular Assemblies and Nanostructures. J Am Chem Soc 2022; 144:22789-22804. [DOI: 10.1021/jacs.2c04817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Won Jin Choi
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Physical and Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Sang Hyun Lee
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Bum Chul Park
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicholas A. Kotov
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| |
Collapse
|
2
|
Bao J, Chen X, Liu K, Zhan Y, Li H, Zhang S, Xu Y, Tian Z, Cao T. Nonvolatile chirality switching in terahertz chalcogenide metasurfaces. MICROSYSTEMS & NANOENGINEERING 2022; 8:112. [PMID: 36193224 PMCID: PMC9525255 DOI: 10.1038/s41378-022-00445-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 07/17/2022] [Accepted: 07/29/2022] [Indexed: 06/16/2023]
Abstract
Actively controlling the polarization states of terahertz (THz) waves is essential for polarization-sensitive spectroscopy, which has various applications in anisotropy imaging, noncontact Hall measurement, and vibrational circular dichroism. In the THz regime, the lack of a polarization modulator hinders the development of this spectroscopy. We theoretically and experimentally demonstrate that conjugated bilayer chiral metamaterials (CMMs) integrated with Ge2Sb2Te5 (GST225) active components can achieve nonvolatile and continuously tunable optical activity in the THz region. A THz time-domain spectroscopic system was used to characterize the device, showing a tunable ellipticity (from ‒36° to 0°) and rotation of the plane polarization (from 32° to 0°) at approximately 0.73 THz by varying the GST225 state from amorphous (AM) to crystalline (CR). Moreover, a continuously tunable chiroptical response was experimentally observed by partially crystallizing the GST225, which can create intermediate states, having regions of both AM and CR states. Note that the GST225 has an advantage of nonvolatility over the other active elements and does not require any energy to retain its structural state. Our work allows the development of THz metadevices capable of actively manipulating the polarization of THz waves and may find applications for dynamically tunable THz circular polarizers and polarization modulators for THz emissions.
Collapse
Affiliation(s)
- Jiaxin Bao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Xieyu Chen
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Kuan Liu
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Yu Zhan
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Haiyang Li
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| | - Shoujun Zhang
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Yihan Xu
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Zhen Tian
- Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, 300072 P. R. China
| | - Tun Cao
- School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian, 116024 P. R. China
| |
Collapse
|
3
|
Yang XD, Chen W, Ren Y, Chu LY. Exploring dielectric spectra of polymer through molecular dynamics simulations. MOLECULAR SIMULATION 2022. [DOI: 10.1080/08927022.2022.2083122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Xue-Dan Yang
- School of Chemical Engineering, Sichuan University, Chengdu, Sichuan, People's Republic of China
- State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan, People's Republic of China
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Wei Chen
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, People's Republic of China
- Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian, Liaoning, People's Republic of China
| | - Ying Ren
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People's Republic of China
- University of Chinese Academy of Sciences, Beijing, People's Republic of China
- Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Liang-Yin Chu
- School of Chemical Engineering, Sichuan University, Chengdu, Sichuan, People's Republic of China
- State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan, People's Republic of China
| |
Collapse
|
4
|
Romo TD, Grossfield A, Markelz AG. Persistent Protein Motions in a Rugged Energy Landscape Revealed by Normal Mode Ensemble Analysis. J Chem Inf Model 2020; 60:6419-6426. [PMID: 33103888 DOI: 10.1021/acs.jcim.0c00879] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proteins are allosteric machines that couple motions at distinct, often distant, sites to control biological function. Low-frequency structural vibrations are a mechanism of this long-distance connection and are often used computationally to predict correlations, but experimentally identifying the vibrations associated with specific motions has proved challenging. Spectroscopy is an ideal tool to explore these excitations, but measurements have been largely unable to identify important frequency bands. The result is at odds with some previous calculations and raises the question what methods could successfully characterize protein structural vibrations. Here we show the lack of spectral structure arises in part from the variations in protein structure as the protein samples the energy landscape. However, by averaging over the energy landscape as sampled using an aggregate 18.5 μs of all-atom molecular dynamics simulation of hen egg white lysozyme and normal-mode analyses, we find vibrations with large overlap with functional displacements are surprisingly concentrated in narrow frequency bands. These bands are not apparent in either the ensemble averaged vibrational density of states or isotropic absorption. However, in the case of the ensemble averaged anisotropic absorption, there is persistent spectral structure and overlap between this structure and the functional displacement frequency bands. We systematically lay out heuristics for calculating the spectra robustly, including the need for statistical sampling of the protein and inclusion of adequate water in the spectral calculation. The results show the congested spectrum of these complex molecules obscures important frequency bands associated with function and reveal a method to overcome this congestion by combining structurally sensitive spectroscopy with robust normal mode ensemble analysis.
Collapse
Affiliation(s)
- Tod D Romo
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, United States
| | - Alan Grossfield
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, United States
| | - Andrea G Markelz
- Department of Physics, University at Buffalo, SUNY, Buffalo, New York 14260, United States
| |
Collapse
|
5
|
Koziol P, Liberda D, Kwiatek WM, Wrobel TP. Macromolecular Orientation in Biological Tissues Using a Four-Polarization Method in FT-IR Imaging. Anal Chem 2020; 92:13313-13318. [PMID: 32854498 PMCID: PMC7547855 DOI: 10.1021/acs.analchem.0c02591] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
![]()
Fourier
transform infrared spectroscopy has emerged as a powerful
tool for tissue specimen investigation. Its nondestructive and label-free
character enables direct determination of biochemical composition
of samples. Furthermore, the introduction of polarization enriches
this technique by the possibility of molecular orientation study apart
from purely quantitative analysis. Most of the molecular orientation
studies focused on polymer samples with a well-defined molecular axis.
Here, a four-polarization approach for Herman’s in-plane orientation
function and azimuthal angle determination was applied to a human
tissue sample investigation for the first time. Attention was focused
on fibrous tissues rich in collagen because of their cylindrical shape
and established amide bond vibrations. Despite the fact that the tissue
specimen contains a variety of molecules, the presented results of
molecular ordering and orientation agree with the theoretical prediction
based on sample composition and vibration directions.
Collapse
Affiliation(s)
- Paulina Koziol
- Solaris National Synchrotron Radiation Centre, Jagiellonian University, Czerwone Maki 98, Krakow 30-392, Poland
- Institute of Nuclear Physics, Polish Academy of Sciences, Krakow PL-31342, Poland
| | - Danuta Liberda
- Solaris National Synchrotron Radiation Centre, Jagiellonian University, Czerwone Maki 98, Krakow 30-392, Poland
- Institute of Nuclear Physics, Polish Academy of Sciences, Krakow PL-31342, Poland
| | - Wojciech M. Kwiatek
- Institute of Nuclear Physics, Polish Academy of Sciences, Krakow PL-31342, Poland
| | - Tomasz P. Wrobel
- Solaris National Synchrotron Radiation Centre, Jagiellonian University, Czerwone Maki 98, Krakow 30-392, Poland
- Institute of Nuclear Physics, Polish Academy of Sciences, Krakow PL-31342, Poland
| |
Collapse
|
6
|
Heo C, Ha T, You C, Huynh T, Lim H, Kim J, Kesama MR, Lee J, Kim TT, Lee YH. Identifying Fibrillization State of Aβ Protein via Near-Field THz Conductance Measurement. ACS NANO 2020; 14:6548-6558. [PMID: 32167289 DOI: 10.1021/acsnano.9b08572] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Progressive Alzheimer's disease is correlated with the oligomerization and fibrillization of the amyloid beta (Aβ) protein. We identify the fibrillization stage of the Aβ protein through label-free near-field THz conductance measurements in a buffer solution. Frequency-dependent conductance was obtained by measuring the differential transmittance of the time-domain spectroscopy in the THz range with a molar concentration of monomer, oligomer, and fibrillar forms of the Aβ protein. Conductance at the lower frequency limit was observed to be high in monomers, reduced in oligomers, and dropped to an insulating state in fibrils and increased proportionally with the Aβ protein concentration. The monotonic decrease in the conductance at low frequency was dominated by a simple Drude component in the monomer with concentration and nonlinear conductance behaviors in the oligomer and fibril. By extracting the structural localization parameter, a dimensionless constant, with the modified Drude-Smith model, we defined a dementia quotient (DQ) value (0 < De < 1) as a discrete metric for a various Aβ proteins at a low concentration of 0.1 μmol/L; DQ = 1.0 ± 0.002 (fibril by full localization, mainly by Smith component), DQ = 0.64 ± 0.013 (oligomer by intermixed localization), and DQ = 0.0 ± 0.000 (monomer by Drude component). DQ values were discretely preserved independent of the molar concentration or buffer variation. This provides plenty of room for the label-free diagnosis of Alzheimer's disease using the near-field THz conductance measurement.
Collapse
Affiliation(s)
- Chaejeong Heo
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Institute for Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Taewoo Ha
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Chunjae You
- Institute for Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
- Department of Biophysics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Thuy Huynh
- Institute for Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
- Department of Biophysics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Hosub Lim
- Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jiwon Kim
- Department of Integrative Biotechnology, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Mallikarjuna Reddy Kesama
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Institute for Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jinkee Lee
- Institute for Quantum Biophysics (IQB), Sungkyunkwan University, Suwon 16419, Republic of Korea
- Department of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Teun-Teun Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
- Department of Energy Science and Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| |
Collapse
|
7
|
Keiderling TA. Structure of Condensed Phase Peptides: Insights from Vibrational Circular Dichroism and Raman Optical Activity Techniques. Chem Rev 2020; 120:3381-3419. [DOI: 10.1021/acs.chemrev.9b00636] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Timothy A. Keiderling
- Department of Chemistry, University of Illinois at Chicago 845 West Taylor Street m/c 111, Chicago, Illinois 60607-7061, United States
| |
Collapse
|
8
|
Choi WJ, Cheng G, Huang Z, Zhang S, Norris TB, Kotov NA. Terahertz circular dichroism spectroscopy of biomaterials enabled by kirigami polarization modulators. NATURE MATERIALS 2019; 18:820-826. [PMID: 31263226 DOI: 10.1038/s41563-019-0404-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 05/15/2019] [Indexed: 05/19/2023]
Abstract
Terahertz circular dichroism (TCD) offers multifaceted spectroscopic capabilities for understanding the mesoscale chiral architecture and low-energy vibrations of macromolecules in (bio)materials1-5. However, the lack of dynamic polarization modulators comparable to polarization optics for other parts of the electromagnetic spectrum is impeding the proliferation of TCD spectroscopy6-11. Here we show that tunable optical elements fabricated from patterned plasmonic sheets with periodic kirigami cuts make possible the polarization modulation of terahertz radiation under application of mechanical strain. A herringbone pattern of microscale metal stripes enables a dynamic range of polarization rotation modulation exceeding 80° over thousands of cycles. Following out-of-plane buckling, the plasmonic stripes function as reconfigurable semi-helices of variable pitch aligned along the terahertz propagation direction. Several biomaterials, exemplified by an elytron of the Chrysina gloriosa, revealed distinct TCD fingerprints associated with the helical substructure in the biocomposite. Analogous kirigami modulators will also enable other applications in terahertz optics, such as polarization-based terahertz imaging, line-of-sight telecommunication, information encryption and space exploration.
Collapse
Affiliation(s)
- Won Jin Choi
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Gong Cheng
- Department of Physics, University of Michigan, Ann Arbor, MI, USA
- Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI, USA
| | - Zhengyu Huang
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - Shuai Zhang
- Taubman College of Architecture and Urban Planning, University of Michigan, Ann Arbor, MI, USA
| | - Theodore B Norris
- Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI, USA.
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA.
| | - Nicholas A Kotov
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, USA.
- Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA.
- Michigan Institute for Translational Nanotechnology, Ypsilanti, MI, USA.
| |
Collapse
|
9
|
Sadrara M, Miri M. Electric and Magnetic Hotspots via Hollow InSb Microspheres for Enhanced Terahertz Spectroscopy. Sci Rep 2019; 9:2926. [PMID: 30814534 PMCID: PMC6393507 DOI: 10.1038/s41598-018-35833-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/11/2018] [Indexed: 11/08/2022] Open
Abstract
We study electric and magnetic hotspots in the gap between hollow InSb microspheres forming dimers and trimers. The outer radius, core volume fraction, distance, and temperature of the microspheres can be chosen to achieve field enhancement at a certain frequency corresponding to the transition between energy levels of a molecule placed in the gap. For example, utilizing 80 μm radius spheres at a gap of 2 μm held at a temperature of 295 K, allow electric field intensity enhancements of 10-2880 and magnetic field intensity enhancements of 3-61 in the frequency window 0.35-1.50 THz. The core volume fraction and the ambient temperature affect the enhancements, particularly in the frequency window 1.5-2 THz. Electric and magnetic hotspots are promising for THz absorption and circular dichroism spectroscopy.
Collapse
Affiliation(s)
- Mahdiyeh Sadrara
- Department of Physics, University of Tehran, P.O. Box 14395-547, Tehran, Iran
| | - MirFaez Miri
- Department of Physics, University of Tehran, P.O. Box 14395-547, Tehran, Iran.
| |
Collapse
|
10
|
Wang P, Wang Y, Liu L, Zhao J, Tian Z, Qi W, Zhang J, Zhao H, He M. Self-assembled chiral nanoribbons studied by terahertz time-domain spectroscopy and other biological methods. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
11
|
Kim TT, Oh SS, Kim HD, Park HS, Hess O, Min B, Zhang S. Electrical access to critical coupling of circularly polarized waves in graphene chiral metamaterials. SCIENCE ADVANCES 2017; 3:e1701377. [PMID: 28975151 PMCID: PMC5621972 DOI: 10.1126/sciadv.1701377] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 09/11/2017] [Indexed: 05/25/2023]
Abstract
Active control of polarization states of electromagnetic waves is highly desirable because of its diverse applications in information processing, telecommunications, and spectroscopy. However, despite the recent advances using artificial materials, most active polarization control schemes require optical stimuli necessitating complex optical setups. We experimentally demonstrate an alternative-direct electrical tuning of the polarization state of terahertz waves. Combining a chiral metamaterial with a gated single-layer sheet of graphene, we show that transmission of a terahertz wave with one circular polarization can be electrically controlled without affecting that of the other circular polarization, leading to large-intensity modulation depths (>99%) with a low gate voltage. This effective control of polarization is made possible by the full accessibility of three coupling regimes, that is, underdamped, critically damped, and overdamped regimes by electrical control of the graphene properties.
Collapse
Affiliation(s)
- Teun-Teun Kim
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon 16419, Republic of Korea
- Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sang Soon Oh
- Blackett Laboratory, Department of Physics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Hyeon-Don Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Hyun Sung Park
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Ortwin Hess
- Blackett Laboratory, Department of Physics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Bumki Min
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Shuang Zhang
- School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
| |
Collapse
|
12
|
Wu X, Wu X, Shao M, Yang B. Structural changes of Bombyx mori fibroin from silk gland to fiber as evidenced by Terahertz spectroscopy and other methods. Int J Biol Macromol 2017; 102:1202-1210. [PMID: 28487194 DOI: 10.1016/j.ijbiomac.2017.05.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 04/17/2017] [Accepted: 05/02/2017] [Indexed: 11/25/2022]
Abstract
Here we investigated the structural changes of silk fibroin during Bombyx mori silkworm spinning and reconstitution process. X-ray diffraction, Fourier transform infrared spectroscopy, polarized optical microscopy, and terahertz (THz) spectroscopy were applied to monitor the structural features of silk fibroin from posterior, middle silk glands, to cocoons, and then to reconstituted silk. Results show that from silk gland to cocoon, fibroin experiences a significant transformation in crystal structure from a typical silk I, to a silk I-rich mixed structure, and finally to a typical silk II state, accompanied with a change in secondary structure from α-helix and random coil structures to preferential orientation β-sheets. Compared with natural silk fibroins, the reconstituted silk fibroin lacks β-sheet conformation and orientation crystallization. Terahertz spectroscopy readily follows these silk fibroin structural changes. Two characteristic peaks for silk fibroin is observed in 2-10 THz. Their strength ratio is strongly correlated with the β-sheet conformation. The absorbance properties in 0.2-2.0THz also significantly change as a function of changing their crystal structures caused by diverse sources. All of these observations will help in the study of overall structure in silk fibroin to understand more completely the fibroin assembly process in natural spinning and reconstitution process.
Collapse
Affiliation(s)
- Xu Wu
- College of Materials and Textile, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Xiaodong Wu
- College of Materials and Textile, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Min Shao
- Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China.
| | - Bin Yang
- College of Materials and Textile, Zhejiang Sci-Tech University, Hangzhou 310018, China; Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China.
| |
Collapse
|
13
|
Slyngborg M, Tsao YC, Fojan P. Large-scale fabrication of achiral plasmonic metamaterials with giant chiroptical response. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:914-925. [PMID: 27547608 PMCID: PMC4979657 DOI: 10.3762/bjnano.7.83] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/09/2016] [Indexed: 06/06/2023]
Abstract
A variety of extrinsic chiral metamaterials were fabricated by a combination of self-ordering anodic oxidation of aluminum foil, nanoimprint lithography and glancing angle deposition. All of these techniques are scalable and pose a significant improvement to standard metamaterial fabrication techniques. Different interpore distances and glancing angle depositions enable the plasmonic resonance wavelength to be tunable in the range from UVA to IR. These extrinsic chiral metamaterials only exhibit significant chiroptical response at non-normal angles of incidence. This intrinsic property enables the probing of both enantoimeric structures on the same sample, by inverting the tilt of the sample relative to the normal angle. In biosensor applications this allows for more precise, cheap and commercialized devices. As a proof of concept two different molecules were used to probe the sensitivity of the metamaterials. These proved the applicability to sense proteins through non-specific adsorption on the metamaterial surface or through functionalized surfaces to increase the sensing sensitivity. Besides increasing the sensing sensitivity, these metamaterials may also be commercialized and find applications in surface-enhanced IR spectroscopy, terahertz generation and terahertz circular dichroism spectroscopy.
Collapse
Affiliation(s)
- Morten Slyngborg
- Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, 9220 Aalborg East, Denmark
| | - Yao-Chung Tsao
- Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, 9220 Aalborg East, Denmark
| | - Peter Fojan
- Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, 9220 Aalborg East, Denmark
| |
Collapse
|
14
|
Kaschke J, Wegener M. Gold triple-helix mid-infrared metamaterial by STED-inspired laser lithography. OPTICS LETTERS 2015; 40:3986-3989. [PMID: 26368693 DOI: 10.1364/ol.40.003986] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In analogy to wire-grid polarizers for linear polarization, metal-helix metamaterials can act as broadband circular polarizers. This concept has brought circular-polarization capabilities to mid-infrared and terahertz frequencies, which were previously difficult to access. Due to the lack of rotational symmetry, however, single-helix metamaterials exhibit unwanted circular-polarization conversions. Recent theoretical work showed that conversions can be fully eliminated by intertwining N=3 or 4 helices within each unit cell. While direct laser writing in positive-tone photo-resist yielded good results for single-helix metamaterials operating at mid-infrared frequencies, the axial resolution is insufficient for N-helix metamaterials. Here, we use stimulated emission depletion-inspired three-dimensional laser lithography to fabricate such microstructures. We measure all entries of the Jones transmission and reflection matrices and show experimentally that polarization conversions are minimized, in good agreement with theory.
Collapse
|