Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy

Takeya Unuma; Yoshiro Shimizu; Shujun Liang; Xiaoju Wang; Martti Toivakka; Jarkko J. Saarinen

doi:10.1364/OME.586226

Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy

Takeya Unuma
, Yoshiro Shimizu
, Shujun Liang
, Xiaoju Wang
, Martti Toivakka
, Jarkko J. Saarinen

Research output: Contribution to journal › Article › Scientific › peer-review

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Abstract

An elaborate combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy in transmission geometry is employed to investigate the optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils (PPy@LCNF). The PPy@LCNF nanocomposite has a core-shell structure for each individual fibril and is made into two films with lightly and heavily protonated polypyrrole. Both spectral features of terahertz complex conductivity and terahertz/infrared transmittance are well reproduced by an extended Drude model in a consistent way, describing the partial localization of carriers. The carriers in the heavily protonated PPy@LCNF film are found to have a lower localization degree as well as a higher density than those in the lightly protonated one.

Original language	English
Pages (from-to)	487-495
Number of pages	9
Journal	Optical Materials Express
Volume	16
Issue number	3
DOIs	https://doi.org/10.1364/OME.586226
Publication status	Published - 1 Mar 2026
MoE publication type	A1 Journal article-refereed

Funding

Japan Society for the Promotion of Science (KAKENHI Grant Number JP22K18791); Ministry of Education, Culture, Sports, Science and Technology (X-NICS Grant Number JPJ011438); Japan Science and Technology Agency (CREST Grant Number JPMJCR2101). S. Liang would like to acknowledge the financial support from the Doctoral Network of Åbo Akademi University (ÅAU) for funding her doctoral study at ÅAU, Finland. X. Wang would like to thank the Research Council of Finland for the Academy Research Fellow funding (333158) at ÅAU.

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10.1364/OME.586226

ome-16-3-487Final published version, 2.45 MBLicence: Publisher rights policy

https://urn.fi/URN:NBN:fi-fe2026050136927

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title = "Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy",

abstract = "An elaborate combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy in transmission geometry is employed to investigate the optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils (PPy@LCNF). The PPy@LCNF nanocomposite has a core-shell structure for each individual fibril and is made into two films with lightly and heavily protonated polypyrrole. Both spectral features of terahertz complex conductivity and terahertz/infrared transmittance are well reproduced by an extended Drude model in a consistent way, describing the partial localization of carriers. The carriers in the heavily protonated PPy@LCNF film are found to have a lower localization degree as well as a higher density than those in the lightly protonated one.",

author = "Takeya Unuma and Yoshiro Shimizu and Shujun Liang and Xiaoju Wang and Martti Toivakka and Saarinen, \{Jarkko J.\}",

note = "Publisher Copyright: {\textcopyright} 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.",

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doi = "10.1364/OME.586226",

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Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy. / Unuma, Takeya; Shimizu, Yoshiro; Liang, Shujun et al.
In: Optical Materials Express, Vol. 16, No. 3, 01.03.2026, p. 487-495.

Research output: Contribution to journal › Article › Scientific › peer-review

TY - JOUR

T1 - Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy

AU - Unuma, Takeya

AU - Shimizu, Yoshiro

AU - Liang, Shujun

AU - Wang, Xiaoju

AU - Toivakka, Martti

AU - Saarinen, Jarkko J.

PY - 2026/3/1

Y1 - 2026/3/1

N2 - An elaborate combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy in transmission geometry is employed to investigate the optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils (PPy@LCNF). The PPy@LCNF nanocomposite has a core-shell structure for each individual fibril and is made into two films with lightly and heavily protonated polypyrrole. Both spectral features of terahertz complex conductivity and terahertz/infrared transmittance are well reproduced by an extended Drude model in a consistent way, describing the partial localization of carriers. The carriers in the heavily protonated PPy@LCNF film are found to have a lower localization degree as well as a higher density than those in the lightly protonated one.

AB - An elaborate combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy in transmission geometry is employed to investigate the optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils (PPy@LCNF). The PPy@LCNF nanocomposite has a core-shell structure for each individual fibril and is made into two films with lightly and heavily protonated polypyrrole. Both spectral features of terahertz complex conductivity and terahertz/infrared transmittance are well reproduced by an extended Drude model in a consistent way, describing the partial localization of carriers. The carriers in the heavily protonated PPy@LCNF film are found to have a lower localization degree as well as a higher density than those in the lightly protonated one.

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DO - 10.1364/OME.586226

M3 - Article

AN - SCOPUS:105031733874

SN - 2159-3930

VL - 16

SP - 487

EP - 495

JO - Optical Materials Express

JF - Optical Materials Express

IS - 3

ER -

Optoelectronic nature of carriers in polypyrrole-coated lignocellulose nanofibrils revealed by a combination of terahertz and far-infrared transmission spectroscopy

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