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Single-molecule spectroscopy as a window to the nano-world of organic materials

We use single molecule detection and spectroscopy to study structural and optical properties and processes in organic and polymeric materials on nanoscale level. Single-molecule spectroscopy is an excellent tool for nanoscale characterization of soft and complex matter, and is also the basis of super-resolution microscopy which was awarded Nobel prize in chemistry in 2014. Measuring light emitted by individual molecules reveals static and dynamic heterogeneities in the organic material and provides new insight into its structure, dynamics and photophysics on nanometer scales. We are interested in the study of basic properties of materials with the perspective of applications in optoelectronic and energy conversion devices.

 

Research topics

  1. Organic semiconductors: conformation and photophysical properties

Conjugated polymers are class of organic semiconducting materials with potential applications in future opto-electronic devices, such as displays, lightning or solar cells. We study single chains of conjugated polymers to explore the relationship between the individual chain conformation and its properties, including emission spectra, exciton migration, photo-oxidation, etc. The research provides important feedback for organic semiconductor design and development.
 

 

 

 

 


T. Nakamura, D. K. Sharma, S. Hirata, M. Vacha, J. Phys. Chem. C 122 (2018) 8137-8146
B. J. Lidster, S. Hirata, S. Matsuda, T. Yamamoto, V. Komanduri, Y. Tezuka, M. Vacha, M. L. Turner, Chem. Sci. 9 (2018) 2934-2941
H. Kobayashi, S. Hirata, M. Vacha, J. Phys. Chem. Lett. 4 (2013) 2591-2596
S. Onda, H. Kobayashi, T. Hatano, S. Furumaki, S. Habuchi and M. Vacha, J. Phys. Chem. Lett. 2 (2011) 2827–2831

  1. Organic electroluminescence characterized on nanometer scales

Organic electroluminescence (EL) is a novel technology that is finding applications, e.g., in TV screens, with expectations for further use in various nanotechnologies. Our research concerns nanoscale characterization of the phenomenon by measuring EL from single molecules of organometallic complexes, single chains of conjugated polymers or single nanocrystals of halide perovskites.
 

 

 

 


Y. Honmou, S. Hirata, H. Komiyama, J. Hiyoshi, S. Kawauchi, T. Iyoda, M. Vacha, Nature Commun. 5 (2014) 4666
B. X. Dong, Y. Honmou, H. Komiyama, S. Furumaki, T. Iyoda and M. Vacha, Macromol. Rapid Commun. 34 (2013) 492-497
Y. Sekiguchi, S. Habuchi and M. Vacha, ChemPhysChem 10 (2009) 1195-1198

  1. Semiconducting quantum dots and perovskite nanocrystals

Semiconducting quantum dots (QD) and halide perovskite nanocrystals are emerging as alternative light-emitting materials for displays, lasers, lightning or bioimaging, and search is going on for non-toxic efficient QD emitters with advanced functionalities. Our study of single QDs and single nanocrystals is indispensable in providing basic information on material properties such as emission spectra, size distributions, emission quantum yields, blinking, effects of environment, etc.
 

 

 

 


D. K. Sharma, S. Hirata, V. Biju and M. Vacha, ACS Nano 13 (2019) 624−632
T. Uematsu, K. Wajima, D. K. Sharma, S. Hirata, T. Yamamoto, T. Kameyama, M. Vacha, T. Torimoto, S. Kuwabata, NPG Asia Mater. 10 (2018) 713–726
D. K. Sharma, S. Hirata, L. Bujak, V. Biju, T. Kameyama, M. Kishi, T. Torimoto, M. Vacha, Nanoscale 8 (2016) 13687-13694

  1. Exciton diffusion and light upconversion

Nanoscale characterization by optical microscopy is not restricted to single-molecule imaging and spectroscopy but can be used also to visualize, e.g., exciton diffusion in molecular solids. In our research we concentrate mainly on triplet exciton diffusion and on the related process of triplet-triplet annihilation which can lead to the phenomenon of photon upconversion. Upconversion transforms low-energy light into light of higher energy, and as such is raising hopes for improved efficiency of solar cells or artificial photosynthesis.
 

 

 

 


K. Narushima, Y. Kiyota, T. Mori, S. Hirata and M. Vacha, Adv. Mater. 31 (2019) 1807268
K. Kamada, Y. Sakagami, T. Mizokuro, Y. Fujiwara, K. Kobayashi, K. Narushima, S. Hirata, M. Vacha, Materials Horizons 4 (2017) 83-87
K. Narushima, S. Hirata, M. Vacha, Nanoscale 9 (2017) 10653-10661

  1. Structure and function of photosynthetic proteins and their artificial analogues

The ability of single-molecule spectroscopy to unmask heterogeneous static and dynamic features that are otherwise hidden in large ensembles is especially important in studying complex biological systems. We have been applying the method to a variety of problems in photosynthetic proteins, ranging from reaction centers to large bacterial light-harvesting complexes.
 

 

 

 


S. Hatazaki, D. K. Sharma, S. Hirata, K. Nose, T. Iyoda, A. Kölsch, H. Lokstein and M. Vacha, J. Phys. Chem. Lett. 9 (2018) 6669-6675
S. Furumaki, F. Vacha, S. Hirata, M. Vacha, ACS Nano 8 (2014) 2176-2182
S. Furumaki, F. Vacha, S. Habuchi, Y. Tsukatani, D.A. Bryant and M. Vacha, J. Am. Chem. Soc. 133 (2011) 6703–6710

  1. Plasmon enhanced molecular photophysics

Interaction of a noble-metal nanoparticle with an organic fluorophore in its vicinity can radically influence the molecular photophysical properties via the effect of localized plasmon. We have been exploring this effect mainly by studying enhancement and control of resonant excited energy transfer. The ability to control actively the energy transfer process may find important roles in light-harvesting applications or imaging.
 

 

 

 


L. Bujak, K. Narushima, D. K. Sharma, S. Hirata, M. Vacha, J. Phys. Chem. C 121 (2017) 25479-25486
L. Bujak, T. Ishii, D. K. Sharma, S. Hirata, M. Vacha, Nanoscale 9 (2017) 1511-1519

  1. Nanoscale relaxation and diffusion in polymers and soft matter

Physical properties of polymers such as glass transition temperature and the related relaxation processes can change dramatically when the size of objects is reduced to nanometer scales, yet the molecular mechanisms behind many such changes are largely unknown. We use fluorescence probes of single dye molecules doped into various systems (polymer films and solutions, elastomers, liquid crystals) and study their 3D nanometer-scale properties by measuring the probe reorientations and diffusion.
 

 

 

 

 


S. Lee, K. Noda, S. Hirata, M. Vacha, J. Phys. Chem. Lett. 6 (2015) 1403−1407
T. Oba and M. Vacha, ACS Macro Lett. 1 (2012) 784-788
S. Habuchi, N. Sato, T. Yamamoto, Y. Tezuka and M. Vacha, Angew. Chem. Int. Ed. 49 (2010) 1418-1421

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Research

Home > Research

Single-molecule spectroscopy as a window to the nano-world of organic materials

 

We use single molecule detection and spectroscopy to study structural and optical properties and processes in organic and polymeric materials on nanoscale level. Single-molecule spectroscopy is an excellent tool for nanoscale characterization of soft and complex matter, and is also the basis of super-resolution microscopy which was awarded Nobel prize in chemistry in 2014. Measuring light emitted by individual molecules reveals static and dynamic heterogeneities in the organic material and provides new insight into its structure, dynamics and photophysics on nanometer scales. We are interested in the study of basic properties of materials with the perspective of applications in optoelectronic and energy conversion devices.

 

Research topics

    1.Organic semiconductors: conformation and photophysical properties

Conjugated polymers are class of organic semiconducting materials with potential applications in future opto-electronic devices, such as displays, lightning or solar cells. We study single chains of conjugated polymers to explore the relationship between the individual chain conformation and its properties, including emission spectra, exciton migration, photo-oxidation, etc. The research provides important feedback for organic semiconductor design and development.


T. Nakamura, D. K. Sharma, S. Hirata, M. Vacha, J. Phys. Chem. C 122 (2018) 8137-8146
B. J. Lidster, S. Hirata, S. Matsuda, T. Yamamoto, V. Komanduri, Y. Tezuka, M. Vacha, M. L. Turner, Chem. Sci. 9 (2018) 2934-2941
H. Kobayashi, S. Hirata, M. Vacha, J. Phys. Chem. Lett. 4 (2013) 2591-2596
S. Onda, H. Kobayashi, T. Hatano, S. Furumaki, S. Habuchi and M. Vacha, J. Phys. Chem. Lett. 2 (2011) 2827–2831

 

    2.Organic electroluminescence characterized on nanometer scales

Organic electroluminescence (EL) is a novel technology that is finding applications, e.g., in TV screens, with expectations for further use in various nanotechnologies. Our research concerns nanoscale characterization of the phenomenon by measuring EL from single molecules of organometallic complexes, single chains of conjugated polymers or single nanocrystals of halide perovskites.


Y. Honmou, S. Hirata, H. Komiyama, J. Hiyoshi, S. Kawauchi, T. Iyoda, M. Vacha, Nature Commun. 5 (2014) 4666
B. X. Dong, Y. Honmou, H. Komiyama, S. Furumaki, T. Iyoda and M. Vacha, Macromol. Rapid Commun. 34 (2013) 492-497
Y. Sekiguchi, S. Habuchi and M. Vacha, ChemPhysChem 10 (2009) 1195-1198

 

    3.Semiconducting quantum dots and perovskite nanocrystals

Semiconducting quantum dots (QD) and halide perovskite nanocrystals are emerging as alternative light-emitting materials for displays, lasers, lightning or bioimaging, and search is going on for non-toxic efficient QD emitters with advanced functionalities. Our study of single QDs and single nanocrystals is indispensable in providing basic information on material properties such as emission spectra, size distributions, emission quantum yields, blinking, effects of environment, etc.


D. K. Sharma, S. Hirata, V. Biju and M. Vacha, ACS Nano 13 (2019) 624-632
T. Uematsu, K. Wajima, D. K. Sharma, S. Hirata, T. Yamamoto, T. Kameyama, M. Vacha, T. Torimoto, S. Kuwabata, NPG Asia Mater. 10 (2018) 713–726
D. K. Sharma, S. Hirata, L. Bujak, V. Biju, T. Kameyama, M. Kishi, T. Torimoto, M. Vacha, Nanoscale 8 (2016) 13687-13694

 

    4.Exciton diffusion and light upconversion

Nanoscale characterization by optical microscopy is not restricted to single-molecule imaging and spectroscopy but can be used also to visualize, e.g., exciton diffusion in molecular solids. In our research we concentrate mainly on triplet exciton diffusion and on the related process of triplet-triplet annihilation which can lead to the phenomenon of photon upconversion. Upconversion transforms low-energy light into light of higher energy, and as such is raising hopes for improved efficiency of solar cells or artificial photosynthesis.


K. Narushima, Y. Kiyota, T. Mori, S. Hirata and M. Vacha, Adv. Mater. 31 (2019) 1807268
K. Kamada, Y. Sakagami, T. Mizokuro, Y. Fujiwara, K. Kobayashi, K. Narushima, S. Hirata, M. Vacha, Materials Horizons 4 (2017) 83-87
K. Narushima, S. Hirata, M. Vacha, Nanoscale 9 (2017) 10653-10661

 

    5.Structure and function of photosynthetic proteins and their artificial analogues

The ability of single-molecule spectroscopy to unmask heterogeneous static and dynamic features that are otherwise hidden in large ensembles is especially important in studying complex biological systems. We have been applying the method to a variety of problems in photosynthetic proteins, ranging from reaction centers to large bacterial light-harvesting complexes.


S. Hatazaki, D. K. Sharma, S. Hirata, K. Nose, T. Iyoda, A. Kölsch, H. Lokstein and M. Vacha, J. Phys. Chem. Lett. 9 (2018) 6669-6675
S. Furumaki, F. Vacha, S. Hirata, M. Vacha, ACS Nano 8 (2014) 2176-2182
S. Furumaki, F. Vacha, S. Habuchi, Y. Tsukatani, D.A. Bryant and M. Vacha, J. Am. Chem. Soc. 133 (2011) 6703–6710

 

    6.Plasmon enhanced molecular photophysics

Interaction of a noble-metal nanoparticle with an organic fluorophore in its vicinity can radically influence the molecular photophysical properties via the effect of localized plasmon. We have been exploring this effect mainly by studying enhancement and control of resonant excited energy transfer. The ability to control actively the energy transfer process may find important roles in light-harvesting applications or imaging.


L. Bujak, K. Narushima, D. K. Sharma, S. Hirata, M. Vacha, J. Phys. Chem. C 121 (2017) 25479-25486
L. Bujak, T. Ishii, D. K. Sharma, S. Hirata, M. Vacha, Nanoscale 9 (2017) 1511-1519

 

    7.Nanoscale relaxation and diffusion in polymers and soft matter

Physical properties of polymers such as glass transition temperature and the related relaxation processes can change dramatically when the size of objects is reduced to nanometer scales, yet the molecular mechanisms behind many such changes are largely unknown. We use fluorescence probes of single dye molecules doped into various systems (polymer films and solutions, elastomers, liquid crystals) and study their 3D nanometer-scale properties by measuring the probe reorientations and diffusion.


S. Lee, K. Noda, S. Hirata, M. Vacha, J. Phys. Chem. Lett. 6 (2015) 1403−1407
T. Oba and M. Vacha, ACS Macro Lett. 1 (2012) 784-788
S. Habuchi, N. Sato, T. Yamamoto, Y. Tezuka and M. Vacha, Angew. Chem. Int. Ed. 49 (2010) 1418-1421

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