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the Keio Research Highlights The website offers more details on this research and other recent research conducted by researchers from Keio University including the potential of molecular materials for the conversion of high efficiency solar energy by Taku Hasobe and his colleagues.
https://research-highlights.keio.ac.jp/
The measurement of the state of charge of atmospheric particles provides accurate data for the formulation of advanced models on the effects of particles on human health
According to the World Health Organization (WHO), inhalation of particles is one of the top ten risks to human health. In 2016, 4.2 million people died from airborne particles. With these alarming statistics, it is not surprising that more and more demands for air sensitization and monitoring for potentially lethal particles have emerged.
"Health risks related to the inhalation of particles smaller than 2.5 micrometers, called PM2.5, are well documented Environmental agencies monitor particulate levels and issue warnings to the public concerning the dangerous levels of PM2.5 in the air, "says an environmental specialist. Tomoaki Okuda, Associate Professor in the Department of Applied Chemistry, Keio University. However, recent reports indicate that individually charged particles are about six times more likely to be adsorbed by the airway than unfiltered particles.Thus, an accurate badessment of the effect of suspended particles on Human health requires a much deeper understanding of just particle size, but also their physico-chemical properties, including charge and surface structure.My research is focused on determining the state of charge. particles in the air that, surprisingly, are not well understood.
Okuda and his colleagues developed K-MACS (Fig. 1, Ref., [1,2]) as an inexpensive and versatile system for continuously separating and quantifying the state of charge of atmospheric particles ranging in size from 300 nm to 500 nm for short periods of time over a period of 12 months. "We have studied this range of particles because they have a higher concentration in the air," says Okuda. Measurements of these particles were taken at University of Keio Yagami Campus from April 2017 at February 2018.
The two main conclusions were that the state of charge of the atmospheric particles was different from the results of the theoretical studies carried out to date (Fig. 2), and that the state of charge of the particles fluctuated markedly in depending on changing atmospheric conditions (amount of water vapor and entrained air mbad). ) due to seasonal variations [3].
"These results offer new information on changes in the state of charge of particles," Okuda said. "They will play an important role in accurately badessing the effects of atmospheric particles on human health on a global scale."
Related searches Tomoaki Okuda
Okuda has performed a theoretical performance evaluation of a parallel plate particle separation instrument (K-MACS) designed to measure the state of charge of PM2.5 particles. The results gave optimal tension to maximize particle types [2]. This research addresses the issue of what happens to aerosol particles in humid conditions, such as haze. A model of discrete elements showed a correlation between the relative humidity and the amount of water contained in the particles that were found to be negatively or positively charged [4].
References
1. Tomoaki Okuda, Yuma Gunji & I.W. Lenggoro, Measurement of the electrostatic charge state of individual particles in an ambient aerosol by means of Kelvin probe force microscopy, Earozoru Kenkyu 30, 190-197 (2015) | article (in Japanese only)
https://doi.org/10.11203/jar.30.190
2. Takuto Yonemichi, Koji Fukagata, Kentaro Fujioka And Tomoaki Okuda, Numerical simulation of a parallel plate particle separator for the estimation of PM2.5 charge distribution, Aerosol Science and Technology (2019).
https://doi.org/10.1080/02786826.2019.1569198
3 Ayumi Iwata, et al., Seasonal variations of electrostatic charge states of atmospheric particles determined using a parallel electrode plate device, Atmospheric environment203, 62-69 (2019).
https://doi.org/10.1016/j.atmosenv.2019.01.040
4 Yuanping He et al., Atmospheric moisture and state of charge of particles during agglomeration of aerosol particles, Atmospheric environment197, 141-149 (2019).
https://doi.org/10.1016/j.atmosenv.2018.10.1035
Search for Taku Hasobe and his colleagues: Exciton Fission for High Efficiency Solar Power Conversion
Quantification of multi-exciton production for the conversion of solar energy into molecular materials
https://research-highlights.keio.ac.jp/2019/03/a.html
In molecular materials, the absorption of a photon can result in the formation of a singlet exciton – a state formed by an electron and a hole bound by their electrostatic attraction and opposite spins. In a process called singlet fission, the exciton singlet splits into two excitons of triplets, that is, two excitons in which the electron and the hole have their spins directed in the same direction . Excitons of triplets are initially strongly correlated, but they can be separated and the electrons they carry can then be transferred to other molecules.
This complex process is very promising for solar energy conversion applications because it offers the possibility of achieving very high power conversion efficiencies because the absorption of a photon single leads to the generation of multiple electrical charges (ie the production of several excitons). .
Singlet fission can occur within a single molecule in systems of two molecular units covalently linked by an organic bridge (the process in this case is called intramolecular fission singlet). This is advantageous because we can quantitatively evaluate photophysical processes and parameters such as kinetic constants and quantum yields. The singlet fission theoretically allows the execution of the sequential photoenergetic conversion process from the singlet state and leading to electron transfer with a quantum yield of the pair of radical ions approaching 200. %. However, the process of quantitative transfer to two electrons by singlet fission has not yet been reported.
Shunta Nakamura, Hayato Sakaiand Taku Hasobe's Keio University, with colleagues from Kobe University and University of Technology of Tempere (Finland) quantitatively characterized a sequential process involving intramolecular singlet fission and intermolecular transfer of two electrons using two tetracene-based molecules linked by a biphenyl unit (Tet-BP-Tet) as a singular fission system and a donor. Electrons and chloranil as an electron acceptor system.
Read more
https://research-highlights.keio.ac.jp/2019/03/a.html
Reference
Shunta Nakamura, Hayato Sakai, Hiroki Nagashima, Yasuhiro Kobori, Nikolai V. Tkachenkoand Taku Hasobe, Sequential photoenergetic quantitative conversion process from singlet fission to intermolecular two electron transfer using tetracene dimer. ACS Energy Letters 4, 26-31 (2019).
DOI: 10.1021 / acsenergylett.8b01964
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Keio University is a private and comprehensive university with six major campuses in the Greater Tokyo region and a number of affiliated university institutions. Keio is proud of the excellence of its teaching and research in a wide range of fields and its state-of-the-art teaching hospital.
Keio was founded in 1858, and it is From Japan first modern institution of higher education. Over the last century and a half, she has evolved to maintain her status as a leading university Japan through his ongoing commitment to training tomorrow's leaders. Founder Yukichi Fukuzawa, highly respected educator and one of the most important intellectuals of the modern world Japan, aspire to Keio to be a pioneer of new discoveries and contribute to society through learning.
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