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Wang, Peili,Koo, Yun Hee,Kim, Woojae,Yang, Wenbo,Cui, Xiaoneng,Ji, Wei,Zhao, Jianzhang,Kim, Dongho American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.21
<P>A N<^>N Pt(II) complex, Pt-1, with two heteroleptic ligands was prepared, which is a rarely reported molecular structure. The two different acetylide ligands, i.e., boron-dipyyromethane (BDP) and naphthalenediimide (NDI) chromophores, show strong absorption in the visible region. The photophysical properties of the complex were investigated by using steady-state and femtosecond/nanosecond time resolved optical spectroscopies, as well as electrochemical characterization. Upon selective photoexcitation of the coordinated BDP acetylide ligand at 503 run, the Forster resonance energy transfer (FRET, k(FRET) = 1.2 x 10(11) s(-1)) process from the BDP to NDI ligand was observed, which leads to the population of the singlet excited state of the latter. After that, intersystem crossing (ISC) process occurs (k(ISC) = 3.3 X 10(9) s(-1)), which generates the triplet excited state of the NDI ligand (tau = 28.1 mu s). The overall excited-state dynamics are fairly similar in both nonpolar toluene and polar benzonitrile, indicating that photoinduced charge separation dynamics between BDP and NDI is insignificant. This is presumably due to the strong interaction between the NDI ligand and central Pt atom which can give rise to strong spin-orbit coupling. This hypothesis can be further supported by the excited-state dynamics obtained after photoexcitation at the S-2 state of the NDI ligand. The ultrafast ISC from the S-2 state of the NDI ligand to a higher triplet state, which corresponds to the breakdown of the Kasha-Vavilov's rule, was observed, suggesting that the NDI core strongly interacts with the heavy Pt atom. Finally, we identified that this broadband visible light-excitable Pt(II) complex can be used as a triplet photosensitizer for two-color excitable triplet-triplet annihilation upconversion, and the upconversion quantum yield was determined as 4.1%.</P>
Stable 2D anti-ferromagnetically coupled fluorenyl radical dendrons
Wang, Jian,Kim, Gakhyun,Sandoval-Salinas, Marí,a Eugenia,Phan, Hoa,Gopalakrishna, Tullimilli Y.,Lu, Xuefeng,Casanova, David,Kim, Dongho,Wu, Jishan Royal Society of Chemistry 2018 Chemical Science Vol.9 No.13
<▼1><P>The first class of stable two-dimensional anti-ferromagnetically coupled dendritic polyradicaloids was synthesized, which show polyradical character and unique properties.</P></▼1><▼2><P>We report the first class of stable, two-dimensional (2D) anti-ferromagnetically coupled dendritic polyradicaloids. A kinetically blocked fluorenyl radical was used to build up the first and second generation dendrons <B>FR-G1</B> and <B>FR-G2</B> containing three and seven fluorenyl units, respectively. The neighboring fluorenyl radicals in <B>FR-G1</B> and <B>FR-G2</B> show moderate anti-ferromagnetic exchange interaction, resulting in a doublet and quartet ground state, respectively, with a small doublet–quartet energy gap. From <B>FR-G1</B> to <B>FR-G2</B>, the energy gap decreased and the two-photon absorption was enhanced owing to more extended 2D π-conjugation. Both compounds showed multiple redox waves due to their polyradical character.</P></▼2>
Zhang, Yuehong,Oh, Juwon,Wang, Kang,Shin, Dongju,Zhan, Xiaopeng,Zheng, Yingting,Kim, Dongho,Jiang, Jianzhuang The Royal Society of Chemistry 2016 Chemical communications Vol.52 No.69
<P>Porphyrin and subphthalocyaninatoboron(III) chromophores have been fused through a quinoxaline moiety, resulting in the first porphyrin-subphthalocyaninatoboron(III)-fused hybrid with intramolecular charge transfer from tetrapyrrole/tripyrrole chromophores to the quinoxaline moiety. The unique plane-bowl molecular structure of this hybrid was revealed based on single crystal X-ray diffraction analysis for the first time.</P>
Study on Treatment Planning for the Prostate in Proton Therapy with Oxygen Enhancement Ratio Effect
Yoo Seung Hoon,Geng Hui,Lam Wai Wang,Kong Chi Wah,Yang Bin,Chiu Tin Lok,Wu Po Man,Cheung Kin Yin,Yu Siu Ki,Shin Dongho,Min Byung Jun 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.7
The purpose of this study was to investigate the oxygen enhancement ratio (OER) effects on treatment planning for a hypoxic prostate tumor with proton scanning beams. Two different OER-based dose calculation models (the average model and the voxel model) were investigated by using hypoxic tumor models in this simulation study. For the hypoxic tumor model, an oxygen distribution with a range of 2.4-9.4 mmHg was used according to the clinical data. The results given by the average model and the voxel model were compared for 50% and 90% tumor control probabilities with variations in the hypoxic tumor volume and fractionation. Comparison between the treatment plans with OER-based higher predicted dose and with the conventional prescription dose was conducted to investigate the organ-at-risk (OAR) doses for the prostate case. The average model showed a higher calculated dose than the voxel model. The voxel model with a 50% control probability showed good agreement with the current prescription dose. The OER values of the average model ranged from 1.05 to 1.25, which were applied to the whole tumor volume in treatment planning. The voxel-model-based OERs were higher (1.50-1.75) than those of average model, and these OERs should be applied only for the hypoxic boost region. Regarding treatment plans, the doses of the rectum and the bladder were reduced to the tolerable range V80Gy (volume receiving equal to or greater than 80Gy) < 15% and V75Gy (volume receiving equal to or greater than 75Gy) < 15% respectively after an optimization, but the maximum dose to femoral heads was higher than 50 Gy. In conclusion, we investigated the possible ranges of the OER (1.3-1.8) for proton-beam treatment of prostate cases. A dose escalation of up to about 1.8 times can be applied for the small hypoxic region. This result, which was obtained using a model study, should be verified through clinical experiment.
Cai, Hao,Fujimoto, Keisuke,Lim, Jong Min,Wang, Chaojie,Huang, Weiming,Rao, Yutao,Zhang, Senmiao,Shi, Hui,Yin, Bangshao,Chen, Bo,Ma, Ming,Song, Jianxin,Kim, Dongho,Osuka, Atsuhiro WILEY‐VCH Verlag 2014 Angewandte Chemie Vol.126 No.41
<P><B>Abstract</B></P><P>Direct β‐to‐β linked branched and cyclic porphyrin trimers and pentamers have been synthesized by the Suzuki–Miyaura coupling of β‐borylporphyrins and β‐bromoporphyrins. The cyclic porphyrin trimer, the smallest directly linked cyclic porphyrin wheel to date, and its twined pentamer, exhibit small electrochemical HOMO–LUMO gaps, broad nonsplit Soret bands, and red‐shifted Q‐bands, thus indicating large electronic interactions between the constituent porphyrin units.</P>
Razi, Syed S.,Koo, Yun Hee,Kim, Woojae,Yang, Wenbo,Wang, Zhijia,Gobeze, Habtom,D’Souza, Francis,Zhao, Jianzhang,Kim, Dongho American Chemical Society 2018 Inorganic Chemistry Vol.57 No.9
<P>A boron dipyrromethane (BDP)-containing Pt(II)-Schiff base complex (<B>Pt-BDP</B>), showing ping-pong singlet-triplet energy transfer, was synthesized, and the detailed photophysical properties were investigated using various steady-state and time-resolved transient spectroscopies. Femtosecond/nanosecond transient absorption spectroscopies demonstrated that, upon selective excitation of the BDP unit in <B>Pt-BDP</B> at 490 nm, Förster resonance energy transfer from the BDP unit to the Pt(II) coordination center occurred (6.7 ps), accompanied by an ultrafast intersystem crossing at the Pt(II) coordination center (<1 ps) and triplet-triplet energy transfer back to the BDP moiety (148 ps). These processes generated a triplet state localized at BDP, and the lifetime was 103.2 μs, much longer than the triplet-state lifetime of <B>Pt-Ph</B> (3.5 μs), a complex without the BDP moiety. Finally, <B>Pt-BDP</B> was used as a triplet photosensitizer for triplet-triplet annihilation (TTA) upconversion through selective excitation of the BDP unit or the Pt(II) coordination center at lower excitation energy. An upconversion quantum yield of up to 10% was observed with selective excitation of the BDP moiety, and a large anti-Stokes shift of 0.65 eV was observed upon excitation of the lower-energy band of the Pt(II) coordination center. We propose that using triplet photosensitizers with the ping-pong energy-transfer process may become a useful method for increasing the anti-Stokes shift of TTA upconversion.</P><P>BDP was attached on the Pt(II)−Schiff base framework. Forward singlet energy transfer (6.7 ps) occurs from BDP to the Pt(II) coordination center, followed by backward triplet energy transfer (148 ps). The T<SUB>1</SUB> state is on BDP (103.2 μs; parent complex, 3.5 μs). The anti-Stokes shift of triplet−triplet annihilation (TTA) upconversion increased to 5290 cm<SUP>−1</SUP> with excitation into the BDP moiety compared to direct excitation into the Pt(II) center (2660 cm<SUP>−1</SUP>). The TTA upconversion quantum yield is up to 10%.</P> [FIG OMISSION]</BR>
Distances between Rats in Reverberation Chambers Used for Large-Scale Experiments
Sangbong Jeon,Wook Jang,Ae-Kyoung Lee,Hyung-Do Choi,Jeong-Ki Pack,Jianqing Wang,Dongho Kim 한국전자파학회JEES 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.2
We investigate the whole-body average specific absorption rate (WBA-SAR) of rats under various plane wave exposure characteristics, including different polarizations, incidence angles, distances between rats, and total number of rats. Unlike many other studies, we start our SAR analysis from one rat and expand it to 27 rats facing random directions in a three-dimensional area. In a one-rat analysis, we examine how the incidence direction and polarization affect the SAR of a single rat. Moreover, we look into how various incidence polarizations behave differently after they are transmited through a rat, the information of which is then used to analyze the effect of spacing among 27 randomly arranged rats. Next, we analyze the effect on spacing of the 27 rats deployed under a 52-plane-wave exposure, which is introduced to mimic a realistic reverberation chamber (RC) environment. We show the deviation in WBA-SAR according to the distance between rats, which provides guidelines for selecting the appropriate rat distance based on the number of animals and the exposure deviation within a limited working volume in an RC for large-scale experiments.