• Advances in nano research
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• 제12권1호
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• pp.25-35
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• 2022

Within the framework of the density functional theory combined with the method of non-equilibrium Green's functions (DFT + NEGF), the features of electron transport in fullerene nanojunctions, which are «core-shell» nanoobjects made of a combination of fullerenes of different diameters C₂₀, C₈₀, C₁₈₀, placed between gold electrodes (in a nanogap), are studied. Their transmission spectra, the density of state, current-voltage characteristics and differential conductivity are determined. It was shown that in the energy range of -0.45-0.45 eV in the transmission spectrum of the "Au-C₁₈₀-Au" nanojunction appears a HOMO-LUMO gap with a width of 0.9 eV; when small-sized fullerenes C₂₀, C₈₀ are intercalation into the cavity C₁₈₀ the gap disappears, and a series of resonant structures are observed on their spectra. It has been established that distinct Coulomb steps appear on the current-voltage characteristics of the "Au-C₁₈₀-Au" nanojunction, but on the current-voltage characteristics "Au-C₈₀@C₁₈₀-Au", "Au-(C₂₀@C₈₀)@C₁₈₀-Au" these step structures are blurred due to a decrease in Coulomb energy. An increase in the number of Coulomb features on the dI/dV spectra of core-shell fullerene nanojunctions was revealed in comparison with nanojunctions based on fullerene C₆₀, which makes it possible to create high-speed single-electron devices on their basis. Models of single-electron transistors (SET) based on fullerene nanojunctions "Au-C₁₈₀-Au", "Au-C₈₀@C₁₈₀-Au" and "Au-(C₂₀@C₈₀)@C₁₈₀-Au" are considered. Their charge stability diagrams are analyzed and it is shown that SET based on C₈₀@C₁₈₀-, (C₂₀@C₈₀)@C₁₈₀- nanojunctions is output from the Coulomb blockade mode with the lowest drain-to-source voltage.

• 공업화학
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• 제19권3호
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• pp.299-303
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• 2008

열경화가 가능한 PPV유도체인 poly[(2,5-dimethoxy-1,4-phenylenevinylene)-alt-(1,4-phenylenevinylene)] (Cross-PPV)를 Heck coupling 반응을 이용하여 합성하였다. Cross-PPV 박막은 $200^{\circ}C$에서 경화 시키면 일반적인 유기용매에 용해되지 않는 불용성의 고분자 박막이 된다. 열경화 전 후의 Cross-PPV의 구조는 FT-IR로 확인하였으며 구조의 차이는 크지 않았다. 경화된 Cross-PPV는 일반적인 유기용매에 대하여 내용매성이 강하다. 순환전압전류법과 흡수분광법으로 측정한 경화된 Cross-PPV의 호모 및 루모 에너지 준위는 각각 -5.11 eV와 -2.56 eV으로 ITO로 부터의 정공주입장벽(hole injection barrier)이 작아(약 0.1 eV) 정공주입층으로 효과적으로 사용 할 수 있다. 호모 및 루모 에너지 준위가 각각 -5.44 eV, -3.48 eV인 poly(1,4-phenylenevinylene-(4-dicyanomethylene-4H-pyran)-2,6-vinylene-1,4-phenylene-vinylene-2,5-bis(dodecyloxy)-1,4-phenylenevinylene) (PM-PPV)을 발광층으로 사용하여 두층의 구조(bilayer structure)를 갖는 소자(ITO/crosslinked Cross-PPV/PM-PPV/Al)를 제작, 특성을 평가한 결과 최대 효율은 0.024 cd/A, 최대 발광세기는 $45cd/m^2$으로 단층형 소자(ITO/PM-PPV/Al)(최대 효율 = 0.003 cd/A, 최대 발광세기 = $3cd/m^2$)에 비하여 매우 월등한 성능을 나타냄을 확인하였다. 또한 두층의 구조를 가지는 다층형 소자의 발광스펙트럼은 단층형 소자의 발광 스펙트럼과 동일하다. 이러한 사실들로 보아 ITO 및 Al에서 주입된 전자는 모두 발광층인 PM-PPV층에서 재결합(recombination)되어 여기자(exciton)가 형성되는 것으로 사료된다.

• 공업화학
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• 제22권1호
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• pp.15-20
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• 2011

2,3-Dimethyl-5,8-dithiophen-2-yl-quinoxaline을 기본 골격으로 한 poly[2,3-dimethyl-5,8-dithiophene-2-yl-quinoxaline-alt-9,9-dihexyl-9H-fluorene] (PFTQT)과 poly[2,3-dimethyl-5,8-dithiophene-2-yl-quinoxaline-alt-10-hexyl-10H-phenothiazine] (PPTTQT)을 Suzuki coupling법을 이용하여 중합 하였다. 합성된 고분자들은 chloroform, chlorobenzene, o-dichlorobenzene, tetrahydrofuran (THF), toluene과 같은 유기용매에 대한 용해도가 우수하였고, PFTQT의 최대흡수파장과 밴드 갭은 각각 440 nm와 2.30 eV이고, PPTTQT의 경우는 각각 445 nm와 2.23 eV이었다. PFTQT의 HOMO 및 LUMO 에너지준위는 -6.05와 -3.75 eV이고, PPTTQT의 경우는 각각 -5.89와 -3.66 eV이었다. 합성된 고분자들과 전자 받개 물질인 (6)-1-(3-(methoxycarbonyl)-{5}-1-phenyl[5,6]-fullerene (PCBM)을 1 : 2의 중량비로 블렌딩하여 제작한 태양전지의 효율은 AM (air mass) 1.5 G, 1 sun 조건($100mA/cm^2$)에서 PFTQT는 0.24%, PPTTQT의 경우는 0.16%로 측정되었다. 그리고 소자의 단락전류 밀도($J_{sc}$), FF (fill factor)와 개방전압($V_{oc}$)은 PFTQT의 경우 각각 $0.97mA/cm^2$, 29%, 0.86 V이며, PPTTQT의 경우 각각 $0.80mA/cm^2$, 28%, 0.71 V이었다.

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1405-1417
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• 2006

The geometrical structures, potential energy surfaces, and energetics for the ligand exchange reactions of tetracoordinated platinum $(PtY_2L_2\;:\;Y,\;L=Cl^-,\;OH^-,\;OH_2,\;NH_3)$ complexes in the ligand-solvent interaction systems were investigated using the ab initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The potential energy surfaces for the ligand exchange reactions used for the conversions of $(PtCl_4\;+\;H_2O)^{^\ast_\ast}\;to\;[PtCl_3(H_2O)\;+\;Cl^-]$ and $[Pt(NH_3)_2Cl_2\;+\;H_2O]$$[Pt(NH_3)_2Cl_2\;+\;H_2O]$ to $[Pt(NH_3)_2Cl(H_2O)\;+\;Cl^-] $ were investigated in detail. For these two exchange reactions, the transition states $([PtY_2L_2{\cdot}{\cdot}{\cdot}L^\prime])^{^\ast_\ast} $ correspond to complexes such as $(PtCl_4{\cdot}{\cdot}{\cdot}H_2O)^{^\ast_\ast}$ and $[Pt(NH_3)_2Cl_2{\cdot}{\cdot}{\cdot}H_2O]^{^\ast_\ast}$, respectively. In the transition state, $([PtCl_4{\cdot}{\cdot}{\cdot}H_2O]^{^\ast_\ast}$ and $[Pt(NH_3)_2Cl_2{\cdot}{\cdot}{\cdot}H_2O]]^{^\ast_\ast})$ have a kind of 6-membered $(Pt-Cl{\cdot}{\cdot}{\cdot}HOH{\cdot}{\cdot}{\cdot}Cl)$ and $(Pt-OH{\cdot}{\cdot}{\cdot}Cl{\cdot}{\cdot}{\cdot}HN)$ interactions, respectively, wherein a central Pt(II) metal directly combines with a leaving $Cl^-$ and an entering $H_2O$. Simultaneously, the entering $H_2O$ interacts with a leaving $Cl^-$. No vertical one metal-ligand interactions $([PtY_2L_2{\cdot}{\cdot}{\cdot}L^\prime]) $ are found at the axial positions of the square planar $(PtY_2L_2)$ complexes, which were formed via a vertically associative mechanism leading to $D_{3h}$ or $C_{2v}$-transition state symmetry. The geometrical structure variations, molecular orbital variations (HOMO and LUMO), and relative stabilities for the ligand exchange processes are also examined quantitatively. Schematic diagrams for the dissociation reactions of {PtCl4(H2O)n(n=2,4)} into {$PtCl_3(H_2O)_{(n-2)}\;+\;Cl^-(H_2O)_2$} and the binding energies {$PtCl_4(H_2O)_n$(n = 1-5)} of $PtCl_4$ with water molecules are drawn.

• 농약과학회지
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• 제7권1호
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• pp.58-65
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• 2003

농업용 약물로서의 활용성 진단과 예측을 위한 기초 자료로서 상용화 된 제초제와 같은 분자량을 가지는 의약 각 245 종에 대한 10 가지의 물리 -화학 파라미터들을 계산하고 제초제와 광합성 (PS-II) 저해제 및 acetolactase synthase (ALS) 저해제들의 특정한 물리-화학 파라미터들에 대한 수치 범위를 비교 검토하였다. 제초제들의 특정 물리-화학 파라미터에 대한 85% 의존적 수치 범위는 소수성 상수 (Obs. logP): $-0.90\sim4.50$, 쌍극자 능율 (DM): $1.80\sim12.22$ Debye, van der Waals 분자부피 (Vol.); $558\sim995Cm^3$ 및 표면적 (S.Area): $194\sim356\;{\AA}^2$, molar refractivity (MR): $53\sim104Cm^3/mol$., 분극율 (Pol): $19\sim37\;{\AA}^3$, 분자량 : $202\sim430(amu)$, 및 수화 에너지 (Hy.E): $-10.16\sim114.7$ Kcal/mol 등 이었다. 그리고 작용 기작에 따라 물리-화학파라미터의 범위값을 특징적으로 나타내고 있음을 알았으며 MR 상수와 분극율은 의약과 제초제 (ALS 저해제)를 구분하는 판별 가능한 요소가 될 것으로 예상되었다.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.139-147
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• 2008

New PPV derivatives which contain electron-withdrawing CF3F4phenyl group, poly[2-(2-ethylhexyloxy)-5-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)-1,4-phenylenevinylene] (CF3F4P-PPV), and poly[2-(4-(2-etylhexyloxy)-phenyl)-5-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)-1,4-phenylenevinylene] (P-CF3F4P-PPV), have been synthesized by GILCH polymerization. As the result of the introduction of the electron-withdrawing CF3F4phenyl group to the phenyl backbone, the LUMO and HOMO energy levels of CF3F4P-PPV (3.14, 5.50 eV) and P-CF3F4P-PPV (3.07, 5.60 eV) were reduced. The PL emission spectra in solid thin film are more red-shifted over 50 nm and increased fwhm (full width at half maximum) than solution conditions by raising aggregation among polymer backbone due to electron withdrawing effect of 2,3,5,6-tetrafluoro-4-trifluoromethylphenyl group. The EL emission maxima of CF3F4P-PPV and P-CF3F4P-PPV appear at around 530-543 nm. The current density-voltage-luminescence (J-V-L) characteristics of ITO/PEDOT/polymer/Al devices of CF3F4P-PPV and P-CF3F4P-PPV show that turn-on voltages are around 12.5 and 7.0 V, and the maximum brightness are about 82 and 598 cd/m2, respectively. The maximum EL efficiency of P-CF3F4P-PPV (0.51 cd/A) was higher than that of CF3F4P-PPV (0.025 cd/A).

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.417-423
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• 2011

A series of new quinoxaline-based thiophene copolymers (PQx2T, PQx4T, and PQx6T) was synthesized via Yamamoto and Stille coupling reactions. The $M_ws$ of PQx2T, PQx4T, and PQx6T were found to be 20,000, 12,000, and 29,000, with polydispersity indices of 2.0, 1.2, and 1.1, respectively. The UV-visible absorption spectra of the polymers showed two distinct absorption peaks in the ranges 350 - 460 nm and 560 - 600 nm, which arose from the ${\pi}-{\pi}^*$ transition of oligothiophene units and intramolecular charge transfer (ICT) between a quinoxaline acceptor and thiophene donor. The HOMO levels of the polymer ranged from -5.37 to -5.17 eV and the LUMO levels ranged from -3.67 to -3.45 eV. The electrochemical bandgaps of PQx2T, PQx4T, and PQx6T were 1.70, 1.71, and 1.72 eV, respectively, thus yielding low bandgap behavior. PQx2T, PQx4T, and PQx6T had open circuit voltages of 0.58, 0.42, and 0.47 V, and short circuit current densities of 2.9, 5.29 and 9.05 mA/$cm^2$, respectively, when $PC_{71}BM$ was used as an acceptor. For the solar cells with PQx2T-PQx6T:$PC_{71}BM$ (1:3) blends, an increase in performance was observed in going from PQx2T to PQx6T. The power conversion efficiencies of PQx2T, PQx4T, and PQx6T devices were found to be 0.69%, 0.73%, and 1.80% under AM 1.5 G (100 mW/$cm^2$) illumination.

• Applied Biological Chemistry
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• 제43권1호
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• pp.52-56
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• 2000

Fenoxaprop-ethyl계 화합물의 amide 형태인 일련의 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)-N-Phenylpropionamide 유도체 중 N-phenyl 고리상 X-치환체들이 변화함에 따른 구조와 수답에서 발아 전(pre)과 후(post), 벼(Oryza sativa L.)에 미치는 약해와의 관계(SAR)를 Free-Wilson 방법과 Hansch방법을 이용하여 정량적으로 검토하였다. 대체적으로 발아 전, 벼에 대한 약해는 N-phenyl 고리상 para-치환된 1 치환체들과 2,3,4-치환된 3 치환체로서 소수성의 적정값, $({\pi})_{opt}=0.91$을 가지는 전자밀게가 영향을 미친 반면에 발아 후에는 meta치환된 1 치환체들과 2,3-치환된 2 치환체로서 적정값(({\pi})_{opt}=0.5)$의 소수성을 갖는 fluoro, acetyl 및 carboxyl등, 주로 전자 끌게 들이 비교적 영향을 미쳤다. 그리고 기질물질은 발아 전 보다 발아 후의 벼에 대하여 더 큰 약해를 미치고 있슴을 알았다. SAR식에 따라 온실내에서 가장 약해를 별 나타내는 화합물은 2-methyl-3-methoxy-4-cyano치환체로 예상되었다. 그리고 가수분해 반응의 유형은 친핵성 첨가제거 $(Ad_{Nu-E})$ 반응에 따른 궤도조절 반응으로 진행되었으며 비(H) 치환체에 대한 분자 정전기 전위(MEP)에 대하여 검토하였다.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.505-512
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• 2014

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2889-2894
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• 2013

A new complex [$Ni(phen)(C_9H_8Br_2NO_3)_2{\cdot}2CH_3OH{\cdot}2H_2O$] [phen: 1,10-phenanthroline $C_9H_8Br_2NO_3$: 3,5-dibromo-L-tyrosine] was synthesized and characterized by IR, elemental analysis and single crystal X-ray diffraction. X-ray crystallography shows that Ni(II) ion is six-coordinated. The Ni(II) ion coordinates with four nitrogen atoms and two oxygen atoms from three ligands, forming a mononuclear Ni(II) complex. The crystal crystallizes in the Orthorhombic system, space group $P2_12_12$ with a = 12.9546 ${\AA}$, b = 14.9822 ${\AA}$, c = 9.9705 ${\AA}$, V = 1935.2 ${\AA}$, Z = 1, F(000) = 1008, S = 0.969, ${\rho}_{calcd}=1.742g{\cdot}cm^{-3}$, ${\mu}=4.688mm^{-1}$, $R_1$ = 0.0529 and $wR_2$ = 0.0738 for 3424 observed reflections (I > $2{\sigma}(I)$). Theoretical study of the title complex was carried out by density functional theory (DFT) method and the B3LYP method employing the $6-3l+G^*$ basis set. The energy gap between HOMO and LUMO indicates that this complex is prone to interact with DNA. CCDC: 908041.