• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.260-275
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• 2018

The corrosion inhibition of cast iron in 1 M HCl by Phenanthroline (Phen) was investigated using potentiodynamic polarization (PDP) curves, electrochemical impedance spectroscopy (EIS), surface analysis and theoretical calculations. It is found that Phen exhibits high inhibition activity towards the corrosive action of HCl and its adsorption obeys the Langmuir adsorption isotherm model. The results showed that inhibition efficiency increases with Phen concentration up to a maximum value of 96% at 1.4 mM, and decreases slightly with the increase in temperature. The free adsorption energy value indicates that Phen adsorbs on cast iron surface in 1 M HCl via a simultaneous physisorption and chemisorption mechanism. Scanning electron microscopy (SEM) micrographs, atomic force microscopy (AFM) and FTIR analysis confirmed the formation of a protective film on cast iron surface, resulting in the improvement of its corrosion resistance in the studied aggressive solution. Quantum chemical calculations at the DFT level were achieved to correlate electronic structure parameters of Phen molecules with their adsorption mode.

• Corrosion Science and Technology
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• 제22권2호
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• pp.73-89
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• 2023

Due to continuous promotion of green alternatives to toxic petrochemicals by government policies, research efforts towards the development of green corrosion inhibitors have intensified recently. The objective of the current work was to develop novel green and sustainable corrosion inhibitors derived from 4-aminoantipyrine to effectively prevent corrosion of mild steel in corrosive environments. Gravimetric methods were used to investigate corrosion inhibition of 4-((furan-2-ylmethylene)amino)antipyrine (FAP) and 4-((pyridin-2-ylmethylene)amino)antipyrine (PAP) for mild steel in 1 M HCl. FAP and PAP were subjected to quantum chemical calculations using density functional theory (DFT). DFT was used to determine the mechanism of mild steel corrosion inhibition using inhibitors tested in HCl. Results demonstrated that these tested inhibitors could effectively inhibit mild steel corrosion in 1.0 M HCl. At 0.0005 M, these inhibitors' efficiencies for FAP and PAP were 93.3% and 96.5%, respectively. The Langmuir adsorption isotherm was obeyed by these inhibitors on the mild steel surface. Values of adsorption free energies, ΔG^o_ads, revealed that FAP followed chemical and physical adsorptions.

• 광물과 암석
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• 제36권4호
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• pp.355-363
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• 2023

지구물질에 존재하는 안정 동위원소의 평형상태에서의 분화(equilibrium isotope fractionation of stable isotope)는 물질의 진동 특성(vibrational properties)에 기인하며, 지구물질이 지구시스템 내에서 겪는 다양한 지질학적 과정들을 정량적으로 이해하는 데 도움을 준다. 본 연구에서는 H₂O 분자의 clumped 동위원소의 특성을 양자화학계산을 이용하여 규명하였다. 특히, 산소 동위원소(¹⁶O, ¹⁷O, ¹⁸O)와 수소 동위원소(수소, 중수소, 삼중수소)의 조합으로 구성된 H₂O 분자에 대한 산소와 수소 동위원소간의 clumping 세기를 정량적으로 계산하고, 온도 변화에 따른 clumping 세기 변화 패턴을 분석하였다. 최적화된 분자구조의 평형 결합길이(bond length)와 결합각(bond angle)은 분자의 질량수와 무관하며, 각각 0.9631-0.9633 Å과 104.59-104.62°로 일정하였다. H₂O 분자의 3개의 진동 모드의 진동수는 동위원소 질량수가 증가함에 따라 감소하였으며, 산소보다 수소 동위원소의 변화에 더 큰 영향을 받는다. 진동수를 바탕으로 계산된 동위원소 치환반응의 평형상수 또한 수소 동위원소 질량수에 따라 더 큰 변화 양상을 보인다. 무거운 동위원소 조합의 clumping 반응의 평형상수는 로그값에서 강한 선형 상관관계를 지시한다. 세 동위원소 조합의 상대적인 clumping 강도는 HD¹⁸O에 대하여 각각 1.86배(HT¹⁸O), 1.16배(HT¹⁷O), 0.703배(HD¹⁷O)로 나타났다. Clumping의 세기인 Δ₂₁ 값은 온도의 증가에 따라 감소하며 이차 상관관계를 보인다. 이는 Δ₂₁이 온도 환경 지시자로서 이용될 가능성이 있음을 지시한다. 본 계산 결과는 ¹⁷O와 삼중수소를 포함한 clumped 동위원소 분배의 경향을 최초로 정립한 연구이다. 향후, 자연계에서 산소-수소 동위원소 조성의 기원을 보다 정량적으로 이해하기 위하여 비조화적(anharmonicity) 진동이 고려된 동위원소 분배계수의 계산 또한 필요하다. 상기한 연구 결과는 H₂O 분자의 다양한 지표환경에서의 clumped 동위원소의 측정과 이를 기반으로 한 지질환경 변화 기작을 설명하는 데 사용될 것으로 기대한다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.564-570
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• 2012

s-Tetrazine is the essential candidate of many energetic compounds due to its high nitrogen content, enthalpy of formation and thermal stability. The present study explores the design of s-tetrazine derivatives in which different $-NO_2$, $-NH_2$ and $-N_3$ substituted azoles are attached to the tetrazine ring via C-N linkage. The density functional theory (DFT) is used to predict the geometries, heats of formation (HOFs) and other energetic properties. The predicted results show that azide group plays a very important role in increasing HOF values of the s-tetrazine derivatives. The densities for designed molecules were predicted by using the crystal packing calculations. The introduction of $-NO_2$ group improves the density as compared to $-N_3$, and $-NH_2$ groups and hence the detonation performance. Bond dissociation energy analysis and insensitivity correlations revealed that amino derivatives are better candidates considering insensitivity and stability.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2093-2098
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• 2013

Density functional theory (DFT) was used to determine the ground state geometries of indigo and new design dyes (IM-Dye-1 IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. All the calculations were performed in both gas and solvent phase. The LUMO energies of all the dyes were above the conduction band of $TiO_2$, while the HOMOs were below the redox couple (except IM-Dye-3). The HOMO-LUMO energy gaps of new design dyes were smaller as compared to indigo. All new design dyes were strongly red shifted as compared to indigo. The improved light harvesting efficiency (LHE) and free energy change of electron injection ${\Delta}G^{inject}$ of new designed sensitizers revealed that these materials would be excellent sensitizers. The broken coplanarity between the benzene near anchoring group having LUMO and the last benzene attached to TPA unit in all new design dyes consequently would hamper the recombination reaction. This theoretical designing will the pave way for experimentalists to synthesize the efficient sensitizers for solar cells.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2588-2592
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• 2010

The potential energy surfaces (PESs) for the primary and secondary dissociations of the phenylarsane molecular ion (1a) were determined from the quantum chemical calculations using the G3(MP2)//B3LYP method. Several pathways for the loss of $H{\cdot}$ were determined and occurred though rearrangements as well as through direct bond cleavages. The kinetic analysis based on the PES for the primary dissociation showed that the loss of $H_2$ was more favored than the loss of $H{\cdot}$, but the $H{\cdot}$. loss competed with the $H_2$ loss at high energies. The bicyclic isomer, 7-arsa-norcaradiene radical cation, was formed through the 1,2 shift of an $\alpha$-H of 1a and played an important role as an intermediate for the further rearrangements in the loss of $H{\cdot}$ and the losses of $As{\cdot}$ and AsH. The reaction pathways for the formation of the major products in the secondary dissociations of $[M-H]^+$ and $[M-H_2]^{+\cdot}$. were examined. The theoretical prediction explained the previous experimental results for the dissociation at high energies but not the dissociation at low energies.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2345-2350
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• 2009

As part of an effort to discover bioactive natural products from marine sources, we investigated the bioactive secondary metabolites from two marine isolates of the fungi, Trichoderma viride and Rhizopus stolonifer. Three cyclopentenones, myrothenones A (1) and B (2) and trichodenone A (3), were isolated from T. viride and two cyclopentenones, 2-bromomyrothenone B (4) and botrytinone (5), were isolated from R. stolonifer. The molecular structures and absolute stereochemistries of the cyclopentenones were determined from chemical and physicochemical evidence, including quantum chemistry calculations, X-ray analysis, and the circular dichroism (CD) exciton chirality method. Myrothenone A (1) displays tyrosinase inhibitory activity, with an I$C_{50}$ value of 6.6 ${\mu}M$, and is therefore more active than the positive control, kojic acid.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.243-243
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• 2012

Self-assembled monolayers (SAMs) prepared by aromatic thiols on gold surfaces have much larger potential for electronic device applications due to their electronic properties. In this study, the formation and structures of SAMs prepared by benzenethiol (BT), toluenethiol (TT), 2-fluorobenzenethiol (2-FBT), 3-fluorobenzenethiol (3-FBT), 4-fluorobenzenethiol (4-FBT), 4-chlorobenzenethiol (4-CBT), 4-fluorobenzenemethanethiol (4-FBMT), and 4-chlorobenzenemethanethiol (4-CBMT) on Au(111) were examined using scanning tunneling microscopy (STM) and Kelvin probe (KP) to explore the structure and electronic interface properties of eight differently substituted aromatic thiol SAMs on Au(111). And these values are compared with gas phase dipole moments computed by quantum chemical calculations for individual thiol molecules. It was revealed that all eight thiol-molecules form uniform SAMs on Au(111) at $75^{\circ}C$ compared to lower solution temperature by STM observation. The work function change obtained in the KP measurements and calculated molecular dipole moments have the linear relationship while the 4-FBMT and 4-CBMT deviate from this tendency.

• Journal of Electrochemical Science and Technology
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• 제6권1호
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• pp.7-15
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• 2015

3-(4-Iodophenyl)-2-imino-2,3-dihydrobenzo[d]oxazol-5-yl 4-methylbenzenesulfonate (4-IPhOXTs) was synthesized and its inhibiting action on the corrosion of stainless steel 316L (SS) in sulfuric acid was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of the investigation show that this compound has excellent inhibiting properties for SS corrosion in sulfuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 4-IPhOXTs onto the SS surface followed the Langmuir adsorption model with the free energy of adsorption ΔG⁰_ads of −8.45 kJ mol⁻¹ . Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 4-IPhOXTs.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.365-376
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• 2021

Two arylamino substituted mercaptoimidazole derivatives namely 4,5-dimethyl-1-(phenylamino)-1H-imidazole-2(3H)-thione (I1) and 4,5- dimethyl-1-((p-chlorophenyl)amino)- 1H-imidazole-2(3H)-thione (I2) were synthesized and investigated as corrosion inhibitors for carbon steel in 0.5 M HCl solution by means of electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, ATR-FTIR spectroscopy and SEM. The results showed that the investigated mercaptoimidazole derivatives act as mixed type inhibitors and inhibition efficiency follows the I2>I1 order. Adsorption of inhibitors on metal surface was found to obey the Langmuir adsorption isotherm. Thermodynamic parameters revealed that adsorption of the inhibitors has both physisorption and chemisorption adsorption mechanism. Electrochemical test results were supported by quantum chemical parameters obtained from DFT calculations.