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A Fundamental Understanding of Catechol and Water Adsorption on a Hydrophilic Silica Surface: Exploring the Underwater Adhesion Mechanism of Mussels on an Atomic Scale

Mian, Shabeer Ahmad,Yang, Li-Ming,Saha, Leton Chandra,Ahmed, E.,Ajmal, Muhammad,Ganz, Eric American Chemical Society 2014 Langmuir Vol.30 No.23
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Mussels have a remarkable ability to bond to solid surfaces under water. From a microscopic perspective, the first step of this process is the adsorption of dopa molecules to the solid surface. In fact, it is the catechol part of the dopa molecule that is interacting with the surface. These molecules are able to make reversible bonds to a wide range of materials, even underwater. Previous experimental and theoretical efforts have produced only a limited understanding of the mechanism and quantitative details of the competitive adsorption of catechol and water on hydrophilic silica surfaces. In this work, we uncover the nature of this competitive absorption by atomic scale modeling of water and catechol adsorbed at the geminal (001) silica surface using density functional theory calculations. We find that catechol molecules displace preadsorbed water molecules and bond directly on the silica surface. Using molecular dynamics simulations, we observe this process in detail. We also calculate the interaction force as a function of distance, and observe a maximum of 0.5 nN of attraction. The catechol has a binding energy of 23 kcal/mol onto the silica surface with adsorbed water molecules.Graphic Abstract <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-23/la500800f/production/images/medium/la-2014-00800f_0011.gif'><A href='http://pubs.acs.org/doi/suppl/10.1021/la500800f'>ACS Electronic Supporting Info</A>
2
이산 쌍극자 근사를 이용한 금-은 합금 나노입자의 소광 스펙트럼 계산

이희미,장준경,Lee, Hee-Mi,Chandra, Saha Leton,Jang, Joon-Kyung 대한화학회 2007 대한화학회지 Vol.51 No.2
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By using the discrete-dipole approximation, we computed the extinction spectrum of a gold-silver alloy nanoparticle. We have examined how the surface plasmon resonance changes with respect to the variation in the composition of the alloy particle. As the fraction of silver increases for a 10nm particle, the peak position of the extinction spectrum blue-shifts linearly. The intensity of the peak however increases exponentially with increasing the silver fraction. These results are in accord with the previous experimental results. 이산 쌍극자 근사를 이용하여 수용액상의 금-은 합금 나노입자의 표면 플라즈몬 공명 스펙트럼을 계산하였다. 직경 10 나노미터의 금-은 합금 입자의 경우에 스펙트럼의 최대 소광 파장이 합금의 은 성분이 높아짐에 따라 선형적으로 짧은 파장대로 이동하며 최대 소광 세기는 지수적으로 증가함을 관측하였다. 이러한 계산결과는 실험 결과들과 잘 일치하는 것을 확인하였다.
3
입자 크기 분포가 금 콜로이드의 광학성질에 미치는 영향에 대한 이론 연구

김효정,장준경,Kim, Hyo-Jeong,Saha Leton Chandra,Jang, Joon-Kyung 대한화학회 2007 대한화학회지 Vol.51 No.5
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  ScienceON
  
  KCI
크기 분포를 가진 금 나노 입자 콜로이드의 소광 스펙트럼을 미 이론으로 계산하고 실험과 비교하였다. 입자 크기 분포를 고려한 계산이 크기 분포를 고려하지 않은 계산보다 실험과 더 가까움을 확인하였다. 최소 자승법을 이용하여 실험에서 얻은 소광 스펙트럼으로부터 입자 크기 분포를 이론적으로 도출하였다. 이렇게 얻은 입자 크기는 입자 지름이 10에서 28 나노미터인 경우 투과전자현미경 분석 결과와 잘 일치하였다. Mie theory has been used to calculate the extinction of a gold nanoparticle in water by varying its diameter from 1 to 1000 nm. Utilizing this size-dependent theoretical spectrum, we have calculated the extinction spectrum of a colloidal gold by taking into account the size distribution of particle. Such calculation is in better agreement with experiment than the calculation without considering the size distribution. A least-squares fitting is used to deduce the size distribution from an experimental extinction spectrum. For particles with their diameters ranging from 10 to 28 nanometers, the fitting gives reasonable agreement with the size distribution obtained from tunneling electron microscope images.