@article{luo_bemelmans_pearl_2011, title={Unveiling Molecular Adsorption Geometry in Cyclohexanethiolate Self-Assembled Monolayers with Local Barrier Height Imaging}, volume={115}, ISSN={["1932-7447"]}, DOI={10.1021/jp205637f}, abstractNote={The Au–S interface of thiol-based, self-assembled monolayers grown on Au(111) surfaces is far less understood than it should be. Local barrier height imaging, which has recently resolved work function variations in the buried interface of alkanethiolate monolayers, is now used to study self-assembled monolayers on Au(111) formed by cyclohexanethiol, a molecule with a flexible aliphatic ring structure. Multiple ordered phases are observed, consistent with its conformational flexibility which makes multiple interadsorbate interactions possible. In one particular phase, the appearance of two readily distinguishable features in local barrier height images implies at least two types of adsorption sites. Correlation of simultaneously acquired topographic and local barrier height data allows for a preliminary structural model that accounts for adsorption geometry.}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Luo, Pengshun and Bemelmans, Norman L. and Pearl, Thomas P.}, year={2011}, month={Sep}, pages={17118–17122} }
 @article{santagata_lakhani_davis_luo_nardelli_pearl_2010, title={Chiral Steering of Molecular Organization in the Limit of Weak Adsorbate-Substrate Interactions: Enantiopure and Racemic Tartaric Acid Domains on Ag(111)}, volume={114}, ISSN={["1932-7447"]}, DOI={10.1021/jp912124v}, abstractNote={The influence of intermolecular interactions involving molecular chiral centers on two-dimensional organization in the limit of a weak adsorbate−surface interaction has been studied with low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT). A model system composed of a chiral organic molecule, tartaric acid, and an inert metallic surface, Ag(111), was employed. Dual component films formed from the serial deposition of (S,S)- and (R,R)-tartaric acid enantiomers onto this surface exhibit homochiral domain formation as revealed by molecularly resolved STM images. In contrast, a unique tartaric acid enantiomeric heteropair is experimentally and computationally verified as the basis unit of films formed via the deposition of both enantiomers simultaneously from a racemic (1:1) mixture. The molecular adsorption geometry relative to the Ag(111) lattice in both enantiomerically pure and racemic domains is determined primarily by the interaction of chiral centers between nearest ...}, number={19}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Santagata, Nancy M. and Lakhani, Amit M. and Davis, Bryce F. and Luo, Pengshun and Nardelli, Marco Buongiorno and Pearl, Thomas P.}, year={2010}, month={May}, pages={8917–8925} }
 @article{luo_bernelmans_woody_pearl_2009, title={Molecular Voids Formed from Effective Attraction in Submonolayer DNA Deposited on Au(111)}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la900470h}, abstractNote={The development of DNA-based biosensors requires a deep understanding of how DNA molecules adsorb and organize on solid state surfaces as well as the electronic properties of individual and aggregates of DNA molecules. Using scanning tunneling microscopy (STM) and atomic force microscopy (AFM), we have successfully characterized an attractive force driven molecular void formation for DNA chemically adsorbed on Au(111) as a function of strand length and deposition conditions. Here we report the observation of these void structures formed on the Au(111) surface by adsorption of both 45 and 90 base pair long, thiolated double-stranded DNA. We found that the average void diameter decreases when increasing the number of base pairs exposed to the surface. The critical determinant in the molecular void formation is the total charge delivered to the surface via the adsorption of the DNA strands and the related counterions, which can ultimately be quantified by the number of base pairs in each adsorbed DNA molecule. Complementary measurements involving STM and AFM suggest that an intact Au(111) surface area is preserved inside the void and is surrounded by a submonolayer of DNA molecules adsorbed on the surface. The discussion of the possible mechanisms for the void formation implies an effective attraction between the DNA molecules.}, number={14}, journal={LANGMUIR}, author={Luo, Pengshun and Bernelmans, Norman L. and Woody, Michael S. and Pearl, Thomas P.}, year={2009}, month={Jul}, pages={7995–8000} }
 @article{santagata_luo_lakhani_dewitt_day_norton_pearl_2008, title={Organizational structure and electronic decoupling of surface bound chiral domains and biomolecules}, volume={8}, ISSN={["1558-1748"]}, DOI={10.1109/JSEN.2008.923187}, abstractNote={For the development of reagentless biological and chemical species detection at the single molecule level using external fields, including terahertz radiation, it is paramount to study model systems that uncover how intermolecular and molecule-surface interactions dictate monolayer ordering and electronic properties. This paper addresses two types of molecule-surface interactions and two distinct molecular systems, both of which impact our fundamental understanding of confined molecular domains and single molecule detection. We will first discuss the ordering and electronic characteristics of a chiral molecule, tartaric acid , weakly bound to an achiral metal surface, Ag(111), as studied with low temperature scanning tunneling microscopy (STM). This particular molecule-surface system contains many key elements, including hydrogen bonding interactions and stereochemical features, that would be common to other functional detection schemes. This paper will also treat the characterization of isolated, thiolated DNA molecules chemically bound to Au(111) terraces. Ambient STM and atomic force microscopy (AFM) measurements of both short and long DNA structures in both single and double strand configurations will be discussed with particular attention paid to imaging mechanisms involved. These results are particularly relevant to systems involving biomolecules anchored to inert metal surfaces, such as those used in external field-based assays.}, number={5-6}, journal={IEEE SENSORS JOURNAL}, author={Santagata, Nancy M. and Luo, Pengshun and Lakhani, Amit M. and DeWitt, Darryl J. and Day, B. Scott and Norton, Michael L. and Pearl, Thomas P.}, year={2008}, pages={758–766} }
 @inproceedings{santagata_lakhani_dewitt_luo_pearl_2008, title={Probing molecular-level organizational structure and electronic decoupling of tartaric acid domains supported on Ag(111)}, volume={100}, booktitle={Proceedings of the 17th international vacuum congress/13th international conference on surface science/international conference on nanoscience and technology}, author={Santagata, N. M. and Lakhani, A. M. and DeWitt, D. J. and Luo, P. and Pearl, T. P.}, year={2008} }