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1.  Automated scanning probe lithography with n-alkanethiol self assembled monolayers on Au(111): Application for teaching undergraduate laboratories 
Journal of Laboratory Automation  2011;16(2):112-125.
Controllers for scanning probe instruments can be programmed for automated lithography to generate desired surface arrangements of nanopatterns of organic thin films, such as n-alkanethiol self-assembled monolayers (SAMs). In this report, atomic force microscopy (AFM) methods of lithography known as nanoshaving and nanografting are used to write nanopatterns within organic thin films. Commercial instruments provide software to control the length, direction, speed, and applied force of the scanning motion of the tip. For nanoshaving, higher forces are applied to an AFM tip to selectively remove regions of the matrix monolayer, exposing bare areas of the gold substrate. Nanografting is accomplished by force-induced displacement of molecules of a matrix SAM, followed immediately by the surface self-assembly of n-alkanethiol molecules from solution. Advancements in AFM automation enable rapid protocols for nanolithography, which can be accomplished within the tight time restraints of undergraduate laboratories. Example experiments with scanning probe lithography (SPL) will be described in this report that were accomplished by undergraduate students during laboratory course activities and research internships in the chemistry department of Louisiana State University. Students were introduced to principles of surface analysis and gained “hands-on” experience with nanoscale chemistry.
PMCID: PMC3072817  PMID: 21483651
2.  Self-assembly of octadecyltrichlorosilane: Surface structures formed using different protocols of particle lithography 
Particle lithography offers generic capabilities for the high-throughput fabrication of nanopatterns from organosilane self-assembled monolayers, which offers the opportunity to study surface-based chemical reactions at the molecular level. Nanopatterns of octadecyltrichlorosilane (OTS) were prepared on surfaces of Si(111) using designed protocols of particle lithography combined with either vapor deposition, immersion, or contact printing. Changing the physical approaches for applying molecules to masked surfaces produced OTS nanostructures with different shapes and heights. Ring nanostructures, nanodots and uncovered pores of OTS were prepared using three protocols, with OTS surface coverage ranging from 10% to 85%. Thickness measurements from AFM cursor profiles were used to evaluate the orientation and density of the OTS nanostructures. Differences in the thickness and morphology of the OTS nanostructures are disclosed based on atomic force microscopy (AFM) images. Images of OTS nanostructures prepared on Si(111) that were generated by the different approaches provide insight into the self-assembly mechanism of OTS, and particularly into the role of water and solvents in hydrolysis and silanation.
PMCID: PMC3304319  PMID: 22428102
atomic force microscopy; nanopatterning; nanostructures; octadecyltrichlorosilane; particle lithography; self-assembled monolayer; self-assembly
3.  Lysine-Based Zwitterionic Molecular Micelle for Simultaneous Separation of Acidic and Basic Proteins using Open Tubular Capillary Electrochromatography 
Analytical chemistry  2010;82(10):3997-4005.
In this work, a zwitterionic molecular micelle, poly-ε-sodium-undecanoyl lysinate (poly-ε-SUK), was synthesized and employed as a coating in open tubular capillary electrochromatography (OT-CEC) for protein separation. The zwitterionic poly-ε-SUK containing both carboxylic acid and amine groups can be either protonated or deprotonated depending on the pH of the background electrolyte; therefore, either an overall positively or negatively charged coating can be achieved. This zwitterionic coating allows protein separations in either normal or reverse polarity mode depending on the pH of the background electrolyte. The protein mixtures contained 4 basic proteins (lysozyme, cytochrome c, α-chymotrypsinogen A, and ribonuclease A) and 6 acidic proteins (myoglobin, β-lactoglobulin A, β-lactoglobulin B, α-lactalbumin, and albumin). Protein separations were optimized specifically for acidic (reverse mode) and basic (normal mode) pH values. Varying the polymer thickness by changing the polymer and salt concentration had a great influence on protein resolution, while all peaks were also baseline resolved in both modes using the optimized poly-ε-SUK coating concentration of 0.4%. Proteins in human sera were separated under optimized acidic and basic conditions in order to demonstrate the general utility of this coating. Nanoscale characterizations of the poly-ε-SUK micellar coatings on silicon surfaces were accomplished using atomic force microscopy (AFM), to gain insight into the morphology and thickness of the zwitterionic coating. The thickness of the polymer coating ranged from 0.9–2.9 nm based on local measurements using nanoshaving, an AFM-based method of nanolithography.
PMCID: PMC2902365  PMID: 20420412
protein separation; zwitterionic; molecular micelle; open tubular capillary electrochromatography; human serum; atomic force microscopy; nanoshaving; lysine coating
4.  Electropolymerizable 2,2′-Carboranyldithiophenes. Structure–Property Investigations of the Corresponding Conducting Polymer Films by Electrochemistry, UV–Visible Spectroscopy and Conducting Probe Atomic Force Microscopy 
Macromolecules  2009;42(8):2981-2987.
Carborane-functionalized conducting polymer films have been electrogenerated in dichloromethane from the anodic oxidation of ortho- (1), meta- (3) and para-carborane (4) isomers linked to two 2-thienyl units. The corresponding electrochemical response was characterized by a broad reversible redox system corresponding to the p-doping/undoping of the polythiophene backbone, the formal potential of which increased in the order poly(1) < poly(3) < poly(4), from ca. 0.50 to 1.15 V vs Ag/Ag+ 10−2 M. From further UV–visible spectroscopy analysis, the optical band gap was estimated at 1.8, 2.0 and 2.2 eV for poly(1), poly(3) and poly(4), respectively. The more conjugated and electroconductive character of poly(1) is ascribed to a more planar conformation of the conjugated backbone resulting from an intramolecular β–β′ cyclization reaction in the monomer, consequently yielding a fused conjugated polymer. Molecular modeling calculations using the DFT method support this hypothesis. The surface topography and maps of the conductive domains of the electropolymerized films were evaluated by conducting probe AFM. The three polymers exhibit fairly similar morphological characteristics and a surface roughness of ~2 nm. Current–voltage (I–V) characteristics of conducting AFM tip-carborane polymer–ITO junctions showed that poly(1) had the highest conductivity.
PMCID: PMC3051405  PMID: 21399746
5.  Polythiophenes Containing In-Chain Cobaltabisdicarbollide Centers 
New cobalt(III) bis(dicarbollide) complexes covalently linked to two 2-oligothienyl units have been synthesized and electropolymerized in acetonitrile electrolyte in order to produce the corresponding polythiophene films containing in-chain metallic centers. The polymer films electrogenerated from the bithienyl (4b) and terthienyl (4c) derivatives display redox processes attributed to the Co(III)/Co(II) couple at ca. −1.1 V vs SCE and to the p-doping/undoping of the expected quaterthienyl and sexithienyl segments at ca. 0.8 V vs SCE. In contrast, the anodic oxidation of the thienyl (4a) derivative leads to passivation of the electrode surface. As the length of the oligothiophene substituents increases, the metallic and dicarbollide cage carbon atoms contributions in the HOMO decrease dramatically so that the highest occupied frontier orbitals of 4b and 4c can be considered as almost purely oligothiophene-based. From further UV–vis spectroscopy analysis, it is demonstrated that the polymer incorporating the sexithienyl segments is more conjugated than that with the quaterthienyl segments as the absorption maximum for the interband π–π* transition was observed at 410 and 448 nm for poly(4b) and poly(4c) respectively. Furthermore, these polymers display a more extended degree of conjugation than the parent oligothiophenes. Such features indicate a significant electronic delocalization through the cobaltabisdicarbollide moiety. Their conducting probe atomic force microscopy characterization indicates that poly(4b) and poly(4c) behave like heavily doped semiconductors rather than pure semiconductors. Mean conductivity values extracted from the current–voltage profiles are 1.4 ×10−4 and 7.5 ×10−4 S cm−1 for poly(4b) and poly(4c), respectively. Such materials are found to be efficient for the electrocatalytic reduction of protons to dihydrogen, as exemplified for poly(4b). The overpotential for hydrogen evolution is significantly decreased by ca. 230 mV with respect to that obtained with the bare electrode (measured for a current density of 1.4 mA cm−2 in the presence of 20 mM HBF4).
PMCID: PMC2919152  PMID: 20356270
conducting polymers; metallopolymers; polythiophenes; carboranes; electropolymerization

Results 1-5 (5)