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Glancing angle deposition was used to produce ~150-nm-thick silver nanoparticle films, which were evaluated as localized surface plasmon resonance (LSPR) biosensors. The films have a strong extinction peak around 368 nm in air due to LSPR. As the refractive index of the surrounding environment is increased, the extinction peak red-shifts with a linear dependence. The films were functionalized with 11-amino-1-undecanethiol and rabbit immunoglobulin G (rIgG) to allow for the detection of anti-rIgG binding. Binding of biomolecules to the nanoparticle surface increases the local refractive index and results in a red-shifting of the extinction peak. The wavelength shift at varying concentrations of anti-rIgG was measured and fit to the Langmuir isotherm. This yielded approximate values for the saturation response, [DELTA] [[lambda].sub.max] = 29.4 [+ or -] 0.7nm, and the surface confined binding constant, [K.sub.a] = (2.7 [+ or -] 0.3) x [10.sup.6] [M.sup.-1]. The response to nonspecific binding was also investigated.

A variety of new methodologies to pattern biomolecules on surfaces and to detect binding events are currently being developed for high-throughput assay applications. Carbohydrates serve as attachment sites for toxins, bacteria, and viruses. Immobilized carbohydrate units can thus be used to directly detect these agents or as a platform for inhibitor assessment. In this work, modified glycosides were patterned on gold surfaces to monitor the binding of the homopentameric B5 cell-recognition subunit of the Shiga-like toxin (SLT). Binding was detected with the label-free method of surface plasmon resonance (SPR) imaging. Two synthetic multivalent inhibitors were used in order to effect inhibitory binding, and SPR imaging is presented as a simple alternative to ELISA for the study of toxin inhibition. In contrast to existing methods for the study of carbohydrate--protein interactions, in particular ELISA, the use of micropatterned sensor surfaces is shown to be advantageous due to a decrease in complications and manual labor from numerous blocking, washing, and labeling steps. Carbohydrate receptor density on the sensor surface was optimized in order to effect the maximum binding of the SLT. The I[C.sub.50] values determined were in the low-nanomolar range for each of the two inhibitors studied.

A simple method is presented for patterning of protein antigens at a gold surface for use in surface plasmon resonance (SPR) imaging experiments. Microfluidic devices fabricated from poly(dimethylsiloxane) were used to flow various fluids over a gold substrate in spatially defined channels. This technique was used to pattern the surface chemistry of the gold as well as to adsorb antigens from solution to the modified substrates. The resulting antigen arrays were probed with complementary antibodies in order to demonstrate the effectiveness of the patterning for antibody capture experiments. SPR imaging was used to aid in the optimization of array fabrication and to observe the interactions of unlabeled antibodies with these microarrays. This work presents a means of fabricating microarrays with controlled surface density of antigens. SPR imaging provides both quantitative and qualitative evaluation of antibody binding in a label free format.

A facile method for the preparation of thin-film carbon electrodes by electron beam evaporation onto highly doped silicon is presented. The physical and electrochemical properties of these films both before and after postdeposition pyrolysis are investigated. Raman spectroscopy establishes the amorphous structure of the nonpyrolyzed carbon films and confirms the formation of graphitic carbon after pyrolysis at 1000[degrees]C. Scanning force microscopy reveals the root-mean-square roughness of nonpyrolyzed films to be ~1 [Angstrom], while pyrolyzed films exhibit an increased roughness of ~4 [Angstrom]. The electrochemical behavior of the electrodes resembles glassy carbon, with measured heterogeneous electron-transfer rate constants among the highest measured for thin carbon films. These carbon film electrodes will potentially find applications in such fields as molecular electronics and scanning probe microscopy of adsorbed species.

Due to the broad impact of microfabrication technology on chemistry and biology, new methods to pattern and etch a variety of materials are being explored in a number of laboratories. Here, we report the design, fabrication, and operation of a glassy carbon (GC) microchip interfaced to a nanoelectrospray ionization source and a quadrupole mass spectrometer. The method involves standard photolithographic pattern transfer to a photoresist layer and anodization of the exposed GC substrate in basic electrolyte to produce a series of channels with well-defined wall structure. The performance of the microchip was evaluated with standard polymer and peptide samples.

In this work, we demonstrate the sensitivity of scanning force microscopy (SFM), operated in friction force mode, to adsorbed protein conformation or orientation. We employ patterned films of methyl- and carboxylate-terminated alkanethiolate monolayers on gold as substrates for protein adsorption to observe the effect of each functional group in the same image. Infrared spectroscopic and SFM studies of bovine fibrinogen (BFG) adsorption to single-component monolayers indicate that complete films of BFG that are stable to imaging are formed at each functional group. After adsorption of BFG to a patterned monolayer, we observe a contrast in friction images due to differences in adsorbed BFG conformation or orientation induced by each functional group. We also observe frictional contrast in films of other proteins adsorbed on patterned monolayers. These observations lead to the conclusion that SFM-measured friction is sensitive to adsorbed protein state.

This paper demonstrates the first application of tapping-mode scanning force microscopy (TM SFM) in the compositional mapping of modified glassy carbon (GC) electrodes. Using TM SFM, we have been able to track both compositional and topographical changes of polished CG induced by electrochemical pretreatment (ECP). Photo-resist-based microfabrication techniques were employed to produce surfaces consisting of segregated modified and unmodified regions for direct comparison in the same image. Our results show that ECP of GC via anodization in basic solutions for short times (approximately 10 s) initially removes the ubiquitous layer of polishing debris via an etching process. Longer anodization in basic electrolyte results in significant etching of GC surface. ECP in acidic solutions yields little topographic change compared to basic electrolytes. Electrochemical results obtained for three redox systems studied on both modified and unmodified GC electrodes correlate with the TM SFM images collected.

A study was conducted to analyze anthraquinone 2,6-disulfonate films adsorbed to ordered graphite electrodes. The study was performed in the electrochemical fluid cell of a nanoscope III multi-Mode system. Experimental results indicated the effectiveness of high-resolution lateral force images in determining the correlation of the structures of adsorbate layers with their electrochemical response.

Scanning force microscopy (SFM) was employed for the tip-assisted base hydrolysis of an ester-terminated alkanethiolate monolayer on Au(111). Results showed that contact imaging accelerates the base hydrolysis of a dithiobis(succinimido undecanoate) monolayer relative to the surrounding unimaged region. It is suggested that the mechanical disruption by the SFM probe tip of the steric barrier from the neighboring adsorbates makes the access of hydroxide ions to the buried acyl carbons in the adlayer easier. Also, the surface area hydrolitically modified by this disruption can be controlled by the SFM imaging conditions.

Polished, fractured, heat-treated, and laser-activated glassy carbon (GC) surfaces were examined by scanning tunneling microscopy (STM) in ambient air. Polished electrodes, as well as those which were vacuum heat treated (VHT) or laser activated (25 mW/[cm.sup.2]) after being polished, were comparably smooth in 2.5-[micro]m STM scans, exhibiting root-mean-square roughness (RMSR) of '4nm. Fractured, unpolished surfaces were significantly rougher (RMSR '20 nm) and exhibited numerous nodules with diameters in the range of 50-300 nm. Polished surfaces laser activated at high-power density (70 MW/[cm.sup.2]) showed unexpected features along polishing scratches, apparently caused by local melting. The heterogeneous electron-transfer rate constant (k[degrees], cm/s) and capacitance (C[degrees],[micro]F/[cm.sup.2]) were also determined for the STM-characterized surfaces. Although rougher surfaces generally exhibited higher C[degrees], major differences in k[degrees] were observed for surfaces with similar roughness and appearance. The results are consistent with the dominance of surface cleanliness in the mechanism of laser activation. Combined with past results based on adsorption, the morphological data indicate that differences in surface roughness are unimportant for laser activation of Fe[(CN).sup.6][.sup.4-/3-] kinetics. Furthermore, the STM images reveal morphological effects of laser activation and polishing which were not apparent from previous electrochemical results., The utilizaton of scanning tunneling microscopy for studying various standard pretreatment procedures for gas chromatography (GC) electrodes is discussed. Correlations on the surface morphology and electrochemical activity characteristics of conventionally polished, laser irradiated, fractured and vacuum heat treated GC surfaces were conducted. Results indicate that surface roughening is not the only cause for the increase in electrode activity.

Contrast mechanisms yielding surface compositional information are an important developed in scanning probe microscopy. The ability of tapping-mode scanning force microscopy (TM-SFM)super3 to distinguish between the segregated domains of functional groups is demonstrated. This was assessed by imaging partial bilayer structures formed by the exposure of gold substrates to ethanolic solutions. The results show that phase contrast TM-SFM can produce surface chemical maps, without significant convolution of topography.