Lawrence A. Bottomley

Microcantilevers: Sensing Chemical Interactions via Mechanical Motion

2.4. Temperature Effects 527 2.4.1. Effect on Material Properties 528 2.4.2. Effect on Geometry 528 3. Detection Schemes 528 3.1. Optical Lever 528 3.2. Interferometer 529 3.3. Piezoresistive 529 3.4. Capacitive 529 4. Design, Materials, and Fabrication 529 4.1. Design Considerations 530 4.2. Fabrication of Silicon-based Cantilevers 530 4.2.1. Film Deposition 530 4.2.2. Photolithography 530 4.2.3. Etching 530 4.2.4. Doping 530 4.3. Fabrication of Polymeric Cantilevers 531 5. Chemical Selectivity 531 6. Chemical Applications 533 6.1. Volatile Organics 533 6.2. Chemical Warfare Agents 534 6.3. Explosives 534 6.4. Toxic Metal Ions 534 7. Biological Applications 534 7.1. Cells 534 7.2. Viruses 534 7.3. Antigen−Antibody Interactions 535 7.4. DNA Hybridization 536 7.5. Enzymes 537 8. Recommendations for Future Work 538 8.1. Guidelines for Reporting Sensor Performance 538 8.2. Experimental Design Considerations 538 8.3. Fruitful Areas for Further Research 539 8.3.1. More Selective Coatings 539 8.3.2. Increased Sensitivity and Faster Response 539

Influence of surface stress on the resonance behavior of microcantilevers

This work presents a model to predict the effect of surface stresses on the ith-mode bending resonant frequency of microcantilevers and its experimental validation. With this model, one can calculate the surface stress acting upon the microcantilever solely by measuring resonant frequencies whereas previously one needed to measure the deflection. Resonant frequency measurement has distinct advantages in terms of ease and accuracy of measurement.

Characterization of thin titanium oxide adhesion layers on gold: resistivity, morphology, and composition

Abstract Group 1B metal films (copper, silver and gold) are attractive for metallizations in multichip modules (MCM) and integrated circuits because they have high electrical conductivities. Unfortunately, Group 1B metals require additional bonding layers for adhesion to insulators (i.e. silicon dioxide or polymers). In this work, thin electrically insulating films of titanium oxide on titanium have been investigated as adhesion layers between gold and a wide variety of insulators. The adhesion layer does not alter the dielectric properties of the insulator surrounding the metal because it is thin. The morphology, composition, and resistivity of the titanium oxide films were studied with angle resolved X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and electrical resistance measurements. The results show that sputter-deposited titanium films grow by an island growth (Volmer-Weber) mechanism. The islands coalesce after 10–20 A of titanium deposition. Following deposition, the titanium films were oxidized by exposure to air at relatively low temperatures (T 20 A) were oxidized, a layered film was also produced with a titanium core and titanium oxide surface layer.

Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4

The effect of operational conditions and initial dye concentration on the reductive transformation (decolorization) of the textile dye Reactive Blue 4 (RB4) using zero-valent iron (ZVI) filings was evaluated in batch assays. The decolorization rate increased with decreasing pH and increasing temperature, mixing intensity, and addition of salt (100gL(-1) NaCl) and base (3gL(-1) Na2CO3 and 1gL(-1) NaOH), conditions typical of textile reactive dyebaths. ZVI RB4 decolorization kinetics at a single initial dye concentration were evaluated using a pseudo first-order model. Under dyebath conditions and at an initial RB4 concentration of 1000mgL(-1), the pseudo first-order rate constant (kobs) was 0.029+/-0.006h(-1), corresponding to a half-life of 24.2h and a ZVI surface area-normalized rate constant (kSA) of 2.9x10(-4)Lm(-2)h(-1). However, as the initial dye concentration increased, the kobs decreased, suggesting saturation of ZVI surface reactive sites. Non-linear regression of initial decolorization rate values as a function of initial dye concentration, based on a reactive sites saturation model, resulted in a maximum decolorization rate (Vm) of 720+/-88mgL(-1)h(-1) and a half-saturation constant (K) of 1299+/-273mgL(-1). Decolorization of RB4 via a reductive transformation, which was essentially irreversible (2-5% re-oxidation), is believed to be the dominant decolorization mechanism. However, some degree of RB4 irreversible sorption cannot be completely discounted. The results of this study show that ZVI treatment is a promising technology for the decolorization of commercial, anthraquinone-bearing, spent reactive dyebaths.

Raman spectroscopic monitoring of carbon deposition on hydrocarbon-fed solid oxide fuel cell anodes

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution for the utilization of a wide variety of fuels beyond hydrogen. One of the chief obstacles to true fuel flexibility lies in anode deactivation by coking as well as a limited mechanistic understanding of coking and its prevention. Here we report Raman spectroscopic mapping and monitoring of carbon deposition on SOFC anode surfaces under both ex situ and in situ conditions. Carbon mapping was successfully demonstrated with a model Ni–YSZ electrode exposed to a CH4-containing atmosphere at high temperature (625 °C), while carbon deposition over time in a wet C3H8 atmosphere was directly monitored on a similar anode system as well as a BaO-modified system. This spectroscopic technique provides valuable insight into the mechanism of carbon deposition, which is vital in achieving rational design of carbon-tolerant anode materials.

Characterization of microcantilevers solely by frequency response acquisition

A method is presented to determine the geometry of tipless microcantilevers by measuring the resonance frequencies of at least one of their bending, lateral and torsional resonance modes, and having knowledge of the beam’s elastic modulus, Poisson’s ratio and density. Once the geometry is known, the beam’s stiffness and mass can be calculated. Measurement of multiple modes allows for multiple estimates of cantilever geometry. Multiple data points from the experimental results show that this approach yields dimensional values accurate to roughly 2.5% as compared to SEM-determined length, width and thickness. Stiffness values determined with this new technique are roughly 4.7% and 6.5% less than two existing characterization methods (i.e., Sader’s method and Euler–Bernoulli beam theory predictions), and roughly 16% greater than Hutter and Bechhoefer’s stiffness determination method.

High-temperature surface enhanced Raman spectroscopy for in situ study of solid oxide fuel cell materials

In situ probing of surface species and incipient phases is vital to unraveling the mechanisms of chemical and energy transformation processes. Here we report Ag nanoparticles coated with a thin-film SiO2 shell that demonstrate excellent thermal robustness and chemical stability for surface enhanced Raman spectroscopy (SERS) study of solid oxide fuel cell materials under in situ conditions (at ∼400 °C).

Electrochemical Patterning of the Surface of Insulators with Electrically Conductive Polymers

The great potential of {pi}-conjugated polymers, especially polyacetylene, polyarylenes, and poly(arylenevinylene)s, as components in optical displays, sensors, rechargeable batteries, electromagnetic interference shielding, and microelectronics is well recognized. This paper presents a protocol for patterning the surface of insulators with electrically conductive polymers. The pattern is formed on a gold electrode surface via electro-oxidation of heteroarene monomers. An adhesion layer is used to bond the surface of the conducting polymer pattern to the surface of an insulator. The pattern is then developed by etching away the gold. The approach is illustrated with polypyrrole and is applicable to a wide range of substituted polyheteroarenes and insulating substrates.

Injection moulding of high aspect ratio micron-scale thickness polymeric microcantilevers

Tipless thermoplastic microcantilevers suitable for chemical and biological sensing applications were fabricated by injection moulding. Their stiffnesses and resonant frequencies were each determined by two techniques. Polystyrene beams produced by this method exhibited stiffnesses ranging from 0.01 to 10 N m−1, making them feasible for biosensing applications. The approach proved repeatable with low standard deviations on the parameters measured on 22 microcantilever beams (stiffness and first-mode resonant frequency) made from the same mould. The variations were much lower than those of similar, commercially available, silicon-type beams. The polymeric microcantilevers were shown to be of at least equal calibre to commercially available microcantilevers.

Thin Films: Preparation, Characterization, Applications

Preface. 1. Highly Ordered Adsorbate Structures on Cu(111) IN The Potential Regime of Hydrogen Evolution: An In Situ STM Study P. Broekmann, et al. 2. Electrochemical Epitaxial Growth, Structure, and Electrocatalytic Properties of Noble Metal Thin Films on Au (111) and Au(100) K. Uosaki, et al. 3. Electrochemical Properties of Pd/Pt(111) Adlayers J.M. Feliu, et al. 4. Temperature-Dependence of the Under-Potential Deposition of Ag on Pt(111) in H2SO4 Z. Radovic-Hrapovic, G. Jerkiewicz. 5. Functionalization of Underpotentially Deposited Metal Layers with Organics, Metals and Ions R. Michalitsch, et al. 6. Morphology in Electrochemical Atomic Layer Epitaxy K. Varazo, et al. 7. Overview on the Ultra Thin Films Formation of Y-VI Compounds Semiconductors on Silver by Electrochemical Atomic Layer Epitaxy M. Innocenti, et al. 8. Electrodeposition of Nanostructured Mesoporous Selenium Films I. Nandhakumar, et al. 9. Experimental and Theoretical Studies on Branched Electrodeposits in Thin-Layer Cells G. Marshall, et al. 10. Self-Assembled Magnetic Nanoparticle Arrays by Anodization and Electrodeposition G. Zangari, et al. 11. Solution Chemical Routes to Two-Dimensional Bismuth Tellurides for Thermoelectric Applications Z. Ding, et al. 12. Growth Kinetics of Multi-Layer CuEtX Films on Copper Piezoelectrodes M. Hepel, M. Scendo. 13. The Interfacial Chemistry in Grignard Reagent Formation: Reactions of Clean Mg (0001) Surfaces J.B. Abreu, et al. 14. Ultra Thin Film Electrodeposition of Conjugated Polymers on Conducting Surfaces: A Precursor Polymer and Surface Grafting Approach R.C. Adviscula, et al. 15. Self-Assembled Monolayers as Models for Polymeric Interfaces C.C. Perry, et al. 16. Structure and Electronic Properties of Self-Assembled Macrocycle and Polymer Multilayers L.S. Li, A.D.Q. Li. 17. Chemically-Attached Organic Monolayers on Silica Nanoparticles as an NMR Relaxation Medium for Embedded Polynuclear Aromatic Hydrocarbons E.W. Hagaman, et al. 18. Preparation of Thin-Film Alumina for Catalytic Activity Studies C.C. Chusuei, et al. 19. EQCN Study of Electrocatalytic Oxidation of Methanol at Nanostructured Catalyst J. Luo, et al. 20. Solid State 13C MAS NMR Investigations of Amorphous Carbon Thin Films: Structural Changes During Annealing T.M. Alam, et al. 21. Comparison of Contact Angle Measurements using Various Probe Liquids on Incomplete Ots Sams Y. Liu, M.C. Messner. 22. Valence Photoelectron Spectroscopy of Non-Volatile Organomettalic Molecules F.K. Padden, et al. 23. Humidity Effect on the Stability of an Octadecyltriethoxysilane Monolayer Self-Assembled on Mica S. Kim, J.E. Curry. 24. Chemical Vapor Deposition of Silanes on Plain and Microfabricated Silicon Surfaces K.C. Popat, T.A. Desai. 25. Characterization of Poly(Ethylene Glycol) Thin Films on Silicon for Implantable Microdevices S. Sharma, et al. 26. AFM Imaging of Liquid Structures: From Droplet Profiles to Molecular Interactions T. Becker, et al. 27. Microcantilever Sensing of Particles in Liquid Streams: Thin-Film Coating Impacts Sensor Performance S. Shen, L.A. Bottomley. Index.