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Amy V. Walker

Associate Professor


1998 PhD Chemistry, University of Cambridge
1995 BA (Hons) Natural Sciences (Physics and Theoretical Physics), University of Cambridge

Research Summary

The ultimate goal of Amy Walker’s research is the development of simple, robust materials for constructing complex two- and three-dimensional surfaces by manipulating interfacial chemistry. Metal/SAM, semiconductor/SAM and biomolecule/SAM structures have applications in organic electronics, sensing, catalysis, photovoltaics and optoelectronics. Her group also develops analytical techniques to probe the structures produced.

The Walker group employs surface science techniques, in particular time-of-flight secondary ion mass spectrometry (TOF SIMS) and reflection absorption infrared spectroscopy (RAIRS) and calculations of molecular structure (density functional theory, DFT) in this work. TOF SIMS is a unique widely applicable technique that provides detailed information about the chemical composition of surfaces with sub-micron lateral resolution, and is used in areas from biological systems to materials science.

Current research interests include:

New Methods for Constructing Metallized Organic Surfaces
In the area of molecular electronics, individual devices (such as diodes and memory elements) are prepared by the deposition of metals (the "contact") onto a SAM. Device-to-device variation and short device lifetimes due to small changes in the structure of these contacts are often observed. With this in mind, we are amassing a database of metal-molecule interactions to help guide the design of metallic contacts. We are also developing new metallization techniques for organic surfaces including chemical vapor deposition (CVD) and electroless deposition.

Chemical Bath Deposition of Semiconductors on Organic Surfaces
There is a need to develop cheap, simple methods to deposit semiconductors on organic surfaces for photovoltaic applications. With this in mind, we are investigating the reaction pathways involved in chemical bath deposition to selectively deposit inorganic nanostructures on organic thin films.

Ionic Liquid Matrices and New Data Analysis Techniques for Imaging Mass Spectrometry
SIMS can be used to obtain mass spectrometric images of surfaces with sub-micron resolution. However, it is often hard to obtain a large number high mass ions (m/z 500) in SIMS leading to a loss of information and degradation of the image (lateral) resolution. To overcome this, we are currently developing a new class of matrix for imaging SIMS – ionic liquids. Our results indicate that ionic liquids are very effective matrices. They are suitable for imaging applications and increase observe ion intensities by 10-100 times. SIMS images contain a lot of data – much of which is currently ignored. In collaboration with Lev Gelb’s group we are developing new data analysis techniques to extract as much information from these images as possible.

Selected Publications

  • A.V. Walker, “Building Robust and Reliable Molecular Constructs: Patterning, Metallic Contacts and Layer-by-Layer Assembly", Langmuir, 26 (2010) 13778-13785
  • A. V. Walker, “Why is SIMS Underused in Chemical and Biological Analysis? Challenges and Opportunities”, Anal. Chem., 80 (2008) 8865-8870
  • P. Lu, A.V. Walker, “Making Nanoflowerbeds: Reaction Pathways Involved in the Selective Chemical Bath Deposition of ZnS on Functionalized Alkanethiolate Self-Assembled Monolayers”, ACS Nano, 3 (2009) 370-378
  • C. Zhou, A. V. Walker, “Formation of Multilayer Ultrathin Assemblies Using Chemical Lithography”, Langmuir, 26 (2010) 8441-8449
  • J.J.D. Fitzgerald, P. Kunnath, A.V. Walker, “Matrix-Enhanced Secondary Ion Mass Spectrometry (ME SIMS) Using Room Temperature Ionic Liquid Matrices”, Analytical Chemistry, 82 (2010) 4413-4419