Researching materials one-billionth the size of a meter.
Associate Professor Andrew Richter’s research involves four major components, all firmly within the area of nanoscience:
- using high-intensity x-ray and neutron scattering to study nano-sized materials
- studying the interaction of proteins with organic films
- making and studying organic thin films
- examining artificial liposomes and nanoporous thin films for use in sensor and drug delivery applications, in collaboration with Dr. Pinkhassik at the University of Memphis
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To help a general audience understand just how small a nanometer is, the National Nanotechnology Initiative makes the following comparisons:
- A single gold atom is about a third of a nanometer in diameter.
- One nanometer is about as long as your fingernail grows in one second.
- A strand of human DNA is 2.5 nanometers in diameter.
- A sheet of paper is about 100,000 nanometers thick.
- On a comparative scale, if the diameter of a marble was one nanometer, the diameter of the Earth would be about one meter.
Professor Richter has given several presentations explaining nanoscience to general audiences. He has published the following resources in PDF form:
- A Trip to the Nanoscale: a graphical introduction to the (tiny) world of the nanoscopic
- How to See Nano: an incomplete list of some of the techniques that allow for study of the nanoworld
- What Makes Nano Special: a short list of some of the reasons nano is different than the macro
- Nano Examples: a few examples of how nanomaterials have been used, or may be used, to create new technologies or to address long-standing problems
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Professor Richter and his team make and study organic thin films as well as the films’ interaction with proteins.
Organic films are fairly easy to make and can be used to modify the surface of a material in order to target a specific functionality. Amazingly, these films are typically only one to five nanometers thick — 10 to 50 times the diameter of a hydrogen atom. Yet just this thin layer can dramatically change the behavior of the surface.
For instance, Professor Richter can coat clean silicon oxide (which is “water loving” or hydrophilic) with a single layer of a molecule (called octadecyltrichlorosilane, OTS) and it becomes water-repellant (hydrophobic). In this way, his team can create surfaces that interact in different ways with various molecules, specifically proteins and peptides.
This work is an extension of Professor Richter’s thesis, for which he studied the formation of OTS films using in situ X-ray reflectivity. (“In situ” refers to the idea that the study was done while the film was forming.)
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Proteins are nature’s nanomachines, performing the required functions of life. Proteins often do their jobs by directly interacting with cell walls, other proteins, and — increasingly — artificial surfaces, such as drug coatings, joint replacements, and stents. Because proteins play vital roles in human health, a large number of research groups are studying how proteins adhere to surfaces.
At Valpo, Professor Richter and his team look at protein adsorption by using a new technique called in situ X-ray reflectivity. Intense beams of X-rays can be produced by labs around the world, but X-rays have not typically been used to look at organic films that are in solution (in which proteins are dissolved). Professor Richter’s work seeks to determine how well X-rays can be used in this area. If they can be, then the extremely high-resolution information that X-ray studies provide will advance scientific knowledge of the important process of protein adsorption.
Professor Richter has obtained and analyzed a fair amount of X-ray data and presented on this area since 2005. The initial results suggest that X-ray reflectivity will be good for looking at the closest region of protein-film contact but is not great for the protein-solution region. In addition, X-ray reflectivity may be used, with some future modification, to perform time-resolved studies, watching how a protein film develops as it adsorps.
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Nanocapsules are nanoporous materials with well-defined pore sizes, created using a “biotemplating” technique. They hold great promise for applications ranging from catalysis to drug delivery. An introduction to nanocapsules (.pdf) »
These materials were developed by Eugene Pinkhassik, Ph.D., at the University of Memphis. Professor Richter, Sam Schaub ’11 and Ben Anderson ’08 have worked with Professor Pinkhassick, each contributing to the publication of a journal article in Langmuir.
Professor Richter’s main contribution to the project is the determination of the structure of the nanomaterials, which is vital for how to design specific pore sizes and shapes for use in particular applications. His team uses neutron and X-ray scattering techniques for this purpose.
The main studies so far have been:
- The way that the liposome scaffolds “load” with the nanocapsule shell material (“monomers”).
- Time-resolved studies of the loading process.
- How changing the type of monomer and the size of the liposome affects the loading process.
- Determining the thickness of the nanocapsule shell walls.
- The formation and testing of a gold substrate preparation method for making large, flat gold electrodes for nanosensor applications.
- The formation and testing of an ultrathin insulating polymer film that will eventually be made porous for use in nanosensor applications.
- The distribution and structure of nanodisks in solution and in polymer matrices for use as nanocomposite materials.