CORE-SHELL NANOPARTICLES AND NANOSTRUCTURED MESOPOROUS MATERIALS(NMMs)
Nanomaterials need no special introduction as interest in them sparked exponential growth in the past couple of decades, not only in scientific laboratories but also in industries around the world. In addition to size and shape effects, newer designs of nanostructures have also begun gaining prominence providing a new opportunity to tailor the properties of nanomaterials and investigate their fundamental behavior as well as explore potential applications. Some of these new designs are core-shell, onion-type, multilayered, alloy, multimetallic, multifunctional nanomaterials such as Nanostructured Mesoporous Materials(NMMs). Of these core-shell nanoparticles and Nanostructured Mesoporous Materials(NMMs) offer a great opportunity to modulate the properties of the materials.
These materials are currently being developed by the nanofabrication’s group at CAMD. CAMD’s Synchrotron radiation based spectroscopy and microfabrication tools also play a vital role in their development. Some of the applications for these materials, currently being investigated, range from effective catalysts for energy applications to superior antioxidants to delay the ageing process. In fact, NMMs are new class of catalysts being developed by the CAMD’s nanofabrication group and will be one of the key class of materials investigated by the recently funded DOE Energy Frontier Research Center (EFRC) at LSU.
MAGNETIC NANOMATERIALS FOR CANCER DIAGNOSIS
At Louisiana State University, the Pennington Biomedical Research Center (PBRC) and Nanofabrication Group of the Center for Advanced Microstructures and Devices (CAMD) are developing novel nanotechnologies for cancer diagnosis. In a conjoint effort cancer specialists of PBRC, lead by Dr. Carola Leuschner, and nanomaterials researchers at CAMD, lead by Dr. Challa Kumar, developed magnetite based nanoparticles, that were functionalized on their surface in order to specifically target cancer cells and metastases without getting trapped in organs of the reticulo endothelial system such as the liver.
The functionalization entity is a hormone ligand that served at the same time as coating and targeting moiety, rendering these particles superior to others under investigation. The functionalized magnetite nanoparticles (LHRH-SPION) have been have been found to a) accumulate within the cancer cells at high efficiency and specificity, b) increase the sensitivity of the Magnetic Resonance image, c) are not toxic and escape macrophage recognition. Highlights of these technologies are a single step attachment of LHRH to iron oxide nanoparticles leading to 65% intracellular accumulation of particles in breast cancer tumors in vivo. It is the highest percentage of iron oxide particles, reported so far, in breast tumors and was reconfirmed by the TEM and MRI experiments carried out at Princeton University and Duke University. The development of these unique nanoparticles (LHRH-SPIONs) as contrast enhancing agents was reported in recent publications and patent applications filed. For more information, see our publications in Breast Cancer Research and Treatment (2006), Biomaterials(2005), Journal of Biomedical Nanotechnology(2005).
POLYMERIC MICRO REACTORS FOR SYNTHESIS OF NANOMATERIALS
Miniaturization affords a direct means of eliminating local variations in reaction conditions and is amenable to scale-up through parallel processing or using continuous processes. Nanofabrication group is one of the very few research groups working to develop this state of the art technology and is the only one focusing on developing inexpensive rapid prototype polymeric micro reactors. Taking advantage of well established LIGA technology in CAMD, we have designed and fabricated a prototype based on multi layer fabrication process using SU-8 and PMMA.
A unique bonding capability using the differential exposure times is being utilized to minimize clogging of micro fluidic channels. One of the major advantages of our fabrication technology is that it is suitable for mass production. A variety of metallic nanomaterials are currently being synthesized using the completely micro reactor. Our main goal is to obtain control over size, shape and crystal structure of nanomaterials synthesized using polymeric micro reactors. For more information, see our publications in Journal of Physical Chemistry B (2005), Journal of Micromachining and Microengineering (2004) and Journal of Nanoscience and Nanotechnology (2004) , Chemistry of Materials (2006)
NOVEL ‘NANO’ DRUG DELIVERY SYSTEMS
In collaboration with Pennington Biomedical Research Center, Baton Rouge and Institute for Micro Manufacturing, Ruston, our group is working towards developing a unique drug delivery system that has in-built controlled delivery and multiple site-specificity using functionalized magnetic-polymeric nanomaterials.
We are developing synthetic methodologies to bind variety of biomolecules such as peptides, antibodies, genes to magnetically sensitive polymeric nanomaterials and studying site-specificity & controlled release of drugs embedded within the polymeric nanomaterials. In vitro as well as in vivo assays are being utilized in order to understand structure-activity relationships. For more information, see our publications in PMSE Preprints (2005), Langmuir (2005) and Journal of Nanoscience and Nanotechnology (2004)
CHARACTERIZATION OF ELECTRONIC AND GEOMETRIC PROPERTIES OF NANOMATERIALS BY X-RAY ABSORPTION SPECTROSCOPY(XAS)
One of the most important challenges of nanoscience is to delineate the Size, size distribution, shape, core-shell dependent electronic and geometric properties of nanomaterials as it should be possible to tune specific properties such as magnetism, heat capacity, optical, photoconductivity and charge transfer, electronic, melting point, catalytic by varying the size/shape of the nanomaterials.
Our group is working on using different wet chemical synthetic techniques to prepare variety of metallic nanomaterials and characterizing them using X-ray absorption spectroscopic techniques. Proximity to the synchrotron radiation based XAS beamlines is a unique opportunity to investigate mechanism of formation of nanomaterials using In-situ probes. For more information see our publications in Journal of Physical Chemistry B (2005), Journal of Applied Physics (2005), Physica Scripta (2005) and Journal of Nanoparticle Research (2004).
Time Resolved In Situ XAS with Unprecedented Resolution Using Micro Reactors
Using a microreactor system one can solve several of these problems, due to possibility of rapidly mixing reagents and better control over the temperature in the channel as well as exchange time with space resolved measurements. Here, the time resolution that is achieved is determined by the length of the channels of the microreactor, the retention time, and the size (here height) of the X-ray beam.
As can be seen from the above figure (left), XAS spectra were taken within the microchannels with points marked where spectra were taken. The figure on the right shows Co K-edge XANES spectra from top to bottom: final product collected at the end of the microreactor (measured in a regular transmission mode), in-situ recorded at the point III, II, and I (raw data and smoothed FFT 4 points) in comparison with cobalt acetate (black dash dot).