Ajay Karakoti, Ph.D.Post-Doctoral Fellow, WR Wiley Environmental Molecular Sciences Laboratory, Interface Spectroscopy/Diffraction
http://emslbios.pnl.gov/id/karakoti_as Updated: July 9, 2014
Current Activities and Projects
Among the several frontiers of technologies in Materials Science and Engineering, nanotechnology stands out alone and in front, driving research and technology to a new era—where small can make big changes in the way we look at materials. The ever-expanding network of nanotechnology has brought scientists from various disciplines in both pure sciences (physics, chemistry, and biology) and engineering (chemical, mechanical, electrical, and electronics) to a common platform, opening several enterprising avenues in the interdisciplinary scientific community.
Ajay Karakoti joined Pacific Northwest National Laboratory after completing his Ph.D., with specialization in nanoscale particulate materials and their use in biomedical- and energy-related applications. Ajay currently is working on synthesis and characterization of the physico-chemical properties of bare and ligand functionalized nanoparticles. At PNNL, his research activities also include the surface functionalization of nanoparticles with various organic ligands, quantitative determination of surface functionalities using techniques such as conventional spectroscopic techniques, non-linear optical measurements, and X-ray photoelectron spectroscopy (XPS). His research also involves probing the effect of ligand capping on the structural, chemical, and charge transfer properties between quantum dots and conducting polymers for hybrid solar cell applications. Much of his research involves the biomedical applications of cerium oxide nanoparticles as antioxidants, understanding the pH-mediated reaction of rare earth oxide nanoparticles with reactive oxygen species, and assessing biological activity of ligand-modified nanoparticles.
Understanding the effect of local environment on the physical and chemical properties of nanomaterials—Ajay's current research is focused on nanoparticles synthesis and understanding the effects of local environment and aging on the stability and reactivity of nanoparticles. Over the past few years, his research has helped show that nanoparticles do not remain the same over a period of time and their ability to interact with the solvent and subtle changes in environment, such as local pH, light, temperature, and humidity, could control their aggregation and self-assembly. He is part of a team studying these aspects of bare and ligand-coated cerium oxide as a material system, seeking to understand their stability and interaction with peroxides under various pH and solvent environments.
Functionalization of nanomaterials: How molecules bind to the surfaces—Surface functionalization of nanomaterials with selected ligands can alter their physico-chemical properties. The interest in modification of nanomaterial surfaces stems from the need to increase their biocompatibility for target-specific delivery and for their use in chemical and biochemical sensors. To take full advantage of surface functionalization, it is important to understand, both qualitatively and quantitatively, the interaction of the nanomaterial's surface with the functional ligand around it. At EMSL, Ajay currently is developing ways and means to characterize the surface of nanoparticles and understand their interaction by using surface-sensitive techniques, including sum frequency generation–vibrational spectroscopy (SFG-VS) and in situ XPS, in combination with various conventional characterization techniques. By combining the experimental results with theoretical validation, Ajay and his colleagues are trying to develop a full-scale visualization of the conformation, orientation, and bonding of the ligands to the nanoparticle surfaces.
Assessing toxicological potential of engineered nanomaterials—Ever since it emerged as a powerful basic and applied science tool, nanotechnology has attracted considerable attention in the scientific community. While beneficial aspects of engineered nanomaterials are well envisioned, several reports have suggested the negative impact of engineered nanomaterials on living cells. The diverse array of interesting surface properties achieved due to reduction in particle size that catalyzes the surface chemistry of nanoparticles are also deemed responsible for their toxic potential. Despite the significant amount of work done in recent years on assessing the toxicity of engineered nanoparticles, a clear trend is far from reality. Moreover, the existing literature is full of conflicting reports on the toxicity exhibited by engineered nanoparticles. Thus, there is a growing awareness to fully characterize and understand the properties of engineered nanomaterials. It is now being appreciated that engineered nanomaterials may not retain the same properties from their point of synthesis to their state of application due to changes in the local environment. Often, it is not easy to fully characterize or understand these dynamic and metastable properties in engineered nanomaterials. Ajay and his colleagues are working to emphasize how engineered nanomaterials are not created equal from different synthesis methods and that processing history and sufficient surface characterization are required to formulate a structure–property relationship for assessing the toxicological response of engineered nanomaterials.
CdSe-P3HT-based hybrid solar cells—Efficiently harvesting solar radiation is essential to meet growing energy demands. Polymer hybrid solar cells are promising solar energy devices because they combine the film-forming ability of π-conjugated conducting polymers (e.g., poly(3-hexylthiophene)) with the unique properties of inorganic semiconductor QDs to facilitate charge separation and transport. Additionally, the size of the semiconductor nanoparticle can be varied to control the optical band gap (quantum size effect), as well as the energy of absorption and emission bands to match the highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gaps of various π-conjugated polymers of interest. Ajay and his colleagues are trying to understand the charge transfer properties between CdSe quantum dots and P3HT conducting polymer with an emphasis on the mechanism of this interaction. It is important to understand the physical and chemical structure of individual quantum dots as a function of size to comprehend their interaction with quantum dots. The researchers currently are developing thin film hybrid structures of CdSe quantum dots and P3HT polymer as a function of size of the quantum dots to predict the effect of local structural rearrangements, defects, and electronic structure of quantum dots on the charge separation, transport, and transfer across the chalcogenide-polymer interface.
Immobilized nanoparticles based chemical sensors—Based on the high reactivity and signal enhancements from functionalized nanoparticles, detection of small chemical analyte by nanoparticles has seen drastic improvements in the limits and response time for discovery. Ajay and his colleagues are working toward strategies to immobilize nanoparticles on various substrates to retain the high surface area of nanoparticles and provide a versatile platform for sensing various analytes of significance to national security, environment, and biology.
- Graduate Research Assistant, University of Central Florida, Orlando, August 2005–June 2010
- Presidential Doctoral Fellow, University of Central Florida, Orlando, August 2005–May 2009
- International Student Exchange Scholar, RWTH Aachen University, Aachen, North Rhine-Westphalia, Germany, April 2007–May 2007
- Student Coordinator for Research Experience of Undergraduates Program (Materials Science) at University of Central Florida, Orlando, May 2006–July 2009
- Research Assistant, Indian Institute of Technology, Mumbai, India, December 2004–July 2005
- Production Trainee, Star Sintered Products, Noida, India, March 2003–May 2004
- Teaching Assistant, Indian Institute of Technology, Mumbai, India, August 2001–January 2003
- Ph.D., Materials Science & Engineering, University of Central Florida, Orlando, 2010
- M. Tech, Corrosion Science & Engineering, Indian Institute of Technology, Bombay, India, 2003
- M.S., Organic Chemistry, University of Delhi, India, 2001
Awards, Honors, & Appointments
- "Presidential Doctoral Fellowship" for pursuing graduate research, University of Central Florida, Orlando, 2005–2009
- Nominated for "Order of Pegasus" (highest award at UCF for overall excellence in academics and community service) by the College of Engineering and College of Graduate Studies, University of Central Florida, Orlando, 2009
- Recipient of "AVS Top Level Graduate Student Award" (Dorothy M. and Earl S. Hoffman Scholarship), 2008
- "Graduate Travel Award," University of Central Florida, Orlando, Spring 2007 and Fall 2008
- NSF-IREE (International Travel Funding) fellowship for International visit to Aachen University, Germany, 2007
- 300 citations and H-index of 9.0 in five years of academic research with five review articles and a cover article
- Qualified the National Eligibility Test (NET) for eligibility for Lectureship in Chemistry organized by Council for Scientific and Industrial Research, India
- Two patent applications on the synthesis and applications of cerium oxide nanoparticles as biomedical antioxidants in treatment of diseases caused by the reactive oxygen species
- Part of patent at the University of Central Florida, Orlando, on conversion of fly ash to self-cementing product using sol-gel chemistry