Controlling Defects(Doping) in Semiconductor Quantum Dots
Semiconductor nanoparticles are potential materials for next generation solar cells, but manipulating defects of these materials remains a challenge. A goal of our research is develop economically viable colloidal methodologies to produce doped quantum confined particles (quantum dots) and study their fundamental properties. Doping nanoparticles and quantum dots results in new and interesting science. Critical components of this research are to find ways to circumvent challenges and to understand the underlying mechanisms of doping quantum dots. The young artist's (Hyeon Jung Kim) conception below shows the structure of a single cadmium selenide quantum dot that is used as a model in our doping studies.
•Luo, H.; Tuinenga, C.; Guidez, E. B.; Lewis, C.; Shipman, J.; Roy, S.; Aikens, C. M.; Chikan, V., Synthesis and Characterization of Gallium-Doped Cdse Quantum Dots. The Journal of Physical Chemistry C (2015), ASAP.
•Sarkany, L.; Wasylenko, J. M.; Roy, S.; Higgins, D. A.; Elles, C. G.; Chikan, V., Investigation of Fluorescence Emission from Cdse Nanorods in Pmma and P3ht/Pmma Films. The Journal of Physical Chemistry C (2013), 117, 18818-18828.
•Roy, S.; Aguirre, A.; Higgins, D. A.; Chikan, V., Investigation of Charge Transfer Interactions in CdSe Nanorod P3HT/PMMA Blends by Optical Microscopy. The Journal of Physical Chemistry C (2011), 116 (4), 3153-3160.
•Chikan, V., Challenges and Prospects of Electronic Doping of Colloidal Quantum Dots: Case Study of CdSe. J. Phys. Chem. Lett. (2011), 2 (21), 2783-2789.
•Santanu Roy, C. T., Fadzai Fungura, Pinar Dagtepe, Jacek Jasinski and Viktor Chikan, Progress towards Producing n-type CdSe Quantum Dots: Tin and Indium Doped CdSe Quantum Dots. J. Phys. Chem. C (2009), 113 (30), 13008–13015.
•Christopher Tuinenga, Jacek Jasinski, Valerie J. Leppert; Takeo Iwamoto, Viktor Chikan, In situ Observation of Heterogeneous Growth of CdSe Quantum Dots; Effect of Indium Doping on the Growth Kinetics, ACS Nano, 2(7), 1411–1421, (2008)
• Mandal, P. K. & Viktor Chikan Terahertz Conductivity of n-type (charged) CdSe Quantum Dots. Nano Lett., 7 (8), 2521 -2528, (2007)
Colloidal Synthesis of Nanomaterials
Our group has been involved in synthesizing a variety of new nanomaterials at Kansas State University. Many of the materials are the result of the hypothesis driven research where we intend to investigate a particular material in terms of its function, however in some instances we have stumbled across some new materials. One of the driving force for exploring new nanomaterials is that the currently available materials are not sustainable to address the specific needs. We are developing materials that are potentially more environmentally friendly and abundant. The picture collage below shows a gallery of nanoparticles developed by our group. The images are obtained by high-resolution transmission electron microscopy.
•Dahal, N.; Jacek Jasinski; Valerie J. Leppert; Viktor Chikan, Synthesis of Water-Soluble Iron-Gold Alloy Nanoparticles. Chem. Mater., 20 (20), 6389–6395, (2008)
•Dahal, N.; Chikan, V., Phase-Controlled Synthesis of Iron Silicide (Fe3Si and FeSi2) Nanoparticles in Solution. Chem. Mater. (2010) 22, (9), 2892-2897.
•Dahal, N.; Chikan, V., Synthesis of Hafnium Oxide-Gold Core-Shell Nanoparticles. Inorganic Chemistry 2012, 51 (1), 518-522.
Mechanism of Colloidal Growth of Nanomaterials
Colloidal synthesis of nanomaterials is a cheap process that can be potentially scaled up for industrial production. Controlling the growth of nanoparticles in colloidal solution is an important step towards developing materials with well-defined optical and physical properties. Our goal is to understand how the interplay of thermodynamics and growth kinetics determines the size and the size distribution of nanoparticles. The thermodynamic control of the nanoparticle growth may lead phenomena such as the formation of magic sized nanoparticles. In the example below, we are observing the birth of magic sized CdTe quantum dots and its 'quantized' aggregation into larger quantum dots by in situ absorption spectroscopy during the growth of nanostructures. LEFT figure shows the 'usual' monomer induced growth of CdSe quantum dots. RIGHT figure shows the time evolution of the absorption spectra of CdTe quantum dot solution during the synthesis. The first step is the formation of magic sized CdTe quantum dot, which subsequently undergoes aggregation.
•Dagtepe, P.; Chikan, V., Quantized Ostwald Ripening of Colloidal Nanoparticles. J. Phys. Chem. C (2010), 114, (39), 16263-16269.
•Dagtepe, P.; Chikan, V., Effect of Cd/Te Ratio on the Formation of CdTe Magic-Sized Quantum Dots during Aggregation. J. Phys. Chem. A (2008), 112, (39), 9304-9311.
•Dagtepe, P., Jacek Jasinski, Valerie J. Leppert; Viktor Chikan, Quantized Growth of CdTe Quantum Dots; Observation of Magic Sized CdTe Quantum Dots. J. Phys. Chem. C, 111 (41), 14977 -14983, (2007)
Magnetic Properties of Colloidal Nanoparticles
Interaction of magnetic field with nanoparticles will be important to remotely manipulating these particles from our macroscopic world to control processes at the microscopic level. In this work, we are interested in exploring the basic science of how magneto-optical phenomena take place in colloidal metal and magnetic nanomaterials. Specifically, we are investigating the Faraday rotation of metal and magnetic nanomaterials and how these materials differ from their bulk counterparts.
•Wysin, G. M.; Viktor, C.; Nathan, Y.; Raj Kumar, D., Effects of Interband Transitions on Faraday Rotation in Metallic Nanoparticles. Journal of Physics: Condensed Matter 2013, 25, 325302.
•Dani, R. K.; Wang, H.; Bossmann, S. H.; Wysin, G.; Chikan, V., Faraday rotation enhancement of gold coated Fe2O3 nanoparticles: Comparison of experiment and theory. J. Chem. Phys. (2011), 135 (22), 224502-9.
Cancer Treatment and Drug Delivery with the help of Magnetic Nanoparticles
Magnetic hyperthermia represents a one step development towards selective and uniform heating of cancerous tissue by introducing nanometer sized magnetic particles close to a tumor site. The temperature increase of the tissue can significantly contribute to the destruction of the cancerous cells. Heating takes place by power absorption of the nanometer sized superparamagnetic and ferromagnetic particles from alternating magnetic field.
•Podaru, G.; Dani, R. K.; Wang, H.; Basel, M. T.; Prakash, P.; Bossmann, S. H.; Chikan, V., Pulsed Magnetic Field Induced Fast Drug Release from Magneto Liposomes Via Ultrasound Generation. J. Phys. B (2014), 118(40), 11715–11722.
•Chikan, V.; Bossmann, S., Biosensors Based on Nanomaterials
and Nanodevices. Wu, J. L. a. N. N., Ed. CRC Press, Taylor & Francis Group: (2013);
•Wang, H.; Shrestha, T. B.; Basel, M. T.; Dani, R. K.; Seo, G.-M.; Balivada, S.; Pyle, M. M.; Prock, H.; Koper, O. B.; Thapa, P. S.; Moore, D.; Li, P.; Chikan, V.; Troyer, D. L.; Bossmann, S. H., Magnetic-Fe/Fe3o4-Nanoparticle-Bound Sn38 as Carboxylesterase-Cleavable Prodrug for the Delivery to Tumors within Monocytes/Macrophages. Beilstein Journal of Nanotechnology (2012), 3, 444-455.
•Basel, M. T.; Balivada, S.; Wang, H.; Shrestha, T. B.; Seo, G. M.; Pyle, M.; Abayaweera, G.; Dani, R.; Koper, O. B.; Tamura, M.; Chikan, V.; Bossmann, S. H.; Troyer, D. L., Cell-Delivered Magnetic Nanoparticles Caused Hyperthermia-Mediated Increased Survival in a Murine Pancreatic Cancer Model. International Journal of Nanomedicine (2012), 7, 297-306.
•Rachakatla, R. S.; Balivada, S.; Seo, G.-M.; Myers, C. B.; Wang, H.; Samarakoon, T. N.; Dani, R.; Pyle, M.; Kroh, F. O.; Walker, B.; Leaym, X.; Koper, O. B.; Chikan, V.; Bossmann, S. H.; Tamura, M.; Troyer, D. L., Attenuation of Mouse Melanoma by a/C Magnetic Field after Delivery of Bi-Magnetic Nanoparticles by Neural Progenitor Cells. Acs Nano (2010), 4, 7093-7104.
•Balivada, S.; Rachakatla, R. S.; Wang, H.; Samarakoon, T.; Dani, R. K.; Pyle, M.; Kroh, F.; Walker, B.; Leaym, X.; Koper, O.; Tamura, M.; Chikan, V.; Bossmann, S.; Troyer, D., A/C Magnetic Hyperthermia of Melanoma Mediated by Iron(0)/Iron Oxide Core/Shell Magnetic Nanoparticles: A Mouse Study. BMC Cancer (2010), 10, 119.
Development of Electromagnets for Biological Applications
Manipulating small magnetic nanoparticles in solution require homogeneous and inhomogeneous magnetic fields. The Chikan group has developed several pulsed magnets that aim to rotate and translate magnetic nanomaterials. The picture below shows an electromagnetic coil designed to produce high strength, homogeneous high frequency magnetic field. The magnetic field of the magnetic is measured via faraday rotation of a known material at the HeNe laser frequency (632 nm). These magnetic fields will be utilized to achieve instantaneous drug release in biological medium.
•Podaru, G.; Moore, J.; Dani, R. K.; Prakash, P.; Chikan, V., Nested Helmholtz coil design for producing homogeneous transient rotating magnetic fields. Review of Scientific Instruments (2015), 86 (3), 034701.