| Research Overview
Doping Semiconductor Quantum
Dots
A challenge in the creation of nanometer sized p-n junctions is the ability to control the free carrier concentration in semiconductor nanostructures. Controlling the carrier concentration in quantum dots(QD) can be done via incorporating a foreign atom in the semiconductor (doping). 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. We are currently exploring strategies for succesful doping of QDs and its application to solar cells.
Growth Kinetics of Quantum Dots
Controlling the growth of semiconductor quantum dot is an important step towards developing materials with well defined optical and physical properties. In a typical semiconductor quantum dot synthesis, the average size and size distribution of QDs is determined by the growth and the dissolution kinetics. There are numerous examples when the size and size distribution of the nanoparticle growth is determined by the thermodynamics of the nanoparticles rather then the kinetics. The thermodynamic control of the nanoparticle growth may lead to the formation of magic sized nanoparticles. Currently, our research focuses on the formation of magic sized CdTe quantum dots and its 'quantized' aggregation into larger quantum dots. 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.
 
Terahertz Spectroscopy of Nanostructures
Terahertz spectroscopy is a powerful technique,
which probes the dynamic changes in the far infrared part of the
electromagnetic spectrum (typically between 10 – 600 cm-1) using
sub-picosecond electromagnetic pulses.The electromagnetic pulse interacts with matter, which is related to thecomplex dielectric response of the sample, therefore its conductivity. Obtaining the
conductivity of nanostructures without electrical connections is
desirable to asses the
electronic efficiency of nanostructures. We are exploring the applicability of the terahertz technique to doped and charged nanostructures.
Magnetic Hyperthermia by Superparamagnetic 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 or from ultrafast magnetic field. We are interested in the relaxation processes of superparamagnetic nanoparticles and its impact on their heating capbility. The images below show the conspectual difference between Brownian and Neel relaxation of a magnetic spin in a superparamagnetic nanparticle, repesctively
 
Sponsors:
Kansas State University, Department of Chemistry, COBRE (NIH) Center for Cancer Experimental Therapeutics, The Terry C. Johnson Center for Basic Cancer Research, University Small Research Grant, President’s Faculty Development Award, American Chemical Society Doctoral New Investigator
Selected Publications
(The complete list of publications is available here)
•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.
•Dahal, N.; Jacek Jasinski; Valerie J. Leppert; Viktor Chikan, Synthesis of Water-Soluble Iron-Gold Alloy Nanoparticles. Chem. Mater., 20 (20), 6389–6395, (2008)
•Dagtepe, P.; Chikan, V., Effect of Cd/Te Ratio on the Formation of CdTe Magic-Sized Quantum Dots during Aggregation. J. Phys. Chem. A:STEPHEN R. LEONE FESTSCHRIFT (2008), 112, (39), 9304-9311.
•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)
•Raj Kumar Dani, Myungshim Kang, Mausam Kalita, Paul E. Smith, Stefan H. Bossmann and Viktor Chikan MspA Porin-Gold Nanoparticle Assemblies: Enhanced Binding through a Controlled Cysteine Mutation. Nano Lett., 8(4); 1229-1236, (2008)
•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)
• Mandal, P. K. & Viktor Chikan Terahertz Conductivity of n-type (charged) CdSe Quantum Dots. Nano Lett., 7 (8), 2521 -2528, (2007) |
