Our research focuses on chemistry, physics and material science of inorganic nanostructures. By combining expertise in colloidal synthesis, self-assembly and characterization of nanomaterial properties our group creates novel materials for electronic, photovoltaic, thermoelectric and catalytic applications.       

Colloidal Synthesis

Colloidal synthesis of inorganic nanostructures is developing into a new branch of synthetic chemistry. Starting with preparations of simple objects like spherical nanoparticles, the field is now moving toward more and more sophisticated structures where composition, size, shape and connectivity of multiple parts of a multicomponent structure can be tailored in an independent and predictable manner.

Examples of semiconductor and magnetic nanomaterials synthesized by colloidal chemistry techniques.

Self-Assembly of nanopaticles

Inspired by the way most solids form in nature, with individual atoms or molecules assembling themselves into rigid, highly uniform arrays, we study assembly of monodisperse nanocrystals into ordered superstructures. Assembling nanoscale functional building blocks provides a powerful modular approach to the design of novel materials and ‘metamaterials’ with programmable physical and chemical properties.

Self-assembly of monodisperse nanocrystals into ordered superlattices and “crystals” constructed from functional nanocrystal building blocks.

Binary nanoparticle superlattice

Bringing together compounds of intrinsically different functionality constitutes a particularly powerful route to creating novel functional materials with synergetic properties found in neither of the constituents. Binary nanoparticle superlattices (BNSL) self-assembled from different combinations of semiconductor, magnetic, metallic and dielectric nanocrystals show amazing structural diversity. The range of materials which can be used as building blocks in BNSL structures seems to be limited only by our ability to make a particular material in form of monodisperse nanoparticles. Self-assembly of functional nanoparticles into single- and multicomponent superlattices offers nearly endless possibilities for creating novel materials for a range of applications from photovoltaic and thermoelectric devices to non-linear optics, multiferroics and multicomponent catalysts. However, we have very limited understanding of the processes which govern BNSL formation and determine stability of different structures. We investigate the fundamental aspects of self-assembly in the nanoworld.

Binary nanoparticle superlattices self-assembled from different combinations of semiconductor, magnetic, metallic and dielectric nanocrystals show amazing structural diversity. The insets show sketches of the superlattice unit cells.

Charge transport of nanocrystals

Nanocrystal superlattices constitute a novel type of condensed matter whose properties originate both from the properties of individual nanocrystals and the collective phenomena caused by the crosstalk of the superlattice building blocks. We study electronic properties (carrier mobility, doping, charge transport mechanism, photoconductivity, thermopower) and heat transport in single- and multicomponent nanocrystal solids. The knowledge obtained from fundamental studies of nanocrystal assemblies will be used for development of practical solution-processed devices utilizing nanocrystals and nanocrystal assemblies. Performance of printable nanocrystal transistors compares favorably with devices based on organic molecules and conducting polymers. The nanocrystal field effect transistors allow reversible switching between n- and p-transport, providing options for printable complementary metal oxide semiconductor (CMOS) circuits and p-n junctions.

D. V. Talapin, E. V. Shevchenko, C. B. Murray, A. V. Titov, P. Král. Nano Letters 2007, vol. 7, pp 1213-1219. Dipole-dipole interactions in nanoparticle superlattices.

J. J. Urban, D. V. Talapin, E. V. Shevchenko, C. R. Kagan, C. B. Murray. Synergistic Effects in Binary Nanocrystal Superlattices: Enhanced p-type Conductivity in Self-Assembled PbTe/Ag₂Te Thin Films.Nature Materials. 2007, vol. 6, pp. 115-121.

E. V. Shevchenko, D. V. Talapin, N. A. Kotov, S. O’Brien, C. B. Murray. Structural Diversity in Binary Nanoparticle Superlattices. Nature 2006, v. 439, pp. 55-59.

D. V. Talapin, C. B. Murray. PbSe Nanocrystal Solids for n- and p-Channel Thin Film Field-Effect Transistors. Science 2005, v. 310, pp. 86-89.

K.-S. Cho, D. V. Talapin, W. Gaschler, C. B. Murray. Designing PbSe Nanowires and Nanorings through Oriented Attachment of Nanoparticles. J. Am. Chem. Soc. 2005, v.127; pp. 7140-7147.

D. V. Talapin, E. V. Shevchenko, C. B. Murray, A. Kornowski, S. Förster and H. Weller. CdSe and CdSe/CdS nanorod solids. J. Am. Chem. Soc. 2004, vol. 126, pp. 12984-12988.

D. V. Talapin, R. Koeppe, S. Götzinger, A. Kornowski, J. M. Lupton, A. L. Rogach, O. Benson, J. Feldmann, H. Weller. Highly emissive colloidal CdSe/CdS heterostructures of mixed dimensionality. NanoLetters, 2003, vol. 3, pp.1677-1681.

D. V. Talapin, A. L. Rogach, E. V. Shevchenko, A. Kornowski, M. Haase, H. Weller. Dynamic Distribution of Growth Rates within the Ensembles of Colloidal II-VI and III-V Semiconductor Nanocrystals as a Factor Governing their Photoluminescence Efficiency. J. Am. Chem. Soc. 2002, vol. 124, pp. 5782-5790.

D. V. Talapin, A. L. Rogach, M. Haase, H. Weller. Evolution of an Ensemble of Nanoparticles in a Colloidal Solution: Theoretical Study. J. Phys. Chem. B 2001, vol. 105, pp. 12278-12285.

D. V. Talapin, A. L. Rogach, A. Kornowski, M. Haase, H. Weller. Highly Luminescent Monodisperse CdSe and CdSe/ZnS Nanocrystals Synthesized in a Hexadecylamine – Trioctylphosphine Oxide – Trioctylphospine Mixture. Nano Lett. 2001, vol. 1, pp. 207-211.