University of Wyoming
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Our long term scientific objective is to develop methods for preparation of organic and inorganic supramolecular nanomaterials with tunable chiroptical, photonic, magnetic and non-linear optical properties. We aim to achieve profound understanding of the intermolecular interactions governing their formation and dictating properties. All of our projects are interdisciplinary.

Current research projects include:
1. Supramolecular DNA-templated porphyrin nanostructures
Templated assembly describes the formation of nanosized materials by template directed arrangement of small molecules into predictable architecture with novel structural and electronic properties. A well-defined and controlled assembly of nanostructures is a critical requirement for their applications in material sciences, sensing and nanotechnology. We explore chiral multichromophoric nanoarrays with attractive structural and photophysical properties formed by oligonucleotide controlled assembly of porphyrin chromophores. We use external stimuli induced structural transitions to tune their functional properties.
representative reference:
Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.
G. Sargsyan, B. M. Leonard, J. Kubelka, M. Balaz
Chem. Eur. J., 2014, 20, 1878-1892.

2. Organic ligand induced chiroptical inorganic nanomaterials
Optically active semiconductor and metallic nanoparticles (NPs) possess unique yet modular structural and optical properties not present in bulk materials. We study how the structure and binding of the chiral organic molecules induce chiroptical activity in achiral semiconductor and metallic NPs. Understanding the structural and electronic origin of induced chiroptical activity in nanomaterials is critical for further systematic research. Chiral NPs are promising candidates for biosensing, labeling, environmental nanoassays and chiral memory as well as attractive building blocks for the bottom-up nanofabrication of chiroptical devices and nanoassemblies.
representative reference:
Ligand induced circular dichroism and circularly polarized luminescence in CdSe quantum dots.
U. Tohgha, K. K. Deol, A. G. Porter, S. G. Bartko, J. K. Choi, B. M. Leonard, K. Varga, J. Kubelka, G. Muller, M. Balaz
ACS Nano., 2013, 7, 11094-11102.

3. Quantum dots sensitized solar cells (QDSSCs)
Quantum dots (QDs) are semiconductor nanocrystals with electronic properties lying between discrete molecules and bulk semiconductors.Their electronic and spectroscopic properties are closely related to their size and are tunable (quantum size effect). QD nanocrystals are attractive candidates for preparation of efficient and robust solar cells. We work on the colloidal synthesis of semiconductor QDs for solar cells. We utilized organic shell to tune QDs electronic and structural properties. Our research is a part of a DOE EPSCoR funded project (DE-FG02-10ER46728).

4. Enhanced circular dichroism detection of chiral biomolecules
Circular dichroism (CD) is the preferred technique for detection and analysis of chiral compounds and their interactions. Currently, moderate sensitivity of CD and undesirable spectral overlaps with other chiral molecules hinder the analysis of multi-component systems. We develop organic and inorganic spectroscopic probes to enhance the sensitivity of electronic circular dichroism. Enhanced sensitivity will allow the study of chiral molecules and their interactions at low, biologically relevant concentrations.
representative reference:
Chiroptical properties, binding affinity, and photostability of a conjugated zinc porphyrin dimer complexed with left-handed Z-DNA and right-handed B-DNA.
J. K. Choi, A. Reed, M. Balaz
Dalton Trans., 2014, 43, 563-567.

      A variety of techniques and approaches are utilized in our research. Graduate students are trained in the areas of synthetic organic chemistry, molecular recognition, supramolecular assemblies, organometallic chemistry, metallic nanoparticles, DNA and peptide synthesis, and quantum dots.
      We use a range of spectroscopic techniques such as NMR, circular dichroism, fluorescence spectroscopy, UV-vis absorption spectroscopy, linear dichroism, resonance light scattering, and dynamic light scattering. We also employ TEM and AFM to characterize our supramolecular nanostructure, DNA assemblies, metallic nanoparticles, and quantum dots.
      In routine use, two methods of mass spectrometry are employed for molecular weight determination: MALDI-TOF (matrix-assisted laser desorption ionization - time of flight) and ESI (electrospray ionisation).
      Our main purification techniques include flash column chromatography, reverse phase HPLC, size exclusion chromatography (SEC), and gel electrophoresis (PAGE).

We graciously acknowledge support from:

  • NSF, Division of Chemical, Bioengineering, Environmental, and Transport Systems:AwardCBET1403947
  • DOE,EPSCoR: Award DE-FG02-10ER46728
  • NSF, Division of Graduate Education: Award DGE0948027
  • UW Academic Affairs: Energy Graduate Assistantship

National Science Foundation Department of Energy University of Wyoming