In the laboratory, we are interested in the design and synthesis of quantum dot (QD) and quantum rod (QR) nanomaterials for applications in self-assembly and energy transfer.
Our first project deals with addressing a major challenge in the field, that of synthesizing QDs under aqueous conditions. Some of the first dots ever made were made this way, but often the products of the QD synthesis do not have optimum properties, such as high quantum yield. To address this, we developed a new strategy that employs microwave mediated hydrothermal processing to improve the QD nucleation and growth. Led by graduate student Hyunjoo Han, we have shown that CdSe, CdSe/CdS, and CdSe/ZnS QD can be fabricated at hydrothermal conditions that are driven by microwave irradiation (MWI). By increasing the temperature (hydrothermal vs. reflux), we have shown that the QD products are more crystalline, and thus, have a improved optoelectronic properties. A potential advantage of this approach is the QD’s are directly produced in aqueous conditions, and thus the approach is a “green” one. In addition, this may lead to better processability in future energy transfer projects. While many experiments are ongoing, recent results can be found at J. Phys. Chem. C.
In our second project, we aim to synthesize the most state of the art quantum dots (QDs) and rods (QR). Led by graduate students Corey Hine and Rabeka Alam, we have developed a great capability to synthesize any class of dot. For example, for use in our self-assembly and energy transfer projects, we have developed the capability to fabricate spherical CdSe/CdS and CdSe/ZnS QDs with tailored core size, and shell thickness. As shown to the right, we have fine control of the optoelectronic properties. Graduate student Corey Hine recently put this capability to good use when we produced CdSe/ZnS QDs with tailored ZnS shell thickness for a state of the art study of hole (h+) transport in QDs by collaborators at Brookhaven National lab. For more information please see ACS Nano.
In our third project, we are synthesizing quantum rods (QR) with controlled length, width, and internal microstructure. Led by graduate student Rabeka Alam, we are able to tailor QR aspect ratios (length/width), and produce rods with “dot-in-dot”, “dot-in-rod” and “rod-in-rod” morphologies. The optical and energy transfer characteristics of the QR change by tailoring these parameters, allowing for the precise design of functional nanomaterials. We recently demonstrated this by showing that a “rod-in-rod” microstructure is critical to achieving high energy transfer efficiencies, as recently shown in Nano Letters.