Functional Nanomaterials Nanotechnology is a hot topic in science and even in popular literature. Most research groups in nanotechnology tend to either develop novel methods of mechanical manipulation of nanoscale materials or study the effect of size on fundamental properties (also called "quantum confinement"). Our group focuses on both topics by synthesizing new materials which display size dependent properties and then developing techniques to impart function to those same materials.

Semiconductor quantum dots are bright inorganic luminescent nanocrystals (NCs) that have photophysical properties that are far superior to organic dyes. First, they are much more stable and do not photobleach like organic fluorophores. Also, they can use almost any excitation source which is not true for most dyes. Unfortunately, semiconductor NCs have two flaws- they are highly toxic and not soluble in water. Our group has recently developed a novel non-toxic bright Manganese doped Zinc Selenide nanocrystal which has the form of a ZnSe core, a ZnS shell doped with manganese, and a final ZnS cap (Nano Lett, 2007, 7, 3429). We have shown that energy transfer from the core to the shell is highly efficient; we further demonstrated that the phosphor may transfer the core excitation to an organic dye bound to the surface of the water solubilized ZnSe/ZnMnS/ZnS NC. Shown here are several samples of this materials under UV light excitation. We are also synthesizing several other types of non-toxic nanomaterials for biological imaging applications.

Lionel Hutz once said, "A town with money is like a mule with a spinning wheel. No one knows how he got it and danged if he knows how to use it!" We can sometimes find ourselves in the same situation with nanotechnology. What good is an unphotobleachable fluorescent nanocrystal if it doesn't "do" anything? Most NCs are not even soluble in water! Consequently, if we want to use the NC to tag a biological agent, then an antigen must be bound to the surface of a water solubilized NC. If we want to use the NC as a chemical sensor, we have to attach a sensing organic dye to the surface (see our article in JACS, 2006, 128, 13320). To impart water solubility many groups includeing our own wrap NCs in amphiphilic polymers [40% octylamine modified poly(acrylic acid)]; however for many complex reasons it is very hard to functionalize this material further with standard techniques. Shown here is our workaround (JACS, 2008, 130, 3744). We used a method of size controlled free radical polymerization that makes highly uniform polymers that contain a single thiol functional group. We then demonstrated that the SH function may be used to functionalize the NCs and avoids many problems associated with other, more standard carbodiimide coupling schemes which causes permanent precpitation of the NC materials. Shown here is one example of a BODIPY dye bound to a polymer coated CdSe/ZnS NC where we demonstrated energy transfer from the NC to the surface bound dye. This paves inroads for the development of chemical sensors as discussed below. We have also recently developed a new class of chemical conjugation agents that is the subject of a provisional patent application.

Our group has a variety of emissive NCs and methods to impart functional elements to their surfaces. What can we develop with this technology? It turns out that the excitation energy of a NC may be transferred to a surface bound organic fluorophore if the dye is closely bound to the NC and has an absorption profile that closely matches the emission of the NC. An interesting aspect of this work is that many dyes have absorption profiles that are environmentally sensitive- thus the local chemical environment may influence the efficiency of energy transfer from NC to dye. Shown here is a NC / dye coupled sensor for an environmentally hazardous element- mercury. As the levels of mercury rise the dye become more absorptive which causes energy transfer from the NC to the dye to occur. What is interesting about this work is that we have avoided the problem of the mercury ion reacting with the NC itself which quenches the NC fluorescence. Note that the sensing is ratiometric- or "self-calibrating," which is much more useful than single response sensing elements that merely "turn-on" in the presence of selected analytes. We are presently designing several types of ratiometric sensing NCs for harmful environmental contaminants, especially toxic metals.

In conjuction with the group of Dr. Randall Meyer at UIC Chemical Engineering, we are also presently developing catalytic materials thaty may impact world energy consumption. We will likely run out of petroleum products for energy production in the year 2050, and without a clean alternative fuel (something other than coal) we will be living out the worst parts of a Mad Max movie. Photocatalysis is a promising source of energy however photocatalytic materials are polycrystalline or amorphous which obfuscates analytical analysis of the catalytic centers. We are presently applying the techniques used to synthesize highly fluorescent NCs for creating highly efficient and crystalline semiconductor photocatalysts for energy production.