Reports: G10
48520-G10 Synthesis of Novel Oxynitride Structures by Soft Chemical Routes
The essence of this research is to exploit novel low-temperature solvothermal routes to obtain stable and metastable oxynitride materials. The ability to synthesize new oxynitride materials will provide fundamental understanding of low temperature synthetic techniques as well as provide new water-splitting photocatalysts. Additionally, as an educator I am passionate about involving undergraduates in the research process. I have developed this research project with undergraduate researchers in mind so they too can become part of the discovery process. To date, three undergraduate students have participated in the project, including one summer research student.
As the first solid-state inorganic chemist in the
department, I have been given me the opportunity to obtain all of the necessary
pieces of equipment needed for my research. Chronologically, the project began
with the acquisition of equipment and supplies required to complete the
proposed work. To this end, funds
from the PRF award have been able to fully or partially fund the purchase of 1)
a box furnace, 2) tube furnace, 3) UV-vis spectrophotometer, 4) departmental FTIR
spectrometer,
5) high-pressure reaction bomb, 6) assorted lab supplies, and 7) provide
stipend support for the PI and a summer student.
Since the inception of the project, undergraduate students have been at work synthesizing literature compounds and attempting to synthesize these same compounds through novel solvothermal methods. To date, the target oxynitride compounds have been limited to lanthanum titanium oxynitride, LaTiO2N, but many oxides have been synthesized. The students have utilized sol-gel methods to synthesize mixed-metal precursor compounds using literature-based polymerized-complex (PC) methods via in-situ ethylene glycol-citric acid polymerization. The PC method is used as it facilitates the synthesis of stoichiometric high surface area oxide compounds that can be reduced to an oxynitride under flowing ammonia or potentially using high-pressure solvothermal techniques. To date, we have successfully synthesized a series of M-RE oxide compounds, where M=Ti, W, Zr, Nb, V and RE=La, Ce as evidenced by XRD and elemental analysis. Several of these compounds form known oxynitrides. We are currently attempting to synthesize these same compounds under low-temperature, high-pressure solvothermal conditions in aprotic solvents (ethylenediamine) and aggressive reducing agents such as sodium borohydride and pyrazine. Solvothermal methods are desired as the solvent can reduce the diffusion barrier among solid-phase reactants. To date, we have not been successful synthesizing these compounds as evidenced by lack of crystallinity and apparent weight loss in thermogravimetric analysis, even after post-treatment annealing. This is most likely due to the stability of the amorphous M-RE oxide and thermal decomposition of ethylenediamine. We are addressing the former through the use of higher reaction temperatures (<450 °C) and the latter by using thermally stable solvents (toluene).
Students in my lab have received an excellent background in various chemistries and techniques, ranging from organic to inorganic and materials work and from simple distillation to x-ray powder diffraction. For all of the students involved in the project to date, this has been the first, if not only, opportunity for them to explore this type chemistry. Interestingly, my summer student was a biochemist by training, but expressed a strong desire to perform inorganic solid-state work in my lab. At the end of the summer, he commented that he is "really confused [about graduate school]", since he does not know what research direction to pursue and is interested in seeking novel ways to link his biochemical and inorganic experiences. Although not a chemistry major, another research student from a culturally underrepresented group, joined my group in the Spring 2009 to begin research for the first time in a chemistry lab. The research experience signified a major change in the way the she viewed chemistry, more as an evolving science rather than a static classroom experience. She is also now in the process of changing from a biology to a chemistry major. My third research student has been working with me before the PRF award and has continually expressed his desires to go to graduate school, seeking ways to immerse himself in some form of alternative energy research. This student is also the president of our Chemistry Club, keeping him very involved with both Outreach and Research while being an academically top-performing student. Unfortunately, my request for an ACS PRF SUMR student was not funded, but this would have provided some much needed research experience to the applicant.
Professionally, the ACS PRF award has allowed me to explore my proposed research and explore new research avenues, making connections among on- and off-campus colleagues, and seek additional funding for continued support. Towards the end of this summer's research season, my student began to explore novel biomimetic templating techniques with oxynitride compounds. We have successfully been able to template oxynitrides from cellulose and we are currently exploring other wood-based templates. This sub-project has the potential to make a significant impact in the field of high-surface area materials and green chemistry, since the template materials are not only natural and renewable, but the oxynitride products are known water-splitting photocatalysts. This work is being carried out in conjunction with an ESF faculty member specializing in wood anatomy. Although an unplanned direction, this new research has significant promise and funding is currently being sought from the USDA and potentially the NSF. This new project significantly adds to my initial research goals. Given this information, I look forward to a second year of successful research and education made possible by the ACS-PRF Type G award.
