AmericanChemicalSociety.com

    During the past year two undergraduate students have been employed in summer research involving studying the interaction of poly(sodium-4-styrene sulfonate) (PSS) and the surfactants benzethonium chloride at the TiO₂/water interface.  In addition two students who were supported on the PRF grant for summer research during the previous year earned their BS in chemistry from Central Washington University and have gone on to more advanced study.  Ryan Scheffelmaier was supported on the PRF grant over the summer of 2009 and has gone on to pharmacy school at Washington State University.  Sarah Hayden was supported on the PRF grant during the summer of 2009 and has gone on to Ph.D. studies at the University of Washington in materials chemistry and nanotechnology.  In addition to these students undergraduates who were not employed directly on the PRF grant but who were in involved in research related to the grant have graduated with a BS in chemistry.  Mark Wirth worked on theoretical aspects of modeling the adsorption of the PSS to TiO₂ surface and has gone on to the Ph.D. program in physical chemistry at the University of Utah.  Adam Alman worked on gels of TiO₂ and PSS and is applying to Ph.D. programs in materials chemistry this year.  Finally, Brittany Best was a MS student in chemistry who was supported on a National Science Foundation GK-12 fellowship whose master’s thesis studied the interaction of PSS/surfactant complexes with water soluble organic compounds and the subsequent interaction of these complexes at the TiO₂/water interface.  This work was in direct line with what was proposed in the PI’s original PRF proposal and undergrads contributed to the thesis work (Hayden, Scheffelmaier, and James Agren).  Brittany successfully defended her thesis and in now employed in the specialty chemical industry for semiconductor and solar cell manufacturing.  The PI hopes that 2 papers will come out of this thesis work within the next year to a year and a half.

            A paper involving work funded by the PRF grant was published in the ACS journal Langmuir during the past year.  The paper was entitled “Quantitative In Situ Attenuated Total Internal Reflection Fourier Transform Infrared Study of the Isotherms of Poly(sodium 4-styrene sulfonate) Adsorption to a TiO2 Surface over a Range of Cetylpyridinium Bromide Monohydrate Concentrations” Langmuir 2010, 26, 5534-5543.  Three undergraduates were co-authors on the paper; Mike Hase, Sarah Hayden, and Ryan Scheffelmaier.  As mentioned in the preceding paragraph both Hayden and Scheffelmaier were supported on the PRF grant.  A poster involving research supported by the PRF grant was also presented at the 2010 national spring meeting of  the ACS in San Francisco.  The paper was entitled “Investigation of surfactant and polyelectrolyte complex interaction with water soluble organics and subsequent adsorption onto the surface of TiO₂” and Best, Hayden, and Scheffelmaier were co-authors.

            Research is continuing on the adsorption of PSS to TiO₂ in the presence of the surfactant benzethonium chloride at different temperatures using ATR-FTIR.  Benzethonium chloride was chosen because it contains infrared features that are easier to analyze than the features of cetylpyridinium bromide.  It has taken more time than originally anticipated to understand the effect of elevated temperature on the adsorption in PSS in the absence of surfactant but we feel we now have a good understanding of this process and can assess the effect of surfactant on the adsorption of PSS to TiO₂ as the solution temperature changes.  We are also continuing UV-Vis studies of PSS/surfactant systems because quantitative information about solution phase concentration of species is of immense help in understanding what is occurring at the TiO₂/water interface which we analyze with ATR-FTIR.  In order to get quantitative information about the PSS, surfactants, and if applicable water soluble organics we have developed a novel multivariate least squares strategy that allows all this information to be extracted from the UV-Vis data simultaneously.  These results show that the number of molecules of surfactant to PSS in the polyelectrolyute/surfactant complex that adsorbs to the TiO₂ surface is ~300 to 1 in the presence of a water soluble organic dye.  This ratio is roughly constant for the dye molecules used (phenol red and bromthymol blue) and the number of dye molecules that are removed from solution per polyelectrolyte/surfactant complex is ~20:1.  Interestingly, these numbers hold for complexes of the polyelectrolyte/surfactant with phenol red at the TiO₂ surface for ionic strengths up to 0.500 M but at ionic strengths of 0.500 M for complexes with bromthymol blue the complex seems to break down and much of the material stays suspended in solution.