Chemistry Education

Chemistry Education

3 - The SHArK Project: A new paradigm in science laboratory experiments
Jennifer Schuttlefield Ph.D.. Department of Chemistry, University of Wisconsin-Oshkosh, Oshkosh, WI, United States
The Solar Hydrogen Activity Research Kit (SHArK) Project is an outreach project that's goal is to find metal oxide semiconductors via a combinatorial chemistry approach that can efficiently split water into hydrogen and oxygen using only sunlight. With about 60 metals in the periodic table combined to form ternary or quaternary metal oxides, millions of different semiconducting compositions are possible. Among this multitude of combinations we believe there are many with the sunlight absorption and stability properties necessary for splitting water that could help provide a long-term solution to the global energy problem. Given that it is not yet possible to compute or identify these semiconductors, this distributed research project allows for endless numbers of combinations to be produced and screened. A simple, flexible and inexpensive kit was developed for distribution so that a “Solar Army” could be created by recruiting high school and college students to help search for efficient, cost effective metal oxide semiconductors. The SHArK kit is comprised of mostly commercially available parts including LEGO Mindstorms® kits and a 532 nm green laser pointer. Other components of the kit include a custom-built electronics box, custom software, and an etched glass electrochemical cell. The idea is to deposit overlapping patterns of metal oxide precursors onto conductive glass substrates and decompose the precursors into mixed metal oxides. The combinations can be deposited one of three ways: pipetting premixed solutions in spots, spray pyrolysis, or by inkjet printer. After deposition, films are scanned for photocurrent activity using the constructed scanning station. Results are then added to a database for screening of potential “hits”. This project provides students at the high school and undergraduate levels the opportunity to be involved in real-time research using LEGOS®, while attempting to solve the world's energy problem

Physical Chemistry

17 - Dynamics of nitrous acid formation in (NO+)(NO3-)-water clusters
Dr. Mychel E. Varner, Prof. Barbara J. Finlayson-Pitts, Prof. R. Benny Gerber. Department of Chemistry, University of California, Irvine, Irvine, CA, United States; Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem, Israel
Nitrous acid (HONO), which is a major source of atmospheric OH, may be formed through hydrolysis of NO2. A proposed surface mechanism for NO2 hydrolysis depends on the reaction of NO+ and water to produce HONO following the formation of an (NO+)(NO3-) ion pair from the NO2 dimer (1). The formation of HONO in NO+(H2O)n clusters is known to occur for n = 4 or greater (2,3). Through ab initio molecular dynamics with forces calculated at the MP2 level (4), the reaction of NO+ and water has been simulated. The effect of NO3- on HONO formation was investigated with small clusters serving as a model for the air-liquid interface. This work is part of a continuing effort to probe the proposed hydrolysis mechanism.
1. B. J. Finlayson-Pitts, L. M. Wingen, A. L. Sumner, D. Syomin and K. A. Ramazan Phys. Chem. Chem. Phys. (2003) 5 223.
2. J-. H. Choi, K. T. Kuwata, B-. M. Haas, Y. Cao, M. S. Johnson and M. Okumura J. Chem. Phys. (1994) 100 7153.
3. R. A. Relph, T. L. Guasco, B. M. Elliott, M. Z. Kamrath, A. B. McCoy, R. P. Steele, D. P. Schofield, K. D. Jordan, A. A. Viggiano, E. E. Ferguson and M. Johnson Science (2010) 327 308.
4. Y. Miller and R. B. Gerber Phys. Chem. Chem. Phys. (2008) 10 1091.

Analytical Chemistry

3 - Balancing redox activity allows spectrophotometric
detection of Au(I) using tetramethylbenzidine dihydrochloride
Gyoung gug Jang, Prof. Donald Keith Roper PhD. Chemical Engineering, University of Arkansas, Fayetteville, AR, United States; Materials Science and Engineering, University of Utah, Salt Lake City, UT, United States; Microelectronics/Photonics, University of Arkansas, Fayetteville, AR, United States
Aqueous monovalent gold (Au(I)) allows bottom-up fabrication of optoelectronic and thermoplasmonic nanostructures and exhibit anti-cancer activity in vivo. But costly instrumentation (e.g. ICP, AA) and/or complex methods and reagents have here-to-fore been required to analyze aqueous gold, primarily as Au(III). We introduce a new approach to sensitively quantitate Au(I) using UV spectrophotometry of the redox indicator 3,3',5,5'-tetramethylbenzidine dihydrochloride (TMB), by balancing concentrations of a strong reductant (formaldehyde, HCHO) and a strong oxidant (N-bromosuccinimde, NBS) in acid solution. Increasing the HCHO/NBS ratio -the key parameter- from low to high values changes Au(I) from a reducing agent to an oxidizing agent, yielding a quantitatable blue charge-transfer TMB complex of diamine and diimine in proportion to gold content. This novel method is simple, quantitative, and sensitive to 0.0025 mgL-1. Using only inexpensive, commercially-available reagents, it provides a critical analytical pathway to characterize biological and chemical activity of monovalent gold ions.

21 - Thickness and composition effects on the potentiometric response of solid contact ion selective electrodes for Pb2+ based on plasticized membranes containing 4,10-diazadibenzo-18-crown-6 as the ionophore
Julio C Aguilar Dr., Germán Cuervo MSc.. Department of Analytical Chemistry, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City, Federal District, Mexico; Department of Chemistry, Universidad del Cauca, Popayán, Departamento del Cauca, Colombia
Solid contact (Au) ion selective electrodes (SCISE) for Pb2+ were constructed based on a selective, plasticized PVC membrane containing 4,10-diazadibenzo-18-crown-6 ether as the ionophore, 2-nitrophenyloctyl ether as the plasticizer and sodium tetraphenylborate as the ion exchanger. Membrane composition and thickness were varied in order to examine the potentiometric response of the electrodes with changing content of ionophore, plasticizer and ion exchanger. The corresponding analytical figures of merit, i.e. slope, detection limit, linear range and potentiometric selectivity coefficient (Kpot), were determined. Typical values obtained under the optimized experimental conditions were as follows: -29 mV/dec (slope); 10-5.9 M (detection limit); 1 mM-10 mM (linear range); Kpot(Pb2+, Mg2+) = 10-3.7, Kpot(Pb2+, Ca2+) = 10-1.9, Kpot(Pb2+, K+) = 1.47, Kpot(Pb2+, NH4+) = 2.76. The thickness effect on the behavior of the SCISE constructed in this work suggests a great influence of the diffusion potential on the overall potentiometric response.

Sample abstracts from the 241st ACS National Meeting

http://portal.acs.org/portal/PublicWebSite/meetings/nationalmeetings/programarchive/index.htm