Academic journal article The Science Teacher

Real Science or Marketing Hype? Student-Designed Experiments Test the Antimicrobial Effects of Silver Nanoparticles

Academic journal article The Science Teacher

Real Science or Marketing Hype? Student-Designed Experiments Test the Antimicrobial Effects of Silver Nanoparticles

Article excerpt

[ILLUSTRATION OMITTED]

Teachers have been asked to engage their students in more and more cutting-edge science (Committee on Prospering in the Global Economy of the 21st Century 2007). One way of doing this is to bring nanotechnology into the classroom. The Center for Nanoscale Chemical-Electrical-Mechanical Manufacturing Systems (Nano-CEMMS) at the University of Illinois, in collaboration with local Champaign-area teachers, has developed classroom activities designed to introduce nanotechnology to secondary students. One such activity investigates the antimicrobial effect of silver nanoparticles, or very small pieces of silver. The diameters of these silver pieces range in size from about 5-50 nm across; for comparison, three or four atoms placed end-to-end are typically about 1 nm in length. These nanoparticles are so small that they remain suspended in water.

Silver nanoparticles have been used to generate antimicrobial surfaces in several new products, including fabrics (to prevent clothes from developing foul odors), doorknobs, and even pacifiers (see "On the web" at the end of this article). With hundreds of new products claiming antimicrobial properties, we at Nano-CEMMS thought it appropriate to put silver nanoparticles to the test.

This article describes a quick, simple, and safe classroom activity in which students make silver nanoparticles and design experiments to test their effectiveness. In less than 30 minutes, students make nanoparticles by mixing a few readily available solutions on a hotplate. Students also generate their own experiments to test the "antimicrobial properties" of the silver nanoparticles they have created by growing bacteria in the absence or presence of these nanoparticles. Based on the level of teacher involvement, the activity can be modified for students with a range of ability levels. Therefore, the activity is appropriate for advanced chemistry or biology classes, yet still suitable for introductory biology or general science classes.

Connections to student learning goals

This investigation is highly adaptive to the needs of individual teachers and can be incorporated into the established curriculum to address a number of key National Science Education Standards focusing on scientific inquiry or discipline-specific concepts (NRC 1996). Regardless of how this investigation is included, students engage in their own inquiry about the antimicrobial effect of silver nanoparticles. Depending on the amount of scaffolding, students can engage in an open inquiry investigation or a more closely scaffolded activity. The intended learning goals determine the type of inquiry undertaken.

In addition to the inquiry standards, different content standards can also be addressed depending on the context in which the activity is embedded. If a more chemical approach is taken, this investigation could address Content Standard B by examining how the structure and properties of matter change following a chemical reaction (NRC 1996, pp. 178, 179). While the context of testing the properties is a biological one, the content focus would be chemistry; this can be used to show the interdisciplinary nature of science.

For illustrative purposes, we have chosen to highlight experimental design in the description of this activity. Research has shown that students have difficulty designing controlled experiments (Chen and Klahr 1999; Toth, Klahr, and Chen 2000). In this article, we provide a description of how a chemistry and biology teacher supports her students as they engage in the activity, which focuses on the identification of experimental variables to control.

The activity

In the teacher's biology class, students were introduced to this activity through a PowerPoint presentation on the making of silver nanoparticles. Similarly, teachers can introduce students through a presentation that reviews student understanding of colloidal chemistry--the study of mixtures containing particles between 1 and 1,000 nm in size--and relates colloids to particle size (nm). …

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