Adding Value to Organic Chemistry Curriculum by Infusing Guided Inquiry Nanoscience Experiments

Nanoscience constitutes a new field, which emerged from the realization that nanomaterials and semiconductors exhibit interesting size-dependent properties. Nanoparticles, which are defined as having a diameter between 1 and 10 nm, offer new and novel materials that are different either from conventional bulk materials or from atoms, the smallest unit of matter. There has been great interest in using nanomaterials in analytical separations, identification, and isolation of complex natural products. Nanoparticles are intrinsically unstable in solution and can aggregate easily if not protected. Several methods have been proposed for stabilization of nanoparticles. The goal of our guided inquiry lab was to answer the following guided inquiry question: What color change(s) occur when an organic or inorganic compound is added to gold nanoparticles (GNPs)? The experiment involved two main steps: synthesizing gold nanoparticles (GNPs) and then using them as indicators. Several organic (acetic acid, sucrose, salicylic acid, aspirin, α-D glucose and vitamin K) and inorganic (sodium chloride (NaCl), iron (III) chloride (FeCl3) and silver chloride (AgCl)) compounds were investigated. The GNPs acted as an indicator to signal a chemical reaction had occurred. Students worked in groups of four. Each group was given specific organic and inorganic compounds to be added to the GNP solution. The colors for the organic compounds were all shades of purple, some darker or lighter than others. The colors for inorganic were more of a dark blue. Sugar, aspirin, and α-D-glucose were dark red. Inorganic compounds such as NaCl and ferric chloride were aqua. These data suggest the colors of organic compounds stayed around purple while the inorganic exhibited darker bluish-green colors. Taken together, the results showed inorganic compounds had a greater change in color than organic compounds. This illustrated inorganic compounds cause an increase in the size of the GNPs, which act as chemical selective sensors towards inorganic compounds more than organic compounds.