One of the fastest growing fields in science today, material science, studies the physical and chemical properties of different materials (metals, ceramics, etc.), and how these properties are related to fundamental characteristics of the materials, such as its structure. The techniques presented here relate directly to techniques and ideas we use in our own research. This lab exercise studies the optical properties of organic gels, while our research studies similar properties of organo-metallic gels. That is, instead of adding food coloring and artificial flavorings into our gels, we add optically-active chemicals. In this lab exercise, we study a fundamental optical property of a material, the index of refraction, while in our own research we study how energy may be transferred or transformed in our materials. Information about the transfer of energy between our additives allows us to make new and better optical materials. One type of energy transfer, upconversion, allows a material to make blue light out of red light. This process could be used to create high-efficiency blue-ray DVD lasers.
In our research, we turn our gels into glasses through a careful heating schedule, driving off the water molecules from the gel, and leaving behind a sample with much improved optical properties. Although this might seem abstract, we observe such careful controlling of temperature when cooking, for instance Jell-O. Jell-O is composed mainly of gelatin, but also of sugar, food coloring, and artificial flavorings. Gelatin gives Jell-O its fun, moldable, jiggly properties by acting as the host material for the additives (sugar, coloring, etc.) that modify its properties. In this lab exercise, we study the properties of gels made out of gelatin and water. Much like in our research, to make gel samples, we will have to control the temperature of the material throughout the synthesis process.
By varying the ratio of gelatin to water, we modify the structure of the gel, which in turn affects its optical properties. Particularly, as the density of the gelatin changes, so does the index of refraction of the gelatin.
We first measure this change in the index of refraction by calculating it from a measurement of the Brewster’s angle of a sample of the material.
We then find the focal length of gel lenses with different gelatin concentrations by using the lens maker equation. This difference in focal lengths allows us to confirm the indices of refraction measured in the Brewster’s angle lab exercise.
Properties of Gelatin
Making gel samples
Finding the index of refraction
Measuring the Focal Length of Gel Lenses
Link to Rare earths in Sol-gel glass webpage
Authored by Dan Boye, A.J. Hergenroeder and Carlos Ortiz.
This website contains information based upon work supported by the National Science Foundation under Grant No. 0421023. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Cyclops examining a gel sample