Revealing the Wavelength Dependence of Photochemical Reactions: Cutting-Edge Research in the Teaching Lab

Abstract

The prompt transfer of cutting-edge science into students’ curricula is a challenging task. Often research experiments are too complex or expensive to be translated into a secondary or tertiary education setting. Herein, we introduce a laboratory experiment that translates the recently developed research technique of a wavelength dependent, photochemical action plot into a student accessible format. The practical incorporates aspects of photophysics, required to calculate a constant photon emission from each different colored LED, as well as polymer chemistry in understanding the mechanism and quantitatively determining the polymerization conversion. During this practical the students (i) learn about areas where photochemical reactions are used to generate everyday materials, (ii) understand and apply the concepts of absorption and Beer–Lambert’s law, (iii) record and evaluate a photochemical action plot, and (iv) critically discuss the disparate nature of action and absorption spectra to generate an understanding of the implications for photochemical material design.

Synthesis and Characterization of a Metal-Free Organic Dye-Sensitizer for Solar Cell: An Advanced Organic Chemistry Research-Based Laboratory

“…In order to gain insight into the light-harvesting properties of dyes, students collect the UV–vis and emission spectra of 4 in CH 2 CI 2 as shown in Figures and . − The absorption spectrum of the dye molecule is red-shifted and extends in the visible region showing that it is able to absorb solar energy (Figure ). − The red-shifting of the spectrum for 4 is attributed to the narrowing of the HOMO–LUMO band gap due to the attachment of the pyrene molecules to the triphenylamine donor moiety which increases its conjugation and enhances its electron-donating properties. − The concept of narrowing the HOMO–LUMO gap to lengthen the absorption wavelength is normally taught in the second year of organic chemistry on the topic “Conjugated Dienes and Ultraviolet Spectroscopy”. Therefore, this principle is reinforced during this part of the project.…”

Amount of Copper(II) Ions in a Solution Cannot Be Determined Using the Hue Values

“…To further reduce the error, we also replaced the computer screen with a commercial white LED flat light source with higher brightness and remeasured the H value of copper nitrate solutions with different concentrations. It was found that the H value still did not change with the concentration.…”

“…For comparison, the results of ref 1 are also shown in the figure (denoted by "○"), which demonstrates that its H value increased significantly with the increase of concentration. To further reduce the error, we also replaced the computer screen with a commercial white LED flat light source with higher brightness 5 and remeasured the H value of copper nitrate solutions with different concentrations. It was found that the H value still did not change with the concentration.…”

Affordable Setup for Studying Photochemistry in Action in Undergraduate Teaching Laboratories: Principles and Applications

“…To date, the majority of the setups which have been implemented in teaching laboratories require a photochemical chamber for irradiation of the sample ex situ. In addition, such setups are predominantly based on the use of visible light which limits their application to the photochemistry of rather large polyaromatic compounds and does not probe the reaction progression as a function of time delay. − …”