Development of a simple amino-modified silica-based colorimetric sensor for the detection of copper (II) ions in aqueous samples

Abstract

Research projects form an important part of learning and preparing students for graduate training. While most cutting edge research requires highly sophisticated instruments, there is no such luxury in the Least Developed Countries, least of all, being accessible to undergraduate students. Consequently, undergraduate research projects require some level of improvisation and innovation to use easily available materials to carry out research, without compromising the quality of science. This paper reports the development of a simple amino-modified colorimetric sensor using silica gel modified with (3-aminopropyl)-triethoxysilane (APS) for the qualitative detection of Cu2+ ions in aqueous solutions in an effort to demonstrate the concept of ligand field strength and imbue interest in research in the undergraduate students. The sensor was immobilized on a glass stirring rod for simulated field applications. It responded considerably well at concentrations above 200 parts per million and neutral pH (7-8) giving response under 60 minutes of exposure with the increase in detection times as the concentration of the ions decreased. Modification of the APS with different substrates reduced its efficiency, demonstrating the necessity for primary amines. The binding of the Cu2+ ions seemed considerably stable for the sensor to be applied as a passive sampling device. This experiment has demonstrated that indeed, science does not only depend on sophisticated instrumentation but also simple ideas can generate interest in students while also achieving credible research results. It further demonstrates the importance of encouraging independent thinking to arouse interest as a way of improving the learning process.