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A handheld refractometer (HHR) is a versatile instrument in the chemistry lab or in the workplace. It is also inexpensive enough (<$25 U.S.) that all students in a chemistry lab can have one or students completing laboratories remotely can purchase one. We report four applications of two different HHRs: one HHR for which the scale reads directly in refractive index from 1.333 to 1.360 and one HHR for which the scale reads from 0 to 80 °Brix corresponding to refractive indices from 1.333 to 1.491. The four applications involve linear relationships between solution concentration and refractive index for sucrose solutions and coffee solutions as well as nonideal solution behavior of methanol/water solutions and 2-propanol/water solutions. The use of an HHR is ideally suited to a range of inquiry-based experiments and can be incorporated into chemistry lab courses at a variety of levels and in remote learning lab experiences. We describe four broad categories of projects involving the use of HHRs.

We report a simple means to build a model atomic force microscope (AFM) using 3D printing of thermoplastic materials that are commercially available. The model has many of the key parts of an actual AFM including a z-axis stage, an AFM head with a cantilever assembly, and a laser source that reflects off of the back of the cantilever. Using a magnet attached to the tip of the cantilever and a metal sample, this model AFM enables acquisition of force-distance profiles with characteristic snap-in, pull-off, separate, and contact regions. The model AFM was designed, printed, and used by first- and second-year undergraduate students. Through completion of this project, students learned scientific instrument design and construction via 3D printing and obtained first-hand practice in the measurement of force-distance profiles and the elastic constants of cantilevers. The open design of the model can easily accommodate additional capabilities in which students are interested, e.g., topographical scanning and using cantilevers made from different materials.

This work presents a lecture and lab series that focuses on teaching the concept of nanophytotoxicity to undergraduate students in a relatively simple experiment. In this experiment, students evaluated the phytotoxicity of engineered nanomaterials (ENMs) using mung beans (i.e., "Vigna radiata") and industrially relevant, commercially available ENMs, silicon dioxide (SiO[subscript 2]) and zinc oxide (ZnO) nanoparticles (NPs). In comparison to the control system using solutions of Nanopure water, the growth of mung beans in solutions of ZnO NPs with a concentration of 20 mg/L was severely stunted, showing clear evidence of a high level of nanophytotoxicity. The growth of mung beans in solutions of SiO[subscript 2] NPs with the same concentration was intermediate to, though statistically separate from, the aforementioned solutions, showing clear evidence of a lower level of nanophytotoxicity than for the ZnO NPs. The simplicity of the experiment and the clear phytotoxic results should make this experiment of interest to many types of students including science majors, nonmajors, and high school students.