Smartphone-Assisted Contact Angle Measurements: A Simple Approach to Determine the Critical Micelle Concentration of Surfactants

The principle of additivity of absorbances is a crucial method that can be used in the determination of two components individually from a mixture using a colorimeter/spectrophotometer. In this laboratory experiment, postgraduate students were introduced to the principle of additivity of absorbances and its application in the determination of nickel (Ni(II)) and cobalt (Co(II)) from unknown samples. The experiment provided students with a hands-on experience in the construction of a do-it-yourself (DIY) photometer containing three different light-emitting diode (LED) filters using low-cost, easily available materials. The students prepared the working standards of Ni(II) and Co(II) and captured their images in three different LED lights: red, green, and blue, which worked as filters. The images captured were then analyzed using ImageJ software, and RGB values from the images were extracted and converted to absorbances. The absorbances obtained from the images of different solutions of Ni(II) and Co(II) were plotted against their respective concentrations. Ni(II) showed a good regression coefficient value for red component absorbance that was recorded in the red LED filter, and Co(II) showed a good regression coefficient value for green component absorbance that was recorded in the green LED filter. The individual calibration curves of Ni(II) and Co(II) constructed in the presence of red and green LED filters were further used to determine individual concentrations of Ni(II) and Co(II). The calibration curves were constructed in Microsoft Excel, enhancing students' data entry skills. This experiment provides an easy method for the construction of a DIY photometer based on a smartphone as a detector with LED light filters, making it useful for teaching the simultaneous analysis of analytes from a mixture by using the principle of additivity of absorbances.

Section: Introductionmentioning

confidence: 99%

Simultaneous Determination of Ni(II) and Co(II) in Aqueous Solution Using an Image-Based Do-It-Yourself Photometer

Kulkarni,

Watwe,

Nirmal

et al. 2024

A Simplified Approach for Dynamic Contact Angle Measurements

Zou,

Ross,

Nawaj

et al. 2024

Contact angle measurement is a valuable tool for analyzing surface properties, including surface structure, cleanliness, and solid–liquid interactions. Typically, this measurement is performed at the static state, capturing the interactions at the solid–liquid interface when the gas, liquid, and solid phases reach equilibrium. In this study, we developed a user-friendly setup for accurately measuring dynamic contact angles using the needle-in-drop method. Our setup consists of a syringe for controlled liquid dispensing and withdrawal on a solid surface, a sample stage with a scale bar for baseline measurements (the diameter of the droplet), a lens to magnify the image of the droplet on the solid surface, and a smartphone camera for recording the dynamic expansion and retraction of the liquid droplet. In addition to obtaining the static sessile-drop contact angle information, our modified setup allows for the acquisition of other relevant parameters, including contact angle hysteresis and the contact-line pinning force. By training students to assemble a cost-effective contact angle measurement setup using laboratory components and guiding them in the utilization of this setup for conducting static and dynamic contact angle measurements, students gain practical experience to determine the surface wettability and interfacial energy from static contact angle measurements and to characterize the interfacial hysteresis and liquid mobility from dynamic contact angle measurements. We anticipate that this approach will benefit students in a wide range of disciplines, including materials science, chemical engineering, and physical chemistry, where understanding surface properties is essential.

Household Experiment Based on Smartphones: Chemical Equilibrium and Acid–Base Titration Experiment Using Red Cabbage and Sodium Carbonate

Wu,

Hu,

et al. 2024

Practical experiments enhance students' understanding of basic concepts and promote deep learning experiences in chemistry. The smartphone application of Lab4Chemistry was utilized to replace colorimeters with smartphone camera sensors. Low-cost and readily available materials, including anthocyanin (fresh red cabbage) and common kitchen substances (vinegar, sodium carbonate, citric acid), were employed to investigate the factors affecting chemical equilibrium (concentration and temperature), making the slight changes visualized. The experiment could also explore the acid−base titrations and quantitatively determine the acetic acid content in white vinegar. This method simplifies the experimental process, making it convenient and easy to implement. It aims to explore smartphone-based household experiments in chemical equilibrium and acid−base titration, improving students' comprehension and offering more interactive scientific exploration. Students' assessment indicated the feasibility of these home experiments, resulting in positive implications for innovating science education postpandemic, especially in economically disadvantaged areas, and the development of students' experimental skills.