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This work reports the first use of rubber latex waste as the hydrophobic reagent for a low-cost, simple, and rapid fabrication of a paper towel-based experimental device (PTED) with a circular design of 5 mm to demonstrate the factors affecting chemical equilibrium; this serves as a user-friendly means for a laboratory experiment. The illustration of the factors affecting chemical equilibrium is implemented in the PTED. In this approach, the color change of a cobalt(II) complex reaction from pink to blue was observed by the naked eye on the PTED when a tiny drop of hydrochloric acid solution and the treatment of heat by using a hot air dryer (1200 W, 2 min) were applied to the PTED with the precoated cobalt solution (pink color), separately or together. The return of the color of the reactions from blue to pink was carried out by using a tiny drop of water and the treatment of cooling by using an ice bath for 10 min. In addition, the chemical equilibrium constant ("K"[subscript c]) can be easily quantified by processing digital images of the detection zones of PTED captured with a smartphone camera under a control light box at room temperature (˜25 °C), while image analysis was performed using ImageJ software. This PTED laboratory is a new approach not only to enhance students' learning of the factors affecting chemical equilibrium based on Le Châtelier's principle, but also to present potential applications of PTED into all levels of chemistry from middle school through college classes.

In this article, a low-cost, simple, and rapid fabrication of paper-based analytical devices (PADs) using a wax screen-printing method is reported here. The acid-base reaction is implemented in the simple PADs to demonstrate to students the chemistry concept of a limiting reagent. When a fixed concentration of base reacts with a gradually increasing concentration of acid, a dramatic demonstration allows students to discover the limiting reagent by naked eyes observing the color change from phenolphthalein as an indicator. This demonstration is not only a new approach to enhancing students' learning of the chemistry concept of the limiting reagent, but also presents potential applications of PADs into all levels of chemistry from middle school through college classes.

This research is trying to evaluate the feedback of Thai secondary school students to inquiry-based teaching and learning methods, exemplified by the study of chemical kinetics. This work used the multiple-choice questions, scientifically practical diagram and questionnaire to assess students' understanding of chemical kinetics. The findings suggest that there was a difference in students' understanding of chemical kinetics as measured via diagnostic tests. While students made significant progress in drawing concept lists, phrasing scientific questions, identifying variables, designing experiments, presenting data and analyzing results, they showed only some improvement about drawing conclusions in practical classes. This more active, student-centred learning seemed to help students enjoy activities and become interested in learning chemical kinetics.

Chemical kinetics is an extremely important concept for introductory chemistry courses. The literature suggests that instruction in chemical kinetics is often teacher-dominated at both the secondary school and tertiary levels, and this is the case in Thailand--the educational context for this inquiry. The work reported here seeks to shift students from passive learning to more active, student-centred learning and involved some 413 first year undergraduate science students in Thailand. Drawing on inquiry-based learning, the participants were asked to design an experiment investigating the reaction of acids and bases. The research findings suggest that participants were able to explain the changes of the rate of a chemical reaction, and developed good conceptual understanding of chemical kinetics both qualitatively and quantitatively. It also showed this more active teaching approach, which is radically different from normal teaching in Thailand, was an enjoyable experience for the students. (Contains 3 tables and 5 figures.)

ABSTRACT Poly(aniline- co-m-ferrocenylaniline) and ferricinium-doped poly(aniline- co-m-ferrocenylaniline) were synthesized by a conventional chemical oxidative polymerization, then characterized by spectroscopic techniques and quantitative analyzes. Increasing of the percentages of m-ferrocenylaniline in the copolymers resulted to a blue shift of UV-Vis absorption spectra. Broader EPR spectra indicated the loss of conjugation and crystallinity of copolymers. 1H NMR spectra confirmed the presence of ferrocene moieties and ferricinium in the polymers. The CV measurements showed that the electron withdrawing power of ferrocene moieties could lead to the decreasing of electron delocalization on the polymer main chain. The VSM results showed that as-prepared copolymers were soft magnetic materials with very low magnetization. Pd-doped poly( m-ferrocenylaniline) as catalysts were utilized in the Suzuki-Miyaura cross-coupling reactions to improve the catalytic activities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1489-1497, 2013 [ABSTRACT FROM AUTHOR]

Herein, we propose a highly sensitive and selective three-dimensional electrochemical paper-based analytical device (3D-ePAD) to determine serotonin (Ser). It uses a graphite-paste electrode modified with nanoparticles coated with molecularly imprinted polymer (MIP). Fe 3 O 4 @Au nanoparticles were encapsulated with silica to create novel nano-sized MIP. Morphology and structural characterization reveal that silica imprinted sites (Fe 3 O 4 @Au@SiO 2 ) synthesized via sol-gel methods provide excellent features for Ser detection, including high porosity, and greatly improve analyte diffusion and adsorption to provide a faster response by the MIP sensor. The template molecule was effectively removed by solvent extraction to provide a greater number of specific cavities that enhance analyte capacity and sensitivity. The 3D-ePAD was fabricated by alkyl ketene dimer (AKD)-inkjet printing of a circular hydrophobic detection zone on filter paper for application of aqueous samples, coupled with screen-printed electrodes on the paper, which was folded underneath the hydrophobic zone. The sensor was constructed by drop coating of Fe 3 O 4 @Au@SiO 2 -MIP nanocomposites on the graphite electrode (GPE) surface. The MIP sensor (Fe 3 O 4 @Au@SiO 2 -MIP/GPE) was used in the detection of Ser by linear-sweep voltammetry (LSV) in 0.1 M phosphate buffer at pH 8.0. The device exhibits high sensitivity toward Ser, which we attribute to synergistic effects between catalytic properties, electrical conductivity of Fe 3 O 4 @Au@SiO 2 , and significantly increased numbers of imprinted sites. Ser oxidation was observed at +0.39 V. Anodic peak currents for Ser show linearity from 0.01 to 1000 μM (y = 0.0075 ± 0.0049 x + 0.4071 ± 0.0052, r 2  = 0.993), with a detection limit of 0.002 μM (3S/N). The device provides good repeatability (%relative standard deviations; RSD) = 4.23%, calculated from the current responses of ten different MIP sensors). The device also exhibits high selectivity and reproducibility (%RSD = 8.35%, obtained from five calibration plots). The analytical performance of the device is suitable for the determination of Ser in pharmaceutical capsules and urine samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)