Automated monitoring the kinetics of homogeneous and heterogeneous chemical processes using a smartphone.

Heterogeneous chemical processes occupy a pivotal position in many fields of applied chemistry. Monitoring reaction kinetics in such heterogeneous systems together with challenges associated with ex-situ analytical methodologies can lead to inaccurate information about the nature of the catalyst surfaces as well as information about the steps involved. The present work explores the possibility of kinetic measurements of chemical reactions and adsorption processes of homogeneous and heterogeneous systems through the variation of RGB intensities of digital images using a smartphone combined with a program written in Python to accelerate and facilitate data acquisition. In order to validate the method proposed, the base promoted hydrolysis of 4-nitrophenyl acetate was initially investigated. The rate constants obtained through RGB analysis (0.01854 min-1) is almost identical to that using traditional UV-Vis spectroscopy (0.01848 min-1). The proposed method was then applied to monitor the kinetics of three heterogeneous processes: (1) reduction of 4-nitrophenolate in the presence of dispersed Pd/C; (2) decomposition of methyl orange with TiO2; and (3) adsorption of rhodamine on montmorillonite. In general, the method via digital images showed high reproducibility and analytical frequency, allowing the execution of simultaneous analyses, with an accuracy comparable to UV-Vis spectrophotometry. The method developed herein is a practical and valuable alternative for obtaining kinetic data of heterogeneous reactions and processes where a color change is involved, bypassing sampling collection and processing which decreases analytical frequency and may lead to data errors.

From the Shelf to the Particle: Preparation of Highly Organic-Functionalized Magnetic Composites via 4-Nitrophenyl Reactive Ester.

Preparation of chemically tunable magnetic nanoparticles (MNPs) is of great interest in many technological fields. Although numerous methods have been developed to prepare MNPs coated with functional organic moieties, most of them are complex, multistep, and involve the preparation of a specific ligand to be inserted on the particle surface. Herein, we describe the preparation of MNPs covered with reactive polymer poly(4-nitrophenyl methacrylate). The composite was prepared by the dispersion polymerization of 4-nitrophenyl methacrylate in the presence of magnetite nanoparticles stabilized by oleic acid. The novel material can be easily modified with amines to give chemically stable amide bonds without installation of pH-dependent features in the link. The extent of particle modification is readily monitored by the release of 4-nitrophenol from the polymer using UV-vis spectrophotometry. Good agreement between the degree of functionalization assessed by colorimetry and elemental analysis was obtained, and functionalization up to 3 mmol g-1 is easily attained. To illustrate the applicability of the method for catalyst development, we prepared imidazole-covered MNPs that accelerate the hydrolysis of a model organophosphate, with rate constants approximately 105-fold higher than the spontaneous hydrolysis. The catalyst can be recovered by a magnet and recycled without appreciable loss of catalytic activity.