The thermochromic behavior of aromatic amine-SO2 charge transfer complexes

A Biomass-Based Colorimetric Sulfur Dioxide Gas Sensor for Smart Packaging

Sulfur dioxide (SO₂) gas, which can effectively prohibit the growth of pathogenic microorganisms, has been internationally used in commercial food packaging to maintain high-quality food and reduce the incidence of foodborne illnesses. However, the current mainstream methods for SO₂ detection are either large and expensive instruments or synthesized chemical-based labels, which are not suitable for large-scale gas detection in food packaging. Recently, we discovered that petunia dye (PD), which is extracted from natural petunia flowers, demonstrates a highly sensitive colorimetric response to SO₂ gas with its total color difference (ΔE) modulation reaching up to 74.8 and detection limit down to 1.52 ppm. To apply the extracted petunia dye in smart packaging for real-time gas sensing and food-quality prediction, a flexible and freestanding PD-based SO₂ detection label is prepared by incorporating PD in biopolymers and assembling the films through a layer-by-layer approach. The developed label is utilized to predict grapes' quality and safety by monitoring the embedded SO₂ gas concentration. The developed colorimetric SO₂ detection label could potentially be used as an intelligent gas sensor for food status prediction in daily life, food storage, and supply chains.

Flame-Retardant, Highly Conductive, and Low-Temperature-Resistant Organic Gel Electrolyte for High-Performance All-Solid Supercapacitors

Traditional liquid electrolytes are volatile, flammable, and easy to leak, which makes the energy storage device easy to burn and explode in the case of overcharge and short circuit. Here, by utilizing the active P-H bond of a flame retardant (DOPO) to graft onto the polymer chain, flame-retardant organic gel electrolytes were fabricated to address these issues. The gel electrolyte had good ionic conductivity of 4 mS cm^-1 at 20 °C and good flame retardant ability. By changing the molar ratio of the monomers and the salt concentrations, the mechanical strength of the gel electrolyte could be adjusted (maximum stress≈28 KPa, maximum strain≈305 %). The transport mechanism of lithium ions in the gel polymer electrolyte was proposed. The gel electrolyte-assembled supercapacitor (SC) possessed better electrochemical properties than that of SC assembled by liquid electrolyte. Importantly, the gel-based SC remained basically unchanged under multiple bending cycles. Additionally, the gel electrolyte had good low-temperature tolerance (0.1 mS cm^-1 at -40 °C). The gel electrolyte-assembled SC could work normally in the temperature range of -20 to 60 °C. The multiple advantages of gel electrolyte expand the applications in ionic conductor and energy storage devices.

Metal-Free Electrochemical Synthesis of Sulfonamides Directly from (Hetero)arenes, SO2 , and Amines

Sulfonamides are among the most important chemical motifs in pharmaceuticals and agrochemicals. However, there is no methodology to directly introduce the sulfonamide group to a non-prefunctionalized aromatic compound. Herein, we present the first dehydrogenative electrochemical sulfonamide synthesis protocol by exploiting the inherent reactivity of (hetero)arenes in a highly convergent reaction with SO2 and amines via amidosulfinate intermediate. The amidosulfinate serves a dual role as reactant and supporting electrolyte. Direct anodic oxidation of the aromatic compound triggers the reaction, followed by nucleophilic attack of the amidosulfinate. Boron-doped diamond (BDD) electrodes and a HFIP-MeCN solvent mixture enable selective formation of the sulfonamides. In total, 36 examples are demonstrated with yields up to 85 %.