Covalently cross-linked rubbers are indispensable in many important fields due to their unique entropic elasticity. For rubbers cross-linking, the addition of toxic curing agents, release of toxic volatile organic compounds (VOCs), and recycling of waste rubber are three important issues. A combination of green curing chemistry and efficient recycling into commercial polyolefin rubbers is of great importance. Herein, we demonstrate a facile and promising way to incorporate dynamic covalent bonds into ethylene-propylene-diene monomer (EPDM)/carbon black (CB) composites. The epoxy-functionalized EPDM (e-EPDM) was prepared using an in situ epoxidation reaction and then cured with biobased decanedioicacid (DA) through the reactions between the epoxy groups in e-EPDM and the carboxylic groups in DA. Because of the existence of exchangeable β-hydroxyl ester, the covalently cross-linked networks in e-EPDM/CB composites were able to rearrange their topological structure at high temperature, endowing the composites with recycled and reshaped abilities. More importantly, the recycled e-EPDM/CB composites still exhibit outstanding mechanical properties which can meet the needs of practical applications. This strategy may provide an efficient, green, and sustainable way to address the problems brought from rubbers cross-linking.

In this work, polydopamine-coated gold nanoparticles (Au@PDAs) were synthesized by the oxidative self-polymerization of dopamine (DA) on the surface of AuNPs and applied for the first time as a signal-amplification label in lateral flow immunoassays (LFIAs) for the sensitive detection of zearalenone (ZEN) in maize. The PDA layer functioned as a linker between AuNPs and anti-ZEN monoclonal antibody (mAb) to form a probe (Au@PDA-mAb). Compared with AuNPs, Au@PDA had excellent color intensity, colloidal stability, and mAb coupling efficiency. The limit of detection of the Au@PDA-based LFIA (Au@PDA-LFIA) was 7.4 pg/mL, which was 10-fold lower than that of the traditional AuNP-based LFIA (AuNP-LFIA) (76.1 pg/mL). The recoveries of Au@PDA-LFIA were 93.80–111.82%, with the coefficient of variation of 1.08–9.04%. In addition, the reliability of Au@PDA-LFIA was further confirmed by the high-performance liquid chromatography method. Overall, our study showed that PDA coating can chemically modify the surface of AuNPs through a simple method and can thus significantly improve the detection sensitivity of LFIA.

Immunochromatographic assay (ICA) is widely applied in various fields. However, severe matrix interference and weak signal output present major challenges in achieving accurate and ultrasensitive detection in ICA. Here, a polydopamine (PDA)-mediated magnetic bimetallic nanozyme (Fe 3 O 4 @PDA@Pd/Pt) with peroxidase-like activity was synthesized and used as a probe in ICA. The magnetic property of Fe 3 O 4 @PDA@Pd/Pt enabled effective magnetic enrichment of targets, thereby reducing the matrix interference in the sample. PDA coating on the magnetic bimetallic nanozyme was employed as a mediator and a stabilizer. It improved the catalytic ability and stability of the magnetic bimetallic nanozyme by providing more coordination sites for Pd/Pt growth and functional groups (−NH and −OH). In addition, the Pd/Pt bimetallic synergistic effect could further enhance the catalytic ability of the nanozyme. A method was developed by integrating Fe 3 O 4 , PDA, and Pd/Pt into Fe 3 O 4 @PDA@Pd/Pt as a probe in ICA. With the proposed method, human chorionic gonadotropin and Escherichia coli O157:H7 were successfully detected to be as low as 0.0094 mIU/mL in human blood serum and 9 × 10 1 CFU/mL in the milk sample, respectively. This method may be readily adapted for accurate and ultrasensitive detection of other biomolecules in various fields.

The vulcanization of rubber is a chemical process to improve the mechanical properties by cross-linking unsaturated polymer chains. Zinc oxide (ZnO) acts as an activator, boosting the rubbers’ sulfur vulcanization. Maintaining the level of ZnO content in the rubber compounds as low as possible is desirable, not only for economic reasons but also to reduce the environmental footprint of the process. In this contribution, octylamine (OA) capped ZnO nanoparticles (5 nm diameter), prepared through a thermal decomposition method, were demonstrated to be efficient activators for the sulfur vulcanization of natural rubber, enabling the reduction of the required amount of ZnO as compared to commercial systems. The effect of different ZnO activators (OA capped ZnO/commercial indirect process ZnO) on the curing characteristics, cross-linking densities, and mechanical performance, as well as the thermal behavior of rubber compounds, were investigated. Compared to the commercial indirect process ZnO, OA capped ZnO nanoparticles not only effectively enhanced the curing efficiency of natural rubber but also improved the mechanical performance of the composites after vulcanization. This was interpreted as, by applying the OA capped ZnO nanoparticles, the ZnO levels in rubber compounding were significantly reduced under the industrial vulcanization condition (151 °C, 30 min).