Wenbo Sheng

Adhesive Polydopamine Coated Avermectin Microcapsules for Prolonging Foliar Pesticide Retention

In this work, we report a conceptual strategy for prolonging foliar pesticide retention by using an adhesive polydopamine (PDA) microcapsule to encapsulate avermectin, thereby minimizing its volatilization and improving its residence time on crop surfaces. Polydopamine coated avermectin (Av@PDA) microcapsules were prepared by emulsion interfacial-polymerization and characterized by Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, field-emission scanning electron microscope, and transmission electron microscopy. The in situ synthesis route confers Av@PDA microcapsules with remarkable avermectin loading ability of up to 66.5% (w/w). Kinetic study of avermectin release demonstrated that Av@PDA microcapsules exhibit sustained- and controlled-release properties. The adhesive property of Av@PDA microcapsules on different surfaces was verified by a comparative study between Av@PDA and passivated Av@SiO2 and Av@PDA@SiO2 capsules with silica shell. Moreover, PDA shell could effectively shield UV irradiation and so protect avermectin from photodegradation, making it more applicable for foliar spraying. Meanwhile, it is determinated that Av@PDA microcapsules have good mechanical stability property.

Effect of interfacial interaction between graphene oxide derivatives and poly(vinyl chloride) upon the mechanical properties of their nanocomposites

In this work, graphene oxide (GO) and poly(methyl methacrylate) (PMMA) grafted GO reduced by dopamine (rGO@PDA-g-PMMA) were employed to determine the key factor responsible for the improved mechanical properties of poly(vinyl chloride) (PVC). Dopamine was utilized to reduce GO and simultaneous coating of polydopamine (PDA) on the GO surface. rGO@PDA-g-PMMA was prepared by a combination of mussel-inspired chemistry and surface-initiated atom transfer radical polymerization techniques. The resulting derivatives were characterized by thermogravimetric analysis, Fourier transforms infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. PVC nanocomposites containing GO derivatives were prepared by solution blend and the nanocomposite films were obtained using a casting method. The mechanical properties of the nanocomposites were studied using both dynamic mechanical thermal analysis and tensile testing. The results revealed that the vital components responsible for the improved mechanical properties and thermal stability of rGO@PDA-g-PMMA/PVC nanocomposites compared to pure PVC are the interfacial interactions between the GO derivatives and the PVC matrix.

Mussel-Inspired Photografting on Colloidal Spheres: A Generalized Self-Template Route to Stimuli-Responsive Hollow Spheres for Controlled Pesticide Release

A thermo-controlled pesticide release system composed of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) thin film grafted polydopamine (PDA) (PDMAEMA-g-PDA) microcapsules is reported. SiO2 microparticles are used as a template to prepare PDA-coated SiO2 microparticles. The thermally-responsive PDMAEMA thin films are grafted on PDA surfaces using a metal-free surface-initiated photopolymerization approach without adding any photo-initiator or photosensitizer under UV light irradiation. The subsequent acid etching yields PDMAEMA-g-PDA hollow microcapsules. PDMAEMA-g-PDA microcapsules exhibit well-controlled release of avermectin (Av). The results show that the loading ability of PDMAEMA-g-PDA microcapsules of Av is up to 52.7% (w/w). The release kinetics of Av demonstrate that Av@PDMAEMA-g-PDA microcapsules exhibit temperature-controlled release performance. This work is significant for controlled release systems. This simple design is expected to be used in various applications, such as in controlled drug release and agriculture-related fields.

Study on the UV-shielding and controlled-release properties of a polydopamine coating for avermectin

Avermectin is susceptible to oxidation and photolysis, resulting in instability under UV irradiation and a short half-life. To solve this problem, many materials have been used to prevent the photodegradation of avermectin, but the complexity of the preparation process, the difficultly in biodegradation and the residual organic solvents, hinder their practical application. Fortunately, PDA emerged with negligible toxicity, environmental friendliness, extraordinary biocompatibility, and good adhesion, and it is widely used, especially as an UV-shielding material, which implies its huge potential in pesticides as a preferred candidate to melanin but this has never been reported. Herein, a gentle and flexible approach to the preparation of PDA coated avermectin was developed, to protect avermectin from photodegradation, through the oxidation self-polymerization of dopamine. The thickness of the polymer coating was controlled using a multistep deposition technique. The as-prepared products were used to study the effects of the coating thickness on the controlled-release and the UV-shielding property for avermectin. The results showed that the release rate of avermectin could be tailored using the thickness of the PDA layer. Most importantly, the PDA coating exhibited remarkable UV-shielding properties for avermectin, and the UV protection of the PDA layer for avermectin was improved with the coating getting thicker. Therefore, the system has a promising future in practical applications, so as to achieve sustained release and prevent the photodegradation of pesticides.

A facile route to fabricate a biodegradable hydrogel for controlled pesticide release

Avermectins are widely used to control weeds, insects, and plant diseases. We have prepared a controllable avermectin release system based on a hydrazone bond inducing hydrogel, which presents good release properties of avermectin triggered by temperature and pH stimuli. This strategy embarks on controllable pesticide release using an environmentally friendly hydrogel.

Engineering plasmonic Ag/AgCl–polydopamine–carbon nitride composites for enhanced photocatalytic activity based on mussel chemistry

The interfacial interaction plays an important role in composites, by affecting the physical and chemical properties of those composites. Herein, we present a simple and versatile approach for the construction of plasmonic Ag/AgCl–polydopamine–CN (SPCN) composites with enhanced photocatalytic properties by mussel chemistry. Dopamine hydrochloride acts as both the reactant and the reducing agent, and the product polydopamine (PDA) serves as the adhesive layer and the electron transfer bridge. The photocatalytic degradation of rhodamine B (RhB) shows that the SPCN50 composite displays excellent photocatalytic activity. A radical trapping experiment indicates that holes are the main oxidative species in the photocatalytic process, and a possible photocatalytic mechanism is proposed. All the results prove that PDA indeed improves the separation efficiency of photogenerated carriers and the photocatalytic activity. This work may provide a green, universal method to synthesize plasmonic photocatalytic composites with high catalytic performance.