Avermectin (Av) is a highly efficient pesticide against a variety of nematodes and is widely used in agriculture. However, it is susceptible to oxidation and photolysis, resulting in instability under UV irradiation and a short half-life. Herein, a rapid and low-cost approach was reported on preparing alkyl chain-coupled lignosulfonate-based polymer coated Av (Av@ALS) microcapsules by the self-assembly of natural and environmentally friendly lignin derivatives. The morphology and UV-shielding of Av@ALS microcapsules were investigated by SEM, EDX, TEM, DLS, FTIR and UV-vis spectroscopy. The self-assembly process and release kinetics of Av@ALS microcapsules were also studied in detail. The results show Av@ALS microcapsules have remarkable avermectin loading ability (up to 57.01% (w/w)), excellent slow-release properties and especially superior UV-shielding properties. The ease and low cost of the assembly process, combined with the natural materials, allows the coating method to open a new avenue for the field of efficient utilization of pesticide.

Graphene-based materials with aerogel structures were developed in recent years for various adsorption applications. In the present study, a hydrothermal process was developed to prepare graphene aerogel by using graphene oxide as a precursor, and the obtained aerogel was employed as a template for the growth of carbon nanotubes (CNTs). Various techniques were employed to study the morphology, surface property and composition of aerogel samples. The results showed that CNTs were in-situ grown on the sheet of graphene aerogel, endowing the material a hierarchical structure with enhanced surface area and meso- and micro-scale pores. These improved properties made the hybrid aerogel a superior material for the selective adsorption of a variety of organics and oils from water.A hybrid aerogel consisting of carbon nanotubes (CNTs) and graphene was prepared. The growth of CNTs on the graphene sheets in the hybrid aerogel endowed the material a hierarchical structure with low density, excellent hydrophobicity and oleophilicity to the organic compounds. The aerogel can adsorb a variety of oily liquids with outstanding reusability.Download high-res image (203KB)Download full-size image

•A turn-on fluorescence technique is developed for dopamine detection by using one-step selective reaction between resorcinol and dopamine.•The limit of detection is 1.8 nM (S/N = 3).•This detection could be completed within 5 min.•The method has been demonstrated to successfully detect dopamine in human urine samples with high recovery ratio of 97.84%–103.50%.A simple, fast and low-cost method for dopamine (DA) detection based on turn-on fluorescence using resorcinol is developed. The rapid reaction between resorcinol and DA allows the detection to be performed within 5 min, and the reaction product (azamonardine) with high quantum yield generates strong fluorescence signal for sensitive optical detection. The detection exhibits a high sensitivity to DA with a wide linear range of 10 nM–20 μM and the limit of detection is estimated to be 1.8 nM (S/N = 3). This approach has been successfully applied to determine DA concentrations in human urine samples with satisfactory quantitative recovery of 97.84%–103.50%, which shows great potential in clinical diagnosis.

We describe a simple yet extremely versatile and generalized surface polymer modification approach based on a surface initiated polymerization from a polydopamine (PDA) layer. PDA deposits on virtually any substrate independent of specific surface chemistries and can act as a photoinitiating layer to initiate the radical polymerization of a variety of (methyl)acrylic/styrene monomers. It does not require any metal/ligand catalyst, additional photoinitiator or dye sensitizer. Another attractive feature of this novel strategy is the ability to spatially control the architectures (pattern, gradient) of the polymer films by altering the areas of light irradiation. It is also adaptable to large area grafting with an ultra-small amount of monomer solution (a thin monomer solution layer).

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.

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 coordination-assisted synthetic approach is reported for the synthesis of N-doped carbon supported highly active and stable gold catalysts starting with polydopamine-Au nanoparticles. The composites with tuning morphology via the control of the polymerization rate of dopamine could be used as efficient catalysts for reduction of 4-nitrophenol.

This work reports a polydopamine-graft-poly(acrylic acid) (Pdop-g-PAA)-coated controlled-release multi-element compound fertilizer with water-retention function by a combination of mussel-inspired chemistry and surface-initiated atom transfer radical polymerization (SI-ATRP) techniques for the first time. The morphology and composition of the products were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC), and inductively coupled plasma (ICP) emission spectrometry. The results revealed that the stimuli-responsive layer formed by a Pdop inner layer and a PAA outer corona exhibit outstanding selective permeability to charged nutrients and the release rate of encapsulated elements can be tailored by the pH values. At low pH, the Pdop-g-PAA layer can reduce nutrient loss, and at high pH, the coating restrains transportation of negative nutrients but favors the release of cations. Moreover, PAA brushes provide good water-retention property. This Pdop-graft-polymer brushes coating will be effective and promising in the research and development of multi-functional controlled-release fertilizer.

A thermoresponsive release multi-element compound fertilizer was first reported on the basis of a polydopamine-graft-poly(N-isopropylacrylamide) bilayer coated on a salty core by a combination of dopamine chemistry and surface-initiated atom transfer radical polymerization techniques, and the control of nutrient release in response to the environmental temperature was investigated. The successful synthesized stimuli–responsive fertilizers were confirmed by transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). The release of elements from fertilizer was determined by an inductively coupled plasma (ICP) emission spectrometer. The thermosensitive fertilizers exhibit outstanding stimuli–responsive permeability to encapsulated nutrients, and the release rate of coated elements can be tailored by the ambient temperature. They can release nutrients easily at T < lower critical solution temperature (LCST) but slow at T > LCST. This strategy of grafting thermoresponsive polymer brushes on polydopamine (Pdop)-coated substrates is useful to prepare a stimuli–responsive release system, which can adjust the release rate according to different conditions, and will be effective and promising in the research and development of a stimuli-sensitive controlled-release system.

Dual-responsive capsules sensitive to pH and temperature changes were successfully prepared by grafting random copolymer brushes of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and oligo(ethylene glycol) methacrylate (OEGMA) from polydopamine (Pdop)-coated SiO2 via a surface-initiated atom-transfer radical polymerization (SI-ATRP) method with subsequent removal of the SiO2 core. The uptake and release properties of the resulting capsules are highly affected by changes in the pH values and temperature of the solution. The capsules can take up cationic dye rhodamine 6G (Rh6G) at high pH and T < LCST but not at low pH and T > LCST. In contrast, the capsules can release Rh6G at pH < 7 and temperature below the LCST, but release is less efficient under the opposite conditions. This dual-responsive property was also observed for the anionic dye methyl orange.

We describe a simple yet extremely versatile and generalized surface polymer modification approach based on a surface initiated polymerization from a polydopamine (PDA) layer. PDA deposits on virtually any substrate independent of specific surface chemistries and can act as a photoinitiating layer to initiate the radical polymerization of a variety of (methyl)acrylic/styrene monomers. It does not require any metal/ligand catalyst, additional photoinitiator or dye sensitizer. Another attractive feature of this novel strategy is the ability to spatially control the architectures (pattern, gradient) of the polymer films by altering the areas of light irradiation. It is also adaptable to large area grafting with an ultra-small amount of monomer solution (a thin monomer solution layer).