Polymer nanoparticles: Preparation techniques and size-control parameters

The amount of nano- and microplastic in the aquatic environment rises due to the industrial production of plastic and the degradation of plastic into smaller particles. Concerns have been raised about their incorporation into food webs. Little is known about the fate and effects of nanoplastic, especially for the freshwater environment. In this study, effects of nano-polystyrene (nano-PS) on the growth and photosynthesis of the green alga Scenedesmus obliquus and the growth, mortality, neonate production, and malformations of the zooplankter Daphnia magna were assessed. Nano-PS reduced population growth and reduced chlorophyll concentrations in the algae. Exposed Daphnia showed a reduced body size and severe alterations in reproduction. Numbers and body size of neonates were lower, while the number of neonate malformations among neonates rose to 68% of the individuals. These effects of nano-PS were observed between 0.22 and 103 mg nano-PS/L. Malformations occurred from 30 mg of nano-PS/L onward. Such plastic concentrations are much higher than presently reported for marine waters as well as freshwater, but may eventually occur in sediment pore waters. As far as we know, these results are the first to show that direct life history shifts in algae and Daphnia populations may occur as a result of exposure to nanoplastic.

Nanoplastic affects growth of S. obliquus and reproduction of D. magna.

Most microplastics are emitted, either directly or via the degradation of plastics, to the terrestrial environment and accumulate in large amounts in soils, representing a potential threat to terrestrial ecosystems. It is very important to evaluate the uptake of microplastics by crop plants because of the ubiquity of microplastics in wastewaters often used for agricultural irrigation worldwide. Here, we analyse the uptake of different microplastics by crop plants (wheat (Triticum aestivum) and lettuce (Lactuca sativa)) from treated wastewater in hydroponic cultures and in sand matrices or a sandy soil. Our results provide evidence in support of submicrometre- and micrometre-sized polystyrene and polymethylmethacrylate particles penetrating the stele of both species using the crack-entry mode at sites of lateral root emergence. This crack-entry pathway and features of the polymeric particles lead to the efficient uptake of submicrometre plastic. The plastic particles were subsequently transported from the roots to the shoots. Higher transpiration rates enhanced the uptake of plastic particles, showing that the transpirational pull was the main driving force of their movement. Our findings shed light on the modes of plastic particle interaction with plants and have implications for crops grown in fields contaminated with wastewater treatment discharges or sewage sludges. The presence of microplastics in wastewaters used for irrigation highlights the urgency of analysing the possible uptake of microplastics by crop plants. This study shows that submicrometre and micrometre plastic particles from treated wastewater enter the steles of crop plants via a crack entry at sites of lateral root emergence.

Effective uptake of submicrometre plastics by crop plants via a crack-entry mode

A growing body of literature reports on the abundance and effects of plastic debris, with an increasing focus on microplastic particles smaller than 5 mm. It has often been suggested that plastic particles in the <100 nm size range as defined earlier for nanomaterials (here referred to as ‘nanoplastics’), may be emitted to or formed in the aquatic environment. Nanoplastics is probably the least known area of marine litter but potentially also the most hazardous. This paper provides the first review on sources, effects and hazards of nanoplastics. Detection methods are in an early stage of development and to date no nanoplastics have actually been detected in natural aquatic systems. Various sources of nanoplastics have been suggested such as release from products or nanofragmentation of larger particles. Nanoplastic fate studies for rivers show an important role for sedimentation of heteroaggregates, similar to that for non-polymer nanomaterials. Some prognostic effect studies have been performed but effect thresholds seem higher than nanoplastic concentrations expected in the environment. The high surface area of nanoplastics may imply that toxic chemicals are retained by nanoplastics, possibly increasing overall hazard. Release of non-polymer nanomaterial additives from small product fragments may add to the hazard of nanoplastics. Because of the presence of such co-contaminants, effect studies with nanoplastics pose some specific practical challenges. We conclude that hazards of nanoplastics are plausible yet unclear, which calls for a thorough evaluation of nanoplastic sources, fate and effects.

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Nanoplastics in the Aquatic Environment. Critical Review

Over the past years, two dimensional (2D) graphitic carbon nitride nanosheets (CNNs) have attained increasing interest in the study of graphitic carbon nitride (g-C3N4) due to their superior physical-optical properties as photocatalyst. More and more researchers attempt to design photocatalytic systems based on CNNs to realize the control of photocatalyst morphology for enhancing performance. Hence their combination with zero dimensional (0D) nanomaterials, which frequently serve as guest materials, has witnessed great progress. Therefore this review introduces the latest fabrication strategies of CNNs based on conventional strategies and firstly summarizes their photocatalytic properties systematically. More important, typical advanced examples combining CNNs with 0D nanomaterials like carbon nanodots, noble metal atoms and semiconductor nanoparticles are presented for their characteristic 0D/2D nanostructures, which have never been reported in any previous reviews up to now. Their preparation, photocatalytic mechanisms and performance influence factors are deeply discussed. In addition, three kinds of multicomponent complex systems, which take advantages of 0D nanomaterials/CNNs ingeniously, are elaborated on their charge-transfer pathways in our review. Finally, the current challenges and development ideas of 0D nanomaterials/CNNs systems in photocatalytic applications are proposed. This review enriches the knowledge in the applications of CNNs and paves road to the combination of 0D materials with CNNs and even other 2D materials.

Megamerger in photocatalytic field: 2D g-C3N4 nanosheets serve as support of 0D nanomaterials for improving photocatalytic performance

Fabrication of Schiff base decorated PAMAM dendrimer/magnetic Fe3O4 for selective removal of aqueous Hg(II)

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization

Preparation of bifunctional polysilsesquioxane/carbon nanotube magnetic composites and their adsorption properties for Au (III)

To further increase the quantity and density of functional groups on adsorbent, terminal triethylenetetramine hyperbranched dendrimer-like polymer modified silica-gel (SG-TETA and SG-TETA2) was synthesized. The hyperbranched dendrimer-like polymer was successfully introduced onto silica gel and new cavities were formed, which was demonstrated by FTIR, SEM, and BET. The highest adsorption capacities of SG-TETA and SG-TETA2 obtained from Langmuir model toward Au(III) were 2.11, and 2.27 mmol g-1, respectively, indicating that SG-TETA2 possessing more functional groups had a better adsorption ability. Moreover, the adsorbents combined with Au(III) ion through chelation and electrostatic attraction mechanism, after which reduction reactions for Au(III) ion loaded on adsorbents proceeded. SG-TETA2 had better adsorption selectivity than SG-TETA in removing Au(III) in Au-existed ion solution systems. SG-TETA2 had higher overall adsorption capacities compared to silica-gel-based hyperbranched polymers functionalized by diethylenetriamine. Therefore, the effective recovery makes SG-TETA2 a practical adsorbent in removing Au(III) ion from e-wastes and industrial effluents with much prospect.

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Fabrication of Triethylenetetramine Terminal Hyperbranched Dendrimer-Like Polymer Modified Silica Gel and Its Prominent Recovery Toward Au (III)

Comparison studies of adsorption properties for copper ions in fuel ethanol and aqueous solution using silica-gel functionalized with 3-amino-1,2-propanediol

Rongjun Qu

Papers

Fabrication of Schiff base decorated PAMAM dendrimer/magnetic Fe3O4 for selective removal of aqueous Hg(II)

Preparation of magnetic polymeric composite nanoparticles by seeded emulsion polymerization

Preparation of bifunctional polysilsesquioxane/carbon nanotube magnetic composites and their adsorption properties for Au (III)

Fabrication of Triethylenetetramine Terminal Hyperbranched Dendrimer-Like Polymer Modified Silica Gel and Its Prominent Recovery Toward Au (III)

Comparison studies of adsorption properties for copper ions in fuel ethanol and aqueous solution using silica-gel functionalized with 3-amino-1,2-propanediol