Diffusion-controlled currents of redox latex particles with polystyrene-core and polyallylamine-ferrocenyl shell

Dispersion properties of nanoplastic spheres in granular media at low Reynolds numbers

Nanoplastic particles (<1 μm) are among the contaminants of emerging concern, and compared to microplastic (<5 mm), our understanding of the transport and fate of nanoplastic in water, sediments and soil is very limited. This paper focuses on developing fundamental insight into the dispersion behaviour (sum of hydrodynamic dispersion and diffusion) of nanoplastic spheres, which are likely the most mobile shape of nanoplastic. We measured the dispersion coefficient and dispersivity of nanoplastic spheres (100 nm, 300 nm and 1000 nm diameter) in granular media with a range of pore sizes. We investigated the mechanisms that control the behaviour at low Reynolds number (smaller than 2), relevant to the dispersion of nanoplastic across the riparian area at water velocities of the common river and shallow groundwater. The measured dispersion coefficients were compared with the predictions by two commonly used models. The results show that there are significant differences between measurements and predictions for the case of colloidal size nanoplastics (MAPE>100%). The retarded dispersion caused by the size-exclusion effect was observed to be important in the case of 1.7 mm and 0.4 mm granular media for 300 nm and 1000 nm nanoplastics, reducing the dispersivity and sensitivity to Reynolds number. The methodology in this paper can be adopted in studies on other sizes and shapes of nanoplastic, assisting with predicting the transport and fate of nanoplastic granular media.

Alcohol-Stable Perovskite Nanocrystals and Their In Situ Capsulation with Polystyrene

In recent years, lead halide perovskite nanocrystals (PNCs) have presented potential scalable applications in all fields due to their outstanding properties. However, most commonly used PNCs capped with oleic acid (OA) and oleylamine (OAm) suffer from bad stability in polar solutions and thus require various surface protections with organic or inorganic materials. Encapsulation with highly hydrophobic polystyrene (PS) is one of the most efficient ways to protect PNCs; however, the presently used swelling-shrinking strategy faces several challenges, such as weak interaction between PS chains and the surface ligands in nonpolar media causing a low encapsulation efficiency, and serious aggregation of PS particles during the shrinkage process leading to very different particle sizes. Herein, alcohol-stable polyacrylic acid-capped CsPbBr3 PNCs (i.e., PAA-PNCs) are first synthesized and then in situ encapsulated with PS shells by polymerizing styrene monomer on the PNC surfaces in a polar organic solvent (e.g., ethanol). The in situ PS-encapsulated PAA-PNCs (i.e., PAA-PNCs@iPS) exhibit outstanding monodispersity, remarkable water, heat, and UV stability, high fluorescence activity, and color purity. The unique synthesis strategy and good performances of PAA-PNCs@iPS will boost the applications of PNCs in LEDs, biological imaging, and chemosensing.

Adsorption force of polyaniline-coated polystyrene latex particles

Visible polyaniline-latex particles 13 microm in diameter were used for obtaining a quantitative relationship between the adsorption force and the electroactivity at a platinum electrode. An optical cell equipped with wire electrodes was filled with the suspension in hydrochloric acid. When electrode potential was switched between the oxidized and the reduced domains, some adsorbed particles showed color change owing to the electroactivity. The numbers of electroactive and the inactive particles in the suspension were counted, including poly(N-vinylpyrrolidone) (PVP). The ratio of the numbers was proportional to the concentration of PVP, as it was in equilibrium. The adsorbed particles were desorbed mechanically by forced flow. The numbers of the desorbed particles did not decrease with an increase in the flow velocity until threshold values. The threshold value for the electroactive particle was 10 times larger than that for the inactive ones, corresponding to 10 times larger adsorption energy of the electroactive particles than of the inactive ones. The adsorption stress was evaluated from the removal of the electropolymerized polyaniline film from the electrode. Then the adsorption area of the particle was estimated.