Facile Control of Structured ZnO Polymeric Nanoparticles through Miniemulsion Polymerization: Kinetic and UV Shielding Effects

Zinc oxide polymeric nanoparticles (ZPPs) of poly (styrene-co-acrylic acid) P(St/AA), containing oleic acid modified zinc oxide nanoparticles (OA-ZnO NPs), were synthesized via miniemulsion polymerization. By simply adjusting the quantity of reactants, i.e., sodium dodecyl sulfate (SDS) surfactant, potassium persulfate (KPS) initiator, and divinyl benzene (DVB) crosslinking agent, the location of ZnO NPs were altered from the inner (core) to the outer (shell), leading to core-shell and Pickering-like morphologies, respectively. The Pickering-like ZPPs were obtained when using SDS at below or equal to the critical micelle concentration (CMC). At above the CMC, the complete encapsulation of OA-ZnO NPs within the ZPPs depicted a kinetically controlled morphology. The transition to Pickering-like ZPPs also occurred when reducing the KPS from 2 to 0.5-1%. Whereas the DVB accelerated the polymerization rate and viscosity in the growing monomer-swollen nanodroplets and, hence, contributed to kinetic parameters on particle morphology, i.e., an increase in the DVB content increased the rate of polymerization. A hollow structure was obtained by replacing styrene with the more hydrophilic monomer, i.e., methyl methacrylate. All ZPPs-incorporated poly (vinyl alcohol) (PVA) films greatly improved shielding performance over the UV region and were relatively transparent on a white paper background. Due to the large number of ZnO NPs in the central region and, hence, the ease of electron transfer, composite films containing core-shell ZPPs possessed the highest UV blocking ability. ZnO NPs in the outer part of the hollow and Pickering-like ZPPs, on the other hand, facilitated the multiple light scattering according to the difference of refractive indices between the inorganic shell and organic/air core. These results confirm the advantage of structured ZPPs and their potential use as transparent UV shielding fillers.

Microfluidic synthesis of monodisperse porous polystyrene microspheres for sorption of bovine serum albumin

Droplet microfluidics offers exquisite control over the flows of multiple fluids in micro-scale, enabling fabrication of advanced microspheres with precisely tuneable structures. The main goal of this work was to design monodispersed carboxylated polystyrene microspheres with a developed pore structure (a specific surface area more than 200 m²/g) using microfluidic technology. We investigated the influence of the composition of monomer phase for the stable formation of droplets. Under the stable region, the resulting microspheres (with diameter 50 µm) showed narrow size distribution having a coefficient of variation of below 2%. The obtained microspheres are characterised by morphology and surface structure by means of electron microscopy. The structure of cross-linked microspheres is investigated by solid-state ¹H NMR spectroscopy. Finally, these microspheres have great potential for the effective sorption of biologically active substances (bovine serum albumin).

Polymeric graphitic carbon nitride (g-C3N4)-based semiconducting nanostructured materials: Synthesis methods, properties and photocatalytic applications

In recent years, various facile and low-cost methods have been developed for the synthesis of advanced nanostructured photocatalytic materials. These catalysts are required to mitigate the energy crisis, environmental deterioration, including water and air pollution. Among the various semiconductors explored, recently novel classes of polymeric graphitic carbon nitride (g-C₃N₄)-based heterogeneous photocatalysts have established much greater importance because of their unique physiochemical properties, large surface area, low price, and long service life, ease of synthesis, product scalability, controllable band gap properties, low toxicity, and high photocatalytic activity. The present comprehensive review focuses on recent achievements in a number of facile chemical synthesis methods for semiconducting polymeric carbon nitrides and their heterogeneous nanohybrids with various dopants, nanostructured metals, metal oxides, and nanocarbons, as well as the parameters influencing their physiochemical properties and photocatalytic efficiency, which are discussed with reference to various catalytic applications such as air (NO_x) purification, wastewater treatment, hydrogen generation, CO₂ reduction, and chemical transformation. The mechanisms for the superior photocatalytic activity of polymeric g-C₃N₄-based heterogeneous photocatalysts are also discussed. Finally, the challenges, prospects, and future directions for photocatalytic polymeric g-C₃N₄-based semiconducting materials are described.