ZnO nanoparticles as polymerisation photo-initiator: Levulinic acid/NaOH content variation

An In-Situ Fabrication Method of ZnO and Other Zn(II) Compounds Containing Polypropylene Composites

This study investigated the methods of preparation of zinc oxide-polypropylene nanocomposites and their antibacterial properties. Seven solutions with ZnO nanoparticles or zinc ions were formulated as a PP additive. Two methods of ZnO NPs syntheses were carried out: (1) a modified hydrothermal method where a water solution of zinc acetate dihydrate, PEI, and ammonia were mixed with a final pH 11; (2) a thermal decomposition of a water solution of zinc acetate in the presence of PEI and ammonia using a two-screw extruder. During the experiments, the influence of various amounts of particle stabilizer, heating of the solutions, and the temperatures of the syntheses were examined. As a result, the simultaneous crystallization of ZnO in the extrusion process confirmed this method's attractiveness from the application point of view. Fabricated PP-ZnO composite shows antibacterial properties against Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae.

Tunable Quantum Photoinitiators for Radical Photopolymerization

This review describes the use of nanocrystal-based photocatalysts as quantum photoinitiators, including semiconductor nanocrystals (e.g., metal oxides, metal sulfides, quantum dots), carbon dots, graphene-based nanohybrids, plasmonic nanocomposites with organic photoinitiators, and tunable upconverting nanocomposites. The optoelectronic properties, cross-linking behavior, and mechanism of action of quantum photoinitiators are considered. The challenges and prospects associated with the use of quantum photoinitiators for processes such as radical polymerization, reversible deactivation radical polymerization, and photoinduced atom transfer radical polymerization are reviewed. Due to their unique capabilities, we forsee a growing role for quantum photoinitiators over the coming years.

Morphology effect on zinc oxide quantum photoinitiators for radical polymerization

Semiconductor nanocrystal based photoinitiators, quantum PIs, are a viable alternative to organic photoinitiators demonstrating unique advantages, including a broad and tunable excitation window, limited migration, and more. Aiming towards efficient quantum PIs with tunable properties, a deeper understanding of the relationships between the nanoparticle properties and their efficiency is required. Herein, we studied the morphological effect on ZnO nanocrystals functioning as photoinitiators in both water-based and solvent-free formulations by comparing rod and pyramidal shaped particles of similar volumes and nearly identical surface area. Superior polymerization performances are measured for the nanorods. Photocatalytic characterization including oxygen consumption and reactive oxygen species formation as well as dyes reduction and oxidation, also showed enhanced activities for the nanorods. The different performances were attributed to the anisotropic nanorod morphology which is beneficial for charge separation as well as to the presence of a reactive [0001] facet in the nanorods, which is known to increase the adsorption of molecular oxygen and anionic molecules, thus affecting the catalytic activity. These observations, along with the higher photoinitiation efficiency of the ZnO nanorods, bring them closer to functionality as photoinitiators in numerous photopolymerization applications.

Quantum Photoinitiators: Toward Emerging Photocuring Applications

Semiconductor nanocrystals are promising photocatalysts for a wide range of applications, ranging from alternative fuel generation to biomedical and environmental applications. This stems from their diverse properties, including flexible spectral tunability, stability, and photocatalytic efficiencies. Their functionality depends on the complex influence of multiple parameters, including their composition, dimensions, architecture, surface coating, and environmental conditions. A particularly promising direction for rapid adoption of these nanoparticles as photocatalysts is their ability to act as photoinitiators (PIs) for radical polymerization. Previous studies served to demonstrate the proof of concept for the use of quantum confined semiconductor nanocrystals as photoinitiators, coining the term Quantum PIs, and provided insights for their photocatalytic mechanism of action. However, these early reports suffered from low efficiencies while requiring purging with inert gases, use of additives, and irradiation by high light intensities with very long excitation durations, which limited their potential for real-life applications. The progress in nanocrystal syntheses and surface engineering has opened the way to the introduction of the next generation of Quantum PIs. Herein, we introduce the research area of nanocrystal photocatalysts, review their studies as Quantum PIs for radical polymerization, from suspension polymerization to novel printing, as well as in a new family of polymerization techniques, of reversible deactivation radical polymerization, and provide a forward-looking view for the challenges and prospects of this field.

Design of new phenothiazine derivatives as visible light photoinitiators

In this article, four new phenothiazine derivatives (denoted as PT1, PT2, PT3 and PT4) are specifically in silico designed by molecular modelling for good light absorption properties @405 nm.

Homogenous photopolymerization of acrylic monomers initiated with ZnO-methacrylate in non-aqueous medium and production of luminescent nanocomposites

Luminescent ZnO quantum dots coated with methacrylic acid initiate photopolymerization of methylmethacrylate in the absence of hole-scavengers producing luminescent nanocomposites.