Self-decontaminating photocatalytic zinc oxide nanorod coatings for prevention of marine microfouling: a mesocosm study.

The antifouling (AF) properties of zinc oxide (ZnO) nanorod coated glass substrata were investigated in an out-door mesocosm experiment under natural sunlight (14:10 light: dark photoperiod) over a period of five days. The total bacterial density (a six-fold reduction) and viability (a three-fold reduction) was significantly reduced by nanocoatings in the presence of sunlight. In the absence of sunlight, coated and control substrata were colonized equally by bacteria. MiSeq Illumina sequencing of 16S rRNA genes revealed distinct bacterial communities on the nanocoated and control substrata in the presence and absence of light. Diatom communities also varied on nanocoated substrata in the presence and the absence of light. The observed AF activity of the ZnO nanocoatings is attributed to the formation of reactive oxygen species (ROS) through photocatalysis in the presence of sunlight. These nanocoatings are a significant step towards the production of an environmentally friendly AF coating that utilizes a sustainable supply of sunlight.

Latent and delayed action polymerization systems.

Various approaches to latent polymerization processes are described. In order to highlight recent advances in this field, the discussion is subdivided into chapters dedicated to diverse classes of polymers, namely polyurethanes, polyamides, polyesters, polyacrylates, epoxy resins, and metathesis-derived polymers. The described latent initiating systems encompass metal-containing as well as purely organic compounds that are activated by external triggers such as light, heat, or mechanical force. Special emphasis is put on the different chemical venues that can be taken to achieve true latency, which include masked N-heterocyclic carbenes, latent metathesis catalysts, and photolatent radical initiators, among others. Scientific challenges and the advantageous application of latent polymerization processes are discussed.

Cr2S3-Co3O4 on polyethylene glycol-chitosan nanocomposites with enhanced ultraviolet light photocatalysis activity, antibacterial and antioxidant studies.

A novel chromium sulfide-cobalt oxide nanostructures and decorated on Polyethylene Glycol (PEG)-chitosan (CS) nanocomposites as catalyst was synthesized by a facile method, and characterized by XRD, SEM, UV-Vis and XPS spectrum. The as-prepared Cr2S3-Co3O4/PEGCS composites represented the photo-decompose efficiency against the decomposition of basic dye (Rhodamine B (RhB)). The band gap of nano-catalyst was determined to be in the range of 2.61 to 3.32 eV. The introduction of Cr2S3 into Co3O4 increased the photocatalytic performance slightly, and decoration of Cr2S3-Co3O4 on PEGCS, which indicated the highest photo-degradation performance. Under the light irradiation, the active species OH and O2- radicals were important active agents in the photocatalysis process. The Cr2S3-Co3O4/PEGCS nanocomposites can maintain a stable photocatalysis performance after five cycles. Finally, the reaction mechanism of photo-degradation of RhB was put forward. The antibacterial test demonstrated the remarkable properties of Cr2S3-Co3O4/PEGCS nanocomposites in this research.

Realizing the concept of a scalable artificial iris with self-regulating capability by reversible photoreaction of spiropyran dyes.

We report a scalable artificial iris with self-regulating spoke patterns of a liquid crystalline polymer that resemble the iris frills of the human eye. The underlying concept relies primarily on the reversible photo-induced conformation change of spiropyran dyes embedded in a transparent polymer. The spoke patterns around the scalable pupil, defined by selective wetting inscription, were produced using reactive liquid crystalline mesogens on a flexible substrate through polymerization. The self-regulation capability of our artificial iris, not requiring driving circuits and peripheral sensors, plays a central role in developing a new class of biomedical and photonic devices in a monolithic architecture.

Synthesis of biologically active and photostable rigid poly(vinyl chloride).

N,N-Dimethyl-N'-(6-oxo-2-thioxo-1H-pyrimidine-4-yl)formamidine has been synthesized and introduced as a substituent in poly(vinyl chloride) (PVC) chains via a chemical reaction. Both the dimethyl derivative and the modified PVC have been characterized via spectroscopic analyses and their biological activities have been evaluated. Both IR and (1) H NMR spectral data confirm the incorporation of the newly prepared bioactive dimethyl pyrimidine derivative in the polymeric chains. The dimethyl pyrimidine derivative has exhibited good antibacterial and antifungal activities. The modified PVC shows higher antibacterial effects than that of the blank one. Photostabilizing efficiency of the modified PVC is determined by measuring the changes that occurred in the molecular weights of modified PVC samples after UV irradiation using the gel permeation chromatography technique. The extent of discoloration of the photodegraded modified PVC samples has also been measured. The results have been compared with that of the blank PVC and that of the PVC stabilized with phenyl salicylate as a reference UV absorber. The lower decrease in the values of weight average molecular weight, M(w) , at the first stages of UV irradiation and the absence of crosslinking at the latter stages of irradiation confirms the photostability of the modified PVC. The extent of discoloration of the modified sample is also decreased when compared with the blank and stabilized PVC samples.

Effect of photoinitiators on the in vitro performance of a dentin adhesive exposed to simulated oral environment.

OBJECTIVES: Our previous study showed poor mechanical durability and nano-sized heterogeneities in cross-linked dentin adhesives cured in the presence of water. To further explore the relationship between nano-scale heterogeneities and the long-term mechanical properties of dentin adhesives, the properties of model dentin adhesives polymerized using hydrophilic photoinitiators were compared with those of adhesives polymerized using hydrophobic camphorquinone-based photoinitiators. METHODS: The model adhesives consisted of HEMA and bisGMA with a mass ratio of 45/55 and were photopolymerized in the presence of 8.3 mass% water. The photo-polymerization of the model adhesives during irradiation was monitored in situ using a Perkin-Elmer Spectrum One FTIR in the ATR sampling mode. The tensile properties were determined for all samples after dry storage at room temperature, or after aqueous storage in distilled deionized water. RESULTS: There was a continuous decline of mechanical properties for the specimens cured in the presence of water during 3 months aqueous storage, especially for the specimens that contained hydrophobic photoinitiators. The multi-component systems containing hydrophilic photoinitiators were shown to produce superior model dental adhesives when these materials are cured in the presence of water. SIGNIFICANCE: Designing initiator systems to perform in this heterogeneous environment may improve the mechanical performance of dentin adhesives, as the results presented here indicate.