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1. Dynamic Microcapsules with Rapid and Reversible Permeability Switching

   https://doi.org/10.1002/adfm.201803385  

   Werner, Jörg G.; Deveney, Brendan T.; Nawar, Saraf; Weitz, David A. (August 2018, Advanced Functional Materials)

   Abstract Dynamic microcapsules are reported that exhibit shell membranes with fast and reversible changes in permeability in response to external stimuli. A hydrophobic anhydride monomer is employed in the thiol–ene polymerization as a disguised precursor for the acid‐containing shells; this enables the direct encapsulation of aqueous cargo in the liquid core using microfluidic fabrication of water‐in‐oil‐in‐water double emulsion drops. The poly(anhydride) shells hydrolyze in their aqueous environment without further chemical treatment, yielding cross‐linked poly(acid) microcapsules that exhibit trigger‐responsive and reversible property changes. The microcapsule shell can actively be switched numerous times between impermeable and permeable due to the exceptional mechanical properties of the thiol–ene network that prevent rupture or failure of the membrane, allowing it to withstand the mechanical stresses imposed on the capsule during the dynamic property changes. The permeability and molecular weight cutoff of the microcapsules can dynamically be controlled with triggers such as pH and ionic environment. The reversibly triggered changes in permeability of the shell exhibit a response time of seconds, enabling actively adjustable release profiles, as well as on‐demand capture, trapping, and release of cargo molecules with molecular selectivity and fast on‐off rates. 

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2. Chitin Nanofibrils Enabled Core–Shell Microcapsules of Alginate Hydrogel

   https://doi.org/10.3390/nano13172470  

   Sapkota, Thakur; Shrestha, Bishnu Kumar; Shrestha, Sita; Bhattarai, Narayan (September 2023, Nanomaterials)

   An engineered 3D architectural network of the biopolymeric hydrogel can mimic the native cell environment that promotes cell infiltration and growth. Among several bio-fabricated hydrogel structures, core–shell microcapsules inherit the potential of cell encapsulation to ensure the growth and transport of cells and cell metabolites. Herein, a co-axial electrostatic encapsulation strategy is used to create and encapsulate the cells into chitin nanofibrils integrated alginate hydrogel microcapsules. Three parameters that are critical in the electrostatic encapsulation process, hydrogel composition, flow rate, and voltage were optimized. The physicochemical characterization including structure, size, and stability of the core–shell microcapsules was analyzed by scanning electron microscope (SEM), FTIR, and mechanical tests. The cellular responses of the core–shell microcapsules were evaluated through in vitro cell studies by encapsulating NIH/3T3 fibroblast cells. Notably, the bioactive microcapsule showed that the cell viability was found excellent for more than 2 weeks. Thus, the results of this core–shell microcapsule showed a promising approach to creating 3D hydrogel networks suitable for different biomedical applications such as in vitro tissue models for toxicity studies, wound healing, and tissue repair. 

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3. Effects of Surface‐Immobilization on Photobleaching of Xanthene Dye Photocatalysts

   https://doi.org/10.1002/macp.202300283  

   Freeburne, Sarah; Sacco, Jessica L.; Gomez, Esther W.; Pester, Christian W. (October 2023, Macromolecular Chemistry and Physics)

   Abstract While organic photocatalysts provide increasingly versatile chemical pathways under mild conditions, their long‐term stability remains understudied. Here, the photobleaching behavior of xanthene dye photocatalysts is investigated. Rose Bengal, Eosin Y, and fluorescein are studied when in solution, when grafted to glass beads, and when incorporated into polymer brushes that are tethered to glass beads. This provides a comparison between xanthene's stability as a homogeneous and as a heterogeneous photocatalyst. Photobleaching is investigated using UV–vis, diffuse reflectance UV–vis (DR UV–vis), and fluorescence microscopy. Xanthene dyes as homogeneous photocatalysts exhibit the highest photostability, while the grafted systems appeared to fade more rapidly. Notably, heterogenization appears to have different effects based on the photocatalyst system, and further altering the photocatalyst environment with reagents may improve stability. 

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4. Facile Synthesis of “Boron-Doped” Carbon Dots and Their Application in Visible-Light-Driven Photocatalytic Degradation of Organic Dyes

   https://doi.org/10.3390/nano10081560  

   Peng, Zhili; Zhou, Yiqun; Ji, Chunyu; Pardo, Joel; Mintz, Keenan J.; Pandey, Raja R.; Chusuei, Charles C.; Graham, Regina M.; Yan, Guiyang; Leblanc, Roger M. (August 2020, Nanomaterials)

   null (Ed.)

   Carbon dots (C-dots) were facilely fabricated via a hydrothermal method and fully characterized. Our study shows that the as-synthesized C-dots are nontoxic, negatively charged spherical particles (average diameter 4.7 nm) with excellent water dispersion ability. Furthermore, the C-dots have a rich presence of surface functionalities such as hydroxyls and carboxyls as well as amines. The significance of the C-dots as highly efficient photocatalysts for rhodamine B (RhB) and methylene blue (MB) degradation was explored. The C-dots demonstrate excellent photocatalytic activity, achieving 100% of RhB and MB degradation within 170 min. The degradation rate constants for RhB and MB were 1.8 × 10−2 and 2.4 × 10−2 min−1, respectively. The photocatalytic degradation performances of the C-dots are comparable to those metal-based photocatalysts and generally better than previously reported C-dots photocatalysts. Collectively considering the excellent photocatalytic activity toward organic dye degradation, as well as the fact that they are facilely synthesized with no need of further doping, compositing, and tedious purification and separation, the C-dots fabricated in this work are demonstrated to be a promising alternative for pollutant degradation and environment protection. 

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5. Green synthesis of CdS/Ni _x S _y nanoparticles as a route towards sustainable and scalable photocatalysts

   https://doi.org/10.1039/D2GC03361E  

   Sakizadeh, John; Cline, Joseph P.; Wolfe, Eva; Thorpe, Ryan; Snyder, Mark A.; Kiely, Christopher J.; McIntosh, Steven (October 2022, Green Chemistry)

   If hydrogen evolution photocatalysis are to be deployed at industrial scale, the synthesis of these photocatalytic materials must be both economically and environmentally scalable. This suggests that we must move towards green synthesis of earth-abundant photocatalysts while also maintaining high catalytic performance. Herein, we present the enzymatically driven, aqueous phase, low temperature, synthesis of an earth-abundant nickel sulfide (Ni x S y ) hydrogen evolution cocatalyst, and its integration into a CdS/Ni x S y heterostructured photocatalyst. This resulting photocatalyst provides hydrogen evolution rates (10 500 μmol h −1 g −1 ) comparable to photocatalysts prepared by more traditional routes. Furthermore, the Ni x S y is demonstrated to provide similar activity enhancement to the more traditional, but also more expensive platinum cocatalysts. To achieve this result, we carefully studied and engineered the synthesis environment to maintain enzyme activity towards HS − production while sustaining a sufficient concentration of free Ni 2+ in solution to enable reaction and formation of Ni x S y . Ultimately, this work provides a methodology to control the coordination of metal precursors in low temperature, aqueous systems to allow for precipitation of catalytically active materials and demonstrates the viability of green synthesis pathways for photocatalysts. 

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