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1. Accessibility and Mechanical Stability of Nanoporous Zinc Oxide and Aluminum Oxide Coatings Synthesized via Infiltration of Polymer Templates

   https://doi.org/10.3390/polym15204088  

   Omotosho, Khalil D.; Lyon, Zachary; Shevchenko, Elena V.; Berman, Diana (October 2023, Polymers)

   The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings—polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions. 

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2. Enhanced photochemical activity and ultrafast photocarrier dynamics in sustainable synthetic melanin nanoparticle-based donor–acceptor inkjet-printed molecular junctions

   https://doi.org/10.1039/d3nr02387g  

   DeMarco, Max; Ballard, Matthew; Grage, Elinor; Nourigheimasi, Farnoush; Getter, Lillian; Shafiee, Ashkan; Ghadiri, Elham (September 2023, Nanoscale)

   Cinzia Casiragi (Ed.)

   Melanin is a stable, widely light-absorbing, photoactive, and biocompatible material viable for energy con- version, photocatalysis, and bioelectronic applications. To achieve multifunctional nanostructures, we synthesized melanin nanoparticles of uniform size and controlled chemical composition (dopamelanin and eumelanin) and used them with titanium dioxide to fabricate donor–acceptor bilayers. Their size enhances the surface-to-volume ratio important for any surface-mediated functionality, such as photo- catalysis, sensing, and drug loading and release, while controlling their chemical composition enables to control the film’s functionality and reproducibility. Inkjet printing uniquely allowed us to control the de- posited amount of materials with minimum ink waste suitable for reproducible materials deposition. We studied the photochemical characteristics of the donor–acceptor melanin–TiO2 nanostructured films via photocatalytic degradation of methylene blue dye under selective UV-NIR and Vis-NIR irradiation con- ditions. Under both irradiation conditions, they exhibited photocatalytic characteristics superior to pure melanin and, under UV-NIR irradiation, superior to TiO2 alone; TiO2 is photoactive only under UV irradiation. The enhanced photocatalytic characteristics of the melanin–TiO2 nanostructured bilayer films, particularly when excited by visible light, point to charge separation at the melanin–TiO2 interface as a possible mechanism. We performed ultrafast laser spectroscopy to investigate the photochemical charac- teristics of pure melanin and the melanin–TiO2 constructs and found that their time-resolved photo- excited spectral patterns differ. We performed singular value decomposition analysis to quantitatively deconvolute and compare the dynamics of photochemical processes for melanin and melanin–TiO2 heterostructures. This observation supports electronic interactions, namely, interfacial charge separation at the melanin and TiO2 interface. The excited-state relaxation in melanin–TiO2 increases markedly from 5 ps to 400 ps. The results are remarkable for the future intriguing application of melanin-based con- structs for bioelectronics and energy conversion. 

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3. Photocatalytic Degradation of Azo Dyes in Aqueous Solution Using TiO2 Doped with rGO/CdS under UV Irradiation

   https://doi.org/10.3390/pr12071455  

   Madduri, Sunith B; Kommalapati, Raghava R (July 2024, Processes)

   Photocatalysis, mainly using TiO2 as a catalyst, has emerged as a promising method to address the issue of wastewater treatment. This study explores the enhanced photocatalytic activity of TiO2 through the introduction of reduced graphene oxide (rGO) and cadmium sulfide (CdS) as selective metal dopants. The incorporation of rGO and CdS into the TiO2 lattice aims to optimize its photocatalytic properties, including bandgap engineering, charge carrier separation, and surface reactivity. The unique combination of CdS and rGO with TiO2 is expected to boost degradation efficiency and reduce the reliance on expensive and potentially harmful sensitizers. This experimental investigation involves the synthesis and characterization of TiO2-based photocatalysts. The photocatalytic degradation of methyl orange (MO) and methylene blue (MB) was assessed under controlled laboratory conditions, studying the influence of metal dopants on degradation kinetics and degradation efficiency. Furthermore, the synthesized photocatalyst is characterized by advanced techniques, including BET, SEM, TEM, XRD, and XPS analyses. The degraded samples were analyzed by UV-Vis spectroscopy. Insights into the photoexcitation and charge transfer processes shed light on the role of metal dopants in enhancing photocatalytic performance. The results demonstrate the potential of a TiO2-rGO-CdS-based photocatalyst in which 100% degradation was achieved within four hours for MO and six hours for MB, confirming efficient azo dye degradation. The findings contribute to understanding the fundamental principles underlying the photocatalytic process and provide valuable guidance for designing and optimizing advanced photocatalytic systems. Ultimately, this research contributes to the development of sustainable and effective technologies for removing azo dyes from various wastewaters, promoting environmental preservation and human well-being. 

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4. Construction from destruction using a photo-triggered self-propagating degradable polyurethane as a one-pot epoxy

   https://doi.org/10.1039/d0py00779j  

   Xu, Yanhua; Morado, Ephraim G.; Zimmerman, Steven C. (October 2020, Polymer Chemistry)

   null (Ed.)

   We report a photo-triggered, base generating, base propagating degradable polyurethane that is triggered by 365 nm UV light irradiation. A small area of this polyurethane material can be exposed to 365 nm UV light irradiation to generate basic species that can initiate a base propagated degradation process within the bulk material leading to global degradation without the need for continous UV irradiation. The polymer was synthesized by a polycondensation polymerization of a small amount of o -nitrobenzene diol 2 , a large amount of Fmoc-based diol 3 , and hexylmethylene diisocyanate. Integrating both photosensitive and base-sensitive carbamate moieties into the polymer 1 backbone provides the UV light-triggered base propagating degradable polyurethane material. Degradation studies of polymer 1 using 1 H NMR and gel permeation chromatography (GPC) suggest that initial UV irradiation triggers the degradation of the photosensitive o -nitrobenzene carbamate linkages, releasing a primary amino group that causes a cascade of amines to form by further degrading the remaining Fmoc carbamate groups. A bulk polyurethane film was prepared using Fmoc-based triol 4 as a monomer. UV-irradiation of a small localized area of the film initiates the propagation throughout, leading to efficient bulk degradation of the entire material. The amine degradation products could be utilized to make a one-pot epoxy adhesive, showing a potential upcycling application of this self-propagating degradable polyurethane system. 

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5. Dual-Function Photocatalysis in the Visible Spectrum: Ag-G-TiO2 for Simultaneous Dye Wastewater Degradation and Hydrogen Production

   https://doi.org/10.3390/catal14080530  

   Ahasan, Tarek; Xu, Pei; Wang, Huiyao (August 2024, Catalysts)

   Photocatalytic processes offer promising solutions for environmental remediation and clean energy production, yet their efficiency under the visible light spectrum remains a significant challenge. Here, we report a novel silver–graphene (Ag-G) modified TiO2 (Ag-G-TiO2) nanocomposite photocatalyst that demonstrates remarkably enhanced photocatalytic activity for both dye wastewater degradation and hydrogen production under visible and UV light irradiation. Through comprehensive characterization and performance analysis, we reveal that the Ag-G modification narrows the TiO2 bandgap from 3.12 eV to 1.79 eV, enabling efficient visible light absorption. The nanocomposite achieves a peak hydrogen production rate of 191 μmolesg−1h−1 in deionized (DI) water dye solution under visible light, significantly outperforming unmodified TiO2. Intriguingly, we observe an inverse relationship between dye degradation efficiency and hydrogen production rates in dye solutions with tap water versus DI water, highlighting the critical role of water composition in photocatalytic processes. This work not only advances the understanding of fundamental photocatalytic mechanisms but also presents a promising photocatalyst for solar-driven environmental remediation and clean energy production. The Ag-G-TiO2 nanocomposite’s enhanced performance across both visible and UV spectra, coupled with its dual functionality in dye degradation and hydrogen evolution, represents a significant step towards addressing critical challenges in water treatment and sustainable energy generation. Our findings highlight the complex interplay between light absorption and reaction conditions, offering new insights for optimizing photocatalytic systems. This research paves the way for developing more efficient and versatile photocatalysts, potentially contributing to the global transition towards sustainable technologies and circular economy in waste management and energy production. 

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