Supramolecular compartmentalized hydrogels via polydopamine particle-stabilized water-in-water emulsions

Compartmentalized hydrogels constitute a significant research area, for example, for catalytic and biomedical applications. As presented here, a generic method is used for compartmentalization of supramolecular hydrogels by using water-in-water emulsions based on aqueous two-phase systems. By forming the supramolecular hydrogel throughout the continuous phase of all-aqueous emulsions, distinct, microcompartmentalized materials were created. The basis for the presented compartmentalized water-in-water hydrogels is polydopamine particle-stabilized water-in-water emulsions from dextran and poly(ethylene glycol) (PEG). Addition of α-cyclodextrin (α-CD) led to supramolecular complexation with PEG and subsequent hydrogel formation showing no signs of creaming. Due to the supramolecular nature of the compartmentalized hydrogels, selective network cleavage could be induced via competing guest addition, while keeping the emulsion substructure intact

Grafting polymers onto carbon nitride via visible-light-induced photofunctionalization

Metal-free graphitic carbon nitride (g-CN) has attracted significant attention recently due to its multiple applications, such as photocatalysis, energy storage and conversion, and biomaterials, albeit formation of g-CN films is challenging. Herein, a “grafting to” route to graft polymer brushes onto g-CN via visible-light irradiation is described. Afterward, g-CN/polymer films can be obtained through spin coating on glass substrates. As such, the present material provides an improved process toward further application of g-CN in thin films. Moreover, an improved dispersibility in organic solvent was realized after grafting and functional groups (such as epoxides) were introduced to g-CN. Subsequently, the epoxy groups were utilized for further functionalization to adjust the surface polarity

Molding and encoding carbon nitride-containing edible oil liquid objects via interfacial toughening in waterborne systems

Charge interaction-driven jamming of nanoparticle monolayers at the oil–water interface can be employed as a method to mold liquids into tailored stable 3D liquid objects. Here, 3D liquid objects are fabricated via a combination of biocompatible aqueous poly(vinyl sulfonic acid, sodium salt) solution and a colloidal dispersion of highly fluorescent organo-modified graphitic carbon nitride (g-C3N4) in edible sunflower oil. The as-formed liquid object shows stability in a broad pH range, as well as flexible pathways for efficient exchange of molecules at the liquid–liquid interphase, which allows for photodegradation of rhodamine B at the interface via visible light irradiation that also enables an encoding concept. The g-C3N4-based liquid objects point toward various applications, for example, all-liquid biphasic photocatalysis, artificial compartmentalized systems, liquid–liquid printing, or bioprinting

Graphitic carbon nitride stabilized water-in-water emulsions

Aqueous multiphase systems have attracted a lot of interest recently espeically due to target applications in the biomedical field, cosmetics, and food. In turn, water‐in‐water Pickering emulsions are investigated frequently. In here, graphitic carbon nitride (g‐CN) stabilized water‐in‐water Pickering emulsions are fabricated via the dextran and poly(ethylene glycol)‐based aqueous two‐phase system. Five different derivatives of g‐CN as the Pickering stabilizer are described and the effect of g‐CN concentration on droplet sizes is investigated. Stable emulsions (up to 16 weeks) are obtained that can be broken on purpose via various approaches, including dilution, surfactant addition, and most notably light irradiation. The novel approach of water‐in‐water emulsion stabilization via g‐CN opens up considerable advances in aqueous multiphase systems and may also introduce photocatalytic properties

Photoactive graphitic carbon nitride‐based gel beads as recyclable photocatalysts

Photocatalysis for clean hydrogen production and waste water remediation holds a great promise on society. However, despite the significant progress in this field the recyclability of the photocatalytic materials together with good photoactivity remain a great challenge. photocatalytic materials for waste water cleaning and hydrogen production based on the utilization of photoactive macrogel beads as the photocatalyst. To do so, we design a graphitic carbon nitride based macrogels with tailored size, swelling behavior and photocatalytic properties. Detailed studies reveal that the catalytic activity is correlated with the polymer particle size, g-C3N4 content and swelling behavior, enabling the optimization of the photocatalytic processes. We believe that the presented strategy together with the good photocatalytic activity and excellent recyclability constitute open the path for a substantial progress in this field

Light-Driven Integration of Graphitic Carbon Nitride into Polymer Materials

As a metal-free polymeric semiconductor with an absorption in the visible range, carbon nitride has numerous advantages for photo-based applications spanning hydrogen evolution, CO2 reduction, ion transport, organic synthesis and organic dye degradation. The combination of g-C3N4 and polymer networks grants mutual benefit for both platforms, as networks are upgraded with photoactivity or formed by photoinitiation, and g-C3N4 is integrated into novel applications. In the present contribution, some of the recently published projects regarding g-C3N4 and polymeric materials will be highlighted. In the first study, organodispersible g-C3N4 were incorporated into a highly commercialized porous resin called poly(styrene-co-divinylbenzene) through suspension photopolymerization, and performances of resulting beads were investigated as recyclable photocatalysts. In the other study, g-C3N4 nanosheets were embedded in porous hydrogel networks, and so-formed hydrogels with photoactivity were transformed either into a ‘hydrophobic hydrogel’ or pore-patched materials via secondary network introduction, where both processes were accomplished via visible light. Since g-C3N4 is an organic semiconductor exhibiting sufficient charge separation under visible light illumination, a novel method for the oxidative photopolymerization of EDOT was successfully accomplished. As a result of the absence of dissolved anions during polymerization, so-formed neutral PEDOT is a highly viscous liquid that can be processed and post-doped easily, and grants facile coating processes

Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media via a One-Pot Grafting Approach

A facile route to synthesize hydrophilically or hydrophobically grafted graphitic carbon nitride (g-CN) is reported. For this purpose, functionalized olefinic molecules with a low polymerization tendency are utilized for grafting onto the surface to preserve the features of g-CN while improving its dispersibility. One-pot, visible light-induced grafting yields highly dispersible g-CNs either in aqueous or organic media. Moreover, functional groups such as amines can be introduced, which yields pH-dependent dispersibility in aqueous media. Compared with unfunctionalized g-CN, low sonication times are sufficient to redisperse g-CN. In addition, because of increased dispersion stability, higher amounts of functionalized g-CN can be dispersed (up to 10% in aqueous dispersion and 2% in organic dispersion) when compared to unfunctionalized g-CN

Reinforced Hydrogels via Carbon Nitride Initiated Polymerization

The utilization of graphitic carbon nitride (g-CN) as photoinitiator for hydrogel formation is reported. On top of the photochemical activity, g-CN entails the role of a reinforcing agent. Hydrogels formed via g-CN (0.6 wt % g-CN and 11 wt % solid content in total) possess significantly increased mechanical strength, around 32 times stronger storage moduli (from 250 Pa for the reference sample up to 8300 Pa for g-CN derived hydrogels) than the ones initiated with common radical initiators. In addition, the g-CN derived hydrogels show mechanical properties that are pH dependent. Therefore, g-CN acts as a photoinitiator for hydrogel formation and as reinforcer at the same time