Adhesive hydrogels are attractive biomaterials for various applications, such as electronic skin, wound dressing, and wearable devices. However, fabricating a hydrogel with both adequate adhesiveness and excellent mechanical properties remains a challenge. Inspired by the adhesion mechanism of mussels, we used a two-step process to develop an adhesive and tough polydopamine-clay-polyacrylamide (PDA-clay-PAM) hydrogel. Dopamine was intercalated into clay nanosheets and limitedly oxidized between the layers, resulting in PDA-intercalated clay nanosheets containing free catechol groups. Acrylamide monomers were then added and in situ polymerized to form the hydrogel. Unlike previous single-use adhesive hydrogels, our hydrogel showed repeatable and durable adhesiveness. It adhered directly on human skin without causing an inflammatory response and was easily removed without causing damage. The adhesiveness of this hydrogel was attributed to the presence of enough free catechol groups in the hydrogel, which were created by controlling the oxidation process of the PDA in the confined nanolayers of clay. This mimicked the adhesion mechanism of the mussels, which maintain a high concentration of catechol groups in the confined nanospace of their byssal plaque. The hydrogel also displayed superior toughness, which resulted from nanoreinforcement by clay and PDA-induced cooperative interactions with the hydrogel networks. Moreover, the hydrogel favored cell attachment and proliferation, owning to the high cell affinity of PDA. Rat full-thickness skin defect experiments demonstrated that the hydrogel was an excellent dressing. This free-standing, adhesive, tough, and biocompatible hydrogel may be more convenient for surgical applications than adhesives that involve in situ gelation and extra agents.

first solid-state perovskite solar cell (PSC) was successfully prepared by introducing Sprio as a hole transport layer (HTL), tremendous efforts have been devoted to further promoting the photovoltaic performance, including surface passivation, bulk doping, processing engineering, and optimizing the structure of the device. [9][10][11][12][13][14][15][16][17][18][19][20][21] Consequently, the power conversion efficiency (PCE) of PSCs has dramatically increased from the initial 9% to an impressive 25.2% in several years. [22,23] To date, the coexistence of high efficiency and long-term stability has become a crucial requirement for successful PSC applications. 2D perovskites (consisting of pure 2D and quasi-2D perovskites) have emerged as a new family of photovoltaic materials that have been proven to resolve the problem of instability in perovskites. Owing to the insulating spacer layer, inherent outstanding long-term stability is obtained in 2D perovskites, including hydrophobicity, suppression of ion migration, and larger formation energy. [24][25][26][27][28] However, severe carrier recombination occurs due to the combined effect of quantum confinement and dielectric confinement, rooted in the natural multiple quantum wells structure (MQWs) (Figure 1), where the inorganic parts act as potential "wells" while the organic parts act as "walls", which shows a boost in the photovoltaic performance of 2D PSCs. [29][30][31] To realize the coexistence of high efficiency and ultrastability in PSCs, researchers began to construct 2D/3D heterostructures by surface passivation. [32][33][34][35][36][37][38][39][40] In fact, before the boosting of the 2D/3D stacking concept, many researchers have applied large ammonium cations (such as phenethylamine (PEA), butylamine (BA), and quaternary ammonium (QA)) as defect passivants to 3D perovskite solar cells. [41][42][43][44][45] During this period, the pure PEA-or BA-based 2D perovskites have been explored as light-absorbing materials for better stability. [25,46] In 2015, Yao et al. introduced in situ grown 2D perovskite (PEI) 2 PbI 4 (PEI: polymeric ammonium) on an MAPbI 3 film, leading to more stable and efficient PSCs. [47] In 2016, discussions and analyses of the surface passivation effect began to emerge, which involved exploring a series of 2D perovskite molecules (such as aniline, benzylamine, and PEA). [42,45,48] The concept of 2D/3D stacking really stood out in 2018 by unveiling the chemical reaction mechanism for heterojunction formation and the mechanism for enhancing stability. For example, Huang 3D perovskite solar cells (PSCs) have shown great promise for use in next-generation photovoltaic devices. However, some challenges need to be addressed before their commercial production, such as enormous defects formed on the surface, which result in severe SRH recombination, and inadequate material interplay between the composition, leading to thermal-, moisture-, and light-induced degradation. 2D perovskites, in which the organic layer functions as a protective barrier ...

A novel poly(acrylic acid) (PAA)-based super-adsorbent nanocomposite hydrogel as an effective dye adsorbent is prepared using non-aggregated calcium hydroxide (Ca(OH)2) nano-spherulites (CNSs) as cross-linkers.