Metallogels: Availability, Applicability, and Advanceability

Abstract

amount of cross-linked solid. According to the nature of solvents, gels are categorized into hydrogel and organogel to indicate whether the solvent is water or organic solvent(s), respectively. As to the gelation driving forces, gels can be classified into physical gels in which intermolecular interactions are responsible for gel formation, and chemical gels in which the gel skeleton is cross-linked by covalent bonds.Incorporation of metal components (metal ions, metal-organic molecules, and metal nanoparticles) is an effective way to locally establish extra interactions among the building blocks and consequently trigger gel formation, [2][3][4] weaken [5] or enhance [6] gel strength, and modify gel morphology. [7,8] Moreover, addition of metal components is a straightforward way to integrate the specific properties of metals with the properties of organic matrix, therefore to tune properties like conductivity, [9] color, [10,11] rheological behavior, [12] adsorption, [13] emission, [14] photophysical properties, [15] magnetism, [16,17] antibacterial activities, [18,19] catalytic activities, [20][21][22][23] redox activities, [24,25] and selfhealing properties. [26][27][28] Therefore, a broad response range to physical and chemical stimuli can be achieved. For instance, the incorporation of multivalence ions such as Fe 2+ /Fe 3+ , [25,29] Co 2+ / Co 3+ , [30] Cu + /Cu 2+ , [31] results in redox reactive hydrogels; the incorporation of magnetic nanoparticles like Fe 3 O 4[17] causes the gel to respond to external magnetic fields. In addition to the abovementioned intrinsically functional superiorities, metallogels can also serve as ideal templates to generate new materials, [13,22,23,32,33] such as 3D networks, [34] porous structures, [35] chiral materials, [36][37][38] quantum dots, [39] and nanorods. [40] Following the rapid advancement of exploration on the knowledge acquisition toward the major roles that metallogels are playing in catalysis, sensing, biomedicine, electronics, and optical devices, the focus of research has been transferred to the design principles of metallogels in the last decade. Owing to the advancements in the instrumental characterizations and theoretical calculations, [41] a number of pioneering efforts on metallogel design have been made and several innovative reviews have summarized these inspiring contributions. [32,[42][43][44] Despite their extensively acknowledged application advantages in many fields, the discovery of new metallogels with expected functionalities is still highly dependent on experimental screening and serendipity. The challenge stems from the susceptible balance among those complicated intermolecular interactions and the elaborate structure requirements of metallogels.Another research niche that needs to be clarified before discussing recent development of metallogels is: how to sort Introducing metal components into gel matrices provides an effective strategy to develop soft materials with advantageous properties such as: optical activity, conductivity, magn...

Near-infrared light-responsive hydrogels via peroxide-decorated MXene-initiated polymerization

“…"Smart" responsive hydrogels are now being widely studied in various elds such as so robotics, 1,2 sensors, 3,4 microdevices, 5 drug delivery, 6,7 cell/tissue engineering scaffolds, 8,9 and reaction vessels. 10,11 Exposure to different stimuli (for example light, temperature, pH, and electric eld) may cause these hydrogels to swell/shrink, bend/unbend, or swim/crawl, mimicking natural creatures with responsive behavior. [12][13][14][15] In particular, light is a distinct stimulus to tune the properties of a hydrogel spatiotemporally in a remote controlled manner with great ease and convenience.…”

Flourishing Self‐Healing Surface Materials: Recent Progresses and Challenges

“…On the one hand, the simple preparation and excellent biocompatibility of hydrogel promote its extensive application, and on the other hand, hydrogel also provides the suitable physiological environment to meet the requirement of cell survive. [199,200] However, when the hydrogel is implanted into the certain position of the body, the process of gelation and the control of gelation bring a new challenge for the bioactivity of embedded cells and proteins. Therefore, a new type of self-healed hydrogel based on dynamic covalent bonds can overcome aforementioned drawbacks.…”

Pathway Dependence in Redox‐Driven Metal–Organic Gels

“…Conceptually, metal–organic gels are synthesized based on strong metal–ligand interactions, in which the organic ligand may compose of a single component or can be derived from the reaction between multiple functional groups. Incorporation of metal ions into the organic frameworks often dramatically changes the optical and chemical properties of the ligand and therefore can be used as a powerful strategy to modify the material properties …”