"The phactalysts": carbon nanotube/TiO2 composites as phototropic actuators for wireless remote triggering of chemical reactions and catalysis

Advances in photocatalytic degradation of tetracycline using graphene-based composites in water: a systematic review and future directions

In this study, a comprehensive systematic review was conducted to better recognize the applicability of graphene-based photocatalytic processes for the degradation of tetracycline (TC) from water. A broad search strategy was developed for English language articles available in PubMed, Scopus, and Web of Science. The effect of parameters such as pH, TC concentration, photocatalyst dose, radiation source intensity, and the effect of graphene on the process, kinetics, and reuse of the photocatalyst were investigated. A total of 63 out of a possible 3498 retrieved records met inclusion criteria. The results showed that most related studies have increased since 2019. About 46.7% of the articles showed 90-100% TC removal efficiency and 59.52% of the studies had optimal pH equal to 5 and 6. Also, the widespread use of visible light had a significant trend. The effect of the dose of graphene in the catalyst was one of the most important and effective factors on the process; hence, the difference in efficiency with and without graphene was completely evident. This review indicated that the presence of graphene has been able to have a positive effect on increasing the efficiency of oxidation processes, and it can be used for environmental pollutants remediation.

Research progress in self-oscillating polymer brushes

Polymer brushes possess unique changes in physical and chemical properties when they are exposed to external stimuli and have a wide range of applications. Self-oscillating polymers are anchored on surfaces of certain materials and are coupled with some self-oscillating reactions (with the Belousov–Zhabotinsky (BZ) reaction as an example) to form self-oscillating polymer brushes. As an independent field of stimulus response functional surface research, the development of new intelligent bionic materials has good potential. This article reviews the oscillation mechanisms of self-oscillating polymer brushes and their classifications. First, the oscillation mechanisms of self-oscillating polymer brushes are introduced. Second, the research progress in self-oscillating polymers is discussed in terms of the type of self-oscillation reactions. Finally, possible future developments of self-oscillating polymer brushes are prospected.

Polymer brushes possess unique changes in physical and chemical properties when they are exposed to external stimuli and have a wide range of applications.

Stimuli-Responsive Phase Change Materials: Optical and Optoelectronic Applications

Stimuli-responsive materials offer a large variety of possibilities in fabrication of solid- state devices. Phase change materials (PCMs) undergo rapid and drastic changes of their optical properties upon switching from one crystallographic phase to another one. This peculiarity makes PCMs ideal candidates for a number of applications including sensors, active displays, photonic volatile and non-volatile memories for information storage and computer science and optoelectronic devices. This review analyzes different examples of PCMs, in particular germanium–antimonium tellurides and vanadium dioxide (VO₂) and their applications in the above-mentioned fields, with a detailed discussion on potential, limitations and challenges.

System Chemistry in Catalysis: Facing the Next Challenges in Production of Energy Vectors and Environmental Remediation

Most of the catalytic processes that assist the production of either renewable energy vectors or degradation of environmental pollutants rely on the interplay among different factors that can be purposely regulated, in order to improve the overall efficiency of reactions. This perspective analyzes some recent examples of ‘systemic catalysts’, which are based on the modification of the reaction microenvironment and exploitation of concurrent/parasitic reactions or different types of chemical looping, in order to bypass some drawbacks that cannot be easily circumvented by standard approaches. Innovative extensions of those concepts and strategies might inspire new breakthroughs in a variety of key catalytic cycles characterized by high complexity.

Oscillating Reactions Meet Polymers at Interfaces

Chemo-mechanical phenomena, including oscillations and peristaltic motions, are widespread in nature-just think of heartbeats-thanks to the ability of living organisms to convert directly chemical energy into mechanical work. Their imitation with artificial systems is still an open challenge. Chemical clocks and oscillators (such as the popular Belousov-Zhabotinsky (BZ) reaction) are reaction networks characterized by the emergence of peculiar spatiotemporal dynamics. Their application to polymers at interfaces (grafted chains, layer-by-layer assemblies, and polymer brushes) offers great opportunities for developing novel smart biomimetic materials. Despite the wide field of potential applications, limited research has been carried out so far. Here, we aim to showcase the state-of-the-art of this fascinating field of investigation, highlighting the potential for future developments and providing a personal outlook.

Gradient Assembly of Polymer Nanospheres and Graphene Oxide Sheets for Dual-Responsive Soft Actuators

Bimorph actuators hold great promise for developing soft robots. However, poor interlayer adhesion between different materials always threatens their stability for long-term usage. In this paper, instead of using a bilayer structure, we reported the gradient assembly of graphene oxide (GO) sheets and polymer nanospheres for developing robust moisture and light dual-responsive actuators. The distribution gradient of poly(methyl methacrylate) (PMMA) nanospheres along the normal direction of a GO paper leads to an asymmetric structure. The front side that mainly consists of GO is quite sensitive to water molecules, which swells upon exposure to moisture, whereas the back side that is rich in PMMA nanospheres expands obviously due to the photothermal effect. The distinct properties of the two sides endow the composite paper with moisture and light dual-responsiveness. Moreover, since GO has been used as a host material, the composite paper shows a moisture-triggered self-healing property, which permits front-to-front and front-to-back healing. The self-healed paper can maintain similar responsive property and reasonable mechanical strength to the pristine one. As a proof of concept, a dual-responsive gripper actuator and a scorpion robot have been fabricated for light and moisture cooperative manipulation. The gradient assembly strategy may open up a new way for developing robust multiresponsive actuators beyond bilayer structures.

Copper nanoparticles with near-unity, omnidirectional, and broadband optical absorption for highly efficient solar steam generation

Solar steam generation provides a renewable and environmentally friendly approach to solve the water shortage issue. The pursuit of efficient, stable, and cheap photothermal agents is thus of great significance. In this work, Cu nanoparticles (NPs) fabricated simply by a substitution reaction, exhibit a near-unity (∼97.7%) light absorption, covering a broad incident angle and wavelength range (200-1300 nm). Thereby, a high photothermal conversion efficiency of 93% is achieved. The excellent photothermal performance offers a unique opportunity for the development of solar steam generation. By coating the Cu NPs on a cellulose membrane, a solar steam generation efficiency up to 73% is acquired at a low irradiation power density of 2 kW m^-2 (1 kW m^-2 = 1 sun). Moreover, the Cu NPs are recyclable with the high stability being resistant to heat, photoirradiation and corrosion of brine.

Switchable Stimuli-Responsive Heterogeneous Catalysis

Heterogeneous catalytic systems based on the use of stimuli-responsive materials can be switched from an “on” active state to an “off” inactive state, which contributes to endowing the catalysts with unique functional properties, such as adaptability, recyclability and precise spatial and temporal control on different types of chemical reactions. All these properties constitute a step toward the development of nature-inspired catalytic systems. Even if this is a niche area in the field of catalysis, it is possible to find in literature intriguing examples of dynamic catalysts, whose systematic analysis and review are still lacking. The aim of this work is to examine the recent developments of stimuli-responsive heterogeneous catalytic systems from the viewpoint of different approaches that have been proposed to obtain a dynamic control of catalytic efficiency. Because of the variety of reactions and conditions, it is difficult to make a quantitative comparison between the efficiencies of the considered systems, but the analysis of the different strategies can inspire the preparation of new smart catalytic systems.