The rapid increase in toxic dye wastewater generated from various industries remains a severe public health issue and prime environmental protection concern, posing a major challenge to existing ...conventional water treatment systems. Consequently, various physicochemical and biological treatment processes have been studied, which exhibit varying removal abilities depending on their experimental constraints. Among them, adsorption is considered to be the most efficient due to its high removal efficiency, easy operation, cost-effectiveness, and recyclability of the adsorbents. Considering this, the present review article focused on presenting a comprehensive summary of the various types of adsorbents such as commercial activated carbon, metal oxide-based, carbon-based, metal-organic framework, and polymer-based adsorbents used in dye remediation of contaminated water. The effects of several critical factors such as initial dye concentration, solution pH, temperature, and adsorbent dose on the dye adsorption performance are also described. In addition, the adsorption mechanisms responsible for dye removal are explained based on electrostatic attraction, ion exchange, surface complexation, and π-π interactions. Finally, critiques, future perspectives, and a summary of the present article are given. Various adsorbents such as carbon-based materials, metal oxides, bio-adsorbents, and polymer-based materials, have been shown to be efficient for the removal of dye pollutants from wastewater. Thus, it is anticipated that dye removal by adsorption can provide a feasible solution for the treatment of dye-laden water.
This review is focused on the origin of dye pollutants, their ecotoxicological effects and adsorptive removal using various types of adsorbents.
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Heteroatom-doped graphene and its derived layered materials play a substantial role in several emerging science fields, demonstrating great potential for implementation in new devices ...and for improving the performance of existing technologies. A wide variety of strategies have been applied for the controlled synthesis and for achieving the intended doping/co-doping levels in the carbon network of graphene-based materials. Precise and reproducible doping is crucial for altering the Fermi energy level and to tune the band gap according to the desired device/application. Heteroatom-doped and co-doped graphene-based materials (n-type and p-type doping) have been synthesized for devices in energy-related applications using various chemical and physical routes. In this review article, we survey the most recent research works on the synthesis of heteroatom-doped graphene materials such as reduced graphene oxide, graphene oxide, graphene quantum dots and graphene nanoribbons. Applications of these materials in energy storage/conversion devices (supercapacitors, batteries, fuel cells, water splitting and solar cells) are also reviewed. Finally, the challenges and future perspectives for heteroatom-doped graphene materials are briefly discussed. We hope this article offers a useful starting point for researchers entering the field, providing an overview of synthesis approaches and energy applications.
Structure-activity relationship of nanozymes provide ideas for the de novo design of nanozymes.
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Nanozymes, nanomaterials with enzyme-like activities, are becoming powerful competitors ...and potential substitutes for natural enzymes because of their excellent performance, including design from scratch, controllable activity, and environmental resistance. In recent years, various nanozymes have been discovered or designed, and gradually applied to molecular detection, biomedical treatment and environmental management. Nevertheless, nanozymes are often regarded as fascinating and confusing black boxes as their catalytic mechanisms remain largely indistinct. Interestingly, recent researches have shed light into these black boxes. It appears that the enzymatic activities of nanozymes are closely related to their size, surface lattice, surface modification and composition, etc. Some regular structure–activity relationships have been elucidated in recent reports. In this review, we systematically summarized the studies on the structure–activity relationship of nanozymes in recent years, aiming to illustrate the catalytic mechanism of nanozymes and clarify the key factors regulating their behavior, so as to provide ideas and inspiration for the de novo design of nanozymes.
Recent advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) have led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, ...and opto-electronics, to name a few. This article reviews the recent progress in 2D materials beyond graphene and includes mainly transition metal dichalcogenides (TMDs) (e.g. MoS2, WS2, MoSe2, and WSe2). These materials are finding niche applications for next-generation electronics and optoelectronics devices relying on ultimate atomic thicknesses. Albeit several challenges in developing scalable and defect-free TMDs on desired substrates, new growth techniques compatible with traditional and unconventional substrates have been developed to meet the ever-increasing demand of high quality and controllability for practical applications. The fabrication of novel 2D TMDs that exhibit exotic functionalities and fundamentally new chemistry is highlighted. And finally, in parallel with the electronics, the considerable effort devoted to using these materials for energy and sensing applications is discussed in detail.
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π-Conjugated chromophores have been investigated for many years and successful theoretical models have been developed to explain their photophysical properties. However, materials ...have appeared sporadically that do not fit within these existing models. Some of these materials possess entirely nonconjugated structures based on saturated C–C, C–O or C–N bonds, but their aggregates or solid-state forms show bright visible emission. This phenomenon is termed as clusterization-triggered emission (CTE) and the materials possessing the property are labeled clusteroluminogens. In this review, we provide a brief summary of the recent development of clusteroluminogens. The materials are classified into three categories: polymers (natural and synthetic polymers), small molecules (with and without aromatic rings) and metal clusters. Possible luminescence mechanisms underpinning the different categories of clusteroluminogens are analyzed individually. Finally, we put forward a comprehensive theory of the through-space conjugation (TSC) for these chromophores. Based on the CTE effect and TSC theory, various applications have been envisioned, for example in the areas of process monitoring, structural visualization, sensors, and probes. It is anticipated that this new research direction will bring many breakthroughs, not only in the theoretical areas, but also in these advanced applications of light-emitting materials.
Peptoid polymers are often crystalline in the solid-state as examined by X-ray scattering, but thus far, there has been no attempt to identify a common structural motif among them. In order to probe ...the relationship between molecular structure and crystal structure, we synthesized and analyzed a series of crystalline peptoid copolymers, systematically varying peptoid side-chain length (S) and main-chain length (N). We also examined X-ray scattering data from 18 previously reported peptoid polymers. In all peptoids, we found that the unit cell dimensions, a, b, and c, are simple functions of S and N: a (Å) = 4.55, b (Å) = 2.98N + 0.35, and c (Å) = 1.86S + 5.5. These relationships, which apply to both bulk crystals and self-assembled nanosheets in water, indicate that the molecules adopt extended, planar conformations. Furthermore, we performed molecular dynamics simulations (MD) of peptoid polymer lattices, which indicate that all backbone amides adopt the cis conformation. This is a surprising conclusion, because previous studies on isolated molecules indicated an energetic preference for the trans conformer. This study demonstrates that when packed into supramolecular lattices or crystals, peptoid polymers prefer to adopt a regular, extended, all-cis secondary structure.
Self-powered system is a system that can sustainably operate without an external power supply for sensing, detection, data processing and data transmission. Nanogenerators were first developed for ...self-powered systems based on piezoelectric effect and triboelectrification effect for converting tiny mechanical energy into electricity, which have applications in internet of things, environmental/infrastructural monitoring, medical science and security. In this paper, we present the fundamental theory of the nanogenerators starting from the Maxwell equations. In the Maxwell's displacement current, the first term ε0∂E∂t gives the birth of electromagnetic wave, which is the foundation of wireless communication, radar and later the information technology. Our study indicates that the second term ∂P∂t in the Maxwell's displacement current is directly related to the output electric current of the nanogenerator, meaning that our nanogenerators are the applications of Maxwell's displacement current in energy and sensors. By contrast, electromagnetic generators are built based on Lorentz force driven flow of free electrons in a conductor. This study presents the similarity and differences between pieozoelectric nanogenerator and triboelectric nanogenerator, as well as the classical electromagnetic generator, so that the impact and uniqueness of the nanogenerators can be clearly understood. We also present the three major applications of nanogenerators as micro/nano-power source, self-powered sensors and blue energy.
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