Black carbon (BC) is ubiquitous in the environments and participates in various biogeochemical processes. Both positive and negative effects of BC (especially biochar) on the ecosystem have been identified, which are mainly derived from its diverse physicochemical properties. Nevertheless, few studies systematically examined the linkage between the evolution of BC molecular structure with the resulted BC properties, environmental functions as well as potential risk, which is critical for understanding the BC environmental behavior and utilization as a multifunctional product. Thus, this review highlights the molecular structure evolution of BC during pyrolysis and the impact of BC physicochemical properties on its sorption behavior, stability, and potential risk in terrestrial and aqueous ecosystems. Given the wide application of BC and its important role in biogeochemical processes, future research should focus on the following: (1) establishing methodology to more precisely predict and design BC propert...

Black Carbon (Biochar) In Water/Soil Environments: Molecular Structure, Sorption, Stability, and Potential Risk.

There exists a technological need for advanced materials with improved properties for emerging biomedical applications. Recent developments in macroporous materials have demonstrated their applicability as indispensable tools in biomedical research. Cryogels, which are materials with a macroporous 3D structure, are produced as a result of controlled freezing during polymerization with a highly interconnected polymer network. Cryogels’ interest lies in their ability to address some of the limitations of their hydrogel analogues. In this review, hydrogel and cryogel basic concepts are discussed as a short primer for readers unfamiliar with the cryogels literature. Next, a general overview of the methods for synthesis and characterization of cryogels is provided, highlighting key concepts relevant to cryogels and explaining their unique properties. Finally an in‐depth overview of specific technologies and fields where cryogels have been applied is given. It is argued that the latest advances in cryogel technologies are able to address challenges in bioseparation, tissue engineering, and other emerging bioengineering disciplines.

Latest Advances in Cryogel Technology for Biomedical Applications

In recent years, as an energy storage device with a fast charge and discharge speed, long cycle life, and good stability, flexible supercapacitors (SCs) have been extensively used in flexible electronic devices such as smart textiles, flexible display screens, and micro-robots. Combining the advantages of conductive materials and hydrogels, conductive polymer hydrogels have good flexibility, biocompatibility, and adjustable mechanical and electrochemical properties, which enable them to be used as electrolyte or electrode materials for flexible SCs, endowing flexible SCs with various excellent properties and meeting their various working requirements. This paper comprehensively reviews the flexible SCs based on conductive polymer hydrogels, from the design, synthesis and application aspects of conductive polymer hydrogels, the various superior functions (e.g., self-healing, high stretchability and compressibility, high toughness, electrochromic and shape memory) of flexible SCs based on conductive polymer hydrogels to different structures of flexible SCs, including fiber-shaped structures, all-in-one sandwich structures, and in-plane interdigital microstructures. Finally, we summarize the challenges faced by flexible SCs based on conductive polymer hydrogels, which provides new research directions and prospects for future development in this field.

Design and fabrication of conductive polymer hydrogels and their applications in flexible supercapacitors

Emerging challenges in the thermal management of cellulose nanofibril-based supercapacitors, lithium-ion batteries and solar cells: A review

Large-scale production of uniform and high-quality graphene is required for practical applications of graphene. The electrochemical exfoliation method is considered as a promising approach for the practical production of graphene. However, the relatively low production rate of graphene currently hinders its usage. Here, we demonstrate, for the first time, a rapid and high-yield approach to exfoliate graphite into graphene sheets via an electrochemical method with small molecular additives; where in this approach, the use of melamine additives is able to efficiently exfoliate graphite into high-quality graphene sheets. The exfoliation yield can be increased up to 25 wt% with melamine additives compared to electrochemical exfoliation without such additives in the electrolyte. The proposed mechanism for this improvement in the yield is the melamine-induced hydrophilic force from the basal plane; this force facilitates exfoliation and provides in situ protection of the graphene flake surface against further oxidation, leading to high-yield production of graphene of larger crystallite size. The residual melamine can be easily washed away by water after collection of the graphene. The exfoliation with molecular additives exhibits higher uniformity (over 80% is graphene of less than 3 layers), lower oxidation density (C/O ratio of 26.17), and low defect level (D/G < 0.45), which are characteristics superior to those of reduced graphene oxide (rGO) or of a previously reported approach of electrochemical exfoliated graphene (EC-graphene). The continuous films obtained by the purified graphene suspension exhibit a sheet resistance of 13.5 kΩ □(-1) at ∼95% transmittance. A graphene-based nanocomposite with polyvinyl butyral (PVB) exhibits an electrical conductivity of 3.3 × 10(-3) S m(-1) for the graphene loading fraction of 0.46 vol%. Moreover, the melamine functionalized graphene sheets are readily dispersed in the aqueous solution during the exfoliation process, allowing for the production of graphene in a continuous process. The continuous process for producing graphene was demonstrated, with a yield rate of 1.5 g h(-1). The proposed method can produce high-crystallinity graphene in a fast and high-yield manner, which paves the path towards mass production of high-quality graphene for a variety of applications.

結合分子臨場吸附與電化學剝離法製備高品質石墨烯;Towards the continuous production of high crystallinity graphene via electrochemical exfoliation with molecular in-situ encapsulation

Optimizing the free radical content of graphene oxide by controlling its reduction

Simultaneous electrochemical-assisted exfoliation and in situ surface functionalization towards large-scale production of few-layer graphene

An electroactive polymer composite with reinforced bending strength, based on tubular micro carbonized-cellulose

The fabrication of conductive composite hydrogels is still challenging mainly because of the heterogeneous distribution of conductivity across the structure. Carbon substrates are mostly used to induce conductivity in the polymer hydrogels. The first step towards an effective induction of conductivity is to reach a uniform dispersion of carbon within the hosting matrix. This paper describes a new cyclic cryogelation method for the fabrication of conductive hydrogels using chitosan as the polymer matrix and conductive cellulose based fibres as the filler. This is achieved by the cyclic thermal treatment of gelatinized chitosan solution, and orderly control of the hydrogen bonding network formation before the solvent evaporation. These networks regularly limit the chain mobility of polymer across the hydrogel and restrict the agglomeration of fibres within the matrix. As a result, a significant improvement in the homogeneity of conductivity across the treated hydrogel was achieved, shown by thermal camera mapping. In addition, the thermally treated chitosan/20 wt% fibres demonstrated a tensile strength improvement of about 50% compared to that of the untreated composite. The proposed method offers a good control of fibre dispersion within the polymer matrix, and can serve as a practical design concept for 3D conductive hydrogels in biotechnological applications.

Zahra Komeily Nia

Papers

Optimizing the free radical content of graphene oxide by controlling its reduction

Simultaneous electrochemical-assisted exfoliation and in situ surface functionalization towards large-scale production of few-layer graphene

An electroactive polymer composite with reinforced bending strength, based on tubular micro carbonized-cellulose

Cyclic cryogelation: a novel approach to control the distribution of carbonized cellulose fibres within polymer hydrogels