Superwetting Monolithic Hollow-Carbon-Nanotubes Aerogels with Hierarchically Nanoporous Structure for Efficient Solar Steam Generation

Chitosan based bioactive materials in tissue engineering applications-A review.

Graphene nanomaterials have been considered as a novel class of nanomaterials that show exceptional structural, optical, thermal, electrical, and mechanical properties. As a consequence, it has been extensively studied in various fields including electronics, energy, catalysis, sensing, and biomedical fields. In the previous couple of years, a significant number of studies have been done on graphene-based nanomaterials, where it is utilized in a wide range of bioapplications that includes delivery of small molecule drugs/genes, biosensing, tissue engineering, bioimaging, and photothermal and photodynamic therapies because of its excellent aqueous processability, surface functionalizability, outstanding electrical and mechanical properties, tunable fluorescence properties, and surface-enhanced Raman scattering (SERS).Therefore, it is necessary to get detailed knowledge about it. In this review, we will highlight the various synthesis procedures of graphene family nanomaterials including graphene oxide (GO), reduced graphene oxide (rGO), and graphene quantum dots (GQDs) as well as their biomedical applications. We will also highlight the biocompatibity of graphene nanomaterials as well as its possible risk factors for bioapplications. In conclusion, we will outline the future perspective and current challenges of graphene nanomaterials for clinical applications.

Biomedical Applications of Graphene Nanomaterials and Beyond

The wide spectral range of the solar flux with undesirable diffused energy distribution remains a substantial impediment to the high-efficiency utilization of the whole spectrum. Here, inspired by the spectrally selective sunlight utilization of plants, a spectrum-tailored solar harnessing aerogel is conceived. It is composed of oxygen vacancy (Ov) defect-rich semiconductor HNb3O8 (D-HNb3O8) nanosheets and polyacrylamide (PAM) framework to perform all-in-one photochemical and photothermal full solar energy conversion. The aerogel selectively utilizes the whole solar spectrum, in which high energy ultraviolet (UV) photon is converted into high redox potential electron–hole pairs, while low energy visible-near infrared (NIR) photons are transformed into heat. The designed solar absorber-polymer composite shows energy harnessing-conversion capability with desired heat insulation, reactant enrichment, rapid mass diffusion and capillary pumping characteristics, thus realizing a high efficient steam generation and photochemical activity. This cooperative photochemical and photothermal solar energy conversion, at respective optimal working spectrum, holds great promise for optimizing and maximizing the solar energy utilization, as well as opening up opportunities to explore simultaneous multifunctional usage of solar energy.

Spectrum Tailored Defective 2D Semiconductor Nanosheets Aerogel for Full‐Spectrum‐Driven Photothermal Water Evaporation and Photochemical Degradation

Solar steam generation by heat localization has attracted much attention for its potential in the treatment of wastewater and seawater desalination. However, the preparation of a single-component solar receiver with low cost, simple preparation process, high mechanical strength and energy conversion efficiency is still a challenge. Herein, we report the preparation of kapok fiber-PPy aerogels with superwetting, porous structure, high light absorption, and high mechanical strength via polypyrrole modification of the Ca2+ crosslinked kapok fiber aerogels. The kapok fiber-PPy aerogels show three-dimensional structure with high porosity (94%), excellent light absorption (ca. 97%), low thermal conductivity (0.0241 W m−1 k−1) and high mechanical strength (0.12 MPa under 75% of strain). As a solar steam generation device, a high energy conversion efficiency of 82.4% was achieved under 1 kW m−2 illumination. The findings of this investigation may open a simple and novel route towards the fabrication of a low-cost a single-component biomass-based solar receivers for solar steam generation.

Conductive hollow kapok fiber-PPy monolithic aerogels with excellent mechanical robustness for efficient solar steam generation

Developing a biodegradable scaffold remains a major challenge in bone tissue engineering. This study was aimed at developing novel alginate-chitosan-collagen (SA-CS-Col)-based composite scaffolds consisting of graphene oxide (GO) to enrich porous structures, elicited by the freeze-drying technique. To characterize porosity, water absorption, and compressive modulus, GO scaffolds (SA-CS-Col-GO) were prepared with and without Ca2+-mediated crosslinking (chemical crosslinking) and analyzed using Raman, Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy techniques. The incorporation of GO into the SA-CS-Col matrix increased both crosslinking density as indicated by the reduction of crystalline peaks in the XRD patterns and polyelectrolyte ion complex as confirmed by FTIR. GO scaffolds showed increased mechanical properties which were further increased for chemically crosslinked scaffolds. All scaffolds exhibited interconnected pores of 10-250 μm range. By increasing the crosslinking density with Ca2+, a decrease in the porosity/swelling ratio was observed. Moreover, the SA-CS-Col-GO scaffold with or without chemical crosslinking was more stable as compared to SA-CS or SA-CS-Col scaffolds when placed in aqueous solution. To perform in vitro biochemical studies, mouse osteoblast cells were grown on various scaffolds and evaluated for cell proliferation by using MTT assay and mineralization and differentiation by alizarin red S staining. These measurements showed a significant increase for cells attached to the SA-CS-Col-GO scaffold compared to SA-CS or SA-CS-Col composites. However, chemical crosslinking of SA-CS-Col-GO showed no effect on the osteogenic ability of osteoblasts. These studies indicate the potential use of GO to prepare free SA-CS-Col scaffolds with preserved porous structure with elongated Col fibrils and that these composites, which are biocompatible and stable in a biological medium, could be used for application in engineering bone tissues.

Pugazhendhi Abinaya Sindu

Papers

Graphene Oxide—A Tool for the Preparation of Chemically Crosslinking Free Alginate–Chitosan–Collagen Scaffolds for Bone Tissue Engineering