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Aerogels are a unique class of nanoporous ultralight materials exhibiting wide range of textural characteristic properties and tunable porosities. Due to their remarkable features such as low density, high surface area, low refractive index, small thermal conductivity, low dielectric constant and low sound velocity, they exhibit a wide range of applications in different areas such as electronics, thermal and acoustic insulation, chemistry, biomedicine and optics. The special advantages of these materials are that they can be produced in different forms such as monoliths/granular, bead/microspheres, thin films or sheets and as blankets. Aerogels are found to be potential materials for the removal of CO2 through adsorption or electrochemical reduction. There is a plethora of research on different kinds of aerogels used for CO2 adsorption process. Research has been going on toward the development of aerogel-based electrocatalyst, which can be used for valorization of CO2 through electrochemical reduction methods. Although most of the review papers have covered applications of aerogels in CO2 capture, very few discuss the processing of aerogels, more so on their applications in CO2 valorization. In this review, we have collated literature of different forms of aerogels currently available and the steps involved in their fabrication process. In addition, we have covered applications of aerogels in CO2 capture. Furthermore, we focussed on the basic principles involved in the development of an aerogel electrocatalyst as well as recent developments of aerogels in electrochemical CO2 reduction. [ABSTRACT FROM AUTHOR]

Over decades, nanozyme has served as a better replacement of bioenzymes and fulfills most of the shortcomings and intrinsic disadvantages of bioenzymes. Recently, manganese-based nanomaterials have been highly noticed for redox-modulated multienzyme mimicking activity and wide applications in biosensing and biomedical science. The redox-modulated multienzyme mimicking activity was highly in tune with their size, surface functionalization, and charge on the surface and phases. On the subject of calcination temperature to Mn 3 O 4 nanoparticles (NPs), its phase has been transformed to Mn 2 O 3 NPs and Mn 5 O 8 NPs upon different calcination temperatures. Assigning precise structure-property connections is made easier by preparing the various manganese oxides in a single step. The present study has focused on the variation of multienzyme mimicking activity with different phases of Mn 3 O 4 NPs, so that they can be equipped for multifunctional activity with greater potential. Herein, spherical Mn 3 O 4 NPs have been synthesized via a one-step coprecipitation method, and other phases are obtained by direct calcination. The calcination temperature varies to 100, 200, 400, and 600 °C and the corresponding manganese oxide NPs are named M-100, M-200, M-400, and M-600, respectively. The phase transformation and crystalline structure are evaluated by powder X-ray diffraction and selected-area electron diffraction analysis. The different surface morphologies are easily navigated by Fourier transform infrared, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy analysis. Fortunately, for the mixed valence state of Mn 3 O 4 NPs, all phases of manganese oxide NPs showed multienzyme mimicking activity including superoxide dismutase (SOD), catalase, oxidase (OD), and peroxidase; therefore, it offers a synergistic antioxidant ability to overexpose reactive oxygen species. Mn 3 O 4 NPs exhibited good SOD-like enzyme activity, which allowed it to effectively remove the active oxygen (O 2 •- ) from cigarette smoke. A sensitive colorimetric sensor with a low detection limit and a promising linear range has been designed to detect two isomeric phenolic pollutants, hydroquinone (H 2 Q) and catechol (CA), by utilizing optimized OD activity. The current probe has outstanding sensitivity and selectivity as well as the ability to visually detect two isomers with the unaided eye.