Green synthesis of MnO2 nanoparticles from Psidium guajava leaf extract: Morphological characterization, photocatalytic and DNA/BSA interaction studies

In this work, a simple, efficient and eco-friendly green synthesis of manganese dioxide nanoparticles (MnO2NPs) by Psidium guajava leaf extract was described. Fourier-Transform infrared spectra results revealed that involvement of the plant extract functional groups in the formation of MnO2NPs. The UV-vis absorption spectra of the synthesized MnO2NPs exhibited absorption peaks at 374 nm, which were attributed to the band gap of the MnO2NPs. Crystal phase identification of the MnO2NPs were characterized by X-ray diffraction analysis and the formation of crystalline MnO2NPs have been confirmed. Furthermore, scanning electron microscopy analysis showed that the synthesized MnO2NPs have a spherical in shape. Interestingly, the prepared green synthesized MnO2NPs showed catalytic degradation activity for malachite green dye. Malachite green's photocatalytic degradation was detected spectrophotometrically in the wavelength range of 250-900 nm, and it was discovered to have a photodegradation efficiency of 75.5 % within 90 min when exposed to solar radiation. Green synthesized MnO2NPs are responsible for this higher activity. An interaction between synthesized NPs and biomolecules, including CT-DNA and BSA was also evaluated. The spectrophotometric and Fluoro spectroscopic analyses indicate a gradual reduction in peak intensities and shifts in wavelengths, indicating binding and affinity between the NPs and the biomolecules.

Fabrication of ATP/PEG/MnO2NWs composite for solar steam generation with high conversion efficiency

Solar steam generation is widely used in seawater desalination because of its high efficiency and environmental protection. However, using low-cost materials to produce efficient solar evaporators is a severe challenge. In this study, a porous carbon material was prepared by combining Attapulgite (ATP), Polyethylene glycol (PEG) and Manganese dioxide nanowires (MnO₂NWs) composite, through freeze-drying and high-temperature carbonization. The prepared CAPM aerogel shows a three-dimensional porous structure, which has high evaporation properties in pure water and simulated seawater. Under 1 sun simulated illumination, the pure water evaporation is 1.4574 kg m^-2h^-1 and the corresponding energy conversion efficiency is 85.94%. The prepared CAPM aerogel showed excellent durability and salt tolerance in 20%Nacl solution, indicating that the CAPM has excellent desalinization performance. In addition, CAPM aerogel has and exhibits super hydrophilic properties, which can transfer water molecules quickly. Due to the advantages of low cost, simple preparation method, and high solar energy conversion efficiency, the CAPM has excellent potential as a photothermal material for solar energy generation.

Atomic scaled modulation strategies and crystal phase transition of flower-like CoAl layered double hydroxide for supercapacitor

In the present work, cobalt aluminum layered double hydroxide and its derivatives were synthesized via hydrothermal method, alkali-etching method and phosphorization route to obtain different crystal phases. The structure, morphology...

Design of a redox-active “water-in-salt” hydrogel polymer electrolyte for superior-performance quasi-solid-state supercapacitors

A carbon-based quasi-solid-state supercapacitor with a redox-active “water-in-salt” hydrogel polymer electrolyte exhibiting wide operating voltage and high specific energy.

Solution-processed graphene oxide electrode for supercapacitors fabricated using low temperature thermal reduction

We present a low temperature and solution-based fabrication process for reduced graphene oxide (rGO) electrodes for electric double layer capacitors (EDLCs). Through the heat treatment at 180 °C between the spin coatings of graphene oxide (GO) solution, an electrode with loosely stacked GO sheets could be obtained, and the GO base coating was partially reduced. The thickness of the electrodes could be freely controlled as these electrodes were prepared without an additive as a spacer. The GO coating layers were then fully reduced to rGO at a relatively low temperature of 300 °C under ambient atmospheric conditions, not in any chemically reducing environment. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that the changes in oxygen functional groups of GO occurred through the heat treatments at 180 and 300 °C, which clearly confirmed the reduction from GO to rGO in the proposed fabrication process at the low thermal reduction temperatures. The structural changes before and after the thermal reduction of GO to rGO analyzed using Molecular Dynamic (MD) simulation showed the same trends as those characterized using Raman spectroscopy and XPS. An EDLC composed of the low temperature reduced rGO-based electrodes and poly(vinyl alcohol)/phosphoric acid (PVA/H₃PO₄) electrolyte gel was shown to have high specific capacitance of about 240 F g⁻¹ together with excellent energy and power densities of about 33.3 W h kg⁻¹ and 833.3 W kg⁻¹, respectively. Furthermore, a series of multiple rGO-based EDLCs was shown to have fast charging and slow discharging properties that allowed them to light up a white light emitting diode (LED) for 30 min.

We present a low temperature and solution-based fabrication process for reduced graphene oxide (rGO) electrodes for electric double layer capacitors (EDLCs).