Enhancing the Mobilization of Native Phosphorus in the Mung Bean Rhizosphere Using ZnO Nanoparticles Synthesized by Soil Fungi

Phosphorus (P) is a limiting factor to plant growth and productivity in almost half of the world’s arable soil, and its uptake in plants is often constrained because of its low solubility in the soil. To avoid repeated and large quantity application of rock phosphate as a P fertilizer and enhance the availability of native P acquisition by the plant root surface, in this study a biosynthesized ZnO nanoparticle was used. Zn acts as a cofactor for P-solubilizing enzymes such as phosphatase and phytase, and nano ZnO increased their activity between 84 and 108%. The level of resultant P uptake in mung bean increased by 10.8%. In addition, biosynthesized ZnO also improves plant phenology such as stem height, root volume, and biochemical indicators such as leaf protein and chlorophyll contents. In the rhizosphere, increased chlorophyll content and root volume attract microbial populations that maintain soil biological health. ICP-MS results showed ZnO nanoparticles were distributed in all plant parts, including seeds. However, the concentration of Zn was within the limit of the dietary recommendation. To the best of our knowledge, this is the first holistic study focusing on native P mobilization using ZnO nanoparticles in the life cycle of mung bean plants

Graphene Oxides in Water: Correlating Morphology and Surface Chemistry with Aggregation Behavior

Aqueous aggregation processes can significantly impact function, effective toxicity, environmental transport, and ultimate fate of advanced nanoscale materials, including graphene and graphene oxide (GO). In this work, we have synthesized flat graphene oxide (GO) and five physically crumpled GOs (CGO, with different degrees of thermal reduction, and thus oxygen functionality) using an aerosol method, and characterized the evolution of surface chemistry and morphology using a suite of spectroscopic (UV–vis, FTIR, XPS) and microscopic (AFM, SEM, and TEM) techniques. For each of these materials, critical coagulation concentrations (CCC) were determined for NaCl, CaCl₂, and MgCl₂ electrolytes. The CCCs were correlated with material ζ-potentials (<i>R</i>² = 0.94–0.99), which were observed to be mathematically consistent with classic DLVO theory. We further correlated CCC values with CGO chemical properties including C/O ratios, carboxyl group concentrations, and C–C fractions. For all cases, edge-based carboxyl functional groups are highly correlated to observed CCC values (<i>R</i>² = 0.89–0.95). Observations support the deprotonation of carboxyl groups with low acid dissociation constants (p<i>K</i>_a) as the main contributors to ζ-potentials and thus material aqueous stability. We also observe CCC values to significantly increase (by 18–80%) when GO is physically crumpled as CGO. Taken together, the findings from both physical and chemical analyses clearly indicate that both GO shape and surface functionality are critical to consider with regard to understanding fundamental material behavior in water

Wood–Graphene Oxide Composite for Highly Efficient Solar Steam Generation and Desalination

Solar steam generation is a highly promising technology for harvesting solar energy, desalination and water purification. We introduce a novel bilayered structure composed of wood and graphene oxide (GO) for highly efficient solar steam generation. The GO layer deposited on the microporous wood provides broad optical absorption and high photothermal conversion resulting in rapid increase in the temperature at the liquid surface. On the other hand, wood serves as a thermal insulator to confine the photothermal heat to the evaporative surface and to facilitate the efficient transport of water from the bulk to the photothermally active space. Owing to the tailored bilayer structure and the optimal thermo-optical properties of the individual components, the wood–GO composite structure exhibited a solar thermal efficiency of ∼83% under simulated solar excitation at a power density of 12 kW/m². The novel composite structure demonstrated here is highly scalable and cost-efficient, making it an attractive material for various applications involving large light absorption, photothermal conversion and heat localization