Search

A recent study using the first 21 months of the OSNAP time series revealed that the export of dense waters in the eastern subpolar North Atlantic―as part of the Atlantic Meridional Overturning Circulation (MOC)―can be almost wholly attributed to surface‐forced water mass transformation (SFWMT) in the Irminger and Iceland basins, thus suggesting a minor role for other means of transformation, such as diapycnal mixing. To understand whether this result is valid over a period that exceeds the current observational record, we use four different ocean reanalysis products to investigate the relationship between surface buoyancy forcing and dense water production in this region. We also reexplore this relationship with the now available 6‐year OSNAP time series. Our analysis finds that although surface transformation in the eastern subpolar gyre dominates the production of deep waters, mixing processes downstream of the Greenland Scotland Ridge are also responsible for the production of waters carried within the AMOC's lower limb both in the observations and reanalyses. Further analysis of the reanalyses shows that SFWMT partly explains MOC interannual variability, the remaining portion can be attributed to basin storage and mixing. Compared to the observations, the reanalyses exhibit stronger MOC variance but comparable SFWMT variance on interannual timescales. Plain Language Summary: The transformation of water masses from lighter to denser density classes due to surface heat and freshwater fluxes is considered as a major source of sustaining the lower limb of the Atlantic Meridional Overturning Circulation (MOC). In this study, we quantify the relationship between surface‐forced water mass transformation and the MOC in the mean state and on seasonal and interannual timescales using ocean observations and data assimilation products. We find that surface‐forced water mass transformation is responsible for a large portion of the time‐mean MOC lower‐limb transport, and it can partly explain MOC interannual variability, highlighting the important role of surface‐forced water mass transformation to the MOC in the mean and variability. Key Points: Surface‐forced water mass transformation (SFWMT) explains a large portion of the mean meridional overturning circulation (MOC) in the eastern subpolar North AtlanticMOC interannual variability can be partly explained by SFWMT variabilityOcean reanalysis products show stronger MOC variance but comparable SFWMT variance on interannual timescales compared to the observations [ABSTRACT FROM AUTHOR]

The reusability of photocatalyst and bactericidal properties plays a crucial role in water pollutant management. Herein, copper ferrite-silver (CuFe2O4-Ag) nanomaterial incorporated Gum Arabic Acrylamide (GAA) hydrogel nanocomposites was fabricated via free radical polymerization method to enhance the photocatalytic efficiency and antimicrobial assay. The structural, morphological, compositional, thermal, optical, and physico-chemical properties of the synthesized hydrogel nanocomposite were analyzed using various techniques. A decrease in direct band gap value as 1.83 eV for CuFe2O4-Ag nanocomposite was observed which would further enhance the photocatalytic ability of nanocomposite. The results suggested that CuFe2O4-Ag nanocomposite was infused inside the matrix of GAA hydrogel. The swelling ability of fabricated hydrogel nanocomposite was found to be 1328%. The photocatalytic degradation followed a pseudo-first-order kinetic reaction model, achieving a 90% removal of methylene blue dye using the nanocomposite, with a rate constant value of 14.09 × 10⁻3 min⁻1 Moreover, photocatalyst maintain 71% degradation efficiency over three consecutive cycles. The antibacterial effects on Escherichia coli (E. coli) were also examined, and the CuFe₂O₄-Ag nanocomposite showed good efficacy, as indicated by the measured zones of inhibition. Hence, the nanocomposite-infused hydrogel demonstrates significant potential as an advanced material for the remediation of water pollution, effectively targeting both organic and biological contaminants. In this work, CuFe2O4-Ag nanocomposite was ultrasonically incorporated into GAA hydrogel for their applicability in photocatalytic degradation of methylene blue dye and antimicrobial assay against E. coli. [ABSTRACT FROM AUTHOR]

In this work, the adsorption of Trypsin on synthesized Silver (Ag), Graphene Oxide: Silver (GO: Ag) nanocomposite (2:1), and Graphene Oxide (GO) nanoparticles (NPs) and, their effect on the conformation of Trypsin was studied by various spectroscopic and microscopic techniques to understand the transition of nano Protein Corona (PC) from "hard" to "soft." The results showed that the adsorption of Trypsin on synthesized NPs followed the Freundlich adsorption isotherm and pseudo‐second‐order kinetics. The conformational changes that occurred in Trypsin upon interaction with synthesized NPs were investigated by using Circular Dichroism (CD), Fluorescence, and Fourier Transform Infrared (FTIR) spectroscopy. The morphological investigation of nano PC using High‐Resolution Transmission Electron Microscopy (HR‐TEM) and Atomic Force Microscopy (AFM) indicated the formation of hard, semi‐soft, and soft nano PC in the presence of Ag, GO: Ag, and GO NPs, respectively. The negative value of the thermodynamic parameters ΔG, ΔH, and ΔS in all three cases suggests the reaction to be exothermic and spontaneous. The van der Waals interaction and hydrogen bonding are the major forces responsible for binding Trypsin on the surface of Ag, GO: Ag, and GO. The catalytic efficiency of trypsin in the absence and presence of NPs was examined by performing the protein assay showing the highest catalytic activity of pure Trypsin compared with trypsin‐NPs constructs. Our findings provide useful information for the applications of GO‐based nanocomposites for various biological applications. [ABSTRACT FROM AUTHOR]

Preparation of transition metal oxides and mixed metal oxides via a microwave‐assisted method that permits processes to be completed in a quicker reaction time with the formation of homogenous and well‐dispersed nanoparticles. Recently, due to the environmentally friendly nature of this technique, it has become an important approach to green chemistry. The major advantage of microwave‐assisted synthesis includes clean, fast, efficient, less time‐consuming, highly accelerated rate, high yield, and an economic method. In this review, we have discussed the process of microwave synthesis and also compared this with other synthetic methods. A discussion of transition metal oxides in groups was performed where we have discussed their synthetic route and reaction conditions along with the effect on morphology and other properties. Additionally, the application of transition metal oxides as supercapacitors was also discussed. Since then, researchers have gained a lot of interest in transition metal oxides as energy storage devices due to their low‐cost, energy efficient, long cycle life, and improved electrical, thermal, and chemical stability, variable oxidation states and excellent redox properties. However, they cannot meet the need for high‐performance energy devices due to their low conductivity. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are promising carbonaceous nanomaterials fortuitously discovered in 2004. CQDs are the rising stars in the nanotechnology ensemble because of their unique properties and widespread applications in sensing, imaging, medicine, catalysis, and optoelectronics. CQDs are notable for their excellent solubility and effective luminescence and, as a result, they are also known as carbon nanolights. Many strategies are used for the efficient and economical preparation of CQDs; however, CQDs prepared from waste or green sustainable methods have greater requirements due to their safety and ease of synthesis. Sustainable chemical strategies for CQDs have been developed, emphasizing green synthetic methodologies based on 'top‐down' and 'bottom‐up' approaches. This review summarizes many such studies relevant to the development of sustainable methods for photoluminescent CQDs. Furthermore, we have emphasized recent advances in CQDs' photoluminescence applications in chemical and biological fields. Finally, a brief overview of synthetic processes using the green source and their associated applications are tabulated, providing a clear understanding of the new optoelectronic materials. [ABSTRACT FROM AUTHOR]

Hybrid dynamical systems have gained a huge momentum not only due to their exotic physical properties but also their compelling engineering standpoint, particularly owing to their potential for coherent information processing. Remarkably, magnon–magnon coupling is experimentally identified in Ni80Fe20 nanocross array with the number of spins reaching a very low value of ≈1012. Moreover, the coupling strength is effectively tuned via different external parameters, viz. microwave excitation power and the bias‐field orientation. Extensive simulations reveal that both the static and dynamical dipolar coupling contribute to the observed anticrossing phenomenon. Simultaneously, mode‐softening of spin wave tunable by subtle changes of bias‐field orientation is also observed. The findings can greatly enrich various hybrid phenomena with a magnonic platform. [ABSTRACT FROM AUTHOR]

Here, in this work, acid-activated bentonite and its nanocomposite with hematite nanoparticles were synthesized using the simple chemithermal and thermal coupling methods, respectively. The synthesized samples were investigated for morphological, compositional, structural, and thermal properties. Results suggested distortion in clay structure on acid activation and nanocomposite formation with improved thermal stability. Nanocomposite acts as a quencher for thermoluminescence and as an insulator in heat transfer reactions. [ABSTRACT FROM AUTHOR]

Clays are widely accepted for dye removal from wastewater. Here, in this work, nanobentonite was synthesized by a simple, rapid, and cost-effective chemithermal method. Additionally, nanobentonite was coupled with hematite nanoparticles via thermal coupling to prepare a nanocomposite with enhanced surface absorption. Surface morphology, compositional and structural analysis of synthesized samples were done using various characterization techniques. Results suggested that nanobentonite and nanocomposite having an average diameter of 35.36 and 21.85 nm respectively were synthesized. Nanocomposite exhibited increased surface area. Additionally, the ability of all samples as an adsorbent for removal of methylene blue (MB) and Congo red (CR), from an aqueous solution was investigated under various optimization conditions. Adsorption kinetics revealed that Pseudo II order equation fits well for the adsorption process following intraparticular diffusion mechanism for both the dyes. The adsorption equilibrium data of MB and CR was fitted well by the Langmuir and Freundlich adsorption isotherm model, respectively. The thermodynamic parameters suggested adsorption process is endothermic and spontaneous in nature with increased entropy value. [ABSTRACT FROM AUTHOR]

The current study focuses on graphene oxide (GO) and its composite with zinc oxide and titanium dioxide nanoparticles to develop a simple nano chemistry-based clean and efficient process for the effective degradation of methylene blue (MB) dye. Graphene oxide composite with zinc oxide and titanium dioxide nanoparticles were fabricated via a thermal coupling process that demonstrates exclusive physiochemical properties. A detailed comparison of the structure, morphology, and surface analysis of synthesized GO and nanocomposites, as well as their electrochemical properties, has been accomplished. By using the degradation of methylene blue (MB) dye the photocatalytic function of nanocomposites was studied. Results reveal that the rate constants of GO, GO-TiO2, and GO-ZnO photocatalysts are 1.06 × 10−3 min−1, 2.56 × 10−3 min−1, and 1.63 × 10−3 min−1 respectively which discloses GO-TiO2 nanocomposite shows maximum degradation of MB dye among both catalysts. The reuse of photocatalyst even after five cycles retained the degradation efficiency of 80, 77, and 49% respectively for GO-TiO2, GO-ZnO, and GO when tested against MB. Hence, as a result, it was determined that these photocatalysts are ideal for the remediation of dye-contaminated wastewater. [ABSTRACT FROM AUTHOR]