Retraction of “Rare Earth- and Iridium-Decorated Silica Nanoparticle as a Single Catalyst for Carbon Dioxide Reduction and Water Oxidation: Buy One Get One Strategy”

Retraction of “Rare Earth- and Iridium-Decorated Silica Nanoparticle as a Single Catalyst for Carbon Dioxide Reduction and Water Oxidation: Buy One Get One Strategy

Cow Dung Derived PdNPs@WO₃ Porous Carbon Nanodiscs as Trifunctional Catalysts for Design of Zinc–Air Batteries and Overall Water Splitting

The main motif of this work is to fabricate a highly efficient, economic, nanodisc shaped trifunctional electrocatalyst using a tungsten trioxide modified carbon nanosheet decorated with palladium nanoparticles. The beauty of this work is that a special carbon precursor is used for the synthesis of the electrocatalyst, a waste material, i.e., cow dung. The performance of the cow dung derived nanodisc electrocatalyst (Pd@WO₃-NDs) toward oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is compared with three other electrocatalysts (derived from graphene oxide, chitosan, and graphite carbon sources) also, and it is found that Pd@WO₃-NDs show superior performance over that of the other three. The electrocatalyst exhibits the lowest onset potential (1.32 V vs NHEs), highest current density (492 mA cm^–2), lowest overpotential (113 mV), and lowest Tafel slope (62.8 mV dec^–1) for OER; an onset potential of 1.02 V, overpotential of 195.0 mV, and Tafel slope of 53.1 mV dec^–1) for ORR; and lowest onset potential (−0.09 V), overpotential (185 mV at 10 mA cm^–2), and a small Tafel slope of (58.2 mV dec^–1) for HER in the same alkaline solution. In addition, the nanomaterial is successfully applied for the fabrication of rechargeable and all-solid-state zinc–air batteries, which are used to illuminate a 4.0 V light emitting diode (LED) bulb. More importantly, real air cathodes made from the trifunctional Pd@WO₃-NDs demonstrated superior performance to state-of-the-art Pt/C catalysts in rechargeable zinc–air batteries. In addition, the same Zn–air battery is further used to power the laboratory-made total alkaline water electrolyzer by employing Pd@WO₃-NDs as catalyst on both anode and cathode. The water electrolyzer showed comparable performance rivalling the state-of-art combination of Pt/C and RuO₂, which is known to be the best of the bifunctional total-water splitting electrocatalysts reported until date. This remarkable performance of Pd@WO₃-NDs indicates their future potential in energy storage and sustainable energy conversion technologies

Fast and Selective Preconcentration of Europium from Wastewater and Coal Soil by Graphene Oxide/Silane@Fe₃O₄ Dendritic Nanostructure

In this study, nanocomposite of graphene oxide and silane modified magnetic nanoparticles (silane@Fe₃O₄) were synthesized in a form of dendritic structure. For this, silane@Fe₃O₄ nanoparticle gets sandwiched between two layers of graphene oxide by chemical synthesis route. The synthesized dendritic structure was used as a monomer for synthesis of europium ion imprinted polymer. The synthesis of imprinted polymer was contemplated onto the surface of the vinyl group modified silica fiber by activated generated free radical atom-transfer radical polymerization, that is, AGET-ATRP technique. The synthesized dendritic monomer was characterized by XRD, FT-IR, VSM, FE-SEM, and TEM analyses. The imprinted polymer modified silica fiber was first validated in the aqueous and blood samples for successful extraction and detection of europium ion with limit of detection = 0.050 pg mL^–1 (signal/noise = 3). The imprinted polymer modified silica fiber was also used for preconcentration and separation of europium metal ion from various soil samples of coal mine areas. However, the same silica fiber was also used for wastewater treatment and shows 100% performance for europium removal. The findings herein suggested that dendritic nanocomposite could be potentially used as a highly effective material for the enrichment and preconcentration of europium or other trivalent lanthanides/actinides in nuclear waste management

Equipment-Free, Single-Step, Rapid, “On-Site” Kit for Visual Detection of Lead Ions in Soil, Water, Bacteria, Live Cells, and Solid Fruits Using Fluorescent Cube-Shaped Nitrogen-Doped Carbon Dots

In this work, we have designed an equipment free, single-step, rapid, cost-effective, “in-house”, and “outdoor” kit for visual detection of lead ions (Pb²⁺) in various real samples viz., soil, water, bacteria, live cells, and solid fruits based on cube-shaped fluorescent carbon dots. The cube-shaped nitrogen-doped carbon dots (CCDs) were prepared using calcein dye as precursor and have potential to be used as better and stable replacement of commercially available dyes. For the visual detection of Pb²⁺, the color of the CCDs changes from yellowish to brown in solution and a limit of detection (LOD) of 10.0 μg L^–1 was obtained for the naked eye. In addition, the same CCD solution was also coated on a filter paper strip to fabricate an easy-to-prepare paper sensor. The paper sensor was used to identify the Pb²⁺ in real samples which proves their applicability toward in-situ on-site detection. In addition, the prepared strip sensor was successfully implemented for analysis of lead ions inside the solid fruit also. For quantitative detection, a photoluminescence (PL) study was carried out for trace level determination of Pb²⁺ with LOD of 2.21 ng L^–1. Both the visual as well as PL study also suggested that the results obtained from the CCD sensing probe is free from any interference. We also incubated the CCDs into live cells (E. coli and MCF-7) through endocytosis and monitored the changes in Pb²⁺ levels within cells. The study demonstrates the role of prepared fluorescent probe for live cell bioimaging and intracellular detection of metal ions

Cow Dung Derived PdNPs@WO₃ Porous Carbon Nanodiscs as Trifunctional Catalysts for Design of Zinc–Air Batteries and Overall Water Splitting

The main motif of this work is to fabricate a highly efficient, economic, nanodisc shaped trifunctional electrocatalyst using a tungsten trioxide modified carbon nanosheet decorated with palladium nanoparticles. The beauty of this work is that a special carbon precursor is used for the synthesis of the electrocatalyst, a waste material, i.e., cow dung. The performance of the cow dung derived nanodisc electrocatalyst (Pd@WO₃-NDs) toward oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is compared with three other electrocatalysts (derived from graphene oxide, chitosan, and graphite carbon sources) also, and it is found that Pd@WO₃-NDs show superior performance over that of the other three. The electrocatalyst exhibits the lowest onset potential (1.32 V vs NHEs), highest current density (492 mA cm^–2), lowest overpotential (113 mV), and lowest Tafel slope (62.8 mV dec^–1) for OER; an onset potential of 1.02 V, overpotential of 195.0 mV, and Tafel slope of 53.1 mV dec^–1) for ORR; and lowest onset potential (−0.09 V), overpotential (185 mV at 10 mA cm^–2), and a small Tafel slope of (58.2 mV dec^–1) for HER in the same alkaline solution. In addition, the nanomaterial is successfully applied for the fabrication of rechargeable and all-solid-state zinc–air batteries, which are used to illuminate a 4.0 V light emitting diode (LED) bulb. More importantly, real air cathodes made from the trifunctional Pd@WO₃-NDs demonstrated superior performance to state-of-the-art Pt/C catalysts in rechargeable zinc–air batteries. In addition, the same Zn–air battery is further used to power the laboratory-made total alkaline water electrolyzer by employing Pd@WO₃-NDs as catalyst on both anode and cathode. The water electrolyzer showed comparable performance rivalling the state-of-art combination of Pt/C and RuO₂, which is known to be the best of the bifunctional total-water splitting electrocatalysts reported until date. This remarkable performance of Pd@WO₃-NDs indicates their future potential in energy storage and sustainable energy conversion technologies

Anisotropic Gold Nanoparticle Decorated Magnetopolymersome: An Advanced Nanocarrier for Targeted Photothermal Therapy and Dual-Mode Responsive T₁ MRI Imaging

Herein, we report the advanced polymer vesicle [made up of triblock polymer: poly­(ethylene oxide)-<i>co</i>-poly­(Cys-AuNP@FA)-<i>co</i>-poly­(3-methoxypropylacrylamide] having encapsulated magnetic nanoparticle capable of targeted methotrexate delivery (having folic acid as tagging agent), photothermal therapy [anisotropic gold nanoparticle (AuNPs)] and stimuli-responsive T₁-imaging (as MRI contrast agent). The prepared polymersome, called as magnetopolymersome (MPS), after encapsulation of magnetic nanoparticle (Gd-doped) is not only high yield and simple in synthesis but also possess very high biocompatibility, more than 95% drug encapsulation efficiency and effective near-infrared (NIR) responsive photothermal therapy. The MPS is highly stable under normal physiological environments and other extreme end conditions (like presence of serum or Triton-X 100) and have excellent stimuli-responsive (temperature and NIR) T₁-contrast effect in vitro conditions (60.57 mM^–1 s^–1). To explore the role of shape of AuNPs on the photothermal therapy and drug delivery behavior of prepared nanocarrier, herein, we have synthesized four different shapes of AuNPs, i.e., spherical, triangle, rod, and flower. It was found that nanoflower-conjugated MPS shows the most efficient NIR responsive behavior in comparison to their other colleagues, which broke the ancient myth that spherical nanoparticle are the best candidate for drug delivery process. These features make nanoflower or other anisotropic nanoparticle-based polymersome a very promising and efficient nanocarrier for drug loading, delivery, imaging, and photothermal therapy

Economic and Ecofriendly Synthesis of Biocompatible Heteroatom Doped Carbon Nanodots for Graphene Oxide Assay and Live Cell Imaging

The present work reports an economic and eco-friendly strategy for fabrication of nitrogen doped fluorescent carbon nanodots (CNDs) by an electrochemical approach. Relative to previously reported approaches using harsh reaction conditions, the electrochemical approach requires less energy and reaction time for the preparation of highly stable CNDs. For the first time, four alkanolamines (ethanolamine, 3-amino-1-propanol, 4-amino-1-butanol, and 5-amino-1-pentanol) have been chosen for the preparation of CNDs, and it is found that with increase in chain length, the quantum yield (QY) value increases. The maximum QY of 51% was found for the CNDs derived from 5-amino-1-pentanol. The as-prepared CNDs have very narrow size distribution and excellent water dispersibility. The CNDs were used for quantitative detection of a nanomaterial i.e. graphene oxide without any cross-reactivity. The label-free, fluorescence sensor was also applied for the detection of graphene oxide in environmental water samples and human blood and urine samples. To explore the multifacet of as-prepared CNDs, their cytotoxicity was also studied using MCF-7 cancer cells. It was found that even at very high concentration of CNDs (2000.0 mg L^–1); more than 95% MCF-7 cells are alive. Furthermore, the internalization of CNDs to the MCF-7 cells was also studied using confocal fluorescence microscopy

Removal and Recycling of Precious Rare Earth Element from Wastewater Samples Using Imprinted Magnetic Ordered Mesoporous Carbon

The present work is devoted toward the development of a highly efficient, low cost, selective and sensitive technique for the detection, removal and recovery of a popular rare earth element, i.e., gadolinium [Gd]. Herein, the magnetic ordered mesoporous carbon (OMMC) is prepared by a green synthesis approach and used as a core for the preparation of imprinted-OMMC using Gd­(III) as a template. The prepared material has been used as a coating sorbent for solid phase microextraction (SPME) fiber as well as filled in a small sized micropipette tip to perform the microsolid phase extraction (μ-SPE) based study. The techniques have been explored for different purposes, i.e., preconcentration and trace level detection of Gd­(III) has been done by SPME; however, μ-SPE is used for removal as well as recycling of Gd­(III) from wastewater samples. The SPME fiber shows a higher preconcentration factor 1400 for Gd­(III) with a limit of detection = 2.34 ng L^–1, whereas the μ-SPE cartridge shows a higher adsorption capacity (30.2 μg g^–1) and removal efficiency (90%) toward Gd­(III). Both the techniques have been successfully applied to the preconcentration, detection and removal of Gd­(III) from pathological laboratory wastewater, drinking water, sewage sludge, tap water, pond water, river water, human sera, fruits and vegetables and soil and water samples collected from the local coal mines. In addition, the μ-SPE cartridge was successfully applied for recycling of Gd­(III) (in solid form) from both pathological laboratory wastewater and coal soil samples

Dual-Responsive Polymer Coated Superparamagnetic Nanoparticle for Targeted Drug Delivery and Hyperthermia Treatment

In this work, we have prepared water-soluble superparamgnetic iron oxide nanoparticles (SPIONs) coated with a dual responsive polymer for targeted delivery of anticancer hydrophobic drug (curcumin) and hyperthermia treatment. Herein, superparamagnetic mixed spinel (MnFe₂O₄) was used as a core material (15–20 nm) and modified with carboxymethyl cellulose (water-soluble component), folic acid (tagging agent), and dual responsive polymer (poly-<i>N</i> isopropylacrylamide-<i>co</i>-poly glutamic acid) by microwave radiation. Lower critical solution temperature (LCST) of the thermoresponsive copolymer was observed to be around 40 °C, which is appropriate for drug delivery. The polymer-SPIONs show high drug loading capacity (89%) with efficient and fast drug release at the desired pH (5.5) and temperature (40 °C) conditions. Along with this, the SPIONs show a very fast increase in temperature (45 °C in 2 min) when interacting with an external magnetic field, which is an effective and appropriate temperature for the localized hyperthermia treatment of cancer cells. The cytocompatibility of the curcumin loaded SPIONs was studied by the methyl thiazol tetrazolium bromide (MTT) assay, and cells were imaged by fluorescence microscopy. To explore the targeting behavior of curcumin loaded SPIONs, a simple magnetic capturing system (simulating a blood vessel) was constructed and it was found that ∼99% of the nanoparticle accumulated around the magnet in 2 min by traveling a distance of 30 cm. Along with this, to explore an entirely different aspect of the responsive polymer, its antibacterial activity toward an <i>E. coli</i> strain was also studied. It was found that responsive polymer is not harmful for normal or cancer cells but shows a good antibacterial property

Both Hyaluronan and Collagen Type II Keep Proteoglycan 4 (Lubricin) at the Cartilage Surface in a Condition That Provides Low Friction during Boundary Lubrication

Wear resistant and ultralow friction in synovial joints is the outcome of a sophisticated synergy between the major macromolecules of the synovial fluid, e.g., hyaluronan (HA) and proteoglycan 4 (PRG4), with collagen type II fibrils and other non-collagenous macromolecules of the cartilage superficial zone (SZ). This study aimed at better understanding the mechanism of PRG4 localization at the cartilage surface. We show direct interactions between surface bound HA and freely floating PRG4 using the quartz crystal microbalance with dissipation (QCM-D). Freely floating PRG4 was also shown to bind with surface bound collagen type II fibrils. Albumin, the most abundant protein of the synovial fluid, effectively blocked the adsorption of PRG4 with HA, through interaction with C and N terminals on PRG4, but not that of PRG4 with collagen type II fibrils. The above results indicate that collagen type II fibrils strongly contribute in keeping PRG4 in the SZ during cartilage articulation <i>in situ</i>. Furthermore, PRG4 molecules adsorbed very well on mimicked SZ of absorbed HA molecules with entangled collagen type II fibrils and albumin was not able to block this interaction. In this last condition PRG4 adsorption resulted in a coefficient of friction (COF) of the same order of magnitude as the COF of natural cartilage, measured with an atomic force microscope in lateral mode