Graphene oxide-sulfated lanthanum oxy-carbonate nanocomposite as an adsorbent for the removal of malachite green from water samples with application of statistical optimization and machine learning computations

Sulfated lanthanum oxy-carbonate nanorods (S-La₂O₂(CO₃) NRs) was synthesized by the reverse micelle microemulsion method and then used to modify graphene oxide nanosheets to synthesize of graphene oxide-sulfated lanthanum oxy-carbonate (GO-S-La₂O₂(CO₃)) nanocomposite. By characterization of S-La₂O₂(CO₃) NRs and GO-S-La₂O₂(CO₃) nanocomposite by the Fourier Transform-Infrared (FT-IR) Spectrophotometry, Field Emission-Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS), Transmission Electron Microscopy (TEM) and X-ray diffraction analysis (XRD), GO-S-La₂O₂(CO₃) was used for treatment of malachite green (MG). To find the optimum removal percentage (RP), influencing parameters were investigated by the response surface methodology based on central composite design (RSM-CCD). Adsorption mechanism was evaluated by Dubinin–Radushkevich (D-R), Langmuir, Temkin, Freundlich (two parameter equations) and Sips (Three parameter equations) isotherms and based on the results the adsorption of MG into the GO-S-La₂O₂(CO₃) nanocomposite obeyed by the Freundlich isotherm with the maximum adsorption capacity of 555.5 mg g^?1. Also, the results of kinetic analysis show that the adsorption of MG onto the GO-S-La₂O₂(CO₃) nanocomposite followed by the pseudo second order kinetic model. For estimation of adsorption behavior, different machine learning techniques are used and based on the results; ANFIS model has the confidential operation because of fuzzy procedure and flexibility of data mining in distributed adsorption data.     

A simple and novel route for the synthesis of water soluble ZnSe quantum dots using the Nano-Se as the reaction intermediate

A new and simple synthesis method for water soluble and low toxic ZnSe QDs is presented in this paper. N-acetyl-l-cysteine (NAC) is chosen as the stabilizer of ZnSe QDs and reducing agent of Na₂SeO₃ in one reaction system. The reaction intermediate Nano-Se generated by the redox reaction between NAC and Na₂SeO₃ is used as the Se source. The water soluble ZnSe QDs obtained by our synthesis method show blue-green light emission. The effects of the pH, stabilizer concentration and synthesis time on the photoluminescence (PL) intensity of ZnSe QDs are also investigated. This new synthesis method simplifies the reaction steps, enhances the utilization rate of chemicals and reduces the cost.     

Biocompatible Near‐Infrared Quantum Dots as Ultrasensitive Probes for Long‐Term in vivo Imaging Applications

A facile synthesis method to produce monodisperse, biocompatible, lysine crosslinked mercaptoundecanoic acid (MUA) CdSe_0.25Te_0.75/CdS near‐infrared (NIR) quantum dots and use them as probes to study their long term in vivo distribution, clearance, and toxicity is presented. Large signal enhancements are demonstrated by these quantum dots, which enables their use as efficient and sensitive probes for live‐animal imaging. An important finding is that mice intravenously injected with ≈10.5 mg kg^?1 of NIR QDs survive for more than three months without any apparent adverse effect to their health. Furthermore, it is determined that there is a significant reduction in the number of the QDs in the liver and spleen three months post injection. In addition, histological analysis of heart, kidney, liver, spleen, and lung tissue indicates that there are no acute toxic effects from these lysine cross‐linked MUA NIR QDs. This study suggests that these NIR QDs can be potentially used for long‐term targeted imaging and therapy studies in vivo.     

Carbon‐Quantum‐Dots‐Loaded Ruthenium Nanoparticles as an Efficient Electrocatalyst for Hydrogen Production in Alkaline Media

Highly active, stable, and cheap Pt‐free catalysts for the hydrogen evolution reaction (HER) are facing increasing demand as a result of their potential use in future energy‐conversion systems. However, the development of HER electrocatalysts with Pt‐like or even superior activity, in particular ones that can function under alkaline conditions, remains a significant challenge. Here, the synthesis of a novel carbon‐loaded ruthenium nanoparticle electrocatalyst (Ru@CQDs) for the HER, using carbon quantum dots (CQDs), is reported. Electrochemical tests reveal that, even under extremely alkaline conditions (1 m KOH), the as‐formed Ru@CQDs exhibits excellent catalytic behavior with an onset overpotential of 0 mV, a Tafel slope of 47 mV decade^?1, and good durability. Most importantly, it only requires an overpotential of 10 mV to achieve the current density of 10 mA cm^?2. Such catalytic characteristics are superior to the current commercial Pt/C and most noble metals, non‐noble metals, and nonmetallic catalysts under basic conditions. These findings open a new field for the application of CQDs and add to the growing family of metal@CQDs with high HER performance.     

CuO Quantum Dots Embedded in Carbon Nanofibers as Binder‐Free Anode for Sodium Ion Batteries with Enhanced Properties

The design of sodium ion batteries is proposed based on the use of flexible membrane composed of ultrasmall transition metal oxides. In this paper, the preparation of CuO quantum dots (≈2 nm) delicately embedded in carbon nanofibers (denoted as 2‐CuO@C) with a thin film via a feasible electrospinning method is reported. The CuO content can be controlled by altering the synthetic conditions and is optimized to 54 wt%. As binder‐free anode for sodium ion batteries, 2‐CuO@C delivers an initial reversible capacity of 528 mA h g^?1 at the current density of 100 mA g^?1, an exceptional rate capability of 250 mA h g^?1 at 5000 mA g^?1, and an ultra‐stable capacity of 401 mA h g^?1 after 500 cycles at 500 mA g^?1. The enhancement of electrochemical performance is attributed to the unique structure of 2‐CuO@C, which offers a variety of advantages: highly conductive carbon matrix suppressing agglomeration of CuO grains, interconnected nanofibers ensuring short transport length for electrons, well‐dispersed CuO quantum dots leading to highly utilization rate, and good mechanical properties resulting in strong electrode integrity.     

Stabilizing High Density Cu Active Sites with ZrO2 Quantum Dots as Chemical Ligand in N-doped Porous Carbon Nanofibers for Efficient ORR

The emerging transition metal-nitrogen-carbon (M N C) materials are considered as a promising oxygen reduction reaction (ORR) catalyst system to substitute expensive Pt/C catalysts due to their high surface area and potential high catalytic activity. However, M N C catalysts are easy to be attacked by the ORR byproducts that easily lead to the deactivation of metal active sites. Moreover, a high metal loading affects the mass transfer and stability, but a low loading delivers inferior catalytic activity. Here, a new strategy of designing ZrO₂ quantum dots and N-complex as dual chemical ligands in N-doped bubble-like porous carbon nanofibers (N-BPCNFs) to stabilize copper (Cu) by forming Cu ZrO_3-x/ZrO₂ heterostructures and Cu N ligands with a high loading of 40.5 wt.% is reported. While the highly porous architecture design of N-BPCNFs builds a large solidelectrolytegas phase interface and promotes mass transfer. The preliminary results show that the half-wave potential of the catalyst reaches 0.856 V, and only decreases 0.026 V after 10 000 cycles, exhibiting excellent stability. The proposed strategy of stabilizing metal active sites with both heterostructures and Cu N ligands is feasible and scalable for developing high metal loading ORR catalyst.