An Eco-Friendly, Interference, and Solvent Free Surfactant-Assisted Dual-Wavelength β-CorrectionSpectrometric Method for Total Determination and Speciation of Cu2+ Ions in Water

Spectral interference through the presence of uninformative variables, excess reagents, and complications in the refinement of the analyte signal is common in the quest to identify complex species in real samples. Therefore, an economical green, facile, and sensitive strategy has been developed for Cu2+ detection using the anionic surfactant sodium dodecylsulphate- (SDS-) assisted dual-wavelength β-correction spectrophotometric strategy combined with the chromogenic reagent zincon (ZI). The low limits of detection (LOD) and quantification (LOQ) of Cu2+ using ordinary (single wavelength) spectrophotometry were 0.19 (3.02) and 0.63 (10.0) μgmL-1, and these values were improved to 0.08 (1.27) and 0.26 μgmL-1 (4.12 μM)) using β-correction (dual wavelength) spectrophotometry, respectively. The LOD and LOQ were improved from 0.08 (1.27) and 0.26 (4.12) μgmL-1 to 0.02 (0.32) and 0.08 μgmL-1 (1.27 μM) using SDS-assisted dual-β-correction spectrometry, respectively. Ringbom, s, and the corrected absorbance (Ac) versus Cu2+ concentration plots were linear over the concentration range 1.10-2.4 (17.4-38.1) and 0.50-2.40 μgmL-1 (7.94-38.1 μM), respectively. Sandell's sensitivity index of 3.0 × 10-3 μg/cm2 was achieved. The selectivity was further confirmed via monitoring the impact of common diverse ions and surfactants on the corrected absorbance. Total determination and Cu2+ speciation in water were favorably implemented and validated by ICP-OES at 95% (P=0.05). Satisfactory Cu2+ recoveries in tap (92.2-98.0%) and mineral (105-111.0%) water samples were achieved. The sensing system is simple, reliable, sensitive, and selective for Cu2+ detection.

Polyphenol-Capped Biogenic Synthesis of Noble Metallic Silver Nanoparticles for Antifungal Activity against Candida auris

In terms of reduced toxicity, the biologically inspired green synthesis of nanoparticles has emerged as a promising alternative to chemically fabricated nanoparticles. The use of a highly stable, biocompatible, and environmentally friendly aqueous extract of Cynara cardunculus as a reducing and capping agent in this study demonstrated the possibility of green manufacturing of silver nanoparticles (CC-AgNPs). UV-visible spectroscopy validated the development of CC-AgNPs, indicating the surface plasmon resonance (SPR) λ_max band at 438 nm. The band gap of CC-AgNPs was found to be 2.26 eV. SEM and TEM analysis examined the surface morphology of CC-AgNPs, and micrographs revealed that the nanoparticles were spherical. The crystallinity, crystallite size, and phase purity of as-prepared nanoparticles were confirmed using XRD analysis, and it was confirmed that the CC-AgNPs were a face-centered cubic (fcc) crystalline-structured material. Furthermore, the role of active functional groups involved in the reduction and surface capping of CC-AgNPs was revealed using the Fourier transform infrared (FTIR) spectroscopic technique. CC-AgNPs were mostly spherical and monodispersed, with an average size of 26.89 nm, and were shown to be stable for a longer period without any noticeable change at room temperature. Further, we checked the antifungal mechanism of CC-AgNPs against C. auris MRL6057. The minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC) were 50.0 µg/mL and 100.0 µg/mL respectively. The cell count and viability assay confirmed the fungicidal potential of CC-AgNPs. Further, the analysis showed that CC-AgNPs could induce apoptosis and G2/M phase cell cycle arrest in C. auris MRL6057. Our results also suggest that the CC-AgNPs were responsible for the induction of mitochondrial toxicity. TUNEL assay results revealed that higher concentrations of CC-AgNPs could cause DNA fragmentation. Therefore, the present study suggested that CC-AgNPs hold the capacity for antifungal drug development against C. auris infections.

Selective adsorption of iron(III) ions based on nickel(II) oxide-copper(II) oxide nanoparticles

Background:

Water contamination and its remediation are currently considered a major concern worldwide. Design of effective methods for water purification is highly demanded for adsorption and removal of such pollutants.

Objective:

This study depicts the effectiveness of nickel oxide-copper oxide nanoparticles (NiO-CuO), which can extract and remediate ferric ions, Fe (III), from aqueous solutions.

Methods:

The NiO-CuO nanoparticles were simply prepared by the co-precipitation method and then used as adsorbent with respectable advantages of high uptake capacity and surface area.

Results:

Adsorption of Fe(III) onto NiO-CuO nanoparticles showed an uptake capacity of 85.86 mgg−1 at pH 5.0. The obtained data from the carried-out experiment of Fe (III) adsorption onto NiO-CuO nanoparticles were well suited to the Langmuir isotherm and pseudo-second-order kinetic models. Moreover, different coexisting ions did not influence the adsorption of Fe(III) onto NiO-CuO nanoparticles. The recommended methodology was implemented on the adsorption and removal of several environmental water samples with high efficiency.

Conclusion:

The design method displayed that NiO-CuO nanoparticles can be used as promising material for the adsorptive removal of heavy metals from water.

Synthesis of Activated Carbon from Trachycarpus fortunei Seeds for the Removal of Cationic and Anionic Dyes

The removal of dyes from industrial effluents is one of the most important industrial processes that is currently on academic demand. In this project, for the first time, Trachycarpus fortunei seeds are used as biosources for the synthesis of activated carbon (AC) using physical as well as acid–base chemical methods. The synthesized AC was initially characterized by different instrumental techniques, such as FTIR, BET isotherm, SEM, EDX and XRD. Then, the prepared activated carbon was used as an economical adsorbent for the removal of xylenol orange and thymol blue from an aqueous solution. Furthermore, the effect of different parameters, i.e., concentration of dye, contact time, pH, adsorbent amount, temperature, adsorbent size and agitation speed, were investigated in batch experiments at room temperature. The analysis of different techniques concluded that the pyrolysis method created a significant change in the chemical composition of the prepared AC and the acid-treated AC offered a high carbon/oxygen composite, which is graphitic in nature. The removal of both dyes (xylenol orange and thymol blue) was increased with the increase in the dye’s initial concentration. Isothermal data suggested that the adsorption of both dyes follows the Langmuir model compared to the Freundlich model. The equilibrium time for AC biomass to achieve the removal of xylenol orange and thymol blue dyes was determined to be 60 min, and the kinetic data suggested that the adsorption of both dyes obeyed the pseudo-second order model. The optimal pH for thymol blue adsorption was pH 6, while it was pH 2 for xylenol orange. The adsorption of both dyes increased with the increase in the temperature. The influence of the adsorbent amount indicated that the adsorption capacity (mg/g) of both dyes reduced with the rise in the adsorbent amount. Thus, the current study suggests that AC prepared by an acid treatment from Trachycarpus fortunei seeds is a good, alternative, cost effective, and eco-friendly adsorbent for the effective removal of dyes from polluted water.

Metal nanoparticles supported chitosan coated carboxymethyl cellulose beads as a catalyst for the selective removal of 4-nitrophenol

In the area of water pollution treatment, the coupling of biopolymers with metal/metal nanoparticles is getting a lot of interest these days. Herein, carboxymethyl cellulose (CMC) beads and chitosan (Cs) coated CMC beads were employed as a support for copper nanoparticles, (Cu/CMC) and (Cu/Cs@CMC), respectively. Following that, a reducing agent (NaBH₄) was used to convert Cu/CMC and Cu/Cs@CMC beads to zero valent. The developed beads were employed for catalytic reductions of nitrophenol, dyes, and potassium hexacyanoferrate (III) in their mixed solution with NaBH₄. Cu/Cs@CMC beads were more efficient compared to Cu/CMC beads toward selected pollutants. The reduction rate constants of 4-NP, MO, EY and K₃[Fe(CN)₆] by utilizing Cu/Cs@CMC were 3.8 × 10^-1, 4.0 × 10^-1, 1.4 × 10^-1 and 4.48 × 10^-1 min^-1, respectively. Further, the catalytic activity of the Cu/Cs@CMC beads were optimized using 4-NP as a model compound for this study. Cu/Cs@CMC beads were able to use up to three cycles compared to Cu/CMC beads without losing catalytic activity in the reduction of 4-NP, according to the recyclability and reusability study of both beads. The chitosan coating beads Cu/Cs@CMC was simply prepared and have good catalytic activity, recyclable, and more efficient than Cu/CMC beads due to their high strength and stability.

The role of size-controlled CeO2 nanoparticles in enhancing the stability and photocatalytic performance of ZnO in natural sunlight exposure

In order to enhance the photocatalytic performance and stability, the various proportions of the size controlled cerium oxide (CeO₂) nanoparticles were dispersed at the pre-synthesized ZnO. Although, the expected dual absorption onsets, probably due to the diminutive difference between the bandgaps of CeO₂ (∼2.9 eV) and ZnO (∼3.1 eV), were not observed however, a blue shift in the bandgap energy of ZnO was witnessed with the increasing surface density of CeO₂ particles. The delayed excitons recombination process with the increasing concentration of CeO₂ nanoparticles was verified by the PL spectra. The structural investigation by Raman and XRD analysis revealed the surface attachment of CeO₂ particles without altering the rock-salt lattice of ZnO. The morphological and fine microstructural analysis established the uniform distribution of evenly sized CeO₂ particles at the surface of ZnO with the discrete fringe patterns of both the entities whereas the XPS analysis confirmed the majority of Ce⁴⁺ in dispersed CeO₂. In comparison to pure ZnO, cyclic voltammetric (CV) analysis, under illumination, exposed the supportive role of surface residing CeO₂ particles in eradicating the photo-corrosion of ZnO whereas the chronopotentiometry (CP) predicted the prolonged life-span of the excitons. Compared to pure ZnO, an appreciably high activity was revealed for 10% CeO₂ loading as compared to pure ZnO for the removal of mono and di-nitrophenol derivatives and their mixtures under natural sunlight exposure. The variations in the removal rates in the mixture as compared to individual nitrophenol exposed the structure-based priority of ROS for the respective phenol. The significantly enhanced photocatalytic activity of the composite catalysts revealed the incremental role of surface-mounted CeO₂ entities in boosting the generation of ROS under sunlight irradiation. The experimental observations were correlated and compiled to establish the mechanism of the removal process.

Green Synthesis of Zinc Oxide Nanoparticles Using Salvia officinalis Leaf Extract and Their Photocatalytic and Antifungal Activities

The facile bio-fabrication of zinc oxide (ZnO) nanoparticles (NPs) is described in this study using an aqueous leaf extract of Salvia officinalis L. as an efficient stabilizing/capping agent. Biosynthesis of nanomaterials using phytochemicals present in the plants has received great attention and is gaining significant importance as a possible alternative to the conventional chemical methods. The properties of the bio-fabricated ZnONPs were examined by different techniques, such as UV-visible spectroscopy, X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric/differential scanning calorimetry analysis (TGA/DTG). The photocatalytic activity of ZnONPs was investigated against methyl orange (MO) under UV light irradiation. Under optimum experimental conditions, ZnONPs exhibited 92.47% degradation of MO. Furthermore, the antifungal activity of bio-fabricated ZnONPs was determined against different clinical Candida albicans isolates following standard protocols of broth microdilution and disc diffusion assay. The susceptibility assay revealed that ZnONPs inhibit the growth of all the tested fungal isolates at varying levels with MIC values ranging from 7.81 to 1.95 µg/mL. Insight mechanisms of antifungal action appeared to be originated via inhibition of ergosterol biosynthesis and the disruption of membrane integrity. Thus, it was postulated that bio-fabricated ZnONPs have sustainable applications in developing novel antifungal agents with multiple drug targets. In addition, ZnONPs show efficient photocatalytic efficiency without any significant catalytic loss after the catalyst was recycled and reused multiple times.

Super adsorption performance of carboxymethyl cellulose/copper oxide-nickel oxide nanocomposite toward the removal of organic and inorganic pollutants

A novel nanocomposite bead based on polymeric matrix of carboxymethyl cellulose and copper oxide-nickel oxide nanoparticles was synthesized, characterized, and applied for adsorptive removal of inorganic and organic contaminants at trace level of part per million (mgL^-1) from aqueous sample. Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) adsorbent beads were selective toward the removal of Pb(II) among other metal ions. The removal percentage of Pb(II) was more than 99% with 3 mgL^-1. The waste beads after Pb (II) adsorption (Pb@CMC/CuO-NiO) and CMC/CuO-NiO nanocomposite beads were employed as adsorbents for removing of various dyes. It was found that Pb@CMC/CuO-NiO can be reused as adsorbent for the removal of Congo Red (CR), while CMC/CuO-NiO nanocomposite beads were more selective for removal of Eosin Yellow (EY) from aqueous media. The adsorption of CR and EY was optimized, and the removal percentages were 93% and 96.4%, respectively. The influence of different parameters was studied on the uptake capacity of Pb(II), CR, and EY, and lastly, the CMC/CuO-NiO beads exhibited responsive performance in relation to pH and other parameters. Thus, the prepared CMC/CuO-NiO beads were found to be a smart material which is effective and played super adsorption performance in the removal of Pb(II), CR, and EY from aqueous solution. These features make CMC/CuO-NiO beads suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial adsorbents.

Bioengineered Matricaria recutita Extract-Assisted Palladium Nanoparticles for the Congo Red Dye Degradation and Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol

The green chemistry method is the preferred approach for synthesizing metal and metal oxide nanoparticles because of its low toxicity, environmental friendliness, feasibility, and safety to human health compared with other chemical or physical methods. The present work reports the phytogenic synthesis of palladium nanoparticles (PdNPs) using an aqueous extract of Matricaria recutita (Chamomile). The phytochemical-mediated synthesis of PdNPs is an economical and eco-friendly approach without using toxic elements as reducing and capping or stabilizing agents. The UV-visible spectroscopic characterization was initially used to confirm the preparation of PdNPs using an aqueous extract of M. recutita flowers as a bioreductant for the reduction of Pd2+ to Pd0 without using any extra capping and reducing agents. The appearance of surface plasmon resonance (SPR) peak at 286 nm confirmed the formation of M. recutita extract-based PdNPs. Furthermore, the PdNPs were characterized by TEM, SEM, EDX, XRD, XPS, and FTIR to confirm their proper synthesis. The thermogravimetric analysis (TGA) was implemented to interpret the decomposition pattern and thermal stability of as-synthesized PdNPs. The biosynthesized PdNPs were further applied as a nanocatalyst in degradation of an azo dye Congo red (CR) in the presence of NaBH4. The catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was also investigated in the presence of NaBH4. All the catalytic reactions were performed in water, and no significant loss in catalytic activity was observed after recovery and reusability of the biosynthesized PdNPs.

Synthesis, characterization and photocatalytic performance of W6+ impregnated g-C3N4 for the removal of chlorophenol derivatives in natural sunlight exposure

The surface of the g-C₃N₄ was altered by impregnating W⁶⁺ ions that transformed to homogeneously coated oxide layer by a calcination process. An enhanced absorption and the suppressed de-excitation in the emission spectra, with the increasing W⁶⁺ loading, exposed the supporting role of the coated layer in extending the spectral response as well as the prolonged life span of excitons. The same was further supported by electrochemical impedance spectroscopy (EIS). The XRD and XPS analysis revealed the coated layer as highly crystalline pure phase monoclinic WO₃ with the majority of impregnated tungsten ions in 6+ oxidation state respectively, whereas the FESEM and HRTEM analysis substantiated the uniformity of the coated layer with the interlayer spacing of the 0.369 nm. Additionally, the probable formation of individual WO₃ nanoparticles or clusters was ruled out. The as-synthesized impregnated photocatalysts, in comparison to pure g-C₃N_4, were subjected to natural sunlight exposure for the photocatalytic removal of chlorophenol derivatives (2-CP, 3-CP, 4-CP, 2,3-DCP, 2,4-DCP, 2,4,6-TCP and PCP) that revealed the 5 wt% coating as the optimum level for significant removal. The progress of the photocatalytic process was monitored by periodic HPLC analysis whereas ion chromatography (IC) was used for the estimation of released ions. The mineralization capability of the as-synthesized W⁶⁺ coated catalysts was measured by the time scale TOC measurements. As the formation of intermediates was indicated in HPLC analysis, selected samples were subjected to GC-MS analysis for the identification of the nature of intermediates. The variable degree of removal of chlorophenol derivatives signified the role of the position and orientation of Cl group. The kinetics of the removal process was evaluated with the calculation of rate constants. The results extracted from the analytical tools and the associated band edge potentials were correlated to speculate the probable mechanism as well as the identification of major reactive oxygen species (ROS) involved in the removal process.

Carboxymethyl cellulose nanocomposite beads as super-efficient catalyst for the reduction of organic and inorganic pollutants

Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) nanocomposite beads were prepared by facile, simple and environmentally friendly method. Initially, CuO-NiO was prepared and applied for the catalytic reduction of 4-nitrophenol (4-NP). The results showed that CuO-NiO demonstrate high catalytic activity toward the reduction of 4-NP to 4-aminophenol (4-AP) with a rate constant of 2.97 × 10^-2 s^-1. Further, CuO-NiO were well-dispersed in the polymeric matrix of carboxymethyl cellulose to prepare CMC/CuO-NiO beads. CMC/CuO-NiO nanocomposite beads were also applied to catalyze the reduction of potassium ferrocyanide (K₃Fe (CN)₆), 4-NP, Congo red (CR) and Eosin yellow (EY) in the presence of sodium borohydride. Experimental data indicated that CMC/CuO-NiO nanocomposite has higher catalytic activity and high rate constant compared to CuO-NiO. The rate constant found to be 6.88 × 10^-2, 6.27 × 10^-2, 1.89 × 10^-2 and 2.43 × 10^-2 for K₃Fe(CN)₆, 4-NP, CR and EY, respectively, using 5 mg CMC/CuO-NiO beads. FE-SEM, EDX, FTER, XRD and XPS were used to characterize the nanocomposites. CMC/CuO-NiO beads catalytically reduced up to 95-99% of K₃Fe(CN)₆, 4-NP, CR and EY within 40, 60, 120 and 120 s. CMC/CuO-NiO beads were found more selective for the reduction of 4-NP. The catalytic reduction performance of CMC/CuO-NiO beads was optimized by studying the influence of different parameters on the catalytic reduction of 4-NP. Hence, the effective and super catalytic performance toward the reduction of different organic and inorganic pollutants makes CMC/CuO-NiO beads a smart material and suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial catalysts.

Adsorptive removal of lanthanum based on hydrothermally synthesized iron oxide-titanium oxide nanoparticles

Iron oxide-titanium oxide (Fe₂O₃-TiO₂) nanoparticles were developed as an effective adsorbent in order to extract and remove lanthanum ions selectively from aqueous media. Fe₂O₃-TiO₂ nanoparticles were prepared by simple hydrothermal method and structurally characterized using FESEM, EDS, XRD, FTIR, and BET techniques. The analytical potential of Fe₂O₃-TiO₂ nanoparticles was interpreted by applying the kinetic and isotherm models. The maximum static uptake capacity was 89.63 mgg^- 1 at pH 7. Adsorption isotherm data evinced that a monolayer adsorption occurred on a homogeneous adsorbent surface which is compatible with Langmuir isotherm model. Data acquired from kinetic models study proved that La (III) adsorption onto Fe₂O₃-TiO₂ nanoparticles followed a pseudo-second-order kinetic equation. Thermodynamic study exhibited that a spontaneous process is favorable for adsorption mechanism of La (III) on Fe₂O₃-TiO₂ nanoparticles. Moreover, the existence of different coexisting ions did not influence the extraction of La (III). Finally, the recommended methodology was applied on several environmental samples.

Facile synthesis of light harvesting semiconductor bismuth oxychloride nano photo-catalysts for efficient removal of hazardous organic pollutants

In the present work, bismuth oxychloride nanoparticles–a light harvesting semiconductor photocatalyst–were synthesized by a facile hydrolysis route, with sodium bismuthate and hydroxylammonium chloride as the precursor materials. The as-synthesized semiconductor photocatalysts were characterized using X-ray diffraction analysis, Fourier transform infra-red spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence spectroscopy techniques. The crystal structure, morphology, composition, and optical properties of these facile synthesized bismuth oxychloride nanoparticles (BiOCl NPs) were compared to those of traditional bismuth oxychloride. In addition, the photocatalytic performance of facile-synthesized BiOCl NPs and traditional BiOCl, as applied to the removal of hazardous organic dyes under visible light illumination, is thoroughly investigated. Our results reveal that facile-synthesized BiOCl NPs display strong UV-Vis light adsorption, improved charge carrier mobility and an inhibited rate of charge carrier recombination, when compared to traditional BiOCl. These enhancements result in an improved photocatalytic degradation rate of hazardous organic dyes under UV-Vis irradiance. For instance, the facile-synthesized BiOCl NPs attained 100% degradation of methylene blue and methyl orange dyes in approximately 30 mins under UV-Vis irradiation, against 55% degradation for traditional BiOCl under similar experimental conditions.

Preparation and characterization of Pd doped ceria-ZnO nanocomposite catalyst for methyl tert-butyl ether (MTBE) photodegradation

A series of binary oxide catalysts (ceria-ZnO) were prepared and doped with different amounts of palladium in the range of 0.5%-1.5%. The prepared catalysts were characterized by SEM, TEM, XRD and XPS, as well as by N2 sorptiometry study. The XPS results confirmed the structure of the Pd CeO2-x-ZnO. The photocatalytic activity of these catalysts was evaluated for degradation of MTBE in water. These photocatalyst efficiently degrade a 100ppm aqueous solution of MTBE upon UV irradiation for 5h in the presence of 100mg of each of these photocatalysts. The removal of 99.6% of the MTBE was achieved with the ceria-ZnO catalyst doped with 1% Pd. In addition to the Pd loading, the N2 sorptiometry study introduced other factors that might affect the catalytic efficiency is the catalyst average pore sizes. The photoreaction was determined to be a first order reaction.