Green synthesis of ZnO2 nanoparticles from hydrozincite and hydrogen peroxide at room temperature

A green method based on the reaction between hydrozincite (Zn₅(CO₃)₂(OH)₆) powder and hydrogen peroxide (H₂O₂, 30 wt.%) in aqueous solution at room temperature was developed for the synthesis of ZnO₂ nanoparticles. Results from X-ray diffraction, transmission electron microscopy and Raman demonstrated that the resultant products were pure cubic phase ZnO₂ nanoparticles, whose sizes were in the range of 3.1-4.2 nm. Thermogravimetric analysis indicated that between 180 and 350 °C, the as-synthesized ZnO₂ nanoparticles had a weight loss of about 16.7%, consistent with the theoretical amount (16.4%) of the O₂ released from ZnO₂ decomposition (ZnO₂ = ZnO + 1/2O₂). The present method was green, simple and cost-effective, which should be suitable for large-scale production of multifunctional ZnO₂ nanoparticles.     

Green hydrothermal synthesis and photoluminescence property of ZnO2 nanoparticles

ZnO₂ nanoparticles were synthesized via a green hydrothermal method using ZnO powder and 30% H₂O₂ aqueous solution as the starting materials, and characterized by X-ray diffraction (XRD), Raman spectra, energy dispersive X-ray (EDX) spectra, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and room temperature photoluminescence (RTPL) spectra. It was found that suitable reaction temperature (e.g., 80-140 °C) played an important role in obtaining pure cubic phase ZnO₂ nanoparticles. The RTPL spectra disclosed that the as-synthesized ZnO₂ nanoparticles exhibit one strong emission band centered at around 400 nm and one very weak emission band at around 474 nm, which may have originated from the band edge emission and the oxygen vacancy, respectively.     

Green synthesis of lanthanum oxide nanoparticles using Moringa oleifera leaves extract and its biological activities

Phytosynthesis is a reliable way to produce metal nanoparticles without affecting the environment. Plant extracts act as reducing agent and favors nanoparticle synthesis. Recently, potential drugs were developed in nanotechnology platforms by the green synthesis approach. In this study, the leaves extract of ‘Moringa Oleifera’ (M. oleifera) used as a reducing agent for the synthesis of Lanthanum oxide nanoparticles (La₂O₃ NPs). The X-ray diffraction (XRD) confirmed the formation of body-centered cubic structure of La₂O₃ NPs. The optical behavior of La₂O₃ NPs was analyzed by UV–Vis spectrum. The bandgap energy of the La₂O₃ NPs was found to be 4.31 eV using Tauc’s plot. The morphology and purity of La₂O₃ NPs was analyzed by using Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray (EDX) spectrum. High Resolution Transmission Electron Microscope (HR-TEM) analysis reveals the morphology, lattice spacing, and selected area electron diffraction (SAED) pattern of the La₂O₃ NPs. The XPS analysis of the La₂O₃ NPs reveals the binding energy of La (3d_5/2 and 3d_3/2) and O 1s at 835.5, 852.3, and 536 eV respectively. The total antioxidant activity (TOA) of La₂O₃ NPs was found to be 75.32% at 500 µg/mL with the standard drug of vitamin C. The anti-inflammatory activity of the La₂O₃NPs was found to be 94.15% at 500 µg/mL using the bovine serum albumin denaturation (BSA) technique. The inhibitory activity of La₂O₃ NPs against α-amylase was found to be 79.99% at 500 µg/mL. In summary, the pure, highly stable and good biocompatible, greener approach based M. oleifera assisted La₂O₃ was synthesized for radical scavenging, α-amylase and BSA denaturation inhibition activities which can play a key role in the future biomedical and nano-biotechnological applications.     

Green synthesis and characterisation of antioxidant-tagged gold nanoparticle (X-GNP) and studies on its potent antimicrobial activity

Alternanthera philoxeroides (Mart.), a weed, mainly from tropical origin and easily available worldwide. People used to eat it as a food mainly in South Africa. In our previous report we have thoroughly characterise several important phenolics, monoterpene and phenylpropane from methanol soluble fraction of Alternenthera leaves (fraction X) and also reported their α-glucosidase inhibitory, antimicrobial and antioxidant activities. All these isolated natural compounds are well characterised and widely studied. In our present study we try to use this beneficial fraction (named fraction X) in green synthesis of gold nanoparticles (X-GNP). We also try to explore the beneficial aspects of green synthesis in comparison with commonly used chemical synthesis method (GNP) in context with their antimicrobial activity. UV/Vis spectroscopy, DLS, Zeta potential, FT-IR, EDAX and other microscopic techniques namely: SEM, AFM were used to characterise the synthesised nanoparticles. Different important microbial strains were used to evaluate the antimicrobial activity of prepared nanoparticles. Overall the studies suggest successful synthesis of green nanoparticles (X-GNP) and also showed the improvement in antimicrobial activity of X-GNP nanoparticles.     

Green synthesis of silver oxide nanoparticles using Panicum miliaceum grains extract for biological applications

In this report, the silver oxide nanoparticles were green synthesized using Panicum miliaceum grains extract and were proposed for the first time. GC–MS analysis explicated 2-Acetylbenzoic acid was the active phytocompound with 97.07% of presence in aqueous grains extract. The synthesized silver oxide nanoparticles were analyzed by several analytical techniques such as UV–visible, XRD, FT-IR, HR-TEM, TG, XPS, EDX and mapping analyses. The results of various analytical techniques confirmed the silver oxide nanoparticles formation. The formed nanoparticles were in 10–25 nm size. The effectual bioactive properties of nanoparticles were revealed through antioxidant, anti-diabetic, anti-inflammatory, larvicidal and insecticidal activities. The high mortality of larvae and insect was observed at 48 h in 100 ppm and 72 h in 100 μg/Kg concentration, respectively. The antibacterial activity explained the bactericidal property of nanoparticles on S. aureus and S. typhi at 150 μg/mL concentration. The effective drug activity of nanoparticles was observed from 98.10 % of toxicity against A549 lung cancer cells at 100 μg/mL concentration. The growth of Vigna unguiculata was efficiently increased by lower concentration (60 ppm) of nanoparticles. According to results, the green synthesized nanoparticles can be applied in pharmaceutical and agricultural sectors as biocompatible, non-toxic and cost-effective material.     

Green hydrothermal synthesis and characterization of CdO2 nanoparticles

A green hydrothermal method has been developed for the synthesis of CdO₂ nanoparticles from Cd(OH)₂ powder and 6 vol.% H₂O₂ aqueous solution at 80-150 °C. The characterization results from X-ray diffraction, transmission electron microscopy, and thermal gravimetric and differential scanning calorimetry analysis disclosed that the resultant products were pure cubic phase CdO₂ nanoparticles with the sizes in the range of about 11-13 nm. The UV-vis absorption spectra revealed that the as-synthesized CdO₂ nanoparticles had similar optical band gaps of about 3.85 eV. The Raman spectra of the as-synthesized CdO₂ nanoparticles displayed two obvious peaks at about 348 and 830/833 cm^-1, a characteristic of pyrite-type IIB-peroxides.     

Green synthesis of nickel oxide nanoparticles and studies of their photocatalytic activity in degradation of polyethylene films

Nickel oxide nanoparticles (NiO NPs) were synthesized using Ananas comosus leaf extract, and were characterized by UV–Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) techniques. The FTIR analysis confirms the formation of the NiO with appearance of NiO band at 468 cm⁻¹. The HRTEM analysis reveals that the NiO NPs size was in the range of 0.63–5.75 nm, with an average particle size of 1.42 ± 1.76 nm. The EDX analysis shows clear peaks of Ni (2.7%) and O (5.74%) in the spectrum. The peaks of XRD analysis at (2θ) 30°, 43.89°, 60.16°, 77.95° and 82.94° were assigned to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of the face-centered cubic (fcc) lattice of NiO. The photocatalytic properties of the NiO NPs were studied through the solid phase degradation of low-density polyethylene (LDPE) film. We observed that polymeric nanocomposites (NCs) showed a significant weight loss of 33 ± 1.6% compared with the pure LDPE (8.6 ± 0.7%) after exposure to solar light irradiation for 240 h, while the nanocomposites under the dark condition gave a weight reduction of 1.90 ± 0.05 at the end of 240 h. The FTIR analysis also confirms the presence of carbonyl group, a degradation product of LDPE, with carbonyl index of 0.4. All these important factors showed that NiO is an effective photocatalyst. The study therefore suggests the incorporation of NiO NPs into the polymer matrix so as to enhance its photodegradation.     

A novel green synthesis of zero valent iron nanoparticles (NZVI) using three plant extracts and their efficient application for removal of Cr(VI) from aqueous solutions

In the present study, NZVI particles were synthesized from the plant extracts including Rosa damascene (RD), Thymus vulgaris (TV), and Urtica dioica (UD). The FTIR arspectshowed that polyphenols, proteins and organic acids which serve as reducing and stabilizing agents play a significant role in the synthesis of NPs and reduce the possibility of aggregation of NPs compared to chemical techniques of NPs synthesis. The amount and type of compounds in plant extracts affect the structure and also agglomeration of NPs after adsorption process. Based on the results, the highest removal efficiency occurred at pH 2. With increase in contact time and amount of dose, the percentage removal increases. Inversely, increase of initial concentration of Cr(VI) decreases the removal efficiency of the contaminant. These nanoparticles have a high adsorption capacity. Accordingly, by applying a dose of 0.2 g/l and contact time of 10 min, the three NPs yielded >90% removal efficiency. Also, for 1 min contact time, the percentage removal was 94.87%, 83.48% and 86.8% for RD-Fe, UD-Fe and TV-Fe, respectively. By an increase to 25 min, the removal percentage reached to 100% for TV-Fe and UD-Fe. Moreover, 30 min was required to remove Cr(VI) completely by RD-F.     

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.     

Green preparation of nano-zero-valent iron-copper bimetals for nitrate removal: Characterization,reduction reaction pathway,and mechanisms

In this study, green tea was used as a reducing agent to prepare GT-nZVI/Cu nano-zero-valent iron-copper bimetallic materials for nitrate degradation. Through single factor experiments, the process conditions for nitrate removal by GT-nZVI/Cu were optimized. By measuring the contents of nitrate, nitrite, and ammonia nitrogen in the reaction products, the reduction pathway of nitrate-nitrogen in GT-nZVI/Cu was studied. In addition, the removal mechanism of nitrate by GT-nZVI/Cu was also analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and kinetic experiments. The results showed that the size of GT-nZVI/Cu particles is between 50 and 70 nm, and they are irregular spherical shapes. The polyphenol antioxidants in green tea make GT-nZVI/Cu have stronger antioxidant properties, and the denitration products are mostly nitrogen. The addition of copper ions accelerates the reaction time and reaction rate. The maximum removal rate of nitrate by GT-nZVI/Cu within 75 min can be up to 99 %. After three repeated experiments, the removal rate of GT-nZVI/Cu can still reach 70 %. The removal mechanism of GT-nZVI/Cu has enhanced nitrate removal through complexation, redox, and adsorption co-precipitation. This study provides a new route for the green preparation and efficient application of nZVI.     

Synthesis and characterization of a mesoporous hydrous zirconium oxide used for arsenic removal from drinking water

Powder (20-50 μm) mesoporous hydrous zirconium oxide was prepared from a zirconium salt granular precursor. The effect of some process parameters on product morphology, porous structure and adsorption performance has been studied. The use of hydrous zirconium oxide for selective arsenic removal from drinking water is discussed.     

Green synthesis of zinc oxide nanoparticles by aloe barbadensis miller leaf extract: Structure and optical properties

Biological methods for nanoparticle synthesis using microorganisms, enzymes, and plants or plant extracts have been suggested as possible ecofriendly alternatives to chemical and physical methods. In this paper, we report on the synthesis of nanostructured zinc oxide particles by both chemical and biological method. Highly stable and spherical zinc oxide nanoparticles are produced by using zinc nitrate and Aloe vera leaf extract. Greater than 95% conversion to nanoparticles has been achieved with aloe leaf broth concentration greater than 25%. Structural, morphological and optical properties of the synthesized nanoparticles have been characterized by using UV-Vis spectrophotometer, FTIR, Photoluminescence, SEM, TEM and XRD analysis. SEM and TEM analysis shows that the zinc oxide nanoparticles prepared were poly dispersed and the average size ranged from 25 to 40 nm. The particles obtained have been found to be predominantly spherical and the particle size could be controlled by varying the concentrations of leaf broth solution.     

A facile and novel way for the synthesis of nearly monodisperse silver nanoparticles

A facile and novel way was reported for the preparation of nearly monodisperse silver nanoparticles with controlled hydrophilic or hydrophobic surface, using trioctylphosphine as the surfactant and stabilizer. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and UV-vis spectroscopy. The monodisperse silver nanoparticles showed a strong surface plasmon resonance band at 402 nm from the UV-vis spectrum.     

A rapid and sensitive method for separation of Cu2+ ions from industrial wastewater sample and water samples with methacrylamide‐ethylene glycol dimethacrylate: A new synthesis of molecularly imprinted polymer

In this study, new molecularly imprinted polymer particles (MIP) were synthesised to extract Cu²⁺ ions from aqueous solutions using radical polymerisation. MIP was developed using the methacrylamide‐ethylene glycol dimethacrylate (EGDMA) cross linking agent, methacrylamide monomer, and ACV initiator by the radical polymerisation method. A comparison of various cross linking agents in MIP production showed that the best cross linking agents are EGDMA and gallic acid. The template ions were removed by leaching with 0.100 M HCl. The polymer particles were characterised by FTIR spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The effect of different parameters such as cross linkers, pH, time, maximum adsorption capacity, and kinetic and isotherm adsorption were investigated. The best conditions were determined (pH = 8.0, t = 10 min, and q _m  = 262.53 mg g⁻¹). The adsorption data were best fitted by Freundlich isotherm and pseudo second order kinetic models, as well. Due to its high adsorption capacity and multi‐layer behaviour, this method is an easy, fast and safe way to extract cations. Removal of Cu²⁺ in certified tap water and rain water was demonstrated and the industrial wastewater sample (Charmshahr, Iran) with which the MIP was developed using Methacrylamide‐ Ethylene Glycol Dimethacrylate (EGDMA) was good enough for Cu²⁺ determination in matrices containing components with similar chemical property such as Co²⁺, Zn²⁺, Fe².