Microwave-assisted green synthesis of (Co, Gd) dual doped ZnO nanoparticles using Phyllanthus emblica extract and their applications.

The biosynthesis is an eco-friendly, reliable, sustainable protocol for preparing nanomaterials where use of natural, biodegradable, non-toxic and safe reagents takes place. In the present work, an efficient, facile and eco-friendly approach has been used for the synthesis of zinc oxide nanoparticles (ZnO-NPs) using Trigonella foenum-graecum (Fenugreek) aqueous seed extract as bio-reducing agents and capping agent, thus eradicating the requirement of conventional reducing agents. Different characterization techniques like UV–Vis spectroscopy, UV–Visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy, photoluminescence (PL) study and energy dispersive X-ray were employed for confirmation of optical properties, shape, size, surface structure, crystalline nature and elemental proportions of the biogenic ZnO-NPs. FTIR analysis confirms the active role of bioactive phytochemical constituents present in the Trigonella foenum-graecum aqueous seed extract. XRD analyses of the as prepared ZnO-NPs are crystalline in nature and have no other impurity phase. UV–Vis spectral data suggested optical band gap energy of 2.97 eV for biosynthesized ZnO-NPs showing their small size owing to quantum confinement. UV–Vis spectra of ZnO-NPs show the characteristic absorption band at 364 nm, which can be assigned to the intrinsic band gap absorption of ZnO-NPs because of the electron transitions from the valence band to the conduction band. In addition, the efficacy of biosynthesized ZnO-NPs to act as highly efficient photocatalyst for methylene blue (MB) dye degradation under UV-light under different experimental conditions was confirmed in this study. The effect of initial dye concentration, ZnO photocatalyst dosage and the reusability tests were investigated. Improved photocatalytic behavior was discussed and influence of active species was further investigated using hydroxyl radical (●OH), superoxide anions (●O2−) and hole (h+) scavengers to explain the possible mechanism of the photocatalytic MB dye degradation under UV light irradiation.

The present study revealed the synthesis of zinc oxide nanoparticles by wet chemical co-precipitation process and were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis spectroscopy, and photocatalysis for Methylene Blue (MB) dye degradation. The crystallite size of the ZnO nanoparticles calculated from XRD using Debye Scherrer Formula is 36.27 nm. The size variation of the ZnO nanoparticles is due to the difference in annealing temperature and precursors. The FTIR spectra confirms the formation of ZnO nanoparticle. From UV-Vis spectra of ZnO nanoparticles, the absorption peak is at 380 nm and decreases with time which shows the dye degradation. MB dye degradation efficiency by ZnO nanoparticle is 91.78% in 21 minutes.

Vernonia amygdalina belongs to the family Asteraceae. Its leaf extract has been used ethnobotanically in the treatment of gastrointestinal disorders, malaria, diabetes mellitus, and hiccups. This study aimed to synthesize zinc oxide nanoparticles using Vernonia amygdalina leaf extract and evaluate their antioxidant, photocatalytic, and antibacterial activities. The synthesized zinc oxide nanoparticles were characterized using UV-Vis spectroscopy, dynamic light scattering, Fourier transform infrared spectroscopy, X-ray diffraction, energydispersive X-ray analysis, and scanning electron microscopy. The photocatalytic activity was evaluated through the degradation of methylene blue dye. At the same time, the antimicrobial properties of Vernonia amygdalina leaf extract and zinc oxide nanoparticles were assessed using the minimum inhibitory concentration assay. Antioxidant activity was determined by measuring the inhibition of 2,2- diphenylpicrylhydrazyl radicals, with ascorbic acid serving as the positive control. The successful synthesis of zinc oxide nanoparticles was confirmed by a UV-Vis absorption peak at 390 nm. The nanoparticles exhibited a smooth, spherical morphology with an average size of 78.25 nm. Fourier transform infrared spectroscopy identified key functional groups responsible for nanoparticle stabilization. X-ray diffraction analysis revealed three characteristic peaks at 2θ angles of 24°, 27°, and 34°, which confirmed the crystalline nature of the synthesized zinc oxide nanoparticles. The antioxidant assay demonstrated that zinc oxide nanoparticles had a significantly higher free radical scavenging effect than Vernonia amygdalina leaf extract (P < 0.05). Energy-dispersive X-ray analysis confirmed the elemental composition of the synthesized zinc oxide nanoparticles, with 44.4% oxygen and 55.6% zinc. The photocatalytic study demonstrated that the synthesized zinc oxide nanoparticles achieved a 75% degradation rate of methylene blue dye after 120 minutes of UV light exposure. Antimicrobial testing revealed mean inhibition zones of 7.88 mm and 6.30 mm for the synthesized zinc oxide nanoparticles and Vernonia amygdalina leaf extract, respectively, indicating significant antibacterial activity against both Gram-positive and Gram-negative bacteria (P < 0.05). The 2,2-diphenylpicrylhydrazyl scavenging effects of Vernonia amygdalina leaf extract and the synthesized zinc oxide nanoparticles were also statistically significant when compared to ascorbic acid (P < 0.05). The biosynthesized Vernonia amygdalina-derived zinc oxide nanoparticles exhibited remarkable photocatalytic, antibacterial, and antioxidant properties.

The present study focuses on the green synthesis of zinc oxide nanoparticles (ZnO NPs) using a novel Lepidagathis ananthapuramensis (LA) leaf extract and a systematic study on the photocatalytic degradation of methylene blue (MB) dye. The structural, thermal, morphological, optical, and surface area analysis of prepared ZnO NPs were examined using X-ray diffraction (XRD), UV-visible spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, thermogravimetric analysis (TGA), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX) and high-resolution transmission electron microscopy (HR-TEM). The LA stabilised ZnO NPs produced NPs with diverse morphologies, low band gap and cost-effective high yield of production. A systematic study has been carried out to determine the crystallinity and crystallite size of ZnO NPs based on the concentration of Zn(NO3)2 precursor, concentration of LA leaf extract, calcination temperature and calcination time. The crystallinity and crystallite size of ZnO NPs were evaluated based on the XRD technique. The photocatalytic activity of ZnO NPs was thoroughly investigated for the degradation of MB dye based on various physicochemical parameters such as reaction time, concentration of catalyst, concentration of precursors, concentration of LA extract, concentration of MB, calcination temperature and calcination time. These systematic photocatalytic studies followed green protocols and provided an excellent photocatalytic efficiency result of 96-98.5% towards the decomposition of MB. Hence, this material can work as a potential candidate for waste water treatment by also degrading other toxic dyes.

Synthesis of nanoparticles through environmentally friendly and biologically mediated routes is the study upon which lot of research attention has been focused in recent times. In the present investigation, fungal-mediated synthesis of zinc oxide nanoparticles was explored using an economical and nature friendly approach. Synthesis of the extracellular zinc oxide nanoparticles was achieved using fungal cultures of Pleurotus, Lentinus and Agaricus spp. The synthesized nanomaterial was thoroughly characterized using physical techniques including UV-Vis Spectroscopy, SEM, XRD, and FTIR. UV-Vis Spectroscopy exposed a distinct absorption peak in the range of 300-400nm, validating the formation of nanoparticles. SEM images revealed the ZnNPs being agglomerated and irregular in shape. The size of the particles is in the average range of 10-100nm. XRD analysis demonstrated the nature of the nanoparticles as crystalline, with prominent diffraction peaks corresponding to the face-centered cubic (fcc) crystal structure of zinc oxide. FTIR analysis provided insights into the functional groups present on the nanoparticle surface. This suggests that there is some involvement of fungal biomolecules in the reduction and stabilization of zinc oxide nanoparticles. The presence of zinc oxide nanoparticles was confirmed by Energy Dispersive X-ray Analysis. Furthermore, the synthesized nanoparticles were assessed for their potential antifungal activity against Alternaria mali, a notorious phytopathogen responsible for causing leaf spot in Apple plant. The antifungal activity was assessed through poison food technique and results indicated a significant inhibition of Alternaria growth by the zinc oxide nanoparticles particularly the ones synthesized from Pleurotus, with a dose-dependent response. The mycogenic synthesis of zinc oxide nanoparticles is an eco-friendly and sustainable approach, minimizing the need for hazardous chemicals and reducing environmental impact. This study showcases the potential of zinc oxide nanoparticles as a novel and effective biofungicide against Alternaria mali and contributes to the growing body of knowledge on sustainable methods of nanoparticle synthesis and their applications in agriculture (disease management) and environmental management.

The commercialization of titanium dioxide-based heterogeneous photocatalysis continues to suffer from various limitations, the major shortcoming being the costly and time consuming post-treatment separation of very fine titanium dioxide particles. In order to eliminate this major hindrance, immobilization of titanium dioxide particles on various substrates continues to be an active area of research. In this work, polystyrene-supported titanium dioxide photocatalyst was prepared using a facile method. The photocatalytic activity of the developed photocatalysts was investigated by photodegradation of aqueous solutions of methylene blue andmethyl orange dyes under UV light for 24 h under non-stirred conditions. The recovery and reuse of the prepared photocatalysts was also investigated. The maximum percentage degradation of methyl orange and methylene blue dyes by the developed photocatalysts was found to be around 60 % and 66 % respectively. The ease of separation after use in addition to a facile, low cost-based method of fabrication and appreciable photocatalytic activity of the developed photocatalyst makes it a promising candidate to be explored further for large scale applications.DOI: http://dx.doi.org/10.3329/jce.v28i1.18103 Journal of Chemical Engineering, Vol. 28, No. 1, December 2013: 9-13

Using natural processes as inspiration, the present study demonstrates a positive correlation between zinc metal tolerance ability of a soil fungus and its potential for the synthesis of zinc oxide (ZnO) nanoparticles. A total of 19 fungal cultures were isolated from the rhizospheric soils of plants naturally growing at a zinc mine area in India and identified on the genus, respectively the species level. Aspergillus aeneus isolate NJP12 has been shown to have a high zinc metal tolerance ability and a potential for extracellular synthesis of ZnO nanoparticles under ambient conditions. UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, and energy dispersive spectroscopy studies further confirmed the crystallinity, morphology, and composition of synthesized ZnO nanoparticles. The results revealed the synthesis of spherical nanoparticles coated with protein molecules which served as stabilizing agents. Investigations on the role of fungal extracellular proteins in the synthesis of nanoparticles indicated that the process is nonenzymatic but involves amino acids present in the protein chains.

Green synthesis of zinc oxide nanoparticles using Ficus carica leaf extract and their bactericidal and photocatalytic performance evaluation

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.

Nanoparticles (especially zinc and titanium oxide) have been found to be effective in photodegrading pollutants (organic/inorganic) from industrial wastewater. Presently, this study aimed at biosynthesizing zinc oxide nanoparticles (ZnO-NPs) from the leaf extract of Pavonia zeylanica, a plant with significant medical value, and evaluating their photocatalytic properties against methylene blue (MB), an azo dye (100 mg L-1, pH 7), using solar irradiation, along with the measurement of their reusability and mineralization efficiency. The characterization of the Pz-ZnO-NPs showed an absorbance peak at 313 nm, with a bandgap value of 3.04 eV and a size of 19.58 nm. This study's results show that the synthesized Pz-ZnO-NPs, upon treatment with MB dye after 2 h of solar irradiation, showed an 89.32% degradation, which was concentration-dependent and followed pseudo-first-order kinetics. The reusability studies indicated that the Pz-ZnO-NPs were able to degrade MB dye after five repeated cycles of its usage. The structural composition of the Pz-ZnO-NPs evaluated by XRD showed that the peak position stayed constant. Nevertheless, the peak intensity dropped, indicating that the ZnO-NPs' crystal structure was unaffected. Furthermore, advanced oxidation process studies, which included an evaluation of COD and TOC, revealed that both the contents decreased significantly during the photocatalysis process, wherein the electron-rich organic dyes were converted to nontoxic products through mineralization.

Enhanced photocatalytic degradation of methylene blue using biologically synthesized “protein-capped” ZnO nanoparticles

An overview of recent work on the low-temperature plasma-assisted synthesis of zinc oxide (ZnO) nanoparticles is presented and interpreted in terms of gas-phase and surface reactions with illustrated examples. The thermodynamical nonequilibrium conditions allow the formation of chemically reactive species with a potential energy of several eV, which readily interact with the Zn precursors and initiate reactions leading to the formation of nanoparticles or nanowires. The high-quality nanowires were synthesized from Zn powders only upon interaction with moderately ionized plasma in a narrow range of plasma parameters. This technique is promising for the synthesis of large quantities of nanowires with aspect ratios well above 10, but the exact range of parameters remains to be determined. Apart from the ex situ techniques, the ZnO nanoparticles can be synthesized by depositing a film of precursors (often Zn salts or Zn-containing organometallic compounds) and exposing them to oxygen plasma. This technique is useful for the synthesis of well-adherent ZnO nanoparticles on heat-sensitive objects but requires further scientific validation as it often leads to the formation of a semicontinuous ZnO film rather than nanoparticles. Both low-pressure and atmospheric plasmas are useful in converting the precursor film into ZnO nanoparticles despite completely different mechanisms.

Annealing of periodic mesoporous organosilica supported with bismuth (Bi@PMOS) and cerium (Ce@PMOS) nanoparticles was carried out to derive bismuth oxide (Bi2O3) and cerium oxide (CeO2) nanosheets. The hydrothermal sol-gel method was used to synthesize hexagonal Bi@PMOS and Ce@PMOS. These PMOS provided an opportunity for bismuth and cerium to retain a hexagonal configuration alongside their traditional crystalline phases (tetragonal and cubic) in Bi2O3 and CeO2 nanosheets. All produced materials were found to be dynamic under sunlight irradiation for the degradation of methylene blue (MB) and methyl orange (MO). However, the Bi2O3 and CeO2 nanosheets showed better potential and photo-catalytic performances than Bi@PMOS and Ce@PMOS due to the presence of the unique blend of crystalline phases. The synthesized Bi@PMOS, Ce@PMOS, Bi2O3, and CeO2 were structurally characterized by FTIR and XRD techniques. These showed characteristic vibrations of successfully loaded bismuth and cerium with hexagonal symmetry. EDX results confirmed the elemental detection of bismuth and cerium, while SEM images revealed the nanosheets in the synthesized materials. The optical response and detection of reactive species were carried out by photoluminescence (PL) and showed emissions at 700 nm. The PL data were also used to calculate band gaps of 3.72, 3.70, 3.35, and 2.88 eV for Ce@PMOS, Bi@PMOS, CeO2, and Bi2O3, respectively. A UV/visible spectrophotometer scanned the photocatalytic competences of the synthesized nanomaterials through the degradation of MB and MO dyes. Then, 10 mg of Bi@PMOS and Ce@PMOS degraded 15 mg and 8.4 mg of MB and 10.8 mg and 8 mg of MO, respectively, in 20 mg/L solutions. However, equivalent quantities of Bi2O3 and CeO2 (10 mg of each) exhibited more efficient photocatalysis of the 20 mg/L solutions of MB and MO, degrading 18.4 mg and 15.4 mg, and 12.4 mg and 17 mg, respectively, in only 1 h. The Bi2O3 and CeO2 photocatalysts were regenerated and their photodegradation results were also recovered. Bi2O3 and CeO2 showed only 10% and 8% (for MB), and 8% and 10% (for MO) decline in catalytic efficiency, respectively, even after four consecutive recycles. These results demonstrate that these materials are dynamic, long-lasting photocatalysts for the rapid degradation of azo dyes in contaminated water.

Fabrication of heterojunction semiconductors for the photodegradation of toxic organic dyes under sunlight exposure has earned significant recognition from researchers nowadays. On that account, we have synthesized and explored a comparative photodegradation study of ZnO/CuO nanocomposite with ZnO and CuO nanoparticles. ZnO and CuO nanoparticles have been synthesized by biosynthesis methods usingFicus benghalensisleaf extract. As-synthesized ZnO and CuO nanoparticles have been further utilized for the synthesis of ZnO/CuO nanocomposite by the mortar pestle crushing/milling method. Both biosynthesis methods and mortar pestle crushing/milling methods are simple, low-cost, and environmentally friendly. Structural, optical, and morphological analysis of all the synthesized nanomaterials havebeen doneby powder X-ray diffraction (PXRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM),Brunauer-Emmett-Teller (BET),field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy.PXRD data reveal that synthesized ZnO nanoparticles are in the hexagonal wurtzite phase, CuO nanoparticles in the monoclinic phase, and ZnO/CuO nanocomposite in the hexagonal wurtzite as well as in monoclinic phase. FE-SEM and TEM images of ZnO/CuO nanocomposite reveal the nanorod-shaped morphology along with micro-sized and nano-sized flakes. The BET analysis shows the surface areas 18.128 m2/g for ZnO nanoparticles, 16.653 m2/g for CuO nanoparticles, and 19.580 m2/g for ZnO/CuO nanocomposite, respectively. Theenergyband gap values of ZnO/CuO nanocomposite are obtained 3.13eV for ZnO and 2.76eV for CuO, respectively. The photocatalytic behaviors of all the synthesized nanomaterialsareexamined against aqueous dye solutions of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO) under sunlight irradiation. The results reveal that the photocatalytic degradation efficiency of ZnO/CuO nanocompositehasbeen found higher than with ZnO and CuO nanoparticles for all the dyes. Also, all the synthesized nanomaterialsindicatehigher photocatalytic degradation efficiency for methylene blue dye among allthreedyes. The kinetics of photodegradation of all the dye solutions has also been investigated in the presence of ZnO, CuO, and ZnO/CuO photocatalysts separately. The results exhibit that rate constant values for all the dyes are higher with ZnO/CuOnanocompositethan with ZnO and CuOnanoparticles.ZnO/CuO nanocomposite demonstrates degradation efficiency for MB dye99.13%, for RhB80.21%, and for MO67.22%after 180min of sunlight exposure.ZnO/CuO nanocomposite and ZnO and CuO nanoparticles also show thebestreusability and stability up to three cycles for photocatalytic degradation of MB dyes amongall the dyes.Therefore, green synthesized ZnO/CuO nanocomposite could be used asan efficientphotocatalyst for the degradation of various toxic dyes.The mineralization of different dyes using ZnO/CuO nanocomposite has been examined by FTIR analysis. Furthermore, the mineralizationof MB dye has been done by total organic carbon (TOC)measurements.

Ultrasound assisted preparation and characterization of Ag supported on ZnO nanoparticles for visible light degradation of methylene blue dye