Photocatalytic studies of silver doped ZnO nanoparticles synthesized by chemical precipitation method

Ag-doped ZnO nanoparticles (Zn_1?xAg_xO; where x = 0.00–0.05) were synthesized by chemical precipitation method. The synthesized products were characterized by X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope (TEM) and UV–Vis spectrometer. The SEM and TEM micrographs revealed the agglomerated spherical-like morphology and the measurements show that the size of crystallites is in the range of 10–40 nm. Optical measurements indicated a red shift in the absorption band edge after Ag doping. The band gap values of as prepared undoped and doped with silver samples were found to decrease with increase in temperature from 300 to 800 °C. Photocatalytic activities of ZnO and Ag doped ZnO were evaluated by irradiating the sample solution to ultraviolet light by taking methylene blue as organic dye. The experiment demonstrated that the photo-degradation efficiency of 1 mol% Ag-doped ZnO was significantly higher than that of undoped and 2–5 mol% Ag doped ZnO under ultraviolet light irradiation.     

Green synthesis and antibacterial effects of aqueous colloidal solutions of silver nanoparticles using clove eugenol

Silver nanoparticles were synthesized using clove extract (CE). Scanning transmission electron microscopy (STEM) revealed the morphology of the metallic Ag nanoparticles obtained via the clove extract synthesis (Ag NPs‐CE), which had a uniform distribution and average sizes varying from 10 nm to 100 nm. Fourier transform infra‐red (FTIR) spectroscopy showed that clove eugenol acts as a capping and reducing agent being adsorbed on the surface of Ag NPs‐CE, enabling their reduction from Ag⁺ and preventing their agglomeration. Formation of the Ag⁰ structure is also confirmed in the FTIR spectrum by the presence in the Ag NPs‐CE sample of the –C=O and –C=C vibrations at wavenumbers 1600 and 2915 cm^‐1, respectively. Antibacterial and antifungal tests using three strains of bacteria and one fungi strain showed that the Ag NPs‐CE performed better compared to pure clove extract (CE) sample.     

Nanosized silver–palm pollen nanocomposite,green synthesis,characterization and antimicrobial activity

Palm pollen (PP) has been widely used in nutrition, pharmaceutical and cosmetic industries. In the present study, we explored the potential of PP in the synthesis of a silver nanoparticle (Ag NP). PP was used as both reducing and stabilizing agent. The Ag/PP nanocomposite was examined by field emission electron microscopy, X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet spectroscopy and zeta potential measurement. The biosynthesized NPs showed surface plasmon resonance centered at 425 nm with an average particle size measured to be 23 nm and a zeta potential of ?30.9 mV. Prominent FT-IR signals were obtained and ascribed to phenolic and carbohydrate compounds involved in the formation of the Ag NPs, and proteins which participated in stabilization of the Ag NPs. The biologically synthesized Ag NPs were found to be extremely effective against E. coli (13.8 ± 0.25 mm) with a minimum inhibitory concentration of 20 µg/mL. Thus, such biosynthesized Ag NPs can be used in medicinal applications.     

Time growing comparison for ZnO nanorod by using microwave irradiation method

In this study, zinc oxide (ZnO) nanorod were successfully prepared at different growth times (15, 30 and 60 min) using the microwave irradiation method. The ZnO nanorods were simply synthesized at a low temperature (90 °C) with low power microwave assisted heating (about 100 W) and a subsequent ageing process. The synthesized nanorod were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and Ultraviolet–Visible spectroscopy (UV–Vis). The FESEM images showed nanorods with diameter ranging between 50 and 150 nm, and length of 150–550 nm. The XRD results indicate that ZnO nanorods of different time of growth exhibits pure wurtzite structure with lattice parameters of 3.2568 and 5.2125 Å. UV–Vis characterization showed that energy gap decreases with increase in time. The result also shows that growth of ZnO at 60 min produces an energy band gap of 3.15 eV. In general, the results of the study confirm that the microwave irradiation method is a promising low temperature, cheap and fast method for the production of ZnO nanostructures.     

Solvothermal preparation,and characterization,of Cu–Ag nanoparticles

Cu–Ag nanoparticles have been successfully synthesized by one-pot solvothermal treatment of a mixture of AgNO₃ and Cu(OAc)₂·H₂O in ethylene glycol solution at 180 °C for 10 h. The samples were characterized by UV–visible absorption, X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that Cu–Ag nanoparticles and a small amount of phase-separated Cu–Ag alloy nanoparticles with an average diameter of 100 ± 30 nm were synthesized by the solvothermal treatment procedure. The mechanism of formation is discussed.     

Synthesis,Characterization and Optical Properties of BaMoO<Subscript>4</Subscript> Synthesized by Microwave Induced Plasma Method

BaMoO₄ crystals were synthesized by a 900 W microwave induced plasma process (MIP) for 40, 60, 120 and 140 min. Phase, morphology, vibrational mode and energy gap were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and UV-visible spectroscopy. In this research, the phase and morphology of product were influenced by microwave heating time. The sample processed for 140 min shows spherical particles tetragonal BaMoO₄ phase with size of 200–700 nm in diameter. BaMoO₄ with band gap of 3.35 eV shows a blue emission wavelength at 440 nm.     

Rapid Synthesis of Silver Nanoparticles by Microwave-Polyol Method with the Assistance of Latex Copolymer

Highly stable and monodispersed silver nanoparticles with uniform morphology have been successfully prepared by microwave (MW) irradiation within a few seconds from the mixture of silver nitrate, ethanol and latex copolymer. The aqueous emulsion of latex copolymer acts as both reducing and stabilizing agent. To the best of our knowledge, it was the first time that the effect of MW irradiation time and latex concentration on the silver nanoparticle preparation and properties was analyzed. The formation of silver nanoparticles was confirmed by Ultraviolet–visible spectroscopy and transmission electron microscopy (TEM). The UV–Vis spectra are marked by the characteristic surface plasmon absorption band in the range 410–420 nm. From TEM images, silver nanoparticles were observed to be spherical with sizes ranging from 4 to 10 nm. Electron diffraction patterns on selected area, indicated that the silver nanoparticles are crystalline with face centered cubic structure.     

Oxygen reduction on electrodeposited silver catalysts in alkaline solution

In this study, silver was electrochemically deposited onto glassy carbon (GC) substrate using constant potential regime and tested for oxygen reduction reaction (ORR) in alkaline media. The surface morphology of Ag/GC electrodes was studied by scanning electron microscopy (SEM). It was established that after 10 s of deposition, a number of Ag nanoparticles with the size of 15 nm are produced that grow to about 45 nm after 300 s of electrodeposition. The ORR studies were conducted in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. The Tafel slope at low current densities for electrodeposited silver is in the range from ?70 to ?80 mV. The RDE measurements showed that the electron transfer number (n) is 3.5 for smaller amounts of electrodeposited Ag, and it increases with increasing the loading of Ag on the GC surface. These n values suggest that the electroreduction of oxygen on Ag/GC electrodes proceeds mainly to water.     

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique is presented. The technique entails splitting kaolin to alumina and silica components. These components were further recombined to synthesize zeolite Y. The as-synthesized NaY zeolite was transformed to REY zeolite. Characterizations of the as-synthesized zeolite Y were carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) texture analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared (FTIR) spectroscopy. Catalytic desulfurization of the as-synthesized REY zeolite was studied using microwave assisted desulfurization of model diesel. The Si/Al molar ratio of the as-synthesized NaY zeolite was 4.27. The crystallinity of the as-synthesized NaY and REY zeolites were 79.1 and 56.5% respectively. The as-synthesized NaY and REY zeolites possessed hexagonal morphology with average crystal sizes of 200 and 100 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized NaY zeolite were 732 m² g^?1, 0.2611 cm³ g^?1 and 1.426 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized REY zeolite were 456 m² g^?1, 0.1591 cm³ g^?1 and 1.395 nm respectively. Zeolite Y synthesized using the split technique possessed physiochemical properties comparable to the commercial zeolite Y, it was also free of quartz and competing phase impurities reported in previous works. The as-synthesized REY zeolite resulted to 79% sulfur reduction when used as a catalyst in a microwave desulfurization of model diesel at 100?°C for 15 min.     

Micronization of Iron Oxide Particles Using Gas Antisolvent Process

Iron oxide particles were micronized by supercritical carbon dioxide (CO₂) as an antisolvent in a batch gas antisolvent (GAS) process. In the present study, the feasibility of GAS process to micronize the iron oxide particles using dimethyl sulfoxide (DMSO) as a solvent was investigated. In this direction, particle size and morphology changes were investigated with changing solution pressure (80–150 bar), temperature (308.15–328.15 K), and concentration (1.5–6 g/l). Based on the different experimental conditions, the particle size of the original iron oxide was decreased in the range of 17.25 to 4.23 µm, which shows a the success of the GAS process to reduce the particle size of the intact iron oxide particles. Simultaneously, morphology changes were observed starting from the irregular morphology for synthesized particles to more regular shapes that included fused and spherical-fused particles.     

Green Synthesized Iron Oxide Nanoparticles Effect on Fermentative Hydrogen Production by Clostridium acetobutylicum

A green synthesis of iron oxide nanoparticles (FeNPs) was developed using Murraya koenigii leaf extract as reducing and stabilizing agent. UV–vis spectra show that the absorption band centred at a wavelength of 277 nm which corresponds to the surface plasmon resonances of synthesized FeNPs. Fourier transform infrared spectroscopy spectrum exhibits that the characteristic band at 580 cm^?1 is assigned to Fe–O of γ-Fe₂O₃. Transmission electron microscopy image confirms that the spherical with irregular shaped aggregates and average size of nanoparticles was found to be ～59 nm. The effect of synthesized FeNPs on fermentative hydrogen production was evaluated from glucose by Clostridium acetobutylicum NCIM 2337. The hydrogen yield in control experiment was obtained as 1.74?±?0.08 mol H₂/mol glucose whereas the highest hydrogen yield in FeNPs supplemented experiment was achieved as 2.33?±?0.09 mol H₂/mol glucose at 175 mg/L of FeNPs. In addition, the hydrogen content and hydrogen production rate were also increased from 34?±?0.8 to 52?±?0.8 % and 23 to 25.3 mL/h, respectively. The effect of FeNPs was compared with supplementation of FeSO₄ on fermentative process. The supplementation of FeNPs enhanced the hydrogen production in comparison with control and FeSO₄. The supplementation of FeNPs led to the change of the metabolic pathway towards high hydrogen production due to the enhancement of ferredoxin activity. The fermentation type was shifted from butyrate to acetate/butyrate fermentation type at the addition of FeNPs.     

Preparation of cellulose-based fluorescent materials using Zinc sulphide quantum dot-decorated graphene by a one-step hydrothermal method

Cellulose-based fluorescent materials using Zinc sulphide (ZnS) quantum dot-decorated graphene were prepared by a one-step hydrothermal method. X-ray photoelectron spectroscopy analysis identified the chemical states of Zn, S, C, O, and N in the composite paper. Transmission electron microscopy showed that the graphite oxide was reduced to graphene sheets, and ZnS nanoparticles (<10 nm) were deposited on the surface of these sheets. Scanning electron microscopy indicated that graphene sheets were attached to the surface of paper fibers, and the paper structure and morphology of the fibers were not observably damaged during the hydrothermal reaction. The cellulose-based composite had strong ultraviolet absorption in the range of 200–340 nm, and its main absorption peak was at approximately 296 nm. The band edge emission of photoluminescence spectrum of the composite occurred at 466 nm with an excitation wavelength of 320 nm. The laser scanning confocal microscope image of the composite exhibited an intense blue fluorescence under UV light at 405 nm.     

19F Dynamic Nuclear Polarization and SEM in Suspensions Consisting of Fluorobenzene Derivatives and Asphaltene Extracted from MC-800 Liquid Asphalt

A variety of analytical techniques, such as scanning electron microscopy and ¹⁹F dynamic nuclear polarization (DNP) methods, are applied to characterize asphaltene extracted from MC-800 liquid asphalt in fluorobenzene derivatives at 1.53 mT and at room temperature. Different solvents show variable affinities for the asphaltene surface. The low field EPR spectrum of the asphaltene/hexafluorobenzene sample was recorded. The DNP parameters were determined. Additionally, the interactions between the nuclei of the solvent and the electrons delocalized on the asphaltene are interpreted. Not only dipolar but also scalar interactions between the nuclear spin and the electron spin were found.     

Improvement in Heat Transfer of a Two-Phased Closed Thermosyphon Using Silver-Decorated MWCNT/Water

Hereby, a comparative study of thermal and thermodynamic properties of nanofluids based on multiwalled carbon nanotubes (MWCNTs) and water is described. The first nanofluid includes pristine MWCNT while the second nanofluid prepared by MWCNT decorated with silver. To achieve the covalent functionalization, morphology of MWCNT-Ag was studied by transmission electron microscopy. Subsequently, the value of the entropy generation and thermal performance of nanofluids (MWCNT/water and MWCNT-Ag/water) were inspected in a two-phased closed thermosyphon (TPCT). The results suggested as the concentration and input power increased, the thermal resistance decreased. Also in different concentrations, the thermal efficiency of nanofluids obeyed the sequence: MWCNT-Ag (1 wt%) > MWCNT-Ag (0.5 wt%) > MWCNT (1 wt%) > MWCNT (0.5 wt%) > water. A variation of the vacuum pressure was also studied in the synthesized nanofluids as compared with pure water. The results were shown a lower pressure drop of MWCNT-Ag/water than MWCNT/water and the water. Also it was found that the higher thermal performance is produced using higher extent of covalent functional groups (with higher thermal conductivity). MWCNT-Ag/water can be an appropriate substitution for the water in the thermal equipment due to the intensive thermal efficiency and/or low thermal resistance compared with pure water.      

Novel photoconductive Ag/nanostructure ruthenium oxide/p-type silicon Schottky barrier diode by sol–gel method

A new Schottky photodiode of Ag/RuO₂/p-Si/Al was successfully fabricated using spin-coating technique. The ruthenium oxide (RuO₂) nanoparticles with an average size of 8 nm were synthesized using a sol–gel method. The crystal structure and morphology of the synthesized RuO₂ were analyzed by means of X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and selective area electron diffraction. The rectification ratio of the diode was found to be 112 at ±2 V. The ideality factor and barrier height values of the Ag/RuO₂/p-Si/Al diode were obtained to be 1.47 and 0.55 eV, respectively. The Cheung–Cheung and Norde’s models were used to determine the diode parameters. The photoresponse behavior of the fabricated Ag/RuO₂/p-Si/Al diode was studied under various illumination intensities. The transient photocurrent results indicate that photocurrent under illumination is higher than the dark current and this indicates that the fabricated diode behaves as a photodiode. The capacitance–voltage–frequency measurements indicate that the capacitance of the diode depends on voltage and frequency. The obtained results suggest that the new Ag/RuO₂/p-Si/Al diode can be used an optical switching device for optical sensor applications and are also expected to be generated in the future study.     

Effect of Curcuma longa tuber powder extract on size of silver nanoparticles prepared by green method

Biosynthesis of noble metal nanoparticles is a vast developing area of research. In the present study, silver nanoparticles (Ag-NPs) were synthesized from aqueous silver nitrate through a simple and biosynthetic route using water extract of Curcuma longa (C. longa) tuber powder, which acted simultaneousl as a reductant and stabilizery. The as-prepared samples are characterized using UV–Visible, XRD, TEM, SEM, EDXF, and FT-IR techniques. The formation of Ag-NPs is evidenced by the appearance of the signatory brown color of the solution and UV–vis spectra. Formation of Ag/C. longa was determined by UV–Vis spectroscopy where surface plasmon absorption maxima can be observed at 457–415 nm from the UV–Vis spectrum. The XRD analysis shows that the Ag-NPs are of a face-centered cubic structure. Well-dispersed Ag-NPs with anisotropic and isotropic morphology for 5, 10, and 20 mL of C. longa water extract having a size less than 10 nm are seen in TEM images. The optimum volume extraction to synthesize smallest particle size was 20 mL with mean diameter and standard division 4.90 ± 1.42 nm. FT-IR spectrum indicates the presence of different functional groups in capping the nanoparticles with C. longa. The zeta potential analysis results indicated that the charge of C. longa was negative and increased in Ag/C. longa emulsion with increasing of volumes of extract used (10–20 mL). The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries.     

Novel bulk synthesis of magnesium oxide nanobelts networks by microwave hydrothermal route

Novel magnesium oxide (MgO) nanobelt structures were successfully synthesized on a large scale, low cost and catalyst free by a microwave hydrothermal route using the magnesium metal and potassium hydroxide precursors at 200 °C for 10 min. The synthesized MgO nanobelts were systemically characterized by power X-ray diffraction (XRD), scanning electron microscopy, energy dispersion spectroscopy and transmission-high resolution electron microscopy. The XRD results indicate that the MgO nanobelts have the well-crystalline cubic phase. The detailed morphological studies revealed that the synthesized products were nanobelts and were grown in large quantity. The optical energy gap of MgO nanobelts was found to be 3.1 eV. The photoluminescence spectra of the MgO nanobelts show a strong and broad green emission band, a weak ultraviolet emission band, and a weak red emission band. This novel method will open new dimensions for synthesized 1-D metal oxide and can be easily extended to the synthesis and assembly of other inorganic nanocrystals.     

Lithographically Cut Multiwalled Carbon Nanotubes: Opening Caps,Controlling Length Distribution,and Functionalization

This work presents a microwave digestion heating method using a 40 ml mixture of potassium permanganate and sulfuric acid (3/1 mol) to cut, end-open, and functionalize as-prepared multiwalled carbon nanotubes (A-MWCNTs). Also, the ability of the microwave digestion method was studied at different reaction times (5, 10, 20, 30, and 40 minutes). To harness the extent of treatment, shortened multiwalled carbon nanotubes (S-MWCNTs) were fully characterized by UV-visible, Fourier transform infrared spectroscopy, and Raman spectroscopies, as well as, transmission electron microscopy and optical microscopy. The results showed that, with this mild treatment, the A-MWCNTs (>80 µm) were efficiently and significantly shortened to below 1 µm after 40 minutes. Also, heating the closed reaction vessel under microwave irradiation at 90°C for 20 minutes was very effective in the functionalization of MWNTs. At the same time, the S-MWCNTs formed the best state of dispersion in water without the help of surfactants that provided possibility for further functionalizations. For the first 10 minutes, crystallinity increased then decreased until 20 minutes, and after that improved slightly. Finally, the mechanism of this process is explained schematically. This method could be used as high-efficiency and damage-free process to the cut, end-open, and functionalization of CNTs that led to dispersion of CNTs and ultimately for such application.      

Cinnamoyl Pluronic F127 as a Stimuli-Sensitive Amphiphile

Cinnamoyl Pluronic F127 (CP F127) was prepared by reacting cinnamoyl chloride and Pluronic F127. On the ¹H NMR spectrum of CP F127, 1.2 moiety of cinnamoyl group was found to be attached to one molecule of CP F127. Using pyrene as a fluorescence probe, it was found that not only Pluronic F127 but also CP F127 could be readily assembled into micelles, and the critical micelle concentration was around 0.015 mg/ml and 0.03 mg/ml, respectively. Pluronic F127 in aqueous solution (2% w/v) could form no particles in 10–20°C, but particles (ca. 30 nm in diameter) were detected on a dynamic light scattering machine in 25–40°C possibly due to the thermal micellization. However, CP F127 was assembled into particles (ca. 230 nm) even in the lower temperature range, possibly because of the intermolecular hydrophobic interaction of the cinnamoyl group. The particle size of CP F127 strongly depended on the medium temperature and UV irradiation time. CP F127 was a good emulsifier for the preparation of O/W emulsions. The oil droplet size markedly increased upon UV irradiation (254 nm, 6 W), possibly because of the photo-dimerization of cinnamoyl group, but it was little affected by the temperature change (10–40°C).     

Silver Metallic Nanoparticles with Surface Plasmon Resonance: Synthesis and Characterizations

Silver nanoparticles were synthesized by the reduction of the silver nitrate (AgNO₃) using the latex copolymer in ethanol solution under microwave (MW) heating. The reaction parameters such as silver precursor concentration (from 0.005 to 0.1 g/l) and MW power (200–800 W) significantly affect the formation rate, shape, size and distribution of the silver nanoparticles. A significant reduction of irradiation time was observed when the MW energy is compared to conventional thermal reduction processes. The prepared silver nanoparticles show uniform and stable sizes from 5 to 11 nm, which can be stored at room temperature for approximately 12 months without any visible change. These peculiarities indicate that the latex copolymer is a good stabilizer for the silver nanoparticles. The optical properties, morphology, and crystalline structure of the silver-latex copolymer nanocomposites were characterized by the Ultraviolet–Visible spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The study of the TEM images at high magnifications identified the silver nanoparticles as face-centered cubic (fcc) structure with spherical and hexagonal shapes.