Iron oxide nanoparticles synthesized by controlled bio-precipitation using leaf extract of Garlic Vine (Mansoa alliacea)

Iron (III) oxide nanoparticles were synthesized through green chemistry by the controlled reduction of hepta hydrous iron sulphate using the leaf extract of Garlic Vine. The crystalline phase of trivalent iron embedded in the primitive lattice of hexagonal β-Fe₂O₃ was obtained under the space group P3 (143). The scattered lines and considerably broadened peaks in the x-ray diffraction pattern indicate that the samples formed are crystallites of nano regime rather than bulk or amorphous in nature. Further, the size and the microstrain of the nanocrystallites were estimated through Hall Williamson analysis. The abundance of elemental iron present in the sample was estimated through Atomic Absorption Spectroscopy, whilst the UV visible analysis and FT-IR measurements, in accordance with XRD result, endorsed the formation of iron (III) oxide nanocrystals with iron predominantly occupying the octahedral sites. The band gap energy (2.84 eV) corresponds to the best fit is found to be for indirect allowed semiconducting transition between valance and conduction bands. Further, the TGA measurements were performed to identify the presence of capped polymer over the surface of nanoparticles, the organic decomposition temperature and phase transformation of meta-stable β-Fe₂O₃ to stable α-Fe₂O₃ at temperature above 500 °C.     

Tinospora cordifolia mediated facile green synthesis of cupric oxide nanoparticles and their photocatalytic,antioxidant and antibacterial properties

The study reports a facile method for the green synthesis of copper oxide nanoparticles (CuO Nps) by a solution combustion method using Tinospora cordifolia water extract. The Nps were characterized by XRD, SEM, TEM and UV–visible studies. XRD data indicates the formation of pure monoclinic crystallite structures of CuO Nps. SEM images show that the particles have sponge like structure with large surface area and the average crystallite sizes were found to be ~6–8 nm. These observations were confirmed by TEM analysis. Photocatalytic activity studies of CuO Nps reveal that they act as very good catalyst for the effective degradation of methylene blue (MB) in the presence of UV and Sun light. Also, the degradation of MB was found to be pH dependent. The Nps found to inhibit the activity of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals effectively. CuO Nps exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The study reveals a simple, ecofriendly and robust method for the synthesis of multifunctional CuO nanoparticle employing underutilized medicinal plants.     

Synthesis and nonlinear optical behavior of Ag nanoparticles in PMMA

In this work we have synthesized silver nanoparticles in Poly (methyl methacrylate) (PMMA). This was achieved by polymerizing the mixture of monomer and corresponding metal compound, followed by post-heating treatment. The linear absorption coefficient of the samples was measured using a spectrophotometer, where an absorption peak at 420 nm was observed. This peak grows up and shifts as a function of the concentration of the radical initiator. The linear refractive index was measured using the Fresnel equations and agrees with previous reported results. The nonlinear properties were obtained using the single lens Z-scan method, where the nonlinear absorption coefficient (Δα) was found between 5.5975514 and 17.9483493 cm⁻¹. The nonlinear refractive index coefficient (Δη) was found to be negative and its value oscillates between 12.9099 E-06 and 22.4276 E-06. Finally, the third-order coefficient (χ⁽³⁾) was calculated in the range of 233-787 E-9 esu.     

Electrochemical investigation of graphene/cerium oxide nanoparticles as an electrode material for supercapacitors

Mechanisms of charge storage, stability, capacitance, morphology and response current of graphene/cerium oxide (CeO₂) nanoparticles as an electrode material for electrochemical capacitors have been investigated. Electrochemical properties of the assembled electrodes were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques in 3 M NaCl, NaOH and KOH electrolytes. Scanning electron microscopy (SEM) is used to characterize the microstructure and the nature of prepared electrodes. SEM images confirm the layered structure (12 nm thickness) of the used graphene. The proposed electrode shows a maximum specific capacitance as high as 11.09 F g⁻¹ in the potential range between −0.55 and 0.3 (V vs. SCE) at scan rate of 5 mV s⁻¹. The charge/discharge cycling test shows a good reversibility and confirms that capacitance will increase after 500 cycles by 37%.     

Low temperature synthesis of PbS and CdS nanoparticles in olive oil

Heterocyclic dithiocarbamate complexes; bis(dipiperidinyldithiocarbamato)M(II) and bis(ditetrahydroquinolinyldithio-carbamato)M(II), M= Pb and Cd, were used as precursors for the synthesis of PbS and CdS in olive oil. The precursors were thermolysed at a relatively low temperature of 180 °C. Distinct cube shaped PbS nanoparticles were obtained with the X-ray diffraction peaks assigned to the cubic rock salt phase. The optical properties of the olive-oil capped CdS particles synthesized at 180 °C showed evidence of quantum confinement. The CdS particles obtained from both precursors were spherical in shape with evidence of agglomeration in the transmission electron microscopy images.     

Influence of the sol gel synthesis parameters on the photoluminescence properties of ZnO nanoparticles

In this work, ZnO NPs were successfully synthesized by the sol–gel method without any organic additives or post annealing. The effect of the preparation process on the structural and optical properties of the resulting NPs was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The structural characterization demonstrated clearly that the NPs crystallize in pure ZnO würtzite structure without any other secondary phases. Furthermore, we show that it is possible to perform the control of the crystalline growth orientation of ZnO NPs, which is a key parameter when seeking to develop ZnO NPs with piezoelectric properties for nano-transducer applications. In fact, TEM observations show that the reduction of the NaOH flow changes the NPs shape from hexagonal NPS to short nanorods grown along the c-axis. The PL spectra of the obtained NPs excited at 280 nm, present an UV emission centered at approximately 380 nm with a slight shift when varying the synthesis temperature and/or the NaOH flow. Moreover, as the visible region (from 400 to 650 nm) is concerned, it was shown that the increasing of the synthesis temperature affects strongly the kind of interstitial defects (O_i, Zn_i and V_oZn_i) formed in ZnO nanostructures. However, the excitation at 320 nm revealed a broad deep-level emission for all the samples that can be deconvoluted into two Gaussian peaks centered at 514 nm (P₁) and 581 nm (P₂). These last results have been discussed in the light of a physical mechanism based on the Schottky barrier.     

Nickel oxide nanoparticles: Synthesis and spectral studies of interactions with glucose

Nickel oxide (NiO) nanoparticles were successfully synthesized by the reaction of nickel chloride with hydrazine at room temperature and thermal decomposition of the precursor nickel hydroxide (Ni(OH)₂) nanoparticles. The products were characterized by X-ray diffraction, Transmission electron microscopy, Fourier transform infrared spectroscopy, and UV–vis absorption spectroscopy. The result of thermogravimetric analysis showed that the Ni(OH)₂ nanoparticles are calcinated at ～400 °C. The interactions between NiO nanoparticles and glucose have been studied using UV–vis absorption and fluorescence spectroscopy. The zeta-potential of NiO nanoparticles was used to gain insight about the interaction mode between NiO nanoparticles and glucose.     

银纳米颗粒印制导电图形的新途径—取代烧结

低温下完成烧结一直被认为是印制电子领域的一大难点,本文记述了一种新方法能够在避免烧结的情况下使银浆印制的图形导电。文中用液相法以硝酸银的乙二醇溶液作为前躯体,聚乙烯吡咯烷酮(PVP)作保护剂,还原得到平均粒径在90 nm的类球状银颗粒。该银颗粒的表面会被PVP包裹着,在一些电解质的作用下会发生脱附作用,使PVP层脱落。由于缺少了有机层的保护,邻近的银颗粒在表面作用力的驱动下会自主地结合在一起,随后会经历奥斯特瓦尔德熟化过程使得银颗粒发生重结晶。经历这些过程后整个银颗粒体系的导电率急速上升,其结果与高温下烧结的相似。用该方法获得的导电银图形的最低电阻率可达9.91Ωcm,导电性相当于块材的16%。     

Enhancement of electrical characteristics of electrospun polyaniline nanofibers by embedding the nanofibers with Ga-doped ZnO nanoparticles

Polyaniline nanofibers embedded with undoped ZnO nanoparticles (NPs) or Ga-doped ZnO (ZnO:Ga) NPs were fabricated and their structural and electrical properties were investigated. The uniform distribution of the NPs inside the polyaniline nanofibers was confirmed by transmission electron microscopy analysis. Polyaniline nanofibers embedded with ZnO:Ga-NPs showed their higher conductivities, compared with polyaniline nanofibers embedded with undoped ZnO-NPs. Single nanofibers electrospun from a mixture of a polyaniline solution with a 30 vol% ZnO:Ga-NPs dispersed-solution showed approximately five times higher conductivity than those electrospun from the polyaniline solution alone. This observation indicates that the embedding of the ZnO:Ga-NPs significantly enhances the electrical characteristics of the polyaniline nanofibers.     

Synthesis of iron oxide nanoparticles at low bath temperature: Characterization and energy storage studies

Ferric oxide powders were cathodically electrodeposited at a fixed bath temperature 8 °C. The obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogramimetric analysis (TGA). Scanning electron microscopic examination of the resultant powders revealed the formation of iron oxide nanoparticles with a grain size of approximately 20 nm. The adhesive deposit is obtained by reducing bath temperature. The increased adhesion is believed to result from the reducing kinetics energy of molecules and the rate of gas bubbling the electrode surface.     

A facile non-organometallic synthesis of hexadecylamine-capped ZnSe nanoparticles

The synthesis of hexadecylamine (HDA)-capped ZnSe nanoparticles via a facile method that is not mediated by organometallic compounds at low temperature is hereby reported. The synthesis involves the addition of an aqueous solution of zinc chloride to a selenide ion solution prepared by the reduction of selenium powder. By varying the reduction time, we studied the size, optical and structural properties of the as-synthesised nanoparticles. The as-synthesised ZnSe nanocrystals were characterised by UV–visible (UV–vis) absorption and PL spectroscopy, transmission electron microcopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). All the particles exhibited strong quantum confinement in their optical properties with band-edge luminescence.     

One-step, solid-state reaction to ZnO nanoparticles in the presence of ionic liquid

ZnO nanoparticles have been synthesized in ionic liquids (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) by one-step solid-state reaction at room temperature for short time. The structure and morphology of the products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM), whose results indicated that the sample was spherical in morphology with diameters of 15–20 nm. The room temperature photoluminescence spectra (PL) showed strong and broad green light emission. In addition, [BMIM]Cl could be collected and reused for subsequent reactions. This method provides a facile, one-step and low-cost route for the synthesis of nanostructures of metal oxides with potential photo-catalysis.     

Synthesis,characterization and optical band gap of La2CuO4 nanoparticles

Pure La₂CuO₄ nanoparticles were synthesized via sol–gel process using stearic acid as complexing reagent. This method consists of the formation of an organic precursor, with metallic cations homogeneously distributed throughout the matrix. The gel was calcined at 700 °C, 800 °C and 900 °C for 4 h. The as-prepared La₂CuO₄ nanoparticles were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy and diffuse reflectance spectroscopy. Results show that the purity of La₂CuO₄ crystallites increases with the increase of heat treatment temperature from 700 °C to 900 °C. Optical properties show that La₂CuO₄ crystallites have broad absorption in the UV–vis region and the corresponding band gap is 1.24 eV.     

Controlled positioning of metal nanoparticles in an organic light-emitting device for enhanced quantum efficiency

It is shown that there exists an optimum distance between the plane where nanoparticles (NPs) are positioned and the active layer of Au-NP-embedded organic light-emitting devices (OLEDs) for the maximum external quantum efficiency. Au NPs are precisely positioned in a specific plane in the hole-transport layer using a dry, room-temperature aerosol technique at atmospheric pressure. By controlling the position of the Au NPs and their density, we optimize the external quantum efficiency of the Au-NP-embedded OLEDs, with the maximum efficiency being 38% larger than that of the control device without Au NPs. In contrast to commonly employed methods to incorporate metal NPs in an organic layer, such as vacuum thermal evaporation or spin coating, the aerosol-deposited Au NPs do not penetrate into the underlying organic layer, not only allowing for precise control of the vertical (perpendicular to the substrate surface) position of the Au NPs, but also minimizing damage to the hole-transport organic material. Our electrical and optical characterizations show that the existence of the optimal distance occurs by the competition between the increased electron–hole recombination probability caused by the electrostatic effects of holes trapped in the Au NPs and the metal induced quenching.     

Microwave assisted synthesis of ZnO nanoparticles in ionic liquid [Bmim]cl and their photocatalytic investigation

In this study, ZnO nanoparticles were synthesized based on the chemical reaction of zinc acetate and NaOH in ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) under microwave irradiation. The prepared ZnO were characterized by utilizing various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, FT-IR spectroscopy, and BET method. XRD pattern reveals the produced ZnO has hexagonal structure and the images of SEM and TEM also reveal it consists of nanoparticles with an average size between 15 and 25 nm. The role of the ionic liquid on morphology of ZnO was investigated. For this purpose, a control ZnO sample was prepared without using any [Bmim]Cl. Photocatalytic properties of the synthesized ZnO on degradation of malachite green dye as model pollutant was investigated. The effect of various parameters such as pH, concentration of the dye and catalyst on the degradation of malachite green was investigated. In order to explore the mechanism of photocatalytic degradation of malachite green, scavenger addition method has been employed. It is found that hydroxide radicals are main reactive species for the degradation.     

Towards atomic-scale design: A theoretical investigation of magnetic nanoparticles and ultrathin films

This paper reports recent theoretical work on nanostructured materials including magnetic alloyed CoRh nanoparticles that are good candidates to combine both a large magnetic moment and a high magnetic anisotropy, and nanoscale Mn films adsorbed on W substrates as an example of artificial magnetic material. It illustrates how modern atomistic modeling and simulation can fruitfully supplement the experiments performed in the laboratory by helping to resolve and understand the experimental information, by predicting new phenomena and providing useful hints to guide the development of innovative materials with original, specifically tailored properties.     

A facile thermal-treatment route to synthesize the semiconductor CdO nanoparticles and effect of calcination

In this research, a thermal treatment method was used to synthesize cadmium oxide nanoparticles. The metal precursor, cadmium nitrate and a capping agent were dissolved in deionized water, which later was dried and crushed into powder. The powder underwent calcination treatment of 500, 550, 600, and 650 °C to crystallize the nanoparticles and to remove organic compounds. The structural studies of CdO nanoparticles have been carried out using EDAX, FTIR, XRD, SEM and TEM. The FTIR and XRD spectra showed that the crystalline structure formation of metal oxide nanoparticles has only occurred after been exposed to calcination. The optical properties which were determined using a UV–vis spectrophotometer showed a decrease in the band gap with increasing calcination temperature. These results prove that the thermal treatment method is a simple technique that can produce pure metal oxide nanoparticles with no other chemicals added.     

Investigation of structural,optical and morphological properties of copper doped zinc sulphide nanoparticles

Semiconductor nanoparticles doped with transition metal ions can influence the transition probabilities and electronic structure. The undoped and copper doped zinc sulphide nanoparticles with various concentrations are synthesized by wet chemical co-precipitation method. These nanoparticles are characterized by using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), UV–visible (UV–vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, conductivity measurement and time-resolved photoluminescence studies. X-ray powder diffraction analysis reveals that the synthesized samples have cubic zinc blende structure. The Scanning Electron Microscope shows the synthesized nanoparticles are agglomerated. The UV–visible spectra reveal the absorption edge is red shifted. The FT-IR spectra show vibrational peaks around 617 cm⁻¹ which indicate the presence of Cu–S stretching modes. The AC conductivity measurement confirms the semiconducting nature and shows a marked increase in conductivity as the doping concentration of copper increases. The photoluminescence shows that the emission at 426 nm may be due to transition from the conduction band to the zinc vacancies. These transition metal ions doped semiconductor nanoparticles have important applications in solid state lighting, imaging, and other photonic devices.     

Preparation of conductive flexible films by in situ deposition of polythiophene nanoparticles on polyethylene naphthalate

Deposition of Polythiophene (PTh) nanoparticles on the unmodified and modified polyethylene naphthalate (PEN) films via solution based in situ chemical polymerization was investigated as conducting transparent anode electrodes in order to produce transparent conducting films with applications in opto-electronic devices, such as flexible displays. The surface of PEN films were modified by different methods. Surface modification was carried out using Piranha and alkaline (KOH) solution and ultraviolet (UV) radiation as a physical method. Combination of chemical and physical treatments (Piranha and UV) was also examined. The effect of surface modification methods on the properties of the in situ deposited PTh nanoparticles was studied. It was found that electrical conductivity increases ~20 times in effect of modification of PEN by the examined methods. Highly ordered morphology of PTh nanoparticles were observed by field emission scanning electron microscope (FESEM) in the case of surface modification by UV radiation. Hydrophilicity, transparency and surface morphology of the PEN films were found to be influenced by surface modification techniques as well.     

Effect of lattice distortion on bandgap decrement due to vanadium substitution in TiO2 nanoparticles

Here we present a simple and effective way of bandgap tuning by V-substitution in TiO₂. The nanoparticles of Ti_(1-x)V_xO₂ (for 0≤x≤0.09) were prepared by controlled and simplified sol-gel method. The pure anatase phase of TiO₂ was confirmed by X-ray diffraction and Raman spectroscopy. Debye-scherrer formula and Williamson-Hall plot give crystallite size decreases from 10.8 to 8.2 nm when strain increases from 0.019 to 0.027 for x=0 to x=0.09. Rietveld refinement show the systematic change in crystal structure with the amount of V-substitutions. Raman shift and broadening of FWHM of first E_g (145.52 cm⁻¹) mode observed in Raman spectroscopy follow interestingly the similar and correlated observation with XRD outcomes. FESEM and UHRTEM represent pictorial view of the morphology of the nanoparticles with information about different micro-agglomerations and crystallinity. The oxidation states and local environment of elements in nanoparticles were studied using XANES. V-substitution in TiO₂ shows band gap moderation: band gap decreases gradually with substitution from 3.06–2.02 eV as concentration of V increases from x=0.0 to 0.09. This extends the application of TiO₂ in UV as well as visible light whereas the application of pure TiO₂ is limited in only UV region. The results of SEM, XRD, Raman spectroscopy and UV-vis spectroscopy are correlated well with lattice distortion and the lattice distortion gives the Urbach energy. We reach to the conclusion that the effective bandgap decreases may be due to creation of impurity energy levels or Urbach energy tails just above valance band and below conduction band.