Electro-exploding Wire Technique Research Articles

Fabrication of WO3 electrochromic devices using electro-exploding wire techniques and spray coating

Electrochromic devices (ECDs) play an important role in smart window applications for blocking heat from sunlight. Tungsten trioxide (WO3) is one of the best candidates for making electrochromic films. Current manufacturing processes are, however, costly, have long processing time, and often use non-eco-friendly precursors. Here an alternative facile method integrating electro-exploding wire and spray coating techniques is demonstrated for applications in large size ECDs. The electro-exploding wire technique is used to synthesize WO3 nanomaterials (NMs) in deionized water. The varied size distribution of WO3 NMs is achieved by changing the exploding voltage. The NMs are characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The exploding voltage of 36 V is selected to generate WO3 NMs in a wide size distribution for making porous WO3 films. Subsequently, spray coating is used to disperse WO3 NM suspension on the ITO/glass substrate to form an electrochromic film. The films are characterized by scanning electron microscopy (SEM) and by cycle voltammetry, chronoamperometry, and chronocoulometry measurements in dilute sulfuric acid. The WO3 NM films prepared at a high exploding voltage and a high substrate temperature present a higher electrochemical stability. Considering porosity and electrochemical stability, WO3 NMs exploded at 36 V are used to prepare WO3 films on substrates heated at 300 °C. The electrochromic WO3 film can be operated for over 1000 cycles. We demonstrate an ECD with an area of 15 × 15 cm2 and propose a way to make large size ECDs with low cost and eco-friendly processes.

Au–ZnO hybrid nanostructures prepared by electro-exploding wire technique: Raman signal enhancement and photoluminescence emission quenching

Electro-exploding wire (EEW) technique was employed to prepare ZnO and Au–ZnO hybrid nanoparticles. Average size of the prepared ZnO nanoparticles is found to be 3.8 nm and uniform throughout. These ultrafine ZnO nanoparticles are found to agglomerate around the highly surface active Au nanoparticles. It also acts as a stabilizer for the Au nanoparticles by avoiding self agglomeration. The hybrid nanocrystals show strong crystallinity of face-centered cubic and hexagonal wurtzite structure of gold (Au) and zinc oxide (ZnO), respectively. Presence of Au3Zn in pristine sample is a clear indication of a strong interaction between ZnO and Au systems. The hybrid system shows strong enhancement in the ZnO Raman signals and quenching in the visible Photoluminescence (PL) emission. Energy-dependent PL analysis shows the dominance of the surface defects over the bulk contribution in these ultrafine ZnO and Au–ZnO hybrid nanostructures.

Processing temperature driven morphological evolution of ZnO nanostructures prepared by electro-exploding wire technique

This article presents an effective approach for the synthesis of ZnO nanoparticles with desired morphology via an environmentally benevolent electro-exploding wire (EEW) technique. In this process, ZnO nanoparticles evolve through the plasma generated from the parent Zn metal. Compared to other typical chemical methods, electro-exploding wire technique is a simple and economical technique that normally operates in water or organic liquids under ambient conditions. The effect of different processing temperatures in the range (5–80 °C), on the morphology of ZnO nanoparticles is clearly demonstrated. At 5 °C, nanoparticles with spherical morphology are observed. However, elliptical morphology is observed at room temperature and multipod nanorods at 50 °C and 80 °C. The evolution of ZnO phase is investigated with the help of time dependent UV-vis absorption and photoluminescence (PL) studies. The mechanism of formation and different morphologies of ZnO nanoparticles formed are also proposed.

Removal of Pb(II) and Cd(II) ions from water by Fe and Ag nanoparticles prepared using electro-exploding wire technique

This work aimed at investigating the adsorption of lead and cadmium onto Fe and Ag nanoparticles for use as a water contaminant removal agent as a function of particle type, sorbent concentration, and contact time. Fe and Ag spherical nanoparticles were prepared in water by the lab-made electro-exploding wire (EEW) system and were investigated for their structure properties. Adsorption experiments were carried out at room temperature and pH 8.3 water solutions. The removal/adsorption of both Pb(II) and Cd(II) ions was found to be dependent on adsorbent dosage and contact time. Pb(II) adsorption onto Fe and Ag nanoparticles showed more or less similar efficiency and behavior. The kinetic data for the adsorption process obeyed pseudo second-order rate equations. The calculated equilibrium adsorption capacities (q(e)) were 813 and 800 mg/g for Pb sorption onto Fe and Ag nanoparticles, respectively. Cd(II) ion adsorption onto Fe nanoparticles obeyed pseudo second-order rate equations with q(e) equal to 242 mg/g, while their adsorption onto Ag nanoparticles obeyed pseudo first-order rate equations with q(e) of 794 mg/g. The calculated q(e)s are in quite agreement with the experimental values. The removal/uptake mechanisms of metal ions involved interaction between the metal ion and the oxide/hydroxyl layer around the spherical metallic core of the nanoparticle in water medium. Fe and Ag nanoparticles prepared using the EEW technique exhibited high potentials for the removal of metal ions from water with very high adsorption capacities, suggesting that the EEW technique can be enlarged to generate nanoparticles with large quantities for field or site water purification.

ZnO nanoparticles prepared by an electroexploding wire technique

AbstractZinc oxide (ZnO) nanoparticles have been successfully prepared by an electroexploding wire (EEW) technique from pure zinc (Zn). The system comprises of a wire‐plate and a series of 12 V batteries. The formation of ZnO and nature of the crystallinity have been studied using X‐ray diffraction (XRD) and Raman analyses. The polycrystalline nature of the prepared nanoparticles is confirmed from the XRD studies. The time‐dependent UV–Visible absorption and photoluminescence (PL) studies confirm the evolution of ZnO nanoparticles from Zn obtained by the EEW technique. The sizes of the as‐prepared and annealed nanoparticles as estimated using the effective mass theory from the UV–Visible absorption are 8.9 and 22.0 nm, respectively. These are in agreement with those obtained from TEM micrographs. A broad and intense PL emission centered about 508 nm that is in the green region is observed. It is characteristic of the presence of defect energy states due to oxygen deficiency. From the energy‐dependent analysis of the PL emission, the green emission observed is concluded to be due to the bulk contribution rather than surface defects.

Study of fluorescence properties of Cu nanoparticles

Cu nanoparticles synthesized by an electro-exploding wire technique, exist in face centered cubic phase and average size is ∼13 nm. These nanoparticles are characterized by disappearance of plasmons. Fluorescence peaks are observed at ∼296 nm for excitation wavelength at ∼213 nm and ∼270 nm. In concomitant with these, resonant absorption are observed at ∼213 nm and ∼270 nm, which establishes a description of the electronic levels operating in this system. Intensity of the fluorescence peak increases with increase in concentration of the Cu nanoparticles. Further, effect of temperature (in range 20–90 °C) on fluorescence of the Cu nanoparticles has been reported for the first time, there intensity of fluorescence peak at ∼296 nm decreases with increase of temperature. In corroboration with these, intensity of the resonant absorption peaks also decreases with increase of temperature and with change in position of the emission wavelength from maximum intensity.

Synthesis and fluorescence properties of Ag nanoparticles

Ag nanoparticles synthesized by employing an electro-exploding wire technique exist in face-centered cubic phase with average size ∼10 nm. A surface plasmon peak is observed at ∼400 nm. Study of fluorescence properties of Ag nanoparticles shows fluorescence peaks at ∼300 nm for excitation wavelength in the range 220–270 nm. In concomitant with these, resonant absorptions are observed at ∼215 nm and ∼270 nm, which allow us to establish the electronic levels operating in the Ag nanoparticles system. Also, intensity of fluorescence emission increases with increase in concentration of Ag nanoparticles till a critical concentration. For the first time, we report temperature dependence of fluorescence of the Ag nanoparticles in the temperature range 20–90 ∘C. Where, the intensity of the fluorescence peak at ∼300 nm decreases with increase in temperature. Also, in conformity with these, probability of resonant absorption decreases with increase of temperature and with change in position of emission wavelength from maximum intensity.

Fluorescence properties of Ag nanoparticles in water, methanol and hexane

Ag nanoparticles, synthesized employing the electro-exploding wire technique, are reported. Absorption in the UV–visible region by these particles is characterized by the features reported in the literature, namely, a possible plasmon peak at ∼404 nm. For Ag nanoparticles dispersed in water, photo-excitation in the ranges 210–235 and 255–280 nm produces similar fluorescence emission at ∼300 nm, whose corresponding resonant absorption takes place at 215 and 270 nm in the excitation spectra. Further, we study the effect of the surrounding medium (solvent effect) on fluorescence from these nanoparticles by comparing fluorescence emission in methanol and hexane for photo-excitation in the same range. Compared to water, fluorescence emission in methanol is observed red-shifted at ∼310 nm, which further red-shifts to ∼325 nm in hexane. The corresponding resonant absorptions in methanol are at 225 and 275 nm. Consequence of this red-shift in a less polar solvent is discussed.

Synthesis and study of fluorescence properties of Cu nanoparticles

Cu nanoparticles have been synthesized by employing a novel electro-exploding wire (EEW) technique. These nanoparticles exist in the face-centred cubic (fcc) phase and their size is ∼6 nm. Further, the nanoparticles are characterized by disappearance of plasmons and show distinct resonant absorption at ∼222, 244, 280, 336 nm. A fluorescence peak at ∼296 nm has been observed at excitation wavelength in the ranges 200–240 and 250–280 nm. Position of the fluorescence peak remains fixed irrespective of the excitation wavelength used. Further, with increase in the concentration of the Cu nanoparticles in the range 0.5 × 1017–6.45 × 1018 atoms/cc, the intensity of the fluorescence peak, at ∼296 nm, increases. In concomitant with these, resonant absorptions are observed at ∼213 and ∼269 nm, evident from the fluorescence excitation spectrum which allows us to give a description of the electronic levels operating in this system. Fluorescence emission of the Cu nanoparticles is attributed to electronic transitions from excited states to 3d levels.

Fluorescence properties of Fe nanoparticles prepared by electro-explosion of wires

A novel electro-exploding wire technique has been employed to synthesize pure Fe nanoparticles. The Fe nanoparticles exist in a body-centered cubic (bcc) phase with an average size of the particles in the range ∼17 nm. A weak feature at ∼352 nm in the UV–vis absorption spectra has been established to be remnants of a surface plasmon peak, broadened due to the reduced particle size. Further, a fluorescence emission peak is observed at ∼303 nm for excitation wavelength in two different ranges, 220–250 nm and 255–280 nm. The position of the fluorescence peak remains fixed, irrespective of the excitation's wavelength employed. The fluorescence is assigned to electronic transitions from excited states to d levels of the Fe nanoparticles. In concomitant with these, two resonant absorptions are observed at 224 nm and 270 nm, evident from the fluorescence excitation spectra which allow us to give a description of the electronic levels operating in this system.

Ag–Au alloy nanoparticles prepared by electro-exploding wire technique

Homogenous Ag–Au alloy nanoparticles having an average size of 12 ± 2 nm were successfully prepared by the exploding wire technique comprising of a wire–plate system and using 12 V batteries. The X-ray photoelectron spectroscopy data reveal the formation of alloy nanoparticles with Ag80-Au20 composition, which agrees with the absorption data, obtained using UV-Visible spectroscopy. XPS also reveals a thin metal-oxide shell on the metallic alloy core. These alloy nanoparticles show visible fluorescence emission that was compared with the observed fluorescence from pure Ag nanoparticles. A mechanism for the observed fluorescence is also provided.

Magnetic Properties of Iron Nanoparticles Prepared by Exploding Wire Technique

Nanoparticles of iron were prepared in distilled water using very thin iron wires and sheets, by the electro-exploding wire technique. Transmission electron microscopy reveals the size of the nanoparticles to be in the range 10 to 50 nm. However, particles of different sizes can be segregated by using ultrahigh centrifuge. X-ray diffraction studies confirm the presence of the cubic phase of iron. These iron nanoparticles were found to exhibit fluorescence in the visible region in contrast to the normal bulk material. The room temperature hysteresis measurements upto a field of 1.0 tesla were performed on a suspension of iron particles in the solution as well as in the powders obtained by filtration. The hysteresis loops indicate that the particles are superparamagnetic in nature. The saturation magnetizations was approximately 60 emu/gm. As these iron particles are very sensitive to oxygen a coating of non-magnetic iron oxide tends to form around the particles giving it a core-shell structure. The core particle size is estimated theoretically from the magnetization measurements. Suspensions of iron nanoparticles in water have been proposed to be used as an effective decontaminant for ground water.

Fluorescence properties of Ag nanoparticles in water

Ag nanoparticles in water phase have been synthesized employing the electro-exploding wire technique. A surface plasmon peak is observed at 400 nm, characteristic of the Ag nanoparticles. A fluorescence emission peak is recorded at 300 nm for excitation wavelengths in two different ranges 215–230 and 255–280 nm. The position of the fluorescence peak remains fixed, irrespective of the excitation wavelength employed. These are assigned to electronic transition from different higher excited states to d levels of the Ag nanoparticles. In concomitant with these, there are two resonant absorptions at 5.76 and 4.59 eV as evident from the fluorescence excitation spectra.

The incorporation of silver nanoparticles into polypyrrole: Conductivity changes

Silver nanoparticles obtained by the electro-exploding wire technique were used to deposit on polypyrrole films prepared electrochemically. The presence of silver nanoparticles deposited was confirmed by X-ray diffraction. Energy dispersive X-ray spectroscopy was used to estimate the amount of silver nanoparticles deposited on polypyrrole. The current–voltage characteristics obtained from scanning tunneling microscopy showed remarkable changes in the electrical and the electronic properties of polypyrrole, which was also observed by the conventional two-probe method. The new approaches are the novel process used to produce pure silver nanoparticles and the simple and clean electro-deposition without the use of any chemical agents.

Fluorescent silver nanoparticles via exploding wire technique

Aqueous solution containing spherical silver nanoparticles of 20–80 nm size have been generated using a newly developed novel electro-exploding wire (EEW) technique where thin silver wires have been exploded in double distilled water. Structural properties of the resulted nanoparticles have been studied by means of X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The absorption spectrum of the aqueous solution of silver nanoparticles showed the appearance of a broad surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. The theoretically generated SPR peak seems to be in good agreement with the experimental one. Strong green fluorescence emission was observed from the water-suspended silver nanoparticles excited with light of wavelengths 340, 360 and 390 nm. The fluorescence of silver nanoparticles could be due to the excitation of the surface plasmon coherent electronic motion with the small size effect and the surface effect considerations