Zn/ZnO core/shell nanoparticles synthesized by laser ablation in aqueous environment: Optical and structural characterizations

Zn/ZnO core/shell nanoparticles are synthesized by pulsed laser ablation (PLA) of Zn metal plate in the aqueous environment of sodium dodacyl sulfate (SDS). Solution of nanoparticles is found stable in the colloidal form for a long time, and is characterized by UV-visible absorption, transmission electron microscopy (TEM), photoluminescence (PL) and Raman spectroscopic techniques. UV-visible absorption spectrum has four peaks at 231, 275, 356, and 520 nm, which provides primary information about the synthesis of core-shell and elongated nanoparticles. TEM micrographs reveal that synthesized nanoparticles are monodispersed with three different average sizes and size distributions. Colloidal solution of nanoparticles has significant absorption in the green region, therefore, it absorbs 514·7 nm light of Ar⁺ laser and emits in the blue region centred at 350 and 375 nm, violet at 457 nm and green at 550 nm regions. Raman shift is observed at 300 cm⁻¹ with PL spectrum, which corresponds to ³E_2N and E_3L mode of vibrations of ZnO shell layer. Synthesis mechanism of Zn/ZnO core/shell nanoparticles is discussed.     

Studies on optical limiting characteristics of silicon nanoparticles synthesized by laser ablation

We present synthesis of silicon nanoparticles dispersed in toluene by laser ablation and studies on their optical limiting properties with nanosecond laser pulses at 532 nm. Silicon nanoparticles in toluene show better optical limiting compared to standard optical limiter fullerene C60 in toluene. Optical limiting threshold of silicon nanoparticles is about three times less than that of C60. Detailed studies using Z-scan experiments, angle dependent scattering, intensity dependent transmission and temporal profile measurements indicate that apart from non-linear scattering, nonlinear absorption and nonlinear refraction also contribute to the optical limiting behavior of silicon nanoparticles.     

Synthesis and optical characterization of copper nanoparticles prepared by laser ablation

The remarkable size-tunable properties of nanoparticles (NPs) make them a hot research topic with applications in a wide range of fields. Hence, copper (Cu) colloidal NPs were prepared using laser ablation (Nd:YAG, 1064 nm, 7 ns, 10 Hz, 6000 pulses) of a copper metal plate at different laser fluences (LFs) in the range of 1–2.5 J cm^?2 in ethylene glycol (EG), at room temperature. Analysis of NPs was carried using different independent techniques such as ultraviolet–visible (UV–vis) spectroscopy; transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. TEM analysis showed that the NPs were spherical with a bimodal distribution and an average particle size of 5 and 16 nm influence of 1.2 J cms^?2, and 9 and 22 nm at 2 J cm^?2. The UV–vis spectra of colloidal NPs revealed the maximum absorbance at around 584 nm, indicating the formation of Cu NPs, which supported using FTIR spectra. Furthermore, the absorption spectra confirmed the metallic nature of Cu NPs. FTIR spectroscopy was utilized to verify information about the NPs surface state and chemical bonds constructed in the atom groups apparent on their surface.     

Effect of temperature on the characteristics of ZnO nanoparticles produced by laser ablation in water

Effect of the water temperature on the characteristics of zinc oxide nanoparticles (NPs) produced by laser ablation process is investigated experimentally. The fundamental wavelength of a Q-switched Nd:YAG laser was employed to irradiate a high-purity zinc plate in distilled water at different temperatures of 0, 20, 40 and 60^°C. The produced NPs were diagnosed by UV–vis–NIR spectroscopy, X-ray diffraction method, transmission electron microscopy and scanning electron microscopy. Results show that with increase in the water temperature from 20 to 60^°C, size of NPs decreases while their bandgap energy increases. Maximum ablation rate occurs at the highest temperature. Crystalinity also increases with increase in the water temperature. The abnormal behaviour of water at 0–4^°C affects the NPs characteristics.     

Effect of pulsed laser annealing on optical and structural properties of ZnO:Eu thin film

Journal of Materials Science - ZnO:Eu thin film fabricated by pulsed laser deposition was treated by pulsed UV laser. The effect of laser fluence from 70 to 125 mJ cm?2 on film...     

Preparation of colloidal cadmium selenide nanoparticles by pulsed laser ablation in methanol and toluene

Colloidal spherical nanoparticles (NPs) of cadmium selenide (CdSe) have been prepared by laser ablation of cadmium target in methanol and toluene solutions. The properties of CdSe nanoparticles ablated in methanol and toluene were investigated and compared. The morphology and structure of synthesised CdSe NPs were analyzed by X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscope (TEM). XRD investigation revealed that the nanoparticles are crystalline and have hexagonal structure. Optical absorption showed that the value of optical energy gap of ablated CdSe nanoparticles depends on the solution type. TEM measurements showed that CdSe NPs with diameters ranging from 25 to 35 nm were synthesised in methanol while, the nanoparticles ablated in toluene have diameters in the range of (40–50) nm.     

Microstructure and optical characterization of nanometric silicon films prepared by pulsed laser ablation

The effect of laser energy density, during pulsed laser ablation, on the microstructure and optical properties of silicon films has been investigated using techniques such as atomic force microscopy, scanning electron microscopy, X-ray diffraction, and UV–visible absorption/transmission spectroscopy. The thickness of prepared films increases with increase in laser energy density. The crystallite size and hence the crystallinity of prepared films have been estimated by X-ray diffraction and found to be dependent on laser energy density. The transmittance of films changes with laser energy density. The absorption coefficient of films has been found to be?>10⁴?cm^?1 in wavelength region 450–1100?nm. The band gap of silicon films has been determined as 2.27, 2.11, and 1.90?eV corresponding to laser energy density of 1.5, 2.5, and 3.5?J?cm^?2, respectively.     

X-ray diffraction of permalloy nanoparticles fabricated by laser ablation in water

Permalloy (NiFeMo) nanoparticles were fabricated by laser ablation of bulk material in water with a UV pulsed laser. Transmission electron microscope images showed that approximately spherical particles about 50 nm in diameter were formed in the ablation process. All diffraction peaks corresponding to the bulk material were present in the nanoparticles. In addition to these peaks several new peaks were observed in the nanoparticles, which were attributed to nickel oxide.     

Effect of hydrolysis ratio on structural,optical and electrical properties of SnO2 nanoparticles synthesized by polyol method

Using the polyol method and a thermal post-treatment, nanoporous tin dioxide (SnO₂) were prepared at different hydrolysis ratio (h = n (H₂O)/n (Sn)). The influence of the hydrolysis ratio on the structural, textural, optical and electrical properties of SnO₂ nanopowders was investigated by employing a set of various techniques including Fourier Transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), Nitrogen Sorption Porosimetry and Impedance Spectroscopy. FTIR and EDX studies revealed that SnO₂ species were obtained. Nanocrystallites of cassiterite, i.e. rutile-like tetragonal SnO₂ structure, were formed after annealing in air at 700 °C and the average crystallite size increased from 12.8 to 29.1 when the hydrolysis ratio rose from 17 to 24. Moreover, TEM, SEM, and N₂ sorption porosimetry investigations indicated that the sample prepared for h = 17 was composed of an aggregated network of almost spherical nanoparticles, the morphology and sizes of which changed with the increase in the hydrolysis ratio to h = 24 and the mesoporosity of which was found to be linked to the interparticle space. Moreover, this increase in mean nanoparticle size was accompanied by a decrease in the band gap value from 3.4 eV (h = 17) to 3.16 eV (h = 24). Finally, bulk conductivity dependence with temperature was found to follow an Arrhenius law for samples annealed at 700 °C with an activation energy of 0.65 eV for h = 17, 0.69 eV for h = 20 and 0.71 eV for h = 24 that is typical of SnO₂ nanopowders.     

Effect of electric field on the properties of bismuth oxide nanoparticles prepared by laser ablation in water

In this work, preparation and characterization of α-Bi₂O₃ by pulsed laser ablation in water under effect of electric field is presented. UV–visible measurements showed that a red shift in the absorption spectra of Bi₂O₃ nanoparticles (NPs) was observed when the electric field increased. Applying electric field during laser ablation of Bi₂O₃ led to increasing the particle size. The morphological investigation, carried out using atomic force microscope, showed that the root mean square roughness and the grain sizes of Bi₂O₃ NPs are increase after applied of the electric field. Energy dispersive X-ray investigations confirm the complete oxidation of ablated bismuth after applying of electric field. X-ray diffraction patterns revealed that the structure of Bi₂O₃ remained polycrystalline with small diffraction intensity around (102) plane after applying of electric field.     

Nanoindentation and nanoscratch measurements on silicone thin films synthesized by pulsed laser ablation deposition (PLAD)

Nanoindentation and nanoscratch studies were conducted on silicone thin films synthesized by pulsed laser ablation deposition (PLAD). The nanoindentation studies showed that the modulus of the silicone films varied as a function of the energy density of deposition. The modulus values measured for PLAD silicone films were in the range of 1–6 GPa compared to 5–10 MPa reported for a typical silicone elastomer. Nanoscratch measurements also showed that PLAD silicone films exhibited much greater scratch resistance compared to silicone elastomer. These studies demonstrated that, even for low energy density depositions, the PLAD process can produced films which were are stronger and more abrasion resistant than conventional cross-linked silicone elastomers. Received: 27 June 2001 / Accepted: 27 June 2001     

Optical and structural characteristics of silicon nanoparticles thin film prepared by laser ablation

In this paper thin film of silicon nanoparticles on glass substrates have been prepared by dip-coating method using colloidal silicon nanoparticles generated by nanosecond laser ablation of silicon wafer in ethanol. The resulting nanoparticles and structural properties and morphology of thin film were characterized by UV-Visible absorption spectrometry, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction pattern and atomic force microscopy image. Nanoparticles with diameters ~ 9 nm were observed to be formed in the colloidal solution. The atomic force microscopy image of Si nanoparticles thin film shows that the overall average width is about 80 nm.     

CO sensing devices based on indium oxide nanoparticles prepared by laser ablation in water

A simple and effective solution route for synthesizing colloidal indium oxide (In₂O₃) nanocrystallites, i.e. laser ablation in liquid (LAL), is reported. The morphology and chemical structure of the as-prepared samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The results showed the formation of In₂O₃ nanoparticles with a bimodal distribution, consisting mainly of particles of small diameters (2-5 nm). Sensor devices prepared by spraying directly the LAL colloidal solutions on interdigitated alumina substrates exhibited good sensing properties for the detection of CO at very low concentrations.     

Synthesis of ceramic nanoparticles by ultrafast laser ablation of solid targets in water

We report production of nanoparticles of several advanced ceramics (Si3N4, SiC, AlN, and Al2O3) by ablation with femtosecond laser pulses of solid targets submerged in deionized water. The products withstand comparison with commercial nanoparticle suspensions obtained by other techniques as they are analyzed by means of transmission electron microscopy. As compared with metal nanoparticles produced with the same technique, we have found that the overall dependence of mean sizes and distribution widths on the laser fluence is similar. We explain why it is difficult to synthetize very small (<5 nm) and monodisperse particles in terms of ablation mechanism and discuss the aplicability of the technique for industrial production.     

Investigation on structural,optical and dielectric properties of Co doped ZnO nanoparticles synthesized by gel-combustion route

We report the synthesis of Co doped ZnO nanoparticles by combustion method using citric acid as a fuel for 0%, 1%, 3%, 5% and 10% of Co doping. The structural, optical and dielectric properties of the samples were studied. Crystallite sizes were obtained from the X-ray diffraction (XRD) patterns whose values are decreasing with increase in Co content up to 5%. The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure and Co²⁺ ions were successfully incorporated into the lattice positions of Zn²⁺ ions. The TEM image shows the average particle size in the range of 10–20 nm for 3% Co doped ZnO nanoparticles. The energy band gap as obtained from the UV–visible spectrophotometer was found gradually increasing up to 5% of Co doping. The dielectric constants (?′, ?″), dielectric loss (tan δ) and ac conductivity (σ_ac) were studied as the function of frequency and composition, which have been explained by ‘Maxwell Wagner Model’.     

Effect of substrate temperature on structural, optical and electrical properties of ZnO thin films deposited by pulsed laser deposition

ZnO thin films were grown by the pulse laser deposition (PLD) method using Si (100) substrates at various substrate temperatures. The influence of the substrate temperature on the structural, optical, and electrical properties of the ZnO thin films was investigated. All of the thin films showed c-axis growth perpendicular to the substrate surface. At a substrate temperature of 500 °C, the ZnO thin film showed the highest (002) peak with a full width at half maximum (FWHM) of 0.39°. The X-ray Photoelectron Spectroscopy (XPS) study showed that Zn was in excess irrespective of the substrate temperature and that the thin film had a nearly stoichiometrical composition at a substrate temperature of 500 °C. The photoluminescence (PL) investigation showed that the narrowest UV FWHM of 15.8 nm and the largest ratio of the UV peak to the deep-level peak of 32.9 were observed at 500 °C. Hall effect measurement systems provided information about the carrier concentration, mobility and resistivity. At a substrate temperature of 500 °C, the Hall mobility was the value of 37.4 cm²/Vs with carrier concentration of 1.36 × 10¹⁸ cm⁻³ and resistivity of 2.08 × 10⁻¹ Ω cm.     

Zinc nanoparticles in solution by laser ablation technique

Colloidal zinc metallic nanoparticles are synthesized using pulsed laser ablation of metal plate in an aqueous solution of suitable surfactant to prevent aggregation. UV-visible absorption, TEM, small angle X-ray diffraction and wide-angle X-ray diffraction are used for the characterization of colloidal zinc metallic nanoparticles. Colloidal nanoparticles are found highly stable for a long time.     

Surface morphology of AlN films synthesized by pulsed laser deposition

Surface morphology of AlN films, synthesized on Si substrates by pulsed laser deposition, has been examined by recording atomic-force-microscopy (AFM) images. The influence of N₂ ambient pressure, ranging from 5 × 10⁻⁴ Pa to 10 Pa, is reflected well in the alteration of the surface roughness and size of crystallites of the AlN films. A tendency of a decrease in the surface roughness with increasing N₂ pressure was observed, which also correlates with the polycrystalline structure of the films. Deposition in vacuum resulted in the highest surface roughness due to the large size of crystallites emerging from the surface, while increasing the nitrogen pressure yielded smaller crystallites and a smoother film surface. The presented results could be useful for applications of pulsed laser deposited AlN in different optical and acoustic devices, where the crystalline quality of the AlN films and the surface is very important.     

Optical measurement in carbon nanotubes formation by pulsed laser ablation

Carbon nanotubes (CNTs) were produced by laser ablation of a graphite composite target in argon and nitrogen ambient gas. To investigate the effect of nitrogen gas on CNTs formation, the plasma plume was examined using optical emission spectroscopy. The vibrational temperature of C₂ molecules was estimated by fitting of a Swan band spectrum. The temperature in N₂ ambient gas is lower than that in Ar ambient gas. In a nitrogen atmosphere, the spectrum intensity of C₂ Swan band was enhanced and CN violet system was also observed. Soot collected in the reaction tube was observed using FE-SEM and TEM. The soot deposited in the nitrogen gas contained more bundled CNTs than those in Ar ambience.