The structural and optical constants of Ag2S semiconductor nanostructure in the far-infrared

Background In this paper a template-free precipitation method was used as an easy and low cost way to synthesize Ag2S semiconductor nanoparticles. The Kramers–Kronig method (K–K) and classical dispersion theory was applied to calculate the optical constants of the prepared samples, such as the reflective index n(ω) and dielectric constant ε(ω) in Far-infrared regime. Results Nanocrystalline Ag2S was synthesized by a wet chemical precipitation method. Ag2S nanoparticle was characterized by X-ray diffraction, Scanning Electron Microscopy, UV-visible, and FT-IR spectrometry. The refinement of the monoclinic β-Ag2S phase yielded a structure solution similar to the structure reported by Sadanaga and Sueno. The band gap of Ag2S nanoparticles is around 0.96 eV, which is in good agreement with previous reports for the band gap energy of Ag2S nanoparticles (0.9–1.1 eV). Conclusion The crystallite size of the synthesized particles was obtained by Hall-Williamson plot for the synthesized Ag2S nanoparticles and it was found to be 217 nm. The Far-infrared optical constants of the prepared Ag2S semiconductor nanoparticles were evaluated by means of FTIR transmittance spectra data and K–K method

Investigation on nonlinear-optical properties of palm oil/silver nanoparticles.

The study carried out using continuous wave diode pumped solid state laser with wavelength of 405 nm and power of 50 mW. The strong spatial selfphase modulation patterns were observed that suggest the palm oil/Ag-NPs have a relatively large nonlinear refractive index. The obtained values of nonlinear refractive index were increased with the increase of volume fractions. The observed experimental patterns were also theoretically modeled which are in good agreement with experimental results

The effect of laser repetition rate on the LASiS synthesis of biocompatible silver nanoparticles in aqueous starch solution.

Laser ablation-based nanoparticle synthesis in solution is rapidly becoming popular, particularly for potential biomedical and life science applications. This method promises one pot synthesis and concomitant bio-functionalization, is devoid of toxic chemicals, does not require complicated apparatus, can be combined with natural stabilizers, is directly biocompatible, and has high particle size uniformity. Size control and reduction is generally determined by the laser settings; that the size and size distribution scales with laser fluence is well described. Conversely, the effect of the laser repetition rate on the final nanoparticle product in laser ablation is less well-documented, especially in the presence of stabilizers. Here, the influence of the laser repetition rate during laser ablation synthesis of silver nanoparticles in the presence of starch as a stabilizer was investigated. The increment of the repetition rate does not negatively influence the ablation efficiency, but rather shows increased productivity, causes a red-shift in the plasmon resonance peak of the silver-starch nanoparticles, an increase in mean particle size and size distribution, and a distinct lack of agglomerate formation. Optimal results were achieved at 10 Hz repetition rate, with a mean particle size of ~10 nm and a bandwidth of ~6 nm 'full width at half maximum' (FWHM). Stability measurements showed no significant changes in mean particle size or agglomeration or even flocculation. However, zeta potential measurements showed that optimal double layer charge is achieved at 30 Hz. Consequently, Ag-NP synthesis via the laser ablation synthesis in solution (LASiS) method in starch solution seems to be a trade-off between small size and narrow size distributions and inherent and long-term stability

Dielectrical Properties of CeO2 Nanoparticles at Different Temperatures

A template-free precipitation method was used as a simple and low cost method for preparation of CeO2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO2 nanoparticles. The FT-IR spectrum of prepared CeO2 nanoparticles showed absorption bands at 400 cm(-1) to 450 cm(-1) regime, which correspond to CeO2 stretching vibration. The dielectric constant (er) and dielectric loss (tan delta) values of sintered CeO2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz

Hydrothermal synthesis of goethite (alpha-FeOOH) nanorods in the presence of ethylenediamine:thiourea

Goethite (alpha-FeOOH) nanorods were synthesized via the hydrothermal method with the assistance of coordinating ligands, i.e. ethylenediamine and thiourea. The homogeneity of the nanorod size distribution increased and the propensity to agglomerate decreased when ethylenediamine and thiourea were used in conjunction; contrary to goethite synthesis in the presence of a single ligand. The type and mode of structure-directing plays a critical role in the morphology of the final products. When using thiourea only or in combination with ethylenediamine, nanorods and nanoparticles of various morphologies were formed. Conversely, when exclusively using ethylenediamine, in addition to the nanorods, fine needles with a significantly smaller diameter were discernible. With all combinations, structurally uniform alpha-FeOOH nanorods were formed. This improved nanorod formation in the presence of both ligands might be attributed to a more ordered alignment and regular conformation of ethylenediamine molecules in the presence of thiourea and thus less susceptibility to thermal perturbations. Finally, higher concentrations of ligand influence the final product and increases particle aggregation

Graphical output of the WPPM modelling of CeO₂ (black open squares are the calculated data, red continuous line the observed data, and the lower blue continuous line is the difference curve between observed and calculated profiles).

<p>In the inset is reported ceria crystalline domain size distribution.</p

Dielectrical Properties of CeO₂ Nanoparticles at Different Temperatures - Fig 2

<p>(a) and (b) SEM images, (c) HRTEM image and (d) EDS analysis of the CeO2 nanoparticle.</p

FT-IR spectrum of CeO₂ nanoparticle.

<p>FT-IR spectrum of CeO₂ nanoparticle.</p