Optical properties of CdS/PVA nanocomposite films synthesized using the gamma-irradiation-induced method

Monodispersed spherical CdS nanoparticles embedded into polyvinyl alcohol (PVA) films are synthesized by using an in-situ gamma-irradiation-induced method. The formation mechanism of CdS nanoparticles capped by two united cells of PVA is purposed by means of surrounding the CdS nanoparticles with OH bonds of the PVA chain. CdS nanoparticles are found to possess an unusual orthorhombic structure in monoclinic crystalline PVA. The polymer matrix affords protection from agglomeration and controls the particle size. It is found that the distribution of the prepared nanoparticles increases and a narrower size distribution is observed when the gamma radiation is varied from 10 to 50 kGy. While the average size of the nanoparticles is found to be less affected by the variation of the gamma radiation doses. The size range of the synthesized nanoparticles is 14±1 nm. The optical absorption spectra of synthesized CdS nanoparticles in a polymer matrix reveal the blue shift in the band gap energy with respect to CdS bulk materials owing to quantum confinement effect. The photoluminescence study of nanocomposite films shows the green emission arising from the crystalline defects

Synthesis and characterization of silicon nanorod on n-type porous silicon

This work reports a new method for growing semiconductor nanorods on a porous silicon substrate. After preparation of n-type porous silicon samples, a thin layer of gold was deposited on them. Gold deposited samples were annealed at different temperatures. The structural, thermal, and optical properties of the samples were studied using a field emission scanning electron microscope (FESEM), photoacoustic spectroscopy, and photoluminescence spectroscopy, respectively. FESEM analysis revealed that silicon nanorods of different sizes grew on the annealed samples. Thermal behavior of the samples was studied using photoacoustic spectroscopy. Photoluminescence spectroscopy showed that the emission peaks were degraded by gold deposition and attenuated for all samples by annealing

Influence of exposure time on structural, optical and electrical properties of zinc sulphide nanoparticles synthesized by microwave technique

Zinc sulphide (ZnS) nanoparticles were synthesized via simple, rapid and energy efficient microwave technique. The obtained nanoparticles were found to possess a cubic structure with an average particle size of less than 5 nm. By changing the microwave irradiation time from 5 to 30 min, the average size of nanoparticles increased and a broader size distribution was obtained. The degree of crystallinity also increased with increasing irradiation time and reached to maximum at 25 min and then fell by rising further the irradiation time. The absorption spectra of prepared ZnS nanoparticles revealed a blue shift in the band gap energy with respect to the bulk counterpart owing to the quantum confinement effect. The photoluminescence study showed the emission intensity increased with increasing the irradiation time up to 25 min due to the increment in crystallinity of the obtained nanoparticles. Further study indicated that the microwave irradiation time has also influenced the electrical properties of nanoparticles, so that the DC conductivity increased from 1.08×10-6 to 1.67×10-4 S/m for irradiation time of 5-25min and decreased to 1.74×10-6 S/m for further irradiation time at 30 min. The dielectric constant showed a power law dispersion with no observed peak for all samples with different irradiation times

Third-order nonlinear optical properties of silver nanoparticles mediated by chitosan

Silver nanoparticles in chitosan medium were prepared by the chemical reduction method. Silver nitrate and hydrazine were used as the precursor and reducing agent in the present of chitosan as a natural host polymer. The samples are characterized by UV–visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The measurements of nonlinear optical properties were defined by Z-scan technique using green CW laser beam operated at 532 nm wavelengths. Thermal effect has a dominant role in the overall material nonlinearity with CW laser. It is shown that the synthesized samples have a negative nonlinear refractive index

Structural, optical and electrical properties of ZnS nanoparticles affecting by organic coating

In this study the influence of the organic polymeric coating and its concentration on the structural, optical and electrical properties of ZnS nanocrystals has been investigated. In this matter, PVP-capped ZnS nanocrystals were prepared by a simple, rapid and energy efficient microwave method. The XRD results confirmed the formation of single phase cubic nano crystalline structure. TEM images showed the formation of well isolated spherical nanoparticles with the average size of less than 5.5 nm. The presence of tensile strain in all samples was determined from Williamson-Hall analysis. The elemental compositions of Zn, S and O were quantitatively obtained from EDX analysis, where the FT-IR spectra confirmed coordination with O atoms of PVP. The band gap and absorption edge shift was determined using UV–visible spectroscopy. The PL spectra of the PVP-capped ZnS nanoparticles appeared broadened from 370 to 500 nm due to the presence of multiple emission bands attribute to the sulfur and zinc vacancies or compounded effect of PVP. The electrical property study of samples indicated the conductivity enhancement from 2.981×10-6 to 7.014 ×10-6 S/m by increasing PVP concentration. Increasing of dielectric constant and decrease in the peak value of tan δ by raising the PVP concentration were observed

Optical Nonlinear Refractive Index of Laser-Ablated Gold Nanoparticles Graphene Oxide Composite

Gold nanoparticles were prepared in graphene oxide using laser ablation technique. The ablation times were varied from 10 to 40 minutes, and the particle size was decreased from 16.55 nm to 5.18 nm in spherical shape. The nanoparticles were capped with carboxyl and the hydroxyl groups were obtained from Fourier transform infrared spectroscopy. Furthermore, the UVvisible peak shifted with decreasing of nanoparticles size, appearing from 528 nm to 510 nm. The Z-scan technique was used to measure the nonlinear refractive indices of graphene oxide with different concentrations and a gold nanoparticle graphene oxide nanocomposite. Consequently, the optical nonlinear refractive indices of graphene oxide and gold nanoparticle graphene oxide nanocomposite were shifted from 1.63 × 10 −9 cm 2 /W to 4.1 × 10 −9 cm 2 /W and from 1.85 × 10 −9 cm 2 /W to 5.8 × 10 −9 cm 2 /W, respectively

Laser ablation synthesis of silver nanoparticle in graphene oxide and thermal effusivity of nanocomposite

In this study, the silver nanoparticle was prepared in graphene oxide by using laser ablation technique. The silver plate immersed in graphene oxide, and irradiated by Q-switch Nd:YAG laser at 532 nm wavelength during 10, 15, 30 and 60 minutes. The size and concentration of silver nanoparticle (Ag-NPs) shifted from 38 nm to 8 nm and 1.3 ppm to 9.6 ppm, respectively. Thermal effusivity was measured by using photoacoustic technique, and the results were analyzed using Rosencwaig-Gersho theory. This results shows the thermal effusivity of nanocomposite was increased with an increasing the concentration of silver nanoparticle from 0.1875 to 0.1979 W.s1/2.cm-2 .K-1

Gamma radiation induced synthesis and characterization of polyvinyl alcohol/polyaniline/CdS nanocomposite

The polymers/semiconductor nanoparticle composites were prepared from 60 g of polyvinyl alcohol (PVA), 12 g of aniline hydrochloride and different cadmium nitrate concentrations of 0.0462, 0.0924, 0.1386 and 0.186 g and different sulphur thiosulfate concentrations of 0.0372, 0.0744, 0.1116 and 0.15 g respectively in 600- ml deionized water at ambient condition. The aqueous composites were dried several days in a dark room to prepare for composite films which then undergone gamma irradiation with doses up to 50 kGy of Co-60 gamma-rays source at a constant dose rate. As a result, aniline monomers were converted to polyaniline (PANI) and cadmium and sulfur ions were converted to cadmium sulfide (CdS) owing to radiation oxidation and reduction processes respectively. The composites have been transformed into PVA/PANI/CdS nanocomposites and their structural, morphological, optical and electrical properties were characterized by using XRD, FESEM, UV-visible spectroscopy and impedance analyzer, respectively. The formation of crystalline growth of CdS nanoparticles was confirmed by sharp XRD peaks in the 2 range of 10° to 30° which possessed orthorhombic structure with crystal lattice parameter a= 7 Ǻ, b=7.9 Ǻ, c= 10.4 Ǻ and V=567 Ǻ 3 . While, the formation of PVA/PANI composites was confirmed by broad XRD peaks and branch shape FESEM images. The optical absorption spectra of PVA/PANI/CdS nanocomposites revealed characteristic peaks at 316 and 375 nm due to Cl powder and CdS nanoparticles, respectively; and a shoulder at 575 nm due to PANI. The band gap energy decreased from 1.85 eV to 1.65 eV for PANI and increased from 2.55 to 2.70 eV for CdS nanoparticles as the doses increased from 0 to 50 kGy. The dc conductivity of the PVA/PANI/CdS nanocomposites increased from about 4.4x10-7 to 2.4x10-4 S/m owing the creation of polarons in the PANI covalent structure as the doses increased from 0 to 50 kGy

A thematic-analytical review of knowledge production culture in architectural design

Architectural design, whether as a knowledge production process or as a ‘means’ for producing knowledge, has been the hot topic of theoretical debates since the late 1990s. Despite the developments, it requires more clarity as a young culture in the discipline. This research aims at deciphering the theoretical body to identify and bring the central themes into sight and provide a legible interpretation of knowledge production in architectural design. To this end, a unique methodology, adopted form content analysis, has been utilized. In this paper, a piece of the relevant literature was analysed by a computer application namely NVivo. The analysis has revealed a set of words from which the central themes are extracted. Out of thirty emphatic words, ten central themes are generated. According to the findings, ‘design and research’, ‘design process and methods’, and ‘newness and novelty’ appeared to be the key themes when knowledge production in architecture matters. The remaining seven themes are mainly included in the key themes. The findings show that knowledge production in architectural design is much more influenced by the field of design studies rather than architecture. This study remarks that the objective and generic aspect of architecture is investigated for knowledge production, however, taking architecture- specific dimensions into account could bring new insights into the discipline