Nanostructural and optical properties of hierarchical ZnO grown via hydrothermal method

A simple hydrothermal method was employed to synthesize 3D hierarchical ZnO nanorods deposited on Si (100) substrate at different growth temperatures (110 and 90oC) within 3 h. The structure, mode and composition of hierarchical ZnO nanorods were investigated by XRD, FESEM and EDX spectroscopy. The polycrystalline ZnO nanostructures products were indexed as hexagonal wurtzite structured, while the morphology was urchin like ZnO nanorods with different aspect ratio of nanorods and stoichiometric. The photoluminescence (PL) properties were studied of as-grown ZnO samples dependent on various growth temperatures. The PL results after UV excitation source were shown a single broad Vis emission peak for both samples with absents of UV emission peak. The emission edge of Vis peak was exhibited blue-shift due to increase temperature growth, and that suggest enhancement in hierarchical ZnO nanorods crystallinity. Oxygen deficiency is evidence on the creation various defects types in hierarchical ZnO nanorods. It is responsible on Vis emission bands. The results demonstrate promising future for the hierarchal ZnO nanostructure which could be applied in optoelectronics and gas sensing

Effect of etching time on optical and morphological features of N-type porous silicon prepared by photo-electrochemical method

Achieving efficient visible photoluminescence from porous-silicon (PSi) is demanding for optoelectronic and solar cells applications. Improving the absorption and emission features of PSi is challenging. Photo-electro-chemical etching assisted formation of PSi layers on n-type (111) silicon (Si) wafers is reported. Samples are prepared at constant current density (~30 mA/cm2) under varying etching times of 10, 15, 20, 25, and 30 min. The influence of etching time duration on the growth morphology and spectral properties are inspected. Room temperature photoluminescence (PL) measurement is performed to determine the optical properties of as-synthesized samples. Sample morphologies are imaged via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The thickness and porosity of the prepared samples are estimated using the gravimetric method. The emission and absorption data is further used to determine the samples band gap and electronic structure properties. Results and analyzed, interpreted with different mechanisms and compared

Fluctuating rainfall as one of the important cause for desertification in Iraq

Desertification is regarded as one of the most problems over the entire world. There are many reasons lead to this problem. Climatic factors such (rainfall, temperature and evaporation) are some of them. Annual rainfall amount is one of the most important parameters that lead to desertification for this reason it chosen to achieve this research. In this paper rainfall data with the help of Geographic Information System (GIS) to produce maps of Iraqi surface climate. In order to achieve this goal, the available data from a number of climate monitoring stations located on the surface of the country has been were adopted. The annual mean of rainfall for the period from 1990 to 2010 has been used. The Iraqi shape file map was used to overlay the results. The output of the research are presented in GIS maps that demonstrating the variation of rainfall over the study period for the monitoring climate stations

The effects of the ambient liquid medium on the ablation efficiency, size and stability of silver nanoparticles prepared by pulse laser ablation in liquid technique

Silver (Ag) nanoparticles (NPs) were synthesized by pulsed laser (Nd:YAG, 1064 nm) ablation of individual target in various solutions. The influence of deionized water (DIW), ethanol and Polyvinylpyrrolidone (PVP) as ambient medium on the fundamental aspects such as ablation efficiency, particle size and stability of Ag NPs was studied. UV-vis spectrophotometer and transmission electron microscopy (TEM) were used to study the optical characterization and morphological analysis of all the synthesized samples, respectively. Preparation in DIW was carried out as a reference sample. The experiments demonstrated that ablation efficiency and stability of NPs in ethanol medium are lowest than those prepared in PVP medium and the reference sample. PVP medium led to higher stability, lower ablation efficiency and finer average particle size compared to reference sample

Optimization of gold and silver nanoparticles production by laser ablation in deionized water

Colloidal solutions of gold and silver nanoparticles (NPs) were synthesized using a Q-switched Nd:YAG laser (1064 nm, 6 ns, 1 Hz ) ablation. Gold and silver bars were immersed in deionized water and irradiated by laser pulses for 4 min. The laser fluence was verified within the range of 21 – 39 J/cm2 with a fixed beam diameter of 1.6 mm. The effect of laser pulse fluence on both size and ablation efficiency of gold and silver nanoparticles were studied. The optical spectral characterization and morphological analysis of these nanoparticles were carried out by UV-Vis spectrophotometer and transmission electron microscopy (TEM), respectively. The average particle size for Au and Ag are 38.0 ± 10.3 nm and 31.3 ± 10.5 nm at corresponding optimized laser fluence of 31 and 25 Jcm-2 respectively

Structure, morphology and photoluminescence attributes of Al/Ga co-doped ZnO nanofilms: Role of annealing time

The influence of annealing time on the structure, morphology and photoluminescence behavior (Al)/(Ga) co-doped ZnO (AGZO). nanofilms are grown on the p-type Si(100) substrate via combined sol-gel, spin coating annealed in air at 500 °C at 0–3 h. Samples are characterized using XRD, TEM, AFM, FESEM, EDX, (PL) and Raman measurements. XRD pattern confirmed the growth of highly poly-crystalline hexagonal wurtzite structure of ZnO with preferred orientation along (101) direction. At (3 h) is found to cause lattice contraction and strain relaxation. TEM images revealed the nucleation of nanoparticles (NPs) and SAED pattern identified the lattice parameter. Raman spectra of AGZO exhibited optical and acoustic modes. FESEM displayed an increase in the particles size and number of nanoflakes with increasing annealing time. EDX detected right elemental traces. PL revealed an intense emission peak centered at 3.23 eV, which is continuously shifted toward lower frequency with increasing time

Proceedings of the Salford Postgraduate Annual Research Conference (SPARC) 2011

These proceedings bring together a selection of papers from the 2011 Salford Postgraduate Annual Research Conference(SPARC). It includes papers from PhD students in the arts and social sciences, business, computing, science and engineering, education, environment, built environment and health sciences. Contributions from Salford researchers are published here alongside papers from students at the Universities of Anglia Ruskin, Birmingham City, Chester,De Montfort, Exeter, Leeds, Liverpool, Liverpool John Moores and Manchester

Surface plasmon resonance effects of gold colloids on optical properties of N719 dye in ethanol

In this work, the light absorption and emission effects of gold nanoparticles on some optical properties of N719 dye solution were studied via transmission electron microscopy, UV-vis absorption, and photoluminescence spectroscopy measurements. A facile method to fabricate four gold colloidal solutions with different concentrations containing ~15 nm gold nanoparticles was presented through pulsed laser ablation of a gold target immersed in ethanol, followed by a post-ablated size modification process. As-prepared gold colloids with different concentrations were mixed with certain dye solution. The absorption and fluorescence enhancement that resulted from the interaction between the dipole moments of the day and the surface plasmon resonance of gold nanoparticles were found to be strongly dependent on the gold colloid concentration. Fluorescence was enhanced by around 9-fold, which was achieved for the dye solution with the highest gold nanoparticles concentration

Photophysical performance of radio frequency sputtered Pt/n-PSi/ZnO NCs/Pt photovoltaic photodetectors

The effect of the annealing temperature on the photoelectrical properties of the nanoporous silicon/zinc oxide nanocrystallites-based (Pt/n-PSi/ZnO NCs/Pt) photodetector was investigated. Different morphologies of 3D ZnO were synthesized onto the n-PSi substrates via radio frequency (RF) sputtering in the absence of a catalyst. The synthesis of ZnO NCs was controlled by varying the growth temperature between 600–700 °C and 800–900 °C. The effect of the synthesis temperature on the structural, morphological, and optical properties of the n-PSi/ZnO NCs was systematically studied using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence spectroscopy (PL) techniques. The roughness was found to be dependent on the anodization current density. The optimal n-PSi/ZnO NCs-based metal-semiconductor-metal UV detector (MSM) was fabricated at 700 °C. The fabricated device showed a high sensitivity of 1007.14, an internal photoconductive gain of 11.07, and a responsivity of 5.99 A/W with a low dark current when illuminated with 380 nm light (1.55 mW/cm2) at +5 V bias voltage. In addition, the response and recovery times were determined to be 0.34 and 0.22 s, respectively. This approach offers a cost-effective substrate and simple synthesis method to improve the growth of the n-PSi/ZnO NCs and demonstrates the successful fabrication of nanoscale photodetectors with potential application in nano-optics devices

Photo-electrochemically synthesized light emtting nanoporous silicon based UV photodetector: influence of current density

Nanoporous silicon (n-PSi) with diverse morphologies was prepared on silicon (Si) substrate via photo-electrochemical etching technique. The role of changing current density (15, 30 and 45 mA cm−2) on the structure, morphology and optical properties was determined. As-prepared samples were systematically characterized using XRD, FESEM, AFM and photoluminescence measurements. Furthermore, the achieved n-PSi sample was used to make metal–semiconductor–metal (MSM) UV photodetector. The performance of these photodetectors was evaluated upon exposing to visible light of wavelength 530 nm (power density 1.55 mW cm−2), which exhibited very high sensitivity of 150.26 with a low dark current. The achieved internal photoconductive gain was 2.50, the photoresponse peak was 1.23 A W−1 and the response time was 0.49 s and the recovery time was 0.47 s. Excellent attributes of the fabricated photodetectors suggest that the present approach may provide a cost effective and simple way to obtain n-PSi suitable for sundry applications