Photoconductivity of Pharma-Grade ZnO under UVA and White Light Exposure

2015 ◽  
Vol 1108 ◽  
pp. 73-78
Author(s):  
Ling Chuo Ann ◽  
Shahrom Mahmud ◽  
Siti Khadijah Mohd Bakhori ◽  
Amna Sirelkhatim
Keyword(s):  
Electron Microscopy ◽  
White Light ◽  
Light Exposure ◽  
Atomic Ratio ◽  
Surface Conductivity ◽  
Light Illumination ◽  
Long Wavelength ◽  
Transmission Electron ◽  
Zno Crystal ◽  
Zno Powder

In this study, we investigated the photoconductivity of pharma-grade zinc oxide (ZnO) which was excited under ultraviolet - long wavelength (UVA) and white light illumination. The morphological structures of ZnO were studied using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The ZnO sample was composed of micro/nanorods, slabs, tripods, tetrapods and irregular-shaped particles. The energy-dispersive X-ray spectroscopy (EDS) result revealed the high purity of ZnO, with the relative O/Zn atomic ratio lower than 1. The absorption spectrum of ZnO suspension was performed using UV-Visible spectroscopy. ZnO sample exhibited strong absorption at 387 nm, corresponding to optical bandgap of 3.23 eV. The ZnO powder was converted into pellets to study its photoconductivity under different intensity of UVA (0.5-2.0 mW/cm-2) and white light exposure (200-1000 lux) from conventional fluorescent lamp. The significant increase in surface conductivity of the ZnO pellets could be due to UVA illumination that produces photo-generated charge carriers on the surface of ZnO pellet. There was a small persistency of current flow after the UVA exposure was terminated. Under the white light exposure, the surface conductivity was slightly higher than that of dark condition. This is probably due to the small amount of defects, particularly oxygen vacancies and zinc interstitials that produce some light-generated charges on the ZnO crystal structures. The white light exposure may cause the excitation of electrons from the defects energy level to the conduction band, this being the underlying cause for the increase in the conductivity. ZnO pellet exhibited a dramatic enhancement of photoconductivity under UVA illumination if compared with small improvement of photoconductivity under white light exposure.

scholarly journals Photocatalytic Degradation of Tetracycline in Aqueous Solution Using Copper Sulfide Nanoparticles

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1238
Author(s):  
Murendeni P. Ravele ◽  
Opeyemi A. Oyewo ◽  
Sam Ramaila ◽  
Lydia Mavuru ◽  
Damian C. Onwudiwe
Keyword(s):  
Electron Microscopy ◽  
Aqueous Solution ◽  
Copper Sulfide ◽  
Degradation Rate ◽  
Light Exposure ◽  
Reaction System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Pure Phase

In this paper, spherical-shaped pure phase djurleite (Cu31S16) and roxbyite (Cu7S4) nanoparticles were prepared by a solvothermal decomposition of copper(II) dithiocarbamate complex in dodecanthiol (DDT). The reaction temperature was used to control the phases of the samples, which were represented as Cu31S16 (120 °C), Cu31S16 (150 °C), Cu7S4 (220 °C), and Cu7S4 (250 °C) and were characterized by using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and absorption spectroscopy. The samples were used as photocatalysts for the degradation of tetracycline (TC) under visible light irradiation. The results of the study showed that Cu7S4 (250 °C) exhibited the best activity in the reaction system with the TC degradation rate of up to 99% within 120 min of light exposure, while the Cu31S16 (120 °C) system was only 46.5% at the same reaction condition. In general, roxbyite Cu7S4 (250 °C) could be considered as a potential catalyst for the degradation of TC in solution.

scholarly journals Structural Changes of Mo/ZSM-5 Catalysts During the Methane Dehydroaromatization

2009 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
Z.R. Ismagilov ◽  
E.V. Matus ◽  
I.Z. Ismagilov ◽  
M.A. Kerzhentsev ◽  
V.I. Zailovskii ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Atomic Ratio ◽  
X Ray ◽  
Reducing Atmosphere ◽  
Structure Changes ◽  
Transmission Electron ◽  
Methane Dehydroaromatization ◽  
Naoh Treatment ◽  
Mo Content

<p>The structure changes of Mo/ZSM-5 catalysts with different Mo content (2 and 10 wt. % Mo) and Si/Al atomic ratio (17, 30 and 45) during the methane dehydroaromatization have been investigated by X-ray powder diffractometry, N<sub>2</sub> adsorption and transmission electron microscopy. The treatment of Mo/ZSM-5 catalysts in reducing atmosphere (CH<sub>4</sub> or H<sub>2</sub>) at about 700 °C promotes development of mesoporous system. The pores are open to the exterior of the zeolite grain and have an entrance diameter of ~ 4-10 nm. It is proposed that mesopore formation in Mo/ZSM-5 catalyst is connected with the dealumination of zeolite. The mesopore formation in the parent H-ZSM-5 zeolite by NaOH treatment does not improve the activity of /ZSM-5 catalyst.</p>

scholarly journals Age Hardening of Extruded AA 6005A Aluminium Alloy Powders

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2316
Author(s):  
Feijoo ◽  
Cabeza ◽  
Merino ◽  
Pena ◽  
Rey
Keyword(s):  
Electron Microscopy ◽  
Heating Temperature ◽  
Hot Extrusion ◽  
Atomic Ratio ◽  
Age Hardening ◽  
Al Alloy ◽  
Ingot Metallurgy ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Peak Aging

Pre-alloyed micron-sized 6005A Al alloy (AA 6005A) powders, with a Mg/Si atomic ratio of 0.75, obtained by high pressure inert gas atomization were consolidated by uniaxial cold pressing at 200 MPa into cylindrical Al containers and hot extruded at 450, 480 and 500 °C with an extrusion rate of 7:1, followed by artificial T6 precipitation hardening. Ageing conditions were varied between 170 °C and 190 °C and times of 6, 7 and 8 hours. The microstructure of the extruded profiles was analysed using X-Ray diffractometry (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) was used to study the possible phase transformations. After our results, the peak-aging hardness condition was achieved at 180 °C for 6 h. Mechanical properties of the powder metallurgy (P/M) aluminium alloys consolidated by hot extrusion were superior to those of the extruded profiles of wrought alloy using conventional ingot metallurgy (I/M) billets. AA 6005A wrought P/M alloy via T6 heat treatment shown yield stress of 317 MPa and elongation of 21% at the extrusion pre-heating temperature of 500 °C.

Identification of the occurrence of minor elements in the structure of diatomaceous opal using FIB and TEM-EDS

2019 ◽  
Vol 104 (9) ◽  
pp. 1323-1335 ◽  
Author(s):  
Peng Yuan ◽  
Dong Liu ◽  
Junming Zhou ◽  
Qian Tian ◽  
Yaran Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Internal Structure ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Minor Element ◽  
Atomic Ratio ◽  
Diatom Frustule ◽  
Minor Elements ◽  
Transmission Electron ◽  
And Storage

Abstract The occurrence of minor elements in the structure of biogenic diatomaceous opal-A is an important issue because it is closely related to biogeochemical processes driven by the precipitation, sedimentation, and storage of diatoms, as well as to the properties and applications of diatomite, which is the sedimentary rock composed of diatomaceous opal-A. However, to date, there is no direct microscopic evidence for the existence of minor elements, such as Al, Fe, and Mg, in the structure of diatomaceous opal-A, because such evidence requires observation of the internal structure of frustules to exclude the disturbance of impurity minerals, which is technically challenging using conventional techniques. In this work, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) mapping analysis were performed on diatomaceous opal-A from three typical diatomite specimens that were pretreated using focused ion beam (FIB) thinning. This technique produces a slice of a diatom frustule for direct TEM observation of the internal structure of the diatomaceous opal-A. The results of this work clearly indicate that minor elements, such as Al, Fe, Ca, and Mg, conclusively exist within the siliceous framework of diatomaceous opal-A. The contents of these minor elements are at atomic ratio levels of 1 (minor element)/10 000 (Si) – 1/100, regardless of the genus of the diatoms. The occurrence of minor elements in the internal structure is likely through biological uptake during biosynthesis by living diatoms. Moreover, surface coatings composed of aluminosilicates on diatom frustules are common, and the contents of elements such as Al and Fe are tens or hundreds of times higher in the coatings than in the internal siliceous structure of diatomaceous opal-A. The discovery of the incorporation of the above-mentioned minor elements in the diatomaceous opal-A structure, both in the internal Si-O framework and on the surface, updates the knowledge about the properties of diatomite.

Oxide Impurities in Silicon Oxide Intermetal Dielectrics and Their Potential to Elevate Via-Resistances

2014 ◽  
Vol 20 (4) ◽  
pp. 1271-1275 ◽  
Author(s):  
Wentao Qin ◽  
Donavan Alldredge ◽  
Douglas Heleotes ◽  
Alexander Elkind ◽  
N. David Theodore ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Silicon Oxide ◽  
Atomic Ratio ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Layer Deposition ◽  
Intermetal Dielectric

AbstractSilicon oxide used as an intermetal dielectric (IMD) incorporates oxide impurities during both its formation and subsequent processing to create vias in the IMD. Without a sufficient degassing of the IMD, oxide impurities released from the IMD during the physical vapor deposition (PVD) of the glue layer of the vias had led to an oxidation of the glue layer and eventual increase of the via resistances, which correlated with the O-to-Si atomic ratio of the IMD being ~10% excessive as verified by transmission electron microscopy (TEM) analysis. A vacuum bake of the IMD was subsequently implemented to enhance outgassing of the oxide impurities in the IMD before the glue layer deposition. The implementation successfully reduced the via resistances to an acceptable level.

TiO2-Al2O3 nanocomposites

1995 ◽  
Vol 10 (5) ◽  
pp. 1264-1269 ◽  
Author(s):  
G. Pacheco-Malagon ◽  
A. Garcia-Borquez ◽  
D. Coster ◽  
A. Sklyarov ◽  
S. Petit ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Critical Radius ◽  
Sol Gel ◽  
Atomic Ratio ◽  
Mas Nmr ◽  
Band Edge ◽  
Alumina Matrix ◽  
Transmission Electron

Nanosized TiO2 is synthesized in a nanosized alumina matrix by a sol-gel procedure. The results of the study of the blueshift of the TiO2 UV band edge are compared to the information obtained from transmission electron microscopy (TEM). As long as the atomic ratio Ti/Al remains smaller than 17.5%, no individualized TiO2 particles are detected by TEM, in spite of the fact that no modification of the alumina structure occurs, as revealed by 27Al MAS NMR. The shift of the UV band edge suggests the growth of homogeneous TiO2 domains in the alumina matrix. Above a critical radius, on the order of 1.2 nm, individual and crystalline TiO2 particles become visible in the TEM picture, and the porosity of the material decreases markedly.

Synthesis and Characterization of Porous Mo-W Oxide Nanostructures

2008 ◽  
Vol 8 (12) ◽  
pp. 6445-6450
Author(s):  
F. Paraguay-Delgado ◽  
Y. Verde ◽  
E. Cizniega ◽  
J. A. Lumbreras ◽  
G. Alonso-Nuñez
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Synthesis Method ◽  
Atomic Ratio ◽  
High Specific Surface Area ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Before And After

The present study reports the synthesis method, microstructure characterization, and thermal stability of nanostructured porous mixed oxide (MoO3-WO3) at 550 and 900 °C of annealing. The material was synthesized using a hydrothermal method. The precursor was prepared by aqueous solution using ammonium heptamolibdate and ammonium metatungstate, with an atomic ratio of Mo/W = 1. The pH was adjusted to 5, and then the solution was transferred to a teflon-lined stainless steel autoclave and heated at 200 °C for 48 h. The resultant material was washed using deionized water. The specific surface area, morphology, composition, and microstructure before and after annealing were studied by N2 physisorption, scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and X-Ray diffraction (XRD). The initial synthesized materials showed low crystallinity and high specific surface area around (141 m2/g). After thermal annealing the material showed higher crystallinity and diminished its specific surface area drastically.

Growth and structures of C60 shells

1997 ◽  
Vol 12 (6) ◽  
pp. 1545-1550 ◽  
Author(s):  
H. Sakuma ◽  
M. Tachibana ◽  
H. Sugiura ◽  
K. Kojima ◽  
S. Ito ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Amorphous Carbon ◽  
White Light ◽  
Shell Formation ◽  
Transmission Electron

The growth of the shells of C60 crystals was carried out under various conditions. The detailed structures of the grown shells were investigated by transmission electron microscopy and Raman spectroscopy. The shells were formed during thermal sublimation of the C60 crystals, which were irradiated with white light in air. The shells were mainly composed of a kind of amorphous carbon. From these results, it is suggested that the oxygen-induced disintegration of C60 cages is responsible for the shell formation.

Synthesis of Ni-Mo-W Sulfide Nanorods as Catalyst for Hydrodesulfurization of Dibenzothiophene

2008 ◽  
Vol 8 (12) ◽  
pp. 6406-6413 ◽  
Author(s):  
F. Paraguay-Delgado ◽  
R. García-Alamilla ◽  
J. A. Lumbreras ◽  
E. Cizniega ◽  
G. Alonso-Núñez
Keyword(s):  
Electron Microscopy ◽  
Physical Adsorption ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Precursor ◽  
Transmission Electron ◽  
Adsorption Of Nitrogen ◽  
Diffraction Patterns ◽  
Scanning Electron

Two trimetallic sulfurs, MoWNiS and MoWSNi, were synthesized to be used as a catalyst in hydrodesulfurization reactions. The mixed oxide mesoporous nanostructured MoO3-WO3 with an Mo:W atomic ratio of 1:1 was used as the precursor. The first catalyst was prepared by impregnating nickel in the oxide precursor and then subsequent sulfiding with an H2S/H2 mix at 400 °C for 2 hours. The second catalyst was prepared by sulfiding the precursor and then impregnating the nickel, and finally reducing the material with a H2/N2 at 350 °C. In both catalysts the Mo:W:Ni atomic ratio was maintained at 1:1:0.5. The materials obtained were characterized by physical adsorption of nitrogen, X-ray diffraction, scanning electron microscopy, transmission electron microscopy. Furthermore, the materials obtained were evaluated by a dibenzothiophene hydrodesulfuration reaction. The diffraction patterns show that both materials are polycrystalline and mainly of MoS2 and WS2 phases.

Morphological and Magnetic Properties of Electrodeposited Ni-Ag Alloy Nanowire Arrays in Modified AAO Template

2014 ◽  
Vol 875-877 ◽  
pp. 14-17 ◽  
Author(s):  
Wei Zheng Shang ◽  
Wei Guo Zhang ◽  
Hong Zhi Wang
Keyword(s):  
Electron Microscopy ◽  
Anodic Aluminum Oxide ◽  
Magnetic Hysteresis ◽  
Magnetic Hysteresis Loop ◽  
Atomic Ratio ◽  
Nanowire Arrays ◽  
Aao Template ◽  
Anodic Aluminum ◽  
Transmission Electron ◽  
Potential Applications

Highly ordered Ni-Ag alloy nanowire arrays have been fabricated successfully by electrodeposition into the pores of anodic aluminum oxide (AAO). This template was prepared with modified two-step anodizing method. The scanning and transmission electron microscopy were utilized to characterize the Ni-Ag alloy nanowire arrays. The results revealed that the nanowire arrays were regularly arranged, about 90nm in diameter and 30µm in length. The nanowires were single crystal and the atomic ratio of Ni and Ag is very close to 79:21. Magnetic hysteresis loop showed that Ni-Ag alloy nanowire arrays embedded in AAO have superparamagnetism, indicating their potential applications in biomedical materials.

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