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Doped Titanium Dioxide Nanostructures for Environmental Applications

Thesis Info

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Author

Siddiqa, Asima

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2484/1/2565S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725925121

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Titanium dioxide (TiO2) nanostructures have enormous application in various fields such as sensors, water splitting, super capacitors and, photovoltaic devices, etc. And they are extensively exploited for number of other energy and environmental applications now-a-days. As, the rapid urbanization and industrialization is polluting both water, air and existing developed technologies do not have adequate potential to overwhelm this environmental dilemma. Photocatalysis based on TiO2 nanostructures have procured significant attention in current era for the complete decomposition of hazardous compounds from water and purification of air due to low cost, thermal stability, chemical stability, huge surface area, non toxicity. This thesis is mainly focused on the use of doped nanostructure titanium dioxide as photocatalyst for environmental application specifically mineralization of dyes (alizarin red S, procion blue MXR, malachite green) and phenol, and photoreduction of carbon dioxide using un-doped and co- doped titanium dioxide nanostructures with anion i.e., sulfur (1 wt%) and transition metal ions (copper, cobalt, ruthenium, iron and chromium with varying the concentration from 1-5 wt %) having excellent chemical and photostability, good crystallite size, homogenous distribution, superior structural properties and excellent surface area and pore volume were synthesized by singe-step sol-gel reaction. The structural and morphological properties of prepared nanostructures were exploited by X-Ray Diffraction (XRD), Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy coupled with Energy Dispersive Spectroscope (FESEM- EDX), High Resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy, Thermal Analysis (TGA/DSC), Brunauer–Emmett–Teller (BET) surface analysis, Rutherford Back Scattering (RBS) and Fourier Transform Infra Red Spectroscopy (FTIR). The synergetic effect of anion and metal ion doping on titanium dioxide tailored the morphological and bulk superficial properties of the samples. Doping induced structural changes, enhancement of the visible light absorption capability, surface area, stability and photocatalytic activity. However, 5% metal ion co-doped titanium dioxide nanostructures demonstrated efficient band gap, thermal stability, good particle size, higher surface area and remarkably higher photocatalytic activity for photodegradation of dyes and phenol and CO2 photoreduction as compared to un-doped, S-doped and co-doped TiO2 with lower amount of metal ion. The parameters that affect the photocatalytic activity of TiO2 nanostructure powders for degradation of pollutants, namely concentration of dyes, catalyst loading, pH, irradiation source, and recyclability were optimized. The CO2 reduction and recycling of CO2 into value added products such as methane, methanol, ethanol, etc. was carried out under both UV and visible range and hydrogen was obtained from water in- situ. TiO2 nanostructures were found to be feasible and attractive for CO2 environment management and waste water treatment due to rapidness, cost effectiveness, catalyst inert nature, photostability and competent reusability. Hence, the activity of titanium dioxide nanostructure in visible range suggested that solar energy can be an alternative cost effective light source to resolve the environmental problems in future and this single step process can useful for industries.
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تدوین کے اصول و ضوابط

یہ بات اظہر من الشمس ہے کہ قدیم کتابوں کے مدونہ مطبوعہ نسخوں کا جب تجزیہ کیا جائے تو یہ بات سامنے آتی ہے کہ ان کتابوں کو صحیح اور مستند انداز میں مدونہ انداز سے نہ پرکھا گیا یعنی مدون حضرات نے اصول تدوین کو پیش نظر نہیں رکھا۔تساہلی اور سستی سے کام لے کر کتاب مرتب کروا کے چھپوا دینے میں عافیت محسوس کی جاتی رہی۔ یہی وجہ ہے کہ ایسی کتابوں نے مغالطے پیدا کرنے میں بڑا اہم کردار ادا کیا ہے۔دوسری طرف تنقید کے میدان کے شہسوار بھی اس کا شکار ہو گئے اور یوں تنقیدی مضامین میں غلطیاں وافر در آئیں، ان سے غلط نتائج اخذ کئے گئے لہذا کتاب کا صحیح اور مناسب طور پر مدون ہونا ضروری ہے تاکہ نہ مغالطے پیدا ہوں اور نہ ہی غلطیاں جنم لے سکیں۔
کتابوں کی تدوین جہاں انتہائی جا ں گسل کام ہے، وہاں نہایت ادق اور کٹھن مرحلہ ہے جس کو عبور کرنا ہر نقاد کے بس میں نہیں۔کسی کتاب یا مخطوطے کی تدوین و ترتیب کے لیے کچھ اصول و ضوابط کا لحاض رکھنا بہت ضروری ہے۔ان میں سے کچھ کا تعلق براہ راست مرتب و مدون کی ذات سے اور کچھ کا تعلق مصنف، کاتب اور کتاب کے متن سے ہے۔ امور ذیل کا ذہن میں رکھنا انتہائی ناگزیر ہے:
• کسی مخطوطے کی ترتیب و تدوین میں سب سے پہلی بات مخطوطے کی کیفییت و حالت بتائی جاتی ہے یعنی مخطوطہ مکمل ہے یا ناقص، اگر ناقص ہے تو نقص کہاں ہے ابتداء یا درمیان میں یا آخر میں۔
• کیا مخطوطہ کردہ خوردہ ہے تو اس کا متن کی صحت پر کیا اثر پڑے گا۔
• اگر آبزدہ ہے تو آبزدگی سے متن کہاں تک متاثر ہوسکتا ہے۔
• مخطوطے کا کاغذ کیسا ہے،کتنا خستہ ہے، خستگی یا...

استحکام خاندان میں زوجین کا کردار: سیرت طیبہ کا عملی و اطلاقی مطالعہ

In this universe, the most important relationship among the humans is marriage, other relations exist on the basis of this relationship. In the Holy Quran, the relationship of spouses has been mentioned as a source of mutual peace and love. In our society, it is said that women organize a home, but in reality a home can not be establish alone, spouses together make and adorn it with painstaking efforts. Man plays pivotal role in the relationship of spouses. So the responsibility of stability of the family lies on the man much more than the women and its reason is superiority. We find many examples from the marital life of our Prophet(S.A.W.W). This paper will highlight the teachings of Prophet Muhammad (S.A.W.W) about the role of spouses in the establishment of a family.

On the Characterization of Periodicity of Pores in Nanoporous Anodic Alumina

Small angle X-ray scattering (SAXS) has been performed on porous anodic alumina prepared at non-ordering conditions. These were prepared by two-step anodizing to have uniform through-thickness structure. The thickness of the membranes was of the order of 100-200 μm. The scattering has been explained based on structure factor; the magnitude of scattering vectors (q) corresponding to well-established peaks being multiples of 2 π /d, where d is the inter-pore distance. The usually studied form factor has not been found to play any profound role to determine the scattering response of anodic alumina. The scattering from PAA samples has been extremely anisotropic, where q always lies at about 90° with respect to the sample’s normal. A deviation from this angle which is limited to about ± 2° has been due to scatter of the pore axis with respect to sample’s normal, which is caused by occasional pore turning, branching or annihilation events. The analysis and methodology adopted in this study has also been suggested as extremely useful for determining the orientation of high-aspect ratio objects in an anisotropic sample along with assessing the degree of misalignment. Theoretically calculated / simulated structure factor (corresponding to interpore distance and interplanar distance) have been sucessfully fitted to SAXS spectra of PAA prepared by variety of conditions such as using single-step anodizing for various durations and double-step anodizing at various voltages. From these fittings useful quantitative informamtion such as lattice constant, interpore distance, long-range ordering (average domain size) and strctural disorder have been obtained, which previously was not possible through direct imaging techniques. PAA, prepared at ordering conditions by single-step and double-step anodizing, exhibit SAXS intensity peaks that correspond to two-dimensional hexagonal lattice. At all of the ordering voltages, long-range hexagonal pore ordering increases and structural disorder decreses with increase in time of anodizing during first-step of anodizing. PAA samples prepared at non-ordering voltages do not have hexagonal pore ordering, however, they exhibit regular interpore distance. SAXS analysis on the doubly-anodized samples prepared at ordering voltages reveal that the variation of pore axes in the ordered PAA is smaller than non-ordered PAA. Fitting of the simulated 2-D hexagonal lattice to the SAXS spectrum of PAA prepared (by both single step and two-step) at 60 V reveals that the sample possesses 2-D hexagonal nanoporous structure. Pore nucleation on surfaces with different pre-texture has been studied in detail. Electropolishing Aluminum surface in Perchloric acid-alcohol solution leads to nano stripes with Protrusions. These troughs in the nano stripes was found to have predominant role as pore nucleation sites in the subsequent anodizing at smaller voltages as well as larger voltage. The role of pre-texture was further investigated and confirmed by preparing a pre-textured surface which was prepared by anodizing at low voltage the electropolished aluminum followed by dissolution of the oxide grown which leaves nanopit surface for the subsequent anodizing at higher voltage. Anodizing at higher voltages on a pre-textured surface leads to the idea of pore exclusion zone that excludes the neighboring pore nucleating sites due to oxide flow in the subsequent anodizing. The study helps to understand pore nucleation at ordering at non-ordering voltages.