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Papers by Patrick S. M. Dunlop

Water Research, 2009

Photocatalysis is a promising method for the disinfection of potable water in developing countrie... more Photocatalysis is a promising method for the disinfection of potable water in developing countries where solar irradiation can be employed, thus reducing the cost of treatment. In addition to microbial contamination, water normally contains suspended solids, dissolved inorganic ions and organic compounds (mainly humic substances) which may affect the efficacy of solar photocatalysis. In this work the photocatalytic and photolytic

Journal of Nanoscience and Nanotechnology

Aligned titanium dioxide nanotubes may be grown on the surface of titanium metal by electrochemic... more Aligned titanium dioxide nanotubes may be grown on the surface of titanium metal by electrochemical oxidation in the presence of fluoride ion. There are a number of salient parameters that have been reported to affect the nanotube growth i.e., the nature, pH and concentration of the fluoride electrolyte, the cell potential and process time for anodisation. Furthermore, it has been reported that the nanotubes as grown are amorphous and can be converted to a mixture of anatase and rutile crystalline phases by heat treatment at elevated temperatures. There have been no studies reported investigating the effect of surface roughness of the parent titanium metal on nanotube growth. In this work the electrochemical growth of titanium oxide nanotubes on titanium foil was investigated using an ammonium fluoride/ammonium sulphate electrolyte. The results confirm that the anodisation potential controls pore diameter. The surface coverage of nanotubes was dependent on the surface roughness of t...

ACS Symposium Series, 2013

This book chapter discusses the syntheses of various nanomaterials, for green nanotechnology appl... more This book chapter discusses the syntheses of various nanomaterials, for green nanotechnology applications in detail. Special attention is given to the development of emerging areas, such as environmental as well as energy materials. Various approaches for preparing nanostructured photocatalysts, such as titanium dioxide, zinc oxide, iron oxide, and metal sulfides, different conventional methods and novel methods, including

Catalysis Science & Technology, 2014

As of 2010, access to clean drinking water is a human right according to UN regulations. Neverthe... more As of 2010, access to clean drinking water is a human right according to UN regulations. Nevertheless, the number of people living in areas without safe drinking water is predicted to increase by three billion by the end of this decade. Several recent cases of E. coli and Cryptosporidium contamination in drinking water are also reported in a number of advanced countries. Therefore ensuring the potability of drinking water is urgent, but highly challenging to both the developing and developed world in the future. A combination of solar disinfection and photocatalysis technology offers real possibilities for removing lethal pathogenic microorganisms from drinking water. The time taken for the conventional SODIS process can be greatly reduced by semiconductor (e.g. TiO 2 , ZnO, nano-heterojunctions) based photocatalysis. This review addresses the fundamental reaction mechanism, advances in materials synthesis and selection and recent developments in the reactor design for solar energy driven photocatalysis using titanium dioxide. The major advantage of using photo-reactors is that they enhance disinfection by increasing photon flux into the photocatalyst. Other major factors affecting such efficiency of solarbased photocatalysis such as the illuminated volume/total volume ratio, catalyst load and flow rate, are discussed in detail. The significance of using immobilised catalysts over the catalyst powder in slurries is also highlighted. It is noted that, despite encouraging early field studies, the commercialisation and mass production of solar photocatalysis systems remains highly challenging. Recommendations for future directions for addressing issues such as mass transfer, requirement of a standard test method, photo-reactors design and visible light absorption by TiO 2 coatings are also discussed.

International Journal of Photoenergy, 2011

It is estimated that 884 million people lack access to improved water supplies. Many more are for... more It is estimated that 884 million people lack access to improved water supplies. Many more are forced to rely on supplies that are microbiologically unsafe, resulting in a higher risk of waterborne diseases, including typhoid, hepatitis, polio, and cholera. Due to poor sanitation and lack of clean drinking water, there are around 4 billion cases of diarrhea each year resulting in 2.2 million deaths, most of these are children under five. While conventional interventions to improve water supplies are effective, there is increasing interest in household-based interventions to produce safe drinking water at an affordable cost for developing regions. Solar disinfection (SODIS) is a simple and low cost technique used to disinfect drinking water, where water is placed in transparent containers and exposed to sunlight for 6 hours. There are a number of parameters which affect the efficacy of SODIS, including the solar irradiance, the quality of the water, and the nature of the contamination. One approach to SODIS enhancement is the use of semiconductor photocatalysis to produce highly reactive species that can destroy organic pollutants and inactivate water pathogens. This paper presents a critical review concerning semiconductor photocatalysis as a potential enhancement technology for solar disinfection of water.

Analyst, 1998

The effect of different hole acceptors on the photocurrent response of particulate TiO 2 anodes w... more The effect of different hole acceptors on the photocurrent response of particulate TiO 2 anodes was investigated. In all cases there was a significant increase in the photocurrent over that observed for the photooxidation of water. The photocurrent efficiency observed in the presence of hole acceptors followed the order: oxalate > formate > acetate > methanol. The order of efficiency of the hole acceptors does not correlate with reported free hydroxyl radical reactivity constants or with reported oxidation potentials for the substrates studied. Adsorption measurements made in the dark showed that oxalate was much more strongly adsorbed on the electrode surface than either acetate or formate. Impedance spectroscopy indicated an increase in the capacitance of the system due to the presence of oxalate, both in the dark and under illumination.

Industrial & Engineering Chemistry Research, 2013

ABSTRACT Innovative sol–gel synthesis based on the self-assembling template method has been appli... more ABSTRACT Innovative sol–gel synthesis based on the self-assembling template method has been applied to synthesize mesoporous anion-doped TiO2 with N–F, S and C atoms using suitable surfactants and reagents, to improve simultaneously the structural, morphological, and electronic properties of TiO2 nanomaterials and achieve anion doping of titania with high visible light photoinduced reactivity. The incorporation of anion species in the titania structure resulted in the effective extension of TiO2 optical absorption in the visible range through the formation of intragap energy states. The anion-doped titania materials immobilized in the form of nanostructured thin films on glass substrates exhibited high photocatalytic efficiency for the degradation of the microcystin-LR (MC-LR) cyanotoxin, a hazardous water pollutant of emerging concern, under visible light irradiation. The development of these visible light-activated nanocatalysts has the potential of providing environmentally benign routes for water treatment.

2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006

There is a need for accurate, reliable methods of detecting bacteria for a range of applications.... more There is a need for accurate, reliable methods of detecting bacteria for a range of applications. One organism that is commonly found in urinary catheter infections is Staphylococcus epidermidis. Current methods to determine the presence of an infection require the removal of catheters. An alternative approach may be the use of in vivo sensing for bacteriavbiofilm detection. This work investigates electrical impedance spectroscopy to detect the growth of Staphylococcus epidermidis RP62A on gold electrodes fabricated on a flexible substrate. Impedance spectra measured during biofilm formation on the electrode surface showed an increase in charge transfer resistance (Rcr) with time.