School of Biological and Chemical Sciences

New microbial quality testing for drinking water device

Supervisor: Dr Ali Zarbakhsh

Project description

The availability of fresh water is of upmost importance in the global context and water pollution is amongst the leading causes of death and disease. There is an urgent need for low cost, broad spectrum and highly sensitive biosensors to efficiently detect the presence of different contaminants (microbes) in water. Analytical methods that are available in laboratories to evaluate water quality are time-consuming and hugely expensive.

Some current devices meet the requirements for an efficient sensor for water quality; however, because of the optical waveguide aspect of the devices, they are cumbersome and lack portability. Hence their applications are limited to laboratory based analysis. It is important that robust, low cost, miniature and real time monitoring techniques with an appropriate sensitivity are available to complement the currently used spot-sampling and conventional laboratory techniques.

A novel way to make such devices portable and hence more practical would be to eliminate the need for the optical waveguide part. This can be achieved by replacing the optical waveguide of the sensor by a multilayer of an aliphatic substituted phthalocyanine and lipid bilayers, which can incorporate a metal centre in contact with NO2.

When contaminants are present in the water, lipid bilayers become compromised (degraded) and NO2 is free to leave the phthalocyanine region of the sensor. This produces a colour change which can be easily detected visually.

Phthalocyanine complexes with copper are known to exhibit a colour change when in contact with NO2. They are colourless when they form a complex with NO2, whereas they are dark green when the gas escapes. The presence or absence of NO2 will determine the colour of the phthalocyanine multilayer, leading to a colour change that can be easily visually detected. This provides a route for a possible design of a portable and relatively simple device. The structure of the proposed biosensor is relatively simple compared to the existing devices. A multilayer of aliphatic substituted phthalocyanine is deposited on a solid substrate which has been rendered hydrophobic by means of silane coupling. The structure is then saturated with NO2 and capped with a lipid monolayer that works as the sensitive biological element. The NO2 remains confined between the solid substrate and the lipid monolayer, keeping the phthalocyanine colourless. When the biosensor is in contact with uncontaminated water, the integrity of the lipid monolayer is maintained and there is no colour change in the sensor. When contaminants are present in the water, the lipid monolayer is compromised (red circles in the figure) and NO2 is free to leave the phthalocyanine region of the sensor.

Dr Zarbakhsh is seeking a PhD student to functionalize the phtalocyanine to be chemically adsorbed rather than physisorbed to the substrate, in addition characterisation of the device would be required using NR, AFM etc. Construction of specialist sample environment will allow small samples to be used in combination with the latest neutron focussing optics available at the Rutherford Appleton Laboratory, Oxfordshire, UK. Protocols will be established to routinely characterise the lipid overlayer structure in the presence and absence of contaminants. The student’s work will contribute in the area of thin film deposition techniques and the development of Neutron Reflectivity from small (2cm x 2cm) samples.

Eligibility and applying

International students must provide evidence of proficient English language skills. See our entry requirements page for further information.

Potential candidates should contact Dr Zarbakhsh by e-mail ( and submit their CV and a cover letter explaining their eligibility and interest in this project.


See also