Current and SnO2. Whilst 50 nm thickness can

Current advancements in the
field of magnetron sputtered thin film for pH sensing have been investigated. Various
metal oxides have been studied for Ph sensing applications. We have discussed
the potential of various metal oxide based pH sensing electrodes, and
highlighted the unique properties of ruthenium oxide and tin oxide electrodes
for various sensing applications, such as high sensitivity, good potential
stability, wide temperature range, fast response and outstanding corrosion


Furthermore, various
applications of magnetron sputtered pH sensors have been discussed, including
fluid quality analysis, glucose and cholesterol concentration monitoring and
bio-sensing. Here, the effects of conditioning-pH, RuO2, SnO2 material
thickness and oxidising/reducing agents on the sensitivity and hysteresis of
RuO2, SnO2  pH
sensitive working electrodes was investigated. It was shown that to obtain pH
sensor that exhibits 0.01 units of precision it is necessary to use an
electrode with at least 300 nm thickens of RuO2 and SnO2.
Whilst 50 nm thickness can be used to achieve a precision of 0.05 pH units.


Investigation of the redox
interference of these electrodes demonstrates that the pH sensitivity of RuO2
electrodes decreases due to the loss of active hydroxyl sites, caused by
oxidisation of RuIII. Whilst, the E0 value changes
depending on the proportion of RuIII to RuIV present in
the material. This provides a concise explanation for the sensitivity,
hysteresis, drift and ageing effects observed for these types of electrodes and
highlights the need protect them from redox interference, to increase their
application and use.


 In this project, the effect of Ar/O2 gas
ratio on the performance of RF sputtered RuO2 and SnO2 thin-film
pH sensors have been experimentally investigated. Several 300nm thin film RuO2
and SnO2 sensing electrodes, prepared by varying Ar/O2 gas
ratio from 10/0 to 7/3 during RF sputtering, have been developed and their
sensitivity, response time, stability, reversibility and hysteresis properties
for pH sensing have been investigated. Experimental investigations have shown
that an Ar/O2 gas ratio of 9/1 results in a RuO2 and SnO2
thin-film of excellent pH sensing properties, namely high sensitivity, low
hysteresis and faster response, using a conventional RuO2 and SnO2
sputtering target. The optimized pH sensor structure has demonstrated a
super-Nernstian response of 57.66 mV/pH, good stability and reversibility. The
developed pH sensor can further be miniaturized as a lab-on-a-chip device and
has application in biological analyses, water quality monitoring, chemical and
environmental monitoring and in vivo clinical tests.




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