We report the development of a chemical sensor based on a Co(II)
phthalocyanine acrylate polymer (Co(II)Pc-AP) for perchlorate anion
detection. We have used two types of transducers, silicon nitride
(Si
Sensors are widely used in various technological applications and have become
basic enabling technologies in many fields, including safety-related areas,
diagnostic and drug discovery, environmental monitoring and the food
industry. However, it is a frequent task of many analytical laboratories to
develop chemical sensors to detect many toxic ions that present an
environmental health risk to humans. Perchlorate can present a danger to the
thyroid gland, as it interferes with its iodine uptake and is associated with
the disruption of its function. The perchlorate can be taken up in place of
the iodide ion through the mammalian thyroid gland, and affects the hormone
production. In this way, perchlorate causes abnormalities in child
development and the thyroid development of cancer. Chemical sensors are based
on two important parameters, namely transducers and membranes. Cobalt
phthalocyanines are well known, with good chemical and thermal stabilities.
Relatively important attention has been paid to the potential utility of
these compounds as active sensing materials, molecular recognition species or
a promising class of ionophores (Kumar et al., 2012). Another important
component in the chemical sensor is the transducer. In the literature, many
chemical sensors are based on an insulator substrate in which the latter
plays an important role as a chemical barrier. Silicon dioxide or silica was
the most widely used in sensor devices (Wang, 2006; Castellarnau et al., 2007; Gustavsson et
al., 2008). However, some inherent disadvantages reduce its effectiveness for
passivation, and its high permeability toward water and other impurities (Chu
et al., 1967). To overcome these problems, the use of other insulators has a
larger permittivity and is more thermodynamically stable in contact with a
silicon like aluminum oxide (Al
In this work, we have developed two perchlorate sensors based on two types of
transducers, silicon nitride (Si
All the chemicals used were of an analytical reagent grade. Deionized
distilled water was used throughout. Tetrahydrofuran (THF), lithium
perchlorate (LiClO
The studied sensors are based on the EIS (electrolyte/insulator/semi-conductor) structure functionalized with Co(II)Pc-AP.
Silicon nitride: the studied Al/Si/SiO
Hafnium dioxide (HfO
Silicon nitride and hafnium dioxide transducers were cleaned for 15 min with
acetone in ultrasonic, and then rinsed with ultra-pure water and dried under
nitrogen flow. Afterwards, we spent time activating these surfaces:
the electrode based on hafnium was put in a
UV-ozone cleaner for 30 min; the nitride electrode has been activated by piranha
solution for 3 min and then rinsed with UPW and dried
with N2.
Using the spin coating technique, we have deposited 50
Contact angle histogram for Al/Si/SiO
Contact angle measurements were performed with a model contact instrument
(Digidrop) form GBX (Romans, France) in order to verify the presence of the
deposited thin film. First, we applied 5
All electrochemical experiments were conducted at
To investigate the hafnium and nitride surface quality, a wettability study
was performed. Before and after thin film deposition, the surfaces were
analyzed with water as the liquid probe. Figure 2 shows the evolution of the
contact angle as a function of the treatments performed on the transducer
surfaces. A contact angle of 76.3
C(V) characteristics of Al/Si/SiO
Variation of capacitance versus potential for the Al/Si/SiO
Figure 3 shows the measured C(V) characteristics before and after
functionalization of the transducer with the sensing molecule. A typical set
of C(V) curves was obtained and a decrease in the capacitance in the
accumulation regime was observed. This is due to the membrane deposited onto
the Si
Variation of the flat band potential of the
Al/Si/SiO
Evolution of the C(V) characteristics of Al/Si/SiO
Figure 4 shows the response of the
Al/Si/SiO
To study the pH sensitivity of the Al/Si/SiO
C(V) characteristics of Al/Si/SiO
Variation of capacitance various potential for the
Al/Si/SiO
Variation of the flat band potential of the
Al/Si/SiO
Evolution of the accumulation capacitance for
Al/Si/SiO
Evolution of the accumulation capacitance as a function of
ClO
The functionalization of the hafnium transducers has been followed by C(V)
measurements, as indicated in Fig. 7. To characterize the response of the
developed Al/Si/SiO
Figure 10 shows a linear capacitance variation as a function of perchlorate
concentration in the accumulation regime. We can notice that the capacitance
variation for the HfO
The specificity of the Al/Si/SiO
In this work, we have developed two capacitance sensors based on
Al/Si/SiO
Metrological parameters of the studied sensors based on Si
This work was partially supported by FP7-PEOPLE-2012-IRSES no. 318053: SMARTCANCERSENS and NATO Science for Peace (CBP.NUKR.SFP 984173) FP7-PEOPLE-2012-IRSES no. 318053: SMARTCANCERSENS.Edited by: M. Penza Reviewed by: two anonymous referees