This document discusses sensing of organic vapors using copper phthalocyanine salt dispersed in sol-gel glass. The researchers dispersed copper phthalocyanine salt in a sol-gel glass matrix and exposed it to methanol and benzene vapors. They found the current increased upon exposure to both vapors, with a greater response to benzene. The activation energy of the material also decreased more after benzene exposure, indicating a change in electronic properties. This demonstrates the ability of copper phthalocyanine salt dispersed glass to sense organic vapors through changes in electrical conductivity and activation energy.

1. Sensing response of copper phthalocyanine salt dispersed glass with organic vapours
R. Ridhi, Sheenam Sachdeva, G. S. S. Saini, and S. K. Tripathi
Citation: AIP Conference Proceedings 1728, 020290 (2016); doi: 10.1063/1.4946341
View online: http://dx.doi.org/10.1063/1.4946341
View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1728?ver=pdfcov
Published by the AIP Publishing
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2. Sensing Response of Copper Phthalocyanine Salt Dispersed
Glass With Organic Vapours.
R.Ridhi, Sheenam Sachdeva, G.S.S. Saini and S.K. Tripathi*
Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014
(INDIA) Fax: +91-172-2783336; Tel.:+91-172-2544362
*Corresponding author: Department of Physics, Center of Advanced Study in Physics, Panjab University,
Chandigarh -160 014 (INDIA) Fax: +91-172-2783336; Tel.:+91-172-2544362.
*Email id: surya@pu.ac.in
Abstract. Copper Phthalocyanine and other Metal Phthalocyanines are very flexible and tuned easily to modify their
structural, spectroscopic, optical and electrical properties by either functionalizing them with various substituent groups
or by replacing or adding a ligand to the central metal atom in the phthalocyanine ring and accordingly can be made
sensitive and selective to various organic species or gaseous vapours. In the present work, we have dispersed Copper
Phthalocyanine Salt (CuPcS) in sol-gel glass form using chemical route sol-gel method and studied its sensing
mechanism with organic vapours like methanol and benzene and found that current increases onto their exposure with
vapours. A variation in the activation energies was also observed with exposure of vapours.
INTRODUCTION
Phthalocyanines modified with the functionalized substituents, which have discrete photoactive, redox active
units and multiple binding sites for various metal ions, are of great importance for a wide range of technological
areas [1]. The electronic properties of Metal Phthalocyanine (MPc) thin films are known to be affected by the
adsorption of oxidizing or reducing gases, which has led to the studies and applications of these materials in the field
of gas sensing [2]. The variation in conductivity or resistance of MPcs in the presence of gas or organic vapours is
one of the most commonly used parameters in sensor devices [3, 4]. MPcs and their functionalization with various
substituent groups make them selective and sensitive to various types of organic vapours or gaseous species [5]. In
the present work we have dispersed Copper Phthalocyanine salt (CuPcS) in sol-gel glass using sol-gel method and
exposed it with organic vapours (methanol and benzene) and studied the variations in current. The sensing response
is studied by taking the change in current of the sample onto the exposure of the vapour from that of initial current.
The sensing principle can be explained on account of charge transfer between the adsorbed vapours and MPcs. The
activation energies of the sample exposed with organic vapours have been found to be different from that of
unexposed and as prepared samples which again confirms the sensing of vapours by CuPcS dispersed glass.
EXPERIMENTAL
CuPcS dispersed glass has been prepared using chemical route sol-gel method. In this we first prepared a silicate
solution using Ethanol and Tetraethoxysilane in 50:50 mole ratio. 50 μl Hydrochloric acid (HCl) was added to
enhance solubility of the various solvents in the solution and for maintaining the required pH value. 4mL of Distilled
water was also added to the solution. The whole solution was then stirred for around 3 hours until a clear transparent
solution was obtained. Thereafter 5 mg of Copper Pthalocyanine-3, 4′, 4″, 4‴ tetrasulfonic acid tetrasodium salt
(CuPcS) was dissolved in 5mL distilled water and added into the prepared silicate solution. The resulting solution
was heated and stirred for about 2-3 hours. As soon as the gel started to form, heating and stirring were stopped and
the gel was allowed to cool and thereafter was vacuum dried for about 12 hours at room temperature to get the final
CuPcS dispersed sol-gel glass.
International Conference on Condensed Matter and Applied Physics (ICC 2015)
AIP Conf. Proc. 1728, 020290-1–020290-3; doi: 10.1063/1.4946341
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020290-1
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3. RESULTS AND DISCUSSION
In order to study the sensing response of adsorbed methanol and benzene vapours on CuPcS dispersed glass we have
studied the variations in current using digital Picoammeter (DPM-111 Model). In this two probe set up voltage was
applied with the help of Keithley (224 programmable current source). An evaluation of gas sensing properties was
carried out using same concentrations of methanol and benzene and passing them separately to CuPcS dispersed sol-
gel glass placed in a sample holder under vacuum and insulating conditions. The sensing response S% of CuPcS
dispersed glass has been calculated using the formula
%.100 S
S
SS
where S is the current of CuPcS dispersed glass in the presence of vapour and S0 is the current in the absence of
vapour. The obtained results are as shown in FIGURE 1.
From Figure 1, we observe that sensing response is more for benzene than for methanol. This is due to the fact that
increase in current with methanol exposure is due to the charge transfer between functionalized substituent group
(tetrasulfonic acid tetrasodium salt) of CuPcS dispersed glass [6] whereas in the case of benzene it is due to the
effect of both functionalized group and the central metal atom (Cu in the present case). As a result there is more
contribution of majority charge carries during the charge transfer mechanism of benzene with CuPcS dispersed glass
glass in the presence of vapour and S0 is the current in the absence of vapour. The obtained results are as shown in
FIGURE 1.
FIGURE 1. Sensing response of CuPcS dispersed glass with organic vapours.
The results of sensing response are confirmed by a decreased activation energy observed for benzene exposed
CuPcS dispersed glass as compared to methanol exposed and pure CuPcS dispersed glass as indicated in Figure 2
and Table 1. The activation energies are calculated using the formula
σ= σ0exp(-∆E0/kT)
where ∆E0 = Activation Energy
σ0= Constant
k= Boltzman Constant
T= Absolute Temperature.
The variations in activation energy is indicative of the fact that the electronic energy levels of CuPcS
dispersed glass are shifted onto exposure with organic vapours and accordingly their electronic energies and hence
conductivities are varied [6].
020290-2
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4. FIGURE 2. Variation of Conductivity with temperature.
TABLE 1. Calculated values of Activation Energies of CuPcS dispersed glass with and without exposure of organic
vapours.
Material Activation Energy (eV)
CuPcS dispersed glass pure 0.122
CuPcS dispersed glass
methanol exposed
0.1153
CuPcS dispersed glass
benzene exposed
0.1023
.
CONCLUSIONS
CuPcS dispersed glass shows an increase in current and hence enhanced sensing response onto the exposure of
organic vapours which is also confirmed by variations in the activation energy of CuPcS dispersed glass onto the
exposure with organic vapours.
ACKNOWLEDGEMENTS
This work is financially supported by University Grant Commission (UGC), N. Delhi [Major Research Project:
F.No. 42-781/2013 (SR)]. R. Ridhi is thankful to DST Inspire, New Delhi for providing the financial support for this
work.
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3. M. Martin, J. Andre, J. Simon, J. Appl. Phys. 54, 2792-2794 (1983).
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5. S. Hiller, D. Schlettwein, N. R. Armstrong, D. Wohrle, J. Mater. Chem. 8, 797-808 (1998).
6. S. Singh, G.S.S. Saini, S.K. Tripathi, Sensing of chemical vapors by Copper Phthalocyanine (CuPc) Thin Films,
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