Ž . Materials Science and Engineering C 7 2000 83–89 www.elsevier.comrlocatermsec wx Comparison of thiacalix 4 arene thin films behaviour on different transducers for copper ion detection M. Ben Ali a,b , C. Bureau c , C. Martelet a, ) , N. Jaffrezic-Renault a , R. Lamartine c , H. Ben Ouada b a Ingenierie et Fonctionnalisation des Surfaces, UMR CNRS 5621, Ecole Centrale de Lyon, BP 163, F-69131 Ecully Cedex, France ´ b Laboratoire de Physique des Interfaces, Faculte des Sciences de Monastir-5000, Monastir, Tunisia c Laboratoire de Chimie Industrielle, CNRS UPRES A-5078 UniÕersite Claude Bernard Lyon I, 43 Bd du 11 noÕembre 1918, ´ 69622 Villeurbanne Cedex, France Received 18 June 1999; accepted 18 June 1999 Abstract wx Thin thiacalix 4 arene films were deposited using a thermal evaporation technique in vacuum in order to functionalize different transducers: EIS, ISFETs and gold electrodes for copper ion detection. Electrochemical measurements allowed to characterise the Ž . wx Ž . membrane sensibility towards Cu II ions. The sensors based on thiacalix 4 arenersemiconductor transducers ISFET, EIS have shown a Ž . y5 Nernstian response towards Cu II with a detection limit of about 10 M. The functionalized gold electrode was used as copper sensor, several conditions were optimized in order to enhance the sensitivities at low concentrations. In particular, the polarisation of the wx electrode was adjusted in order to neglect the Warburg effects at low frequencies. The thiacalix 4 arenergold electrodes have shown a good sensitivity and a low detection limit of about 10 y7 M which has to be compared to the behaviour obtained with ISFET and EIS type sensors. q 2000 Elsevier Science S.A. All rights reserved. wx Keywords: Thiacalix 4 arene; EIS; ISFET; Impedance spectroscopy; Copper ions 1. Introduction Different transducers may be applied to convert a chem- ical input signal, i.e., the interaction of ions with organic supramolecular or polymeric compounds into an electrical output signal. In particular, both gold and siliconrsilicon dioxide substrates are well suited for signal transduction w x wx via electrochemical 1–3 and optical 4 methods. Among the devices based on such materials, one of the most w x studied is the field effect transistor ISFET 5–7 . A previ- ous work done on semiconductorrinsulatorrelectrolyte Ž . wx EIS structure 8 for understanding the working of the ISFET has also shown that these structures constitute a convenient model to investigate the behaviour of insulator electrolyte interface. To render these transducers ion sensi- tive, it is necessary to functionalize them with a suitable sensitive membrane based on ionophores which are able to recognize selectively cations and molecules according to a keyrlock interaction mechanism. Different materials have ) Corresponding author. been used in sensitive membranes for copper ion detection, wx wx specifically substituted calix 4 arenes 9 and electropoly- w x merized undoped polyinodole 10 . Calixarenes, firstly synthesized by C.D. Gutsche in the last years, are recognized to be important materials in the w x molecular and supramolecular chemistry field 11,12 . wx Calix 4 arenes are known to exhibit a great extractability against alkaline and alkaline earth cations but generally w x low affinity for transitions metal ions 13–16 . Consider- able efforts have been made to improve this behavior in particular by functionalization and introduction of het- eroatoms on the calixarene basis. For example, several reports deal with sulfur containing calixarenes. In the frame of these investigations, the synthesis of di- or tetra- wx w x mercaptocalix 4 arene has been described 17,18 . Another synthetic way to form a new calixarene consists of replac- ing the methylene bridge by a sulfur linkage but this was w x achieved with a poor yield 19 . The tetra substituted wx macrocycle is named p-tert-butylthiacalix 4 arene. Re- cently, a new one-step synthetic access has been investi- wx gated for thiacalix 4 arene synthesis with a satisfactory 0928-4931r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. Ž . PII: S0928-4931 99 00128-9