A route was developed for the synthesis of three different cyclodextrin adsorbates:  heptakis{6-O-[3-(thiomethyl)propionyl)]-2,3-di-O-methyl}-β-cyclodextrin, heptakis{6-O-[12-(thiododecyl)dodecanoyl)]-2,3-di-O-methyl}-β-cyclodextrin (a short and long alkyl chain sulfide cyclodextrin adsorbate, respectively), and heptakis[6-deoxy-6-(3-mercaptopropionamidyl)-2,3-di-O-methyl]-β-cyclodextrin (a short alkyl chain thiol adsorbate). Self-assembled monolayers on gold of these three cyclodextrin adsorbates with seven sulfur moieties were fully characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The electrochemical capacitance measurements show the differences between the thicknesses of the β-cyclodextrin monolayers, and the XPS-(S2p) measurements show the different effectivenesses of the sulfur moieties of the three monolayers in their binding to the gold surface. Sulfide-based β-cyclodextrin monolayers use on average 4.5 of the 7 attachment points whereas the thiol-based cyclodextrin monolayer only uses 3.2 of the 7 sulfurs. These experiments show that, for adsorbates with multiple attachment points, sulfides may be more effective than thiols. TOF-SIMS measurements confirm the robust attachment of these adsorbates on gold obtained by XPS.

We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of a-, b-, and g-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electrochemistry and wettability studies. On average about 70 % of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for b-cyclodextrin monolayers a quasihexagonal lattice with a lattice constant of 20.6 , which matches the geometrical size of the adsorbate. The a-cyclodextrin and g-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolay-ers of heptapodant b-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a b-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations ( 5 mm). The association constant for the binding of 1,8-ANS (K 289 000 AE 13 000 m À1 ) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the b-cyclodextrin strongly decreases the binding.

We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding.

Three different conformers of 1,3-diethoxy-p-tert-butylcalix [4] arene crown ethers have been used to study the effect of the ionophore preorganization on the potentiometric K + -selectivity. Selectivities were measured for chemically modified field effect transistors (CH EM FETs) and membrane ion-selective electrodes (ISEs) by two different methods. The ionophores show decreasing K + / N a + selectivities in the order: partial cone > 1.3-alternate > cone. As a function of time the cone conformer maintained a constant selectivity whereas a continuous decrease of the selectivity values was observed for the other two conformers. This supports our prediction based on the association constants and our previous 'H N MR studies on conformational stability.