Chiral ligand exchange potentiometric aspartic acid sensors with polysiloxane films containing a chiral ligand N-carbobenzoxy-aspartic acid.

An enantioselective molecular sensor was fabricated by inserting a chiral ligand, N-carbobenzoxy-L-aspartic acid (N-CBZ-L-Asp) or N-CBZ-D-Asp, into an octadecylsiloxane (ODS) monolayer by polysiloxane film immobilization (PFI). The resulting system can recognize one enantiomer of aspartic acids (Asps) due to the chiral ligand exchange reaction at the N-CBZ-L-/D-Asp modified indium-tin oxide (ITO)-coated electrode. The enantioselective formation of diastereoisomeric complexes of Cu(II) with target enantiomers, in here L-/D-Asps, and N-CBZ-L-/D-Asp immobilized by PFI on the ITO electrode. Those diastereoisomeric complexes have different thermodynamic stabilities and Nernst factors and thus enable the sensors to convert the enantioselective recognition event into potential changes by detecting Asp enantiomers in a concentration range of (4.0 x 10(-8))-(8.9 x 10(-5)) M without any pre- or postseparation process. The enantiomeric selectivity coefficients of the sensors for the counterisomers were in the range of (4.0 x 10(-5))-(5.0 x 10(-5)).

A potentiometric protein sensor built with surface molecular imprinting method.

Surface molecular imprinting, as compared to molecular imprinted bulk polymers, has the advantages of higher re-occupation percentage of the reception sites, fast response, integration of sensing element and transducer, etc. In this study, a potentiometric protein sensor was developed based on the surface molecular imprinting technique. Using the self-assembled monolayers of alkanethiol with hydroxyl terminal groups as the matrix material, and target protein molecules as the template, the sensing layer was created on the surface of the gold-coated silicon chip-an electrochemical transducer. Potentiometric measurement demonstrated that the sensor could selectively detect myoglobin or hemoglobin molecules, either with or without the presence of other protein molecules in the same solution.

Potentiometric sensor for dipicolinic acid.

A potentiometric chemosensor for selective determination of dipicolinic acid (2,6-pyridinedicarboxylic acid, DPA) was developed based on the surface imprinting technique coupled with a nanoscale transducer: an indium tin oxide (ITO)-coated glass plate. The sensor fabrication conditions, optimal recognition condition, as well as selectivity, sensitivity, and stability of the DPA sensor have been investigated. The DPA sensor could recognize DPA from 3,5-pyridinedicarboxylic acid. Potentiometric measurements demonstrated selective detection of DPA in a concentration range of 1.5 x 10(-6) to 0.0194 M. The response time of DPA sensor for 4 x 10(-4) M DPA was 25 s. The potentiometric response of the DPA sensor to DPA is at 90% of its initial magnitude after 550 times measurement. The viability of such a modified ITO electrode in the presence of other inorganic, organic, and biological materials was probed.

Potentiometric sensing of chemical warfare agents: surface imprinted polymer integrated with an indium tin oxide electrode.

Rapid and specific recognition of methylphosphonic acid (MPA), the degradation product of nerve agents sarin, soman, VX, etc., was achieved with potentiometric measurements using a chemical sensor fabricated by a surface imprinting technique coupled with a nanoscale transducer, indium tin oxide (ITO). An octadecylsiloxane thin layer was covalently bound to the ITO-coated glass surface in the presence of MPA. After extraction of MPA, potentiometric measurements showed selective detection of MPA. The selectivity of the sensor has been tested on other alkylphosphonic acids, such as ethylphosphonic acid and propylphosphonic acid, as well as tert-butylphosphonic acid. The viability of the sensor in the presence of other chemical analogues, such as organophosphorus pesticides and herbicides, was investigated.