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Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Surface modification is a hot topic in electrochemistry and material sciences because it affects the way materials are used. In this paper, a method for covalently attaching carboxyphenyl (PhCOOH) groups to a gold electrode is presented. These groups were grafted onto the electrode surface electrochemically via reduction of aryldiazonium salt. The resulting grafted surface was characterized using cyclic voltammetry (CV) before and after the functionalization procedure to validate the presence of the grafted layer. The grafting of PhCOOH groups was confirmed by analyzing electrode thickness and composition by ellipsometry and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations indicated that the grafted layers provide a stable platform and resolved, for the first time, their interactions with oxygen.

Herein, a sensor platform, Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE), is presented for the detection of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV). The sensor was obtained through electrografting of the GCE using 4-carboxybenzene diazonium tetrafluoroborate (4-CBD) and in situ electrodeposition of Bi3+. The stability of the grafted layer and the proposed mechanism of interaction between the metal ions and the grafted layer is supported by DFT calculations. Under the optimized conditions, Pb2+ had a linear working range of 25–500 μg L−1 with LOD of 10 μg L−1 (S/N = 3) and Cd2+ provided linear range of 50–500 μg L−1 and LOD of 25 μg L−1. The fabricated electrode presented good repeatability and reproducibility. The applicability of the electrode was tested for determination of Cd2+ and Pb2+ in tap water resulting in recoveries of 96.2–101% for Cd2+ and 98.1–104% for Pb2+, Originally included in thesis in manuscript form with title: In situ Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE) as a sensor platform in square wave anodic stripping voltammetry: detection of Pb2+ and Cd2+ in tap water

Herein, a sensor platform, Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE), is presented for the detection of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV). The sensor was obtained through electrografting of the GCE using 4-carboxybenzene diazonium tetrafluoroborate (4-CBD) and in situ electrodeposition of Bi3+. The stability of the grafted layer and the proposed mechanism of interaction between the metal ions and the grafted layer is supported by DFT calculations. Under the optimized conditions, Pb2+ had a linear working range of 25–500 μg L−1 with LOD of 10 μg L−1 (S/N = 3) and Cd2+ provided linear range of 50–500 μg L−1 and LOD of 25 μg L−1. The fabricated electrode presented good repeatability and reproducibility. The applicability of the electrode was tested for determination of Cd2+ and Pb2+ in tap water resulting in recoveries of 96.2–101% for Cd2+ and 98.1–104% for Pb2+, Originally included in thesis in manuscript form with title: In situ Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE) as a sensor platform in square wave anodic stripping voltammetry: detection of Pb2+ and Cd2+ in tap water

Herein, a sensor platform, Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE), is presented for the detection of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV). The sensor was obtained through electrografting of the GCE using 4-carboxybenzene diazonium tetrafluoroborate (4-CBD) and in situ electrodeposition of Bi3+. The stability of the grafted layer and the proposed mechanism of interaction between the metal ions and the grafted layer is supported by DFT calculations. Under the optimized conditions, Pb2+ had a linear working range of 25–500 μg L−1 with LOD of 10 μg L−1 (S/N = 3) and Cd2+ provided linear range of 50–500 μg L−1 and LOD of 25 μg L−1. The fabricated electrode presented good repeatability and reproducibility. The applicability of the electrode was tested for determination of Cd2+ and Pb2+ in tap water resulting in recoveries of 96.2–101% for Cd2+ and 98.1–104% for Pb2+, Originally included in thesis in manuscript form with title: In situ Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE) as a sensor platform in square wave anodic stripping voltammetry: detection of Pb2+ and Cd2+ in tap water

Herein, a sensor platform, Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE), is presented for the detection of Cd2+ and Pb2+ using square wave anodic stripping voltammetry (SWASV). The sensor was obtained through electrografting of the GCE using 4-carboxybenzene diazonium tetrafluoroborate (4-CBD) and in situ electrodeposition of Bi3+. The stability of the grafted layer and the proposed mechanism of interaction between the metal ions and the grafted layer is supported by DFT calculations. Under the optimized conditions, Pb2+ had a linear working range of 25–500 μg L−1 with LOD of 10 μg L−1 (S/N = 3) and Cd2+ provided linear range of 50–500 μg L−1 and LOD of 25 μg L−1. The fabricated electrode presented good repeatability and reproducibility. The applicability of the electrode was tested for determination of Cd2+ and Pb2+ in tap water resulting in recoveries of 96.2–101% for Cd2+ and 98.1–104% for Pb2+, Originally included in thesis in manuscript form with title: In situ Bi/carboxyphenyl-modified glassy carbon electrode (Bi/CP/GCE) as a sensor platform in square wave anodic stripping voltammetry: detection of Pb2+ and Cd2+ in tap water

In this study, a 5-diazonium isophthalic acid was synthesized and electrografted onto glassy carbon (GCE) and screen-printed carbon (SPCE) electrodes. SPCE was used to demonstrate fabrication of a miniature device and to compare with conventional glassy carbon electrodes. The isophthalic acid (IPA) electrografted thin film was used for the immobilization of anti-methotrexate antibody (Ab) using carbodiimide activation chemistry to form antibody modified surfaces, GCE-IPA-Ab and SPCE-IPA-Ab. The GCE -IPA-Ab and SPCE-IPA-Ab surfaces were used as capacitive biosensors for the detection of methotrexate (MTX) in phosphate buffer (pH 7.4) using capacitive electrochemical impedance spectroscopy (EIS). The EIS data was analyzed using singular value decomposition (SVD). Principal component regression analysis gave R2 values of 0.99 for both the GCE-IPA-Ab and SPCE-IPA-Ab surfaces. The detection limit from the calibration curve of the GCE-IPA-Ab and SPCE-IPA-Ab was calculated to be 7.0 pmol.L−1 and 5.5 pmol.L−1 respectively.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Finding novel strategies for surface modification is of great interest in electrochemistry and material sciences. In this study, we present a strategy for modification of a gold electrode through covalent attachment of triazole (TA) groups. Triazole groups were electrochemically grafted at the surface of the electrode by a reduction of in situ generated triazolediazonium cations. The resulting grafted surface was characterized before and after the functionalization process by different electrochemical methods (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS)) confirming the presence of the grafted layer. The grafting of TA on the electrode surface was confirmed using analysis of surface morphology (by atomic force microscopy), the thickness of the grafted layer (by ellipsometry) and its composition (by X-ray photoelectron spectroscopy). Density functional theory (DFT) calculations imply that the grafted triazole offers a stronger platform than the grafted aryl layers.

Grafting of electrodes with diazonium salts using cyclic voltammetry (CV) is a well-established procedure for surface modification. However, little is known about the effect of the concentration of the diazonium salt on the number of layers grafted on the electrode surface. In this work, the impact of concentration on the grafting of 4-carboxybenzenediazonium (4-CBD) onto a glassy carbon electrode (GCE) is elucidated. The number of layers grafted on the GCE was linearly dependent on the concentration of 4-CBD and varied between 0.9 and 4.3 when the concentration was varied between 0.050 and 0.30 mmol/L at 0.10 V.s−1. Characterization of modified glassy carbon surface with X-ray photoelectron spectroscopy (XPS) confirmed the grafting of carboxyphenyl layer on the surface. Grafting with 0.15 mmol/L 4-CBD (1 CV cycle) did not form a detectable amount of carboxyphenyl (CP) moieties at the surface, while a single scan with higher concentration (2.5 mmol/L) or multiple scans (22 cycles) gave detectable signals, indicating formation of multilayers. We also demonstrate the possibility of removing the thin layer grafted on a glassy carbon electrode by applying high oxidation potential +1.40 V.

Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors. This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+). The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports. The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demo

Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors. This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+). The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports. The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demo

Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors. This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+). The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports. The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demo

Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors. This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+). The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports. The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demo

Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors. This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+). The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports. The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demo

The classical way to modify a gold electrode surface for immunosensor development is through self-assembly of functionalised thiols for subsequent attachment of antibodies. Here is described a new pathway for surface modification using a diazonium salt-based immunosensor for detection of methotrexate (MTX) with electrochemical immittance spectroscopy (EIS). The diazonium salt, 4-carboxybenzenediazonium tetrafluoroborate was synthesized using a diazotization reaction and characterized by IR and cyclic voltammetry (CV). The Au electrode was electrografted with diazonium and used for anti-MTX antibody immobilization. The EIS detection of MTX was studied with and without application of redox probe; Fe(CN)63−/4−. MTX could not be detected using Fe(CN)63−/4−as redox probe, whereas EIS measurements without redox probe and analysis of the data with singular decomposition (SVD) gave good results. A multivariate calibration model showed good linear behavior on a logarithmic scale with a detection limit for MTX of 7×10−12molL−1.

Surface modification of materials is accomplished using a vast number of molecules that possess a special affinity (SAMS) or are prone to undergo chemical reactions with the surface groups of the substrate-usually hydroxylated oxide layers (phosphonic or carboxylic acids, silanes, etc.). Probably the most direct mode to achieve this task is the use of the diazonium salts. This surface modification permits an easy way for tuning the properties of materials and adding some new interesting functionality that can be explored for: sensor construction, corrosion protection, catalysis, etc. In this work, we explored the use of diazonium heterocyclic compound to graft the surface of the glassy carbon electrode through di electrochemical reaction of the transformed amino heterocyclic moiety into the corresponding diazonium salt. The grafted surface is analyzed by a number of electrochemical and surface analysis techniques.

Surface modification of materials is accomplished using a vast number of molecules that possess a special affinity (SAMS) or are prone to undergo chemical reactions with the surface groups of the substrate-usually hydroxylated oxide layers (phosphonic or carboxylic acids, silanes, etc.). Probably the most direct mode to achieve this task is the use of the diazonium salts. This surface modification permits an easy way for tuning the properties of materials and adding some new interesting functionality that can be explored for: sensor construction, corrosion protection, catalysis, etc. In this work we explored the use of diazonium heterocyclic compound to graft the surface of the glassy carbon electrode through direct grafting (by the isolation of the diazonium salt) and "in situ" electrochemical reaction of the transformed amino heterocylic moiety into the corresponding diazonium salt. The grafted surface is analyzed by a number of electrochemical and surface analysis techniques.

This article describes an attempt to develop a sensor based on multi-frequency immittance spectroscopy for the determination of methotrexate (MTX) in blood serum using gold electrodes modified with antibodies. The attachment of antibodies was monitored with electrochemical immittance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS measurements of MTX resulted in a data matrix of size 39 × 55. The data were analysed using multivariate data analysis and showed a concentration dependence and time dependence that could be separated. This allowed the calculation of a multivariate calibration model. The model showed good linear behavior on a logarithmic scale offering a detection limit of 5 × 10−12 mol L−1.