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A low-cost, fast, disposable and sensitive biosensor study: flow injection analysis of glucose at poly-methylene blue-modified pencil graphite electrode
(Springer, 2018) Dilgin, Didem Giray; Ertek, Bensu; Dilgin, Yusuf
In this work, firstly methylene blue (MB) was electropolymerized onto pencil graphite electrode (PGE) surface for the electrocatalytic oxidation of NADH. Cyclic voltammograms show that oxidation potential of NADH at Poly-MB/PGE shifted to negative direction about 300 mV compared with bare PGE. These results indicate that Poly-MB/PGE exhibits a good electrocatalytic activity toward NADH oxidation. Then, a glucose biosensor study was performed based on the determination of enzymatically generated NADH by glucose dehydrogenase (GDH) which immobilized onto Poly-MB/PGE using glutaraldehyde cross-linking procedure. The biosensing of glucose in flow injection analysis (FIA) system was performed at GDH/Poly-MB/PGE for the first time. The electrocatalytic oxidation currents of enzymatically produced NADH obtained from FI amperometric current-time curves recorded at + 200 mV and in phosphate buffer solution at pH 7.0 containing 1.0 M KCl were linearly related to the concentration of glucose. Linear calibration plots are obtained in the concentration range from 0.01 to 1.0 mM. The limit of detection (LOD) was found to be 4.0 mu M. A fast, sensitive, low-cost and disposable glucose biosensor was constructed in FIA system using GDH/Poly-MB/PGE; therefore, it might provide a new perspective for the fabrication of biosensor of other compounds such as glutamate, lactate and alcohol.
A novel enzyme-free FI-amperometric glucose biosensor at Cu nanoparticles modified graphite pencil electrode
(Elsevier, 2020) Ayaz, Selen; Karakaya, Serkan; Emir, Gamze; Dilgin, Didem Giray; Dilgin, Yusuf
In this work, graphite pencil electrode (GPE) was modified with Cu nanoparticles (CuNPs) for enzyme-free flow injection (FI) amperometric detection of glucose. To modify electrode, CuNPs were electrodeposited onto GPE surface by recording 10 successive cyclic voltammograms (CVs) of 2.0 mM Cu(NO3)(2) in 100 mM KNO3. The electrochemical characterizations of the electrodes were realized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry techniques. The SEM images and EDX spectra of the pencil leads were recorded to investigate the surface morphologies of the electrodes. Then, the electrochemical response of both unmodified GPE and CuNPs/GPE towards electrochemical oxidation of glucose was performed by recording CVs in the supporting electrolyte consisted of 100 mM NaOH and 100 mM KCl. CVs recorded at GPE showed that the electron transfer rate of glucose is relatively slow and oxidation of glucose irreversibly observed with very low current at a high positive potential (+ 0.70 V). On the other hand, glucose oxidized at more negative potential value ( + 0.45 V) than that of unmodified GPE with a view of sharp peak at CuNPs/GPE. These results show that CuNPs/GPE exhibits excellent electrocatalytic activity and high electrochemical response towards oxidation of glucose because electron transfer rate of glucose was remarkably enhanced by modification of GPE with CuNPs. In the flow injection (FI) amperometric experiments, + 0.45 V and 2.5 mL/min were used as optimal values for applied potential (E-ap) and flow rate (f(r)), respectively. A linear calibration curve was obtained in the range from 0.10 to 400 mu M glucose with a detection limit and sensitivity of 0.04 mu M and 0.830 mu A mu M-1 cm(-2), respectively. The selectivity of glucose sensor was tested in the presence of various interferences. At last step, constructed glucose biosensor was successfully tested on some real glucose samples.
Amperometric determination of sulfide based on its electrocatalytic oxidation at a pencil graphite electrode modified with quercetin
(Elsevier, 2012) Dilgin, Yusuf; Kizilkaya, Bayram; Ertek, Bensu; Erena, Nuri; Dilgin, Didem Giray
This study describes a new approach for the investigation of electrocatalytic oxidation of sulfide using a pencil graphite electrode modified with quercetin (PGE/QH(2)). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/QH(2) showed a significant electrocatalytic activity toward sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifts from +450 mV at bare PGE to +280 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag/AgCl/KClsat and at pH 8.0 BR buffer solution containing 0.1 M NH4Cl were linearly related to the concentration of sulfide. The calibration graph consisted of two linear segments of 1-20 mu M and 20-800 mu M with a detection limit of 0.3 mu M (based on 3s(b)). The proposed method was successfully applied to the determination of sulfide in waste waters and was compared with the spectrophotometric method. (C) 2012 Elsevier B.V. All rights reserved.
Determination of Calcium Dobesilate by Differential Pulse Voltammetry at a Disposable Pencil Graphite Electrode
(Taylor & Francis Inc, 2018) Dilgin, Didem Giray
The electrochemistry of calcium dobesilate was investigated by recording cyclic and differential pulse voltammograms at a disposable and inexpensive pencil graphite electrode (PGE). Cyclic voltammograms of calcium dobesilate recorded in 0.1 M HCl showed a pair of well-defined redox peaks at the PGE indicating excellent electro-chemical activity. The oxidation peak current of the calcium dobesilate was used for its determination by recording its differential pulse voltammograms. The anodic peak current increased linearly with the concentration of calcium dobesilate in the range from 0.2 to 100 mu M with a detection limit 0.065 mu M. Relative standard deviations of 2.0 and 1.1% for innerday and 3.6 and 2.0% for intraday precision were obtained for three successive determinations of 0.5 and 10 mu M calcium dobesilate, respectively, which indicates acceptable repeatability and reproducibility. This voltammetric method was also successfully applied to the direct determination of calcium dobesilate in pharmaceutical samples. The effect of various interfering compounds on the calcium dobesilate peak current was studied. Thus, an unmodified PGE provides a new, promising, and alternative method of achieving sensitive, inexpensive, and selective determination of calcium dobesilate.
Differential pulse voltammetric determination of acyclovir in pharmaceutical preparations using a pencil graphite electrode
(Elsevier Science Bv, 2016) Dilgin, Didem Giray; Karakaya, Serkan
In this study, a new selective and sensitive voltammetric procedure for determination of acyclovir (ACV) was proposed using a disposable electrode, pencil graphite electrode (PGE). Cyclic and differential pulse voltammograms of ACV were recorded in Britton-Robinson buffer solution containing 0.10 M KCI with pH of 4.0 at PGE. The PGE displayed a very good electrochemical behavior with significant enhancement of the peak current compared to a glassy carbon electrode (GCE). Under experimental conditions, the PGE had a linear response range from 1.0 mu M to 100.0 mu M ACV with a detection limit of 0.3 mu M (based on 3 S-b). Relative standard deviations of 4.8 and 3.6% were obtained for five successive determinations of 10.0 and 50.0 mu M ACV, respectively, which indicate acceptable repeatability. This voltammetric method was successfully applied to the direct determination of ACV in real pharmaceutical samples. The effect of various interfering compounds on the ACV peak current was studied. (C) 2016 Elsevier B.V. All rights reserved.
Differential pulse voltammetric determination of eugenol at a pencil graphite electrode
(Elsevier Science Bv, 2016) Saglam, Ozlem; Dilgin, Didem Giray; Ertek, Bensu; Dilgin, Yusuf
In this study, the electrochemical behavior of eugenol, a widely used herbal drug, was investigated at a pencil graphite electrode (PGE). A low-cost, disposable, sensitive and selective electrochemical sensor is proposed for the determination of eugenol by recording its differential pulse voltammograms in Britton-Robinson buffer solution containing 0.1 M KCl with pH of 2.0 at the PGE. The PGE displayed a very good electrochemical behavior with significant enhancement of the peak current compared to a glassy carbon electrode. Under experimental conditions, the PGE had a linear response range from 0.3 mu M to 50.0 mu M eugenol with a detection limit of 0.085 mu M (based on 3S(b)). Relative standard deviations of 2.4 and 4.8% were obtained for five successive determinations of 30.0 and 5.0 mu M eugenol, respectively, which indicate acceptable repeatability. This voltammetric method was successfully applied for the direct determination of eugenol in real samples. The effect of various interfering compounds on the eugenol peak current was also studied. (C) 2015 Elsevier B.V. All rights reserved.
Electrocatalytic oxidation and flow injection analysis of formaldehyde at binary metal oxides (Co3O4-NiO and CuO-Co3O4) modified pencil graphite electrodes
(Springer, 2021) Emir, Gamze; Karakaya, Serkan; Ayaz, Selen; Dilgin, Didem Giray; Dilgin, Yusuf
In this work, a highly efficient performance of bimetallic thin films as their oxide forms (Co3O4-NiO and CuO-Co3O4) modified on pencil graphite electrodes (PGEs) was presented for electrocatalytic oxidation of formaldehyde. In addition, a sensitive and selective amperometric determination of formaldehyde in flow injection analysis system have been first performed using binary transition metal oxides modified PGEs. Co3O4-NiO and CuO-Co3O4 films were electrochemically deposited on the PGE surface using cyclic voltammetric procedures. The recorded cyclic voltammograms in the presence of formaldehyde in 0.10 M NaOH containing 0.10 M KCl showed that the prepared binary transition metal oxides modified PGEs exhibited a higher electrocatalytic activity than single metal oxide thin films modified PGEs towards oxidation of formaldehyde. The linear responses based on electrocatalytic oxidation of formaldehyde were determined as 2.5-5000 mu M and 0.25-1000 mu M for Co3O4-NiO/PGE and CuO-Co3O4/PGE, respectively. Moreover, limit of detections and sensitivities were estimated as 0.73 mu M and 81.8 mu A mM(-1) cm(-2) and 0.09 mu M and 166 mu A mM(-1) cm(-2) for Co3O4-NiO/PGE and CuO-Co3O4/PGE, respectively. The results from real sample studies proved that the fabricated FI-amperometric sensors enable high applicability towards determination of formaldehyde in real water samples.
Electrocatalytic Oxidation of NADH Using a Pencil Graphite Electrode Modified with Hematoxylin
(Amer Scientific Publishers, 2012) Dilgin, Yusuf; Ertek, Bensu; Kizilkaya, Bayram; Dilgin, Didem Giray; Gokcel, H. Ismet
In the present study, the electrocatalytic oxidation of reduced p-Nicotinamide Adenine Dinucleotide (NADH) was investigated using a pencil graphite electrode modified with hematoxylin (PGE/HMT). The PGE/HMT was prepared by adsorption of HMT on the PGE via immersion of bare PGE into 1.0 mM HMT solution (in methanol) for 60 s at room temperature. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +450 mV at bare PGE to +200 mV at PGE/HMT. The electrocatalytic currents obtained from the amperometric measurements at +200 mV versus Ag/AgCl/KClsat and pH 7.0 phosphate buffer solution containing 0.1 M KCl were linearly related to the concentration of NADH. The calibration graph consisted of two linear segments of 0.5-10 mu M and 10-300 mu M with a detection limit of 0.2 mu M (based on 3s(b), s(b) is the standard deviation of the blank response). The amperometric measurements exhibited that the response of the modified PGE/HMT towards the oxidation of NADH is reproducible, fast, sensitive and stable. Finally, the results obtained in the present study conclusively show that PGE modified with HMT can be effectively used to detect NADH.
Electrocatalytic oxidation of NADH using a pencil graphite electrode modified with quercetin
(Elsevier, 2013) Dilgin, Yusuf; Kizilkaya, Bayram; Dilgin, Didem Giray; Gokcel, H. Ismet; Gorton, Lo
In the present study, the electrocatalytic oxidation of reduced beta nicotinamide adenine dinucleotide (NADH) was investigated using a pencil graphite electrode modified with quercetin (PGE/QH(2)). The PGE/QH(2) was prepared through two steps: (i) the pre-treatment of PGE at 1.40V vs. Ag vertical bar AgCl vertical bar KCl(sat.) in pH 7.0 phosphate buffer containing 0.1 M KCl for 60 s and (ii) adsorption of QH(2) on the PGE via immersion of PGE into a 1.0 mM QH(2) solution (in ethanol) for 60 s. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +500 mV at bare PGE to +300 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag vertical bar AgCl vertical bar KCl(sat.) and in phosphate buffer solution at pH 7.0 containing 0.1 M KCl were linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 0.5 mu M to 100 mu M. The limit of detection was found to be 0.15 mu M. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.
Electrocatalytic oxidation of sulphide using a pencil graphite electrode modified with hematoxylin
(Elsevier Science Sa, 2012) Dilgin, Yusuf; Kizilkaya, Bayram; Ertek, Bensu; Isik, Firat; Dilgin, Didem Giray
The present study describes a new approach for the investigation of electrocatalytic oxidation of sulphide using a pencil graphite electrode modified with hematoxylin (PGE/HMT). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/HMT showed a significant electrocatalytic activity toward sulphide oxidation. Cyclic voltammetric studies showed that the peak potential of sulphide shifted from +480 mV at bare PGE to +220 mV at PGE/HMT. The electrocatalytic currents obtained from amperometric measurements at +200 mV versus Ag/AgCl/KClsat and at pH 8.0 BR buffer solution containing 0.1 M KCl were linearly related to the concentration of sulphide. The calibration graph consisted of a linear segment of 1-200 mu M with a detection limit of 0.4 mu M (based on 3s(b)). The proposed method was successfully applied to the determination of sulphide in waste waters and was compared with the spectrophotometric method. (C) 2012 Elsevier B.V. All rights reserved.
Flow-Injection Amperometric Determination of Glucose Using Nickel Oxide-Cobalt (II,III) Oxide and Nickel Oxide-Copper Nanoparticle Modified Pencil Graphite Electrodes
(Taylor & Francis Inc, 2022) Ayaz, Selen; Karakaya, Serkan; Emir, Gamze; Usakligil, Nihan; Dilgin, Didem Giray; Dilgin, Yusuf
This study features an enzyme-free amperometric determination of glucose with flow injection analysis (FIA) using pencil graphite electrodes (PGEs) modified with nickel oxide-cobalt (II,III) oxide (NiO-Co3O4/PGE) and nickel oxide-copper nanoparticle (NiO-CuNPs/PGE). Both modified PGEs exhibited excellent electrocatalytic activity toward oxidation of glucose in strong alkaline media since they enhanced the peak current compared with the bare PGE and single metal oxide- or metal nanoparticle-modified PGEs. Flow-injection (FI) amperometry showed the linear response range, the limit of detection and sensitivity for NiO-Co3O4/PGE and NiO-CuNPs/PGE were 1.0-1000 mu M, 0.23 mu M and 586 mu A mM(-1) cm(-2), and 0.10-250 mu M, 0.03 mu M and 949 mu A mM(-1) cm(-2), respectively. Glucose was determined in real samples with good accuracy and precision.
Glassy carbon electrode modified with poly-Neutral Red for photoelectrocatalytic oxidation of NADH
(Springer Wien, 2011) Dilgin, Didem Giray; Gligor, Delia; Gokcel, H. Ismet; Dursun, Zekerya; Dilgin, Yusuf
A new approach is described for the photoelectrocatalytic oxidation of Reduced -Nicotinamide Adenine Dinucleotide (NADH). It is based on a glassy carbon electrode (GCE) modified with a film of poly-Neutral Red (poly-NR) that is obtained by electropolymerization. Electrochemical measurements revealed that the modified electrode displays electrocatalytic and photo-electrocatalytic activity towards oxidation of NADH. If irradiated with a 250-W halogen lamp, the electrode yields a strongly increased electrocatalytic current compared to the current without irradiation. Amperometric and photo-amperometric detection of NADH was performed at +150 mV vs. Ag/AgCl/KClsat and the currents obtained are linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 1.0 mu M to 1.0 mM for both methods. However, the slope of the current-NADH concentration curve of the photo-electrocatalytic procedure was 2-times better than that obtained without irradiation.
Highly sensitive voltammetric determination of the fungicide fenhexamid using a cost-effective and disposable pencil graphite electrode
(Springer Wien, 2024) Ersan, Teslime; Dilgin, Didem Giray; Oral, Ayhan; Skrzypek, Slawomira; Brycht, Mariola; Dilgin, Yusuf
A differential pulse voltammetric (DPV) method is proposed for the highly sensitive determination of fenhexamid (FHX) based on both electrooxidation and electroreduction processes using a disposable and cost-effective pencil graphite electrode (PGE). The electrochemical oxidation and reduction mechanisms of FHX at the PGE were elucidated by recording cyclic voltammograms at various pH values of Britton-Robinson buffer (BRB) solutions at a scan rate of 50 mV s-1 and different scan rate values in the range 10-400 mV s-1 at selected pH of BRB (pH 2.0). Differential pulse voltammograms recorded under optimized conditions revealed an oxidation peak of FHX around + 0.65 V and a reduction peak of FHX around + 0.45 V. The DPV analysis of FHX revealed two linear ranges: 0.001-0.01 mu mol L-1 and 0.01-5.0 mu mol L-1 for the anodic peak, and 0.001-0.1 mu mol L-1 and 0.1-5.0 mu mol L-1 for the cathodic peak. The limits of detection were 0.34 nmol L-1 and 0.32 nmol L-1 for the anodic and cathodic peaks, respectively. The proposed methodology demonstrated satisfactory selectivity, as selected pesticides, certain electroactive compounds, and cationic species tested did not interfere with the voltammetric determination of FHX, particularly during its reduction. The recovery results, showing values close to 100% obtained from the analysis of real samples spiked with FHX, indicated that this methodology can accurately determine FHX in water and soil samples.
Low-cost determination of cetirizine by square wave voltammetry in a disposable electrode
(Springer Wien, 2019) Karakaya, Serkan; Dilgin, Didem Giray
In the present study, an antihistamine drug, cetirizine hydrochloride (CTZN), was determined using square wave voltammetry and cyclic voltammetry based on its oxidation in a disposable and unmodified/bare graphite pencil electrode. To see the electrochemical behavior of CTZN, cyclic voltammograms of 0.10 mM CTZN in various types of carbon-based electrodes such as glassy carbon electrode (GCE), carbon paste electrode, multi-walled carbon nanotube (MWCNT) modified GCE, graphite pencil(GP), and pretreated graphite pencil (p.GP) were recorded in pH 3.0 Britton Robinson Buffer (BRB) solution. The result showed that CTZN is irreversibly oxidized at around + 1.0 V in all electrodes and among the studied electrodes p.GP showed the highest oxidation current for CTZN. Thus, the effect of pH on the electrochemical response of CTZN was investigated at the p.GP electrode by recording cyclic voltammograms of 0.10 mM CTZN in the BRB solutions in which pH was ranging from 2.0 to 10.0. The highest oxidation current of CTZN was observed at pH 2.0 BRB solution. Under the optimized SW voltammetric conditions, a linear response for the determination of CTZN was obtained in the range from 0.50 to 10.0 mu M CTZN with a detection limit (LOD) of 0.16 mu M. Applicability of the proposed sensor was also tested for determination of CTZN in antihistamine syrup (Zyrtec). Results of the measurements indicated that p.GP can be successfully used for CTZN detection in real samples.
Photoelectrocatalytic determination of NADH in a flow injection system with electropolymerized methylene blue
(Pergamon-Elsevier Science Ltd, 2011) Dilgin, Yusuf; Dilgin, Didem Giray; Dursun, Zekerya; Gokcel, H. Ismet; Gligor, Delia; Bayrak, Burcu; Ertek, Bensu
It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min(-1): transmission tubing length, 10 cm; injection volume, 100 mu L; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 x 10(-7)-2.0 x 10(-4) M. The detection limit was found to be 4.0 x 10(-8) M for photoamperometric determination of NADH. (C) 2010 Elsevier Ltd. All rights reserved.
Photoelectrocatalytic oxidation of NADH in a flow injection analysis system using a poly-hematoxylin modified glassy carbon electrode
(Elsevier Advanced Technology, 2010) Dilgin, Didem Giray; Gligor, Delia; Gokcel, H. Ismet; Dursun, Zekerya; Dilgin, Yusuf
A stable electroactive thin film of poly-hematoxylin (poly-HT) was successfully prepared on a glassy carbon electrode (GCE) surface by recording successive cyclic voltammograms of 0.3 mM HT, in a phosphate buffer solution (pH 7.0) containing 0.1 M NaNO3, in the potential range of -0.5 to +2.0 V vs. Ag/AgCl. The deposition of HT on GCE surface can be explained through the electropolymerization process. This poly-HT modified electrode exhibited a good electrocatalytic activity towards the NADH oxidation in a phosphate buffer solution (pH 7.0), and led to a significant decrease in the overpotential by more than 320 mV compared with the bare GCE. In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed. Flow rate of carrier solution, transmission tubing length, injection volume and applied potential for the amperometric and photoamperometric FIA studies were optimized as 1.3 mL min(-1),10 cm, 100 mu L and +300 mV vs. Ag/AgCl, respectively. The currents obtained from amperometric and photoamperometric measurements in FIA system at optimum conditions were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 X 10(-7)-1.5 X 10(-4) M and in the range of 1.0 x 10(-7)-2.5 X 10(-4) M NADH, respectively. The relative standard deviation (RH)) of six replicate injections of 6.0 x 10(-5) M NADH was calculated as 2.2% and 4.3% for the amperometric and the photoamperometric method, respectively. The limit of detection was found to be 3.0 x 10(-8) M for the photoamperometric determination of NADH. (C) 2010 Elsevier B.V. All rights reserved.
Photoelectrochemical glucose biosensor in flow injection analysis system based on glucose dehydrogenase immobilized on poly-hematoxylin modified glassy carbon electrode
(Royal Soc Chemistry, 2015) Dilgin, Didem Giray; Gokcel, H. Ismet
In this study, a photoelectrochemical glucose biosensor is presented, comprising electropolymerized hematoxylin film on poly-amidoamine (PAMAM) dendrimers adsorbed on glassy carbon electrode (polyHT/PAMAM/GCE). After immobilization of glucose dehydrogenase (GDH) onto the poly-HT/PAMAM/GCE, photoelectrochemical biosensing of glucose was investigated using cyclic voltammetry and amperometry in a flow injection analysis (FIA) system dependent on the NAD+/NADH redox coupledehydrogenase enzyme. The linear range was from 1 x 10(-5) M to 1 x 10(-3) M with a sensitivity of 0.76 mu A mM(-1) and detection limit of 3.0 mM without irradiation in the FIA system. After irradiation, the linear range was from 5 x 10(-6) M to 1 x 10(-3) M with a sensitivity of 1.90 mu A mM(-1) and a detection limit of 1.5 mM. Comparing the results obtained from irradiation of the electrode surface with those from the reaction without irradiation, the sensitivity and the detection limit increased around 2.5- and 2.0-fold, respectively. The photoelectrochemical biosensor showed good performance with high upper detection limit, acceptable repeatability, and selectivity, providing a rapid alternative method for monitoring biomolecules and extending photoelectrochemical determination in the FIA system. The proposed electrochemical and photoelectrochemical biosensor was successfully applied to determination of glucose in real samples. The results obtained from this study provide a basis for future studies in these directions.
Quantum dots-based photoelectrochemical sensors and biosensors
(Elsevier, 2021) Dilgin, Yusuf; Karakaya, Serkan; Dilgin, Didem Giray
Photoelectrochemistry has been one of the most frequently studied branches of chemistry for the past 2 decades and its principle is based on monitoring a photocurrent generated by the irradiation of photosensitive material on an electrode surface with a light source. Photoelectrochemical (PEC) analysis has found wide applications in various fields such as water splitting, hydrogen or oxygen production, pollutant degradation, CO2 reduction, and construction of sensors and biosensors. In PEC studies, various photosensitive materials such as organic redox mediators (ORMs), semiconductors, heterostructures, and composite nanomaterials have been used. Among these, quantum dots (QDs) are of great interest to researchers because of their unique and superior optical and electronic properties. In this chapter the principles and mechanisms of PEC-sensing strategies using ORMs, QDs or their hybrid nanostructures are described and applications of PEC-sensing platforms such as in small analyte detection, immunoassays, nucleic acids, and enzyme-based biosensors.
Simple, sensitive, and cost-effective voltammetric determination of salbutamol at a pencil graphite electrode modified with Nafion and functionalized multi-walled carbon nanotubes
(Springer, 2024) Dilgin, Didem Giray; Vural, Kader; Karakaya, Serkan; Dilgin, Yusuf
This study describes a simple, highly sensitive, and cost-effective electrochemical determination of salbutamol (SBT) at a disposable pencil graphite electrode modified with Nafion/functionalized multi-walled carbon nanotubes composite material (Nf/f-MWCNTs/PGE). The electrochemical response of SBT at this modified electrode was investigated by both differential pulse voltammetry (DPV) and cyclic voltammetry techniques. The voltammetric measurements confirmed that the combination of f-MWCNTs with Nafion shows remarkable electrocatalytic activity on the oxidation of SBT due to a synergistic effect of Nafion via electrostatic interaction and f-MWCNTs via excellent conductivity and large specific surface area. Differential pulse voltammetry results show that the composite electrode gives two linear ranges of 0.10-17.5 mu M and 17.5-100 mu M with a detection limit (LOD) of 0.027 mu M SBT. Moreover, the studies of some potential interferants show that there is no significant interference in the determination of SBT. The proposed procedure was successfully applied to determine SBT in tube- and syrup-type pharmaceutical formulations, animal feed, and beef meat samples, and acceptable results were obtained with high accuracy and precision. Moreover, the proposed sensor displays good intra-day and inter-day precisions for the voltammetric determination of SBT.
Voltammetric Determination of Favipiravir Used as an Antiviral Drug for the Treatment of Covid-19 at Pencil Graphite Electrode
(John Wiley and Sons Inc, 2023) Erşan, Teslime; Dilgin, Didem Giray; Kumrulu, Elif; Kumrulu, Umur; Dilgin, Yusuf
This work describes the sensitive voltammetric determination of favipiravir (FAV) based on its reduction for the first time with a low-cost and disposable pencil graphite electrode (PGE). In addition, the determination of FAV was also performed based on its oxidation. Differential pulse (DP) voltammograms recorded in 0.5 M H2SO4 for the reduction of FAV show that peak currents increase linearly in the range of 1.0 to 600.0 μM with a limit of detection of 0.35 μM. The acceptable recovery values (98.9–106.0 %) obtained from a pharmaceutical tablet, real human urine, and artificial blood serum samples spiked with FAV confirm the high accuracy of the proposed method.

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