Oxidation Of DA Research Articles

One-Step Electrodeposition of MnO2-Graphitic Carbon Nitride Composite Layer on Screen Printed Electrode for Electrocatalytic Dopamine Sensing

Electroanalysis using screen-printed electrodes offers a cost-effective, rapid, and on-site analyte quantification. Nevertheless, ensuring the necessary stability, sensitivity, and selectivity of SPE in order to perform precise ultra-low-level analyses is critical. The use of nano-structured materials for surface functionalization is one of the most prevalent strategy to augment the sensitivity and selectivity of sensors. However, the selection of the surface functionalization technique and material plays a crucial role. The present study outlines a single step electro-functionalization of the screen-printed sensor (SPE) with a carbon–metal oxide composite consisting of graphitic carbon nitride and manganese oxide (gCN.MnxOy). The electrodeposited gCN.MnO2 layer has been thoroughly analysed using spectroscopic, microscopic, and electrochemical techniques. As a test case, the electro-functionalized SPE was used to quantify dopamine by monitoring its electrocatalytic oxidation. Due to π-π interaction between the aromatic ring structures of the gCN and dopamine molecules, H-bonding, enhanced electroactive site, and facilitated charge transfer at the MnO2.gCN surface layer, the modified SPEexhibited a 15-fold higher peak current and a negative potential shift of 150 mV for DA oxidation. Being 44 times more sensitive, gCN.MnO2|SPE exhibited a detection limit of 10 nM compared to 5.36 µM for the unmodified electrode. As proof of application, the gCN.MnO2|SPE successfully estimated dopamine in pharmaceutical formulations, banana peel, and clinical samples namely saliva, urine and blood serum with an error of less than 9 %. We believe, the proposed modification protocol has the potential to create low-cost disposable functional interfaces that match the desirable properties of commercial products.

Oxidation of dopamine and related catechols in dopaminergic brain regions in Parkinson's disease and during ageing in non-Parkinsonian subjects.

The present study was performed to examine if catechol oxidation is higher in brains from patients with Parkinson's disease compared to age-matched controls, and if catechol oxidation increases with age. Brain tissue from Parkinson patients and age-matched controls was examined for oxidation of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylalanine (DOPA) to corresponding quinones, by measurement of 5-S-cysteinyl-dopamine, 5-S-cysteinyl-DOPAC and 5-S-cysteinyl-DOPA. The cysteinyl catechols are assumed to be biomarkers for DA, DOPAC and DOPA autoxidation and part of the biosynthetic pathway of neuromelanin. The concentrations of the 5-S-cysteinyl catechols were lower, whereas the 5-S-cysteinyl-DA/DA and 5-S-cysteinyl-DOPAC/DOPAC ratios tended to be higher in the Parkinson group compared to controls, which was interpreted as a higher degree of oxidation. High 5-S-cysteinyl-DA/DA ratios were found in the substantia nigra of a sub-population of the Parkinson group. Based on 5-S-cysteinyl-DA/DA ratios, dopamine oxidation was found to increase statistically significantly with age in the caudate nucleus, and non-significantly in the substantia nigra. In conclusion, the occurrence of 5-S-cysteinyl-DA, 5-S-cysteinyl-DOPAC and 5-S-cysteinyl-DOPA was demonstrated in dopaminergic brain areas of humans, a tendency for higher oxidation of DA in the Parkinson group compared to controls was observed as well as a statistically significant increase in DA oxidation with age. Possibly, autoxidation of DA and other catechols are involved in both normal and pathological ageing of the brain. This study confirms one earlier but small study, as well as complements one study on non-PD cases and one study on both PD cases and controls on NM bound or integrated markers or catechols.

Voltammetric oxidation behavior of single-stranded DNA on carbon screen printed electrodes: From short oligonucleotides to ultralong amplification products

To deeper understand the electrochemical behavior of nucleic acids, the synthetic DNA oligonucleotides of general formula (ACTG)n, where n = 1–12, as well as 16-mer DNA oligonucleotides varying in the number of guanine (dG; G-n, n = 0–7) or adenine (dA; A-n, n = 0–8) residues, and single-stranded DNA (ssDNA) amplification products were employed to systematically investigate their oxidation in the ‘dissolved’ and ‘adsorbed’ forms on carbon screen printed electrodes by square wave and cycling voltammetry in the potential range of 0.5–1.5 V (vs. Ag/AgCl). Two signals at 0.9–1.0 V and 1.1–1.2 V, attributed to the oxidation of dG and dA, respectively, were registered for the most of oligonucleotides. The oxidation process of ‘dissolved’ (ACTG)n with n = 1–2 via dG was found diffusion-controlled, while (ACTG)3 has demonstrated a mixed mechanism of oxidation reaction. At the same time, ‘adsorbed’ oligonucleotides demonstrated adsorption-limited responses, except for (ACTG)1 showing a mixed reaction mechanism. At a constant nucleotide or oligonucleotide molar concentration, the registered signals for (ACTG)n exponentially decreased with the molecule length. The signals of all studied oligonucleotides after pre-adsorption on electrode surface were up to 10-fold higher than those in the soluble form, except for (ACTG)1. The dG oxidation signal for G-n oligonucleotides, registered at about 0.9 V, was practically insensitive to the position of a single dG (at the end or in the middle of polynucleotide chain), while demonstrating a bell-shaped dependence on the dG amount with a maximum at n = 3–4. The dG oxidation signal for A-n oligonucleotides with a constant portion of dG also increased with the number of dA residues in the bell-shaped fashion with a maximum at n = 5. The folding of oligonucleotides into hairpins with a stem formed via dG/dC pairing resulted in a shift of the peak potential for dG oxidation to higher values. Finally, ultralong ssDNA products generated by rolling circle amplification (RCA) were found to produce strong non-Faradaic current masking the dG and dA oxidation signals. The electrochemical detection of RCA products via dG and dA oxidation was found possible if ultralong ssDNA is fragmented by carrying out RCA in the presence of an appropriate restrictase.

Mussel-inspired ferric ion-polydopamine complex as a facile, green and efficient platform to functionalize carbon fiber for improving interfacial adhesion of composites

A mussel inspired co-deposition of ferric ion-polydopamine (PDA) is explored and constructed on carbon fiber via facile dip-coating strategy for the first time to realize the enhancement in interfacial adhesion of epoxy composites. Varied contents of ferric ion are designed to allow comparison how the contents of formed complexes affect the surface characteristics of fiber and interfacial adhesion of composites. Compared with pure PDA modified fiber, the size and number of PDA nanospheres attached on fiber first declines distinctly and then increases as the addition level of ferric ions raises, but the coordination product of both bis-and tris-Fe3+-catechol complexes exist, only the yield of complexes varies with the addition amount of FeCl3. This indicates that the level of Fe3+ ions obviously impact DA oxidation, not the complex product. Increments in interfacial shear strength across all ferric ion-PDA complex modified fibers are noticed, associating with the stronger Fe3+…O coordination bonds that could enhance the interfacial crosslinking density. However, the optimal IFSS is attainable when appropriate amount of Fe3+ ions were added, which endows the fiber with good resin wettability. The ferric ion-PDA complex assisted surface modification demonstrated to be an effective and feasible avenue in interphase tuning of fiber reinforced composites, which could be also anticipated to extend to other metallic ion-PDA complexes.

An Electrochemical Sensor Based on Carbon Quantum Dots and Ionic Liquids for Selective Detection of Dopamine

AbstractDopamine (DA) as a neurotransmitter has a pivotal role in the central nervous system. Because of altered levels of DA in various neuroscience diseases, development of a quick, sensitive, and simple analytical approach to determine DA in biological fluids could be very applicable. In this research, a novel electrochemical sensor based on a carbon paste electrode (CPE) modified with ionic liquid (IL) and carbon quantum dots (CQDs) for measuring DA with uric acid and ascorbic acid was developed. IL and CQDs were synthesized and characterized for their specific properties such as composition, emission, size distribution, and morphology structure. Then, the modified CPE and different DA concentration was determined via cyclic voltammetry. The modified electrode exhibited great electrocatalytic activity for DA oxidation. Under optimal conditions, the calibration diagram for DA was linear within the range of 0.1–50 μM in phosphate buffer (pH=7.4) and limit of detection was 0.046 μM. The electrode was successfully used in the determination of DA in real samples and generated acceptable outputs. The proposed electrochemical sensor could be an exceptional step forward in DA detection and pave the way for the molecular diagnosis of neurological illnesses.

Electrodeposited copper nanocubes on multi-layer graphene: A novel nanozyme for ultrasensitive dopamine detection from biological samples

In this paper, copper nanocubes (CuNCs) were grown on top of few-layer and multi-layer graphene (FLG and MLG) nanomaterial by electrodeposition, to develop a sensitive and selective nanozyme based electrochemical sensor for the determination of dopamine from plasma samples. The copper electrodeposition process was intensively studied and optimized to obtain cubic shape CuNPs on top of graphene that increased the active area of the sensor. The surface of the nanomaterial was investigated with several microphysical characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), and Fourier-transform infrared (FTIR), Raman, and X-ray photoemission spectroscopies (XPS). Further, the nanozyme sensor based on CuNCs-Gr/SPCE was electrochemically characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and the response towards the oxidation of DA was investigated using the differential pulse voltammetry (DPV) technique. The signal recorded with CuNCs-Gr/SPCE was linear in a wide range (0.001 – 100 µM), with a low limit of detection of 0.33 nM and a very high sensitivity of 196 mA/moL-1. The developed sensor showed high selectivity towards DA in presence of other neurotransmitters. The detection of DA in human plasma samples was obtained with 95.8–100.2 % recovery percentage, proving the reliability of the method.

ZnS Nanoparticles‐decorated Composite Graphene Paper: A Novel Flexible Electrochemical Sensor for Detection of Dopamine

AbstractDopamine (DA) is a significant catecholamine neurotransmitter in human metabolism, and DA is related to several critical illnesses. Accurate detection of DA is important to diagnose these diseases. Here, we demonstrated a flexible electrochemical sensor, ZnS nanoparticles decorated composite graphene paper electrode (CGPE), for the detection of DA. CGPE was prepared via mold‐casting method using ZnS/graphene oxide dispersion followed by thermal reduction treatment. The characterization of the flexible CGPE was investigated through various techniques. The electrochemical tests were carried out to study the electrocatalytic properties of CGPE against DA oxidation. Compared to graphene paper electrode (GPE), the oxidation of DA occurred at about 250 mV lower potential on CGPE, and peak current density increased about 2 times. Our sensor exhibited high sensitivity in linear range of 0.1–2300 μM of DA with a limit of detection (LOD) of 0.0042 μM. Furthermore, CGPE has selectively detected DA even in the medium containing AA and UA which are biologically active interfering molecules. Besides, the sensor showed many attractive properties such as high durability, stability, and reproducibility and it was successfully applied for the determination of DA in real samples for practical applications.

The construction of CoP nanoparticles coated with carbon layers derived from core-shell bimetallic MOF for electrochemical detection of dopamine

Design of catalysts with unique structures in enhancing electrochemical activity and stability has still been pursued. An eco-friendly method for preparing CoP with improved electrochemical performances was proposed in this work. A novel P-doped bimetallic ZIF-67@ZIF-8 (ZIF-67@ZIF-8-P) was prepared as the precursor for constructing of CoP@C/NCS, in which CoP nanospheres coated with carbon layers (CoP@C for short) were well-dispersed on N-doped carbon spheres (NCS for short). P was strategically pre-introduced into ZIF-67@ZIF-8 for preparing of ZIF-67@ZIF-8-P through the selective phosphorylation on ZIF-8 shell. DA was selected to investigate the electrochemical properties of CoP@C/NCS. Glassy carbon electrode (GCE) modified by CoP@C/NCS exhibited excellent properties in detection of DA by square wave stripping voltammetry (SWV), that a high sensitivity of 9.4 μA μM−1, and low limit of detection of 0.03 μM. In addition, CoP@C/NCS showed enhanced performances on electrocatalytic oxidation of DA than that of CoP/C prepared based on ZIF-67 by the common phosphorization method reported in literatures. Moreover, a wide linear range from 5.0 μM to 400.0 μM was achieved at CoP@C/NCS/GCE by amperometric i-t. The practical application of CoP/NCS/GCE was evaluated by detection of DA in human serum. The satisfactory recoveries in diluted serum demonstrated the promising application of CoP@C/NCS.

Determination of homocysteine using a dopamine-functionalized graphene composite

The electrochemical sensors have an essential role in the detection of amino acids which has clinical uses as a biomarker for a wide range of diseases. In this paper, the dopamine-functionalized graphene oxide was used to develop a screen printed electrochemical sensor (DA-GO/SPE). This sensing platform was used for simultaneous detection of homocysteine and folic acid. An efficient strategy was used for immobilization of dopamine on graphene oxide sheets based on NH2 group of dopamine with the COOH group of GO using the EDC/NHS reaction. The electrochemical investigation of prepared sensing platform confirmed that the DA-GO composite shows excellent catalytic activity toward homocysteine based on EC′ mechanism. A pair of redox peaks with one anodic peak (Ep = 220 mV), which related to the oxidation of DA to its quinone structure and one cathodic peak (Ep = 160 mV) was obtained at the DA-GO modified SPE. The values of α and ks for DA at the DA-GO/SPE were calculated to be 0.45 and 2.32 s−1, respectively. The DA-GO/SEP shows good catalytic response toward homocysteine and folic acid with a linear range of 0.5–900 μM and 1.0–260 μM, respectively. The limit of detection of 0.15 μM and 0.32 μM were obtained for homocysteine and folic acid, respectively (S/N = 3). Moreover, the RSD of three measurements using DA-GO/SPE was 1.9%, indicating good repeatability.

A simple dopamine sensor using graphdiyne nanotubes and shortened carbon nanotubes for enhanced preconcentration and electron transfer

High-quality tremella-like graphdiyne (GDY) nanotubes composed of intertwined ultrathin nanosheets were acidified. Shortened and acidified multi-walled carbon nanotubes (S-MWCNTs) were simply blended with GDY in a certain proportion to modify glassy carbon electrode (GCE). Electrochemical behavior of DA was studied on different modified electrodes. GDY showed high preconcentration to DA. S-MWCNTs facilitated the electron transport and promoted the oxidation of DA. Differential pulse voltammetry (DPV) was applied to determine low concentrations of DA. It exhibited a linear response in the concentration range of 0.02 to 20.0 μM with an estimated detection limit of 8.6 nM (S/N = 3). This sensor showed excellent performances for detection of DA in biological fluids.

Electrocatalytic oxidation of dopamine on the surface of ferrocene grafted hydroxyl terminated polybutadiene modified electrode

In this study, 4-(dimethylsilyl)butylferrocene was prepared using 4-chlorobutylferrocene via Grignard reaction in dry THF and the reaction of prepared reagent with chlorodimethylsilane. In continue, obtained ferrocenylsilane derivative was grafted to hydroxyl terminated polybutadiene (HTPB) via hydrosilylation reaction. Ferrocenyl units in polymer backbone gave a couple of reversible peaks of cyclic voltammetry (CV). Additionally, FT-IR, 1H NMR, UV–Vis spectroscopy along with molecular weight and TGA analysis confirmed the polymer modification. The modified polymer was coated onto the surface of glassy carbon electrode (GCE); meanwhile, fresh egg white (FEW) and terephthaldehyde (TFA) were used as cross-linking agents. The successful immobilization of polymer was demonstrated using Electrochemical impedance spectroscopy (EIS). The modified electrode showed an electrocatalytic effect on the oxidation of DA, the Fc/Fc+ couple mediate the oxidation of DA on the surface of GC/Butacene/(TFA + FEW) electrode. The optimum pH = 7 was obtained for this response. The electrode protected 86% of its initial electrocatalytic after 500 cycles and 90% of its initial current after 30 day storage at 4 °C. The results indicated that GC/Butacene/(TFA + FEW) electrode possessed satisfactory linear ranges and detection limits for detection of DA.

Functionals Aspects and Simultaneous Detection of Dopamine, Ascorbic Acid and Uric Acid Using Chitosan-Catechol Graphene and Carbon Nanotube Modified Electrodes

Dopamine functions as a neurotransmitter in the brain. The dysfunction of the dopaminergic system is the leading cause of numerous diseases such as Parkinson’s disease. Hence, it is important to find selective and sensitive detection methods for the early diagnosis of diseases related to the abnormal levels of dopamine. In this study, we show a new electrochemical sensing platform based on carbon nanotube (SWCNT) and a sheet of graphene (GRA). The novelty of our sensor is the coating of the substrates with chitosan-catechol (CC) by electrodeposition, enhancing the dopamine response by 70%. The dose-response for each set of electrodes (bare CNT, bare GRA, and coated CNT as well as coated GRA) was measured. Finally, the electrodes were tested in cerebrospinal fluid (artificial and human), for the detection of millimolar to nanomolar levels of dopamine. The electrodes exhibited high sensitivity (2.03mA mol·L-1, 1.45 mA mol·L-1, 0.0298 mA mol·L-1, and 0.0559 mA mol·L-1 for the modified CNT, bare CNT, modified GRA and bare GRA, respectively, for the oxidation of DA. The oxidation peak current was proportional to the concentration of DA in the range from 50×10-6 to 50x10-9 M (n= 6, r2 =0.98). The dopamine recovery in human CSF were, 49-78% and 65-65% with coated graphene and CNT electrodes, respectively. Our results indicate that the CC modified CNT electrodes achieved the best recovery, sensitivity, limit of detection, and selectivity compared to the uncoated CNT as well as the coated and uncoated graphene electrodes.

Ultrasensitive Reduced Graphene Oxide-Poly(Procion)/Gold Nanoparticles Modified Glassy Carbon Electrode for Selective and Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid

A highly ultrasensitive electrochemical sensor based on electrochemically reduced graphene oxide (ERGO), Procion Red MX-5B (PR) and gold nanoparticles (AuNPs) modified glassy carbon electrode (GCE) was developed. Cyclic voltammetry (CV) was employed to electropolymerize GO-PR mixture on GCE followed by deposition of AuNPs to obtain ERGO-poly(PR)/AuNPs/GCE. The physical properties of the nanocomposite were explored through field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance of the ERGO-poly(PR)/AuNPs/GCE showed remarkable enhancement in the peak current toward oxidation of AA, DA, and UA with peak potentials separation of 0.21 V for AA-DA, and 0.15 V for DA-UA. Differential pulse voltammetry (DPV) was applied to perform individual and simultaneous analysis of the aforementioned analytes at optimized pH. DPV responses of AA, DA, and UA concentration were obtained over the range of 0.4–110, 0.4–170 and 0.4–150 μM with sensitivities of 0.48, 0.40, and 0.63 μA/μM (S/N = 3), respectively. Limit of detections for AA, DA, and UA were 54, 5.6 and 5.8 nM, respectively. Good repeatability, reproducibility as well as long-term stability were obtained. The developed modified electrode was used successfully to monitor AA, DA, and UA in vitamin C tablets, and human urine samples with favorable recoveries.

Self-stacking of exfoliated charged nanosheets of LDHs and graphene as biosensor with real-time tracking of dopamine from live cells

This study introduces a new strategy for periodic stacking of positively charged NiAl layered double hydroxides (LDHs) nanosheets with negatively charged monolayers of graphene (G) by systematically optimizing several parameters in a controlled co-feeding fashion and resultant heterostacked NiAl LDH/G LBL nanocomposites have been practically applied in sensitive detection of dopamine released from live cells as early Parkinson's disease (PD) diagnostic tool. PD is the second most chronic neurodegenerative disorder with gradual progressive loss of movement and muscle control causing substantial disability and threatening the life seriously. Unfortunately majority of dopaminergic neurons present in substantia nigra of PD patients are destroyed before it is being clinically diagnosed, so early stages PD diagnosis is essential. Because of direct neighboring of extremely conductive graphene to semiconductive LDHs layers, enhanced intercalation capability of LDHs, and huge surface area with numerous active sites, good synergy effect is harvested in heteroassembled NiAl LDH/G LBL material, which in turn shows admirable electrocatalytic ability in DA detection. The interference induced by UA and AA is effectively eliminated especially after the modifying the electrode with Nafion. The outstanding electrochemical sensing performance of NiAl LDH/G LBL modified electrode has been achieved in terms of broad linear range and lowest real detection limit of 2 nM (S/N = 3) towards DA oxidation. Benefitting from superior efficiency, biosensor has been successfully used for real-time in-vitro tracking of DA efflux from live human nerve cell after being stimulated. We believe that our biosensing platform of structurally integrated well-ordered LBL heteroassembly by inserting graphene directly to the interlayer galleries of LDHs material will open up new avenue in diseases determination window.

A comparison of dry and wet aging on physicochemical and sensory characteristics of pork loin with two aging times.

This study investigated the effects of aging methods (wet aging and dry aging) and aging times (7 and 14 days) on the physicochemical and sensory characteristics of meat quality using pork loin. Dry-aged loin (DA) had significantly lower moisture content and higher crude fat protein content than wet-aged loin (WA). The pH of DA was significantly higher than that of WA and it increased with the aging time. DA showed lower cooking loss and higher aging loss than WA (p < 0.001). Lipid oxidation and metmyoglobin content of DA were higher than those of WA (p < 0.001). Shear force in DA was lower than that in WA (p < 0.001) and myofibril protein index (MFI) increased in DA. In addition, DA recorded higher scores of roast color, flavor and overall acceptability compared to WA. These results suggested that the application of dry-aging on pork improved physicochemical, textural and sensory characteristics.

Silver nanoparticles decorated eggshell membrane as an effective platform for interference free sensing of dopamine

ABSTRACTIn this paper a simple electrochemical sensing of dopamine by a new effective immobilization of tyrosinase (Tyr) enzyme on eggshell membrane (ESM) along with silver nanoparticles (AgNPs) is reported. The modified membrane was characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDAX), X-Ray diffraction (XRD). A simple solution based approach was used to prepare AgNPs on biomembrane followed by glutaraldehyde activation to immobilize Tyr on the nanoparticles decorated ESM. The direct electrochemistry of DA oxidation was performed through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Characterization of membrane was accomplished by electrochemical impedance spectroscopy (EIS). Prepared electrode showed very good stability, reproducibility, high selectivity, easy preparation and regeneration of electrode. The proposed sensor exhibited low detection limits 1.7ngL−1 with wide linear range 10–1000 ngL−1, excellent sensitivity (14.28µA µgL−1cm−2) with good storage and operational stabilities. The accurate measurement of dopamine in blood serum and good recoveries in spiked serum samples ensured great potential for medical diagnostics.

In Situ Structural Elucidation and Selective Pb2+ Ion Recognition of Polydopamine Film Formed by Controlled Electrochemical Oxidation of Dopamine.

Owing to the versatility and biocompatibility, a self-polymerized DA (in the presence of air at pH 8.5 tris buffer solution) as a polydopamine (pDA) film has been used for a variety of applications. Indeed, instability under electrified condition (serious surface-fouling) and structural ambiguity of the pDA have been found to be unresolved problems. Previously, pDA films (has hygroscopic and insoluble property) prepared by various controlled chemical oxidation methods have been examined for the structural analysis using ex situ solid-state NMR and mass spectroscopic techniques. In this work, a new in situ approach has been introduced using an electrochemical quartz crystal microbalance (EQCM) technique for the improved structural elucidation of pDA that has been formed by a controlled electrochemical oxidation of DA on a carboxylic acid functionalized multiwalled carbon nanotube-Nafion (cationic perfluoro polymer) modified electrode (f-MWCNT-Nf) system in pH 7 phosphate buffer solution. Key intermediates like 5,6-dihydroxy indole (DHI; 150.7 g mol-1), dopamine (154.1 g mol-1), Na+, PO42-, and polymeric product of high molecular weight, 2475 g mol-1, have been trapped on f-MWCNT-Nf surface via π-π (sp2 carbon of MWCNT and aromatic e-s), covalent (amide-II bonding, minimal), hydrogen, and ionic bonding and identified its molecular weights successfully. The new pDA film system showed well-defined peaks at E°' = 0.25 V and -0.350 vs Ag/AgCl corresponding to the surface-confined dopamine/dopamine quinone and DHI/5,6-indolequinone redox transitions without any surface-fouling complication. As an electroanalytical application of pDA, selective recognition of Pb2+ ion via {(pDA)-hydroquinone-Pb0} complexation with detection limit (signal-to-noise ratio = 3) 840 part-per-trillion has been demonstrated.

Phthalocyanine Doped Metal Oxide Nanoparticles on Multiwalled Carbon Nanotubes Platform for the detection of Dopamine

The electrocatalytic properties of metal oxides (MO = Fe3O4, ZnO) nanoparticles doped phthalocyanine (Pc) and functionalized MWCNTs, decorated on glassy carbon electrode (GCE) was investigated. Successful synthesis of the metal oxide nanoparticles and the MO/Pc/MWCNT composite were confirmed using UV-Vis, EDX, XRD and TEM techniques. Successful modification of GCE with the MO and their composite was also confirmed using cyclic voltammetry (CV) technique. GCE-MWCNT/ZnO/29H,31H-Pc was the best electrode towards DA detection with very low detection limit (0.75 μM) which compared favourably with literature, good sensitivity (1.45 μA/μM), resistance to electrode fouling, and excellent ability to detect DA without interference from AA signal. Electrocatalytic oxidation of DA on GCE-MWCNT/ZnO/29H,31H-Pc electrode was diffusion controlled but characterized with some adsorption of electro-oxidation reaction intermediates products. The fabricated sensors are easy to prepare, cost effective and can be applied for real sample analysis of dopamine in drug composition. The good electrocatalytic properties of 29H,31H-Pc and 2,3-Nc were related to their (quantum chemically derived) frontier molecular orbital energies and global electronegativities. The better performance of 29H,31H-Pc than 2,3-Nc in aiding electrochemical oxidation of DA might be due to its better electron accepting ability, which is inferred from its lower ELUMO and higher χ.

Sunlight assisted synthesis of silver nanoparticles in zeolite matrix and study of its application on electrochemical detection of dopamine and uric acid in urine samples

Sunlight assisted reduction of silver ions were accomplished for the synthesis of silver nanoparticles incorporated within the mesoporous silicate framework of zeolite Y. The zeolite-Y and AgNP/Zeo-Y were characterized by field emission scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption BET isotherm and X–ray diffraction techniques. The incorporation of silver nanoparticles within the porous framework was further confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. An enhanced electrocatalytic oxidation of biologically important molecules like dopamine and uric acid using AgNP/Zeo-Y modified glassy carbon electrode has been developed. A simultaneous oxidation of DA and UA peaks were obtained at +0.31V and +0.43V (vs. Ag/AgCl) using AgNP/Zeo-Y/GCE under the optimum experimental condition. A well-resolved peak potential window (~120mV) for the oxidation of both DA and UA were observed at AgNP/Zeo-Y/GCE system. The calibration curves for DA and UA were obtained within the dynamic linear range of 0.02×10−6 to 0.18×10−6M (R2=0.9899) and 0.05×10−6 to 0.7×10−6M (R2=0.9996) and the detection limits were found to be 1.6×10−8M and 2.51×10−8M by using differential pulse voltammetry (DPV) method. The proposed method was successfully applied for the determination of both DA and UA in human urine samples with a related standard deviation was <3%, and n=5 using the standard addition method.

Sensitive electrochemical determination of dopamine and uric acid using AuNPs(EDAS)–rGO nanocomposites

AuNPs(EDAS) – rGO nanocomposites were prepared by a facile one step sonochemical synthesis process. Here, EDAS acts as an interlinker for anchoring gold on rGO and it also acts both as a reducing agent and a stabilizing agent. The AuNPs(EDAS) – rGO nanocomposites show excellent electro-catalytic activity towards oxidation of DA and UA. The AuNPs(EDAS) – rGO nanocomposites exhibit low detection limits, high sensitivity, it could be a potential candidate for sensing application and in biosensor technology in the future.