Hydrazo Pyrazole-Pyridone Fluorescent tag for NLO, Live cell imaging, LFPs visualization, Photophysical probing, and Electrochemical sensor for Dopamine detection

The present communication reports on the synthesis of a novel methyl-pyridone azo fluorescent tag (MPAFT) were proven through 1H (NMR), FT-IR, UV-vis, and high-resolution mass spectrometry. The quantum chemical parameters of MPAFT were evaluated using density functional theory (DFT) analysis. It was further investigated for its latent fingerprint (LFPs) in various surfaces and anticounterfeiting applications. By exposing Level I-Level III, ridge features to UV light with a wavelength of 365 nm, a bioimaging investigation has also demonstrated the potential of MPAFT's emission behaviour. The cyclic voltammetry (CV) and linear sweep voltammetry (LSV) at MPAFT/MGCE (modified glassy carbon electrode) were used to explore the electrochemical sensitivity and reliable detection of dopamine (DA) in neutral PBS (pH 7) electrolyte solution, and the results show good sensitivity and detection. The lower detection limit for LSV was 0.81 μM under optimum conditions.

Laser Scribing Turns Plastic Waste into a Biosensor via the Restructuration of Nanocarbon Composites for Noninvasive Dopamine Detection

The development of affordable and compact noninvasive point-of-care (POC) dopamine biosensors for the next generation is currently a major and challenging problem. In this context, a highly sensitive, selective, and low-cost sensing probe is developed by a simple one-step laser-scribing process of plastic waste. A flexible POC device is developed as a prototype and shows a highly specific response to dopamine in the real sample (urine) as low as 100 pmol/L in a broad linear range of 10-10-10-4 mol/L. The 3D topological feature, carrier kinetics, and surface chemistry are found to improve with the formation of high-density metal-embedded graphene-foam composite driven by laser irradiation on the plastic-waste surface. The development of various kinds of flexible and tunable biosensors by plastic waste is now possible thanks to the success of this simple, but effective, laser-scribing technique, which is capable of modifying the matrix's electronic and chemical composition.

Reactive argon-plasma activation of screen-printed carbon electrodes for highly selective dopamine determination

Dopamine (DA) deficiency has been linked to several psychiatric disorders. Electrochemical determination of the level of DA suffers from abundant ascorbic acid (AA) and uric acid (UA) in body fluids. In this work, a facile argon (Ar) plasma treatment was utilized to enhance the electrocatalytic reactivity of screen-printed carbon electrodes (SPCEs) for selective DA detection. Surface characterization of the Ar-treated SCPEs verified that the carbon paste binders were successfully removed and single-bonded oxygenated moieties (-OH and C-O-C) were generated. Interestingly, the sharper D* and D'' Raman interbands were new key evidence of a higher exposure of carbon defect sites. Electrochemical studies further revealed that the Ar-treated SPCEs possessed faster heterogeneous electron-transfer rates, larger electroactive surface areas, and much higher conductivity when compared with untreated electrodes. As a result, the oxidation potentials of AA, DA, and UA in the mixture could be well-resolved and the current responses were significantly increased. The selective determination of DA in the presence of AA and UA by differential pulse voltammetry gave two linear responses with the limit of detection of 0.27 μM (0.15-10 μM range). Moreover, this Ar-treated SPCE had high reproducibility and good storage stability. These results suggest that Ar-plasma treatment could be a promising method to enhance the electrocatalytic properties of SPCEs for the detection of biomolecules.

Microporous carbon in the selective electro-oxidation of molecular biomarkers: uric acid, ascorbic acid, and dopamine

Herein, we demonstrate the superior electrocatalytic activities of microporous carbon in the oxidation of three molecular biomarkers, ascorbic acid (AA), dopamine (DA), and uric acid (UA), which are co-present in biological fluids.

Elucidating the roles of oxygen functional groups and defect density of electrochemically exfoliated GO on the kinetic parameters towards furazolidone detection

Using electrochemically exfoliated graphene oxide (GO)-modified screen-printed carbon electrodes for the detection of furazolidone (FZD), a nitrofuran antibiotic, was explored. In this study, we designed some GO samples possessing different oxygen functional group content/defect density by using ultrasonic irradiation or microwave techniques as supporting tools. The difference in physical characteristics of GO led to the remarkable change in kinetic parameters (electron transfer rate constant (k_s) and transfer coefficient (α)) of electron transfer reactions at K₃/K₄ probes as well as the FZD analyte. Obtained results reveal that the GO-ultrasonic sample showed the highest electrochemical response toward FZD detection owing to the increase in defect density and number of edges in the GO nanosheets under ultrasonic irradiation. The proposed electrochemical nanosensor enabled the monitoring of FZD in the linear range from 1 μM to 100 μM with an electrochemical sensitivity of 1.03 μA μM⁻¹ cm⁻². Tuning suitable electronic structures of GO suggests the potentiality of advanced GO-based electrochemical nanosensor development in food-producing animal safety monitoring applications.

In this study, we have investigated the role of changes in the microstructure of graphene oxide (GO) on the analytical kinetic parameters of GO-based electrochemical sensors for detection of furazolidone (FZD) antibiotic drug.

Molecular Engineered Carbon-Based Sensor for Ultrafast and Specific Detection of Neurotransmitters

In the quest for designing affordable diagnostic devices with high performance, precisely functionalized carbon-based materials with high accuracy and selectivity are required. Every material has its own unique ability to interact with the analyte, and its performance can be enhanced by probing the interaction mechanism. Herein, p-aminophenol (PAP)-functionalized reduced graphene oxide (rGO) nanoscale material is developed by a one-step synthetic route as an all-organic-based sensor. As the PAP molecules are precisely covalently interacted with the rGO at the basal plane and form a wrinkled-paper-like structure, the functionalized material exhibits an outstanding sensing ability (7.5 nM neurotransmitter dopamine (DA) at a wide linear range, 0.01-100 μM) with fast electrical transduction (<3 s) and good recyclability (∼10 cycles) in a real sample. Combining various analytical and density functional theory (DFT) calculation methods, physicochemical properties and the interaction mechanism of analyte-materials transduction are discussed exclusively. Besides, the potential application of the well-dispersed rGO-PAP gravure ink in flexible-printed electronics fields is explored. This study not only provides new insights into the surface/interface chemistry and working principle of this unique anchoring of PAP on rGO but also offers a new pathway for developing other forms of metal-free/organic functionalized biosensors with high efficiency.

Cobalt Ferrite Nanocomposite as Electrochemical Sensor for The Detection of Guanine, Uric Acid and Their Mixture

Cobalt ferrite nanocomposite was synthesized and characterized by analytical techniques such as FESEM, EDS and XRD. The average crystallite size was found to be in the range of 10–12 nm with a cubic structure. Further, the nanocomposite was used for the detection of guanine (GU) and uric acid (UA) and found to be an efficient electrode modifier. The lower limit of detection for GU and UA was found to be 300 nM and 400 nM, respectively

Concurrent and Selective Determination of Dopamine and Serotonin with Flexible WS2 /Graphene/Polyimide Electrode Using Cold Plasma

Makers of point-of-care devices and wearable diagnostics prefer flexible electrodes over conventional electrodes. In this study, a flexible electrode platform is introduced with a WS₂ /graphene heterostructure on polyimide (WGP) for the concurrent and selective determination of dopamine and serotonin. The WGP is fabricated directly via plasma-enhanced chemical vapor deposition (PECVD) at 150 °C on a flexible polyimide substrate. Owing to the limitations of existing fabrication methods from physical transfer or hydrothermal methods, many studies are not conducted despite excellent graphene-based heterostructures. The PECVD synthesis method can provide an innovative WS₂ /graphene heterostructure of uniform quality and sufficient size (4 in.). This unique heterostructure affords excellent electrical conductivity in graphene and numerous electrochemically active sites in WS₂ . A large number of uniform qualities of WGP electrodes show reproducible and highly sensitive electrochemical results. The synergistic effect enabled well-separated voltammetric signals for dopamine and serotonin with a potential gap of 188 mV. Moreover, the practical application of the flexible sensor is successfully evaluated by using artificial cerebrospinal fluid.

Unveiling the Fundamental Mechanisms of Graphene Oxide Selectivity on the Ascorbic Acid, Dopamine, and Uric Acid by Density Functional Theory Calculations and Charge Population Analysis

The selectivity of electrochemical sensors to ascorbic acid (AA), dopamine (DA), and uric acid (UA) remains an open challenge in the field of biosensing. In this study, the selective mechanisms for detecting AA, DA, and UA molecules on the graphene and graphene oxide substrates were illustrated through the charge population analysis from the density functional theory (DFT) calculation results. Our substrate models contained the 1:10 oxygen per carbon ratio of reduced graphene oxide, and the functionalized configurations were selected according to the formation energy. Geometry optimizations were performed for the AA, DA, and UA on the pristine graphene, epoxy-functionalized graphene, and hydroxyl-functionalized graphene at the DFT level with vdW-DF2 corrections. From the calculations, AA was bound to both epoxy and hydroxyl-functionalized GO with relatively low adsorption energy, while DA was adsorbed stronger to the electronegative epoxy groups. The strongest adsorption of UA to both functional groups corresponded to the largest amount of electron transfer through the pi orbitals. Local electron loss created local electric fields that opposed the electron transfer during an oxidation reaction. Our analysis agreed with the results from previous experimental studies and provided insight into other electrode modifications for electrochemical sensing.

Electrochemical sensor based on CuSe for determination of dopamine

A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sensor for dopamine detection. The hydrothermally synthesized and electrodeposited CuSe nanostructures showed high sensitivity for dopamine detection with low limit of detection (LOD). A sensitivity of 26 μA/μM.cm² was obtained with this electrochemical sensor which is ideal to detect even small fluctuations in the transient dopamine concentration. Apart from high sensitivity and low LOD, the dopamine oxidation on the catalyst surface also occurred at a low applied potential (< 0.18 V vs Ag|AgCl), thereby significantly increasing selectivity of the process specifically with respect to ascorbic and uric acids, which are considered to be the most prominent interferents for dopamine detection. Electrochemical redox tunability of the catalytic Cu center along with low coordination geometry is believed to enhance the rate of dopamine attachment and oxidation on the catalyst surface thereby reducing the applied potential. The presence of Cu also increases conductivity of the catalyst composite which further improves the charge transfer thus increasing the sensitivity of the device. This is the first report of electrochemical dopamine sensing with a simple binary selenide comprising earth-abundant elements and can have large significance in designing efficient sensors that can be transformative for understanding neurodegenerative diseases further. Graphical abstract.

Facile Development of a Fiber-Based Electrode for Highly Selective and Sensitive Detection of Dopamine

A facile one-step method was used to create a selective and sensitive electrode for dopamine (DA) detection based upon a stainless steel (SS) filament substrate and reduced graphene oxide (rGO). The electrode successfully and selectively detects DA in the presence of uric acid and ascorbic acid without the need for a Nafion coating. The proposed electrode is easy to fabricate, low-cost, flexible, and strong. The rGO-SS electrode could also be incorporated into a three-dimensional braided structure enabling DA detection in a two-electrode fiber system. The sensor is an excellent candidate for production of an affordable, robust, and flexible wearable and portable sensor and expands the application of textiles in point of care diagnostic devices.

A ZIF-8 derived nitrogen-doped porous carbon and nitrogen-doped graphene nanocomposite modified electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid by a nanocomposite modified electrode was realized.

Fluorographite to hydroxy graphene to graphene: a simple wet chemical approach for good quality graphene

Good quality graphene is prepared in a scalable manner from fluorographite by nucleophilic substitution of F with OH⁻ ions.

New Approach for Porous Chitosan-Graphene Matrix Preparation through Enhanced Amidation for Synergic Detection of Dopamine and Uric Acid

Amide-functionalized materials have emerged as promising nonprecious catalysts for electrochemical sensing and catalysis. The covalent immobilization of chitosan (CS) onto graphene sheet (GS) (denoted as CS-GS) has been done via higher degree of amidation reaction to develop an electrochemical sensing matrix for simultaneous determination of dopamine (DA) and uric acid (UA). The enhanced amidation between CS and GS has not been reported previously. However, electrochemical results have revealed that the CS-GS enhances the electrocatalytic performance in terms of the oxidation potential and peak current due to the higher degree of amide functionalization compared to that of CS/GS, which has a lower amidation. Differential pulse voltammetry-based studies have indicated that the CS-GS matrix works at a lower detection limit (0.14 and 0.17 μM) (S/N = 3) and over a longer linear range (1-700 and 1-800 μM), with a comparatively higher sensitivity (2.5 and 2.0 μA μM^-1 cm^-2), for DA and UA, respectively. In addition, the CS-GS matrix demonstrates good selectivity toward the detection of DA and UA in the presence of a 10-fold higher concentration of AA and glucose. The as-prepared three-dimensional porous CS-GS also endows selective determination toward DA and UA in various real samples.

Electrodeposition synthesis of reduced graphene oxide–carbon nanotube hybrids on indium tin oxide electrode for simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Reduced graphene oxide–carbon nanotube (rGO–CNT) hybrids have been synthesized by electrodeposition of GO stabilized CNT using indium tin oxide (ITO) as working electrode, followed by electrochemical reduction of GO–CNT into rGO–CNT.