Evaluation of a New Biosensor Based on in Situ Synthesized PPy-Ag-PVP Nanohybrid for Selective Detection of Dopamine

A Dopamine Detection Sensor Based on Au-Decorated NiS2 and Its Medical Application

This article reports a simple hydrothermal method for synthesizing nickel disulfide (NiS2) on the surface of fluorine-doped tin oxide (FTO) glass, followed by the deposition of 5 nm Au nanoparticles on the electrode surface by physical vapor deposition. This process ensures the uniform distribution of Au nanoparticles on the NiS2 surface to enhance its conductivity. Finally, an Au@NiS2-FTO electrochemical biosensor is obtained for the detection of dopamine (DA). The composite material is characterized using transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties of the sensor are investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and time current curves in a 0.1 M PBS solution (pH = 7.3). In the detection of DA, Au@NiS2-FTO exhibits a wide linear detection range (0.1~1000 μM), low detection limit (1 nM), and fast response time (0.1 s). After the addition of interfering substances, such as glucose, L-ascorbic acid, uric acid, CaCl2, NaCl, and KCl, the electrode potential remains relatively unchanged, demonstrating its strong anti-interference capability. It also demonstrates strong sensitivity and reproducibility. The obtained Au@NiS2-FTO provides a simple and easy-to-operate example for constructing nanometer catalysts with enzyme-like properties. These results provide a promising method utilizing Au coating to enhance the conductivity of transition metal sulfides.

Bovine Serum Albumin Template-Mediated Fabrication of Ruthenium Dioxide/Multiwalled Carbon Nanotubes: High-Performance Electrochemical Dopamine Biosensing in Human Serum

The presence of abnormal dopamine (DA) levels may cause serious neurological disorders, therefore, the quantitative analysis of DA and its related research are of great significance for ensuring health. Herein, the bovine serum albumin (BSA) template method has been proposed for the preparation of catalytically high-performance ruthenium dioxide/multiwalled carbon nanotube (RuO2/MWCNT) nanocomposites. The incorporation of MWCNTs has improved the active surface area and conductivity while effectively preventing the aggregation of RuO2 nanoparticles. The outstanding electrocatalytic performance of RuO2/MWCNTs has promoted the electro-oxidation of DA at neutral pH. The electrochemical sensing platform based on RuO2/MWCNTs has demonstrated a wide linear range (0.5 to 111.1 μM), low detection limit (0.167 μM), excellent selectivity, long-term stability, and good reproducibility for DA detection. The satisfactory recovery range of 94.7% to 103% exhibited by the proposed sensing podium in serum samples signifies its potential for analytical applications. The aforementioned results reveal that RuO2/MWCNT nanostructures hold promising aptitude in the electrochemical sensor to detect DA in real samples, further offering broad prospects in clinical and medical diagnosis.

Advances in the Use of Conducting Polymers for Healthcare Monitoring

Conducting polymers (CPs) are an innovative class of materials recognized for their high flexibility and biocompatibility, making them an ideal choice for health monitoring applications that require flexibility. They are active in their design. Advances in fabrication technology allow the incorporation of CPs at various levels, by combining diverse CPs monomers with metal particles, 2D materials, carbon nanomaterials, and copolymers through the process of polymerization and mixing. This method produces materials with unique physicochemical properties and is highly customizable. In particular, the development of CPs with expanded surface area and high conductivity has significantly improved the performance of the sensors, providing high sensitivity and flexibility and expanding the range of available options. However, due to the morphological diversity of new materials and thus the variety of characteristics that can be synthesized by combining CPs and other types of functionalities, choosing the right combination for a sensor application is difficult but becomes important. This review focuses on classifying the role of CP and highlights recent advances in sensor design, especially in the field of healthcare monitoring. It also synthesizes the sensing mechanisms and evaluates the performance of CPs on electrochemical surfaces and in the sensor design. Furthermore, the applications that can be revolutionized by CPs will be discussed in detail.

Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives-including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)-and the CPs is usually governed by non-covalent functionalization through π-π interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of π orbitals.

Nanofiber Based on Electrically Conductive Materials for Biosensor Applications

Biosensors are analytical tools that enable the transmission of different signals produced from the target analyte to a transducer for the production of real-time clinical diagnostic devices by obtaining meaningful results. Recent research demonstrates that the production of structured nanofiber through various methods has come to light as a potential platform for enhancing the functionality of biosensing devices. The general trend is towards the use of nanofibers for electrochemical biosensors. However, optical and mechanical biosensors are being developed by functionalization of nanofibers. Such nanofibers exhibit a high surface area to volume ratio, surface porosity, electroconductivity and variable morphology. In addition, nanosized structures have shown to be effective as membranes for immobilizing bioanalytes, offering physiologically active molecules a favorable microenvironment that improves the efficiency of biosensing. Cost effective, wearable biosensors are crucial for point of care diagnostics. This review aims to examine the electrically conductive materials, potential forming methods, and wide-ranging applications of nanofiber-based biosensing platforms, with an emphasis on transducers incorporating mechanical, electrochemical and optical and bioreceptors involving cancer biomarker, urea, DNA, microorganisms, primarily in the last decade. The appealing properties of nanofibers mats and the attributes of the biorecognition components are also stated and explored. Finally, consideration is given to the difficulties now affecting the design of nanofiber-based biosensing platforms as well as their future potential.

Facile one-pot method of AuNPs/PEDOT/CNT composites for simultaneous detection of dopamine with a high concentration of ascorbic acid and uric acid

In this research, a facile one-pot method was used to synthesize gold/poly-3,4-ethylene-dioxythiophene/carbon nanotube (AuNPs/PEDOT/CNTs) composite material. The composite material was investigated by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Then the synthesized nanocomposite material was dropped on a bare glassy carbon electrode (GCE) to improve the detection performance of dopamine with a high concentration of ascorbic acid and uric acid. The electrochemical behavior of AuNPs/PEDOT/CNTs/GCE was studied by Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimum conditions, AuNPs/PEDOT/CNTs/GCE showed a good linear response in the concentration range from 9.14 to 29.704 μM with a detection limit (LOD) and sensitivity of 0.283 μM and 1.557 μA μM-1, respectively. This sensor was applied to detect practical samples with good average recovery. It also exhibited good reproducibility and stability.

Immunomodulatory and Antiprotozoal Potential of Fabricated Sesamum radiatum Oil/Polyvinylpyrrolidone/Au Polymeric Bionanocomposite Film

A unique morphological Sesamum radiatum oil/polyvinylpyrrolidone/gold polymeric bionanocomposite film was synthesized using the S. radiatum oil dispersed in a polymeric polyvinylpyrrolidone (PVP) matrix and decorated with gold nanoparticles (AuNPs). The chemical and physical characteristics as well as the thermal stability of the synthesized bionanocomposite film were investigated using various spectroscopic and microscopic techniques. The microscopic analysis confirmed well dispersed AuNPs in the PVP- S. radiatum oil matrix with particle size of 100 nm. Immunomodulatory and antiprotozoal potentials of the suggested bionanocomposite film were evaluated for lipopolysaccharide-induced BV-2 microglia and against L. amazonensis, L. mexicana promastigotes and T. cruzi epimastigotes, respectively. The results exerted outstanding reduction of inflammatory cytokines' (IL-6 and TNFα) secretions after pretreatment of bionanocomposite. The bionanocomposite exhibited large inhibitory effects on certain cell signaling components that are related to the activation of expression of proinflammatory cytokines. Additionally, AuNPs and bionanocomposite exhibited excellent growth inhibition of L. mexicana and L. amazonensis promastigotes with IC50 (1.71 ± 1.49, 1.68 ± 0.75) and (1.12 ± 1.10, 1.42 ± 0.69), respectively. However, the nanomaterials showed moderate activity towards T. cruzi. All outcomes indicated promising immunomodulatory, antiprotozoal, and photocatalytic potentials for the synthesized S. radiatum oil/PVP/Au polymeric bionanocomposite.

Enzymeless copper microspheres@carbon sensor design for sensitive and selective acetylcholine screening in human serum

Follow up of neuronal disorders, such as Alzheimer's and Parkinson's diseases using simple, sensitive, and selective assays is urgently needed in clinical and research investigation. Here, we designed a sensitive and selective enzymeless electrochemical acetylcholine sensor that can be used in human fluid samples. The designed electrode consisted of a micro spherical construction of Cu-metal decorated by a thin layer of carbon (CuMS@C). A simple and one-pot synthesis approach was used for Cu-metal controller formation with a spherical like structures. The spherical like structure was formed with rough outer surface texture, circular build up, homogeneous formation, micrometric spheres size (0.5 -1 µm), and internal hollow structure. The formation of a thin layer of carbon materials on the surface of CuMS sustained the catalytic activity of Cu atoms and enriched negatively charge of the surface. CuMS@C acted as a highly active mediator surface that consisted of Cu metal as a highly active catalyst and carbons as protecting, charge transport, and attractive surface. Therefore, the CuMS@C surface morphology and composition played a key role in various aspects such as facilitated ACh diffusion/loading, increased the interface surface area, and enhanced the catalytic activity. The CuMS@C acted as an electroactive catalyst for ACh electrooxidation and current production, due to the losing of two electrons. The fabricated CuMS@C could be a highly sensitive and selective enzymeless sensor for detecting ACh with a detection limit of 0.1 µM and a wide linear range of 0.01 - 0.8 mM. The designed ACh sensor assay based on CuMS@C exhibited fast sensing property as well as sensitivity, selectivity, stability, and reusability for detecting ACh in human serum samples. This work presents the design of a highly active electrode surface for direct detection of ACh and further clinical investigation of ACh levels.

Effective and reliable platform for nonenzymatic nanomolar-range quinol detection in water samples using ceria doped polypyrrole nanocomposite embedded on graphitic carbon nitride nanosheets

A glassy carbon electrode modification by a novel ternary nanocomposite of advantageously united ceria, polypyrrole, and graphitic carbon nitride (CeO₂/Ppy@g-C₃N₄) is reported here. It can be used to tailor the sensor surface for the electrochemical detection of nanomolar-level quinol (Qnl), a chemical widely used as a developing agent in photography and lithography, as a cosmetic, and as an antioxidant in rubber and food industries. The occupational exposure of Qnl may occur by inhalation or dermal contact, leading to lot of health hazards. The synthesized nanocomposite was characterized by various analytical techniques such as UV-Vis, Fourier transformed infrared (FTIR), X-ray powder diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, selected area electron diffraction, and elemental mapping analyses. The oxidation current of Qnl is linear to its concentration in the range of 0.01-260 μM and the lowest detection and quantification limit are found to be 1.5 nM and 0.004 μM, respectively, with a sensitivity of 283.33 μA mM^-1 cm^-2. The performance of the modified electrode was compared with those of high-performance liquid chromatography, which indicates that the proposed sensor can be used as an effective and reliable platform for nano-molar detection of Qnl in various environmental and biological fluids.

A simple one-step electrochemical deposition of bioinspired nanocomposite for the non-enzymatic detection of dopamine

A simple and cost-effective electrochemical synthesis of carbon-based nanomaterials for electrochemical biosensor is of great challenge these days. Our study describes a single-step electrochemical deposition strategy to prepare a nanocomposite of electrochemically reduced graphene oxide (ErGO), multi-walled carbon nanotubes (MWCNTs), and polypyrrole (PPy) in an aqueous solution of pH 7.0 for dopamine (DA) detection. The ErGO/MWCNTs/PPy nanocomposites show enhanced electrochemical performance due to the strong π–π* stacking interactions among ErGO, MWCNTs, and PPy. The efficient interaction of the nanocomposites is confirmed by evaluating its physical and electrochemical characteristics using field-emission scanning electron microscopy, Raman spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The deposited nanocomposites are highly stable on the substrates and possess high surface areas, which is vital to improve the sensitivity and selectivity for DA detection. The controlled deposition of the ErGO/MWCNTs/PPy nanocomposites can provide enhanced electrochemical detection of DA. The sensor demonstrates a short time response within 2 s and is a highly sensitive approach for DA detection with a dynamic linear range of 25–1000 nM (R2 = 0.999). The detection limit is estimated to be 2.3 nM, and the sensor sensitivity is calculated to be 8.96 μA μM−1 cm−2, with no distinct responses observed for other biological molecules.

"Nano": An Emerging Avenue in Electrochemical Detection of Neurotransmitters

The growing importance of nanomaterials toward the detection of neurotransmitter molecules has been chronicled in this review. Neurotransmitters (NTs) are chemicals that serve as messengers in synaptic transmission and are key players in brain functions. Abnormal levels of NTs are associated with numerous psychotic and neurodegenerative diseases. Therefore, their sensitive and robust detection is of great significance in clinical diagnostics. For more than three decades, electrochemical sensors have made a mark toward clinical detection of NTs. The superiority of these electrochemical sensors lies in their ability to enable sensitive, simple, rapid, and selective determination of analyte molecules while remaining relatively inexpensive. Additionally, these sensors are capable of being integrated in robust, portable, and miniaturized devices to establish point-of-care diagnostic platforms. Nanomaterials have emerged as promising materials with significant implications for electrochemical sensing due to their inherent capability to achieve high surface coverage, superior sensitivity, and rapid response in addition to simple device architecture and miniaturization. Considering the enormous significance of the levels of NTs in biological systems and the advances in sensing ushered in with the integration of nanotechnology in electrochemistry, the analysis of NTs by employing nanomaterials as interface materials in various matrices has emerged as an active area of research. This review explores the advancements made in the field of electrochemical sensors for the sensitive and selective determination of NTs which have been described in the past two decades with a distinctive focus on extremely innovative attributes introduced by nanotechnology.

One-pot sonochemical synthesis of CuS nanoplates decorated partially reduced graphene oxide for biosensing of dopamine neurotransmitter

The sonochemical methods have been used as a straight forward method for the synthesis of various composite materials, including the transition metal dichalcogenide composites. In the present work, we report a simple sonochemical synthesis of CuS nanoplates decorated partially reduced graphene oxide (PrGO) nanocomposite for the first time. The PrGO-CuS nanocomposite was synthesized using bath-sonication (frequency: 37 kHz; power: 150 W) of graphene oxide (GO), and CuS precursors at 80 °C for 60 min. The physicochemical characterization (FESEM, XRD, FTIR, and Raman spectroscopy) results confirmed the successful formation of CuS nanoplates on PrGO nanosheets. The as-synthesized PrGO-CuS nanocomposite was further utilized for electroanalysis of dopamine neurotransmitter. The obtained electroanalytical results revealed that PrGO-CuS nanocomposite has superior electrochemical activity towards dopamine than those obtained for GO, CuS, and GO-CuS composite. The fabricated biosensor shows a lower limit of detection (0.022 µM) with a more comprehensive linear response range (0.1-155.1 µM) for the detection of dopamine. Moreover, the PrGO-CuS nanocomposite electrode was successfully used for the detection of dopamine in bovine serum albumin.

Ultrasonic assisted functionalization of MWCNT and synergistic electrocatalytic effect of nano-hydroxyapatite incorporated MWCNT-chitosan scaffolds for sensing of nitrofurantoin

In the present work, we report the fabrication of stable composite of chitosan hydrogels (CHI) on multiwalled carbon nanotubes (MWCNT) using a simple ultrasonic-assisted method. Also, rod-like hydroxyapatite nanoparticles (HA NPs) were synthesised using a hydrothermal route and were incorporated into the highly conductive MWCNT-CHI scaffolds using an ultrasonication method. The functionalization of MWCNT and preparation of HA NPs on MWCNT-CHI nanocomposite were done using the sonication over the frequency of 37 kHz with the ultrasonic power capable of 150 W (Elmasonic Easy 60H bath sonicator). The resulting hybrid HA NPs/MWCNT-CHI nanocomposites have an excellent surface area and high surface to volume ratio, which leads to the sensitive detection of nitrofurantoin than pristine MWCNT and HA NPs. The complete elemental and morphological analyses of the HA NPs/MWCNT-CHI nanocomposites were characterised by XRD, FTIR, RAMAN, FESEM, TEM, EDX, and elemental mapping techniques. Electrochemical analysis of the HA NPs/MWCNT-CHI nanocomposites was carried out by cyclic voltammetry, electrochemical impedance spectroscopy and amperometry methods. The modified glassy carbon electrode (GCE) of HA NPs/MWCNT-CHI nanocomposites exhibit the nitrofurantoin detection activity at the linear range of 0.005-982.1 µM with the detection limit of 1.3 nM. The synergistic electrocatalytic activity of HA NPs/MWCNT-CHI nanocomposites modified GCE is correlated to the sensitivity of 0.16 µAµM^-1 cm^-2 with excellent precision and accuracy towards the sensing of nitrofurantoin.

Tin disulfide nanorod-graphene-β-cyclodextrin nanocomposites for sensing dopamine in rat brains and human blood serum

In the present work describes a facile synthesis of tin disulfide (SnS₂) nanorods decorated graphene-β-cyclodextrin (SnS₂/GR-β-CD) nanocomposite for robust and novel dopamine (DA) electrochemical biosensor applications. The DA biosensor was fabricated using the glassy carbon electrode (GCE) modified with SnS₂/GR-β-CD nanocomposite. The sonochemical and hydrothermal methods have been used for the synthesis of SnS₂/GR-β-CD. Different physicochemical methods were used to confirm the formation of the GR-β-CD, SnS₂, and SnS₂/GR-β-CD nanocomposite. The cyclicvoltammetric cathodic current response of DA was 5 folds higher than those observed at bare, β-CD, SnS₂-β-CD, and GR-β-CD modified GCEs. Under optimised conditions, the biosensor's DPV response current is linear to DA from the concentration of 0.01-150.76 μM. The detection limit of the biosensor was 4 nM. The SnS₂/GR-β-CD biosensor shows an excellent selectivity towards DA in the presence of common interfering species, including ascorbic acid and uric acid. Also, the as-prepared nanocomposite-modified electrode exhibited satisfactory long-term stability, sensitivity (2.49 μAμM^-1 cm^-2) along with reusability for detection of DA. The fabricated SnS₂/GR-β-CD biosensor was successfully used for the detection of DA in the rat brain and human blood serum samples.

Gold nanoparticle decorated polypyrrole/graphene oxide nanosheets as a modified electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

AuNPs, GO and PPy are combined effectively to form a novel composite showing a huge enhancement in electrochemical performance compared to the single materials.

Novel electrochemical sensors from poly[N-(ferrocenyl formacyl) pyrrole]@multi-walled carbon nanotubes nanocomposites for simultaneous determination of ascorbic acid, dopamine and uric acid

Novel multi-walled carbon nanotubes coated with poly[N-(ferrocenyl formacyl) pyrrole] (MWCNTs@PFFP) nanocomposites were prepared through the in situ oxidation polymerization reaction of N-(ferrocenyl formacyl) pyrrole in the presence of MWCNTs. The MWCNTs@PFFP nanocomposites were characterized by FT-IR, Raman, TGA, XRD, XPS, SEM and TEM techniques. The MWCNTs@PFFP nanocomposites were fabricated into novel electrochemical sensors for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The electrochemical behavior of the MWCNTs@PFFP/GCE sensors was examined, and the parameters that influence electrochemical signals were optimized. The experimental results showed that the fabricated modified electrode sensors exhibited good sensitivity, selectivity, specificity, repeatability and a long lifetime, remaining the initial current of at least 92.5% after 15 days storage in air. The sensors possessed a linear response concentration range over 200-400 μM for AA, 2-16 μM for both DA and UA, and a limit of detection as low as 40.0, 1.1 and 7.3 × 10-1 μM for AA, DA and UA, respectively. They are expected to be used as a potential tool for the simultaneous detection of DA, AA and UA in the human body.

Ultrasonic energy-assisted in-situ synthesis of Ru0/PANI/g-C3N4 nanocomposite: Application for picomolar-level electrochemical detection of endocrine disruptor (Bisphenol-A) in humans and animals

Bisphenol A (BPA) is an endocrine-disrupting chemical which resembles structurally the hormone estrogen. Even a trace amount of BPA can bind estrogen receptors resulting in the inducement of reproductive disorders, cancers and problems related to sexual growth such as manliness in female and womanliness in male. So the determination of BPA in human and animal bodies is very essential. For this purpose, a new nanocomposite composed of ruthenium nanoparticles, polyaniline and graphitic carbon nitride (Ru⁰/PANI/g-C₃N₄) has been synthesized ultrasonically (40 ± 3 kHz, 200 W). A modification on glassy carbon electrode (GCE) with the nanocomposite detects BPA in human and animal urine samples with wide linear range (0.01-1.1 µM) and the limit of detection is pico molar-level. The synthesized nanocomposite was characterized by Ultraviolet-Visible and Fourier Transform-Infra Red spectroscopies, thermo gravimetric analysis, transmission electron microscopy, X-ray diffraction study, energy dispersive X-ray analysis, and elemental mapping analysis. This sensing system is selective, stable and reusable, by which the detection of BPA in various physiological fluids is very much possible.

Fabrication of Ag@Co-Al Layered Double Hydroxides Reinforced poly(o-phenylenediamine) Nanohybrid for Efficient Electrochemical Detection of 4-Nitrophenol, 2,4-Dinitrophenol and Uric acid at Nano Molar Level

In this paper, Co-Al layered double hydroxides (LDHs), Co-Al LDHs/poly(o-phenylenediamine) (PoPD) and Ag nanoparticles decorated Co-Al LDHs/PoPD (Ag@Co-Al LDH/PoPD) samples were prepared. The as-prepared samples were characterized by XRD, Raman, XPS, FT-IR, DRS-UV-Vis, PL and TGA techniques. The salient features of morphology and size of the samples were determined using FESEM, and HR-TEM. Then, the samples were coated on glassy carbon electrode (GCE) and employed for sensing of 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP)) and uric acid (UA). It was found that Ag@Co-Al LDH/PoPD/GCE showed superior electrochemical sensing behaviour than other modified electrodes. It exhibits the detection limit (DL) of 63 nM, 50 nM and 0.28 µM for 4-NP, 2,4-DNP and UA respectively.

Golf ball-like MoS2 nanosheet arrays anchored onto carbon nanofibers for electrochemical detection of dopamine

Arrays of molybdenum(IV) disulfide nanosheets resembling the shape of golf balls (MoS₂ NSBs) were deposited on carbon nanofibers (CNFs), which are shown to enable superior electrochemical detection of dopamine without any interference by uric acid. The MoS₂ NSBs have a diameter of ∼ 2 μm and are made up of numerous bent nanosheets. MoS₂ NSBs are connected by the CNFs through the center of the balls. Figures of merit for the resulting electrode include (a) a sensitivity of 6.24 μA·μM^-1·cm^-2, (b) a low working voltage (+0.17 V vs. Ag/AgCl), and (c) a low limit of detection (36 nM at S/N = 3). The electrode is selective over uric acid, reproducible and stable. It was applied to the determination of dopamine in spiked urine samples. The recoveries at levels of 10, 20 and 40 μM of DA are 101.6, 99.8 and 107.8%. Graphical abstract Schematic presentation of the golf ball-like MoS₂ nanosheet balls/carbon nanofibers (MoS₂ NSB/CNFs) by electrospining and hydrothermal process to detect dopamine (DA).

Photoinduced holes transfer based visual determination of dopamine in human serum

A simple unexplored strategy was followed to construct ratiometric fluorescence-based sensing system for the detection of dopamine (DA) in human serum. Ratiometric fluorescence system was constructed through bonding energy transfer (TBET) by conjugating carboxyl functionalized CdTe quantum dots (QDs) and amine-capped Carbon quantum dots (CQDs). The photophysical properties of sensing system were characterized by standard methods. Photoluminescence (PL) of sensing system under excitonic wavelength (350 nm) depends on dual emission at 440 and 595 nm that corresponds to CQDs and CdTe QDs respectively. The developed sensing system was utilized for visual determination of DA, an unquenched blue fluorescence of CQDs in ratiometric system reveals the visual color differentiation for DA binding with CdTe QDs among the possible interferences (Alanine, Glycine, Glucose, Sucrose, Urea and Ascorbic acid). The limit of detection (LOD) and quantification (LOQ) was calculated as 8.1 and 27.2 nm respectively by using regression analysis. Photoinduced holes transfer (PHT) might have attributed the possible sensing mechanism for DA that quench the photoluminescence sequentially to enhance the sensing performance of QDs. The matrix interferences and reliability of the developed sensing platform were evaluated by testing DA spiked human serum and the sensing response was found to be field deployable.

A review of the advanced developments of electrochemical sensors for the detection of toxic and bioactive molecules

The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.

A novel highly selective and sensitive detection of serotonin based on Ag/polypyrrole/Cu2O nanocomposite modified glassy carbon electrode

A silver/polypyrrole/copper oxide (Ag/PPy/Cu₂O) ternary nanocomposite was prepared by sonochemical and oxidative polymerization simple way, in which Cu₂O was decorated with Ag nanoparticles, and covered by polyprrole (PPy) layer. The as prepared materials was characterized by UV-vis-spectroscopy (UV-vis), FT-IR, X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) with EDX, high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Sensing of serotonin (5HT) was evaluated electrocatalyst using polypyrrole/glassy carbon electrode (PPy/GCE), polypyrrole/copper oxide/glassy carbon electrode (PPy/Cu₂O/GCE) and silver/polypyrrole/copper oxide/glassy carbon electrode (Ag/PPy/Cu₂O/GCE). The Ag/PPy/Cu₂O/GCE was electrochemically treated in 0.1MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with 5-HT concentration from 0.01 to 250 µmol L^-1 and the detection limit was found to be 0.0124 μmol L^-1. It exhibits high electrocatalytic activity, satisfactory repeatability, stability, fast response and good selectivity against potentially interfering species, which suggests its potential in the development of sensitive, selective, easy-operation and low-cost serotonin sensor for practical routine analyses. The proposed method is potential to expand the possible applied range of the nanocomposite material for detection of various concerned electro active substances.

Catalytic hydrogenation performance of an in situ assembled Au@g-C3N4–PANI nanoblend: synergistic inter-constituent interactions boost the catalysis

A novel gold–graphitic carbon nitride–polyaniline (Au@g-C₃N₄–PANI) nanoblend was synthesized via in situ oxidative polymerization of aniline using auric acid as an oxidant in the presence of g-C₃N₄.