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The present work reports the preparation of advanced functional nanostructures based on cobalt oxide supported mesoporous carbon framework (Co

Breast cancer is one of the most common cancers and an issue of high concern among women all over the world. Today researchers have received much attention by developing reliable biosensors for breast cancer biomarkers. Electrochemical detection strategies together with immunosensing platforms offer multiple advantages for the development of highly sensitive, selective, portable, and low cost, point-of-care systems for clinical diagnosis. Recent advancements in electrochemical immunoassays have greatly improved the sensitivity of the developed detection methods to quantify breast cancer biomarkers at ultra-trace level which is very impressive. Further, various signal amplification strategies have been followed to fabricate extremely specific biosensing interfaces using signal tags labeled with conducting nanomaterials, enzymes/multienzymes, or magnetic beads. This chapter discusses recent advances in the development of electrochemical immunosensors for the quantification of clinically relevant protein biomarkers of breast cancer tumors. Details regarding multilabeled detection antibodies coupled with specific capture antibodies at sensor surfaces and electrochemical screening of biomarkers as antigens are discussed. Possible opportunities for further improvement in the area of electrochemical immunoassays toward cancer diagnostics are also provided.

Graphene (GR) and its derivatives are highly interesting carbon nanoforms which possess layered morphology and unique structural/chemical/physical features. These extraordinary properties make GR materials highly applicable for multiple scientific applications, however, zero band gap, hydrophobic nature are among few limitations which make its functionalization a mandatory step to expand its practical applications. To achieve the best out of GR materials, different covalent and noncovalent functionalization schemes have been proposed governed by disruption of sp2 lattice in case of covalent scheme and retention of its structural integrity in case of noncovalent functionalization. The chapter addresses a brief discussion on different GR functionalization schemes. Moreover, it focuses on noncovalently functionalized GR nanohybrids with metal based nanoparticles (MNPs) as electrochemical sensors taking some relevant examples. Synergistic effects of GR materials and MNPs enhance the electro-activity of nanohybrids for electrochemical detection of different targets.

Molecularly imprinted polymers (MIPs) are considered as advanced nanostructured materials and highly efficient sensing platforms. Owing to their template-driven recognition cavities within the polymer matrix and excellent selectivity toward a target template, MIPs find multiple applications in analytical chemistry including separation science, environmental analysis, sensors, and biochemical assays. MIP-based detection strategies are tuned with various selectivity patterns by the choice of template analytes during the imprinting process. These unique properties of MIPs benefit environmental monitoring of toxic pharmaceuticals through advanced sensing techniques including electrochemical, fluorescence, and so on. Pharmaceutical contaminants have become one of the serious threats toward the clean environment, biosafety, and human health. Taking this extremely concerned issue into consideration, the present chapter aims at MIP-based sensors which have been utilized for pharmaceuticals detection in environmental matrices. Moreover, current aspects and future possibilities related to pharmaceutical analysis have also been focused at the end.

The growth in different types of synthetic polymer micro and nanomaterials in variant configurations and designs for sensing of environmental contaminants have been explored. Evolution of stationary phases for analytes extraction, starting with the traditional selective extraction materials, namely (silica and carbon based) microparticles and lately nanoparticles and silica monoliths, variants of synthetic organic polymer particles and monoliths, as well as hybrid (inorganic-organic) polymer materials fabricated to afford smart selectivity of analytes of interest, have been explored. In particular the review chapter focuses on the advanced selective synthetic molecular receptors, often referred as intelligent polymers, specifically, molecularly imprinted polymers, and the different variations of responsive polymer materials. These smart polymers are based on the concept of biomimicry toward solving the selectivity problem in chemical analysis. The chapter highlights examples of interesting integration of these synthetic polymer receptors into standalone analytical sensing devices via electrochemical and optical methods. To highlight innovative examples of the latter, Three-dimensional optical crystals and nonconventional spectroscopic techniques such as surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS), as well spectro electrochemical transduction modes will be discussed. The selected examples of applications for these sensors will be toward analytes of interests in environmental toxicology, principally pesticides and to lesser extent heavy metals. The chapter will end with a perspective predicting the future of intelligent polymers in sensors integration.

Bisphenols (BPs), which have more than ten kinds of structural analogues, are emerging as the most important endocrine disrupting chemicals that adversely affect human health and aquatic life. A tyrosinase nanosensor based on metal-organic frameworks (MOFs) and chitosan was developed to investigate the electrochemical response characteristics and mechanisms of nine kinds of BPs for the first time. The developed tyrosinase nanosensor showed a sensitive response to bisphenol A, bisphenol F, bisphenol E, bisphenol B, and bisphenol Z, and the responsive sensitivities were highly dependent on their respective log Kow values. However, the nanosensor showed no response to bisphenol S (BPS), bisphenol AP (BPAP), bisphenol AF (BPAF), or tetrabromobisphenol A, although BPS, BPAP, and BPAF have structures similar to those of the responsive BPs. The obtained results reveal that the electrochemical response of different BPs is affected not only by the molecular structure, especially the available ortho positions of phenolic hydroxyl groups, but also by the substituent group properties (electron acceptor or electron donor) on the bisphenol framework. The electronic cloud distribution of the phenolic hydroxyl groups, which is affected by the substituent group, determines whether the available ortho positions of phenolic hydroxyl groups can be oxidized by the tyrosinase biosensor. These response mechanisms are very significant as they can be used for predicting the response characteristics of many BPs and their various derivatives and metabolites on biosensors. The unexpected anti-interference ability of the biosensor to nine heavy metal ions was also discovered and discussed. The MOF-chitosan nanocomposite proves to be a promising sensing platform for the construction of diverse biosensors for selective detection of targets even in the presence of a high concentration of heavy metal ions.

A new graphene/zinc oxide nanorods modified glassy carbon electrode (GR/ZnORs/GCE) based electrochemical sensor has been developed for the sensitive determination tizanidine (TZ) in solubilized system. The fabricated sensor was characterized by various electrochemical methods. Different kinetic parameters affecting the monitored electrocatalytic response were investigated and optimized for tizanidine determination at fabricated GR/ZnORs/GCE sensor and successfully compared with the results obtained at GR/SiO 2 /GCE, GR/GCE and at bare GCE. Under optimized conditions the square wave current is linear over the concentration range 0.80 ng mL −1 to 10.0 μg mL −1 with detection limit and quantification limit of 0.10 ng mL −1 and 3.45 ng mL −1 respectively. The applicability of proposed method is further extended to in vitro determination of the drug in pharmaceutical formulation with an acceptable recovery from 97.89% to 101.09%.

Bisphenol A (BPA), one of the most important endocrine disrupting chemicals, is a threat to human and wildlife health. Electrochemical enzyme biosensor has been regarded as ideal alternative analytical technique for ultrasensitive and rapid detection of BPA, while the unstable and easily deactivated nature of enzyme limits its development. In order to improve the stability of enzyme, tyrosinase was chosen as a model enzyme, and tyrosinase nanocapsules (nTyr) were prepared by encapsulating a single tyrosinase molecule into a thin network polymer shell through in-situ polymerization method in aqueous solution. The characterization of particle size distribution, TEM and FTIR indicated the successful formation of single tyrosinase molecule nanocapsule. And the porous network polymer shell of nTyr ensured the maintenance of tyrosinase activity and fast substrate transportation. The obtained nTyr was used to construct an electrochemical biosensor for BPA detection, exhibiting a low detection limit of 12 nmol L-1 and a wide linear range from 5 × 10-8 to 2 × 10-6 mol L-1. Compared with native tyrosinase, the nTyr based biosensor displayed dramatically enhanced stability including thermal stability, organic solvent tolerance and acid/base tolerance. The excellent performance of nTyr based biosensor was not only attributed to the protection of biocompatible rigid polymer shells, but also the multipoint covalent attachments between tyrosinase cores and polymer shells. The robust biosensor was further used for rapid detection of BPA leached from plastic products with satisfactory results. The nTyr based nano-biosensor provides a prospective solution to resolve the stability problem of enzyme biosensors in different application scenarios.

Electrochemical (bio) sensors are now widely acknowledged as a sensitive detection tool for disease diagnosis as well as the detection of numerous species of pharmaceutical, clinical, industrial, food, and environmental origin. The term 'green' demonstrates the development of electrochemical (bio) sensing platforms utilizing biodegradable and sustainable materials. Development of green sensing platforms is one of the most active areas of research minimizing the use of toxic/hazardous reagents and solvent systems, thereby further reducing the production of chemical wastes in sensor fabrication. The present review includes green electrochemical (bio) sensors which are based on firstly, green sensors comprising natural and non-hazardous materials (e.g., paper/clay/zeolites/biowastes), secondly sensors based on nanomaterials synthesized by green methods and lastly sensors constituting green solvents (e.g., ionic liquids/deep eutectic solvents). Electrochemical performances of such green sensors and their benefits such as biodegradability, non-toxicity, sustainability, low-cost, sensitive surfaces, etc. Have been discussed for quantification of various target analytes. Associated challenges, possible solutions, and opportunities towards fabricating green electrochemical sensors and biosensors have been provided in the conclusion section.

Environmental contextRemediation of wastewater containing polycyclic aromatic hydrocarbons and metals is essential to limit adverse effects on the environment and human health. Using a simple precipitation method, we prepared porous magnetic MgO hybrids for use as a material for removing pollutants from wastewater. The material showed excellent removal performance for 12 polycyclic aromatic hydrocarbons and cadmium ions, and thus has potential applications in wastewater treatment. AbstractHierarchical porous magnetic MgO hybrids (Fe3O4/MgO) are controllably synthesised based on a facile precipitation process. The resulting material displays a three-dimensional architecture with nest-like morphology, large surface area (135.2m2 g−1) and uniform mesochannels (5–35nm). The adsorption equilibrium data of target polycyclic aromatic hydrocarbons (PAHs) on Fe3O4/MgO sorbents are described by the Langmuir isotherm model. The composites show a strong tendency for the removal of PAHs owing to their porous structure that possesses an excellent affinity for PAHs. Under the optimal conditions, a removal of more than 70% is achieved for 12 PAHs. The materials also exhibit a good removal ability of cadmium (Cd2+) from water with fast adsorption (80%). Moreover, the composites possess sufficient magnetism for separation. To demonstrate the performance of the sorbents, Fe3O4/MgO is exposed to aqueous samples spiked with low concentrations of PAHs and Cd2+. In almost all cases, the composites are superior to the commercially available sorbents as well as un-functionalised Fe3O4 nanoparticles. Therefore, this work provides a promising approach for the simultaneous removal of PAHs and Cd2+ from water using multifunctional MgO microspheres.

Graphene (GR), as an outstanding material, has shown powerful applications in microbial fuel cells (MFCs) promoting the concept of bioenergy production. Featuring unique physical and chemical characteristics, GR exhibits great possibilities for designing its novel hybrids. GR as an anode material accelerates extracellular electron transfer (EET) between microbes and electrode surface and as potent cathodic catalyst facilitates oxygen reduction reaction (ORR) kinetics. A bulk of dimension-tailored GR nanocomposites with conducting polymers, metal nanoparticles, metal oxides, ionic liquids, and doped heteroatoms have been designed as novel electrodes leading to enhanced performance of MFCs. GR-based bioactive architectures hold great promise for their effective applications in bioelectrochemical systems. The present chapter deals with different nanohybrids of GR as anodes and cathodes improving the overall efficiency of MFCs. Future perspectives addressing some key challenges pertaining to implication of GR materials in MFCs have been concluded at the end.

A novel graphene/silicon dioxide nano-composite modified glassy carbon electrode (GR/SiO 2 /GCE) sensor has been developed for the sensitive determination of an adrenergic agonist, muscle relaxant drug tizanidine (TZ) in solubilized system. The influence of experimental parameters on analytical performance of the developed sensor was investigated. GR/SiO 2 /GCE sensor exhibits excellent electrocatalytic performance toward reduction of tizanidine in Britton Robinson buffer at pH 6.5 in solubilized system of 0.1% cetyltrimethyl ammonium bromide (CTAB). Under optimized conditions, square wave cathodic peak current shows a linear response for tizanidine reduction over a concentration range of 5 (ng mL −1 ) to 10 (μg mL −1 ) with a correlation coefficient ( r 2 ) of 0.9928. The detection limit (LOD) and quantification limit (LOQ) were found to be 40.05 ng mL −1 and 133.50 ng mL −1 , respectively. The fabricated sensor shows great promise for simple, sensitive, quantitative screening and detection of tizanidine using voltammetric techniques.

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.

The present work represents a simple and effective preparation of a novel mixed-mode anion-exchange (MAX) sorbent based on porous poly[2-(diethylamino)ethyl methacrylate-divinylbenzene] (poly(DEAEMA-DVB)) spherical particles synthesized by one-step Pickering emulsion polymerization. The poly(DEAEMA-DVB) particles were quaternized with 1,4-butanediol diglycidyl ether (BDDE) followed by triethylamine (TEA) via epoxy-amine reaction to offer strong anion exchange properties. The synthesized MAX sorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption measurements and elemental analysis. The MAX sorbent possessed regular spherical shape and narrow diameter distribution (15–35 μm), a high IEC of 0.54 meq/g, with carbon and nitrogen contents of 80.3% and 1.62%, respectively. Compared to poly(DEAEMA-DVB), the MAX sorbent exhibited decreased SBET (390.5 vs. 515.3 m2 g−1), pore volume (0.74 vs. 0.85 cm3 g−1) and pore size (16.8 vs. 17.3 nm). Moreover, changes of N content for producing the MAX sorbent reveal a successful two-step quaternization, which can be highly related to such a high IEC. Finally, the MAX sorbent was successfully evaluated for selective isolation and purification of some selected acidic pharmaceuticals (ketoprofen, KEP; naproxen, NAP; and ibuprofen, IBP) from neutral (hydrocortisone, HYC), basic (carbamazepine, CAZ; amitriptyline, AMT) pharmaceuticals and other interferences in water samples using solid phase extraction (SPE). An efficient analytical method based on the MAX-based mixed-mode SPE coupled with HPLC-UV was developed for highly selective extraction and cleanup of acidic KEP, NAP and IBP in spiked wastewater samples. The developed method exhibited good sensitivity (0.009–0.085 μg L−1 limit of detection), satisfactory recoveries (82.1%–105.5%) and repeatabilities (relative standard deviation

Bismuth (III) oxide-multiwalled carbon nanotubes hybrid film sensor was used to determine anticoagulant acenocoumarole (ACN) by square wave and cyclic voltammetry. The bismuth oxide-multiwalled carbon nanotubes (Bi2O3-MWCNTs) hybrid film sensor exhibits enhanced sensitivity for acenocoumarole detection as compared with the MWCNTs film modified, bismuth oxide film modified and bare GC electrodes. Various parameters such as working electrode surface area (A), number of electrons transferred (n), and charge transfer resistance (Rct) were calculated and examined for optimum analytical performance of the proposed sensor. The peak current response increased linearly over the concentration range of 30 ng mL−1–20 μg mL−1 with the limit of detection (LOD) of 0.4 ng mL−1 and limit of quantification (LOQ) of 1.3 ng mL−1. The proposed Bi2O3-MWCNTs hybrid film sensor has a good operational stability and was successfully applied to the determination of acenocoumarole in pharmaceutical formulation. © 2013 The Electrochemical Society. [DOI: 10.1149/2.078401jes] All rights reserved.

A sensitive escitalopram sensor has been developed using a bismuth (III) oxide (Bi 2 O 3 ) nano-particles-modified-glassy carbon electrode (GCE). The bismuth (III) oxide was mechanically deposited on to the surface of GCE in N,N-dimethylformamide solution and was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor showed an excellent electro-catalytic activity toward oxidation of escitalopram. Micellar media was also used for solubilizing the escitalopram and it shows enhancement effect. The oxidative current increased linearly with increasing concentration of escitalopram at Bi 2 O 3 /GCE from 150 μg/mL to 400 μg/mL and detection limit was calculated to be 53.67 μg/mL. The fabricated sensor can be used for the determination of escitalopram in pharmaceutical formulation.

An ultrasensitive electrochemical sensor based on the electrocatalytic properties of nano graphene (nGN) and multiwalled carbon nanotubes (MWCNTs) for the detection of quinidine (QD) in solubilized systems has been developed. This nano graphene-multiwalled carbon nanotube (nGN-MWCNT) composite film modified sensor shows the higher stability and stronger catalytic activity towards oxidation of quinidine and the over-potential decreased significantly compared with the bare glassy carbon electrode (GCE). The electrochemical characterization of the sensor was done by scanning electron microscopy (SEM) and cyclic voltammetry (CV) with working electrode surface area 0.56 cm2 and diffusion coefficient 2.15 × 10−3 cm2 s−1. Under the optimized conditions, the oxidation peak current of QD is found to be proportional to its concentration in the range of 60 ng–50 μg with a detection limit of 0.186 ng. The sensor was successfully employed for the detection of quinidine in bulk drugs and in its commercial pharmaceutical formulation.

A highly sensitive and stable TiO2multi walled carbon nanotubes (TiO2-MWCNTs) composite film modified glassy carbon electrode was fabricated and characterized. The excellent electrocatalytic activity and the influence of composite film results in good characteristics such as low potential detection of satranidazole (STZ) with a low detection limit, fast response, good stability and anti-interferent ability. The incorporation of TiO2 nanoparticles with multi walled carbon nanotubes (MWCNTs) greatly increases the voltammetric peak current and electrochemical reactivity of STZ in comparison to that at the MWCNTs film. The morphologies and electrochemical performance of the modified TiO2-MWCNTs/GC electrode was investigated by scanning electron microscopy (SEM), impedance spectroscopy, cyclic voltammetry (CV) and square wave voltammetry. The electrochemical sensor shows excellent analytical performance and exhibits wide linear range of 80 ng mL−1−100 μg mL−1 with detection limit of 2.809 ng mL−1 and quantification limit of 9.365 ng mL−1. © 2013 The Electrochemical Society. [DOI: 10.1149/2.086308jes] All rights reserved.

An ultrasensitive electrochemical sensor based on the synergistic effect of nano ZnO and multi-walled carbon nanotubes (MWCNTs) for electrochemical sensing of calcium antagonist cilnidipine has been developed. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy, electrochemical impedance spectroscopy, chronocoulometry, square wave voltammetry and cyclic voltammetry. The developed electrochemical sensor exhibited good analytical performance including high sensitivity and selectivity as compared to multiwalled carbon nanotubes modified (MWCNTs/GCE), nano zinc oxide modified (nZnO/GCE) and bare glassy carbon electrode (GCE). The potential utility of developed sensor was demonstrated by applying successfully to the electroanalytical determination of cilnidipine in its pharmaceutical formulation. Under optimal conditions, the peak current is linear to cilnidipine concentration ranging from 5 ng mL −1 −5 μ gm L −1 with a detection limit of 1.5 ng mL −1 . The ease of fabrication, excellent electrochemical performance and long term stability are the promising features of the fabricated sensor.

Magnesium oxide microspheres functionalized with phenyltrichlorosilane (PTS-MgO) were synthesized by surface modification through silanization reaction, which was confirmed by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and N2 adsorption-desorption. The result indicated that PTS-MgO not only possessed the ability of enhancing the retention with PAHs, but also weakening the interference from chlorinated compounds. As a sorbent for the matrix solid-phase dispersion (MSPD) extraction, PTS-MgO was used to selectively extract seven dioxin-like polycyclic aromatic hydrocarbons (DL-PAHs) from soil samples. Various parameters affecting the recoveries of seven DL-PAHs were investigated and optimized, such as sorbent/sample mass ratio, grinding time, rinsing and eluting conditions. Under the optimized conditions, the developed method combining MSPD with HPLC-FLD exhibited good sensitivity (0.02–0.12 ng g−1 detection of limits) and linearity (linear correlation coefficient greater than 0.9997). Satisfactory recoveries with DL-PAHs spiked at two levels (10 and 80 ng g−1) were obtained in the range of 72.2–113.1% with RSD

School of Studies in Chemistry, Jiwaji University, Gwalior-474 011, Madhya Pradesh, India E-mail : rajeevjain54@yahoo.co.in Manuscript received 01 January 2014, accepted 15 January 2014 A multi-walled carbon nanotubes (MWCNTs) modified sensor was used for the electrocatalytic quantification of nevirapine in solubilized system. The electrochemical characteristics of the MWCNTs film coated modified GCE towards nevirapine oxidation were investigated by electrochemical impedance spectroscopy (EIS), square-wave and cyclic voltammetry. The results showed an efficient electrocatalytic activity at modified sensor for the electro-oxidation of nevirapine. The morphological characterization of multi-walled carbon nanotubes was investigated by scanning electron microscopy (SEM). The multi-walled carbon nanotubes film coated glassy carbon electrode (MWCNTs/GCE) exhibits an efficient electron mediating behaviour together with well defined oxidation peaks of nevirapine. The potential utility of the constructed MWCNTs film coated modified GCE was demonstrated by applying them to the analytical quantification of nevirapine in solubilized system of sodium lauryl sulphate (SLS). Under the optimum conditions, the anodic peak current shows a linear relationship with nevirapine concentration in the range of 100–400 µg/mL with detection limit of 38.45 µg/mL.

A sensitive electroanalytical method for quantification of clomiphene citrate in pharmaceutical formulation has been developed on the basis of the enhanced electrochemical response at glassy carbon electrode modified with nano-composite film of bismuth (III) oxide -multiwalled carbon nanotubes (Bi2O3-MWCNTs).A well developedanodic peak for the oxidation of clomiphene was obtained in acidic medium using BR buffer at modified and unmodified electrodes. The influence of optimisation parameters such as pH and optimal loading of composite mixture on the analytical performance of the sensor was evaluated. The morphological characteristics, effective electrode surface area and charge transfer properties of the developed Bi2O3-MWCNTs/GCE sensor were studied by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy (EIS) respectively. The fabricated sensor based on the Bi2O3-MWCNTs modified electrode showed electrocatalytic activity in terms of significant improvement of the anodic current of clomephene and lowering of the detection limit. Under optimized conditions, the squarewave oxidation peak current of clomiphene was linear over the concentration range of 50 ng mL-1 to10 µg mL-1. The obtained results suggest that the developed sensor can be successfully used for the determination of clomiphene in its commercial pharmaceutical formulations.

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