Amperometric Determination

The use of a multi-wall carbon nanotube, ionic liquid and gold nanoparticle film glassy carbon electrode to determine oxytetracycline (OTC), one of the mostly used antibiotics in salmon industry, by amperometry and adsorptive stripping voltammetry (AdSV) is reported. Electrodes were coated with [BMIM]3F 5 EPF 3 , [EMIM]F 3 MSO 3 , [BMIM]PF 6 and [BMIM]BF 4 , achieving the highest sensitivity with [BMIM]BF 4 . Using AdSV, variables like pH, scan rate (ν), accumulation potential, and time (E acc , t acc ) were optimized. The best experimental conditions were: pH = 7.0; ν = 0.60 V s -1 ; E acc = 0.40 V, and t acc = 70 s. The relative standard deviation obtained was 1.5% (n=5) for a solution containing 5.0x10 -6 mol L -1 of OTC. Using AdSV and amperometric techniques, the linear calibration curves ranged up to 8.0x10 -6 mol L -1 and the detection limits (3) were 1.5x10 -7 and 2.0x10 -8 mol L -1 , respectively. The methods were validated using fish tissue spiked with OTC. Because the sensitivity of the amperometric technique is higher than AdSV, the analysis of fish tissue samples was made using the former technique, getting a LoD of 5.3x10 -10 mol L -1 .

The development of biosensors has seen recent growth owing to their wide range of potential applications from the defending of bioterrorism to the detection of various diseases. Recent investigations in highly sensitive nanomaterials containing nanotechnology suggest the possibility of its advanced applications as biosensors in different biomedical fields. Besides highlighting the characteristic features of different classes of advanced biosensor across different fields of potential application, this article gives a clear overview of some specific investigations related to the surface immobilizations of piezoelectric biosensors employing effective materials and advanced technologies. Further, the current development of piezoelectric biosensors in the detection of potential biomolecules for advanced biomedical applications is critically reviewed. The qualitative and quantitative sensitivity of piezoelectric biosensors, various expressions of resonant frequency shift with changes in mass, thickness, density, and stress for piezoelectric materials are distinctly explored. The importance of several novel nanomaterials for the detection of various diseased biomolecules is clearly illustrated. This study concludes that proper selection of materials is potential to bring improvement in quality as well as reduction in cost of advanced biosensor devices.

In this study, a sorbent flow preconcentration system coupled to amperometric detector for the chloroguaiacol (4-chloro-2-methoxyphenol) determination at submicromolar levels is described. The satisfactory selectivity of the proposed method was attained by means of the use of a chloroguaiacol-imprinted polymer, whose the synthesis was carried out by bulk polymerization. Flow and chemical parameters associated to the preconcentration system, such as sample pH, preconcentration and elution flow rates, concentration of the carrier solution (KCl) and eluent volume were investigated through multivariate analysis. The flow preconcentration of chloroguaiacol was not affect by equimolar presence of structurally similar phenolic compounds including catechol, 4-chloro-3-methylphenol, 4-aminophenol and 2-cresol, thus showing the good performance of the imprinted polymer. Under the best experimental conditions, it was obtained a preconcentration factor of 110-fold and low detection and quantification limits of 27 and 78 nmol L −1 , respectively. The analytical curve covered a wide linear range from 0.05 up to 5.0 mol L −1 (r > 0.999) and satisfactory precision (n = 8) evaluated by relative standard deviation (R.S.D.) were respectively, 5.5 and 4.2%, for solutions of 1.0 and 5.0 mol L −1 chloroguaiacol. Other parameters related to the performance of the flow system were also evaluated including concentration efficiency of 27.5 min −1 and consumptive index of 0.09 mL. Recoveries varying from 93 up to 112% for water samples (tap water and river water) spiked with chloroguaiacol concentration were achieved, thus assuring the accuracy of the proposed flow preconcentration system.

Nowadays a growing number of biosensing systems in microand nanoscale rely in expensive and bulky equipment that must capable acc ur tely to resolve the angle or wavelength of optical interrogation. The costs, size, sensitiv ity, properties and etc which are required to assemble these biosensing tools, may limit the port ability of such systems, and may restrict their usefulness in sensing applications outside of a con trolled environment. This research covers creation and investigations of new piezoelectric ma teri ls based on PVDF and PZT with unique properties, i.e. synthesis, piezoelectric thin film formation, imprint of microperiodic structures, analysis of surface morphology by Atomic Force Micr oscopy, and analysis of diffraction efficiencies using laser diffractometer. These deve lopments of new piezoelectric films have made it possible to understand the strengthening an d deformation mechanisms in microand nanoscales together by bringing new insights in bio sensing applicat...

A chromatographic column was constructed which could be operated with an electrically conductive stationary phase of graphite particles. This column allowed chromatographic experiments at variable electric potentials of the column material. The chromatographic behavior of selected carboxylic acids was significantly influenced at positive column potentials. An equimolar mixture of three different carboxylic acids were separated at a potential of 600 mV (versus. Ag/AgCl). Surprisingly, the stereoisomers maleic and fumaric acid, which are identical in molecular mass and charge, could also be separated. Further improvements to the chromatographic performance were achieved by applying potential drops and linear potential gradients.

In this study, a sorbent flow preconcentration system coupled to amperometric detector for the chloroguaiacol (4-chloro-2-methoxyphenol) determination at submicromolar levels is described. The satisfactory selectivity of the proposed method was attained by means of the use of a chloroguaiacol-imprinted polymer, whose the synthesis was carried out by bulk polymerization. Flow and chemical parameters associated to the preconcentration system, such as sample pH, preconcentration and elution flow rates, concentration of the carrier solution (KCl) and eluent volume were investigated through multivariate analysis. The flow preconcentration of chloroguaiacol was not affect by equimolar presence of structurally similar phenolic compounds including catechol, 4-chloro-3-methylphenol, 4-aminophenol and 2-cresol, thus showing the good performance of the imprinted polymer. Under the best experimental conditions, it was obtained a preconcentration factor of 110-fold and low detection and quantification limits of 27 and 78 nmol L −1 , respectively. The analytical curve covered a wide linear range from 0.05 up to 5.0 mol L −1 (r > 0.999) and satisfactory precision (n = 8) evaluated by relative standard deviation (R.S.D.) were respectively, 5.5 and 4.2%, for solutions of 1.0 and 5.0 mol L −1 chloroguaiacol. Other parameters related to the performance of the flow system were also evaluated including concentration efficiency of 27.5 min −1 and consumptive index of 0.09 mL. Recoveries varying from 93 up to 112% for water samples (tap water and river water) spiked with chloroguaiacol concentration were achieved, thus assuring the accuracy of the proposed flow preconcentration system.

The development of biosensors has seen recent growth owing to their wide range of potential applications from the defending of bioterrorism to the detection of various diseases. Recent investigations in highly sensitive nanomaterials containing nanotechnology suggest the possibility of its advanced applications as biosensors in different biomedical fields. Besides highlighting the characteristic features of different classes of advanced biosensor across different fields of potential application, this article gives a clear overview of some specific investigations related to the surface immobilizations of piezoelectric biosensors employing effective materials and advanced technologies. Further, the current development of piezoelectric biosensors in the detection of potential biomolecules for advanced biomedical applications is critically reviewed. The qualitative and quantitative sensitivity of piezoelectric biosensors, various expressions of resonant frequency shift with changes in mass, thickness, density, and stress for piezoelectric materials are distinctly explored. The importance of several novel nanomaterials for the detection of various diseased biomolecules is clearly illustrated. This study concludes that proper selection of materials is potential to bring improvement in quality as well as reduction in cost of advanced biosensor devices.

Arylthioureas, which are toxic, on oxidation by cetyltrimethylammonium dichromate in acetic acid undergo desulphurization to the corresponding non-toxic arylureas. The mechanism of the oxidation reaction has been studied spectrophotometrically. The rate of reaction is found to be dependent on [CTADC], [phenylthiourea], [acid], [surfactant], polarity of the solvents and reaction temperature. The reaction is fractional order with respect to [substrate] and is catalyzed by acid. With increase in [CTADC], the rate constant decreases. The structure of the substituents has no significant effect on the rate constant. On the basis of various observations, a mechanism has been proposed for the oxidation reaction.

Phenylthioureas have been subjected to oxidation in acetonitrile medium in neutral condition to investigate the oxidation behaviour of cetyltrimethylammonium permanganate on multifunctional groups. The oxidation product in each reaction is found to be the corresponding phenylurea. The rate of reaction is dependent on [CTAP], [phenylthiourea], [surfactant] and reaction temperature. A Michaelis-Menten type kinetics is observed with respect to the substrate. A reaction mechanism involving the formation of a cyclic intermediate in the slow step is proposed for the oxidation reaction.

Arylthioureas, which are toxic, on oxidation by cetyltrimethylammonium dichromate in acetic acid undergo desulphurization to the corresponding non-toxic arylureas. The mechanism of the oxidation reaction has been studied spectrophotometrically. The rate of reaction is found to be dependent on [CTADC], [phenylthiourea], [acid], [surfactant], polarity of the solvents and reaction temperature. The reaction is fractional order with respect to [substrate] and is catalyzed by acid. With increase in [CTADC], the rate constant decreases. The structure of the substituents has no significant effect on the rate constant. On the basis of various observations, a mechanism has been proposed for the oxidation reaction.

The development of biosensors has seen recent growth owing to their wide range of potential applications from the defending of bioterrorism to the detection of various diseases. Recent investigations in highly sensitive nanomaterials containing nanotechnology suggest the possibility of its advanced applications as biosensors in different biomedical fields. Besides highlighting the characteristic features of different classes of advanced biosensor across different fields of potential application, this article gives a clear overview of some specific investigations related to the surface immobilizations of piezoelectric biosensors employing effective materials and advanced technologies. Further, the current development of piezoelectric biosensors in the detection of potential biomolecules for advanced biomedical applications is critically reviewed. The qualitative and quantitative sensitivity of piezoelectric biosensors, various expressions of resonant frequency shift with changes in m...

The development of biosensors has seen recent growth owing to their wide range of potential applications from the defending of bioterrorism to the detection of various diseases. Recent investigations in highly sensitive nanomaterials containing nanotechnology suggest the possibility of its advanced applications as biosensors in different biomedical fields. Besides highlighting the characteristic features of different classes of advanced biosensor across different fields of potential application, this article gives a clear overview of some specific investigations related to the surface immobilizations of piezoelectric biosensors employing effective materials and advanced technologies. Further, the current development of piezoelectric biosensors in the detection of potential biomolecules for advanced biomedical applications is critically reviewed. The qualitative and quantitative sensitivity of piezoelectric biosensors, various expressions of resonant frequency shift with changes in mass, thickness, density, and stress for piezoelectric materials are distinctly explored. The importance of several novel nanomaterials for the detection of various diseased biomolecules is clearly illustrated. This study concludes that proper selection of materials is potential to bring improvement in quality as well as reduction in cost of advanced biosensor devices.

A surface plasmon resonance based biosensor has been proposed for a simple, label-free, highly selective and sensitive detection of cholesterol employing the flavoenzyme, cholesterol oxidase, as the sensing element. The immobilization of cholesterol oxidase conjugated with bovine serum albumin on to the gold sensor chip has been accomplished by covalent binding through an activated self-assembled 11-mercaptoundecanoic acid monolayers. The surface morphology of the biosensor has been recorded using atomic force microscopy. Sensitivity of 1.41m°/mg dl -1 of cholesterol has been achieved using the biosensor. The biosensor is highly specific for cholesterol and shows no significant interference from potent interferents such as ascorbic acid and uric acid.

Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to environmental sciences. In recent years, there has been a significant improvement in sensor design along with the advances in micro- and nano-fabrication technology and the use of newly designed materials, leading to the development of high-performance gas sensors. Advanced micro- and nano-fabrication technology enables miniaturization of these sensors into micro-sized gas sensor arrays while maintaining the sensing performance. These capabilities facilitate the development of miniaturized integrated gas sensor arrays that enhance both sensor sensitivity and selectivity towards various analytes. In the past, several micro- and nano-gas sensors have been proposed and investigated where each type of sensor exhibits various advantages and limitations in sensing resolution, operating power, response, and recovery time. This paper presents an overview of the recent progress made in a wide ra...

Novel flower-like silver particles with triangular plates as building block along with functionalized graphene (straggled sheets) and enzymes horseradish peroxidase (HRP) or cholesterol oxidase (ChOx), were obtained on graphite electrode by galvanostatic electrodeposition method. The morphology of the electrodeposits has been characterized using scanning electron microscopy and energy-dispersive analysis of X-ray. The resulting biosensors named Nf/(HRPf-graphene-Ag)/Gr and Nf/(ChOx-f-graphene-Ag)/Gr were evaluated for electrochemical activity using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. Optimization of the interdependent experimental parameters such as pH and temperature were achieved and maintained constant throughout the experiments. An activation energy of 2.5 kJ mol −1 was obtained for Nf/(HRP-f-graphene-Ag)/Gr electrode while Nf/(ChOx-fgraphene-Ag)/Gr showed an activation energy of 2.06 and 3.12 kJ mol −1. Furthermore, the former electrode demonstrated a good linear range of 25 μM to 19.35 mM with rapid response time of 3 s and detection limit of 5 μM for hydrogen peroxide. Similarly, the Nf/(ChOx-f-graphene-Ag)/Gr electrode revealed a linear range of 0.1-4.5 mM with rapid response time of 3 s and an excellent detection limit of 0.514 mM for cholesterol. Besides this, the Nf/(HRP-f-graphene-Ag)/Gr and Nf/(ChOx-fgraphene-Ag)/Gr electrodes displayed a Michaelis-Menten constant of 0.26 and 0.57 mM, respectively, suggesting high affinity and enzymatic activity. The enhanced performance of biosensors towards detection of substrate and rejection of interferents, provided an evidence for its high antiinterference ability. Additionally the biosensors exhibit long term storage stability and reproducibility with antifouling properties.

Hybridization of nanoscale metals and carbon nanostructures into composite nanomaterials has produced some of the best-performing super capacitors and biosensors to date. The challenge remains to develop scalable nanofabrication methods that are amenable to the development of biosensors. A scalable nanostructured composite based on graphene oxide nanosheets (GO), Ag nanoparticles, and a biorecognition element (glucose oxidase) was presented. In addition to good conductivity and biocompatibility, this matrix had a low total cost. The surface of composite was rough due to the presence of GO in PVA matrix that could increase contact area between composite and enzyme layer and consequently enhanced biosensor electrochemical response. Surface morphology was analyzed by SEM and characterization of the composite elements was carried out using FTIR and XRD. Finally, impedance of different samples was determined by electrochemical impedance spectroscopy (EIS) and the effect of GO amount on impedance of the composite was investigated. This method to synthesis of the nanocomposite was devoted to glucose sensing succeeded a favorable device design that also exhibited remarkable glucose biosensing performance such as improved glucose sensitivity (25 nM limit of detection, 15.32 mAM −1 cm −2 of sensitivity, 150 nM to 10 mM of linear range), and excellent selectivity. To the best our knowledge, this device is the first biosensor protocol that used the nanocomposite for glucose determination.

In this study, we integrate plasmonic metal nanomaterials with a piezoelectric polyvinylidene fluoride (PVDF) polymer and lithium niobate (LiNbO 3) based composite to form an all-solid-state flexible self-energized sensor. We demonstrate that following the application of a load, the film enhances the surface-enhanced Raman spectroscopy (SERS) signal of an analyte molecule up to 14 times. The piezoelectric β-phase of PVDF in the film is optimized through the introduction of multi-walled carbon nanotubes and post-fabrication UV irradiation annealing. Additionally, the SERS signal enhancement can be further increased by the application of in situ UV light irradiation of the sample, resulting in the generation of photoexcited electrons from LiNbO 3 microparticles introduced into the composite. Both the application of a mechanical displacement and the UV light-induced charge generation result in an improved charge transfer between the film and an analyte molecule. The piezoelectric PVDF/LiNbO 3 film has been shown to be a suitable SERS platform for the detection of important biological molecules, demonstrating the potential of the substrate for fast on-site detection applications.

Ethanol is a highly flammable chemical and is widely used for medical and industrial applications. In this paper, optical sensing performance of aqueous ethanol with different concentrations is investigated using multimode fiber coated with carbon nanotubes (CNT). The multimode optical fiber tip is coated with CNT via a drop-casting technique and is annealed at 70 C to improve the binding of the nanomaterial to the silica fiber. The optical fiber tip and the CNT sensing layer are microcharacterized using field emission scanning electron microscopy, Raman spectroscopy, and X-ray diffraction techniques. The reflectance response of the developed fiber sensor is measured using a spectrophotometer in the optical wavelength range of 500-800 nm. Upon exposure to ethanol with concentration ranges of 5%-80%, the sensor reflectance reduced proportionally. The dynamic response decreased by 4% when the sensor is exposed to ethanol with concentration of 80% in distilled water. It is found that the sensor shows fast response and recovery as low as 38 and 49 s, respectively.

Piezoelectric materials have been widely adopted for sensing, actuation, and energy harvesting in structural health monitoring applications. To date, most of the piezoelectric materials employed are piezoceramics such as lead zirconate titanate (PZT) or piezoelectric polymers such as poly(vinylidene fluoride) (PVDF). Although PZTs exhibit high piezoelectricity, they are extremely brittle; on the other hand, PVDF and their copolymers are inherently very flexible but cannot generate large actuation forces due to their low stiffness. Thus, the main objective of this research is to develop a piezoelectric zinc oxide nanoparticle-based thin film that possesses high piezoelectricity with enhanced mechanical properties (i.e., high stiffness, strength, and flexibility). In order to explore the influence of film fabrication parameters on the bulk nanocomposite's piezoelectric and mechanical performance, different concentrations of zinc oxide nanoparticles are dispersed in polyelectrolyte solutions. These solutions are then employed for fabricating thin films via a simple thermal evaporation procedure to evaporate the excess solvent. Upon nanocomposite fabrication, these prototype films are surface-mounted to cantilevered beam specimens. Piezoelectric response is validated by measuring the thin film's generated voltages during free vibration of the cantilever due to an applied initial displacement at the free end. Evaluation of mechanical performance is then conducted by mechanically cutting the nanocomposites to small rectangular specimens. Then, these films are loaded in monotonic uniaxial tension to extract their stress-strain response for determining the films' Young's modulus, ultimate tensile strength, and ultimate failure strain.

A bioreceptor that is an immobilized sensitive biological element (e.g. enzyme, DNA probe, antibody) recognizing the analyte (e.g. enzyme substrate, complementary DNA, antigen). Although antibodies and oligonucleotides are widely employed, enzymes are by far the most commonly used biosensing elements in biosensors. 2. A transducer is used to convert (bio)chemical signal resulting from the interaction of the analyte with the bioreceptor into an electronic one. The intensity of generated signal is directly or inversely proportional to the analyte concentration. Electrochemical transducers are often used to develop biosensors. These systems offer some advantages such as low cost, simple design or small dimensions. Biosensors can also be based on gravimetric, calorimetric or optical detection [1]. www.intechopen.com A Roadmap of Biomedical Engineers and Milestones 116 Biosensors are categorized according to the basic principles of signal transduction and biorecognition elements. According to the transducing elements, biosensors can be classified as electrochemical, optical, piezoelectric, and thermal sensors [3]. Electrochemical biosensors are also classified as potentiometric, amperometric and conductometric sensors. The application of biosensor areas [4] are clinic, diagnostic, medical applications, process control, bioreactors, quality control, agriculture and veterinary medicine, bacterial and viral diagnostic, drag production, control of industrial waste water, mining, military defense industry [5], etc.

We report on a novel matrix of solgel organicinorganic nanocomposite that was fabricated from silica sol gel and dextran. It was used for the immobilization of horseradish peroxidase (HRP) to give a biosensor for hydrogen peroxide (H 2 O 2). The sensor film was characterized by Fourier transform infrared and UV-vis spectroscopy with respect to structural features and the conformation of the enzyme. The topographies of the surface of the electrode were investigated by field emission scanning electron microscopy. The biosensor was used to determine H 2 O 2 quantitatively in the presence of Methylene blue as a mediator with high electron transfer efficiency. A pair of stable and well defined quasi-reversible redox peaks of the HRP [Fe (III)]/HRP [Fe (II)] redox couple was observed at pH 7.0. The biosensor responds to H 2 O 2 in the 0.5 mM to 16.5 mM concentration range, and the limit of detection is 0.5 mM.

Twenty-five thiobenzamide derivatives were separated on a reversed-phase system on various stationary phases, with UV photometric and voltammetric detection. The best results were obtained using a Partisil ODS column (10 pm, 250 mm x 4.6 mm I.D.) with a mobile phase consisting of 0.05 M sodium dihydrogen phosphate with 30% (v/v) methanol, containing 1.2 . lop4 A4 EDTA, at a flow-rate of 1 .O ml/min. Voltammetric detection on a carbon-fibre electrode at + 1.4 V (silver-silver chloride) is more sensitive than UV photometric detection at 254 nm, typical detection limits being cu. 0.1 and 1 .O ng. Voltammetric calibration curves exhibit good linearity and the measurements are reproducible (relative standard deviation of cu. 2%).

The liquid chromatographic behaviour of various neuroleptics from the classes of tricyclic dibenzothiepins, -oxepins, -selenepins and similar substances was studied in an ion-pair reversed-phase system using a C4180 chemically bonded stationary phase and a methanol-water-acetic acid mobile phase. The best separation was attained with 70% methanol, 1.8% acetic acid and water, containing 0.005 M sodium pentanesulphonate, 1.2 x lo-4 M EDTA and 0.5 g/l Na2S04. For the detection, an ultraviolet spectrophotometric and a polarographic detector were connected in series. The detection was carried out at 254 nm and at a potential of a dropping mercury electrode of -1.0 V (vs. Ag/AgCl). The UV detector is universal, while the polarographic detector does not respond to compounds simultaneously containing two heteroatoms (0, S) in the central seven-membered ring. The detection limits are of the order of one to tens of nanograms, the polarographic detector being somewhat more sensitive for most of the compounds; the error of the determination is a few per cent. The method was applied to the determination of isofloxythepin and oxyprothepin in pharmaceutical preparations.

The increase in rate of demand of electricity is not commensurable with the available energy despite the effort of increasing electric energy continuously, many alternate has been provided to balance the demand of electricity ( solar, wind , hydro etc.) whilst energy is still not 100% available to be as expected. So there is a need to continuously make effort in making sure electrical energy requirement (electricity) is met even if not 100% but at higher percentage (%) 70% above. Hence the problem is centers on generating electricity from a readily available resources (which we consider to be sound) which is cheap and affordable.

Biosensors are expository gadgets that change over an organic reaction into an electrical flag, containing a natural
component and a physiochemical identifier which are utilized to distinguish analytes. These instruments have an extensive
variety of uses extending from clinical through to ecological,food industry,marine sector and agricultural etc. Despite the fact
that the potential analytic applications are boundless, the most essential current applications are anticipated in the zones of
biomarker revelation, tumor finding, and recognition of infectious microorganisms. The development and deployment of savvy
assistive innovations in the biosensors, like artificial intelligence and neural networking, that adjust for the particular physical
and intellectual deficiencies, is the need of time.The various types of biosensors such as enzyme-based, immuno sensors, tissue based,DNA
biosensors, thermal and piezoelectric biosensors, embedded with artificial neural networking techniques, have been pondered here
to focus their essentialsolicitations in the field of personalized healthcare.This article portrays and describes distinctive classes of biosensors and strategies for ensnarement. Working standards, preferences, and utilizations of numerous biosensors are displayed.

facile and cost effective chemical reduction method is employed for the preparation of reduced
graphene oxide/hydroxyapatite (rGO/HAp) nanocomposites. The transmission electron microscopy
images revealed that the HAp
flakes are well decorated on the surface of rGO. The morphological
structure of the as-synthesized rGO/HAp nanocomposites was confirmed through X-ray diffraction,
Fourier transform infrared spectroscopy and Raman spectroscopy, while the composition and thermal
stability were analyzed by energy dispersive spectra and thermogravimetric analysis, respectively.
Furthermore, the effect of rGO/HAp nanocomposites for the proliferation of Human Mesenchymal Stem
Cell (hMSC) was performed to confirm the biocompatibility. A selective chemical sensor based on rGO/
HAp modified glassy carbon electrode (GCE) for sensitive detection of Bis-phenol A (BPA) has been
developed. Several important parameters controlling the performance of the BPA chemi-sensor were
investigated and optimized at room conditions. The rGO/HAp/Nafion/GCE sensor offers a fast response
and highly sensitive BPA detection. Under the optimal conditions, a linear range from 0.2 nmol L-1 to
2.0 mmol L-1 for the detection of BPA was observed with the detection limit of 60.0 pmol L
1 (signal-to noise
ratio, at an SNR of 3) and sensitivity of 18.98
x104mA.L/mmol.m2. Meanwhile, the fabricated
chemi-sensor showed an excellent, specific and selective recognition to target BPA molecules among
coexistence of other analytes in the buffer system. This novel effort initiated a well-organized way of
efficient rGO/HAp/Nafion/GCE sensor development and practically analyzed the real hazardous
environmental pollutants at room conditions.

A green version of the BFe^ impurity-induced per-oxidase mimicry exhibited by simple and cheap substrate Bnanoclay (NC)^ along with the highly sensitive amperomet-ric and spectrophotometric determination of cholesterol is demonstrated. The BFe^ impurity can act as the catalyst center for hydrogen peroxide reduction similar to the horseradish peroxidase (HRP)-catalyzed reaction. The Michaelis– Menten constant for the NC-catalyzed reaction is found to be lower than that of the HRP-catalyzed reaction indicating high affinity for the substrate. The NC-modulated peroxidase-like catalytic activity originates from the electron transfer between the reducing substrate in the catalyst center and H 2 O 2 with the intermediate generation of hydroxyl radicals. The peroxidase mimicry is successfully applied for the low-potential electrochemical detection of H 2 O 2 (linear detection range 1.96–10.71 mM, R 2 = 0.97). The H 2 O 2 sensing platform is further modified with cholesterol oxidase (CHOx) for the spectrophotometric (linear detection range 50–244 μM, R 2 = 0.99) and amperometric detection of cholesterol (linear detection range 0.099–1.73 mM, R 2 = 0.998).

Nanocomposites are combinations of nanomaterials with other molecules or nanoscaled materials, such as nanoparticles or nanotubes. In general, these novel nanocomposites have different physical and chemical properties from the constituent particles or wires, and will thus allow new kinds of applications. Among these nanocomposites, gold-carbon nanotube (Au-CNT) composites are of particular interests, due to their easy fabrication protocols and broad potential applications. Au-CNT nanocomposites commonly refer to gold nanoparticles deposited on carbon nanotubes. To obtain Au-CNT nanocomposites, different methods have been developed, including direct and linked deposition of gold nanoparticles on CNT. Au-CNT nanocomposites combine the excellent physical and chemical properties of both gold nanoparticles and carbon nanotubes. The easy modification surface of gold nanoparticle and the excellent conductivity of carbon nanotube as well the high surface area, point towards a broad range of applications, such as biosensing, gas sensing, and electrochemistry. This paper reviews the recent progress of different kinds of Au-CNT nanocomposites and their synthesis and applications. properties of nanomaterials and on the developments of instruments such as the combination of scanning probe microscopes with transmission electron microscopes.

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The evolution of 1st to 3rd generation electrochemical biosensors reflects a simplification and enhancement of the transduction pathway. However, in recent years, modification of the transducer with nanomaterials has become increasingly studied and imparts many advantages. The sensitivity and overall performance of enzymatic biosensors has improved tremendously as a result of incorporating nanomaterials in their fabrication. Given the unique and favorable qualities of gold nanoparticles, graphene and carbon nanotubes as applied to electrochemical biosensors, a consolidated survey of the different methods of nanomaterial immobilization on transducer surfaces and enzyme immobilization on these species is beneficial and timely. This review encompasses modification of enzymatic biosensors with gold nanoparticles, carbon nanotubes, and graphene.

This work aims at demonstrating the possibility of using advanced nanocomposite materials with tuned features in order to develop innovative pressure and deformation sensors suitable for a series of applications, including sensorization in narrow environments, implanted deformable devices, artificial skin and flexible multifunctional surgical instruments. By combining metal sputtering and spin-assisted deposition, we developed thin and flexible polymeric membranes made of polydimethylsiloxane doped with barium titanate nanoparticles, carbon nanotubes and boron nitride nanotubes. By exploiting their piezoelectric properties, the nanocomposites were able to transduce applied pressures and strains into electrical signals. Different combinations of nanoparticles, embedded in the polymeric matrix, were tested. We also highlighted the possibility to tune matrix stiffness, thus adding a "degree of freedom" in the development of nanocomposite sensing elements.

Surface biofunctionalization of capacitive micromachined ultrasonic transducer (CMUT) based sensor can develop non-informative stress and elasticity, which are distorting sensor readings related with the mass of established immune complex. The prototype sensor calibration function, using polimethylmetacrylate (PMMA) films from 7 to 100 nm, was developed to relate the sensor readings with the changing mass, elasticity and stress of the film on the CMUT surface. The range of calibration in terms of mass is from 1 to 80 pg per single CMUT cell, 0 -20 MPa in terms of stress with corresponding sensor resonance frequency and resistance readings from 10 to -35 kHz and from 4.5 to -0.5 Ω. Antigen and antibody specific interaction sensing experiment was performed and obtained results showed that informativity of CMUT based immunosensor is much greater than expected, since most of the sensor readings were out of the calibration function, developed for PMMA, range. At the same time, immunosensing experiment demonstrated clear distinction between antigen and antibody mass, which is more than threefold.

A wall-jet ring disc electrode was constructed by adapting a wall-jet¯ow through electrochemical cell. Commercially available spectral graphite and glassy carbon were used as working disc electrodes and the ring electrode was made of stainless steel. The eciency and rate constants, measured in a planar parallel¯ow hydrodynamic regime, indicated the partial electroreduction of dissolved oxygen as a quasi-reversible two-electron process for both electrode materials tested.

Abstract: Some authors use the term “nanosensor” for biomolecules in nano molar concentrations
acting as signals for living cells. In our review we emphasize on microbial sensors for detecting pathogens and on the “hardware” – the type of nanostructures used as a pad of bio sensing element. The main object is different type of nano-structured material used in the sensing process – non functionalized metal nanoparticles, metal oxides forming thin films and functionalized sensors as antibody-coated and aptamer-coated nanostructures and thin films.
The latter have shown high selectivity and sensitivity and appear to be promising for future applications in medicine and
environmental testing. Our investigation proved the sensitivity of thin zinc oxide films to bacterial quantity of Gracilicutes and Firmicutes bacteria. The observed sensitivity was a single cell in a drop of water, but the change of potential to Pseudomonas cells  was almost ten times higher than to Bacillus. It could be due not only to the bacterial type of cell wall but also to the type of dopant and the crystal structure of the ZnO thin film. Recent patents based on nanostructures for detection of clinically important pathogens are discussed.

The surface of biochips prepared on the basis of silicon wafers for studies of reactions of pre-immobilized oligonucleotides and protein molecules was analyzed by high-resolution scanning ellipsometry. The hybridization interactions of nucleic acid (duplex formation in the reaction of an amplicon of the influenza A virus matrix protein gene with probe molecules), sorption of protein molecules, and protein-protein interactions on the surface of the biochip were detected. It was shown that pre-sorption of gold nanoparticles led to greater efficiency of immobilization of protein molecules on the biochip. The experimental data suggest that that ellipsometry is a highly sensitive, nondestructive and inexpensive label-free method for the detection of the biochip surface, which is suitable for quantitative analysis of reactions of biomolecules.

The fabrication of a cholesterol biosensor using gold nanoparticles decorated graphene nanoplatelets has been reported. Thermally exfoliated graphene nanoplatelets act as a suitable support for the deposition of Au nanoparticles. Cholesterol biosensor electrodes have been constructed with nafion solubilized functionalized graphene nanoplatelets (f-G) as well as Au nanoparticles decorated f-G, immobilized over glassy carbon electrode. f-G and Au/f-G thin film deposited glassy carbon electrodes were further functionalized with cholesterol oxidase by physical adsorption. Au nanoparticles dispersed over f-G demonstrate the ability to substantially raise the response current. The fabricated electrodes have been tested for their electrochemical performance at a potential of 0.2 V. The fabricated Au/f-G based cholesterol biosensor exhibits sensitivity of 314 nA/μM cm 2 for the detection of cholesterol with a linear response up to 135 μM. Furthermore, it has been observed that the biosensor exhibits a good anti-interference ability and favorable stability over a month's period.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

The direct amperometric detection of low levels of formaldehyde in the gas phase with an acidic electrochemical cell based on a gold coated Na®on membrane as working electrode was investigated. The sensor was found to show a linear response from the detection limit of 13 ppb up to at least 10 ppm. In¯uences of the¯ow rate and the humidity of the gas stream were studied. Also determined were the crosssensitivities to a number of organic and inorganic gases. A new approach to overcome the interferences from NO, NO 2 and SO 2 is proposed whereby formaldehyde is selectively adsorbed from the sample stream with an aluminum oxide ®lter. By forming the difference for the measurements with and without ®lter a net signal for formaldehyde could be obtained in presence of the interferants.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

Starting from the electromechanochemical principles of bioenergetics formulated by Green and Ji, a theory is proposed which describes enzymic catalysis in terms of piezoelectricity in semiconductors. The choice of this particular physical effect for describing catalytic processes is founded on the following experimental observations: most of the amino-acid residues of enzymes, as well as a large number of other biologically important molecules, exhibit piezoelectric resonances; besides, enzymes can behave like semiconductors. In the pro-

A wall-jet ring disc electrode was constructed by adapting a wall-jet flow through electrochemical cell. Commercially available spectral graphite and glassy carbon were used as working disc electrodes and the ring electrode was made of stainless steel. The efficiency and rate constants, measured in a planar parallel flow hydrodynamic regime, indicated the partial electroreduction of dissolved oxygen as a quasi-reversible two-electron process for both electrode materials tested.

A spectro¯uorimetric method for the determination of methyl paraben based on derivatization with the labelling reagent dansyl chloride (DNS-Cl), is presented. The effect of the reaction variables (pH, DNS-Cl concentration, temperature, reaction time) and instrumental parameters, has been examined. A linear calibration graph in the ng/ml range has been established. The limit of detection is 18 ng/ml with relative standard deviation less than 37. The proposed method has been satisfactorily applied to determination of the paraben in two pharmaceutical preparations.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.

Liquid chromatography with amperometric oxidative detection is proposed as a sensitive method for the determination of aliphatic amines previously converted in thioureido derivatives by reaction with phenylisothiocyanate (PIT). The phenylthioureas of four model amines, methylamine (MA), propylamine (PA), n-butylamine (BA) and isobutylamine (IBA) have been synthesized and isolated. Their electrochemical behavior on a glassy carbon electrode has been explored by cyclic voltammetry. The thioureido derivatives can be oxidized through two one-electron steps at acidic pH values, presumably involving the intermediacy of proton transfers. A mechanistic pathway is also proposed on the basis of experimental data. Liquid chromatographic parameters as mobile phase composition and¯ow rate, temperature and working electrode potential have been optimized. The method permits the simultaneous determination of the phenylthioureas of the selected amines with detection limits in the lower mgL 71 range.