Search

In this work, electrodes based on laser-scribed reduced graphene oxide were fabricated using filter paper as the substrate. To fabricate the electrodes, a water suspension of graphene oxide was filtered to produce a continuous and uniform film of graphene oxide on the filter paper surface. Subsequently, a CO2 laser was used to "write" the working, counter and reference eelctroes by reducing graphene oxide in specific areas to define complete sensors. Referecnce electrodes were then coated with a commercial Ag/AgCl conductive paste to produce a quasi Ag/AgCl reference. As fabricated devices were employed as electrochemical sensors for detection of phosphate ions in water by employing the molybdenum blue method. This method exploits the reaction between molybdate and phosphate ions in acidic media leading to a Keggin-type complex (PMo12O3 40) which, being electrochemically active, enables the indiret detection of phosphate ions. Sensors exhibited high selectivity and sensitive detection of phosphate ions in a wide linear range, from 1 to 20 & mu;M; with a limit of detection of 0.4 & mu;M. To demonstrate that sensors could be utilized for in-situ phosphate ion detection, paper substrate was first pre-loaded with sul-phuric acid and molybdate ions. During analysis, these chemicals were then desorbed directly into the test sample eliminating the need for any kind of external manipulation or reagent addition. Thus, this paper presents the fabrication of a portable, easy-to-use, biodegradable and fast phosphate ions sensor for in situ and real-time monitoring of water quality.

Calcium phosphate/Bioglass composite coatings on AISI 316L were investigated with regard to their potential role as a beneficial coating for orthopedic implants. These coatings were realized by the galvanic co-deposition of calcium phosphate compounds and Bioglass particles. A different amount of Bioglass 45S5 was used to study its effect on the performance of the composite coatings. The morphology and chemical composition of the coatings were investigated before and after their aging in simulated body fluid. The coatings uniformly covered the AISI 316L substrate and consisted of a brushite and hydroxyapatite mixture. Both phases were detected using X-ray diffraction and Raman spectroscopy. Additionally, both analyses revealed that brushite is the primary phase. The presence of Bioglass was verified through energy-dispersive X-ray spectroscopy, which showed the presence of a silicon peak. During aging in simulated body fluid, the coating was subject to a dynamic equilibrium of dissolution/reprecipitation with total conversion in only the hydroxyapatite phase. Corrosion tests performed in simulated body fluid at different aging times revealed that the coatings made with 1 g/L of Bioglass performed best. These samples have a corrosion potential of −0.068V vs. Ag/AgCl and a corrosion current density of 8.87 × 10−7 A/cm2. These values are better than those measured for bare AISI 316L (−0.187 V vs. Ag/AgCl and 2.52 × 10−6 A/cm2, respectively) and remained superior to pure steel for all 21 days of aging. This behavior indicated the good protection of the coating against corrosion phenomena, which was further confirmed by the very low concentration of Ni ions (0.076 ppm) released in the aging solution after 21 days of immersion. Furthermore, the absence of cytotoxicity, verified through cell viability assays with MC3T3-E1 osteoblastic cells, proves the biocompatibility of the coatings.

Over the last decade, as a consequence of the global decarbonization process, the interest towards green hydrogen production has drastically increased. In particular a substantial research effort has focused on the efficient and affordable production of carbon-free hydrogen production processes. In this context, the development of more efficient electrolyzers with low-cost electrode/electrocatalyst materials can play a key role. This work, investigates the fabrication of electrodes of nickel-zinc alloys with nanowires morphology cathode for alkaline electrolyzers. Electrodes are obtained by the simple method of template electrosynthesis that is also inexpensive and easily scalable. Through the analysis of the morphological and chemical composition of nanowires, it was found that the nanowires composition is dependent on the concentration of two metals in the deposition solution. Electrocatalytic tests were performed in 30% w/w potassium hydroxide aqueous solution at room temperature. In order to study the electrodes stability, mid-term galvanostatic test was also carried out. All electrochemical tests show that nanowires with about 44.4% of zinc have the best performances. Particularly, at −50 mAcm−2, these electrodes have an overpotential 50 mV lower than pure Ni nanowire. NiZn nanowires show also a good stability over time without noticeable signs of performance decay.

The performance of electrochemical sensors using an in situ pH control technique for detection of mercury and copper in neutral solutions is described herein. Sensors are comprised of two distinct parallel gold interdigitated microband electrodes each of which may be polarised separately. Biasing one interdigitated “protonator” electrode sufficiently positive to begin water electrolysis, resulted in the production of H+ ions, which, consequently droped the interfacial pH at the other second interdigitated “sensing” electrode. This decrease in pH permitted the electrodeposition (and consequent stripping) of metals at a sensing electrode without the need to acidify the whole test solution. In this work, the local pH could be adjusted in the acidic pH range in a stable and reproducible way just by tailoring the polarization of the protonator electrode. Using this approach, a linear range for copper 5 to 100 ppb and for mercury 1 to 75 ppb were obtained. The sensors also have an extremely high sensitivity for the metals. The in-situ pH control, coupled with electrochemical stripping, allowed metal detection in a complex water matrix, e.g., river water without the need for sample pre-treatment. The electrochemical results were confirmed by comparison to those obtained using inductively coupled plasma – optical emission spectroscopy. A very good agreement was observed between both sets of results. The electrode reproducibility was high (RSD < 10%) and the metals could be co-detected simultaneously. Thus, this work shows a fast and easy approach for in-situ pH control for multi metal detection using solid state sensors.

The fabrication and characterization of nickel-alloy electrodes for alkaline electrolysers is reported. Three different alloys (Ni–Co, Ni–Zn and Ni–W) at different composition were studied in order to determine the optimum condition. Nanostructured electrodes were obtained by template electrodeposition into a nanoporous membrane, starting from aqueous solution containing the two elements of the alloy at different concentrations. Composition of alloys can be tuned by electrolyte composition and also depends on the difference of the redox potential of elements and on the presence of complexing agents in deposition bath. Electrochemical and electrocatalytic tests, aimed at establishing the best alloy composition, were carried out for hydrogen evolution reaction. Then, test conducted at a constant current density in potassium hydroxide (30% w/w) aqueous solution were also performed. For all investigated alloys, very encouraging results were obtained and in particular Ni–Co alloys richer in Co showed the best performance.

This preliminary work shows a new and innovative way to produce silver based electrodes from compact discs and its application towards the detection of chloride ions. A complete sensor was obtained from the compact discs with working, reference and counter electrode made of silver. Chloride ions were detected by exploiting the high affinity of silver with this anion to produce silver chloride. This electrochemical oxidation of silver can be monitored by using an electrochemical technique such as linear scan voltammetry. Indeed, during linear scan voltammetry the oxidation of silver to silver chloride lead to a peak current that increases linearly with chloride concentration. Using this technique, a limit of detection

In this work, a systematic investigation of the different parameters that control the electrodeposition processes was carried out at the aim to synthetizing AgGaSe₂ nanostructures. We found that pH is a key parameter to control both the morphology and composition of the nanostructures. Low pH favours mainly the formation of Ag2Se nanotubes with a scarce mechanical stability, while multi-phase nanowires well anchored to the substrate were obtained at higher pH. We also found that it was necessary to increase dramatically the concentration of the gallium precursor into the deposition bath in order to obtain AgGaSe₂ owing to lower redox potential of the Ga3+/Ga couple than Ag2+/Ag and Se4+/Se. Besides, the addition of specific complexing agents to deposition bath was necessary to better control the composition of the nanostructures. By increasing gallium precursor concentration and adding complexing agents, it was possible to obtain for the first time nanostructures of amorphous AgGaSe₂ with different amount of Ga via one-step electrodeposition. In this work, a systematic investigation of the different parameters that control the electrodeposition processes was carried out at the aim to synthetizing AgGaSe2 nanostructures. We found that pH is a key parameter to control both the morphology and composition of the nanostructures. Low pH favours mainly the formation of Ag2Se nanotubes with a scarce mechanical stability, while multi-phase nanowires well anchored to the substrate were obtained at higher pH. We also found that it was necessary to increase dramatically the concentration of the gallium precursor into the deposition bath in order to obtain AgGaSe2 owing to lower redox potential of the Ga3+/Ga couple than Ag2+/Ag and Se4+/Se. Besides, the addition of specific complexing agents to deposition bath was necessary to better control the composition of the nanostructures. By increasing gallium precursor concentration and adding cornplexing agents, it was possible to obtain for the first time nanostructures of amorphous AgGaSe2 with different amount of Ga via one-step electrodeposition.

In this work electrochemical sensors fabricated from compact disc material (waste or new) are used to quantify chloride ions in different types of samples. All three electrodes, working, counter, and pseudo-reference electrodes, were fabricated from the compact disc and directly used. Different parameters were studied in order to demonstrate the possibility of using this waste material for efficient and low-cost electrochemical sensors. Chloride sensing performance was evaluated using linear scan voltammetry as the detection technique. A sensitivity of 0.174 mA mM−1 cm−2 with a limit of detection of 20 μM and excellent selectivity against many interferents was observed. Selectivity and reproducibility tests were also carried out, showing excellent results. Sensors were also validated with real samples (drinking and sea water, milk, sweat and physiological solutions) with results comparable to conventional techniques. Our results show the applicability and suitability of these low-cost sensors, for detection of those analytes for which, silver, has high sensitivity and selectivity.

In electroanalysis, the benefits accrued by miniaturisation are a key driver in sensor development. Finite element simulations of electrochemical processes occurring at ultramicro- and nano-electrodes are used to provide key insight into experimental design in relation to diffusion profiles and expected currents. The most commonly used method, the diffusion domain approach (DDA) offers a means of reducing a three dimensional design to two dimensions to ease computational demands. However, the DDA approach can be limited when using basic assumptions which can be incorrect, for example that all electrodes in an array are equivalent. Consequently, to get a more realistic view of molecular diffusion to nanoelectrodes, it is necessary to undertake simulations in 3D. In this work, two and three dimensional models of electrodes comprising of (i) single nanowires, (ii) arrays of nanowires and (iii) interdigitated arrays of nanowires operating in generator-collector mode, were undertaken and compared to experimental results obtained from fabricated devices. The 3D simulations predicted a higher extracted current for a single nanowires and diffusionally independent nanowire arrays when compared to 2D simulations since, unlike the 2D model, they take into account molecular diffusion to and from nanowire termini. These current differences were observed to increase with increasing electrode width and decrease with electrode length. When the nanowire arrays were diffusionally overlapped, they behaved as an electrode of larger width, and the divergence between both models increased further. By contrast, using interdigitated nanowire arrays in generator-collector mode, the differences between extracted current values obtained using the 2D and 3D models were significantly lower. Simulations indicated however, that a higher collection efficiency was predicted by the 2D model when compared to the 3D model. Electrochemical experiments were undertaken to confirm the simulation study and demonstrated that the extracted currents from 3D simulations more closely mapped onto experimentally measured currents.

Immunoglobulin G (IgG), a type of antibody, represents approximately 75% of serum antibodies in humans, and is the most common type of antibody found in blood circulation. Consequently, the development of simple, fast and reliable systems for IgG detection, which can be achieved using electrochemical sandwich-type immunosensors, is of considerable interest. In this study we have developed an immunosensor for human (H)-IgG using an inexpensive and very simple fabrication method based on ZnO nanorods (NRs) obtained through the electrodeposition of ZnO. The ZnO NRs were treated by electrodepositing a layer of reduced graphene oxide (rGO) to ensure an easy immobilization of the antibodies. On Indium Tin Oxide supported on Polyethylene Terephthalate/ZnO NRs/rGO substrate, the sandwich configuration of the immunosensor was built through different incubation steps, which were all optimized. The immunosensor is electrochemically active thanks to the presence of gold nanoparticles tagging the secondary antibody. The immunosensor was used to measure the current density of the hydrogen development reaction which is indirectly linked to the concentration of H-IgG. In this way the calibration curve was constructed obtaining a logarithmic linear range of 10–1000 ng/mL with a detection limit of few ng/mL and good sensitivity.

Nitrogen, in the forms of nitrate (NO3-), nitrite, or ammonium, is a nutrient needed for plant growth and it is a common constituent of fertilizers [1]. When fertilizers are overused, they contaminate the ground water and then the food chain. For humans, a low level of nitrate is advisable because it increases the blood flow and has a good effect on both blood pressure and cardiovascular system. On the contrary, a high concentration of nitrate can be dangerous for humans. Nitrate ions undergoes different chemical transformations (i.e. to nitrite ions by Escherichia coli) producing different nitrogen-based compound such as nitrite ions, nitric oxide and ammonia [2]. These chemicals lead to several problems such as cancer, neurodegenerative disease and gastritis. Furthermore, nitrate ions are responsible of the blu-baby disease because they oxide hemoblogin to methemoglobine which has a lower capability to transport oxygen [3]-[4]. Considering all these hazards, the Environmental Protection Agency (EPA) has fixed the maximum allowed concentration of nitrates in drinking water to 44 ppm [5]. Nowadays, nitrate ions quantification is performed by spectroscopy ensuring Limit Of Detection (LOD) in the ppb range [6]-[7]. However, this technique consists of hard procedure (conversion of nitrates to nitrite using cadmium or zinc salts) and requires skilled personnel. Furthermore, it lacks of sensitivity when coloured or opaque samples are analysed. Such disadvantages confine this technique to a lab-based analysis making impossible to detect nitrate ions in real time and/or in situ.

Nowadays, we are assisting in the exceptional growth in research relating to the development of wearable devices for sweat analysis. Sweat is a biofluid that contains useful health information and allows a non-invasive, continuous and comfortable collection. For this reason, it is an excellent biofluid for the detection of different analytes. In this work, electrochemical sensors based on polyaniline thin films deposited on the flexible substrate polyethylene terephthalate coated with indium tin oxide were studied. Polyaniline thin films were abstained by the potentiostatic deposition technique, applying a potential of +2 V vs. SCE for 90 s. To improve the sensor performance, the electronic substrate was modified with reduced graphene oxide, obtained at a constant potential of −0.8 V vs. SCE for 200 s, and then polyaniline thin films were electrodeposited on top of the as-deposited substrate. All samples were characterized by XRD, SEM, EDS, static contact angle and FT-IR/ATR analysis to correlate the physical-chemical features with the performance of the sensors. The obtained electrodes were tested as pH sensors in the range from 2 to 8, showing good behavior, with a sensitivity of 62.3 mV/pH, very close to a Nernstian response, and a reproducibility of 3.8%. Interference tests, in the presence of competing ions, aimed to verify the selectivity, were also performed. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance.

Lead-acid batteries are now widely used for energy storage, as result of an established and reliable technology. In the last decade, several studies have been carried out to improve the performance of this type of batteries, with the main objective to replace the conventional plates with innovative electrodes with improved stability, increased capacity and a larger active surface. Such studies ultimately aim to improve the kinetics of electrochemical conversion reactions at the electrode-solution interface and to guarantee a good electrical continuity during the repeated charge/discharge cycles. To achieve these objectives, our contribution focuses on the employment of nanostructured electrodes. In particular, we have obtained nanostructured electrodes in Pb and PbO2 through electrosynthesis in a template consisting of a nanoporous polycarbonate membrane. These electrodes are characterized by a wider active surface area, which allows for a better use of the active material, and for a consequent increased specific energy compared to traditional batteries. In this research, the performance of lead-acid batteries with nanostructured electrodes was studied at 10 C at temperatures of 25, −20 and 40 °C in order to evaluate the efficiency and the effect of temperature on electrode morphology. The batteries were assembled using both nanostructured electrodes and an AGM-type separator used in commercial batteries.

Dopamine is an important neurotransmitter involved in many human biological processes as well as in different neurodegenerative diseases. Monitoring the concentration of dopamine in biological fluids, i.e., blood and urine is an effective way of accelerating the early diagnosis of these types of diseases. Electrochemical sensors are an ideal choice for real-time screening of dopamine as they can achieve fast, portable inexpensive and accurate measurements. In this work, we present electrochemical dopamine sensors based on reduced graphene oxide coupled with Au or Pt nanoparticles. Sensors were developed by co-electrodeposition onto a flexible substrate, and a systematic investigation concerning the electrodeposition parameters (concentration of precursors, deposition time and potential) was carried out to maximize the sensitivity of the dopamine detection. Square wave voltammetry was used as an electrochemical technique that ensured a high sensitive detection in the nM range. The sensors were challenged against synthetic urine in order to simulate a real sample detection scenario where dopamine concentrations are usually lower than 600 nM. Our sensors show a negligible interference from uric and ascorbic acids which did not affect sensor performance. A wide linear range (0.1–20 μm for gold nanoparticles, 0.1–10 μm for platinum nanoparticles) with high sensitivity (6.02 and 7.19 μA μM-1 cm-2 for gold and platinum, respectively) and a low limit of detection (75 and 62 nM for Au and Pt, respectively) were achieved. Real urine samples were also assayed, where the concentrations of dopamine detected aligned very closely to measurements undertaken using conventional laboratory techniques. Sensor fabrication employed a cost-effective production process with the possibility of also being integrated into flexible substrates, thus allowing for the possible development of wearable sensing devices.

The paper reports some preliminary results concerning the manufacturing process of CuZnSnSe (CZTSe) and CuInGaSe (CIGS) nanowire arrays obtained by one-step electrodeposition for p-n junction fabrication. CZTSe nanowires were obtained through electrodeposition in a polycarbonate membrane by applying a rectangular pulsed current, while their morphology was optimized by appropriately setting the potential and the electrolyte composition. The electrochemical parameters, including pH and composition of the solution, were optimized to obtain a mechanically stable array of nanowires. The samples were characterized by scanning electron microscopy, Raman spectroscopy, and energy-dispersion spectroscopy. The nanostructures obtained showed a cylindrical shape with an average diameter of about 230 nm and a length of about 3 µm, and were interconnected due to the morphology of the polycarbonate membrane. To create the p-n junctions, first a thin film of CZTSe was electrodeposited to avoid direct contact between the ZnS and Mo. Subsequently, an annealing process was carried out at 500 °C in a S atmosphere for 40 min. The ZnS was obtained by chemical bath deposition at 95 °C for 90 min. Finally, to complete the cell, ZnO and ZnO:Al layers were deposited by magnetron-sputtering.

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

Cigarette smoke exposure induces oxidative stress within the airways. Increased oxidative burden contributes to the pathogenesis of chronic lung disorders and is associated with aging and chronic inflammation. Airway epithelial cells highly contribute to Reactive Oxygen Species (ROS) generation within injured and inflamed lung tissues. Among ROS, hydrogen peroxide (H2O2) can be monitored in the extracellular space. Herein, we present an amperometric/voltammetric sensor based on gold nanoparticles and graphene oxide able to detect H2O2 with good sensitivity and selectivity. Using this sensor, H2O2 release was measured in conditioned medium from primary bronchial epithelial cells (PBEC), bronchial epithelial cell line, 16HBE, and adenocarcinoma alveolar basal epithelial cell line, A549, exposed to cigarette smoke extracts (CSE). 16HBE were also treated with resveratrol, an anti-oxidant compound. The results were compared with those obtained by flow cytometry using the same cells stained with Carboxy-H2DCFDA and MitoSOX Red, which detect intracellular ROS and mitochondrial superoxide, respectively. The exposure to CSE resulted in a significant increase of the cathodic current due to the reduction of H2O2 indicating an increased release. Addition of resveratrol decreased CSE-induced release of H2O2 in 16HBE. All the results paralleled those obtained by flow cytometry. The proposed sensor is highly sensitive and selective, fast and cost effective and can potentially be applied for real time and easy monitoring of oxidative stress.

In this work, nickel-iron alloy nanostructured electrodes obtained by template electrosynthesis method are investigated for both hydrogen and oxygen evolution reactions. Electrodes consist of nanowire arrays with high surface area that are able to ensures a high electrolytic activity. To obtain different alloy compositions, the concentration of the elements in the deposition baths is appropriately tuned. Results show that the composition of nanowires does not change linearly with the composition of deposition bath but are richer in Fe. Nanostructured electrodes are tested as both cathodes and anodes in 30 wt% KOH aqueous solution, at room temperature to determine the best alloy composition. In all electrochemical tests, the electrodes that performed best are those with iron content of 78.95 at%. Particularly, the results are very promising for the oxygen evolution reaction, with a Tafel's slope of 40 mV and a potential of 1.532 V vs. RHE after 6 h at constant current of 50 mA cm−2. Besides, preliminary tests in 0.5 M NaCl alkaline aqueous solution are also reported showing very promising results.

Increased oxidative burden contributes to the pathogenesis of most inflammatory diseases and is associated with aging and chronic inflammation. Macrophages contribute to the generation of reactive oxygen species (ROS) within inflamed tissues. Currently, ROS generation is measured using fluorescent probes and colorimetric/fluorimetric biochemical assays. Hydrogen peroxide (H2O2) diffuses through the cell membrane and can be monitored in the extracellular space. Herein, we present a sensor for H2O2 detection released by cells in culture supernatants. H2O2 sensing performance was evaluated using chronoamperometric detection. A sensitivity of 0.0641 μA μM−1 cm−2 with a limit of detection of 6.55 μM and excellent selectivity against many interferents was found. H2O2 release was also measured in conditioned medium from human THP-1 macrophages exposed to pro-oxidant and anti-oxidant treatments. The results were compared with those obtained by flow cytometry using the same cells stained with carboxy-H2DCFDA and MitoSOX Red, which detect intracellular ROS and mitochondrial superoxide, respectively. The addition of pro-oxidants lipopolysaccharide (LPS) and nigericin resulted in a significant increase in the cathodic current due to the H2O2 reduction, indicating an increased release of H2O2. The addition of 17-oxo-DHA, which inhibits LPS- and nigericin-dependent responses, decreased the LPS- and nigericin-induced release of H2O2. All the results obtained with the sensor were consistent with those obtained using flow cytometry. The operation of the sensor directly in the cell culture growth medium had no impact on cell viability. The sensor is highly sensitive, fast, and cost effective, and it can potentially be used for real time monitoring of oxidative stress.

Aim of this work is to develop a new nano-structured and nano-composite lead acid negative electrode with reduced graphene oxide (rGO). Nanostructured electrodes are fabricated by template electrodeposition of lead nanowires on a lead current collector. A polycarbonate track-etched membrane was used as a template (200 nm mean pores diameter). rGO was deposited on the nanostructured electrode from a graphene oxide (GO) dispersion in acetate buffer solution (ABS) (0.2 g/L). Potentiostatic deposition of rGO at -0.8 V vs. standard calomel electrode (SCE) was performed. Electrode with rGO was tested as negative electrode in cell with 5M sulfuric acid solution, a commercial pasted positive plate, as counter-electrode, and an AGM separator. The electrodes well performed at 2C-rate in deep cycling tests (cut off cell voltage 1.2 V). Its capacity grew during cycling test and reached 232.9 mAh/g, which corresponds to a degree of active material utilization of 90%. Its faradaic efficiency reached 90%. Electrodes with similar morphology were obtained treating the electrodes with a HNO3 solution at -0.8 V vs SCE or with a dispersion of GO in HNO3. These electrodes showed lower active material utilization and lower faradaic efficiency.

Organometallic perovskites are one of the most investigated materials for high-efficiency thin-film devices to convert solar energy and supply energy. In particular, methylammonium lead iodide has been used to realize thin-film perovskite solar cells, achieving an efficiency higher than 20%. Different fabrication procedures based on the spin-coating technique have been proposed, which do not ensure homogenous morphologies. In this work, we present a scalable process to fabricate methylammonium lead iodide thin films directly on conductive substrates, consisting of electrodeposition and two subsequent chemical conversions. A thorough investigation of the morphological, structural and compositional properties of the layer is performed after each fabrication step. It is demonstrated that this method allows fine control of the thickness of the layer by tuning the cell parameters during the electrodeposition step. X-ray diffraction patterns and energy-dispersive X-ray analysis indicate the achievement of high-purity methylammonium lead iodide layers. Micro-Raman analyses were used to demonstrate the formation of methylammonium lead iodide. Finally, ultraviolet-visible absorption spectra were acquired to determine the optical band edge of the layer ( 1.56 eV) and the absorbance of methylammonium lead iodide as a function of the film thickness. As expected, the material exploits excellent optical properties, achieving an absorption ≥ 99.9% in the entire visible range for a layer thickness of 1.3 µm. The results presented here pave the way for the application of cost-friendly solution-based processes to fabricate high-quality perovskite solar cells.

A sensitive and selective electrochemical sensor, based on reduced graphene oxide and gold nanoparticles obtained by simple co-electrodeposition, was developed for the detection of uric acid and ascorbic acid. Because of the electrochemical oxidation of both uric and ascorbic acid depending on the pH, the sensor performances were studied at different pH values. Excellent results were obtained for uric acid detection in a linear range from 10 to 500 µmol dm−3 with a sensitivity of 0.31 µA cm−2 µM−1. A limit of detection and quantification of 3.6 µM and 10.95 µmol dm−3, respectively, was calculated. Sensors showed good selectivity toward different interfering species present in the matrix of milk, fruit juice and urine (Na+, NH4+, Cl− and glucose). A simultaneous detection of uric acid and ascorbic acid was also carried out reaching a limit of detection of 2.26 and 5.63 µmol dm−3, respectively. Sensors were also validated measuring both acids in real samples of foods and body fluids (commercial milk and fruit juice and urine). Excellent results were achieved in good agreement with conventional techniques.

In electroanalysis, solution pH is a critical parameter that often needs to be tailored and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without the need for additional reagents. Finite element analysis (FEA) simulations have been performed on interdigitated electrodes, to guide experimental design in relation to both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode arrays in solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap between the electrode combs. The final pH achieved after 1 second, at both protonator and sensor electrodes, was shown to be largely uninfluenced by a solution's initial pH. The impact of buffer concentration was also modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., to identify the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model's prediction. Finally, we show that in-situ pH controlled detection of mercury in water, using square wave stripping voltammetry, is almost identical to samples acidified to pH 3.5 using nitric acid.

Dopamine (DA) is one of the most important neurotransmitters released from the brain, and is involved in many different biological processes. This neurotransmitter influences the processes that involve memory, sleep, mood, learning, and so on. Besides, in the last years, dopamine concentration in human body fluids has been related to some neurodegenerative pathologies, such as Parkinson and Alzheimer’s diseases [1]. It is well known that these pathologies are due to the formation of amyloids plaques that block part of the brain. Many literature data reports that DAergic neurons (areas of midbrain where DA is synthesized) shows a different activity when amyloid plaques are present with a consequent release of a different amount of DA during the development of these pathologies [2]. Despite the involvement of DA in dementia is still under debate, the possibility to have a bio-marker for these diseases is of extreme importance. In fact nowadays, diseases related to dementia are diagnosed when they are already developed so that their management is almost impossible. The possibility to continuously monitor DA concentration in fluids such as blood and urine, can be a valid help to accelerate the early diagnosis of these diseases. The principal analytical methods currently used to detect dopamine are Enzyme Linked ImmunoSorbet Assay (ELISA) and High Pressure Liquid Chromatography (HPLC). Through these methods, it is possible to reach different LOD depending on the analyzed medium, such as 0.05 µM in the case of urine and 0.5 µM for plasma. Despite these techniques are highly performant (low LOD, high selectivity and sensitivity), they are expensive, hard to handle, and time consuming. All these drawbacks make the screening of DA difficult to be achieved. In fact, the sample has to be collected by the patient and sent to the lab that after many days, will give the result. To achieve a real-time screening of DA, electrochemical sensors are ideal candidates. Indeed, just a cheap battery is requested for such a sensor, so that the system is small and portable, compared to HPLC or ELISA, which are big analytical machines. The electrodes fabrication is cheap, reproducible and fast. The features of these sensors are good enough to compete with the standard techniques. The main disadvantage of this technique is the interference from uric acid (UA) and ascorbic acid (AA, vitamin C). These compounds are always present in body fluids and have redox potential close to the DA one. This make the detection of DA harder because the peaks of AA and UA can overlap with the DA one. Therefore, it is necessary to develop a sensor with electrochemical active materials that present a high selectivity to DA in comparison to AA and UA. In this work, we show the preliminary results concerning the development and the optimization of a flexible and cheap electrochemical DA sensor. The active material is based on reduced graphene oxide mixed with either Au or Pt nanoparticles (NPs), and it was obtained by co-electrodeposition on ITO-PET substrate (Figure 1a). The electrodeposition parameters, such as concentration, deposition time and potential have been optimized in order to increase the DA peak and to obtain a low LOD, in the nM range (Figure 1b). The detection of DA was performed by square wave voltammetry and linear cyclovoltammetry. The sensors were also tested using synthetic urine (in order to simulate a real sample where DA concentration is usually lower than 500 nM). Preliminary results show: i) negligible interference from ascorbic and uric acid, ii) very wide linear range, and iii) low LOD. The current findings are very satisfying, suggesting to start a pre-screening of dementia related diseases.

An electrochemical sensor for the detection of lead, mercury and copper in neutral solutions is described. The electrode is made of two distinct parallel gold interdigitated microband electrodes that can be polarized separately. Biasing one electrode “protonator” sufficiently positive to begin water electrolysis, results in the production of H+ ions which consequently drops the pH in the locality around the other second interdigitated “sensing” electrode. This decrease in pH permits the electodeposition (and consequent stripping) of metals at the sensing electrode without the need to acidify the whole test solution. In this work, the local pH can be adjusted from 1 to 7 in a stable and reproducible way by tailoring the applied potential to the protonator electrode. Using this approach, linear ranges for lead 10-100 ppb, copper 5-100 ppb and mercury 1-75 ppb, respectively were demonstrated which exhibit extremely high sensitivity. This technique allowed detection of these metals in a complex water matrix (river water) without sample pretreatment, with excellent results. The electrode reproducibility is high (RSD < 10%) and the metals can be co-detected when present all together. This is the first demonstration of the in-situ pH control for heavy metal detection using solid state sensors and will unable real time and in situ analysis of heavy metals by unskilled personnel in remote settings.

It is well known that physical and surface properties of nanomaterials are promising to enhance efficiency of nanostructured devices for sensing, and for sustainable energy production, conversion, and storage. However, the practical use of nanomaterials is often complicated by the lack of scalable and cost-efficient synthesis procedures and the challenge of integrating into devices 1D nanomaterials saving their structural features. In this field, one of the most severe challenges is to find suitable methods for fabricating nanomaterials. Over the years, numerous preparation methods were proposed in the literature, but not all of them are easily scalable and economically advantageous for industrial application. In this context, electrochemical deposition in template is a facile method for fabricating either two- or one-dimensional nanostructured materials because it allows to easily adjusting the fundamental parameters controlling their final features. Electrochemical processes are, usually, cheap and environmental friendly, and they can be easily scaled-up from lab to industrial level. In this chapter we will describe different electrochemical methods, electrodeposition, galvanic deposition, electroless deposition, and electrogeneration of base, that permit to obtain different types of nanomaterials such as metals, oxide, and semiconductors. In addition, also the performances of different nanostructured materials are presented.

Indium tin oxide (ITO) coated on flexible polyethylene terephthalate (PET) substrate electrode was modified with reduced graphene oxide and gold nanoparticles by simple co-electrodeposition performed at -0.8 V vs SCE for 200 s. All samples were characterized by electron scan microscopy. The as prepared electrode was used as electrochemical sensor to selective detection of ascorbic acid using linear sweep voltammetry. Excellent results were obtained in a linear range from 20 to 150 µM of ascorbic acid with a limit of detection of about 3.1 µM (S/N=3.3). The sensors have a reproducibility of about 5.5% and also show high selectivity towards different interferents such as chlorine, calcium, magnesium, sulphate ions, sodium and glucose. Ascorbic acid was detected also in milk samples demonstrating the possibility quantify this analyte in real samples with a very cheap method.

A nanostructured electrochemical sensor of hydrogen peroxide was fabricated growing self-standing Pd nanowires (Pd NWs) into polycarbonate (PC) membranes through a simple metal galvanic deposition. Conditions of deposition were adjusted in order to attain 2–5 μm long Pd wires. Characterization of Pd-NWs was performed by scanning electrode microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Properties of the nanostructured sensor were studied by cyclic voltammetry and chronoamperometry in phosphate buffer—ethanol solution. Addition of pure ethanol to the test solution was essential in order to increase wettability of the nanostructures. Sensing features were compared with those of both compact and nanoparticle film. Results show stable behavior and sensitive response of Pd NWs towards H 2 O 2 with a wide linear dependence over H 2 O 2 concentration for the electrodes consisting of long Pd nanowires/nanotubes, which display an increase of sensitivity and lower limit of detection (LOD) in comparison with the other sensors. Also the linear-response interval widens with electrode specific surface area. Accuracy and selectivity (towards different electroactive species) is excellent.

In this work, a systematic investigation of the different parameters that control the electrodeposition processes was carried out at the aim to synthetizing AgGaSe₂ nanostructures. We found that pH is a key parameter to control both the morphology and composition of the nanostructures. Low pH favours mainly the formation of Ag2Se nanotubes with a scarce mechanical stability, while multi-phase nanowires well anchored to the substrate were obtained at higher pH. We also found that it was necessary to increase dramatically the concentration of the gallium precursor into the deposition bath in order to obtain AgGaSe₂ owing to lower redox potential of the Ga

Dopamine (DA) is one of the most important neurotransmitters that influences the processes that involve memory, sleep, mood, learning among others [1]. In fact, in the last years, dopamine concentration in human body fluids has been related to some neurodegenerative diseases, such as Parkinson and Alzheimer's diseases [2]. The possibility to have a bio-marker for these disease is of extreme importance because, disease related with dementia, are diagnosed when they are already developed and their management become almost impossible. The possibility to continuously monitor DA level in fluids, such as blood and urine, could accelerate the early diagnosis of these diseases. The principal analytical method to detected dopamine is High Pressure Liquid Chromatrography (HPLC), but this technique does not allow any kind of real time or in situ analysis and, furthermore, is highly expensive and hard to use [3] - [4]. To achieve a real-time screening of DA, electrochemical sensors are perfect candidates [5]. In this work we show the preliminary results concerning the development and the optimization of a flexible and cheap electrochemical DA sensor. The active material of sensors is based on reduced graphene oxide with Au nanoparticles (NPs) and was obtained by co-electrodeposition into a ITO-PET substrate. The electrodeposition parameters have been optimized in order to increase the DA peak in Phosphate Buffer Solution (PBS) and obtain a Limit Of Detection (LOD) in the nM range. A very wide linear range (0.1-30 μM) and a low LOD, down to 50 nM, have been found. The main issue to electrochemically detect dopamine concern the presence of other compounds able to react on the surface of the electrode, leading overlapping peak [6-9]. Ascorbic acid (AA) and Uric Acid (UA), two of these interference species, have oxidation peak of about 0.1 V and 0.4 V, respectively [10]. Furthermore, in biological samples, these chemicals are present in a concentration range of about 100-1000 times higher than dopamine one, making this issue even more challenging [10]. We found by voltammetry studies that in presence of all these chemicals (AA,UA and DA) DA can be still detected. Moreover, we found that is possible to use our electrode to quantify even UA at low concertation. In order to validate the technology, the sensor was also tested using synthetic urine and cerebrospinal fluid, from a patient with alcoholic neuropathy. Excitingly, we have found that both these matrixes don't interfere with DA detection (or in a negligible way). The results of this work are so really promising and thrilling because can allow a in-situ, low cost and real time screening of DA to permits early diagnosis of different diseases.

In this work, we present some results concerning the electrochemical behavior of nanostructured-based electrochemical sensors. In particular, the attention has been focused on Pd and Cu nanowires for detection of hydrogen peroxide and NiO thin film or Ni@NiO core–shell nanowires for detection of mercury ions. Ordered array of Pd and Cu nanowires was obtained through displacement deposition reaction in a commercial polycarbonate membrane acting as a template. The method leads to stable nanostructured electrodes of Pd and Cu with high surface area. For the detection of mercury ions, we have fabricated a Ni/NiO electrochemical sensor, obtained by mild thermal oxidation of Ni-foil. Some results on Ni@NiO core–shell nanowires were also reported. The effect of oxidation time and temperature was studied in order to compare performances of the Ni@NiO nanowire array with those of NiO thin film. All samples were characterized by XRD, SEM and EDS analysis. Electrochemical tests have been conducted in order to characterize specific electrode performance such as sensibility, selectivity, and accuracy. Highly satisfying results have been obtained.