1,721,168 research outputs found
Ascorbic Acid determination using linear sweep voltammetry on flexible electrode modified with gold nanoparticles and reduced graphene oxide
No full textIndium 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
Anodic Alumina Membranes: From Electrochemical Growth to Use as Template for Fabrication of Nanostructured Electrodes
Get PDFThe great success of anodic alumina membranes is due to their morphological features coupled to both thermal and chemical stability. The electrochemical fabrication allows accurate control of the porous structure: in fact, the membrane morphological characteristics (pore length, pore diameter and cell density) can be controlled by adjusting the anodizing parameters (bath, temperature, voltage and time). This article deals with both the fabrication and use of anodic alumina membranes. In particular, we will show the specific role of the addition of aluminum ions to phosphoric acid-based anodizing solution in modifying the morphology of anodic alumina membranes. Anodic alumina membranes were obtained at −1◦ C in aqueous solutions of 0.4 M H3 PO4 added with different amounts of Al(OH)3 . For sake of completeness, the formation of PAA in pure 0.4 M H3 PO4 in otherwise identical conditions was also investigated. We found that the presence of Al(OH)3 in solution highly affects the morphology of the porous layer. In particular, at high Al(OH)3 concentration (close to saturation) more compact porous layers were formed with narrow pores separated by thick oxide. The increase in the electric charge from 20 to 160 C cm−2 also contributes to modifying the morphology of porous oxide. The obtained anodic alumina membranes were used as a template to fabricate a regular array of PdCo alloy nanowires that is a valid alternative to Pt for hydrogen evolution reaction. The PdCo alloy was obtained by electrodeposition and we found that the composition of the nanowires depends on the concentration of two metals in the deposition solution
Application of a Multiphase Interleaved DC-DC Converter for Power-To-Hydrogen Systems
Get PDFPower electronics plays a crucial role in the implementation of a clean hydrogen production system, whose last stage consists of a water electrolyzer requiring a DC power supply to be in operation. The most recent architectural solutions imply the use of an isolated DC-DC converter, collecting energy from medium voltage (MV) and delivering it to the electrolyzer. An equivalent electrical model of the electrolyzer is therefore needed, as well as an accurate design of the power converter stage, aiming at a high-efficiency operation of the electrolyzer's cells and at a low-ripple supply current, to avoid premature degradation. This work investigates a full-bridge step-down isolated DC-DC converter, focusing on the opportunity of a multiphase interleaved configuration, particularly convenient for the proposed application. The considered maximum power level is 400 kW, representing a small-scale example of an industrial water electrolyzer supplied by a maximum DC voltage of 700 V. Input DC voltage is 7 kV. Power electronics' simulation have been carried out, as well as model analysis of the proposed converter
Reduced graphene oxide decorated with metals nanoparticles electrode as electrochemical sensor for dopamine
No full textDopamine (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
Energy consumption model of aerial urban logistic infrastructures
Get PDFIn the last decade, logistic systems based on small aerial vehicles (drones) have become attractive for urban delivery operations as a sustainable alternative to ground vehicles because they are not affected by the congestion of the road network, thus allowing for faster and more reliable services. Aerial logistic systems, however, require a substantially different approach to operations management and need specifically designed supportive infrastructures. While the research on urban aerial delivery mostly focuses on the optimization vehicle operations, the appropriate design of supportive infrastructures is seldom considered. This paper focuses on the energy efficiency of aerial logistic systems, and proposes a new original methodology to obtain a realistic estimate of the overall energy consumed by a swarm of drones employed for urban delivery, taking into account the extension of the area served and its specific features. The methodology proposed offers relevant information for the decision problems related to the appropriate sizing of the infrastructures, the dimensioning of the swarm of drones and the capacity of the energy storage system. The paper also reports a comparison with ground vehicles in the same scenarios, showing the relevant tradeoffs. The results obtained demonstrate how an appropriate design of the supportive infrastructures for urban aerial logistics may significantly impact the overall efficiency of the delivery system
Fabrication of nanostructured Ni-Co electrodes for hydrogen and oxygen evolution reaction in water-alkaline electrolyzer
Get PDFTemplate electrosynthesis is a facile and cheap approach for obtaining nanostructures with very high surface area. This fabrication method has been used to produce electrodes for different applications, among which the electrolysis. In previous works, Ni and IrO2 nanostructured electrodes were tested for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution, respectively, without and with addition of Pd nanoparticles. In this work, Ni-Co alloy electrodes were fabricated by the same method, starting from a bath containing a mixture of Ni and Co. After fabrication of the nanostructures and template dissolution, electrodes were characterized by EDS and SEM. The results show that i) alloy deposition is possible by this method, and ii) alloy is richer in Co compared to the composition of the bath employed for deposition. In order to evaluate the electrocatalytic properties of Ni-Co electrode, electrochemical tests were performed and the results were compared with pure Ni and Co electrodes. The tests were conducted through either cyclic or linear sweep voltammetry in 30% w/w KOH aqueous solution at room temperature. For the HER, pure Ni electrode was found to be more performing. Whereas, with regard to the OER, performance of the nanostructured Ni-Co electrodes show an improvement more than 20% in terms of electrocatalysis, in comparison with pure Ni and Co electrodes
Vertical standing copper nanowires for electrochemical sensor of nitrate in water
No full textNitrogen, 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
Optimization of Urban Delivery Systems Based on Electric Assisted Cargo Bikes with Modular Battery Size, Taking into Account the Service Requirements and the Specific Operational Context
Get PDFThe implementation of new forms of urban mobility is a fundamental challenge for improving the performance of city logistic systems in terms of efficiency and sustainability. For such purposes, the exploitation of electric vehicles is currently being investigated as an alternative to traditional internal combustion engines. In particular, the employment of lightweight electric cargo bikes is seen as an attractive possibility for designing improved city distribution systems. Such vehicles, however, present substantial limitations related to their endurance, speed, power, and recharging times; therefore, their configuration must be optimized considering the actual operational context and the specific characteristics of the service operated. This paper proposes the employment of modular electric cargo bikes for urban parcel delivery, with the possibility of customizing some features of the vehicle in order to optimize the performance of the system. This research initially focuses on the design of the modular vehicle and subsequently on the selection of the best configuration through a multi criteria decision method. A numerical application demonstrates the effectiveness of the approach proposed by analysing different design options and determining the most efficient solution in a specific context
Performance Enhancement of Alkaline Water Electrolyzer Using Nanostructured Electrodes Synthetized by Template Electrosynthesis
No full textThe increase of power generation by renewable sources is causing problems in the management of the electricity grid. In order to favor the transition from the current energy production towards renewable energy sources, it is necessary to plan strategy to develop suitable energy storage systems. Certainly, the electrochemical hydrogen production can be considered as one of the most promising storage technologies. In this work, an innovative alkaline electrolyzer is presented from its design based on the use of nanostructured electrodes up to its implementation suggested by the results of tests simulating real operation. The nanostructured electrodes were fabricated by template electrosynthesis that is a simple and inexpensive process. The lab-scale electrochemical reactor was made by a 3D printer. The electrolysis results from the innovative cell operated in 30% w/w KOH aqueous solution were compared with those from a conventional one employing planar electrodes in otherwise identical conditions
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