Porous 3D composite materials are interesting anode electrodes for single chamber microbial fuel cells (SCMFCs) since they exploit a surface layer that is able to achieve the correct biocompatibility ...for the proliferation of electroactive bacteria and have an inner charge transfer element that favors electron transfer and improves the electrochemical activity of microorganisms. The crucial step is to fine-tune the continuous porosity inside the anode electrode, thus enhancing the bacterial growth, adhesion, and proliferation, and the substrate's transport and waste products removal, avoiding pore clogging. To this purpose, a novel approach to synthetize a 3D composite aerogel is proposed in the present work. A 3D composite aerogel, based on polydimethylsiloxane (PDMS) and multi-wall carbon nanotubes (MWCNTs) as a conductive filler, was obtained by pouring this mixture over the commercial sugar, used as removable template to induce and tune the hierarchical continuous porosity into final nanostructures. In this scenario, the granularity of the sugar directly affects the porosities distribution inside the 3D composite aerogel, as confirmed by the morphological characterizations implemented. We demonstrated the capability to realize a high-performance bioelectrode, which showed a 3D porous structure characterized by a high surface area typical of aerogel materials, the required biocompatibility for bacterial proliferations, and an improved electron pathway inside it. Indeed, SCMFCs with 3D composite aerogel achieved current densities of (691.7 ± 9.5) mA m
, three orders of magnitude higher than commercial carbon paper, (287.8 ± 16.1) mA m
.
Flexible sensors are fundamental devices for human body monitoring. The mechanical strain and physiological parameters coupled sensing have attracted increasing interest in this field. However, ...integration of different sensors in one platform usually involves complex fabrication process-flows. Simplification, even if essential, remains a challenge. Here, we investigate a piezoresistive and electrochemical active electrospun nanofibers (NFs) mat as the sensitive element of the wearable physiological flex sensing platform. The use of one material sensitive to the two kinds of stimuli reduces the process-flow to two steps. We demonstrate that the final NFs pH-Flex Sensor can be used to monitor the deformation of a human body joint as well as the pH of the skin. A unique approach has been selected for pH sensing, based on Electrochemical Impedance Spectroscopy (EIS). A linear dependence of the both the double layer capacitance and charge transfer re-sistance with the pH value was obtained by EIS, as well as a linear trend of the electrical resistance with the bending deformation. Gauge factors values calculated after the bending test were 45.84 in traction and 208.55 in compression mode, reflecting the extraordinary piezoresistive behavior of our nanostructured NFs.
For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval ...overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.
We report on an easy, fast, eco-friendly, and reliable method for the synthesis of reduced graphene oxide/SnO2 nanocomposite as cathode material for application in microbial fuel cells (MFCs). The ...material was prepared starting from graphene oxide that has been reduced to graphene during the hydrothermal synthesis of the nanocomposite, carried out in a microwave system. Structural and morphological characterizations evidenced the formation of nanocomposite sheets, with SnO2 crystals of few nanometers integrated in the graphene matrix. Physico-chemical analysis revealed the formation of SnO2 nanoparticles, as well as the functionalization of the graphene by the presence of nitrogen atoms. Electrochemical characterizations put in evidence the ability of such composite to exploit a cocatalysis mechanism for the oxygen reduction reaction, provided by the presence of both SnO2 and nitrogen. In addition, the novel composite catalyst was successfully employed as cathode in seawater-based MFCs, giving electrical performances comparable to those of reference devices employing Pt as catalyst.
The gelation of ionic liquid-based solutions with inorganic or organic fillers is one of the strategies commonly adopted in the Dye-Sensitized Solar Cells (DSSCs) field for preparing quasi-solid ...electrolytes characterized by good photovoltaic performance and long-term stability. In the present paper, the application of a gel electrolyte based on unmodified microcrystalline cellulose and ionic liquids in a DSSC is reported. The gel electrolyte has been characterized evaluating its conductive, thermogravimetric, viscous and crystalline properties, while the photoelectrochemical behavior of the quasi-solid DSSCs has been investigated measuring current-voltage, Electrochemical Impedance Spectroscopy and Linear Sweep Voltammetry curves. The photovoltaic performance of cellulose gel-based DSSCs has been optimized by monitoring some key parameters, such as ionic liquid volume ratios and cellulose content. A maximum photoconversion efficiency of 3.33% has been obtained with the total absence of organic solvents, and a good stability has been demonstrated during more than 8 hours of exposition (replicated over months) to simulated solar light. Moreover, a peculiar and reversible trend in the short-circuit current density and in the overall efficiency of the cell has been observed during prolonged photovoltaic measurements. The present findings suggest the necessity to adopt a new protocol for the measurement of the photovoltaic parameters of quasi-solid DSSCs.
We present a direct evidence of Bloch surface waves (BSWs) waveguiding on ultrathin polymeric ridges, supported by near-field measurements. It is demonstrated that near-infrared BSWs sustained by a ...silicon-based multilayer can be locally coupled and guided through dielectric ridges of nanometric thickness with low propagation losses. Using a conventional prism-based configuration, we demonstrate a wavelength-selective BSW coupling inside and outside the ridge. Such a result can open interesting opportunities in surface wave-mediated sensing applications, where light could be selectively coupled in specific regions defined by nanometric reliefs.
This work demonstrates that microbial fuel cells (MFCs), optimized for energy recovery, can be used as an effective tool to detect antibiotics in water-based environments. In MFCs, electroactive ...biofilms function as biocatalysts by converting the chemical energy of organic matter, which serves as the fuel, into electrical energy. The efficiency of the conversion process can be significantly affected by the presence of contaminants that act as toxicants to the biofilm. The present work demonstrates that MFCs can successfully detect antibiotic residues in water and water-based electrolytes containing complex carbon sources that may be associated with the food industry. Specifically, honey was selected as a model fuel to test the effectiveness of MFCs in detecting antibiotic contamination, and tetracycline was used as a reference antibiotic within this study. The results show that MFCs not only efficiently detect the presence of tetracycline in both acetate and honey-based electrolytes but also recover the same performance after each exposure cycle, proving to be a very robust and reliable technology for both biosensing and energy recovery.
This work investigates a new nanostructured gas diffusion layer (nano-GDL) to improve the performance of air cathode single-chamber microbial fuel cells (a-SCMFCs). The new nano-GDLs improve the ...direct oxygen reduction reaction by exploiting the best qualities of nanofibers from electrospinning in terms of high surface-area-to-volume ratio, high porosity, and laser-based processing to promote adhesion. By electrospinning, nano-GDLs were fabricated directly by collecting two nanofiber mats on the same carbon-based electrode, acting as the substrate. Each layer was designed with a specific function: water-resistant, oxygen-permeable polyvinylidene-difluoride (PVDF) nanofibers served as a barrier to prevent water-based electrolyte leakage, while an inner layer of cellulose nanofibers was added to promote oxygen diffusion towards the catalytic sites. The maximum current density obtained for a-SCMFCs with the new nano-GDLs is 132.2 ± 10.8 mA m−2, and it doubles the current density obtained with standard PTFE-based GDL (58.5 ± 2.4 mA m−2) used as reference material. The energy recovery (EF) factor, i.e., the ratio of the power output to the inner volume of the device, was then used to evaluate the overall performance of a-SCMFCs. a-SCMFCs with nano-GDL provided an EF value of 60.83 mJ m−3, one order of magnitude higher than the value of 3.92 mJ m−3 obtained with standard GDL.
The oxygen inhibition of UV curable polymers is exploited in novel technology for the fabrication of patterns and closed devices. Multiscale structures with thicknesses ranging from few micrometers ...to millimeters are rapidly fabricated. Multipolymeric and multifunctional structures are also prepared: adequately choosing the material of each layer, a set of different properties is arranged in the same device.
In the present work, sedimentary microbial fuel cells (s-MFC) have been proposed as effective tools to power remote sensors in different aquatic environments, thanks to their ability to produce ...renewable and sustainable energy continuously and autonomously. The present work proposes the optimization of cylindrical sedimentary microbial fuel cells (s-MFC) as a compact and cost-effective system suitable to be integrated as a payload in an Autonomous Underwater Vehicle (AUV). To this purpose, a new AUV payload, named MFC-payload, is designed to host the cylindrical s-MFC and a data acquisition system to collect and store information on the voltage produced by the cell. Its overall performance was evaluated during two field measurement campaigns carried out in the Mediterranean Sea. This investigation demonstrates the power production by s-MFC during operation of the AUV in seawater and analyzes the actual influence of environmental conditions on the output power. This study demonstrates that energy production by s-MFCs integrated in AUV systems is decoupled by the navigation of the autonomous vehicle itself, showing the effectiveness of the application of MFC-based technology as a power payload for environmental analysis. All these latter results demonstrate and confirm the ability of the devices to continuously produce electricity during different AUV operation modes (i.e., depth and speed), while changing environmental conditions (i.e., pressure, temperature and oxygen content) demonstrate that cylindrical s-MFC devices are robust system that can be successfully used in underwater applications.
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