Studies of the complexation behavior of tetramorpholinylo-PNP-lariat ether with Ag(I), Ca(II), Cd(II), Cu(II) and Pb(II) using Electrospray Ionization Mass Spectrometry

In this publication the cationic metal complexes of tetramorpholinylo-PNP-lariat ether have been studied using electrospray ionization mass spectrometry (ESI-MS). The tandem mass spectra (MS/MS) of these complexes have also been tested to evaluate the stability of the different types of the complexes formed. As occurred, all selected metal cations form the complexes with 1 : 1 stoichiometry with the investigated ligand. Only silver ions create a ‘‘sandwich’’ type complex. Furthermore, the divalent cations form complexes with the nitrate anion adduct. In the case of Ca(II), Cd(II) and Pb(II) we also observed another type of the species with an additional water molecule attached to the parent complex

Dynamic evolution of anodic biofilm when maturing under different external resistive loads in microbial fuel cells. Electrochemical perspective

© 2018 The Authors Appropriate inoculation and maturation may be crucial for shortening the startup time and maximising power output of Microbial Fuel Cells (MFCs), whilst ensuring stable operation. In this study we explore the relationship between electrochemical parameters of MFCs matured under different external resistance (Rext) values (50 Ω - 10 kΩ) using non-synthetic fuel (human urine). Maturing the biofilm under the lower selected Rext results in improved power performance and lowest internal resistance (Rint), whereas using higher Rext results in increased ohmic losses and inferior performance. When the optimal load is applied to the MFCs following maturity, dependence of microbial activity on original Rext values does not change, suggesting an irreversible effect on the biofilm, within the timeframe of the reported experiments. Biofilm microarchitecture is affected by Rext and plays an important role in MFC efficiency. Presence of water channels, EPS and precipitated salts is distinctive for higher Rext and open circuit MFCs. Correlation analysis reveals that the biofilm changes most dynamically in the first 5 weeks of operation and that fixed Rext lefts an electrochemical effect on biofilm performance. Therefore, the initial conditions of the biofilm development can affect its long-term structure, properties and activity

Self-powered, autonomous Biological Oxygen Demand biosensor for online water quality monitoring

© 2017 The Authors Standard Biological Oxygen Demand (BOD) analysis requires 5days to complete. To date, microbial fuel cell biosensors used as an alternative method for BOD assessment requires external apparatus, which limits their use for on-line monitoring in remote, off-grid locations. In this study, a self-powered, floating biosensor was developed for online water quality monitoring. This approach eliminated the need for external apparatus and maintenance that would otherwise be required by other techniques. The biosensor was able to detect urine in freshwater and turn ON a visual and sound cues (85dB). The energy needed to operate the biosensor was produced by the system itself with the use of electroactive microorganisms, inside microbial fuel cells. The Chemical Oxygen Demand (COD) was used as a fast method of biosensor validation. When urine concentration exceeded the lower threshold, corresponding to a COD concentration of 57.7±4.8mgO2L−1, the biosensor turned the alarm ON. The shortest observed actuation time, required to switch ON the alarm was 61min, when the urine concentration was 149.7±1.7mgO2L−1. Once the sensor was switched ON, the signal was emitted until the urine organic load decreased to 15.3±1.9mgO2L−1. When ON, the microbial fuel cell sensor produced a maximum power of 4.3mW. When switched OFF, the biosensor produced 25.4μW. The frequency of the signal was proportional to the concentration of urine. The observed frequencies varied between 0.01 and 0.59Hz. This approach allowed to correlate and quantitatively detect the presence of water contamination, based on signal frequency. The sensor was operating autonomously for 5 months. This is the first report of a self-powered, autonomous device, developed for online water quality monitoring

Fate of three bioluminescent pathogenic bacteria fed through a cascade of urine microbial fuel cells

Microbial fuel cell (MFC) technology is currently gaining recognition as one of the most promising bioenergy technologies of the future. One aspect of this technology that has received little attention is the disinfection of effluents and the fate of pathogenic organisms that find their way into the waste stream. In this study, three independent trials were carried out to evaluate the fate of three bioluminescent pathogenic bacteria (Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa and Staphylococcus aureus) introduced into the anodic chamber of a urine-fed cascade of 9 MFCs with matured, electroactive biofilms. These are common examples of enteric human pathogens, which could contaminate urine or waste streams. The results showed that the average power generation in the closed circuit cascade reached 754 ± 16 µW, with an average pathogen log-fold reduction of 6.24 ± 0.63 compared to 2.01 ± 0.26 for the open circuit cascade for all three pathogens. The results suggest that the bio-electrochemical reactions associated with electricity generation were the primary driving force for the inactivation of the introduced pathogens. These findings show that pathogenic organisms introduced into waste streams could be inactivated by the power-generating process within the MFC cascade system, thereby preventing propagation and thus rendering the effluent safer for possible reuse

Biosurfactants and synthetic surfactants in bioelectrochemical systems: a mini-review

Bioelectrochemical systems (BESs) are ruled by a complex combination of biological and abiotic factors. The interplay of these factors determines the overall efficiency of BES in generating electricity and treating waste. The recent progress in bioelectrochemistry of BESs and electrobiotechnology exposed an important group of compounds, which have a significant contribution to operation and efficiency: surface-active agents, also termed surfactants. Implementation of the interfacial science led to determining several effects of synthetic and natural surfactants on BESs operation. In high pH, these amphiphilic compounds prevent the cathode electrodes from biodeterioration. Through solubilization, their presence leads to increased catabolism of hydrophobic compounds. They interfere with the surface of the electrodes leading to improved biofilm formation, while affecting its microarchitecture and composition. Furthermore, they may act as quorum sensing activators and induce the synthesis of electron shuttles produced by electroactive bacteria. On the other hand, the bioelectrochemical activity can be tailored for new, improved biosurfactant production processes. Herein, the most recent knowledge on the effects of these promising compounds in BESs is discussed

Regenerated silk fibroin membranes as separators for transparent microbial fuel cells

Abstract In recent years novel applications of bioelectrochemical systems are exemplified by phototrophic biocathodes, biocompatible enzymatic fuel cells and biodegradable microbial fuel cells (MFCs). Herein, transparent silk fibroin membranes (SFM) with various fibroin content (2%, 4% and 8%) were synthesised and employed as separators in MFCs and compared with standard cation exchange membranes (CEM) as a control. The highest real-time power performance of thin-film SFM was reached by 2%-SFM separators: 25.7 ± 7.4 μW, which corresponds to 68% of the performance of the CEM separators (37.7 ± 3.1 μW). Similarly, 2%-SFM revealed the highest coulombic efficiency of 6.65 ± 1.90%, 74% of the CEM efficiency. Current for 2%-SFM reached 0.25 ± 0.03 mA (86% of CEM control). Decrease of power output was observed after 23 days for 8% and 4% and was a consequence of deterioration of SFMs, determined by physical, chemical and biological studies. This is the first time that economical and transparent silk fibroin polymers were successfully employed in MFCs

High-throughput 96-well bioelectrochemical platform for screening of electroactive microbial consortia

The development of bioelectrochemical systems reinforces the necessity for the identification and engineering of electroactive bacteria with improved performance and novel biochemical properties. In this study, using a newly designed 96-well-plate array of microbial fuel cells (MFCs), we compared the electroactive capabilities of microbial communities derived from four mine drainages. The maximum power density of individual wells after two weeks of inoculation was 102 mW/m3, whereas the maximum current density was 1.6 A/m3. Transferring communities from individual wells into larger MFCs comprising low (20 mg/L) and high (200 mg/L) concentrations of Cu yielded maximum power densities of 445 and 58 mW/m3, respectively, with up to a 3.7 fold decrease in Cu2+ ions within 24 h. Electrochemical data analysis revealed that microbial consortia can be distinguished based on their electrochemical profiles. Our results showed that a 96-well MFC array is a suitable platform for high-throughput screening, selection, and subsequent source of enriched electroactive consortia. The quantitative and comparative analysis followed by principal component analysis indicated that the initial environmental conditions, as well as physical and chemical parameters of the lakes were crucial to develop an efficient electroactive community. Further applications of the proposed platform include genetic engineering, phenotype screening, and mutagenesis studies of both microbial communities and single cultures. This is the first time that a high-throughput MFC platform is used to evaluate the performance of multiple electroactive consortia towards Cu removal

Graphene growth on Ge(100)/Si(100) substrates by CVD method

The successful integration of graphene into microelectronic devices is strongly dependent on the availability of direct deposition processes, which can provide uniform, large area and high quality graphene on nonmetallic substrates. As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm−1

Quality of corrosion specimens prepared from material obtained during autopsies - a preliminary study

Aim: Aim of this study was to assess the quality of the corrosion specimens obtained during autopsies of human body for scanning electron microscopy procedures. Materials and Method: Ninety seven uteri were obtained upon autopsy of women aged 25-56 years, deceased due to causes not related to disorders of the reproductive system. Fourty three of them contained large subserosal uterine leiomyomata. Twenty uteri were injected with acrylic emulsion Liquitex R via the arteries or veins. Five of these uteri were next dissected and cut into slides on a microtom. The remaining uteri were injected with 60–80 ml of Mercox CL-2R resin, next macerated and studied under scanning electron microscope (JEOL SEM 35-CF scanning electron microscope at 20-25 kV) Results: Best human specimens were obtained from the autopsies carried out possibly early after the decease, young aged (between 25 and 45) and died because of multitrauma not associated with the pelvic injury. Conclusions: Specimens obtained from autopsies can be used for scanning electron microscopy however under several conditions, specially the time between death and undertaking the injection procedures and the age of the individual, because of the process of artherosclerosis