Enhancing electrochemical nitrite sensing with a novel nanocomposite of activated carbon/carbon cloth derived from microbial biofilm.

A novel approach was employed to fabricate a biofilm-derived activated carbon (BioAc) electrode on a carbon cloth (Cc) substrate for electrochemical nitrite sensing in water samples. The biofilm/Cc electrode was developed using a bioelectrochemical reactor, featuring a three-electrode system with nutrient media and microbial sources. The resultant biofilm electrode was activated at 450 °C for 2 h to eliminate impurities and enhance porosity. Morphological analysis of the BioAc/Cc electrode revealed a surface characterized by a compact film composed of numerous carbon nanoparticles. X-ray diffraction (XRD) analysis exhibited broad, highly crystalline peaks, enhancing both the electrode surface area and conductivity. Amperometry tests on the modified BioAc/Cc electrodes demonstrated a detection limit of 0.015 µM, a sensitivity of 1946.54 µA mM-1 cm-2, and a linear range spanning 0.35-478.21 µM at neutral pH conditions. Moreover, the electrodes demonstrated good stability with a RSD of 2.25% after 60 days and high reproducibility with an RSD of 1.64%. Real-time results showed 99.2 and 100.1% recovery for tap water and drinking water, respectively, highlighting the potential for commercialization in the future. These findings suggest that the BioAc/Cc electrode holds substantial potential for precise nitrite detection in environmental and wastewater applications.

A critical review on microbe-electrode interactions towards heavy metal ion detection using microbial fuel cell technology.

Implicit interaction of electroactive microbes with solid electrodes is an interesting phenomenon in nature, which supported development of bioelectrochemical systems (BESs), especially the microbial fuel cell (MFCs) for valorization of low-value waste streams into bioelectricity. Intriguingly, the metabolism of interacted microbes with electrode is affected by the microenvironment at electrodes, which influences the current response. For instance, when heavy metal ions (HMIs) are imposed in the medium, the current production decreases due to their intrinsic toxic effect. This event provides an immense opportunity to utilize MFC as a sensor to selectively detect HMIs in the environment, which has been explored vastly in recent decade. In this review, we have concisely discussed the microbial interaction with electrodes and mechanism of detection of HMIs using an MFC. Recent advancement in sensing elements and their application is elaborated with a future perspective section for follow-up research and development in this field.

Copper ferrite supported reduced graphene oxide as cathode materials to enhance microbial electrosynthesis of volatile fatty acids from CO2.

Copper ferrite/reduced graphene oxide (CF/rGO) nanocomposites (NCs) was synthesized using the bio-combustion method and applied as a cathode catalyst in the microbial reduction of CO2 to volatile fatty acids (VFAs) in a single chamber microbial electrosynthesis system (MES). The synthesized NCs exhibited a porous network-like structure with a high surface area of CF/rGO (158.22 m2/g), which was 2.24 folds higher than that of CF. The Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) analysis for CF/rGO/Carbon cloth (Cc) revealed a high reduction current density of -7.3 A/m2 and a low charge transfer resistance of 2.8 Ω. The isobutyrate and acetate in MES-2 (Cu/rGO/Cc) were produced at 35.37 g/m2/d, which was 1.53 folds higher than that of MES-1 (bare Cc: 23.10 g/m2/d). The columbic efficiency (77.78%) and total VFA concentration (1941.13 ± 83 mg COD/L) were noted to be 1.97 and 1.6 folds higher for MES-2 than MES-1, respectively. The Tafel plot drawn from the CV curves exhibited an exchange current density value of MES-2 that was 3.46 A/m2, and this value was 1.19 and 33.92 folds higher than that of MES-1 and abiotic CF/rGO/Cc, respectively. Field emission scanning electron microscopy (FESEM) observations revealed enhanced rod-shaped bacteria had grown on the cathode suggesting excellent biocompatible and multi-length scale porosity of CF/rGO catalysts for enhanced colonization of microbes. The phyla Proteobacteria (Betaproteobacteria), Bacteroidetes, and Firmicutes were highly abundant as the dominant microbial communities on the cathode, which might played a major role in bioelectrochemical CO2 reduction to VFAs. The results from this study clearly demonstrate that the CF/rGO/Cc electrode could serve as a conductive element between microbes and bactericidal electrodes with excellent electrochemical properties to enable performance of the MES.

Progress of Advanced Nanomaterials in the Non-Enzymatic Electrochemical Sensing of Glucose and H2O2.

Non-enzymatic sensing has been in the research limelight, and most sensors based on nanomaterials are designed to detect single analytes. The simultaneous detection of analytes that together exist in biological organisms necessitates the development of effective and efficient non-enzymatic electrodes in sensing. In this regard, the development of sensing elements for detecting glucose and hydrogen peroxide (H2O2) is significant. Non-enzymatic sensing is more economical and has a longer lifetime than enzymatic electrochemical sensing, but it has several drawbacks, such as high working potential, slow electrode kinetics, poisoning from intermediate species and weak sensing parameters. We comprehensively review the recent developments in non-enzymatic glucose and H2O2 (NEGH) sensing by focusing mainly on the sensing performance, electro catalytic mechanism, morphology and design of electrode materials. Various types of nanomaterials with metal/metal oxides and hybrid metallic nanocomposites are discussed. A comparison of glucose and H2O2 sensing parameters using the same electrode materials is outlined to predict the efficient sensing performance of advanced nanomaterials. Recent innovative approaches to improve the NEGH sensitivity, selectivity and stability in real-time applications are critically discussed, which have not been sufficiently addressed in the previous reviews. Finally, the challenges, future trends, and prospects associated with advanced nanomaterials for NEGH sensing are considered. We believe this article will help to understand the selection of advanced materials for dual/multi non-enzymatic sensing issues and will also be beneficial for researchers to make breakthrough progress in the area of non-enzymatic sensing of dual/multi biomolecules.