All-Solid-State Double-Layer Capacitors Using Binderless Reduced Graphene Oxide Thin Films Prepared by Bipolar Electrochemistry

Novel application of electrochemical bipolar exfoliated graphene for highly sensitive disposable label-free cancer biomarker aptasensors

Label-free aptasensors can be a promising point-of-care biosensor for detecting various cancer diseases due to their selectivity, sensitivity, and lower cost of production and operation. In this study, a highly sensitive aptasensor based on gold-covered polyethylene terephthalate electrodes (PET/Au) decorated with bipolar exfoliated graphene is proposed as a possible contender for disposable label-free aptasensor applications. Bipolar electrochemical exfoliation enables simultaneous exfoliation, reduction, and deposition of graphene nanosheets on prospective electrodes. Our comparative study confirms that the bipolar exfoliated graphene deposited on the negative feeding electrode (i.e., reduced graphene oxide) possesses better electrochemical properties for aptasensing. The optimized aptasensor based on bipolar exfoliated graphene deposited on PET/Au electrodes exhibits a highly sensitive response of 4.07 μA log c -1 (unit of c, pM) which is linear in the range of 0.0007-20 nM, and has a low limit of detection of 0.65 pM (S/N = 3). The aptasensor establishes highly selective performance with a stability of 91.2% after 6 days. This study demonstrates that bipolar electrochemistry is a simple yet efficient technique that could provide high-quality graphene for biosensing applications. Considering its simplicity and efficiency, the BPE technique promises the development of feasible and affordable lab-on-chip and point-of-care cancer diagnosis technologies.

On the mechanistic pathways of exfoliation-and-deposition of graphene by bipolar electrochemistry

Amongst the different graphene fabrication techniques, bipolar electrochemistry (BPE) has been recently reported as a simple, controllable, low cost, eco-friendly, and scalable method. It consists of a wirelessly placed carbon source between two feeding electrodes subjected to direct current (DC) voltage in a deionized water bath. Although the physicochemical characteristics of produced graphene have been evaluated, the exfoliation and deposition mechanisms are still unclear. In this study, a novel modified BPE system with an electrically-connected graphite-platinum couple acting as the bipolar electrode has been designed in order to decouple and investigate the contribution of anodic/cathodic exfoliation and deposition of graphene in the BPE process. Electron microscopy and Fourier transform infrared spectroscopy results indicate that both anodic and cathodic exfoliation of graphene could take place regardless of the type of polarization; however, the morphology and deposition rate highly depend on the polarization. Furthermore, the graphene fabricated by anodic exfoliation was found to show higher levels of oxidation compared to the graphene produced by cathodic exfoliation.

Recent progress in environmentally friendly bio-electrochemical devices for simultaneous water desalination and wastewater treatment

Bio-electrochemical systems (BESs) use electroactive micro-organisms for degrading organic materials in wastes for energy and/or chemical production. Microbial based desalination system is a cost-effective and environmentally friendly technique that can be used for water desalination with simultaneous wastewater treatment and energy harvesting. These systems can be used as a standalone technology for water desalination such as microbial desalination cell, microbial electrolysis desalination cell, or a hybrid with other desalination technology. This review summarized the recent progress in using BESs for water desalination, including microbial fuel cell-based desalination (MDC) and microbial electrolysis cell-based desalination (MEDC). The different scaling up trials to commercialize this technology, including the controlling parameters, are discussed. Moreover, the different hybrid desalination systems based on BES are summarized. Finally, the challenges facing the commercialization of the MDC systems were summarized.

Closed bipolar electrochemistry in a four-electrode configuration

The thermodynamic theory underpinning closed bipolar electrochemistry in a 4-electrode configuration is presented; a technique applicable to spectro-electroanalysis, energy storage, electrocatalysis and electrodeposition.

Acid-functionalized carbon nanofibers for high stability, thermoelectrical and electrochemical properties of nanofluids

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties.