Arsenic is considered as a toxic heavy metal which is highly detrimental to ecological systems, and long-term exposure to it is highly dangerous to life as it can cause serious health effects. Timely detection of traces of active arsenic (As 3+ ) is very crucial, and the development of simple, cost-effective methods is imperative to address the presence of arsenic in water and food chain. Herein, we present an extensive study on chemical-free electrogenerated nanotextured gold assemblage for the detection of ultralow levels of As 3+ in water up to 0.08 ppb concentration. The gold nanotextured electrode (Au/GNE) is developed on simple Au foil via electrochemical oxidation–reduction sweeps in a metal-ion-free electrolyte solution. The ultrafine nanoscale morphological attributes of Au/GNE substrate are studied by scanning electron microscopy. Square wave anodic stripping voltammetry (ASV) response for different concentrations of arsenites is determined and directly correlated with As 3+ detection regarding the type of electrolyte solution, deposition potential, and deposition time. The average of three standard curves are linear from 0.1 ppb up to 9 ppb ( n = 15) with a linear regression coefficient R 2 = 0.9932. Under optimized conditions, a superior sensitivity of 39.54 μA ppb –1 cm –2 is observed with a lower detection limit of 0.1 ppb (1.3 nM) (based on the visual analysis of calibration curve) and 0.08 ppb (1.06 nM) (based on the standard deviation of linear regression). Furthermore, the electrochemical Au/GNE is also applicable for arsenic detection in a complex system containing Cu 2+ , Ni 2+ , Fe 2+ , Pb 2+ , Hg 2+ , and other ions for the selective and sensitive analysis. Au/GNE substrate also possesses remarkable reproducibility and high stability for arsenic detection during repeated analysis and thus can be employed for prolonged applications and reiterating analyses. This electrochemically generated nanotextured electrode is also applicable for As 3+ detection and analysis in a real water sample under optimized conditions. Therefore, fabrication conditions and analytical and electroanalytical performances justify that because of its low cost, easy preparation method and assembly, high reproducibility, and robustness, nanosensor Au/GNE can be scaled up for further applications.

With lithium-ion (li-ion) batteries as energy storage devices, operational safety from thermal runaway remains a major obstacle especially for applications in harsh environments such as in the oil industry. In this approach, a facile method via microwave irradiation technique (MWI) was followed to prepare co 3 o 4 /reduced graphene oxide (RGO)/hexagonal boron nitride (h-BN) nanocomposites as anodes for high temperature li-ion batteries. Results showed that the addition of h-BN not only enhanced the thermal stability of Co 3 o 4 /RGO nanocomposites but also enhanced the specific surface area. co 3 o 4 /RGO/h-BN nanocomposites displayed the highest specific surface area of 191 m 2 /g evidencing the synergistic effects between RGO and h-BN. Moreover, Co 3 o 4 /RGO/h-BN also displayed the highest specific capacity with stable reversibility on the high performance after 100 cycles and lower internal resistance. Interestingly, this novel nanocomposite exhibits outstanding high temperature performances with excellent cycling stability (100% capacity retention) and a decreased internal resistance at 150 °C. Li-ion batteries energy storage devices are used as a power source for almost all electronic devices due to the superior benefits over other types of batteries 1-4. However, the safety feature and the narrow temperature operating range of li-ion batteries remain a major obstacle for more complex applications of li-ion batteries such as in the oil industry, defense, automotive applications and aerospace that demand safe operation at wide temperature range (up to 150 °C). Li-ion batteries are known to operate effectively between −20 °C and 60 °C 5. With the increasing demand for li-ion batteries, many research has been made on increasing its thermal stability and the upper operating temperature range. When considering safety issues of li-ion batteries it is mainly related to thermal runaway. Conditions such as elevated temperature and high charge levels or overcharging abuses one or more of the battery components that results in what is called a short circuit leading to heat, fire or explosion. A process referred to as thermal runaway 6. Thermal runaway mechanisms occur mainly at the electrodes and electrolytes. Thermal decomposition of the electrodes or electrolytes and reduction or oxidation of the electrolyte is the main cause of thermal runaways. To solve this issue, many preventative measures have been investigated. Preventative measures can be the use of safety devices, that is, design devices that release high pressure and heat before thermal runaway but this is for engineers to set up new safe li-ion battery devices. However, what concerns scientists more is the inherent safety from electrodes, to electrolytes 7. Compromising between the electrochemical performances and thermal stability is a challenge.

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We report a microwave irradiation method for the preparation of reduced graphene oxide (RGO) based Co3O4 nanocomposites as anodes for lithium-ion (li-ion) batteries. The Co3O4/RGO nanocomposites displayed good electrochemical behavior as anodic materials for li-ion batteries when compared to pure Co3O4. The Co3O4/RGO nanocomposites with low RGO content resulted in stable electrochemical performance with 100% coulombic efficiency at a high current density of 500 mA/g for 50 cycles. The enhanced capacity of the Co3O4/RGO nanocomposites is due to the incorporation of RGO, which resulted in a four times larger surface area than that of Co3O4. This increased surface area could facilitate the absorption of more lithium ions, resulting in excellent electrochemical performance. Interestingly, the novelty of this work is that the designed li-ion batteries showed stable electrochemical performance even at a high temperature of 100 °C, which might be useful for rechargeable battery applications in a wide temperature range.

In this work, nitrogen doped carbon dots (N-CDs) derived from kiwi seeds, white sesame seeds, and black sesame seeds were prepared by a simple, feasible and green route. Then a novel nitrite electrochemical sensor was successfully constructed. The morphology and composition of N-CDs were characterized by Field emission transmission electron microscopy, Fourier transform infrared spectra, Raman spectra and electrochemical methods. The particle size of the as-prepared N-CDs from the three kinds of natural seeds were in the range of 1.4 ∼ 4.9 nm, 1.4 ∼ 4.6 nm, and 1.2 ∼ 4.7 nm, respectively. Moreover, these N-CDs nanomaterials exhibited excellent electrocatalytic performances for nitrite sensing with a detection limit of 0.23 μM (S/N = 3) by electrochemical methods. Additionally, the stability, anti-interference ability and real sample analysis of the sensors had been evaluated. Finally, the electrochemical sensor was successfully applied for nitrite determination in real samples (ham sausages). Based on the present study, more natural seeds could be expected as preferred candidates for N-CDs synthesis, and a general platform of novel electrochemical sensors for nitrite detection is provided.

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