Preparation of mixed-valent manganese-vanadium oxide and Au nanoparticle modified graphene oxide nanosheets electrodes for the simultaneous determination of hydrazine and nitrite

Phenothiazine-based fluorescent probes for the detection of hydrazine in environment and living cells

As an important chemical raw material, hydrazine brings convenience to people's lives and provides opportunities for human development. However, the misuse or leakage of hydrazine has brought pollution to the environment, including water, soil and living organisms. At the same time, hydrazine poses a potential threat to human health as a carcinogen. Despite the enormous challenges, it is crucial to develop an effective method to detect hydrazine in environmental samples. In this work, we have synthesized a series of probes based on phenothiazine fluorophore by the introduction of different substituents and developed a novel probe for the detection of hydrazine. The probe is capable of detecting hydrazine in aqueous solutions with high sensitivity and selectivity, and can be easily fabricated into paper test strips for use in in situ samples. In addition, the probe is effective in detecting hydrazine in water, soil, cells, and zebrafish, providing an excellent tool for detecting hydrazine in the environment.

Simultaneous modification of dual-substitution with CeO2 coating boosting high performance sodium ion batteries

Na3V2(PO4)3 (NVP) is highly valued based on the stable construction among the polyanionic compounds. Nevertheless, the drawback of low intrinsic conductivity has been impeded its further application. In this paper, the internal channels of the crystal structure are extended by the introduction of larger radius Ce3+, which increases the transport rate of Na+. The introduction of Mo6+ replacing the V site leads to a beneficial n-type doping effect and facilitates the transportation of electrons. Besides, CeO2 cladding is introduced to further enhance the electronic conductivity of NVP system. Initially, CeO2 serves as an n-type semiconductor and functions as a conductive additive to significantly enhance the electronic conductivity of the electrode, thereby improving the electrochemical characteristics. Moreover, CeO2 functions as an oxygen buffer, aiding in the maintenance of active metal dispersion during operation and enabling efficient electron transfer between CeO2 and [VO6] octahedra in NVP, thus fostering outstanding electrical connectivity between the oxides. CeO2 cladding can be effectively integrated with the carbon layer to stabilize the NVP system. Comprehensively, the modified Na3V1.79Ce0.07Mo0.07(PO4)3/C@8wt.%CeO2 (CeMo0.07@8wt.%CeO2) composite exhibits excellent rate and cycling properties. It delivers a capacity of 113.4 mAh/g at 1C with a capacity retention rate of 80.3 % after 150 cycles. Even at 10C and 40C, it also submits high capacities of 84.7 mAh/g and 76 mAh/g, respectively. Furthermore, the CHC//CeMo0.07@8wt.%CeO2 asymmetric full cell possesses excellent sodium storage property, indicating its prospective application potentials.

A high-energy-density NASICON-type Na3V1.25Ga0.75(PO4)3 cathode with reversible V4+/V5+ redox couple for sodium ion batteries

The stable three-dimensional framework and high operating voltage of sodium superionic conductor (NASICON)-type Na3V2(PO4)3 has the potential to work with long cycle life and high-rate performance; however, it suffers from the poor intrinsic electronic conductivity and low energy density. Herein, Ga3+ is introduced into Na3V2(PO4)3 to activate the V4+/V5+ redox couple at a high potential of 4.0 V for enhancing energy density of the materials (Na3V2-xGax(PO4)3). After the partial substitution of Ga3+ for V3+, three redox couples (V2+/V3+, V3+/V4+ and V4+/V5+) of V are reversibly converted in the voltage range of 1.4-4.2 V, suggesting multi-electrons (>2e-) involved in the reversible reaction, and simultaneously the electronic conductivity of the materials is effectively enhanced. As a result, the cathode with x = 0.75 exhibits excellent electrochemical properties: in the voltage range of 2.2-4.2 V, delivering an initial capacity of 105 mAh/g at 1C with a capacity retention rate of 92.3% after 400 cycles, and providing a stable reversible capacity of 88.3 mAh/g at 40C; and in the voltage range of 1.4-4.2 V, presenting the reversible capacity 152.3 mAh/g at 1C (497.6 Wh kg-1), and cycling stably for 1000 cycles at 20C with a capacity decay of 0.02375% per cycle. It is found that the Na3V2-xGax(PO4)3 cathodes possess the sodium storage mechanism of single-phase and bi-phase reactions. This investigation presents a useful strategy to enhance the energy density and cycling life of NASICON-structured polyanionic phosphates by activating high-potential V4+/V5+ redox couple.

Electrochemical Sensors Based on a Composite of Electrochemically Reduced Graphene Oxide and PEDOT:PSS for Hydrazine Detection

In this study, hydrazine sensors were developed from a composite of electrochemically reduced graphene oxide (ErGO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), deposited onto a glassy carbon electrode (GCE). The structural properties, electrochemical characterization, and surface morphologies of this hydrazine sensor were characterized by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). In addition, the proposed hydrazine sensor also demonstrates good electrochemical and analytical performance when investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry techniques under optimal parameters. Using these investigated parameters, DPV and amperometry were chosen as techniques for hydrazine measurements and showed a linear range of concentration in the range of 0.2-100 μM. The obtained limits of detection and limits of quantitation for hydrazine measurements were 0.01 and 0.03 μM, respectively. In addition, the proposed sensor demonstrated good reproducibility and stability in hydrazine measurements in eight consecutive days. This fabricated hydrazine sensor also exhibited good selectivity against interference from Mg²⁺, K⁺, Zn²⁺, Fe²⁺, Na⁺, NO₂ ^-, CH₃COO^-, SO₄ ^2-, Cl^-, ascorbic acid, chlorophenol, and triclosan and combined interferences, as well as it depicted %RSD values of less than 5%. In conclusion, this proposed sensor based on GCE modified with ErGO/PEDOT:PSS displays exceptional electrochemical performance for use in hydrazine measurements and have the potential to be employed in practical applications.