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 (As³⁺) 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 As³⁺ 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 As³⁺ 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 R² = 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 Cu²⁺, Ni²⁺, Fe²⁺, Pb²⁺, Hg²⁺, 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 As³⁺ 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.

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.