Catharanthus roseus (Apocynaceae family) extract is rich in organic phytochemicals such as alkaloids, polyphenolic compounds, and flavonoids. It contains several functional entities such as fused heterocycles, and hydroxyl and carbonyl groups, which could be useful for corrosion inhibition of mild steel in NaCl environments. In the present work, ultrasonic energy was used to obtain the ethanolic extracts of root and stem which were then tested as corrosion inhibitors for mild steel in the presence of 3.5% NaCl. The corrosion inhibition process was studied by UV-visible spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, weight loss, and electrochemical methods. After immersing in the corrosive medium, the microstructures of mild steel were investigated by scanning electron microscopy, X-ray diffraction, and ellipsometry. The extract of C. roseus showed excellent adsorption on mild steel surface as confirmed by DFT calculations. The results indicate that the extract of C. roseus acts as a mixed type corrosion inhibitor, where the stem extract is the most efficient inhibitor in 3.5% NaCl solution possibly due to the higher active area of stem phytochemicals.

In the current work, we present a new self-organizing anodization approach of metallic Sn layers to obtain vertically aligned tin oxide nanochannel structures. For this, we use a sulphide-containing electrolyte and a set of optimized anodizing parameters. The resulting high aspect ratio nanochannel morphologies can be converted into crystalline SnO₂ by high temperature annealing and show highly promising H₂ sensing properties. We show that these anodic layers can operate at relatively low temperatures (∼80 °C), detecting concentrations as low as 9 ppm, and with extremely fast response and recovery times. This excellent gas-sensing performance is ascribed to the advanced structure, characterized by a crack-free, straight and top-open nanochannel geometry.