Wettability-Based Colorimetric Test Strips for Gasoline/Oil Mixture Differentiation

As inspired by the pH paper for the determination of the acidity levels of solutions, we have developed a wettability-based colorimetric test strip to differentiate the composition of gasoline/oil mixtures. These mixtures are widely used in two-stroke motor engines. A method that is rapid, low cost and simple-to-use will facilitate the differentiation of these gasoline/oil mixtures, and ensure the use of these mixtures in the proper ratios in two-stroke engines for optimized engine performance and endurance. An inverse opal film (IOF) consisting of nanopores was synthesized on the silicon strips. These strips were then functionalized with alkysilanes through chemical vapor deposition. Based on the observation that the silanized nanopores are wetted or not wetted by the gasoline/oil mixtures, we are able to differentiate between the 16:1 and 1:1 mixtures.

Highly reversible switching from P- to N-type NO2 sensing in a monolayer Fe2O3 inverse opal film and the associated P–N transition phase diagram

A monolayer α-Fe2O3 inverse opal film with single-crystalline rotocenters shows reversible NO2 p–n sensing switches tuned by a T–C transition diagram.