Zinc oxide (ZnO), as a new type of inorganic chemical semiconductor material, is generally an N-type semiconductor with good photoelectric, stability, photocatalytic properties, and a wide bandgap (3.37eV). These characteristics make it applicable to various devices, such as field-effect transistors, ultraviolet light detectors, piezoelectric sensors, electrochemical sensors, etc. At the same time, as a very environmentally friendly material, it has attracted great attention from more and more researchers. In recent years, ZnO materials have become one of the most popular transition metal oxides in research. ZnO nanomaterials are white powders with small particle size and large specific surface area. They have advantages such as environmental friendliness, biocompatibility, and good electrochemical performance, which make them exhibit excellent physical and chemical properties in chemistry, optics, and electronics. This has promoted the broader development prospects of ZnO nanomaterials in the fields of medicine, field emission research, and sensors.

Oxygen plasma treatment

Plasma is a state of matter that exists alongside solids, liquids, Bose Einstein condensates, fermion condensates, and others. Normally, plasma contains a large number of neutral particles (atoms, molecules, or free radicals, etc.) as well as positively and negatively charged particles, making it an ionized gas system that exhibits macroscopic electrical neutrality. Under high temperature or specific excitation, plasma discharge can generate abundant chemically active particles and plasma sheath, therefore it is widely used in surface treatment and modification fields.

Oxygen plasma treatment technology is a time-saving and environmentally friendly method for surface modification of various substrates and geometric shapes. It can improve the physical and chemical properties of material surfaces, such as conductivity and biocompatibility, in a very short period of time. Compared with strong acid treatment methods, oxygen plasma treatment can easily modify the surface of thin films or semiconductor materials, and this structure has a larger specific surface area than bulk materials, making it more suitable for the treatment of nanomaterials. By introducing reactive gases through oxygen plasma treatment, chemical reactions occur on the surface of nanomaterials, forming new functional groups such as hydroxyl and carboxyl groups, which react with surface free radicals to form cross-linked structural layers, leading to a sudden change in the surface properties of the material and obtaining new chemical structures. After oxygen plasma treatment, the introduction of more oxygen-containing groups can significantly improve the interaction between the material surface and biomolecules, enhance the number of active sites on the electrode surface, thereby significantly improving the reactivity of the material and improving the electrical and optical properties of electrochemical sensors.

Oxygen plasma treatment improves the gas sensing performance of ZnO

After oxygen plasma treatment, the grain size of ZnO material decreases, the specific surface area of the material increases, and the proportion of adsorbed oxygen on the material surface increases significantly. These factors collectively enhance the gas sensing response of ZnO nanofiber material to acetone.

The mechanism of improving the gas sensing performance of ZnO nanofibers by oxygen plasma treatment: After oxygen plasma treatment, the depletion layer on the material surface widens, the intergranular potential barrier increases, the range of material resistance changes increases, and the gas sensing response value of the material increases; The local polarity change of the material enhances its adsorption capacity for strongly polar molecules, reduces its adsorption capacity for weakly polar analysis, and improves its anti-interference ability for acetone adsorption.