The development of energy-efficient, sensitive, and reliable gas sensors for monitoring NO₂ concentrations has garnered considerable attention in recent years. In this manuscript, TiO₂ nanotube arrays/reduced graphene oxide nanocomposites with varying rGO contents (TiO₂ NTs/rGO) were synthesized via a two-step method for room temperature NO₂ gas detection. From SEM and TEM images, it is evident that the rGO sheets not only partially surround the TiO₂ nanotubes but also establish interconnection bridges between adjacent nanotubes, which is anticipated to enhance electron–hole separation by facilitating electron transfer. The optimized TiO₂ NTs/rGO sensor demonstrated a sensitive response of 19.1 to 1 ppm of NO₂, a 5.26-fold improvement over the undoped TiO₂ sensor. Additionally, rGO doping significantly enhanced the sensor’s response/recovery times, reducing them from 24 s/42 s to 18 s/33 s with just 1 wt.% rGO. These enhancements are attributed to the increased specific surface area, higher concentration of chemisorbed oxygen species, and the formation of p-n heterojunctions between TiO₂ and rGO within the nanocomposites. This study provides valuable insights for the development of TiO₂/graphene-based gas sensors for detecting oxidizing gases at room temperature.

In extreme working conditions such as deep-sea and aerospace, failure due to friction and wear of key metal components is very frequent. Traditional binary or ternary nitride protective coatings are unable to achieve a coordinated improvement in terms of hardness, wear resistance, and structural stability. In this manuscript, a high-entropy composite nano-coating of CrWNbTaMoVSiN with an alternating structure of metal and nitride layers was prepared by using anode layer ion source-assisted magnetron sputtering technology. The influence of substrate bias voltage on the microstructure, phase structure, surface chemical state, friction and wear properties of coatings was systematically studied. The findings demonstrate that the substrate bias voltage has a substantial impact on the structure and performance of the CrWNbTaMoVSiN coatings. As the bias voltage increases, the coating deposition rate and thickness decrease, while the grain growth morphology gradually transitions from directionally aligned columnar crystals to equiaxed crystals. The primary phase of the coating is a solid solution with a face-centered cubic (FCC) crystal structure. At a bias voltage of 60 V, the coating exhibits a denser surface and cross-sectional microstructure, fewer structural defects, higher hardness, superior wear resistance, and enhanced electrochemical corrosion protection performance. This study provides critical experimental evidence and theoretical insights into the bias-voltage-dependent regulation mechanism of high-entropy nano-multilayer coatings, thereby supporting the process optimization of high-performance protective coatings and their engineering deployment under extreme service conditions.