Carbon dots (CDs) with excellent cytocompatibility, tunable optical properties, and simple synthesis routes are highly desirable for use in optical bioimaging. However, the majority of existing CDs are triggered by ultraviolet/blue light, presenting emissions in the visible/first near‐infrared (NIR‐I) regions, which do not allow deep tissue penetration. Emerging research into CDs with NIR‐II emission in the red region has generated limited designs with poor quantum yield, restricting their in vivo imaging applications due to low penetration depth. Developing novel CDs with NIR‐II emissions and high quantum yield has significant and far‐reaching applications in bioimaging and photodynamic therapy. Here, it is developed for the first time Fe‐doped CDs (Fe‐CDs) exhibiting the excellent linear relationship between 900–1200 nm fluorescence‐emission and pH values, and high quantum yield (QY‐1.27%), which can be used as effective probes for in vivo NIR‐II bioimaging. These findings demonstrate reliable imaging accuracy in tissue as deep as 4 mm, reflecting real‐time pH changes comparable to a standard pH electrode. As an important example application, the Fe‐CDs probe can non‐invasively monitor in vivo gastric pH changes during the digestion process in mice, illustrating its potential applications in aiding imaging‐guided diagnosis of gastric diseases or therapeutic delivery.

High selectivity and sensitivity were measured using a novel type of sensor device, based on ZnO nanowires (NWs) coated with a thin layer of boron nitride (BN) decorated with palladium nanoparticles (NPs). Vapor–Liquid–Solid (VLS) growth and Atomic Layer Deposition (ALD) routes, two scalable technologies, have been used for the synthesis of the sensing device nanomaterials. X-Ray Photoelectron Spectroscopy (XPS), Electron Energy Loss Spectroscopy (EELS), Energy-dispersive X-ray (EDX) spectroscopy and Transmission Electron Microscopy (TEM) studies revealed the presence of both the 5 nm layer of BN and metallic Pd NPs around the ZnO NWs. The nanomaterials were then integrated within a miniaturized sensor device in order to measure their performance for H₂ detection at different concentrations and temperatures, in the presence of various gases such as C₆H₆, C₇H₈, C₂H₅OH, and CH₃COCH₃. High hydrogen response signals of 12.28 (±0.61) have been measured, even for H₂ concentrations as low as 10 ppm, confirming the efficiency of the novel designed Pd/BN/ZnO NW sensor. Due to the beneficial synergistic effect of ZnO, BN and Pd nanomaterials, the new sensing device clearly outperformed other sensors based on ZnO NWs. In addition, the sensor was resistant to humidity, and hydrogen gas could be detected for concentrations as low as 0.5 ppm. The high performance obtained with the novel Pd/BN/ZnO NW based sensor along with its easy gas phase processing opens new perspectives and opportunities for the sensing community and will hopefully promote the hydrogen economy.