AlN, with its ultra-wide bandgap, is highly attractive for modern applications in deep ultraviolet light-emitting diodes and electronic devices. In this study, the surface and cross-sectional properties of AlN films grown on flat and nano-patterned sapphire substrates are characterized by a variety of techniques, including photoluminescence spectroscopy, high-resolution X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Raman spectroscopy. The results indicate that different sapphire substrates have minimal impact on the photoluminescence spectrum of the epitaxial films. As the temperature increased, the radius of curvature of the AlN films increased, while the warpage decreased. The AlN films grown on nano-patterned substrates exhibited superior quality with less surface oxidation. During the growth of AlN thin films on different types of substrates, slight shifts in the energy bands occurred due to differences in the introduction of carbon-related impurities and intrinsic defects. The Raman shift and full width at half maximum (FWHM) of the E₂(low), A₁(TO), E₂(high), E₁(TO), and E₁(LO) phonon modes for the cross-sectional AlN films varied with the depth and temperature. The stress state within the film was precisely determined with specific depths and temperatures. The FWHM of the E₂(high) phonon mode suggests that the films grown on nano-patterned substrates exhibited better crystalline quality.

Biomass corn was utilized as both carbon and nitrogen precursors to synthesize nitrogen self-doped carbon quantum dots (N-CQDs) via a hydrothermal method. The N-CQDs were further used as a nano-fluorescent probe for multicolor cellular imaging and real-time intracellular pH sensing. Experimental results showed that the N-CQDs exhibited a quantum yield of 18.13%, along with excellent biocompatibility, outstanding photoelectrochemical properties, and pH-responsive fluorescence sensing capabilities. The fluorescence intensity of the N-CQDs nanoprobes showed a strong linear correlation with pH values in the range of 4.2–8.4. In live HeLa cells, the N-CQDs nanoprobes displayed high-performance multicolor imaging, and their blue fluorescence intensity also maintained a good linear relationship with pH (4.2–8.4). These findings indicate that the synthesized N-CQDs nanoprobes can be used for the semi-quantitative measurement of intracellular pH, holding great potential for biomedical applications such as cellular imaging and intracellular pH sensing.