SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4202-3
Carbon dots (CDs) with absorption in the second near-infrared window (NIR-II, 900-1700 nm) hold promise for tumor theranostics, yet existing synthesis methods often involve complex procedures, harsh conditions, or lack precise control. Here we report a 'self-photooxidation-restructuring' strategy that enables structural reorganization of the carbon core in CDs, achieving a significant redshift of absorption into the NIR-II region. Under ultraviolet (UV) light irradiation, the precursor (B-CDs, absorption in UV region) generates singlet oxygen, which self-oxidizes aldehyde groups and the carbon skeleton of B-CDs to stronger electron-withdrawing carboxyl groups and carbon radicals, respectively. These processes facilitate the formation of new C=C bonds between isolated aromatic domains, thereby transforming B-CDs into novel CDs (N-CDs) characterized by enhanced donor-acceptor interactions and a redshift in absorption toward the NIR-II window. Various experimental data, including high-resolution XPS, FTIR, NMR, EPR, have proved the proposed formation mechanism. The novel N-CDs afforded a high photothermal conversion efficiency of up to 71.33%, which enabled 1064 nm laser-activated photoacoustic imaging (PAI)-guided photothermal therapy (PTT) in tumors. This work opens a new avenue for the synthesis and modulation of CDs in the NIR-II region.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4220-x
High-temperature electronics demand non-volatile memories (NVMs) capable of stable operation above 500 °C for applications in space exploration, nuclear energy, and autonomous driving. Conventional silicon-based devices fail above ~250 °C, and silicon carbide (SiC) cannot process data above 300 °C. Memristors offer a promising solution due to their simple structure, low power consumption, and scalability. A recent breakthrough by Yang et al. (Science) demonstrated a graphene (Gra)/HfOx/W memristor achieving data retention at 700 °C, with retention time of 50 h, endurance of 10^9 cycles, ON/OFF ratio exceeding three orders of magnitude, and operation voltage ~1.5 V. The key innovation is replacing the Pt bottom electrode with in-situ grown graphene, which suppresses high-temperature diffusion of the W top electrode through the HfOx layer. In contrast, Pt/HfOx/W devices fail after annealing at 800 °C for 10^4 s due to W migration, forming conductive filaments that lock the device in the ON state. High-resolution TEM and EDS reveal tungsten oxide (WOx) formation at the W/HfOx interface in Pt-based devices, while Gra-based devices show no such degradation. STEM-EELS confirms W migration across the HfOx layer in Pt devices, but graphene acts as a diffusion barrier, preserving stable switching behavior. This interfacial engineering approach provides a viable pathway for high-temperature NVM, addressing the critical bottleneck of electrode diffusion.
Environmental Chemistry•2026•DOI: 10.7524/j.issn.0254-6108.2024122406
The effects of different vegetation types on soil quality in the Green Heart Area of the Changsha-Zhuzhou-Xiangtan City Cluster were evaluated to provide a reference for selecting suitable afforestation species and improving forest soil quality. Seven vegetation types (mixed forest, broad-leaved forest, coniferous forest, economic forest, shrub forest, grassland, and abandoned cropland) with similar site conditions were studied. Eleven soil physicochemical indicators were measured, and soil quality was assessed using principal component analysis (PCA), Pearson correlation, total data set (TDS), minimum data set (MDS), and entropy-weighted TOPSIS methods. Results showed no significant differences in soil water content, soil bulk density, and C:N ratio among vegetation types, while significant differences were found in total porosity, capillary porosity, saturated water content, field water holding capacity, total carbon, total nitrogen, available potassium, and available phosphorus. Compared with abandoned cropland, soil water content, total porosity, field water holding capacity, saturated water content, total carbon, total nitrogen, available potassium, and available phosphorus were significantly higher, and soil bulk density was significantly lower. Mixed forest soil exhibited the highest values for field water holding capacity, total porosity, saturated water content, total nitrogen, total carbon, available potassium, and available phosphorus. Correlation analysis revealed that soil bulk density was extremely significantly negatively correlated with soil water content, total porosity, and saturated water content, and significantly negatively correlated with field water holding capacity, total carbon, and total nitrogen. Soil capillary porosity, field water holding capacity, total porosity, and saturated water content were extremely significantly positively correlated with soil nutrients, while soil bulk density showed varying degrees of negative correlation with soil chemical nutrients. Soil chemical properties and stoichiometric ratios showed varying degrees of significant positive correlation. The order of soil quality under different vegetation types was mixed forest > broad-leaved forest > shrub forest > economic forest > grassland > coniferous forest > abandoned cropland. Mixed forest soil quality was the best and significantly higher than other vegetation types, with significant differences among vegetation types. Mixed forest soil quality was clearly superior. In vegetation restoration and plantation establishment in the Green Heart Area, the principle of matching tree species to site conditions should be followed, with a focus on mixed forests to improve overall soil quality and enhance ecological benefits of artificial vegetation restoration.