Detecting trace ppb-level of formaldehyde (HCHO) in indoor ambient and human exhaled breath using metal oxide semiconductor (MOS) gas sensor has attracted increasing attention. Herein, Ag nanoparticles (Ag NP) modified In 2 O 3 and Au nanocage (Au NC) modified In 2 O 3 as well as bimetal Ag NP and Au NC co-modified In 2 O 3 were successfully prepared via one-step microwave-assisted solvothermal method and were used to construct semiconductor gas sensor. It is exciting to observe that the sensor based on Ag 6 Au 1 /In 2 O 3 exhibits the highest response of 277 toward 5 ppm HCHO at low operating temperature (170 °C), which is about 7 times, 38 times and 102 times higher than 6 wt. % Ag/In 2 O 3 , 1 wt. % Au/In 2 O 3 and pristine In 2 O 3 , respectively. Moreover, the selectivity and detection limit (down to 26 ppb) of Ag 6 Au 1 /In 2 O 3 sensor to HCHO have been proven to be greatly improved. This excellent sensing performance indicates that the proposed bimetal Ag and Au co-modification with synergistic catalysis effect offers an effective design for highly sensitive and efficient HCHO detection devices. Moreover, the mechanism of HCHO sensing with Au and Ag co-loaded In 2 O 3 was explored by the calculations obtained from first-principle density functional theory studies .
The detection of volatile organic compounds (VOCs) markers in exhaled breath based on surface-enhanced Raman scattering (SERS) technology is expected to become a non-invasive diagnosis method for lung cancer patients. However, the inherently low Raman scattering efficiency of trace VOCs in exhaled breath, coupled with the inadequate stability and uniformity of conventional Raman substrates, has hampered the practical application of SERS technologies for lung cancer biomarker detection. Additionally, the development of nanomaterials that simultaneously exhibit superior electromagnetic enhancement capabilities and efficient molecular enrichment functions remains a significant challenge. Herein, we have reported a size-effect-driven strategy for constructing Au nanocube (Au NC) @ zeolite imidazolate framework-8 (ZIF-8) core-shell nanoparticles. Tunability of Au NC@ZIF-8 shell thickness from 3 nm to 40 nm was achieved through cetyltrimethylammonium bromide (CTAB) concentration gradient control (0.5–2 mL) and ice bath kinetics control. This method requires no harsh conditions, featuring simple operation, mild reaction, and short synthesis time, successfully fabricating thin ZIF-8 shell layers with controllable structural properties. This unique architecture integrates the strong localized surface plasmon resonance (LSPR) effect of Au NCs with the porous adsorption capability of ZIF-8, realizing ultrasensitive detection of benzaldehyde (BA) with a limit of detection (LOD) of 2.5 ppb. As a straightforward approach for synthesizing homogeneous and controllable core-shell SERS-active nanoparticles, this method not only offers valuable insights for the preparation of analogous core-shell materials but also provides a robust material foundation and technical support for the non-invasive screening of lung cancer.
Jun Zhao,Hanhan Wang,Hongqi Geng,Qi Yang,Yuping Tong,Weiwei He
Disturbances in the redox state of a biological system can cause diverse effects and clinical functions. The key and difficulty lies in controlling the balance between reduction and oxidation. Nanomaterials with oxidoreductase-like activity offer an appealing way to adjust anti- and pro-oxidation in response to biological conditions. To this end, we design and prepare visible light-responsive hybrid nanozymes by combining Au and N-doped carbon dots (Au/NC). It is found that Au/NC can efficiently scavenge reactive oxygen species (ROS) and free radicals and exhibit SOD-like activity, showing intrinsic antioxidant activity. Upon irradiation with visible light, we observe that Au/NC can generate ROS (e.g., hydroxyl radicals, superoxide, and singlet oxygen) and exhibit enhanced oxidase-like activity to accelerate the oxidation of chromogenic substrates, showing pro-oxidant capability. The light-activated oxidative activity is ascribed to the synergistic effects of photoexcitation of N-doped carbon dots and the surface plasmon resonance of Au nanoparticles. In addition, we demonstrate the application of the anti- and pro-oxidant capability of Au/NC in inhibition or acceleration of oxidation of Monascus pigments and Fe2+, which is switched by the incident light. These results will be of significant interest in modulating the biological redox conditions through responsive and precise nanozymes.
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