Metal-organic framework materials exhibit considerable potential as molecularly selective surfaceenhanced Raman spectroscopy(SERS)substrates because of their microporous structures,which enrich small molecules while e...Metal-organic framework materials exhibit considerable potential as molecularly selective surfaceenhanced Raman spectroscopy(SERS)substrates because of their microporous structures,which enrich small molecules while excluding larger ones.In this study,we develop a template-assisted chemical-etching strategy to prepare layered tuneable SERS substrates based on hierarchical porous zeolitic imidazolate framework-67(HP-ZIF-67)with a rhombic dodecahedral structure.The synergistic SERS enhancement mechanisms of HP-ZIF-67,which combine electromagnetic(EM)and chemical(CM)effects,were systematically studied through numerical simulations and experiments.Calculations revealed that under 633-nm laser excitation,the contributions of the EM and CM effects to the total SERS enhancement factor of HP-ZIF-67 were 60%and 40%,respectively.The hierarchical porous structure enhanced the fluid-flow flux over the microporous ZIF-67 because the increased pore radius reduced the viscous resistance and facilitated rapid molecular transport through the interconnected macro-meso-channels.Precise modulation of the CM and EM effects,combined with enhanced mass transfer,facilitated the development of HP-ZIF-67and HP-ZIF-67@Au as efficient SERS sensors.An investigation of the relationship between pore-size distribution and EM effects revealed the pivotal role of light confinement by whispering-gallery-mode microcavities in enhancing the SERS performance.The optimised HPZIF-67@Au composites functioned as flexible and highly sensitive in situ SERS sensors for gases and liquids,including volatile organic-compound gas and liquid-pesticide residues.This study introduces a novel design concept and provides a robust theoretical foundation for the future development of exhaled-breath point-of-care diagnostic devices and sweat-based wearable biomedical sensors.展开更多
大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流...大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流固耦合和谐响应分析等多种方法,研究了管道振动的产生原因和机制。结果表明,由调相机本身产生的周期性激振力是管道振动的主要原因。进一步提出基于调谐质量阻尼器(Tuned Mass Damper,TMD)的管道减振措施,试验和仿真数据表明,在润滑油供油管道系统4和5、6和7支吊架中间位置各安装一个TMD,减振效果最佳,可将该管系的振动加速度降低90%以上,具有良好的减振效果。展开更多
基金supported by the National Natural Science Foundation of China(Nos.62475128 and 12274055)Youth Innovation Team Program of Shandong Higher Education Institution(No.2024KJN016)+1 种基金Research Grants Council of Hong Kong through an ANR/RGC Joint Research Scheme grant(No.A-CityUl01/20)Centre for Functional Photonics of City University of Hong Kong,and Hong Kong Branch of National Precious Metals Material Engineering Research Center(ITC Fund)
文摘Metal-organic framework materials exhibit considerable potential as molecularly selective surfaceenhanced Raman spectroscopy(SERS)substrates because of their microporous structures,which enrich small molecules while excluding larger ones.In this study,we develop a template-assisted chemical-etching strategy to prepare layered tuneable SERS substrates based on hierarchical porous zeolitic imidazolate framework-67(HP-ZIF-67)with a rhombic dodecahedral structure.The synergistic SERS enhancement mechanisms of HP-ZIF-67,which combine electromagnetic(EM)and chemical(CM)effects,were systematically studied through numerical simulations and experiments.Calculations revealed that under 633-nm laser excitation,the contributions of the EM and CM effects to the total SERS enhancement factor of HP-ZIF-67 were 60%and 40%,respectively.The hierarchical porous structure enhanced the fluid-flow flux over the microporous ZIF-67 because the increased pore radius reduced the viscous resistance and facilitated rapid molecular transport through the interconnected macro-meso-channels.Precise modulation of the CM and EM effects,combined with enhanced mass transfer,facilitated the development of HP-ZIF-67and HP-ZIF-67@Au as efficient SERS sensors.An investigation of the relationship between pore-size distribution and EM effects revealed the pivotal role of light confinement by whispering-gallery-mode microcavities in enhancing the SERS performance.The optimised HPZIF-67@Au composites functioned as flexible and highly sensitive in situ SERS sensors for gases and liquids,including volatile organic-compound gas and liquid-pesticide residues.This study introduces a novel design concept and provides a robust theoretical foundation for the future development of exhaled-breath point-of-care diagnostic devices and sweat-based wearable biomedical sensors.
文摘大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流固耦合和谐响应分析等多种方法,研究了管道振动的产生原因和机制。结果表明,由调相机本身产生的周期性激振力是管道振动的主要原因。进一步提出基于调谐质量阻尼器(Tuned Mass Damper,TMD)的管道减振措施,试验和仿真数据表明,在润滑油供油管道系统4和5、6和7支吊架中间位置各安装一个TMD,减振效果最佳,可将该管系的振动加速度降低90%以上,具有良好的减振效果。
