Construction And Characterization Of SERS-Based Microfluidic Gas Sensors

Gas sensors are of great importance in a wide range of applications from environment to healthcare.However,multiplex detection of complex gas mixtures with high sensitivity and selectivity is long-waited but have never been realized.For traditional gas sensors,the contact between gas molecules and the sensors relies on the slow process of passive diffusion,which inhibits the reaction efficiency and sensitivity.Besides,the traditional sensors can hardly figure out similar analytes due to the barren readout information,which disables the direct connection between the output signal and the molecular structure.In this work,we combined the advantages of microfluidic chips and surface-enhanced Raman spectroscopy（SERS）technology to develop a series of gas sensing chips and a portable device for simultaneous high-sensitivity and high-selectivity pan-species gas identification.The main innovative achievements of this paper are introduced as follows:（1）For the first time,it is proposed to use the on-chip microstructure to modulate the micro-air flow for efficient enrichment.An array-assisted SERS-microfluidic chip（Array SERS chip）was prepared,which showed ultra-high sensitivity.With the help of composite SERS probes consisted of zeolite imidazolate framework-8（ZIF-8）,Au@Ag nanocubes and cysteamine（CA）,the Array SERS chip achieves an ultra-low limit of detection,which is 2 orders of magnitude lower than that of traditional methods.（2）A gas detection chip（SERS-Vortexene Chip）based on an MXene-modified 3D ordered substrate is proposed,which realizes highly sensitive multiplex detection.Specifically,Ti₃C₂T_xMXenes on substrates endows the sensor with a general affinity to various gases,while the in-situ gas vortices in the nano-microstructures prolong the residence time of molecules in the SERS-active area.The combination ensures the improved performance of the proposed chip,providing a new way to break the bottleneck of the trade-off between high throughput and high sensitivity.（3）A smart on-chip SERS sensor that can simultaneously identify a wide range of gases is proposed.By being compatible with different sensing mechanisms such as physical adsorption and chemical adsorption,it provides a new technical platform for the simultaneous identification of cross-species gases.The sensor is used for simultaneous identification of 9gases belonging to aromatic compounds,aldehydes,ketones and sulfides in mixtures,with high sensitivity（ppb level）,high resolution（single methyl）and high robustness（RSD～8%）.Further,we evaluate the sensor in two application scenarios,which are indoor air pollution monitoring and exhaled breath-based disease diagnosis.（4）A portable SERS-microfluidic gas detection device is designed and prepared,which provides technical support for possible high-throughput and high-sensitivity on-field detection requirements.The device adopts a domestic microcontroller unit and a low-cost laser diode,effectively reduce the production costs.At the same time,the device is expected to be adapted to a variety of microfluidic chips,with excellent scalability and detection accuracy comparable to traditional benchtop Raman spectrometers.