Whispering Gallery-regulated Upconversion Luminescent Nanoprobes For Gas Sensitivity

For a long time,manufacturing and chemical plants have used gas sensors to detect gas leaks.At present,most of the types used are electrochemical sensors,which are complicated in operation,and still have shortcomings in terms of response speed and detection accuracy.As a new type of sensor technology,infrared gas sensor has a big advantage in dependence.It is not easy to be poisoned and fails,so it can extend its service life.It has high detection accuracy,a fast response speed,and is easy to carry and operate.It will become the mainstream gas sensor in the future.Up-conversion nanoparticles(UCNPs)have been skillfully used as infrared probes,but problems such as low detection accuracy and complex nonlinear response still exist.In this paper,a composite nano system is constructed:using two types of whispering gallery modes,an optical gas sensor with good linear response and high accuracy is realized.At room temperature,its detection limit can reach 0.052 ppm methanol gas.The first is the whispering gallery mode of glass microfibers.By coupling the graphene intermediate layer with glass microfibers,the local optical mode and surface scattering and surface absorption of the core-shell upconversion nanoparticles can be manipulated.The addition of graphene can adjust the refraction and scattering of the excitation light by the glass microfibers,and at the same time realize the photon transmission from the glass microfibers to the up-conversion nanoparticles,making the composite nanosystem with graphene participation compared to the composite nanosystem without graphene The system showed different luminous response performance.Due to the"light gate"function of graphene,the linear stimulation response upconversion luminescence is realized indirectly through the stimulation of graphene in the composite nanosystem;the second is the whispering wall mode of the nano-microcavity,which regulates the nanostructure and changes the light-emitting layer It grows on the cavity to form the whispering wall effect of the nano-microcavity,and Yb³⁺doping with a high energy absorption cross-section is introduced to further enhance the use of excitation light..The research on infrared gas sensors in this paper can be divided into these four aspects:The composition method and use process of gas-sensitive materials are designed.In this paper,the flexible substrate glass microfiber is selected,which can ensure good repeatability and stability in the bent and/or stretched and relaxed positions,and its whispering gallery mode can concentrate the beam to enhance the use of incident light;In order to reduce the result deviation caused by external controllable factors during use,an auxiliary device is designed to reduce the change of luminescent intensity created by the change of the position of the excitation light source.Graphene is inserted into the primary structure to improve the gas sensitivity.In this paper,graphene,an excellent optoelectronic material,is selected to optimize the structure.The superwetting effect of graphene can actively adsorb the gas to be measured,and at the same time,it can reduce the loss of emitted light;and insert between the glass microfibers and the upconversion nanoparticles The graphene thin layer forms a composite secondary structure to further amplify the optical signal.Multiple advantages greatly improve the performance of the gas sensor.The multi-shell nanostructure of cavity whispering gallery mode is designed to complete the structural adjustment of up-conversion nanoparticles.Based on the light-gathering effect of the whispering gallery mode,this paper improves the nanostructure and introduces the Yb³⁺ doping with high energy absorption cross-section.The experimental structure confirms that the Y layer between the light-emitting layer and the cavity layer is highly doped.The concentration of the sensitizer Yb³⁺ builds an energy transmission bridge between the photon energy and the activator Er³⁺,which can greatly improve the quantum efficiency of the crystal.This theory is also confirmed by spectral characterization.Using a variety of composite fibers to complete the methanol gas detection experiment.This paper has completed the detection experiment of methanol gas by GMUN and GMGUN with core-shell nanoparticles as the gas sensor,and realized the good linear response of the composite material as a gas sensor;and the multi-shell cavity nanostructure as the gas sensor CS3C's methanol gas detection experiment has been proved that the composite material can be used as a new type of gas sensor with fast response and high detection accuracy.