| The miniaturization and intelligence of optoelectronic devices have become an important driving force for the development of artificial intelligence era.Two dimensional(2D)materials,represented by graphene,have attracted extensive attention due to their novel physical and chemical properties,which are different from bulk materials.Moreover,their low dimensional properties perfectly meet the needs of current miniaturized and intelligent optoelectronic devices.Among them,transition metal carbides,nitrides or carbonitrides(MXenes)have rich physical and chemical properties due to their rich element composition and structural adjustability,and gradually stand out in the 2D material family.In recent years,MXenes have shown great potential in the field of micro integrated optoelectronic devices,and are expected to become a new generation of optoelectronic integration platform.As the basic light source of photoelectric devices,laser plays an irreplaceable role in optical communication,interconnection and sensing applications.However,at present,MXenes materials are mostly mined and applied in the field of laser modulation and detection.MXenes have not yet achieved a breakthrough in the generation of laser light source,which greatly limits the development of MXenes materials in more extensive application fields.The gain medium,resonator and excitation source are usually needed to obtain the laser source.Based on these three elements,since the laser was invented in the 1960s,because of its high light intensity and coherence characteristics,especially after the realization of a variety of band light sources,the laser light sources have gradually become the basis of ultra-high speed,ultra large capacity information technology and photoelectric devices.However,in the face of the development and application of miniaturized and integrated optoelectronic devices and their optical interconnection,communication and sensing,it is difficult for traditional laser source to participate in the high integration of optoelectronic devices due to the limitations of its cavity type,technology and volume.In this context,the compact configuration of random laser without external resonator provides an opportunity for microchip level laser source.The cavity can be provided by the scattering environment of nanostructures.After multiple scattering,photons can form a local closed-loop loop to oscillate,and then generate stimulated emission and laser.MXenes materials have been proved to have good water solubility,excellent light absorption and photothermal conversion performance.Under the action of external light excitation source,its stable colloid liquid has the ability to build the inhomogeneous refractive index of medium in the local liquid environment,so as to generate light scattering and force light to change the direction of propagation,thus forming the optical feedback cavity.Therefore,MXenes materials are expected to play an active role in the field of micro laser light source by virtue of its low dimensional characteristics and local liquid scattering environment,and even MXenes with optical gain attribute under certain adjustment means,are more likely to achieve a complete MXenes based laser.Based on the platform of MXenes materials,the generation of laser will make MXenes materials show greater charm in the field of miniaturization and integration of optoelectronic devices.It will also bring new development opportunities to materials,optics,communication,biomedicine and other fields.In this thesis,based on the excellent characteristics of light absorption and phototheemal conversion of Ti3C2-MXene,the local solvent bubble effect,i.e.the nonuniformity of the refractive index of the medium,is triggered by its photothermal properties in a stable colloidal solution pumped by a pulse laser,and then a nonlinear scattering mechanism is constructed.Based on the characteristics of its wavelength insensitive broadband scattering,combined with the broadband optical emission carbon quantum dots,the supercontinuum random laser from yellow to deep red has been successfully realized by optimizing the pump source and pump volume.Using quantum confinement and edge effect to adjust band structure and fluorescence characteristics of low dimensional materials,MXenes quantum dots(MQDs)in zero dimensional state were prepared by hydrothermal tailoring method.Furthermore,MXenes was endowed with its own optical gain property,and the effect of hydrothermal environment regulated by ammonia on surface passivation and fluorescence enhancement of MQDs was confirmed.By comparing the structure and fluorescence characteristics of the finite atom system,we obtained the optimized V2C-MQDs which have stronger luminous ability covering the whole visible region.By adjusting the colloid surface tension and optimizing the pump,we realized the local light scattering and constructed the multiple light feedback cavity.Based on V2C-MQDs,we realized the white laser with 490,545,587 and 613 nm four primary colors.The realization of MXenes-based laser source lays a foundation for its miniaturization and intelligent application development.The specific research works of this thesis are as follows:(1)The single or few layered MXenes with large specific surface area and good aqueous colloidal stability,can meet the requirements of nonuniformity of refractive index,and then the local scattering mechanism can be triggered under the action of external excitation source,which meet the needs of optical feedback of random laser.Therefore,the preparation of single-layer or few layer MXenes with high-quality will be the basis of constructing random laser system.Although a large number of multi-layer Ti3C2-MXene materials can be obtained from MAX phase ceramics by HF selective etching,in order to obtain single/few layer Ti3C2-MXene,subsequent step-by-step intercalation and wash are still needed.In order to avoid multi-step operation and the effect of intercalator,LiF/HCl mixed solution is preferred to etch the MAX phase.By optimizing the reaction temperature and the ratio of fluorine-containing salt and acid,a large number of single-layer or few layer Ti3C2-MXene with large sheet can be prepared in one step,and characterized by SEM and TEM.Meanwhile,according to specific characteristics,M2C-MXene can also be etched with HF or LiF/Cl mixed solution and obtained with the aid of ultrasound.Based on the MXenes raw materials obtained here,subsequent post-processing adjustments can be made for special needs to obtain the most suitable materials and their states.(2)Using Ti3C2-MXene prepared in(1)as raw material,a uniform and stable.MXenes colloidal solution with sheets scale in hundreds nanometer was obtained by further ultrasonic crushing.Using the excellent light absorption and photothermal conversion characteristics of Ti3C2-MXene,the local solvent bubble effect was triggered under the action of external light excitation source,and the nonuniformity of the medium refractive index was constructed,which was indirectly proved by light scattering test.And the scattering mechanism has the characteristics of wavelength insensitive broadband.By combining the stable colloid solution with the carbon quantum dots with wide-band light emission,and using the optical feedback formed by the scattering mechanism under the excitation of the pulse laser with the appropriate wavelength,the supercontinuum random laser from yellow to deep red is realized by optimizing the component concentration ratio and the pump volume,and the wavelength coverage is about 150 nm.(3)Based on the effect of quantum confinement and edge effect on adjusting band structure and fluorescence properties of low dimensional materials,this thesis attempts to use this strategy to make MXenes obtain optical gain attributes,and then explore the realization of laser in a single MXenes system.Therefore,the typical MQDs were prepared and their basic optical properties were analyzed.First,we try to obtain MQDs by means of ultrasonic mechanical cutting.Although ultrasound can effectively break up a large area of MXenes,the size is still in the hundred nanometer level,and the ability to obtain MQDs is limited.In view of this,a large number of MQDs have been efficiently obtained by the way of hydrothermal cutting,and the hydrothermal environment regulated by ammonia can produce a certain surface passivation effect on MQDs.The results of fluorescence and UV-Vis absorption show that the surface passivation can enhance the fluorescence of MQDs.In addition,the mechanism of fluorescence quenching and enhancement effect of Fe3+ and Cr3+ on passivated MQDs was preliminarily analyzed.(4)The passivated V2C-MQDs were obtained in the hydrothermal cutting environment under the condition of ammonia.The light emission ability of MQDs in the whole visible range was enhanced successfully.The solvent bubble effect was successfully triggered by the colloid concentration-mediated liquid surface tension regulation under the excitation of pump light,and the excitation power-dependent nonlinear scattering mechanism was obtained and characterized.Through enhanced optical gain and nonlinear scattering,the local multiple optical feedback cavity is established,and a hybrid white laser is realized with 490,545,587 and 613 nm primary colors simultaneously lasing.To sum up,based on the MXenes material platform,combining with its unique physical and chemical properties in different dimensions and compositions,by constructing the local wavelength non-sensitive wide-band light scattering and the formed microcavity,the yellow to deep red supercontinuum random laser and white laser are realized respectively in the two-dimensional and zero-dimensional states of MXenes.This microscale laser source will be conducive to the development and application of micro optoelectronic devices,such as nanofluid based biological and chemical monitoring and sensing.Therefore,the development of MXenes-based miniaturization and special forms of laser source in this thesis will have an important impact on the further development of micro devices. |
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