Studies On Near-infrared Light Modulated Liquid Crystal/upconversion Nanoparticle Composites

Upconverting nanoparticles(UCNPs)are materials that have the ability to convert long-wavelength light into short-wavelength light.These optical properties make UCNPs a promising application in the fields of optics,biomedical materials and auxiliary photochemical reactions.Among them,UCNPs can be used to construct near-infrared light-sensitive composite materials.In the system,UCNPs can convert near-infrared light into ultraviolet light or visible light,thereby triggering the photochemical reaction of the photosensitive material.In this paper,two UCNPs/cholesteric liquid crystal(Ch-LCs)composite systems were studied.The photoisomerization reaction was carried out by using a chiral fluorescent optical switch induced by 980 nm near-infrared light to control the optical properties of Ch-LCs.The main research contents include:(1)The UCNPs/Ch-LCs composite system with 980 nm near-infrared light irreversibly regulated was prepared.In the system,chiral fluorescent switch CFM1 was used as a chiral additive,and UCNP1 with better comprehensive performance was used as a composite system in three kinds of UCNPs with 980nm near-infrared light excitation 365nm and 450nm dual-band fluorescence.Doped particles.Studies have shown that the addition of UCNP1 induces isomerization and photolysis of M1 molecules at 980 nm near-infrared light,which in turn can achieve irreversible regulation of fluorescence and reflection in UCNPs/Ch-LCs composite systems.(2)The UCNPs/Ch-LCs composite system with 980 nm near-infrared light reversible regulation was further studied.Firstly,UCNP I which can emit fluorescence in multiple bands and has selective luminescence properties was prepared.UCNP I emits blue dominant light at high power 980 nm near-infrared light excitation and green dominant light at low power 980 nm near-infrared light.Subsequently,it was introduced into a Ch-LCs system constructed by a chiral fluorescent optical switch CFM2.CFM2 can undergo a reversible trans-cis isomerization reaction under the excitation of green light and blue light.The selective luminescence band of UCNP I is consistent with the reversible regulation band of CFM2,so the high-low power 980 nm near-infrared light is used to control the fluorescence of Ch-LCs in the UCNP I-liquid crystal composite system,and finally the fluorescent pattern is written.in and erase.In this paper,two near-infrared light-regulated UCNPs/liquid crystal composite systems were studied,which opened up a new way for the construction and dynamic regulation of UCNPs and liquid crystal composite systems.