The Construction Of Functional Silicon-Based Hydrogels And Their Use For Dynamic Optical Anti-counterfeiting

Traditional optical anti-counterfeiting materials are usually limited to the single static encryption and authentication modality,which would lead to the risk of information storage security.Hydrogels with outstanding mechanical property show great potential in the field of flexibility and dynamic memory anti-counterfeiting.Silicon nanomaterials with excellent luminescence property and surface modifiability are promising as new optical anti-counterfeiting materials.This thesis aims to construct novel functional silicon-based composite hydrogels system for advanced anti-counterfeiting applications.In particular,taking advantages of the unique optical properties of silicon nanomaterials(e.g.,room temperature phosphorescence and UV-responsive fluorescence)and the excellent mechanical properties of the hydrogels(e.g.,self-healing and elasticity properties),the functional silicon-based composite hydrogels system is explored for dynamic encryption application at both temporal and spatial scales.The research contents of this paper are summarized as follows:Chapter 1:we briefly introduce the development of fluorescence and phosphorescence materials for anti-counterfeiting application in recent years,then illustrate the preparation strategies of silicon nanomaterials and hydrogels as well as their representative progress in anti-counterfeiting field.Subsequently,we discuss the design thought of silicon-based composite hydrogels system for anti-counterfeiting applications.On the basis of which,we present a discussion about the significance and content of this thesis.Chapter 2:boric acid-doped silicon nanoparticles(BSiNPs)are prepared by hydrothermal synthesis method using organosilicon and boric acid as precursor.The BSiNPs are further combined with polyvinyl alcohol to produce functional silicon-based composite hydrogels(BSiNPs-Hydrogels)system,which simultaneously feature strong fluorescence,long room temperature phosphorescence and self-healing properties.Typically,the as-prepared BSiNPs-Hydrogels show outstanding fluorescence(quantum yield:22.4%;fluorescence lifetime:8.26 ns;fluorescence maximum emission wavelength:420 nm)and phosphorescence(lasts 15 s to naked eye;phosphorescence lifetime:264 ms;phosphorescence maximum emission wavelength:500 nm)characteristics.In addition,the BSiNPs-Hydrogels exhibit excellent mechanical properties(the elastic strain:～281%;self-healing efficiency:91.5%).In the virtue of the above unique merits,multi-color dynamic information encryption model is established by using the resultant BSiNPs-Hydrogels as high-performance anti-counterfeiting label.Of note,static blue fluorescence and dynamic green phosphorescence can encode double-layer information encryption in space scale;and moreover,the anti-counterfeiting label can provide more than five kinds of time-dependent information during 15 s of dynamic phosphorescent decay process in time scale.Chapter 3:1,8-naphthalicanhydride-modified silicon nanoparticles(NASiNPs)are prepared under ultraviolet radiation.Subsequently,the NAS iNPs are further combined with boric acid and polyvinyl alcohol to obtain the silicon-based composites hydrogels system(NASiNPs-Hydrogels),which simultaneously features light-responsive fluorescence and self-healing properties.The NASiNPs-Hydrogels show the obvious red shift from blue fluorescence(maximum emission wavelength:440 nm;lifetime:9 ns)to green fluorescence(maximum emission wavelength:525 nm;lifetime:14 ns).In additional,the NASiNPs-Hydrogels manifest outstanding elasticity(the elastic strain reaches to 475%)and high self-healing ability(self-healing efficiency:95%).Taking advantages of the above optical and self-healing characteristics,the NASiNPs-Hydrogels is used for constructing the dynamic anti-counterfeiting authentication model.The system can produce information patterns with fluorescence transformations are realized by UV irradiation,providing high security levels for achieving photoresponsive and dynamic anti-counterfeiting.Chapter 4:we summarize the research results of this thesis,point out the innovation and shortcomings of current studies.Then we illustrate the prospect of the future research work.In summary,silicon nanomaterials and hydrogels are employed to construct novel silicon-based composite hydrogels system,which simultaneously possesses with excellent optical and mechanical properties.Such resultant silicon-based composite hydrogels system is further explored for information encryption with dynamic optics modality.These results are promising for promoting the development of silicon-based composite hydrogels materials in the field of anti-counterfeiting.