| Fluorescence materials have been applied in wide fields including molecular analysis and detecctions,anti-counterfeiting and traffic signs,fluorescent painting,etc.Their fluorescence intensity is influenced by the surrounding environment which is always a hot topic among researchers.The local free electrons of the metal nanoparticle collectively oscillate when the metal nanoparticles or nanostructures were irradiated by a certain frequency light,which is known as local surface plasmon resonance(LSPR).When the fluorophore is placed around metal nanoparticls,the fluorescence intensity can be enhanced or quenched.Using the LSPR effect of metal nanoparticles to control the fluorescence properties and prepare the functional materials are the hot spots of researchers in recent years.Spray layer-by-layer assembly technique is a method to prepare specific functional multicomponent coatings relying on non-covalent bonding interactions such as electrostatic attraction,hydrogen bonds,coordination bonds,etc.It has the properties of simple operation,fast film-forming speed,environment-friendly and is suitable for large-scale production.More importaintly,the morphology and structure of the prepared functional materials can be regulated by adjusting the parameters of the spraying process and the assembly system.In our work,the spray-assisted assembly technique was employed to prepare metal NP coating on planar substrate and the flexible fabric.The adsorption kinetics of metal nanoparticles by spraying method was explored to reveal spray-assisted assembly mechanism.The metal NP coatings were used for fluorescence detection and functional finishing of fabric contributing to further expanding the application flieds of spraying method.In this research,we firstly prepare two kinds of single-layer metal nanoparticle coatings,gold nanopartcle(Au NP)coating and silver nanoparticle(Ag NP)coating by spray-assisted assembly and study their deposition kinetics by adjusting the spraying parameters including the spray time and spray pressure.Compared to the dipping deposition behaviors,the deposition mechanism of NPs in spray process is revealed.Then the prepared 2D Ag platform were used for fluorescence enhancement,the morphology and electric intensity distribution of Ag NPs were studied along with the assembly proceeding.The Ag platform with hightest fluorescence enhancement factor was used for biomolecules detection.Subsequently,the Ag platform were strip-patterned by the room-temperature imprinting method to study the influence of pattern structure on the fluorescence enhancement effect.Finally,Ag NP coating were spray-assembled on the fabric.The deposition behaviour of the nanoparticles and the fluorescence intensity on the fabric were studied.Photothermal conversion efficiency of the NPs coated fabric was also explored.The research contents are as following:In the second chapter,the single-layer metal NP coatings including Au and Ag NP coatings were prepared through spray-assisted assembly technique.Both Au NPs and Ag NPs were prepared by sodium citrate reduction method and were negatively charged by the encapsulation of citrate.They were respecyively sprayed on the positively modified substrates and bonded to the surface of the substrate by electrostatic interaction.The deposition kinetics of the both NPs were discussed with the alteration of spray parameters including spray time and spray pressure.The results show that the spray process accelerates the deposition rates for Au and Ag NPs.While they have different response to the spray pressure.Under the spray pressure of 10,30,50 psi,the whole deposition behaviors of Au NPs exhibit the pressure-dependent kinetics.Using 30 and 50 psi spraying for 20 s,the Au deposition curve showed a rapid increase at first and then to a slow increase.The amount of Au nanoparticles deposition accounted for 76.4% of dipping saturation deposition amount at 30 psi for 20 s.The deposition kinetics of Ag NPs is independent on the spray pressure.When spraying time increased to 60 s,there is always a linear growth trend for Ag NPs,and the deposition amount is 38.3% of the dipping saturation state under 30 psi spraying for 20 s.In the third chapter,we present the preparation of fluorescence-based bioassay platforms using spray-assisted layer-by-layer assembly of Ag NPs and poly(diallyldimethylammonium chloride)(PDDA).Due to the multiple non-covalent interactions between PDDA and Ag NPs,especially the screening of the interparticle repulsion by the PDDA,the Ag NPs are anchored on the surface and their surface density is subsequently increased through step-by-step clustering.The clustering transferred from two-dimensional aggregation into three-dimensional steric packing state.Compared to the individual metal NP,this clustering then further increases the plasmonic enhancement of the fluorescence of dyes in the vicinity.However,the enhancement is gradually decreasing along with the clustering state from 2D to 3D.More importantly,the layer-by-layer assembly process allows the controllable construction of metal nanoparticle platforms and fluorescence enhancement effect.The assembled metal platform can enhance the fluorescence intensity of Rhodamine B(RhB),fluorescein isothiocyanate(FITC)and Cyanine-5(Cy5),which has universal application.The 12-layer Ag platform yielded a substantial fluorescence enhancement(maximum ~12.3-fold)for the near-infrared fluorescent dye of Cy5.In the fourth chapter,we report the preparation of strip patterned Ag platforms by room-temperature imprinting and their fluorescence enhancement performance for Cy5.The poly(acrylic acid)/poly(allylamine hydrochloride)(PAA/PAH)multilayer film was constructed as the underlying film before the deposition of Ag NPs for providing the prerequisites of the room-temperature imprinting.Subsequently,Ag NPs were spray assembled on the underlying film of PAA/PAH.Depending on the sequence between the room-temperature imprinting and the spraying of Ag NPs,the pattern-spraying and the spray-patterning procedures were respectively implemented for fabricating strip patterned Ag NP platforms.The resulting patterned Ag NP platforms both exhibited stronger capabilities in fluorescence enhancement,compared to the planar Ag NP platform.The pattern-sprayed Ag NP platform has a convex strip structure of Ag NP film and improved 1.39 times of the planar Ag NP platform in fluorescence enhancement.In contrast,the spray-patterned Ag NP platform possessed a higher improvement of 2.05 times,relying on a concavo-convex strip structure.This work developed an alternative strategy for improving the fluorescence enhancement of metal NP platforms.In the fifth chapter,the Ag NPs were sprayed on the plain cotton fabric.The deposition amount of the Ag NPs was improved a lot(2.3 times)compared to the one on the quartz due to the complicated three-dimensional fabric multistage structure.The fluorophore of RhB was adsorbed on the fabric.In contrary,its fluorescence intensity was decreased which resulted from the uncontrolled gap between the fluorophore and NPs.The patterned fluorescent fabric was obtained by selective deposition of nanoparticles on the surface of the fabric using patterned templates.At the same time,due to the LSPR effect of metal nanoparticle coatings,the photo-thermal conversion efficiency of fabrics has been greatly improved. |
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