| The self-assembly of ABC triblock copolymers as routes to generate various highly ordered periodic nanostructures have received a great deal of attention.The ABC triblock copolymer films with various periodic nanostructures can be employed as patterning templates,which are attractive for many applications,such as hybrid materials,drug delivery,membranes,nanoreactor,holographic gratings,and so on.Generally,solvent vapor annealing and thermal annealing can be used to adjust the orientation of the microdomains in order to fabricate ordered self-assemblied nanostructures.However,the exact relationship between process(spin-coating and solvent vapor annealing)conditions and structural transformation of ABC triblock copolymer thin films were rarely reported.Meanwhile,there was a few of studies about nanopattern transformation behaviors of ABC triblock copolymers with salts addition.On the other hand,the unique optical,electronic,and magnetic properties of noble metal nanostructures have stimulated considerable interest and have been exploited in wide range of applications,including biological and chemical sensing,medical diagnosis,microscopy imaging and optical devices.Various noble metal nanostructures,including nanoparticles,nanowires,nanorods,nanocubes etc.,have been reported to be substrates for surface enhanced fluorescence(SEF)and surface-enhanced Raman scattering(SERS)for different molecules.However,electromagnetic enhancement of periodic metal nanomaterials with the optical performance of conjugated polymer was rarely reported.And the mechanism was still unclear.In this study,the micro phase behaviors of ABC triblock copoly merspolystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide)(PS-b-P2VP-b-PEO)and polyisoprene-block-polystyrene-block-poly(2-vinylpyridine)(PI-b-PS-b-P2VP)were systematically investigated with various parameters in the process of spin-coating and solvent vapor annealing with salts addition to fabricate various nanopatterns.Then different gold nanoparticle arrays were prepared by the template of PI-b-PS-b-P2VP nanpattems and the PI-b-PS-b-P2VP micelles in order to study the relationships between the geometrical parameters of gold nanoparticle arrays and the intensity of electromagnetic field.Meanwhile,the optical signal of poly(3-hexylthiophene)(P3HT)thin films in various substrates were studied in great detail.Firstly,microphase behaviors of PS-b-P2VP-b-PEO during spin-coating and solvent vapor annealing were systematically investigated based on various parameters,including the type of the solvent,spin speed,thickness and annealing time.The results that nanopattem of nanoporous array was spin-coated from PS-b-P2VP-b-PEO toluene solution with the concentration of 0.1 wt%.With increasing thickness,the order-order transition from nanopores array to the pattern of nanostripes was observed due to microdomain coarsening.When the thickness of thin film was 22.594 nm,ordered pattern of parallel stripes could be obtained when the thin film was annealing in toluene vapor for 12 h at 30 ?.And the sphere of PEO block uniformly depressed in striated structure of P2VP block,which surrounded by PS matrix.In order to obtain ordered nanopattern by spin-coating without any further treatments,the solution of lithium chloride(LiCl)in tetrahydrofuran(THF)with ultrasound was introduced to fabricate novel ordered nanopattern of PS-b-P2VP-b-PEO thin film.It was obvious that nanopattern of fingerprint was obtained when the molar ratio of Li+ ions to the total number of oxygen atoms(O)in PEO block and the nitrogen atoms(N)in P2VP block was 1:32.2([Li+]:[O+N]=1:32.2)with ultrasonic treatment for 30min at room temperature.The introduction of THF was benificial to the dispersion of Li+ ions in the polymer solution and its loading in the polymer chain.The obvious increase in domain spacing of P2VP and PEO blocks was observed after the addition of LiCl.Moreover,it was found that the LiCl loading in PEO block decreased with increasing volume of LiCl-THF solution.And the LiCl loading in P2VP block increased at the same time.In order to further simplify our work,toluene was used as the solvent for LiCl instead of THF to prepared ordered nanostructure of PS-b-P2VP-b-PEO thin films with ultrasound.The results indicated that LiCl could uniformly disperse in toluene in a short time after ultrasonic treatment,which was a useful method to improve the efficiency of coordination between Li+ ions and polymer chains.Nanopattems of stripes and cylindrical microdomains could be obtained by adjusting the LiCl loading in P2VP and PEO blocks.The results in FT-IR spectra demonstrated that the LiCl loading in PEO block increased with increasing addition of LiCl.Meanwhile,the results of UV-vis spectra proved that the LiCl loading in P2VP block decreased when the molar ratio decreased from 1:40.25 to 1:32.2.However,the salts loading in P2VP block increased when the molar ratio decreased from 1:32.25 to 1:8.05,which mean that the LiCl loading was the least in five samples when the molar ratio was 1:32.2.Nanopattem transformation and applications of PI-b-PS-b-P2VP thin films were investigated systematically with various parameters in the process of spin-coating and solvent vapor annealing.The results indicated that microphase separation occurs obviously when the film was spin-coated from 0.4 wt%PI-b-PS-b-P2VP toluene solution at 3000 rpm Nanopatterns of ordered hexagonally-arranged cylinders and ordered nanostripes were observed when the film was exposed in saturated toluene vapor for different times at 30 ?.Moreover,the fingerprint nanopattern could be obtained with the treatment of THF vapor for 24 h at 30 ?.Various nanopatterns of PI-b-PS-b-P2VP thin films were used as template to prepare gold nanoparticle arrays with different particle sizes.The intensity of surface plasmon resonance(SPR)peak for gold nanoparticle array was enhanced with increasing average particle size without obvious red-shift.In order to further investigate the SPR effect and applications of gold nanoparticle array,PI-b-PS-b-P2VP self-assembled micelles were used to prepare Au nanoparticle arrays with different particle sizes and interparticle distances.The ratio of average particle size to average interparticle distance(R)was then introduced to study the relationship between the geometrical parameters and the optical properties(SERS and SEF)of the gold nanoparticle arrays.The geometrical parameters of gold nanoparticle arrays(particle size and interparticle distance)could be controlled by adjusting the molar ratio of HAuCl4 precursor to vinyl pyridine units in PI-b-PS-b-P2VP and the spin speed during spin-coating.The SPR peaks of the gold nanoparticle arrays in extinction spectra were enhanced with increasing R without obvious red-shift.Meanwhile,the fluorescence intensity and Raman intensity of P3HT film on the gold nanoparticle arrays was enhanced as compare with the film on a bare silicon substrate.Moreover,the fluorescence intensity and Raman intensity of P3HT film increased with increasing value of R.In this work,the self-assemblied properties of PS-b-P2VP-b-PEO and PI-b-PS-b-P2VP were systematically investigated based on spin-coating,solvent vapor annealing and the addition of salts in order to reveal the relationship between experimental parameters and self-assemblied nanostructures with mechanism.Moreover,the template of PI-b-PS-b-P2VP nanpatterns and the PI-b-PS-b-P2VP micelles were used to prepare Au nanoparticle arrays and systematically studied the relationship among self-assemblied nanostructure,Au nanoparticle arrays with its properties of SPR.The results were useful for fabrication and optimization of chemical sensing and optical devices with roadmap and technology. |
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