Photonic Crystal Improves the Absorptiometric Sensitivity of Colorimetric Membrane By Cavity-Induced Light-Matter Interaction
Photonic Crystal Improves the Absorptiometric Sensitivity of Colorimetric Membrane By Cavity-Induced Light-Matter Interaction
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光子晶体通过腔引起的光-物质相互作用提高比色膜的吸收灵敏度
DOI：
10.1149/ma2020-01332391mtgabs
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Endo Tatsuro
中科院分区：
文献类型：
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作者：
Kawasaki Daiki;Oishi Ryoutarou;Kobayashi Nao;Mizuta Tatsumi;Sueyoshi Kenji;Hisamoto Hideaki;Endo Tatsuro
光子晶体（PhC）使得利用光子带隙对光进行时空限制成为可能。高度局域化的光与PhC产生的强增强电场极大地增强了光-物质相互作用，已被应用于增强自发发射[1]。2D-PhC将光子带边缘频率的光集中在其平板上，并将其重新发射到自由空间。我们已经实现了聚合物或tio2基2D-PhC在光学离子传感器[2]上的各种应用。另一方面，最近，我们开发了一种基于聚氯乙烯的膜，其具有高度亲脂性的离子液体（IL），由极浓的两种功能化学传感分子，阴离子钙离子载体和阳离子染料组成。我们已经将这种基于il的膜应用于钙离子[3]的高灵敏度、快速和简单的吸收测量。在膜厚度一定的情况下，其吸收灵敏度取决于染料分子的浓度和吸收效率两个因素。前者几乎达到其极限，而后者可以通过分子设计略微增加。因此，需要另一种方法来大幅提高il基膜的灵敏度。本文设计了一种由tio2基2D-PhC和IL基膜组成的杂化结构（PhC/IL杂化）（图1）。实验结果表明，与不含PhC （Plane/IL hybrid）的杂化结构相比，其灵敏度提高了78倍。时域有限差分（FDTD）计算表明，光在PhC板中的高度局域化大大提高了灵敏度增强因子。采用液相沉积法制备了tio2基2D-PhC材料。根据先前报道的方法[3]制备了比色钙响应离子液体[KD-M13][OP2P]。将PVC （10 wt%）和[KD-M13][OP2P] （90 wt%）的混合物溶解在THF （80 wt%）和乙醇（20 wt%）的混合溶液中。然后，将制备好的溶液自旋涂覆在PhCs表面，制备了不同厚度的il基膜的杂化结构。膜的厚度(T)分别为50、100、230和300 nm。制备了与上述PhC/IL杂化结构具有相同材料成分（厚度为170 nm）的平面/IL杂化结构作为对照样品。利用自制光学显微镜进行反射光谱分析。混合结构在0.1 M H3PO4aq水溶液中的反射光谱。， 0或10-6至10-1M钙离子含50 mM Tris-HCl缓冲液（pH 7.0），或0.1 M NaOH aq)。首先计算PhC/IL杂化结构的灵敏度增强因子为反射强度衰减量(R)与厚度(T)之比；s=DR / T[nm-1]，其中edr =R(Ca(-6)) -R (Ca(-1))，然后计算PhC与平面结构的比值，σ ': σ ' =sPhC/ splane。利用时域有限差分法（FDTD）模拟计算了偶极子在特定位置的Purcell因子PL（PL= LDOScavity/ LDOSfree-space， LDOS为局域态密度）和PhC空穴中偶极子与空穴底部之间的距离l (Lis)，并基于Purcell效应对杂化结构对吸收效率的增强进行了理论建模。结果与讨论从电磁模拟和实验两方面进行了观察。
IntroductionPhotonic crystal (PhC) makes it possible to spatially and temporally confine light based on photonic bandgap. A highly localized light with the strongly enhanced electric field generated by PhC extremely enhances light-matter interactions, which has been applied to the enhancement of spontaneous emission [1]. 2D-PhC concentrates light in the photonic band-edge frequency in its slab and re-emits it into free-space. We have achieved various applications of the polymer- or TiO2-based 2D-PhC to optical ion sensors [2].On the other hand, very recently, we have developed a poly(vinyl chloride)-based membrane with a highly lipophilic ionic liquid (IL) consisting of extremely concentrated two functional chemical sensing molecules, an anionic calcium ionophore, and a cationic dye. We have applied this IL-based membrane to highly sensitive, rapid and simple absorptiometric sensing of calcium ions [3]. Its absorption sensitivity depends on two factors under the definite thickness of membrane, the concentration and the absorption efficiency of the dye molecules. The former almost reaches its limit while the latter can be little increased by the molecular design. Therefore, another approach is necessary to drastically increase the sensitivity of the IL-based membrane.Here, a hybrid structure consisting of TiO2-based 2D-PhC and IL-based membrane (PhC/IL hybrid) was designed (Fig. 1). It was demonstrated by and the experimental results that the sensitivity was 78 times higher than that of hybrid structure without PhC (Plane/IL hybrid). The Finite-difference time-domain (FDTD) calculation revealed that highly localized light in PhC slab greatly enhanced the sensitivity enhancement factor.Material and methodTiO2-based 2D-PhC was fabricated by using the liquid-phase deposition method. Colorimetrically calcium responsive ionic liquid, [KD-M13][OP2P], was prepared according to a previously reported method [3]. A mixture of PVC (10 wt%) and [KD-M13][OP2P] (90 wt%) was dissolved in mixture solutions of THF (80 wt%) and ethanol (20 wt%). Then, prepared solutions were spin-coated onto the surface of PhCs, and the hybrid structures with different thicknesses of IL-based membrane were prepared. The thickness (T) of the membrane was 50, 100, 230 or 300 nm respectively. A plane/IL hybrid structure with the same material composition (thicknessT: 170 nm) of the PhC/IL hybrid structures above was fabricated as the control sample.Reflection spectroscopy was carried out by using a home-built optical microscope. The reflection spectra of the hybrid structures in aqueous sample solutions (0.1 M H3PO4aq., 0 or 10-6to 10-1M calcium ions-contained 50 mM Tris-HCl buffers (pH 7.0), or 0.1 M NaOH aq.) were obtained. The sensitivity enhancement factor of the PhC/IL hybrid structure was first calculated as the ratio of the decrement of reflection intensity (R) to the thickness (T);s=DR / T[nm-1], whereDR =R(Ca(-6)) –R(Ca(-1)), and then the ratio ofsof the PhC to the plane structure, σ’: σ’=sPhC/sPlanewas calculated.Purcell factorPL(PL= LDOScavity/ LDOSfree-space, where LDOS is local density of state.) of the dipole at certain positions andL(Lis the distance between the dipole and bottom of the hole) in the holes of PhC was calculated by using FDTD simulation, and then the enhancement of the absorption efficiency by the hybrid structure was theoretically modeled based on Purcell effect.Results and discussionIt was observed from both the electromagnetic simulation and the experimental …