## 2 Materials and Methods  
Poly [5-methoxy-2-(3-sulfopropyl)-1,4-phenylenevinylene] (APPV, 0.25 wt % in H\({}_{2}\)O) was provided by Sigma Chemical Co. Ltd. (Beijing, China) Mg(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O, Al(NO\({}_{3}\))\({}_{3}\cdot\)9H\({}_{2}\)O were supplied by Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China) NaOH, H\({}_{2}\)O\({}_{2}\) (30%), H\({}_{2}\)SO\({}_{4}\) (95%-98%) were provided by Beijing Chemical Reagent Company (Beijing, China). Na-montmorillonite (MMT) was manufactured by Zhejiang Feng Hong New Materials Co. Ltd. (Huzhou, China), and polyvinyl alcohol (PVA, DP = 1750 \(\pm\) 50) was supplied from Tianjin Fuchen Chemical Reagent Plant (Tianjin, China).  
UV-vis absorption spectra were recorded by double beam Persee UV-vis spectrophotometer (TU-1901, Beijing, China). Fluorescence spectra was performed on a fluorescence spectrophotometer (F-4600, Hitachi, Tokyo, Japan). X-ray diffraction pattern was recorded by Rigaku X-ray Diffractometer (XRD, RIGAKU D/Max-2550 with Cu K\(\alpha\) radiation, Tokyo, Japan) under the conditions: 40 kV, 30 mA. The morphology of the sample was investigated by Hitachi S-4300 Scanning Electron Microscope (SEM, Tokyo, Japan). The fluorescence decay was tested by using Edinburgh Instruments' steady and transient time-resolved fluorescence spectrometer, and the 375 nm pulse laser radiation was used as the excitation source (FLS-920, Livingston, UK).  
An aqueous mixed nitrate solution (50 mL) dissolved Mg(NO\({}_{3}\))\({}_{2}\cdot\)6H\({}_{2}\)O (0.4 mol), Al(NO\({}_{3}\))\({}_{3}\cdot\)9H\({}_{2}\)O (0.2 mol) was prepared, and then mixed with the solution of NaOH (50 mL, 2.4 mol/L) with vigorous stirring at 80 \({}^{\circ}\)C for 24 h under N\({}_{2}\) gas, and then solid were centrifuged and dried at 60 \({}^{\circ}\)C.  
Figure 1: The sketch map of APPV in electronic microenvironment (EME) between the montmorillonite (MMT) and layered double hydroxides (LDHs) monolayers. (**a**) MgAl-LDHs monolayer; (**b**) MMT monolayer; (**c**) Poly [5-methoxy-2-(3-sulfopropyl-1,4-phenylenevinylene] (APPV). In this figure, the pink stands for aluminum element, green stands for magnesium element, yellow stands for silicon element.  
0.1 g MgAl-LDHs was mixed with 100 mL formamide, and flake by a mechanical shaker for 2 days. One gram of MMT was added to 1 L deionized water an unremittingly stirred for 28 days. Then, centrifuge this turbid liquid at 10,000 rpm for 10 min in order to obtain a solution with exfoliated MMT nanosheets. Quartz slides were cleaned in H\({}_{2}\)SO\({}_{4}\) and H\({}_{2}\)O\({}_{2}\) solution for 30 min. PVA aqueous solution (1 wt %) acted as the border to connect the different components, and then 0.025 wt % APPV aqueous solution was mixed with isopyknic PVA aqueous solution to form APPV@PVA solution. (MMT/APPV@PVA/MgAl-LDHs/APPV@PVA)\({}_{n}\) (marked as MALA(\(n\))-films) were obtained by repeating as follow: (i) steeping the substrate into MMT solution for 5 min, and then thoroughly cleaning it; (ii) steeping it into APPV@PVA solution for 5 min, and cleaning it; (iii) steeping it into MgAl-LDHs suspension for 5 min, and cleaning it; (iv) steeping it into APPV@PVA solution for 5 min, then cleaning it. (MMT/APPV@PVA)\({}_{n}\) (recorded as MA(\(n\))-films) were obtained by depositing the MMT suspension, APPV@PVA solution in turn for each 5 min, respectively.