# Supplementary Material (ESI) for Chemical Communications# This journal is © The Royal Society of Chemistry 2015

Supporting Information for

A luminescent ultrathin film with reversible sensing toward

pressure

Mingwan Li, Rui Tian, Dongpeng Yan, Ruizheng Liang,* Min Wei,* David G. Evans and

Xue Duan

M. Li, R. Tian, Prof. D. Yan, Dr. R. Liang, Prof. M. Wei, Prof. D. G. Evans, Prof. X. DuanState Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBox 98, Beijing 100029, P. R. ChinaFax: (+86)10-6442-5385E-mail: liangruizheng2000@163.com (R. Liang); weimin@mail.buct.edu.cn (M. Wei)

List of Contents

Figure S1. The structure formula of BTBS.

Figure S2. UV-vis absorption spectra of BTBS (0.01 g/L), PAA (0.005 g/L) aqueous solution

and BTBS@PAA (BTBS: 0.02 g/L; PAA: 0.01 g/L) micelle solution.

Figure S3. Fluorescence emission spectra of BTBS (1 g/L), PAA (0.5 g/L) aqueous solution

and BTBS@PAA (BTBS: 1 g/L; PAA: 0.5 g/L) micelle solution. The inset shows the

photographs of BTBS solution (left) and BTBS@PAA micelle solution (right) under UV-light

irradiation.

Figure S4. ITC titration measurements of PAA (5.0103 mol/L) and BTBS (1.0102 mol/L):

(A) the integrated heat for each injection as well as the fitting parameters are depicted (the

black line represents the best fit obtained for an independent model) and (B) the

thermodynamic parameters of the interaction.

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Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2016

Figure S5. Top-view SEM images of (BTBS@PAA/LDH)n (n=030) UTFs; from (A) to (D):

n=6, 12, 18 and 24, respectively.

Figure S6. Side-view SEM images of (BTBS@PAA/LDH)n (n=030) UTFs; from (A) to (D):

n=6, 12, 18 and 24, respectively.

Table S1. Film thickness and RMS roughness for (BTBS@PAA/LDH)n (n=030) UTFs with

various bilayer numbers

Figure S7. Tapping-mode AFM topographical images of (BTBS@PAA/LDH)n (n=030)

UTFs; from (A) to (D): n=6, 12, 18 and 24, respectively.

Figure S8. Fluorescence microscopy images of (BTBS@PAA/LDH)n (n=030) UTFs; from

(A) to (D): n=6, 12, 18 and 24, respectively.

Figure S9. Confocal microscopy images of the (BTBS@PAA/LDH)30 UTF with various film

thickness.

Table S2. Film thickness and RMS roughness for the (BTBS@PAA/LDH)30 UTF at different

states

Figure S10. (A) Fluorescence emission spectra of the (BTBS@PAA/LDH)30 UTF in the

presence of 10 MPa pressure at various response time; (B) the correlation between the

emission intensity at 450 nm and response time.

Figure S11. Fluorescence emission spectra of control samples in the presence of external

pressure: (A) (BTBS/LDH)30 UTF, (B) (BTBS@PAA/PDDA)30 film and (C) BTBS@PAA

drop-casting film. The insets show the correlation between fluorescence intensity and pressure.

Figure S12. The fluorescence lifetime of the original, compressed and recovered

(BTBS@PAA/LDH)30 UTF, respectively.

Table S3. The fitting of fluorescence decay data for the original, compressed and recovered

(BTBS@PAA/LDH)30 UTF

Table S4. Quantum yield and lifetime for the (BTBS@PAA/LDH)30 UTF at different states

Figure S13. Tapping-mode AFM topographical images of the (BTBS@PAA/LDH)30 UTF in a

compressing-recovering cycle: (A) original, (B) compressed, and (C) recovered UTF.

Figure S14. FT-IR spectra of the original, compressed and recovered (BTBS@PAA/LDH)30

UTF, respectively. The absorption bands at 3430, 2968, 1248 cm1 are ascribed to the

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stretching vibrations of R2NH, CH3, CN of BTBS respectively while the absorption bands

at 1097 and 1018 cm1 are ascribed to the stretching vibrations of S=O of BTBS.

Figure S15. Photostability tests upon irradiation by UV light (365 nm) for 300 min: (a)

(BTBS@PAA/LDH)30 UTF, (b) (BTBS@PAA/PDDA)30 film, and (c) BTBS@PAA drop-

casting film.

Experimental section:

Materials: analytical-grade chemicals including formamide, Mg(NO3)2·6H2O, Al(NO3)3·9H2O,

urea, sodium polyacrylate (PAA), poly(sodium 4-styrenesulfonate) (PSS),

poly(diallyldimethylammonium chloride) solution (PDDA), NaNO3 and HNO3 were purchased

from Aladdin Chemical. Co. Ltd. 2,2'(1,2-Ethenediyl) bis[5-[[4-(diethylamino)-6-[(2,5-

disulfophenyl) amino]-1,3,5-triazin-2-yl]amino] benzene sulfonic acid] hexasodium salt

(BTBS) was purchased from Sigma Chemical. Co. Ltd. The deionized and de-CO2 water was

used in all the experimental processes.

Fabrication of (BTBS@PAA/LDH)n UTFs: the synthesis and exfoliation of MgAl-LDH are

similar to the procedure described in our previous work.1 Briefly, 0.1 g of MgAl-LDH was

shaken in formamide solution (100 mL) for 48 h to produce a colloidal suspension of

exfoliated MgAl-LDH nanosheets. The transparent and flexible PET film, which was used as

substrate, was cleaned by ultrasonic treatment in ethanol, acetone and deionized water for 30

min, respectively. Prior to use, the PET substrate was firstly treated by alternate dipping into

poly(sodium 4-styrenesulfonate) aqueous solution (PSS, 0.5 g/L) and

poly(diallyldimethylammonium chloride) solution (PDDA, 12.5 g/L). Subsequently, the key

process for the preparation of (BTBS@PAA/LDH)n UTFs involves two steps: (1) modification

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of anionic styrylbiphenyl derivative (BTBS) with sodium polyacrylate (PAA) to obtain

BTBS@PAA micellar solution (BTBS: 1 g/L, PAA: 0.5 g/L); (2) alternate assembly of

negatively-charged BTBS@PAA with positively-charged LDH nanosheets (LDH: 1 g/L) via a

layer by layer (LBL) method on the activated PET film for n cycles. Finally, the UTFs are

dried in a flow of nitrogen gas at room temperature.

For comparison, three control samples were prepared. The (BTBS/LDH)30 and

(BTBS@PAA/PDDA)30 film were prepared by a similar LBL technique. The drop-casting

BTBS@PAA film was prepared by the solvent evaporation method.

Characterizations: UV-vis absorption spectra were collected in the range from 200 to 700 nm

on a Shimadzu U-3000 spectrophotometer, with the slit width of 1.0 nm. The fluorescence

emission spectra were performed on a RF-5301PC fluorospectrophotometer with the excitation

wavelength of 380 nm. The fluorescence emission spectra range in 400700 nm, and the

widths of excitation and emission slit are set to be 3 nm. Luminescence lifetime and quantum

yield measurements were recorded with an Edinburgh Instruments FL 900 fluorimeter. Fourier

transform infrared (FT-IR) spectra were obtained using a Vector 22 (Bruker)

spectrophotometer with a resolution of 2 cm1. Fluorescence image was observed by a TCS

SP5 two-photon confocal microscope (Leica, the excitation wavelength is 760 nm). To capture

the fluorescence slides for assembled UTFs, the step length was set to be 40 nm with capture

interval of 40 nm along the vertical and top-down direction. The photobleaching was tested by

the UV lighting with CHF-XQ 500W and RF-5301PC fluorospectrophotometer. X-ray

diffraction patterns (XRD) were recorded using a Rigaku 2500 VB2+PC diffractometer under

the conditions: 40 kV, 50 mA, Cu K radiation (λ=0.154056 nm) with step-scanned in step of

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0.04 (2θ) in the range from 0.5° to 5° using a count time of 10 s/step. The morphology of thin

films was investigated using a scanning electron microscope (SEM Hitachi S-3500) equipped

with an EDX attachment (EDX Oxford Instrument Isis 300), and the accelerating voltage

applied was 20 kV. The surface roughness data were obtained by using a NanoScope IIIa

atomic force microscope (AFM) from Veeco Instruments. The pressure-responsive data of

fluorescence emission spectra were obtained after compressing the UTFs by a 769YP-15A

Infrared tablet press for 10 s.

Figure S1. The structure formula of BTBS.

Figure S2. UV-vis absorption spectra of BTBS (0.01 g/L), PAA (0.005 g/L) aqueous solution

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and BTBS@PAA (BTBS: 0.02 g/L; PAA: 0.01 g/L) micelle solution.

Figure S3. Fluorescence emission spectra of BTBS (1 g/L), PAA (0.5 g/L) aqueous solution

and BTBS@PAA (BTBS: 1 g/L; PAA: 0.5 g/L) micelle solution. The inset shows the

photographs of BTBS solution (left) and BTBS@PAA micelle solution (right) under UV-light

irradiation.

Figure S4. ITC titration measurements of PAA (5.0103 mol/L) and BTBS (1.0102 mol/L):

(A) the integrated heat for each injection as well as the fitting parameters are depicted (the

black line represents the best fit obtained for an independent model) and (B) the

thermodynamic parameters of the interaction.

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Figure S5. Top-view SEM images of (BTBS@PAA/LDH)n (n=030) UTFs; from (A) to (D):

n=6, 12, 18 and 24, respectively.

.

Figure S6. Side-view SEM images of (BTBS@PAA/LDH)n (n=030) UTFs; from (A) to (D):

n=6, 12, 18 and 24, respectively.

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Table S1. Film thickness and RMS roughness for (BTBS@PAA/LDH)n (n=030) UTFs with

various bilayer numbers

n 6 12 18 24 30

SEM thinckness/nm [a]

RMS roughness/nm[b]

~73 2.48

~149 5.58

~220 7.55

~304 8.91

~378 10.08

[a] SEM thickness values were obtained from the side-view images of (BTBS@PAA/LDH)n UTFs (see

Figure 2B and Figure S6).

[b] Statistical RMS roughness values were obtained by AFM (see Figure 2C and Figure S7).

Figure S7. Tapping-mode AFM topographical images of (BTBS@PAA/LDH)n (n=030)

UTFs; from (A) to (D): n=6, 12, 18 and 24, respectively.

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Figure S8. Fluorescence microscopy images of (BTBS@PAA/LDH)n (n=030) UTFs; from

(A) to (D): n=6, 12, 18 and 24, respectively.

Figure S9. Confocal microscopy images of the (BTBS@PAA/LDH)30 UTF with various film

thickness.

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Table S2. Film thickness and RMS roughness for the (BTBS@PAA/LDH)30 UTF at different

states

State Original Compressed Recovered

XRD thinckness/nm [a] 373.8 272.1 406.5

RMS roughness/nm [b] 10.08 4.68 8.21

[a] XRD thickness values were obtained from the small angle XRD patterns of (BTBS@PAA/LDH)30 UTF

(Figure 3D).

[b] Statistical RMS roughness values were obtained by AFM (Figure S13).

Figure S10. (A) Fluorescence emission spectra of the (BTBS@PAA/LDH)30 UTF in the

presence of 10 MPa pressure at various response time; (B) the correlation between the

emission intensity at 450 nm and response time.

Figure S11. Fluorescence emission spectra of the control samples in the presence of external

pressure: (A) (BTBS/LDH)30 UTF, (B) (BTBS@PAA/PDDA)30 film and (C) BTBS@PAA

drop-casting film. The insets show the correlation between fluorescence intensity and pressure.

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Figure S12. The fluorescence lifetime of the original, compressed and recovered

(BTBS@PAA/LDH)30 UTF, respectively.

Table S3. The fitting of fluorescence decay data for the original, compressed and recovered

(BTBS@PAA/LDH)30 UTF

Sample τi (ns)[a] Ai (%) <τ> (ns) χ2[b]

0.18 76.40

1.26 18.78Original UTF

7.07 4.82

0.71 1.209

0.34 60.32

1.27 27.64Compressed UTF

4.81 12.04

1.13 1.057

0.28 70.70

Recovered UTF 1.23 24.40 0.85 1.198

7.22 4.90

[a] τi (i =1, 2, 3) is the fitted fluorescence lifetime; Ai is the percentage of τi. In this case, <τ> = ΣAiτi; ΣAi

=1).

[b] The goodness of fit is indicated by the value of χ2.

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Table S4. Quantum yield and lifetime for the (BTBS@PAA/LDH)30 UTF at different states

State Original Compressed Recovered

Quantum yield 12.82% 23.15% 13.71%

Lifetime (ns) 0.71 1.13 0.85

Figure S13. Tapping-mode AFM topographical images of the (BTBS@PAA/LDH)30 UTF in a

compressing-recovering cycle: (A) original, (B) compressed, (C) recovered UTF.

Figure S14. FT-IR spectra of the original, compressed and recovered (BTBS@PAA/LDH)30

UTF, respectively. The absorption bands at 3430, 2968, 1248 cm1 are ascribed to the

stretching vibrations of R2NH, CH3, CN of BTBS respectively while the absorption bands

at 1097 and 1018 cm1 are ascribed to the stretching vibrations of S=O of BTBS.

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Figure S15. Photostability tests upon irradiation by UV light (365 nm) for 300 min: (a)

(BTBS@PAA/LDH)30 UTF, (b) (BTBS@PAA/PDDA)30 film, and (c) BTBS@PAA drop-

casting film.

References:

1 (a) R. Liang, D. Yan, R. Tian, X. Yu, W. Shi, C. Li, M. Wei, D. G. Evans and X. Duan,

Chem. Mater., 2014, 26, 2595; (b) R. Tian, S. Zhang, M. Li, Y. Zhou, B. Lu, D. Yan, M.

Wei, D. G. Evans and X. Duan, Adv. Funct. Mater., 2015, 25, 5006.

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