1
Supporting Information for
Mass-amplifying electrochemiluminescence film (MAEF) for visual detection of dopamine in aqueous media
Zihua Li, Wei Qin, and Guodong Liang*
PCFM lab, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou, 510275,
China.
* Corresponding author: E-mail address: [email protected] (G. L.)
Table of Contents
1. Materials and instruments
1.1 Chemicals
1.2 Preparation of BTD-TPA films
1.3 Characterizations
1.4 Electrochemical and ECL measurements
1.5 Density functional theory (DFT) calculations
2. Synthesis of BTD-TPA
3. Supplementary figures
Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2020
2
1. Materials and instruments
1.1 Chemicals
4,7-dibromo-2,1,3-benzothiadiazole, 4-(diphenylamino)phenylboronic acid, potassium carbonate,
tetrahydrofuran, tetrakis(triphenylphosphine)palladium, dichloromethane, toluene, cyclohexane, N,N-
Dimethylformamide and tetrabutylammonium hexafluorophosphate were purchased from Energy
Chemical or Soochiral Chemical Science & Technology in China. Dopamine hydrochloride, ascorbic
acid, uric acid, gulcose, TEOA, DBAE, TPrA, Na2C2O4 and Na2SO4 were purchased from Macklin.
Gold, copper, and type 304 stainless steel wafers were obtained from Aidahengsheng (Tianjin, China).
ITO wafers were purchased from Shenzhen Laibao Hi-Tech Co., Ltd. Glassy carbon electrode (GCE)
was obtained from Chenhua instrument (China). Phosphate buffer solutions were prepared by mixing
balanced amounts of 0.2 M Na2HPO4 and NaH2PO4. All regents or chemicals were used as received
without any further purification.
1.2 Preparation of BTD-TPA films
The BTD-TPA films were facilely prepared by drop-casting 5 μL of DCM solution of BTD-TPA on
different electrodes, allowing it to air dry. The film thickness is controlled by dropping BTD-TPA
solutions with different concentrations on the electrode surface.
1.3 Characterizations
The NMR spectra were measured on a Bruker AV 400 spectrometer in CDCl3 with tetramethylsilane
(TMS) as internal reference. The high-resolution mass spectra (HRMS) were recorded using a mass
spectrometer (LTQ XL, ThermoFisher, America) operating in matrix-assisted laser desorption
ionization time-of-flight (MALDI-TOF) mode. UV-vis absorbance spectra were recorded with a
SOPTOP 752 spectrometer. PL spectra were measured on a GANGDONG F-380 spectrofluorometer.
Fluorescent lifetime was recorded on an LTD FLSP 920 spectrometer (Edinburgh Instruments, UK).
Quantum yield of BTD-TPA in solid powder was recorded by using an Edinburgh Instruments
3
spectrometer (FLSP920) with a calibrated integrating sphere. The morphologies of BTD-TPA films
were characterized by scanning electron microscopy (SEM, Quanta 400, FEI Company). Transmission
electron microscopy (TEM) was carried out using a transmission electron microscope (JEOL, JEM-
2010F) operated at an acceleration voltage of 200 kV. The X-ray diffraction (XRD) pattern was
recorded on an X-ray diffractometer (XRD, D8 Advance, Bruker) with Cu Ka radiation. The thickness
of BTD-TPA films measured using a profilometer (Ambios XP-1, Ambios Technology Inc.). The
fluorescence images of BTD-TPA single crystal and films were measured by a fluorescence microscope
instrument (LEICA M205 FA). All the optical photos of ECL and PL were recorded using a commercial
mobile phone camera (HUAWEI P30).
1.4 Electrochemical and ECL measurements
All electrochemistry experiments were performed with a three-electrode cell on an electrochemical
work station (CHI 660D, Chenhua instrument, China). Au, Cu and type 304 stainless steel wafers (1×1
cm2), GCE (3 mm diameter) and ITO (2×2 cm2) were employed as the working electrodes. Platinum
wire was used as the counter electrode and Ag/AgCl was served as the reference electrode. Before
usage, all working electrodes were polished with 0.5, 0.3, and 0.05 μm alumina powder dispersed in
water and sonicated in ethanol and deionized water. A photomultiplier tube detector (PMT, Hamamatsu,
Japan) with the voltage at 800V was employed to collect the ECL signal. The ECL spectrum was
obtained via pulsing 80 mV past the peak potentials of the oxidation waves for BTD-TPA with a pulse
width of 1 s by differential pulse amperometry. The ECL stability profile was obtained by plusing
between 80 mV past the oxidation peak and 0 V for BTD-TPA by means of multi-potential steps, with a
pulse width of 2 s.
4
1.5 Density functional theory (DFT) calculations
Optimized geometries and molecular orbitals of HOMO and LUMO levels of BTD-TPA, p-
benzoquinone and oxidized species of DA were calculated using a density functional theory (DFT)
method (B3LYP/6-31+(d) of the optimized structures; Gaussian 09).
2. Synthesis of BTD-TPA
The compound was synthesized by following the procedure reported in literature 1. A mixture of 4,7-
dibromo-2,1,3-benzothiadiazole (147 mg, 0.5 mmol), 4-(diphenylamino)phenylboronic acid (434 mg,
1.5 mmol), Pd(PPh3)4 (50 mg, 0.04 mmol), K2CO3 (690 mg, 5 mmol), THF (40 mL) and water (8 mL)
was heated to 60 °C for 24 h under nitrogen and stirring. The mixture was cooled to room temperature.
The solvents were removed under reduced pressure. Dichloromethane (150 mL) and water (50 mL)
were added. The organic layer was separated and washed with water (150 mL) three times, dried over
anhydrous Na2SO4 and evaporated to dryness under reduced pressure. The crude product was purified
by column chromatography on silica gel using hexane/dichloromethane as eluent. Yield: 52%. 1H NMR
(400 MHz, CDCl3) δ (ppm): 7.06 (t, 2H, Ar H), 7.20 (t, 12H, Ar H), 7.29 (t, 8H, Ar H), 7.74 (t, 2H, Ar
H), 7.88 (d, 4H, Ar H); 13C NMR (125 MHz, CDCl3) δ (ppm): 123.3, 124.9, 127.4, 129.4, 129.9, 131.0,
132.2, 147.5, 148.0, 154.2; HRMS (MALDI-TOF) m/z: [M+] calcd for C42H30N4S, 622.2191; found,
622.1989.
5
3. Supplementary figures
Br
Br
NS
NB
+Pd(PPh3)4
NS
N
OHHO
K2CO3, THF/H2O
N
N N
Scheme S1 Synthetic route for BTD-TPA.
BTD-TPA was facilely synthesized through a one-step Suzuki coupling reaction with a high yield
(Scheme S1). It is soluble in common organic solvents such as tetrahydrofuran (THF) and
dichloromethane (DCM), but insoluble in water. Red-shifted fluorescence with increasing solvent
polarity and density functional theory (DFT) calculations of BTD-TPA (Fig. S1 and S2) indicate strong
charge transfer effects from electron-donating triphenylamine (TPA) wings to the electron-withdrawing
BTD core. Cyclic voltammograms (CV) of BTD-TPA show a stable and reversible redox pair at +1.1 V
due to the presence of arylamine moieties (Fig. S3). The ipa/ipc value is close to unity, revealing that
radical cations produced during anodic potential scanning are stable 2.
6
350 400 450 500 550 600
CH Tol THF DCM DMF
N
orm
aliz
ed A
bsor
banc
e (a
u)
Wavelength (nm)
a
480 600 720 840
CH Tol THF DCM DMF
Nor
mal
ized
PL
Inte
nsity
(au)
Wavelength (nm)
b
Fig. S1 Normalized UV-vis (a) and photoluminescence (PL) (b) spectra of BTD-TPA in solvents with
different polarities including cyclohexane (CH), toluene (Tol), tetrahydrofuran (THF), dichloromethane
(DCM), N, N-dimethylformamide (DMF). Compound concentration: 10 μM.
Fig. S2 Optimized geometries and molecular orbitals of HOMO and LUMO levels of BTD-TPA.
7
1.5 1.0 0.5 0.0 -0.5 -1.0-60
-20
20
60
Cur
rent
(mA
)
Potential (V vs SCE)
Fig. S3 CV of BTD-TPA in anhydrous DCM containing 0.1M TBAPF6. Scan rate: 0.1V/s. Compound
concentration: 1mM.
8
500 600 700 800
fw (vol %) 90 80 70 60 50 40 30 20 10 0
PL In
tens
ity (a
u)
Wavelength (nm)
a
0 20 40 60 80 1000.0
0.3
0.6
0.9
1.2
Water Fraction (vol %)I 0/I
TICT AIE
b
Fig. S4 (a) Photoluminescence (PL) spectra and (b) the plot of relative PL intensity (I/I0) of BTD-TPA
versus water fraction (fw) in THF/water mixtures. I0: emission intensity in pure THF. Compound
concentration: 10 μM; λex = 460 nm.
To study the effect of aggregation on its emission process, the photoluminescence (PL) spectra of
the luminogen were explored in THF/water mixtures with different water fractions (fw). As shown in Fig.
S4, the luminogen in pure THF emits orange-red fluorescence with an emission maximum at 609 nm.
With gradual addition of water into THF (fw ≤ 60%), the emission is weakened and red-shifted to ca.
625 nm due to twisted intramolecular charge transfer (TICT) in polar solvent mixtures 3. The mixture is
transparent without formation of aggregates at fw ≤ 60%. Afterwards (fw> 70%), the mixture becomes
turbid, and PL intensity starts to increase due to the AIE effect from the freely rotating rotors of
arylamino units. The higher the water fraction, the stronger the emission intensity. At fw = 90%, PL
intensity recovers remarkably, and the emission maximum moves to 609 nm.
9
0 20 40 60 80 1000
100
200
300
ECL
Inte
nsity
Water Fraction (%)
ECL
Inte
nsity
Potential (V vs Ag/AgCl)0.0 0.5 1.0 1.50
100
200
300fw (vol %)
100 90 80 70 60 50 40 30 20 10 0
a b
Fig. S5 (a) ECL intensity-potential profiles, and (b) ECL intensity plots of the film on GCE as a
function of water fraction in THF/H2O mixed solvent. Luminogen loading was 600 ng/mm2.
It is noted that PL intensity of BTD-TPA is strongest in pure THF (Fig. S4), while ECL signal is
not detected in pure THF solutions using glassy carbon (Fig. S5). PL spectra of BTD-TPA/THF solution
are excited by UV light at 350 nm. Most of luminogen molecules are excited and involved in light
emission, leading to strong PL intensity. In contrast, ECL of BTD-TPA/THF solution is triggered by
electrochemical reactions near the electrode surface. Luminogen concentration near electrode surface is
low in BTD-TPA/THF solution, leading to low concentration of excited luminogen molecules and faint
ECL.
10
0.0 0.5 1.0 1.5 2.00
1k
2k
3k
BTD-TPA film/Au Bare Au
0.0 0.5 1.0 1.5 2.00
1k
2k
3k
Au GC Cu SS ITO
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
a
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
b
Fig. S6 (a) ECL intensity profiles of the BTD-TPA film on different electrodes in PBS solutions. (b)
ECL intensity of the BTD-TPA film on Au wafers and bare Au wafers in identical conditions.
Luminogen loading was 260 ng/mm2.
0.0 0.5 1.0 1.5 2.00
500
1000
1500
2000
2500fw (vol %)
100 90 80 70 60 50 40 30 20 10 0
Potential (V vs Ag/AgCl)
ECL
Inte
nsity
Fig. S7 ECL intensity-potential profiles of the BTD-TPA film on Au wafers as a function of water
fraction in THF/H2O mixed solvent. Luminogen loading was 520 ng/mm2.
11
1.5 1.0 0.5 0.0-60
-40
-20
0
20
ITO SS Cu GC Au
Cur
rent
Den
sity
(μA
mm
-2)
Potential (V vs Ag/AgCl)
a
1.5 1.0 0.5 0.0-500
-300
-100
100
ITO SS Cu GC Au
Cur
rent
Den
sity
(μA
mm
-2)
Potential (V vs Ag/AgCl)
b
Fig. S8 LSV curves of (a) BTD-TPA films on different electrodes and (b) TEOA (300 mM) in 0.2 M
PBS solutions. pH = 8. Luminogen loading was 520 ng/mm2.
0 1 2 30
1
2
3
4
5
Thic
knes
s (μ
m)
Cross-section (mm)
a
500 600 700 8000
500
1000
1500
2000
AuGlass Au Glass
PL In
tens
ity
Wavelength (nm)
b
Fig. S9 (a) Profilometry traces for BTD-TPA films at loadings of 520 ng/mm2 with a thickness of 3.67
um. (b) PL spectra of BTD-TPA films on Au and glass wafers. λex = 460 nm.
12
Qua
ntum
Yie
ld (%
)
Loading (ng mm-2)0 200 400 600 800 1000
35
40
45
50
55
Bulk
Fig. S10 Fluorescence quantum yields of BTD-TPA films on Au wafers at various loadings.
0 200 400 600 800 10003.0
3.5
4.0
4.5
5.0
0 10 20 30 40 500
1
2
3
4
5
6Loading (ng mm-2)
bulk 1040 936 780 624 520 416 312 260 208 104 52 26 13
Inte
nsity
(cou
nts
×10
4 )
Time (ns)
a
Life
time
(ns)
Loading (ng mm-2)
Bulk
b
Fig. S11 (a) Time-resolved photoluminescence spectra, and (b) lifetime of BTD-TPA film on Au wafers
at various loadings. λex = 460 nm.
13
Calculation of radiative and non-radiative decay rate constants.
Fluorescence typically follows first-order kinetics:
(S1)[𝑆] = [𝑆]0𝑒 ‒ 𝑡/𝜏
[S] is the concentration of exited state molecules at time t, [S]0 is the initial concentration and τ is the
fluorescence lifetime.
Decay rate (k) is the inverse of lifetime, consisting of radiative and non-radiative decay rate constants:
(S2)𝑘 = 𝑘𝑟𝑎𝑑 + 𝑘𝑛𝑟𝑎𝑑
where krad is the radiative decay rate constant and knrad is the non-radiative decay rate constant. The
quantum yield (Φ) is defined as the fraction of emission process in which emission of light is involved:
(S3)Φ =
𝑘𝑟𝑎𝑑
𝑘𝑟𝑎𝑑 + 𝑘𝑛𝑟𝑎𝑑
The values of radiative and non-radiative rate constants of the film were tabulated in Table 1.
14
50 150 250 350 450 5500
2k
4k
6k
8k
10k
N
OH
OH
HO
ECL
Inte
nsity
Concentration (mM)
b
0.0 0.5 1.0 1.5 2.00
3k
6k
9kConcentration (mM)
50 100 150 200 250 300 350 400 450 500 550
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
a
Fig. S12 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in 0.2 M PBS
solutions containing various amounts of TEOA and (b) the plots of the maximum ECL intensity against
TEOA concentration. pH= 8. Luminogen loading was 520 ng/mm2.
0 50 100 150 2000
400
800
1200
N
OH
ECL
Inte
nsity
Concentration (mM)
b
0.0 0.5 1.0 1.50
400
800
1200
Concentration (mM) 25 50 75 100 125 150 200
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
a
Fig. S13 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in 0.2 M PBS
solutions containing various amounts of DBAE and (b) the plots of the maximum ECL intensity against
DBAE concentration. pH= 8. Luminogen loading was 520 ng/mm2.
15
5 15 25 350
50
100
150
N
ECL
Inte
nsity
Concentration (mM)
b
0.0 0.5 1.0 1.50
50
100
150
Concentration (mM)
5 10 15 20 25 30 35
Potential (V vs Ag/AgCl)
ECL
Inte
nsity
a
Fig. S14 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in 0.2 M PBS
solutions containing various amounts of TPrA and (b) the plots of the maximum ECL intensity against
TPrA concentration. pH= 8. Luminogen loading was 520 ng/mm2.
10 40 70 1000
2
4
6
8
O
OO
ONa
Na
ECL
Inte
nsity
Concentration (mM)
b
0.0 0.5 1.0 1.50
2
4
6
8
Concentration (mM) 10 25 50 75 100
Potential (V vs Ag/AgCl)
ECL
Inte
nsity
a
Fig. S15 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in 0.2 M PBS
solutions containing various amounts of Na2C2O4 and (b) the plots of the maximum ECL intensity
against Na2C2O4 concentration. pH= 8. Luminogen loading was 520 ng/mm2.
16
4 6 8 10 120
2k
4k
6k
8k
10k
ECL
Inte
nsity
pH
b
0.0 0.5 1.0 1.5 2.00
2k
4k
6k
8k
10k
pH
4 5 6 7 8 9 10 11 12
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
a
Fig. S16 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in 0.2 M PBS
solutions at various pH and (b) the plots of the maximum ECL intensity against pH value. TEOA: 300
mM. Luminogen loading was 520 ng/mm2.
0 200 400 600 800 10000
2k
4k
6k
ECL
Inte
nsity
Concentration (mM)
b
0.0 0.6 1.2 1.8 2.40
2k
4k
6k
Concentration (mM) 50 100 200 500 1000
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
a
Fig. S17 (a) ECL intensity-potential profiles of BTD-TPA films on Au electrodes in PBS solutions at
different concentrations and (b) the plots of the maximum ECL intensity against PBS concentration.
pH= 8. Luminogen loading was 520 ng/mm2.
17
ECL
Inte
nsity
Potential (V vs Ag/AgCl)0.0 0.5 1.0 1.5 2.00
2k
4k
6k
8kLoading (ng/mm2)
1040 936 780 624 520 416 312 260 208 104 52 26
Fig. S18 ECL intensity-potential profiles of BTD-TPA films on Au electrodes at various loadings.
Calculation of the ECL efficiency
The ECL efficiency refers to its relative ECL efficiency compared with the ECL system of
(Ru(bpy)32+/TprA) by integration of both ECL intensity and current value versus time, and is calculated
through the following equation 4,5:
Ф𝐸𝐶𝐿 = Ф𝐸𝐶𝐿, 𝑠𝑡 × [𝑏
∫𝑎
𝐸𝐶𝐿𝑑𝑡
𝑏
∫𝑎
𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑑𝑡]𝑥 ∕ [𝑏
∫𝑎
𝐸𝐶𝐿𝑑𝑡
𝑏
∫𝑎
𝐶𝑢𝑟𝑟𝑒𝑛𝑡𝑑𝑡]𝑠𝑡
where ΦECL, x,and st represent ECL efficiency, BTD-TPA and Ru(bpy)32+, respectively. ΦECL,st value is
set to 1 as the standard from the measurable ECL emission of 1mM Ru(bpy)32+ in 0.2 M PBS solution
(pH = 8) with 0.1 M TprA at +1.2 V.
18
20 40 60 80 1000
5
10
15
20
25
Perc
enta
ge (%
)
Diameter (nm)
Fig. S19 Diameter distribution of BTD-TPA nanowires on gold wafers.
Fig. S20 SEM images of BTD-TPA films on Au wafers at different loadings. (a) 104 ng/mm2 and (b)
312 ng/mm2.
19
5 μm
Fig. S21 SEM images of BTD-TPA films on glassy carbon electrode (GCE).
Fig. S22 Fluorescence microscopy images of BTD-TPA crystals at low magnification (a) and high
magnification (b).
20
Fig. S23 XRD pattern of BTD-TPA films.
Fig. S24 Fluorescence microscopy images of BTD-TPA films on Au wafers at loadings of (a) 26
ng/mm2, (b) 52 ng/mm2, (c) 104 ng/mm2, (d) 208 ng/mm2, (e) 260 ng/mm2, (f) 312 ng/mm2, (g) 416
ng/mm2, and (h) 520 ng/mm2.
21
1.5 1.0 0.5 0.0-50
-40
-30
-20
-10
0Loading (ng/mm2)
1040 936 780 624 520 416 312 260 208 104 52 26
Cur
rent
Den
sity
(μA
mm
-2)
Potential (V vs Ag/AgCl)
Fig. S25 LSV curves of BTD-TPA film at different loadings on Au wafers in 0.2 M PBS solutions. pH
= 8.
0 2000 4000 6000 80000
1000
2000
3000
4000 Loading(ng mm-2)
520 416 312 260 208 104 52 26 0
Zʹ (Ω)
-Zʺ
(Ω)
a
Loading (ng/mm2)
Rct
(Ω)
b
0 100 200 300 400 500 6000
1000
2000
3000
4000
5000
6000
Fig. S26 (a) EIS profiles of BTD-TPA films on GCE at different loadings in 5 mM
K3[Fe(CN)6]/K4[Fe(CN)6] (molar ratio = 1:1) solutions containing 0.1 M KCl. (b) The plot of Rct value
versus BTD-TPA loading.
22
Fig. S27 Crystal structures of BTD-TPA. (a) View along X, Y, and Z axes, respectively. (b) Interaction
between adjacent molecules.
23
0
1k
2k
3k
4k
a
0
1k
2k
3k
4k
blank
-15-14
-13-12
-11
-10-8
ECL
Inte
nsity
lgcDA (M)
-9
lgcDA (M)
ECL
Inte
nsity
blank
-15-14
-13-12
-11-10
-9-8
b
0
1k
2k
3k
4k
ECL
Inte
nsity
lgcDA (M)
blank
-15-14
-13-12
-11-10
-8-9
c
Fig. S28 ECL intensity of the BTD-TPA film (loading: 260 ng/mm2) in the presence of various
concentrations of DA. Three parallel experiments were carried out for checking reproducibility.
24
Table S1 Comparison of the present work with reported ECL sensors for DA detection.
Electrodes Linear range (M) Detection limit (M) Reference
Cu NCs/HZ/GCE[a]
DSP-QDs/CNTs/GCE[b]
MIECLS/GCE[c]
NCD@PEI-rGO/RuNSs/GCE[d]
ZnSe/GO@MWNTs/Ru(bpy)32+[e]
Au-WS2/GE[f]
Pd NCs/GCE[g]
APTES-PTCA/GCE[h]
WOx QDs/GCE[i]
G-CdTe QDs/TAEA-Ru/GCE[j]
MIP/QDs/AuNPs/MWCNTs/GCE[k]
BTD-TPA film/GE
1.0×10-12 - 1.0×10-8
5.0×10-11 - 1.0×10-8
1.0×10-14 - 1.0×10-6
1.0×10-8 - 5.0×10-5
1.0×10-9 - 1.0×10-5
5.0×10-9 - 2.0×10-4
1.0×10-12 - 1.0×10-8
1.0×10-12 - 1.0×10-8
1.0×10-15 - 1.0×10-5
1.0×10-14 - 1.0×10-9
1.0×10-14 - 2.5×10-12
1.0×10-15- 1.0×10-8
3.5 × 10-13
2.6 × 10-11
2.0 × 10-15
1.0 × 10-8
6.0 × 10-8
3.23 × 10-9
4.6 × 10-13
2.9 × 10-13
1.0 × 10-15
2.9 × 10-15
3.3 × 10-15
3.3 × 10-16
6
7
8
9
10
11
12
13
14
15
16
This work
[a]Cu NCs/HZ: A ECL system consists of Cu nanoclusters aqueous solution and modified GCE with
hydrazine. [b]DSP-QDs/CNTs: 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester)-
functionalized CdTe quantum dots/multiwalled carbon nanotubes. [c]MIECLS: A quenching-type
electrochemiluminescence sensor consists of up-conversion nanoparticles, COFs-based ECL
enhancement material and oligoaniline-crosslinked gold nanoparticles imprinting recognition sites.
[d]NCD@PEI-rGO/RuNSs: N-doped carbon dots@poly(ethylenimine)-reduced graphene
oxide/Ru(bpy)32+ nanosheets. [e]ZnSe/GO@MWNTs/Ru(bpy)3
2+: ZnSe quantum dots/graphene
oxide@multiwalled carbon nanotubes/Ru(bpy)32+. [f]Au-WS2/GE: Au nanoparticles-WS2
nanosheets/gold electrode. [g]Pd NCs: Pd nanocones. [h]APTES-PTCA: 3-aminopropyltriethoxysilane
functionalized 3,4,9,10-perylenetetracar-boxylic acid. [i]WOx QDs: tungsten oxidequantum dots. [j]G-
CdTe QDs/TAEA-Ru/GCE: graphene-CdTe quantum dots/selfenhanced Ru(II) composite. [k]MIP/QDs/AuNPs/MWCNTs/GCE: molecularly imprinted polymer/CdSeTe/ZnS QDs/Au
nanoparticles/multiwalled carbon nanotubes.
25
0
200
400
600
ECL
Inte
nsity
blank-14
-13-12
-11-10
a
-9-8
lgcDA (M)-14 -12 -10 -8
0.0
0.2
0.4
0.6
0.8
1.0
(I0-I)/I0 = 0.12lgcDA + 1.82R = 0.9979
lgcDA (M)
(I 0-I)
/I 0
b
Fig. S29 (a) ECL intensity of the BTD-TPA film (loading: 52 ng/mm2) in the presence of various
concentrations of DA. (b) The plot of (I0-I)/I0 value against logarithm of DA concentration.
-16 -14 -12 -10 -80.0
0.2
0.4
0.6
0.8
1.0
(I0-I)/I0 = 0.13lgcDA + 2.07R = 0.9941
lgcDA (M)
(I 0-I)
/I 0
b
0
600
1200
1800
ECL
Inte
nsity
blank-15
-13 -12-11
-10
a
-9
-14
lgcDA (M)
Fig. S30 (a) ECL intensity of the BTD-TPA film (loading: 208 ng/mm2) in the presence of various
concentrations of DA. (b) The plot of (I0-I)/I0 value against logarithm of DA concentration.
26
0
1k
2k
3k
4k
ECL
Inte
nsity
lgcDA (M)
blank-15
-14
-13-12
-11
-10
a
-15 -14 -13 -12 -11 -100.0
0.2
0.4
0.6
0.8
1.0
(I0-I)/I0 = 0.15lgcDA + 2.44R = 0.9912
lgcDA (M)
(I 0-I)
/I 0
b
Fig. S31 (a) ECL intensity of the BTD-TPA film (loading: 312 ng/mm2) in the presence of various
concentrations of DA. (b) The plot of (I0-I)/I0 value against logarithm of DA concentration.
0
2k
4k
6k
ECL
Inte
nsity
blank
-14
-13-12
-11-10
a
lgcDA (M)
-9-8
-14 -12 -10 -80.0
0.4
0.8
1.2
(I0-I)/I0 = 0.12lgcDA + 1.92R = 0.9947
lgcDA (M)
(I 0-I)
/I 0
b
Fig. S32 (a) ECL intensity of the BTD-TPA film (loading: 416 ng/mm2) in the presence of various
concentrations of DA. (b) The plot of (I0-I)/I0 value against the logarithm of DA concentration.
27
Loading (ng mm-2)
LOD
(×10
-15
M)
0 100 200 300 400 5000
2
4
6
8
Fig. S33 The plot of limit of detection (LOD) versus luminogen loading.
1.5 1.0 0.5 0.0-40
-30
-20
-10
0
DA: μM 0 0.05 0.1 0.2 0.3 0.4 0.5 1 5 10 50 100 200 500 1000
Cur
rent
(mA
)
Potential (V vs Ag/AgCl)
a
0.0 0.5 1.0 1.5 2.00.0
0.5
1.0
1.5
Nor
mal
ized
Cur
rent
DA (μM)
b
Fig. S34 (a) LSVs of BTD-TPA films in 0.2 M PBS containing different concentrations of DA. Scan
rate: 0.1 V/s. (b) The plot of relative current (I0/I) versus the concentration of DA. I0 denotes the current
of BTD-TPA films in the absence of DA.
ECL of the film is almost quenched in the presence of 10-8 M of DA (Fig. 6). Change in current of
the film during ECL process was monitored in the presence of DA up to 1 mM, 5 orders of magnitude
than the concentration required to quench ECL.
28
HO
HONH3
+-2H+ -2e- O
ONH3
+
Dopamine (1) Dopaminequinone (2)
-H+
O
ONH2
HO
HO NH
O
HO N
-2H+ -2e-
Dopaminechrome (4) Leucodopaminechrome (3)
HO
HO NH
5,6-dihydroxyindole (5)
-2H+ -2e- O
HO NH
+
Indole quinone (6)
Melanoid pigment
Fig. S35 Oxidation of dopamine.
Dopamine undergoes a series of reactions during electrochemical oxidation. Its reaction pathway is
summarized in Fig. S35 17-19. Following the facile two-electron oxidation of dopamine (1) to dopamine-
oquinone (2), ring closure via deprotonation of the amine side chain to leucodopaminechrome (5,6-
dihydroxyindoline,3) occurs irreversibly. Compound 3 is then oxidized to dopaminechrome (4), which
rearranges to 5,6-dihydroxyindole (5). Compound 5 is further oxidized to indole quinone (6), which
begins the polymerization process.
29
-3.44
-6.61
Eg = 3.17 eV
Benzoquinone (2)
-2.60
-6.56
Eg = 3.96 eV
Benzoquinone (4)
-3.12
-5.62
Eg = 2.50 eV
Benzoquinone (6)
-3.54
-7.36
Eg = 3.82 eV
p-benzoquinone
Eg = 2.53 eV
-2.27
-4.80
BTD-TPA
HOMO
LUMO
Fig. S36 Energy levels, energy gaps and molecular orbitals of the HOMO and LUMO of BTD-TPA, p-
benzoquinone, and oxidized species of DA calculated by B3LYP/6-31+(d) program.
Fig. S37 (a) PL spectra of BTD-TPA containing different concentrations of p-benzoquinone. (b) Plots
of the relative PL intensity (I0/I) of BTD-TPA in THF solution versus concentration of p-benzoquinone.
Luminogen concentration: 10 μM; λex = 460 nm.
30
0.0 0.5 1.0 1.5 2.00
1k
2k
3k
4k
5k
ECL
Inte
nsity
Potential (V vs Ag/AgCl)
BTD-TPA film
BTD-TPA film + DA
BTD-TPA film + DA + βME
0
1k
2k
3k
4k
5k
ECL
Inte
nsity
Film + DA + βME
a b
Fig. S38 (a) ECL-potential profiles and (b) ECL intensity of the BTD-TPA film, with 1 nM of DA, with
1 nM of DA and 20 nM of 2-mercapoethanol (βME).
ECL
Inte
nsity
Different quencher
(I 0-I)
/I 0
Different quencher
a b
+DA+UA
0
1k
2k
3k
4k+DA
+DA+glucose+DA+AA
+DA+glucose+AA+UA
Blank
+DA
+DA+glucose
+DA+AA+DA+UA
+DA+glucose+AA+UA
0.0
0.2
0.4
0.6
0.8
1.0
Fig. S39 ECL-potential profiles (a), and (b) (I0-I)/I0 of the BTD-TPA film with 1 pM of DA containing
1000-fold concentrations of AA, UA and glucose. Luminogen loading was 260 ng/mm2.
31
blank -15 -14
-11-12-13
-8-9-10
lgcDA (M)
cblank -15 -14
-13 -12 -11
-10 -9 -8
a blank -15 -14
-13 -12 -11
-10 -9 -8
b
lgcDA (M) lgcDA (M)
Fig. S40 ECL images of BTD-TPA films in the presence of various concentrations of DA. Three
parallel experiments were carried out for checking reproducibility.
32
Blank
DA
Fig. S41 ECL images of BTD-TPA films in the absence and presence of DA (2 × 10-12 M). Five parallel
experiments were carried out for checking reproducibility.
Table S2 Grayscale analysis data of the ECL film.
Grayscale Average
value
G0-G/G0 cDA
(×10-12 M)
Relative
error (%)
blank 27.6, 26.8, 25.4,
25.6, 24.426.0 1.2
with DA
(2×10-12 M)
11.3, 12.4, 13.5,
14.7, 14.913.4 1.5
0.48 0.08 2.04 1.50 2
33
References
1. S. i. Kato, T. Matsumoto, T. Ishi i, T. Thiemann, M. Shigeiwa, H. Gorohmaru, S. Maeda, Y.
Yamashita and S. Mataka, Chem. Commun., 2004, 23422343.
2. J. Suk, Z. Wu, L. Wang and A. J. Bard, J Am Chem Soc, 2011, 133, 1467514685.
3. W. Qin, D. Ding, J. Liu, W. Z. Yuan, Y. Hu, B. Liu and B. Z. Tang, Adv. Funct. Mater., 2012, 22,
771779.
4. Z. Han, Z. Yang, H. Sun, Y. Xu, X. Ma, D. Shan, J. Chen, S. Huo, Z. Zhang, P. Du and X. Lu,
Angew. Chem., 2019, 131, 59765980.
5. K. N. Swanick, S. Ladouceur, E. Zysman-Colman and Z. Ding, Chem Commun (Camb), 2012, 48,
31793181.
6. M. Zhao, A. Y. Chen, D. Huang, Y. Zhuo, Y. Q. Chai and R. Yuan, Anal. Chem., 2016, 88, 11527
11532.
7. L. Zhang, Y. Cheng, J. Lei, Y. Liu, Q. Hao and H. Ju, Anal. Chem., 2013, 85, 80018007.
8. Y. Gu, J. Wang, H. Shi, M. Pan, B. Liu, G. Fang and S. Wang, Biosens. Bioelectron., 2019, 128,
129136.
9. L. Li, D. Liu, H. Mao and T. You, Biosens. Bioelectron., 2017, 89, 489495.
10. L. Tian, X. Wang, K. Wu, Y. Hu, Y. Wang and J. Lu, Sensor Actuat. B-Chem., 2019, 286, 266271.
11. Z. Wang, X. Wang, X. Zhu, J. Lv, J. Zhang, Q. Zhu and Z. Dai, Sensor Actuat. B-Chem., 2019, 285,
438444.
12. H. M. Wang, C. C. Wang, A. J. Wang, L. Zhang, X. Luo, P. X. Yuan and J. J. Feng, Sensor Actuat.
B-Chem., 2019, 281, 588594.
13. X. Fu, Y. Yang, N. Wang and S. Chen, Sensor Actuat. B-Chem., 2017, 250, 584590.
14. H. Peng, P. Liu, W. Wu, W. Chen, X. Meng, X. Lin and A. Liu, Anal. Chim. Acta, 2019, 1065, 21
28.
15. X. Fu, X. Tan, R. Yuan and S. Chen, Biosens. Bioelectron., 2017, 90, 6168.
34
16. Z. Wang, Y. Qian, X. Wei, Y. Zhang, G. Wu and X. Lu, Electrochim. Acta, 2017, 250, 309-319.
17. M. Hawley, S. Tatawawadi, S. Piekarski and R. N. Adams, J. Am. Chem. Soc., 1967, 89, 447-450.
18. T. E. Young and B. W. Babbitt, J. Org. Chem., 1983, 48, 562-566.
19. H. Muguruma, Y. Inoue, H. Inoue and T. Ohsawa, J. Phys. Chem. C, 2016, 120, 12284-12292.
