N
N
N
N
N
N
Ru
2+
Ru(bpy)32+
ECL:Electrochemiluminesenceor Electrogenerated Chemiluminesence
(CH3CH2CH2)3N:
TPrA
(TriPropyl Amine)
(As coreactant)
IIECLECL & & IICVCV ~ ~ EE Profiles forProfiles forRu(bpy)Ru(bpy)33
22++(1 mM) /(1 mM) /TPrA TPrA (10 mM)(10 mM) SystemSystem(3 mm GC, 0.10 M PBS, pH 7, 100 mV/s)(3 mm GC, 0.10 M PBS, pH 7, 100 mV/s)
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0-0.4
-0.2
0.0
0.2
0.4
CV
ECL
E (V va Ag/AgCl)
I CV(m
A)
-0.6
-0.3
0.0
0.3
0.6
IEC
L (mA
)
Direct Ru(bpy)Direct Ru(bpy)332+2+ Oxidation RoutesOxidation Routes
Elec
trode
eRu(bpy)3
3+
TPrA TPrAH+-H+e
hvRu(bpy)3
2+
TPrA.+ -H+
TPrA.
Ru(bpy)32+
H2O P2
Ru(bpy)32+*
P1
AlternativelyAlternatively
Ru(bpy)33+
Ru(bpy)32+
e
e
TPrA TPrAH+-H+
TPrA -H+TPrA.+ .
Ru(bpy)3+
P1
Ele
ctro
de
P2H2O
Ru(bpy)32+*
Ru(bpy)32+
hv
e
Ele
ctro
de Ru(bpy)32+
Ru(bpy)33+
TPrA TPrAH+-H+
TPrA -H+TPrA.+ .
Problems with the DirectProblems with the DirectRu(bpy)Ru(bpy)33
2+2+ Oxidation MechanismOxidation Mechanism
1. Mysterious ECL Pre-wave;
2. ECL at Labeled Magnetic Beads;
3. Proof of Energetic and Existence of Intermediates.
Ru(bpy)Ru(bpy)332+2+ Concentration Effects Concentration Effects
on on iiECLECL-- EE ProfilesProfiles
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
2nd
1st
iECL 300 nA/cm2
(b) 1 µM Ru(bpy)3
2+, i ECL
/160
(a) 1 mM Ru(bpy)3
2+, i ECL
/2x104
E (V, vs Ag/AgCl)
0.10 M TPrA + 0.20 M PBSpH 8, v = 20 mV/s, 3 mm GC
0.10 M TPrA/0.10 M Tris/0.10 M LiClO4pH 8, v = 50 mV/s, 3 mm GC
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
100 µA/cm2iECL
iCV 2.5 mA/cm2
(c) 1 nM Ru(bpy)3
2+
2nd
1st
E (V vs Ag/AgCl)
11stst ECL Peak Intensity vs ECL Peak Intensity vs ccTPrATPrA & & ccRu(bpy)Ru(bpy)332+2+
1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10
0.1
1
10
100
1000 (b) 100 mM TPrA
i EC
Lp1 (µ
A/c
m2 )
cRu(bpy)
3
2+ (mM)0 20 40 60 80 100
0
5
10
15
20
(a) 1µM Ru(bpy)3
2+
i EC
Lp1 (
µA/c
m2 )
cTPrA
(mM)
0.20 M PBS, pH ~ 8, 100 mV/s, GC
11stst & 2& 2ndnd ECL ResponsesECL ResponsesWhen When ccRu(bpy)Ru(bpy)332+ 2+ >= 0.050 mM>= 0.050 mM
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0
0
5
10
15
cRu(bpy)
3
2+ (mM)
1.0 0.50 0.10 0.050
2nd
1st
(c) 100 m M T P rA
i EC
L (m
A/c
m2 )
E (V vs. Ag/AgCl)
0.20 M PBS, pH ~ 8, 100 mV/s, GC
Si NH2
5% 3-aminopropyltrimethoxysilan
SiO
2
OH
OH
OHBenzene, in Desiccator, 24 hr Si
O2
O
O
O
Schematic Structure of Silanized ITO Surface
Ru[(bpyMe2)]2[(bpy(COOH)2]2+
10 mM EDAC in1-methylimidazole(pH 7), 70oC for 45 min
Si NH
SiO
2
O
O
O
N
N
N
N
Ru*
CH3
CH3
HOOC
O
O2
ITO/OSiRuII
ITO
Silanization
Approach curve (tip current vs. distance)(φ =1.5 mm hemispherical Au at +0.85 V vs Ag/AgCl, in 10 mM
TPrA+100 mM LiClO4+100 mM Tris buffer (pH = 8) Soln)
-600 -500 -400 -300 -200 -100 00
2
4
6
8
10
12
14
-0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15
0
10
20
30
40
50
60
70
80
i T (µ
A)
d (µm)
i T (µA
)
d (µm)
TPrA TPrA+.
ITO
ECL Detection Without Touching ECL Detection Without Touching with Ru(bpy)with Ru(bpy)33
2+2+/ITO/ITO
1.0 0.8 0.6 0.4 0.2 0.0
-30
-20
-10
0
10
20
30
d = -5.0 µm (ITO/OSi---Ru(II))
CV ECL
E (V vs Ag/AgCl)
i CV (µ
Α)
-100
-75
-50
-25
0
25
50
75
100
iEC
L (pA)
Tip ~ Substrate Separation Effect Tip ~ Substrate Separation Effect on ECL Intensityon ECL Intensity
Notdetectable
7.68
604.80
693.84
862.88
922.40
1301.92
1331.44
1840.96
ECLIntensity
(pA)
- d (µm)
0 1 2 3 4 5 6 7 8 9
0
40
80
120
160
200
The data fitting equation
iECL
p = -5.13 + 219.75e0.289d (d <= 0)
Not detectable
i EC
Lp (pA
)
- d (µm)
TPrAH = TPrA + H+
TPrA+. TPrA .
0.88 V
P1-1.7 V-H+
E vs SCE
R u ( b p y ) 32 + *
R u ( b p y ) 33 + R u ( b p y ) 3
2 + R u ( b p y ) 3+
- 1 .0 6 V
0 .6 4 V
2 .1 2
eV
/ion
1 .0 6 V - 1 .4 8 V
E v s A g / A g C l
A New Route for the Generation ofA New Route for the Generation ofRu(bpy)Ru(bpy)33
2+*2+* in Ru(bpy)in Ru(bpy)332+2+/TPrA /TPrA
SystemSystem
Elec
trod
e TPrA TPrAH+-H+
e
TPrA-H+
TPrA
.+
.
Ru(bpy)32+P1
Ru(bpy)3+ Ru(bpy)3
2+*
TPrA
+H+
hvRu(bpy)3
2+
Reaction Processes InvolvedReaction Processes Involvedfor the Oxidation of TPrAfor the Oxidation of TPrA
T P rA + H +T P rA H + p K a = 1 0 .4
T P rA.+ + e
T P rA.+ T P rA
. + H +
T P rA.
P 1 + H 2 O = P 2
T P rA.+
+ T P rA. = T P rA + P 1an d
T P rA
P 1 + e
k f
k bk s
k s
HalfHalf--life of TPrAlife of TPrA++.. Cation Radical Cation Radical Based on CV SimulationBased on CV Simulation
0 1 2 3 4 5 6 7 8 9 10
0.0
0.5
1.0
1.5
2.0
1.0 0.8 0.6 0.4 0.2 0.0
-50
-40
-30
-20
-10
0
A
i CV (µ
A/c
m2 )
E (Ag/Ag/Cl)
at p
oten
tial A
CTP
rA+. (µ
M)
x (µm)
TPrA+. TPrA. + H+kf
kf = 3500
τ2/1 = 0.693/kf ~ 0.2 ms
EPR EPR Detection of Detection of
TPrATPrA++..
Solution A: 0.03 M Ru(bpy)33+
Freshly Generated By Oxidized Ru(bpy)3
2+ Using Cl2
Solution B: 0.10 M TPrA at pH 7
Flow Rate: 2 to 5 mL/s
EPR Reference: Fremy’s Salt(K2[NO(SO3)2])
3 3 6 0 3 3 8 0 3 4 0 0 3 4 2 0 3 4 4 0 3 4 6 0 3 4 8 0 3 5 0 0 3 5 2 0 3 5 4 0
- 3 0 0 0
- 2 0 0 0
- 1 0 0 0
0
1 0 0 0
2 0 0 0
3 0 0 0
E P R o f TP rA + . o b ta ined by m ixin g 0 .03 M R u (bpy )3
3 + a n d0 .10 M T P r A ( p H = 7 ) s o lu t ions in a quar tz f l a t EPR ce l l
g = 2 . 0 0 3 8
Inte
nsity
M a g n e tic F ie ld (G )
Simulation
Simulation Parameters:14N (1N, I = 1), Hyperfine = 19.87G,
α−1H (6H, I = 0.5), Hyperfine = 20.05 G
Simulated EPR for TPrASimulated EPR for TPrA.
2 0 G
P a r a m e t e r s u s e d f o r t h e c a r b o n f r e e r a d i c a l s im u la t i o n :1 3 C ( 1 , I = 1 / 2 , h y p e r f i n e 2 0 G ) ,
α 1 H ( 1 , I = 1 / 2 , h f = 2 0 G ) , β 1 H ( 2 , I = 1 / 2 , h f = 1 8 G )
( C H3C H
2C H
2)
2N - C .H - C H
2C H
3
Fast Scan Cyclic VoltammetryFast Scan Cyclic Voltammetry
0.10 V/s,3mm GC
3mm GC
10 µm C Fiber
5 µm Pt
1.2 1.0 0.8 0.6 0.4 0.2 0.0
2 µA
TPA_sim_E&i
(d) v = 1000 V/s, i/60
(c) v = 100 V/s, i/30
(b) v = 1.0 V/s, i/5
(a) v = 20 mV/s
E (V)
Fast Scan CV Digital Simulations
900 V/s
1.2 0.8 0.4 0.0-5
-4
-3
-2
-1
0 (a)
DC
A
B
i CV (m
A/c
m2 )
E (V vs Ag/AgCl)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0
20
40
60
80
100
120
140
160 at potential A(b)
c (µ
M)
x (µm)
TPrA+. TPrA.
900 V/s
1.2 0.8 0.4 0.0-5
-4
-3
-2
-1
0 (a)
DC
A
B
i CV (m
A/c
m2 )
E (V vs Ag/AgCl)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0
20
40
60
80
100
120
140
160
at potential B(c)
TPrA+. TPrA.
c (µ
M)
x (µm)
900 V/s
1.2 0.8 0.4 0.0-5
-4
-3
-2
-1
0 (a)
DC
A
B
i CV (m
A/c
m2 )
E (V vs Ag/AgCl)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0
20
40
60
80
100
120
140
160
(d)
TPrA+. TPrA.
x (µm)
c (µ
M)
at potential C
900 V/s
1.2 0.8 0.4 0.0-5
-4
-3
-2
-1
0 (a)
DC
A
B
i CV (m
A/c
m2 )
E (V vs Ag/AgCl)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0
20
40
60
80
100
120
140
160
(e) at potential D
TPrA+. TPrA.
x (µm)
c (µ
M)
ConclusionsConclusions
TPrA+. is sufficiently stable in neutral aqueous solution to oxidize Ru(bpy)3
+ to generate Ru(bpy)3
2+*;
Under some ECE conditions, fast scan CV will not show short-lived species;
The ECL behavior of the Ru(bpy)32+/TPrA system is
complicated and involves several paths to the generation of excited state.