Electronic Supporting Information

Investigation into fluorescence quenching behaviors and applications of carbon dots

Yubin Song+, Shoujun Zhu,+ Siyuan Xiang, Xiaohuan Zhao, Junhu Zhang, Hao Zhang, Yu Fu and Bai Yang*

Figure S1 The normalized PL spectra of CDs in phosphate buffer solution with different pH values. The concentration of CDs was 0.01 mg/mL; The PL was excited at 360 nm.

350 400 450 500 550 600

0.0

0.2

0.4

0.6

0.8

1.0

PL In

tens

ity /

a.u.

Wavelength / nm

5.7 6 6.5 7 7.5 8

pH

Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2014

Figure S2 The influence of pH in CDs aqueous solution. The concentrations of CDs were at identical value; The PL was excited at 360 nm.

0 1 2 3 4 5 6 7 8 9 10111213140

100

200

300

400

500

600

PL In

tens

ity

pH

Figure S3 The lifetime of CDs by adding different amount of Fe3+.

0 20 40 60 80 100

0

2000

4000

6000

8000

10000 In

tens

ity /

a.u.

Decay time / ns

0 20 40 60 80 100 250 1750 2500 IRF

Fe3+ /

Fe3+ / M τ1 / ns p1 / % τ2 / ns p2 / % 2average

lifetime / ns0 1.50 1.83 14.78 98.17 1.324 14.54

20 2.17 2.52 14.50 97.48 1.348 14.19 40 2.21 3.21 14.22 96.79 1.351 13.83 60 2.35 3.65 13.94 96.35 1.175 13.52 80 2.29 3.77 13.58 96.23 1.271 13.15

100 2.27 3.96 13.25 96.04 1.323 12.82 250 2.47 6.32 12.65 93.68 1.283 12.01

1750 2.48 7.37 10.86 92.63 1.157 10.24 2500 2.63 8.37 10.41 91.63 1.116 9.76

Figure S4 a) The PL spectra of CDs with different concentration of I-. b) Relative PL intensity (F0/F-1) of CDs solution as a function of the addition amount of I- . The concentration of CDs was 0.01 mg/mL; The PL was excited at 360 nm.

400 450 500 550 6000

50

100

150

200

250

300

PL In

tens

ity

Wavelength / nm

0 0.01M 0.1M 1M

concentration of I-

0.00 0.02 0.04 0.06 0.08 0.10

0.0

0.5

1.0

1.5

2.0

2.5

3.0

F 0/F-1

I- / M

y=-0.00764+26.25011xr=0.99877

a)

b)

Figure S5 Ferric ion detection curve with different concentration of CDs.

0 50 100 150 200 2500.00.51.01.52.02.53.03.54.0

F 0/F-1

Fe3+M

0.05 0.01 0.001 0.0001

CDs / mg/mL

Figure S6 The PL peak of CDs as a function of the concentration of Fe3+ (CDs=0.01 mg/mL).

0 50 100 150 200 250448450452454456458460462464

PL P

eak

/ nm

Fe3+ /

y=450.32+0.0569xr=0.99194

Figure S7 The PL spectra of CDs with different concentration of Fe3+. The concentration of CDs was 0.01 mg/mL; The PL was excited at 360 nm.

350 400 450 500 550 6000

100

200

300

400

500PL

Inte

nsity

Wavelength / nm

0 50 100 250

In HAC-NaACbuffer solution

Fe3+ /

Figure S8 Relative PL intensity (F0/F-1) of CDs as a function of hemin concentration. The concentration of CDs was 0.01 mg/mL; The PL was excited at 360 nm.

0 50 100 150 200012345678

F 0/F-1

Hemin /

Figure S9 The lifetime of CDs exposure to high power UV light.

0 20 40 60 80 100

0

2000

4000

6000

8000

10000In

tens

ity /

a.u.

Decay time / ns

0 10 30 60 120 180 400 600 900 1200 IRF

UV Time / s

UV time / s τ1 / ns p1 / % τ2 / ns p2 / % 2average

lifetime / ns0 1.72 2.00 14.85 98.00 1.205 14.59

10 1.60 1.92 14.83 98.08 1.458 14.58 30 3.19 5.68 14.56 94.32 1.316 13.91 60 4.25 16.41 14.28 83.59 1.431 12.63

120 4.47 33.42 13.22 66.58 1.623 10.30 180 4.52 45.62 12.24 54.38 1.848 8.72 400 3.40 37.38 8.99 62.62 2.067 6.90 600 3.01 36.49 8.82 63.51 2.112 6.70 900 2.58 36.60 8.90 63.40 2.124 6.59

1200 2.34 37.82 8.87 62.18 2.288 6.40

Figure S10 The PL intensity of different adding sequences in H2O2/Fe2+/CDs system. The concentration of CDs, Fe2+ and H2O2 is 0.01 mg/mL, 250 μM and 5*10-5%, respectively. 1, the adding sequence was CDs, Fe2+ and H2O2, respectively. 2, the adding sequence was CDs, H2O2 and Fe2+, respectively. 3, the adding sequence was Fe2+, CDs and H2O2, respectively. 4, the adding sequence was Fe2+, H2O2, and CDs, respectively. 5, the adding sequence was H2O2, Fe2+ and CDs, respectively. 6, the adding sequence was H2O2 and CDs, Fe2+, respectively. Note: Two reagents were mixed and stayed for 5 min before the third reagent was added.

237.6 246.4 236.6

489.0 482.3

241.1

0.0

100.0

200.0

300.0

400.0

500.0

600.0

1 2 3 4 5 6

PL

Inte

nsity

Figure S11 The influence of Fe2+ concentration in CDs/H2O2 system (CDs 0.01 mg/mL, H2O2 5*10-5%). The concentration of Fe2+ (higher than 40 M) hardly affected the detection system, since Fe2+ mainly played catalysis role.

0 10 20 30 400

100200300400500600700

PL In

tens

ity

FeCl2 /

Figure S12 The lifetime of CDs/Fe2+ with adding different amount of H2O2.

0 20 40 60 80 100

0

2000

4000

6000

8000

10000In

tens

ity /

a.u.

Decay time / ns

0 2 4 6 8 10 IRF

H2O2 / *10-5%

H2O2 / % τ1 / ns p1 / % τ2 / ns p2 / % 2average

lifetime / ns0 1.80 2.03 14.85 97.97 1.258 14.59

2*10-5 3.02 7.27 14.58 92.73 1.261 13.74

4*10-5 3.35 13.11 14.34 86.89 1.397 12.90

6*10-5 3.61 22.32 13.92 77.68 1.570 11.62

8*10-5 3.65 31.03 12.86 68.97 1.754 10.00

10*10-5 3.66 38.83 11.87 61.17 1.717 8.68

Figure S13 a) Relative PL intensity (F0/F-1) of CDs/Fe2+ as a function of H2O2 solution mass fraction with low concentration. The concentration of CDs was 0.001 mg/mL and the concentration of ferrous ion was 10 M. b) H2O2/Fe2+/CDs system in PBS buffer solution. c) H2O2/Fe2+/CDs system in HAC-NaAC buffer solution. d) The H2O2/Fe2+/CDs quenching system can be achieved by adding H2O2 step by step (Inset is linear relation). The concentration of CDs was 0.01 mg/mL in b-d.

Figure S14 AFM images of CDs in different concentrations. a) 0.003 mg/mL CDs, b) 0.1 mg/mL CDs c) 1 mg/mL CDs

m

m

m

a)

b)

c)

Figure S15 a) Excitation-dependent PL of CDs. b) Excitation-dependent PL of CDs, which were synthesized in acid condition.

350 400 450 500 550 600

PL In

tens

ity /

a.u.

Wavelength / nm

300 320 340 360 380 400 420 440

EX / nm

350 400 450 500 550 600 650

PL In

tens

ity /

a.u. 300

320 340 360 380 400 420 440 460 480

Wavelength / nm

EX / nm

a)

b)