Supplementary Material

Ratiometric fluorescent sensing of Pb2+ and Hg2+ with two types of

carbon dot nanohybrids synthesized from the same biomass

Zhaoying Liua, Wenying Jina,*, Fangxiao Wanga, Tuanchuan Lia, Jinfang Niea,*,

Wencheng Xiaoa, Qing Zhangb, Yun Zhanga,*

a College of Chemistry and Bioengineering, Guilin University of Technology, Guilin

541004, P.R. China.

b College of Environmental Science and Engineering, Guilin University of

Technology, Guilin 541004, P.R. China.

*Corresponding author.

E-mail addresses: wyjin@glut.edu.cn; Niejinfang@glut.edu.cn; zy@glut.edu.cn.

Tel: +86 773 5896453; Fax: +86 773 5896839.

S1

Fig. S1. Fluorescence emission spectra of a dilute aqueous solution of dual-emission

CD nanohybrids at various excitation wavelengths.

S2

Fig. S2. Fluorescence emission spectra of a dilute aqueous solution of three-emission

CD nanohybrids at various excitation wavelengths.

S3

Fig. S3. Fluorescence lifetime of two-emission CD nanohybrids (A) before and (B)

after the addition of Pb2+.

S4

Fig. S4. Fluorescence lifetime of three-emission CD nanohybrids (A) before and (B)

after the addition of Hg2+.

S5

Fig. S5. Infrared spectra of the two-emission CD nanohybrids before and after the

addition of (A) Pb2+ and (B) other metal ions.

S6

Fig. S6. Infrared spectra of the three-emission CD nanohybrids before and after the

addition of (A) Hg2+ and (B) other metal ions.

S7

Fig. S7. (A) Full XPS spectrum, (B) C 1s XPS spectrum, (C) N 1s CPS spectrum and

(D) O 1s XPS spectrum of the dual-emission CD nanohybrid.

S8

Fig. S8. (A) Full XPS spectrum, (B) C 1s XPS spectrum, (C) N 1s CPS spectrum and

(D) O 1s XPS spectrum of the three-emission CD nanohybrid.

S9

Fig. S9. UV/Vis spectra of the sixteen types of metal ions, i.e., Al3+, Fe3+, Cr3+, Cu2+,

Mg2+, Hg2+, Pb2+, Zn2+, Ca2+, Cd2+, Mn2+, Co2+, Ag+, Na+ and K+.

S10

Fig. S10. Optimization of the concentration of the dual-emission CD nanohybrids,

i.e., the volume ratio of original CD nanohybrid to buffer applied for Pb2+ detection.

The results suggested that the volume ratio of 10/490 should be chosen as the optimal

level of the dual-emission CD nanohybrids because it gave the highest I653/I493 value.

S11

Fig. S11. Optimization of reaction pH applied for Pb2+ detection. The results

suggested that pH 7 should be chosen as the optimal pH because it gave the highest

I653/I493 value.

S12

Fig. S12. Optimization of the reaction temperature applied for Pb2+ detection. The

results suggested that the tested reaction temperatures ranging from 4 to 60 oC did not

show significant effects on the I653/I493 values. Thus, all the following experiments

were carried out at room temperature.

S13

Fig. S13. Optimization of the reaction time applied for Pb2+ detection. The results

suggested that 120 min should be chosen as the optimal reaction time because no

significant increase was observed in the I653/I493 value when the longer reaction time

was applied.

S14

Fig. S14. Optimization of the concentration of the three-emission CD nanohybrids,

i.e., the volume ratio of original CD nanohybrid to buffer applied for Hg2+ detection.

The results suggested that the volume ratio of 12.5/487.5 should be chosen as the

optimal level of the three-emission CD nanohybrids because it gave the highest

I611/I491 value.

S15

Fig. S15. Optimization of reaction pH applied for Hg2+ detection. The results

suggested that pH 7 should be chosen as the optimal pH because it gave the highest

I611/I491 value.

S16

Fig. S16. Optimization of the reaction temperature applied for Hg2+ detection. The

results suggested that the tested reaction temperatures ranging from 25 to 60 oC did

not show significant effects on the I611/I491 values. Thus, all the following experiments

were carried out at room temperature.

S17

Fig. S17. Optimization of the reaction time applied for Hg2+ detection. The results

suggested that 120 min should be chosen as the optimal reaction time because no

significant increase was observed in the I611/I491 value when the longer reaction time

was applied.

S18

Table S1 Recovery of Pb2+ in Lijiang river water samples

Sample No. Founda

(nM)Added(nM)

Calculatedb

(nM)Recovery

(%)RSDc

(%, n = 6)

1 0.00 5.00 5.28 105.6 5.70

2 0.00 10.00 9.97 99.7 1.99

3 0.00 20.00 18.28 91.4 1.40

a Original Pb2+ concentrations in the samples detected using atomic absorption spectroscopy;

b The total Pb2+ concentrations in the samples determined using the proposed method;

c RSD, relative standard deviations.

S19

Table S2 Recovery of Hg2+ in Lijiang river water samples

Sample No. Founda

(nM)Added(nM)

Calculatedb

(nM)Recovery

(%)RSDc

(%, n = 6)

1 0.00 2.00 1.96 98.0 4.10

2 0.00 3.00 3.15 105.0 5.98

3 0.00 4.00 3.81 95.3 6.90

a Original Hg2+ concentrations in the samples detected using atomic absorption spectroscopy;

b The total Hg 2+ concentrations in the samples determined using the proposed method;

c RSD, relative standard deviations.

S20