Supplementary material
Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent
hetero-interactions
Xiao Dai, 1Hao Wang, 1 Zhicheng Qian, 2Qinghua Yi, 1Yun Wang, 1Shan Cong, 1Jie Zhao,
1
Yinghui Sun, 1 Jianwen Huang, 3Jie Xiong, 3Hongmei Luo, 4 Guifu Zou1
1
College of Physics, Optoelectronics and Energy & Collaborative Innovation Center of Suzhou
Nano Science and Technology, Soochow University, Suzhou 215006, China
2
School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049,
China
3
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic
Science and Technology of China, Chengdu 610054 People's Republic of China
4
Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces,
NM 88003, USA
Experiments
Materials
Tellurium powder (Te, 99%), Cadmium chloride (CdCl2, 99%), Thioglycolic acid (TGA, 90%),
Glucose, Aqueous Ammonia (30%), Sodium hydroxide and Acetic acid were purchased from
Shanghai
Chemical
Reagents
Company.
1-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride (EDC, 96%) and N-hydroxysuccinimide (NHS, 98%) were purchased from 9 Ding
Chemistry Technology Company Limited.
Preparation of CdTe QDs and carbon dots
Water-soluble TGA-capped CdTe QDs were prepared by mild synthetic route according to the
procedure reported in the literature [24]. Briefly, sodium hydrogen telluride (NaHTe) solution
was synthesized by reacting NaBH4 (6 mmol) with Te (1 mmol) in water protected by N2. CdCl2
(2mmol ) and TGA ( 0.2 mL ) were dissolved in 100 mL deionized water, and adjusted the
solution pH value to 11 with 1 M NaOH solution under vigorous stirring. After the mixture has
been degassed by high-purity N2 for 30 minutes, the prepared oxygen-free NaHTe solution was
injected. Finally the complex solution was refluxed at 120 oC for 4/48 hours to get green/red
emission CdTe QDs. Carbon dots was synthesized by a facile method. Briefly, 1.0 g glucose and
1 mL aqueous ammonia (30%) was dissolved in deionized water (100 mL), and heated at 110 oC
under stirring for 20 hours. The obtained deep brown aqueous solution, which was abundant of
fluorescent Carbon dots, was further purified by semipermeable membrane method to remove
the unreacted chemicals. Finally, the as-obtained carbon dots were dispersed in water for further
characterizations and subsequent experiments.
Preparation of CDQDs
CDQDs were prepared by forming peptide bonds between amino groups of carbon dots and
carboxyl groups of CdTe QDs’ ligand (Fig.1), being catalyzed by 1(3-dimethylamino-propyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide
(NHS). 20 mg NHS, 100 mg EDC and 1 mL CdTe QDs solution (0.01 M) were added to 100 mL
deionized water, and stirred at room temperature for 20 minutes. Then 2 mL of the carbon dots
solution (10 mg/mL) was added in drop by drop and keep stirring overnight. The obtained
products were centrifuged and washed by deionized water for several times. Finally, the
as-obtained CDQDs were re-dispersed in deionized water for further characterizations and
subsequent experiments.
Characterization
The microstructures of CDQDs were characterized by high-resolution transmission electron
microscope (HRTEM, FEI Tecnai G-20). The UV–visible absorption spectrum is recorded on a
UV2501PC (Shimadzu). The photoluminescence spectrums and emission decay rate were
recorded on a FluoroMax-4 (HORIBA).
2
FIG. S1. The prepared processes of the CDQDs. Carbon dots were conjugated to CdTe QDs by
forming peptide bonds between –NH3 of carbon dots and -COOH of CdTe QDs’ ligand, being
catalyzed by EDC and NHS.
3
FIG. S2. Low resolution (a) and high resolution (b) TEM images of CDQDs. The clear lattices of
cores mean the good crystalline of CdTe QDs in the encapsulating carbon.
4
FIG. S3. Solution pH dependent PL of pure carbon dots (a), and pure CdTe QDs (b). The orange
and blue doted arrow denotes the PL variation of carbon dots and CdTe quantum dots,
respectively.
5
Table. S1. PL intensity corrected by absorption intensity at different excitation wavelength
(EX). Herein, I0 corresponds to as tested PL intensity without correction. IC corresponds to PL
intensity corrected by absorption intensity. Abs corresponds to absorption intensity. The equation
for corrected calculation is IC = I0/Abs.
Pure Carbon dots
EX
(nm)
Abs
(a.u.)
Carbon dots in CCQDs
Pure CdTe QDs
I0
(a.u.)
IC
(a.u.)
Abs
(a.u.)
I0
(a.u.)
IC
(a.u.)
Abs
(a.u.)
I0
(a.u.)
CdTe in CCQDs
IC
(a.u.)
Abs
(a.u.)
I0
(a.u.)
IC
(a.u.)
320
1.164
4.92
4.2
0.731
11.5
15.7
0.447
3.15
7.0
0.731
3.4
4.6
360
0.585
8.15
13.9
0.359
8.5
23.7
0.2
2.71
13.6
0.359
3.89
10.8
400
0.343
6.6
19.2
0.204
5.2
25.5
0.1
2.29
22.9
0.204
4.2
20.6
6