Supporting Information physiological oxidant graphene ...3 graphene quantum dots and their...
Transcript of Supporting Information physiological oxidant graphene ...3 graphene quantum dots and their...
1 Supporting Information
2 Title Direct transformation of lignin into fluorescence-switchable
3 graphene quantum dots and their application in ultrasensitive profiling of
4 physiological oxidant
5 Ruibin Wang,a† Guangjie Xia,b† Wentao Zhong,a Lei Chen,a Liheng Chen,c Yanggang
6 Wang,b* Yonggang Min a* and Kaixin Li a*
7
8 Experimental Section
9 A-acid recyclability
10 We conducted a preliminary evaluation of the reusability of A-acid by fractionating
11 AL under the same condition. First, after the above-mentioned second filtration, the
12 obtained filter cake was thoroughly washed by DI water, and then air-dried (Fig. S2a).
13 Second, we calculated the amount of fresh makeup A-acid needed for the next cycle
14 on the basis of the mass of the as-dried solids with the assumption that A-acid
15 consumption by reaction was negligible. Next, the predetermined amount of makeup
16 A-acid was mixed with the as-dried solids along with the desire amount of DI water in
17 prior to heating liquor to the desired reaction temperature. Finally, 2 g of A-acid was
18 added then initiate the second cycle of the fractionation. We compared the chemical
19 compositions from the first and second cycles (Fig. S2b). The differences were within
20 measurement error, suggesting good reusability and (reactivity) of A-acid. The A-acid
Electronic Supplementary Material (ESI) for Green Chemistry.This journal is © The Royal Society of Chemistry 2019
21 recovery rate for 5 consecutive cycles is obtained as 85.18 % (Details are listed in
22 Table S1).
23 A HPLC system (Dionex Ultimate 3000, Thermo Fisher Scientific, Germany)
24 equipped with the RefractoMax521 RI Detector that could be used for gel permeation
25 chromatography (GPC) characterization, of which the mobile phase was
26 tetrahydrofuran (0.6 mL/min at a column temperature of 35 °C) with linear
27 polystyrene standards for the molecular weight calibration curve. By means of a
28 sample loop, aliquots of 20 μL of the liquor were analyzed at a time.
29
30 Table S1. The single cycle recovery rate with corresponding rate data obtained by
31 conducting the A-acid fractionation of AL in a consecutive five cycles.
Cycle 1 2 3 4 5
RX (%) * 95.82 97.49 97.36 96.67 96.88
R (%) ** 95.82 93.42 90.95 87.92 85.18
32 * The singe cycle recovery rate, RX, could be calculated by referring eq. 1 shown
33 below, where mX is the weight of the A-acid recovered after the cycle X was finished
34 (X=1, 2, 3, 4, 5 and m0=1.0022 g).
35 eq.1𝑅𝑋 = 𝑚𝑋/𝑚𝑋 ‒ 1 ∗ 100 %
36 ** Recovery rate, R, could be calculated by referring eq. 2 shown below, where RX was
37 obtained above (X=1, 2, 3, 4, 5).
38 eq.2𝑅 =
𝑋
∏𝑘 = 1
𝑅𝑘 ∗ 100 %
39
40 The cytotoxicity test of LGQDs
41 The cytotoxicity of LGQDs was evaluated in vitro by using the mouse fibroblast cell
42 L929 with the Cell-Counting Kit-8 assay as reported in our previous study. In brief,
43 cells of the mouse fibroblast cell line L929 were seeded onto 96-well plates (7×103
44 cells/well) and incubated at 37 °C for 8 h. Then, the cell medium was replaced with
45 fresh medium containing various concentrations of LGQDs. The cells treated with
46 LGQDs, and phosphate-buffered saline (PBS), respectively, were incubated at 37 °C
47 for 48 h. After the incubation, all the cells were washed with PBS and then incubated
48 in 100 μL of Dulbecco’s modified Eagle’s medium containing 10 μL of CCK-8 (5
49 mg/mL in PBS) for another 4 h. The absorbance in each well was measured using a
50 microplate reader at a wavelength of 450 nm, to calculate the number of viable cells.
51 Computational details
52 Density functional theory (DFT) calculations were performed within the generalized
53 gradient approximation with the exchange correlation functional of PBE by
54 employing the CP2K package.1-3 The atomic core regions are described by
55 Goedecker-Teter-Hutter (GTH) pseudopotentials,4-6 while the valence wave functions
56 were expanded in terms of double-ζ Gaussian basis sets.7 An additional auxiliary
57 plane-wave basis set with a 360 Ry cutoff is also implemented in electrostatic
58 calculation. The Grimme’s third-generation correction is also involved during the
59 calculation to take into account the dispersion interactions.2 The simulated system is
60 typically consisted of the LGQDs and H2O2 with 294 explicit water molecules(with a
61 density around 0.99 g/mL) inside a periodic cubic box with length of 30 x 30 x 12 Å.
62 When NaH2PO4 is added, the number of water molecules is reduced to 288 to
63 maintain the water density.
64
66 Table S2. GQD-based H2O2 detection from the reported literatures and this study.
Method Material Linear
range (M)
Limit of
detection (M)
Reference
Fluorescence MnO2-nanosheet-
modified
upconversion
nanoparticles
1-35 × 10-5 10 × 10-6 8
Fluorescence AgNP-
DNA@GQDs
4-2000 ×
10-7
1 × 10-7 9
Fluorescence FeTMPyP@GQD
s
2-300 × 10-6 3 × 10-7 10
Colorimetry AgNPs@GQDs 1-1000 ×
10-7
3.3 × 10-7 11
Colorimetry GQDs 1 -1000×
10-8
1 × 10-8 12
Fluorescence Graphitic C3N4
nanosheets
1-20000 ×
10-7
5 × 10-8 13
Electrochemistry GQDs 2-8000 ×
10-6
7 × 10-8 14
Fluorescence tyramine@GQDs 1-150 × 10-9 3.2 × 10-10 15
Fluorescence LGQDs 1-150 × 10-9 1.3 × 10-11 Our data
67
68
69 Fig. S1. The structural differences between A-acid, P-acid, B-acid, and C-acid.
70
71
72
73 Fig. S2. (a) Schematic flow diagram shows the recycling process of A-acid for the
74 recyclability test, the inset is the filtrate obtained from the first vacuum filtration
75 (Filtration Ⅰ) and has been air-cooled to room temperature. (b) Elemental
76 composition comparison between LGQDs and the LGQDs prepared by using recycled
77 A-acid.
78
79
80
81
82
83 Fig. S3. UV-vis absorbance spectra of the AL aqueous solution.
84
85
86
87 Fig. S4. (a) PLE spectra of LGQDs at 377, 490 and 576 nm. Single-particle PL
88 emission images of LGQDs under excitations at (b) 535 nm, (c) 475 nm, (d) 360 nm,
89 and (e) their overlaid image.
90
91
92
93 Fig. S5. (a) Particle size comparison among AL, LGQDs, and other three LGQDs. (b)
94 PL spectra of AL excited within 280-500 nm.
95
96
97
98
99 Fig. S6. High resolution XPS spectra of (a) C 1s, (b) O 1s, (c) N 1s and (d) S 2p of
100 LNPs.
101
102
103
104 Fig. S7. The side-chain regions in the two-dimensional HSQC NMR spectra of AL,
105 LNPs, and LGQDs with the chemical structures of three main components.
106 The HSQC data of Alkaline-lignin (AL) indicate the native structure of lignin
107 includes the β-aryl-ether linkages (A), phenylcoumarane structures (B), resinol
108 linkages (C) and methoxyl groups (OCH3).
109 In comparison, the spectrum of LNPs shows no A (α & γ) compounds, which
110 qualitatively demonstrates that AL is strongly de-etherified under A-acid treatment
111 via β-aryl-ether bond cleavage. Meanwhile, the XPS data (Fig. 4b) displayed the N
112 and S dual-doping in LNP, resulting in asymmetric charge density distribution of the
113 host carbon domain (which is also evidenced by our DFT calculations in Fig.6). A lot
114 of active sites will be exposed for further transformation of LNPs (Angewandte
115 Chemie International Edition, 2012, 51(46): 11496-11500.).
116 After further hydrothermal treatment, the obtained LGQDs share a similar HSQC
117 spectrum with LNPs, indicating that the aromatic skeleton is reserved in LGQD. That
118 is, under hydrothermal treatment, the edge groups (eg. epoxy groups, hydroxy groups,
119 carboxylic groups and ketone groups) adjacent to doped N, S are decomposed into
120 CO2, CO, and H2O (J. Mater. Chem., 2012, 22, 25471-25479). In this regard, the
121 hydrogen bonding and electrostatic interactions in LNPs will be strongly weakened.
122 Accordingly, LNPs were transformed into LGQDs due to the prompt π-π stacking and
123 the increased sp2 hybridization. These results are in consistent with the XPS spectra.
124 According to the data shown above, the chemical mechanism of the
125 transformation of lignin into GQDs has been proposed as follows: The mechanism for
126 chemical transformation of lignin into LGQDs includes two steps. In the 1st step, AL
127 is transformed into LNPs by de-etherification via β-aryl-ether bond cleavage and N, S
128 dual-doping via convalent conjugation. In the 2nd step,the edge groups (mostly the
129 oxygen containing groups) adjacent to doped N, S in LNPs are decomposed into CO2,
130 CO, and H2O. Subsequently LGQDs are formed via π-π stacking and sp2
131 hybridization under hydrothermal treatment. The detailed pathway is shown below:
132
133
134
135
136 Fig. S8. Designed LGQDs with (a) SO in the middle and (b) SO2 on the edge.
137
138
139
140
141 Fig. S9. 3D structures of designed LGQDs in the water box. For brevity the water
142 molecules are omitted in the right column.
143
145 400 450 500 550 600 650 700
0
40000
80000
120000
160000PL
inte
nsity
(a.u
.)
Wavelength (nm)
DI water NMP 2-Propanol CS2
(a)
400 500 600 700
10000
20000
30000
40000
50000
60000
70000
80000(b)
PL in
tens
ity (a
.u.)
Wavelength (nm)
0 15nM 150nM
146400 500 600 700
10000
20000
30000
40000
50000
60000
70000
80000(c)
PL in
tens
ity (a
.u.)
Wavelength (nm)
0 15nM 150nM
147 Fig. S10. (a) The PL intensity of LGQDs in various solution with different polarity
148 (N-Methyl pyrrolidone (NMP) > DI water > 2-prapanol > CS2); (b) A PL spectra
149 summary of LGQDs in sodium tetraborate buffer(pH=9.18) with H2O2 concentration
150 of 15 and 150 nM; (c) A PL spectra summary of LGQDs in KMnO4 solutions of 15
151 and 150 nM.
152 According to the XPS analysis, the molar ratio of C/S/N/O of LGQDs is
153 0.061667/0.0003688/N 0.0015286/0.014156, which is close to: C167S1N4O38. By
154 further comparing and referring the previous theoretical study that C170H32 with doped
155 S and N is used as the model, we choose C167S1N4O37-38Hn since it has the similar size
156 as theirs (25-26 Å), though the terminal groups of LGQDs are -OH, -COOH, etc.,
157 considering they are originated from alkaline lignin.16, 17
158 According to the reported literature,18 the doped S can exist as C-S unit and C-SO2
159 unit on the edge or C¬SO in the middle of LGQDs. Given that C-S without O
160 obviously cannot have a strong interaction with H2O2, we build two models of
161 C167S1N4O37-38Hn: one with C-SO in the middle, C167S1N4O38H42 (Fig. S7a); and the
162 other with C-SO2 on the edge, C167S1N4O37H34 (Fig. S7b). In both cases the four N
163 exit as two CO-NH2, one C=NH-OH, and one NH2.
164 a) Edge groups: 6 -COOH, [1 =O, 1 -COH-NH2], 1 -CO-NH2, 1 -C=NH-OH, 1
165 -NH2, 21 -OH, 1 center –SO;
166 b) Edge groups: 6 -COOH, [1 =O, 1 -COH-NH2], 1 -CO-NH2, 1 -C=NH-OH, 1
167 -NH2, 19 -OH, 1 edge -SO2.
168 [1 =O, 1 -COH-NH2] is initially 1-OH and 1-CO-NH2. After optimization, as the
169 phenol -OH is acidic, the near -CO-NH2 will be protonated. When water molecules
170 are introduced, the -COH-NH will also be potentiated by a near phenol -OH. In
171 addition, with water solvation, sometimes one extra phenol -OH and -COOH will lose
172 the proton to form the anion. For all the structures, both the -CO-NH2 and -COH-NH2
173 groups will capture an adjacent H on -OH to form the -O- ~ -COH+-NH2
174 intramolecular ion pair. At the beginning of the design, we implement one -NH2, two
175 -CO-NH2 and one -COH-NH2. In most cases, one -CO-NH2 and one -COH-NH2 will
176 be protonated while the remaining one -CO-NH2 is unable to be protonated.
177
178 References
179 1. J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett., 1996, 77, 3865-3868.
180 2. J. H. Parrinello and Michele, Mol. Phys., 1997, 92, 477-488.
181 3. J. VandeVondele, M. Krack, F. Mohamed, M. Parrinello, T. Chassaing and J. Hutter, Comput.
182 Phys. Commun., 2005, 167, 103-128.
183 4. S. Goedecker, M. Teter and J. Hutter, Physical Review B, 1996, 54, 1703-1710.
184 5. C. Hartwigsen, S. Goedecker and J. Hutter, Physical Review B, 1998, 58, 3641-3662.
185 6. M. Krack, Theor. Chem. Acc., 2005, 114, 145-152.
186 7. J. VandeVondele and J. Hutter, The Journal of Chemical Physics, 2007, 127, 114105.
187 8. J. Yuan, Y. Cen, X.-J. Kong, S. Wu, C.-L. Liu, R.-Q. Yu and X. Chu, ACS Applied Materials &
188 Interfaces, 2015, 7, 10548-10555.
189 9. L. Wang, J. Zheng, Y. Li, S. Yang, C. Liu, Y. Xiao, J. Li, Z. Cao and R. Yang, Anal. Chem., 2014, 86,
190 12348-12354.
191 10. L. Zhang, D. Peng, R.-P. Liang and J.-D. Qiu, Chemistry – A European Journal, 2015, 21, 9343-
192 9348.
193 11. S. Chen, X. Hai, X.-W. Chen and J.-H. Wang, Anal. Chem., 2014, 86, 6689-6694.
194 12. A.-X. Zheng, Z.-X. Cong, J.-R. Wang, J. Li, H.-H. Yang and G.-N. Chen, Biosens. Bioelectron.,
195 2013, 49, 519-524.
196 13. J.-W. Liu, Y. Luo, Y.-M. Wang, L.-Y. Duan, J.-H. Jiang and R.-Q. Yu, ACS Applied Materials &
197 Interfaces, 2016, 8, 33439-33445.
198 14. Y. Zhang, C. Wu, X. Zhou, X. Wu, Y. Yang, H. Wu, S. Guo and J. Zhang, Nanoscale, 2013, 5,
199 1816-1819.
200 15. N. Li, A. Than, X. Wang, S. Xu, L. Sun, H. Duan, C. Xu and P. Chen, ACS Nano, 2016, 10, 3622-
201 3629.
202 16. H. Li, C. Sun, R. Vijayaraghavan, F. Zhou, X. Zhang and D. R. MacFarlane, Carbon, 2016, 104,
203 33-39.
204 17. H. Li, C. Sun, M. Ali, F. Zhou, X. Zhang and D. R. MacFarlane, Angew. Chem., 2015, 127, 8540-
205 8544.
206 18. C. K. Chua and M. Pumera, Chem. Soc. Rev., 2014, 43, 291-312.
207