Supporting Information Graphene and g-C3N4 nanosheets co ...
Supporting Information Graphene and g-C3N4 nanosheets co-wrapped elemental α-sulfur as a novel metal-free heterojunction photocatalyst for bacterial inactivation under visible-light
Wanjun Wang1, Jimmy C. Yu1,*, Dehua Xia2, Po Keung Wong2, Yecheng Li1 1
Department of Chemistry Sustainability,
The Chinese
and
University
Hong 2
Institute
Kong,
of Environment, of Hong Kong,
Energy Shatin,
and N.T.,
CHINA
School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, CHINA
______________________________________________________________ *
Corresponding author: Tel.: +852 3943 6268; fax: +852 2603 5057,
E-mail address: [email protected] (J.C. Yu)
Contents:
Figures (12 figures) 1. Three types of semiconductor heterojunctions organized by band alignment. 2. XRD, TEM and AFM of graphene-like g-C3N4 nanosheets. 3. XRD, FT-IR, XPS, Raman and UV-vis absorption intensity of GO and RGO. 4. XRD of RGO and CN co-wrapped α-S8 microspheres. 5. TGA curves of GO, RGO, CN, α-S8, RGOCNS8 and CNRGOS8. 6. SEM images of commercial available α-S8 and synthesized α-S8 without RGO/CN wrapping. 7. EDX spot scan spectra of spots in Figure 2(c) and (f). 8. XPS spectra of RGOS8, CNS8, RGOCNS8 and CNRGOS8 9. Photocatalytic inactivation efficiency against E. coli K-12 in the presence of GO, RGO, CN and RGOCN. 10. Photocatalytic inactivation efficiency against E. coli K-12 in the presence of Cr (VI) as e- scavenger. 11. Induction of CAT activity during VLD photocatalytic inactivation of E. coli K-12. 12. XRD patterns of CNRGOS8 before and after photocatalytic treatment, and recycling experiments of photocatalytic inactivation of E. coli K-12 by CNRGOS8 and RGOCNS8.
Figure S1. Three types of semiconductor heterojunctions organized by band alignment. The CB offset between g-C3N4 and α-sulfur can drive the migration of photogenerated electrons from g-C3N4 to α-sulfur, while the photoinduced holes are transferred from α-sulfur to g-C3N4 by the VB offset.
(B) (A)
(C)
Figure S2. (A) XRD patterns of bulk g-C3N4 and g-C3N4 nanosheets. (B) Typical TEM images of graphene-like g-C3N4 nanosheets. (C) Tapping-mode AFM image of a single g-C3N4 nanosheet deposited on the silicon wafer substrate. The low-angle reflection peak at 13.2°, stemmed from the lattice planes parallel to the c-axis as depicted in XRD pattern, becomes less pronounced in the nanosheets, and the peak originated from the periodic stacking of layers in the nanosheets is shifted from 27.2°
to 27.8°, indicating a decreased gallery distance between the basic sheets in the nanosheets. AFM confirms the thickness of g-C3N4 nanosheets is below 2.18 nm. These results match well with the previous reports, suggesting the successful production of graphene-like g-C3N4 nanosheets.1-3
(B)
(A)
(C)
(D)
(E)
Figure S3. (A) XRD, (B) Raman, (C) FT-TR, (D) High-resolution XPS spectra of C1s, and (E) UV-vis absorption spectra of GO and RGO prepared by photo-reduction method. The XRD shows a decrease in the interlayer distance from 8.66 Å (2θ = 10.2o for the original GO) to 3.80 Å (2θ = 23o for RGO). The decrease of Raman D/G intensity ratio from 0.75 to 0.738 indicates the increase in the size of sp2 domains, and the decrease of S3/2D intensity ratio further reveals the decrease of structural defects. In contrast, the GO reduction by other methods, such as NaBH4 reduction4 and photothermal flash treatment,5 would result in the increase of D/G intensity ratio and more defects.6 The FT-IR and high-resolution XPS of C1s confirm the majority of oxygen-containing bonds in GO was removed in RGO after light irradiation, and the UV-vis absorption of RGO was much higher than GO. These evidences confirm the successful reduction of GO to RGO by the photo-reduction method
Figure S4. X-Ray diffraction (XRD) patterns of the RGO and CN co-wrapped α-sulfur.
Figure S5. Thermogravimetric analysis (TGA) curves of RGOCNS8 (a); CNRGOS8 (b); CN (c); GO (d); RGO (e); α-S8 (f).
(A)
(B)
Figure S6. Scanning electron microscopy (SEM) images of (A) commercial available α-S8, and (B) synthesized α-S8 without RGO/CN wrapping.
(a)
(b)
(c)
(d)
(e)
(f)
Figure S7. Energy-dispersive X-ray (EDX) spot scan spectra of spots on (a, b and c) CNRGOS8 (in Figure 2(c)), and (d, e, f) RGOCNS8 (in Figure 2(f)). For the RGO and CN layer, sulfur element was only detected in the inner layer of CNRGOS8 and RGOCNS8, suggesting the two-layered structure of the prepared microspheres.
(A)
(B)
(C)
(D)
Figure S8. High-resolution XPS spectra of RGOS8, CNS8, RGOCNS8 and CNRGOS8: (A) C1s, (B) O1s, (C) N1s and (D) S2p. It was found that the C-bonding configurations were similar in RGOCNS8 and CNRGOS8, but a higher signal arising from C-N bonds (288.3 eV)
7
was observed on CNRGOS8. In addition, a higher N
content of CNRGOS8 was also found in N1s peak, because C3N4 was wrapped on the surface of CNRGOS8 giving more N1s intensity. This further distinguished the different structures of RGOCNS8 and CNRGOS8. The S2p peak at 162.2 ~ 163.2 eV could be ascribed to S-H bonds, while the peak at 164.0 ~ 164.4 eV was due to =C-S-C= bonds. The broad peak from 166.8 to 170 eV was ascribed to S-O and S0.8,9 These results indicate that besides C-S bonding, the α-S8 may also chemically bond to
the C sites of RGO/CN via O bridging.
Figure S9. Photocatalytic inactivation efficiency against E. coli K-12 (2×106 cfu/mL, 50 mL) in the presence of GO, RGO, CN and RGOCN under VL irradiation.
Figure S10. Photocatalytic inactivation efficiency against E. coli K-12 (2×106 cfu/mL, 50 mL) with 0.05 mmol/L Cr(VI) in the presence of the samples (100 mg/L) under VL irradiation. No inactivation occurs in the dark and light controls.
Figure S11. Induction of CAT activity during VLD photocatalytic inactivation of E. coli K-12 by CNRGOS8 in aerobic and anaerobic conditions.
(A)
(B)
Figure S12. (A) XRD patterns of CNRGOS8 before and after photocatalytic treatment for 16 h; (B) Repeated experiments of photocatalytic inactivation of E. coli K-12 (2×106 cfu/mL, 50 mL) by CNRGOS8 and RGOCNS8 (100 mg/L) under VL irradiation.
References (1) Niu, P.; Zhang, L. L.; Liu, G.; Cheng, H. M. Graphene-like carbon nitride nanosheets for improved photocatalytic activities. Adv. Funct. Mater. 2012, 22, 4763-4770. (2) Lotsch, B. V.; Doblinger, M.; Sehnert, J.; Seyfarth, L.; Senker, J.; Oeckler, O.; Schnick, W. Unmasking melon by a complementary approach employing electron diffraction, solid-state NMR spectroscopy, and theoretical calculations-structural characterization of a carbon nitride polymer. Chem. Eur. J. 2007, 13, 4969-4980. (3) Groenewolt, M.; Antonietti, M. Synthesis of g-C3N4 nanoparticles in mesoporous silica host matrices. Adv. Mater. 2005, 17, 1789-1792. (4) Shin, H. J.; Kim, K. K.; Benayad, A.; Yoon, S. M.; Park, H. K.; Jung, I. S.; Jin, M. H.; Jeong, H. K.; Kim, J. M.; Choi, J. Y.; Lee, Y. H. Efficient reduction of graphite oxide by sodium borohydride and its effect on electrical conductance. Adv. Funct. Mater. 2009, 19, 1987-1992. (5) Cote, L. J.; Cruz-Silva, R.; Huang, J. Flash reduction and patterning of graphite oxide and its polymer composite. J. Am. Chem. Soc. 2009, 131, 11027-11032. (6) Li, X H.; Chen, J. S.; Wang, X. C.; Schuster, M. E.; Schlögl, R.; Antonietti, M. A. green chemistry of graphene: photochemical reduction towards monolayer graphene sheets and the role of water adlayers. ChemSusChem 2012, 5, 642-646. (7) Ge, L.; Han, C. C.; Liu, J.; Li, Y. F. Enhanced visible light photocatalytic activity of novel polymeric g-C3N4 loaded with Ag nanoparticles. Appl. Catal. A: Gen. 2011, 409-410, 215-222.
(8) Zhu, Y. J.; Zheng, M. D. Coal Prep. Technol. 2010, 3, 55-57. (9) Dai, S. F.; Ren, D. Y.; Song, J. F.; Qin, S. F. Application of XPS in research on occurrence of organic sulfur in vitrain. J. China Univ. Mining & Technol. 2002, 31, 225-228.
Wanjun Wang1, Jimmy C. Yu1,*, Dehua Xia2, Po Keung Wong2, Yecheng Li1 1
Department of Chemistry Sustainability,
The Chinese
and
University
Hong 2
Institute
Kong,
of Environment, of Hong Kong,
Energy Shatin,
and N.T.,
CHINA
School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, CHINA
______________________________________________________________ *
Corresponding author: Tel.: +852 3943 6268; fax: +852 2603 5057,
E-mail address: [email protected] (J.C. Yu)
Contents:
Figures (12 figures) 1. Three types of semiconductor heterojunctions organized by band alignment. 2. XRD, TEM and AFM of graphene-like g-C3N4 nanosheets. 3. XRD, FT-IR, XPS, Raman and UV-vis absorption intensity of GO and RGO. 4. XRD of RGO and CN co-wrapped α-S8 microspheres. 5. TGA curves of GO, RGO, CN, α-S8, RGOCNS8 and CNRGOS8. 6. SEM images of commercial available α-S8 and synthesized α-S8 without RGO/CN wrapping. 7. EDX spot scan spectra of spots in Figure 2(c) and (f). 8. XPS spectra of RGOS8, CNS8, RGOCNS8 and CNRGOS8 9. Photocatalytic inactivation efficiency against E. coli K-12 in the presence of GO, RGO, CN and RGOCN. 10. Photocatalytic inactivation efficiency against E. coli K-12 in the presence of Cr (VI) as e- scavenger. 11. Induction of CAT activity during VLD photocatalytic inactivation of E. coli K-12. 12. XRD patterns of CNRGOS8 before and after photocatalytic treatment, and recycling experiments of photocatalytic inactivation of E. coli K-12 by CNRGOS8 and RGOCNS8.
Figure S1. Three types of semiconductor heterojunctions organized by band alignment. The CB offset between g-C3N4 and α-sulfur can drive the migration of photogenerated electrons from g-C3N4 to α-sulfur, while the photoinduced holes are transferred from α-sulfur to g-C3N4 by the VB offset.
(B) (A)
(C)
Figure S2. (A) XRD patterns of bulk g-C3N4 and g-C3N4 nanosheets. (B) Typical TEM images of graphene-like g-C3N4 nanosheets. (C) Tapping-mode AFM image of a single g-C3N4 nanosheet deposited on the silicon wafer substrate. The low-angle reflection peak at 13.2°, stemmed from the lattice planes parallel to the c-axis as depicted in XRD pattern, becomes less pronounced in the nanosheets, and the peak originated from the periodic stacking of layers in the nanosheets is shifted from 27.2°
to 27.8°, indicating a decreased gallery distance between the basic sheets in the nanosheets. AFM confirms the thickness of g-C3N4 nanosheets is below 2.18 nm. These results match well with the previous reports, suggesting the successful production of graphene-like g-C3N4 nanosheets.1-3
(B)
(A)
(C)
(D)
(E)
Figure S3. (A) XRD, (B) Raman, (C) FT-TR, (D) High-resolution XPS spectra of C1s, and (E) UV-vis absorption spectra of GO and RGO prepared by photo-reduction method. The XRD shows a decrease in the interlayer distance from 8.66 Å (2θ = 10.2o for the original GO) to 3.80 Å (2θ = 23o for RGO). The decrease of Raman D/G intensity ratio from 0.75 to 0.738 indicates the increase in the size of sp2 domains, and the decrease of S3/2D intensity ratio further reveals the decrease of structural defects. In contrast, the GO reduction by other methods, such as NaBH4 reduction4 and photothermal flash treatment,5 would result in the increase of D/G intensity ratio and more defects.6 The FT-IR and high-resolution XPS of C1s confirm the majority of oxygen-containing bonds in GO was removed in RGO after light irradiation, and the UV-vis absorption of RGO was much higher than GO. These evidences confirm the successful reduction of GO to RGO by the photo-reduction method
Figure S4. X-Ray diffraction (XRD) patterns of the RGO and CN co-wrapped α-sulfur.
Figure S5. Thermogravimetric analysis (TGA) curves of RGOCNS8 (a); CNRGOS8 (b); CN (c); GO (d); RGO (e); α-S8 (f).
(A)
(B)
Figure S6. Scanning electron microscopy (SEM) images of (A) commercial available α-S8, and (B) synthesized α-S8 without RGO/CN wrapping.
(a)
(b)
(c)
(d)
(e)
(f)
Figure S7. Energy-dispersive X-ray (EDX) spot scan spectra of spots on (a, b and c) CNRGOS8 (in Figure 2(c)), and (d, e, f) RGOCNS8 (in Figure 2(f)). For the RGO and CN layer, sulfur element was only detected in the inner layer of CNRGOS8 and RGOCNS8, suggesting the two-layered structure of the prepared microspheres.
(A)
(B)
(C)
(D)
Figure S8. High-resolution XPS spectra of RGOS8, CNS8, RGOCNS8 and CNRGOS8: (A) C1s, (B) O1s, (C) N1s and (D) S2p. It was found that the C-bonding configurations were similar in RGOCNS8 and CNRGOS8, but a higher signal arising from C-N bonds (288.3 eV)
7
was observed on CNRGOS8. In addition, a higher N
content of CNRGOS8 was also found in N1s peak, because C3N4 was wrapped on the surface of CNRGOS8 giving more N1s intensity. This further distinguished the different structures of RGOCNS8 and CNRGOS8. The S2p peak at 162.2 ~ 163.2 eV could be ascribed to S-H bonds, while the peak at 164.0 ~ 164.4 eV was due to =C-S-C= bonds. The broad peak from 166.8 to 170 eV was ascribed to S-O and S0.8,9 These results indicate that besides C-S bonding, the α-S8 may also chemically bond to
the C sites of RGO/CN via O bridging.
Figure S9. Photocatalytic inactivation efficiency against E. coli K-12 (2×106 cfu/mL, 50 mL) in the presence of GO, RGO, CN and RGOCN under VL irradiation.
Figure S10. Photocatalytic inactivation efficiency against E. coli K-12 (2×106 cfu/mL, 50 mL) with 0.05 mmol/L Cr(VI) in the presence of the samples (100 mg/L) under VL irradiation. No inactivation occurs in the dark and light controls.
Figure S11. Induction of CAT activity during VLD photocatalytic inactivation of E. coli K-12 by CNRGOS8 in aerobic and anaerobic conditions.
(A)
(B)
Figure S12. (A) XRD patterns of CNRGOS8 before and after photocatalytic treatment for 16 h; (B) Repeated experiments of photocatalytic inactivation of E. coli K-12 (2×106 cfu/mL, 50 mL) by CNRGOS8 and RGOCNS8 (100 mg/L) under VL irradiation.
References (1) Niu, P.; Zhang, L. L.; Liu, G.; Cheng, H. M. Graphene-like carbon nitride nanosheets for improved photocatalytic activities. Adv. Funct. Mater. 2012, 22, 4763-4770. (2) Lotsch, B. V.; Doblinger, M.; Sehnert, J.; Seyfarth, L.; Senker, J.; Oeckler, O.; Schnick, W. Unmasking melon by a complementary approach employing electron diffraction, solid-state NMR spectroscopy, and theoretical calculations-structural characterization of a carbon nitride polymer. Chem. Eur. J. 2007, 13, 4969-4980. (3) Groenewolt, M.; Antonietti, M. Synthesis of g-C3N4 nanoparticles in mesoporous silica host matrices. Adv. Mater. 2005, 17, 1789-1792. (4) Shin, H. J.; Kim, K. K.; Benayad, A.; Yoon, S. M.; Park, H. K.; Jung, I. S.; Jin, M. H.; Jeong, H. K.; Kim, J. M.; Choi, J. Y.; Lee, Y. H. Efficient reduction of graphite oxide by sodium borohydride and its effect on electrical conductance. Adv. Funct. Mater. 2009, 19, 1987-1992. (5) Cote, L. J.; Cruz-Silva, R.; Huang, J. Flash reduction and patterning of graphite oxide and its polymer composite. J. Am. Chem. Soc. 2009, 131, 11027-11032. (6) Li, X H.; Chen, J. S.; Wang, X. C.; Schuster, M. E.; Schlögl, R.; Antonietti, M. A. green chemistry of graphene: photochemical reduction towards monolayer graphene sheets and the role of water adlayers. ChemSusChem 2012, 5, 642-646. (7) Ge, L.; Han, C. C.; Liu, J.; Li, Y. F. Enhanced visible light photocatalytic activity of novel polymeric g-C3N4 loaded with Ag nanoparticles. Appl. Catal. A: Gen. 2011, 409-410, 215-222.
(8) Zhu, Y. J.; Zheng, M. D. Coal Prep. Technol. 2010, 3, 55-57. (9) Dai, S. F.; Ren, D. Y.; Song, J. F.; Qin, S. F. Application of XPS in research on occurrence of organic sulfur in vitrain. J. China Univ. Mining & Technol. 2002, 31, 225-228.
