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NATURE NANOTECHNOLOGY | www.nature.com/naturenanotechnology 1

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NNANO.2016.138

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Supplementary Information

Rapid Water Disinfection Using Vertically Aligned MoS2 Nanofilms and Visible Light

Chong Liu1, Desheng Kong1, Po-Chun Hsu1, Hongtao Yuan1, Hyun-Wook Lee1, Yayuan Liu1, Haotian Wang2, Shuang Wang3, Kai Yan1, Dingchang Lin1, Peter A. Maraccini4, Kimberly M. Parker4, Alexandria B. Boehm4, Yi Cui*1,5

Rapid water disinfection using vertically alignedMoS2 nanofilms and visible light

© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

http://dx.doi.org/10.1038/nnano.2016.138

2 NATURE NANOTECHNOLOGY | www.nature.com/naturenanotechnology

SUPPLEMENTARY INFORMATION DOI: 10.1038/NNANO.2016.138

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Table of Contents

Figures Supplementary Fig. 1. Bandgap extraction for indirect bandgap semiconductor.

Supplementary Fig. 2. UPS data measuring the valence band edge of FLV-MoS2 and bulk MoS2.

Supplementary Fig. 3. Regrowth test of E. coli after photocatalytic water disinfection by FLV-MoS2.

Supplementary Fig. 4. Thickness dependence of FLV-MoS2.

Supplementary Fig. 5. Temperature profile and temperature control on photocatalytic disinfection.

Supplementary Fig. 6. Disinfection performance of FLV-MoS2 to both E. coli and Enterococcus under visible light illumination.

Supplementary Fig. 7. Photocatalytic disinfection performance comparison between different E. coli strains.

Supplementary Fig. 8. Real sunlight spectrums on March 30, 2013 at Stanford experiment site estimated by SMARTS (from 1:00 pm to 3:00 pm).

Supplementary Fig. 9. ORR polarization curves of Cu and Au.

Supplementary Fig. 10. Top view SEM images showing the morphologies of Cu-MoS2 and Au-MoS2 after sputtering.

Supplementary Fig. 11. Statistic data of Cu-MoS2 and Au-MoS2 layer spacing measured from TEM images.

Supplementary Fig. 12. Measurement of ROS concentrations in the bulk solution phase.

Supplementary Fig. 13. Scavengers quenching experiments of FLV-MoS2.

Supplementary Fig. 14. Scavengers quenching experiments of Cu-MoS2.

Supplementary Fig. 15. Stability of FLV-MoS2 and Cu-MoS2.

Table Supplementary Table 1. Details for photocatalytic disinfection experiment conditions in comparison of Fig. 4e (sample concentration, light source and intensity and bacteria strain).

Methods

References





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Supplementary Fig. 1. Bandgap extraction for indirect bandgap semiconductor. α is the absorption coefficient and hʋ is the photon energy.





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Supplementary Fig. 2. UPS data measuring the valence band edge of FLV-MoS2 and bulk MoS2.





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Supplementary Fig. 3. Regrowth test of E. coli after photocatalytic water disinfection by FLV-MoS2. The 1st, 2nd and 3rd incubation indicates regrowth at 0 hour, 24 hours and 48 hours after photo disinfection experiment.





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Supplementary Fig. 4. Thickness dependence of FLV-MoS2. (a) Absorption spectrum of 40 nm and 80 nm FLV-MoS2. (b) Comparison of disinfection performances between 40 nm and 80 nm FLV-MoS2. In the disinfection performances, error bars represent the standard deviation of three replicate measurements and data point with grey circle means no live bacteria was detected.





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Supplementary Fig. 5. Temperature profile and temperature control on photocatalytic disinfection. (a) Temperature change with time during photocatalytic experiment. (b) Disinfection performance of FLV-MoS2 at constant temperature of 40 ºC. In the disinfection performances, error bars represent the standard deviation of three replicate measurements and data point with grey circle means no live bacteria was detected.





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Supplementary Fig. 6. Disinfection performance of FLV-MoS2 to both E.coli and Enterococcus under visible light illumination. In the disinfection performances, error bars represent the standard deviation of three replicate measurements and data point with grey circle means no live bacteria was detected.





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Supplementary Fig. 7. Photocatalytic disinfection performance comparison between different E. coli strains JM109 and ATCC K-12. (a) Disinfection performances using FLV-MoS2. (b) Disinfection performances using Cu-MoS2. In the disinfection performances, error bars represent the standard deviation of three replicate measurements and data point with grey circle means no live bacteria was detected.





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Supplementary Fig. 8. Real sunlight spectrums on March 30, 2013 at Stanford experiment site estimated by SMARTS (from 1:00 pm to 3:00 pm).





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Supplementary Fig. 9. ORR polarization curves of (a) Cu and (b) Au on glassy carbon rotating disk electrodes in O2 saturated 0.5 M Na2SO4 solution at various rotation rates. Corresponding Koutecky−Levich plots of (c) Cu and (d) Au at different potentials. The n number is the electron transfer number during ORR reduction reactions.





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Supplementary Fig. 10. Top view SEM images showing the morphologies of Cu-MoS2 and Au-MoS2 after sputtering. Scale bar 500 nm.





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Supplementary Fig. 11. Statistic data of Cu-MoS2 and Au-MoS2 layer spacing measured from TEM images.





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Supplementary Fig. 12. Measurement of ROS concentrations in the bulk solution phase. (a) Steady state concentration of [1O2]ss calculated from the decay of FFA. (b) Steady state concentration of [•O2

-]ss calculated from the decay of NBT. (c) Steady state concentration of [OH•]ss calculated from the generation of hydroxybenzoic acid. (d) H2O2 accumulation over time.





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Supplementary Fig. 13. Scavengers quenching experiments of FLV-MoS2. Colored lines represent the results of disinfection experiments conducted with the presence of scavengers. (a) Photocatalytic disinfection performance with scavenger sodium chromate to quench photo generated e-. (b) Photocatalytic disinfection performance with scavenger TEMPO to quench photo generated •O2

-. (c) Photocatalytic disinfection performance with scavenger L-histidine to quench photo generated 1O2. (d) Photocatalytic disinfection performance with scavenger catalase to quench photo generated H2O2. (e) Photocatalytic disinfection performance with scavenger isopropanol to quench photo generated OH•. (f) Photocatalytic disinfection performance with scavenger sodium oxalate to quench photo generated h+. In the disinfection performances, error bars represent the standard deviation of three replicate measurements and data point with grey circle means no live bacteria was detected.





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Supplementary Fig. 14. Scavengers quenching experiments of Cu-MoS2. Colored lines represent the results of disinfection experiments conducted with the presence of scavengers. (a) Photocatalytic disinfection performance with scavenger sodium chromate to quench photo generated e-. (b) Photocatalytic disinfection performance with scavenger TEMPO to quench photo generated •O2

-. (c) Photocatalytic disinfection performance with scavenger L-histidine to quench photo generated 1O2. (d) Photocatalytic disinfection performance with scavenger catalase to quench photo generated H2O2. (e) Photocatalytic disinfection performance with scavenger isopropanol to quench photo generated OH•. (f) Photocatalytic disinfection performance with scavenger sodium oxalate to quench photo generated h+. In the disinfection performances, error bars represent the standard deviation of three replicate measurements.





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Discussion on ROS disinfection mechanism.

All four types of ROSs were presented in both FLV-MoS2 and Cu-MoS2 systems and all four

ROSs were of higher concentration in the Cu-MoS2 system than FLV-MoS2. This is consistent

with the fact that Cu-MoS2 had faster disinfection rate than FLV-MoS2. The concentrations

measured in each system represent the concentration in the bulk solution phase, while the

concentration of ROS at the vicinity of Cu-MoS2 or FLV-MoS2 could be much higher 1. Also, the

band structure of FLV-MoS2 suggested that ROS from oxygen reduction related reactions (•O2-

and H2O2) would occur more easily, and the measured concentrations of •O2- and H2O2 are indeed

higher than the other two types of ROS in both FLV-MoS2 and Cu-MoS2 system.

Due to the oxidative strength difference, the disinfection capability of each ROS was investigated

through scavenger quenching experiments in Supplementary Figure 13 &14. Scavengers Cr (VI),

TEMPO, L-histidine, catalase, isopropanol and sodium oxalate were used to quench e-, •O2-, 1O2,

H2O2, OH• and h+, respectively. The scavenging effect from high to low in the FLV-MoS2 system

according to the reaction rate is catalase (for H2O2), L-histidine (for 1O2), Cr (VI) (for e-),

TEMPO (for •O2-), isopropanol (for OH•), followed by oxalate (for h+). This result is consistent

with the ROS concentration measurement that ORR related ROS played a critical role in the

inactivation of bacteria. H2O2, which showed significantly higher concentration than other ROSs,

also showed the highest contribution in inactivating bacteria. h+ did not show much inactivation

effect since no slowing down of bacterial inactivation rate was observed. This could be due to the

fast recombination of electron-hole pair. Also it is possible that quenching of h+ could promote e-

and related ROS generation so that the overall disinfection rate did not change much.





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For the scavenger quenching results in the Cu-MoS2 system, the trend of ROS scavenging effect

was similar to that of FLV-MoS2, but the change in disinfection rate is more obvious. This result

supports the higher ROS concentrations in the Cu-MoS2 system comparing to FLV- MoS2. The

scavenging effect from high to low in Cu-MoS2 system is catalase (for H2O2), TEMPO (for •O2-),

L-histidine (for 1O2), isopropanol (for OH•), Cr (VI) (for e-) and oxalate (for h+). Still H2O2

contributes most to bacteria disinfection and ORR related ROS dominates the disinfection effect.

The difference in the Cu-MoS2 system comparing to FLV-MoS2 system is that, the scavenging

effect of h+ and OH• becomes more obvious in the Cu-MoS2 system. This indicates that a better

electron-hole pair separation was enabled by adding Cu as catalyst so that in the Cu-MoS2 system,

h+ itself plays an important role in inactivating bacteria. Also, h+-related generation of 1O2 by

reacting with •O2- is of higher concentration than that of FLV-MoS2.

In summary, the ROS measurement and scavenging experiments proves that in both FLV-MoS2

and Cu-MoS2 system, ORR related ROS contributes most to the bacteria inactivation. With Cu as

catalyst, the electron-hole separation was facilitated and the generation of ROS was enhanced.





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Supplementary Fig. 15. Stability of FLV-MoS2 and Cu-MoS2. (a) Photocatalytic disinfection performance of FLV-MoS2 continuously used for 5 cycles. (b) Photocatalytic disinfection performance of Cu-MoS2 continuously used for 5 cycles. In the disinfection performances, error bars represent the standard deviation of three replicate measurements.





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Sample Size/Concentration Light Wavelength & Intensity

Bacteria Strain

1* Cu-MoS2 2 cm2 film (1.6 mg/L)

> 400nm, 100 mW/cm2 E.coli, K-12/E.coli JM109

2 TiO2-CdS 1 cm2 film Xenon, 150 mW/cm2 E.coli, XL1 Blue 3 ZnO-Cu 100 mg/L > 400nm, 100 mW/cm2 E.coli, ATCC 8739 4 GO-CdS 100 mg/L > 420nm, 100 mW/cm2 E.coli, K-12 5 BV 100 mg/L > 400nm, 193 mW/cm2 E.coli, K-12 6 GO-C3N4 100 mg/L > 400nm, 193 mW/cm2 E.coli, K-12 7 SGO-ZnO-Ag 100 mg/L > 420nm, 100 mW/cm2 E.coli, K-12

Supplementary Table 1. Details for photocatalytic disinfection experiment conditions in comparison of Fig. 4e (sample concentration, light source and intensity and bacteria strain). *This work2-7.





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Methods

Regrowth test. After photocatalytic disinfection experiment, the bacteria water solution was put

in dark stirring at mild rate of 200 rpm. At 10 min, 24 hours and 48 hours after dark recovery, 5

mL of bacteria solution was added to a 30 mL TSB liquid medium and incubate at 37 ºC on shake

bed. The optical density at 670 nm was monitored each 6 hours.

ROS Measurements. 1O2 steady state concentration was calculated by measuring the decay of

furfuryl alcohol (FFA) (Sigma, 98%) using High Performance Liquid Chromatography (HPLC,

Agilent 1260 Infinity) with an Inertsil ODS-3 column (250 mm x 4.6 mm, 5 µm particle size).

FFA was separated using an isocratic mobile phase (80% acetonitrile and 20% phosphoric acid,

0.1%, pH 3.75) at 1 mL/min and detected using UV absorbance at 218 nm. The rate constant for 1O2 and FFA reaction is 1.8 ×108 M-1s-1 8, 9. •O2

- steady state concentration was calculated by

measuring the decay of nitroblue tetrazolium (NBT, Sigma, 98%) using UV-vis spectroscopy.

NBT has an absorption peak at 260 nm. The rate constant for •O2- and NBT reaction was 5.9×104

M-1s-110. H2O2 concentration was measured using an Amplex Red (Sigma, 98%) fluorescence

probe. The fluorescence of the product was monitored. The excitation wavelength was 550 nm

and emission wavelength is 580 nm11. The steady state concentration of OH• was calculated by

measuring the product of OH• reacting with benzoic acid (Sigma, 99.5%) using HPCL.

Hydroxybenzoic acid was separated using a mobile phase (80% acetonitrile and 20% water) at 1

mL/min and detected using UV absorbance at 255 nm for the p-isomer, and 300 nm for the o- and

m-isomers. The concentration factor used to convert total hydroxybenzoic acid from p-isomer

was 5.87. The rate constant for OH• and benzoic acid reaction is 6.0×109 M-1s-1 12.

Scavenger quenching experiments. The scavengers used was sodium chromate (VI) (0.05 mM,

Sigma, 99.5%) for electron, TEMPO for •O2- (1 mM, Sigma, 99%), L-histidine for 1O2 (0.5 mM,

Sigma, 99%), catalase for H2O2 (200 U/mL, Sigma), and isopropanol (0.5 mM, Sigma) for OH•

and sodium oxalate (0.5 mM, Sigma, 99.5%)8, 10. The scavengers were added in to the bacteria

water solution before photo illumination. Bacterial concentrations were measured at different

time of illumination using standard spread plating techniques. Each sample was serially diluted

and each dilution was plated in triplicate onto trypticase soy agar and incubated at 37°C for 18 h.





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References

1. Latch, D.E. & McNeill, K. Microheterogeneity of singlet oxygen distributions in irradiated humic acid solutions. Science 311, 1743-1747 (2006).

2. Hayden, S.C., Allam, N.K. & El-Sayed, M.A. TiO2 nanotube/CdS hybrid electrodes: extraordinary enhancement in the inactivation of Escherichia coli. J. Am. Chem. Soc. 132, 14406-14408 (2010).

3. Gao, P., Liu, J.C., Sun, D.D. & Ng, W. Graphene oxide-CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation. J. Hazard. Mater. 250, 412-420 (2013).

4. Gao, P., Ng, K. & Sun, D.D. Sulfonated graphene oxide-ZnO-Ag photocatalyst for fast photodegradation and disinfection under visible light. J. Hazard. Mater. 262, 826-835 (2013).

5. Wang, W.J. et al. Visible-light-driven photocatalytic inactivation of E. coli K-12 by bismuth vanadate nanotubes: bactericidal performance and mechanism. Environ. Sci. Technol. 46, 4599-4606 (2012).

6. Wang, W.J., Yu, J.C., Xia, D.H., Wong, P.K. & Li, Y.C. Graphene and g-C3N4 nanosheets cowrapped elemental alpha-sulfur as a novel metal-free heterojunction photocatalyst for bacterial inactivation under visible-light. Environ. Sci. Technol. 47, 8724-8732 (2013).

7. Bai, H.W., Liu, Z.Y. & Sun, D.D. Hierarchical ZnO/Cu "corn-like" materials with high photodegradation and antibacterial capability under visible light. Phys. Chem. Chem. Phys. 13, 6205-6210 (2011).

8. Romero, O.C., Straub, A.P., Kohn, T. & Nguyen, T.H. Role of Temperature and Suwannee River Natural Organic Matter on Inactivation Kinetics of Rotavirus and Bacteriophage MS2 by Solar Irradiation. Environ. Sci. Technol. 45, 10385-10393 (2011).

9. Parker, K.M., Pignatello, J.J. & Mitch, W.A. Influence of ionic strength on triplet-state natural organic matter loss by energy transfer and electron transfer pathways. Environ. Sci. Technol. 47, 10987-10994 (2013).

10. Xia, D.H. et al. Red phosphorus: an earth-abundant elemental photocatalyst for "green" bacterial inactivation under visible light. Environ. Sci. Technol. 49, 6264-6273 (2015).

11. Gomes, A., Fernandes, E. & Lima, J. Fluorescence probes used for detection of reactive oxygen species. J. Biochem. Biophys. Methods 65, 45-80 (2005).

12. Zhou, X.L. & Mopper, K. Determination of photochemically produced hydroxyl radicals in seawater and fresh-water. Mar. Chem. 30, 71-88 (1990).



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