Supporting Information

Danyun Xu, Zhe Guo, Yudi Tu, Xinzhe Li, Yu Chen, Zhesheng Chen, Bingbing Tian, Shuqing Chen, Yumeng Shi, Ying Li, Chenliang Su, and Dianyuan Fan

Controllable Nonlinear Optical Properties of

Different-Sized Iron Phosphorus Trichalcogenide

(FePS3) Nanosheets

Corresponding authors: Bingbing Tian and Shuqing Chen, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, China, E-mail:tianbb2011@szu.edu.cn; shuqingchen@szu.edu.cnDanyun Xu, Zhe Guo, Yudi Tu, Xinzhe Li, Yu Chen, Zhesheng Chen, Yumeng Shi, Ying Li, Chenliang Su, and Dianyuan Fan:International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, ChinaZhesheng Chen: Laboratoire de Physique des Solides, CNRS, Université Paris Saclay, Orsay 91405, France

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1. Photography of bulk FePS3 crystals

Figure S1. (a) Photograph of bulk FePS3 crystals obtained by CVT method in an

evacuated quartz tube. (b) Bulk FePS3 crystals are shown in opened quartz tube with a

radius of 5.5 mm.

2. XRD spectra of Bulk FePS3 crystals

Figure S2. XRD spectra of bulk FePS3 crystals

3. XRD spectra of exfoliated FePS3 nanosheets

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Figure S3. (a) XRD spectra of exfoliated FePS3 nanosheets. (b) XRD spectra of

exfoliated FePS3 nanosheets and bulk crystals with 2 Theta range from 20 to 80

degree.

4. Illumination of electrochemical exfoliation process

Figure S4. Photograph of the morphology and volume change of the bulk FePS3

crystals with reaction time during electrochemical cathodic exfoliation.

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Figure S5. SEM images from left to right show cross section of bulk FePS3 crystals

and FePS3 crystals after employing a DC bias voltage of -2.5 V for 1 min

(intercalation) and 2 min (expansion) by using tera-n-butylammonium as an

electrolyte salt respectively.

5. The process of gradient centrifugation

Figure S6. Procedure illustration of the gradient centrifugation to obtain the different

sized FePS3 nanosheets.

6. Stability of the FePS3 nanosheets suspensions

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Figure S7. Transmittance spectra of FePS3 nanosheets suspensions from 300 to 1000

nm. Here take the FePS3 nanosheets suspensions obtained at centrifugal speed of 5000

rpm as an example. Here the transmittance of the FePS3 nanosheets at the wavelength

of 532 nm and 633 nm are respectively 13.93% and 18.71%.

7. Determination of lateral size distribution

Methods: an image J software was used to obtain the lateral area (S) of each

nanosheets from the raw AFM, SEM or optical images. The corresponding formula

S=π(D/2)^2 was applied to approximate the lateral size (D) of these nanosheets.

Figure S8. Raw AFM data for lateral size analysis.

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Figure S9. The corresponding profiles of these nanosheets in Figure S5 analyzed by

image J.

8. Determination of thickness distributions

Figure S10. Raw AFM data for thickness analysis.

9. Sizes distribution

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Figure S11. (a) Comprehensive statistics of all nanosheets obtained under the

centrifugal speed of 1000 rpm or above. Lateral dimension distribution diagrams at

different centrifugation speeds of 1000 rpm (b), 3000 rpm (c), 5000 rpm (d), 7000

rpm (e) and 9000 rpm (f), which were measured by particle size description analyser

(PSDA).

10. TEM images

Figure S12. TEM images of FePS3 nanosheets under different centrifugation speeds

of 1000 rpm (a), 3000 rpm (b), 5000 rpm (c), 7000 rpm (d) and 9000 rpm (e) with the

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corresponding scale bar of 1 μm. (f) Mapping analysis of representative FePS3

nanosheet obtained at a centrifugation speed of 5000 rpm with a scale bar of 200 nm.

11. Raman analysis

Figure S13. The Raman spectrum of the silicon substrate at 532 nm laser excitation

wavelength [1].

12. Nonlinear optical properties of different sized FePS3 nanosheets with

different incident intensities

Figure S14. The diffraction rings of the FePS3 dispersion at 5000 rpm obtained by

CCD at λ = 532 nm with different incident intensities.

13. Equations for Power-Dependent Nonlinear Refractive Index

Under the conditions of D ≫ RH or R’H, the relation can be expressed as[2, 3]:

θH =RH

D (1)

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θH' =

RH'

D (2)

θD = θH - θH' =

RD

D (3)

θH = λ2π

(dΔψdr )

max (4)

θH =n2 IC (5)

Here, C= [- 8r Leff

ω02 exp (-2 r2

ω02 )] , r∈[0, +⋈ ) (6) is a constant.

θD =θH - θH' = (n2- n2

' ) IC= ∆ n2 IC (7)

∆ n2

n2 =

θD

θH

(8)

14. n2 and χsingle layer(3) of various two-dimensional materials

Table 1 n2 and χsingle layer(3) of various two-dimensional materials

2D materials Wavelength (nm)

n2 (m2 W–

1)χsingle layer

(3)

(e . s . u .)

Ref.

Graphene 473 10–7 10–7 [4] and [5]532 10–7 10–7

MoS2 488 10–7 10–9

BP 600 10–5 10–8 [6]700 10–5 10–8

1160 10–5 10–8

NbSe2 457 10–5 10–9 [7]532 10–5 10–9

671 10–5 10–9

WSe2 457 10–9 10–6 [8]532 10–10 10–6

671 10–11 10–6

FePS3 532 10–5 10–9 This work

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633 10–5 10–9

References

[1] Kuo CT, Neumann M, Balamurugan K, Park HJ, Kang S, Shiu HW et al., "Exfoliation and Raman Spectroscopic Fingerprint of Few-Layer NiPS3 Van der Waals Crystals," Sci Rep 2016, 6, 20904.

[2] Wu LM, Xie ZJ, Lu L, Zhao JL, Wang YZ, Jiang XT et al., "Few-Layer Tin Sulfide: A Promising Black-Phosphorus-Analogue 2D Material with Exceptionally Large Nonlinear Optical Response, High Stability, and Applications in All-Optical Switching and Wavelength Conversion," Adv Opt Mater 2018, 6(2), 1700985-1700994.

[3] Wang GZ, Zhang SF, Umran FA, Cheng X, Dong NN, Coghlan D et al., "Tunable effective nonlinear refractive index of graphene dispersions during the distortion of spatial self-phase modulation," Appl Phys Lett 2014, 104(14), 141909-141913.

[4] Wu R, Zhang Y, Yan S, Bian F, Wang W, Bai X et al., "Purely coherent nonlinear optical response in solution dispersions of graphene sheets," Nano Lett 2011, 11(12), 5159-5164.

[5] Wu YL, Zhu LL, Wu Q, Sun F, Wei JK, Tian YC et al., "Electronic origin of spatial self-phase modulation: Evidenced by comparing graphite with C60 and graphene," Appl Phys Lett 2016, 108(24), 241110.

[6] Zhang J, Yu X, Han W, Lv B, Li X, Xiao S et al., "Broadband spatial self-phase modulation of black phosphorous," Opt Lett 2016, 41(8), 1704-1707.

[7] Jia Y, Liao Y, Wu L, Shan Y, Dai X, Cai H et al., "Nonlinear optical response, all optical switching, and all optical information conversion in NbSe2

nanosheets based on spatial self-phase modulation," Nanoscale 2019, 11(10), 4515-4522.

[8] Jia Y, Shan YX, Wu LM, Dai XY, Fan DY, and Xiang YJ, "Broadband nonlinear optical resonance and all-optical switching of liquid phase exfoliated tungsten diselenide," Photonics Research 2018, 6(11), 1040-1047.

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