Fig. 1. Schematic illustration of the synthesis procedure of G/CdS NHs.

Fig. 2. Typical FTIR spectra of S1, S2, S4, and S6.

Fig. 3. Typical XPS spectra of (a) S1, (b) typical C 1s, and (c) O 1s. (d) Ratio of O and C of the samples.

Fig. 4. TEM images of (a) S1 and (b) S5. HRTEM image of CdS [inset of (a)]. EDX spectra of (c) S2 and (d) S6.

Fig. 5. XRD patterns of the samples.

Fig. 6. (a) Raman spectra and (b) nD of the samples.

Fig. 7. (a) Absorption spectra of S6 compared with CdS and graphene. (b) Typical absorption spectra of the samples.

Fig. 8. Measured OA Z-scan traces of (a) S6, CdS, and graphene and (b) S3, S4, and S6. (c) The typical β of S6 as a function of intensity. (d) Typical CA Z-scan traces of S6, CdS, graphene, and DMF. The red solid lines in (a) and (d) are the fitting curves by NLO absorption and refraction Z-scan theoretical formulas, respectively.

Fig. 9. Imχ(3) (red), Reχ(3) (blue), and χ(3) (black) plots of these six samples. The inset shows Reχ(3) alone to illustrate its variation clearly.

Fig. 10. Typical NLO transmission spectrum (S2). The red solid line is the theoretical fitting curve.

Fig. 11. (a) OA Z-scan curves of S6 at 4.2, 5.6, and 6.8  GW/cm2. OA Z-scan curves of the six samples at (b) 4.1  GW/cm2 and (c) 5.2  GW/cm2. (d) Typical TP−V plots of S2 and S4. (e) The intensity region value and the valley appearance intensity of the samples.

Fig. 12. PL spectra of S6, GO, and CdS.

Fig. 13. Structural models of G/CdS at different stages of reduction of (a) S2, (c) S4, (e) and S6. The dark gray areas represent sp2 carbon clusters and the dark blue small dots represent sp3 carbon bonded to oxygen groups. The light blue areas represent CdS NCs. The overlap of electron and hole of (b) S2, (d) S4, and (f) S6.