Fig. 1. Preparation and microscopy characteristics of the graphene nanoscrolls. (a) Schematic diagram of the preparation process of graphene nanoscrolls; (b) optical microscopy image of graphene before scrolling; (c) optical microscopy image of graphene nanoscrolls, where L represents the scrolled length of graphene; (d) atomic force microscopy (AFM) image of graphene nanoscrolls, where the white solid line represents the height profile of the AFM measurement at the corresponding positions

Fig. 2. Raman characterization of graphene nanoscrolls. (a) Raman spectra in different regions of graphene nanoscrolls; (b) spatial mapping of G peak of the nanoscrolls, where marks of different colors represent the focusing position of the laser during Raman measurement; (c) polar plot of the G peak signal intensity measured at different positions in Fig. (b) relative to the incident light polarization; (d) Raman spectrum of nanoscrolls in the range of G peak wavenumber, with a Lorentzian double peak fitting of the G peak (the inset shows schematic diagram of the G^- and G⁺ vibration modes, which are parallel and perpendicular to the axis of curvature, respectively); (e) Raman spectra within the G peak wavenumber range (The scattered Raman signal polarization is fixed, while the incident light polarization is rotated relative to the horizontal direction. Dashed lines represent the fitted peak positions of the G^- and G⁺ peaks, respectively); (f) intensity of the Raman G^- and G⁺ peaks, fitted according to equation (3), as a function of the incident light polarization angle

Fig. 3. Nonlinear optical microscopy characteristics of graphene nanoscrolls. (a) THG mapping of annealed graphene nanoscrolls, with a scanning step size of 0.5 μm, where different colored pentagrams represent the focusing position of the laser during the measurement of respective spectrum; (b) nonlinear optical spectra of the nanoscroll sample at different positions as shown in Fig. (a), where an additional SHG peak can be observed in the nanoscrolls area; (c) spatial mapping of SHG of annealed nanoscrolls; (d) polar plot of SHG signal of position B in Fig. (a) as a function of the incident light polarization angle

Fig. 4. Optoelectronic response of graphene nanoscroll device. (a) Optical micrograph of the graphene nanoscroll device, red and white dashed boxes indicating the regions corresponding to photocurrent and near-field scanning region, respectively; (b) spatial response of photocurrent of the graphene nanoscroll device, with dashed lines representing the source and drain electrodes; (c) near-field optical signal of the graphene nanoscroll device, corresponding to the white dashed box region in the optical micrograph; (d) spatial distribution of Raman G mode signals in the nanoscroll device, with red dashed lines comparing Raman signals with photocurrent signals, indicating that regions with strong Raman signals correspond to the areas of sign change in photocurrent signals; (e) photocurrent I_PC as a function of bias voltage under irradiation at 1500 nm, photocurrent signal exhibits a linear relationship with the incident light power; (f) polar plot of photocurrent at position P₁ of the nanoscroll as a function of incident light polarization, with bias voltage fixed at 0 V