Unicam uv 500

The UV-visible absorption spectra were recorded using a (UNICAM UV 500, Thermo Electron Corporation) spectrophotometer in the range of 200–800 nm. FT-IR spectrum was recorded over the range of 4000–400 cm⁻¹ using a SHIMADZU-IR PRESTIGE-2 spectrometer. Raman spectrum was obtained using FT-Raman spectroscopy (Bruker RFS 27, USA) with laser source Nd (YAG 1064 nm) at 2 cm⁻¹ resolution. 16+ mW laser power was irradiated on rGO/Fe₃O₄ NCs to collect Raman spectrum over the wide range 4000–50 cm⁻¹. XRD patterns were recorded by PANalytical X'pert pro diffractometer at 0.02 degree per sec scan rate using Cu Kα₁ radiation (λ = 1.5406 Å, 45 kV, 40 mA). TEM images were acquired through (TEM model FEI TECNAI G2 S-Twin) at an accelerating voltage of 200 kV. The morphology of the sample was characterized using FE-SEM (FE-SEM, Zeiss Ultra-60) equipped with EDX. VSM was used to examine the magnetic property of rGO/Fe₃O₄ NCs (Lakeshore Cryotronics, Inc., Idea-VSM, model 7410, USA).

UV-Vis absorption spectra of the synthesised NCQDs, Fe₃O₄ NPs and Fe₃O₄@NCQDs NCs were obtained using a UNICAM UV 500(Thermo Electron Corporation). Fourier transform infrared spectra (FTIR) were obtained over the range of 400–4000 cm⁻¹ using a SHIMADZU-IR PRESTIGE-2 Spectrometer. X-ray powder diffraction (XRD) pattern were recorded using PANalyticalX'pert pro diffractometer using Cu-Kα1 radiation (45 kV, 1.54056 Å; scan rate of 0.02 degree per s). The morphology and microstructures of the synthesized Fe₃O₄@NCQDs NCs were investigated by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM, Jeol/JEM 2100, LaB6) operated at 200 kV. Further morphology and composition of Fe₃O₄@NCQDs NCs were characterized using field emission scanning electron microscopy (FESEM, Zeiss Ultra-60) equipped with X-ray energy dispersive spectroscopy (EDS). Magnetic property of the material was determined at room temperature using vibrating sample magnetometer (Lakeshore VSM 7410). Composition of the Fe₃O₄@NCQDs NCs was further confirmed by thermal analysis using thermogravimetric and differential thermal analysis (TGA/DTA) of Perkin Elmer STA 6000 with TG sensitivity of 0.2 mg and DTA sensitivity of 0.06 mV.