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Behrooz Maleki,Ehsan Esmaeilnezhad,최형진,Ehsan Koushki,Hossein Asghar Rahnamaye Aliabad,Mozafar Esmaeili 한국물리학회 2020 Current Applied Physics Vol.20 No.6
Core-shell structured magnetic Fe3O4@glutathione composite nanoparticles were synthesized and examined using diverse methods including Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive Xray analysis, transmission electron microscope, thermogravimetric analysis, and vibrating sample magnetometer analysis. In addition, the nonlinear optical measurements were performed by both open and closed aperture zscan methods using an aqueous colloidal solution of the fabricated nanoparticles. The colloidal system exhibited a positive nonlinear refractive index because of the self-focusing effect arising from optical re-orientation. Although optical re-orientation is a rare phenomenon in nanocolloids, high polarizability of the enveloping organic ligands caused optical re-orientation of the composite nanoparticles in the electrical field direction of the incident beam. Finally, the effect of external voltage on the nonlinear optical index was further investigated.
The effect of in-situ cellulosic matrix on the photophysical properties of white emissive CQDs
Montazeri Fereshteh,Ghasedi Arman,Mahdavi Behnam,Koushki Ehsan 한국탄소학회 2024 Carbon Letters Vol.34 No.1
Carbon quantum dots (CQDs), the newest member of carbonaceous nanomaterials, have drawn many considerations since the past two decades. A vast number of researchers made their efforts to demystify optical behavior of these materials despite being demanding. Nevertheless, their emission origin is still a controversial issue and this area suffers from a lack of hypothesis to explain the radiative transitions of these materials. White emissive CQDs are more prized among the other ones since it has provided an affordable warm white light source for many applications. In this paper, white emissive CQDs samples were prepared through a one-step hydrothermal synthesis approach. By using the advantage of possessing cellulosic networks in the Aloe Vera gel an in-situ matrix was created to encase CQDs particles. During the formation of CQDs particles, they were entrapped and created RGB nanoemitters in the cellulosic units. The leakage of the emitted photons during the radiative transitions followed by inner-filter effect (IFE) and self-/re-absorption acted as white light emissive sources. To scrutinize the validity and possibility of the hypothesis given in this paper, a series of spectroscopic analyses, including transmission electron microscopy (TEM), surface-enhanced Raman scattering (SERS), Fourier Transform Infrared (FT-IR), ultraviolet–visible (UV–Vis), and photoluminescence (PL) were conducted.