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Abstract Gd3+- free carbon dots (CDs) were synthesized by one-step solvothermal method using urea, citric acid and 3-(trifluoromethyl)aniline as precursors. Additionally, Gd3+-doped CDs were prepared by incorporating gadolinium chloride (Gd3+ ions) into the synthesis. Size selection of the purified CDs was achieved through filter membranes ranging from 3 kDa to 100 kDa. The chemical composition and optical properties of the obtained samples were characterized by Energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), Dynamic Light Scattering (DLS), proton relaxation time measurements, Ultraviolet–visible (UV-vis) and fluorescence spectroscopies. A comparative analysis revealed a strong size-dependent behavior in the optical properties of both Gd3+-doped and Gd3+-free CDs. Furthermore, in vitro tests confirmed the non-cytotoxicity of Gd3+-doped CDs, indicating their potential applicability in biomedicine for magnetic resonance imaging (MRI) and red fluorescence-based cell and tissue imaging.

ABSTRACTThe unsaturated fatty acid content of beef meat is an important property that affects the health and sense of taste of the consumer and determines price. Fresh beef fat samples were measured by a bilateral low-field time-domain proton magnetic resonance (MR) apparatus. The proton transverse relaxation time (T2) for 18 fat samples were measured at 40.0°C using the Carr-Purcell-Meiboom-Gill method. The results showed that T2 increased linearly with unsaturated fatty acid content. By using the linear dependence of T2 on the unsaturated fatty acid content, we successfully estimated the contents of oleic acid, total monounsaturated fatty acid, and total unsaturated fatty acid with root-mean-square errors of 2.5, 2.8, and 3.2 wt%, respectively. The proposed T2-relaxometry-based method could be performed using a portable unilateral MR surface scanner, which would enable in-vivo nondestructive noninvasive measurements of live cattle for the optimization of the feeding and fattening timing from calf to adult and for the best choice of the shipment timing in terms of the maximization of unsaturated fatty acid content of beef meat.