In this study, phosphate glasses embedded with Fe 2 O 3 quantum dots were prepared via a conventional melt quenching technology with further heat treatment. The effect of Fe 2 O 3 content on the structural, optical and magneto-optical properties was investigated. The results showed that the addition of Fe 2 O 3 had no obvious influence on the structure units that built up the host glass and the amorphous nature of glass. In the glass matrix , the existence of Fe 2 O 3 quantum dots was confirmed by high resolution transmission electron microscope . Meanwhile, optical study clearly demonstrated a red shift in optical cut-off wavelength resulted from the size quantization effect. The highest Verdet constant (22.33°/T-cm) was measured for the glass containing 1 mol% Fe 2 O 3 , which was ~ 7 times higher than that of the glass matrix. As the increment of Fe 2 O 3 contents, a phase evolution of Fe 2 O 3 quantum dots from amorphous phase to γ-Fe 2 O 3 phase was recorded due to the Ostwald Ripening effect. Interestingly, a concentration quenching phenomenon in Verdet constant was observed along with the phase evolution of Fe 2 O 3 quantum dots. When the content of Fe 2 O 3 is up to 2 mol%, the glass exhibited paramagnetism with the Verdet constant of − 2.833°/T-cm. This finding can provide a new idea for the development of quantum dot embedded magneto-optical glass.
Chan Cao,Jie Yu,Meng-Yin Li,Ya-Qian Wang,He Tian,Yi-Tao Long
Direct, low-cost, label-free, and enzyme-free identification of single nucleobase is a great challenge for genomic studies. Here, this study reports that wild-type aerolysin can directly identify the difference of four types of single nucleobase (adenine, thymine, cytosine, and guanine) in a free DNA oligomer while avoiding the operations of additional DNA immobilization, adapter incorporation, and the use of the processing enzyme. The nanoconfined space of aerolysin enables DNA molecules to be limited in the narrow pore. Moreover, aerolysin exhibits an unexpected capability of detecting DNA oligomers at the femtomolar concentration. In the future, by virtue of the high sensitivity of aerolysin and its high capture ability for DNA oligomers, aerolysin will play an important role in the studies of single nucleobase variations and open up new avenues for a broad range of nucleic-acid-based sensing and disease diagnosis.
2D nonlayered materials have attracted more and more attention due to their novel properties and special surface structures. However, due to isotropic chemical bonds within the crystal, the synthesis of ultrathin 2D nonlayered materials is an urgent challenge. Herein, α -Fe 2 O 3 2D nanosheets as thin as ≈8.2 nm on different substrates using self-designed ultralow concentration precursors combined with Gibbs free energy and Se catalysts design are successfully synthesized. The thickness-dependent growth mechanism is systematically studied, demonstrating the thermodynamic and kinetic controlling factors. The as-grown α -Fe 2 O 3 nanosheets are demonstrated with single-crystal structures without any other elements doping. The α -Fe 2 O 3 nanosheets photodetectors show the reasonable response performance with the positive photoconductive mechanism. This improved chemical vapor deposition method provides a promising idea for the synthesis of ultrathin 2D nonlayered materials.
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