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Fluorescent nanoparticles (NPs) have been increasingly studied as contrast agents for better understanding of biological processes at the cellular and molecular level. However, their use as bioimaging tools is strongly dependent on their optical emission as well as their biocompatibility. This work reports the fabrication and characterization of silk fibroin (SF) coated magnesium oxide (MgO) nanospheres, containing oxygen, Cr3+ and V2+ related optical defects, as a nontoxic and biodegradable hybrid platform for bioimaging applications. The MgO-SF spheres demonstrated enhanced emission efficiency compared to noncoated MgO NPs. Furthermore, SF sphere coating was found to overcome agglomeration limitations of the MgO NPs. The hybrid nanospheres were investigated as an in vitro bioimaging tool by recording their cellular uptake, trajectories, and mobility in human skin keratinocytes cells (HaCaT), human glioma cells (U87MG) and breast cancer cells (MCF7). Enhanced cellular uptake and improved intracellular mobilities of MgO-SF spheres compared to MgO NPs was demonstrated in three different cell lines. Validated infrared and bright emission of MgO-SF NP indicate their prospects for in vivo imaging. The results identify the potential of the hybrid MgO-SF nanospheres for bioimaging. This study may also open new avenues to optimize drug delivery through biodegradable silk and provide noninvasive functional imaging feedback on the therapeutic processes through fluorescent MgO.

In this work, a nonenzymatic electrochemical sensor based on nanoporous magnesium oxide (MgO) was developed for the rapid screening of hydrogen-peroxide (H 2 O 2 ) in milk. The nanoporous MgO was synthesized by a novel one-pot reaction process at low temperature, which showed a large specific surface area and was favorable to construct biosensors. Based on the nanoporous MgO, a nano-sensor for H 2 O 2 was developed. The sensor exhibited extremely high electrocatalytic activity toward the oxidation of H 2 O 2 with detection limit of 3.3 µM and wide linear range from 0.05 to 0.2 and 0.2 to 10 mM. Averaged recovery was determined from 94.3% to 119% for spiked milk samples. The proposed method is ideally suited for the screening of H 2 O 2 abuse in milk fast and at low cost.

CH 3 NH 3 PbBr 3 single crystal, one of organometal halide perovskites, as novel optoelectronic and photovoltaic materials could be easily precipitated using an antisolvent method. Understanding of the growth mechanism will significantly improve reproducibility, quality, and controllability of the single crystals. However, it is difficult to capture the growth process due to the super solubility of CH 3 NH 3 PbBr 3 crystals in N,N-dimethylformamide solution.Here, filter paper was used to separate the intermediate states of CH 3 NH 3 PbBr 3 crystals out of N,N-dimethylformamide solution in the growth process. The developed fabrication approach can monitor the morphology evolution of CH 3 NH 3 PbBr 3 single crystals as a whole. Meanwhile, the precursor solution's properties and degradation of CH 3 NH 3 PbBr 3 single crystals were also investigated systematically. It indicates that the CH 3 NH 3 PbBr 3 single crystal growth process is similar to sodium chloride crystals grown from solution in the presence of nitrilotriacetamide. The results help us to deeply discern the growth mechanism of CH 3 NH 3 PbBr 3 single crystal in N,Ndimethylformamide solution and design controllable optoelectronic devices.