Growth and properties of the self‐catalyzed heterostructured GaP nanowires (NWs) with GaP1 − xAsx insertions in the form of nanodiscs (NDs) grown by means of molecular‐beam epitaxy on Si (111) substrate are studied. To obtain the NDs with the different composition and optoelectronic properties, the ratio of As and P fluxes is varied. Structural properties of the synthesized heterostructures are characterized by means of transmission electron microscopy. Energy dispersive X‐ray spectroscopy is used to study chemical composition of the NDs. The maximum achieved fraction x in the NDs is nearly 60%. Sublinear dependence of As concentration in the ND on the As/P flux ratio is observed and theoretical description for the observed phenomenon is provided. The proposed model can be used to estimate the predicted As/P ratio for the synthesis of GaPAs NDs as well as NWs of the required composition. Microphotoluminescence (μPL) studies demonstrate the appearance of broadband PL signal in the spectral range between 600 and 700 nm, corresponding to the NDs with different compositions. Spectra intensity modulation is found due to longitudinal Fabry–Pérot‐type resonances in the individual NWs.

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In living organisms, redox reactions play a crucial role in the progression of disorders accompanied by the overproduction of reactive oxygen and reactive chlorine species, such as hydrogen peroxide and hypochlorous acid, respectively. We demonstrate that green fluorescence graphene quantum dots (GQDs) can be employed for revealing the presence of the hypochlorous acid in aqueous solutions and cellular systems. Hypochlorous acid modifies the oxygen-containing groups of the GQD, predominantly opens epoxide rind C–O–C, forms excessive C=O bonds and damages the carbonic core of GQDs. These changes, which depend on the concentration of the hypochlorous acid and exposure time, manifest themselves in the absorbance and fluorescence spectra of the GQD, and in the fluorescence lifetime. We also show that the GQD fluorescence is not affected by hydrogen peroxide. This finding makes GQDs a promising sensing agent for selective detecting reactive chlorine species produced by neutrophils. Neutrophils actively accumulate GQDs allowing to visualize cells and to examine the redox processes via GQDs fluorescence. At high concentrations GQDs induce neutrophil activation and myeloperoxidase release, leading to the disruption of GQD structure by the produced hypochlorous acid. This makes the GQDs a biodegradable material suitable for various biomedical applications.

A method of hybrid integration of quantum dot microdisk lasers with silicon wafer is proposed and realized. In addition to the possibility of combining microlasers with various silicon-based electronic and photonic devices, this makes it possible to significantly improve heat removal from the active region of the microlaser. The thermal resistance normalized to the mesa area reaches the level of about 0.002 (K/W)*cm 2 , which is significantly lower than the corresponding values of QD microlasers on GaAs substrate and monolithically grown on Si. As a result, the threshold current as well as current-induced shift of emission wavelength are reduced in continuous-wave regime.