RESUMEN
Producing heterostructures of cesium lead halide perovskites and metal-chalcogenides in the form of colloidal nanocrystals can improve their optical features and stability, and also govern the recombination of charge carriers. Herein, the synthesis of red-emitting CsPbI3/ZnSe nanoheterostructures is reported via an in situ hot injection method, which provides the crystallization conditions for both components, subsequently leading to heteroepitaxial growth. Steady-state absorption and photoluminescence studies alongside X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy analysis evidence on a type-I band alignment for CsPbI3/ZnSe nanoheterostructures, which exhibit photoluminescence quantum yield of 96% due to the effective passivation of surface defects, and an enhancement in carrier lifetime. Furthermore, the heterostructure growth of ZnSe domains leads to significant improvement in the stability of the CsPbI3 nanocrystals under ambient conditions and against thermal and UV irradiation stress.
RESUMEN
Carbon dots can be used for the fabrication of colloidal multi-purpose complexes for sensing and bio-visualization due to their easy and scalable synthesis, control of their spectral responses over a wide spectral range, and possibility of surface functionalization to meet the application task. Here, we developed a chemical protocol of colloidal complex formation via covalent bonding between carbon dots and plasmonic metal nanoparticles in order to influence and improve their fluorescence. We demonstrate how interactions between carbon dots and metal nanoparticles in the formed complexes, and thus their optical responses, depend on the type of bonds between particles, the architecture of the complexes, and the degree of overlapping of absorption and emission of carbon dots with the plasmon resonance of metals. For the most optimized architecture, emission enhancement reaching up to 5.4- and 4.9-fold for complexes with silver and gold nanoparticles has been achieved, respectively. Our study expands the toolkit of functional materials based on carbon dots for applications in photonics and biomedicine to photonics.
RESUMEN
Detection of nitroaromatic compounds (NACs) is an important applied task for environmental monitoring, medical diagnostics, and forensic analysis. However, detection of NAC vapors is challenging owing to their low vapor pressure and relatively weak sensitivity of the existing detection techniques. Here, we propose a novel concept to design fluorescence (FL) detection platforms based on chemical functionalization of nanotextured dielectric surfaces exhibiting resonant light absorption, trapping, and localization effects. We demonstrate highly-efficient NAC vapor sensor with selective FL-quenching response from monolayers of carbazole moieties covalently bonded to a spiky silicon surface, "black" silicon, produced over the centimeter-scale area using simple reactive ion etching. The sensor is shown to provide unprecedented ppt (10-12) range limits of detection for several NAC vapors. Easy-to-implement scalable fabrication procedure combined with simple and versatile functionalization techniques applicable to all-dielectric surfaces make the suggested concept promising for realization of various gas sensing systems for social and environmental safety applications.
