It is very crucial to select appropriate plant lighting sources to supplement light for plants according to their different requirements for light during different growth periods. However, LED-driven plant lighting sources confront the challenges of long-term operation stability and modular light color switching requirements. Herein, red emitting, far-red emitting, and patterned multi-color emitting phosphor–sapphire composite (PSC) samples were fabricated by co-sintering CaAlSiN3:Eu2+/Gd2.4Lu0.6Ga4AlO12:Cr3+ and low-melting glass powder on sapphire plates. The phase, microstructure, and luminescent properties of these PSC specimens were systematically investigated. Notably, after 34 days of continuous operation, the luminescence intensity of the fabricated high power plant lighting LED device can maintain 93% of its initial integrated intensity, benefitting from robust resistance to light irradiation and thermal shock. Moreover, the emitting color of these modular high power LED devices can be easily switched by using different PSC samples depending on the light color need of the plants. All these results indicate that the PSC samples reported in this paper have merits of easy fabrication, low cost and long-lifetimes, showing promising applications in the field of plant growth lighting.
Conventional fluorescent probes are either easily photobleached or non-biodegradable, which often leads to the unstable fluorescence signal output and long-term biological toxicity. Therefore, the development of novel fluorescent materials with both excellent photostability and biodegradability is of great significance for further broadening their application in numerous research fields. In this work, Nb 2 C quantum dots (Nb 2 C QDs) with pristine crystallographic structures of Nb 2 C MXene phases and surface oxygen-containing species are synthesized by an ultrasound assisted physicochemical exfoliation in tetrapropylammonium hydroxide. Detailed analyses indicate that the Nb 2 C QDs not only possess excellent chemical- and photo-stable fluorescence emission but also achieve successful application in fluorescence sensing of heavy metal ions and fluorescence imaging. More importantly, it is confirmed that the Nb 2 C QDs present high biocompatibility and unique biodegradation property responsive to human myeloperoxidase, implying the application safety of Nb 2 C QDs in vivo . Under the background of ever-growing and stringent requirements for biosafety and technical stability, the chemical- and photo-stability, biocompatibility, biodegradability, and most importantly the promising fluorescence sensing/imaging characteristic of the obtained Nb 2 C QDs may argue well for their future applications in environmental monitoring, biomedical diagnosis, visual display, and anti-counterfeiting.
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