Research Progress of Light Wavelength Conversion Materials and Their Applications in Functional Agricultural Films

Dicyanopyridine derivatives: One-pot preparation, ACQ-to-AIE transformation, light-conversion quality and photostability

Low cost and strong fluorescence emission are two important guarantees for luminogens used as light conversion agents. By one-pot multicomponent approach and inexpensive starting materials, three dicyanopyridine (DP) derivatives named as DCP (2-amino-6-methoxy-4-phenylpyridine-3,5-dicarbonitrile), DCO (2-amino-6-methoxy-4-(4-methoxyphenyl) pyridine-3,5-dicarbonitrile) and DCC (2-amino-4-(4-cyanophenyl)-6-methoxypyridine-3,5-dicarbonitrile) were designed and synthesized. Meanwhile, the ACQ-to-AIE transformation was successfully realized by altering substituent groups rather than traditional rotor-stator theory. Based on crystal analysis and theoretical calculations, the ACQ-to-AIE transformation is attributed to the tunable stacking modes and intermolecular weak interactions. Owing to matched fluorescence emission, low lost, high yield, and AIE activity, DCC is used as light conversion agents and doped in EVA matrix. The light conversion quality confirms that DCC can not only convert ultraviolet light, but also significantly improve the transmittance of 25 %/40 % EVA, whose photosynthetic photon flux density at 400-500 nm and 600-700 nm increased to 30.67 %/30.21 % and 25.37 %/37.82 % of the blank film, respectively. After 20 h of UV irradiation (365 nm, 40 W), the fluorescence intensities of DCC films can maintain 92 % of the initial values, indicating good photostability in the doping films. This work not only provides an excellent and low-cost light conversion agent, but also has important significance for ACQ-to-AIE transformation of luminogens.

Insight into effects of terbium on cell growth, sporulation and spore properties of Bacillus subtilis

Recovery of rare earth elements (REEs) from wastewater with Bacillus subtilis (B. subtilis) during culture is promising due to its environmental benefits. However, the effects of REEs in the culture media on B. subtilis are poorly understood. This study aims to investigate the effects of the terbium (Tb(III)), a typical rare earth element, on the cell growth, sporulation, and spore properties of B. subtilis. Tb(III) can suppress bacterial growth while enhancing spore tolerance to wet heat. Spore germination and content of dipicolinic acid (DPA) were promoted at low concentrations of Tb(III) while inhibited at a high level, but an inverse effect on initial sporulation appeared. Scanning electron microscope and energy dispersive spectrometer detection indicated that Tb(III) complexed cells or spores and certain media components simultaneously. The germination results of the spores after elution revealed that Tb(III) attached to the spore surface was a key effector of spore germination. In conclusion, Tb(III) directly or indirectly regulated both the nutrient status of the media and certain metabolic events, which in turn affected most of the properties of B. subtilis. Compared to the coat-deficient strain, the wild-type strain grew faster and was more tolerant to Tb(III), DPA, and wet heat, which in turn implied that it was more suitable for the recovery of REEs during cultivation. These findings provide fundamental insights for the recovery of rare earths during the culture process using microorganisms.

Recent Advances in Light-Conversion Phosphors for Plant Growth and Strategies for the Modulation of Photoluminescence Properties

The advent of greenhouses greatly promoted the development of modern agriculture, which freed plants from regional and seasonal constraints. In plant growth, light plays a key role in plant photosynthesis. The photosynthesis of plants can selectively absorb light, and different light wavelengths result in different plant growth reactions. Currently, light-conversion films and plant-growth LEDs have become two effective ways to improve the efficiency of plant photosynthesis, among which phosphors are the most critical materials. This review begins with a brief introduction of the effects of light on plant growth and the various techniques for promoting plant growth. Next, we review the up-to-date development of phosphors for plant growth and discussed the luminescence centers commonly used in blue, red and far-red phosphors, as well as their photophysical properties. Then, we summarize the advantages of red and blue composite phosphors and their designing strategies. Finally, we describe several strategies for regulating the spectral position of phosphors, broadening the emission spectrum, and improving quantum efficiency and thermal stability. This review may offer a good reference for researchers improving phosphors to become more suitable for plant growth.

Tunable Red Clusteroluminescence Polymers Prepared by a Simple Heating Process

Clusteroluminescence (CL) has drawn much attention in recent years. However, the design of red emission clusteroluminogens (CLgens) with tunable CL is still in its infancy. Herein, we report a simple heating process to prepare red emission poly(maleic anhydride-alt-vinyl acetate) (PMV) derivatives with a tunable maximum emission wavelength between 620 and 675 nm. First, heating above the glass transition temperature (T_g) would promote the movement of polymer chains and facilitate the formation of clusters in both solid and solution states. Then, heating beyond the decomposition temperature at which vinyl acetate converts into C═C is favorable to the formation of new clusters and large through-space conjugation among subgroups in polymer chains. Their synergistic effects realize the adjustable emission wavelength and higher quantum yield of polymers. Additionally, low-cost and eco-friendly core-shell PMV particles are prepared as agricultural light conversion agents and exhibit great compatibility with polyethylene.

Breaking the bottleneck of organic light conversion agents: Preparation, performance evaluation and intrinsic mechanism

Poor photostability has become a major obstacle of organic fluorescent dyes (OFD) used as light conversion agent. To explore the intrinsic mechanisms of photodegradation and highly efficient means to enhance photostability, here, three s-triazine dyes and two 1,3,5-triphenylbenzene luminescent agents were designed and synthesized. Further, the relationships of photostability, intramolecular charge transfer effect, energy gap between singlet and triplet, and active oxygen generating capacity are analyzed and discussed. AIE activity, solid-state fluorescence emission, light conversion quality, and photostability combined with thermostability show TPT-DB (2,4,6-tris(4-(3,6-ditertbutyl-9H-carbazol-9-yl)phenyl)-1,3,5-triazine) is the best light conversion agent among of the dyes, whose photosynthetic photon flux density at 400-500 nm and 600-700 nm in doping film increased successively to 6.20% and 25.78% of the blank film, emission intensity can maintain 93.4% of the initial value after intensified UV radiation of 20 h (365 nm, 40 w), and has good thermal stability, Td up to 374 °C. Furthermore, oxygen-free environment was confirmed to be the most effective measure to enhance the photostability of OFD, thereby a simple and efficient method is adopted to block the diffusion of oxygen and significantly enhance the photostability of OFD by amphiphilic ethylene-vinyl alcohol copolymer. The work not only provides an excellent light conversion agent, but also clears the obstacles for the large-scale application of OFD as light conversion agents.

A New Year's Message 2023

We wish you all happiness, health and progress in the new year [...].

Effects of rare-earth light conversion film on the growth and fruit quality of sweet pepper in a solar greenhouse

Light is an important environmental factor influencing plant growth and development. However, artificial light supplement is difficult to spread for its high energy consumption. In recent years, rare-earth light conversion film (RPO) covering is being focused on to be a new technology to study the mechanism of light affecting plant growth and development. Compared with the polyolefin film (PO), the RPO film advanced the temperature and light environment inside the greenhouse. Ultimately, improved growth and higher yield were detected because of a higher photosynthesis, Rubisco activity and Rubisco small subunit transcription. Compared with that in the greenhouse with polyolefin film, the plant height, stem diameter and internode length of sweet pepper treated with RPO increased by 11.05, 16.96 and 25.27%, respectively. In addition, Gibberellic acid 3 (GA3), Indole-3-acetic acid (IAA), Zeatin Riboside contents were increased by 11.95, 2.84 and 16.19%, respectively, compared with that with PO film. The fruit quality was improved, and the contents of ascorbic acid (Vc), soluble protein and soluble sugar were significantly higher than those of PO film, respectively, increased by 14.29, 47.10 and 67.69%. On the basis of improved fruit quality, the yield of RPO treatment increased by 20.34% compared with PO film. This study introduces an effective and low-energy method to study the mechanism and advancing plant growth in fruit vegetables production.