Characterization and properties of a Sr2Si5N8:Eu^2+-based light-conversion agricultural film

In this paper,the fracture surfaces of a light-conversion film were observed using a scanning electron microscope(SEM),and then,the fluorescence spectra and mechanical properties of the film were tested.The SEM results show that the average diameter of the light conversion agent is 500 nm.The results of the mechanical properties tests show that the tensile strengths of light-conversion film increase from9.86 to 12.16 MPa and that the strain at breakage increases from 2.37%to 2.75%.In addition,the application effects of the light-co nversion film were studied.The results indicate that plant height,length of the maximum leaf,width of the maximum leaf and breadth of the plants increase by 24.43%,15.30%,15.60%and 19.07%,respectively.The quality of Chinese flowering cabbages treated with the lightconversion film is superior,including a 9.09%increase in the soluble protein content,a 21.27%increase in the polyphenol content,and a 19.15%increase in the soluble sugar content.Based on these results,light-conversion films can be applied in agricultural production.

Recent developments in luminescent nanoparticles for plant imaging and photosynthesis

Luminescent nanoparticles(upconversion nanoparticles,carbon dots,silicon nanoparticles and nanophosphors)have the advantages of tunable photoluminescence,good biocompatibility,low cytotoxicity and chemical/physical stability.Recently,the luminescent nanoparticles have been involved in the plant research for imaging plant phenotype and improving the photosynthesis efficiency.Luminescent nanoparticles are applied for the plant imaging in vivo and in vitro,while the plant photosynthesis is dependent on the specific light wavelength,providing the luminescent nanoparticles an opportunity to optimize the agriculture light.This review presents the recent developments of luminescent nanoparticles applied on the plant imaging and photosynthesis and discusses the trend for future research.

Luminescence enhancement of CaMoO_(4):Eu^(3+) phosphor by charge compensation using microwave sintering method

CaMoO_(4):Eu^(3+)and CaMoO_(4):Eu^(3+),A+(A=Li,Na,K)phosphors for light-emitting diode(LED)applications have been prepared by microwave sintering method(MSM),and their structure and luminescence properties are investigated.The influences of microwave reaction time and concentration of different kinds of charge compensation A+and Eu^(3+)on luminescence have also been discussed.The samples emit a red luminescence at 615 nm attributed to the^(5)D0→^(7)F2 transition of Eu^(3+)under 464 nm excitation.It is observed that adding charge compensation A+in the sample synthesis increases luminescence intensity.The optimized sample made with 32 mol%Li+and 32 mol%Eu^(3+)has an enhancement factor of 4 in photoluminescence compared to the sample made without charge compensation.The CIE(Commission Internationale de l'Eclairage)coordinates of Ca0.36MoO_(4):0.32Eu^(3+),0.32Li+are x=0.661 and y=0.339,which indicate that the obtained phosphor can be a promising red color candidate for white LED fabrications.

The role of fluorescent carbon dots in crops:Mechanism and applications

Fluorescent carbon dots(CDs)have been widely studied in biosensing,imaging,information encryption,and optoelectronic devices due to excellent optical properties,such as photostability,tunable luminescence range,and resistance to photobleaching.In recent years,CDs have been explored for use in agriculture.Based on their light harvest and light conversion capacity,as well as their characteristics of easy synthesis and low toxicity,CDs show great potential in improving crop photosynthesis.In addition,CDs can also be used for smart and anticounterfeiting packing,food safety detection,and preservation of crops after harvest.In this study,the application of CDs with excellent optical properties in crops has been summarized,including preharvest processes(photosynthesis and plant imaging),and postharvest processes(crop preservation and food safety).Then the toxicity of CDs to crops is introduced.Finally,the present challenges and future prospects are discussed.

Temperature-Dependent Luminescence Characteristic of SrSi_2O_2N_2:Eu^(2+) Phosphor and Its Thermal Quenching Behavior

The yellow SrSi2O2N2：Eu2＋ phosphor has been synthesized by using a simple solid-state reaction method with Sr2SiO4：Eu2＋ as the precursor. It shows a broad excitation band extending from 250 to 520 nm and an asymmetric emission band with a main peak at about 550 nm. The emission intensity of the SrSi202N2：Eu2＋ is about 1.2 times higher than the commercial yellow phosphor YAG：Ce3＋ （P46-Y3）. The temperature- dependent luminescence characteristic of SrSi202N2：Eu2＋ has been investigated in this paper. With increasing temperature, the emission band of SrSi202N2：Eu2＋ shows anomalous blue-shift along with decreasing emission intensity and the broadening full width at half maximum （FWHM）. Particularly, compared with YAG：Ce3＋ （P46-Y3）, the yellow SrSi202N2：Eu2＋ phosphors exhibit higher thermal stability due to their weaker electron-phonon coupling strength （1.1）, lower stokes shift （0.0576 eV） and larger activation energy （0.288 eV）. All these results indicate that SrSi202N2：Eu2＋ yellow phosphors have potential application for white light-emitting diodes （LEDs）, What＇s more, an energy level scheme is constructed to explain the anomalous blue-shift phenomenon.

Red, green and blue aggregation-induced emissive carbon dots

As one of the most promising fluorescent nanomaterials, carbon dots(CDs) have been extensively studied for their fluorescent properties in solution. However, research on the synthesis of multicolor solid-state fluorescence(SSF) CDs(from blue to red) is rarely reported. Herein, we used o-phenylenediamine, mphenylenediamine and p-phenylenediamine with dithiosalicylic acid(DTSA) in the solvothermal reaction using acetic acid as a solvent to obtain aggregation-induced emissive(AIE) CDs of red(620 nm), green(520 nm), and blue(478 nm), respectively. XPS spectra and TEM image show that with the red-shift of luminescence, the particle size and content of C=O of the CDs gradually increases. Finally, based on the non-matrix solid-state multicolor luminescence characteristics of CDs, the application of white light LED devices is realized. Besides, based on the fat-soluble properties of CDs, fingerprint detection applications are realized.