Ce和Dy在Cd_(0.5)Zn_(0.5)B_4O_7中的发光特性及能量双向传递

采用高温固相法制备了自蓝光双发射为一体的Cd0．5Zn0．5B4O7：Ce／Dy系列发光材料．由XRD测得Cd0.41Zn0．5B4O7：Ce0.04／Dy0．02的晶胞参数：a=1．3885nm，b=0．8020nm，c=0．8670nm，属于正交晶系，Pbca空间群．在Ce／Dy双掺的体系中存在Ce^3＋和Dy^3＋两种发光中心，254～350nm激发主要是Dy^3＋的^4F9/2→^6H15／2和^4F19／2→^6H13／2跃迁发射，而355～390nm激发主要为Ce^3＋的5d→4f跃迁发射．340nm激发Ce／Dy双掺发光体的发射强度是同浓度Dy^3＋单掺的31倍，Ce^3＋是Dy^3＋的高效敏化剂，而355～390nm激发Dy^3＋＋是Ce^3＋的敏化剂．体系中存在少见的Ce^3＋→Dy^3＋与Dy^3＋→Ce^3＋的能量双向传递．

不同LED光质对乒乓菊植株生长和开花性状的影响

【目的】针对华南地区高温环境下菊花花色等性状不稳定的现象,探索有效的LED光质组合以调控菊花的生长和花色等开花性状,为菊花实际生产提供LED光照栽培技术的理论参考。【方法】通过对商业流行菊花品种粉乒乓和紫乒乓苗龄为35 d的盆栽苗进行RBFR(光通量PPFD比值为红光∶蓝光∶远红光≈10∶7∶2.5)、RBUV(红光∶蓝光∶紫外光≈10∶6∶0.5)、WB(白光∶蓝光≈10∶4.8)等LED光质组合处理,以LED白光处理为对照(CK),各组均设置总光强约为240μmol/m^(2)·s,共处理80 d,定期观测乒乓菊从幼苗到成熟开花生长过程中的性状指标变化。【结果】(1)RBFR处理粉乒乓80 d、紫乒乓70 d,株高分别比CK增加1 8.3%和27.3%、茎粗增加14.1%和38.1%、叶柄长增加0.4%和34.8%,且处理70 d的紫乒乓叶长、叶宽、叶片鲜质量、叶片干质量分别比CK增加18.6%、5.8%、25.6%、45.5%,以上指标均为所有光质处理组中最大。(2)处理70 d时,以WB处理的粉乒乓顶花花梗长度、顶花花径、顶花舌状花瓣长和宽、侧花花径等指标最大,分别比CK增加4.5%、2.3%、10.9%和17.3%、19.1%,而且花瓣粉红色加深程度最大;同时,WB处理紫乒乓的最大花朵直径和花瓣紫色加深程度也最大。开花性状提升效果次之的是RBFR处理,其中粉乒乓的侧花花梗长度在所有处理中最大,比CK显著增加28.3%;紫乒乓以花苞数量、展开的头状花序数量、侧花花梗长度、最大花朵舌状花瓣长和宽等指标值最大,分别比CK增加32.3%、15.0%、38.4%、5.8%和12.8%,且RBFR处理还促使乒乓菊花朵提前开放。(3)RBUV处理的乒乓菊生长指标与CK相差不大,而叶片数增多、叶片SPAD值增大、叶片干质量比率明显升高,但Fv/Fm值下降幅度大于其他处理,且花朵品质明显下降。【结论】RBFR处理可明显促进乒乓菊植株营养生长和侧花花梗长度增长,且促进花朵提前开放;而WB处理可明显提升乒乓菊的花朵品质,两种LED光质组合可为利用人工光源提升菊花品质提供参考。

Development and Practical Applications of Blue Light-Emitting Diodes

The practical application of semiconductor-based high-efficiency white-light sources, also known as light-emitting diodes, or LEDs, is a recent development of Japanese engineering. This development could be a game-changer for lighting worldwide, given that current power consumption for lighting accounts for 16% of the total electricity consumption in Japan.

Photosynthetic Excitation Pressure Causes Violaxanthin De-epoxidation in Aging Cabbage （Brassica Oleracea L.） Leaves

The purpose of the present studies was analysis of the age induced changes in photochemical efficiency and xanthophyils cycle pigments of the primary cabbage （Brassica oleracea L. cv. Capitata f. alba） leaves. Photochemical efficiency of photosystem Ⅱ （PS Ⅱ） was studied by a pulse amplitude modulated chlorophyll fluorescence apparatus, chlorophyll concentration was analysis spectrophotometrically and xanthophyll cycle pigments were estimated by high-pressure liquid chromatography （HPLC）. Leaf senescence was accompanied with a decrease both in chlorophylls concentration, the photochemical efficiency and rate constant for PS Ⅱ photochemistry whereas non-photochemical parameters increased. Excitation pressure （1-qP） which is a measure of relative lumen acidification increased by 1.2x in aging leaves. The maximum quantum yield of PS Ⅱ showed no significant change. The level of de-epoxidised xanthophylls increased but the concentration of mono- and di-epoxy xanthophylls decreased in aging leaves. A linear relationship between the excitation pressure and the depoxidation state of the xanthophyll cycle pigments and lutein, during the onset of senescence suggests that excitation pressure can be used as a sensor for monitoring the onset of senescence as well for the de-epoxidation state of the xanthophylls responsible for non-photochemical quenching in stressed leaves.

A potential red-emitting phosphors scheelite-like triple molybdates LiKGd_2(MoO_4)_4:Eu^(3+) for white light emitting diode applications

A series of novel red-emitting phosphors scheelite-like triple molybdates LiKGd2.xEux（MoO4）4（0.1≤ x ≤ 1.9） were synthesized by solid state reaction method and their photoluminescence properties were investigated. The photoluminescence results show that all samples can be excited efficiently by UV （396 nm） light and blue （466 nm） light and emit red （615 nm） light with line spectra, which are coupled well with the characteristic emission from UV-LED and blue LED, respectively. The experimental results and their analysis suggest that the energy transfer occurs due to dipole-dipole interactions among Eu3＋ ions in LiKGd2-xEux（MoO4）4. Compared with Cao.8MoO4： Eu0.2^3-, the emission intensity of LiKGdo.9（MoO4）4： Eu1.1^3- is about 1.4 times higher and the CIE chromaticity coordinates are as close to the National Television System Committee （NTSC） standard values as those of Cao.8MoO4： Eu0.2^3-. The optical properties suggest that LiKGdo.9（MoO4）4： Eu1.1^3- is an efficient red-emitting phosphor for white LEDs applications.

Luminescence properties of Eu^(2+) doped BaAl_2Si_2O_8 phosphor for white LEDs

The BaAl2Si2O8:Eu2+blue emitting phosphor was obtained through the one-step calcination process of precursors prepared bychemical co-precipitation method. The phase structure and luminescence propertied of the phosphor were investigated usingX-ray diffraction (XRD) and a fluorescence spectrophotometer. The excitation spectrum exhibited a broad band between 230nm and 400 nm and the emission peaking at about 470 nm was observed, which originated from the allowed f-d transition ofEu2+ions at Ba2+sites. Owing to the different optimal concentrations under different excitation wavelengths (254 nm and 365nm), the energy-transfer mechanism in this phosphor has changed from the dipole-dipole interaction to the exchange interac-tion of Eu2+ions.