Well Width Dependence of Band Gap Renormalization of Single ZnO/MgZnO Quantum Well

通过室温下的时间积分光致发光(Pl)谱,研究了阱宽lW渐变的znO/Mg0.1zn0.9O单量子阱在高激发强度下的能带重正化与阱宽的关系。实验中光生载流子浓度为n=1.6x1014CM-2,在lW从2.3 nM渐变到4.3 nM,Pl谱峰位的红移量从5.9 MEV变化到97.1 MEV。红移量随阱宽增大而增加,但增加率却逐渐减少。当lW>2αb(αb,znO体材料激子玻尔半径,约为2 nM)时,红移量逐渐呈现出饱和的趋势(100 MEV)。研究发现峰位的红移是由于多体效应所导致的能隙收缩以及在高的激发强度下带内填充效应的这两种机理相互竞争的结果。Band gap renormalization of ZnO/Mg0.1Zn0.9O single quantum well(QW) with gradual well width(Lw) is studied by room-temperature time integrated photoluminescence(PL) spectra at high excitation power density.The photo-generated carrier density is n=1.6×1014 cm-2 and the magnitude of red shift of PL spectrum peak increases from 5.9 meV to 97.1 meV with Lw changing from 2.3 nm to 4.3 nm.With Lw increaseing,the red shift increases but the increase rate gradually decreases.When Lw>2αB(αB,the exciton Bohr radius of ZnO bulk,is about 2 nm),the red shift starts to be gradually saturated.It is found that the red shift is the competition result of energy gap contraction due to many body effect and intraband filling effect at high excitation power density.The result is useful for designing and application of ZnO QW-based optoelectronic devices.国家973计划(2004CB719804);国家自然科学基金(60876007);广州市科技局推荐项目(2005Z3-C7451)资助课

Damage to mangroves from extreme cold in early 2008 in southern China

通讯作者Author for correspondence (E-mail: [email protected])2008年初,我国南方19个省经历了50年一遇的持续低温雨雪冰冻天气。极端气候对华南沿海各省的红树林区造成不同程度的危害。2008年3月,在我国南方各省红树林区的10个代表性地点,对这次寒害造成的红树植物伤害程度进行了系统的调查。结果表明:冬季低温对红树林的影响极为显著,特别是在低纬度的海南、广西和广东湛江,由于极端低温正值夜间退潮,对红树林的影响更为显著;在纬度较高的福建,本地红树种类秋茄(Kandelia obovata)、桐花树(Aegiceras corniculatum)和白骨壤(Avicennia marina)及引种的木榄(Bruguiera gymnorrhiza)等,由于长期适应于冬季较低的气温或在种植前经过抗寒锻炼,具有较强的抗寒能力。各地主要红树植物中,广布种秋茄、桐花树和白骨壤最为耐寒,其耐寒性均大于红树科的木榄、海莲(Bruguiera sexangula)和红海榄(Rhizophora stylosa)。海桑(Sonneratia caseolaris)对温度的敏感性最强,抗寒能力最低,因此,即使在其原产地海南也受到较为严重的寒害,在纬度更高的引种地出现大面积受害甚至全部死亡,而从孟加拉国引种的无瓣海桑(Sonneratia apetala)却显示出一定的抗寒能力。同一地点的红树植物幼苗的抗寒能力低于大树。此次寒害也造成了苗圃场的种苗大量死亡,成熟的植株提前落花落果,这势必会影响后继一两年内红树林的自然更新和人工造林。因此,在未来红树林造林或人工引种中,一定要考虑到红树植物的抗寒能力。国家自然科学基金(30671646和30700092);厦门大学“闽江学者”启动基

Ir/CeO_2催化剂上乙醇水蒸气重整反应的研究

研究了Ir/CeO2催化剂在乙醇水蒸气重整反应中的催化性能。用沉积沉淀法在高比表面的CeO2载体上制备了Ir/CeO2催化剂，采用X射线衍射光谱、程序升温还原和透射电子显微镜对催化剂的晶相组成、还原性能和形貌进行了表征。结果表明，Ir和CeO2之间发生了强烈的相互作用，从而明显改善了Ir粒子的分散。Ir具有优异的C—C键断裂性能，在低温下即可实现乙醇的完全转化，而在高温区具有很好的甲烷重整性能，可获得很高的氢气产率

Ir/CeO_2催化剂上乙醇水蒸气重整反应的研究

研究了Ir/CeO2催化剂在乙醇水蒸气重整反应中的催化性能。用沉积沉淀法在高比表面的CeO2载体上制备了Ir/CeO2催化剂，采用X射线衍射光谱、程序升温还原和透射电子显微镜对催化剂的晶相组成、还原性能和形貌进行了表征。结果表明，Ir和CeO2之间发生了强烈的相互作用，从而明显改善了Ir粒子的分散。Ir具有优异的C—C键断裂性能，在低温下即可实现乙醇的完全转化，而在高温区具有很好的甲烷重整性能，可获得很高的氢气产率

effectofpreparationmethodandcalcinationtemperatureonlowtemperaturecooxidationoverco3o4ceo2catalyst

Co3O4/CeO2 mixed oxides were prepared by coprecipitation-oxidation, homogeneous precipitation, and complexation-combustion methods. The catalysts were used to catalyze low-temperature CO oxidation under dry and humid conditions. The Co3O4/CeO2 catalyst prepared by the coprecipitation-oxidation method followed by calcination at 538 K exhibited excellent activity and good resistance to water vapor poisoning. Remarkably, a CO conversion of 99% was achieved at a temperature as low as 196 K and was maintained more than 400 min under the dry condition. When the reaction was carried out at 298 K, a CO conversion of 94% was obtained after running the reaction for 2 400 min. Even when 3.1% steam was added, a CO conversion of 79% could be kept after 2 400 min time-on-stream at 383 K. It is suggested that the strong interaction between Co3O4 and CeO2 is closely related to the preparation route and the calcination temperature and plays a crucial role in the CO oxidation over the Co3O4/CeO2 catalyst