Recent progress in the green synthesis of rare-earth doped upconversion nanophosphors for optical bioimaging from cells to animals

Rare-earth doped upconversion nanophosphors (UCNPs), which convert low energy near-infrared (NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented, with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.     

水热法对Eu3＋掺杂CaMoO4微纳米荧光体的制备及其发光性能

采用水热法成功的制得了不同形貌的CaMoO4：Eu3＋微纳米荧光体。实验结果表明,溶液的pH值在控制产物形貌上起了决定性的作用。用X射线粉末衍射（XRD）、场发射扫描电镜（FE—SEM）和荧光光谱（PL）等分析手段研究了荧光体的结构和光致发光性能。结果表明,CaMoO4：Eu3＋荧光体的激发光谱由两部分组成：1个宽的激发带（240～360nm）和属于Eu3＋的f—f跃迁的锐线谱（395nm、465nm）,它的发射光谱只出现常见的2个发射峰：592nm（5D0→F1）、615nm（5D0→7F2）,中5D0→7F2跃迁发射峰强度明显高于5D0→7F1跃迁发射峰强度,这表明Eu3＋在CaMoO4基质中处于无反演中心或偏离反演中心的格位上。本文还对造成发射峰强度变化的原因进行了分析,认为影响发射峰强度的原因有两个：表面积和对称性,材料的表面积越大,发光的猝灭越严重,荧光发射越弱;材料的结构对称性越差,跃迁戒律打破地越彻底,荧光发射越强。     

Scalable synthesis of ytterbium and erbium codoped calcium molybdate phosphors as upconversion luminescent thermometer

Luminescent thermometry is a noninvasive method of temperature detection with high sensitivity and response speed. The present study demonstrated the process-intensified synthesis of ytterbium and erbium codoped calcium molybdate phosphors (CaMoO₄:Yb³⁺/Er³⁺). The experiment involved the initial premixing of the precursors using a high-gravity rotating packed bed (RPB) reactor and subsequent calcination processing. The pronounced mass transfer and micromixing of the reactants in the RPB facilitated the scalable and controllable synthesis of CaMoO₄:Yb³⁺/Er³⁺ particles with submicron sizes and regular morphologies. The CaMoO₄:Yb³⁺/Er³⁺ particles exhibited a bright-green emission with temperature-dependent luminescence characteristics under 980 nm laser irradiation. Furthermore, the maximum absolute sensitivity was determined to be 0.02837 K⁻¹. These results indicated that the synthesized product was a suitable candidate for application in upconversion luminescent thermometers capable of temperature sensing at the microscale.     

Production and purification of glutamic acid: A critical review towards process intensification

Amidst growing environmental awareness and stringent discharge regulations, chemical and allied process industries are now desperately seeking replacement of the conventional, polluting processes by clean and green processes. In this context, production and purification of amino acids like l-glutamic acid assumes significance. Concerned conventional process involves several steps like fermentation, centrifugation, carbon adsorption, evaporation, crystallization, ion-exchange and so on to get glutamic acid in desired concentration and purification. Despite its tremendous potential for large scale use in a wide variety of applications, cost-effective production of high purity glutamic acid has remained a challenge for decades, mainly due to several downstream processing steps and the associated cost factors. With emergence of tailor-made membranes and modules, possibility of using membranes in downstream purification of glutamic acid appears imminent with expectation of a turnaround in amino acid manufacturing industry. The present study through a brief yet comprehensive review of the very critical aspects of glutamic acid production and purification, attempts to direct research efforts towards process intensification encompassing the concepts of green processing, compact and flexible design with promise of more economically attractive production with better quality.     

旋转床填料中的传质及其模型化

用氮气解吸水中溶解氧,发现了三个在前人研究中未曾提及的重要现象：（１）保持填料外径而扩大内径,平均体积传质系数增大;（２）比表面积大小并不是传质好坏的决定因素;（３）转子填料与旋转床机壳间空腔中液滴表面的传质量,对整个装置中的传质总量,有不可忽略的贡献。据此,建立了基于液体在填料内微粒化,传质同时在填料和液滴表面进行的传质模型。模型计算结果较好地与实验结果吻合,并对上述三个现象作出了合理的解释。