Intelligent food packaging with the multisensory analysis is promising as the next generation technology of food packaging. The oxygen content in food packaging is one of the crucial parameters affecting the food quality and shelf life. Caviar is among the most nutritious and costly food sources. Here, a photonic oxygen-sensing system, based on the time-resolved phosphorescence spectroscopy of a platinum complex, is developed for non-contact, non-intrusive, and real-time vacuum packaging quality control, and implemented for caviar packaging. The sensor is embedded in protective polyethylene layers and excited with a short-pulsed light emitting diode (LED) source. Integration of a blue pulsed light source, a fast and amplified silicon photodiode controlled by the Spartan-6 field programmable gate array (FPGA), and a long lifetime platinum complex results in a photonics-based oxygen sensor with a fast response and high sensitivity to the vacuum packaging damage, which is suitable for caviar. It is revealed that applying the polyethylene layers protects the caviar from the platinum complex, leaching while not interfering with the sensor functionality. Characterizing the photonic system based on its sensitivity, repeatability, stability, and long-term operation demonstrates its capability for this application.

采用紫外-可见-近红外分光光度计和稳态/瞬态荧光光谱仪,分别测量了离散在水溶液中的CdS_xSe_1-x/ZnS量子点的吸收-辐射荧光谱以及及荧光强度随时间的变化,得到了荧光寿命随粒径、x和温度的变化。荧光寿命主要取决于量子点带间的直接跃迁,缺陷态间接跃迁的影响为次。得到了荧光峰值波长和荧光寿命随粒径、x变化的经验公式。结果表明:荧光寿命随粒径增大而增大,随S组分增加而减小,且对温度的变化不敏感;当量子点粒径为4.06~9.22 nm、x为9.45~0.366、温度为15~55 ℃时,荧光寿命为2.51~3.22 μs。

通过测量PbS量子点的吸收谱、时间分辨的荧光谱以及透射电子显微镜图, 确定了不同粒径、不同温度、不同本底PbS量子点的光致荧光寿命, 得到了描述第一吸收峰波长随量子点粒径变化的经验公式。结果表明, 荧光寿命强关联于量子点粒径, 可用负指数经验公式表达; 荧光寿命弱依赖于温度; 本底材料由于表面极化效应对荧光寿命也有影响。

利用透射电镜、近红外吸收谱、荧光光谱和时间分辨光谱等技术，在室温下测量离散在正己烷有机溶剂中，不同粒径的PbSe量子点的吸收谱和荧光谱，给出了第一吸收峰和荧光峰随粒径变化的经验公式。通过对瞬态荧光衰减曲线的测量和分析，得到了PbSe量子点的荧光寿命，其寿命与量子点的表面缺陷有关。在研究的粒径范围内，由于荧光跃迁仅为带间直接跃迁和仅为缺陷态跃迁两种极端情况，可得荧光寿命最宽分布区间位于1.44~11.96 μs。荧光寿命弱关联于粒径，并随粒径的增大而呈线性减小。当PbSe 量子点的粒径为2.7~5.7 nm 时，其实测的平均荧光寿命为7.17~6.72 μs。

制备了Mn掺杂Zn-In-S量子点并研究了Zn/In的量比和反应温度对其发光性质的影响。在Mn掺杂的Zn-In-S量子点的发光谱中观测到一个600 nm发光带。通过改变Zn/In的量比,掺杂量子点的吸收带隙可从3.76 eV(330 nm)调谐到2.82 eV(440 nm),但600 nm发光峰的波长只有略微移动。这些掺杂量子点的最长荧光寿命为2.14 ms。当反应温度从200 ℃增加到230 ℃时,掺杂量子点的发光强度增加并达到最大值;而继续升高温度至260 ℃时,发光强度迅速减弱。此外,测量了Mn掺杂Zn-In-S量子点的变温发光光谱。发现随着温度的升高,发光峰位发生蓝移,发光强度明显下降。分析认为,Mn掺杂Zn-In-S量子点的600 nm发光来自于Mn2+离子的4T1和6A1之间的辐射复合。