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Recently, luminescent metal-organic framework (MOF) materials have attracted considerable attention in fluorescence sensing. In this essay, we prepared a new cluster-based CaII-MOFs {[Ca1.5(μ8-HL1)(DMF)2]·DMF}n (1) with good water dispersibility, excellent photoluminescence properties (FL quantum yield of 20.37%) and great fluorescence stability. Further, it was employed to design as an "off-on" fluorescence sensor for sensitive detection of l-cysteine. This proposed strategy was that fluorescence of CaII-MOFs 1 was quenched for providing a low fluorescence background by the introduction of Pb2+ forming the CaII-MOFs 1/Pb2+ hybrid system. The quenching effect could be ascribed to the static quenching mechanism because of the formation of ground-state complexes and coordination interactions between the free carboxyl of H4L1 ligands of CaII-MOFs 1 and Pb2+. Then, with the addition of l-cysteine into the CaII-MOFs 1/Pb2+ hybrid system, the fluorescence signal was immediately restored. This result was because the Pb2+ was gradually released from the hybrid system by chelation interactions between the -SH groups of l-cysteine and Pb2+. This method received a relative wide linear range varying from 0.05 to 40 μM and a low detection limit of 15 nM for detection of l-cysteine. This proposed strategy was also successfully applied to detect l-cysteine in human serum samples with satisfactory recoveries from 95.9 to 101.5%.

Folic acid (FA, Vitamin B9), as a water-soluble chemical compound of the vitamin B groups, plays an important role to human health. Thus, it is of great significance to develop sensitive assays for detection of FA. Herein, we prepared a water-stable metal-organic frameworks {[Ag2(μ2-abtz)(μ3-abtz)(ClO4)]⋅(ClO4)}n (MOF-AgClO4-abtz; abtz = 1-(4-aminobenzyl)-1, 2, 4,-triazole) material, which exhibited a high fluorescent quantum yield of 78.97%, good water dispersibility and excellent chemical stability. Then MOF-AgClO4-abtz was developed as a “turn-off” fluorescent sensor for detection of FA via inner filter effect (IFE). The IFE mechanism was mainly originated from the spectrum overlap between fluorescence emission of MOF-AgClO4-abtz at 350 nm and UV–vis absorption band of FA ranging from 340 to 360 nm, resulting in fluorescence quenching. Furthermore, the proposed method exhibited a good linear response to FA in the concentration range of 0.1–30 μM, and the limit of detection (LOD) was calculated to be 49 nM (S/N = 3). The great reproducibility of the method was checked for three replicate detections of 20 μM FA to find relative standard deviation (RSD) of 3.4%. This method also exhibited excellent long-term stability by detecting 30 μM FA for 7 days, the RSD value was obtained to be 2.8%. Ultimately, this method was employed for sensitive detection of FA in human serum and plasma samples with quantitative spike recoveries ranging from 95.3% to 104.6%.

In recent years, the ever-growing number of mobile users and demands for mobile services exert great pressure on wireless content transmission. It is still a challenge to provide high-quality service in mobile scenario. To improve the quality of mobile service, proactive caching is proposed to push popular and requested service content to the nearest base stations or access points from mobile users through mobility prediction and content prefteching and caching. Despite a lot of proactive caching algorithms have been proposed, there is few research has been done to design and establish a network architecture which is capable of providing smart and native support for proactive caching. Therefore, in this paper, a Smart Proactive Caching Network (SPCN) is proposed to fill the gap. The architecture and working procedure of SPCN is presented and network model is established. The performance is also evaluated.