Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging

Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation.Due to the ultra-long decay time of persistent luminescence (PersL),autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely,thus the imaging contrast and sensing sensitivity can be significantly improved.Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues,near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging.In this review,we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging,such as transition metal ions-doped NIR PLNPs,lanthanide ions-doped NIR PLNPs,organic molecules-based NIR PLNPs,and semiconducting polymer self-assembled NIR PLNPs.Notably,organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs,for the first time,were introduced to the review of PLNPs.Secondly,the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism.It includes the regulation of valence band and conduction band of different host materials,alteration of defect types,depth and concentration changes caused by ion doping,effective radiation transitions and energy transfer generated by different luminescence centers.Given the design and potential of NIR PLNPs as long-lived luminescent materials,the current challenges and future perspective in this rapidly growing field are also discussed.

Recent progress in background-free latent fingerprint imaging

Owing to their unique pattern and abundant chemical composition, latent fingerprints （LFPs） can serve as ＂ID cards＂ and ＂information banks＂ of donors and therefore are valuable for forensic investigation, access control, and even medical diagnosis. LFP imaging has attracted considerable attention, and a great variety of contrast agents has been developed. In LFP imaging, background signals such as background fluorescence from the underlying surface can seriously blur the LFP images and decrease imaging sensitivity; thus, great efforts have been made to eliminate background interference. Here, we stratify the recent progress in background-free LFP imaging by making use of the difference in properties between contrast agents and background compounds. For example, near-infrared （NIR） light-activatable contrast agents can efficiently remove background signals in LFP imaging because the background compounds cannot be excited by NIR light, showing that the difference in excitation properties between contrast agents and background compounds can be employed to eliminate background interference. This review is organized around background-free LFP imaging based on the difference in optical properties between contrast agents and background compounds： （i） different excitation wavelengths, （ii） different emission wavelengths, （iii） different luminescence lifetime values, （iv） different plasmonic properties, （v） different photothermal properties, and （vi） different electrochemiluminescence properties.

Controlling disorder in host lattice by hetero-valence ion doping to manipulate luminescence in spinel solid solution phosphors

Phosphor materials have been rapidly developed in the past decades. Developing phosphors with desired properties including strong luminescence intensity and long lifetime has attracted widespread attention. Herein, we show that hetero-valence ion doping can serve as a potent strategy to manipulate luminescence in persistent phosphors by controlling disorder in the host lattice. Specifically, spinel phosphor Zn(Ga_(1-x)Zn_x)(Ga_(1-x)Ge_x)O_4:Cr is developed by doping ZnGa_2O_4:Cr with tetravalent Ge^(^(4+)).Compared to the original ZnGa_2O_4:Cr, the doped Zn(Ga_(1-x)Zn_x)(Ga_(1-x)Ge_x)O_4:Cr possesses significantly enhanced persistent luminescence intensity and prolonged decay time. Rietveld refinements show that Ge^(4+)enters into octahedral sites to substitute Ga^(3+), which leads to the co-substitution of Ga^(3+) by Zn^(2+) for charge compensation. The hetero-valence substitution of Ga^(3+) by Ge^(4+)and Zn^(2+) enriches the charged defects in Zn(Ga_(1-x)Zn_x)(Ga_(1-x)Ge_x)O_4:Cr, making it possible to trap large amounts of charge carriers within the defects during excitation. Electron paramagnetic resonance measurement further confirms that the amount of Cr^(3+) neighboring charged defects increases with Ge^(4+)doping. Thus charge carriers released from defects can readily combine with the neighboring Cr^(3+) to produce bright persistent luminescence after excitation ceases. The hetero-valence ion doping strategy can further be employed to develop many other phosphors and contributes to lighting, photocatalysis and bioimaging.

Highly efficient and multidimensional extraction of targets from complex matrices using aptamer-driven recognition

Adsorbents are widely employed in both fundamental and applied research areas such as separation technology, biotechnology, and environmental science. Selectivity and reusability are two most important requirements for adsorbents. Aptamers exhibit perfect selectivity and easy regeneration, which make them uniquely effective adsorption materials. Herein, we have rationally designed novel aptamer-based adsorbents and investigated their performance in extraction/ separation of targets from an aqueous solution. These adsorbents can selectively extract targets from complicated sample matrices containing background compounds. Moreover, they can also be easily recycled without a significant loss of adsorption capacity. Notably, the adsorbents did not affect the activity of isolated biological samples, revealing their potential for the purification/separation of biomolecules. Composite adsorbents were constructed using aptamer-based adsorbents and a porous polymer, displaying highly efficient target separation from aqueous solution. Finally, separation columns were constructed, and targets in the aqueous solution were efficiently separated by these columns. The aptamerbased adsorbents described here exhibit great promise for potential applications in separation technology, biotechnology, and environment-related areas.