The rod-like NaNbO 3 :Er 3+ /Yb 3+ nanocrystals codoped with Mg 2+ ions were firstly synthesized by hydrothermal method. The effect of Mg 2+ ions on the phase structure and morphology of NaNbO 3 :Er 3+ /Yb 3+ was investigated by XRD and SEM spectra. Addition of Mg 2+ ions enhanced the intensities of green and red UC emissions by about 3 times and prolonged the lifetime of the 4 S 3/2 → 4 I 15/2 transition of Er 3+ ions. The pump power dependences were measured to understand the upconversion mechanism under 980 nm excitation. The tailored local environment of Er 3+ ions by codoping Mg 2+ ions was responsible for the improved optical characteristics of NaNbO 3 :Er 3+ /Yb 3+ /Mg 2+ nanocrystals.
Han Tang,Feiyang Chao,Hongyu Luo,Kesong Yu,Juan Wang,Huibiao Chen,Runmin Jia,Fangyu Xiong,Yuqiang Pi,Ping Luo,Qinyou An
Graphical The preinserted Mg 2+ ions effectively improve the reaction kinetics and structural stability of NH 4 V 4 O 10 (NHVO) in aqueous zinc-ion batteries. Compared with pristine NHVO, the intrinsic conductivity and the specific capacity after 6000 cycles of Mg-NHVO are improved by 5 times. DFT calculation reveals that the preinserted Mg 2+ ions introduce the overlap of electron cloud with vanadium oxygen layer which improve the density of states of Mg-NHVO in Fermi level. Aqueous zinc-ion batteries (AZIBs) attract much attention owing to their high safety, environmentally friendliness and low cost. However, the unsatisfactory performance of cathode materials is one of the unsolved important factors for their widespread application. Herein, we report NH 4 V 4 O 10 nanorods with Mg 2+ ion preinsertion (Mg-NHVO) as a high-performance cathode material for AZIBs. The preinserted Mg 2+ ions effectively improve the reaction kinetics and structural stability of NH 4 V 4 O 10 (NHVO), which are confirmed by electrochemical analysis and density functional theory calculations. Compared with pristine NHVO, the intrinsic conductivity of Mg-NHVO is improved by 5 times based on the test results of a single nanorod device. Besides, Mg-NHVO could maintain a high specific capacity of 152.3 mAh g −1 after 6000 cycles at the current density of 5 A g −1 , which is larger than that of NHVO (only exhibits a low specific capacity of 30.5 mAh g −1 at the same condition). Moreover, the two-phase crystal structure evolution process of Mg-NHVO in AZIBs is revealed. This work provides a simple and efficient method to improve the electrochemical performance of ammonium vanadates and enhances the understanding about the reaction mechanism of layered vanadium-based materials in AZIBs.
A two-color fluorescent sensing strategy based on a functionalized tetrahedral DNAzyme nanotweezer (FTDN) was developed to detect ochratoxin A (OTA) utilizing the multifunctional properties of DNA nanotechnology. The FTDN enables rapid OTA detection directly through a Cy5 fluorescent group, modified to respond to the target signal. Additionally, FTDN exhibits DNAzyme cutting activity in the presence of Mg 2 ⁺ ions, enabling it to traverse DNA nanoflower-functionalized magnetic beads. This process results in the continuous cleavage of DNA nanoflowers labeled with numerous FAM fluorescent groups, thereby amplifying the detection signal and enhancing OTA sensitivity. The linear ranges for the Cy5 and FAM signals in response to OTA were 5–1000 ng/mL and 0.05–100 ng/mL, respectively, with corresponding limits of detection (LOD) of 1.59 ng/mL and 0.03 ng/mL. This study demonstrates that dual-color fluorescence via Cy5 and FAM can effectively verify OTA detection in food, significantly reducing false-positive and false-negative rates. The proposed platform offers sensitive and accurate detection of mycotoxins in food and can be adapted for monitoring other trace contaminants by simply altering the aptamer.
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