Build 3D Nanoparticles by Using Ultrathin 2D MOF Nanosheets for NIR Light-Triggered Molecular Switching

Dynamic Aggregation Triggering Reversible Spin-State Switching

The manipulation of spin-state switching (SSS) under ambient conditions is of significant importance for the construction of molecular switches. Herein, we demonstrate that reversible SSS can be mediated by the aggregation state of a near-infrared (NIR)-sensitive ferrous complex. The ferrous complex was J-aggregated in a DMF suspension and with a low-spin (LS) state; however, with the addition of water, it changed to H-aggregation and reached a high-spin (HS) state, owing to the enhanced intramolecular charge transfer and metal-to-ligand charge transfer. Interestingly, the following NIR irradiation can restore the J-aggregation and LS states owing to the enhanced ligand-to-ligand charge transfer. More interestingly, the ferrous complex can be further incorporated into a hygroscopic sponge that was capable of capturing humidity effectively for all weather conditions, which displayed reversible SSS via alternating atmospheric humidity capture and NIR irradiation under ambient conditions in the sponge state. This study thus opens up a new avenue for the development of novel smart molecular switches at the device level.

An enhanced fluorescent probe through the strategy of using MgWO4 nanosheets to enhance terbium ion luminescence for highly sensitive and point-of-care visual quantitative testing of ciprofloxacin integrated with a low-cost smartphone-based platform

In this work, MgWO₄ nanosheets have been successfully synthesized by a simple hydrothermal method, and the morphology and composition of the MgWO₄ nanosheets are characterized by SEM, TEM, XPS, and UV-vis. The results show that the as-prepared MgWO₄ nanosheets have a triclinic symmetry phase and an obvious two-dimensional layered structure. Studies have shown that the MgWO₄ semiconductor nanosheets can adjust the energy level, which significantly enhances the visible light absorption and the separation and transfer of photogenerated electrons, which facilitates the generation of photogenerated electrons. We use this feature to boost a terbium ion (Tb³⁺)-ciprofloxacin (CIP) system to enhance the luminescence, so as to achieve highly sensitive detection of CIP. The mechanism of Tb³⁺-MgWO₄ for CIP detection is the effective energy transfer from WO₄^2- in MgWO₄ nanosheets to Tb³⁺-CIP, thereby enhancing the characteristic emission of Tb³⁺ and enhancing the sensitivity of CIP detection. The linear response of the Tb³⁺-MgWO₄ enhanced fluorescent probe is in the range from 10 nM to 20 μM, and the detection limit (LOD) is 2 nM. In addition, we tested the recovery in spiked river water and mouse serum. Experiments have shown that the recovery of spiked samples is 97-102.2%, while the relative standard deviation (RSD) is less than 5.53%. The possible interfering substances in environmental samples will not interfere with the detection of CIP with the Tb³⁺-MgWO₄ enhanced fluorescent probe. At the same time, the development of a smartphone-based portable device provides the possibility of CIP on-site detection. Our work provides a simple, fast, highly sensitive and stable method for detecting CIP in living organisms and the environment. Importantly, the strategy of MgWO₄ nanosheet boosted terbium ion luminescence expands the application range of semiconductor nanomaterials.

2-D spin crossover materials at the nanometric scale: the effects of the size-reduction on the magnetic properties

Spin Crossover (SCO) particles at the nanometric scale provide an alternative point of view and a new perspective concerning the development of a new generation of spintronic, electronic, photonic and mechanical devices. The coexistence of the SCO phenomenon with the accompanying hysteresis loop enhances the functionality of future devices for storing and processing information. Despite all promising facts, the SCO phenomena are greatly affected by cooperativity issues resulting in a direct relation between the decrease of the size of nanopatricle and the overall decrease of cooperativity towards more gradual spin transitions. This minireview aims to summarise the synthetic techniques for the synthesis of 2-D FeII SCO particles at the nanometric scale, an underexplored area of research, highlighting the effects of the size-reduction on the magnetic properties of the corresponding nanoparticles and hopefuly showcasing the importance of studying in the context of 2D limit the SCO phenomena.

2D hydrogen-bonded organic frameworks: in-site generation and subsequent exfoliation

By using in-site generated formate, 2D HOFs of TCPP, with excellent stability and permanent porosity (BET surface area larger than 560 m2 g-1), have been obtained. The constructed 2D square-like TCPP-HCO2 grid sheets have shown considerable in-plane stability that comparable to the TCPP-based 2D MOFs, that can be exfoliated into atomically thin 2D nanosheets with efficient photocatalytic activity in aqueous system. These results are expected to shed light on the application-orientated one-pot synthesis for new kinds of multi-dimensional HOFs.