Highly dispersive AuNCs/ChOx@ZIF-8/PEI nanocomplexes for fluorescent detection of cholesterol in human serum

Gold nanoclusters (AuNCs) are widely used in the fluorescence detection of biomolecules in human serum due to their good fluorescence properties, low toxicity, and better biocompatibility. However, the weak fluorescence intensity of AuNCs limits the fluorescence detection of molecules within a wide concentration range. It is reported that coating AuNCs in ZIF-8 with adjustable pore size can effectively improve the fluorescence intensity of AuNCs and broaden the detection range. And the AuNCs wrapped in the gaps of ZIF-8 can prevent the fluorescence quenching caused by the aggregation of AuNCs. However, ZIF-8 has high crystallinity, poor dispersion, and easy deposition, which reduces the fluorescence stability of the detection system and affects the detection. Based on the above research, the highly hydrophilic polymer PEI was modified to the surface of ZIF-8, and a kind of nanocomposite material AuNCs/ChOx@ZIF-8/PEI was obtained by co-encapsulating AuNCs prepared with glutathione as a ligand and cholesterol oxidase (ChOx) into ZIF-8 modified with PEI. The composite material emits strong red light at 650 nm under the excitation of 395-nm light, and the system can sensitively detect cholesterol (Chol) in human serum. Compared with other materials, the PEI-modified composite has better solubility and stability, so the detection effect of Chol is better. Encapsulation of ChOx in the ZIF-8 shell can protect the enzyme and increase the local concentration of ChOx, thereby speeding up the reaction rate. Compared with free AuNCs/ChOx, the quenching rate of AuNCs/ChOx@ZIF-8/PEI system is doubled. Secondly, the addition of Fe²⁺ to the detection process results in higher quenching rate and detection sensitivity. The system can detect Chol in the concentration range 0.1-2.4 μM, with a detection limit of 0.073 μM. The determination is a fast and sensitive strategy. In addition, the practicability of this assay in the detection of Chol in human serum has been verified. Due to its selectivity and sensitivity, it has potential application value in clinical diagnosis.

Purification and separation of ultra-small metal nanoclusters

Metal nanoclusters (NCs) are ultra-small nanoparticles intermediate in size between small molecule complexes and nanoparticles. NCs with tunable surface functionality feature unique physical and chemical properties, however these properties are frequently compromised by the presence of undesired components such as excess ligands or mixtures of NCs. In a typical synthesis process, different NCs can be formed with varying numbers of metal atoms and/or ligands, and even NCs with the same number of metal atoms and ligands can have different spatial structures. The separation of pure NCs is important because different species have distinct optical and catalytic behavior. However, NCs can be difficult to purify or separate for a range of reasons. In this review, we discuss established and emerging approaches for NC purification/separation, with a focus on choosing the appropriate method depending on NC and application.

Development of ratiometric sensing and white light-harvesting materials based on all-copper nanoclusters

Herein, we developed a special strategy for the fast sensitization of red emitting copper nanoclusters with the assistance of green emitting copper nanoclusters. Compared to most previous methods based on AIE, which do not maintain the water solubility or tiny size of nanoclusters, the charming features of the copper nanoclusters were retained after the fabrication. Furthermore, the product was employed for the detection of sulphide, which revealed its ratiometric sensing ability in water since the ratio of the intensity change for green and red emission was related to the sulphide concentration. In addition, after the addition of Zn²⁺, the green and red emission was either enhanced or quenched via the corresponding mechanism. This enables the facile fabrication of promising white light-harvesting materials since the species of the emitting color can be simply tuned.

Engineering the Self-Assembly Induced Emission of Copper Nanoclusters as 3D Nanomaterials with Mesoporous Sphere Structures by the Crosslinking of Ce3

Aggregation-induced emission has provided fluorescence enhancement strategies for metal nanoclusters. However, the morphology of the aggregated nanoclusters tended to be irregular due to the random aggregated route, which would result in the formation of an unstable product. Herein, copper nanoclusters were directly synthesized by using l-cysteine as both the reducing and protection ligand. Initially, the structure of the product was irregular. Furthermore, Ce3+ was introduced to re-arrange the aggregates through a crosslinking avenue. It was interesting to find that well-ordered three-dimensional nanomaterials with mesoporous sphere structures were obtained after re-aggregation. On the basis of the stability test at a relatively high temperature and the light-emitting diode fabrication investigation, it revealed that the regulated product demonstrated more promising stability and color purity for practical applications than the random aggregated product with irregular structures.

One-pot development of water soluble copper nanoclusters with red emission and aggregation induced fluorescence enhancement

The binding of Zn²⁺ and Al³⁺ to OH on the copper core of Cu NCs promotes the formation of Cu NC–OH–Zn–OH–Cu NCs and Cu NC–OH–Al–OH–Cu NCs aggregates, which enables aggregation induced fluorescence enhancement.

A chemodosimetric approach for the selective detection of Pb2+ions using a cesium based perovskite

We have synthesized a lead free inorganic perovskite as a fluorescence turn-on chemodosimeter for selective sensing of Pb²⁺ions.