Novel ultrabright luminescent copper nanoclusters and application in light-emitting devices

Pargyline-phosphine copper(I) clusters with tunable emission for light-emitting devices

Three pargyline-phosphine copper(I) clusters, [Cu4(CC-C9H12N)3(PPh3)4](PF6) (1) and [Cu6(CC-C9H12N)4(dppy)4](X)2 (dppy = diphenyl-2-pyridylphosphine; X = PF6 for 2 and X = ClO4 for 3), were synthesized. Their structures were fully characterized using various spectroscopic methods and X-ray crystallography, which showed that the stoichiometry and nature of pargyline and phosphine ligands play an important role in tuning the structure and photophysical features of Cu(I) clusters. Interestingly, clusters 1, 2 and 3 exhibited red, orange and yellow phosphorescence with high quantum yields of 88.5%, 22.0% and 40.2%, respectively, at room temperature. Moreover, clusters 1-3 show distinct temperature-dependent emissions. The excellent luminescence performance of 1 and 3 was designed and employed for the construction of monochrome and white light-emitting devices (LEDs).

Ionic Liquids-Driven Cluster-to-Cluster Conversion of Polyhydrido Copper(I) Clusters Cu7H5 to Cu8H6 and Cu12H9

Although ionic liquids (ILs) are of prime interest for the synthesis of various nanomaterials, they are scarcely utilized for the polyhydrido copper(I) [Cu(I)H] clusters. Herein, two air-stable Cu(I)H clusters, [Cu8H6(dppy)6](NTf2)2 (Cu8H6) and {Cu12H9(dppy)6[N(CN)2]3} (Cu12H9), are synthesized in high yields for the first time from the ILs-driven conversion of an unprecedented cluster [Cu7H5(dppy)6](ClO4)2 (Cu7H5) by a facile three-layers diffusion crystal (TLDC) method, strategically introducing IL-NTf2 and IL-N(CN)2 as two types of unusual interfacial crystallized templates, respectively. Their structures are fully characterized by various spectroscopic methods and X-ray crystallography, which shows that the anion of IL plays an important role as an anion template and an anion ligand in controlling the structural conversion of Cu(I)H clusters. Their photophysical properties are also investigated, and it is found that all reported clusters exhibit red luminescence with λem ranging from 600 to 690 nm.

Solvent-Induced Modulation in the Optical Properties of Copper Nanoclusters and Revealing the Isomeric Effect of Templates

The solvent plays an influential role in controlling the nucleation process of metal nanoclusters (MNCs) and thereby significantly modulates their optical signatures. Herein, we have demonstrated the solvent-induced modulation in the optical properties of copper nanoclusters (CuNCs), primarily governed by the solvent polarity. During the preparation of para-mercaptobenzoic acid (p-MBA)-templated CuNCs, the simultaneous formation of blue-emitting CuNCs (B-CuNCs) and red-emitting CuNCs (R-CuNCs) were observed up to 7 h of reaction time, reflected from the systematic increment in the photoluminescence (PL) intensity at 420 nm and 615 nm, respectively. However, after 7 h of reaction time, the exclusive formation of B-CuNCs was observed. Such simultaneous growth and depletion dynamics of CuNCs result in a significant modulation in their optical properties. The variation of the solvent from water to less polar solvents such as DMSO and DMF restricts this inter-cluster dynamics by stabilizing both the CuNCs (B-CuNCs and R-CuNCs). Thereby, a single-component White Light Emission (WLE) was realized in DMSO with CIE coordinates (0.37, 0.36). The isomeric effect of the templates has also been investigated which extensively controls the optical and catalytic properties of the CuNCs.

Label-Free, High-Throughput, Sensitive, and Logical Analysis Using Biomimetic Array Based on Stable Luminescent Copper Nanoclusters and Entropy-Driven Nanomachine

The development of an array for high-throughput and logical analysis of biomarkers is significant for disease diagnosis. DNA-templated copper nanoclusters (CuNCs) have a strong potential to serve as a label-free photoluminescence source in array platforms, but their luminescent stability and sensitivity need to be improved. Herein, we report a facile, sensitive, and robust biomimetic array assay by integrating with stable luminescent CuNCs and entropy-driven nanomachine (EDN). In this strategy, the luminescent stability of CuNCs was improved by adding fructose in CuNCs synthesis to offer a reliable label-free signal. Meanwhile, the DNA template for CuNCs synthesis was introduced into EDN with excellent signal amplification ability, in which the reaction triggered by target miRNA would cause the blunt/protruding conformation change of 3'-terminus accompanied by the production or loss of luminescence. In addition, a biomimetic array fabricated by photonic crystals (PCs) physically enhanced the emitted luminescent signal of CuNCs and achieved high-throughput signal readout by a microplate reader. The proposed assay can isothermally detect as low as 4.5 pM of miR-21. Moreover, the logical EDN was constructed to achieve logical analysis of multiple miRNAs by "AND" or "OR" logic gate operation. Therefore, the proposed assay has the advantages of label-free property, high sensitivity, flexible design, and high-throughput analysis, which provides ideas for developing a new generation of facile and smart platforms in the fields of biological analysis and clinical application.

A Red-Emitting Cu(I)–Halide Cluster Phosphor with Near-Unity Photoluminescence Efficiency for High-Power wLED Applications

Solid-state lighting technology, where light-emitting diodes (LEDs) are used for energy conversion from electricity to light, is considered a next-generation lighting technology. One of the significant challenges in the field is the synthesis of high-efficiency phosphors for designing phosphor-converted white LEDs under high flux operating currents. Here, we reported the synthesis, structure, and photophysical properties of a tetranuclear Cu(I)–halide cluster phosphor, [bppmCu₂I₂]₂ (bppm = bisdiphenylphosphinemethane), for the fabrication of high-performance white LEDs. The PL investigations demonstrated that the red emission exhibits a near-unity photoluminescence quantum yield at room temperature and unusual spectral broadening with increasing temperature in the crystalline state. Considering the excellent photophysical properties, the crystalline sample of [bppmCu₂I₂]₂ was successfully applied for the fabrication of phosphor-converted white LEDs. The prototype white LED device exhibited a continuous rise in brightness in the range of a high bias current (100–1000 mA) with CRI as high as 84 and CCT of 5828 K, implying great potential for high-quality white LEDs.

Calcium Phosphate Nanoclusters for the Repair of Tooth Enamel Erosion

The artificial repair of tooth enamel is still an urgent requirement because it has a complicated and well-arranged structure. Herein, calcium phosphate nanoclusters (CaP NCs) were synthesized, via a facile approach, for application in the repair of tooth enamel erosion. Structural and optical characterizations validated the successful preparation of spherical CaP NCs, with an average size of 2.1 ± 0.11 nm. By evaporating the ethanol and triethylamine (TEA) solvents, pure CaP was produced, which was further used to repair the tooth enamel. Simulated caries lesions were achieved via phosphoric acid etching to cause damage to enamel rods. After repair, the damaged enamel rods were directly covered with CaP. According to microhardness testing, after repair with CaP NCs, the hardness value of the tooth enamel with acid etching increased to a similar level to that of normal tooth enamel. The results of the microhardness test indicated that CaP NCs revealed great potential for repairing tooth enamel erosion. Our work demonstrates a promising potential for treating the early stage of tooth erosion with CaP NCs. Based on these findings, we believe that stable CaP NCs can be employed as a precursor for the tunable, effective repair of tooth enamel in the near future.