Ligand-Driven Supramolecular Assembly of Gold Nanoclusters with Ultralong Lifetime and Large Stokes Shift for High-Efficiency Electrochemiluminescence.
Achieving high-efficiency electrochemiluminescence (ECL) with an ultralong lifetime and a large Stokes shift in a single emitter is highly desirable yet challenging. Herein, we report the supramolecular assembly of gold nanoclusters (Au NCs) protected by a custom-designed ligand, 1-(4-carboxyphenyl)-5-mercapto-1H-tetrazole (CPMT), which achieved the aforementioned outstanding performance. The CPMT ligand not only stabilized the Au NCs through bidentate Au-S/Au-N coordination, but also induced supramolecular assembly via intermolecular π-π interactions and hydrogen bonding. The obtained self-assembled CPMT-Au NCs exhibited an exceptionally long ECL lifetime of 60.48 μs, since their rigid spherical superstructure effectively minimized interfacial nonradiative decay, leading to an intrinsically prolonged excited-state lifetime, and passivated the emissive cores against oxygen quenching, preserving the long-lived emission under ambient conditions. Concurrently, the assembly showcased a remarkably large Stokes shift of 490 nm, which virtually eliminated self-absorption even in the solid state. The assembled CPMT-Au NCs displayed dramatically enhanced ECL efficiency of 353.37%, a 15-fold enhancement over their nonassembled counterparts, attributable to the synergistic suppression of interfacial energy dissipation and self-absorption as well as the improved electrochemical excitation. Additionally, a sensitive sensing platform for carboxylesterase (CE) activity related to early hepatocellular carcinoma was developed with a detection limit of 1.98 × 10-7 U/L. Therefore, this work establishes supramolecular assembly driven by ligand engineering as a rational platform for regulating the excited-state properties of metal nanoclusters, opening new avenues for high-performance ECL emitters in lifetime-based sensing, high-brightness devices, and multiplexed bioassays.
While single thiolate-stabilized silver nanoclusters (NCs) are well studied, multiligand-protected analogues remain rare. Herein, we report a luminescent Ag24 nanocluster, co-stabilized by two distinct heterocyclic thiols, 2-mercapto-5-n-propylpyrimidine and 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol, together with triphenylphosphine, whose composition was confirmed by high resolution electrospray ionization (HR-ESI) mass spectrometry. It shows aggregation-caused quenching as it self-assembles into nonemissive sheets, but the emission reappears after mechanical grinding, demonstrating mechanoresponsive luminescence. Interestingly, individual ligands form nonluminescent clusters exhibiting no aggregation behavior. Femtosecond transient absorption measurements indicate that aggregation alters the excited-state dynamics, reflecting the effect of multiligand stabilization on structural rigidity and photophysical behavior in the NCs.
Deepak Kumar Patel, Ankit Sharma, Arijit Jana et al.· Inorganic Chemistry· 0 citations
Simultaneously overcoming aggregation-induced quenching and sluggish interfacial kinetics remains a pivotal challenge in electrochemiluminescence. Herein, we have successfully synthesized dual-functional nanoconfined metal-organic frameworks encapsulating Pt-A-COOH complexes (Pt@UiO-67 MOFs) as electrochemiluminescence emitters and co-reaction accelerators by a ligand-similarity-driven doping strategy. The dual-functional Pt@UiO-67 MOFs unlocked aggregation-induced electrochemiluminescence and expedited interfacial reaction kinetics by spatial nanoconfinement, the electrochemiluminescence efficiency of which was ca. 5.4-fold higher than that of the Pt-A-COOH as co-reactant to catalyze the decomposition of S2O8 2-. Density functional theory calculations and electrochemical electron paramagnetic resonance measurements indicated that the nanoconfinement structure reduced the activation energy barrier for the reduction of S2O8 2-, thereby optimizing the kinetics of SO4 •- (0.92 eV) and OH• (0.63 eV) radical generation. Based on the Pt@UiO-67 MOFs and DNAzyme motor, the ultrasensitive biosensor has been successfully constructed and had wide linear range (from ∼10 aM to ∼10 nM) and an ultralow detection limit of ∼4.1 aM. In the preliminary proof-of-concept evaluation using acute kidney injury clinical samples, the assay results had excellent concordance with those of quantitative reverse transcription polymerase chain reaction. This work provides a paradigm integrating supramolecular engineering with DNA nanotechnology, which paves the way for sensitive biodetection and preliminary clinical screening.
Wanzhen Chen, Ying Ma, Jiaju Mo et al.· Small· 0 citations
Blue-excitable lead-free metal halide microcrystals (MCs) with high efficiency and narrow emission are highly desired for next-generation wide-gamut displays. Herein, an ultrafast self-assembly strategy is developed to prepare hybrid manganese bromide MCs with tunable alkyl-chain lengths. With increasing alkyl-chain length, the emission intensity of the obtained MCs first improves significantly and then deteriorates, accompanied by a gradual narrowing of the full width at half maximum (FWHM) from 46.37 to 41.97 nm. The optimized [(C2H5)4N]2MnBr4 MCs exhibit strong narrow-band green emission at 518 nm with a FWHM of 43.30 nm and a high photoluminescence quantum yield of 98.70% under 455 nm excitation. This superior emission performance is ascribed to cooperative weak interactions, an appropriate Mn-Mn distance, and highly localized electronic transitions within isolated [MnBr4]2− tetrahedra. Moreover, the [(C2H5)4N]2MnBr4 MCs show moderate thermal stability, retaining 52.03% of their initial emission intensity at 413 K. By integrating [(C2H5)4N]2MnBr4 with K2SiF6: Mn4+ red phosphors on a blue chip, a white light-emitting diode with a high luminous efficacy of 134.60 lm/W and a wide gamut of 112.6% NTSC is achieved, demonstrating the great promise of ultrafast-assembled hybrid manganese bromides for efficient and wide gamut display backlighting.
Two-dimensional (2D) supramolecular architectures have attracted considerable attention owing to their unique structural anisotropy and collective electronic and optical properties. In this study, a terpyridine-based dinuclear platinum(II) complex (Pt2-L) incorporating chiral R-aminoethyl moieties was synthesized as a building block for supramolecular polymerization. The self-assembly behavior of Pt2-L was systematically investigated as a function of H2O content in DMSO, revealing the formation of well-defined supramolecular architectures. Very interestingly, the self-assembled Pt2-L exhibits two strong emission bands at approximately 420 nm and in the 570-650 nm region, which are attributed to aggregation-indued emission (AIE) and metal-metal-to-ligand charge transfer (MMLCT) transitions arising from Pt···Pt interactions, respectively. Time-dependent morphological studies showed that the thermodynamically stable 2D structures were generated through spherical aggregates as kinetic intermediates. Notably, the helicity of the thermodynamic 2D supramolecular architectures was opposite to that of the intermediate structures. Thermodynamic analysis using a van't Hoff plot revealed a Gibbs free energy change of -31.9 kJ mol-1 for the supramolecular polymerization process. Furthermore, FT-IR, photoluminescence, and WAXS analyses suggest that intermolecular hydrogen bonding, π-π stacking, and Pt···Pt metallophilic interactions cooperatively act as key driving forces for the formation of the supramolecular architecture.
Hyewon Jeon, Minju Nam, Tomoki Nishimura et al.· Chemistry - An Asian Journal· 0 citations
Controlling the photophysical properties of metal clusters without altering their intrinsic cores remains challenging because molecular structure and crystal packing are often strongly coupled in such system. Herein, we show that a cyclic trinuclear gold (I) complex (Au3) can serve as a structurally defined precursor for hierarchical assembly, enabling packing-controlled photoluminescence while changing the metal core composition. By varying the feed ratio of Au3 and AgBF4, two polymorphs, Au6Ag-α and Au6Ag-β, were obtained, both featuring distorted trigonal-prismatic Au3-Ag-Au3 sandwich structures. Despite their identical compositions, they exhibit distinct solid-state emission, with Au6Ag-α showing yellow emission and Au6Ag-β displaying red-shift orange emission with a higher quantum yield. Single-crystal structure analysis and theoretical calculations reveal that Au6Ag-α is governed by a ligand-dominated heptanuclear unit, whereas tighter packing in Au6Ag-β induces intersandwich interactions, giving rise to a stacked decanuclear emissive unit with pronounced ligand-to-metal-metal charge transfer (LMMCT) character. These findings demonstrate that the use of an appropriate cluster precursor enables spatial packing control over compositionally identical clusters, providing a viable route to tune photophysical properties without altering the intrinsic metal core.
Jing-Jing Wu, Ye-Ting Wang, Yan Liu et al.· Inorganic Chemistry· 0 citations
In this work, red-fluorescent silver nanoclusters (MMTA@Ag NCs) with aggregation-induced emission (AIE) properties were synthesized via a facile one-pot strategy at room temperature using 2-mercapto-4-methyl-5-thiazoleacetic acid (MMTA) as the capping ligand. The as-prepared Ag NCs initially exhibited weak fluorescence in aqueous solution with a quantum yield of only 0.0037. Upon the introduction of Mn2+, the metal ions acted as electrostatic bridges by coordinating with the carboxylate groups (-COO-) on the NCs surface, triggering significant aggregation of the nanoclusters. This aggregation effectively restricted intramolecular motion, leading to a remarkable "turn-on" fluorescence enhancement with a 100-fold increase in quantum yield to 0.38. Based on this AIE mechanism, a novel fluorescent sensing platform for Mn2+ detection was established. The method exhibited a satisfactory linear response over the Mn2+ concentration range of 0.01-0.50 µmol L-1 with a low detection limit of 9.79 nmol L-1 and excellent selectivity over other interfering ions. The proposed method was successfully applied to the determination of Mn2+ in milk samples, with satisfactory recoveries ranging from 99.0% to 106.2% and RSD below 2.7%. Furthermore, a highly luminescent PVA composite film was fabricated using the MMTA@Ag NCs-Mn2+ system, demonstrating promising potential in anti-counterfeiting applications.
