Noble metal nanoclusters protected with carboranes, a 12-vertex, nearly icosahedral boron–carbon framework system, have received immense attention due to their different physicochemical properties. We have synthesized ortho-carborane-1,2-dithiol (CBDT) and triphenylphosphine (TPP) coprotected [Ag42(CBDT)15(TPP)4]2– (shortly Ag42) using a ligand-exchange induced structural transformation reaction starting from [Ag18H16(TPP)10]2+ (shortly Ag18). The formation of Ag42 was confirmed using UV–vis absorption spectroscopy, mass spectrometry, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and multinuclear magnetic resonance spectroscopy. Multiple UV–vis optical absorption features, which exhibit characteristic patterns, confirmed its molecular nature. Ag42 is the highest nuclearity silver nanocluster protected with carboranes reported so far. Although these clusters are thermally stable up to 200 °C in their solid state, light-irradiation of its solutions in dichloromethane results in its structural conversion to [Ag14(CBDT)6(TPP)6] (shortly Ag14). Single crystal X-ray diffraction of Ag14 exhibits Ag8–Ag6 core–shell structure of this nanocluster. Other spectroscopic and microscopic studies also confirm the formation of Ag14. Time-dependent mass spectrometry revealed that this light-activated intercluster conversion went through two sets of intermediate clusters. The first set of intermediates, [Ag37(CBDT)12(TPP)4]3– and [Ag35(CBDT)8(TPP)4]2– were formed after 8 h of light irradiation, and the second set comprised of [Ag30(CBDT)8(TPP)4]2–, [Ag26(CBDT)11(TPP)4]2–, and [Ag26(CBDT)7(TPP)7]2– were formed after 16 h of irradiation. After 24 h, the conversion to Ag14 was complete. Density functional theory calculations reveal that the kernel-centered excited state molecular orbitals of Ag42 are responsible for light-activated transformation. Interestingly, Ag42 showed near-infrared emission at 980 nm (1.26 eV) with a lifetime of >1.5 μs, indicating phosphorescence, while Ag14 shows red luminescence at 626 nm (1.98 eV) with a lifetime of 550 ps, indicating fluorescence. Femtosecond and nanosecond transient absorption showed the transitions between their electronic energy levels and associated carrier dynamics. Formation of the stable excited states of Ag42 is shown to be responsible for the core transformation.

Phenothiazines with a dimesityl boron moiety, a new class of aminoboranes with B-N linkage, were synthesized. These aminoboranes exhibited interesting photophysical behavior including aggregation-induced emission (AIE), mechanochromism (MC), mechanoluminescence (ML), and a mega Stokes shift (up to 312 nm in hexane). The solid-state emission of the aminoboranes could be switched reversibly by grinding-fuming processes. Furthermore, the phenothiazine derivative with a bromo and an arylborane group at 3- and 7-positions exhibited bright mechanoluminescence.

atomically precise nanocluster (NC)-based metal−organic frameworks (MOFs) with properties richer than those of NCs themselves are emerging materials. However, fabricating such materials with good stability has not been easy. In this work, a facile synthetic strategy was employed for t h e c r e a t i o n o f s i l v e r N C − M O F s s t a r t i n g f r o m [Ag 12 (TBT) 7 (TFA) 4 (CH 3 CN) 6 ] + , facilitated by heterocyclic amines, 4,4′-bipyridine (bpy) and pyrazine (pyz), via metal−metal and metalsulfide rearrangement reactions, where TBT and TFA are tertiarybutylthiolate and trifluoroacetate, respectively. In one of the reactions, the pyz ligand facilitates the formation of a 2D framework with a trigonal crystal system, which exhibits high stability and emits bright green luminescence at low temperatures. Owing to its facile synthesis, good stability, efficient luminescence, uniform porosity, and layered structure, the resultant hexagonal 2D nanosheets can be efficiently exfoliated from parent crystals. The 2D nanosheets are structurally similar to graphene. A top-down approach was employed for the exfoliation of stable 2D nanosheets with lateral dimensions in the range of 0.156 μm. In another case, the bpy ligand induces the construction of a 3D framework with an orthorhombic crystal system. Owing to its interpenetrated AB•••AB structure, robustness, and efficient green luminescence at room temperature, the resultant 3D MOF is capable of functioning as a high-performance luminescent sensor for selective detection of explosive analogues, 2-nitrotoluene and 2,4-dinitrotoluene, with excellent recyclability. However, in the absence of the heterocyclic amines, a pristine AgNC was formed. Time-dependent density functional theory calculations were employed to understand the mechanism of energy transfer in AgNC-MOFs. Our strategy offers an unprecedented approach in which heterocyclic amines facilitate intramolecular rearrangement reactions, resulting in 2D and 3D atomically precise NC framework materials. This work not only demonstrates the creation of 2D and 3D materials but also provides new insights into the critical surface coordination chemistry controlled by heterocyclic amines for defining the morphology and properties of cluster frameworks.

Higher levels of fluoride (F – ) in groundwater constitute a severe problem that affects more than 200 million people spread over 25 countries. It is essential not only to detect but also to accurately quantify aqueous F – to ensure safety. The need of the hour is to develop smart water quality testing systems that would be effective in location-based real-time water quality data collection, devoid of professional expertise for handling. We report a cheap, handheld, portable mobile device for colorimetric detection and rapid estimation of F – in water by the application of the synthesized core–shell nanoparticles (near-cubic ceria@zirconia nanocages) and a chemoresponsive dye (xylenol orange). The nanomaterial has been characterized thoroughly, and the mechanism of sensing has been studied in detail. The sensor system is highly selective toward F – and shows unprecedented sensitivity in the range of 0.1–5 ppm of F – , in field water samples, which is the transition regime, where remedial measures may be needed. It addresses multiple issues expressed by indicator-based metal complexes used to determine F – previously. Consistency in the performance of the sensing material has been tested with synthetic F – standards, water samples from F – affected regions, and dental care products like toothpastes and mouthwash using a smartphone attachment and by the naked eye. The sensor performs better than what was reported by prior works on aqueous F – sensing.

A new and simple electrospray deposition to induce ambient phase transition in copper sulphide nanostructures.

In this communication, we present the synthesis of 2-pyrene imine thiol (2-PIT)-protected Ag35 nanoclusters using a ligand exchange-induced structural transformation reaction. The formation of the nanocluster and its composition were...

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu4@oCBT, Cu4@mCBT and...

Superstructures made by assemblies of metal nanoclusters (NCs) have gained interest due to their atomic precision and exciting photophysical properties. Although there are some reports of cluster-assembled materials of NCs protected with thiols, the preparation of stable thiol-free analogs is largely unexplored due to the poor stability of such structures. Herein, we report the synthesis of phosphine-protected alloy NCs of silver with varying gold doping and superstructures of such systems. We show that alloying of phosphine-protected silver clusters with gold results in comparatively more stable clusters than weakly ligated hydride-and phosphine-coprotected silver clusters. Two new Ag− Au alloy cluster series, [Ag 11−x Au x (DPPB) 5 Cl 5 O 2 ] 2+ , where x = 1− 10 (Ag 11−x Au x in short), and [Ag 15−x Au x (DPPP) 6 Cl 5 ] 2+ , where x = 1−6 (Ag 15−x Au x in short), have been synthesized using two different phosphines, 1,4-bis(diphenylphosphino)butane (DPPB) and 1,3-bis(diphenylphosphino)propane (DPPP), respectively. These alloy clusters possess aggregation-induced emission (AIE) property, which was unexplored till now for phosphine-protected silver clusters. A visibly nonluminescent methanol solution of these clusters showed strong red luminescence in the presence of water due to the formation of cluster-assembled spherical hollow superstructures without any template. A solvophobic effect along with π•••π and C−H•••π interactions in the ligand shell make the alloy NCs assemble compactly within the hollow spheres. The assembly makes them highly emitting due to the restriction of intramolecular motion. The emissive states of the alloy clusters show a many-fold increase in lifetime in the presence of water. Femtosecond transient absorption studies revealed the lifetime of the excited-state charge carriers in their monomeric and aggregated states. Apart from enriching the limited family of phosphine-protected silver alloy NCs, this work also provides a new strategy to build a controlled assembly of NCs with tailored luminescence. These materials could be new phosphors for applications in composites, sensors, thin films, and photonic materials.