Semiconductor nanoplatelets exhibit spectrally pure, directional fluorescence. To make polarized light emission accessible and the charge transport effective, nanoplatelets have to be collectively oriented in the solid state. We discovered that the collective nanoplatelets orientation in monolayers can be controlled kinetically by exploiting the solvent evaporation rate in self-assembly at liquid interfaces. Our method avoids insulating additives such as surfactants, making it ideally suited for optoelectronics. The monolayer films with controlled nanoplatelets orientation (edge-up or face-down) exhibit long-range ordering of transition dipole moments and macroscopically polarized light emission. Furthermore, we unveil that the substantial in-plane electronic coupling between nanoplatelets enables charge transport through a single nanoplatelets monolayer, with an efficiency that strongly depends on the orientation of the nanoplatelets. The ability to kinetically control the assembly of nanoplatelets into ordered monolayers with tunable optical and electronic properties paves the way for new applications in optoelectronic devices.

For the first time, multinuclear noble-metal clusters have been successfully stabilized by Ti-oxo clusters. Two unprecedented Ag @Ti -oxo nanoclusters with precise atomic structures were prepared and characterized. The octahedral Ag core has strong Ag-Ag bonds (ca. 2.7 Å), and is further stabilized by direct Ag-O-Ti coordination interactions. Moreover, as a result of different acidic/redox conditions in synthesis, the Ag core can adopt diverse geometric configurations inside the Ti -O shell. Correspondingly, structural differences greatly influence their optical limiting effects. The transmittance reduction activity of the clusters towards 532 nm laser shows a nearly linear concentration dependence, and can be optimized up to about 43 %. This work not only opens a new direction for multimetallic semiconductive nanoclusters with interesting optical properties, but also provides molecular models for important noble-metal/TiO heterogeneous materials.

Six crystalline polyoxo-titanium clusters (PTCs) derived from oximes, namely, Ti(μ-O)(OMe)(L1) (PTC-125; HL1 = salicylaldoxime), H[Ti(μ-O)(μ-O)(OMe)(L1)] (PTC-126), Ti(μ-O)(μ-O)(O Pr)(OAc)(L2) (PTC-127; HL2 = salicylhydroxamic acid; HOAc = acetic acid), Ti(μ-O)(OEt)(L2) (PTC-128), Ti(μ-O)(μ-O)(OEt)(L2) (PTC-129), and Ti(μ-O)(μ-O)(μ-O)(OEt)(L3) (PTC-130; HL3 = acetoxime) have been solvothermally synthesized and structurally characterized. Compared with the reported solid-state monomer, dimer, trimer, and tetramer titanium oximes, these compounds possess high nuclearity structures in the range Ti, Ti, Ti, Ti, Ti, and Ti as a result of the presence of oxo bridges. Even though three examples of tetranuclear and hexanuclear derivatives have been documented, PTC-130 with a centrosymmetric Ti cluster core represents the currently highest PTC compound in the oxime system. In addition, Ti/oximate ratio by solvothermal synthesis in this work possessed a broad range from 0.83:1 to 9:1, different from the constant ratio of 1:1 in the reported ones. According to the solid-state UV-vis diffuse reflectance measurement, the existence of oxime ligands largely enhanced their visible light harvest. Furthermore, their photocurrent response properties are also studied.