Gold and Silver Nanoparticles Functionalized by Luminescent Iridium Complexes: Synthesis and Photophysical and Electrofluorochromic Properties

Gold and silver nanoparticles in the 5 nm range functionalized by luminescent and electroactive iridium complexes are synthesized and characterized. Cyclometalated iridium complexes with a modified phenanthroline ligand bearing a pyridine end group are able to cap gold nanoparticles without changing their size and shape, while for silver the size slightly increases and aggregation starts to occur but without any flocculation. The luminescence of iridium is partially quenched by gold nanoparticles even when interactions with the complex do not involve surface functionalization (simple mixture). This quenching is much weaker in the case of silver, and capped nanoparticles retain the same luminescence as the free complex. Both iridium complexes display electrofluorochromism, that is, a reversible electrochemically driven luminescence switch when changing the redox state of the metal center

Thermodynamics of Oiling-Out in Antisolvent Crystallization. II. Diffusion toward Spinodal Decomposition

The extensive use of antisolvent crystallization for poorly soluble chemicals is hindered by oiling-out. This study delves into solute diffusion kinetics upon antisolvent addition. We conducted time-dependent simulations on a hypothetical micrometric diffusion couple, utilizing chemical potential gradients as driving forces within the Maxwell–Stefan model. Our computations compared two types of interflux coupling: drags and thermodynamics. The thermodynamic force dominates solute diffusion behavior. Antisolvent influx elevates solute chemical potential. This energy wave drives the solute to focus toward the good solvent and leads to the competition between crystallization and oiling-out. Through microfluidics and simulations, characteristic times of oiling-out and two sites of antisolvent-induced spinodal decomposition were identified. Diffusion trajectories on the phase diagram unveiled local thermodynamic conditions and impacts of mixing parameters. Initial antisolvent gradient dominates the strength of the focusing effect. Initial solute concentration acts as an offset in diffusion trajectories. Faster agitation in antisolvent and smaller droplets of solution both effectively enhance solute focusing. These findings are general, allowing mixing processes to be designed into metastable phase regions, with local compositions staying above the designed concentrations for prolonged durations. Elevated supersaturations and extended diffusion times offer favorable conditions for nucleation of metastable phases

Thermodynamics of Oiling-Out in Antisolvent Crystallization. II. Diffusion toward Spinodal Decomposition

The extensive use of antisolvent crystallization for poorly soluble chemicals is hindered by oiling-out. This study delves into solute diffusion kinetics upon antisolvent addition. We conducted time-dependent simulations on a hypothetical micrometric diffusion couple, utilizing chemical potential gradients as driving forces within the Maxwell–Stefan model. Our computations compared two types of interflux coupling: drags and thermodynamics. The thermodynamic force dominates solute diffusion behavior. Antisolvent influx elevates solute chemical potential. This energy wave drives the solute to focus toward the good solvent and leads to the competition between crystallization and oiling-out. Through microfluidics and simulations, characteristic times of oiling-out and two sites of antisolvent-induced spinodal decomposition were identified. Diffusion trajectories on the phase diagram unveiled local thermodynamic conditions and impacts of mixing parameters. Initial antisolvent gradient dominates the strength of the focusing effect. Initial solute concentration acts as an offset in diffusion trajectories. Faster agitation in antisolvent and smaller droplets of solution both effectively enhance solute focusing. These findings are general, allowing mixing processes to be designed into metastable phase regions, with local compositions staying above the designed concentrations for prolonged durations. Elevated supersaturations and extended diffusion times offer favorable conditions for nucleation of metastable phases

Thermodynamics of Oiling-Out in Antisolvent Crystallization. II. Diffusion toward Spinodal Decomposition

The extensive use of antisolvent crystallization for poorly soluble chemicals is hindered by oiling-out. This study delves into solute diffusion kinetics upon antisolvent addition. We conducted time-dependent simulations on a hypothetical micrometric diffusion couple, utilizing chemical potential gradients as driving forces within the Maxwell–Stefan model. Our computations compared two types of interflux coupling: drags and thermodynamics. The thermodynamic force dominates solute diffusion behavior. Antisolvent influx elevates solute chemical potential. This energy wave drives the solute to focus toward the good solvent and leads to the competition between crystallization and oiling-out. Through microfluidics and simulations, characteristic times of oiling-out and two sites of antisolvent-induced spinodal decomposition were identified. Diffusion trajectories on the phase diagram unveiled local thermodynamic conditions and impacts of mixing parameters. Initial antisolvent gradient dominates the strength of the focusing effect. Initial solute concentration acts as an offset in diffusion trajectories. Faster agitation in antisolvent and smaller droplets of solution both effectively enhance solute focusing. These findings are general, allowing mixing processes to be designed into metastable phase regions, with local compositions staying above the designed concentrations for prolonged durations. Elevated supersaturations and extended diffusion times offer favorable conditions for nucleation of metastable phases

Understanding the Spectroscopic Properties and Aggregation Process of a New Emitting Boron Dipyrromethene (BODIPY)

Aggregation of organic dyes often has consequences on their spectroscopic properties in materials. Here, we study a new sterically hindered boron-dipyrromethene (BODIPY), with adamantyl moieties grafted for the first time on the BODIPY core. Its aggregation behavior was investigated in poly­(methyl methacrylate) (PMMA) and on drop-casted films by monitoring absorption, fluorescence emission, relative quantum yield (Φ_Fluo,Rel), lifetime and time-resolved anisotropy. Aggregates only appear from 0.067 mol·L^–1. A multicomponent analysis demonstrated that the aggregation process can be described by three distinguishable components which correspond to a monomer species (M) and J and H aggregates. The results also indicated a concentration frontier: when the dye concentration increased up to 0.29 mol·L^–1, the concentration of M decreased in favor of the aggregates. Φ_Fluo,Rel is yet only divided by 5 compared to the dye in solution. Above 0.29 mol·L^–1, an equilibrium between M and the J aggregates is established, showing meanwhile a steady Φ_Fluo,Rel. The J aggregates are found to be dimers, whereas the aggregation number is varying for the H aggregates. Analysis of fluorescence and anisotropy decays showed that the excitation energy was transferred from M to the J dimers, and very probably trapped by H aggregates

Understanding the Spectroscopic Properties and Aggregation Process of a New Emitting Boron Dipyrromethene (BODIPY)

Aggregation of organic dyes often has consequences on their spectroscopic properties in materials. Here, we study a new sterically hindered boron-dipyrromethene (BODIPY), with adamantyl moieties grafted for the first time on the BODIPY core. Its aggregation behavior was investigated in poly­(methyl methacrylate) (PMMA) and on drop-casted films by monitoring absorption, fluorescence emission, relative quantum yield (Φ_Fluo,Rel), lifetime and time-resolved anisotropy. Aggregates only appear from 0.067 mol·L^–1. A multicomponent analysis demonstrated that the aggregation process can be described by three distinguishable components which correspond to a monomer species (M) and J and H aggregates. The results also indicated a concentration frontier: when the dye concentration increased up to 0.29 mol·L^–1, the concentration of M decreased in favor of the aggregates. Φ_Fluo,Rel is yet only divided by 5 compared to the dye in solution. Above 0.29 mol·L^–1, an equilibrium between M and the J aggregates is established, showing meanwhile a steady Φ_Fluo,Rel. The J aggregates are found to be dimers, whereas the aggregation number is varying for the H aggregates. Analysis of fluorescence and anisotropy decays showed that the excitation energy was transferred from M to the J dimers, and very probably trapped by H aggregates