Raman Spectroscopy of Single Light-Absorbing Carbonaceous Particles Levitated in Air Using an Annular Laser Beam

A laser trapping technique is a powerful means to investigate the physical and chemical properties of single aerosol particles in a noncontact manner. However, optical trapping of strongly light-absorbing particles such as black carbon or soot is quite difficult because the repulsive force caused by heat is orders of magnitude larger than the attractive force of radiation pressure. In this study, a laser trapping and Raman microspectroscopy system using an annular laser beam was constructed to achieve noncontact levitation of single light-absorbing particles in air. Single acetylene carbon black or candle soot particles were arbitrarily selected with a glass capillary connected to a three-axis oil hydraulic micromanipulator and introduced into a minute space surrounded by a repulsive force at the focal point of an objective lens. Using the developed system, we achieved optical levitation of micrometer-sized carbonaceous particles and observation of their Raman spectra in air. Furthermore, we demonstrated in situ observations of changes in the morphology and chemical composition of optically trapped carbonaceous particles in air, which were induced by heterogeneous oxidation reactions with ozone and hydroxyl radicals

Directional Energy Transfer in Mixed-Metallic Copper(I)–Silver(I) Coordination Polymers with Strong Luminescence

Strongly luminescent mixed-metallic copper­(I)–silver­(I) coordination polymers with various Cu/Ag ratio were prepared by utilizing the isomorphous relationship of the luminescent parent homometallic coordination polymers (Φ_em = 0.65 and 0.72 for the solid Cu and Ag polymers, respectively, at room temperature). The mixed-metallic polymer with the mole fraction of copper even as low as 0.005 exhibits a strong emission (Φ_em = 0.75) from only the copper sites as the result of the efficient energy migration from the silver to the copper sites. The migration rates between the two sites were evaluated from the dependence of emission decays upon the mole fraction of copper

Viscosity of Freeze-Concentrated Solution Confined in Micro/Nanospace Surrounded by Ice

An aqueous solution separates into ice and a freeze-concentrated solution (FCS) when frozen at temperatures above the eutectic point. The FCS acts as important reaction media in natural environment and industrial processes. The viscosities of the FCS in frozen glycerol/water solutions are evaluated by two spectrometric methods with different principles: (1) the reaction rate of the diffusion-controlled emission quenching and (2) fluorescence correlation spectroscopy. Thermodynamics indicates that the concentration of glycerol in the FCS is constant at a constant temperature regardless of the glycerol concentration in the original solution before freezing (<i>c</i>_glyⁱⁿⁱ). However, the viscosity of the FCS measured at a given temperature increases with decreasing <i>c</i>_glyⁱⁿⁱ, and this trend becomes more pronounced with decreasing measurement temperature. Further, the viscosity of the FCS in a rapidly frozen solution is higher than that in a slowly frozen solution. These results suggest that the viscosity of the FCS depends on the size of the space in which the FCS is confined and is enhanced in smaller spaces. This result agrees well with several reports of anomalous phenomena in a microspace confined in ice. These phenomena should originate from the fluctuation of the ice/FCS interface, which is macroscopically stable but microscopically dynamic and undergoes continuous freezing and thawing. Thus, the FCS near the interface has ice-like physicochemical properties and structures, giving higher viscosity than the corresponding bulk solution

Syntheses and Luminescent Properties of 3,5-Diphenylpyrazolato-Bridged Heteropolynuclear Platinum Complexes. The Influence of Chloride Ligands on the Emission Energy Revealed by the Systematic Replacement of Chloride Ligands by 3,5-Dimethylpyrazolate

Heteropolynuclear Pt^II complexes with 3,5-diphenylpyrazolate [Pt₂Ag₄(μ-Cl)₂(μ-Ph₂pz)₆] (<b>3</b>), [Pt₂Ag₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (<b>4</b>), [Pt₂Cu₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (<b>5</b>), [Pt₂Ag₄(μ-Cl)­(μ-Me₂pz)­(μ-Ph₂pz)₆] (<b>7</b>), and [Pt₂Ag₄(μ-Me₂pz)₂(μ-Ph₂pz)₆] (<b>8</b>) have been prepared and structurally characterized. These complexes are luminescent except for <b>5</b> in the solid state at an ambient temperature with emissions of red-orange (<b>3</b>), orange (<b>4</b>), yellow-orange (<b>7</b>), and green (<b>8</b>) light, respectively. Systematic red shift of the emission energies with the number of chloride ligands was observed for <b>3</b>, <b>7</b>, and <b>8</b>. DFT calculations indicate that the highest occupied molecular orbital (HOMO) as well as HOMO-1 of the heterohexanuclear complexes, <b>3</b>, <b>7</b>, and <b>8</b>, having Pt₂Ag₄ core, mainly consist of dδ orbital of Pt^II and π orbitals of Ph₂pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase combination of 6p of two Pt^II centers and 5p of four Ag^I centers. It is likely that the emissions of <b>3</b>, <b>7</b>, and <b>8</b> are attributed to emissive states derived from the Pt₂(d)/π → Pt₂Ag₄ transitions, the emission energy of which depends on the ratio of chloride ligands to pyrazolate ligands

Syntheses and Luminescent Properties of 3,5-Diphenylpyrazolato-Bridged Heteropolynuclear Platinum Complexes. The Influence of Chloride Ligands on the Emission Energy Revealed by the Systematic Replacement of Chloride Ligands by 3,5-Dimethylpyrazolate

Heteropolynuclear Pt^II complexes with 3,5-diphenylpyrazolate [Pt₂Ag₄(μ-Cl)₂(μ-Ph₂pz)₆] (<b>3</b>), [Pt₂Ag₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (<b>4</b>), [Pt₂Cu₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (<b>5</b>), [Pt₂Ag₄(μ-Cl)­(μ-Me₂pz)­(μ-Ph₂pz)₆] (<b>7</b>), and [Pt₂Ag₄(μ-Me₂pz)₂(μ-Ph₂pz)₆] (<b>8</b>) have been prepared and structurally characterized. These complexes are luminescent except for <b>5</b> in the solid state at an ambient temperature with emissions of red-orange (<b>3</b>), orange (<b>4</b>), yellow-orange (<b>7</b>), and green (<b>8</b>) light, respectively. Systematic red shift of the emission energies with the number of chloride ligands was observed for <b>3</b>, <b>7</b>, and <b>8</b>. DFT calculations indicate that the highest occupied molecular orbital (HOMO) as well as HOMO-1 of the heterohexanuclear complexes, <b>3</b>, <b>7</b>, and <b>8</b>, having Pt₂Ag₄ core, mainly consist of dδ orbital of Pt^II and π orbitals of Ph₂pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase combination of 6p of two Pt^II centers and 5p of four Ag^I centers. It is likely that the emissions of <b>3</b>, <b>7</b>, and <b>8</b> are attributed to emissive states derived from the Pt₂(d)/π → Pt₂Ag₄ transitions, the emission energy of which depends on the ratio of chloride ligands to pyrazolate ligands