Similar to its popular older cousins the fullerene, the carbon nanotube, and graphene, the latest form of nanocarbon, the carbon nanodot, is inspiring intensive research efforts in its own right. These surface-passivated carbonaceous quantum dots, so-called C-dots, combine several favorable attributes of traditional semiconductor-based quantum dots (namely, size- and wavelength-dependent luminescence emission, resistance to photobleaching, ease of bioconjugation) without incurring the burden of intrinsic toxicity or elemental scarcity and without the need for stringent, intricate, tedious, costly, or inefficient preparation steps. C-dots can be produced inexpensively and on a large scale (frequently using a one-step pathway and potentially from biomass waste-derived sources) by many approaches, ranging from simple candle burning to in situ dehydration reactions to laser ablation methods. In this Review, we summarize recent advances in the synthesis and characterization of C-dots. We also speculate on their future and discuss potential developments for their use in energy conversion/storage, bioimaging, drug delivery, sensors, diagnostics, and composites.

Ionic liquids are being employed in almost all areas of chemistry and materials, yet there are inherent issues which arise if the utmost care is not taken in the preparation and purification of these materials. They are not easily synthesized and purified using the existing methods. We describe a reliable method for producing large quantities of high quality ionic liquids. Additionally, we show that imidazoliums are not 'special' due to their 'inherently fluorescent' nature, that spectroscopically clean imidazoliums are attainable, and most classes of ionic liquids do exhibit fluorescent backgrounds when extreme care is not taken during their synthesis and purification.

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Within the last decade, ionic liquids have come to the fore as environmentally-responsible designer solvents. But what are ionic liquids and what can they offer the analytical scientist? This article addresses these questions and chronicles recent progress made in the application of ionic liquids toward analytical problem-solving. While further progress is required before ionic liquids become mainstream analytical solvents, results to date commend their use in various modes of chemical analysis. It is our aim that the findings reported herein draw other researchers into this area and encourage the increased application of ionic liquids in this manner.

We report on the local microenvironment that surrounds three fluorescent solutes (i.e., the cybotactic region) when they are dissolved in a 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) roomtemperature ionic liquid as a function of temperature and added CO 2 (T ) 308 K; P ) 0-150 bar). In dry [bmim][PF 6 ] at 293 K, the cybotactic region exhibits a dielectric constant and refractive index of 11.4 ( 1.0 and 1.523 ( 0.025, respectively. The activation energy that describes the [bmim][PF 6 ] viscous flow is 38.4 ( 0.9 kJ mol -1 . The activation energy for solute rotational reorientation in [bmim][PF 6 ] is equivalent to the activation energy for [bmim][PF 6 ] viscous flow, indicating that solute rotational dynamics are correlated entirely with the [bmim][PF 6 ] dynamics. There is nanosecond dipolar relaxation surrounding a solute dissolved in dry [bmim][PF 6 ] at 293 K. Even though CO 2 is highly soluble in [bmim][PF 6 ] (CO 2 mole fraction ) 0.6 at 313 K and 68 bar), addition of up to 150 bar CO 2 to [bmim][PF 6 ] at 308 K causes the solute's cybotactic region dipolarity to decrease by less than 15%. At a fixed temperature (308 K), we observe a 5-fold decrease in the apparent [bmim][PF 6 ] bulk viscosity between 0 and 150 bar CO 2 .

Using the single tryptophan residue in the sweet protein monellin as a spectroscopic handle, we show the extreme thermodynamic stabilization offered by an ionic liquid; T(un) approximately 105 degrees C in [C4mpy][Tf2N] compared to 40 degrees C in bulk water.

Task-specific ternary deep eutectic solvent (DES) systems comprising choline chloride, glycerol, and one of three different superbases were investigated for their ability to capture and release carbon dioxide on demand. The highest-performing systems were found to capture CO2 at a capacity of ∼10% by weight, equivalent to 2.3–2.4 mmol of CO2 captured per gram of DES sorbent. Of the superbases studied, 1,5-diazabicyclo[4.3.0]-non-5-ene (DBN) gave the best overall performance in terms of CO2 capture capacity, facility of release, and low sorbent cost. Interestingly, we found that only a fraction of the theoretical CO2 capture potential of the system was utilized, offering potential pathways forward for further design and optimization of superbase-derived DES systems for further improved reversible CO2 sequestration. Finally, the shear rate-dependent viscosities indicate non-Newtonian behavior which, when coupled to the competitive CO2 capture performance of these task-specific DESs despite a 1 to 2 orders of magnitude higher viscosity, suggest that the Stokes–Einstein–Debye relation may not be a valid predictor of performance for these structurally and dynamically complex fluids.

We report on the picosecond time-resolved fluorescence of 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]-[PF 6 ]) at 298 K as a function of solubilized water in the [bmim][PF 6 ] phase. The observed solvent relaxation dynamics can be described by three components with apparent relaxation times that occur over a large time regime (<15 ps to >10 ns). The average relaxation dynamics become faster as the water concentration in the [bmim][PF 6 ] phase increases. Libration and vibration, ion ballistic motion, ion local basin exploration, and ion basin hopping, ion diffusion, and/or the ultrafast relaxation from water (or other small molecules/impurities) are suggested as possible reasons for the yet unquantified sub-15-ps dynamics. The sub-nanosecond dynamics are consistent with [PF 6 ] anion relaxation. This process was found to be water-dependent, slowing as the amount of solubilized water in the [bmim][PF 6 ] phase increased. We speculate that this slowing arises from the formation of 1:2 H-bonded [PF 6 ]‚‚‚HOH‚‚‚[PF 6 ] complexes. The nanosecond dynamics are consistent with the cation, decreasing slightly with an increase in the amount of solubilized water. We suggest that the decrease in this relaxation time arises from a decrease in the bulk viscosity on adding water.