We report on the development of a facile, one-pot synthesis of single-crystalline magnetite (Fe3O4) nanoparticles (NPs) based on the thermal decomposition of the nontoxic iron precursor iron(III)acetylacetonate within the ionic liquid trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P6,6,6,14][Tf2N]) using 1,2-hexadecanediol as a polyol reducing agent in an “iono-polyol” process. In this expedient approach, the [P6,6,6,14][Tf2N] acts both as a low-volatility, thermostable solvent and as the colloid-stabilizing agent, eliminating the requirement for additional surface-capping agents. Performing the synthesis at 300 or 350 °C yielded quasi-spherical, monodispersed Fe3O4 NPs with a mean size of 14 nm. Evidence from thermogravimetry, X-ray fluorescence, and infrared analysis is consistent with nanocrystal coverage by a partial bilayer of [P6,6,6,14][Tf2N], accounting for the excellent dispersibility of the Fe3O4 NPs in solvents such as hexane, toluene, and methylene chloride. Time-dependent thermogravimetric analysis reveals that [P6,6,6,14][Tf2N] is transiently stable at 300 °C for 30 min (sufficient for nanocrystal formation) but rapidly degrades at 350 °C or higher. By employing a reaction temperature of 300 °C, the [P6,6,6,14][Tf2N] can be recycled and reused multiple times for the subsequent preparation of Fe3O4 NPs with no ill effects in terms of particle size, uniformity, or agglomeration. Finally, we demonstrate that the Fe3O4 NPs can be dispersed into [P6,6,6,14][Tf2N] as a solventless carrier fluid to produce an “iono-ferrofluid” responsive to an external magnetic field.

The synthesis, characterization, and fluorescence spectroscopy of E(C16H9)3 complexes (E = P, As, Sb, and Bi), as well as OP(C16H9)3, OAs(C16H9)3, and SP(C16H9)3, is reported. These compounds exhibit fluorescence quantum yields that span two orders of magnitude, from well below 1% to ca. 14%.

Since their discovery over a decade ago, fluorescent carbon nanodots, or C-dots, have seen a drastic rise in various synthetic approaches as well as widespread applicability across diverse research fields. More recently, carbon nanodots have shown particular promise in a wide range of photovoltaic devices as inexpensive sensitizer candidates and as functional dopants within photoactive materials, electrolytes, and counter electrodes. While still in their infancy, carbon nanodot-incorporated devices already show encouraging enhancements in device performance, although due to current limiting factors such as poor charge collection and photocurrent generation, there is still much room for further discovery and improvement. Herein, we provide a detailed overview of the current state-of-the-art carbon nanodot-incorporated devices (and their limitations) and suggest some paths forward in the hopes of sparking new ideas on how to better synthesize and purify these materials, which will ultimately lead to a more thorough understanding of their properties so that further performance enhancements within carbon nanodot-incorporated solar-energy harvesting systems may be realized.

Layered transition metal dichalcogenides (TMDs) have attracted increased attention due to their enhanced hydrogen evolution reaction (HER) performance. More specifically, ternary TMD nanohybrids, such as MoS2(1–x)Se2x or bimetallic sulfides, have arisen as promising electrocatalysts compared to MoS2 and MoSe2 due to their electronic, morphologic, and size tunabilities. Herein, we report the successful synthesis of few-layered MoS2/rGO, SnS2/rGO, and (MoS2)x(SnO2)1–x/rGO nanohybrids anchored on reduced graphene oxide (rGO) through a facile hydrothermal reaction in the presence of ionic liquids as stabilizing, delayering agents. Spectroscopic and microscopic techniques (electron microscopy, X-ray diffraction, Raman spectroscopy, neutron activation analysis, and UV–vis spectrophotometry) are used to validate the hierarchical properties, phase identity, and the smooth compositional tunability of the (MoS2)x(SnO2)1–x/rGO nanohybrids. Linear sweep voltammetry measurements reveal that incorporation of Sn into the ternary nanohybrids (as a discrete SnO2 phase) greatly reduces the overpotential by 90–130 mV relative to the MoS2 electrocatalyst. Significantly, the (MoS2)0.6(SnO2)0.4/rGO nanohybrid displays superior catalytic performance over MoS2 alone, exhibiting a low overpotential (η10) of 263 ± 5 mV and a small Tafel slope of 50.8 mV dec–1. The hybrid catalyst shows high stability for the HER in acidic solutions, with negligible activity loss after 1000 cycles. The hierarchical structures and large surface areas possessing exposed, active edge sites make few-layered (MoS2)x(SnO2)1–x/rGO nanohybrids promising nonprecious metal electrocatalysts for the HER.Keywords: electrocatalysis; hydrogen evolution reaction; ionic liquids; reduced graphene oxide; transition metal dichalcogenides;

It is widely held that the melanosome is an exemplar of the absorption features of melanin-containing cells, which are assumed to be uniform in both size and optical characteristics. In recent years, however, it has become increasingly apparent that this is a strikingly poor assumption. Indeed, melanin extracted from natural sources and synthetic melanin both show wide variability in their degree of polymerization (molecular weight) and spectroscopic characteristics. In the current study, imaging spectrophotometry performed on individual cells of immortalized melanin-producing cell lines revealed broad distributions in their sizes: 9.5–36.2 μm for Hs936 human melanoma cells, 10.9–20.8 μm for T47D human breast cancer cells, 5.3–43.5 μm for B16F1 mouse melanoma cells, and 6.4–54.2 μm for B16F10 mouse melanoma cells. The color appearance (from translucent to yellow to nearly black), absorption spectrum, and absorption (extinction) coefficient at 532 nm (28.73 to 364.75, 0.01 to 40.17, 5.88 to 977.19, and 0.01 to 1120 cm−1 for Hs936, T47D, B16F1, and B16F10 cells, respectively) of an individual cell also vary widely and cannot be adequately described by a ‘typical’ value. In comparison, human red blood cells are much more uniform in size (6.0–8.1 μm diameter; 1.9–3.2 μm thickness), although they too show a broad range of absorptivities, with extinction coefficients in the range of 65 to 370 cm−1 when measured at 532 nm. To further evaluate the impact of these findings on photoacoustic bioanalysis, we performed simulations of the generation of photoacoustic signals expected from these cell types. These simulations revealed that their variation in optical features exerts a pronounced effect on the amplitude and shape of the photoacoustic signals generated from these cell types. Finally, we compared the photoacoustic signal generated from these cells under ideal conditions (i.e., a single cell in isolation) versus a heterogeneous real-world sample, demonstrating that when a single or few cancer cells are present within a blood droplet, the photoacoustic signal is indistinguishable from that measured from blood alone. These outcomes have important ramifications for the early photoacoustic detection of cancer cells and circulating tumor emboli, while pointing to the potential of single-cell imaging spectrophotometry to assess heterogeneity within cell populations in more quantitative terms.

We present a snapshot of the current status of understanding structure, dynamics, and molecular interactions within deep eutectic solvents (DESs) gained from a computational perspective. The simulations reported thus far have been largely aimed at unravelling the relationship between the molecular features within a DES and the depressed melting temperature at its eutectic composition. Computational efforts consistently reveal that the addition of hydrogen bond donors significantly disrupts long-range ordering of the cation–anion arrangement in choline chloride, resulting in significant moderation of the interaction energies between the components of the DES. These studies paint a picture of DES formation being accompanied by hydrogen-bond directed charge transfer processes yielding transient cage-like formation and nanoscale ordering entailing segregation of the ionic and molecular domains. Computational insights further uncover how unique solvation features present within DESs may lead to enhanced biomolecular (e.g., protein, nucleic acid, polysaccharide) stability and/or activity while also offering advantages as environmentally-responsible gas sorbents.

We have demonstrated an easy, economic, one-step synthetic route to water-soluble fluorescent carbon dots derived from the thermal upcycling of urine. These “pee-dots” (PDs), which primarily comprise hydrophile-decorated amorphous carbon, exhibit bright, stable, excitation wavelength dependent fluorescence in aqueous solution and are shown to be useful nanoscale labels in cell imaging applications. Cytotoxicity studies demonstrate that these PDs are benign toward model cell lines, even at concentrations as high as 500 μg mL−1. Notably, this approach converts an otherwise useless, negatively-valued byproduct of human life into a value-added nanoscale product while simultaneously pasteurizing the waste stream. The reported PDs proved to be effective nanoprobes for the fluorescence-based detection of heavy metal ions of environmental concern, particularly Cu2+ and Hg2+ ions which were found to be strong quenchers of their fluorescence. Interestingly, the optical properties and nanoscale dimensions of the PDs are a direct reflection of the diet (e.g., vitamin C or asparagus (sulfur) fortified) followed by the urine donor.

We describe a straightforward tactic to boost the inherently low peroxidase-like activity of the heme-protein equine cytochrome c (cyt c) following its electrostatic assembly onto the carbon nanodot surface. This represents the first time that carbon nanodot interaction has been demonstrated to switch a protein into a high-performance enzyme for speeding up a reaction it was not evolved to catalyze. The dramatic enhancement in peroxidase-like activity stems in part from favorable local perturbations within the heme microenvironment of cyt c which are influenced by the chemistry presented at the carbon dot surface. That is, the observed peroxidase activity is clearly moderated by the choice of molecular precursors used to prepare the carbon dots, a choice which ultimately determines the surface charges present. An exceptional catalytic efficiency (kcat/KM) of 8.04 (±1.74) × 107 M−1 s−1 was determined for carbon dot/cyt c co-assemblies, close to the theoretical diffusion-controlled limit. Notably, the activity of the carbon dot/cyt c assembly can be switched off simply by increasing the ionic strength which results in dissociation into non-catalytic components.

Making direct, intimate connections between individual nano-objects is crucial for the fabrication of hierarchical and multifunctional nanostructures with inherited properties superior to those arising from an individual entity. In this review, we introduce and discuss the significance of cold welding, an intriguing ambient condition route for making connections between nanoparticles, thin metal films, or nanowires. Factors such as the surface chemistry (activation, passivation) and the chemical nature of the material strongly influence the process of cold welding. Irrespective of the parent particle sizes and morphologies, the process is driven by a need to minimize the surface chemical potential. It is evident from recent studies that rapid atomic rearrangements, surface diffusion, and atomic hopping are the fundamental modes for atomic transport on nanoscale metal surfaces. In this fashion, highly curved surfaces generally become filled in order to minimize the surface curvature, satisfying the criterion for reduced free energy. It is possible to generate defect-free single-crystalline nanomaterials via three-dimensional (3-D) rotation or atom-by-atom orientation of the crystallographic planes at the inter-particle boundary, a novel remodelling process characteristic to cold welding. Cold welding has been successfully applied in the template-assisted synthesis of diverse and interesting morphologies, including nanogratings, nanotubules, and multipods, as well as the transfer of metal nano-objects onto metallic surfaces. Even though there has been significant progress in making nano-junctions, it remains largely limited to template-assisted synthesis. There is immense scope, however, for the improvement and expansion of the cold welding phenomenon toward site-specific coalescence, precise morphological and dimensional control of nano-junctions, and the construction of defect-free heterometallic junctions, among other areas. Although we acquaint the reader with the ground-breaking examples of cold welding reported by the few pioneers in the area, numerous examples discussed in this review are “found” examples which, in the original publication are not actually referred to as cold welding, although in hindsight they plainly should be categorized as such and they make important contributions to our understanding of the phenomenon. Given the infancy of the concept of cold welding, we anticipate that this review will serve as a call to arms, bringing broader awareness to this exciting and virtually-unexploited area of controlled nanoscale synthesis. With proven utility in the construction of diverse nanoassemblies and morphologically-distinct nanomaterials required for next-generation plasmonic, sensing, and catalytic efforts, cold welding surely has a role to play in the genesis of shape-controlled nanostructure and deserves wider attention.

We present a straightforward, environmentally-benign, one-pot photochemical route to generate alloyed AgAu bimetallic nanoparticle decorated aminoclays in water at room temperature. The protocol uses no reducing agent (e.g., NaBH4) nor is photocatalyst required. These hybrid materials show excellent promise as dual catalysts/antibacterial agents.

We report on a simple and green route toward monometallic (Au or Ag) and alloyed bimetallic AuAg nanoparticles using citric acid-derived carbon nanodots (C-dots) as the reducing and stabilizing agent. Simple variation in the initial C-dot:metal ratio yields a smoothly tunable surface plasmon resonance and the resulting nanomaterials show excellent catalytic activity for 4-nitrophenol reduction which is fully preserved following 5 months of storage. The Au@C-dot catalyst further demonstrated intrinsic peroxidase activity.

Research on graphene—monolayers of carbon atoms arranged in a honeycomb lattice—is proceeding at a relentless pace as scientists of both experimental and theoretical bents seek to explore and exploit its superlative attributes, including giant intrinsic charge mobility, record-setting thermal conductivity, and high fracture strength and Young's modulus. Of course, fully exploiting the remarkable properties of graphene requires reliable, large-scale production methods which are non-oxidative and introduce minimal defects, criteria not fully satisfied by current approaches. A major advance in this direction is ionic liquid-assisted exfoliation and dispersion of graphite, leading to the isolation of few- and single-layered graphene sheets with yields two orders of magnitude higher than the earlier liquid-assisted exfoliation approaches using surface energy-matched solvents such as N-methyl-2-pyrrolidone (NMP). In this Minireview, we discuss the emerging use of ionic liquids for the practical exfoliation, dispersion, and modification of graphene nanosheets. These developments lay the foundation for strategies seeking to overcome the many challenges faced by current liquid-phase exfoliation approaches. Early computational and experimental results clearly indicate that these same approaches can readily be extended to inorganic graphene analogues (e.g., BN, MoX2 (X = S, Se, Te), WS2, TaSe2, NbSe2, NiTe2, and Bi2Te3) as well.

From macroscopic measurements of deep eutectic solvents such as glyceline (1:2 molar ratio of choline chloride to glycerol), the long-range translational diffusion of the larger cation (choline) is known to be slower compared to that of the smaller hydrogen bond donor (glycerol). However, when the diffusion dynamics are analyzed on the subnanometer length scale, we find that the displacements associated with the localized diffusive motions are actually larger for choline. This counterintuitive diffusive behavior can be understood as follows. The localized diffusive motions confined in the transient cage of neighbor particles, which precede the cage-breaking long-range diffusion jumps, are more spatially constrained for glycerol than for choline because of the stronger hydrogen bonds the former makes with chloride anions. The implications of such differential localized mobility of the constituents should be especially important for applications where deep eutectic solvents are confined on the nanometer length scale and their long-range translational diffusion is strongly inhibited (e.g., within microporous media).

DESs offer tremendous opportunities and open intriguing perspectives for generating sophisticated nanostructures within an anhydrous or low-water medium. We conclude this Account by offering our thoughts on the evolution of the field, pointing to areas of clear and compelling utility which will surely see fruition in the coming years. Finally, we highlight a few hurdles (e.g., need for a universal nomenclature, absence of water-immiscible, oriented-phase, and low-viscosity DESs) which, once navigated, will hasten progress in this area.

We explore the analytical performance and limitations of optically monitoring aqueous-phase temperature using protein-protected gold nanoclusters (AuNCs). Although not reported elsewhere, we find that these bio-passivated AuNCs show pronounced hysteresis upon thermal cycling. This unwanted behaviour can be eliminated by several strategies, including sol–gel coating and thermal denaturation of the biomolecular template, introducing protein-templated AuNC probes as viable nanothermometers.

An emerging thrust in the design of advanced materials is nanoscale functional materials possessing multiple capabilities, such as those possessing a core–shell architecture. Nanoparticles comprising a dielectric core (e.g., silica, polystyrene) and a gold shell are particularly attractive due to the desirable optical (plasmonic) and biocompatibility characteristics of gold. While these materials are bio-inert, they generally present limited tunability. In this regard, a core composed of a solid-state ionic liquid represents an interesting and unexplored alternative for generating unique core–shell architectures. In recent years, we have developed an emergent class of morphology-controlled tailored organic salt particles, so-called GUMBOS (group of materials based on organic salts). GUMBOS are reminiscent of traditional ionic liquids with the important distinction that they possess elevated melting points (generally, from 100 to 250 °C), making possible the fabrication of ambient-stable nanoscale salts of various sizes, compositions, and morphologies by means of a variety of thermal, sonochemical, colloidal, or hard-template synthetic routes. In this work, we advance our recent examination of GUMBOS to demonstrate proof of concept for their use in elaborating novel plasmonic nanostructures by using a seed-mediated growth to generate gold shells atop nanoscale quasi-spherical GUMBOS as well as uni-dimensional GUMBOS nanorods. We present here our general strategy for preparing gold-shelled nanoGUMBOS, alongside systematic monitoring of the evolution of the gold-coating process. We also report on a preliminary investigation of the catalytic properties of the near-infrared absorbing gold-shelled nanorod GUMBOS in the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride.

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.Keywords: 1,5-Diazabicyclo[4.3.0]-non-5-ene (DBN); Carbon dioxide capture; CO2 sequestration; Deep eutectic solvent; DES;

The pyrogallol[4]arenes have been shown to act as versatile host macrocycles for a wide variety of guest molecules, including the imidazolium-based cations of ionic liquids. This report demonstrates the use of alkyl-linked geminal dications in the design of bilayers comprising dimeric host–guest complexes. The pivotal role of solvent choice in controlling the resultant solid-state structure is particularly highlighted. The synthesis and single-crystal X-ray diffraction structures of two dimeric host–guest cocrystals generated by the use of different solvents while employing identical host and guest species are presented to illustrate this point. In one solvent, a “Pac-man”-type dimeric host–guest complex is assembled into bilayer galleries. With a switch to an alternate crystallization solvent, a bilayer-type structure in which each layer is composed of alternating complexes of a capsule and two “offset dimers” is instead constructed.

The host–guest complexes of seven unique cocrystals containing pyrogallol[4]arenes and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate are fully described. The investigation of these cocrystals is directed at expanding the control of the solid-state structures of these unique host–guest assemblies. The effects of varying conditions such as solvent choice and aliphatic tail length appended on the host macrocycle are explored and shed new light on the resultant supramolecular structures.

Deep eutectic solvents (DESs) have shown tremendous promise as green solvents with low toxicity and cost. Understanding molecular aggregation processes within DESs will not only enhance the application potential of these solvents but also help alleviate some of the limitations associated with them. Among DESs, those comprising choline chloride and appropriate hydrogen-bond donors are inexpensive and easy to prepare. On the basis of fluorescence probe, electrical conductivity, and surface tension experiments, we present the first clear lines of evidence for self-aggregation of an anionic surfactant within a DES containing a small fraction of water. Namely, well-defined assemblies of sodium dodecyl sulfate (SDS) apparently form in the archetype DES Reline comprising a 1:2 molar mixture of choline chloride and urea. Significant enhancement in the solubility of organic solvents that are otherwise not miscible in choline chloride-based DESs is achieved within Reline in the presence of SDS. The remarkably improved solubility of cyclohexane within SDS-added Reline is attributed to the presence of spontaneously formed cyclohexane-in-Reline microemulsions by SDS under ambient conditions. Surface tension, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), density, and dynamic viscosity measurements along with responses from the fluorescence dipolarity and microfluidity probes of pyrene and 1,3-bis(1-pyrenyl)propane are employed to characterize these aggregates. Such water-free oil-in-DES microemulsions are appropriately sized to be considered as a new type of nanoreactor.

The crystal structure of a cocrystal comprising a complex of a bis(imidazolium) ionic liquid hosted by pyrogallol[4]arene (PgC) macrocycles is reported. Introduction of the dicationic species yields complexation by two PgC macrocycles, the resulting bilayer structure formed from alternately arranged dimeric host–guest complexes.

We describe the development of a fluorescent biosensor platform for soluble cholesterol based on bovine serum albumin-stabilized gold nanocluster probes co-dissolved with cholesterol oxidase (ChOx) in a surfactant emulsion system. Selective enzymatic oxidation of cholesterol to cholest-4-en-3-one by ChOx produces stoichiometric amounts of H2O2 by-product, generating a quenching response signaling the presence of cholesterol at clinically relevant levels (LOD ∼12 μM).

The free energies of exfoliation and dispersion for hexagonal boron nitride (h-BN) monolayers from a model h-BN bilayer calculated using adaptive bias force–molecular dynamics (ABF–MD) simulations advocate the use of ionic liquids (ILs) in the liquid exfoliation of h-BN to yield individually stabilized (isolated) nanosheets. These calculations should tantalize experimentalists and open up avenues for exploring the IL exfoliation and dispersion of BN and other layered materials, such as the metal chalcogenides.

Using quantum mechanical calculations performed at the density functional level of theory, the present study explores the binding energetics, orbital energies, and charge transfer behavior accompanying sorption of 12 different ionic liquids (ILs) onto 6 archetypal polyaromatic hydrocarbons (PAHs). The ILs were based on combinations of three different onium cations (i.e., 1-butyl-3-methylimidazolium, 1-butylpyridinium, 1-butyl-1-methylpyrrolidinium) paired with four common anions, that is, bromide, tetrafluoroborate, hexafluorophosphate, and bis(trifluoromethylsulfonyl)imide. In general, the size of the anion as well as interaction of the butyl side chain present on the cation with the paired anion exerted significant influence over the cation ring orientation with respect to the PAH surface. A smaller highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy band gap was observed for pyridinium-based ILs upon adsorption on the PAH surface in comparison to imidazolium and pyrrolidinium analogs, hinting at stronger interactions between PAHs and pyridinium ILs. Of the 12 ILs investigated, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide displays the least favorable free energy of adsorption with PAHs whereas PAH interactions with 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide are the most favored thermodynamically. Charges determined from a Mulliken population analysis were consistent with charge transfer (CT) from the IL to the PAH. On the contrary, charges determined via electrostatic potential using the more reliable grid based analysis method (i.e., CHELPG) suggested the reverse direction of CT from the PAH to the IL. The direction of the CT occurring from the HOMO of the PAH to the LUMO of the IL, as shown by CHELPG analysis, is consistent with the physical location of the orbitals and the negative shift in the Fermi energy level observed for the IL–PAH complex. A more favorable enthalpy of adsorption for ILs onto a PAH is observed with an increase in the size of the PAH considered. The free energy of adsorption, however, does not change significantly with an increase in the PAH surface area. The adsorption of an IL on the PAH surface leads to a small change in the entropy of the adsorbate/adsorbent system. The thermochemistry computed at variable temperature indicates a significant increase in the free energy of adsorption (i.e., a less favorable adsorption) as temperature rises. Additionally, decomposition of the entropic contribution suggests a greater contribution from translational and rotational entropies upon cooling, again consistent with stronger association at lower temperatures. Overall, the thermochemical analyses suggest an entropically driven process of desorption of an IL from the PAH surface, generally leading to fairly weak interactions between ILs and ordinary PAHs under normal laboratory conditions.

We present a new approach for fabricating robust, regenerable antimicrobial coatings containing an ionic liquid (IL) phase incorporating silver nanoparticles (AgNPs) as a reservoir for Ag0/Ag+ species within sol–gel-derived nanocomposite films integrating organosilicate nanoparticles. The IL serves as an ultralow volatility (vacuum-compatible) liquid target, allowing for the direct deposition and dispersion of a high-density AgNP “ionosol” following conventional sputtering techniques. Two like-anion ILs were investigated in this work: methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, [N8881][Tf2N], and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][Tf2N]. Silver ionosols derived from these two ILs were incorporated into silica-based sol–gel films and the resultant antimicrobial activity evaluated against Pseudomonas aeruginosa bacteria. Imaging of the surface morphologies of the as-prepared films established a link between an open macroporous film architecture and the observation of high activity. Nanocomposites based on [N8881][Tf2N] displayed excellent antimicrobial activity against P. aeruginosa over multiple cycles, reducing cell viability by 6 log units within 4 h of contact. Surprisingly, similar films prepared from [emim][Tf2N] presented negligible antimicrobial activity, an observation we attribute to the differing abilities of these IL cations to infiltrate the cell wall, regulating the influx of silver ions to the bacterium’s interior.Keywords: antibacterial; ionic liquid; polymethsilsesquioxane; Pseudomonas aeruginosa; silver nanoparticles; sol−gel;

Modulation in the local viscosity and polarity within a reversible carbamate ionic liquid system forms the basis for the fluorescence excimer-based estimation of CO2. Inherently self-referencing, the photonic response to CO2 recognition shows excellent sensitivity and complete reversibility, making possible a striking visual display discernible to the naked eye.

We report on a cocrystal between C-propyl pyrogallol[4]arene and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate exhibiting a remarkable bilayer topology comprising two unique host–guest complexes resulting from the ionic liquid cation binding in two distinctive orientations relative to the macrocycle.

We report on a new class of highly fluid ionic liquids integrating a cation that resembles an opened imidazolium structure with two distinct anions, bis(trifluoromethylsulfonyl)imide, [Tf2N], and a nitrile-containing anion, [C(CN)3]. These new ionic liquids show exceptional CO2 permeability values in liquid membrane gas separations with results that equal or exceed the Robeson upper bound. Moreover, these ionic liquids offer ideal CO2/N2 selectivities competitive with the best results reported to date, exhibiting values that range from 28 to 45. The nitrile containing ionic liquid displayed the highest ideal CO2/N2 selectivity with a value of 45 which primarily results from a reduction in the nitrogen permeability. In addition to permeability results, CO2 solubilities were also measured for the this new class of ionic liquids with values similar to the popular 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The CO2 solubility results were compared to predicted values obtained using both a modified regular solution theory and the quantum chemical Conductor-like Screening Model for Real Solvents (COSMO-RS) method. Agreement between predicted and measured solubility values is also discussed.Highlights► Novel ionic liquids with structure of ring-opened heterocycle are described. ► The ionic liquids show high CO2 permeability and CO2/N2 selectivity. ► Performance attains and exceeds Robeson limit. ► Regular solution theory and COSMO-RS are used to describe solubility.

Free energies for graphene exfoliation from bilayer graphene using ionic liquids based on various cations paired with the bis(trifluoromethylsulfonyl)imide anion were determined from adaptive bias force–molecular dynamics (ABF–MD) simulation and fall in excellent qualitative agreement with experiment. This method has notable potential as an a priori screening tool for performance based rank order prediction of novel ionic liquids for the dispersion and exfoliation of various nanocarbons and inorganic graphene analogues.

The fascinating and attractive features of ionic liquids (ILs) can be considerably expanded by mixing with suitable cosolvents, opening their versatility beyond the pure materials. We show here that mixtures of the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 2,2,2-trifluoroethanol (TFE) display the intriguing phenomenon of hyperpolarity, examples of which are notably sparse in the literature. From the perspective of the ETN polarity scale and Kamlet–Taft parameters for hydrogen bond acidity (α) and basicity (β), the polarity of this mixture exceeds that of either neat component. Fluorescent molecular probes capable of engaging in hydrogen bonds (e.g., 2-(p-toluidino)naphthalene-6-sulfonate, TNS; 6-propionyl-2-(dimethylamino)naphthalene, PRODAN) also exhibit this curious behavior. The choice of IL anion appears to be essential as hyperpolarity is not observed for mixtures of TFE with ILs containing anions other than hexafluorophosphate. The complex solute–solvent and solvent–solvent interactions present in the [bmim][PF6] + TFE mixture were further elucidated using infrared absorbance, dynamic viscometry, and density measurements. These results are discussed in terms of Coulombic interactions, disruption of TFE multimers, formation of hyperanion preference aggregates, and “free” [bmim]+. It is our intent that these results open the door for computational exploration of related solvent mixtures while inspiring practical questions, such as whether such systems might offer the potential for stabilization of highly charged transition states or ionic clusters during (nano)synthesis.

Ionic liquids display an array of useful and sometimes unconventional, solvent features and have attracted considerable interest in the field of green chemistry for the potential they hold to significantly reduce environmental emissions. Some of these points have a bearing on the chemical reactivity of these systems and have also generated interest in the physical and theoretical aspects of solvation in ionic liquids. This review presents an introduction to the field of ionic liquids, followed by discussion of investigations into the solvation properties of neat ionic liquids or mixed systems including ionic liquids as a major or minor component. The ionic liquid based multicomponent systems discussed are composed of other solvents, other ionic liquids, carbon dioxide, surfactants or surfactant solutions. Although we clearly focus on fluorescence spectroscopy as a tool to illuminate ionic liquid systems, the issues discussed herein are of general relevance to discussions of polarity and solvent effects in ionic liquids. Transient solvation measurements carried out by means of time-resolved fluorescence measurements are particularly powerful for their ability to parameterize the kinetics of the solvation process in ionic liquids and are discussed as well.

We report on the founding member of a unique class of luminescent ionic liquids integrating a photoacidic anion that responds to the presence of both condensed- and gas-phase basicity; the analytical response is ratiometric in nature, visible to the naked eye, and offers fascinating prospects in smart photofluids, liquid logic gates, electronic noses, and sensory inks.

We report on a simple and eco-friendly approach that employs a domestic pressure cooker as an inexpensive hydrothermal reactor for the batch synthesis of water-soluble, photoluminescent nanoscale carbon dots derived from benign and cheap commercial starting materials. The resulting carbon nanodots, which consist primarily of hydrophile-decorated amorphous carbon and boast bright, stable, excitation wavelength-dependent fluorescence, were shown to be viable cellular imaging agents for mice embryonic fibroblast cells, displaying little or no cytotoxicity for carbon dot concentrations up to 0.667 mg/mL. In addition, the carbon dots proved useful as nanoprobes for the fluorescence-based detection of environmentally-relevant heavy metal ions such as Cu2+, displaying detection limits below 6μM, sufficient to determine potable water safety (20μM is the limit for safe drinking water set by the U.S. Environmental Protection Agency). More generally, these results highlight the utility of a household pressure cooker as a cost-effective hydrothermal vessel relevant to nanocarbon synthesis, opening up other possibilities for nanosynthesis, particularly in resource-limited settings, educational venues, and the classroom itself.

We describe a straightforward tactic to boost the inherently low peroxidase-like activity of the heme-protein equine cytochrome c (cyt c) following its electrostatic assembly onto the carbon nanodot surface. This represents the first time that carbon nanodot interaction has been demonstrated to switch a protein into a high-performance enzyme for speeding up a reaction it was not evolved to catalyze. The dramatic enhancement in peroxidase-like activity stems in part from favorable local perturbations within the heme microenvironment of cyt c which are influenced by the chemistry presented at the carbon dot surface. That is, the observed peroxidase activity is clearly moderated by the choice of molecular precursors used to prepare the carbon dots, a choice which ultimately determines the surface charges present. An exceptional catalytic efficiency (kcat/KM) of 8.04 (±1.74) × 107 M−1 s−1 was determined for carbon dot/cyt c co-assemblies, close to the theoretical diffusion-controlled limit. Notably, the activity of the carbon dot/cyt c assembly can be switched off simply by increasing the ionic strength which results in dissociation into non-catalytic components.

We report on a simple and green route toward monometallic (Au or Ag) and alloyed bimetallic AuAg nanoparticles using citric acid-derived carbon nanodots (C-dots) as the reducing and stabilizing agent. Simple variation in the initial C-dot:metal ratio yields a smoothly tunable surface plasmon resonance and the resulting nanomaterials show excellent catalytic activity for 4-nitrophenol reduction which is fully preserved following 5 months of storage. The Au@C-dot catalyst further demonstrated intrinsic peroxidase activity.

Free energies for graphene exfoliation from bilayer graphene using ionic liquids based on various cations paired with the bis(trifluoromethylsulfonyl)imide anion were determined from adaptive bias force–molecular dynamics (ABF–MD) simulation and fall in excellent qualitative agreement with experiment. This method has notable potential as an a priori screening tool for performance based rank order prediction of novel ionic liquids for the dispersion and exfoliation of various nanocarbons and inorganic graphene analogues.

Since their discovery over a decade ago, fluorescent carbon nanodots, or C-dots, have seen a drastic rise in various synthetic approaches as well as widespread applicability across diverse research fields. More recently, carbon nanodots have shown particular promise in a wide range of photovoltaic devices as inexpensive sensitizer candidates and as functional dopants within photoactive materials, electrolytes, and counter electrodes. While still in their infancy, carbon nanodot-incorporated devices already show encouraging enhancements in device performance, although due to current limiting factors such as poor charge collection and photocurrent generation, there is still much room for further discovery and improvement. Herein, we provide a detailed overview of the current state-of-the-art carbon nanodot-incorporated devices (and their limitations) and suggest some paths forward in the hopes of sparking new ideas on how to better synthesize and purify these materials, which will ultimately lead to a more thorough understanding of their properties so that further performance enhancements within carbon nanodot-incorporated solar-energy harvesting systems may be realized.

The crystal structure of a cocrystal comprising a complex of a bis(imidazolium) ionic liquid hosted by pyrogallol[4]arene (PgC) macrocycles is reported. Introduction of the dicationic species yields complexation by two PgC macrocycles, the resulting bilayer structure formed from alternately arranged dimeric host–guest complexes.

We report on the founding member of a unique class of luminescent ionic liquids integrating a photoacidic anion that responds to the presence of both condensed- and gas-phase basicity; the analytical response is ratiometric in nature, visible to the naked eye, and offers fascinating prospects in smart photofluids, liquid logic gates, electronic noses, and sensory inks.

Modulation in the local viscosity and polarity within a reversible carbamate ionic liquid system forms the basis for the fluorescence excimer-based estimation of CO2. Inherently self-referencing, the photonic response to CO2 recognition shows excellent sensitivity and complete reversibility, making possible a striking visual display discernible to the naked eye.

We report on a cocrystal between C-propyl pyrogallol[4]arene and the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate exhibiting a remarkable bilayer topology comprising two unique host–guest complexes resulting from the ionic liquid cation binding in two distinctive orientations relative to the macrocycle.

An emerging thrust in the design of advanced materials is nanoscale functional materials possessing multiple capabilities, such as those possessing a core–shell architecture. Nanoparticles comprising a dielectric core (e.g., silica, polystyrene) and a gold shell are particularly attractive due to the desirable optical (plasmonic) and biocompatibility characteristics of gold. While these materials are bio-inert, they generally present limited tunability. In this regard, a core composed of a solid-state ionic liquid represents an interesting and unexplored alternative for generating unique core–shell architectures. In recent years, we have developed an emergent class of morphology-controlled tailored organic salt particles, so-called GUMBOS (group of materials based on organic salts). GUMBOS are reminiscent of traditional ionic liquids with the important distinction that they possess elevated melting points (generally, from 100 to 250 °C), making possible the fabrication of ambient-stable nanoscale salts of various sizes, compositions, and morphologies by means of a variety of thermal, sonochemical, colloidal, or hard-template synthetic routes. In this work, we advance our recent examination of GUMBOS to demonstrate proof of concept for their use in elaborating novel plasmonic nanostructures by using a seed-mediated growth to generate gold shells atop nanoscale quasi-spherical GUMBOS as well as uni-dimensional GUMBOS nanorods. We present here our general strategy for preparing gold-shelled nanoGUMBOS, alongside systematic monitoring of the evolution of the gold-coating process. We also report on a preliminary investigation of the catalytic properties of the near-infrared absorbing gold-shelled nanorod GUMBOS in the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride.