Organic solar cells have desirable properties, including low cost of materials, high-throughput roll-to-roll production, mechanical flexibility and light weight. However, all top-performance devices are at present processed using halogenated solvents, which are environmentally hazardous and would thus require expensive mitigation to contain the hazards. Attempts to process organic solar cells from non-halogenated solvents lead to inferior performance. Overcoming this hurdle, here we present a hydrocarbon-based processing system that is not only more environmentally friendly but also yields cells with power conversion efficiencies of up to 11.7%. Our processing system incorporates the synergistic effects of a hydrocarbon solvent, a novel additive, a suitable choice of polymer side chain, and strong temperature-dependent aggregation of the donor polymer. Our results not only demonstrate a method of producing active layers of organic solar cells in an environmentally friendly way, but also provide important scientific insights that will facilitate further improvement of the morphology and performance of organic solar cells. The processing of high-performance organic solar cells usually requires environmentally hazardous solvents. Now, hydrocarbon-based processing is shown to achieve relatively high performance in a more environmentally friendly way.

Efficient organic solar cells processed from hydrocarbon solvents

Stratospheric ozone depletion through cat- alytic chemistry involving man-made chlorofluorocar- bons is an area of focus in the study of geophysics and one of the global environmental issues of the twentieth century. This review presents a brief history of the sci- ence of ozone depletion and describes a conceptual framework to explain the key processes involved, with a focus on chemistry. Observations that may be considered as evidence (fingerprints) of ozone depletion due to chlorofluorocarbons are explored, and the related gas phase and surface chemistry is described. Observations of ozone and of chlorine-related trace gases near 40 km provide evidence that gas phase chemistry has indeed currently depleted about 10% of the stratospheric ozone there as predicted, and the vertical and horizontal struc- tures of this depletion are fingerprints for that process. More striking changes are observed each austral spring in Antarctica, where about half of the total ozone col- umn is depleted each September, forming the Antarctic ozone hole. Measurements of large amounts of ClO, a key ozone destruction catalyst, are among the finger- prints showing that human releases of chlorofluorocar- bons are the primary cause of this change. Enhanced ozone depletion in the Antarctic and Arctic regions is linked to heterogeneous chlorine chemistry that oc- curs on the surfaces of polar stratospheric clouds at cold temperatures. Observations also show that some of the same heterogeneous chemistry occurs on the surfaces of particles present at midlatitudes as well, and the abundances of these particles are enhanced following explosive volcanic eruptions. The partition- ing of chlorine between active forms that destroy ozone and inert reservoirs that sequester it is a central part of the framework for our understanding of the 40-km ozone decline, the Antarctic ozone hole, the recent Arctic ozone losses in particularly cold years, and the observation of record midlatitude ozone de- pletion after the major eruption of Mount Pinatubo in the early 1990s. As human use of chlorofluorocarbons continues to decrease, these changes throughout the ozone layer are expected to gradually reverse during the twenty-first century.

https://iri.columbia.edu/~goddard/EESC_W4400/CC/solomon_1999.pdf

Stratospheric ozone depletion: A review of concepts and history

We report that homogeneous colloidal suspensions of chemically modified graphene sheets were readily produced in a wide variety of organic solvent systems. Two different sets of solubility parameters are used to rationalize when stable colloidal suspensions of graphene oxide sheets and, separately, of reduced graphene oxide sheets in a given solvent type are possible and when they are not. As an example of the utility of such colloidal suspensions, “paperlike” materials generated by very simple filtration of the reduced graphene oxide sheets had electrical conductivity values as high as 16 000 S/m.

/pdf/colloidal-suspensions-of-highly-reduced-graphene-oxide-in-a-2qrfwxdmd6.pdf

Colloidal Suspensions of Highly Reduced Graphene Oxide in a Wide Variety of Organic Solvents

and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems.

/pdf/the-potential-risks-of-nanomaterials-a-review-carried-out-t45f9crq14.pdf

The potential risks of nanomaterials: a review carried out for ECETOC

The room temperature solubility of pure C[sub 60] has been determined in 47 solvents. The solubilities cover a wide range, from 0.01 mg/mL in methanol to 50 mg/mL in 1-chloronaphthalene. The solubilities in CS[sub 2], toluene, and hexane, three of the commonly employed solvents, are 7.9, 2.8, and 0.04 mg/mL, respectively. An examination of the solubilities of C[sub 60] as a function of the solvent properties such as index of refraction, dielectric constant, molecular size, Hildebrand solubility parameter, and H-bonding strength reaffirms the century-old principle like dissolves like. No single solvent parameter can uniformly predict the solubility of C[sub 60], but a composite picture of solvents with high solubility for C[sub 60] emerges: large index of refraction, dielectric constant around 4, large molecular volume, Hildebrand solubility parameter equal to 10 cal[sup 1/2] cm[sup [minus]3/2], and tendency to act as a moderate strength nucleophile. 18 refs., 4 figs., 1 tab.

Solubility of fullerene (C60) in a variety of solvents

Single-domain microcrystals of LaC2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La and C are the only elements present. Characteristic interatomic distances of 3.39 and 2.78 angstroms identify the compound inside the nanoparticle cavities as α-LaC2, the phase of LaC2 that is stable at room temperature. Bulk α-LaC2 is metallic and hydrolytic. Observation of crystals of pure encapsulated α-LaC2 that were exposed to air for several days before analysis indicates that the LaC2 is protected from degradation bythe carbon polyhedral shells of the nanoparticles. A high percentage of the carbon nanoparticles have encapsulated LaC2 single crystals. These carbon-coated metal crystals form a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.

https://science.sciencemag.org/content/sci/259/5093/346.full.pdf

Single crystal metals encapsulated in carbon nanoparticles.

A study of synthetic methods of nitration and the mechanisms involved, covering aromatic nitration and aliphatic nitration, as well as its use in the preparation of dyes, pharmaceuticals, plastics, chemical intermediates, high energy materials and the mechanistic aspects of organic chemistry.

Nitration : methods and mechanisms

A new, convenient, inexpensive alternative to iodotrimethylsilane reagent is explored. A mixture of chlorotrimethylsilane/sodium iodide in acetonitrile is found to be a better reagent than iodotrimethylsilane for the cleavage of esters, lactones, carbamates, and ethers. Cleavage of esters and lactones (10 examples) occurred somewhat slower with the present system than with iodotrimethylsilane. On the other hand, ethers (7 examples) cleaved much more readily with the present system. A feasible mechanism is proposed for this disparity. Carbamates (6 examples) also underwent facile cleavage to give the corresponding amines. The general applicability of the method has been shown using various types of substrates. The facile conversion of alcohols to iodides using the present method is also reported. Ccinversion of alcohols to iodides is much faster with chlorotrimethylsilane/sodium iodide than with iodotrimethylsilane, and iodides are formed in excellent yield.

Synthetic methods and reactions. 62. Transformations with chlorotrimethylsilane/sodium iodide, a convenient in situ iodotrimethylsilane reagent

Laboratory studies of heterogeneous reactions important for ozone depletion over Antarctica are reported. The reaction of chlorine nitrate (ClONO2) with H2O and HCl on surfacers that simulate polar stratospheric clouds are studied at temperatures relevant to the Antarctic stratosphere. The gaseous products of the resulting reactions, HOCl, Cl2O, and Cl2, could readily photolyze in the Antarctic spring to produce active chlorine for ozone depletion. Furthermore, the additional formation of condensed-phase HNO3 could serve as a sink for odd nitrogen species that would otherwise scavenge the active chlorine.

Ripudaman Malhotra

Papers

Solubility of fullerene (C60) in a variety of solvents

Single crystal metals encapsulated in carbon nanoparticles.

Nitration : methods and mechanisms

Synthetic methods and reactions. 62. Transformations with chlorotrimethylsilane/sodium iodide, a convenient in situ iodotrimethylsilane reagent

Reaction of chlorine nitrate with hydrogen chloride and water at Antarctic stratospheric temperatures