Visible Light Production of Hydrogen by Ablated Graphene: Water Splitting or Carbon Gasification?

Reduced graphene oxide modified by pulsed laser ablation causes water splitting under visible light illumination (532 nm). When the light source is a pulsed laser, water splitting is accompanied by carbon gasification (CO formation); however, conventional (LED) light sources produce water splitting exclusively.

Stabilizing the Performance of High-Capacity Sulfur Composite Electrodes by a New Gel Polymer Electrolyte Configuration.

Increased pollution and the resulting increase in global warming are drawing attention to boosting the use of renewable energy sources such as solar or wind. However, the production of energy from most renewable sources is intermittent and thus relies on the availability of electrical energy-storage systems with high capacity and at competitive cost. Lithium-sulfur batteries are among the most promising technologies in this respect due to a very high theoretical energy density (1675 mAh g-1 ) and that the active material, sulfur, is abundant and inexpensive. However, a so far limited practical energy density, life time, and the scaleup of materials and production processes prevent their introduction into commercial applications. In this work, we report on a simple strategy to address these issues by using a new gel polymer electrolyte (GPE) that enables stable performance close to the theoretical capacity of a low cost sulfur-carbon composite with high loading of active material, that is, 70 % sulfur. We show that the GPE prevents sulfur dissolution and reduces migration of polysulfide species to the anode. This functional mechanism of the GPE membranes is revealed by investigating both its morphology and the Li-anode/GPE interface at various states of discharge/charge using Raman spectroscopy.

A Gel-Polymer Sn-C/LiMn0.5Fe0.5PO4 Battery Using a Fluorine-Free Salt.

Safety and environmental issues, because of the contemporary use of common liquid electrolytes, fluorinated salts, and LiCoO2-based cathodes in commercial Li-ion batteries, might be efficiently mitigated by employing alternative gel-polymer battery configurations and new electrode materials. Herein we study a lithium-ion polymer cell formed by combining a LiMn0.5Fe0.5PO4 olivine cathode, prepared by simple solvothermal pathway, a nanostructured Sn-C anode, and a LiBOB-containing PVdF-based gel electrolyte. The polymer electrolyte, here analyzed in terms of electrochemical stability by impedance spectroscopy (EIS) and voltammetry, reveals full compatibility for cell application. The LiBOB electrolyte salt and the electrochemically delithiaded Mn0.5Fe0.5PO4 have a higher thermal stability compared to conventional LiPF6 and Li0.5CoO2, as confirmed by thermogravimetric analysis (TGA) and by galvanostatic cycling at high temperature. LiMn0.5Fe0.5PO4 and Sn-C, showing in lithium half-cell a capacity of about 120 and 350 mAh g(-1), respectively, within the gelled electrolyte configuration are combined in a full Li-ion polymer battery delivering a stable capacity of about 110 mAh g(-1), with working voltage ranging from 2.8 to 3.6 V.

Thermoplasmonic ssDNA Dynamic Release from Gold Nanoparticles Examined with Advanced Fluorescence Microscopy.

Plasmon excitation of spherical gold nanoparticles carrying a fluorescent labeled 30 bp dsDNA cargo, with one chain covalently attached through two S-Au bonds to the surface, results in release of the complementary strand as ssDNA that can be examined in situ using high-resolution fluorescence microscopy. The release is dependent on the total energy delivered, but not the rate of delivery, an important property for plasmonic applications in medicine, sensors, and plasmon-induced PCR.

Liposomes as nanoreactors for the photochemical synthesis of gold nanoparticles.

A simple and novel method for the photochemical synthesis of AuNPs in liposomes is described. Gold salt is co-encapsulated with the photoinitiator Irgacure-2959 in POPC liposomes prepared via traditional thin-film hydration technique. UVA irradiation for 15 min results in encapsulated AuNPs of 2.8±1.6 nm in diameter that are primarily dispersed in the aqueous interior of the liposomes.

Photochemical synthesis of biocompatible and antibacterial silver nanoparticles embedded within polyurethane polymers.

In situ light initiated synthesis of silver nanoparticles (AgNP) was employed for AgNP incorporation within the polymeric matrices of medical grade polyurethane. The resulting materials showed improved antibacterial and antibiofilm activity against Pseudomonas aeruginosa with negligible toxicity for human primary skin cells and erythrocytes.

Aspartame-stabilized gold-silver bimetallic biocompatible nanostructures with plasmonic photothermal properties, antibacterial activity, and long-term stability.

Gold-silver core-shell nanoparticles stabilized with a common sweetener, aspartame (AuNP@Ag@Asm), combine the antimicrobial properties of silver with the photoinduced plasmon-mediated photothermal effects of gold. The particles were tested with several bacterial strains, while biocompatibility was verified with human dermal fibroblasts.

Photochemical strategies for the seed-mediated growth of gold and gold-silver nanoparticles.

Gold nanoparticles (AuNP) can be used as seeds for the synthesis of larger AuNP of controllable size with narrow size distribution by photochemical reduction of additional Au(III) using water-soluble benzoins or H(2)O(2) as sources of reducing radicals. Further, beyond simply enlarging the AuNP, it is possible to add a shell of another metal, such as silver, leading to Au/Ag core-shell structures with controllable dimensions for both core and shell. This strategy illustrates the fine spatial and temporal control achievable using clean photochemical techniques without the addition of hard surface ligands often necessary to control the size and structure of gold-silver nanostructures. The mild nature of the surface coverage makes these nanomaterials ideal for further surface modification.

Dual-stage lithography from a light-driven, plasmon-assisted process: a hierarchical approach to subwavelength features.

A hierarchy of lithographic-type imaging generating 3 µm lines incorporating subdiffraction limit features was obtained through a novel two-step reaction process. Photochemically generated ketyl radicals were used to make defined lines of silver nanoparticles. The excitation of nanoparticle surface plasmons was then used to generate highly localized heat that causes polymerization selectively on the surfaces of excited particles. The nylon-6 polymer that is generated serves as a solubility switch used to retain the features on the substrate selectively; various imaging techniques were used to establish the nature of the nylon shells. This work shows that the heat generated by plasmon excitation can be exploited to generate negative-type lithographic features with dimensions well below the diffraction limit.

High-temperature organic reactions at room temperature using plasmon excitation: decomposition of dicumyl peroxide.

Photoexcitation of gold nanoparticles in their plasmon transition around 530 nm provides the means to carry high-energy reactions at room temperature. In the case of dicumyl peroxide (with activation energy of 34.3 kcal/mol) the reaction occurs in less than 1 min under 532 nm laser excitation. The results suggest that the peroxide is exposed to temperatures of ~500 °C for submicrosecond times, and provides a guide as to which type of organic reactions may benefit from plasmon-mediated energy delivery.

Reaction of singlet oxygen with thioanisole in ionic liquid-acetonitrile binary mixtures.

A study of the reaction of thioanisole with singlet oxygen in different ionic liquid-acetonitrile binary mixtures has shown that ILs are able to accelerate the thioanisole sulfoxidation when used as additives. With imidazolium ILs, the maximum efficiency is reached at x(IL) ∼ 0.1-0.2, whereas for the pyrrolidinium IL a plateau is reached. These results are discussed in terms of the ILs' tendency to form ionic aggregates and of differences in sulfoxidation reaction mechanism.

Reaction of singlet oxygen with thioanisole in ionic liquids: a solvent induced mechanistic dichotomy.

A study of the reaction of thioanisole with singlet oxygen in pyrrolidinium- and imidazolium-based ionic liquids has been carried out. In these solvents, thioanisole shows a strongly enhanced reactivity with respect to molecular aprotic solvents, probably due to a stabilization of the persulfoxide intermediate in the ionic medium. Product isotope effects suggest a mechanistic change ongoing from pyrrolidinium to imidazolium solvents.