Delaminated carbon nitride nanosheets
were prepared by high-temperature H2 treatment of bulk
carbon nitride with defects being introduced during this treatment.
Although the defects can act as traps for charge carriers, reducing
photoluminescence lifetime, they also form highly active photocatalytic
sites for hydrogen evolution. The nanostructured materials exhibit
substantially enhanced photocatalytic activity due to a synergistic
effect between delamination, the presence of defects, and associated
band gap changes.
An unprecedented diversity of high-order bromine catenates (anionic polybromides) was generated in a tetraalkylphosphonium-based room temperature ionic liquid system. Raman spectroscopy was used to identify polybromide monoanions ranging from [Br5 ](-) to [Br11 ](-) in the bulk solution, while single-crystal X-ray diffraction identified extended networks of linked [Br11 ](-) units, forming a previously unknown polymeric [Br24 ](2-) dianion. This represents the largest polybromide species identified to date. In combination with recent work, this suggests that other, higher order molecular polybromide ions might be isolated.
The unique properties exhibited by nanoscale materials, coupled with the multitude of chemical surface derivatisation possibilities, enable the rational design of multifunctional nanoscopic devices. Such functional devices offer exciting new opportunities in medical research and much effort is currently invested in the area of "nanomedicine", including: multimodal imaging diagnostic tools, platforms for drug delivery and vectorisation, polyvalent, multicomponent vaccines, and composite devices for "theranostics". Here we will review the surface derivatisation of nanoparticulate oxides of iron and iron@iron-oxide core-shells. They are attractive candidates for MRI-active therapeutic platforms, being potentially less toxic than lanthanide-based materials, and amenable to functionalisation with ligands. However successful grafting of groups onto the surface of iron-based nanoparticles, thus adding functionality whilst preserving their inherent properties, is one of the most difficult challenges for creating truly useful nanodevices from them. Functionalised catechol-derived ligands have enjoyed success as agents for the masking of superparamagnetic iron-oxide particles, often so as to render them biocompatible with medium to long-term colloidal stability in the complex chemical environments of biological milieux. In this perspective, the opportunities and limitations of functionalising the surfaces of iron-oxide nanoparticles, using coatings containing a catechol-derived anchor, are analysed and discussed, including recent advances using dopamine-terminated stabilising ligands. If light-driven ligand to metal charge transfer (LMCT) processes, and pH-dependent ligand desorption, leading to nanoparticle degradation under physiologically relevant conditions can be suppressed, colloidal stability of samples can be maintained and toxicity ascribed to degradation products avoided. Modulation of the redox behaviour of iron catecholate systems through the introduction of an electron-withdrawing substituent to the aromatic π-system of the catechol is a promising approach towards achieving these goals.
We report a reinterpretation of the reduction of 4-nitrophenol catalyzed by silver nanoparticles. Mass spectrometry and ultraviolet−visible light spectroscopy measurements support the existence of 4-nitrosophenol as a stable reaction intermediate. We propose that dissolved oxygen is consumed, both by oxidizing 4nitrosophenol (an intermediate) and reoxidizing the reduced catalyst surface, resulting in the commonly observed "induction period" in the reaction kinetics. Upon complete consumption of dissolved oxygen, subsequent reduction to 4-aminophenol can occur. A complete kinetic analysis including modeling is presented, conceptually fitting data from recent reports in the literature, as well as fitting data from our own experiments.
The redox-transmetalation ligand-exchange reaction of ytterbium or calcium metal with 2 equiv of pentaphenylcyclopentadiene (C5Ph5H) and 1 equiv of HgPh2 in thf afforded the solvent-separated ion pairs (SSIPs) [M(thf)6][C5Ph5]2 (M = Yb, Ca), which were characterized by single-crystal X-ray analyses. Addition of toluene to the isolated SSIPs led to the precipitation of the homoleptic sandwich complexes [M(C5Ph5)2] (M = Yb, Ca). In the reaction of barium metal with C5Ph5H and HgPh2 the corresponding SSIP was observed in situ, and only the sandwich complex [Ba(C5Ph5)2] could be isolated. Single-crystal X-ray analyses were carried out for [M(C5Ph5)2] (M = Yb, Ba), which confirmed the highly symmetric structure of these complexes with two parallel cyclopentadienyl ligands. Oxidation and metal-ligand exchange reactions were investigated for the divalent ytterbium complexes.
Ionic liquids have been proposed as functional replacements for harmful and hazardous volatile organic solvents. However, limiting their use in this way does not fully explore the potential chemical benefits of their solvating properties, which stem from the inherent differences between ionic liquids and single molecule solvents. These differences can be used to facilitate alternative and improved reaction outcomes. This review will highlight a range of examples, involving materials preparation and organic synthesis, in which substantial progress towards the understanding and targeted application of ionic liquids is demonstrated. In addition, a number of studies will be cited where unanticipated outcomes have been observed and the relationships between these outcomes and ionic liquid structural effects will be analysed, casting new light onto these studies.
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