Technique for modified transantral orbital decompression for improved cosmesis in stable thyroid eye disease

Functional and aesthetic rehabilitation of exophthalmos in stable thyroid eye disease (TED) can be achieved with a variety of surgical approaches. This article illustrates modifications of the classic transantral technique to provide a graded orbital decompression and achieve improved cosmesis. A retrospective chart review was performed of stable TED patients who elected to undergo the modified transantral decompression; illustrative cases are described. This modified transantral orbital decompression allows for graded orbital decompression surgery, adding to the range of treatment options for stable TED patients.

Antibacterial Activity of Nitrogen-Doped Carbon Dots Enhanced by Atomic Dispersion of Copper

Antibiotic resistance is an imminent threat to human health, requiring the development of effective alternate antibacterial agents. One such alternative includes nanoparticle (photo)catalysts that are good at producing reactive oxygen species (ROS). Herein, we report the design and preparation of nitrogen-doped carbon dots functionalized with atomically dispersed copper centers by Cu-N coordination (Cu/NCD) that exhibit apparent antibacterial activity toward Gram-negative Escherichia coli (E. coli) under photoirradiation. The growth of E. coli cells is found to be markedly inhibited by Cu/NCD under 365 nm photoirradiation, whereas no apparent inhibition is observed in the dark or with the copper-free carbon dots alone. This is ascribed to the prolonged photoluminescence lifetime of Cu/NCD that facilitates the separation of photogenerated electron-hole pairs and ROS formation. The addition of tert-butyl alcohol is found to completely diminish the antimicrobial activity, suggesting that hydroxyl radicals are responsible for microbial death. Consistent results are obtained from fluorescence microscopic studies using CellROX green as the probe. Similar bactericidal behaviors are observed with Gram-positive Staphylococcus epidermidis (S. epidermidis). The copper content within the carbon material is optimized at a low loading of 1.09 wt %, reducing the possibility of toxic copper-ion leaching. Results from this study highlight the significance of carbon-based nanocomposites with isolated metal species as potent antimicrobial reagents.

Platinum Oxide Nanoparticles for Electrochemical Hydrogen Evolution: Influence of Platinum Valence State

Electrochemical hydrogen generation is a rising prospect for future renewable energy storage and conversion. Platinum remains a leading choice of catalyst, but because of its high cost and low natural abundance, it is critical to optimize its use. In the present study, platinum oxide nanoparticles of approximately 2 nm in diameter are deposited on carbon nitride (C3N4) nanosheets by thermal refluxing of C3N4 and PtCl₂ or PtCl₄ in water. These nanoparticles exhibit apparent electrocatalytic activity toward the hydrogen evolution reaction (HER) in acid. Interestingly, the HER activity increases with increasing Pt⁴⁺ concentration in the nanoparticles, and the optimized catalyst even outperforms commercial Pt/C, exhibiting an overpotential of only -7.7 mV to reach the current density of 10 mA cm^-2 and a Tafel slope of -26.3 mV dec^-1 . The results from this study suggest that the future design of platinum oxide catalysts should strive to maximize the Pt⁴⁺ sites and minimize the formation of the less active Pt²⁺ species.

Antimicrobial activity of graphene oxide quantum dots: impacts of chemical reduction

Design and engineering of graphene-based functional nanomaterials for effective antimicrobial applications has been attracting extensive interest. In the present study, graphene oxide quantum dots (GOQDs) were prepared by chemical exfoliation of carbon fibers and exhibited apparent antimicrobial activity. Transmission electron microscopic measurements showed that the lateral length ranged from a few tens to a few hundred nanometers. Upon reduction by sodium borohydride, whereas the UV-vis absorption profile remained largely unchanged, steady-state photoluminescence measurements exhibited a marked blue-shift and increase in intensity of the emission, due to (partial) removal of phenanthroline-like structural defects within the carbon skeletons. Consistent results were obtained in Raman and time-resolved photoluminescence measurements. Interestingly, the samples exhibited apparent, but clearly different, antimicrobial activity against Staphylococcus epidermidis cells. In the dark and under photoirradiation (400 nm), the as-produced GOQDs exhibited markedly higher cytotoxicity than the chemically reduced counterparts, likely because of (i) effective removal by NaBH₄ reduction of redox-active phenanthroline-like moieties that interacted with the electron-transport chain of the bacterial cells, and (ii) diminished production of hydroxyl radicals that were potent bactericidal agents after chemical reduction as a result of increased conjugation within the carbon skeletons.

Nanocomposites Based on Ruthenium Nanoparticles Supported on Cobalt and Nitrogen-Codoped Graphene Nanosheets as Bifunctional Catalysts for Electrochemical Water Splitting

Rational design and engineering of high-efficiency electrocatalysts toward overall water splitting is crucial for the development of hydrogen energy technology. Herein, a facile procedure is described for the preparation of effective bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), where ruthenium nanoparticles are supported on graphene nanosheets that are codoped with atomic cobalt and nitrogen by controlled pyrolysis of melamine-functionalized graphene oxide and metal ion precursors. The obtained nanocomposites (CoNG/Ru) exhibit a remarkable electrocatalytic activity toward both HER and OER in alkaline media, with a respective overpotential of only -15 and +350 mV to reach the current density of 10 mA cm^-2, which is much better than the monometallic counterparts and relevant catalysts in the literature. With CoNG/Ru as bifunctional catalysts for overall water splitting in a two-electrode system, a low potential of 1.58 V is needed to reach the current density of 10 mA cm^-2, which is even better than that with commercial Pt/C and RuO₂ catalysts. This is ascribed to the synergistic interactions between the metal species by metal-metal charge transfer. These results highlight the significance of exploiting the electronic interactions between metal species in carbon-based nanocomposites to develop bifunctional catalysts for electrochemical energy technologies.

Oxygen Reduction Reaction Catalyzed by Black-Phosphorus-Supported Metal Nanoparticles: Impacts of Interfacial Charge Transfer

Development of effective catalysts for oxygen reduction reaction (ORR) plays a critical role in the applications of a range of electrochemical energy technologies. In this study, thin-layered black phosphorus (TLBP) was used as a unique supporting substrate for the deposition of metal nanoparticles (MNPs, M = Pt, Ag, Au), and the resulting M-TLBP nanocomposites were found to exhibit apparent ORR activity that was readily manipulated by interfacial charge transfer from TLBP to MNPs. This was confirmed by results from X-ray photoelectron spectroscopic measurements and density functional theory calculations. In comparison to the carbon-supported counterparts, Ag-TLBP and Au-TLBP showed enhanced ORR performance, while a diminished performance was observed with Pt-TLBP. This was consistent with the predictions from the "volcano plot". Results from this study suggest that black phosphorus can serve as a unique addition in the toolbox of manipulating electronic properties of supported metal nanoparticles and their electrocatalytic activity.

Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media

Hydrogen evolution reaction is an important process in electrochemical energy technologies. Herein, ruthenium and nitrogen codoped carbon nanowires are prepared as effective hydrogen evolution catalysts. The catalytic performance is markedly better than that of commercial platinum catalyst, with an overpotential of only -12 mV to reach the current density of 10 mV cm-2 in 1 M KOH and -47 mV in 0.1 M KOH. Comparisons with control experiments suggest that the remarkable activity is mainly ascribed to individual ruthenium atoms embedded within the carbon matrix, with minimal contributions from ruthenium nanoparticles. Consistent results are obtained in first-principles calculations, where RuCxNy moieties are found to show a much lower hydrogen binding energy than ruthenium nanoparticles, and a lower kinetic barrier for water dissociation than platinum. Among these, RuC2N2 stands out as the most active catalytic center, where both ruthenium and adjacent carbon atoms are the possible active sites.

Point of Anchor: Impacts on Interfacial Charge Transfer of Metal Oxide Nanoparticles

Photoinduced charge transfer across the metal oxide-organic ligand interface plays a key role in the diverse applications of metal oxide nanomaterials/nanostructures, such as photovoltaics, photocatalysis, and optoelectronics. Thus far, most studies are focused on molecular engineering of the organic chromophores, where the charge-transfer properties have been found to dictate the photo absorption efficiency and eventual device performance. Yet, as the chromophores are mostly bound onto the metal oxide surfaces by hydroxyl or carboxyl anchors, the impacts of the bonding interactions at the metal oxide-ligand interface on interfacial charge transfer have remained largely unexplored. Herein, acetylene derivatives are demonstrated as effective surface capping ligands for metal oxide nanoparticles, as exemplified with TiO₂, RuO₂, and ZnO. Experimental studies and first-principles calculations suggest the formation of M-O-C≡C- core-ligand linkages that lead to effective interfacial charge delocalization, in contrast to hopping/tunneling by the conventional M-O-CO- interfacial bonds in the carboxyl-capped counterparts. This leads to the generation of an interfacial state within the oxide bandgap and much enhanced sensitization of the nanoparticle photoluminescence emissions as well as photocatalytic activity, as manifested in the comparative studies with TiO₂ nanoparticles functionalized with ethynylpyrene and pyrenecarboxylic acid. These results highlight the significance of the unique interfacial bonding chemistry by acetylene anchoring group in facilitating efficient charge transfer through the oxide-ligand interfacial linkage and hence the fundamental implication in their practical applications.

Plasmonic circular dichroism of vesicle-like nanostructures by the template-less self-assembly of achiral Janus nanoparticles

Chiral nanostructures have been attracting extensive interest in recent years primarily because of the unique materials properties that can be exploited for diverse applications. In this study, gold Janus nanoparticles, with hexanethiolates and 3-mercapto-1,2-propanediol segregated on the two hemispheres of the metal cores (dia. 2.7 ± 0.4 nm), self-assembled into vesicle-like, hollow nanostructures in both water and organic media, and exhibited apparent plasmonic circular dichroism (PCD) absorption in the visible range. This was in contrast to individual Janus nanoparticles, bulk-exchange nanoparticles where the two ligands were homogeneously mixed on the nanoparticle surface, or nanoparticles capped with only one kind of ligand. The PCD signals were found to become intensified with increasing coverage of the 3-mercapto-1,2-propanediol ligands on the nanoparticle surface. This was accounted for by the dipolar property of the structurally asymmetrical Janus nanoparticles, and theoretical simulations based on first principles calculations showed that when the nanoparticle dipoles self-assembled onto the surface of a hollow sphere, a vertex was formed which gave rise to the unique chiral characteristics. The resulting chiral nanoparticle vesicles could be exploited for the separation of optical enantiomers, as manifested in the selective identification and separation of d-alanine from the l-isomer.

Covalent Crosslinking of Graphene Quantum Dots by McMurry Deoxygenation Coupling

Graphene quantum dots were covalently crosslinked forming ensembles of a few hundred nanometers in size by McMurry deoxygenation coupling reactions of peripheral carbonyl functional moieties catalyzed by TiCl₄ and Zn powders in refluxing THF, as evidenced by TEM, AFM, FTIR, Raman and XPS measurements. Photoluminescence measurements showed that after chemical coupling, the excitation and emission peaks blue-shifted somewhat and the emission intensity increased markedly, likely due to the removal of oxygenated species where quinone-like species are known to be effective electron acceptors and emission quenchers.