Aerodynamically Levitated Droplets as Small-scale Reactors and Liquid Microprinters.

A thin liquid film spread over the inner surface of a rapidly rotating vial creates an aerodynamic cushion on which one or multiple droplets of various liquids can levitate stably for days or even weeks. These levitating droplets can serve as wall-less ("airware") chemical reactors that can be merged without touching - by remote impulses - to initiate reactions or sequences of reactions at scales down to hundreds of nanomoles. Moreover, under external electric fields, the droplets can act as the world's smallest chemical printers, shedding regular trains of pL or even fL microdrops. In one modality, the levitating droplets operate as completely wirelesss aliquoting/titrating systems delivering pg quantities of reagents into the liquid in the rotating vial; in another modality, they print microdroplet arrays onto target surfaces. The "airware", levitated reactors are inexpensive to set up, remarkably stable to external disturbances and, for printing applications, require operating voltages much lower than in electrospray, electrowetting, or ink jet systems.

Stirring-Controlled Synthesis of Ultrastable, Fluorescent Silver Nanoclusters.

This paper describes how macroscopic stirring of a reaction mixture can be used to produce nanostructures exhibiting properties not readily achievable via other protocols. In particular, it is shown that by simply adjusting the stirring rate, a standard glutathione-based method-to date, used to produce only marginally stable fluorescent silver nanoclusters, Ag NCs-can be boosted to yield nanoclusters retaining fluorescence for unprecedented periods of over 2 years. This enhancement derives not simply from increased homogenization of the reaction mixture but mainly from an appropriately timed delivery of oxygen from above the reaction mixture. In effect, oxygen serves as a reagent that dictates size, structure, stability, and functional properties of the growing nanoobjects.

One-Pot, Three-Phase Recycling of Metals from Li-Ion Batteries in Rotating, Concentric-Liquid Reactors.

Efficient recycling of spent lithium-ion batteries (LIBs) is essential for making their numerous applications sustainable. Hydrometallurgy-based separation methods are an indispensable part of the recycling process but remain limited by the extraction efficiency and selectivity, and typically require numerous binary liquid-liquid extraction steps in which the capacity of the extracting organic phase or partition coefficient of extracted metals become an overall bottleneck. Herein, rotating reactors are described, in which the aqueous feed, organic extractant, and aqueous acceptor phases are all present in the same rotating vessel and can be vigorously stirred and emulsified without the coalescence of aqueous layers. In this arrangement, the extractant molecules are not equilibrated with the feed and, instead, "shuttle" between the feed/extractant and the extractant/acceptor interfaces multiple times, with each such molecule ultimately transferring approximately ten metal ions. This shuttling allows for using extractant concentrations much lower than in previous designs even for extremely concentrated feeds and, simultaneously, ensures unprecedented speed and selectivity of the one-pot processes. These experimental results are accompanied by theoretical considerations of the selectivity versus speed trends as well as discussion of parameters essential for system upscaling.

Proving Cooperativity of a Catalytic Reaction by Means of Nanoscale Geometry: The Case of Click Reaction.

Establishing whether a reaction is catalyzed by a single-metal catalytic center or cooperatively by a fleeting complex encompassing two such centers may be an arduous pursuit requiring detailed kinetic, isotopic, and other types of studies─as illustrated, for instance, by over a decade-long work on single-copper versus di-copper mechanisms of the popular "click" reaction. This paper describes a method to interrogate such cooperative mechanisms by a nanoparticle-based platform in which the probabilities of catalytic units being proximal can be varied systematically and, more importantly, independently of their volume concentration. The method relies on geometrical considerations rather than a detailed knowledge of kinetic equations, yet the scaling trends it yield can distinguish between cooperative and non-cooperative mechanisms.

Identification of the Pseudomonas fluorescens group as being responsible for blue pigment on fresh cheese.

New cases of blue cheese discoloration has led to recent research to identify the causal agent and factors that favor blue pigment appearing. Nonetheless, very few reports have described the source of contamination and the measurements to eradicate the microbiological source on cheese farms by determining the relation between blue discoloration on fresh cheese and the Pseudomonas fluorescens group. Thus, 60 samples from a cheese farm (cheese, equipment surfaces, tap water, and raw and pasteurized milk) were analyzed by phenotypical, MALDI-TOF, 16S rRNA sequencing and pulsed-field gel electrophoresis tests to determine the causal agent. The results obtained by pulsed-field gel electrophoresis with restriction enzymes XbaI and SpeI confirmed tap water as the initial contaminated source. The above-mentioned result was essential to avoid Pseudomonas contamination due to the most residual microorganisms being inactivated through a new disinfection program.

Transition metal complex/gold nanoparticle hybrid materials.

Gold nanoparticles (AuNPs) are of considerable interest for diverse applications in areas such as medicine, catalysis, and sensing. AuNPs are generally surface-stabilized by organic matrices and coatings, and while the resultant organic compound (OC)/AuNP hybrids have been explored extensively, they are not suitable for certain applications (e.g. those necessitating reversible redox behaviour and/or long excited-state lifetimes), and they often suffer from low photo- and/or thermal stability. Transition metal complex (TMC)/AuNP hybrids have recently come to the fore as they circumvent some of the aforementioned shortcomings with OC/AuNP hybrids. This review summarizes progress thus far in the nascent field of TMC/AuNP hybrids. The structure and composition of extant TMC/AuNP hybrids are briefly reviewed and the range of TMCs employed in the shell of the hybrids are summarized, the one-phase, two-phase, and post-nanoparticle-synthesis synthetic methods to TMC/AuNP hybrids are discussed and contrasted, highlighting the advantages of variants of the last-mentioned procedure, and the utility of the various characterization techniques is discussed, emphasizing the need to employ multiple techniques in concert. Applications of TMC/AuNP hybrids in luminescence, electrochemical, and electro-optical sensing are described and critiqued, and their uses and potential in imaging, photo-dynamic therapy, nonlinear optics, and catalysis are assessed.

Syntheses and quadratic nonlinear optical properties of 2,7-fluorenylene- and 1,4-phenylene-functionalized o-carboranes.

o-Carboranes C-functionalized by (4-substituted-phen-1-yl)ethynyl-1,4-phenyl groups or (2-substituted-fluoren-7-yl)ethynyl-2,7-fluorenyl groups, in which the pendant functionalization is electron-withdrawing nitro or electron-donating diphenylamino groups, have been synthesized and in many cases structurally characterized. Diphenylamino-containing examples coupled via the two π-delocalizable bridges to the electron-accepting o-carborane unit exhibit the greater quadratic optical nonlinearities at 1064 nm (hyper-Rayleigh scattering, ns pulses), the nonlinearities also increasing on proceeding from 1,4-phenylene- to 2,7-fluorenylene-containing bridge. The most NLO-efficient example 2-(n-butyl)-1-(2-((9,9-di(n-butyl)-2-(N,N-diphenylamino)-9H-fluoren-7-yl)ethynyl)-9,9-di(n-butyl)-9H-fluoren-7-yl)-1,2-ortho-carborane, consisting of diphenylamino donor, fluorenyl-containing bridge, o-carborane acceptor, and solubilizing n-butyl units, exhibits large 〈ß〉HRS (230 × 10-30 esu) and frequency-independent (two-level model) 〈ß0〉 (96 × 10-30 esu) values. Coupling two (2-((9,9-di(n-butyl)-2-(N,N-diphenylamino)-9H-fluoren-7-yl)ethynyl)-9,9-di(n-butyl)-9H-fluoren-7-yl) units to the 1,2-ortho-carborane core affords a di-C-functionalized compound with enhanced nonlinearities (309 × 10-30 esu and 129 × 10-30 esu, respectively).

Exceptional Two-Photon Absorption in Alkynylruthenium-Gold Nanoparticle Hybrids.

Ruthenium alkynyl "star" complexes with tri(2-thienyl)-, tris(1,2,3-triazolyl)-, or triphenyl-benzene cores stabilize gold nanoparticles (AuNPs). Cyclic voltammetry, transmission electron microscopy, molecular modeling, dynamic light scattering, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy studies are consistent with ca. 5 trithienyl- or triazolyl-benzene-cored star complexes decorating the exterior of each AuNP. The ca. 2.5 nm diameter (by transmission electron microscopy) trithienylbenzene-cored gold nanoparticle hybrids are significantly less absorbent than classical Brust nanoparticles stabilized by 1-dodecanethiol; with femtosecond pulsed radiation, they exhibit exceptionally strong saturable absorption and two-photon absorption across the visible range and into the near-infrared region (3 000 000 GM at 500 nm and 46 000 GM at 750 nm; 1 GM is equal to 10-50 cm4 s photon-1).

Quadratic and cubic hyperpolarizabilities of nitro-phenyl/-naphthalenyl/-anthracenyl alkynyl complexes.

1-Nitronaphthalenyl-4-alkynyl and 9-nitroanthracenyl-10-alkynyl complexes [M](C[triple bond, length as m-dash]C-4-C10H6-1-NO2) ([M] = trans-[RuCl(dppe)2] (6b), trans-[RuCl(dppm)2] (7b), Ru(PPh3)2(η5-C5H5) (8b), Ni(PPh3)(η5-C5H5) (9b), Au(PPh3) (10b)) and [M](C[triple bond, length as m-dash]C-10-C14H8-9-NO2) ([M] = trans-[RuCl(dppe)2] (6c), trans-[RuCl(dppm)2] (7c), Ru(PPh3)2(η5-C5H5) (8c), Ni(PPh3)(η5-C5H5) (9c), Au(PPh3) (10c)) were synthesized and their identities were confirmed by single-crystal X-ray diffraction studies. Electrochemical studies and a comparison to the 1-nitrophenyl-4-alkynyl analogues [M](C[triple bond, length as m-dash]C-4-C6H4-1-NO2) ([M] = trans-[RuCl(dppe)2] (6a), trans-[RuCl(dppm)2] (7a), Ru(PPh3)2(η5-C5H5) (8a), Ni(PPh3)(η5-C5H5) (9a), Au(PPh3) (10a)) reveal a decrease in oxidation potential for ruthenium and nickel complexes on proceeding from the phenyl- to naphthalenyl- and then anthracenyl-containing bridge. HOMO → LUMO transitions characteristic of MC[triple bond, length as m-dash]C-1-C6H4 to 4-C6H4-1-NO2 charge transfer red-shift and gain in intensity on proceeding to the ruthenium complexes; the low-energy transitions have increasing ILCT character on proceeding from the phenyl- to naphthalenyl- and then anthracenyl-containing bridge. Spectroelectrochemical studies of the Ru-containing complexes reveal the appearance of low-energy bands corresponding to chloro-to-RuIII charge transfer that red-shift on proceeding from the phenyl- to naphthalenyl- and then anthracenyl-containing bridge. Second-order nonlinear optical (NLO) studies at 1064 nm employing ns pulses and the hyper-Rayleigh scattering technique reveal an increase in quadratic optical nonlinearity upon introduction of metal to the precursor alkyne to afford alkynyl complexes and on proceeding from ligated-gold to -nickel and then to -ruthenium for a fixed alkynyl ligand. Quadratic NLO data of the gold complexes optically transparent at the second-harmonic wavelength reveal an increase in ßHRS on proceeding from the phenyl- to the naphthalenyl-containing complex. Broad spectral range third-order nonlinear optical studies employing fs pulses and the Z-scan technique reveal an increase in two-photon absorption cross-section on replacing ligated-gold by -nickel and then -ruthenium for a fixed alkynyl ligand. Computational studies undertaken using time-dependent density functional theory have been employed to assign the nature of the key optical transitions and suggest that the significant optical nonlinearities observed for the ruthenium-containing complexes correlate with the low-energy formally Ru → NO2 band which possesses strong MLCT character, while the more moderate nonlinearities of the gold complexes correlate with a band higher in energy that is primarily ILCT in character.

Linear Optical, Quadratic and Cubic Nonlinear Optical, Electrochemical, and Theoretical Studies of "Rigid-Rod" Bis-Alkynyl Ruthenium Complexes.

The syntheses of oligo(p-phenylene ethynylene)s (OPEs) end-functionalized by a nitro acceptor group and with a ligated ruthenium unit at varying locations in the OPE chain, namely, trans-[Ru{(C≡C-1,4-C6 H4 )n NO2 }(C≡CR)(dppe)2 ] (dppe=1,2-bis(diphenylphosphino)ethane; n=1, R=1,4-C6 H4 C≡C-1,4-C6 H4 C≡CPh, 1,4-C6 H4 NEt2 ; n=2, R=Ph, 1,4-C6 H4 C≡CPh, 1,4-C6 H4 C≡C-1,4-C6 H4 C≡CPh, 1,4-C6 H4 NO2 , 1,4-C6 H4 NEt2 ; n=3, R=Ph, 1,4-C6 H4 C≡CPh), are reported. Their electrochemical properties were assessed by cyclic voltammetry, their linear optical properties and quadratic and cubic nonlinear optical properties were assayed by UV/Vis/NIR spectroscopy, hyper-Rayleigh scattering studies employing nanosecond pulses at 1064 nm, and broad spectral range Z-scan studies employing femtosecond pulses, respectively, and their linear optical properties and vibrational spectroscopic behavior in the formally RuIII state was examined by UV/Vis/NIR and IR spectroelectrochemistry, respectively. The potentials of the metal-localized oxidation processes are sensitive to alkynyl-ligand modification, but this effect is attenuated on π-bridge lengthening. Computational studies employing time-dependent density functional theory were undertaken on model complexes, with a 2D scan revealing a soft potential-energy surface for intra-alkynyl-ligand aryl-ring rotation; this is consistent with the experimentally observed blueshift in optical absorption maxima. Quadratic optical nonlinearities are significant and cubic NLO coefficients for these small complexes are small. The optimum length of the alkynyl ligands and the ideal metal location in the OPE to maximize the key coefficients have been defined.

Exceptionally large two- and three-photon absorption cross-sections by OPV organometalation.

Oligo(p-phenylenevinylene)s (OPVs) containing up to 8 PV units and end-functionalized by ruthenium alkynyl groups have been prepared and their nonlinear absorption properties assessed using the Z-scan technique and employing low repetition rate femtosecond pulses. Exceptionally large two-photon absorption (ca. 12 500 GM at 725 nm) and three-photon absorption cross sections (ca. 1.6 × 10(-76) cm(6) s(2) at 1100 nm) are found for the 8PV-containing example, highlighting the potential of an "organometalation" approach to NLO-efficient organic materials.

Synthesis, Optical, Electrochemical, and Theoretical Studies of Dipolar Ruthenium Alkynyl Complexes with Oligo(phenylenevinylene) Bridges.

The syntheses of oligo(p-phenylenevinylene)s (OPVs) end-functionalized with a ligated ruthenium alkynyl unit as a donor and a nitro as acceptor, namely trans-[Ru{C≡C-1-C6 H4 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H4 -4-NO2 }Cl(dppe)2 ] (Ru4), trans-[Ru{C≡C-1-C6 H4 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H2 -2,5-(n-hexyl)2 -4-(E)-CH=CH-1-C6 H2 -2,5-(n-hexyl)2 -4-(E)-CH=CH-1-C6 H4 -4-NO2 }Cl(dppe)2 ] (Ru6), and trans-[Ru{C≡C-1-C6 H4 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H2 -2,5-Et2 -4-(E)-CH=CH-1-C6 H2 -2,5-(n-hexyl)2 -4-(E)-CH=CH-1-C6 H2 -2,5-(n-hexyl)2 -4-(E)-CH=CH-1-C6 H2 -2,5-(2-ethyl-n-hexyl)2 -4-(E)-CH=CH-1-C6 H2 -2,5-(2-ethyl-n-hexyl)2 -4-(E)-CH=CH-1-C6 H4 -4-NO2 }Cl(dppe)2 ] (Ru8), are reported, together with those of precursor alkynes. Their electrochemical properties were assessed by cyclic voltammetry (CV), their linear optical and quadratic nonlinear optical (NLO) properties assayed by UV/Vis-NIR spectroscopy and hyper-Rayleigh scattering studies at 1064 nm, respectively, and their linear optical properties in the formally RuIII state examined by UV/Vis-NIR spectroelectrochemistry. Computational studies employing time-dependent density functional theory were undertaken on model complexes to rationalize the optical observations.

Syntheses and Optical Properties of Azo-Functionalized Ruthenium Alkynyl Complexes.

The syntheses of trans-[Ru(C≡C-1-C6 H4 -4-N=N-1-C6 H4 -4-C≡C-1-C6 H4 -4-NO2 )Cl(L2 )2 ] (L2 =dppm (Ru1), dppe) (Ru2)), trans-[Ru(C≡C-1-C6 H4 -4-N=N-1-C6 H4 -4-(E)-CH=CH-1-C6 H4 -4-NO2 )Cl(dppe)2 ] (Ru3), and trans-[Ru(C≡C-1-C6 H4 -4-(E)-CH=CH-1-C6 H2 -2,6-Et2 -4-N=N-1-C6 H4 -4-NO2 )Cl(dppe)2 ] (Ru4) are reported, together with those of precursor alkynes. Their electrochemical properties were assessed by cyclic voltammetry (CV), linear optical and quadratic nonlinear optical (NLO) properties assayed by UV/Vis-NIR spectroscopy and hyper-Rayleigh scattering studies at 1064 nm, respectively, and their linear optical properties in the formally RuIII state examined by UV/Vis-NIR spectroelectrochemistry. These data were compared to those of analogues with E-ene and yne linkages in place of the azo groups. Computational studies using time-dependent density functional theory were undertaken on model compounds (Ru2'-Ru4') to rationalize the optical behaviour of the experimental complexes.

[Prevalence and risk factors of multi-drug resistant organism colonization among long-term care facilities in Gran Canaria (Spain)]. / Prevalencia y factores asociados a la colonización de microorganismos multirresistentes en centros de larga estancia de Gran Canaria.

INTRODUCTION: Multidrug resistant organisms (MDRO) are an important cause of nosocomial infections, with complicated clinical-therapeutic management and elevated morbidity-mortality, and an increase in healthcare costs. In long term care facilities (LTCFs) colonization/infection by MDRO among residents is increasing, and they may act as reservoirs and vehicles for the dissemination and production of outbreaks by resistant strains in acute hospitals. This study aimed at determining the prevalence of carriers of some common MDRO, and identifying factors associated with carrier state. MATERIAL AND METHODS: A cross-sectional prevalence study was conducted on 235 residents in two LTCFs in the province of Las Palmas de Gran Canaria (Canary Islands, Spain) between October and November of 2012. The presence of MMR was investigated in nasal, pharyngeal and rectal swabs using selective media. Risk factors associated with carrier state were calculated using univariate and multivariate analysis. RESULTS: More than one-third (36.2%) of residents were found to be carriers of ≥ 1 distinct MDROs. More than one-quarter (26.6%) were carriers of ESBL producing Enterobacteriaceae, and 10.2% were MRSA carriers. Factors found to be associated with colonization by any MDRO were: prior colonization or infection by MDRO, hospitalization in the past 3 months, recurrent infections of the urinary tract, and peripheral arterial disease. CONCLUSIONS: The prevalence of MDRO in the LTCFs settings studied is greater than that found in the literature, and in particular ESBL producing Enterobacteriaceae. Due to the high prevalence of infection/colonization by MDRO, it is possible that residents of LTCFs could act as important reservoirs of MDRO, and facilitate their spread into the acute care setting.

[Antibiotic ointments and methicillin-resistant Staphylococcus aureus with a reservoir in a healthcare worker in a tertiary hospital]. / Staphylococcus aureus resistente a la meticilina y a descolonizadores habituales con reservorio en un trabajador sanitario en un hospital de tercer nivel.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) has become an important hospital-acquired pathogen, with transfer of the organism from a carrier or infected patient to uninfected patients by the hands or clothing of staff as the main mode of transmission. METHODS: Investigation of a cluster of new cases of MRSA resistant to mupirocin and fusidic acid, using epidemiological and microbiological resources. RESULTS: From September 2010 to February 2012, sixteen patients had at least one culture positive for MRSA resistant to mupirocin and fusidic acid. Some not apparently related cases and outbreaks appeared. By analysing cultures taken from patients and staff using pulsed-field gel electrophoresis, it was demonstrated that most likely this situation was started by an auxiliary nurse who was a carrier of the MRSA. Healthcare worker decontamination using oral antibiotic therapy was unsuccessful. Eventually, the situation was controlled by placing the carrier in a different job, with no further cases to date (September, 2012). CONCLUSION: This report illustrates the risk of nosocomial transmission linked to care delivered by healthcare workers.