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The structure, chemistry, and charge of interfaces between materials and aqueous fluids play a central role in determining properties and performance of numerous water systems. Sensors, membranes, sorbents, and heterogeneous catalysts almost uniformly rely on specific interactions between their surfaces and components dissolved or suspended in the water-and often the water molecules themselves-to detect and mitigate contaminants. Deleterious processes in these systems such as fouling, scaling (inorganic deposits), and corrosion are also governed by interfacial phenomena. Despite the importance of these interfaces, much remains to be learned about their multiscale interactions. Developing a deeper understanding of the molecular- and mesoscale phenomena at water/solid interfaces will be essential to driving innovation to address grand challenges in supplying sufficient fit-for-purpose water in the future. In this Review, we examine the current state of knowledge surrounding adsorption, reactivity, and transport in several key classes of water/solid interfaces, drawing on a synergistic combination of theory, simulation, and experiments, and provide an outlook for prioritizing strategic research directions.
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Kenneth Mellanby was a distinguished biologist specialising in entomology. He helped to establish the first university in Nigeria and undertook pioneering work on the use of insecticides in agriculture. However, he will best be remembered for a series of experiments which he undertook on human volunteers during the Second World War. These experiments established the mechanism of transmission of scabies and allowed its effective control at a time when the condition had reached epidemic proportions, causing a significant adverse effect on public morale and military effectiveness. Mellanby's wartime monograph on scabies remains to this day the definitive work on the disease and is still studied by dermatologists. His subsequent book Human Guinea Pigs is a remarkable account of the privations to which wartime volunteers willingly submitted themselves in a way that would have never passed any current medical ethics committee.
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Medicina Militar/historia , Salud Pública/historia , Escabiosis/historia , Historia del Siglo XX , Humanos , Escabiosis/prevención & control , Escabiosis/psicología , Escabiosis/transmisiónRESUMEN
We report the results of grazing incidence X-ray diffraction (GIXD) measurements from water supported Langmuir monolayers of gold nanoparticles ligated with dodecanethiol (12 carbons), tetradecanethiol (14 carbons), hexadecanethiol (16 carbons), and octadecanethiol (18 carbons). These monolayers are formed from solutions with varying concentrations of the respective thiols. We show that equilibrium between adsorbed thiol molecules and the thiols in the bulk solution implies fractional coverage of the Au nanoparticle core. We also show that the nanoparticle-nanoparticle separation and the correlation length of particles in these ordered films increases with thiol concentration in the parent solution, and that excess thiol can be found in the space between particles as well as in islands away from the particles. Using the equilibrium constant relating ligand solution concentration and nanoparticle surface coverage of the gold core by the ligand molecules, we interpret the way in which varying thiol concentration affects the nanoparticle-nanoparticle separation as a function of surface coverage of the gold core by the ligand molecules.
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Herein, we present a light-gated protocell model made of plasmonic colloidal capsules (CCs) assembled with bacteriorhodopsin for converting solar energy into electrochemical gradients to drive the synthesis of energy-storage molecules. This synthetic protocell incorporated an important intrinsic property of noble metal colloidal particles, namely, plasmonic resonance. In particular, the near-field coupling between adjacent metal nanoparticles gave rise to strongly localized electric fields and resulted in a broad absorption in the whole visible spectra, which in turn promoted the flux of photons to bacteriorhodopsin and accelerated the proton pumping kinetics. The cell-like potential of this design was further demonstrated by leveraging the outward pumped protons as "chemical signals" for triggering ATP biosynthesis in a coexistent synthetic protocell population. Hereby, we lay the ground work for the engineering of colloidal supraparticle-based synthetic protocells with higher-order functionalities.
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Adenosina Trifosfato/síntesis química , Células Artificiales/química , Luz , Fotones , Resonancia por Plasmón de Superficie , Adenosina Trifosfato/química , Bacteriorodopsinas/química , Ingeniería Celular , Concentración de Iones de Hidrógeno , Tamaño de la Partícula , Propiedades de SuperficieRESUMEN
Concentrated wastewaters from agricultural industries represent a key opportunity for the upcycling of organics, nitrogen and phosphorus to higher value products such as microbial protein. Phototrophic or photosynthetic microbes very effectively capture input organics and nutrients as microbial protein. This study compares purple phototrophic bacteria (PPB) and microalgae (photosynthesis) for this purpose, treating real, high strength poultry processing wastewater in continuous photo bioreactors utilising infrared (IR) and white light (WL) respectively. Both reactors could effectively treat the wastewaters, and at similar loading rates (4 kgCOD m-3d-1). The infrared reactor (IRR) was irradiated at 18â¯Wâ¯m-2 and the white light reactor (WLR) reactor at 1.5-2 times this. The IRR could remove up to 90% total chemical oxygen demand (TCOD), 90% total nitrogen (TN) and 45% total phosphorus (TP) at 1.0â¯d hydraulic retention time (HRT) and recover around 190â¯kg of crude protein per tonne of influent COD at 7.0â¯kWh per dry tonne-1 light input, with PPB dominating all samples. In comparison, the WLR removed up to 98% COD, 94% TN and 44% TP at 43-90% higher irradiance compared to the PPB reactor. Microalgae did not dominate the WLR and the community was instead a mix of microbes (algae, bacteria, zooplankton and detritus - ALBAZOD) with a production of approximately 140â¯kg crude protein per tonne influent COD.
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Fotobiorreactores , Aguas Residuales , Animales , Análisis de la Demanda Biológica de Oxígeno , Reactores Biológicos , Aves de Corral , Eliminación de Residuos LíquidosRESUMEN
Low wastewater temperatures affect microbial growth rates and microbial populations, as well as physical chemical characteristics of the wastewater. Wastewater treatment plant design needs to accommodate changing temperatures, and somewhat limited capacity is a key criticism of low strength anaerobic treatment such as Anaerobic Membrane Bioreactors (AnMBR). This study evaluates the applicability of an alternative platform utilizing purple phototrophic bacteria for low temperature domestic wastewater treatment. Two photo-anaerobic membrane bioreactors (PAnMBR) at ambient (22 °C) and low temperatures (10 °C) were compared to fully evaluate temperature response of critical processes. The results show good functionality at 10 °C in comparison with ambient operation. This enabled operation at 10 °C to discharge limits (TCOD < 100 mg L(-1); TN < 10 mg L(-1) and TP < 1 mg L(-1)) at a HRT < 1 d. While capacity of the system was not limited, microbial community showed a strong shift to a far narrower diversity, almost complete dominance by PPB, and of a single Rhodobacter spp. compared to a more diverse community in the ambient reactor. The outcomes of the current work enable applicability of PPB for domestic wastewater treatment to a broad range of regions.
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Temperatura , Aguas Residuales , Anaerobiosis , Bacterias , Bacterias Anaerobias , Reactores Biológicos/microbiología , Frío , Aguas del Alcantarillado/microbiología , Eliminación de Residuos LíquidosRESUMEN
A key future challenge of domestic wastewater treatment is nutrient recovery while still achieving acceptable discharge limits. Nutrient partitioning using purple phototrophic bacteria (PPB) has the potential to biologically concentrate nutrients through growth. This study evaluates the use of PPB in a continuous photo-anaerobic membrane bioreactor (PAnMBR) for simultaneous organics and nutrient removal from domestic wastewater. This process could continuously treat domestic wastewater to discharge limits (<50 mgCOD L(-1), 5 mgN L(-1), 1.0 mgP L(-1)). Approximately 6.4 ± 1.3 gNH4-N and 1.1 ± 0.2 gPO4-P for every 100 gSCOD were removed at a hydraulic retention time of 8-24 h and volumetric loading rates of 0.8-2.5 COD kg m(3) d(-1). Thus, a minimum of 200 mg L(-1) of ethanol (to provide soluble COD) was required to achieve these discharge limits. Microbial community through sequencing indicated dominance of >60% of PPB, though the PPB community was highly variable. The outcomes from the current work demonstrate the potential of PPB for continuous domestic (and possibly industrial) wastewater treatment and nutrient recovery. Technical challenges include the in situ COD supply in a continuous reactor system, as well as efficient light delivery. Addition of external (agricultural or fossil) derived organics is not financially nor environmentally justified, and carbon needs to be sourced internally from the biomass itself to enable this technology. Reduced energy consumption for lighting is technically feasible, and needs to be addressed as a key objective in scaleup.
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Reactores Biológicos/microbiología , Aguas Residuales/microbiología , Bacterias , Bacterias Anaerobias , Biomasa , Carbono , Eliminación de Residuos LíquidosRESUMEN
Monolayers composed of colloidal nanoparticles, with a thickness of less than ten nanometers, have remarkable mechanical strength and can suspend over micron-sized holes to form free-standing membranes. We discuss experiments probing the tensile strength and bending stiffness of these self-assembled nanoparticle sheets. The fracture behavior of monolayers and multilayers is investigated by attaching them to elastomer substrates which are then stretched. For different applied strain, the fracture patterns are imaged down to the scale of single particles. The resulting detailed information about the crack width distribution allows us to relate the measured overall tensile strength to the distribution of local bond strengths within a layer. We then introduce two methods by which freestanding nanoparticle monolayers can be rolled up into hollow, tubular "nano-scrolls", either by electron beam irradiation during imaging with a scanning electron microscope or by spontaneous self-rolling. Indentation measurements on the nano-scrolls yield values for the bending stiffness that are significantly larger than expected from the response to stretching. The ability to stretch, bend, and roll up nanoparticle sheets offers new possibilities for a variety of applications, including sensors and mechanical transducers.
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Nanopartículas , Microscopía Electrónica de RastreoRESUMEN
From proton exchange membranes in fuel cells to ion channels in biological membranes, the well-specified control of ionic interactions in confined geometries profoundly influences the transport and selectivity of porous materials. Here we outline a versatile new approach to control a membrane's electrostatic interactions with ions by depositing ligand-coated nanoparticles around the pore entrances. Leveraging the flexibility and control by which ligated nanoparticles can be synthesized, we demonstrate how ligand terminal groups such as methyl, carboxyl and amine can be used to tune the membrane charge density and control ion transport. Further functionality, exploiting the ligands as binding sites, is demonstrated for sulfonate groups resulting in an enhancement of the membrane charge density. We then extend these results to smaller dimensions by systematically varying the underlying pore diameter. As a whole, these results outline a previously unexplored method for the nanoparticle functionalization of membranes using ligated nanoparticles to control ion transport.
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Oro/química , Membranas Artificiales , Nanopartículas del Metal/química , Aminación , Transporte Biológico , Ácidos Carboxílicos/química , Concentración de Iones de Hidrógeno , Transporte Iónico , Cinética , Metilación , Porosidad , Electricidad EstáticaRESUMEN
We present an experimental investigation of fracture in self-assembled gold nanoparticle mono- and multilayers attached to elastomer substrates and subjected to tensile stress. Imaging the fracture patterns down to the scale of single particles provides detailed information about the crack width distribution and allows us to compare the scaling of the average crack spacing as a function of strain with predictions by shear-lag models. With increasing particle size, the fracture strength is found to increase while it decreases as the film thickness is built up layer by layer, indicating stress inhomogeneity in the thickness dimension.
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Coalescence is an essential phenomenon that governs the equilibrium behaviour in a variety of systems from intercellular transport to planetary formation. In this report, we study coalescence pathways of circularly shaped two-dimensional colloidal membranes, which are one rod-length-thick liquid-like monolayers of aligned rods. The chirality of the constituent rods leads to three atypical coalescence pathways that are not found in other simple or complex fluids. In particular, we characterize two pathways that do not proceed to completion but instead produce partially joined membranes connected by line defects-π-wall defects or alternating arrays of twisted bridges and pores. We elucidate the structure and energetics of these defects and ascribe their stability to a geometrical frustration inherently present in chiral colloidal membranes. Furthermore, we induce the coalescence process with optical forces, leading to a robust on-demand method for imprinting networks of channels and pores into colloidal membranes.
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We combine simulations and experiments to elucidate the molecular forces leading to the assembly of two dimensional membrane-like structures composed of a one rod-length thick monolayer of aligned rods from an immiscible suspension of hard rods and depleting polymers. Computer simulations predict that monolayer membranes are thermodynamically stable above a critical rod aspect ratio and below a critical depletion interaction length scale. Outside of these conditions alternative structures such as stacked smectic columns or nematic droplets are thermodynamically stable. These predictions are confirmed by subsequent experiments using a model system of virus rod-like molecules and non-adsorbing polymer. Our work demonstrates that collective molecular protrusion fluctuations alone are sufficient to stabilize membranes composed of homogenous rods with simple excluded volume interactions.
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BACKGROUND: In the past decade spherical and rod-like viruses have been used for the design and synthesis of new kind of nanomaterials with unique chemical positioning, shape, and dimensions in the nanosize regime. Wild type and genetic engineered viruses have served as excellent templates and scaffolds for the synthesis of hybrid materials with unique properties imparted by the incorporation of biological and organic moieties and inorganic nanoparticles. Although great advances have been accomplished, still there is a broad interest in developing reaction conditions suitable for biological templates while not limiting the material property of the product. RESULTS: We demonstrate the controlled synthesis of copper nanorods and nanowires by electroless deposition of Cu on three types of Pd-activated rod-like viruses. Our aqueous solution-based method is scalable and versatile for biotemplating, resulting in Cu-nanorods 24-46 nm in diameter as measured by transmission electron microscopy. Cu2+ was chemically reduced onto Pd activated tobacco mosaic virus, fd and M13 bacteriophages to produce a complete and uniform Cu coverage. The Cu coating was a combination of Cu0 and Cu2O as determined by X- ray photoelectron spectroscopy analysis. A capping agent, synthesized in house, was used to disperse Cu-nanorods in aqueous and organic solvents. Likewise, reactions were developed to produce Cu-nanowires by metallization of polyaniline-coated tobacco mosaic virus. CONCLUSIONS: Synthesis conditions described in the current work are scalable and amenable for biological templates. The synthesized structures preserve the dimensions and shape of the rod-like viruses utilized during the study. The current work opens the possibility of generating a variety of nanorods and nanowires of different lengths ranging from 300 nm to micron sizes. Such biological-based materials may find ample use in nanoelectronics, sensing, and cancer therapy.
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Bacteriófago M13/química , Cobre/química , Nanotecnología/métodos , Nanotubos/química , Nanocables/química , Virus del Mosaico del Tabaco/química , Compuestos de Anilina/química , Catálisis , Nanotubos/ultraestructura , Nanocables/ultraestructura , Oxidación-Reducción , Paladio/químicaRESUMEN
From determining the optical properties of simple molecular crystals to establishing the preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical and optical properties of both synthetic and biological matter on macroscopic length scales. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials. An example of particular interest is smectic liquid crystals, where the two-dimensional layered geometry cannot support twist and chirality is consequently expelled to the edges in a manner analogous to the expulsion of a magnetic field from superconductors. Here we demonstrate a consequence of this geometric frustration that leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This suggests an analogy between chiral twist, which is expelled to the edges of two-dimensional membranes, and amphiphilic surfactants, which are expelled to oil-water interfaces. As with surfactants, chiral control of interfacial tension drives the formation of many polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ allows dynamical control of line tension, which powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials that can easily be moved, stretched, attached to one another and transformed between multiple conformational states, thus allowing precise assembly and nanosculpting of highly dynamical and designable materials with complex topologies.
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Bacteriófago M13/química , Sustitución de Aminoácidos , Bacteriófago M13/genética , Fenómenos Biomecánicos , Coloides/química , Simulación por Computador , Microscopía Electrónica de Transmisión , Aceites/química , Estereoisomerismo , Tensión Superficial , Tensoactivos/química , Agua/químicaRESUMEN
We demonstrate that homogeneous monodisperse rods in the presence of attractive interactions assemble into equilibrium 2D fluid-like membranes composed of a one-rod length thick monolayer of aligned rods. Unique features of our system allow us to simultaneously investigate properties of these membranes at both continuum and molecular lengthscales. Analysis of thermal fluctuations at continuum lengthscales yields the membranes' lateral compressibility and bending rigidity and demonstrates that the properties of colloidal membranes are comparable to those of traditional lipid bilayers. Fluctuations at molecular lengthscales, in which single rods protrude from the membrane surface, are directly measured by comparing the positions of individual fluorescently labeled rods within a membrane to that of the membrane's continuum conformation. As two membranes approach each other in suspension, protrusion fluctuations are suppressed leading to effective repulsive interactions. Motivated by these observations, we propose an entropic mechanism that explains the stability of colloidal membranes and offers a general design principle for the self-assembly of 2D nanostructured materials from rod-like molecules.
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Liposuction is a standard for removing fat. Recently developed, laser lipolysis can be used to simultaneously remove unwanted fat and tighten skin. Laser lipolysis is accomplished with single or multiple sequential wavelengths. Development of an optimal method requires detailed understanding of tissue heating for the wavelengths employed. This study systematically evaluates tissue heating for superficial and deep laser lipolysis using three approaches, and correlates temperature rise with histology changes, defining appropriate system parameters. Two individuals scheduled for abdominoplasty had laser testing on healthy abdominal skin scheduled for excision. Each treatment was applied to 3 x 3 cm squares with various laser parameters. Treatment was conducted in the fatty layer for lipolysis and subdermally for skin tightening. Individual squares were treated with SmartLipo (Cynosure, Inc. Westford, MA, USA) using 1064 nm, 1320 nm, or MultiPlex (1064 nm/1320 nm) with laser doses of 8.3 to 333 J/cm2. Exposures were applied at 3-5 mm or approximately 20 mm depth below the skin surface. Skin temperatures at the surface and at depths of 5 mm to 37 mm were recorded immediately post-treatment for each exposure. Treated tissue was excised and evaluated for thermal injury using H&E and transmission polarization microscopy. Histology was correlated to tissue temperature to determine appropriate treatment limits. Superficial treatment with surface temperatures exceeding 47 degrees C (50 degrees C and 55 degrees C at 5 mm depth) typically caused epidermal and dermal injury, with blistering above 58 degrees C. Below this threshold, focal collagen change and dermal inflammatory response were found in many samples without epidermal injury. These acute thermal effects may link to skin tightening during the healing process. Deep treatments, at up to 133 J/cm2, exhibited minimal temperature rise and induced thermal effects in vessels and ligaments. Higher laser doses were associated with a significant temperature increase. In conclusion, superficial subdermal heating (within approximately 5 mm of the surface) during laser lipolysis should limit skin surface temperature to 42 degrees C. The laser dose per surface temperature rise in treatments are 4.5 J/cm2/degrees C for 1320 nm, 6 J/cm2/degrees C for MultiPlex and 7.5 J/cm2/degrees C for 1064 nm. Clinical studies should be performed to validate these results.
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Grasa Abdominal , Calor , Láseres de Estado Sólido/uso terapéutico , Lipectomía/métodos , Piel , HumanosRESUMEN
In the 1970s, deGennes discussed the fundamental geometry of smectic liquid crystals and established an analogy between the smectic A phase and superconductors. It follows that smectic layers expel twist deformations in the same way that superconductors expel magnetic field. We make a direct observation of the penetration of twist at the edge of a single isolated smectic A layer composed of chiral fd virus particles subjected to a depletion interaction. Using the LC-PolScope, we make quantitative measurements of the spatial dependence of the birefringence due to molecular tilt near the layer edges. We match data to theory for the molecular tilt penetration profile and determine the twist penetration length for this system.
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Virus/química , Coloides/química , Cristales Líquidos/química , Modelos Químicos , Tamaño de la Partícula , Propiedades de Superficie , Virión/químicaRESUMEN
Bimolecular fluorescence complementation (BiFC) is based on the complementation between two nonfluorescent fragments of the yellow fluorescent protein (YFP) when they are united by interactions between proteins covalently linked to them. We have successfully applied BiFC in Neurospora crassa using two genes involved in meiotic silencing by unpaired DNA (MSUD) and observed macromolecular complex formation involving only SAD-1 proteins, only SAD-2 proteins, and mixtures of SAD-1 and SAD-2 proteins.
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Proteínas Bacterianas/metabolismo , ADN de Hongos/metabolismo , Silenciador del Gen , Mediciones Luminiscentes/métodos , Proteínas Luminiscentes/metabolismo , Meiosis , Neurospora crassa/citología , Neurospora crassa/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Secuencia de Bases , Núcleo Celular/metabolismo , Fluorescencia , Proteínas Fúngicas/metabolismo , Datos de Secuencia Molecular , Plásmidos/genética , Unión Proteica , Transporte de ProteínasRESUMEN
We study the liquid-crystalline phase behavior of a concentrated suspension of helical flagella isolated from Salmonella typhimurium. Flagella are prepared with different polymorphic states, some of which have a pronounced helical character while others assume a rodlike shape. We show that the static phase behavior and dynamics of chiral helices are very different when compared to simpler achiral hard rods. With increasing concentration, helical flagella undergo an entropy-driven first order phase transition to a liquid-crystalline state having a novel chiral symmetry.