Synergism at the Nanoscale

2016 ◽  
pp. 42-77
Author(s):  
Raquel Eugenia Galian ◽  
Julia Pérez-Prieto
Keyword(s):  
Optical Properties ◽  
High Surface ◽  
Organic Ligand ◽  
Volume Ratio ◽  
Colloidal Dispersions ◽  
Organic Ligands ◽  
Organic Media ◽  
Intrinsic Properties ◽  
Smart Systems ◽  
Size Dependent

Photoactive nanoparticles are smart systems that exhibit unique optical properties. In general, their intrinsic properties are size dependent. The degree and type of response to size are both related to their composition. Nanoparticles usually require to be capped with organic ligands in order to be dispersible in an aqueous or organic media, thus leading to nanoparticle colloidal dispersions and enhancing the processability of the material. The organic ligand also plays a key role in their preparation. In addition, the high surface-to-volume ratio of the nanoparticles combined with the affinity of the ligands for the nanoparticle surface can be used to place a large number of functional molecules at their periphery. The purpose of this chapter is to understand the synergism between nanoparticles and organic ligands with regard to their preparation, performance, and applicability.

scholarly journals The surface tension of surfactant-containing, finite volume droplets

2020 ◽  
Vol 117 (15) ◽  
pp. 8335-8343 ◽  
Author(s):  
Bryan R. Bzdek ◽  
Jonathan P. Reid ◽  
Jussi Malila ◽  
Nønne L. Prisle
Keyword(s):  
Surface Tension ◽  
Finite Volume ◽  
Climate Models ◽  
High Surface ◽  
Finite Size ◽  
Volume Ratio ◽  
Cloud Droplet ◽  
Reaction Rates ◽  
Hygroscopic Growth ◽  
Size Dependent

Surface tension influences the fraction of atmospheric particles that become cloud droplets. Although surfactants are an important component of aerosol mass, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. By studying picoliter droplet coalescence, we demonstrate that surfactants can significantly reduce the surface tension of finite-sized droplets below the value for water, consistent with recent field measurements. Significantly, this surface tension reduction is droplet size-dependent and does not correspond exactly to the macroscopic solution value. A fully independent monolayer partitioning model confirms the observed finite-size-dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation, potentially substantially increasing cloud droplet number concentration and modifying radiative cooling relative to current estimates assuming a water surface tension. The results highlight the need for improved constraints on the identities, properties, and concentrations of atmospheric aerosol surfactants in multiple environments and are broadly applicable to any discipline where finite volume effects are operative, such as studies of the competition between reaction rates within the bulk and at the surface of confined volumes and explorations of the influence of surfactants on dried particle morphology from spray driers.

scholarly journals Sulfidization of ferrihydrite in the presence of organic ligands

2021 ◽  
Author(s):  
Laurel K. ThomasArrigo ◽  
Sylvain Bouchet ◽  
Ralf Kaegi ◽  
Ruben Kretzschmar
Keyword(s):  
Trace Elements ◽  
High Surface ◽  
Organic Ligand ◽  
Organic Ligands ◽  
Molar Ratios ◽  
Iron Mineral ◽  
Surface Areas ◽  
Secondary Reactions ◽  
Mineral Components ◽  
The Impact

<p>In soils and sediments, short-range order (SRO) iron minerals constitute one of the most abundant and reactive mineral components. With high surface areas and points of zero charge near pH 7-8, SRO minerals like ferrihydrite (Fe<sub>10</sub>O<sub>14</sub>(OH)<sub>2</sub>+mH<sub>2</sub>O) are often linked to high adsorption of nutrients (C, N, P, S) and trace elements (e.g. As, Zn). However, under oxygen-limiting conditions, microbially derived sulfide (S(−II)) may cause the rapid reductive dissolution of ferrihydrite and the release of associated nutrients and trace elements, thus influencing the biogeochemical cycling of trace elements and nutrients, particularly in redox dynamic environments.</p><p>Sulfidization of ferrihydrite occurs rapidly, whereby electron transfer between surface complexed sulfide and the ferrihydrite surface results in (partially) oxidized sulfur species and Fe(II). Depending on the S(-II):Fe molar ratios, secondary reactions then lead to mackinawite (FeS) or pyrite (FeS<sub>2</sub>) precipitation. In nature, however, ferrihydrite is often found associated with natural organic matter (NOM). Because coprecipitation of ferrihydrite with NOM decreases particle size, alters the surface charge, and may block surface sorption sites, we speculated that kinetics and pathways of sulfidization of organic-associated ferrihydrite may differ from those of the pure mineral. Therefore, in this study, we followed iron mineral transformations and sulfur speciation during sulfidization of a pure ferrihydrite over one year and compared this to ferrihydrite coprecipitated with model organic ligands (polygalacturonic acid, galacturonic acid, and citric acid). Using a combination of solid- and aqueous phase Fe and S speciation techniques, we show that the impact of OM on ferrihydrite sulfidization kinetics and pathways varies with the chemical structure of the organic ligand, and that secondary reactions continue well past the initial rapid consumption of S(-II).</p>

scholarly journals Surface Tension of Surfactant-Containing, Finite Volume Droplets

2020 ◽  
Author(s):  
Bryan Bzdek ◽  
Rachael Miles ◽  
Jussi Malila ◽  
Hallie Boyer ◽  
Jim Walker ◽  
...  
Keyword(s):  
Surface Tension ◽  
Climate Models ◽  
High Surface ◽  
Particle Surface ◽  
Volume Ratio ◽  
Droplet Surface ◽  
Submicron Particles ◽  
Cloud Droplets ◽  
Droplet Shape ◽  
Size Dependent

<p>Surface tension influences the fraction of atmospheric particles that become cloud droplets. Recent field studies have indicated that surfactants, which lower the surface tension of macroscopic solutions, are an important component of aerosol mass. However, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. For surfactants to be relevant to particle activation into cloud droplets, multiple parameters must be considered. First, the concentration of surfactant in the initial particle must be sufficiently large that surface tension depression is maintained during activation, despite the dilution that occurs as water condenses onto the particle. Second, the high surface to volume ratio of micron and submicron particles necessitates partitioning a larger fraction of the surfactant molecules to the particle surface than in a typical solution, resulting in a depletion of the bulk concentration and an increase in the surface tension relative to a bulk sample. Third, the timescale for establishing equilibrium at the droplet surface must be known. The interplay of these parameters highlights the necessity of direct measurements of picolitre droplet surface tension.</p><p>This presentation will describe two cutting-edge approaches we have developed to directly measure the surface tension of microscopic droplets. In the first approach, ejection of ~20 µm radius surfactant-containing droplets from a dispenser excites oscillations in droplet shape that can be used to retrieve the droplet surface tension on microsecond timescales. These measurements allow investigation of surfactant partitioning timescales in aerosol and, crucially, test the assumption that droplet surfaces are generally in their equilibrium state. In the second approach, the coalescence of ~8 µm radius droplets is investigated. Coalescence excites droplet shape oscillations which again permit quantification of droplet surface tension. We demonstrate that surfactants can significantly reduce the surface tension of finite sized droplets below the value for water, consistent with recent field measurements. This surface tension reduction is droplet size dependent and does not correspond exactly to the macroscopic solution value. A new monolayer partitioning model confirms the observed size dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation and a 30% increase in cloud droplet number concentration, in line with a radiative cooling effect larger than current estimates assuming a water surface tension by 1 W·m<sup>-2</sup>. The results imply that one single value for surface tension cannot be used to predict the activated aerosol fraction.</p>

scholarly journals Facile Size-Controlled Synthesis of Fluorescent Carbon Nanoparticles with Size-Independent Optical Properties

2019 ◽  
Author(s):  
Aaron Schwartz-Duval ◽  
Neal Mistry ◽  
Indrajit Srivastava ◽  
Jasleena Singh ◽  
Kelsey Golk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Carbon Nanoparticles ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Gold Silver ◽  
Imaging Probes ◽  
Fluorescent Carbon Nanoparticles ◽  
Sugar Source ◽  
Fluorescent Carbon

Nanoparticle imaging probes and drug delivery systems have distinct advantages over free or diffusive delivery in that they can concentrate the imaging contrast agent and/or drug, elicit controlled release/degradation, and have a high surface area to volume ratio beneficial for attaching targeting ligands. The size of these nanoparticles affects delivery, retention, degradation rate, and sometimes the radiological properties of the particles. For many optically active nanoparticles (such as gold, silver, and quantum dots), the optical properties are directly dependent on the size and shape of the nanoparticles. While this provides a simplistic outlet for modifying the optical properties of those nanoparticles, it is limiting in that their applications are also dependent on morphology. In these works, we aim to determine if the optical properties of fluorescent carbon nanoparticles are dependent on size through variations in synthetic parameters. Fluorescent carbon nanoparticles with hydrodynamic diameters ranging from 10 – 500 nm were prepared through variations of sugar source, concentration of agave (as a sugar source) and incubation time. Through comparisons made between these nanoparticles, we found no change in the local absorbance maxima and refractive index, with < 5 nm shifting in fluorescence maxima location. We have observed that fluorescent carbon nanoparticles can be prepared within a large range of sizes (10 – 500 nm) without considerable shift in optical properties. Because of this observation, we can infer that the optical properties of fluorescent carbon nanoparticles are largely size independent.

Surface Stress Effect on the Vibrational Response of Circular Nanoplates With Various Edge Supports

2013 ◽  
Vol 80 (2) ◽  
Author(s):  
R. Ansari ◽  
R. Gholami ◽  
M. Faghih Shojaei ◽  
V. Mohammadi ◽  
S. Sahmani
Keyword(s):  
Differential Equation ◽  
Boundary Conditions ◽  
Surface Stress ◽  
High Surface ◽  
Continuum Theory ◽  
Volume Ratio ◽  
Stress Effect ◽  
Size Dependent ◽  
Surface Stress Effect ◽  
Generalized Differential

The classical continuum theory cannot be directly used to describe the behavior of nanostructures because of their size-dependent attribute. Surface stress effect is one of the most important size dependencies of structures at this submicron size, which is due to the high surface to volume ratio of nanoscale domain. In the present study, the nonclassical governing differential equation together with corresponding boundary conditions are derived using Hamilton's principle, into which the surface energies are incorporated through the Gurtin-Murdoch elasticity theory. The model developed herein contains intrinsic length scales to take the size effect into account and is used to analyze the free vibration response of circular nanoplates including surface stress effect. The generalized differential quadrature (GDQ) method is employed to discretize the governing size-dependent differential equation along with simply supported and clamped boundary conditions. The classical and nonclassical frequencies of circular nanoplates with various edge supports and thicknesses are calculated and are compared to each other. It is found that the influence of surface stress can be different for various circumferential mode numbers, boundary conditions, plate thicknesses, and surface elastic constants.

scholarly journals Electrostatic charging of wind-blown dust and implications on dust transport

2019 ◽  
Vol 99 ◽  
pp. 02011
Author(s):  
Joseph R. Toth ◽  
Siddharth Rajupet ◽  
Henry Squire ◽  
Blaire Volbers ◽  
Jùn Zhou ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Surface ◽  
Charged Particles ◽  
Volume Ratio ◽  
Dust Storms ◽  
Dust Transport ◽  
Size Dependent ◽  
Surprising Effect ◽  
Electrostatic Charging ◽  
Triboelectric Charging

It is well known that electric fields occur in wind-blown dust, due to the triboelectric charging of particles as they collide. Triboelectric charging, or contact electrification, is a poorly understood and complex phenomenon. It is especially important in granular systems, as the high surface-to-volume ratio can lead to the build-up of large amounts of charge. A particularly surprising effect, which is important in dust systems, is that charge transfer occurs in systems of a single composition, such that there is a particle-size dependent polarity of the particles. Here, we use a combined experimental and theoretical approach to elucidate the electrostatic charging that occurs during dust storms, and the effects of this electrostatic charging on dust transport. We create laboratory-scale wind-blown dust systems, and study the electrostatic charging. We find that larger particles tend to charge positive and to stay at or near the sand bed, while smaller particles tend to charge negative and get lofted to higher elevations. This self-segregating of charged particles would lead to electric fields within a dust storm. Our results show that electric fields then increase the dust transport by more easily lofting charged particles.

scholarly journals Facile Size-Controlled Synthesis of Fluorescent Carbon Nanoparticles with Size-Independent Optical Properties

2019 ◽  
Author(s):  
Aaron Schwartz-Duval ◽  
Neal Mistry ◽  
Indrajit Srivastava ◽  
Jasleena Singh ◽  
Kelsey Golk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Carbon Nanoparticles ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Gold Silver ◽  
Imaging Probes ◽  
Fluorescent Carbon Nanoparticles ◽  
Sugar Source ◽  
Fluorescent Carbon

Nanoparticle imaging probes and drug delivery systems have distinct advantages over free or diffusive delivery in that they can concentrate the imaging contrast agent and/or drug, elicit controlled release/degradation, and have a high surface area to volume ratio beneficial for attaching targeting ligands. The size of these nanoparticles affects delivery, retention, degradation rate, and sometimes the radiological properties of the particles. For many optically active nanoparticles (such as gold, silver, and quantum dots), the optical properties are directly dependent on the size and shape of the nanoparticles. While this provides a simplistic outlet for modifying the optical properties of those nanoparticles, it is limiting in that their applications are also dependent on morphology. In these works, we aim to determine if the optical properties of fluorescent carbon nanoparticles are dependent on size through variations in synthetic parameters. Fluorescent carbon nanoparticles with hydrodynamic diameters ranging from 10 – 500 nm were prepared through variations of sugar source, concentration of agave (as a sugar source) and incubation time. Through comparisons made between these nanoparticles, we found no change in the local absorbance maxima and refractive index, with < 5 nm shifting in fluorescence maxima location. We have observed that fluorescent carbon nanoparticles can be prepared within a large range of sizes (10 – 500 nm) without considerable shift in optical properties. Because of this observation, we can infer that the optical properties of fluorescent carbon nanoparticles are largely size independent.

Experimental and Theoretical Investigations of Complex Formation of Substituted Phenylazo-Derivatives of Methylphloroglucinol

2016 ◽  
Vol 12 (8) ◽  
pp. 295-300
Author(s):  
Olga Kovalchukova ◽  
Amangdam A.T. ◽  
Strashnova S.B. ◽  
Strashnov P.V. ◽  
Romashkina E.P. ◽  
...  
Keyword(s):  
Complex Formation ◽  
Organic Ligand ◽  
Spectrophotometric Titration ◽  
Organic Ligands ◽  
Oh Groups ◽  
Tautomeric Forms ◽  
Theoretical Investigations ◽  
Derivatives Of ◽  
Theoretical Results ◽  
Titration Technique

Using spectrophotometric titration technique, the processes of complex formation of some phenylazo-derivatives of methylphloroglucinol (MPG) containing hydroxo-, nitro- and nitroso-substituents were studied. The spectral criteria of neutral and ionized forms of the organic ligands in their different tautomeric forms were determined.It was detected that the complex formation is accompanied by formation of one or two chelate cycles which involve azo- or nitroso-fragments and neighboring OH-groups of the organic ligands. Different types of coordination lead to different changes in the electronic absorption spectra.The DFT-B3LYP modeling of a Ni(II) complex of α-hydroxyphenylazo MPG established the most probable coordination mode of the organic ligand: tridentate chelating dianion, distorted square coordination of Ni-cations including one water molecule.  The theoretical results are in a good accordance with the experimental data.

scholarly journals Electrospun Nanofibers for Sensing and Biosensing Applications—A Review

2021 ◽  
Vol 22 (12) ◽  
pp. 6357
Author(s):  
Kinga Halicka ◽  
Joanna Cabaj
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Toxic Metal ◽  
Volume Ratio ◽  
Electrospun Nanofibers ◽  
Clinical Diagnostics ◽  
Loading Capacity ◽  
Electrospun Nanofiber ◽  
Sensing Platforms ◽  
Different Types

Sensors and biosensors have found applications in many areas, e.g., in medicine and clinical diagnostics, or in environmental monitoring. To expand this field, nanotechnology has been employed in the construction of sensing platforms. Because of their properties, such as high surface area to volume ratio, nanofibers (NFs) have been studied and used to develop sensors with higher loading capacity, better sensitivity, and faster response time. They also allow to miniaturize designed platforms. One of the most commonly used techniques of the fabrication of NFs is electrospinning. Electrospun NFs can be used in different types of sensors and biosensors. This review presents recent studies concerning electrospun nanofiber-based electrochemical and optical sensing platforms for the detection of various medically and environmentally relevant compounds, including glucose, drugs, microorganisms, and toxic metal ions.

scholarly journals Study of the geometry of open channels in a layer-bed-type microfluidic immobilized enzyme reactor

2021 ◽  
Author(s):  
Cynthia Nagy ◽  
Robert Huszank ◽  
Attila Gaspar
Keyword(s):  
Immobilized Enzyme ◽  
High Surface ◽  
Volume Ratio ◽  
Volumetric Flow Rate ◽  
Enzyme Reactor ◽  
Channel Pattern ◽  
Immobilized Enzyme Reactor ◽  
Split Flow ◽  
Parallel Streams ◽  
Enzymatic Microreactors

AbstractThis paper aims at studying open channel geometries in a layer-bed-type immobilized enzyme reactor with computer-aided simulations. The main properties of these reactors are their simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make these devices one of the simplest yet efficient enzymatic microreactors. The high surface-to-volume ratio of the reactor was achieved using narrow (25–75 μm wide) channels. The simulation demonstrated that curves support the mixing of solutions in the channel even in strong laminar flow conditions; thus, it is worth including several curves in the channel system. In the three different designs of microreactor proposed, the lengths of the channels were identical, but in two reactors, the liquid flow was split to 8 or 32 parallel streams at the inlet of the reactor. Despite their overall higher volumetric flow rate, the split-flow structures are advantageous due to the increased contact time. Saliva samples were used to test the efficiencies of the digestions in the microreactors. Graphical abstract

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