scholarly journals Importance of Surface Topography in Both Biological Activity and Catalysis of Nanomaterials: Can Catalysis by Design Guide Safe by Design?

2021 ◽  
Vol 22 (15) ◽  
pp. 8347
Author(s):  
Mary Gulumian ◽  
Charlene Andraos ◽  
Antreas Afantitis ◽  
Tomasz Puzyn ◽  
Neil J. Coville
Keyword(s):  
Physicochemical Property ◽  
Surface Topography ◽  
Surface Area ◽  
Surface Properties ◽  
Active Sites ◽  
Active Surface ◽  
Predictive Toxicology ◽  
Surface Sites ◽  
Active Surface Sites ◽  
Safe By Design

It is acknowledged that the physicochemical properties of nanomaterials (NMs) have an impact on their toxicity and, eventually, their pathogenicity. These properties may include the NMs’ surface chemical composition, size, shape, surface charge, surface area, and surface coating with ligands (which can carry different functional groups as well as proteins). Nanotopography, defined as the specific surface features at the nanoscopic scale, is not widely acknowledged as an important physicochemical property. It is known that the size and shape of NMs determine their nanotopography which, in turn, determines their surface area and their active sites. Nanotopography may also influence the extent of dissolution of NMs and their ability to adsorb atoms and molecules such as proteins. Consequently, the surface atoms (due to their nanotopography) can influence the orientation of proteins as well as their denaturation. However, although it is of great importance, the role of surface topography (nanotopography) in nanotoxicity is not much considered. Many of the issues that relate to nanotopography have much in common with the fundamental principles underlying classic catalysis. Although these were developed over many decades, there have been recent important and remarkable improvements in the development and study of catalysts. These have been brought about by new techniques that have allowed for study at the nanoscopic scale. Furthermore, the issue of quantum confinement by nanosized particles is now seen as an important issue in studying nanoparticles (NPs). In catalysis, the manipulation of a surface to create active surface sites that enhance interactions with external molecules and atoms has much in common with the interaction of NP surfaces with proteins, viruses, and bacteria with the same active surface sites of NMs. By reviewing the role that surface nanotopography plays in defining many of the NMs’ surface properties, it reveals the need for its consideration as an important physicochemical property in descriptive and predictive toxicology. Through the manipulation of surface topography, and by using principles developed in catalysis, it may also be possible to make safe-by-design NMs with a reduction of the surface properties which contribute to their toxicity.

scholarly journals Irreversible loss of ice nucleation active sites in mineral dust particles caused by sulphuric acid condensation

2010 ◽  
Vol 10 (23) ◽  
pp. 11471-11487 ◽  
Author(s):  
R. C. Sullivan ◽  
M. D. Petters ◽  
P. J. DeMott ◽  
S. M. Kreidenweis ◽  
H. Wex ◽  
...  
Keyword(s):  
Sulphuric Acid ◽  
Active Sites ◽  
Mineral Dust ◽  
Active Surface ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Ammonia Gas ◽  
Surface Sites ◽  
Active Surface Sites ◽  
Acid Coating

Abstract. During the FROST-2 (FReezing Of duST) measurement campaign conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS), we investigated changes in the ice nucleation properties of 300 nm Arizona Test Dust mineral particles following thermochemical processing by varying amounts and combinations of exposure to sulphuric acid vapour, ammonia gas, water vapour, and heat. The processed particles' heterogeneous ice nucleation properties were determined in both the water subsaturated and supersaturated humidity regimes at −30 °C and −25 °C using Colorado State University's continuous flow diffusion chamber. The amount of sulphuric acid coating material was estimated by an aerosol mass spectrometer and from CCN-derived hygroscopicity measurements. The condensation of sulphuric acid decreased the dust particles' ice nucleation ability in proportion to the amount of sulphuric acid added. Heating the coated particles in a thermodenuder at 250 °C – intended to evaporate the sulphuric acid coating – reduced their freezing ability even further. We attribute this behaviour to accelerated acid digestion of ice active surface sites by heat. Exposing sulphuric acid coated dust to ammonia gas produced particles with similarly poor freezing potential; however a portion of their ice nucleation ability could be restored after heating in the thermodenuder. In no case did any combination of thermochemical treatments increase the ice nucleation ability of the coated mineral dust particles compared to unprocessed dust. These first measurements of the effect of identical chemical processing of dust particles on their ice nucleation ability under both water subsaturated and mixed-phase supersaturated cloud conditions revealed that ice nucleation was more sensitive to all coating treatments in the water subsaturated regime. The results clearly indicate irreversible impairment of ice nucleation activity in both regimes after condensation of concentrated sulphuric acid. This implies that the sulphuric acid coating caused permanent chemical and/or physical modification of the ice active surface sites; the possible dissolution of the coating during droplet activation did not restore all immersion/condensation-freezing ability.

scholarly journals Irreversible loss of ice nucleation active sites in mineral dust particles caused by sulphuric acid condensation

2010 ◽  
Vol 10 (7) ◽  
pp. 16901-16940 ◽  
Author(s):  
R. C. Sullivan ◽  
M. D. Petters ◽  
P. J. DeMott ◽  
S. M. Kreidenweis ◽  
H. Wex ◽  
...  
Keyword(s):  
Sulphuric Acid ◽  
Active Sites ◽  
Mineral Dust ◽  
Active Surface ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Ammonia Gas ◽  
Surface Sites ◽  
Active Surface Sites ◽  
Acid Coating

Abstract. During the FROST-2 (FReezing Of duST) measurement campaign conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS), we investigated changes in the ice nucleation properties of 300 nm Arizona test dust mineral particles following thermochemical processing by varying amounts and combinations of exposure to sulphuric acid vapour, ammonia gas, water vapour, and heat. The processed aerosol's heterogeneous ice nucleation properties were determined in both the water subsaturated and supersaturated humidity regimes at −30 °C and −25 °C using Colorado State University's continuous flow diffusion chamber. The amount of sulphuric acid coating material was estimated by an aerosol mass spectrometer and from CCN-derived hygroscopicity measurements. The condensation of sulphuric acid decreased the dust particles' ice nucleation ability in proportion to the amount of sulphuric acid added. Heating the coated particles in a thermodenuder at 250 °C – intended to evaporate the sulphuric acid coating – reduced their freezing ability even further. We attribute this behaviour to accelerated acid digestion of ice active surface sites by heat. Exposing sulphuric acid coated dust to ammonia gas produced particles with similarly poor freezing potential; however a portion of their ice nucleation ability could be restored after heating in the thermodenuder. In no case did any combination of thermochemical treatments increase the ice nucleation ability of the coated mineral dust particles compared to unprocessed dust. These first measurements of the effect of identical chemical processing of dust particles on their ice nucleation ability in both water subsaturated and mixed-phase supersaturated cloud conditions revealed that ice nucleation was more sensitive to all coating treatments in the water subsaturated regime. The results clearly indicate irreversible impairment of ice nucleation activity in both regimes after condensation of concentrated sulphuric acid. This implies that the sulphuric acid coating caused permanent chemical and/or physical modification of the ice active surface sites; the possible dissolution of the coating during droplet activation did not restore all immersion/condensation-freezing ability.

Oxygen vacancies as active sites for H2S dissociation on the rutile TiO2(110) surface: a first-principles study

2016 ◽  
Vol 18 (9) ◽  
pp. 6706-6712 ◽  
Author(s):  
Fang Wang ◽  
Shiqian Wei ◽  
Zhi Zhang ◽  
Great R. Patzke ◽  
Ying Zhou
Keyword(s):  
First Principles ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Active Surface ◽  
Energy Barriers ◽  
Rutile Tio2 ◽  
Surface Sites ◽  
First Principles Study ◽  
Active Surface Sites

Bridged oxygen vacancies act as active surface sites markedly reducing the energy barriers for the paths along H2S dissociation on the rutile TiO2(110) surface.

Etching-Assisted Route to Heterophase Au Nanowires with Multiple Types of Active Surface Sites for Silane Oxidation

Nano Letters ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 6363-6369 ◽  
Author(s):  
Chaoqi Wang ◽  
Xiang Li ◽  
Lei Jin ◽  
Peng-Han Lu ◽  
Catherine Dejoie ◽  
...  
Keyword(s):  
Active Surface ◽  
Surface Sites ◽  
Active Surface Sites ◽  
Au Nanowires

scholarly journals Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

2016 ◽  
Vol 16 (20) ◽  
pp. 13359-13378 ◽  
Author(s):  
Hassan Beydoun ◽  
Michael Polen ◽  
Ryan C. Sullivan
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
Particle Surface ◽  
Active Surface ◽  
Freezing Temperature ◽  
Ice Nucleation ◽  
Critical Surface ◽  
Cold Plate ◽  
Particle Surface Area ◽  
Immersion Freezing

Abstract. Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general active site density functions, such as the popular ns parameterization, cannot be reliably extrapolated below this critical surface area threshold to describe freezing curves for lower particle surface area concentrations. Freezing curves obtained below this threshold translate to higher ns values, while the ns values are essentially the same from curves obtained above the critical area threshold; ns should remain the same for a system as concentration is varied. However, we can successfully predict the lower concentration freezing curves, which are more atmospherically relevant, through a process of random sampling from g distributions obtained from high particle concentration data. Our analysis is applied to cold plate freezing measurements of droplets containing variable concentrations of particles from NX illite minerals, MCC cellulose, and commercial Snomax bacterial particles. Parameterizations that can predict the temporal evolution of the frozen fraction of cloud droplets in larger atmospheric models are also derived from this new framework.

Control of the Surface Reactivity of the Si(100) Surface

1986 ◽  
Vol 75 ◽  
Author(s):  
John T. Yates ◽  
M. J. Bozack ◽  
L. Muehlhoff ◽  
W. J. Choyke
Keyword(s):  
Vapor Deposition ◽  
Active Sites ◽  
Surface Reaction ◽  
Adsorbed Layer ◽  
Chemical Vapor ◽  
Active Surface ◽  
Surface Reactivity ◽  
Surface Kinetics ◽  
Active Surface Sites ◽  
Kinetics Of

AbstractWe have used molecular beam methods and temperature programmed desorption to probe the reaction of several hydrocarbons with the Si(100) surface at cryogenic temperatures. It has been found that the kinetics of the surface reaction with the C=C bond can be strongly influenced by the production of active surface sites using prebombardment with Ar ions. The chemistry of the adsorbate is also influenced by electron bombardment of the adsorbed layer. Conversely, capping of active sites with atomic hydrogen retards the kinetics of the surface reaction. This work forms a first step in using the methods of surface kinetics and spectroscopy to probe the details of the elementary steps at work in chemical vapor deposition and plasma vapor deposition, leading to the production of SiC films.

scholarly journals Unveiling the Active Surface Sites in Heterogeneous Titanium-Based Silicalite Epoxidation Catalysts: Input of Silanol-Functionalized Polyoxotungstates as Soluble Analogues

ACS Catalysis ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 2330-2342 ◽  
Author(s):  
Teng Zhang ◽  
Louis Mazaud ◽  
Lise-Marie Chamoreau ◽  
Céline Paris ◽  
Anna Proust ◽  
...  
Keyword(s):  
Active Surface ◽  
Surface Sites ◽  
Active Surface Sites

Bound Rubber and Elastomer-Filler Interaction

1995 ◽  
Vol 68 (2) ◽  
pp. 297-310 ◽  
Author(s):  
B. Meissner
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Active Sites ◽  
Quantitative Description ◽  
Interfacial Area ◽  
Active Surface ◽  
Unit Surface Area ◽  
Bound Rubber ◽  
The Difference ◽  
High Structure

Abstract The statistical theory of bound rubber and the polymer-filler gel formation theory are shown to offer a satisfactory quantitative description of a set of experimental bound-rubber data recently obtained by Wolff, Wang, Tan (Rubber Chem. Technol. 66, 163 (1993)) on SBR compounds filled with 17 furnace blacks covering the whole range of rubber grades. The observed decrease of bound-rubber content per unit of interfacial area with increasing loading and/or specific surface area of carbon black is explained by the theory as being due to the statistical nature of the adsorption process. A correlation was found to exist between specific surface activity of filler D (adjustable parameter of the theory, number of active sites per unit surface area) and filler structure, the latter being characterized by the difference between DBP absorption and crushed DBP absorption. Also, D was found to increase with loading of a high-structure black. The two effects are ascribed to filler aggregates breakdown during mixing, which leads to a new active surface formation for polymer bonding.

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