Structure, Aggregation and Characterization of Nanoparticles
01 Jan 2001-Reviews in Mineralogy & Geochemistry (Mineralogical Society of America)-Vol. 44, Iss: 1, pp 105-166
TL;DR: In this article, various techniques by which nanoparticle structure, size, microstructure, shape and size distribution are determined are then considered with examples, emphasizing natural processes and compositions.
Abstract: ### Structural aspects of natural nanomaterials
A large number of mineral species occur only as micron-sized and smaller crystallites. This includes most of the iron and manganese oxyhydroxide minerals, and other species whose formation processes and growth conditions limit ultimate size. Microscopic investigation of these species generally reveals sub-micron structure down to the nanometer level, including evidence of aggregation, agglomeration and assembly of nanometer units into larger crystals and clots. The bulk of studies in the literature dealing with nanoparticle structure and growth deal with metals, silicon, and other semiconductor materials. A great deal of attention has been given to the electronic properties of such solids, owing to both new commercial applications and new fundamental physics and chemistry tied to this area. Most applicable mineralogical or geochemical studies have not addressed the same issues, instead being more concerned with relatively bulk chemical properties. Very little has been done to understand how natural nanoparticulates (and related types of natural nanomaterials) form, how their microstructure is related to the growth process, and how their structure varies from larger crystallites or bulk material of the same composition. Magnetic and electronic properties of natural nanomaterials are similarly understudied.
In this chapter aspects of nucleation, aggregation and growth processes that give rise to specific microstructures and forms of nanomaterials are considered. Next the way in which the surface structure of nanoparticulates may differ from the interior, and how physical structure may be modified by reduced particle size is examined. The various techniques by which nanoparticle structure, size, microstructure, shape and size distribution are determined are then considered with examples. Finally some of the outstanding problems associated with nanoparticle structure and growth are identified, emphasizing natural processes and compositions.
### Definitions
Naturally occurring nanomaterials exist in a variety of complex forms. In this chapter a short set of definitions will be stated for clarity. …
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TL;DR: Biomineralization refers to the processes by which organisms form minerals and is a discipline that is certain to see major advancements as a new generation of scientists brings cross-disciplinary training and new experimental and computational methods to the most daunting problems as mentioned in this paper.
Abstract: “Biomineralization links soft organic tissues, which are compositionally akin to the atmosphere and oceans, with the hard materials of the solid Earth. It provides organisms with skeletons and shells while they are alive, and when they die these are deposited as sediment in environments from river plains to the deep ocean floor. It is also these hard, resistant products of life which are mainly responsible for the Earth’s fossil record. Consequently, biomineralization involves biologists, chemists, and geologists in interdisciplinary studies at one of the interfaces between Earth and life.” (Leadbeater and Riding 1986)
Biomineralization refers to the processes by which organisms form minerals. The control exerted by many organisms over mineral formation distinguishes these processes from abiotic mineralization. The latter was the primary focus of earth scientists over the last century, but the emergence of biogeochemistry and the urgency of understanding the past and future evolution of the Earth are moving biological mineralization to the forefront of various fields of science, including the earth sciences.
The growth in biogeochemistry has led to a number of new exciting research areas where the distinctions between the biological, chemical, and earth sciences disciplines melt away. Of the wonderful topics that are receiving renewed attention, the study of biomineral formation is perhaps the most fascinating. Truly at the interface of earth and life, biomineralization is a discipline that is certain to see major advancements as a new generation of scientists brings cross-disciplinary training and new experimental and computational methods to the most daunting problems. It is, however, by no means a new field. The first book on biomineralization was published in 1924 in German by W.J. Schmidt (Schmidt 1924), and the subject has continued to intrigue a dedicated community of scientists for many years. Until the early 1980s the field was known as …
879 citations
19 Jun 2008-Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment
TL;DR: An overview of the characteristics of nanoparticles that could affect their behaviour and toxicity, as well as techniques available for their determination are provided, which could be optimized to provide the necessary information.
Abstract: Nanotechnology is developing rapidly and, in the future, it is expected that increasingly more products will contain some sort of nanomaterial. However, to date, little is known about the occurrence, fate and toxicity of nanoparticles. The limitations in our knowledge are partly due to the lack of methodology for the detection and characterisation of engineered nanoparticles in complex matrices, i.e. water, soil or food. This review provides an overview of the characteristics of nanoparticles that could affect their behaviour and toxicity, as well as techniques available for their determination. Important properties include size, shape, surface properties, aggregation state, solubility, structure and chemical composition. Methods have been developed for natural or engineered nanomaterials in simple matrices, which could be optimized to provide the necessary information, including microscopy, chromatography, spectroscopy, centrifugation, as well as filtration and related techniques. A combination of these is often required. A number of challenges will arise when analysing environmental and food materials, including extraction challenges, the presence of analytical artifacts caused by sample preparation, problems of distinction between natural and engineered nanoparticles and lack of reference materials. Future work should focus on addressing these challenges.
643 citations
638 citations
TL;DR: The “life history of nanoparticles” is presented, tracking it from its formation to its potential use and eventual fate in the environment, and the ability to characterize and capture these nanoparticles as well as their control is discussed.
Abstract: Nanoparticles are a class of materials with properties distinctively different from their bulk and molecular counterparts. A critical review of the very broad topic of environmental nanoparticles is presented. Because of the vast nature of the topic, the review is focused primarily on gas-borne nanoparticles. The "life history of nanoparticles" is presented, tracking it from its formation to its potential use and eventual fate in the environment. Nanoparticle sources, anthropogenic emissions from industrial and occupational settings, and conversion and formation in the atmosphere are discussed. The ability to characterize and capture these nanoparticles (as would be necessary in a nanoparticle production system), as well as their control (of emissions from an industrial source) is discussed. A description on the use of nanoparticles in environmental technologies and the potential impact on the energy sector is provided. The potential effects on human health and the environment, both adverse and beneficial, are important aspects that need to be considered. As will be evident, the study of "environmental nanoparticles" is a new and fast-growing field. Much work remains to be done before we can fully harness the advantages of nanoparticles and ensure that there are no potential adverse consequences. A set of recommendations for additional work in each area is provided.
637 citations
TL;DR: This paper presented a kinetic model evaluating the supply of bioavailable Fe to surface seawater by ferrihydrite dissolution, photoreduction and siderophore-aided dissolution.
Abstract: Presented here is a combined historical account, current synthesis and a perspective of how the modern Fe cycle functions, and how this cycle has evolved through geologic time. We begin by highlighting how new developments in nanogeoscience demonstrate the importance of nanoparticulate Fe (oxyhydr) oxide aggregates in the modern iron cycle. We further document how these aggregates are supplied from shelf sediments, aeolian dust and icebergs to the global ocean. Based on these observations, we present a kinetic model evaluating the supply of bioavailable Fe to surface seawater by ferrihydrite dissolution, photoreduction and siderophore-aided dissolution. The model indicates that the rate of delivery of bioavailable Fe from icebergs to the Southern Ocean is at least as large as that by wind-blown dust. However estimates of all the main aqueous, nanoparticulate and colloidal (and potentially bioavailable) Fe inputs to the ocean are poorly-constrained.
We provide a historical perspective on the evolution of ideas as to how sedimentary pyrite formation is controlled and how these ideas led to the development of the Fe-based palaeoenvironmental proxies widely used today. This provides a springboard into our discussion of the ancient Fe cycle, which begins with a survey of how Fe interacts with a variety of other elements of biogeochemical interest including sulphur, oxygen and nitrogen. We highlight how interactions between these elements have evolved through geologic time, and how these interactions define the evolution of ocean and atmospheric chemistry. It is clear that the Fe cycle has gained a prominent role in regulating the biogeochemical function of the oceans through time. We offer, in the end, suggestions and a geochemical perspective as to how recent momentum in our understanding of the Fe cycle may be harnessed into catalysing future progress in the field.
558 citations
References
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TL;DR: The forces between atoms and molecules are discussed in detail in this article, including the van der Waals forces between surfaces, and the forces between particles and surfaces, as well as their interactions with other forces.
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18,048 citations
TL;DR: In this paper, a structure refinement method was described which does not use integrated neutron powder intensities, single or overlapping, but employs directly the profile intensities obtained from step-scanning measurements of the powder diagram.
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14,360 citations
TL;DR: In this paper, a simple route to the production of high-quality CdE (E=S, Se, Te) semiconductor nanocrystallites is presented, based on pyrolysis of organometallic reagents by injection into a hot coordinating solvent.
Abstract: A simple route to the production of high-quality CdE (E=S, Se, Te) semiconductor nanocrystallites is presented. Crystallites from ∼12 A to ∼115 A in diameter with consistent crystal structure, surface derivatization, and a high degree of monodispersity are prepared in a single reaction. The synthesis is based on the pyrolysis of organometallic reagents by injection into a hot coordinating solvent. This provides temporally discrete nucleation and permits controlled growth of macroscopic quantities of nanocrystallites. Size selective precipitation of crystallites from Portions of the growth solution isolates samples with narrow size distributions (<5% rms in diameter). High sample quality results in sharp absorption features and strong «band-edge» emission which is tunable with particle size and choice of material
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