Environmental transformations of nanomaterials & Environmental corona Flashcards
What is nanotechnology?
creation and utilization of materials, devices, and systems through the control of matter on the nanometer-length scale
How can nanoparticles be thought of as enabling technologies
they allow other technologies/ products to function better
What are the main application areas of nanoparticles?
Textiles
Biomedical
Healthcare
Food agriculture
Industrial
Electronics
Environment
Renewable energy
What forms can nanomaterials be found in?
Nanoparticles
Nanorods/ nanowires
Arrays of nanoparticles
Nanostructure surfaces
What are the dimensions of nanoparticles?
less then 100nm in all 3 dimensions
What are the dimensions of nanowires?
2 dimensions less then 100nm with “length” being larger then 100nm
What can nanostructures develop materials to be?
anti-fouling= prevent attachment of unwanted organisms
What happens as you make an object smaller?
more exposed to surface
What is the equation for the surface area of a sphere?
4πr*2
What is the equation for volume of a sphere?
4/3πr*3
What is the equation for volume of a cube?
s*3
What is the equation for volume of a rectangular solid?
lwh
(length, width, height)
What is the equation for volume of a right circular cylinder?
πr*2h
What is the equation for the surface area of a cube?
6s*2
What is the equation for the surface area of a rectangular solid?
2wl+2lh+2wh
What is the equation for the surface area of a right circular cylinder?
2πr*2+2πrh
What nanoparticles properties can affect environmental fate?
Concentration
Shape
Size
Size distribution
Structure/ crystallinity
Composition
Porosity/ surface area
Surface functionality
Surface change
Surface speciation
Agglomeration state
What 2 forces are there in colloids/ nanomaterials?
Electrostatic stabilisation
Steric stabilisation
What is electrostatic stabilisation?
Wander Vaals attraction counterbalanced by electrostatic repulsion of atoms with same charge
What is more stable between electrostatic stabilisation and steric stabilisation?
Steric as less environmentally sensitive
What theory describes electrostatic stabilisation?
DLVO
What happens if the charge of electrostatic stabilisation is neutralised?
particles will become unstable and agglomerate
What is an acid? (in relation to water)
a substance which produces H+ (aq) ions when dissolved in water
What is the word formula for the neutralisation reaction?
Acid + base ↔ salt + water
What happens to nanomaterials if a stabilising agent (i.e., stabilising steric) is added?
there will be no aggregation
How do nanoparticle surfaces acquire charge?
Ionisation of surface groups (attraction between positive NP and negative ions)
Specific adsorption of ions (ionic surfactants)
What is an example of an ionic surfactant which can be attributed to nanoparticles acquiring charge?
Anionic surfactant
What is zeta potential?
measure of the surface charge of particles in aqueous solution
What is the electrical double layer when considering nanoparticles?
Double layer- where some water and counter ions are pulled along with particle
What is the slipping plane when considering nanoparticles?
the plane defined by the distance at which the structure with its chemically bound water and ions moves in bulk through the solution
What process can be used to measure zeta potential?
electrophoresis
How does electrophoresis work?
2 electrodes one positive charge and one negative with opposite chare particles being pulled to each one
Cells and particles move with a velocity dependant on which properties?
Electrical field strength
Dielectric constant of the medium
Viscosity of the medium
Zeta potential
What occurs at the isoelectric point?
all charges are neutralised
What is the zeta potential dependant on?
pH
What is stability like around the isoelectric point?
Unstable until either +20 or -20 zeta potential
What does stabilisation of nanoparticles depend on?
strength of acid
What is a strong acid?
acid which is completely ionised in water
What is a weak acid? (with example)
partially ionises in water
e.g., ethanoic acid
What does a higher Ka (acidity dissociation constant) mean?
A stronger acid
What is the difference acid strength and acidity?
Acid strength in water= molecule property
Acidity= qualitive measure of its pH
What is the Lewis theory? (acids and bases)
Bases donate electron pairs
Acids accept electron pairs
What are the advantages of the Lewis theory?
Compliments redox
Suggest acid react with bases to share electron with no REDOX number change
Expands number of acid and bases and their reactions
What is the HSAB theory?
Pearson’s Hard and Soft Acid and Bases theory
How does HSAB further the Lewis theory?
Lewis acids and bases can be further split into hard or soft or boder-line
What are hard Lewis acids characterised by?
small ionic radii,
high positive charge,
strongly solvated,
empty orbitals in the
valence shell and with high energy LUMO
What dies LUMO stand for?
Lowest Unoccupied Molecular Orbital
What are soft Lewis acids characterised by?
large ionic radii,
low positive charge,
completely filled atomic orbitals and with low energy LUMO
What is the principle of HSAB?
hard acids prefer binding to the hard bases
to give ionic complexes, whereas the soft
acids prefer binding to soft bases to give
covalent complexes
How does the HSAB theory affect precipitation reactions?
The softer acids like Ag+, Hg+, Hg2+ etc., and border line acids like Fe2+, Ni2+, Cu2+, Zn2+, Pb2+ etc., can be precipitated as sulphides from aqueous solutions since S2- ion is a softer base
What can the photodegradation of nanoparticle coatings lead to?
aggregation
What does oxidation of nanoparticles lead to?
dissolution and release to toxic Ag+ (aq)
What can nanoparticle interaction with different ligands do?
Promote or inhibit oxidation and dissolution
What can Thiol Ligands increase in nanoparticles?
dissolution
What does sulfidation do to nanoparticles?
Inhibits dissolution
What does sulfidation of Ag nanoparticles surface do?
Reduces their ecotoxicity
What is the oxidative dissolution timescale of Ag0 nanoparticles?
Relatively short - days to weeks
Why is oxysulphidation?
mechanism by which silver is oxidized and sulfidized at the metal without dissolution and release of Ag+ ions
What might the result be of oxysulfidation at high sulfide to AgNP Molar ratios?
formation of a passivating layer of Ag2S around the Ag0 core of AgNPs, thus slowing or preventing further Ag+ release
What is a passivating layer?
creation of an outer layer of shield material
What is homoaggregation?
this is when just nanoparticles agglomerate together to form a larger molecule
What does agglomeration do to nanoparticles?
Increases size but reduces surface area and reactivity
What can happen to a molecule that has undergone homoaggregation?
the homoaggregated molecules can end up undergoing heteroaggregation
What is heteroaggregation?
Can occur to nanoparticles individually or aggregated and is when they join a larger different particle
What does heteroaggregation do to nanoparticles?
increases particle size and affects transport and reactivity
What can biological oxidation result in?
Carboxylation of CNTs (carbon nano tube) or formaiton of an insoluble metal oxide shell
What can biological degredation of polymer coatings on nanomaterial affect?
surface properties and lead to aggregation
What does adsorption of biomacromolecule affect?
Aggregation
Uptake
Biodistribution
Dissolution
What can adsorption of Natural Organic Matter (NOM) do when nanoparticles interact with bio-macromolecules?
Can displace smaller ligands and stabilise the nanomaterial against aggregation
or
Causes flocculation
What can adsorption of natural organic matter do to layering in the molecule?
can lead to poorly characterised heterogeneous mixed polymer-NOM layers
How can bacteria and toxicity be affected by adsorption of Natural Organic matter on nanoparticles?
Decrease nanoparticle-bacteria interactions
Decrease ion dissolution and thus toxicity
What is the distribution of environmental corona in different resevoirs?
Atmospheric - air =1.5%
Industrial - land fill= 63-91%
Terrestrial- soils= 8-28%
Aquatic- surface water= 7%
What are the atmospheric sources of environmental corona?
Humans- breath condensate
Atmo bacteria- Pseudomonas syringae
Pollen generating plants- grass
What are the terrestrial sources of environmental corona?
Crops- rice, wheat, maize
Rhizosphere- Rhizobiaceae, nitrobacter, azotobacter
What are the industrial sources of environmental corona?
Proteobacteria- Alphaproteobacteria, Delta” and Beta”
What are the aquatic sources of environmental corona?
Biofilms- E.coli, cyanobacteria
Crustaceans- Daphnia
Fish- Dani rerio, Oncorhynchus mykiss
What will nanomaterials bind to in the environment?
bio-molecules or co-pollutants
What is the effect of nanomaterials binding to bio-molecules or co-pollutants?
Reduce surface reactivity
New particle identity (i.e., more like food)
What are the environment factors for protein corona?
Composition
Exposure time
pH
Temperature
Shear stress
What does the binding of nanoparticles depend on in the environment?
affinities of available molecules
What do nanoparticle and environmental characteristics play a role in determining?
what proteins/ biomolecules bind
What are some examples of protein characteristics?
Charge,
Hydrophobicity,
Molecular weight,
Abundance
What are the Cooperativity effects?
the presence of one protein attracts another
What are the main parts of the complex soup of secretions?
Bacterial gut secretions
Moulting
Moulting fluid
Signalling/ Kairomones
Undigested matter
What are the parts of bacterial gut secretions?
Bacteria released by conspecific horizontal transmission
Release of Enzyme/ structural proteins from degraded bacteria
By-product- harmful algae
What is the moulting part of the complex soup of secretions?
carbohydrate chitin-based exoskeleton
What is the moulting fluid of the complex soup of secretions made up of?
Digestion enzymes (proteins) chitinase/ chitinobase
What occurs in the signalling/ Kariomones part of the complex soup of secretions?
Overcrowding/ stress induced signalling to regulate population
Signalling to algae
What is the undigested matter of the complex soup of secretions made up of?
Undigested algae
Organic detrius (dead organic matter)
Bacteria
Algae
What are the different types of environmental corona?
simplified corona
Complex corona
Corona formed in vivo
Corona formed insitu
What is simplified corona?
ex-vivo (outside organism)
One or few biomolecule
What are the characteristics of complex corona?
ex-vivo
biomolecular diversity
What are the characteristics in vivo corona?
in-vivo = in organism formed
biomolecular diversity in & near organisms
