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76 Cards in this Set

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Where are silver NPs

electronics, paints, sunscreens

Function of silver NPs

Disinfection of air, water, surface



silver NPs mechanisms

Adhesion to cell membranes, penetrates cell to damage DNA, release of Ag+ ion

Synthesis of Ag NPs (2 routes)

Physical: evaporation/condensation, laser ablation


Chemical: chemical reduction

Evaporation-condensation technique




Laser ablation

Tube furnace at atmospheric pressure, ceramic heater




Pure colloids

chemical reduction

most frequently applied, ag+ions-->silver atoms-->colloidal Ag particles

Green synthesis of Ag NPs

Selection of solvent medium, environmentally benign reducing agent, selection of nontoxic substances for Ag NPs stability




Aqueous stem extract, antidiabetic/antioxidant activity, inhibit free radicals

Antibacterial mechanisms

Disrupts membrane permeability and inhibits DNA replication

Toxicity?

To organisms and the ecosystem

Biosensors applications silver NPs

Surface enhanced raman spectroscopy

silver NPs water treatment application

Coat, foams by overnight exposure, antibacterial

silver NPs paints (antibacterial application)

eco-friendly raw materials, no extra purification process

Advantages of silver NPs

Low toxicity to humans, antibacterial, prevents coagulation of paint, biocide, scratch-free film

silver NPs future

Photocatalyst, pathogen detection (surface coatings)


reactivity, anti-fouling (membranes)

Carbon nanotubes synthesis

cylindrical graphite sheets rolled up into tube-like structure, single-walled/multi-walled

Carbon nanotubes beneficial properties

low energy consumption, thermal stability, anti-fouling/antibacterial, self cleaning

Carbon nanotubes surfactant design leads to...

Adsorption of heavy metals

Carbon nanotubes use in desalination membranes

removes unwanted compounds, can be vertically aligned (large water flux) or mixed matrix (easily produced, cost reduction)

Carbon nanotubes beneficial properties for water filtration/desalination

Provides near frictionless water flow with high retention, highly efficient transport of water molecules, insoluble

Carbon nanotubes toxicology

enter body, manifest as inflammation/oxidative stress

Carbon nanotubes environmental significance

substantial production volumes, non-biodegradable, transport pollutants

Carbon nanotubes fabrication


Arc-discharge (current, anode, inert gas in vacuum)


Laser ablation

Carbon nanotubes, why gas sensors?

Tunable electrical properties, highly sensitive, used in extreme environments, low power consumption

Carbon nanotubes chemiresistor


ChemFET

Measures changes in resistance, limited working temp


Measures carrier current, Higher sensitivity, more expensive

Carbon nanotubes sensing through...

improved sensitivity and selectivity

Carbon nanotubes toxic properties similar to...

Asbestos


Antibacterial via cell membrane damage

Carbon nanotubes general...

Better electrical properties, improved sensitivity, can be functionalized to detect numerous gas species, decreasing CNT production costs

Problems with current desal techniques

Membrane fouling

Graphene structure

Thinnest compound, can be single/few layered, nano sheets, ribbons

Graphene features


Very strong and durable, transparent/flexible, electrical/mechanical/optical properties

Graphene synthesis

Chemical exfoliation of graphite, unzipping CNT to form graphene ribbons

Graphene desal: Capacitive deionization

Based on electrosorption, lower operating costs and energy consumption

Graphene desal: nanocomposite membranes

Thin film, fabricated via layer-by layer deposition of cross linked GO nanosheets

Graphene desal: free-standing grapheme membranes

selective permeability, hydroxylated pores

Graphene desal advantages

Faster water flow, low pressure requirements, higher pure water permeability




lower salt rejection rates than CNTs

Graphene health concerns

ROS generation, cytotoxic, membrane toxic, respiratory

Graphene sponge is...

Polyurethane sponges coated with reduced graphene oxide particles

Why graphene oxide? How to make it?

Compound with low-cost, chemical stability, and environmentally friendly




Comes from graphite, reduce it to make it hydrophobic

3 ways to create graphene oxide foams

Unidirectional freezing drying, non-directional freezing drying, air freezing drying (


Use liquid nitrogen in all 3 for freezing agent, vary the amount of time exposed to it and container the rGO is stored in

Foams successful with what 2 tests?

Drop method: organic liquid dropped on foam until no more absorbed


Soaked method: foam place in water and allowed to soak up oil

Environmental impacts of Graphene

reusability goal to be practical, easy to clean and recycle, used up to ten cycles

How to recycle Graphene sponge

Just apply heat, or direct combustion

Skimmers


Natural adsorbents

Mechanical devices designed to recover oil from the water's surface, oil attracting surfaces




Low oil loading and adsorption, can cause other types of pollution

In situ burning of oil

Burn by-products into the air, but reduces volume/need for collection and storage

Advantage of graphene to conventional methods

Higher adsorption ability, highly selective, reusable




BUT toxicological risks of inhalation or absorption

MgO properties

Polyhedral with a cubic internal structure, porous, adsorbent

MgO synthesis

Aerogel, precipitation, reflux, hydrothermal




Creates nano rods or nanoflakes

MgO sorbs pollutants (dyes in rivers), has the highest rate of...

Adsorption, dye molecules embed into porous structure

MgO may mitigate...




Adsorbs...

Eutrophication




phosphate and nitrate

MgO removes what metal in water




Also de-(somethings) water

Copper, defluoridate

MgO in air adsorption called...


What is AP-MgO

Chemisorption


Aerogel-prepared (adsorbs more)

MgO is toxic to...

microbes and humans

MgO environmental applications

Water remediation (removal of dyes, copper, fluorine, and organic pollutants via sorption)




Air remediation (removal of SO2, CO2, VOCs via adsorption)

Commonalities between UFPs and NPs




Differences

Surface area/volume


Exposure route of inhalation




Uniformity


Source


Organic chemical content


Adverse health effects (though probably same)

Modes of NP delivery in human

Ingestion, respiration, dermal contact

2 processes that remove nano particles in respiratory tract

Chemical clearance: chemical dissolution mediated by respiratory tract components




Physical translocation: movement of an intact particle, location dependent

Properties that make nano materials potentially toxic

Redox cycling, photo activation, membrane damage, cytotoxicity, inflammation, ROS

Primary cellular responses to NPs

Antioxidative response!


Pro-inflammatory response


Lysosome permeation


Decrease in mitochondrial membrane potential


Ca2+ release


Capase activation


Cell apoptosis

ROS are continually generated where?




At low concentrations they are...

In the mitochondrion




Easily neutralized

3 tiers of oxidative stress

Tier 1: Anti-oxidant defense (induction of antioxidant and detoxification enzymes)


2: inflammation (initiated through the activation of pro-inflammatory signaling cascades)


3: cytotoxicity (programmed cell death results from perturbation of the mitochondrion)

What is oxidative stress?

Too much ROS




Antioxidants lead to ROS lacking

3 immune responses when nano materials are recognized

Antigenicity (response of an antibody to an antigen)


Adjuvant properties (Agents added to augment the immune response to a vaccine)


Inflammatory response (immune system cells activated, cytokines secreted)

Cytokines




Opsonins

Signaling molecules whose presence leads to the attraction of additional cells to destroy the foreign substance




Blood serum proteins that signal cells to ingest a foreign material

Importance of opsonization

binding of blood proteins to carbon nanotubes reduces cytotoxicity

Environmental impacts of NPs in general

Disposal/accidental discharge can affect microbial ecology and disrupt biogeochemical cycles




Antimicrobial activity indicative of toxicity to higher level organisms

How do NPs move through soils?


Water?


Air?

Pores maybe?


Bio-uptake/degradation/aggregation/sorption


Aerosolization

What is risk?

Hazard*exposure




Shark cage: hazard but no exposure


Sand shark at aquarium: exposure but no hazard


Great white and a surfer: hazard and exposure

Bacterial toxicity mechanisms

Release of toxic ions, protein oxidation, disruption of membrane/cell wall, ROS, DNA damage

nC60

Highly stable water suspension, negatively charged surface, antibacterial




Doesn't puncture cells

Fullerenes does respose

More branches are less toxic, but more mobile

nC60 particle size vs toxicity

100x difference in antibacterialness for greater than and less than 100nm particles




BUT only a 2x difference in surface area:volume

What reduces nC60 toxicity?

NOM

Quantum dots applications


Weathering

Biomedical and electronics


Toxicity is due to free metal, so weathering increases their toxicity to cells




Coated QDs retard cell growth, weathered QDs kill bacteria

Salinity increases...


Organic ligands mitigate...

QD aggregation


Toxicity

Copper nanoparticles

Cheaper antimicrobial than Ag


Sustainable applications in solar panels and groundwater remediation


Aquatic anti-fouling and anti-algal coating

Copper NP energy/environmental relevance

Carbon sequestration


Biofuel production


Eutrophication