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6BER01 Nanomaterials: Chemistry & Fabrication > Chapter 1: An introduction to Nanochemistry Concepts > Flashcards

Chapter 1: An introduction to Nanochemistry Concepts Flashcards

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1
Q

What are interfaces?

A

Volumes in space, often approximated as a surface, which separates much larger volumes of dissimilar substances, such as two different solids, a solid and a liquid, and so on.

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2
Q

What are dangling bonds?

A

These bonds occur at a surface when atoms have unfilled outer orbital (valence) shells.

Such bonds are unsaturated (unsatisfied), they often bear a partial electric charge, and they increase the energy of the surface, and of the whole material.

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3
Q

What is γ, n(db) and Φ?

A

γ is the surface energy

n(db) is the surface density of dangling bonds

Φ is the energy of the bond

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4
Q

What can we learn from the formula of surface energy?

A

The surface energy increases with the density of dangling bonds, which is determined by the composition of the surface, and also by its roughness and curvature.

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5
Q

What does the surface energy determine?

A

Surface energy determines how a surface interacts with the environment; a surface with higher energy is more reactive as it is more prone to reduce its own energy by interacting with the environment.

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6
Q

What does the density of dangling bonds determine?

A

The density of dangling bonds not only determines the surface energy but also the local electron density and reactivity.

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7
Q

What is a substrate?

A

A reagent on which a chemical reaction occurs but also a solid surface on which some material is deposited.

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8
Q

What is Laplace law?

A

A mathematical relation between the surface pressure of a sphere and its radius and surface energy.

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9
Q

What is surface pressure?

A

Pressure generated on the surface by its surface energy and increases with increasing surface curvature.

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10
Q

What is perovskite?

A

A class of solid-state structures of general formula ABC where A and B are metallic elements, and C is generally oxygen or one of S, Se and Te.

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11
Q

What is a core-corona particle?

A

A particle whose interior composition and/or phase is different from the outer composition and/or phase.

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12
Q

What is surface functionalisation?

A

Changing the properties of a surface by changing its chemical composition, by adding or substituting an impurity.

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13
Q

What is strain?

A

A deformation of the atomic lattice of a crystal usually due to pressure, defects, or electronic effects.

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14
Q

What is grafting?

A

The chemical attachment (usually by covalent bonds) of a molecular moiety to a solid substrate or a polymer chain.

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15
Q

What is the passivation layer?

A

This is formed by the reaction of a surface with its environment that renders it more stable.

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16
Q

What is extensive property or function?

A

A material property or function that is proportional to the material/s volume.

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17
Q

What is an intensive property function?

A

A material property or function that is not dependent on the material’s volume, e.g., density.

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18
Q

What is anisotropy?

A

Being dependent on spatial direction.

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19
Q

What is isotropy?

A

Being independent of spatial direction.

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20
Q

What are liquid crystals?

A

A state of matter with behaviour intermediate between that of an isotropic liquid and a crystal with long-range translational periodicity.

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21
Q

What is the nematic phase?

A

One of the possible structures liquid crystals can adopt.

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22
Q

What is ferromagnetism characterised by?

A

Weiss domains

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23
Q

What is a meso-phenomenon?

A

phenomenon that manifests between bulk (classical) & molecular (quantum) regimes where length of characteristic property can be compared with object’s size.

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24
Q

What is an exciton?

A

An exciton is an excited electron and a hole, forming a hydrogen-like system with energy levels, Bohr radius, and labelled orbitals. Excitons have a finite lifetime and can produce heat or light when recombining.

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25
Q

What is ferromagnetism?

A

The magnetic analogue to ferroelectricity; see the Iron Oxide chapter.

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26
Q

What is superparamagnetim?

A

A magnetic ordering phase in which the material is constituted by a single Weiss domain; the whole material can thus orient its magnetic dipole with the applied magnetic field, and this leads to the absence of remanent magnetic field and to very large maximum magnetizations.

27
Q

What is the effect of shape?

A

It affects the relative size-dependent effects in a directional way and the directionality of self-assembly.

28
Q

What is size-invariant behavior?

A

Usually related to a geometrical configuration

29
Q

What is monodispersity?

A

The amount of size homogeneity; in chemistry it is used to describe a set of molecules or particles with identical size

30
Q

What is polydispersity?

A

The amount of size
inhomogeneity.

31
Q

What does shape determine?

A

When building blocks assemble together autonomously, their shape often determines the architecture they will form; shape in fact determines the directionality of their reciprocal interaction.

32
Q

What is nucleation?

A

Nucleation and growth are the names by which the different phases in the growth of most nanomaterials are called; for example, ice in freezing water does not form all at once; sometimes you can underfreeze water without any ice forming (think of waterfalls); what you need is to create enough stable nuclei, which are particles of ice large enough to be thermodynamically stable; this initial phase is called nucleation; the later phase is when the remaining material grows on top of the stable nuclei.

33
Q

What is self-assembly?

A

Apparently spontaneous self organization of objects; it arises as a system strives to find minimal free energy.

34
Q

What is co-assembly?

A

A self-assembly process where two or more different components self assemble contemporaneously and interdependently to form a complex architecture where the two components are usually segregated and not entirely mixed.

35
Q

What is hierarchical self-assembly?

A

When the fundamental building block is self-assembled in primary structures kept together by short range forces.

36
Q

What is directed self-assembly?

A

When an external force, created and controlled by us, is used to direct the self-assembly of the fundamental building
blocks.

37
Q

What is static self-assembly?

A

self-assembly determined by
the state of minimal free energy in a confined system that energy can neither enter nor leave.

38
Q

What is defect-tolerance?

A

A design principle by which a device which performs a function can tolerate a certain amount of defectivity in its components; it can also refer to a property if this property is only marginally affected by a moderate defectivity.

39
Q

What is templating?

A

Using an existing material of a certain shape as a mould to create a negative reproduction in a new material.

40
Q

What is a bottom-up procedure?

A

As when you
start from the smallest components
and you assemble your desired structure from the ground up.

41
Q

What is top-down?

A

When you start from a large chunk of material and you cut it and trim it till you get your nanosized architecture.

42
Q

Describe the templating strategy.

A

A template possessing holes is first produced. The holes are infiltrated with the material of choice (sol–gel precursor, molecules, polymers, nanocrystals, nanorods, nanowires, etc.) and then the template is selectively dissolved, leaving behind the inverse structure composed of the infiltrated material of choice.

43
Q

What is dynamic self-assembly?

A

Self-assembly in out of equilibrium conditions where the state of minimal free energy is determined by the flux of energy in and out of the
system.

44
Q

What are hierarchical systems?

A

Integrated systems built from matter organised at different length scales.

45
Q

What is directed self-assembly?

A

When external forces are used to guide objects into a desired pattern.

46
Q

What are point defects?

A

These occur in a lattice when an atom is missing, misplaced, or different from what it should be.

47
Q

What is doping?

A

Creating point defects that allow electronic charge to be conducted.

48
Q

What are line defects?

A

These occur in a lattice when the position of an entire string of atoms in the lattice is misplaced
(dislocations).

49
Q

What are planar defects?

A

These occur in a lattice when a whole plane of atoms is missing or misplaced (stacking faults).

50
Q

What are grain boundaries?

A

Interfaces between misaligned crystalline grains within a polycrystalline material.

51
Q

What are thermoelectrics?

A

Devices that exhibit a voltage when exposed to a gradient in temperature, or exhibit a gradient in temperature when a voltage is applied to them.

52
Q

Why are thermoelectrics very inefficient?

A

The reason is that they need to be made of materials that conduct heat extremely slowly, while conducting electricity very well.
And this is a bit of a headache since the electrons, which are responsible for the current, also transport heat.

53
Q

What are phonons?

A

Quantistic vibrations of the atoms in the
lattice.

54
Q

What is surface-enhanced Raman spectroscopy?

A

An analytical technique that uses the amplification of the Raman vibrational spectra of molecules adsorbed on metal nanoparticles or rough metal surfaces.

55
Q

What happens to the colour of nanoscopic gold particles upon aggregation?

A

It changes colour from red to blue.

55
Q

What is molecular imaging?

A

Monitoring the movement of a target molecule by using an attached probe.

56
Q

Where does the colour come from in aggregation?

A

It comes from plasmon resonances, which originate from the oscillation of the free electrons on the surface of the metal.

57
Q

What happens when something binds or comes close to an oscillating cloud of electrons?

A

Anything that binds to or comes close to such an oscillating cloud of electrons, like another metal nanoparticle, changes its frequency, often dramatically.

58
Q

What is drug delivery?

A

When a therapeutic drug is brought by a carrier to the specific site in the body where it is needed to effect treatment.

59
Q

What is an advantage of drug delivery?

A

Another advantage of drug delivery is that it can allow the tailored administration of the drug and thus maintain the right level of concentration at the target, without risks of insufficient or excessive dosages.

60
Q

What is photothermal treatment?

A

Destroying cancer cells hyperthermally, using heat generated from light-activated reactions or transitions.

61
Q

What is active targeting?

A

Active targeting is accomplished by attaching a targeting vector to the nanostructures which would specifically attach to the target.

62
Q

What is passive targeting?

A

The passive targeting is using the leakiness of tumors vessels to segregate nanoscopic probes into the malignant tissue.

63
Q

What is tissue engineering?

A

Introducing a porous scaffold to the body at a damaged site to encourage cells to replicate and propagate; tricking the body into healing itself.

6BER01 Nanomaterials: Chemistry & Fabrication (2 decks)

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