General properties Flashcards
What is top-down synthesis? Pros and cons?
Top-down –> start with bulk material and break down to what you want.
(+) quick way to produce large amounts
(-) require a lot of force and energy, poor control of the material
What is bottom-up synthesis? Pros and cons?
bottom-up -> where you build what you want from smaller pieces.
(+) controlled, less defects, possibilities to produce synthetic materials
(-) high costs, not easy to scale up, high quality material required
What is Bohrs radius?
Bohrs radius is the distance between the hole and the excited electron of an exciton
The smaller particles will have a larger Bohrs radius as the gap between the energy level increases. The larger Bohr radius, the stronger quantum confinement effects
Give some examples how quantum confinement can be utilized in real-life applications for life sciences
Difference in energy levels gives the material different properties
Quantum dots –> fluorescerar –> real-time guided surgery
Different size –> different Bohr radius –> emit different light. Multiplexing
Can you describe the typical physical-chemical properties of quantum dots, e.g., particle size, chemical composition, conductivity, optical properties?
Nano meter scale, 2-10 nm
Group 2-4 in periodic table
Semiconductors
Fluorescent – dependent on size
Definition of nanomaterial?
-Nanomaterial is a material composed of particles where at least one dimension of the particles are in the nano range 1-100 nm
-Nanomaterial can occur naturally, be created as by-products or be produced purposefully
-These materials can have different physical and chemical properties to their bulkform.
Universal properties of matter? Which are affected by nano-scale?
Extensive: depend on the size of sample. Length, volume, weight
Intrinsic: characteristics of material. Density, melting point, identity
Colligative: depend on number. Osmotic pressure, concentration
Intrinsic properties will be affected of the nano-scale
What is quantum confinement effect?
Electrons can move between different energetic levels if additional energy is supplied. When electrons move onto another energy level –> a hole is left.
Excited electron + hole = exiton. Distance between them = Bohr radius.
When the size of particle decreases the distance between energy levels increase, the Bohr radius increase.
Stronger quantum confinement effects are observed with smaller size. More energy is required to excite electron. But more energy is also released.
What is the infinite well model? (Ball in the box, ball is rolling back and forward)
As the distance between the walls of the box is reduced, the band gap increases. If the boundaries of the wall represent the size of the nanoparticle, quantum confinement effects will be significant
Amplitude of movement increases larger gap
List 3 distinctive properties of Quantum dots
- high photostability –> Shine for long time
- High quantum yield –> shine efficient
- High molar extinction coefficients –> shine bright
