Chemistry at nanometer scale

Vakinformatie

Chemistry at nanometer scale, taught by Prof. De Feyter

Examenvragen

Also check vtk wiki: https://wiki.vtk.be/Chemistry_at_Nanometre_Scale_(H06A6A)

2025

1. Si substrate with thin layer of graphene (non conducting) with functionalized patched of 2 different groups.

a. How to create without soft litho or ...: answer: SAM (but then the correct chemistry for graphene: covalent grafting?)

b. How to image the functionalized structures with differenct chemical properties (when you know substrate is non conduction): Answer: so no STM, then AFM but chemicaly modified tip.

c. Measure thickness of layers (but no ellipsometry and EM)

2. create chess board structure of mum dimentions and explain technique. answer: microcontact printing

3. right, wrong or it depends statements:

a. ...

b. slow addition of reducing agent, for Au nanoparticle synthesis, narrows the UV/Vis spectrum

c. increasing temperature causes disassembly of supramolecular structures

d. Graphene and 2D materials readily disperse in water

4. In a solution containing compound-P and ZnP-8, adding SWNTs decreases the fluorescence emission spectrum. If you do the same for compound-P ZnP+8, nothing happens. (this paper "Integrating Single-Wall Carbon Nanotubes into Donor–Acceptor Nanohybrids" contains the info given. ZnP-8 and ZnP+8 are given in image 1 alongside compound-P which here is called pyrene+, the emission spectrum given on the exam is figure 3b). Image shown below as well. (see 9 June 2023 question 3)

Chemistry at Nanometre Scale (H06A6A) -- Nanochemistry exam 2023 pyrene.jpgChemistry at Nanometre Scale (H06A6A) -- Nanochemistry exam 2023 absorption.jpg

a. What can be the role of the compound P? Draw the structure that is formed.

b. Why is the fluorescence decreasing with increasing CNT concnetration?

c. What is the mechanism in which this is happening. (I think he was referring to energy transfer)

5. LbL approach, for X (poly-anion) and Y (poly-cation). pKa's given en pH's of solutions is well. Fill in the table of LCD and SCD (like in lecture and excersise session). Say in which situation (A or B) X is thicker, or Y is thicker. Explain your reasoning.

2024

Exam 07/06/2024 08h30 and 09h30

Question one:

• How can you make a gold surface hydrophobic or hydrophilic?
• How can you change the hydrophobicity/hydrophilicity of the surface?
• How would you determine this macroscopically?
• How can you detect this microscopically?

Question two: Si nanowire n-type semiconductor, DNA absorbed to it to detect positively charged proteins.

• Explain the mechanism used for protein sensing.
• Right/wrong: The thicker the diameter, the more sensitive. (Ignore band gap)
• What is the function of PEG on this wire?
• Photo's shown, what kind of visualization technique would you use?

Question three: hybrid-LBL with Au and Fe

• How can you simple separate Fe and Au?
• Explain how to make water-soluble Au NPs
• Protocol given for iron oxide particles, draw molecule/structure of Fe NPs
• When the LBL is assembled, a red-shift is observed, how come?

Exam 06/06/2024 14h00 and 15h00

Question one: Description of a paper with a picture of a dendrimer encapsulating a chromophore with a heterocycle.

1. Na ions are selectively absorbed by this dendrimer. Why? (heterocycle is specific for Na)
2. Discuss an approach to synthesize this dendrimer. (I explained the actual organic synthesis, but apparently he was after convergent and divergent synthesis and what the (dis)advantages of each method are)
3. Discuss the change in viscosity of this dendrimer type upon going from low to high generations.

Question two: Both carbon NTs and graphene have some disadvantages, in terms of their properties, when it comes to electronic applications. Why?

Question three: Why is it sometimes observed that upon diluting a solution of ligand-shell protected NPs, based on non-covalent chemistry, the particles aggregate?

Question four: Again discription of a paper (see slide 34 of chapter 16!)

1. Suggest a way to make the "chemical contrast" lines. There is almost no difference in topography between the lines. What is the purpose of the chemical contrast lines?
2. What is the surface property of the darkes lines in the figure (specific for this paper but analogous to silde 34) if you know that the PMMA blocks of the PMMA-PS block-copolymer preferentially absorb here?
3. What Scanning Probe Technology would you use to reveal the topography and nanostructuring?

2023 (from VTK website)

9 June 16:00

1. A SiO₂ surface with a graphene layer on top are functionalized with aryl-COOH and aryl-NO₂ in a chess board pattern (but with some spacing in between the squares, so small lines of unfunctionalized surface), with squares of size 5 µm.

a. Explain how you can functionalize covalently it without using SPM or soft lithography. It is top-down. Explain the chemistry used.

b. Which technique can you use to determine whether graphene is covalently functionalized or if the molecules are just adsorpted?

c. How do you find out which type of aryl functionalization is on which square, explain in detail how it works?

d. How to measure the thickness of a square (so the length of the functionalized molecules) if you would have a full chess-board pattern, without unfunctionalized parts in between (so no spacings between the tiles)?

e. If you had a gold substrate and you had to functionalize it with a phenyl group with -NO₂ attached. How would you do that? Explain the chemistry. Here there was no space between the squares (so as in 1d, but with half of the squares nonfunctionalized)

2. Right or wrong

a. Is starting from CNT, a good way of making high-quality graphene?

b. Fast addition of reducing agent to thiol-gold NPs gives a narrow absorbance spectrum?

c. Catanene: multifunctional stations. Are they unidirectional?

d. Is it easy to disperse graphene and 2D materials in H₂O?

e. Forgot

3. In a solution containing compound-P and ZnP-8, adding SWNTs decreases the fluorescence emission spectrum. If you do the same for compound-P ZnP+8, nothing happens. (this paper "Integrating Single-Wall Carbon Nanotubes into Donor–Acceptor Nanohybrids" contains the info given. ZnP-8 and ZnP+8 are given in image 1 alongside compound-P which here is called pyrene+, the emission spectrum given on the exam is figure 3b). Image shown below as well.

Bestand:Chemistry at Nanometre Scale (H06A6A) -- Nanochemistry exam 2023 pyrene.jpgBestand:Chemistry at Nanometre Scale (H06A6A) -- Nanochemistry exam 2023 absorption.jpg

a. What can be the role of the compound P with ZnP^8- and the CNT?

b. Why is the fluorescence of the CNT decreasing?

c. What is the mechanism in which this is happening. (I think he was referring to energy transfer)

d. Draw the structure that you see for the entire hybrid structure

4. LbL approach, but for different polymers (not PAA and PAH). pKa's given en pH's of solutions is well. Say which one is thicker.

5. Some siloxane structure (APTMS , but it was just given as '3-Aminopropyl-trimethoxysilan') --> make surface of Si hydrophobic. What's correct and what is wrong in this recipe? Explain.

1. Add block co-polymer with Si wafer

2. Mix APTMS in high concentration of octane in other glass beaker.

3. Put this solution on Si wafer with the block co-polymer, just for a few seconds.

2022 (from VTK website)

10 June 16:00

1.

a. Why graphene can be used as a lubricant?

b. How to make graphene chiral and how to characterise that?

c. How to prepare a graphene sheet on silicon oxide substrate? Given that mechanical exfoliation is not available.

d. How to n-dope or p-dope graphene? Given that the doping process is reversible.

2. A FET sensor based on single-wall CNT (SWNT) with Pd as electrodes is built on SiO2 on Si substrate. Some adamantane compounds are given. Transfer characteristic (Ids vs Vg) curves of FET under bare-SWNT, host-guest complex on SWNT are also given.

a. How to build the SWNT FET on SiO2 on Si substrate?

b. Design host for adamantane compounds (same host for all compounds). Explain the host-guest interactions.

c. How to ensure "contact" between host-guest and SWNT? Which characterisation technique to visualise this adsorption?

d. When host-guest complexes interact with SWNT, explain why the threshold voltage is more negative and conductance is reduced?

e. Statement (right/wrong and why): we can use alkyl thiol terminated PEG as a protective coating for SWNT.

3. Statement (right/wrong and why): Quantum confinement can be used to explain the shift of UV/Vis and fluorescence spectra of CdSe NPs to shorter wavelength upon the evaporation of solvent.

2021

Exam 4 June 2021

1.Give the optimal way to make a gold surface:

a. Hydrophobic

b. Hydrophilic

c. To tune hydrophobicity and hydrophilicity

d. What kind of technique would u use to measure the tickness

e. Explain this technique

f. Right/Wrong: I don't remember

2. A silicon nanowire bind a negative charged protein.

a. How would u make the silicon nanowire

b. Explain the principle of an N-type silicon nanowire and the set-up

c. How can you read out the binding of the negative charged protein

d. How can you improve the binding of the protein

e. Eight/Wrong: a larger diameter gives a better readout

3. Something with gold nanoparticles and iron-oxide that bind in ordered structure or layer

a. How would you produce a gold NP, which is soluble in H2O

b. Draw the structure of iron in n-octylamine and ethyleenglycol

c. Draw the structure and explain the chemistry of b) in APTMS and methanol

d. Right/Wrong: ch9emical force microscopy is designed to measure these structures and is the best technique

4. The UV-Vis and fluorescence spectra of a semiconductor NP of 6 nm with a 1.2 nm organic coat in solution shifts (I don't remember to which side) upon evaporation of the solvent. Comment on al the concepts and explain (right/wrong)

2016

14 June 2016 8:00 (of course I only notice they're the same questions as 15th june 2015 after I typed all this)

1. Give the optimal way to create:

a) A thiol monolayer on a graphene substrate (extra question: what does this layer look like?) b) A thiol layer on a gold substrate with a certain alkyn chain length but at five locations at positions you can control with a diameter of a couple tens of nanometers, place thiols with a longer chain c) A thiol layer on a gold substrate in a regular band structure, bands have a width of several micrometer (extra questions: what is PDMS? what is the ink composed of?) d) A thiol layer on a gold substrate with the thiol in an array of regular sized dots (about 3 nm in diameter) spaced 1.5 - 2 nm apart e) A thiol "drawing" on gold substrate, the drawing lines have a width of about 70 nm f) Gold nanoparticles (d = 10 nm) on a silicon substrate in a regular but noncrystalline array, spaced 60 nm apart g) What probing method would you use to visualise d)? Can you use the same method to visualise f)? (extra questions: how does feedback work in AFM? what is the resonant frequency of the tip?)

2. Correct/wrong and why?

a) It does not matter what type of amphiphiles you add to a solution (positively charged, negatively charged or neutral), the surface tension decreases at increasing concentration b) Gold nanoparticles have the major drawback of having a much smaller quantum yield than semiconducting nanoparticles for fluorescence spectroscopy purposes

13 June 2016 10:00

Same questions as 05 June 2015 10:00

2015

22 June 2015

1. Dendirmers PAMAM(chap 5) take me a lot of time to find where it is...

(1) Na+ adsorption why? (2) structure (3) how to synthesis? (4) viscosity change with higher generation (5) difference between dendrimer and micelle is dendrimer needs lower concentration, right?

2.copolymer, epitaxial SA on Si(chap 15) only two slides but you need to know the whole process and the mechanism. also about AFM i think so go over chap 19 AFM!

(1) how to make chemical contrast? (2) how copolymer ordered on that? (3) how to characterise this pattern? 3.LbL pH sensor just like exercise 1.

23 June 2015

1)

a. how to change hidrophilicity/phobicity of a surface b. how to tune it (not completely philic or phobic but also with different degrees) c. how to detect polarity of surface macro and nanoscopically

2) n-siNW sensor for positively charged protein: how it works

a. reaction with PEG b. how to characterize it c. something else I dont remember

3) LbL of iron and gold nanoparticles linked by covalently-bonded crosslink

a) how to separate the different np b) how to synthetize np in water. c) he provides you the protocol for the synthesis of iron oxide NPs with different agents. then they are mixed with APTMS and someother molecule with COOH. write what happens chemically and draw the composition of NPs d) red shift in absorption of the nps: what does it mean?

4)(true false) mie theory explains fluorescence of semiconductor nps at higher energies.

15th June 2015

1. Many small questions about patterning, monolayers, etc, almost everything with alkyl thiols.

a) How would you make a monolayer in graphene? b) How would you make a monolayer in gold and then substitute some islands of nm size with another alkyl thiol of longer tail? c) How would you make stripes of alkyl thiol in gold that are micrometer sized? d) How would you create small islands of aklyl thiols that are 2-3 nm sized and separated also by very few nanometers? e) How would you make an irregular pattern (like a drawing) of alkyl thiols in gold with precision? f) How would you deposit gold nanoparticles in Si forming small island in a regular but not crystalline pattern that are separated by 60 nm or so? g) Which techniques would you use to measure that pattern in Si and the one of the small islands in gold?

2. True/False

a) Something like: the surface energy is independent of the amphiphile you use: positively charged, negatively charged or neutral. (it was something a little bit different but more or less) b) GNPs are not really used as biolabels because they have low quantum yield in comparison to QDs of the same size.

19th June 2015

1. Diagram of a DNA functionalised gold NP designed to detect Ascorbic acid. An explanation of how the device work is provided. Basically It fluoresces after the DNA gets cleaved because of a radical produced by the ascorbic acid.

a) describe how one can prepare gold nanoparticles b) describe how one can functionalise the NPs with the DNA strands c) which spectroscopic technique would you use to determine the concentration of gold NP d) What do you think is the reason why the sensitivty is 100x better with the Gold NP than in a device without gold NPs?

2. True or false and why: Keeping a low precursor concentration when synthesising gold NPs results in a broad spectrum of the fluorescence curve

3. He gives you a diagram of a molecule with three fused aromaticc rings, a number of C=O bonds, some N atoms and an alkyl chain. He says some researchers showed this can be useful for dispersing SWCNTS.

a) why is it hard to disperse SWCNTS? b) Describe a possible mechanism of how this molecule achieves dispersion

5 June 2015 10:00 For a given application it is necessary to make a silicon wafer, with its natural oxide layer, hypdrophobic. Looking into the scientific literature, I found the following recipe: "After dissolving trichlorooctylsilane molecule in a new glass beaker with ethanol, at rather low concentrations, a gold substrate is dipped into the solution for a few seconds, followed by a rinsing step with water.'"' Analyse this statement, and discuss in terms of chemistry, indicating what's correct/wrong/nonsense and why. Comment on this statement (correct/wrong and why?): "Metal nanoparticle synthesis is governed by kinetics, rather than thermodynamics." On top of this multilayered substrate, shown below (so with the chromium top layers), a photoresist polymer is coated. The sample is irradiated through a square-shaped mask, and the irradiated area (so having the shape of a square) is washed away. Then the following manipulations were done: gold is deposited via electrodeposition on top of the substrate; a chromium layer is deposited; then the sample is subsequently treated with 1) acetone, 2) nitric acid (dissolves the silver layer), 3) sonicated in a hexadecanethiol solution, though not necessarily in the order indicated. Figure with this top-to-down structure: chromium-silver-chromium-Si/SiO2. Draw the object formed and describe its chemical nature (bulk and surface) What is the role of acetone, an organic solvent sonication in hexadecanethiol solution in ethanol. Define the order of the different steps in the treatment Describe two methods you would use to evaluate the degree of polarity of surfaces: a macroscopic technique and a technique which operates at the nano to micro scale

A mixture of oppositely charged spheres (diameter not defined) forms a highly ordered phase (see figure below). The red particles are negatively charged and the green ones positively charged. Discuss the different aspects of the energetics involved in this self-assembly process (in terms of Gibbs free energy) Alt

+/- Charged spheres assembled lattice In another experiment, rod like objects of identical length, carrying no charge, and with only minimal interrod interactions, were found to self-assemble. Draw the outcome of the self-assembly process. Explain in terms of the energetics of the process. [edit]Old NanoForum questions These questions are copied from the old nano forum so the format might not be ideal.

Unknown date

1. How to make a gold surface hydrophobic or hydrophylic? How to switch the hydrophobicity / hydrophylicity of the gold surface by electrochemical stimuli?

2. Comment (right/wrong and why)

a ) The most important motivation for the development of field-effect-transistors and solar cells based upon organic molecules isthe improved efficiency compared to inorganic semiconductor materials.

What are the requirements in order to use low molecular weight organic molecules as active components in organic field-effect-transistors?

b) The formation of 'objects' with a well-defined size and shape on the basis of selfassembly is an impossible task. c) A continuous flux of energy into the 'system' is bad for the formation of ordered patterns.

d) The Mie-theory explains why the fluorescence of nanometer-sized semiconductor particles is observed at lower energy upon increasing the size of the particles.

3. How does the surface tension of an aquous solution evolve if the concentration of the solute increases?

4. Mixing the calixarene (left) and the barbiturate (right) in the appropriate stoichiometric conditions leads to the formation of a complex (see picture).

a) What's the driving force for the formation of these complexes? b) What structure will be formed: the (P)-enantiomer, the (M)-enantiomer or both? Explain by using an energy diagram.

c) What will happen if one adds to the existing solution a new barbiturate with a chiral side chain?

d) These complexes have also been visualised on graphite by a scanning probe microscopy method. Which technique has been used and why? Give a short description how this technique works.

5. How to make an ultrasmall pH sensorbased upon conductivity measurements. How does it work?

Unknown date

1. Nanowire

a) A silicion nanowire is made using 20nm nanocluster of gold. Explain which technique is used and how it works (really know how it works and what it needs and different changes in the process). the nanowire is mixed into a solution of 1%functionalizing thing that I can’t remember and ethanol, write down the product.

c) You want to use the nanowire as a sensor for viruses in a ‘device’, Explain how to make this device? (explain and really know what parts are needed and how it works, but not how it is produced) d) There are many long 1 micron wires and you want to order them (picture similar to logs in a pond). Explain how you can do this using a bottom-up technique. (Basically what technique???) e) How can you image the ‘device’ that you explained on c) Which technique is the best for this and how does it work? Why are the other techniques worse??

2. True or false:

a) Sometimes a constant energy flux is needed to make ordered patterns. Adding surfactants to water makes the surface tension higher

c) Can’t remember the other ones!!! But you get the style basically write down why it is write/wrong and really know and explain why.

3. “self-healing” There is a thermoreversible polymer that when you cut or break it is only necessary to bring these parts together and the parts reattach themselves. This is done at room temperature. (Wording in this question is key to recognizing what we are working with in this question, since I am an oversimplifying person I do not remember all the exact wording: Basically it dealt with supramolecular polymers)

a) What is the ‘principle’ behind this? What interactions are behind this and how can we tune them? (Really know which ones and how we can lower/increase them) c) Mention a similar material that has becomes useful because of it temperature dependance properties that are not common for regular polymers (basically difference between supramolecular polymers and regular ones)

2014

June 14th 2014, afternoon

1.

You get a picture of a new photovoltaic cell. It is made from CdSe nanorods and organic semiconductor. HOMO and LUMO for both materials are given. and also a graph with the absorbency for each wavelength of the photovoltaic cell for CdSe quantum dots, short nanorods, and a bit longer nano rods.

a) What are the function of the materials and how does this device work How do you change the bandgap of the CdSe nanorods c) why is the efficiency of the device bigger for nanorods then for quantum dots d) How do you make nanorods in stead of quantum dots e) How would you study the structure of this device

2.

a) How can you make a sensor for for instance negatively charged proteins by using nanowires? ? c) What are the benefits of this kind of device.

3.

The structure of a molecule to that could dispense CNTs in organic solvents was given, it contained a aromatic group and an alkyl chain.

a) Why is it not so easy to dispense CNTs in a solven b) How does the molecule dispence the CNT c) What molecular interactions are involved in this mechanism

4.

True are false questions

a) Is the Mie therory valid for semiconductor nanoparticles with a diameter of 10 nm b and c) can't remember d) are all molecular interactions for self assembly where entropic forces are involved only possible in water? 5th: a question about the layer by layer method, can't remember it exactly

Unknown date answers are not all exactly correct, but gives you a thinking in the right way

1. detection of adsorbic acid in for instance fruit juice you get a picture and I'll try to give an explanation. Sensing goes via functionalized nano particle. A gold nanoparticle has 4 DNAenzymes, with a fluor atom in the middle of enzyme (DNAenzyme: SH-ATTC...G-fluor-AGGGTCC....) and there is a DNA strand with complementary nucleotides of the dna enzyme, and it has a loop (on the place were the fluor is) with Ca2+ in the loop. if this sensor detect AA, then you have left the gold nano-particles, still with some dnaenzyme (just only a little part), 4 fluor atoms still bounded on the other half of the enzyme, en 4 dnastrands with Ca2+. The intensity of the fluor is enhanced.

a) how is gold nano particle, not yet functionalized with DNA, prepared knowing that the experiments and synthesis carried out in aqueous solution --> Chapter 16, metal nanoparticles in aqueous solution, it is with the citrate (that gives also stability)

detection is based on fluorescence; why does the intensity of the fluorescence increases after adsorption of AA? --> something with the gold: if the flour is too close to the gold, the gold inhibits the fluorescence

c) how are the oglionucleotides bounded to the gold nano particle? explain --> receptor ligand, (receptor is the thiol) and this binding is stronger than the one of the citrate

d) wich spectroscopy? eg: UV/Vis e) what is the (chemical) role of Au particle here? --> catalysation of breaking the dna enzyme and the dna

2.goldnanoparticles are grown like the classical nucleation model, have broad spectrum plasman resonance. --> explain everything of SPR, explain everything of (de)focussing, so the growth procedure of a nano particle, and finally: you have different nanoparticles with diff sizes and all together they result in a broad SPR

3. picture of molecule with aromatic part en alkyl part this molecule helps to dispersce SWCNT a) give a posible mechanism (draw) it was something with H-bonding of the N en =O from the aromatic part wat are the reactions of the alkyl and the aromatic part (alkyl will disolve in the organic solution..)

4. a rod goes to an ordered structure, explain the energetics something with delta G = detla H - T*delta S and look to chapter LC, similar to Onsager hard-rod model)

5. how would you make a drawing of 70 nm width form thiols on gold substrate en how do you change the witdt? - dip pen nano lithography

Unknown date Similar like previous years:

- How do you make a n-type siliconwire from gold particles (VLS) - It is covered with some alkyls, draw the chemistry and how would you do that (SAM) - It is used as protein sensor, how does it work? - How would we measure this? AFM - How can we prevent non-specific interactions with proteins?

True/false:

20nm gold particles are chosed for their better quantum yield then semicondutors when used as fluorescence sensor --> wrong, no fluorescence, particle is too large

A wire like above is better for sensing lower concentration proteins when it has a larger diameter. --> wrong i think, not sure. Smaller diameter = lower conduction --> bigger effect from proteins, more sensitive.

LBL question like in excercise session 1, in fact it is the exact same question but he uses polymer X and polymer Y and he reversed the question, asking when polymer X would have the thinnest layer. You have to make a table with = ~ > < in.

He does go pretty deep into it with extra questions during the oral examination, for instance he asked me how many times the AFM tip will tap per second in tapping mode... (had no idea)

Unknown date

Right or Wrong Discuss the chemistry of a silane agent ( trichlorooctylsilane) in a ethanol solution, when a gold substrate is dipped into the solution. Or something like that.

So the silane hydrolises and forms a SAM on the surface, but since you're using gold and gold forms no oxide , this doesn't work. So the answer was wrong

Right or wrong Nanoparticle formation is driven by kinetics instead of thermodynamics

Question about soft lithography, Substrate is given and drawn, then photo-resist is spun unto it and a square is etched out, gold is deposited and then chromium layer is deposited,after this acetone is used, HNO3 and then some surface layer draw the new substrate, so after al these steps.add what is what so surface and bulk materials than he asks why you use acetone ( remove Photo-resist) HNO3 ( oxidize chromium) and then the surface layer .

give two methods for evaluating polarity of a surface on macro scale and on nano scale I said AFM for nano ,the AFM with the chemically modified tip don't remember the name and contact angle measurements for the macro

last question was a picture of + and - charged ballz and then they self assemble and you had to sum up all the energetics involved.

So the questions are quit easy when you have your book, but as stated above, he does go into a lot of detail when asking smaller questions.

Unknown date

1. Contained several part. All were related to forming patterns with Alkyl thiols on substrate except for one. Need to explain the approach that will be taken to form the following patterns and motivation for the same

a. Monolayer on top of gold substrate b. First, Monolayer on top of gold substrate. After this, the height of alkyl thiols have to be changed at certain islands (diameter ~ 10 nm) c. Stripes of alkyl thiols (dimensions in um) d. Alkyl thiol islands at certain positions of gold (dimensions in nm) e. A drawing made of alkyl-thiol f. Pattern made of naked Au clusters on top of Si g. How do you visualize the structures made in d? Provide the Best method

2. True/False

a. +ve/-ve amphiphiles reduce the surface tension. Neutral ones dont reduce it. b. Gold nanoparticles have less quantum yield than semiconducting ones and so not used for fluorescent labeling of cells.

27/06 exam 1. from paper: hybrid polymer-CdSe solar cells.. there are pics of the device and efficiency of solar cells vs length of CdSe nanorods (positive relation)

a. explain how it works and state the function of each in the device (there are Al, PEDOT:PSS, polymer-CdSe blend, ITO, Substrate)

b. how to play with bandgap?

c. why longer nanorods is more efficient?

d. how you make nanorods instead of nanodot?

e. how you measure the topography and composition?

2. a. explain nanowire-based protein detection

b. draw the output

c. what is the advantage?

3. a. why CNT can't be dispersed?

b. what is ur suggested solution?

c. (pic is shown consist of benzene) why this molecules can disperse the CNT?

4. T/F

a. mie theory explains flouroscense of CdSe at 10nm

b. entropy-driven self assembly can only happen in water

Unknown date

1) A solar cell built from an organic donor and a CdSe nanorod blend acceptor: -explain the working principle -why nanorods? do they have a better efficiency than quantumdots? (shape is better, rods are electronic highways (that's what he said to me )) -how would you examine the structure at nm scale (i just explained stm and it seemed fine for him)

2) true/false -a solution of CdSe nanoparticles has a broad absorption spectrum. when we evaporate the solute, the remaining nanoparticles must have a broad spectrum too, as a result of ostwald ripening. (ostwald has nothing to do here, the particles are allready stable and won't grow) -the insolubility of benzene (and aromats in general) is an enthalpic effect

3)-You want to make a uniform monolayer of an alkyl thiol on gold, how? -> he asked me to give the reaction of the S on AU releasing H2 -You want to make specific islands with thyiols that have a longer alkyl chain -You want to make "trench-shaped" structures of 5µm width -> pdms stamping can go to 50nm -> he asked the chemical structure of PDMS and how the thiols bind to it and how long you would have to press (wtf?)

4) Something about layer by layer deposition and linear charge distrubution vs surface charge distribution. We had to make a table and compare LCD and SCD in several dippings.

20 June 2014

Q#1: Detection of adsorbic acid in for instance fruit juice you get a picture and I'll try to give an explanation. Sensing goes via functionalized nano particle. A gold nanoparticle has 4 DNAenzymes, with a fluor atom in the middle of enzyme (DNAenzyme: SH-ATTC...G-fluor-AGGGTCC....) and there is a DNA strand with complementary nucleotides of the dna enzyme, and it has a loop (on the place were the fluor is) with Ca2+ in the loop. if this sensor detect AA, then you have left the gold nano-particles, still with some dnaenzyme (just only a little part), 4 fluor atoms still bounded on the other half of the enzyme, en 4 dnastrands with Ca2+. The intensity of the fluor is enhanced.

a) How is gold nano particle, not yet functionalized with DNA, prepared knowing that the experiments and synthesis carried out in aqueous solution. b) Detection is based on fluorescence; why does the intensity of the fluorescence increases after adsorption of AA?. c) How are the oglionucleotides bounded to the gold nano particle? explain. d) Which spectroscopy technique can you use to detect gold nanoparticles concentration in solution?. e) Why does using gold nanoparticles in solution gives you 2X better results that using ordinary techniques... Explain the methods and comparisons for both techniqes in detail.

Q#2 Gold nanoparticles are grown like the classical nucleation model, have broad spectrum plasmon resonance. a) What is the effect on emission spectrum if low precursor concentration in used to make gold nanoparticles ?

Q#3 Picture of molecule with aromatic part and alkyl part this molecule helps to dispersce SWCNT. a) Give a possible mechanism for this molecule interation with SWCNT(draw). Also explain the details about this molecule b) What are the reactions of the alkyl and the aromatic part? c) Why is it difficult to separate these SWCNTs ?

June 23rd 2014 8:00

Q#1 There is a picture of organic molecule given that self-assembles into conductive rod. It has N atom in the middle with 2 extra elextrons and 3 single bonds with 3 benzene rings and then hydro-carbon chains. On second picture there are these rods aligned between two electrodes perpendicular to their surface |----| a) what drives that to assemble b) what makes it align between electrodes

Q#2 There is picture of lamellar and pillars structure. In the middle of one of the materials there are CdSe nano-particles a) what compound and how can form these structures b) assume the surface of structure is perfectly flat, how can you visualize what material is where on nanoscale c) particles start to aggregate, haw will it affect florescence spectra (with and shift)

Q#3 There is a picture of rods that are positively charged. When concentration increases they form LC phase. What is the driving force?

Q#4 There is picture from the paper showing a new way of forming a monocrystal. First there is an amorphous phase formed on a surface, then there are crystal domains that with help of this surface merge into one crystal that then continue to grow. What is the difference between that and classical crystallisation theory?

b)

June 24th 2014 10.00 Q#1

How do you make a gold surface hydrophilic/hydrophobic? How do you tune the hydrophobicity (he doesnt want the switching mechanisms but a 'continuous' tuning by adding a certain ratio of different molecules to the SAM) How would you detect the macroscopic hydrophobicity? Explain the method. The hydrophobicity varies on the micrometer scale. What method do you use to measure local hydrophobicity?

Q#2

An n-type SiNW is used for the detection of a positively charged protein

Describe the operation (not the fabrication) of this device. Right/Wrong: The sensitivity of this device increases when the SiNW diameter increases Describe the characterization method (full AFM description)

Q#3

Researchers have made an aggregate of gold NP and ironoxide NP, so-called NP hyperclusters. This method is proposed as an alternative to the electrostatic polymer LBL method to create alternating layers. The researchers added linker molecules to stabilize the aggregate and to give the film a more homogeneous thickness.

Give a method to separate gold and ironoxide NP in solution (you can give a variety of methods but he says magnetism is the simplest) Describe a protocol to make a solution of gold NP in water (straight from the course) Ironoxide NP are made using an inhouse method and functionalized using octylamine. The NP themselves are formed using FeCl3 and PEG (polyethyleneglycol) as reductans and solvent. Afterwards the functionalization is modified by substituting APTMS (aminopropyl-trimethoxysilane) using trace amounts of CH3COOH. Write down the chemistry and give a cartoon diagram of the result.

Q#4

Right/wrong and explain: Mie theory describes the significant shift of plasmon frequency (540-->650nm) upon aggregation.