Quantum dots go on (SONY) display

[Jie Xiang]

http://www.nature.com/news/quantum-dots-go-on-display-1.12216

We just talked about replacing biological fluorescent molecules with quantum dots that emit various colored lights for tumor imaging in class, now we see big box electronics makers such as Sony will use these quantum dots to replace the colored fluorophores on the pixels of their TV screen. 

 

[symay]

Regarding this topic, it is a great alternative. One thing to take into account would be the Quantum Yield (efficiency of the energy transferred from incident light to emitted fluorescence). One of the problems of fluorophores is that the light that they emit has a wavelength shift compared to the excitation light (Stokes shift). This may be not as controllable as the diameter of the Quantum Dots (we saw in class that QD's emission spectra change as we change the diameter of the QD due to the change in energy). The last problem of fluorophores may be the lifetime (the duration of the excited state before returning to the ground state). Normally this values are really tiny (in the order of picoseconds). It is good to have a more stable source as QDs for this kind of applications.

[faridazzazy]

The article mentioned that most of the QD industry is fueled by bio-inspired technology. Here at UCSD there is a lot of work being done with quantum dots for imaging. I came across the NCMIR (National Center for Microscopy and Imaging Research and they have done some really cool work with bio-tissue. Here is a link to their gallery:

http://ncmir.ucsd.edu/gallery/index.shtm

The article mentions these quantum dots can be as much as $10,000 per gram. If this QD technology is to become more commercialized, QD's have to become cheaper to stay competitive with LED. A kg of gold is still orders of magnitude cheaper than a kg of QD's at that price.

[ajkerr]

This is a cool application of QD's that I had no idea was in the works.  I am very curious to see how much one of these TV's costs when they show up in stores.  QD's are still so expensive.

The nature article mentions another technology with QD's embedded in plastic films.  Here are two articles about that.  They mention this as a potential enhancement to solar cells.  Interesting stuff.

http://spectrum.ieee.org/consumer-electronics/audiovideo/quantum-dots-are-behind-new-displays

http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/nanosys-gets-3m-to-bring-its-quantum-dot-technology-to-lcds

[thoughtandthinker]

Like Farid said, the main use of quantum dots that I'm familiar with is bio-imaging. There's some interest in using it to replace things like green fluorescent protein (GFP) in fluorescent microscopy, but it's still way to expensive in comparison. GFP is used by transfecting the desired cell in a way that causes the desired structure to emit light under a laser, so it's a bit different from traditional immunohistostaining. Quantum dots would be a lot better if they can be made with wide absorption spectra and very specific emission spectra, but if the price is really as high as Farid says, I can't see the labs I work with adopting it any time soon.

[symay]

I think that using QD to replace GFP is actually more difficult than using GFP by itself. The GFP is a protein that you use to attach to any strain of DNA and see if that particular part of the DNA is expressing, so you already have a biocompatible approach that you can use to see the expression. On the other hand, you would need to attach your Quantum Dot to a protein and figure out how to turn on the quantum dot as you get a gene expression from the region of interest. Long story short, you can do it, but its going to take you longer and it's going to be more complicated.

Best,

Salomon.

[thoughtandthinker]

I think you're probably right, Salomon, but the main point I was getting at is that GFP's emission and absorption spectra, at least in my experience, aren't adaptable. What biologists would really like is to be able to shine one laser onto a specimen and have the different components emit a distinguishably different frequency from eachother. GFP is definitely biocompatible. I haven't seen much success in the way of engineering a protein with broad absorption and narrow emission. If there are any recent publications you'd recommend, I'd be glad to read them. I'm basing my opinion off of one of my research rotations last year.

[matthias.engh]

So, after a limited amount of research I came upon this article
http://www.sciencemag.org/content/298/5599/1759.short
, which describes bio compatible quantum dots structures, encapsuled in stable non-toxic micelles.
For the convenience of anyone who, like me doesn't know what a micelle is:
http://en.wikipedia.org/wiki/Micelle
I wonder if this technology could be used in DNA memory..

[infinitexh]

(Mathias, sorry for spamming but I accidentally only replied to your post previously so it's not visible to the entire forum, sorry for the duplicate) It's interesting that you bought up micelle as that's a system that I recently had the experience of reading up on for my research. This system is actually very flexible in its applications as the surfactants (the components that make up the micelle) comes in extremely diverse groups and with the correct tunning, will definitely be DNA compatible (ionic surfactants for example, as almost anything biological is charged). However, it's biggest advantage (flexibility and scalability, as that's the compound they use to separate out Au catalysts for CVD growth, which the catalysts themselves can go down to ~5nm in diameter) is also it's biggest disadvantage: my roommate works in Professor Lal's lab in bioengineering and he tells me nightmarish stories of micelle fabrication of smaller scales as the process is extremely tricky (not to mention the imaging - if you want to observe the structure itself vs. just trying to tell if micelle exists are not - is extremely complicated and relies on cryo TEM for accurate results; which as you imagine, is more complicated than even a TEM). I've not personally have done any experimental work on the topic yet but for anyone who's interested I recommend an extremely comprehensive book on the topic by a UCSB faculty http://compare.ebay.com/like/281045089516?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar 

On the flip side, here's also a paper that involves encapsulating CNTs with micelles for PL applications, related to a few of the previous posts

http://link.springer.com/article/10.1007%2Fs00339-003-2460-6?LI=true

Happy Reading and Good luck on the final everyone!

[symay]

I think that a good course for the kind of research would be 247a. There are a bunch of different fluorescent proteins that you can use at the same time, such as GFP mentioned earlier, RFP (red), YFP (yellow) as well as CFP (Cyan or blue). You can use all of them at the same time and see that the fluorescence spectra of them is way different so you can actually see a difference between two different gene expressions. Quantum dots are a good alternative for non biological applications, but GFP may be the main reason that professor Roger Tsien at UCSD was awarded with the Nobel prize in Chemistry back in 2008. GFP use triggered the evolution of different color probes for gene expression, so in my experience, it is really specific because you can see different colors as you have different gene expression. Apart from GFP you also have Photoacoustics that have amazing resolution and really good specificity, but the application of that in real life may be limited by tissue penetration.

Salomon.

[thoughtandthinker]

I'm aware there are other variants of fluorescent proteins, and I've even analyzed images where four were used simultaneously. My original comment wasn't that there's a problem with the fluorescent proteins themselves; indeed, I can see why the discovery and use of it won Dr. Tsien the Nobel. However, we're limited in how finely we can tune and engineer specific spectra. But there are many many proteins and structures inside a cell, like in my case, a neuron, and I think anyone who could simultaneously label all of them with a single method would be hero for a day. Granted, there are more problems to simultaneously labeling 100s of molecular components besides distinguishable emission spectra (e.g. the fluorophores need to have a high enough affinity that we don't need to cram so many into a cell that it interferes with normal function). I know nothing of photoacoustics, so I'm curious what the mechanism behind that is.

[samontoy]

Quantum Dots in Televisions ?

I’m particularly surprised that Sony has announced the introduction of quantum dots in televisions. Specially since the average cost per gram is around 10,000. So being hard to convince, I decided to compare the highest resolution television available in the market and perform some quick calculations to determine some estimates in cost.  Without a surprise, according to a quick google search I found that the highest resolution television is  from Sony: ‘4K Ultra HD TV’ which has its specs available at: http://store.sony.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&identifier=S_4KTV .

The resolution of the device is 3840x2150 pixels (so about ~ 8.3 million pixels) in a surface area of 44” by 84”. Now let us suppose that 1gr of quantum dots is just Avogadro’s number ~ 6e23 (thats a lot of quantum dots). The article mentions that they will place some quantum dots in each pixel to eliminate the white backlight that gets through each pixel. Suppose they added 100 quantum dots in each LED, then we would need 8.3e9 quantum dots which would cost about 1.38e-10 dlls...  so nothing. If we suppose instead that for 1gr there are 6e11 quantum dots, then it would cost us an additional 138 dlls to install quantum dots on this HD TV which costs 25,000.  The questions remains how many quantum dots are going to be used in every pixel. From this robust calculation it does appear to be as expensive. 

Since the article also mentions that these Quantum Dots will be introduced to existing LED TV's, I don't expect their products to noticeably increase in price. Either way, I can't wait to see one of these TV's to check out the resolution improvement. 

Cheers, 

Sergio 

[matthias.engh]

Quickly, see if you can still reply.. I don't understand how you need cryo TEM for something encapsuling whole nanotubes. How small are those micelles?
Also having a quantum dot in the micelle will make it easier to show it exists :D.
Yeah, this is great stuff to read about and I'll probably keep myself updated on new technologies in the area in the future.
Have a nice spring break!
Matthias out.