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IgorSokolov
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re: Brightest nanoparticles shun quantum
IgorSokolov   1/20/2011 4:32:35 PM
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I would just add that quantum dots have a number of issues which organic dyes do not. For example, toxicity, blinking, fast degradation in aqueous media, etc. Thus, the dyes are preferable in a number of applications.

IgorSokolov
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re: Brightest nanoparticles shun quantum
IgorSokolov   1/20/2011 4:29:21 PM
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Yes, you are absolutely right. We will try to make it smaller. Although it may already be used in a number of applications. The sizes are not far from water dispersable quantum dots (coated), which are 15-25nm.

IgorSokolov
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re: Brightest nanoparticles shun quantum
IgorSokolov   1/20/2011 4:26:29 PM
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Thank you for your interest. We tried to do simulations of the internal multiple reflection of captured light. It works only for large (micron size) particles.

IgorSokolov
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re: Brightest nanoparticles shun quantum
IgorSokolov   1/20/2011 4:19:05 PM
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Thank you for your interest. If you email me, I can send you a PDF copy of the paper. As to your note, brightness is a well defined quantity. It is proportional to the quantum yield and (!important) the cross-section of absorption (or absorptivity). Just quantum yield does not tell your much. For example, the brightest quantum dots have the quantum yield not more than ~20%, whereas 20 times dimmer dye molecules have almost 100% q. yield..

R_Colin_Johnson
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re: Brightest nanoparticles shun quantum
R_Colin_Johnson   1/20/2011 2:03:11 AM
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These researchers are not using quantum dots, but instead are using traditional organic fluorescent dyes--but packing then more tightly than is possible without the channels inside their silica shells. I asked them about quantum dots, but they said they could get a wider gamut of colors by using different combinations of colored organic dyes.

Warren3
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re: Brightest nanoparticles shun quantum
Warren3   1/20/2011 1:02:07 AM
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The positive impact from improved sensetivity (smaller number of indicators needed to create a given visual response) should be significant. Size does matter though and even 20nm particles might be too much for some (many?) applications.

R_Colin_Johnson
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re: Brightest nanoparticles shun quantum
R_Colin_Johnson   1/20/2011 12:20:01 AM
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I checked with the researchers, and they say that the fluorescent dyes inside are not quantum dots, but conventional organic marker-dyes already used in biomedical applications. The reason they can make conventional fluorescent marker-dyes brighter than quantum dots, is that their silicon dioxide shells are porous--thus they can pack more dye into its internal channels. Usually you can't pack the dyes together tightly, because they clump, degrading fluorescence, but by packing them in separate internal channels, the mesoporous silica shells allow more dye per unit area.

R_Colin_Johnson
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re: Brightest nanoparticles shun quantum
R_Colin_Johnson   1/20/2011 12:03:02 AM
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The researchers started with ultra-bright but micron-sized silica particles in 2007, and since then have been working to downsize them to the nanoscale. At first brightness suffered from the downsizing, but now they are going public because they claim to have succeeded in making ultra-bright, yet very small, fluorescent nanoparticles.

wilber_xbox
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re: Brightest nanoparticles shun quantum
wilber_xbox   1/19/2011 11:38:37 PM
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If i go by the logic that the bigger the size of porous SiO2 nanoparticle the higher the number of fluorescent organic molecules trapped into it, then why the brightness is only 34 times than that of quantum dot? Are they comparing the same size particles and dots or is there any limit on the size of produced SiO2 nanoparticles?

wilber_xbox
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re: Brightest nanoparticles shun quantum
wilber_xbox   1/19/2011 11:29:44 PM
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If i understood the news correctly then large number of fluorescent organic molecules are trapped into nanoporous SiO2, which has higher brightness than a quantum dot. Although each organic fluorescent molecules is a quantum dot, nanoporous SiO2 is acting as a medium only to confine all the molecules at one place. So it is not SiO2 which is fluorescent. And the higher brightness is due to the higher number of the organic molecules (quantum dots).

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