Fwd: Enhancing the "blinking" of quantum dots

[George McNamara]

Hi Colin,

Add a photochromic/photoswitching, or environmentally controllable molecule(s) on the dot. See papers by Francisco Raymo and others.

Optical control of quantum dot luminescence via photoisomerization of a surface-coordinated, cationic dithienylethene.

Erno Z, Yildiz I, Gorodetsky B, Raymo FM, Branda NR.

Photochem Photobiol Sci. 2010 Feb;9(2):249-53. Epub 2010 Jan 18.PMID: 20126802

pH-sensitive ligand for luminescent quantum dots.

Tomasulo M, Yildiz I, Kaanumalle SL, Raymo FM.

Langmuir. 2006 Nov 21;22(24):10284-90.PMID: 17107034

George

Date:         Wed, 28 Apr 2010 17:34:33 +0100
From: Colin Rickman <[hidden email]>
Subject: Enhancing the "blinking" of quantum dots
To: [hidden email]

Hi

Thanks for the archive email. My question wasn't so much about observing blinking but enhancing it (hence I have changed the subject line to reflect this). Most recent research has been focused on trying to reduce or eliminate the blinking observed by Quantum dots. I would like to know if anybody has any ideas on how to increase either the frequency of blinking or increase the time the quantum dot spends in the "off" state.

Any advice gratefully received

Regards

Colin

--
Dr Colin Rickman
Department of Chemistry (WP 2.03)
School of Engineering and Physical Sciences
Heriot-Watt University
Edinburgh
EH14 4AS

Tel: [phone] (Office)
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On 28/04/2010 17:24, Maria Calvo wrote:

Hi,

Answering the question from Colin Rickman, I found in the archives from 2006 an answer from Mike Ignatius to a similar question (he talks about blinking).

My question was also related to that mail, what types of mounting media are compatible to Quantum dots?

Thank you!
Maria Calvo

Find below the mail from the archives:

Dear Laurent,

Caution, Vendor's somewhat torn response.

We sell both products and have of course compared them. (I will assume since you call them QDots that you are using our product.) You asked about size and blinking.

Size:

The QDot nanocrystal conjugates are indeed larger than organic dyes. Depending on the color (the redder the bigger) they can reach 10 to 15 nm's and with full IgGs decorating them (2-4 on average) even larger. So like DPI for printers, larger is not better for high resolution ICC. However, we only see real big differences when we deconvolve the images, since this is all sub-resolution.

However, the packing density is less. So while QDot nanocrystals are brighter in the vial, on your prep they are more likely equivalent in terms of brightness to Alexa dyes - less dots per unit area when compared to dyes.

A cautionary note: Please do not use Prolong or Prolong Gold or anything but cytoseal or PBS glycerol type mountants, such as our SlowFade gold for mounting QDot Nanocrystals. They will disappear overnight. We have an ever growing "n" value on this behavior. Our PIS stipulates this with the product.)

Blinking:

The blinking is certainly apparent to the eye and thus to fast cameras. Integrating over time avoids this concern - merely reduce your lamp intensity to help out. We see the blinking with individual dots the most, while ensembles tend to average out. It is worth noting that some have found the blinking a nice confirmation that they are looking at a nanocrystals, not background or organic dyes.

When to use Organic dyes when to use Nanocrystals?

This is where we are sometimes torn. The narrow full width half maximums of Qdot nanocrystals, as you describe, indeed allow more colors. The photostability, while terrific for live cell work, rare event detection and repeated scanning of confocal stacks, is less of a boon in wide field, single scan experiments. Especially with good dyes and antifades. So when you need photostability or more colors, nanocrystals are worth considering.

Mike Ignatius

Molecular Probes/Invitrogen.

George McNamara, Ph.D.
Image Core Manager
Analytical Imaging Core Facility
University of Miami, Miller School of Medicine
Miami, FL 33136
[hidden email]
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305-243-8436 office
http://www.sylvester.org/AICF (Analytical Imaging Core Facility)
http://www.sylvester.org/AICF/pubspectra.zip (the entire 2000+ spectra .xlsx file is in the zip file)
http://home.earthlink.net/~geomcnamara