A molecular ruler based on plasmon coupling of single gold and silver nanoparticles

Carsten Sönnichsen1, 3, Björn M Reinhard2, 3, Jan Liphardt2 & A Paul Alivisatos1

1 Department of Chemistry, University of California, Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
2 Department of Physics, University of California, Berkeley and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

Förster Resonance Energy Transfer has served as a molecular ruler that reports conformational changes and intramolecular distances of single biomolecules. However, such rulers suffer from low and fluctuating signal intensities, limited observation time due to photobleaching, and an upper distance limit of approx10 nm. Noble metal nanoparticles have plasmon resonances in the visible range and do not blink or bleach. They have been employed as alternative probes to overcome the limitations of organic fluorophores, and the coupling of plasmons in nearby particles has been exploited to detect particle aggregation by a distinct color change in bulk experiments. Here we demonstrate that plasmon coupling can be used to monitor distances between single pairs of gold and silver nanoparticles. We followed the directed assembly of gold and silver nanoparticle dimers in real time and studied the kinetics of single DNA hybridization events. These 'plasmon rulers' allowed us to continuously monitor separations of up to 70 nm for >3,000 s.


This a more application based work but quite interesting. A very simple application of a complex phenomenon.

Date : 1st Nov '07
Time: 10:30 am - 11:30 am
Venue: E3A, 7th Floor Lounge

Comsol User Conference 2007

Please find sign-up info for following workshop info of Comsol Physics by clicking above.

The workshop is held on 15 Nov 2007

Microscopy at 29 nm optical resolution

Dear Bioimaging People
Hello

Here is an interesting paper to discuss that I believe may generate some ideas. It is about Stimulated Emission Depletion (STED) fluorescence microscopy, invented by Stefen Hell's group in Germany, and has apparently removed the barriers of classical diffraction limit in optical resolution. In this paper they are claiming a resolution of 29 nm ( who needs near-field microscopy like NSOM or other scanning probe techniques now!). Anyway, let's talk about it on 25th.

Cheers

Shakil

Citation: "STED microscopy with continuous wave beams", Katrin I. Willig, Benjamin Harke, Rebecca Medda and Stefan W. Hell, Nature Methods 21 October, 2007.
Published online at http://www.nature.com/naturemethods

http://www.nature.com.libproxy1.nus.edu.sg/nmeth/journal/vaop/ncurrent/pdf/nmeth1108.pdf

Journal Club Oct 17 10.30am

Sub–Diffraction-Limited Optical Imaging with a Silver Superlens
Nicholas Fang, Hyesog Lee, Cheng Sun, Xiang Zhang

Science, Vol. 308, 534-537 (2005)

Recent theory has predicted a superlens that is capable of producing sub–
diffraction-limited images. This superlens would allow the recovery of evanescent
waves in an image via the excitation of surface plasmons. Using silver as a natural
optical superlens, we demonstrated sub–diffraction-limited imaging with 60-
nanometer half-pitch resolution, or one-sixth of the illumination wavelength. By
proper design of the working wavelength and the thickness of silver that allows
access to a broad spectrum of subwavelength features, we also showed that
arbitrary nanostructures can be imaged with good fidelity. The optical superlens
promises exciting avenues to nanoscale optical imaging and ultrasmall optoelectronic
devices.

WITec Workshop at NTU.

Hi friends,
Sorry i am a bit late in posting this announcement. There is an optics related workshop being held in NTU on 18th Oct. The details are as follows:

Combining Confocal Raman, High Resolution Optical and Scanning Probe Microscopy.

With application in the field of material science, pharmaceutics, life science, semiconductors and nanotechnology.

On the 18^th of October 2007 at NTU School of Material Science and Engineering, Polymer Lab.

Further details is in the flyer attached to this email.

Limited places is available so if you are interested, please register early to avoid disappointment.

Best regards,

Shawn

Extrad Instrumentation

371 Beach Road, #02-32 Keypoint

Singapore 199597

Tel: +65 6296 6908 Fax: +65 6296 6906

Hp: 9026 5667

Journal club schedule

Journal Club Oct 11 07 10.30am

Paper Details:

Nat Methods. 2007 Sep;4(9):717-9. Epub 2007 Aug 12.

Tomographic phase microscopy.

Choi W, Fang-Yen C, Badizadegan K, Oh S, Lue N, Dasari RR, Feld MS.

G.R. Harrison Spectroscopy Laboratory, 77 Massachusetts Avenue 6-014, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

We report a technique for quantitative three-dimensional (3D) mapping of refractive index in live cells and tissues using a phase-shifting laser interferometric microscope with variable illumination angle. We demonstrate tomographic imaging of cells and multicellular organisms, and time-dependent changes in cell structure. Our results will permit quantitative characterization of specimen-induced aberrations in high-resolution microscopy and have multiple applications in tissue light scattering.

Discussion leader: Shan
Time: Oct 11 10.30am
Venue: Div pantry area

first to post

Hi welcome all! Hope this will be an enriching place for all of us.