Fluorescence enhancement in noncontact and dynamic-force apertureless near-field scanning optical microscopy

The fluorescence of single ZnS overcoated CdSe quantum dots (QDs) and dye doped polystyrene spheres (PSs) embedded in the evanescent optical field has been studied using an apertureless near-field scanning optical microscope (ANSOM) operating in non-contact and dynamic-force modes. The fluorescence intensity of an individual QD can be enhanced 5 times when an HF etch-cleaned silicon probe is located over the QD and spatially resolved with ~30 nm full width at half maximum when the ANSOM is operating in non-contact mode. Furthermore, we show that the fluorescence contrast in ANSOM is typically 5 times greater than the above enhancement coefficient. In the case of ANSOM dynamic-force mode, the fluorescence of QDs and PSs depends on the pressure applied by the probe to the sample.

[1]  M. Bawendi,et al.  The band edge luminescence of surface modified CdSe nanocrystallites: Probing the luminescing state , 1997 .

[2]  D. Rugar,et al.  Frequency modulation detection using high‐Q cantilevers for enhanced force microscope sensitivity , 1991 .

[3]  G. W. Ford,et al.  Electromagnetic interactions of molecules with metal surfaces , 1984 .

[4]  T. Ha.  Fluorescence spectroscopy of single molecules at room temperature and its applications , 1996 .

[5]  Olivier J. F. Martin,et al.  Scanning near-field optical microscopy with aperture probes: Fundamentals and applications , 2000 .

[6]  Y. Martin,et al.  Scanning Interferometric Apertureless Microscopy: Optical Imaging at 10 Angstrom Resolution , 1995, Science.

[7]  Alivisatos,et al.  Shape change as an indicator of mechanism in the high-pressure structural transformations of CdSe nanocrystals , 2000, Physical review letters.

[8]  S. Tolbert,et al.  The wurtzite to rock salt structural transformation in CdSe nanocrystals under high pressure , 1995 .

[9]  W. E. Moerner,et al.  A Dozen Years of Single-Molecule Spectroscopy in Physics, Chemistry, and Biophysics , 2002 .

[10]  D. Nesbitt,et al.  Field enhancement in apertureless near-field scanning optical microscopy. , 2001, Journal of the Optical Society of America. A, Optics, image science, and vision.

[11]  T. J. Watson,et al.  Apertureless near-field optical microscope , 1999 .

[12]  A. Nitzan,et al.  Spectroscopic properties of molecules interacting with small dielectric particles , 1981 .

[13]  David J. Nesbitt,et al.  Molecular fluorescence in the vicinity of a nanoscopic probe , 2001 .

[14]  Hendrik F. Hamann,et al.  Strength of the electric field in apertureless near-field optical microscopy , 2001 .

[15]  R. R. Ernst,et al.  Energy transfer in surface enhanced luminescence , 1983 .

[16]  Franz J. Giessibl,et al.  Forces and frequency shifts in atomic-resolution dynamic-force microscopy , 1997 .

[17]  R. Zare,et al.  Optical detection of single molecules. , 1997, Annual review of biophysics and biomolecular structure.

[18]  R. Ober,et al.  (CdSe)ZnS Core—Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites. , 1998 .

[19]  D. Nesbitt,et al.  Fluorescence of single ZnS overcoated CdSe quantum dots studied by apertureless near-field scanning optical microscopy , 2002 .

[20]  Louis E. Brus,et al.  Nucleation and Growth of CdSe on ZnS Quantum Crystallite Seeds and Vice Versa, in Inverse Micelle Media , 1990 .