Katrin Kneipp

Bio: Katrin Kneipp is an academic researcher from Harvard University. The author has contributed to research in topics: Raman spectroscopy & Raman scattering. The author has an hindex of 32, co-authored 49 publications receiving 12362 citations. Previous affiliations of Katrin Kneipp include Charité & Technical University of Berlin.

Single Molecule Detection Using Surface-Enhanced Raman Scattering (SERS)

Abstract: By exploiting the extremely large effective cross sections ( ${10}^{\ensuremath{-}17}--{10}^{\ensuremath{-}16}{\mathrm{cm}}^{2}/\mathrm{molecule}$) available from surface-enhanced Raman scattering (SERS), we achieved the first observation of single molecule Raman scattering. Measured spectra of a single crystal violet molecule in aqueous colloidal silver solution using one second collection time and about $2\ifmmode\times\else\texttimes\fi{}{10}^{5}\mathrm{W}/{\mathrm{cm}}^{2}$ nonresonant near-infrared excitation show a clear ``fingerprint'' of its Raman features between 700 and $1700{\mathrm{cm}}^{\ensuremath{-}1}$. Spectra observed in a time sequence for an average of 0.6 dye molecule in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1, 2, or 3 molecules.

SERS--a single-molecule and nanoscale tool for bioanalytics.

Abstract: Surface enhanced Raman scattering (SERS) at extremely high enhancement level turns the weak inelastic scattering effect of photons on vibrational quantum states into a structurally sensitive single-molecule and nanoscale probe. The effect opens up exciting opportunities for applications of vibrational spectroscopy in biology. The concept of SERS can be extended to two-photon excitation by exploiting surface enhanced hyper-Raman scattering (SEHRS). This critical review introduces the physics behind single-molecule SERS and discusses the capabilities of the effect in bioanalytics (100 references).

Surface-enhanced Raman scattering in local optical fields of silver and gold nanoaggregates-from single-molecule Raman spectroscopy to ultrasensitive probing in live cells.

Abstract: This Account discusses surface-enhanced Raman scattering at extremely high enhancement levels that can occur for molecules attached to silver and gold nanoclusters. Strongly enhanced and highly confined local optical fields enable surface-enhanced Stokes and anti-Stokes Raman spectroscopy of single molecules even under nonresonant excitation conditions as well as extremely large effective cross sections in two-photon excited Raman spectroscopy. The ability for very sensitive and spatially confined molecular structural probing makes gold and silver nanoclusters very promising tools for studies of small structures in biological materials, such as cellular compartments.

Detection and identification of a single DNA base molecule using surface-enhanced Raman scattering (SERS)

Abstract: Nonresonant Raman cross sections of $\ensuremath{\sim}{10}^{\ensuremath{-}16} {\mathrm{cm}}^{2}$ per molecule are shown to be related to surface-enhanced Raman scattering (SERS) on colloidal silver clusters at near-infrared (NIR) excitation. The enhancement is found to be independent of cluster sizes between 100 nm and 20 \ensuremath{\mu}m. These experimental findings demonstrate that NIR SERS on colloidal silver clusters is an excellent technique for single molecule detection that is applicable for a broad range of molecules including ``colorless'' biomolecules, for example nucleotides in DNA sequencing. As an example, we present the detection of a single adenine molecule without any labeling based on its intrinsic surface-enhanced Raman scattering.

Origin of the Breit-Wigner-Fano lineshape of the tangential G-band feature of metallic carbon nanotubes

Abstract: A detailed line-shape analysis of the tangential G-band feature attributable to metallic single-walled carbon nanotubes is presented. Only two components are needed to account for the entire G-band feature for metallic nanotubes. The higher-frequency component has a Lorentzian line shape, and the lower one has a Breit-Wigner-Fano (BWF) line shape. Through comparisons of the Raman tangential G-band spectra from three different diameter distributions of carbon nanotubes, we find that both the frequency and linewidth of the BWF component are diameter dependent and show functional forms consistent with theory. The nanotube curvature is responsible for both the frequency differences between the two components of the characteristic metallic G-band spectrum and the BWF coupling of the lower-frequency component. Surface-enhanced Raman spectroscopy studies provide supporting evidence that the phonon BWF coupling is to an electronic continuum.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Surface plasmon subwavelength optics

Abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering

Abstract: Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15 , much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.

Plasmonics: Fundamentals and Applications

Abstract: Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

Biosensing with plasmonic nanosensors

Abstract: Recent developments have greatly improved the sensitivity of optical sensors based on metal nanoparticle arrays and single nanoparticles. We introduce the localized surface plasmon resonance (LSPR) sensor and describe how its exquisite sensitivity to size, shape and environment can be harnessed to detect molecular binding events and changes in molecular conformation. We then describe recent progress in three areas representing the most significant challenges: pushing sensitivity towards the single-molecule detection limit, combining LSPR with complementary molecular identification techniques such as surface-enhanced Raman spectroscopy, and practical development of sensors and instrumentation for routine use and high-throughput detection. This review highlights several exceptionally promising research directions and discusses how diverse applications of plasmonic nanoparticles can be integrated in the near future.