TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - Kneipp, K. T1 - Two-photon vibrational spectroscopy for biosciences based on surface-enhanced hyper-Raman scattering PY - 2006 SN - 0027-8424 SN - 1091-6490 VL - 103 IS - 46 SP - 17149 EP - 17153 PB - National Academy of Sciences CY - Washington, DC AN - OPUS4-13934 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - McLaughlin, M. A1 - Brown, D. A1 - Kneipp, K. T1 - In Vivo Molecular Probing of Cellular Compartments with Gold Nanoparticles and Nanoaggregates N2 - Surface-enhanced Raman (SERS) signatures were measured from single living cells at different times after the uptake of gold nanoparticles. The spectra are indicative of chemical changes in the environment of the nanostructures over time. The increase of the SERS signal strength and parallel TEM studies indicate the formation of nanoaggregates providing optimum SERS enhancement for ultrasensitive probing inside the endosomal compartment. The results have implications for medical and biotechnology applications of SERS nanosensors in cells. PY - 2006 U6 - https://doi.org/10.1021/nl061517x SN - 1530-6984 SN - 1530-6992 VL - 6 IS - 10 SP - 2225 EP - 2231 PB - American Chemical Society CY - Washington, DC AN - OPUS4-13935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - Wittig, B. A1 - Kneipp, K. T1 - One- and Two-Photon Excited Optical pH Probing for Cells Using Surface-Enhanced Raman and Hyper-Raman Nanosensors N2 - We demonstrate spatially resolved probing and imaging of pH in live cells by mobile and biocompatible nanosensors using surface-enhanced Raman scattering (SERS) of 4-mercaptobenzoic acid (pMBA) on gold nanoaggregates. Moreover, we also show that this concept of pH nanosensors can be extended to two-photon excitation by using surface-enhanced hyper-Raman scattering (SEHRS). In addition to the advantages of two-photon excitation, the SEHRS sensor enables measurements over a wide pH range without the use of multiple probes. PY - 2008 U6 - https://doi.org/10.1021/nl071418z SN - 1530-6984 SN - 1530-6992 VL - 7 IS - 9 SP - 2819 EP - 2823 PB - American Chemical Society CY - Washington, DC AN - OPUS4-18230 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Li, X. A1 - Sherwood, M. A1 - Panne, Ulrich A1 - Kneipp, H. A1 - Stockman, M.I. A1 - Kneipp, K. T1 - Gold Nanolenses Generated by Laser Ablation-Efficient Enhancing Structure for Surface Enhanced Raman Scattering Analytics and Sensing N2 - Nanoaggregates formed by metal spheres of different radii and interparticle distances represent finite, deterministic, self-similar systems that efficiently concentrate optical fields and act as “nanolenses”. Here we verify experimentally the theoretical concept of nanolenses and explore their potential as enhancing nanostructures in surface enhanced Raman scattering (SERS). Self-similar structures formed by gold nanospheres of different sizes are generated by laser ablation from solid gold into water. These nanolenses exhibit SERS enhancement factors on the order of 109. The “chemically clean” preparation process provides several advantages over chemically prepared nanoaggregates and makes the stable and biocompatible gold nanolenses potent enhancing structures for various analytical and sensing applications. KW - SERS KW - Ablation KW - Gold-Nanopartikel PY - 2008 U6 - https://doi.org/10.1021/ac8002215 SN - 0003-2700 SN - 1520-6882 VL - 80 IS - 11 SP - 4247 EP - 4251 PB - American Chemical Society CY - Washington, DC AN - OPUS4-18231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - Rajadurai, A. A1 - Redmond, R.W. A1 - Kneipp, K. T1 - Optical probing and imaging of live cells using SERS labels N2 - During surface-enhanced Raman scattering (SERS), molecules exhibit a significant increase in their Raman signals when attached, or in very close vicinity, to gold or silver nanostructures. This effect is exploited as the basis of a new class of optical labels. Here we demonstrate robust and sensitive SERS labels as probes for imaging live cells. These hybrid labels consist of gold nanoparticles with Rose Bengal or Crystal Violet attached as reporter molecules. These new labels are stable and nontoxic, do not suffer from photobleaching, and can be excited at any excitation wavelength, even in the near infrared. SERS labels can be detected and imaged through the specific Raman signatures of the reporters. In addition, surface-enhanced Raman spectroscopy in the local optical fields of the gold nanoparticles also provides sensitive information on the immediate molecular environment of the label in the cell and allows imaging of the native constituents of the cell. This is demonstrated by images based on a characteristic Raman line of the reporter as well as by displaying lipids based on the SERS signal of the C—H deformation/bending modes at ~ 1470 cm-1. KW - Surface-enhanced Raman scattering KW - Gold nanoparticles KW - Cells KW - SERS imaging PY - 2008 U6 - https://doi.org/10.1002/jrs.2060 SN - 0377-0486 SN - 1097-4555 IS - -Early View- SP - 1 EP - 5 PB - Wiley CY - Chichester AN - OPUS4-18232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - Wittig, B. A1 - Kneipp, K. T1 - Following the dynamics of pH in endosomes of live cells with SERS nanosensors N2 - The surface enhanced Raman scattering (SERS) spectrum of a reporter molecule attached to gold or silver nanostructures, which is pH-sensitive, can deliver information on the local pH in the environment of the nanostructure. Here, we demonstrate the use of a mobile SERS nanosensor made from gold nanaoaggregates and 4-mercaptobenzoic acid (pMBA) attached as a reporter for monitoring changes in local pH of the cellular compartments of living NIH/3T3 cells. We show that SERS nanosensors enable the dynamics of local pH in individual live cells to be followed at subendosomal resolution in a timeline of cellular processes. This information is of basic interest for a better understanding of a broad range of physiological and metabolic processes as well as for a number of biotechnological applications. PY - 2010 U6 - https://doi.org/10.1021/jp910034z SN - 1932-7447 SN - 1089-5639 VL - 114 IS - 16 SP - 7421 EP - 7426 PB - Soc. CY - Washington, DC AN - OPUS4-23214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Kneipp, H. A1 - Wittig, B. A1 - Kneipp, K. T1 - Novel optical nanosensors for probing and imaging live cells N2 - This review introduces multifunctional optical nanosensors based on surface-enhanced Raman scattering (SERS) and demonstrates their application in live cells. The novel nanosensors have the potential to improve our understanding of cellular processes on the molecular level. The hybrid sensor consists of gold or silver nanoparticles with an attached reporter species. The sensor can be detected and imaged based on the SERS signature of the reporter. This results in several advantages, such as high spectral specificity, multiplex capabilities, improved contrast, and photostability. SERS sensors not only highlight cellular structures, based on enhanced Raman spectra of intrinsic cellular molecules measured in the local optical fields of the gold nanoparticles, they also provide molecular structural information on their cellular environment. Moreover, the SERS signature of the reporter can deliver information on the local pH value inside a cell at subendosomal resolution. SERS sensors are suitable for one- and two-photon excitation. KW - Cells KW - Optical nanosensors KW - Nano gold KW - Spectroscopy KW - SERS KW - ph probing PY - 2010 U6 - https://doi.org/10.1016/j.nano.2009.07.009 SN - 1549-9634 SN - 1549-9642 VL - 6 IS - 2 SP - 214 EP - 226 PB - Elsevier CY - New York AN - OPUS4-23943 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eichelbaum, M. A1 - Kneipp, Janina A1 - Schmidt, B.E. A1 - Panne, Ulrich A1 - Rademann, K. T1 - SERS and Multiphoton-Induced Luminescence of Gold Micro- and Nanostructures Fabricated by NIR Femtosecond-Laser Irradiation KW - Gold KW - Luminescence KW - Multiphoton fabrication KW - Sol-gel processes KW - Surface-enhanced Raman scattering PY - 2008 U6 - https://doi.org/10.1002/cphc.200800417 SN - 1439-4235 SN - 1439-7641 VL - 9 IS - 15 SP - 2163 EP - 2167 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-18233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Simo, A. A1 - Merk, Virginia A1 - Fenger, R. A1 - Kneipp, Janina A1 - Rademann, K. T1 - Long-term stable silver subsurface ion-exchanged glasses for SERS applications N2 - We report on the formation of silver subsurface ion-exchanged metal oxide (silver SIMO) glasses and their surface-enhanced Raman scattering (SERS) activity. The samples were prepared by a combined thermal and chemical three-step methodology and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), environmental electron scanning microscopy (ESEM), and UV/Vis spectroscopy. This unique method provides SERS substrates with protection against contamination and strong, reliable and reproducible SERS enhancement. The Raman enhancement factors of the long-term stable SIMO glasses were estimated to approximately 107. KW - AFM/TEM/SEM KW - Ion-exchange KW - Nanoparticles KW - Glasses KW - Surface-enhanced Raman scattering PY - 2011 U6 - https://doi.org/10.1002/cphc.201100098 SN - 1439-4235 N1 - Geburtsname von Merk, Virginia: Joseph, V. - Birth name of Merk, Virginia: Joseph, V. VL - 12 IS - 9 SP - 1683 EP - 1688 PB - Wiley-VCH CY - Weinheim AN - OPUS4-23872 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Klimakow, Maria A1 - Leiterer, Jork A1 - Kneipp, Janina A1 - Rössler, E. A1 - Panne, Ulrich A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Combined synchrotron XRD/Raman measurements: In situ identification of polymorphic transitions during crystallization processes N2 - A combination of two analytical methods, time-resolved X-ray diffraction (XRD) and Raman spectroscopy, is presented as a novel tool for crystallization studies. An acoustic levitator was employed as sample environment. This setup enables the acquisition of XRD and Raman data in situ simultaneously within a 20 s period and hence permits investigation of polymorphic phase transitions during the crystallization process in different solvents (methanol, ethanol, acetone, dichloromethane, acetonitrile). These real time measurements allow the determination of the phase content from the onset of the first crystalline molecular assemblies to the stable system. To evaluate the capability of this approach, the setup was applied to elucidate the crystallization process of the polymorphic compound nifedipine. The results indicate the existence of solvent-dependent transient phases during the crystallization process. The quality of the data allowed the assignment of the lattice constants of the hitherto unknown crystal structure of the β-polymorph. KW - Synchrotron radiation KW - XRD KW - Raman spectroscopy KW - Polymorphism KW - Crystallization KW - Acoustic levitation KW - Nifedipine PY - 2010 U6 - https://doi.org/10.1021/la100540q SN - 0743-7463 SN - 1520-5827 VL - 26 IS - 13 SP - 11233 EP - 11237 PB - American Chemical Society CY - Washington, DC AN - OPUS4-21396 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -