TY - CONF A1 - Radunz, Sebastian T1 - Development of UCL-based reporters for monitoring microbial induced corrosion 2 N2 - Recent results concering analyte-responsive chromophores for UCL-based sensor systems T2 - Projekttreffen MIC CY - BAM, Berlin, Germany DA - 06.10.2016 KW - Fluoreszenz KW - UCNP KW - Optical Assay KW - Quantum Yield PY - 2016 AN - OPUS4-37823 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grauel, Bettina A1 - Würth, Christian A1 - Wiesholler, L. M. A1 - Hirsch, T. A1 - Resch-Genger, Ute T1 - Nd as sensitizer in NaYF4:Yb,Er,Nd tri-doped upconversion nanocrystals N2 - In recent years, upconversion nanocrystals (UCNC) have shown great promise for biological and medical applications, mainly because of their excitation in the NIR region, which provides minimum fluorescence background and a rather deep penetration into biological samples, as opposed to excitation in the visible or UV region. Moreover, they show a multitude of characteristic narrow emission bands as basis for ratiometric measurements. Commonly, Yb is the sensitizer of choice, because of a comparatively high absorption cross section, simple energy scheme, and rather efficient energy transfer to the activator, mostly Er, Tm or Ho. A main disadvantage of the use of Yb as sensitizer for biological and medical applications is its absorption band at 976 nm and hence the use of an excitation wavelength at which water has a non-negligible absorption. This can lead to significant sample heating, especially at long illumination times or high excitation power densities, and thus, tissue damage or even cell death. A possible solution is the tri-doping of UCNC with Nd as sensitizer, which can be excited efficiently at around 800 nm, where water absorption is at minimum. The use of Nd as a sensitizer and Yb as a bridge between Nd and the activator Er in NaYF₄ nanocrystals is a relatively new way to overcome the problems of heating of samples in an aqueous environment. Disadvantages can arise from the tri-doping, which can favor non-radiative relaxation due to the more complicated excitation process compared to e.g., simple Yb,Er-doped UCNC, which might lower the upconversion quantum yields in these tri-doped systems. In order to quantify clear advantages, NaYF₄:Yb,Er,Nd nanoparticles were synthesized and spectroscopically studied using an 8 W 804 nm laser diode and a custom-designed Edinburgh instruments FSP980 spectrometer. Wavelength-dependent studies of the emission intensities and the decay kinetics of these tri-doped UCNC at different excitation power densities and excitation pulse widths revealed the clear advantages of preventing water absorption on measurable luminescence signals. We were able to show the influence of pulse width and excitation power density on the luminescence intensities and decay kinetics lifetimes at different emission wavelengths. Additionally, we can clearly discern power density-dependent and independent peaks in the emission spectra. In summary, we demonstrate that the tri-doping of NaYF₄:Yb,Er,Nd nanoparticles is a very promising approach to render UCNC more efficient and to make them better suitable for biological and medical applications requiring measurements in aqueous environment. T2 - UPCON 2016 Conference CY - Breslau, Poland DA - 23.05.2016 KW - UCNP KW - Nd-sensitizer KW - excitation power density PY - 2016 AN - OPUS4-37224 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grauel, Bettina T1 - Nd-sensitized tri-doped UCNP systems N2 - This presentation gives a short overview of the PhD student's research topics and interests, within the scope of the 2016 UPCON Spring School. T2 - UPCON 2016 Spring School CY - Breslau, Poland DA - 25.05.2016 KW - UCNP KW - Nd-sensitizer PY - 2016 AN - OPUS4-37223 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radunz, Sebastian T1 - Development of UCL-based reporters for monitoring microbial induced corrosion N2 - Kurzpräsentation zur Vorstellung der Promotionsthematik während der SpringSchool der UpCon2016 in Polen. T2 - Konferenz UpCon2016 CY - Breslau, Poland DA - 23.05.2016 KW - UCNP PY - 2016 AN - OPUS4-36265 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -