title: Determination of photoluminescence quantum yields of scattering media with an integrating sphere: direct and indirect illumination.
abstract: The ever-increasing use of fluorescent nanomaterials and micrometer-sized beads in the life and material sciences requires reliable procedures for the measurement of the key performance parameter fluorescence quantum yield (Φf) of scattering particle dispersions and reference systems to evaluate the performance of such measurements. This encouraged us to systematically study, both theoretically and experimentally, the optical determination of photoluminescent quantum yield as a function of the scattering and absorption properties of the sample and the illumination geometry with an integrating sphere method. The latter included measurements with a direct and an indirect illumination. As a representative and easy-to-prepare reference system, we used ethanolic dispersions of 250 nm sized silica particles and the dye rhodamine 101 and systematically varied the concentration of the dye and particles within the typical ranges of spectroscopic and (bio)analytical applications of fluorescent nanomaterials. Based on our measurements, we recommend indirect sample illumination geometry for the accurate measurement of Φf of samples with low or unknown absorption and high scattering coefficients such as dispersions of luminescent particles or fluorescent reporters in biological matrices. This finding is of utmost relevance for all (bio)analytical applications of fluorescent nanomaterials ranging from particle labels and probes over assay platforms to safety barcodes.
authors.affiliation: BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Str. 11, 12489 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Würth
authors.forename: Ute
authors.initials: U
authors.lastname: Resch-Genger
mesh_terms: D004867:Equipment Design; D005456:Fluorescent Dyes / Q000737:chemistry; D008027:Light; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D012235:Rhodamines / Q000737:chemistry; D012542:Scattering, Radiation; D012822:Silicon Dioxide / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000295:instrumentation* / Q000379:methods*
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; D012822:Silicon Dioxide