Measuring and tracking vitamin B12: a review of current methods with a focus on optical spectroscopy

Published online: 13 Sep 2016Vitamin B12 deficiency has been associated with an increased risk of cognitive decline. This literature review explores the current methods available for measuring vitamin B12 in human blood, serum, and urine, and the need for a globally accepted reference range for vitamin B12. We present optical spectroscopy, including chemiluminescence measurements, absorption and fluorescence spectroscopy, surface plasmon resonance, and Raman spectroscopy, as a promising technique for detection and tracking of vitamin B12. Considerations for future research are highlighted, including enhancing the sensitivity of optical spectroscopy and prospective pathways to improve the reproducibility, selectivity, and speed of vitamin B12 detection.Georgios Tsiminis, Erik P. Schartner, Joanna L. Brooks, and Mark R. Hutchinso

Measurements of vitamin B12 in human blood serum using resonance Raman spectroscopy

Vitamin B12 (cobalamin and its derivatives) deficiency has been identified as a potential modifiable risk factor for dementia and Alzheimer’s disease. Chronic deficiency of vitamin B12 has been significantly associated with an increased risk of cognitive decline. An effective and efficient method for measuring vitamin B12 concentration in human blood would enable ongoing tracking and assessment of this potential modifiable risk factor. In this work we present an optical sensor based on resonance Raman spectroscopy for rapid measurements of vitamin B12 in human blood serum. The measurement takes less than a minute and requires minimum preparation (centrifuging) of the collected blood samples.G. Tsiminis, E. P. Schartner, J. L. Brooks, M. R. Hutchinso

Novel imaging tools for investigating the role of immune signalling in the brain

Abstract not availableJonathan Henry W. Jacobsen, Lindsay M. Parker, Arun V. Everest-Dass, Erik P. Schartner, Georgios Tsiminis, Vasiliki Staikopoulos, Mark R. Hutchinson, Sanam Mustaf

Quantification of the fluorescence sensing performance of microstructured optical fibers compared to multi-mode fiber tips

Published 3 Aug 2016Microstructured optical fibers, particularly those with a suspended-core geometry, have frequently been argued as efficient evanescent-field fluorescence-based sensors. However, to date there has not been a systematic comparison between such fibers and the more common geometry of a multi-mode fiber tip sensor. In this paper we make a direct comparison between these two fiber sensor geometries both theoretically and experimentally. Our results confirm that suspended-core fibers provide a significant advantage in terms of total collected fluorescence signal compared to multi-mode fibers using an equivalent experimental configuration.Erik P. Schartner, Georgios Tsiminis, Matthew R. Henderson, Stephen C. Warren-Smith, and Tanya M. Monr

Extruded single ring hollow core optical fibers for Raman sensing

Abstract not availableG. Tsiminis, K. J. Rowland, H. Ebendorff-Heidepriem, N. A. Spooner and T. M. Monr

Amplified spontaneous emission and lasing properties of bisfluorene-cored dendrimers

A study of the amplified spontaneous emission (ASE) properties of three bisfluorene-cored dendrimers in the solid state is reported. The results show that the dendron type has a strong impact on the photoluminescence quantum yield and affects the ASE threshold, the optical gain, and loss coefficients. Optically pumped distributed feedback lasers operating in the blue spectral region were fabricated by spin coating the dendrimer films on top of a two-dimensional corrugated fused silica substrate. A best lasing threshold of 4.5 mu J/cm(2) and a slope efficiency of 8.3% were obtained, which demonstrate the high potential of these materials for laser applications. (c) 2007 American Institute of Physics

Impact of rare earth doping on the luminescence of lanthanum aluminum silicate glasses for radiation sensing

Large core soft glass fibers have been demonstrated to be promising candidates as intrinsic fiber sensors for radiation detection and dosimetry applications. Doping with rare earth ions enhanced their radiation sensitivity. SiO2-Al2O3-La2O3 (SAL) glasses offer easy fabrication of large core fibers with high rare earth concentration and higher mechanical strength than soft glasses. This paper evaluates the suitability of the SAL glass type for radiation dosimetry based on optically stimulated luminescence (OSL) via a comprehensive investigation of the spectroscopic and dosimetric properties of undoped and differently rare earth doped bulk SAL glass samples. Due to the low intensity of the rare earth luminescence peaks in the 250–400 nm OSL detection range, the OSL response for all the SAL glasses is not caused by the rare earth ions but by radiation-induced defects that act as intrinsic centers for the recombination of electrons and holes produced by the ionizing radiation, trapped in fabrication induced defect centers, and then released via stimulation with 470 nm light. The rare earth ions interfere with these processes involving intrinsic centers. This dosimetric behavior of highly rare earth doped SAL glasses suggests that enhancement of OSL response requires lower rare earth concentrations and/or longer wavelength OSL detection range

Laser-based metastable krypton generation

We demonstrate the generation of metastable krypton in the long-lived 1s^{5} state using laser excitation. The atoms are excited through a two-photon absorption process into the 2p^{6} state using a pulsed optical parametric oscillator laser operating near 215 nm, after which the atoms decay quickly into the metastable state with a branching ratio of 75%. The interaction dynamics are modeled using density matrix formalism and, by combining this with experimental observations, we are able to calculate photoionization and two-photon absorption cross sections. When compared to traditional approaches to metastable production, this approach shows great potential for high-density metastable krypton production with minimal heating of the sample. Here, we show metastable production efficiencies of up to 2% per pulse. The new experimental results gained here, when combined with the density matrix model we have developed, suggest that fractional efficiencies up to 30% are possible under optimal conditions.M. A. Dakka, G. Tsiminis, R. D. Glover, C. Perrella, J. Moffatt, N. A. Spooner, R. T. Sang, P. S. Light, and A. N. Luite

Luminescence effects in reactive powder sintered silica glasses for radiation sensing

Silica glasses doped with rare‐earth ions are potential materials for optical fiber radiation detection and dosimetry applications. High sensitivity to radiation requires fibers with large cores that can be reliably fabricated using glass made in a novel process from the reactive powder sintering of silica. The luminescence and dosimetric properties of a range of rare earth‐doped silica materials produced using this novel technique are reported here. Radioluminescence and optically stimulated luminescence (OSL) are the fundamental mechanisms enabling radiation detection in optical fibers. It was found that thermoluminescence, radioluminescence, and OSL are observed if the glass contains luminescent transitions in the detection wavelength range. Cerium‐ and thulium‐doped silica glasses were found to be promising candidates for optical fiber dosimetry. Samples showed intense luminescence signals in response to both photo‐stimulation and irradiation from alpha and beta sources. OSL results for cerium are three times larger than results for irradiated fluoride phosphate glasses previously tested for dosimetry use. Spectroscopic measurements indicate emission in the 300‐500 nm region, suitable for detection with photomultiplier tubes.Ruth E. Shaw, Christopher A. G. Kalnins, Nigel Antony Spooner, Carly Whittaker, Stephan Grimm, Kay Schuster, David Ottaway, Jillian Elizabeth Moffatt, Georgios Tsiminis, Heike Ebendorff‐Heideprie

Dual Laser Study of Non-Degenerate Two Wavelength Upconversion Demonstrated in Sensitizer-Free NaYF4:Pr Nanoparticles

Published online: February 1, 2021Understanding the upconversion pathways of a rare-earth dopant is crucial to furthering the use of that material, either toward applications in imaging or elsewhere. This work outlines a new analysis approach that consists of using two synchronized widely-tunable laser sources to explore the properties of upconverting materials. By examining sensitizer-free rare-earth nanoparticles based on a matrix of hexagonal sodium yttrium tetrafluoride (β-NaYF4) doped with praseodymium but no ytterbium sensitizer, a “non-degenerate” two-color upconversion fluorescence at a combined excitation of 1020–850 nm is shown. This insight demonstrates the ability of this technique to locate and interrogate novel upconversion pathways. The dopant level of the nanoparticles could be modified without altering other factors, such as the particle's shape or size, that would also change optical properties and this allows investigation of the dopant-level dependency of the optical properties. The approach also allows exploration of the time delay domain between the arrival times of the two non-degenerate excitation pulses, which allows modulation of the brightness from the visible light emissions. This work opens up the parameter space for the systematic synthesis and characterization of new materials with non-degenerate upconversion emission.Thomas J. de Prinse, Afshin Karami, Jillian E. Moffatt, Thomas B. Payten, Georgios Tsiminis, Lewis Da Silva Teixeira, Jingxiu Bi, Tak W. Kee, Elizaveta Klantsataya, Christopher J. Sumby, and Nigel A. Spoone