Author
Daniel Biner
Bio: Daniel Biner is an academic researcher from University of Bern. The author has contributed to research in topics: Photon upconversion & Photoluminescence. The author has an hindex of 23, co-authored 56 publications receiving 3851 citations.
Papers published on a yearly basis
Papers
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TL;DR: In this article, it was shown that the hexagonal phase is isostructural to the chlorides Na3xM2-xCl6 with M = La−Sm.
Abstract: Hexagonal sodium yttrium fluoride, NaYF4, is the most efficient host material to date for green (Yb3+/Er3+ doped) and blue (Yb3+/Tm3+ doped) upconversion (UC) phosphors, i.e., phosphors which emit visible light upon infrared (IR) excitation. The structure of the hexagonal phase gives rise to controversy about the cation sites and distribution. The X-ray diffraction patterns of our phosphors do not fit well with the crystal structure reported for NaNdF4 (space group P6, Z = 1.5). The Na:M ratio (M = Y, Nd, Er, Tm, Yb) of the hexagonal phase deviates significantly from 1:1, and it depends on M and the preparation temperature. It is proposed that the hexagonal phase is isostructural to the chlorides Na3xM2-xCl6 with M = La−Sm. This structure (space group P63/m, Z = 1) contains only one M3+ site which is partially occupied by Na+, and the formula Na3xM2-xF6 (x ≈ 0.45) accounts for the nonstoichiometry. The model was derived from powder X-ray diffraction on the green and blue phosphor materials as well as the...
1,058 citations
TL;DR: In this article, an overview of the recent results on upconversion spectroscopy obtained in our group is presented, where it is demonstrated that as much as 50% of the NIR excitation photons contribute to the up-conversion emission.
587 citations
TL;DR: In this article, a spectroscopic investigation of NaYF4 powders doped with several different concentrations of Er 3 +, Tm 3 + and/or Yb 3 + is described.
543 citations
TL;DR: In this article, the optical UC efficiency of trivalent erbium doped sodium yttrium fluoride (NaYF4:20%Er3+ +) was investigated for silicon solar cells.
Abstract: Upconversion (UC) of subband-gap photons is a promising possibility to enhance solar cell efficiency by making also the subband-gap photons useful. For this application, we investigate the material system of trivalent erbium doped sodium yttrium fluoride (NaYF4:20%Er3+), which shows efficient UC suitable for silicon solar cells. We determine the optical UC efficiency by calibrated photoluminescence measurements. Because these data are free from any influence of losses associated with the application of the upconverter to the solar cell, the obtained values constitute the upper limit that can be achieved with an optimized device. Subsequently, we compare the results of the optical measurements with the results obtained by using solar cells as detectors on which the upconverter material is applied. We find an optical UC quantum efficiency of 5.1% at a monochromatic irradiance of 1880 W m−2 (0.27 cm2 W−1) at 1523 nm. The device of silicon solar cell and applied upconverter showed an external quantum efficien...
266 citations
TL;DR: In this paper, the authors reported efficient downconversion for the Er-Yb couple in Cs3Y2Br9, where the low phonon energy in this bromide host suppresses multiphonon relaxation and efficient two-step energy transfer from the F47/2 level of Er3+ was observed and results in strong 1000 nm emission from Yb3+.
Abstract: Downconversion of one visible photon to two near-infrared photons may increase the efficiency of c-Si solar cells by 30%. The lanthanide ion couple Er3+–Yb3+ is well known for efficient upconversion but for the reverse process, downconversion, fast multiphonon relaxation from the F47/2 level has been shown to compete with downconversion. Here we report efficient downconversion for the Er–Yb couple in Cs3Y2Br9. The low phonon energy in this bromide host suppresses multiphonon relaxation and efficient two step energy transfer from the F47/2 level of Er3+ is observed and results in strong 1000 nm emission from Yb3+. Based on emission spectra and luminescence life time measurements an intrinsic downconversion efficiency close to 200% is determined.
178 citations
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TL;DR: This critical review describes the latest developments in the sensitization of near-infrared luminescence, "soft" luminescent materials (liquid crystals, ionic liquids, ionogels), electroluminescentmaterials for organic light emitting diodes, with emphasis on white light generation, and applications in luminecent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation.
Abstract: Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).
2,895 citations
TL;DR: The results suggest that the doping-induced structural and size transition, demonstrated here in NaYF4 upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels to volumetric three-dimensional displays.
Abstract: Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase, modifying electronic properties, modulating magnetism as well as tuning emission properties. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF(4) nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF(4) upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels to volumetric three-dimensional displays.
2,835 citations
TL;DR: This tutorial review focuses on the recent development of various synthetic approaches and possibilities for chemical tuning of upconversion properties, as well as giving an overview of biological applications of these luminescent nanocrystals.
Abstract: Lanthanide ions exhibit unique luminescent properties, including the ability to convert near infrared long-wavelength excitation radiation into shorter visible wavelengths through a process known as photon upconversion. In recent years lanthanide-doped upconversion nanocrystals have been developed as a new class of luminescent optical labels that have become promising alternatives to organic fluorophores and quantum dots for applications in biological assays and medical imaging. These techniques offer low autofluorescence background, large anti-Stokes shifts, sharp emission bandwidths, high resistance to photobleaching, and high penetration depth and temporal resolution. Such techniques also show potential for improving the selectivity and sensitivity of conventional methods. They also pave the way for high throughput screening and miniaturization. This tutorial review focuses on the recent development of various synthetic approaches and possibilities for chemical tuning of upconversion properties, as well as giving an overview of biological applications of these luminescent nanocrystals.
2,594 citations
TL;DR: This paper presents a meta-modelling study of the response of the immune system to chemotherapy and its applications in the context of central nervous system disorders.
Abstract: Sasidharan Swarnalatha Lucky,†,§ Khee Chee Soo,‡ and Yong Zhang*,†,§,∥ †NUS Graduate School for Integrative Sciences & Engineering (NGS), National University of Singapore, Singapore, Singapore 117456 ‡Division of Medical Sciences, National Cancer Centre Singapore, Singapore, Singapore 169610 Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore 117576 College of Chemistry and Life Sciences, Zhejiang Normal University, Zhejiang, P. R. China 321004
2,194 citations
TL;DR: Applications in Theranostics Guanying Chen,*,†,‡ Hailong Qiu,*,‡ and Xiaoyuan Chen.
Abstract: Applications in Theranostics Guanying Chen,*,†,‡ Hailong Qiu,†,‡ Paras N. Prasad,*,‡,§ and Xiaoyuan Chen* †School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China ‡Department of Chemistry and the Institute for Lasers, Photonics, and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York 14260, United States Department of Chemistry, Korea University, Seoul 136-701, Korea Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892-2281, United States
1,994 citations