Author
A.C. Yanes
Bio: A.C. Yanes is an academic researcher from University of La Laguna. The author has contributed to research in topics: Luminescence & Sol-gel. The author has an hindex of 22, co-authored 56 publications receiving 1321 citations.
Topics: Luminescence, Sol-gel, Doping, Photon upconversion, Nanocrystal
Papers published on a yearly basis
Papers
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TL;DR: In this article, the authors show new down-conversion mechanisms in Er3+−Yb3+ co-doped glass-ceramics, where the ions are hosted by fluoride nanoparticles embedded in silica glass.
118 citations
TL;DR: In this article, a fraction of the Eu3+ ions were incorporated to the SnO2 nanocrystals in the process of thermal treatment of sol-gel glasses, and it was possible to excite selectively Eu 3+ ions located in SnO 2 nanocrysts, by energy transfer from the host, obtaining emission spectra that depend on the nanocrystal size.
Abstract: Glass ceramics of composition 95SiO2-5SnO2 doped with 0.4mol% Eu3+ have been prepared by thermal treatment of sol-gel glasses. The segregated SnO2 nanocrystals present a mean size comparable to the bulk exciton Bohr radius (about 2.4nm), corresponding to a wide band-gap quantum-dot system in an insulator SiO2 glass. A fraction of the Eu3+ ions is incorporated to the SnO2 nanocrystals in the process. In these strong confinement conditions, the energy gap presents a high dependence on the nanocrystal size. Taking advantage of this effect, it has been possible to excite selectively the Eu3+ ions located in the SnO2 nanocrystals, by energy transfer from the host, obtaining emission spectra that depend on the nanocrystal size. The Eu3+ ions environment in small nanocrystals (radius under 2nm) are very distorted, meanwhile they are like crystalline for nanocrystals with a radius of some nanometers.
101 citations
TL;DR: In this article, the temporal evolution of the blue-green upconversion emissions coming from Tb3+ ions and their dependence on the excitation intensity at about 1 μm has been studied.
Abstract: Optical properties of Yb3+–Tb3+ codoped silica sol-gel samples have been studied after the gel to glass transition. Different upconversion emissions have been observed under near infrared excitation at about 1 μm. The Tb3+ ions are excited by means of energy transfer processes from Yb3+ ions. The temporal evolution of the blue-green upconversion emissions coming from Tb3+ ions and their dependence on the excitation intensity at about 1 μm has been studied. The experimental results are in good agreement with a cooperative resonant energy transfer mechanism from Yb3+ ions. An efficient backtransfer process is observed from Tb3+ ions towards Yb3+ ions. The upconversion efficiency, which is limited by this backtransfer process, has been obtained and compared with other upconversion results in similar matrix.
82 citations
TL;DR: The mean radius of the obtained SnO2 nanocrystals, ranging from 2 to 5 nm, is comparable to the exciton Bohr radius, corresponding to wide bandgap semiconductor quantum dots in an insulator SiO2 glass as discussed by the authors.
Abstract: Nanostructured silica based ceramic samples of composition (100− x)SiO2–xSnO2, doped with 0.4 mol% of Eu3+ and with x from 1 to 10, have been developed after a thermal treatment of precursor sol–gel glasses. A structural analysis has been performed by x-ray diffraction and high resolution transmission electron microscopy. The mean radius of the obtained SnO2 nanocrystals, ranging from 2 to 5 nm, is comparable to the exciton Bohr radius, corresponding to wide bandgap semiconductor quantum dots in an insulator SiO2 glass. A spectroscopy study in terms of emission and excitation spectra has been carried out as a function of SnO2 concentration. Moreover, time-resolved fluorescence measurements have also been performed in order to discern the emission of ions in glassy and nanocrystalline environments. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations.
69 citations
TL;DR: In this article, the fraction of Eu 3+ ions partitioned into LaF 3 nanocrystals, substituting La 3+ ion, is comparable to the one staying in the SiO 2 glassy phase.
65 citations
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2,877 citations
TL;DR: The trivalent europium ion (Eu3+) is well known for its strong luminescence in the red spectral region, but this ion is also interesting from a theoretical point of view as mentioned in this paper.
1,906 citations
TL;DR: This review will survey recent progress in the development of spectral converters, with a particular emphasis on lanthanide-based upconversion, quantum-cutting and down-shifting materials, for PV applications, and present technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.
Abstract: Photovoltaic (PV) technologies for solar energy conversion represent promising routes to green and renewable energy generation. Despite relevant PV technologies being available for more than half a century, the production of solar energy remains costly, largely owing to low power conversion efficiencies of solar cells. The main difficulty in improving the efficiency of PV energy conversion lies in the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the bandgap of a semiconductor material. In recent years, luminescent materials, which are capable of converting a broad spectrum of light into photons of a particular wavelength, have been synthesized and used to minimize the losses in the solar-cell-based energy conversion process. In this review, we will survey recent progress in the development of spectral converters, with a particular emphasis on lanthanide-based upconversion, quantum-cutting and down-shifting materials, for PV applications. In addition, we will also present technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.
1,391 citations
TL;DR: In this article, the authors focus on the research efforts that have been made so far for H2 generation from water splitting by UV and visible light-driven photocatalysis and discuss a number of synthetic modification methods for adapting the electronic structure to enhance the charge separation in the photocatalyst materials.
567 citations
TL;DR: In this paper, the authors reviewed the recent progress made in the fields of UV-visible quantum cutting (QC) and the mechanism involved, including QC in single RE ion activated fluorides- and oxides-based phosphors, energy transfer and downconversion, QC in dual/ternary ions activated phosphors; and NIR QC in RE3+-Yb3+ (RE=Tb, Tm, and Pr) dual ions doped phosphors via cooperative energy transfer.
517 citations