Recovery of furfural by extraction and distillation: Appendices

Document uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science

Sensitization of p-type NiO using n-type conducting polymers

We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B leading to the formation of electron-accepting states. Photoconductance measurements using the time-resolved microwave conductance (TRMC) technique demonstrate that these electron-accepting states are required for the hopping-like charge transport within the metal oxide. Polymer/NiO hybrid bilayers were prepared by spin-coating poly(fluorenebis(1-cyanovinylenethienylene)phenylene) (PF1CVTP) or poly(fluorene-bis(2-cyanovinylenethienylene)phenylene) (PF2CVTP) on top of NiO B. By determining the photoluminescence quenching, long exciton diffusion lengths were found amounting to 25 ± 2 nm and to 17 ± 2 nm, respectively. From I-V measurements on prototype n-type polymer/NiO hybrid solar cells carried out in the dark and under illumination, hole transfer from the polymer to the NiO is confirmed. The photovoltaic effect in cells based on PF2CVTP/NiO B bilayers was much larger than in PF1CVTP/NiO bilayers, which is related to the higher photoconductance observed in pristine PF2CVTP. It is proposed that only those photoexcitations leading to the formation of charge carriers within the bulk of the polymer film can be collected, while excitons reaching the NiO interface are lost by fast (surface) recombination. © 2010 American Chemical Society

Accurate calibration of a laboratory beta particle dose rate for dating purposes

This paper describes a novel method for calibration of the dose rate provided by a beta source used for luminescence dating. The calibration has been performed using an in-house calibration quartz that is given a dose in a Co-60 gamma ray facility. The gamma dose to the calibration quartz was calculated using Fricke dosimetry on simultaneously irradiated Fricke solution and Monte-Carlo simulations. An overall uncertainty in the dose to quartz of 0.6% (1 sigma) was achieved. The single aliquot regenerative dose (SAR) procedure was used to determine the irradiation time of the beta source needed to deliver the same dose to the sample. Results for a range of doses were combined by plotting irradiation time versus dose. A fit through the data points yielded the dose rate provided by the beta source at the sample position. This procedure resulted in an overall uncertainty in the beta dose rate of 0.9% (1 sigma). The beta dose rate was found to be in perfect agreement with an independent calibration using irradiated quartz provided by the Nordic Laboratory for Luminescence dating

Concentration and temperature dependent luminescence properties of the SrI2-TmI2 system

The concentration dependent luminescence of the SrI2-TmI2 system was investigated. For Tm2+ concentrations up to 5 mol %, the quantum efficiency (QE) of the 2F5/2→2F7/2 emission exhibits a constant value above 50%. The QE drops for higher Tm2+ concentrations, partly due to concentration quenching, as evidenced by a decreasing luminescence lifetime of the 2F5/2→2F7/2 emission, and partly due to the formation of a second crystal phase with CdCl2 structure, in which the 2F5/2→2F7/2 emission is quenched. The temperature and time dependent relaxation dynamics were studied to identify the origin of the limited QE for Tm2+-doping levels below 5 mol %. An anti-correlation between the 5d-4f (3H6,t2g)S=3/2→2F7/2 and 4f-4f 2F5/2→2F7/2 emission intensities was found and rationalised by non-radiative, thermally stimulated, inter-configurational 5d-4f relaxation to the emitting 2F5/2 level of Tm2+. Both, the rise time of the 4f-4f and the decay time of the 5d-4f emission become shorter with increasing temperature. We suggest a similar non-radiative relaxation from the 5d level towards the 2F7/2 ground state to limit the QE below unity. This route becomes more efficient when the 5d (3H6,t2g)S=3/2 state moves closer to the 4f 2F5/2 and 2F7/2 states, which is the case for the CdCl2 phase with a QE close to zero

Concentration and temperature dependent luminescence properties of the SrI₂-TmI₂ system

The concentration dependent luminescence of the SrI2-TmI2 system was investigated. For Tm2+ concentrations up to 5 mol %, the quantum efficiency (QE) of the 2F5/2→2F7/2 emission exhibits a constant value above 50%. The QE drops for higher Tm2+ concentrations, partly due to concentration quenching, as evidenced by a decreasing luminescence lifetime of the 2F5/2→2F7/2 emission, and partly due to the formation of a second crystal phase with CdCl2 structure, in which the 2F5/2→2F7/2 emission is quenched. The temperature and time dependent relaxation dynamics were studied to identify the origin of the limited QE for Tm2+-doping levels below 5 mol %. An anti-correlation between the 5d-4f (3H6,t2g)S=3/2→2F7/2 and 4f-4f 2F5/2→2F7/2 emission intensities was found and rationalised by non-radiative, thermally stimulated, inter-configurational 5d-4f relaxation to the emitting 2F5/2 level of Tm2+. Both, the rise time of the 4f-4f and the decay time of the 5d-4f emission become shorter with increasing temperature. We suggest a similar non-radiative relaxation from the 5d level towards the 2F7/2 ground state to limit the QE below unity. This route becomes more efficient when the 5d (3H6,t2g)S=3/2 state moves closer to the 4f 2F5/2 and 2F7/2 states, which is the case for the CdCl2 phase with a QE close to zero.</p

Solid-State Infrared Upconversion in Perylene Diimides Followed by Direct Electron Injection

In this contribution we demonstrate a solid-state approach to triplet-triplet annihilation upconversion for application in a solar cell device in which absorption of near-infrared light is followed by direct electron injection into an inorganic substrate. We use time-resolved microwave photoconductivity experiments to study the injection of electrons into the electron-accepting substrate (TiO2) in a trilayer device consisting of a triplet sensitizer (fluorinated zinc phthalocyanine), triplet acceptor (methyl subsituted perylenediimide), and smooth polycrystalline TiO2. Absorption of light at 700 nm leads to the almost quantitative generation of triplet excited states by intersystem crossing. This is followed by Dexter energy transfer to the triplet acceptor layer where triplet annihilation occurs and concludes by injection of an electron into TiO2 from the upconverted singlet excited state.ChemE/Opto-electronic MaterialsChemE/O&O groe