24 research outputs found
Ruthenium polypyridyl complexes as photosensitizers for molecular photovoltaic devices: influence of the dye structure and the presence of additives to the device performance
Les cel·les solars sensitivitzades amb un colorant són un tipus de dispositius que han cridat molt l'atenció com a una alternativa menys costosa econòmicament a les actuals cel·les solars comercials de silici. Aquesta tesi s'ha focalitzat en la determinació de la influència de l'estructura molecular dels colorants i la presència d'un coadsorbent en l'eficiència de les cel·les solars sensitivitzades amb un colorant. Les etapes principals d'aquesta tesi han sigut: el disseny, la síntesi i la caracterització d'una sèrie de complexes de ruteni que contenen lligands polipiridílics amb diferents substituents; l'estudi de les propietats fotofísiques i electroquímiques dels complexes de ruteni; la introducció dels colorants a la preparació de dispositius fotovoltaics; i la caracterització dels diferents paràmetres que permeten avaluar l'eficiència d'una cel·la solar, així com la determinació de les cinètiques de les reaccions que tenen lloc en aquests tipus de dispositius fotovoltaics
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Dye-sensitised semiconductors modified with molecular catalysts for light-driven H2 production.
The development of synthetic systems for the conversion of solar energy into chemical fuels is a research goal that continues to attract growing interest owing to its potential to provide renewable and storable energy in the form of a 'solar fuel'. Dye-sensitised photocatalysis (DSP) with molecular catalysts is a relatively new approach to convert sunlight into a fuel such as H2 and is based on the self-assembly of a molecular dye and electrocatalyst on a semiconductor nanoparticle. DSP systems combine advantages of both homogenous and heterogeneous photocatalysis, with the molecular components providing an excellent platform for tuning activity and understanding performance at defined catalytic sites, whereas the semiconductor bridge ensures favourable multi-electron transfer kinetics between the dye and the fuel-forming electrocatalyst. In this tutorial review, strategies and challenges for the assembly of functional molecular DSP systems and experimental techniques for their evaluation are explained. Current understanding of the factors governing electron transfer across inorganic-molecular interfaces is described and future directions and challenges for this field are outlined.This work was supported by the EPSRC (EP/H00338X/2 to E.R.; DTG scholarship to E.P.), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development; E.R. and J.W.), the OMV Group (E.R. and J.W.), the Advanced Institute for Materials ResearchCambridge Joint Research Centre (K.O.), European Commission Marie Curie CIG (303650 to A.R.) and the ERC (291482 to J.D.).This is the final version of the article. It was first available from RSC via http://dx.doi.org/10.1039/C5CS00733
Dye-sensitised semiconductors modified with molecular catalysts for light-driven H<sub>2</sub> production
This is the final version of the article. It was first available from RSC via http://dx.doi.org/10.1039/C5CS00733JThe development of synthetic systems for the conversion of solar energy into chemical fuels is a research goal that continues to attract growing interest owing to its potential to provide renewable and storable energy in the form of a ?solar fuel?. Dye-sensitised photocatalysis (DSP) with molecular catalysts is a relatively new approach to convert sunlight into a fuel such as H? and is based on the self-assembly of a molecular dye and electrocatalyst on a semiconductor nanoparticle. DSP systems combine advantages of both homogenous and heterogeneous photocatalysis, with the molecular components providing an excellent platform for tuning activity and understanding performance at defined catalytic sites, whereas the semiconductor bridge ensures favourable multi-electron transfer kinetics between the dye and the fuel-forming electrocatalyst. In this tutorial review, strategies and challenges for the assembly of functional molecular DSP systems and experimental techniques for their evaluation are explained. Current understanding of the factors governing electron transfer across inorganic-molecular interfaces is described and future directions and challenges for this field are outlined.This work was supported by the EPSRC (EP/H00338X/2 to E.R.; DTG scholarship to E.P.), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development; E.R. and J.W.), the OMV Group (E.R. and J.W.), the Advanced Institute for Materials ResearchCambridge Joint Research Centre (K.O.), European Commission Marie Curie CIG (303650 to A.R.) and the ERC (291482 to J.D.)
Development of Vaccines Against Burkholderia Pseudomallei
Burkholderia pseudomallei is a Gram-negative bacterium which is the causative agent of melioidosis, a disease which carries a high mortality and morbidity rate in endemic areas of South East Asia and Northern Australia. At present there is no available human vaccine that protects against B. pseudomallei, and with the current limitations of antibiotic treatment, the development of new preventative and therapeutic interventions is crucial. This review considers the multiple elements of melioidosis vaccine research including: (i) the immune responses required for protective immunity, (ii) animal models available for preclinical testing of potential candidates, (iii) the different experimental vaccine strategies which are being pursued, and (iv) the obstacles and opportunities for eventual registration of a licensed vaccine in humans
Kinetic Analysis of an Efficient Molecular Light-Driven Water Oxidation System
We
report an efficient molecular light-driven system to oxidize
water to oxygen and a kinetic analysis of the factors determining
the efficiency of the system. The system comprises a highly active
molecular catalyst ([Ru<sup>IV</sup>(tda)(py)<sub>2</sub>(O)]), [Ru<sup>II</sup>(bpy)(bpy-COOEt)<sub>2</sub>]<sup>2+</sup> (<b>RuP</b>), as sensitizer and Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub> as
sacrificial electron acceptor. This combination exhibits a high quantum
yield (25%) and chemical yield (93%) for photodriven oxygen evolution
from water. The processes underlying this performance are identified
using optical techniques, including transient absorption spectroscopy
and photoluminescence quenching. A high catalyst concentration is
found to be required to optimize the efficiency of electron transfer
between the oxidized sensitizer and the catalyst, which also has the
effect of improving sensitizer stability. The main limitation of the
quantum yield is the relatively low efficiency of S<sub>2</sub>O<sub>8</sub><sup>2–</sup> as an electron scavenger to oxidize the
photoexcited ruthenium sensitizer <b>RuP*</b> to 2 <b>RuP</b><sup><b>+</b></sup>, mainly due to competing back electron
transfers to the <b>RuP</b> ground state. The overall rate of
light-driven oxygen generation is determined primarily by the rate
of photon absorption by the molecular sensitizer under the incident
photon flux. As such, the performance of this efficient light-driven
system is limited not by the properties of the molecular water oxidation
catalyst, which exhibits both good kinetics and stability, but rather
by the light absorption and quantum efficiency properties of the sensitizer
and electron scavenger. We conclude by discussing the implications
of these results for further optimization of molecular light-driven
systems for water oxidation
Distance dependent charge separation and recombination in semiconductor/molecular catalyst systems for water splitting
The photoinduced reduction of three Co electrocatalysts immobilised on TiO(2) is 10(4) times faster than the reverse charge recombination. Both processes show an exponential dependence on the distance between the semiconductor and the catalytic core
Improving the photocatalytic reduction of CO2 to CO through immobilisation of a molecular Re catalyst on TiO2.
The photocatalytic activity of phosphonated Re complexes, [Re(2,2'-bipyridine-4,4'-bisphosphonic acid) (CO)3(L)] (ReP; L = 3-picoline or bromide) immobilised on TiO2 nanoparticles is reported. The heterogenised Re catalyst on the semiconductor, ReP-TiO2 hybrid, displays an improvement in CO2 reduction photocatalysis. A high turnover number (TON) of 48 molCO molRe(-1) is observed in DMF with the electron donor triethanolamine at λ>420 nm. ReP-TiO2 compares favourably to previously reported homogeneous systems and is the highest TON reported to date for a CO2-reducing Re photocatalyst under visible light irradiation. Photocatalytic CO2 reduction is even observed with ReP-TiO2 at wavelengths of λ>495 nm. Infrared and X-ray photoelectron spectroscopies confirm that an intact ReP catalyst is present on the TiO2 surface before and during catalysis. Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50% >1 s for ReP-TiO2 compared with t50% = 60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers. This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics.Financial support from the EPSRC (EP/H00338X/2 to E.R.; studentship and Doctoral
Prize to C.D.W.; DTP scholarship to E.P.), the Christian Doppler Research
Association (Austrian Federal Ministry of Science, Research and Economy and the
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National Foundation for Research, Technology and Development) and the OMV
Group (to E.R.), the ERC (project Intersolar to J.D.) and the European Commission
Marie Curie CIG (PCIG10-GA-2011-303650 to A.R.) is gratefully acknowledged.This is the final published version. It first appeared in Chemistry - a European Journal, 2015, 21, 3746 – 3754, DOI: 10.1002/chem.20140504
Diastereoselectivity and molecular recognition of mercury(II) ions
Two diastereoisomers of a new heteroleptic ruthenium cis-dithiocyanate dicarboxy-bipyridyl phenanthrolyl complex have been synthesized and characterized. This type of complexes can selectively bind mercury ions through the sulphur atoms on the thiocyanate groups. The properties of these complexes as chemosensor towards Hg2+ in solution and anchored onto a mesoporous Al2O3 film have been studied and analysed. A different level of sensitivity versus mercury ions in aqueous solutions was observed for each stereoisomer.</p