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may give some important information on the photochemical characteristics of several other
β-diketones inwater.
The energy transfer in organic systems can also beused tomonitor distinct environments by
enabling severalmechanismsof tracking the changes in the electronic excited states involved
in thephotophysical orphotochemicalprocesses. Sensingand imagingare, therefore,ways to
collect informationondistinct environments.
In our researchgroup [25],wehave focusedon theproposal of newmaterials that are able to
efficientlyformenergytransfercomplexesandgiverisetonewphotophysicalcharacteristicsthat
are very sensitive to specific environmental changes. An example is a newmaterial based on
supramolecular structuresof adipeptide,diphenylalanine, composinganexciplexwitha chro-
mophore, coumarin. In distinct proportions, this systemwas able tomodulate the coumarin
sensibilitytoO2(g)dissolvedinwater,presentingdistinct fluorescencespectrafromthatexpected
forcoumarin,whichwasaresultoftheenergytransfercomplexformationandthenewelectronic
excitedstatesthatresultedfromtheinteractionsbetweenthecomponents.Wangetal. [8],onthe
other hand, developed amethod for monitoring photochemical reaction kinetics, presenting
spatialresolution, thelaser-excitedmuonpump-probespinspectroscopy(photo-μSR).Withthis,
they expected to monitor the dynamic of excitations and to explore the mechanism of
photophysical andphotochemical processes. Using pentacene as subject, they temporally and
spatiallymappedtheseprocessesat thesingle-carbonlevelandobservedthat thephotochemical
reactivityofaspecificcarbonatomismodifiedinthepresenceofaspecificexcitedstate.
Energy conversion can also be based on hole transfers or proton transfers and can involve
photophysical processes, photochemical reactions or both processes in a collaborative way.
Elbin andBazan [7] proposed a newelectron-deficient compoundbased on three-coordinate
boryl substituents adjacent to highly conjugated distyrylbenzene derivative (DSB) or poly
(aryleneethynylene)s (PAE). In thesematerials, boron atomprovides a vacant pz-orbital that
confers thema strong electron acceptor character, enabling a significant delocalization. They
showed that due to the distinct photophysical characteristics of the constituents, the excited
state migration by FRET is modulated and, depending on the substituent, light of distinct
colors are emitted from these systems. Based on that, they believed that thesematerials can
findapplication indisplays.
Also based on hole transfer to promote energy conversion is the electrochemical energy
conversion in a system called fuel cell. It consists of an additional way for chemical energy
conversion, without photocatalytic effect. It is an electrochemical system which converts
chemical energy into electricity through the oxidation of a fuel [26, 27],which takes place in
theanodeof thecell, andthereductionof theoxygenfromatmosphere inthecathode.Someof
these fuel cells are classifiedby temperatureoperation [28], especially,ProtonExchangeMem-
brane Fuel Cells (PEMFCs) work at low temperatures (from room to 100 C) [29] with a
Nafion®membrane electrolyte. Low temperatures requires a very active catalyst in the elec-
trodes, usually beingplatinum (Pt) [30].Adirect ethanol fuel cell (DEFC) is a veryattractive
electrochemical energy converter [31], and its unitary fuel cell scheme is shown in Figure 8.
Thefuel is supplied intotheanodesideandtheair (orpureO2(g)) is supplied intothecathode.
The electrolyte carries protons from the anode to the cathode and the electrons are availed at
anexternal electrical circuit toproducework.
Advanced Chemical
Kinetics70
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Buch Advanced Chemical Kinetics"
Advanced Chemical Kinetics
- Titel
- Advanced Chemical Kinetics
- Autor
- Muhammad Akhyar Farrukh
- Herausgeber
- InTech
- Ort
- Rijeka
- Datum
- 2018
- Sprache
- englisch
- Lizenz
- CC BY 4.0
- ISBN
- 978-953-51-3816-7
- Abmessungen
- 18.0 x 26.0 cm
- Seiten
- 226
- Schlagwörter
- Engineering and Technology, Chemistry, Physical Chemistry, Chemical Kinetics
- Kategorien
- Naturwissenschaften Chemie