Biomedical Engineering Reference
In-Depth Information
N
N
Mg
N
N
O
O
O
O
O
FIGURE 22.5
Chlorophyll.chromophore.structure..Variations.of.this.light-harvesting.dye.are.at.the.core.of.many.photoactive.
proteins..Note.the.similarity.of.conjugated.π-bonding.with.coordinated.metal,.similar.to.Ru-based.dye.
morphologies..Investigations.on.the.possibility.of.employing.naturally.occurring.organic.
molecular. materials. in. energy. conversion. devices. for. charge. generation. and. separation.
have. been. ongoing. for. some. time,. especially. with. a. focus. on. chlorophyll. derivatives. as.
the.sensitizer.in.TiO
2
-based.solar.cells.
5
.An.alternative.to.Ru-based.dyes,.which.are.highly.
effective. but. potentially. in. short. supply,. is. needed.. Importantly,. the. sensitizer. should.
exhibit.thermal.robustness.and.maintain.its.functional.activity.long.term.while.absorbing.
solar.radiation.capable.of.producing.charge.generation/separation.eficiently.
In.considering.alternative.dyes,.replacement.of.the.Ru.dye.in.a.DSSC.by.environmentally.
friendly.and.lower-cost.light-harvesting.proteins.is.most.attractive..A.rational.approach.is.
to.use.a.light-activated.protein.as.the.source.of.photogenerated.carriers..They.are.biologi-
cally.synthesized.and.require.neither.high.temperature.nor.any.rare.elements.to.produce..
Biodegradability.and.renewability.are.implicit.in.their.design,.and.because.the.pigmenta-
tion.is.responsible.for.plant.coloration,.this.its.the.very.deinition.of.“green.technology.”
Aside.from.concerns.of.sustainability.and.cost,.millions.of.years.of.selective.evolution.
have.yielded.nanoscale.protein.structures.with.intricate.functionalities.that.are.still.irre-
producible.by.man-made.technology..If.fact,.much.evidence.suggests.that.photosynthetic.
proteins.can.only.operate.at.the.nanoscale.by.taking.advantage.of.quantum.mechanical.
properties.such.as.quantum.coherence.and.entanglement
6
.to.maximize.photon.adsorption.
and.energy.transfer..As.ubiquitous.as.plants.and.photosynthesis.are,.human.understand-
ing.of.the.quantum.world.has.only.begun.to.develop.in.the.past.several.decades..While.
practical.application.of.quantum.mechanics.promises.to.bring.about.a.new.era.of.comput-
ing. and. information. technology,. plants. and. bacteria. have. been. relying. on. these. exotic.
properties.for.millions.of.years..With.this.in.mind,.it.is.not.unreasonable.to.use.biological.
systems.as.nanoscale.components.that.perform.functions.that.we.are.currently.unable.to.
simulate.
