Biomedical Engineering Reference
In-Depth Information
22.5.2.3. Induced.Protein.Aggregation.......................................................... 449
22.5.2.4. Particle.Curvature............................................................................. 449
22.6. Engineering.Strategies.in.BSSCs.................................................................................... 450
22.6.1. Protein.Engineering:.Genetic.Modiication.................................................... 450
22.6.2. Lipid/Surfactant.Coabsorbants........................................................................ 451
22.6.3. Quantum.Dot.Enhancement............................................................................. 452
22.7. Conclusions....................................................................................................................... 452
Acknowledgments....................................................................................................................... 453
References..................................................................................................................................... 453
22.1 Introduction
In.this.chapter.we.will.explore.science.and.engineering.involved.in.utilizing.and.integrat-
ing.photoactive.proteins.with.man-made.solid-state.materials.for.electronic.applications,.
with. a. focus. on. developing. a. photovoltaic. device. based. on. integrating. photoactive. pro-
teins.onto.solid-state.electrodes.
Increasing.energy.demands.and.growing.environmental.concerns.are.driving.the.search.
for.new,.sustainable.sources.of.energy..Global.energy.consumption,.now.running.at.13.5.TW,.
is.estimated.to.reach.27.TW.by.2050..Nearly.85%.of.today's.energy.usage.originates.from.fos-
sil.fuels..Imminent.shortages.of.fossil.fuels
1
.and.CO
2
.induced.global.warming.are.driving.
the.demand.for.new.sustainable.energy.sources..While.no.single.source.is.likely.to.satisfy.
all.energy.needs,.solar.energy,.with.120,000.TW.of.solar.energy.striking.the.surface.of.the.
earth.at.all.times,.is.by.far.the.most.abundant.clean.energy.source.available..However,.only.
0.04%.of.energy.needs.are.presently.generated.by.photovoltaics..An.increase.to.20.TW.peak.
power.would.require.covering.0.16%.of.the.surface.of.the.earth.with.10%.eficient.solar.cells,
2
.
an.area.nearly.equivalent.to.the.entire.states.of.Arizona,.New.Mexico,.and.Utah.combined.
3
,.
Clearly,.large-scale.solar.cell.deployment.will.become.feasible.only.if.it.becomes.possible.to.
supply.electricity,.cheaply.and.eficiently,.while.keeping.in.mind.the.environmental.impact.
of.making.and.recycling.the.solar.cell.materials.
In. a. short. while,. man-made. solar. technology. has. made. signiicant. progress. in. harness-
ing.the.power.of.the.sun.with.efforts.in.solar-thermal,.photohydrogen,.and.photovoltaics..
However,.as.is.often.the.case,.there.are.analogs.in.nature.that.already.perform.these.feats.of.
physics.and.electrochemistry,.and.have.been.doing.so.eficiently.and.sustainably.for.hun-
dreds.of.millennia..Photosynthesis.is.one.such.example..Through.millions.of.years.of.evolu-
tion,.nature.has.crafted.elaborate.photosynthetic.machinery.for.harnessing.solar.energy.that.
is.responsible.for.essentially.all.life.functions.on.the.earth's.surface,.from.simple.single-celled.
organisms.to.all.plant.matter,.which.in.turn.fuel.the.world's.foods.chains..It.does.this.with.
a.number.of.photoactive.proteins.and.a.series.of.complex.biochemical.reactions,.harnessing.
solar.energy.and.storing.it.as.chemical.energy.in.the.form.of.biomass.
There. is. a. distinct. similarity. in. the. physics. behind. solid-state. solar. cells. and. particu-
lar. photoactive. proteins. responsible. for. light-activated. metabolic. processes.. The. parallel.
that. is. of. the. most. fundamental. and. practical. signiicance. is. that. both. man-made. solar.
cells.and.natural.photosynthesis.rely.on.photonic.energy.to.create.excited.electronic.states..
Likewise,. natural. and. man-made. systems. also. face. similar. challenges. and. limitations,.
such. as. limited. photon. adsorption,. maintaining. separation. of. charges,. and. transport. of.
charge.species.to.reaction.sites..Ultimately,.it.is.in.the.logistics.of.environmental.sustain-
ability.and.longevity.where.both.man-made.and.synthetic.solar.cells.differ,.suffering.from.
