Antimicrobial Nanomaterials in the Textile Industry - Bionanotechnology: Global Prospects - page 351

TABLE 18.1
The.Effect.of.Calcium.Oxide.Nanoparticles.on.the.Bacteria. E. coli, . S.
epidermidis, .and. S. aureus

InhibitionZoneDiameter(cm)

CaONanoparticle E. coli S. epidermidis S. aureus

0.ppm 0 0 0

1,000.ppm 0 0 0

3,000.ppm 0.60 0.53 0.35

5,000.ppm 0.83 0.68 0.45

Source: . Channei,. D.,. et. al.,. Antimicrobial. Activity. of. Nano. Calcium. Oxide.

Synthesized.by.the.Thermal-Decomposition.Method,.paper.presented.
at. Proceedings. of. the. 26th. Microscopy. Society. of. Thailand. (MST).
Annual.Conference,.Chiang.Mai,.Thailand,.January.28-30,.2009.

of.the.clear.zone,.as.shown.in.Figure 18.4..The.CaO.concentrations.at.3,000.and.5,000.ppm.
were.found.to.effectively.inhibit.bacterial.growth.
In.our.studies, 34-42 .zinc.oxide.(ZnO),.titanium.dioxide.(TiO 2 ),.and.silver.(Ag).nanopar-
ticles. have. been. synthesized. by. wet. chemical. methods. such. as. precipitation,. thermal.
decomposition,. sol-gel,. and. evaporation. to. dryness. processes.. Nanoparticles. have. been.
characterized.by.x-ray.diffraction.(XRD),.speciic.surface.area.analysis,.scanning.electron.
microscopy.(SEM),.and.transmission.electron.microscopy.(TEM)..Antimicrobial.activities.
have.been.tested.on.the.ZnO.nanoparticles.in.Gram-positive.( S. aureus ).and.Gram-negative.
( E. coli ).bacteria..In.our.investigation.on.the.effect.of.nanoparticle.sizes.on.the.antimicro-
bial.eficacy,.we.found.that.smaller-sized.(~20.nm).ZnO.nanoparticles.had.antimicrobial.
activities.toward.both.Gram-positive.and.Gram-negative.bacteria,.while.larger-sized.ZnO.
nanoparticles.only.affect.the.Gram-negative.bacteria..The.antimicrobial.activities.toward.
bacteria. E. coli .ATCC.25922.and. S. aureus ATCC.25923.of.zinc.oxide.and.titanium.dioxide.
nanoparticles.are.shown.in.Table 18.2..Interestingly,.TiO 2 .nanoparticles.showed.no.antimi-
crobial.activity.in.the.absence.of.UV.light.
In. practice,. zinc. oxide. is. advantageous. when. compared. to. titanium. dioxide. in. terms.
of.cost.of.production..We.also.attempted.to.further.reduce.the.cost.in.our.experiment.by.
using.the.paper.disc.method.with.cotton.fabric.instead.of.ilter.paper..It.was.found.that.
zinc.oxide.nanoparticles.with.an.average.size.of.20.nm.inhibited.the.growth.of.four.kinds.
of. fungi,. Rhizopus oligosporus, Pennicillium oxalicum, Aspergillus awamori, and Aspergillus
fumigatus ,. and. three. kinds. of. bacteria,. Escherichia coli, Bacillus subtilis, . and Staphylococcus
aureus. The.antimicrobial.activity.of.zinc.oxide.nanoparticles.toward.both.fungi.and.bac-
teria.is.shown.in.Table 18.3..The.growth.inhibition.of.zinc.oxide.nanoparticles.toward. A.
awamori is.shown.in.Figure 18.5..Putting.the.experiment.into.actual.use,.ZnO.nanoparticles.
were. padded.on. white. and.green.fabric. used. for.a.medical. protective.garment.with. the.
appropriate.concentrations.of.0.3.w/v%.with.polyethyleneimine.as.mordant.and.0.2.w/v%.
for.white.and.green.fabric,.respectively.
Also. proposed. is. the. mechanism. of. the. interaction. between. cotton. and. zinc. oxide.
nanoparticles: 34 .the.hydroxylic.groups.on.cotton.lose.hydrogen.atoms,.leaving.the.nega-
tively. charged. O - ,. which. repels. the. electron. on. zinc. oxide. nanoparticles.. In. this. model,.
polyethyleneimine.(PEI),.used.as.a.binder.with.amino.groups,.would.react.with.O - .on.cot-
ton.to.form.strong.electrostatic.forces,.as.shown.in.Figure 18.6.