CHEM 397 Experiment Q (1)

7/25/2019 CHEM 397 Experiment Q (1)

1/20

CHEM 397

Experiment Q: Contact Angle and Zeta PotentialMeasurements with ur!ace Modi"ed #old

Alexander Cohen and Alex Zheng

tudent $: %&&9'3(%) %&&9*+(,

-.A. /aoting Zheng


2/20

0ntroduction:el!1assem2led monolaers 4AMs5 are ordered molecular assem2lies !ormed

2 the adsorption o! an acti6e sur!actant on a solid sur!ace%8. AMs are !ormedwhen a thin "lm o! an organic molecule is applied to the sur!ace o! a material) in thecase o! this experiment) the material is gold and the organic molecules are

alanethiols. ong1chain thiols) H4CH*5n; adsor2 !rom solution onto gold and !ormdensel paced) sel!1oriented monolaers*8. -he o6erall process is produced 2 aspontaneous chemical snthesis at the inter!ace) as the sstem approacheseerent sur!ace structures andproperties) while maintain the same 2ul properties o! the adsor2ing material.

-he determination o! ?eta potential) @) and particle si?e will allow us toanalse the e>ect alanethiol AMs ha6e on the electroinetic properties o! gold4Au5 colloids. -wo electroinetic phenomena will 2e studied to gi6e !urther insight onsur!ace properties o! Au colloids: electrophoresis and electro1osmosis.Electrophoresis occurs when there are charged particles suspended in solution.

-hese particles will 2e !orced to mo6e 2 appling an electric "eld across thesstem(8. = measuring the 6elocit o! the particles under a nown "eld) it ispossi2le to deduct their net electric charge or their sur!ace potential with respect tothe 2ul o! the suspending phase. Electro1osmosis is the motion o! li


3/20

Figure 1[3]. 6erall charge and potential distri2ution o! colloid particles insolution

Dor an charged inter!ace) the e2e length) F1%) is an important parameterthat descri2es electroinetic en6ironments. ooing at Digure %) it is possi2le to seethat there is a net negati6e charge on the sur!ace o! the particle. -here!ore the ionsin the solution !orm a net surplus o! positi6e charges to counter the negati6echarge) maing the o6erall charge ?ero. -he length o! the second laer is the e2elength. -his length can 2e used to "nd the e2e1Hucel parameter) which allowsone to approximate the ionic distri2ution in the dou2le laer78. -he e


4/20

I=1

2 zi

2[ i ]

Bhere i8 is the concentaration o! ion species Iand ?iis the charge num2er onspecies i.

E


5/20

0n part * o! the experiment[9]) the e>ect o! wetta2ilit o! di>erent modi"edgold sur!aces will 2e o2ser6ed. Betta2ilit is the maOor macroscopic propertstudied in this experiment. Betta2ilit is a phsical propert that descri2es theinteraction 2etween a uid and a solid sur!ace and is


6/20

Preparation o! CH1) and CH31deri6ati?ed gold nanoparticles

Kpon addition o! water and 2u>er to %1undecanetiol) turns completel clear

Procedure:

Te!er to the CHEMJEGCH 397J39,J399 a2 Manual !or in depth details !or theprocedure.

-a2le !or the changes made to the experimental procedure

Tesults:E


7/20

+HAu3H2$HAu "l43H2 $%4"l

"l

"l

Eer using Henderson1Hassel2ac e


8/20

I=1.27#ol /#3

E


9/20

&

(1)1

)=

)=1.17E+08

E


10/20

E (H)=1.78E-17

E


11/20

Compound pH -emp 4VC5Au1=ase ,.3+ *(.&T1CH3 ,.(& *(.&

T1CH ,.*7 *(.&Au1acid (.%7 *(.3

Table 3.-a2le o! 6alues !or the 6arious ionic concentrations o! species in solution!or the T1CH3solution.

0on Concentration 4molJm35 Charge

Cl1 *.3%E1&% W%GaW '.7,E1&% W%

C+H'731 %.93E1&% 13GH(W *.,*E1&' W%

Cl-(from buffer) 3.9,E1&+ 1%H+ 3.9,E1&+ W%

Table 4.-a2le o! 6alues !or calculating the gold colloid in T1CH3solution energterms.

ColloidTadius 4m5

ZetaPotential

4L5

0 4molJm35 X1% # term B term ; -erm / -er

%.'7E1&7 1*.99E1&* %.*7 ,.'3E1&9 *.,3E1&% '.,&E1%9 1.17E+08 1.83

Table 5.-a2le o! 6alues !or the gold colloid in T1CH3solution with 6aringseparation distances.

H (m) E-repulsive E-attractive E(H) E/KbT

1.00E-10 5.7E-1 -1.!E-17 -1.!E-17 -".#E+0#

$.00E-10 5.7E-1 -.$E-1! -!.%E-1! -$.1E+0#

".00E-10 5.5E-1 -".%E-1! -".0E-1! -.!E+0$

%.00E-10 5."E-1 -#.1E-1! -$.5E-1! -%.1E+0$

!.00E-10 5.#E-1 -$.#E-1! -1.!E-1! -".#E+0$

1.00E-0 5.$E-1 -1.!E-1! -1.#E-1! -#.$E+0$

$.00E-0 ".%E-1 -.$E-1 -".%E-1 -1.1E+0$

".00E-0 #.%E-1 -".%E-1 -.5E-$0 -$.#E+01

%.00E-0 $.E-1 -#.1E-1 -1.!E-$0 -"."E+00

!.00E-0 $.#E-1 -$.#E-1 -1.E-$1 -".5E-01


12/20

1.00E-0! 1.!E-1 -1.!E-1 -#.5E-$1 -!.5E-01

$.00E-0! 5.%E-$0 -.$E-$0 -#.%E-$0 -!.7E+00

".00E-0! 5.#E-$1 -".%E-$0 -".0E-$0 -.!E+00

%.00E-0! 5.1E-$$ -#.1E-$0 -#.0E-$0 -7.#E+00

!.00E-0! ".E-$# -$.#E-$0 -$.#E-$0 -5.%E+00

1.00E-07 ".7E-$" -1.!E-$0 -1.!E-$0 -".5E+00

&%.

Figure 1. 'lot for ol colloi i* -CH#solutio* emo*strates a correlatio* i* curve tre* ,it

acoaulatio* activatio* e*er barrier at -".5 KbT a* flocculatio* e*er at !7 KbT.

& %& *& 3& (& '& +& 7& ,&

1'.&&EW&%

1(.'&EW&%

1(.&&EW&%

13.'&EW&%

13.&&EW&%

1*.'&EW&%

1*.&&EW&%

1%.'&EW&%

1%.&&EW&%

1'.&&EW&&

&.&&EW&&

:L Plot !or eparation istance !rom #old Colloid in T1CH3 olution

eparation istance H 4nm5

Get Potential Energ EJF=-


13/20

& *& (& +& ,& %&& %*&

1'.&EW&%

13.&EW&%

1%.&EW&%

%.&EW&%

3.&EW&%

'.&EW&%

7.&EW&%

9.&EW&%

%.%EW&*

:LC Plot !or the 1(, mL Zeta Potential Tespecti6e to the eparation istance

eparation istance) H 4nm5

Potential Energ3) HJF=S-

Figure 2. iure belo, escribes te lo,eri* i* pote*tial e*er (i*crease i* termo*amic

stabilit) of colloi flocculatio* ,it respect to i*creasi* colloi sie from 1 *m to $0 *m.

& *& (& +& ,& %&&

1'.&EW&&

1(.&EW&&

13.&EW&&

1*.&EW&&

1%.&EW&&

&.&EW&&

%.&EW&&

L Plot !or Laring #old Colloid Tadii in T1CH3 olution

% nm ' nm %& nm %' nm *& nm


Potential Energ) HJF=S-

Figure 3. iure belo, escribes te rop i* coaulatio* e*er barrier ,it respect to te

i*creasi* solutio* io*ic stre*t from 1mol/m#to $0 mol/m#.


14/20

& %& *& 3& (& '& +&

1+.&&EW&%

1'.&&EW&%

1(.&&EW&%

13.&&EW&%

1*.&&EW&%

1%.&&EW&%

&.&&EW&&

%.&&EW&%

:L Plot !or the !or Laring 0onic Concentrations o! #old Colloid in T1CH3 olution

% molJm3 ' molJm3 %& molJm3 %' molJm3 *& molJm3

*' molJm3


Potential Energ) EJF=S-

& %& *& 3& (& '& +& 7&

1%.&&EW&%

1'.&&EW&&

&.&&EW&&

'.&&EW&&

%.&&EW&%

%.'&EW&%

:L Plot !or 1(, mL Zeta Potential !or Laring #old Colloid Tadii in T1CH3 olution

% nm ' nm %& nm %' nm *& nm

eparation istance) H4nm5

Potential Energ)HJF=S-


15/20

& %& *& 3& (& '& +&

1%.'EW&*

1%.&EW&*

1'.&EW&%

&.&EW&&

'.&EW&%

%.&EW&*

%.'EW&*

:L Plot !or 1 (,mL Zeta Potential !or Laring 0onic Concentrations !or #old Colloid in T1CH3 olution

% molJm3 ' molJm3 %& molJm3 %' molJm3 *& molJm3

*' molJm3

eparation distance) H 4nm5

Potential Energ) HJF=S-

&.&% &.&% &.&% &.&% &.&% &.&* &.&* &.&* &.&*&

&.*

&.(

&.+

&.,

%!4x5 Y %&+.(%x 1 %

T Y &.97

/oung[s E


16/20

4ietle*e

lcol

5.E+0

1

5.7#E+01 5.$1E-01 1.0%E+0$ "".! 1.1$E-0$ 150E+0$

Etle*e

lcol

7.#0E+0

1

7.15E+01 #.0"E-01 1.0%E+0$ "7.7 1.05E-0$

8lcerol 7.#E+0

1

.0$E+01 .1%E-0$ 1.0%E+0$ %".0 7.!1E-0#

Table 7. Table of values for te measure roplet a*les o* te aci termi*ate ol surface.

C99H 2eft *le (4erees) it *le (4erees) :ea* *le (4erees)

Eta*ol %.5E+01 %.57E+01 %.5!E+01

C99H ".1%E+01 5.1!E+01 ".%7E+01

CH# !.!0E+01 !."!E+01 !.%"E+01

HCl %."$E+01 %.$%E+01 %.#"E+01

a9H $.7"E+01 $.!7E+01 $.!1E+01

iscussion:&1.

9*e rece*t applicatio* of colloi cemistr a* self-assemble mo*olaers (6:s) ,as

performe i* $01" at ;uee*perime*t. Tis is ue to te i*crease stabilit of ol?

carbo* bo*s i* compariso* ,it ol-sulfur bo*s. Tere are ma* applicatio*s for te use of

6:s o* ol@ suc as electrocemistr@ ru eliver@ surface protectio*@ microelectro*ic@ a*

microelectromeca*ical sstems.

C.:. Crue*@ A.H. Horto*@ B.B. Ebralie@ 9.3. e*Di*a@ .. :c2ea*@ . 4rev*ioD@ . 6e@ H.-

. Kraat@ .A. :ose@ T. 6eDi@ E.C. KesDe@ A.4. 2eaDe@ . ousi*a-Febb@ 8. Fu@ Gltra 6table

6elf-ssemble :o*olaers of -Heterocclic Carbe*es o* 8olINature

Chemistry,2014@ 6@"0-"1".

&$.

a.

Te -CH#mo*olaer termi*al metl roup is as mostl covale*t bo*i* bet,ee* te

roe*s a* carbo* roup a* terefore e>ibits a *o*-polar (*ot *et ipole) properties.

Terefore ,e* te roplets are ae to te-CH#surface@ te polarit of te compou*s ,ill


17/20

affect te i*teractio* bet,ee* te surface a* te roplet. reater i*teractio* bet,ee* te

surface a* te roplet@ si*ifies a reater ,ettabilit of te surface a* terefore@ a ecreasi*

co*tact a*le bet,ee* te roplet a* te surface. Bt is e>pecte tat te co*tact a*le bet,ee*

te *o*-polar roplets ,oul be smaller as a result of reater ,ettabilit of soli surface from te

roplet. Terefore te U62-U63 value ,ill be reater for te *o*-polar roplets. Ho,ever as te

compou* roplets become more polar@ it is e>pecte tat te aesive i*teractio* bet,ee* teroplet a* surface ,ill ecrease@ a* terefore coesive forces taDe over a* te resulti* a*le

is larer@ a* te U62-U63 value ,ill be smaller.

or te -C99H termi*ate mo*olaer@ te opposite tre* is e>pecte as te carbo>lic

aci e* as a *et polarit@ terefore as te compou*s become more polar@ te aesive

i*teractio*s bet,ee* te roplet a* te surface are reater a* terefore reater ,ettabilit

occurs a* te resulti* roplet a*le ecreases@ a* te U62-U63 value ,ill be proressivellarer.

b.

Te effect o* pH ,it te -C99H termi*ate mo*olaer is ;uite simple@ as te lo,er te pH is

for roplet@ te reater te aesio* (a* terefore lo,er co*tact a*le) of te surface mo*olaer

to te roplet. Tis is ue to simple aci base i*teractio*s bet,ee* te surface a* te roplet.

Te lo, pH roplet i*teracts ,it te -C99H b eproto*atio*. Tis reactio* is escribe as

a* aci-base e;uilibrium.

+H2$ K,eproto-atio-Kproto-atio-." $2

." $2H+$H

Termo*amicall@ te stro* base as a reater stabilit as co*=uate aci (H$9) i* solutio*

because it *o lo*er co*tai*s a free care i* solutio*. urtermore te acetate a*io* is stabilie

b its reso*a*ce structure@ a* terefore te eproto*atio* is favoure a* te aesive

i*teractio* occurs bet,ee* te base roplet a* aci termi*ate laer.

Ho,ever as te pH is i*crease@ te species becomes more aciic a* tereb te e;uilibrium

sifts@ a* te eproto*atio* is *o lo*er favoure termo*amicall@ si*ce te prouct as a

ouble care tat is ver u*stable.

Terefore as te pH i*crease te aesive forces roplet to te surface are mi*imal a* te

coesive forces taDe over@ te resulti* roplet a*le is si*ifica*tl larer a* te U62-U63 value,ill be less.

c.

eferri* to table % a* fiure % i* te results sectio* for te CH#termi*ate alDe*e aree ,it

te preicte tre* mae earlier o* i* te iscussio* for te co*tact a*le@ o,ever te U62-U63values are proressivel i*crease as te roplet compou*s i*crease i* polarit.


18/20

.

Te releva*ce of setti* te cosJ1 represe*ts is te critical surface te*sio* (U23-critical) of tesurface mo*olaer. Tis simpl escribes te caracteristics of te soli o*l@ a* te coesive

forces bet,ee* te mo*olaers. Tis relatio*sip maDes se*se because te co*tact a*le J0@

a* is assume tat te surface bei* ieall flat e>ibits *o i*teractio*s ,it a li;ui roplettat ,oul form a* a*le reater ta* 0V,it te surface.

#.

iure 1 4239 plot for te -CH#base colloi solutio* emo*strates at sarp peaD *ear te >-

a>is tat is i*icative of te coaulatio* reio* of te colloi@ ,e* colloi precipitates out of

solutio*. Tis e*otes te ista*ce of colloi separatio* ,ere te attractive pote*tial is reater

ta* te repulsive pote*tial a* te colloi particles become estabilie. ollo,i* te

estabiliatio* of te colloi@ flocculatio* occurs ,ereb te estabilie colloi particles come

toeter to form flocs (precipitate) i* solutio*. Tis ca* be see* i* fiure 1@ as te ma>imum is

follo,e b a local mi*imum@ ,ic represe*ts te flocculatio* reio* as te particles come

toeter a* opposite cares *eate eac oter a* are more stabilie.

".

Te fiure # 4239 plot i* te CHE: #7 lab ma*ual (pae &-5) sourcefor a eta

pote*tial of -"! m3 co*sieri* te io*ic co*ce*tratio* of 1.% mol/m#i* compariso* to te io*ic

co*ce*tratio* of 1.$7 mol/m# (-$.m3) from te 4239 plot i* tis e>perime*t@ te colloi

solutio* is ver stable@ as tere is a i pote*tial e*er barrier to overcome i* orer to

coaulate. Tis suests tat te solutio* ,ill coaulate at a slo,er rate i* compariso* ,it te

results from fiure 1 i* tis e>perime*t@ ,ere te pote*tial e*er barrier is si*ifica*tl lo,er.

urtermore te ista*ce re;uire for flocculatio* from te coaulatio* reio* is larer for tis

solutio* (L"0-"5 *m) i* compariso* ,it te results obtai*e for te solutio* i* tis e>perime*t(L10 *m). Tis i*icates tat te ier eta pote*tial u*stable collois re;uire a larer

separatio* ista*ce i* orer to flocculate.

5. Te mi*imum separatio* ista*ce for a colloi solutio* represe*ts te ista*ce at ,ic te

i*teractio*s bet,ee* collois is so lare tat te forces of i*teractio* become *o lo*er

omi*a*t. B* te case for tis e>perime*t@ base off fiure 1@ te mi*imum separatio* ista*ce to

mai*tai* te stabilit of te CH#base colloial solutio* is appro>imatel 70 +/- 10 *m.

Ho,ever for te plotte fiure replaci* te e>perime*tal eta pote*tial ,it a pote*tial of -"!

m3@ te mi*imum separatio* ista*ce is tereb L100+/- 10 *m. Tis ma be ue to te reater

repulsio* effects from te resulti* larer eta pote*tial values tat effect pote*tial e*er

bet,ee* collois.

%.

iure $ 4239 plot for te vari* colloi raii i* solutio* at te e>perime*tal eta pote*tial

value@ te observe tre* is tat te flocculatio* mi*ima pote*tial e*er ecreases as te raius

of te colloi i*creases. Tis ma be attribute to te larer care istributio* amo* te

colloi tat mi*imies te coulombic repulsio* bet,ee* liDe cares a* terefore is more stable


19/20

i* e*er as a* areate. Ho,ever te tre* for te 4239 plot for fiure " (-"! m3) is vastl

iffere*t from tat of fiure $. ot o*l oes te flocculatio* reio* ecrease@ but te

coaulatio* activatio* e*er barrier i*creases si*ifica*tl@ a* at a muc lo,er separatio*

ista*ce@ ,ic mit si*if tat at larer eta pote*tial values te i*crease i* colloial raius

as a stro*er force of attractio*. Ho,ever te rate at ,ic te solutio* coaulates@ is slo,er

ue to steric i*ra*ce as a results of larer colloi sie@ tis maDes se*se i* te tre* for fiure"@ as te i*crease i* colloi raius i*creases te activatio* e*er a* terefore affects te rate.

7.

iure # 4239 plot for te vari* io*ic co*ce*tratio*s at te e>perime*tal eta pote*tial value@

te observe tre* is tat coaulatio* activatio* e*er barrier si*ifica*tl ecreases ,it

i*creasi* io*ic co*ce*tratio*@ a* terefore te rate of coaulatio* is Di*eticall faster. Te

i*crease i* co*ce*tratio* of io*s i* solutio*@ te electrical ouble laer i*creases i* e*sit a*

terefore 4ebe le*t is smaller as te care colloi particles are more siele. Te i*crease

i* io* co*ce*tratio* eve*tuall leas to te collapse of te colloi ouble laer@ as a result of te

3a* er Faals attractive forces overcomi* care repulsio*. Terefore te tre* is ecrease i*colloi stabilit as te io*ic stre*t i*creases. iure 5 4239 plot for -"! m3 vari* io*ic

co*ce*tratio*s emo*strates a ver similar tre*@ o,ever te rop i* coaulatio* e*er barrier

is more u*iform i* compariso* ,it te fiure # plot. Te ^-value represe*ts te viscosit of tesolutio*@ a* is ,at over*s colloi coaulatio* ue to ro,*ia* motio*. ro,*ia* motio* is

te bombarme*et of solute moleulces b te solve*t i* orer to preve*t te solve*t from

settli* out. 6olve*t bombareme*t is larel epe*e*t o* viscosit. s te viscosit i*creases

te solve*t bombareme*t ecreases a* coaulatio* occurs.

Co*clusio*M

ttpM//,,,.o,l*et.rice.eu/Lce*"0$/pro=0$/c,*ot/"0$pro=ect.tm

ttpM//,,,.brooDave*i*strume*ts.com/literature/librar/colloial-stabilit-i*-a;ueous-

suspe*sio*s

ttpM//pubs.acs.or/oi/pf/10.10$1/i#%00#%a005

ttpM//,,,.particles.or.uD/particleNtec*oloNbooD/capterN1#.pf

Sharfrin, E.; Zisman, William A. (1960). "Constitutive relations in the ettin! of lo ener! surfa#es an$ the

theor of the retra#tion metho$ of %re%arin! monolaers". &he 'ournal of hsi#al Chemistr 64()* 19+-.$oi*10.101/100-a00.

efere*cesM

%

Klman) A. Dormation And tructure o! el!1Assem2led Monolaers.ChemicalReviews Chem. Rev.%'33_%''(.
http://www.owlnet.rice.edu/~ceng402/proj02/cwynot/402project.htmhttp://www.brookhaveninstruments.com/literature/library/colloidal-stability-in-aqueous-suspensionshttp://www.brookhaveninstruments.com/literature/library/colloidal-stability-in-aqueous-suspensionshttp://pubs.acs.org/doi/pdf/10.1021/i360036a005http://www.particles.org.uk/particle_technology_book/chapter_13.pdfhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1021%2Fj100834a002http://www.brookhaveninstruments.com/literature/library/colloidal-stability-in-aqueous-suspensionshttp://www.brookhaveninstruments.com/literature/library/colloidal-stability-in-aqueous-suspensionshttp://pubs.acs.org/doi/pdf/10.1021/i360036a005http://www.particles.org.uk/particle_technology_book/chapter_13.pdfhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1021%2Fj100834a002http://www.owlnet.rice.edu/~ceng402/proj02/cwynot/402project.htm


20/20

* =ain) C. . ` Bhitesides) #. M. Modelling rganic ur!aces with el!1Assem2led Monolaers. Har6ard Kni6ersit o! Cam2ridge epartment o! Chemistr.Ma %9,9.

3 Farim) A. Electrical ou2le aer Zeta Potential.http:JJimage.slidesharecdn.comJemulsionsta2ilit1%3&,&3&'3''+1

phpapp&*J9'Jemulsion1sta2ilit1%&1+3,.Opgbc2Y%37''&,*'' 4accessed ct. %&)*&%'5. Copright *&%3 2 A2d Farim.

( Ali Hassanali and herwin . inger) A model !or the waterJamorphoussilica inter!ace: the undissociated sur!ace[[)J. Phys. Chem.B11143,5:%%%,% 4*&&75.

'

#rahame) . C. -he Electrical ou2le aer And the -heor o!Electrocapillarit. Chemical Reviews Chem. Rev.((%_'&%.

+8 Hunter) T. .Zeta Potential in Colloid Science: Principles and Applications)Gew paper2ac.` Academic Press) *&%3.

[7] Paul. ennett and . P. li6ier.C0A 0PET0G) EEC-TF0GE-0C

EDDEC-) AG

-HE CGCEP- D ZE-A P-EG-0A. Industrial & EnineerinChemistry195!"4,5) 3*1'&

,8 http:JJwww.mal6ern.comJenJproductsJproduct1rangeJ?etasi?er1rangeJ?etasi?er1nano1rangeJ?etasi?er1nano1?s9&J

CHEM 397 Experiment Q (1)

Documents