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化学修饰电极的研究及应用


西南大学 硕士学位论文 化学修饰电极的研究及应用 姓名:蒋依娜 申请学位级别:硕士 专业:物理化学 指导教师:李念兵 20070401

摘要

化学修饰电极的研究及应用
物理化学专业硕士研究生 指导教师

蒋依娜

李念兵教授

摘要
化学修饰电极白70年代

发展至今,已经成为当前电化学。电分析化学中十分活跃的研究 领域。化学修饰电极最突出的特性是,在电极表面接着或涂敷了具有选择性化学基团的一层 薄膜(从单分子到几个微米)。它是按人们意图设计的,并赋予了电极某种预定的性质.如化
学的,电化学的,光学的,电学的和传输性等。由于其具有易自动化、便于携带、灵敏度和

准确度高。选择性好等优点,在电分析化学中具有广泛的用途。本文中。我们研究了几种化
学修饰电极的制各和在电分折化学中的应用。 主要研究工作如下: 1.2,5.二巯基一1。3,4-噻二唑(DMTD)自组装电极的研究及用于金属离子的测定

分子自组装修饰电极可按预先设计在电极表面形成具有特殊功能的单分子层结构.它在
分子尺寸,组织模型和膜的自然形成方面与天然生物膜有类似之处。同时。它具有分子识别功

能和选着选择性响应。在本论文中采用自组装膜组装技术将DMTD分子组装在Au电极上形 成单分子自组装膜,利用循环伏安和交流阻抗技术探讨了单分子自组装膜的电化学性质,该 自组装膜在Au电极上具有很好的稳定性,考察了铜离子在此自组装膜电极上的电化学行为. 讨论了溶液pH和沉积电位,沉积时间等实验条件,建立起用DMTD自组装单分子膜测定铜 离子的电化学方法,并用于自来水中铜离子的测定。 2.聚吖啶红修饰玻碳电极的研究及应用
聚合物膜修饰电极制备简便,性能稳定,利用恒电位或循环伏安法还可在电极表面导入

高浓度的功能团。因此在化学和生物化学中的应用越来越受到重视。本论文中.采用电化学 聚合方法将吖啶红修饰于玻碳电极表面制备了聚吖啶红薄膜修饰电极,研究了该修饰电极的 电化学性质。尿酸在聚吖啶红修饰电极上有很好的电化学响应,建立起测定尿酸的电化学新
方法。利用循环伏安和差分脉冲技术探讨了利用此修饰电极测定UA最佳实验条件,并用予实 际样品中UA的测定并取得满意结果。

3.2,3-二巯基乙二酸(DMSA)自组装电极的研究及在离子通道传感器中的应用

酣南大学硕十学位论文 ?离子通道是细胞膜上的一类特殊亲水性蚩白质微孔道,是神经,肌肉细胞电活动的物质 基础.随着生物化学的发展,人们将这一概念心丁化学修饰电极。如果将包含离子通道的膜 修饰在电极表面,当通道打开时,人量的标记离子可以透过膜到达电极表面发生电化学反 应。借助较强的金硫键,嘲sA可以臼组装到金电极的表面,该自组装膜时掰1离子表面活性刺 (CRAB)具有离子通道行为。利用循环伏安,差分脉冲和交流阻抗技术考察了K3[Fe(CN)。】 希I[Ru(NH3)s]Cl,标记离子在此膜电极上的电化学响应。由于膜电极表面带负电荷,在pH值为 7.4的条件下,通道是关闭的,当加入阳离子表面活性剂后,通道打开,标记离子可到达电极 表面发生电化学反应。

4.金纳米修饰玻碳电极的研究及应用
将纳米修饰电极用于电化学和电分析化学的研究近年来已经取得了很大的进展,各种金 属、金属氧化物和非金属氧化物纳米粒子或团簇破组装在各种经典电极材料上如金、铂、银、

碳等,显示出卓越的表面吸附和分子识别特性,电催化活性、高度的表面反应活性等。在本
论文里。利用电沉积的方法制备了金纳米修饰电极,并探讨了此电极的电化学性质。距硝酸 根和复合胺都在此电极表面显示了良好的电化学响应,我们分别讨论了它们各自的擐佳实验

条件和反应机理.建立起测定亚硝酸根和复合胺的电化学新方法。用于弧硝酸掇糸j复合胺实
际样品的检测,结果满意。 5.金纳米和复合胺相互作用的研究 纳米微粒由于具有一系列新奇的物理、化学特性引起了人们的浓厚兴趣,并在物理学、

化学、生物学、光学、电子学、电磁学,药物及临床医学等领域得到广泛的研究和应用。其
中纳米微粒独特的光学现象。如等离子体共振吸收、表面等离子体共振技术、表面增强拉曼 散射和共振光散射等受到了人们的关注。这些研究不仅对于认识纳米微粒的新光学性质,而且

对于研究纳米微粒的新表征方法及探索纳米微粒的分析应用均有重要意义。在纳米微粒的分
析应用研究方面,金纳米微粒占有十分重要的地位,本论文利用共振光散射,荧光,紫外一可 见光谱和透射电子显微镜技术在pH值等于7.0的BR缓冲溶液中讨论了金纳米和复合胺的相 互作用。建立了利用共振光散射技术测定复合胺的新方法,考察了实验的最优条件,用于合

成样品的测定.得到满意结果.

关键词:化学修饰电极,自组装膜,离子通道传感器,共振散射光谱,金纳米, 铜,尿酸,阳离子表面活性剂,亚硝酸根,复合胺

II

Abstract

Chemically

Modified

Electrode and its

Application
Master ofPhysical Chemistry:Yina Jiang
Supervisor:Professor Nianbing Li Abstract
Chemically modified electrodes(CMEs)have had



dominant position in many electrochemical


studies since the 197ffs.The distinguishing feature of a CME is that

generally thin film of



selected chemical is bonded or coated onto the electrode surface to endow the

electrode

with the


chemical。electrochemical,optical,electrical。transport,and other desirable properties ofthe film in

rational,chemically designed manner.For analytical applications,CMEs should possess certain
properties;good mechanical and chemical stability of elecla'ode

surface,good short—term

reproducibility and long-term stability of the
range ofresponds.10w and stable background

modifiers activity
currents
oVcr

towards the

analyte.谢de dynamic’

the potential range reguired,simple and

reliable fabrication that results in consistency of the

response

from

one

electrode

to

another.In this

work,one of the principal researches is about the preparation of the CEM and its application in
electroanalysis. The primary research work is
as

follows:

1.Research of 2,S-dimercapto-l,3,4-thiadiazol(DMTD)self-nssembled monolayer modified
electrode and its application in the determination ofmetal ion The fabrication

and

electrochemical characteristics of the were investigated.The

DMTD self-assembled monolayer
exhibited selective

(SAND-modified
voltammetric

gold

electrode
to

DMTD SAM electrode

response

CuOD.The

effects of various parameters.such as the pH values of the solution,the

preconcentration

solution

and measurement

accumulation

potential,and

the

accumulation time,were investigated.The
to

proposed

voltammetric method was utilized successfully

detect the concentration ofCu(ID ions in tap water
Research

samples.

2.

ofpoly(acri椰ne red)modified

electrode and its application been deposited on the surface of


A stable electroactive thin film of

poly(acridine red)has


glassy carbon electrode by potantiostatic technique in red.The poly(acridine red)/glassy carbon

pH 7.0 phosphate buffer containing acridine

electrode

is easy to be

prepared

with good stability

and

reproducibility.The voltammetric
WaS studied by cyclic

behavior ofuric

acid(UA)at

the modified glassy carbon electrode

voltammetry and different pulse

voltammetry.The

modified electrode

¨l

坚!!!!!!!:墅!!!!!!生坚墨!!!:兰!生

exhibited



I'd【gh stability in phosphate buffer.The proposed voltammetric method was utilized

successfully to detect the concentration ofUA in urine samples. 3?Research of

meso-2,3-dimercaptoanccinic

acid

self-assembled

monolayer modified

electrode and its application in ion-channel sensors Self-assembled

monolayers(SAMs)of meso?2,3-dimercaptosuccjnic acid(DMSA)on SAMs
on

gold gold

electrodes were used for ion-chromel mimetic sensing of cationic surfactants.The electrodes

were

characterized

with

reductive-desorption

and

electrochemical

impedance

measurements.The pH dependence of the cyclic voltanm309rams(CVs)of K3[Fe(CN)61 and

【Ru(NH3)0]C13
groups of the

as

electroactive markers suggested

an

electrostatic repulsion between charged head

SAMs

and the equally charged marker ions with the half current values in the plot
as

reflecting the apparent pKa of the SAMs.In the presence of cationic surfactanta

the analyte and
WaS

【Fe(CN)6]’anions as

the marker ions,the self-assembled monolayers channel

open

and

exhibited distinct channel curfent. 4.Research ofgold colloid modified electrode and its application Colloidal gold modified glass carbon electrode was prepared by electrodeposit.The modified electrode showed an obvious eleetrocatalytic activity for the oxidation of nitrite at O.850 VⅧ.the Ag/AgCI electrode in O.05 mol L-1 H2S04 solution and for出e oxidation of the optimum COnditions,the possible reaction mechanism has also been electrode has


serotonin(5.HD.Under discassed.The
NG/GC

hirgll stability and Can bc applied

to

the determination ofnitrite in rain water and of

5一HT in human blood sample with simplicity,rapidness and accurate results. 5.Research ofthe interaction ofcolloid gold and serotonin in optical labels In pH 7.0 discussed by Britton-Robinson buffer
resonance

solution,binding

of colloidal gold witIl serotonin was

ultraviolet-visible(I嗍S)absorption
The optimum conditions investigated.Based
Oil

light

scattering(RLs)spectrum,fluorescence spectrum,and
interaction


emission

spectrum,

transmission electron

microscopy(TEM).
factors have been

of the

binding

and

the

influencing

the study,we proposed

highly sensitive gold colloid-based assay using RLS

spectrum

to

detect semtonin for the first time.The mechanism of binding interaction

between

Au

colloid and scrotonin Was also discussed.

Keywords:chemical sensoB
resonance

modified

electrode,self-assembled

monolayer,ion.channel

light scattering spectrum,gold colloid,eoppeb uric acid,cationic

snrfactants,nitrite,serotonin

IV

独创性声明
学位论文题目:

丝堂堡箜电拯鲍叠塞区座垣

本人声明所呈交的学位论文是本人在导师指导下进行的研究工作及取得的研究成果。据 我所知,除了文中特别加以标注和致谢的地方外,论文中不包含其他人已经发表或撰写过的

研究成果.也不包含为获得西南大学或其他教育机构的学位或证书而使用过的材料.与我一
同工作的同志对本研究所傲的任何贡献均已在论文中作了明确的说明并表示谢意。

学位论文作者:

签字日期:2007年4月20日

学位论文版权使用授权书
本学位论文作者完全了解西南大学有关保留、使用学位论文的规定,有权保留并向国家 有关部门或机构送交论文的复印件和磁盘,允许论文被查阅和借阅。本人授权西南大学研究 生院可以将学位论文的全部或部分内容编入有关数据库进行检索,可以采用影印、缩印或扫 描等复制手段保存、汇编学位论文。

(保密的学位论文在解密后适用本授权书,本论文:口不保密,
口保密期限至 学位论文作者签名



月止)。

签字日期:》一/
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工作单位:

导师签名:锣

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通讯地址:

邮编:——
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Segment I

Segment I

Introduction

1.Introduction of chemically modified electrodes
1.1 Introduction Chemically modified electrode-?-?(CME)一nil electrode made of material that is coated with
chemical modifier and that




conducting

or

semiconducting


selected monomolecular,multimolecular,ionic,or polymeric film of mealE of

by

faradaic(charge?transfer)reactions

or

interracial potential
optical properties of

differences(no
the film.

net

charge

transfer)exhibits chemical,electrochemical,and/or

Compared with other electrode concepts in

electrochemistry,the


distinguishing feature of
to



CMEs is that



generally

quite

thin

film(from

molecular
or

monolayer

perhaps



few

micrometers—thick multilayer)ofa selected
to

chemical

is bonded to

coated on the electrode surface

endow

the

electrode诵m

the

chemical,electrochemical,optical,electrical,transport,and


other

desirable properties of the film in

rational。chemically

designed manner.The range of electrode ion-selective

surface properties includes,but is moi'e diverse

than,that of

electrodes(ISEs)which

also involve,in their highest fumas。rational design of the phase-boundary,partition and transport properties ofmembranes on
or

between
are

electrodes.While

CMEs c∞operate both amperometrically

and potentiometrically,they

generally used amperometrically,a faradaic(charge妇nsfeO measurement
or

reaction being the basis ofexperimental

study,whereas ISEs

are

generally

used in the

potentiometric formats

where a phase-boundary

I南tential(interfacial

potential

difference)is

measured quantity【1】.Gas-sensing electrodes(e.g.,for C02,NH3,NOx)are also potentiometrically

based【2】although

the oxygen electrode,which functions amperometrically,is

all

exception【31.

Chemically sensitive

field effect transistors(cHEMFETs)are basically non-faradaie electrode

systems in which electric field variations in the semiconductor gate region control the magnitude of
the source-drain

current【4】.Enzyme—based electrodes


detect the

product(s)ofa

reaction

between

nil

immobilized enzyme layer and
potentiometric

reaction substrate in many ways,including both amperometric between

and

means.The

distinction

CMEs and
on a

amperometric

enzyme-modified


electrodes is thus very narrow,the latter being based

natural biological catalyst,but also with the following

rational(bio)molecular electrode
important properties
to

design goal in

mind.In

discussion of CMEs,it

is

keep in mind the concept of film

homogeneity.The

presence of variations

in film

between the

interfaces witll the electrode and solution Can dramatically affect many ofthe
not


other properties discussed below.While film homogeneity is
the others
not
are

necessity,without this property,

dimcult

to

estimate and



complete description ofthe behavior ofa CME is difficult.if

impossible,to achieve.

CMEs attempted

have

attracted considemble
more direct control

interest

over

the past
nature

two
of

decades

as

researchers have
have found

to exert

over

the chemical

an electrode.CMEs

坚竺!!三!!!!!!!!!!竺!∑!竺望!!:!璺堡
and

numerous

important

applications

in,e.g.,solar

energy

conversion

storage,selective devices,corrosion

electro-organic

synthesis,molecular

electronics,electrochromic
to

display

protection.and electroanalysis.111e ability

manipulate the molecular architecture of the bulk
to


matrix of an electrode and its surface in particular has led
of CMEs

wide range of analytical applications

and
be

created powerful opportunities for electroanalysis.For eleetroanalytical purposes,a

CME

can

designed【5-8】as
also



powerful,(predominantly voltammetric,amperometric,

potentiometric,and

impedimetric
or

and

microgravimetric)sensing
material of the electrode

device,by


deliberate

modification
(monomeric
molecular

of the surface
or

bulk matrix

with

selected reagent

polymeric)that

governs its electrochemical properties.Such manipulation of the

composition of

the electrode aims at improving sensitivity,selectivity
to

and/or stability

allowing for tailoring its

response in order
of the

meet analytical needs.

1.2

Modificatory methods

CEMs
one

CMEs are usually chemically modified by

of four approaches:

(1)Chemisorption--adsorption

in which the forces involved are the valence forces ofthe same

kind as those operating in the formation ofchemical

compounds[9】.In this

method,the

electrode

is

simply soaked for
water.The electrode



period

of time in



solution of the modifier substance then washed wim pure

chemical

film is strongly and,ideally,irreversibly adsorbed(chemisorbed)onto the approach usually yields monolayar(or less)coverage.Included in this type of

surface.This

modification are the substrate-coupled self-assembled monolayers(SAMs)in which uncorrelated molecules spontaneously chemisorb
at

specific

sites

on

the surface of the electrode to form a

superlattice【9】,The
substrate plate into

self-assemble ofmono layers(SAMs)ofadsorption types ofmodification have
in
recent

been actively studied


years.SAMs are formed

spontaneously

by

the immersion of



solution of suitably

polar

molecules.Representative chemical species for the
on

preparation ofhighly ordered gold,silver

SAMs

involve

silanes
on

silica【10-121,alkanethiols

on

metals such as
on

and copper【13-151,phosphonates

metal phosphonates【16],carboxylic acids

metal

oxides【17】andtalcoholsoraminesOilplatinum【18】. (2)Covalent
to

binding-一linking agent,such
one

as,e.g.,organosilanes

or

cyanuric chlodde。are

used

covalently attach from

to

several monomolecular layers

of the chemical modifier to the is performed by coating with

electrode surface.For silicon oxide based surface,the


fanctionalization


bifuoctional organosilane,i.e,,organosilane having
to

first functional group enabling covalent group,as the

binding

the

Surface(often


all

Si?halogen
group

or

Si—alkoxy
react

in—SiCI.or-Si(OCH.),
group of


respectively)and biomolecule(often

second functional

to

with

functional

giveu

all

aldehyde,amino

or

carboxyl group).Interestingly,the functional group Can be

modified
groups
on

by using single?or multi—step the surface,such
as

synthetic

procedures to provide a wide range of reactive

N?acylimidazole,2一or 3-bromoacrylate,cyanuric chloride,disulfide,

N-hydroxysuccinimide

ester,hydrazide,iodoacetyl,imidoester,isocyanate,isothiocyanate,
with biopolymers under the mildest

maleimide,succinimidyl carbonate,suitable for further reactions


conditions possible.

(3)Polyer fill
electrode solution

coating--electron-conductive and nonconductive polyer films

are

held on the

surface by SOtl*combination of
or

chemisorption

and

low solubility polymer

in the contacting
can
or

by

physical
or

anchoring

in



porous

electrode.The

film

be organic,

organometallic
Call

inorganic;it Call already contain the desired chemical

modifier

that chemical


be added to the polymer in a second,fonctionalizing

step;and

can

contain the equivalent of

few up to many thousands ofmonomolecular layers ofthe chemical

modifier.Included
are

in this form

ofmodification

are

the substrate-decoupled SAMs in which adsorbate molecules

arranged on the
can

electrode surface independently

of any substrate
droplct solvent

structure.Polymer

film coated CMEs
or

be

prepared

by

using dipcoating and

evaporation,oxidation

reduction deposition,

electropolymerization,cross-linking,and radiofrequeney polymerization.As

come

to

the types of

Polymer

film

modified electrode,it

has

been sum up

four

kinds

of

films

contained:A)

Electroinactive conducting

Film;B)Electroacfive(redox)Polymer Film;C)Ion-exchange Polymer film;D)
last
one

polymer film.Among the films,the
an


is fashionable.
art

(4)Composite…the chemical modifier is simply
the
case

mixed with

electrode matrix material,as in with the carbon

of

electron-transfer carbon

mediator(electrocatalyst)combined

particles(plus
as

binder)of

paste

electrode.Alternatively.intercalation matrices
can

such

certain

Langmuir-Blodgett films,zeolites,clays and molecular sieves

be

used to contain the modifier.

CMEs

can

also contain multiple chemical


modifiers,and

sometimes these modifiers

andor the

electrode

substrate may have

particularly designed spatial


configuration.That
as


is,a CME may acceptor,and


contain one electrocatalyst that reacts with second one to of
to


substrate

or

acts

photodonur

or

transport

charge between the first catalyst

and

the

electrode.Or,the

CME may consist
on

substrate coated with


form

bilayer
or

polymers,the second polymer overlaid the first of polymer films.These more complex CMEs may be called microstmctured
CMEs

two different chemical

electrodes

integrated chemical system electrodes.

1.3 Applications of

in electroanalysis

Several phenomena occurring at CMEs are exploited for electroanalytical purposes.These,

aSsessed,classified and illustrated with

selected examples

below,include

analyte

and/or

reagent

accumulation,chemical transformation,electrocatalysis,permeability,ionic equilibria,controlled

release,and

change
ors

of

mass.They are

employed

separately

or

in

mutual

combinations,

simultaneously

most commonly,in sequence.

|.3,|Application in the determination

ofmetal

ions

The knowledge ofmetal content in


various environmental

matrices
are

is very

important.They

are

threat to the

environment and

to

human health,because they

not

biodegradable and

therefore ofheavy

are

retained indefinitely in the ecological

systems

and in the food

chain.The accumulation Can
result in
an

metals,such as lead,cadmium and mercury,in living

organisms

impairment of



坚苎!堡!!!!墅1 21兰竺竺!!!!坠竺坐:三竺!生

function,or in extreme ca.∞s,death.For example,the Euro J—carl Union guideline level fur lead in drinking water is set at 10

ppb【19】since

severe

effects car)bo obserced upon exposure to higher

levels.The toxicity of lead is derived from its ability to interim:re directly with calcium signaling.by substitution since lead has


similar ionic radius

to

Ca2+【20],and

the inhibition of several zinc

enzymes【20-24].The
represent


uses

of conventional electrochemical cells and of classical bulky electrodes

problem fur decentralised measurement,due to the large volume ofsolution needed.The


metal accumulation in main purpose is
to

small volume at the CME modifying layer usually precedes detection and its

improve detectability.If this accumulation is preferential,because of selective
Call

intemctious
separation

between the metal and the immobilized reagent then,it

seⅣe additionally

as



step,thus an

improving the

electrode selectiviIy.For instance,molecular

recognition

is

displayed towards terminal host
or

analyte in solution by immobilized group.

self-assembled

monolayer films with

guest

CEMhasbeen appliedtothedetermination ofmetal
have

cations.Forexample,Hemandez etal.【25】
trace

optimised

the voltammelric

analysis
with


of

mercury(II)at

levels after accumulation at



carboh paste electrode

modified

natural

zeolite.Copper(IO

species were determined by

square wave voltammetry in ammonia buffer

tPH

91 after accumulation at open circuit in phosphate

buffer(pH 6)using
applied to the



zeolite X-modified carbon paste of

electrode【26,271.The

procedure was also

determination

cadmium(ID and Zinc(II),by performing 6)【26].

the preconcentration in

ammonia buffer

QH 9)and the

detection in phosphate buffer(pH

Recendy,an proteins[35—371

active research asea was that

bacteria【28—30l,DNA【311,enzymes【32—34],other
been exploited as the biorecognition molecule on

and

peptides【38-46]all having

the chemically modified electrode.Assays based on the inhibition of alkaline phosphatase witll Pb

(ID【40】and

the activation of the apoenzyme by
call

Zn(II)[41 l

show sub-ppb

detection

limits,thus

demonstrating the exquisite sensitivity that have

be

achieved.For example,Godwin and co-workers

used

zinc fingers as highly selective electrode for

Zn”【38】by modifying

the zinc finger

COBSeTISBS

peptide with fluoreseein as the donor and lissamine as the accepter.Takehara et a1.used gold electrodes as ion gates fur

glutathione(g-Glu—Cys-Gly)self-assembled monolayem(SAM)on
detecting lanthanide in the

ions【391.Glutathione

has also been used

as



recognition

element fur copper(II)
onto

mM

to

mM range without preconcentration by self-assembling the glutathione

gold

electrodes via llle thiol side chain of the cysteine by using

residue【471.Detection
to
an

ofCdz+was

made possible
and

glutathione

us

the

ligand

attached

MPA SAM【48].The oligopeptides

polypeptides have been aRached to gold electrodes as biorecognition elements for the determination

ofcopper【42-451,lead【46】and silver【49】as well
J.3.2 Application in electrochemical biosensors Biosensor is coupled to


as

cadmium.

special

type of

CME

or

ISE in which



biochemical

recognition process is is modified by the receptors,enzymes,

an

appropriate electrochemical transducer.The electrode surface


attachment of

biocomponent(e.g.tissue,microorganisms,organdies,cell



antibodies,nucleic acids

etc.)which

functions is

aS

the biological recognition element biosensor with
an

or

biochemical

receptor【501.An electrochemical biosensor
considered to be
or a



electrochemical transducer.It is

chemically

medlfied electrode化ME)∞electronic conducting,semiconducting


ionic

conducting material


is coated with

biochemical film.
in biosensors.the most successful to-date being

There am

number of commercial

Successes

the home blood glucose monitor fur me by people suffering from diabetes.111c biosensors in this application
are

all electronically-based

and

rely upon alzymes that recognize and catalyse reactions that
age

ofglucose witll the generation

ofredox-actiye species

detected electrochemically.So.in

this

paper,wegivethe
biosensot售.

exampleofglucose SensortO showthe

applicationoftheCMEinelectrochemical

墨瓣筑∞譬嚣
Fig.1.The reaction sequence for glucose measurement

011

the Accu-Chek Advantage∞rl¥oL

Since the development of the enzyme-based sensor fur glucose,first described by Clark and Lyons in 1962。in which

glucose

oxidase was entrapped between

two

membranes,all impressive

litemtare

on

methods of immobilization and related biosensor development has appeared.Its simple
in Figure 1.For
can

mechanismⅧshown
enzyme with avidin
biotinylated in work
on or

example,SnejdaRkova et以【51],the conjugate strongly
attached to the surface ofa

of the

streptavidin

be

BLM

prepared from

phospholipids.This
glucose
on

mode of immobilisation of the enzyme

conjugate
wim

has

been

applied

biosensors【52,531,∞well as谢也urea biosensurs

urease

aRached tO an

s-BLM formed



metallic support modiged xxith electrodeposited polypyrrole(PPy)[52].Many
various polymers,and there
are nurncrons

membranes

have

been prepared with

developments
such
as

reported,for example by

Wang and co-workers[53】on

carbon paste

and

other帅es

polyester-sulfonic acid coatings and metallized carbon.Other membrane polystyrene

materials

reported include

sulfonate,polyethylene
hybrid

glycol,moditied

zeolite[54],poly(vinyl)pyridine(pvP)【551,
date,there

Nation【56],sol?gel
appears to be
no

materials【57],and graphite【58】composite mixtures.At this
on

general

consensus

which membranes described


or

composites

are

superior for particular

applications of GOx.Chen et biosensor based
on

a1.【59】have

selective and robust glucose amperometric thiol


the immobilization of COx

and Os(bpy)2Cl—poly(4-vinyl)pyridine on
et

self-assembled monolayers glucose

surface.Yegnaraman
011 a

a1.【60】have

proposed the

construction of

biosensor

prepared

gold electrode modified by the

sequential incorporation of 1,



Master Thesis ofSouthwest Umversity

4?anthraquinone and GOx through covalent linkage onto



self-assembled monolayer configuration.
to

Tmw and Rennemberg f61】have proposed an interesting method

immobilize encapsulated

microparticles
deposition

of glucose oxidase within
et



nanoscale polyelectrolyte film using the layer-by-layer


technique.Li[621

aL has reported
onto

glucose biosensor based

on

electrodeposition

of

palladium nanoparticles and glucose oxidase

Nafion-solubilized carbon nanotube electrode biosensor

and

Wang【63】et

a1.describes



novel

glucose

based

on

the

nanoscaled

cobalt

phthalocyanine--glucose
Recently,a

oxidase biocomtmsite.

developing
to

field

in

electrochemical

biosensors

is

the

us@of

chips

and

electrochemical methods

detect binding of
on a

oligonucleotides(gene probes).DNA electrode
can

electrochemical

biosensors,realized by immobilizing

suitable

surface

an

oligonucleotide sequence of results.DNA based to the unique stranded


the calf thymus DNA,are simple
biosensors hold
a11

to

assemble and

provide reliable

enormous

potential for environmental
as

monitoring【64,65】due
and Crick in

complementary
DNA molecules

structure
arc

of DNA

described by

Watson

1953【66],single

able to reanneal and form

hydrogen bends with


matching DNA strands in

process referred to弩hybridization.A

major

application of

DNA

biosensor will be

the testing of

water,food,soil,and plant samples for the

presence

of

analytas(carcinogens,drugs,mutagenic analyte
is chosen to

pollutants,etc.)研m


binding affinities for the structure ofDNA.Ifthe target

be

sequence of single stranded DNA that is already known,the complementary sequence,or probe,
be immobilized
on

Can

the

biosensor to‘'catch'’the biosensor

analyte.Since

no

two strains of bacteria have

identical DNA fingerprints,a DNA based its genome has been

is able to single out

any strain,presuming that

determined,and

the sequence

ofanalyte

chosen is highly specific to the strain.

Binding of small molecules to DNA

and

generally DNA damage by ionizing radiation,dimethyl

sulphate,ete.has been 681.

described

throrI曲the variation

ofthe electrochemical signal ofguanine【67,

1.3.3 Appltcn“on in ion—channelsensom Ion—channel sensors,involves the effect of the

analyte

species

on

the surface charge density of
can

the receptor membrane【69—72].That is,a
negatively charged receptor.As


positively

charged analyte

be selectively bound to a

result,the negative surface charge

of the membrane is
charged

compensated and intermolecular voids arc

formed between

receptor molecules.A negatively analyte,Can

redox marker,which cannot penetrate the membrane in the absence of the
traverse

therefore

through the
on

membrane

intermolecular voids.For

example,in



synthetic lipid membrane

deposited
by
t11e

the electrode by means of the Langmuir-Blodgett technique,the channels are opened channel

cd+analyte

switches【69].Specific

intemctions of the

analyte with

the membrane

components result in channel opening.The detection signal

ofthe【Fe(CN)6r redox
all

marker anions。

permeating through the open channels in the membrane,serves as an amplified measure of the Caz+
analyte concentration.The channels

Can be

reversibly closed by means of
all

analyte quencher,e.g.,

EDTA.This


Ca2+determination

call

seⅣc as

iliastration

of indirect

vohammetric determination

of

an

electro.inactive species.There
or

are

also similar sensing systems using

recep觚of different

charge signs

neutral

rec印tors 170,711.

Fig.2.Ion

channel(mimetic)sensors

based

on:(I)intramoleculer ligand-gated,(11)intermolecular

analyte-charge

gated
no or

at analyte sensitive

membrane modified electrode surfaces and(III)nanotubule membranesr Closed(a)refer to ofblocked marker ions gating and open Co)refer to higher marker

lower marker ion current as the consequence
as

ion current

the consequence

ofmaximum marker ions Cating, elaborated

As shown in Figure

2【73],more

mechanisms

on

the issue have appeared sparsely in
call

the literature.For instance,Hart and behave
as an

Wang【741 reported

that the marker ion ferricyanide

itself

analyte

and

open the electron transfer barrier for positively

charged ruthenium

hexamine at



membrane consisting of positively charged didodecyl dimethyl ammonium bromide.

Similarly,Chen and coworkers[75】presented evidence
ferricyanide electron transfer at


for the formation

of pinholes

for

phospholipids modified electrode upon addition of C矿+as analyte.

Moreover,electrocatalysis

of electron transfer found for polyelectrolyte modified

and

for DNA

modified electrodes should be talcen iato consideration when the mechanism of electron transfer iII ion channel
sensors

is

discussed【76].Besides,the

impact

ofsensing

based on preconcentration of



MasterThesisofSouthwestUniversity

electroactive analytes at electrode-covered with charged

SAMs【77】may
sensor's.

also help to establish



more elaborate picture ofthe signal amplification in ion-channel 1.4Advantages and disadvantages ofthe CMEs
once

CEMs
in electrochemical
as

optimized,call
or

also

be

used

detectors

for

the

effective

monitoring of flowing stream
or

hydrodynamic

processes,such

Liquid

chromatograpy(LC-EC)

amperometric detection with flow injection analysis(FIA).For analytical applications,CMEs

should possess certain properties,good mechanical and chemical stability of electrode surface,good

short—term reproducibility and long-term stability ofthe modifiers activity towards the analyte,wide dynamic range of responds。low and stable background simple and
currents
over

the

potential

range reguired,

reliable fabrication that results in consistency ofthe resi:,onse from olle electrode. the great potential


Despite

of

CMEs

for analytical applications revealed by

voluminous
described.

fundamental research.only

few examples of the commercial use of CMEs have been

These include,for instance,metalimetal oxide reusable amperometric electrodes for determination of, e.g.,alcohols,amines in liquid
or

carbohydrates【781.For

successful practical applications,such∞detection analysis
or

chromatography【79],flow injection

batch determinations,the

long-term

stability and reproducibility of CMEs need to

be
Of

improved while sensitivity and detectability of superior to that of non—modified electrodes.For

analytical CMEs
such


should

be made comparable
area
as

rapidly

growing

analytical

CMEs,the

definitions,classifications

and

recommendations
It is apparent that applications.

presented herein cannot

address

every construction detail and operation principle.

periodical

updating is needed with the further development of CMEs f.or

analytical

2.Introduction of colloid gold
2.1 Preparation of colloid gold

With

the advent of nanotechnology,the prospects for using

engineered nanomaterials

with

diameters of<100

m in industrial

applications,medical imaging,disease diagnoses,drug delivery,
other areas have progressed rapidly.The potential

cancer treatment,gene therapy,and nsnoparticles(NPs)in these area5
Natan presented the

for

is ird'mite,with novel new

applications constantly

being explored.

preparation methods
as

of Au colloid and characterized the Au colloid monolayer.

One of the methods is

Frens’with slightly modification.All glassware used in these

preparations

Was thoroughly cleaned in aqua regia(3 parts HCI,l part HN03),rinsed in triply distilled H20,and
oven—dried prior to u∞.In HAuCl4 was brought to
a a

l L round-bottom flask equipped with



condenser,500 ml of

lmM

rolling boil with vigorous stirring.RApid addition of 50mL of 38.8 mM


sodium citrate to the vortex ofthe solution resulted in

color change form pale yellow to burgundy.

Boiling Wag continued for 10 min;the heating mantle Was then removed,and stirring was continued for
an

additional 15 rain.after the solution reached room temperature,it Was filtered through



0.8



Segment I

pm Gelman membrane filter.The resulting solution of colloidal particles was characterized by
absorption maximum at 520 nm.Transmission electron

all

microscopy(TEM)indicated



particle size

of 13

m(100 particles sampled)【801.

2.2 Application ofcolloid gold in electrochemistry

The

use

ofnanoparticles ofdifferent metals like Au,Pt,Pd has been suggested as a

promising

criterion for the fabrication of highly active through,reduction

electrodes.The

nanoparticles we∞prepared mainly

nⅪc6Ⅻin

aqueous solutions

containing the corresponding chloro-metallate

anions,metal vapor synthesis routes,or electrochemical depositions on inert bases.Some other

methods like

sol-gel,impregnation,deposition-precipitation

and dip-coating have also

been

used to

fabricate gold
been

nanoparticles-deposited electrodes.Recently,surface-modified
for many
over

Au electrodes

have

suggested

electrocatalytic

and electroanalytical

applications【81?84】in

view oftheir

sop盯ior activity

the bulk Au electrode that is known to be inactive or poorly active towards

many electrochemical

reactions【s5].On

the other hand,the electrodeposition ofa highly dispersed

Aunanoparticleon allinertbase attractsgrowinginterest。becauseofitsexla-aordinaryhighcatalytic

activity in many reactions like the CO oxide ion【85—871. 2.3 Application ofcolloid gold in optical labels
Au nanoparticles

fi舯s)are

often used as optical

labels

for the detection of bioreeognition

6'vents

such as DNA

hybridization or antigen-antibody events on

complex formation oi"for the analysis ofthe

camlytic functions of nuleic acids.Alternatively,Au NPs amplify specific biomaterial binding between the localized

conjugated

to

biomaterials are used

to

sul'faces by stimulating the electronic coupling

plasmon oftbe

NPs and the surface plasmon wave associated with the bulk Au

surface.Surface plasmom are accepted

collective

electromagnetic oscillations at metallic surfaces.It is widely

that for optical processes the primary role of the roughness in

metals

or

the small size of

noble metal particles is to enhance the local optical fields via inlprove the efficiency of light

localized plasmon iesoaance,and thus
et

absorption

and

emission【88@0].Hayakawa
resonant

a1.【91】have

described the increase of europium ion

fluorescence owing to

plasma oscillation of silver

particles in silica gla鼹.The Pastemack’s group has firstly reported that RLS technique call be used
to

investigate the

formation of

aggregated choromophores in complex

systems【92,931.Resonance
by

light scattering

occm

when the incident

beam is

close in

energy to∞absorption band produced coupled,to

an

oscillating dipole.This

phenomenon


is amplified when dipoles are strongly

the level

where it can be detected by
to


common spectrofluofimcter.Since

then,the technique has been applied

large variety

ofaggregation

systems including porphyrin[94-96],dye-nucleic acids【97,98】and
these experiments,RLS not only

dye-protein【99—101】aggregates.In selectivity criteria

meets sensitivity and

but also offers the additional benefits ofsimplicity

and versatility.

竺竺!!!!!!:!:21兰2竺!!=三!!竺2::!:!!生

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15

坚!:堡!!!!墅!!!!!!!!∑:坠!!!:!竺!Z

Segment II
its application

Research of chemical modified electrode and

Chapter 1 voltammetry
at

Determination of


copper(11)by anodic stripping

2,5-dimercapto-1,3,4-thiadiazol self-assembled

monolayer-based gold electrode
1.Introduction
Copper is in at least 30 iron and
to
one

ofthe most comrnon trace heavy metals and is

all

essential micronu仃ient,present

enzymes【l】.In
its

humans,copper is the third most abundant trace element,following is

zinc,and

presence

fundamental

in many metabolic processes.It is relatively non—toxic

mammals,but the intake oflarge quantities Can be toxic.The toxicity is generally attnibumd to the
than to its organic
or

aquo-complexed“丘∞”copper(II)ion rather

inorganic

complex【21.Sources

of

copper poisoning inchide bevemges from vending machines,copper 01'brass ve¥¥els,and sometimes water

supplies【3】.
are

Several methods for the determination of copper

available,including inductively coupled
absorption spectrometot,

plasma-mass

spectrometry,flen打on

activation

analysis,atomic

ion—selective electrodes,and

emission

spectrometry.However,most

of them require seyeral

time-consuming manipulation
controllable

steps,sophisticated instruments and special

training【4,5】.A common

method for the determination ofcopper is anodic stripping voltammetry(ASV)【6,7】.The design of
electrodes with surface properties
can

be

effectively
one

achieved

by

employing

self-assembled
create

monotayers(SAMs)[8】,which

have become

of the most popular techniques to

well?defined functional

surfaces【9】.SAM elec仃odes
call

arc very

promising for the

construction

of electrochem/cal selLsOP3 because they

enhance the selectivity and sensitivity,improve the

response time,and decrease stability【lO-12].Based
on

the overpotential ofthe redox process ofanalytes,while exhibiting good such prominent properties,the application of SAMs to the estimation of

copper

has been investigated.

2.ExperimentaI
2.1 Reagents

2,5?Dimercapto-I,3,4-thiadiazol(DMTD)solution(o,01 mol I-’)and stock solution(5.8X
mol l-t)ofCu(II)was prepared using doubly distilled water,A phosphate buffer was used
the pH.All other
to

10"3

control

chemicals we∞of anal州cal?reagent w越used thronghouL

grade All the

and

Were

used without

fulthes

purification.Doubly distilled water

experiments

Wc撑carried out at

room temperature(approx 25℃1.
16

Segment II Chapter 1

2.2 lnstrumen协 Electrochemical measurements were carried
011 a

out

CHI

440(CH Instruments,us).
Elektfik Co.,

Electrochemical impedance measurement was carded

out

on



Model IM 6e(Zahner


Germany).A
mm)Or
Ag/AgCl


three-electrode system used in the measurements consists of
as

gold

electrode(d=2


DMTD SAM electrode

the working

electrode,Pt

as

the counter electrode,and

electrode as

the reference

electrode.All

potentials were given wim respect to the Ag/AgCl

electrode.
2.3 Preparation of DMTD

SAM

electrode mirror-like surface wi仙0.3 Ah03

A bare gold electrode Was polished to with



powder

and then

O.05岬A1203

powder.The
and

polished electrode was immersed in Piranha

solution(a mixed

solution of 30%H202

concentrated H2S04,volume ratio

1:3),then

rinsed

ultrasonically谢m

water and absolute ethanol for 3 H2SOa until


min.This

electrode Was voltammetrically cycled in 0.1 mol r1

stable cyclic voltammogram was obtained.The potential range is between 0.4 V and

1.2 v.Aider being washed with sonication,the

electrode was
at

immersed in

an

ethanol solution of 1.0

×10。mol 1-1 DMTD for approximately 12 h

room temperature.Upon removal from the

DMTD

solution,the

electrode

Was thoroughly rinsed with absolute ethanol
gold electrode Was

to remove the physically

adsorbed species.The

DMTD SAM at the

then prepared.

2.4 Results and discussion
2.4.1 Characterization

ofthe DMTD SAMin



Fe(CN)65.solution






pc)

Fig.1

Cyclic

voltammograms of 5.0



l旷tool
s-’.

l_I Fe(C'N),at



bare gold

electrode(a)and



DMTD

SAM

electrode(b);1.0 mol l-l

KCI;scan rate,100 mV


The

redox behavior of

reversible couple

can

he

used to probe the packing structure of the

17

坚竺:!!!坠皇!!!!!!!!翌!!望墨:!釜!竺
monolayer.Figure 1 shows the cyclic voltammograms of the bare gold electrode and the DMTD SAM electrode in 1.OX 10-3 mol 1-’K3[Fe(CN)6]solution containing 0.1 mol I~KCI.For the bare
gold electrode,a couple ofwell-defined waves of

Fe(CN)63-/Fe(CN),appeared

and it

call

be

sccn

that the pealc current was decreased and the AEp,the difference between the

anodic

and cathodic
one

peak potentials,was increased for the DMTD SAM,elect'ode.The large AEp is
evidence for the blocking effect of probing species by the monolayer banier.As

piece of seen,the

Can be


DMTD SAM significantly impedes the electron transfer rate.Because DMTD is
ring

five-membered
in

mercaptan/n61ecule。there

are

some pinhole

defects

and

collapsed
as

sites

the DMTD

monolayer.The electron
DMTD monolayer.
2.4.2 Characterization

transfer rate constant at
call

pinhole defects

is the same

that at the bare gold

electrode;therefore,the redox couples

reach the gold SUne3ce through pinhole

defects

in the

for

the

DMTD SAM

by complex impedance analysis in the presence

of

Fe(CN)63-
Figure 2 shows gold

the complex

impedance

plots

of

the

bare

gold

electrode and

the

DMTD-modified

electrode.A comparison of complex

impedance plots

of the bare gold

electrode and the monolayer-covered gold electrode shows the effect of the absorbed DMTD monolayer
on

the AC response.For the monolayer-covered electrode,Rcb which is the diameter of

the semicircle at

high

fi'equency,is clearly greater than that of bare gold electrode due to

all

inhibition of the DMTD

SAM

to

electrode transfer.This proves the presence of DMTD

on

the gold

elec缸ode.

、一






Z’∞)
Fig.2 Complex impedance plots measured in 1.0


10‘mo!i-I

R辑=N)‘■?0.I

mol l-’KCI

at

the

formal potential

of0.14 V for the bare gold 106Hz.

electrode(a)and the DMTD SAM electrode(b).The frequency range is between 10。2and

2.4.3 Electrochemical response Figure 3

ofCu(10

at

the

DMTD SAMelectrode
electrode
covered with DMTD

shows the linear-sweep voltammogram of the gold



!!暨!!坐!!兰!12111 1

monolayer obtained in
in




copper.fiee phosphate buffer for 40

solution(curve a),and

after



deposition step

8.0xl旷tool

F。Cu(11)solution

S(curve

b 1.Successful incorporation of

Cu(II)in

the

SAM-modified

electrode surface is clearly“idenced by the presence ofa well?defined anodic pealc, the potential of about 0.26 vI The pcalc undoubtedly resulted from the


which印pe;m at

Cu(II)-Cu

redox transition,since

blank

experiment(curve a)shows

no

signal

OVer this potential range

associated with the redox ofpredeposited copper when the electrodes were immersed in copper-free solution.Figure 3 also shows


the stripping

peak cmTent of the bare gold electrode through
CUre



deposition step
CUlt

in

8.0xlO。tool r1

Cu(II)solution for 40 S(curve c).Ifone compares

b wim

c,one

Carl

s∞that the stripping peal【current response ofthe DMTD SAM

electrode to Cu(ID
to

Was larger than that ofthe bare gold electrode.The response ofthe DMTD SAM electrode
should be attributed to the interaction

Cu(II)

between

the

DMTD self-assemblod

monolayer

and Cu(tI).

DMTD is assembled
which
age

on

the gold electrode by the Au-thiolate linkage,leaving the nitrogen atoms,

in the 3 and 4 sites free for complexation witll

excellent metal ion complexant group because of its indicate that the DMTD SAM electrode

Cu(ID.The nitrogen atom is well known lone pair electron.These experimental results
Cu(II).In
this paper the

as

possessed

strong complexing action and sorption,which

could gready improve the sensitivity for the determination of

anodic

wave

ofCu(if)Was

systematically studied by

anodic

stripping voltammetry.





E(V)
Fig.3 Linear-sweep voltammograms ofthe


DMTD SAM electrode obtained in acopper-free buffered solution(a)
ofanaked V;

and afteradeposition stepin gold electrode

8.0xIO-’mol


rI Cuor)solutionfor40s(b),linear-sweepvoltammograms
8.0x10-s mol

through
s-I.



deposition step in

l一。Cu(11)solution

for 40

s(cl

Deposition

potential,-0 6

∞Ⅻrate.50mV 2.4.4

Effects ofpHon

thepeak current

ofCu《ID and
on

The

effects of solution pH

on

the preconcentration

the detection of complexed copper

were investigated and the results are shown in Figure 4.A pH 4.6 phosphate buffer Was supporting electrolyte.At because the


taken∞the

lower pH,the complexation between

Cu(tO and DMTD

was inhibited

nitrogen

of DMTD Was protonated.Once the protonation of DMTD occurred,it was
19

坚!!!!!!!!:坐!!!!!!!竺坠望!堡!!堂
difficult to form



complex between Cu(II)and DMTD.At the higher pH,the low response of the
call

DMTD SAM

electrode

be ascribed to the hydrolysis of

Cu(II).For

the pH value of 5.0 was

selected for further studies in the stripping step.

Fig,4

Effects of deposition

pH

on

the

peak cu丌cnt in pbosphate buffemt the stripping pH of 5.4’and effects of

stripping pH Ollthe peak ctlrrentin phosphatebuffer atthe deposition PH of46.Cu(11)concentration。8.Oxlo-smol

l-l:
Z4.5

Effects ofdepositionpotential

and deposition time

on

thepeak current

ofCu(Z0

E(V)
Fig.5 Effect

Tam(s)
potential
on

ofdeposition

the

Fig?6
cufrenL

Effect ofaccumulation oftime

on

pcak

peak tool

cufrenL

Cu(11)concentration.8.0 3<l旷

CII(II)concentration,8×10"Stool F J;scan

I-I;¥Call late,50 mV rl;deposition。pH

rate,50 mV s-。;deposition,pH 4 6;stripping,pH

4.6:stripping,pa

5.0:deposition time。20s.

50;depositionpotential.--06V
on

The dependence of the anodie

stripping peak cm-rent

the

accumulation potential was
are

examined

over

the potential range of 0.2 V to一1.2、‘and the results

shown in Figure 5.This

Segment II Chapter 1

figure indicates that the maximum resp,?rise for copper

Occurs

at

the potential of,or more negative
our

than.-4).6 V Therefore。-0.6 V was chosen as the accumulation potential in The effect of the

measurement.

anodic

stripping peak current on the

deposition time

for 8.0x 10-s mol 1-1 Cu

(II)is

shown in Figure 6.The

peal【current
at

increased with increasing

deposition

time,indicating

an

enhancement ofCu(II)concentration
exceeded 40 s。the peak
current

the surface ofthe

SAM electrode.When
for

the deposition time

became

constant.Hence

all subsequent

measurements,a

deposition time of40 s was employed. 2.4.6

Calibrationl弼Ot"and detection
to

lhnit

According

the

optimum experimental conditions

and

the procedure described above,the concentration WaS

relationship between the stripping peak current dependence ofthe current lo-'to g.0X 10-5 mol

and the Cu(ID

examined.The
of8.OX

response

onthe

concentrationofCu(IDWaslinearintherange

1-1.The
follows:

linear response equation for the peak

enrrent(曲and Cu(ID

concentration(C)was as

‘=o.4665+o.1976C

讳:IO-6 A,c.1旷tool 1-I)

andthecorrelationcoefficientwas0.9978.Thedetectionlimit(three-times signaltonoise)was4.0X10-7
molFm.

2,4.7StabilityoftheDMTDSAMelectrode
The modified electrode showed


good reproduc佑ility

and has



long

life.The relative
and

standard

deviations for eight successive determinations were 4.3

and 2.9%for

1.0x10-s

2.0x10-5 mol 1—1

Cu(II),respectively.The

relative eFrorofpeak current valueswasinthelimit of3.O%afterplacing

the electrode in a phosphate buffer ofpH 5.0 for 1
had


month.The

results indicated that the electrode

high stability.

2.4.8 Tolerance

offoreign

substances

The

influence ofvarious foreign

species

on

the determination of 5.0X 10-5 mol 1-1 Cu(1I)was
as a

investigated.The tolerable ±5%.The tolerated ratio
Zn2+;50 for

limit ofa foreign substance Was taken
of

relative

eITOr

not

greater than

foreign substance

to

5.0X10-s mol

I-’Cu(II)was

10 for Pb”,A13+,

M92+,c,and Ni”,100

for Baz+,Fe2+,5 for Fe“and 2 for Bi”.

2.4.9 Analytical application ThetapwaterWaS used asthe

sampleofCu(II)solution.The differentconcentrationsofCu(II)
Cu(II)solutions.The determination
results

solution were acquired by adding standard

ofCu(II)are

listed in Table 1,in which the original concentration Was obtained by determining the tap water with the

modified
96.3

electrode

directly.The recoveries

to

sample solutions of different concentrations were

between

and 101.2%.The Cu(ID

concentration of tap water Was also determined by atomic
to

emission spectrometry(AES).The result was O.188X 10-s mol 1-1。which was quite close

the

2I

竺!坐:!!!坐!!!!!!!=璺望尘:!::坚

value obtained by the proposed method.

Table 1 Results ofCu(II)determination in water Original found/ Added/

samples(n=3)
Total/ l 0-s Found after addition/Recovery/ 10-5mol 1-‘ 2.67 4.25 5.97

10-5molrl
0.188

10_5mol 1-1
2.50 4.0l 6.oo

mol一


99.3 101.2 96.5

2.688 4.198 6.188

3.References
1.Honeychurch



C..Hawkins


D.M.,Hart J.P.el'以,Voltammetric

behaviour and trace

determination of copper al 565.574.

mercury-free screcn—printed carbon electrode,Talanta,2002,57,

2.Sadeghi S,,Eslahi M,,Naseri

M.丸el aL,Copper

ion§etective

membrane

electrodes based

on

some schifrbase derivatives。Electroanalysis,2003,15,1327?1333.’ 3.R/chief

E.M.,Augelli M.A.,Magarotto

S.el a1.。Compact disks,a new

source

for gold

electrodes,application to the 760.764. 4.Vibha S.,Vinay

quantification of copper by

PSA,Electroanalysis,2001,13,

S.,Rajiv P.,Copper(11)ion-selective microelectroehemieal

transistor,J.Solid

State Electrochem.,2000,4,234.236.

5.Prakash&。Srivastava&C.,Seth P.K.,Estimation
anodic stripping

ofcopper in natural water and
over a

blood

using

differential

pulse

voltammetry

rotating

side

disk

electrode,

Electroanalysis。2002,14,303-308.
6.Bond A.M.,“Modern polarographie methods in analytical chemistry",1980,Marcel Dekker,
Inc.,New York.USA. 7.Dong Z.Z..J.S.Hart,“Potentiometrie stripping analysis'’,1992,Nankai University Press,

Tianjin,China.
8.Gao

Z.Q..k
on

S.Siow,Reversible chemical doping of selBassembled gold

poly(3-Octylthiophene)

monolayers

electrodes。J.Electroanal.Chem.,1996,412,179-182.

9.Mandler D.,Turyan I.,Applications
Electroanalysis,1996,8,207-213. 10.Lisdat F.,Ge

ofself-assembled

monolayers in electroanalytical chemistry

B.,Forster E.E.el a1.,Superoxide dismutase activity measurement using

cytechrome c.modified electrode,Anal.Chem.,1999,71,1359?1365.
I I.Nakminami T.。lto S.I.,Kuwabata S.et a1.,A biominetie

phospholipid/alkanethiolate
Au electrode for

bilayer

immobilizing uricase

and

all

electron

mediator

on

an

amperometric

determinationofuricacid,Anal.Chem.,1999,71,4278-4283.

Segment II Chapter 1

12.Niu L.M.,Luo

H.Q.,Li N.B.,Electrochemical

behavior of epinephrine at



penicfllamine 50,87—93.

self-assembled gold electrode and its analytical

application,Microchim.Acta,2005,1

Master l-hesis of Southwest University

Chapter 2

Electrochemical behavior of uric acid at



glassy

carbon electrode modified by eIectrodeposited films of acridine red
1.IⅡtroductiOn
Uric

acid(UA)is

the waste product produced from the degradation of purines.In healthy

human,uric acid is filtered and removed from the blood by the kidneys and excreted into urine.The level of uric acid in biological fluids is excretion.It is
all a

balance between its synthesis in the liver and urinary

important diagnostic marker in medicine—high levels of uric acid are associated

with kidney damage and gout,a condition where uric acid precipitates in the and

joints

leading to pain

inflammation【l】,Low levels

may

occur

in people with AIDS

or

cancer.So,simple,direct and
are

automation-ready procedures for measuring uric
Research and Drug Discovery.

acid concentration in urine


becoming popular

in

Methods based

on

fluorometric[2】and photometric【3】techniques

have

been described.At

present,enzymes【4-6】are
interfere with the
one

used to monitor uric acid levels but other compounds a”known to incubation period ofat least 30 minutes is

measurement and aN

required.Recently,

new way tO determine uric acid levels,devised by David Parker and colleagues at the University

ofDurham,exploits the luminescence ofa mixture oftwo lanthanide complexes.The method Can be
used to accurately detect the target molecule in dilute urine and sernm samples and is faster

than the

enzymatic route.
Polymer modified electrodes have been widely used for the immobilization of mediators enzytnd3 by
or

their

matrix

structure,electrocatalysis of molecules and construction of molecule behaviors of UA
nO On

devices,etc[7,8】.The determination and voltammetric
electrodes we”reported behaviors

the polymer-modified

before【9,lO】.To
ofUA at


our

knowledge,there is

report about the voltammetric

and determination

poly(acridine red)modified
modifier to fabricate

glassy carbon electrode.In the glassy

present work。we applied acridine red carbon

as a

apoly(acridine red)modified
modified electrodes

electrode

by

electropolymerization

method.The

showed

an

electrocatalytic

activity for the oxidation ofUA.

2.ExperimentaI
2.1 Reagents and apparatus
0.10 tool l-’phosphate buffets with various pH Wel'e prepared 0.10 tool l-。NaH2P04

by mixing

the stock solutions of

and

Na2HP04.Acridine red Was purchased from Hungary and Uric

acid(UA)
to

Was from Shanghai reagent factory.UA and acridine red solutions Were prepared jlist prior
and an experiments were carried out at room

u∞

temperature(23±2℃).All the chemicals

were of

!!罂!!!!!兰!竺!!!!
analytical—reagent grade,and doubly distilled water was used throughout.

The electrochemical experiments were carried

out


using



CHI 440

Electrochemical

Station

(CH Instruments).A glassy

carbon disk electrode with
as

diameter of 3 toni was used for working
electrode and

electrode.A platinum wire was employed

the

counter

an
to

Ag/AgCI electrode was

served

as

the reference electrode.All potentials were given with respect

the Ag/AgCl electrode.A

pHs一3B pH

meter(Dazhong,Shanghai)was

used for measuring pH.

2.2 Electrode preparation
Pd6r to each

experiment.the

glassy carbml electrode was first polished with 0.05 pm alumina

inawater slurryusingapolishing cloth and rinsed谢tlll:lHN03,acetoneandwater.Aftercleaning, the electrode was disposed by cyclic sweeping from 1.0
to

1.7 V at 60 mV s.‘for 6 min in phosphate

containing 0.91×104 mol I-1 arcidine red.After rinsing the carried out in phosphate buffer

electrode

with water’the electrode

0H 7.14)by

cyclic sweeping from 1.0 to 1.7 V at 100 mV s。for 10

min.The modified electrode was obtained in phosphate buffer 2.3 Results and discussion
voltammograms and

QH 7.14)at low

temperature.

2.3.,Cyclic electrodes

different

pulse

voltammograms

of

UA at

bare and

modified

EgO
Fig.1 Cyclic

voltammograms anddifferentpulsevoltammogramsof2.0xl旷mol/lUAin pH7.0PBS.(a)

Modified electrode in blank solution,(b)At the bare electrode,(c)At the modified electrode.Scan rate:100 mV/s. Figure l show cyclic voltammograms and different pulse

voltammograms

of UA at



bare

glassy carbon electrode(GCE)and

at



poly(acridine red)modified

GCE.At the bare glassy carbon

electrode,UA exhibited a poor electrochemical response,but at the

poly(acridine red)modified

electrode,the redox peaks were raised clearly.And it could be observed that oxidation peak potential
ofUA shifted negatively from 610

mV(bare

glass carbon

electrode)to

420

mV(modified electrode)
could

and

the overpotenfial decreased 190 mV.These results indica

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