application of starch-stabilized silver nanoparticles as a...

Research ArticleApplication of Starch-Stabilized Silver Nanoparticles asa Colorimetric Sensor for Mercury(II) in 0005molL Nitric Acid

Penka Vasileva1 Teodora Alexandrova1 and Irina Karadjova2

1Department of General and Inorganic Chemistry Faculty of Chemistry and Pharmacy Laboratory of Nanoparticle Scienceand Technology University of Sofia ldquoSt Kliment Ohridskirdquo 1 J Bourchier Blvd 1164 Sofia Bulgaria2Department of Analytical Chemistry Faculty of Chemistry and Pharmacy University of Sofia ldquoSt Kliment Ohridskirdquo1 J Bourchier Blvd 1164 Sofia Bulgaria

Correspondence should be addressed to Penka Vasileva pvasilevachemuni-sofiabg

Received 12 December 2016 Revised 13 March 2017 Accepted 28 March 2017 Published 13 April 2017

Academic Editor Roberto Comparelli

Copyright copy 2017 Penka Vasileva et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A sensitive and selective Hg2+ optical sensor has been developed based on the redox interaction of Hg2+ with starch-coated silvernanoparticles (AgNPs) in the presence of 0005mol Lminus1 HNO

3 The relative intensity of the localized surface plasmon absorption

band of AgNPs at 406 nm is linearly dependent on the concentration of Hg2+ with positive slope for the concentration range0ndash125 120583g Lminus1 and negative slope for the concentration range 25ndash500120583g Lminus1 Experiments performed demonstrated that metal ions(Na+ K+ Mg2+ Ca2+ Pb2+ Cu2+ Zn2+ Cd2+ Fe3+ Co2+ and Ni2+) do not interfere under the same conditions due to the absenceof oxidative activity of these ions which guarantees the high selectivity of the proposed optical sensor towards Hg2+ The limits ofdetection and quantification were found to be 09 120583g Lminus1 and 27 120583g Lminus1 respectively and relative standard deviations varied in therange 9ndash12 for Hg content from 09 to 125 120583g Lminus1 and 5ndash9 for Hg levels from 25 to 500 120583g Lminus1 The method was validated byanalysis of CRM Estuarine Water BCR505 A possible mechanism of interaction between AgNPs and Hg2+ for both concentrationranges was proposed on the basis of UV-Vis TEM and SAED analyses

1 Introduction

Monitoring of toxicmetals in aquatic ecosystems is an impor-tant analytical task as far as these contaminants adverselyaffect the environment and have serious medical effects onhuman health One of the most harmful pollutants amongthem is Hg which is still released in the environment andwidely distributed in air water and soil [1] At very lowconcentrations Hg affects humanrsquos health causing a varietyof diseases to the heart kidneys brain and nervous andendocrine systems [2] Naturally occurring levels of mercuryin groundwater and surface water are less than 05120583g Lminus1although local mineral deposits may produce higher levelsin groundwaters Essential quality standard for Hgmaximumpermissible limit of 1 120583g Lminus1 has been adopted at EU level andrequires regularmonitoring ofHg content in drinkingwatersIt is well known that Hg exists in natural waters as differentspecies Hg0 methyl-Hg and inorganic Hg(II) however thedominant toxic species in drinking waters is Hg(II) Various

instrumental methods and techniques have been developedfor Hg determination at low environmentally relevant con-centrations like atomic absorptionemission spectrometry(AASAES) [3] atomic fluorescence spectrometry (AFS) [45] and high-performance liquid chromatography (HPLC)[6 7] In spite of being very sensitive and precise forHg deter-mination these methods often require a time-consumingsample preparation step as well as expensive instrumentationVarious colorimetric assays (based on the use of sensitivechromophores or fluorophores [8ndash11] polymers [12 13]oligonucleotides [14 15] DNA [16 17] and metal nanopar-ticles [18ndash20]) have been developed and reported in theliterature as convenient and simple alternative methods forthe detection of target analytes without the requirement ofsophisticated apparatus

Metal nanoparticles have unique properties and applica-tions in numerous fields which are attributed to the collectivedipole oscillation known as Surface Plasmon Resonance(SPR) [21] This phenomenon makes them very desirable

HindawiJournal of ChemistryVolume 2017 Article ID 6897960 9 pageshttpsdoiorg10115520176897960

2 Journal of Chemistry

for colorimetric sensing of Hg2+ ions because the inter-action between the nanoparticles and the analyte changesthe intensity andor position of the absorption band in thevisible spectrum which often might be observed with thenaked eye [22]The limitations observed for these systems aremainly connected with poor selectivity high detection limitfor Hg(II) complicated synthesis of the probe materials orcomplicated analytical procedures

In this study we present a new colorimetric assay forHg2+ ions in 0005mol Lminus1 HNO

3using starch-stabilized

silver nanoparticles (AgNPs) A change in the absorbancestrength is expected as a result of the redox interactionbetween AgNPs and either Hg2+ ions or NO

3

minus ions The Hgconcentration determines which of these two redox reactionsdominates as the two oxidants compete with each other forAg oxidationThisway detection of very low environmentallyrelevant Hg contents is possible Several sensing systemshave been already reported based on the interaction betweenAgNPs and Hg(II) ions [23ndash32] however detailed study ofHg behavior in the presence of another competitive oxidantis rarely performed and discussed A dual functional sensorfor determination of Hg and H

2O2has been developed

based on a similar approach addition of H2O2to a mixture

of AgNPs and Hg(II) ions [33] The method presented inthis study however differs not only as a mechanism ofthe process but also as a behavior of Hg2+ ions at verylow concentrations (below 25 120583g Lminus1) towards AgNPs in thepresence of NO

3

minus ions as a second oxidant A simple andfast analytical procedure for determination of Hg in drinkingwaters is developed and verified by the analysis of a certifiedreference material

2 Materials and Methods

21 Apparatus UV-Vis absorption spectra were recorded onan Evolution 300 spectrometer (Thermo Scientific USA)within the 200ndash800 nm range using quartz cuvettes with 1 cmoptical path length High-purity water was used as a ref-erence sample for background absorption The morphologyand particle sizes were examined using a high-resolutiontransmission electron microscope (TEM JEOL JEM-2100operating at an accelerating voltage of 200 kV) A volumeof 5 120583L AgNPs suspension was placed on a carbon-coveredcopper grid for TEM and air-dried The histogram of AgNPssize distribution and the mean diameter of nanoparticleswere determined by counting at least 200 nanoparticlesfrom the different TEM images using ImageJ software Somestructural details of the nanoparticles were analyzed usingthe high-resolution TEM image and SAED pattern The zeta(120577) potential of nanoparticles was measured with a ZetaSizerNano ZS (Malvern) instrument

22 Chemicals All chemicals used were of analytical-reagentgrade and all aqueous solutions were prepared in high-puritywater (Millipore Corp Milford MA USA) Silver nitrate(AgNO

3 998) soluble starch sodium hydroxide (NaOH

99) nitric acid (HNO3 65) salts of the different cations

studied (NaCl KCl MgCl2 CaCl

2 Pb(NO

3)2 ZnCl

2 CuCl

2

NiCl2 CdCl

2 CoCl

2 and FeCl

3) (from Merck Germany)

and pharmaceutical grade D-(+) glucose (from Alfa AesarGermany) were used Stock Hg standard solution TraceCEPT 998 120583gmLminus1 in 2mol Lminus1 HNO

3(Sigma-Aldrich

USA) was used to prepare a working standard solution of1000 120583g Lminus1 Hg2+ in 001mol Lminus1 HNO

3 Standard solutions

for Hg within the concentration range of 0ndash1000 120583g Lminus1were prepared weekly by serial dilution of this solution in001mol Lminus1 HNO

3 All diluted Hg solutions were stored in

dark glass flasks and kept refrigerated at 4∘C

23 Synthesis and Characterization of Silver NanoparticlesThesynthesis ofAgNPs follows a green synthetic procedure asdescribed in our previous study [34]The silver nanoparticleswere obtained through a reduction reaction of silver nitratewith D-glucose as a reducing agent in the presence of starchas a stabilizer and suitable sodium hydroxide amount as areaction catalyst Briefly 24mL of 0001MAgNO

3and 48mL

of 02 solution of starch were mixed and left for at least 15minutes to form a complex under an ultrasonic treatment(ultrasonic bath power 100W frequency 38MHz) Afterthat 720120583L of 01M D-glucose was added and sonicatedfor 5 minutes The reaction was started by the addition of36mL of 01M NaOH and continued for one hour at aconstant temperature (30∘C) in an ultrasonic bath to ensurethe homogeneous formation of the silver nanoparticles

The as-prepared AgNPs were purified and concentratedthree times by ultracentrifugation (90min 14000 rpm) Thedispersion obtainedwas denoted as a stock solution of AgNPsand used in the experiments for colorimetric determinationof Hg2+ The AgNPs stock solution was kept in a darkglass flask at room temperature and was homogenized in anultrasonic bath for 30min prior to each experiment

24 Colorimetric Detection of Hg2+ Ions The colorimetricdetection of Hg2+ ions via starch-stabilized silver nanopar-ticles was conducted as follows an aliquot of 200120583L AgNPsstock solution and 300 120583L high-purity water were consecu-tively added to a small quartz cuvette followed by additionof 500 120583L Hg2+ solution with varying concentrations Theresultingmixturewas equilibrated by stirring onVortex for anoptimum incubation time and then the UV-Vis spectrum inthe wavelength range of 200ndash800 nm was recorded In orderto investigate the sensitivity of the colorimetric assay towardsother ions starch-stabilized AgNPs were allowed to interactunder the same conditions with 50 120583mol Lminus1 solutions ofalkali (Na+ K+) alkaline earth (Mg2+ Ca2+) Pb2+ andtransition-metal ions (Cu2+ Zn2+ Cd2+ Fe3+ Co2+ andNi2+) (separately for each ion) The resulting solutions weremonitored by optical absorption spectroscopy

25 Determination of Hg in TapUnderground Water Tapunderground water sample (20mL) was filtered through a045 120583m filter and acidified with HNO

3until reaching pH

in the range 2ndash23 Sample aliquot of 500120583L was transferredto a quartz cuvette and 200120583L stock solution of AgNPswas added and the mixture was stirred by the Vortex Afterthe incubation time of 5min the UV-Vis absorbance was

Journal of Chemistry 3

200 400 600 80000

05

10

15

20

25

30

Abso

rban

ce (a

u)

Wavelength (nm) 5 9 13 17 21 25Particle diameter (nm)

5nm20 nm

nmSt dev plusmn394 nmMean diameter 15

Figure 1 TEM image of starch-stabilized silver nanoparticlesinsets UV-Vis absorption spectrum and digital photographs (left)high-resolution TEM image of single nanoparticles and histogramof nanoparticle size distribution (right)

measured at 407 nm Parallel sample aliquot of 250 120583L isdiluted twice with 0005mol Lminus1 HNO

3and passed through

the procedure described above The response of this sample(increase or decrease related to the original one Figure 4) isused to distinguish the low from the high linear concentrationrange of Hg and to choose an appropriate calibration curve

3 Results and Discussion

31 Characterization of AgNPs TheUV-Vis absorption spec-trum of starch-stabilized AgNPs recorded at 25∘C is shownin Figure 1 (inset) A single and sharp SPR band appears at407 nm which indicates the formation of nanometer-sizedparticles This is further confirmed by the TEM observationand size distribution histogram shown in Figure 1

The spherical-like AgNPs exhibit a relatively narrowsize distribution with a mean diameter of 154 plusmn 39 nmIn addition to the nanospheres some typical polyhedralnanoparticles (multiple twined nanocrystals) can be easilyobservedThe crystalline nature of AgNPs is clearly observedon the HRTEM image in Figure 1 (inset) and proved bythe lattice characterization (eg the spacing between theindividual lattice fringes of 0235 nm which corresponds to(111) plane lattice spacing of pure silver)The colloidal stabilityof starch-coated AgNPs is confirmed by the 120577-potential valueof minus253 plusmn 13mV measured in 0001mol Lminus1 KCl at pH 68

32 The Optimization of Colorimetric Sensing of Hg2+ Sev-eral parameters were investigated systematically in orderto establish optimal conditions for the direct colorimetricdetection of Hg2+ As a first step the pH value was adjustedtaking into account the analysis of real samples and HNO

3

which is typically used for water sample preservation Theexperiments performed showed that 0005mol Lminus1 HNO

3

ensured the highest sensitivity and could be accepted as anoptimal sample medium In order to evaluate the optimumcontact time the kinetic of interaction between AgNPs and

Hg2+ in the presence of 0005mol Lminus1 nitric acid was followedwithin one hour by measurements of UV-Vis absorbanceTypical evolution of UV-Vis absorbance spectrum with timedue to the interaction of AgNPs with 400 120583g Lminus1 Hg2+ andrespective color change of the AgNPs dispersion is shown inFigure 2

The changes that occurred in the LSPR absorption bandof AgNPs are reflected on the color of the samples which canbe seen even with the naked eye It is seen that the sensorrsquosresponse is significant during the first five minutes of thereaction process and a negligible change in the absorptionintensity is observed over time This fact allows convenientanalytical detection of Hg2+ within only five minutes

As a next step the sensitivity and applicability of starch-coated AgNPs for quantitative determination of Hg2+ ionsunder the defined optimal conditions were studied The col-orimetric response and LSPR band behavior were monitoredas a function of Hg2+ concentrations ranging from 0 to500 120583g Lminus1 in the presence of 0005mol Lminus1 HNO

3(Figure 3)

As seen from the UV-Vis absorbance spectra (5-minuteincubation time) the addition of 0005mol Lminus1 HNO

3results

in a considerable decrease of the intensity of AgNPs charac-teristic plasmon band at 407 nm accompanied by a slight blueshift (Figure 3(a)) In addition a shoulder band appears atthe wavelength range of 450ndash600 nm The increase of Hg2+concentration from 0 to 125 120583g Lminus1 in 0005mol Lminus1 HNO

3

leads to a gradual increase of the intensity of the characteristicplasmon band of AgNPs at 407 nm and its value gradu-ally approximates to the absorption intensity of the blanknanoparticle solution (without both NO

3

minus and Hg2+) Inaddition the intensity of the shoulder band decreases alongwith increasing intensity of the main plasmon absorbanceband The spectra show a clear isosbestic point at 445 nmupon addition of Hg2+ in 0005mol Lminus1 HNO

3 demon-

strating that the aggregation of AgNPs is directly related tothe concentration of Hg2+ Contrariwise a gradual decreaseof the intensity of the characteristic plasmon band of theAgNPs at 407 nm is observed for the Hg concentration rangefrom 25 to 500 120583g Lminus1 The spectra presented in Figure 3(b)also show that the decrease of intensity of the absorbancemaximum at 407 nm is accompanied with a slight blueshift which is strengthened for the higher concentrations ofHg2+ This phenomenon is already reported and describedas a change of the refractive index of the particles and theformation of a mercury layer around AgNPs yielding anamalgam-like structure [25 35 36] It might be suggestedthat for the first Hg concentration range (0ndash125 120583g Lminus1) aredox reaction proceeds between zero-valent silver (Ag0) andeither Hg2+ or NO

3

minus ions The values of standard electrodepotentials of the components in the system confirm thissuggestion119864

0(Ag+Ag0) = 0799V119864

0(Hg2+Hg0) = 0854V

1198640(NO3

minusNH4

+) = 0864V Because the standard electrodepotential of NO

3

minusNH4

+ is commeasurable with that ofHg2+Hg0 two competitive oxidizing agents are involved inthe studied sensing system The most probable explanationfor the decrease of LSPR band intensity in the presence of0005mol Lminus1 HNO

3and further increase upon addition of


Ag blank

400 휇g Lminus1 Hg2+

Abso

rban

ce (a

u)

00

05

10

15

20

25

30

60min45min30min

15 min5min

407 nm

399 nm

400 500 600 700 800300Wavelength (nm)

(a) (b)

Figure 2 (a) Evolution of UV-Vis absorbance spectrum of AgNPs and (b) color change of the AgNPs dispersion upon the addition of400 120583g Lminus1 Hg2+ in the presence of 0005mol Lminus1 HNO

3

AgNPs blank

Abso

rban

ce (a

u)

400 500 600 700 800300Wavelength (nm)

00

05

10

15

20

25

30

0 휇g Lminus1

25 휇g Lminus1

125 휇g Lminus1

Hg2+

(a)

AgNPs blank

Abso

rban

ce (a

u)

00

05

10

15

20

25

30

400 500 600 700 800300Wavelength (nm)

25 휇g Lminus1

50 휇g Lminus1

100 휇g Lminus1

200 휇g Lminus1

300 휇g Lminus1

400 휇g Lminus1

500 휇g Lminus1

Hg2+

(b)

Figure 3 UV-Vis absorption responses of starch-stabilized AgNPs recorded 5min after the addition of Hg2+ with various concentrations (a)0ndash125 120583g Lminus1 Hg2+ and (b) 25ndash500 120583g Lminus1 Hg2+ in the presence of 0005mol Lminus1 HNO

3

Hg2+ (Figure 3(a)) is that at low Hg2+ concentrations theoxidative effect of NO

3

minus ions towards surface silver atoms isdominant In the presence of higher concentrations of Hg2+(Figure 3(b)) the surface of nanoparticles is protected by thelayer of Ag-Hg-amalgam due to the sorption and reduction

of positively charged Hg2+ on the surface of negativelycharged AgNPs followed by amalgamation In this way thesurface of AgNPs is inaccessible for oxidation by NO

3

minusEvidently within the range of 25ndash500 120583g Lminus1 Hg2+ the mainredox interaction is between the AgNPs and Hg2+ Such


Experimental data Linear fit

25 50 75 100 12500Hg2+ (휇g Lminus1)

076

078

080

082

084

086

088

090

092

094

096A

tA

0at

407

nm

(a)


100 200 300 400 5000Hg2+ (휇g Lminus1)

068

072

076

080

084

088

092

096

100

AtA

0at

407

nm

(b)

Figure 4 Plot of At1198600 as a function of the Hg2+ concentration over the ranges of (a) 0ndash125 120583g Lminus1 and (b) 25ndash500 120583g Lminus1 in the presence of0005mol Lminus1 HNO

3

behavioral dissimilarities of the analyte (Hg2+) for differentconcentration ranges have not been observed and reportedin the previous studies on the AgNPs-based optical sensingsystem for Hg2+ colorimetric detection We have to pointout however that none of these reports mention the acidityof the reaction media which most probably determines theoxidizing power of reagents in the system

For quantitative determination of Hg2+ the change ofthe intensity of LSPR band maximum of silver nanoparti-cles at 407 nm upon the addition of analyte with variousconcentrations was estimated as a ratio At1198600 where 1198600corresponds to the intensity of the absorbance maximumof blank AgNPs solution (without both NO

3

minus and Hg2+ions) and At corresponds to the intensity of the absorbancemaximum of silver nanoparticles 5min after the addition ofHg2+ standard solutions (Figure 4)

As indicated in Figures 4(a) and 4(b) linear correlationsexist between the relative value of the absorbance maximumintensity and the concentration of Hg2+ over the concentra-tion ranges 0ndash125 120583g Lminus1 (A = 07814 + 130 times 10minus2c with1198772 = 0995) and 25ndash500 120583g Lminus1 (A = 0991 minus 590 times 10minus4cwith 1198772 = 0993) respectively As a conclusion the opticalsensor studied using starch-stabilized AgNPs ensures a linearresponse over the concentration range from 09 to 125 120583g Lminus1which covers all environmentally relevant concentrationsof Hg and might be used for fast screening of Hg in theaquatic environment The second concentration range from25 to 500120583g Lminus1 Hg2+ can be successfully applied for thedetermination ofHg in highly contaminated and rarely foundindustrial wastewaters

33 Selectivity of Hg2+ Optical Sensing by Starch-CoatedAgNPs From an analytical point of view it is very important

K(I)

Na(

I)

Mg(

II)

Ca(I

I)

Cu(I

I)

Zn(I

I)

Pb(I

I)

Cd(

II)

Fe(I

II)

Co(

II)

Ni(I

I)

Hg(

II)

000

005

010

015

020

025

030

(A0minusA

t)A

0

Figure 5 Colorimetric response of starch-stabilized AgNPsrecorded 5min after the addition of 5 times 10minus5mol Lminus1 metal ions

to define the selectivity of the proposed system for colori-metric Hg2+ determinationThis has been evaluated throughthe response of the assay to various environmentally relevantmetal ions including Na+ K+ Mg2+ Ca2+ Pb2+ Cu2+ Zn2+Cd2+ Fe3+ Co2+ and Ni2+ under the same conditions as inthe case of Hg2+ The optical response of AgNPs to the testedions (concentration level of 50120583mol Lminus1) after 5min of theiraddition (separately for each ion) is illustrated in Figure 5 Forcomparison the optical response of AgNPs to the Hg2+ ionsat a concentration level of 25 120583mol Lminus1 is also presented

It is easy to observe that all other metal ions producea much weaker signal (almost at baseline level) except Fe3+which shows modest interference The reason is that onlyHg2+ can be reduced by surface atoms of AgNPs to formstable Ag-Hg amalgamThe addition of Fe3+ resulted in a tinyintensity decrease and red shift of the absorption band This


(a) (b)

20 nm

Figure 6 (a) TEM image (scale bar is 20 nm) and (b) corresponding SAED pattern of starch-coated silver nanoparticles after treatment byHg2+ solution at a concentration of 500 120583g Lminus1 in the presence of 0005mol Lminus1 HNO

3

Ag Hg2+

(1) Redox process

(2) Amalgamation

Metal bridging forceAggregation

Hg2+ ionsAgNPs

Ag+ ionsAgnHgm orand mercury atoms

eminus

eminus

Figure 7 The proposed mechanism of the interaction between starch-coated AgNPs and Hg2+ solution

effect could be interpreted in terms of Fe(III) complexationwith oxidized species of carbohydrates (starch and glucose)which are sorbed on the surface of silver nanoparticles [37]

34 Mechanism of Interaction between AgNPs and Hg2+ Toelucidate the mechanism of sensing activity of the starch-coated AgNPs towards Hg2+ the nanoparticles were exam-ined before and after Hg2+ exposure using TEM with SAEDobservations Figure 6 shows TEM micrograph with thecorresponding SAED pattern obtained from the agglomerateformed during interaction of AgNPs with Hg2+ solution at aconcentration of 500120583g Lminus1

As can be seen from Figure 6(a) the nanoparticles areof varying sizes and there is a large distribution after Hg2+exposure The TEM image shows a larger particle which issurrounded by smaller particles It seems that larger particlesare undergoing Ostwald ripening A similar observation isalready reported for gold nanoparticles utilized for mercuryremoval from drinking water [38] and for colorimetric detec-tion of Hg2+ using the AgNPs embedded in cyclodextrin-silicate composite [39]

The data from the analysis of SAED pattern (Figure 6(b))are summarized with interpretation accuracy of 1 in Table 1The analysis shows the existence of Ag

2Hg3amalgam (PDF

65-3156) and Ag (PDF 89-3722) as main phases in theaggregated mass formed during the interaction of starch-coated AgNPs with Hg2+ Some impurities of metallic Hg(PDF 01-1017) are also detected

On the basis of TEMSAED results a multistep inter-action of Hg2+ with the silver nanoparticles could beinferred The interaction involves (i) the electrostatic attrac-tion between negatively charged silver nanoparticles andpositively charged Hg2+ species decreasing the distancebetween nanoparticles (ii) adsorption of Hg2+ on the surfaceof AgNPs and their reduction to Hg0 by the surface Ag atoms(simultaneously obtained Ag+ diffuse into the solution)(iii) amalgamation of the freshly generated mercury atomswith the surface Ag atoms [25 32 39] (iv) the interactionof Hg2+ with AgNPs which decreases surface charges ofnanoparticles leading to their destabilization and aggrega-tion The latter one is confirmed by the shape evolution ofAgNPs observed in Figure 6(a)The suggested mechanism ofoptical sensing of Hg2+ by starch-coated silver nanoparticlesis illustrated in Figure 7

35 Analytical Application In order to test the applicabilityof the sensor developed for Hg2+ and total Hg determinationsamples of tap water (Sofia) andmineral water (Gorna Bania


Table 1 SAED data of AgNPs aggregates formed after exposure of silver nanoparticles to Hg2+ at concentration of 500120583g Lminus1 in the presenceof 0005mol Lminus1 HNO

3 (ℎ119896119897)f double electron diffraction effects SAED interpretation accuracy 1

d (A) Relative intensity

AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23

2438 s mdash 101 (410)f2136 s mdash mdash 3321506 s mdash mdash 6221287 s (310)f mdash 2371057 w mdash 205 9300979 w (410)f mdash 059s strong w weak

Table 2 Comparison of different methods using silver nanoparticles as a colorimetric sensing probe for Hg2+ determination

Sensing probe Linear concentration range Detection limit RefStarch-stabilized AgNPs 50 nmol Lminus1ndash5000 nmol Lminus1 25 nmol Lminus1 [23]Unmodified AgNPs stabilized withextract of soap-root plant 10ndash100 120583mol Lminus1 22 120583mol Lminus1 [26]

Gum kondagogu-stabilized AgNPs 50ndash500 nmol Lminus1 50 nmol Lminus1(LOQ) [31]

Citrate-capped AgNPs 002 nmol Lminus1ndash09 120583mol Lminus1 mdash [33]1-Dodecanethiol-capped Ag nanoprismsupon the presence of iodides 10ndash4000 nmol Lminus1 33 nmol Lminus1 [40]

Poly(vinylpyrrolidone)-stabilized AgNPs 1 nmol Lminus1ndash30 120583mol Lminus1 1 nmol Lminus1 [41]Carrageenan-functionalized AgAgClNPs 1ndash100 120583mol Lminus1 1 120583mol Lminus1 [42]

Starch-coated AgNPs in the presence of0005mol Lminus1 HNO

3

45ndash2500 nmol Lminus1 45 nmol Lminus1 This work

Kniagevo) were spiked at levels close to the permissiblelimit (drinking water) of 1 120583g Lminus1 Total Hg content in thesesamples was defined preliminarily by ICP-MS and results forall samples were below 005120583g Lminus1 Hg Recoveries achievedusing the described procedure are in the range 93ndash97thus confirming the possibility of fast Hg2+ screening indrinking waters using the proposed sensor based on starch-coated AgNPs The limits of detection (LOD) and limits ofquantification (LOQ) were evaluated on the basis of repeatedanalysis of blank (AgNPs) The calculations were based on3120590 and 10120590 criteria using the linear regression equationsand slopes of calibration graphs for Hg2+ (Figure 4) Thedefined values for LOD (09 120583g Lminus1) and LOQ (27 120583g Lminus1)show that the proposed sensor is not suitable for surfacewater monitoring but might be successfully used for faston-site control of the quality of sources for drinking waterWithin-batch precision strongly depends on the analyteconcentration in the measuring solution 9ndash12 for Hg2+ inthe range 09ndash125 120583g Lminus1 and 5ndash9 forHg2+ in the range over25ndash500 120583g Lminus1 Table 2 further summarizes the linear rangesand detection limits of variousHg2+ detectionmethods based

on silver nanoparticles as a colorimetric sensing probe It isevident that the proposed method ensures higher or equalsensitivity with those of earlier reported colorimetric AgNPs-based sensors [23 26 31 33 40ndash42]

For partial validation of the procedure CRM EstuarineWater BCR505 was analyzed after solid phase extraction (10-fold Hg enrichment) [43] Three sample aliquots of 800120583Lwere analyzed according to the proposed analytical proce-dureThe result of 073 plusmn 008 nmol Lminus1 Hg was in reasonableagreement with the (additional material information) valueof 069 nmol kgminus1 Hg (138 120583g Lminus1)

4 Conclusions

A simple fast and low cost analytical procedure is developedfor easy and sensitive quantification of Hg2+ in the presenceof 0005mol Lminus1 HNO

3by using starch-coated AgNPs as a

LSPR-based optical sensor The Hg2+ sensing is based onthe optical response (change in the absorbance strength ofLSPR band) of silver nanoparticles depending on the Hg2+concentration Possible mechanism of interaction between


AgNPs and Hg2+ was proposed An accurate and reliabledetermination of Hg is achieved in two concentration ranges09ndash125 120583g Lminus1 and 25ndash500120583g Lminus1 The limits of detectionand quantification achieved were 09120583g Lminus1 and 27120583g Lminus1respectively and relative standard deviations varied in therange 9ndash12 for Hg content from 09 to 125 120583g Lminus1 and 5ndash9for Hg levels from 25 to 500120583g Lminus1 The LSPR-based opticalsensor for Hg(II) might be used for simple and fast on-sitescreening of sources for abstraction of drinking water and forHg determination in wastewaters

Conflicts of Interest

The authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

The authors acknowledge the support by the Horizon 2020program of the European Commission (project MaterialsNetworking)

References

[1] D W Boening ldquoEcological effects transport and fate ofmercury a general reviewrdquo Chemosphere vol 40 no 12 pp1335ndash1351 2000

[2] P Holmes K A F James and L S Levy ldquoIs low-levelenvironmentalmercury exposure of concern to human healthrdquoScience of the Total Environment vol 408 no 2 pp 171ndash1822009

[3] H Erxleben and J Ruzicka ldquoAtomic absorption spectroscopyfor mercury automated by sequential injection and miniatur-ized in lab-on-valve systemrdquo Analytical Chemistry vol 77 no16 pp 5124ndash5128 2005

[4] L-P Yu and X-P Yan ldquoFlow injection on-line sorption precon-centration coupled with cold vapor atomic fluorescence spec-trometry and on-line oxidative elution for the determination oftrace mercury in water samplesrdquo Atomic Spectroscopy vol 25no 3 pp 145ndash153 2004

[5] M J Bloxham S J Hill and P J Worsfold ldquoDeterminationof mercury in filtered sea-water by flow injection with on-lineoxidation and atomic fluorescence spectrometric detectionrdquoJournal of Analytical Atomic Spectrometry vol 11 no 7 pp 511ndash514 1996

[6] M Lombardo I Vassura D Fabbri and C Trombini ldquoAstrikingly fast route to methylmercury acetylides as a newopportunity for monomethylmercury detectionrdquo Journal ofOrganometallic Chemistry vol 690 no 3 pp 588ndash593 2005

[7] L Liu Y-W Lam and W-Y Wong ldquoComplexation of 441015840-di(tert-butyl)-5-ethynyl-221015840-bithiazole with mercury(II) ionsynthesis structures and analytical applicationsrdquo Journal ofOrganometallic Chemistry vol 691 no 6 pp 1092ndash1100 2006

[8] A Caballero R Martınez V Lloveras et al ldquoHighly selectivechromogenic and redox or fluorescent sensors of Hg2+ in aque-ous environment based on 14-disubstituted azinesrdquo Journal ofthe American Chemical Society vol 127 no 45 pp 15666ndash156672005

[9] H Zheng Z-H Qian L Xu F-F Yuan L-D Lan and J-G Xu ldquoSwitching the recognition preference of rhodamine B

spirolactam by replacing one atom design of rhodamine Bthiohydrazide for recognition of Hg(II) in aqueous solutionrdquoOrganic Letters vol 8 no 5 pp 859ndash861 2006

[10] Y Zhao and Z Zhong ldquoTuning the sensitivity of a foldamer-based mercury sensor by its folding energyrdquo Journal of theAmerican Chemical Society vol 128 no 31 pp 9988ndash99892006

[11] HWang YWang J Jin andR Yang ldquoGold nanoparticle-basedcolorimetric and ldquoturn-onrdquo fluorescent probe for mercury(II)ions in aqueous solutionrdquo Analytical Chemistry vol 80 no 23pp 9021ndash9028 2008

[12] X Liu Y Tang LWang et al ldquoOptical detection ofmercury(II)in aqueous solutions by using conjugated polymers and label-free oligonucleotidesrdquo Advanced Materials vol 19 no 11 pp1471ndash1474 2007

[13] I-B Kim and U H F Bunz ldquoModulating the sensory responseof a conjugated polymer by proteins an agglutination assayfor mercury ions in waterrdquo Journal of the American ChemicalSociety vol 128 no 9 pp 2818ndash2819 2006

[14] S-J Liu H-G Nie J-H Jiang G-L Shen and R-Q Yu ldquoElec-trochemical sensor for mercury(II) based on conformationalswitchmediated by interstrand cooperative coordinationrdquoAna-lytical Chemistry vol 81 no 14 pp 5724ndash5730 2009

[15] Z Zhu Y Su J Li et al ldquoHighly sensitive electrochemi-cal sensor for mercury(II) ions by using a mercury-specificoligonucleotide probe and gold nanoparticle-based amplifica-tionrdquo Analytical Chemistry vol 81 no 18 pp 7660ndash7666 2009

[16] D ZhangM Deng L Xu Y Zhou J Yuwen and X Zhou ldquoThesensitive and selective optical detection of mercury(II) ions byusing a phosphorothioate DNAzyme strategyrdquo ChemistrymdashAEuropean Journal vol 15 no 33 pp 8117ndash8120 2009

[17] M Hollenstein C Hipolito C Lam D Dietrich and D MPerrin ldquoA highly selective DNAzyme sensor for mercuric ionsrdquoAngewandte ChemiemdashInternational Edition vol 47 no 23 pp4346ndash4350 2008

[18] M Rex F E Hernandez and A D Campiglia ldquoPushingthe limits of mercury sensors with gold nanorodsrdquo AnalyticalChemistry vol 78 no 2 pp 445ndash451 2006

[19] Y Wang F Yang and X Yang ldquoColorimetric detection ofmercury(II) ion using unmodified silver nanoparticles andmercury-specific oligonucleotidesrdquo ACS Applied Materials andInterfaces vol 2 no 2 pp 339ndash342 2010

[20] Y-R Kim R K Mahajan J S Kim and H Kim ldquoHighlysensitive gold nanoparticle-based colorimetric sensing of mer-cury(II) through simple ligand exchange reaction in aqueousmediardquo ACS Applied Materials and Interfaces vol 2 no 1 pp292ndash295 2010

[21] D V Talapin J-S Lee M V Kovalenko and E V ShevchenkoldquoProspects of colloidal nanocrystals for electronic and optoelec-tronic applicationsrdquo Chemical Reviews vol 110 no 1 pp 389ndash458 2010

[22] Y-L Hung T-M Hsiung Y-Y Chen Y-F Huang and C-CHuang ldquoColorimetric detection of heavymetal ions using label-free gold nanoparticles and alkanethiolsrdquoThe Journal of PhysicalChemistry C vol 114 no 39 pp 16329ndash16334 2010

[23] Y Fan Z Liu L Wang and J Zhan ldquoSynthesis of starch-stabilized Ag nanoparticles and Hg2+ recognition in aqueousmediardquoNanoscale Research Letters vol 4 no 10 pp 1230ndash12352009


[24] G V Ramesh and T P Radhakrishnan ldquoA universal sensorfor mercury (Hg HgI HgII) based on silver nanoparticle-embedded polymer thin filmrdquo ACS Applied Materials amp Inter-faces vol 3 pp 988ndash994 2011

[25] E Sumesh M S Bootharaju Anshup and T Pradeep ldquoApractical silver nanoparticle-based adsorbent for the removal ofHg2+ from waterrdquo Journal of Hazardous Materials vol 189 no1-2 pp 450ndash457 2011

[26] K Farhadi M Forough R Molaei S Hajizadeh and ARafipour ldquoHighly selective Hg2+ colorimetric sensor usinggreen synthesized and unmodified silver nanoparticlesrdquo Sensorsand Actuators B Chemical vol 161 no 1 pp 880ndash885 2012

[27] G Maduraiveeran and R Ramaraj ldquoEnhanced sensing of mer-curic ions based on dinucleotide-functionalized silver nanopar-ticlesrdquo Analytical Methods vol 8 no 44 pp 7966ndash7971 2016

[28] A Jeevika andD R Shankaran ldquoFunctionalized silver nanopar-ticles probe for visual colorimetric sensing of mercuryrdquoMateri-als Research Bulletin vol 83 pp 48ndash55 2016

[29] Y Ma Y Pang F Liu H Xu and X Shen ldquoMicrowave-assistedultrafast synthesis of silver nanoparticles for detection of Hg2+rdquoSpectrochimica Acta Part A Molecular and Biomolecular Spec-troscopy vol 153 pp 206ndash211 2016

[30] Z Guo G Chen G Zeng et al ldquoUltrasensitive detection andco-stability of mercury(II) ions based on amalgam formationwith Tween 20-stabilized silver nanoparticlesrdquo RSC Advancesvol 4 no 103 pp 59275ndash59283 2014

[31] L Rastogi R B SashidharDKarunasagar and J ArunachalamldquoGum kondagogu reducedstabilized silver nanoparticles asdirect colorimetric sensor for the sensitive detection of Hg2+ inaqueous systemrdquo Talanta vol 118 pp 111ndash117 2014

[32] S S Ravi L R Christena N Saisubramanian and S PAnthony ldquoGreen synthesized silver nanoparticles for selectivecolorimetric sensing of Hg2+ in aqueous solution at wide pHrangerdquo Analyst vol 138 no 15 pp 4370ndash4377 2013

[33] G-L Wang X-Y Zhu H-J Jiao Y-M Dong and Z-J LildquoUltrasensitive and dual functional colorimetric sensors formercury (II) ions and hydrogen peroxide based on catalyticreduction property of silver nanoparticlesrdquo Biosensors andBioelectronics vol 31 no 1 pp 337ndash342 2012

[34] P Vasileva B Donkova I Karadjova and C Dushkin ldquoSynthe-sis of starch-stabilized silver nanoparticles and their applicationas a surface plasmon resonance-based sensor of hydrogenperoxiderdquo Colloids and Surfaces A Physicochemical and Engi-neering Aspects vol 382 no 1ndash3 pp 203ndash210 2011

[35] PMulvaney ldquoSurface plasmon spectroscopy of nanosizedmetalparticlesrdquo Langmuir vol 12 no 3 pp 788ndash800 1996

[36] T Morris H Copeland E McLinden S Wilson and GSzulczewski ldquoThe effects of mercury adsorption on the opticalresponse of size-selected gold and silver nanoparticlesrdquo Lang-muir vol 18 no 20 pp 7261ndash7264 2002

[37] S Komulainen J Pursiainen P Peramaki and M LajunenldquoComplexation of Fe(III) with water-soluble oxidized starchrdquoStarch vol 65 no 3-4 pp 338ndash345 2013

[38] K P Lisha Anshup and T Pradeep ldquoTowards a practicalsolution for removing inorganic mercury from drinking waterusing gold nanoparticlesrdquo Gold Bulletin vol 42 no 2 pp 144ndash152 2009

[39] SManivannan andR Ramaraj ldquoSilver nanoparticles embeddedin cyclodextrin-silicate composite and their applications inHg(II) ion and nitrobenzene sensingrdquo Analyst vol 138 no 6pp 1733ndash1739 2013

[40] L Chen X Fu W Lu and L Chen ldquoHighly sensitive andselective colorimetric sensing ofHg2+ based on themorphologytransition of silver nanoprismsrdquo ACS Applied Materials andInterfaces vol 5 no 2 pp 284ndash290 2013

[41] L Li L Gui and W Li ldquoA colorimetric silver nanoparticle-based assay forHg(II) using lysine as a particle-linking reagentrdquoMicrochimica Acta vol 182 no 11-12 pp 1977ndash1981 2015

[42] K B Narayanan and S S Han ldquoHighly selective and quantita-tive colorimetric detection of mercury(II) ions by carrageenan-functionalizedAgAgCl nanoparticlesrdquoCarbohydrate Polymersvol 160 pp 90ndash96 2017

[43] E K Mladenova I G Dakova D L Tsalev and I B KaradjovaldquoMercury determination and speciation analysis in surfacewatersrdquo Central European Journal of Chemistry vol 10 no 4pp 1175ndash1182 2012

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 201

International Journal ofInternational Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal ofInternational Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


for colorimetric sensing of Hg2+ ions because the inter-action between the nanoparticles and the analyte changesthe intensity andor position of the absorption band in thevisible spectrum which often might be observed with thenaked eye [22]The limitations observed for these systems aremainly connected with poor selectivity high detection limitfor Hg(II) complicated synthesis of the probe materials orcomplicated analytical procedures

In this study we present a new colorimetric assay forHg2+ ions in 0005mol Lminus1 HNO

3using starch-stabilized

silver nanoparticles (AgNPs) A change in the absorbancestrength is expected as a result of the redox interactionbetween AgNPs and either Hg2+ ions or NO

3

minus ions The Hgconcentration determines which of these two redox reactionsdominates as the two oxidants compete with each other forAg oxidationThisway detection of very low environmentallyrelevant Hg contents is possible Several sensing systemshave been already reported based on the interaction betweenAgNPs and Hg(II) ions [23ndash32] however detailed study ofHg behavior in the presence of another competitive oxidantis rarely performed and discussed A dual functional sensorfor determination of Hg and H

2O2has been developed

based on a similar approach addition of H2O2to a mixture

of AgNPs and Hg(II) ions [33] The method presented inthis study however differs not only as a mechanism ofthe process but also as a behavior of Hg2+ ions at verylow concentrations (below 25 120583g Lminus1) towards AgNPs in thepresence of NO

3

minus ions as a second oxidant A simple andfast analytical procedure for determination of Hg in drinkingwaters is developed and verified by the analysis of a certifiedreference material

2 Materials and Methods

21 Apparatus UV-Vis absorption spectra were recorded onan Evolution 300 spectrometer (Thermo Scientific USA)within the 200ndash800 nm range using quartz cuvettes with 1 cmoptical path length High-purity water was used as a ref-erence sample for background absorption The morphologyand particle sizes were examined using a high-resolutiontransmission electron microscope (TEM JEOL JEM-2100operating at an accelerating voltage of 200 kV) A volumeof 5 120583L AgNPs suspension was placed on a carbon-coveredcopper grid for TEM and air-dried The histogram of AgNPssize distribution and the mean diameter of nanoparticleswere determined by counting at least 200 nanoparticlesfrom the different TEM images using ImageJ software Somestructural details of the nanoparticles were analyzed usingthe high-resolution TEM image and SAED pattern The zeta(120577) potential of nanoparticles was measured with a ZetaSizerNano ZS (Malvern) instrument

22 Chemicals All chemicals used were of analytical-reagentgrade and all aqueous solutions were prepared in high-puritywater (Millipore Corp Milford MA USA) Silver nitrate(AgNO

3 998) soluble starch sodium hydroxide (NaOH

99) nitric acid (HNO3 65) salts of the different cations

studied (NaCl KCl MgCl2 CaCl

2 Pb(NO

3)2 ZnCl

2 CuCl

2

NiCl2 CdCl

2 CoCl

2 and FeCl

3) (from Merck Germany)

and pharmaceutical grade D-(+) glucose (from Alfa AesarGermany) were used Stock Hg standard solution TraceCEPT 998 120583gmLminus1 in 2mol Lminus1 HNO

3(Sigma-Aldrich

USA) was used to prepare a working standard solution of1000 120583g Lminus1 Hg2+ in 001mol Lminus1 HNO

3 Standard solutions

for Hg within the concentration range of 0ndash1000 120583g Lminus1were prepared weekly by serial dilution of this solution in001mol Lminus1 HNO

3 All diluted Hg solutions were stored in

dark glass flasks and kept refrigerated at 4∘C

23 Synthesis and Characterization of Silver NanoparticlesThesynthesis ofAgNPs follows a green synthetic procedure asdescribed in our previous study [34]The silver nanoparticleswere obtained through a reduction reaction of silver nitratewith D-glucose as a reducing agent in the presence of starchas a stabilizer and suitable sodium hydroxide amount as areaction catalyst Briefly 24mL of 0001MAgNO

3and 48mL

of 02 solution of starch were mixed and left for at least 15minutes to form a complex under an ultrasonic treatment(ultrasonic bath power 100W frequency 38MHz) Afterthat 720120583L of 01M D-glucose was added and sonicatedfor 5 minutes The reaction was started by the addition of36mL of 01M NaOH and continued for one hour at aconstant temperature (30∘C) in an ultrasonic bath to ensurethe homogeneous formation of the silver nanoparticles

The as-prepared AgNPs were purified and concentratedthree times by ultracentrifugation (90min 14000 rpm) Thedispersion obtainedwas denoted as a stock solution of AgNPsand used in the experiments for colorimetric determinationof Hg2+ The AgNPs stock solution was kept in a darkglass flask at room temperature and was homogenized in anultrasonic bath for 30min prior to each experiment

24 Colorimetric Detection of Hg2+ Ions The colorimetricdetection of Hg2+ ions via starch-stabilized silver nanopar-ticles was conducted as follows an aliquot of 200120583L AgNPsstock solution and 300 120583L high-purity water were consecu-tively added to a small quartz cuvette followed by additionof 500 120583L Hg2+ solution with varying concentrations Theresultingmixturewas equilibrated by stirring onVortex for anoptimum incubation time and then the UV-Vis spectrum inthe wavelength range of 200ndash800 nm was recorded In orderto investigate the sensitivity of the colorimetric assay towardsother ions starch-stabilized AgNPs were allowed to interactunder the same conditions with 50 120583mol Lminus1 solutions ofalkali (Na+ K+) alkaline earth (Mg2+ Ca2+) Pb2+ andtransition-metal ions (Cu2+ Zn2+ Cd2+ Fe3+ Co2+ andNi2+) (separately for each ion) The resulting solutions weremonitored by optical absorption spectroscopy

25 Determination of Hg in TapUnderground Water Tapunderground water sample (20mL) was filtered through a045 120583m filter and acidified with HNO

3until reaching pH

in the range 2ndash23 Sample aliquot of 500120583L was transferredto a quartz cuvette and 200120583L stock solution of AgNPswas added and the mixture was stirred by the Vortex Afterthe incubation time of 5min the UV-Vis absorbance was


200 400 600 80000

05

10

15

20

25

30

Abso

rban

ce (a

u)


5nm20 nm




3and passed through






3


3





3(Figure 3)


3results


3


3


3 demon-


3


0(Ag+Ag0) = 0799V119864

0(Hg2+Hg0) = 0854V

1198640(NO3

minusNH4


3

minusNH4




Ag blank


Abso

rban

ce (a

u)

00

05

10

15

20

25

30

60min45min30min

15 min5min

407 nm

399 nm

400 500 600 700 800300Wavelength (nm)

(a) (b)


3

AgNPs blank

Abso

rban

ce (a

u)

400 500 600 700 800300Wavelength (nm)

00

05

10

15

20

25

30

0 휇g Lminus1

25 휇g Lminus1

125 휇g Lminus1

Hg2+

(a)

AgNPs blank

Abso

rban

ce (a

u)

00

05

10

15

20

25

30

400 500 600 700 800300Wavelength (nm)

25 휇g Lminus1

50 휇g Lminus1

100 휇g Lminus1

200 휇g Lminus1

300 휇g Lminus1

400 휇g Lminus1

500 휇g Lminus1

Hg2+

(b)


3


3



3




25 50 75 100 12500Hg2+ (휇g Lminus1)

076

078

080

082

084

086

088

090

092

094

096A

tA

0at

407

nm

(a)


100 200 300 400 5000Hg2+ (휇g Lminus1)

068

072

076

080

084

088

092

096

100

AtA

0at

407

nm

(b)


3



3




K(I)

Na(

I)

Mg(

II)

Ca(I

I)

Cu(I

I)

Zn(I

I)

Pb(I

I)

Cd(

II)

Fe(I

II)

Co(

II)

Ni(I

I)

Hg(

II)

000

005

010

015

020

025

030

(A0minusA

t)A

0





(a) (b)

20 nm


3

Ag Hg2+

(1) Redox process

(2) Amalgamation


Hg2+ ionsAgNPs


eminus

eminus






2Hg3amalgam (PDF








AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


200 400 600 80000

05

10

15

20

25

30

Abso

rban

ce (a

u)


5nm20 nm




3and passed through






3


3





3(Figure 3)


3results


3


3


3 demon-


3


0(Ag+Ag0) = 0799V119864

0(Hg2+Hg0) = 0854V

1198640(NO3

minusNH4


3

minusNH4




Ag blank


Abso

rban

ce (a

u)

00

05

10

15

20

25

30

60min45min30min

15 min5min

407 nm

399 nm

400 500 600 700 800300Wavelength (nm)

(a) (b)


3

AgNPs blank

Abso

rban

ce (a

u)

400 500 600 700 800300Wavelength (nm)

00

05

10

15

20

25

30

0 휇g Lminus1

25 휇g Lminus1

125 휇g Lminus1

Hg2+

(a)

AgNPs blank

Abso

rban

ce (a

u)

00

05

10

15

20

25

30

400 500 600 700 800300Wavelength (nm)

25 휇g Lminus1

50 휇g Lminus1

100 휇g Lminus1

200 휇g Lminus1

300 휇g Lminus1

400 휇g Lminus1

500 휇g Lminus1

Hg2+

(b)


3


3



3




25 50 75 100 12500Hg2+ (휇g Lminus1)

076

078

080

082

084

086

088

090

092

094

096A

tA

0at

407

nm

(a)


100 200 300 400 5000Hg2+ (휇g Lminus1)

068

072

076

080

084

088

092

096

100

AtA

0at

407

nm

(b)


3



3




K(I)

Na(

I)

Mg(

II)

Ca(I

I)

Cu(I

I)

Zn(I

I)

Pb(I

I)

Cd(

II)

Fe(I

II)

Co(

II)

Ni(I

I)

Hg(

II)

000

005

010

015

020

025

030

(A0minusA

t)A

0





(a) (b)

20 nm


3

Ag Hg2+

(1) Redox process

(2) Amalgamation


Hg2+ ionsAgNPs


eminus

eminus






2Hg3amalgam (PDF








AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Ag blank


Abso

rban

ce (a

u)

00

05

10

15

20

25

30

60min45min30min

15 min5min

407 nm

399 nm

400 500 600 700 800300Wavelength (nm)

(a) (b)


3

AgNPs blank

Abso

rban

ce (a

u)

400 500 600 700 800300Wavelength (nm)

00

05

10

15

20

25

30

0 휇g Lminus1

25 휇g Lminus1

125 휇g Lminus1

Hg2+

(a)

AgNPs blank

Abso

rban

ce (a

u)

00

05

10

15

20

25

30

400 500 600 700 800300Wavelength (nm)

25 휇g Lminus1

50 휇g Lminus1

100 휇g Lminus1

200 휇g Lminus1

300 휇g Lminus1

400 휇g Lminus1

500 휇g Lminus1

Hg2+

(b)


3


3



3




25 50 75 100 12500Hg2+ (휇g Lminus1)

076

078

080

082

084

086

088

090

092

094

096A

tA

0at

407

nm

(a)


100 200 300 400 5000Hg2+ (휇g Lminus1)

068

072

076

080

084

088

092

096

100

AtA

0at

407

nm

(b)


3



3




K(I)

Na(

I)

Mg(

II)

Ca(I

I)

Cu(I

I)

Zn(I

I)

Pb(I

I)

Cd(

II)

Fe(I

II)

Co(

II)

Ni(I

I)

Hg(

II)

000

005

010

015

020

025

030

(A0minusA

t)A

0





(a) (b)

20 nm


3

Ag Hg2+

(1) Redox process

(2) Amalgamation


Hg2+ ionsAgNPs


eminus

eminus






2Hg3amalgam (PDF








AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



25 50 75 100 12500Hg2+ (휇g Lminus1)

076

078

080

082

084

086

088

090

092

094

096A

tA

0at

407

nm

(a)


100 200 300 400 5000Hg2+ (휇g Lminus1)

068

072

076

080

084

088

092

096

100

AtA

0at

407

nm

(b)


3



3




K(I)

Na(

I)

Mg(

II)

Ca(I

I)

Cu(I

I)

Zn(I

I)

Pb(I

I)

Cd(

II)

Fe(I

II)

Co(

II)

Ni(I

I)

Hg(

II)

000

005

010

015

020

025

030

(A0minusA

t)A

0





(a) (b)

20 nm


3

Ag Hg2+

(1) Redox process

(2) Amalgamation


Hg2+ ionsAgNPs


eminus

eminus






2Hg3amalgam (PDF








AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(a) (b)

20 nm


3

Ag Hg2+

(1) Redox process

(2) Amalgamation


Hg2+ ionsAgNPs


eminus

eminus






2Hg3amalgam (PDF








AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





AgPDF 89-3722a = 40855(1) ASG Fm3m

AgPDF 87-0598a = 28862 Ac = 10000 AP63mmc

Ag2Hg3

PDF 65-3156a = 100506 A

SG I23








3





4 Conclusions








Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





Acknowledgments


References























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

application of starch-stabilized silver nanoparticles as a...

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