Reduction of silver ions in gold nanoparticle suspension for detection of dihydroxybenzene isomers

Accepted Manuscript Title: Reduction of silver ions in gold nanoparticle suspension for detection of dihydroxybenzene isomers Author: Hoon Choi Taegyeong Kang Kiju Um Jinku Kim Kangtaek Lee PII: DOI: Reference:

S0927-7757(14)00596-2 http://dx.doi.org/doi:10.1016/j.colsurfa.2014.06.050 COLSUA 19329

To appear in:

Colloids and Surfaces A: Physicochem. Eng. Aspects

Received date: Revised date: Accepted date:

25-3-2014 25-6-2014 30-6-2014

Please cite this article as: H. Choi, T. Kang, K. Um, J. Kim, K. Lee, Reduction of silver ions in gold nanoparticle suspension for detection of dihydroxybenzene isomers, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2014), http://dx.doi.org/10.1016/j.colsurfa.2014.06.050 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Reduction of silver ions in gold nanoparticle suspension for

ip t

detection of dihydroxybenzene isomers

cr

Hoon Choia, Taegyeong Kanga, Kiju Uma, Jinku Kimb, Kangtaek Leea,*

a

Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul, Korea

us

To whom correspondence should be addressed:

M

*

Department of Bio and Chemical Engineering, Hongik University, Sejong, Korea

an

b

Ac ce p

te

d

TEL: +82-2-2123-2760; FAX: +82-2-312-6401; E-mail: [email protected]

1 Page 1 of 29

Abstract We have investigated the reduction of silver ions in a gold nanoparticle suspension by dihydroxybenzene isomers: hydroquinone (1,4-dihydroxybenzene), catechol (1,2-dihydroxybenzene), and resorcinol (1,3-dihydroxybenzene). We found that using these isomers as reducing agents

ip t

resulted in distinctive color changes of suspensions. When hydroquinone was added to suspensions

cr

containing cysteamine-modified gold nanoparticles and silver nitrate, the suspension changed from red to yellow because a silver shell formed on the gold nanoparticles. With catechol, the suspension

us

initially turned yellow from formation of core-shell nanoparticles, and then it became black following the polymerization of catechol on the nanoparticle surfaces. This caused charge reversal

an

followed by aggregation of core-shell nanoparticles. The addition of resorcinol, however, did not produce core-shell nanoparticles because its high oxidation peak potential prevented the reduction of

M

silver ions, keeping the suspension color unchanged. Based on the color changes, we could detect the concentration of hydroquinone and catechol with high sensitivity. Moreover, the addition of Fe(III)

d

ions enabled selective detection of hydroquinone in a mixture of dihydroxybenzene isomers by

Ac ce p

te

forming a chelate complex with catechol.

Keywords: dihydroxybenzene isomer; hydroquinone; catechol; resorcinol; silver ions; gold nanoparticles

2 Page 2 of 29

1. Introduction Three isomers of dihydroxybenzene, hydroquinone (HQ), catechol (CC), and resorcinol (RC), are widely used in the production of dyes, rubber, pesticides and pharmaceuticals in industry and agriculture [1]. In particular, HQ and CC have drawn much attention due to their unique oxidation

ip t

properties that permit them to be readily oxidized to quinone structures depending on the pH or

cr

presence of enzymes [2]. They can also be used in many applications: as reducing agents in the synthesis of various metal nanoparticles [3, 4] like other dihydroxyl organic molecules [5], inhibitors

us

of polymerization [6], and acceptors of electron transfer process [7]. For example, Jacob et al. reported that HQ and CC have weak reducibility to make silver nanoparticles [8]. Moreover, they

an

could be oxidized by peroxidase enzymes or pH adjustment for use as electron acceptors for fluorescence quenching [7, 9]. On the other hand, these isomers are regarded as environmental

M

pollutants because of their high toxicity and low degradability. In addition, it has also been reported that HQ and CC could promote tumors and increase the metastasis of lung cancer [10, 11]. Therefore,

d

it is important to develop a simple method to detect these isomers.

te

Detection of these isomers is usually based on their structures and oxidation properties, and

Ac ce p

several different techniques have been used for detection, including HPLC [12], spectrophotometry [13], chromatography [14], electrochemical methods [2, 15], fluorescence quenching of quantum dots [7] or silver nanoclusters [16], chemiluminescence [17], and pH-dependent phosphorescence of quantum dots [1]. In spite of the high sensitivity and accuracy of those methods, they still require expensive detection equipment, time-consuming processes, and complicated procedures. Recently, localized surface plasmon resonance (LSPR) has been extensively studied as a new tool for detection of analytes. For instance, colorimetric detection of analytes based on the change in the LSPR of gold or silver nanoparticle suspensions has many advantages over the conventional methods due to its simplicity, high sensitivity, and facile detection [3, 18]. Colorimetric tools using LSPR, however, have not been used to detect dihydroxybenzene isomers because of their similar redox potentials. Even though recent work by Liu et al. reported detection of silver ions using HQ as 3 Page 3 of 29

a reducing agent to form a silver shell on negatively-charged gold nanoparticles [19], reduction of silver ions on gold nanoparticles by three different isomers of dihydroxybenzene has not been systematically studied to date. Herein, we investigate the reduction of silver ions in gold nanoparticle suspensions by three

ip t

dihydroxybenzene isomers. In particular, we elucidate mechanisms responsible for distinctive color changes in suspensions with different isomers. Based on our findings, we demonstrate colorimetric

cr

detection of HQ and CC with high sensitivity. To the best of our knowledge, this is the first report

us

to systematically investigate color change of gold nanoparticle suspensions from reduction of silver

an

ions by three different dihydroxybenzene isomers, and apply in detection of those isomers.

M

2. Materials and methods 2.1. Materials

d

We purchased cysteamine hydrochloride, tetrachloroauric(III) acid (HAuCl4), silver nitrate

te

(AgNO3), sodium borohydride (NaBH4), hydroquinone (1,4-dihydroxybenzene, HQ), resorcinol

Ac ce p

(1,3-dihydroxybenzene, RC), catechol (1,2-dihydroxybenzene, CC), iron nitrate (Fe(NO3)3), potassium nitrate (KNO3), magnesium nitrate (MgNO3), copper nitrate (Cu(NO3)2), zinc nitrate (Zn(NO3)2), glucose (GL), sodium nitrate (NaNO3), ammonium nitrate (NH4NO3), sodium citrate dihydrate, and calcium chloride (CaCl2) from Aldrich. Deionized (DI) water from a Millipore water purification system was used for all experiments.

2.2. Preparation of gold nanoparticles A method modified from Lee et al. [20] was used to prepare cysteamine-modified gold nanoparticles ((+)AuNPs). Briefly, 400 μL of 213 mM cysteamine solution was added to 40 mL of 1.42 mM HAuCl4 solution at room temperature. After stirring for 20 min, 1 mL of freshly prepared 1 mM NaBH4 solution was added dropwise into the orange colored mixture for 2 min and stirred for 3 4 Page 4 of 29

h at room temperature in the dark. The resulting red colored suspension was centrifuged at 3,000 rpm for 30 min to remove large aggregates. Because the chloride ions from cysteamine hydrochloride and chloroauric acid can form AgCl in the detection step and interfere with UV-vis spectra, extensive dialysis with a Spectra/Por dialysis membrane (MW: 10 kDa) was performed for

ip t

48 h. After dialysis, the pH of the (+)AuNP suspension was 7.1, and it was stored at 4oC and used within 7 days.

cr

Negatively-charged gold nanoparticles ((-)AuNPs) were prepared by the citrate reduction method

us

[21]. Briefly, 100 mL of 1 mM HAuCl4 solution was heated in a heating mantle with vigorous stirring. Upon boiling, 10 mL of 38.8 mM sodium citrate solution was added quickly. The solution

an

was further boiled for 30 min and cooled to room temperature with stirring. The rest of the

2.3. Reduction of silver ions on AuNPs

M

experimental procedures were identical to those for (+)AuNPs.

d

For reduction of silver ions on AuNPs, 20 μL of as-prepared AuNP suspension was diluted with

te

950 μL of DI water. Then, 20 μL of 10 mM AgNO3 and 10 μL of 10 mM HQ, CC, or RC solution

Ac ce p

were added to the AuNP suspension. In all experiments, the concentration of AuNPs was adjusted so that absorbance at 521 nm was 0.15.

For comparison, we also performed three control experiments with suspensions containing (+)AuNPs and 100 μM HQ, (+)AuNPs and 200 μM AgNO3, or 100 μM HQ and 200 μM AgNO3. These mixtures were allowed to react for 1 h at room temperature, and UV-vis absorption spectroscopy was used to observe spectral changes. To examine the effect of CC polymers on UVvis spectra, we induced aggregation of particles formed by HQ by adding 50 μL of 1 mM NaCl to 950 μL of suspension.

2.4. Detection of hydroquinone and catechol

5 Page 5 of 29

Concentration of silver ions was optimized for detection of HQ and CC. Different volumes (0 – 30 μL) of 10 mM AgNO3 solution were added to the (+)AuNP suspensions, followed by addition of 20 μL of 10 mM HQ and DI water so that the final volume was 1 mL. Next, detection experiments for HQ and CC were carried out by adding HQ or CC at varying concentrations (1 – 150 μM) to the

ip t

(+)AuNP suspensions in which the concentration of AgNO3 was set to 200 μM.

To test selective detection of HQ, 50 μL of solution containing various ions and molecules (RC,

cr

GL, Fe3+, K+, Mg2+, Cu2+, Zn2+, Na+, NH4+, Ca2+) at 10 mM was added to the mixture of HQ and CC

us

with or without Fe(III) ions. The mixture was incubated for 10 min and then added to the (+)AuNP suspensions. The final concentration of CC was set to 100 μM, those of Ag and Fe(III) ions to 200

an

μM, and HQ concentration was varied from 0 to 120 μM.

UV-vis absorption spectra of all samples were taken after 1 h, and the variations in absorbance

M

were recorded at 400 nm for HQ and at 700 nm for CC. In kinetic study, UV-vis spectra were taken

te

2.5. Characterization

d

every 10 min until saturated.

Ac ce p

A UV-vis spectrometer (Analytik Jena Specord 210) was used to monitor spectral changes of the (+)AuNP suspensions. We used quasi-elastic light scattering (QELS) and zeta potential measurement (Malvern Nano-ZS) to determine the size distribution and zeta potential of (+)AuNPs. Transmission electron microscopy (TEM, JEOL JEM-2010, 200kV) and high-resolution transmission electron microscopy with energy dispersive X-ray analysis (TEM-EDX, JEOL JEM2100, 200kV) were used to observe the morphology and composition of nanoparticles. Weight loss of the particles formed by HQ or CC was measured by thermogravimetric analysis (TGA, TA instruments SDT Q600) at a heating rate of 10ºC min-1 and an N2 gas purging rate of 100 ml cc-1.

3. Results and discussion 6 Page 6 of 29

3.1. Reduction of silver ions on the cysteamine-modified AuNPs by HQ, CC, and RC The average hydrodynamic diameter, as determined by QELS, and zeta potential of (+)AuNPs were 16 nm and +33.4 ± 6.5 mV, respectively. This is consistent with the TEM micrograph in Fig. 1a. As-synthesized (+)AuNPs exhibited a localized surface plasmon band at 521 nm, as shown in Fig.

ip t

2b.

The suspension was then mixed with AgNO3 solution, followed by addition of a

cr

dihydroxybenzene isomer (HQ, CC, or RC). Addition of HQ or CC to (+)AuNP suspensions

us

containing silver ions caused a change in suspension color, but addition of RC did not: After reacting for 1 h at room temperature, HQ changed the color from red to yellow, and CC changed the color to

an

black, as shown in Fig. 2a. The color change of suspensions with HQ and CC is believed to be caused by the formation of silver by reduction of silver ions. This is consistent with the UV-vis

M

absorption spectra in Fig. 2a that shows the appearance of a new resonance peak at ~400 nm only with HQ and CC due to formation of silver. In addition, the suspension with CC exhibited a broad

d

peak at >600 nm, which was responsible for its black color.

te

TEM micrographs in Figs. 1b-d demonstrate formation of spherical Au-Ag core-shell

Ac ce p

nanoparticles when HQ or CC was used: HQ formed ~4 nm thick Ag shell on (+)AuNPs, whereas the core-shell particles formed by CC exhibited an aggregated structure. Elemental analysis from TEM-EDX data also supported the formation of Ag shells on the (+)AuNPs (Fig. S1). It is interesting to note that a thin polymer-like film appeared on the aggregated nanoparticles when CC was used, which was not observed with HQ. Note that the suspension with CC became transparent after 24 h because sedimentation of the aggregates occurred. Since the LSPR of Au/Ag bimetallic nanoparticles is known to be governed by their composition, size, structure, and dielectric constant, it is reasonable to expect that the shape of core-shell particles, relative Ag concentration, and aggregation state of particles should determine LSPR in our system [22, 23].

3.2. Rationalization of color changes with HQ, CC, and RC 7 Page 7 of 29

Because HQ and CC possess similar reducing ability, they have widely been used as mild reducing agents in the synthesis of metal nanoparticles [3, 4]. The dihydroxyl groups of HQ and CC are believed to provide two electrons and change to quinone form when they are oxidized in the presence of enzymes or a catalyst, which allows the reduction of two silver ions [8]. This was

ip t

confirmed by the decrease of solution pH from ~7 to ~4 after the redox reaction as the oxidized HQ or CC released protons, making the solution more acidic. On the other hand, RC did not show any

cr

color change because it has a high oxidation peak potential, so it rarely participates in a redox

us

reaction [1]. This could be due to its meta structure that could provide resonance-stabilized species [24].

an

Control experiments (Fig. 2b) show that no peak was observed when HQ and Ag ions were present without (+)AuNPs. When (+)AuNPs were mixed with only Ag ions or HQ, the resonance

M

peak at 521 nm did not change except that slight aggregation occurred with Ag ions. This suggests that (+)AuNPs are required to initiate a redox reaction between Ag ions and HQ. It is well known

d

that metal nanoparticles can have catalytic activity that is not exhibited in the bulk state because

te

electron density on the surface is much higher in nanoscale [25, 26]. Accordingly, high electron

Ac ce p

density on the surface of (+)AuNPs could be beneficial to the electron transfer process. In addition, similar lattice parameters between Au and Ag could enhance reduction of Ag ions on (+)AuNPs [22]. Therefore, both HQ and CC could readily donate two electrons to Ag ions, which results in deposition of a Ag shell onto the (+)AuNPs. This confirms that the (+)AuNPs were used not only as colloidal substrates, but also as a catalyst, which is consistent with previous reports [19, 23]. Furthermore, aggregation of core-shell particles with CC could be explained as follows. It is known that CC can undergo polymerization upon oxidation under basic condition or in the presence of enzymes or a catalyst, producing brown melamine-like pigments [27]. This is because quinone forms of oxidized CC can easily make radical intermediate species that can react with phenoxyl radicals or other functional groups, such as amines and thiols [28]. In addition, it has been reported that CC could be polymerized in the presence of Ag nanoparticles [29]. Thus, we suspect that the Ag 8 Page 8 of 29

shell of core-shell particles acted as a catalyst to polymerize CC and form a thin film on the surface of (+)AuNPs through electrostatic attraction between the negatively-charged CC polymer and the positively-charged particles. To confirm this hypothesis, the difference in weight loss between the samples with CC and HQ was compared using TGA. Fig. S2 shows no significant weight loss with

ip t

HQ, indicating that no organic compounds were attached on the Au-Ag core-shell particles. However, the sample with CC exhibited 3.3 % weight loss in the 200 – 400ºC region where most

cr

carbon-based materials could be decomposed [30]. This is consistent with a rough estimate (4.8 %

us

loss) calculated by assuming spherical particles with uniform size distribution and confirms that the thin polymer-like film on the particles seen in the TEM micrographs consisted of polymerized CC.

an

We have also investigated the effect of surface charge on AuNPs by using negatively-charged ()AuNPs. We found that the addition of HQ, CC, and RC to the mixtures of (-)AuNPs and AgNO3

M

showed similar changes in suspension color except that CC changed the color to yellow instead of black (Fig. 3a). Moreover, a TEM micrograph of the particles formed by CC showed neither

d

significant aggregation nor formation of a CC polymer film on the particles (Fig. 3c). When (-

te

)AuNPs were used, TEM showed that CC polymers formed separately from core-shell particles

Ac ce p

because of electrostatic repulsion between the negatively-charged CC polymer and the (-)AuNPs (results not shown). This is supported by the TGA data of the core-shell particles formed by CC on (-)AuNPs because only 0.5 % weight loss was observed over the entire region except for a slight weight loss due to moisture in the 100 – 150 ºC region (Fig. S2). Moreover, all the particles made from (-)AuNPs showed negative zeta potential (-34.5 – -50 mV) before and after formation of the Ag shell. On the other hand, the zeta potential of the particles made from (+)AuNPs was +22.5 ± 4.8 mV with HQ, but it changed from +17 ± 9.5 mV (after 30 min) to 18.1 ± 4.0 mV (after 60 min) with CC. Therefore, charge reversal occurred for (+)AuNPs with CC because of the high content of negatively-charged CC. We suspect that aggregation occurred when (+)AuNPs were used, not only by crosslinking of particles during CC polymerization, but also by

9 Page 9 of 29

destabilization of particles during charge reversal. A schematic illustration of particle morphology formed by the addition of HQ, CC, and RC to (+)AuNPs is shown in Fig. 4.

ip t

3.3. Detection of HQ and CC from color change of (+)AuNP suspensions Based on the above results, we examined the possibility of using the distinctive color change of a

cr

(+)AuNP suspension to detect HQ and CC. First, we investigated the effect of Ag ion concentration and kinetics using UV-vis absorption spectroscopy. Increasing Ag ion concentration increased the

us

absorption intensity at 400 nm that was caused by reduction of Ag ions and subsequent formation of an Ag shell on (+)AuNPs (Fig. S3). Upon addition of HQ or CC, absorption intensity at 400 nm

an

rapidly increased, and >90% conversion was achieved within 30 min, reaching a plateau after 60 min (Fig. 5a).

M

Next, we studied the effect of analyte concentration. Figs. 6a-b show that a new peak appeared at ~400 nm 60 min after addition of HQ, and its intensity increased monotonically as the HQ

d

concentration increased, which is consistent with the color change of the suspension. Because the

te

intensity of the resonance peak is known to depend on the thickness of the Ag shell [19], an increase

Ac ce p

in the HQ concentration increased the thickness of the Ag shell and hence the absorption intensity at 400 nm. The inset in Fig. 6b shows the linear regression of absorption intensity as a function of HQ concentration in the range of 1 – 100 μM. The limit of detection (3.3δ/slope) was calculated to be 54 nM, which is comparable to results from other methods [1, 7, 15]. In the case of CC, Ag ions were initially reduced to form a Ag shell on (+)AuNPs, which increased absorbance at 400 nm for 30 min (Fig. 5b). After 30 min, however, absorbance at 400 nm decreased, and a new peak appeared at >600 nm, which turned the color of the suspension to black after ~45 min. Moreover, the intensity of the new peak increased and showed a redshift as the concentration of CC increased, as shown in Fig. 6c. Note that the color of the suspension changed from yellow (30 min) to black (60 min) at high CC concentrations (Fig. 6d). There are two possible

10 Page 10 of 29

explanations for the appearance of a new peak at >600 nm: (1) aggregation of particles; (2) presence of CC polymers on particles. To test whether aggregation was responsible for the new peak, we induced aggregation of particles formed by HQ using salt addition. Fig. S4 demonstrates that aggregated particles did not exhibit a new peak at >600 nm even though the suspension showed a

ip t

similar color change to dark brown. In most studies concerning Au-Ag core-shell nanoparticles, a distinctive peak at >600 nm has been reported rarely, except for asymmetrical structural changes or

cr

polymer-covered particles [23, 30]. Because our core-shell particles were covered with a CC

us

polymer, and the polymers on the surface of the Ag shell could be regarded as asymmetric dielectric coatings [23, 32], it is reasonable to expect that a CC polymer on the core-shell particles is

an

responsible for the strong absorption band at >600 nm. This is also supported by the fact that the absorbance at 700 nm increased with an increase in CC concentration, as shown in Fig. 6c. We

M

selected 60 min as the detection time because absorption intensity at both 400 nm and 700 nm reached a plateau after 60 min (Fig. 5b). We could thus successfully detect the CC concentration

d

with a detection limit of 5 μM by monitoring the absorbance at 700 nm, as shown in Fig. 6d.

te

To see if we could selectively detect HQ from mixtures of dihydroxybenzene isomers, we added

Ac ce p

HQ and CC to the suspensions containing (+)AuNPs and AgNO3. We found that aggregation of core-shell particles occurred when the concentration of CC was above 50 μM or higher than the concentration of HQ. This suggests that HQ might act as an inhibitor to CC polymerization [6], or HQ could predominantly adsorb on the surface of core-shell particles, preventing CC polymerization on the surface [33]. To minimize the effect of aggregation caused by CC, we use CC’s ironsequestering ability to form a chelate complex with Fe(III) ions due to its unique structure [1]. We believe that adding iron nitrate to the mixture of HQ and CC should cause Fe(III) ions to form a chelate complex with CC, but not with HQ (Fig. 7a), which could prevent aggregation even at a high concentration of CC. Fig. 7b shows that when Fe(III) ions were not present, absorption intensity at 400 nm did not increase monotonically with HQ concentration due to aggregation. When Fe(III) ions were added to the mixture, however, a monotonic increase in absorption intensity at 400 nm was 11 Page 11 of 29

restored, as shown in Fig. 7c. Fig. 7d also confirms that absorption intensity did not increase monotonically with HQ concentration when Fe(III) ions were not present, but increased linearly with Fe(III) ions. In addition, absorption intensity was not significantly influenced by changing CC concentration (Fig. S5). This suggests that it is possible to detect the concentration of HQ even at

ip t

high concentrations of CC when Fe(III) ions are present.

Finally, we tested the selectivity of HQ detection by examining the interference of various

cr

molecules and ions. Fig. 8 shows that an excess amount of other ions and molecules had little effect

us

on the results, confirming the high selectivity of HQ detection. It should be noted that RC neither participated in the redox reaction nor interfered with the absorbance, which is in accordance with

an

previous results in which RC did not have binding affinity to metal ions and also had the lowest

M

reducibility [1].

4. Conclusions

d

Despite their wide applications in industry and agriculture, dihydroxybenzene isomers,

te

hydroquinone, catechol, and resorcinol, are harmful to humans and the environment, which

Ac ce p

necessitates development of a simple tool to detect them. In this paper, we have used those isomers to reduce silver ions in gold nanoparticle suspensions, which resulted in distinctive color changes. We investigated the mechanisms for the color changes of the suspensions and applied our understanding to colorimetric detection of those isomers. Our method showed a detection sensitivity comparable to previously reported values. Furthermore, addition of Fe(III) ions allowed selective detection of HQ from a mixture of dihydroxybenzene isomers because they formed a chelate complex with CC. Our method has advantages over previous methods because it allows a simple, inexpensive, and naked-eye detection of dihydroxybenzene isomers.

Acknowledgements 12 Page 12 of 29

This work was supported by National Research Foundation of Korea (NRF) grants funded by the

Ac ce p

te

d

M

an

us

cr

ip t

Korean government (MEST) (No.2011-0029118, 2009-0082417).

13 Page 13 of 29

References [1] H.-F. Wang, Y.-Y. Wu, X.-P. Yan, Room-temperature phosphorescent discrimination of catechol from resorcinol and hydroquinone based on sodium tripolyphosphate capped Mn-doped ZnS quantum dots, Anal. Chem., 85 (2012) 1920-1925.

ip t

[2] L. Tang, Y. Zhou, G. Zeng, Z. Li, Y. Liu, Y. Zhang, et al., A tyrosinase biosensor based on

cr

ordered mesoporous carbon-Au/l-lysine/Au nanoparticles for simultaneous determination of hydroquinone and catechol, Analyst, 138 (2013) 3552-3560.

growth of Au nanoparticles:

us

[3] R. Baron, M. Zayats, I. Willner, Dopamine-, l-DOPA-, adrenaline-, and noradrenaline-induced assays for the detection of neurotransmitters and of tyrosinase activity,

an

Anal. Chem., 77 (2005) 1566-1571.

[4] K.C.L. Black, Z. Liu, P.B. Messersmith, Catechol redox induced formation of metal

M

core−polymer shell nanoparticles, Chem. Mater., 23 (2011) 1130-1135. [5] W.-G Qu, S.-M. Wang, Z.-J. Hu, T.-Y. Cheang, Z.-H. Xing, X.-J. Zhang, et al., In situ synthesis

te

Chem. C, 114 (2010) 13010-13016.

d

of gold@3,4-dihydroxy-l-phenylalanine core−shell nanospheres used for cell imaging, J. Phys.

Ac ce p

[6] N.N. Pozdeeva, E.T. Denisov, Mechanism of hydroquinone-inhibited oxidation of acrylic acid and methyl methacrylate, Kinet. Catal., 52 (2011) 506-512. [7] J. Yuan, W. Guo, E. Wang, Utilizing a CdTe quantum dots−enzyme hybrid system for the determination of both phenolic compounds and hydrogen peroxide, Anal. Chem., 80 (2008) 11411145.

[8] J.A. Jacob, H.S. Mahal, N. Biswas, T. Mukherjee, S. Kapoor, Role of phenol derivatives in the formation of silver nanoparticles, Langmuir, 24 (2007) 528-533. [9] X. Ji, G. Palui, T. Avellini, H.B. Na, C. Yi, K.L. Knappenberger, et al., On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine, J. Am. Chem. Soc., 134 (2012) 6006-6017.

14 Page 14 of 29

[10] J.L. Bolton, M.A. Trush, T.M. Penning, G. Dryhurst, T.J. Monks, Role of quinones in toxicology, Chem. Res. Toxicol., 13 (2000) 135-160. [11] R. Gopalakrishna, Z.H. Chen, U. Gundimeda, Tobacco smoke tumor promoters, catechol and

of lung carcinoma cells, Proc. Natl. Acad. Sci. USA, 91 (1994) 12233-12237.

ip t

hydroquinone, induce oxidative regulation of protein kinase C and influence invasion and metastasis

[12] L.-H. Wang, Y.-P. Kuo, Simultaneous quantitative determination of resorcinol and 1-Naphthol

cr

in haircolor products by high-performance liquid chromatography, Chromatographia, 49 (1999) 208-

us

211.

[13] P. Nagaraja, R.A. Vasantha, K.R. Sunitha, A new sensitive and selective spectrophotometric

an

method for the determination of catechol derivatives and its pharmaceutical preparations, J. Pharmaceut. Biomed., 25 (2001) 417-424.

M

[14] S. Dong, L. Chi, S. Zhang, P. He, Q. Wang, Y. Fang, Simultaneous determination of phenylenediamine isomers and dihydroxybenzene isomers in hair dyes by capillary zone

d

electrophoresis coupled with amperometric detection, Anal. Bioanal. Chem., 391 (2008) 653-659.

te

[15] X. Cao, X. Cai, Q. Feng, S. Jia, N. Wang, Ultrathin CdSe nanosheets: synthesis and application

105.

Ac ce p

in simultaneous determination of catechol and hydroquinone, Anal. Chim. Acta., 752 (2012) 101-

[16] X. Guo, L. Deng, J. Wang, Oligonucleotide-stabilized silver nanoclusters as fluorescent probes for sensitive detection of hydroquinone, RSC Advances, 3 (2013) 401-407. [17] L. Zhao, B. Lv, H. Yuan, Z. Zhou, D. Xiao, A sensitive chemiluminescence method for determination of hydroquinone and catechol, Sensors, 7 (2007) 578-588. [18] J. Homola, Surface plasmon resonance sensors for detection of chemical and biological species, Chem. Rev., 108 (2008) 462-493. [19] B. Liu, H. Tan, Y. Chen, Visual detection of silver(I) ions by a chromogenic reaction catalyzed by gold nanoparticles, Microchim. Acta, 180 (2013) 331-339.

15 Page 15 of 29

[20] S.H. Lee, K.H. Bae, S.H. Kim, K.R. Lee, T.G. Park, Amine-functionalized gold nanoparticles as non-cytotoxic and efficient intracellular siRNA delivery carriers, Int. J. Pharm., 364 (2008) 94101. [21] P.C. Lee, D. Meisel, Adsorption and surface-enhanced Raman of dyes on silver and gold sols, J.

ip t

Phys. Chem., 86 (1982) 3391-3395.

[22] Q. Zhang, J. Xie, J.Y. Lee, J. Zhang, C. Boothroyd, Synthesis of Ag@AgAu metal core/alloy

cr

shell bimetallic nanoparticles with tunable shell compositions by a galvanic replacement reaction,

us

Small, 4 (2008) 1067-1071.

[23] C.B. Norris, P.R. Joseph, M.R. Mackiewicz, S.M. Reed, Minimizing formaldehyde use in the

an

synthesis of gold−silver core−shell nanoparticles, Chem. Mater., 22 (2010) 3637-3645. [24] E.J. Land, Preparation of unstable quinones in aqueous solution via pulse radiolytic one-

M

electron oxidation of dihydroxybenzenes, J. Chem. Soc. Faraday T., 89 (1993) 803-810. [25] J. Han, Y. Liu, R. Guo, Facile synthesis of highly stable gold nanoparticles and their unexpected

te

131 (2009) 2060-2061.

d

excellent catalytic activity for Suzuki−Miyaura cross-coupling reaction in water, J. Am. Chem. Soc.,

Ac ce p

[26] X. He, L. Tan, D. Chen, X. Wu, X. Ren, Y. Zhang, et al., Fe3O4-Au@mesoporous SiO2 microspheres: an ideal artificial enzymatic cascade system, Chem. Commun., 49 (2013) 4643-4345. [27] S. Dubey, D. Singh, R.A. Misra, Enzymatic synthesis and various properties of poly(catechol), Enzyme Microb. Technol., 23 (1998) 432-437. [28] E. Faure, C. Falentin-Daudré, C. Jérôme, J. Lyskawa, D. Fournier, P. Woisel, et al., Catechols as versatile platforms in polymer chemistry, Pro. Polym. Sci., 38 (2013) 236-270. [29] S. Sanchez-Cortes, O. Francioso, J.V. Garcia-Ramos, C. Ciavatta, C. Gessa, Catechol polymerization in the presence of silver surface, Colloid Surf. A, 176 (2001) 177-184. [30] J.F. Shen, Y.Z. Hu, M. Shi, N. Li, H.W. Ma, M.X. Ye, One step synthesis of graphene oxidemagnetic nanoparticle composite, J. Phys. Chem. C, 114 (2010) 1498-1503.

16 Page 16 of 29

[31] J.-H. Lee, G.-H. Kim, J.-M. Nam, Directional synthesis and assembly of bimetallic nanosnowmen with DNA, J. Am. Chem. Soc., 134 (2012) 5456-5459. [32] Y.P. Wu, P. Nordlander, Plasmon hybridization in nanoshells with a nonconcentric core, J. Chem. Phys., 125 (2006) 124708.

ip t

[33] D.A. Perry, T.M. Razer, K.M. Primm, T. Chen, J.B. Shamburger, J.W. Golden, et al., Surfaceenhanced infrared absorption and density functional theory study of dihydroxybenzene isomer

Ac ce p

te

d

M

an

us

cr

adsorption on silver nanostructures, J. Phys. Chem. C, 117 (2013) 8170-8179.

17 Page 17 of 29

Figure Captions

Fig. 1. TEM micrographs of (a) as-synthesized (+)AuNPs; (b) core-shell nanoparticles formed by

ip t

HQ; (c) nanoparticle aggregates formed by CC; (d) enlarged part of (c) (red arrows indicate CC polymer film)

cr

Fig. 2. (a) UV-vis absorption spectra and pictures (inset) of (+)AuNP suspensions containing AgNO3

us

and HQ, CC, or RC; (b) UV-vis absorption spectra of (+)AuNP suspensions containing AgNO3 or HQ, and a mixture of AgNO3 and HQ

an

Fig. 3. (a) UV-vis absorption spectra and pictures (inset) of (-)AuNP suspensions containing AgNO3

M

and HQ, CC, or RC; TEM micrographs of core-shell nanoparticles formed by (b) HQ and (c) CC Fig. 4. Schematic illustration of particle morphology after addition of dihydroxybenzene isomers in

d

(+)AuNPs

te

Fig. 5. Change in absorbance of (+)AuNP suspensions formed by (a) HQ and (b) CC as a function of

Ac ce p

time

Fig. 6. (a) UV-vis absorption spectra and pictures (inset) of nanoparticle suspensions formed by HQ at different concentrations (0, 1, 5, 8, 16, 25, 36, 45, 60, 90, 120, 150 μM; arrow indicates direction of increasing concentration); (b) Relationship between absorbance at 400 nm and HQ concentration; (c) UV-vis absorption spectra of core-shell nanoparticle suspensions formed by CC at different concentrations (0, 2, 5, 8, 16, 25, 36, 45, 60, 90, 120, 150 μM; arrow indicates direction of increasing concentration); (d) Relationship between absorbance at 700 nm with pictures (inset) and CC concentration

18 Page 18 of 29

Fig. 7. (a) Schematic illustration of proposed reaction mechanism for selective detection of HQ; UVvis absorption spectra of nanoparticle suspensions formed by HQ at different concentrations (30, 50, 70, 90, 120 μM (b) without Fe(III) and (c) with Fe(III) ions; (d) Relationship between absorbance at

ip t

400 nm and HQ concentration

cr

Fig. 8. Effect of various ions and molecules on the absorbance at 400 nm. The composition of the

us

control sample (Ctrl) was 100 μM CC, 50 μM HQ, 200 μM AgNO3. and Fe(NO3)3, and the asterisk

Ac ce p

te

d

M

an

represents the sample without CC.

19 Page 19 of 29

ip t cr us an M d te Ac ce p

Fig. 1

(intended for color reproduction on the Web only)

20 Page 20 of 29

ip t cr us an M te

d

Fig. 2

Ac ce p

(intended for color reproduction on the Web only)

21 Page 21 of 29

ip t cr us an

M

Fig. 3

Ac ce p

te

d

(intended for color reproduction on the Web only)

22 Page 22 of 29

ip t cr us an M te

d

Fig. 4

Ac ce p

(intended for color reproduction on the Web only)

23 Page 23 of 29

ip t cr us an M te

d

Fig. 5

Ac ce p

(intended for color reproduction on the Web only)

24 Page 24 of 29

ip t cr us an M d te Ac ce p

Fig. 6

(intended for color reproduction on the Web only)

25 Page 25 of 29

ip t cr us an M d te Ac ce p

Fig. 7

(intended for color reproduction on the Web only)

26 Page 26 of 29

ip t cr us an M d

Fig. 8

Ac ce p

te

(intended for color reproduction on the Web only)

27 Page 27 of 29

Ac ce p

te

d

M

an

us

cr

ip t

Graphical Abstract

28 Page 28 of 29

Highlights

Reduction of Ag ions in AuNP suspension by dihydroxybenzene isomers was studied. Three different isomers caused distinctive color changes of suspensions.

ip t

Hydroquinone and catechol changed color to yellow and black, respectively.

cr

Hydroquinone and catechol could be detected from color change of suspensions.

Ac ce p

te

d

M

an

us

Addition of Fe(III) ions enabled selective detection of hydroquinone.

29 Page 29 of 29