Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa

Colorimetric detection of Bi (III) in water and drug samples using pyridine-2,6-dicarboxylic acid modified silver nanoparticles Somayeh Mohammadi, Gholamreza Khayatian ⇑ Department of Chemistry, Faculty of Science, University of Kurdistan, P.O. Box 416, 66177-15175 Sanandaj, Iran

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Silver nanoparticles coated with DPA

acted as colorimetric probes for bismuth sensing.  DPA–AgNPs were induced to aggregate quickly with bismuth.  Method can be performed in environmental water and drug samples with high selectivity.

a r t i c l e

i n f o

Article history: Received 29 December 2014 Received in revised form 14 March 2015 Accepted 27 March 2015 Available online 9 April 2015 Keywords: Colorimetric detection Bismuth (III) sensor Pyridine-2,6-dicarboxylic acid Silver nanoparticles

a b s t r a c t A new selective, simple, fast and sensitive method is developed for sensing assay of Bi (III) using pyridine2,6-dicarboxylic acid or dipicolinic acid (DPA) modified silver nanoparticles (DPA–AgNPs). Silver nanoparticles (AgNPs) were synthesized by reducing silver nitrate (AgNO3) with sodium borohydride (NaBH4) in the presence of DPA. Bismuth detection is based on color change of nanoparticle solution from yellow to red that is induced in the presence of Bi (III). Aggregation of DPA–AgNPs has been confirmed with UV–vis absorption spectra and transmission electron microscopy (TEM) images. Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.995) is obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) in the 0.40–8.00 lM range. This colorimetric probe allows Bi (III) to be rapidly quantified with a 0.01 lM limit of detection. The present method successfully applied to determine bismuth in real water and drug samples. Recoveries of water samples were in the range of 91.2–99.6%. Ó 2015 Elsevier B.V. All rights reserved.

Introduction Bismuth and its compounds are used in environmental chemistry, cosmetic industry, medicine for the treatment of syphilis, semiconductors, alloys, metallurgical additives, recycling of uranium nuclear fuels and fabrication of catalysts. Nowadays, bismuth has many applications in medicine and health care because of its high effectiveness on the treatment a variety of diseases caused ⇑ Corresponding author. Tel.: +98 9181719609; fax: +98 8733624133. E-mail addresses: [email protected], [email protected] (G. Khayatian). http://dx.doi.org/10.1016/j.saa.2015.03.127 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

by bacterial infections and its potential effects against viruses and tumors [1]. Therefore, new methods are required for the low cost and rapid determination of bismuth in environmental chemistry, cosmetic industry, medicine, etc. Owing to their essential roles, great efforts have been attempted on the development of several analytical methods for the determination of bismuth such as flame atomic absorption spectrometry (FAAS) [2–4], electrothermal atomic absorption spectrometry (ET-AAS) [5–7], hydride generation-electrothermal atomic absorption spectrometry (HG-ETAAS) [8], atomic fluorescence spectrometry (AFS) [9], hydride generation atomic fluorescence

406

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411 O-

C O N

O

C

O

O- C

N

O

C O

O

C

O

O O

O

N

O

C

C

O-

O

N

C O-

NO Ag

3

DPA Ag NO 3

I) (II Bi

O- C O N

O O- C

O OC O

N

C O-

N

C

O

O

N C

O C O

O-

O

N

O C O-

C O O O

O C O

O C

N

O C O

O O

O O C O -C N

C N C O O O OC O

N

O O C N C O

O

O-

O O

HO

C

N

O

C

C

N

C O-

O

C O O O

C

N

O

C O-

OH

O

DPA

AgNP

Bi(III)

Fig. 1. Possible mechanism of colorimetric determination of bismuth with DPA–AgNPs.

spectrometry (HG-AFS) [10], inductively coupled plasma optical emission spectrometry (ICP-OES) [11] and spectrophotometry [12–15]. Some instruments such as ET-AAS and ICP-OES have high cost operation and are not available in many laboratories. But, FAAS offers some advantages such as, low cost and simplicity, availability in most laboratories. High detection limit is an important drawback for FAAS. So, it is difficult to measure trace amounts of metals in complex matrix [16]. The development of new methods for selective separation and determination of Bi in sub-micro levels always could be useful. Colorimetric methods based on the use of gold and silver nanoparticles have recently emerged.

a

Colorimetric sensors have attracted special attention because of their simplicity of synthesis method, cost effectiveness, ease of measurement, minimal sample preparations and rapidity. The colorimetric signal of these sensors can be easily viewed by the naked eye or using a UV/vis spectrophotometer, without needing any expensive or complex instrumentation [17]. Metal NPs such as Au and Ag have been widely used as colorimetric sensors due to their unique optical properties. One of the most important optical properties of Au and AgNPs is their localized surface plasmon resonance (LSPR). The LSPR of the metal NPs mainly depends on a number of parameters such as the size and shape of the particle, interparticle distance and the dielectric constant of the surrounding medium [18]. One of the most attractive areas of work in analytical nanotechnology is related to aggregation of metal NPs in the presence of analyte. The color change between dispersed and aggregated species from red to blue for AuNPs and yellow to brown for AgNPs can be observed [17]. In metallic nanoparticles-based colorimetric sensors, AgNPs have some advantages compared to AuNPs, since they possess higher extinction coefficients relative to AuNPs with the same size. As a result, various colorimetric sensors based on silver nanoparticles have been used for detection of metal ions such as Ba2+ [19], Cu2+ [20,21], Co2+ [22], Cr (VI) [23], Hg2+ [24,25], Mn2+ [26], Ni2+ [27], Pb2+ [28] and amino acids such as tryptophan [29], cysteine [30], the other materials such as thiram and paraquat pesticides [31] and melamine [32]. The selection of surface modification agent plays a key role in improving the stability and analytical applicability of AgNPs. In this paper, a novel, simple, rapid and direct colorimetric method for determination of bismuth in environmental water (tap and river) and drug samples is reported. Pyridine-2,6-dicarboxylic acid or dipicolinic acid (DPA) was used for modification Ag nanoparticles. As a result, the groups –COOH in DPA can interact with metal ions [33]. Bismuth is considered to be a borderline metal ion, but it forms complexes of high stability with multidentate ligands containing O and N donor atoms [34]. Hence, the synthesis, modification of AgNPs and the aggregation of functionalized AgNPs in the presence of bismuth as shown in Fig. 1. To the best of our knowledge, this is the first report for colorimetric sensing of bismuth by Ag nanoparticles.

Experimental Materials Deionized water was used to prepare all solutions. Stock standard solutions of Bi (III) (1000 mg L 1) were purchased from

b

Fig. 2. TEM images (right) of DPA–AgNPs sensing system in the absence (a) and presence (b) of 10 lM Bi (III).

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

Fig. 3. (a) EDS spectrum of the prepared DPA–AgNPs and (b) EDS spectrum of AgNPs in the presence of 10 lM of Bi (III).

407

408

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

Merck Company (Darmstadt, Germany, http://www.merck.com). More dilute solutions were prepared daily by suitable dilution of the stock solution with deionized water. Silver nitrate (AgNO3), sodium borohydride (NaBH4), DPA, hydrochloric acid and sodium hydroxide were obtained from Merck Company (Darmstadt, Germany). All the chemicals used were of analytical grade. Standard stock solutions of Na+, K+, Mg2+, Ba2+, Ca2+, Zn2+, Cu2+, Co2+, Ni2+, Mn2+, Cd2+, Cr6+, Pb2+, As5+, Hg2+, Fe2+, Fe3+, Tl+, Tl3+, Zr4+, Ag+ and Sn4+ to investigate of interference effect were prepared by dissolving appropriate amount of their corresponding nitrate and chloride salts in deionized water. Synthesis of silver nanoparticles coated with DPA In order to prepare Ag nanoparticles modified with DPA, 1.0 mL of AgNO3 solution 0.01 mol L 1 was added to 100 mL of 0.05 mmol L 1 DPA aqueous solution. The sample was stirred for 10 min. Then, under vigorous stirring, 8.8 mg of NaBH4 was added into aqueous solution. The solution was stirred for 2 h to assemble DPA onto the surfaces of AgNPs. After 2 h, a light yellow colored solution was prepared. All of the experiments were performed in dark place. Characterization of DPA–AgNPs All absorption spectra of AgNPs were recorded with a UV–visible spectrophotometer (analytikjena specord 210, Germany). FTIR spectroscopy analysis of AgNPs was measured using an infrared spectrometer (Bruker-Vector22, Germany) with KBr discs in the range of 4000–400 cm 1. Transmission electron microscopy (TEM) images were acquired on Zeiss-EM10C-80 kV (Germany). For this purpose, about 8 lL of the AgNPs solution was coated onto a carbon/formvar-coated copper grid, after sonication for 15 min. The grid was subsequently dried in air and then imaged. The energy dispersive X-ray spectra (EDS) data were recorded from a Carl Zeiss MERLIN™ instrument (Germany). The zeta potential of DPA–AgNPs was determined by zeta sizer (Nanoseries, Nano-ZS, UK).

a 3.0

b

Absorbance

2.5

0 µM

2.0 1.5

8 µM

1.0 0.5 0.0 300

400

500 Wavelenght (cm-1)

600

700

Fig. 4. (a) Color changes of DPA–AgNPs solution after the addition of different concentrations of Bi (III). (b) The absorption spectra of DPA–AgNPs solution with various concentrations of Bi (III) were 0.0, 0.4, 0.6, 0.8, 1.5, 2.0, 4.0, 6.0, and 8.0  10 6 M, respectively.

Colorimetric determination of bismuth (III) For the bismuth determination, 20 lL of aqueous solutions of bismuth (III) with various concentrations were added to 2.0 mL of DPA–AgNPs (pH 10.0), and the mixture was stirred for 60s at room temperature. Depending on the concentration of soluble bismuth, the color of solution was changed from orange to brown. Then, the absorbance spectra were recorded with 1 cm path-length cells. The application of present method for determination of bismuth was tested in environmental samples such as tap water (Department of analytical chemistry, Sanandaj, Iran) and river water (Zarine rood, Saghez, Iran). River sample was filtered through whatman filter paper. The standard addition method was performed by spiking a specified concentration of bismuth standard solution into water samples and quantified by the aforesaid procedure. For preparation of tablet samples, three pieces of bismuth subcitrate (ARYA Pharmaceutical Co. Tehran-Iran) tablet were powdered in a mortar and homogenized. Each tablet contains bismuth subcitrate equivalent to 120 mg of bismuth oxide. Then, 0.01 g of powdered sample was immersed in water and 1.0 mL concentrated sulfuric acid. The mixture was dispersed under ultrasonication for 30 min then centrifuged and the supernatant solution was diluted with deionized water to the mark in a 100.0 mL volumetric flask [35]. Results and discussion Characterization of DPA–AgNPs The bonding status of DPA on the surface of the Ag nanoparticle was characterized using FTIR spectroscopy and the results are shown in Fig. S1 (in Supplementary materials). The strong peak at 1643 cm 1 is attributed to –COO stretching vibration in DPA. When DPA are coated onto the surface of AgNPs, the above peak is shifted to 1616 cm 1. Comparing of the two spectra of pure DPA and DPA–AgNPs, it is concluded that DPA located on AgNPs. The synthesized DPA–AgNPs solution gave a mean zeta potential value of 36.9 mV. This result evidenced that the DPA–capped silver nanoparticles prepared in this work have negative charge and can be dispersed from each other in water by electrostatic repulsion [36]. The TEM images of dispersed DPA–AgNPs and aggregated DPA–AgNPs in the presence of bismuth are shown in Fig. 2a and b. As can be seen, the prepared DPA–AgNPs were stable and highly dispersed. The average size of dispersed DPA–AgNPs was about 6 nm as shown in Fig. S2 (in Supplementary materials). The EDS result in Fig. 3a indicates that DPA is coated on the surface of AgNPs due to the existence of C, and O elements. Also, the EDS spectrum of the aggregated DPA–AgNPs with Bi (Fig. 3b) clearly shows presence of this element in the aggregated nanoparticles [26]. Fig. S3 (in Supplementary materials) shows, absorption band of DPA–AgNPs in UV–vis spectroscopy, at about 390 nm that is due to surface plasmon resonance bond of dispersed silver nanoparticles. After injection of bismuth solution, aggregation of DPA– AgNPs solution was occurred due to strong coordination bond between bismuth and donor groups of DPA. The –COOH groups in DPA may be used to bind with metal ions [33]. As shown in Fig. S3 (in Supplementary materials), the addition of bismuth solution led to a red-shift of the peak at 390 nm and appearance of a new peak at about 525 nm in the UV–vis spectra, which used for a simple and highly selective determination of bismuth. Effect of DPA concentration The concentration of DPA is a very important parameter to synthesize monodisperse DPA–AgNPs in aqueous solution [28]. The

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

409

Fig. 5. Selectivity of this assay, intensity ratio of A525/A390 (a) of DPA–AgNPs solution after mixing with 10 lM Bi (III) (control) and other metal ions in absence of Bi (III) and (b) of DPA–AgNPs solution after mixing with 10 lM Bi (III) and other anions in absence of Bi (III) in pH 10 aqueous solution.

sensitivity of determination with AgNPs is affected by the DPA concentration. So, the molar concentration ratio of Ag/DPA was evaluated in four different ratios (1:0.25, 1:0.5, 1:1 and 1:2) and the results are shown in Fig. S4. As can be seen, in the molar concentration ratios of 1:0.5 and 1:0.25, the sensitivity for the bismuth measurement is higher than the other ratios. However, Qi have shown that, the size of the ligand-AgNPs increase with increasing of the ligand concentration, that it may cause the sensitivity decreases with increasing the particle size [28]. As shown in Fig. S4 (in Supplementary materials), the best results were obtained for the molar concentration ratio of 1:0.5 of Ag/DPA. Therefore, the molar concentration ratio of 1:0.5 of Ag/DPA was selected for subsequent studies. The effect of pH The effect of pH on the absorption spectra of the DPA–AgNPs was also investigated (Supplementary materials Fig. S5). The pH of solutions was adjusted using either hydrochloric acid or sodium hydroxide solutions (0.1–1.0 mol L 1). The pKa values for DPA were reported equal to 2.2 and 4.6 for pKa1 and pKa2, respectively, documenting that in neutral and alkaline solutions H2dipic exists as dianion dipic2 [33]. The modified Ag nanoparticles are considered to be stable at pH range of 5.0–11.0 and are extremely stable at pHs 5.0–10.0, probably due to strong interparticle electrostatic

repulsion between the carboxylate anion of DPA on the nanoparticle surfaces. As can be seen in Fig. S5 (in Supplementary materials), no obvious color change was found at pHs 5.0–8.0. The absorption value was increased from pH 8.0 to pH 10.0 but decreased at a pH higher than 10.0. These observations may be due to formation of complexes such as ML2OH, ML3OH and ML (OH)3 in these pH ranges (8.0–10.0) that cause aggregation of DPA–AgNPs and thus color change [34]. The best results were obtained for pH 10.0. Therefore, pH 10.0 was selected as the optimum pH for subsequent studies. Sensitivity and selectivity for bismuth determination In order to evaluate the sensitivity of the present method, different concentrations of Bi (III) ranging from 0.4 lM to 10 lM were added into DPA–AgNPs and the absorption peak of the system was monitored by UV–vis spectroscopy. As shown in Fig. 4a with increasing concentrations of bismuth, color of DPA–AgNPs solution was changed from yellow to deep red. Fig. 4b indicates the absorption spectra changes of DPA–AgNPs after addition of different concentrations of Bi (III). The UV–vis absorbance ratio (A525/A390) was plotted versus the concentration of Bi (III). A good linear relationship (correlation coefficient r = 0.995) was obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) ranging from 0.40 lM to 8.00 lM. The detection limit of Bi (III) by

410

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

7

Conclusions

6

DPA-Ag NPs

Absorbance

5 DPA-AgNPs+Bi (III)+ EDTA

4 3

DPA-AgNPs+ Bi (III)

2 1 0 300

500 700 Wavelenght (nm)

900 Acknowledgements

Fig. 6. Absorption spectra of DPA–AgNPs system in the presence of 15 lM Bi (III), 15 lM Bi (III) + 30 lM EDTA.

Table 1 Determination of Bi (III) in real water samples. Sample

Bi (III) added (lM)

Bi (III) found (lM)

Recovery (%) (n = 3)

RSD (%) (n = 3)

Tap water

0 2 6

– 1.82 5.72

– 91.2 95.3

1.5 0.8

0 2 6

– 1.99 5.78

99.6 96.3

6.2 2.1

River water

A new selective, simple and sensitive method was developed for the detection of bismuth ions. DPA–AgNPs are prepared by reduction of AgNO3 in the presence of DPA. The functionalized colorimetric sensor for detection of trace amount of bismuth shows high selectivity in the presence of different interfering ions. The mechanism of aggregation is based on the interaction of the donating groups of pyridine-2,6-dicarboxylic acid with bismuth ions. A good linear relationship was obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) ranging from 0.40 lM to 8.00 lM. The present method successfully applied to determine bismuth in real water and drug samples.

The authors are grateful for the financial supports of this study from University of Kurdistan (2014). We would like to thank Prof. Cristina Nerin and her group, Department of Analytical Chemistry, University of Zaragoza, Zaragoza, Spain for providing of NaBH4, DPA and bismuth nitrate and helping to do TEM and EDS in the revised version of the manuscript.

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2015.03.127. References

equation LOD = 3Sb/m was 0.01 lM, where Sb is the standard deviation (SD) of the blank measurements (n = 10), and m is the slope of the calibration curve. In order to evaluate the selectivity of the present method, various concentrations of cations and anions were added into DPA– AgNPs in absence of bismuth. As shown in Fig. 5a and b, in the presence of 10 lM bismuth, a distinct color change from yellow to deep red was clearly observed, whereas no obvious color change was obtained in the presence of concentration of 10 lM of Fe (III), Tl (I), Tl (III), Ca (II), Cd (II), Cu (II), Pb (II), Zn (II), Mn (II), Ag (I), As (V), Mg (II), Sn (IV), Zr (IV), Ba (II), Co (II), Cr (VI), K+, Na+, Ni (II), Hg (II), Fe (II) (Fig. 5a) and 2500 lM of (CO23 , F , HCO3 , I , NO2 , NO3 , SO23 , SO24 , Br , SCN , CH3COO , ClO4 ) and 1500 lM of PO34 (Fig. 5b). The results confirmed that this sensing system is highly selective to bismuth ions. Also, these results were probably due to strong coordination of bismuth with donating groups of DPA– AgNPs which form a stable complex under this condition compared to other metallic ions. In order to prove, the DPA interacts with bismuth; EDTA as a strong complexing agent is added to DPA–AgNPs-Bi (III) solution, as can be seen from Fig. 6 colorimetric change of solution is not observed in the presence of EDTA. Detection of Bi (III) in real samples In order to investigate applicability of this sensing method, the analysis of bismuth was performed in two water samples (tap water (Sanandaj, Iran), river water (Saghez, Iran)) and drug samples. The results are presented in Table 1. Using this method, satisfying recoveries of Bi (III) were obtained in the range of 91.2–99.6%, with RSD (%) values 0.8–6.2% in two water samples. The value of bismuth as Bi2O3 in bismuth subcitrate was reported 120 mg per tablet and the result 120.12 mg per tablet was obtained by this procedure.

[1] N. Yang, H. Sun, Bismuth: Environmental pollution and health effects, in: J.O. Nriagu (Ed.), Encyclopedia of Environmental Health, Elsevier, 2011, pp. 414– 420. [2] K. Suvardhan, K. Suresh Kumar, D. Rekha, B. Jayaraj, G. Krishnamurthy Naidu, P. Chiranjeevi, Preconcentration and solid-phase extraction of beryllium, lead, nickel, and bismuth from various water samples using 2-propylpiperidine-1carbodithioate with flame atomic absorption spectrometry (FAAS), Talanta 68 (2006) 735–740. [3] S. Sahan, S. Sacmacı, U. Sahin, A. Ulgen, S. Kartal, An on-line preconcentration/ separation system for the determination of bismuth in environmental samples by FAAS, Talanta 80 (2010) 2127–2131. [4] N. Pourreza, K. Sheikhnajdi, Multi-walled carbon nanotube modified with 1buthyl 3-methyl imidazolium hexaflouro phosphate supported on sawdust as a selective adsorbent for solid phase extraction of Bi (III), Talanta 99 (2012) 507–511. [5] Y.H. Sung, Sh.D. Huang, On-line preconcentration system coupled to electrothermal atomic absorption spectrometry for the simultaneous determination of bismuth, cadmium, and lead in urine, Anal. Chim. Acta 495 (2003) 165–176. [6] A.S. Ribeiro, M.A. Zezzi Arruda, S. Cadore, Determination of bismuth in metallurgical materials using a quartz tube atomizer with tungsten coil and flow injection hydride-generation atomic absorption spectrometry, Spectrochim. Acta B 57 (2002) 2113–2120. [7] F. Shemirani, M. Baghdadi, M. Ramezani, M.R. Jamali, Determination of ultratrace amounts of bismuth in biological and water samples by electrothermal atomic absorption spectrometry (ET-AAS) after cloud point extraction, Anal. Chim. Acta 534 (2005) 163–169. [8] C. Moscoso-Perez, J. Moreda-Pineiro, P. Lopez-Mahıa, S. Muniategui-Lorenzo, E. Fernandez-Fernandez, D. Prada-Rodrıguez, Bismuth determination in environmental samples by hydride generation-/electrothermal atomic absorption spectrometry, Talanta 61 (2003) 633–642. [9] L. Rahman, W.T. Corns, D.W. Bryce, P.B. Stockwell, Determination of mercury, selenium, bismuth, arsenic and antimony in human hair by microwave digestion atomic fluorescence spectrometry, Talanta 52 (2000) 833–843. [10] X.J. Feng, B. Fu, Determination of arsenic, antimony, selenium, tellurium and bismuth in nickel metal by hydride generation atomic fluorescence spectrometry, Anal. Chim. Acta 371 (1998) 109–113. [11] M. Sun, Q. Wu, Determination of trace bismuth in human serum by cloud point extraction coupled flow injection inductively coupled plasma optical emission spectrometry, J. Hazard. Mater. 192 (2011) 935–939. [12] P.D. Tzanavaras, D.G. Themelis, A. Economou, Sequential injection method for the direct spectrophotometric determination of bismuth in pharmaceutical products, Anal. Chim. Acta 505 (2004) 167–171. [13] D.Th. Burns, N. Tungkananuruk, S. Thuwasin, Spectrophotometric determination of bismuth after extraction of tetrabutylammonium

S. Mohammadi, G. Khayatian / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 405–411

[14]

[15]

[16]

[17]

[18] [19]

[20]

[21]

[22]

[23]

[24]

tetraiodobismuthate(III) with microcrystalline benzophenone, Anal. Chim. Acta 419 (2000) 41–44. T. Madrakian, A. Afkhami, A. Esmaeili, Spectrophotometric determination of bismuth in water samples after preconcentration of its thiourea-bromide ternary complex on activated carbon, Talanta 60 (2003) 831–838. F.M. Abdel-Gawad, Ion-pair formation of Bi (III)–iodide with some nitrogenous drugs and its application to pharmaceutical preparations, J. Pharm. Biomed. Anal. 16 (1998) 793–799. X. Wen, Y. Zhao, Q. Deng, Sh. Ji, X. Zhao, J. Guo, Investigation of novel rapidly synergistic cloud point extraction pattern for bismuth in water and geological samples coupling with flame atomic absorption spectrometry determination, Spectrochim. Acta A 89 (2012) 1–6. D. Vilela, M.C. Gonzalez, A. Escarpa, Sensing colorimetric approaches based on gold and silver nanoparticles aggregation: chemical creativity behind the assay, Anal. Chim. Acta 751 (2012) 24–43. H. Li, Zh. Cui, C. Han, Glutathione-stabilized silver nanoparticles as colorimetric sensor for Ni2+ ion, Sensor Actuator B Chem. 143 (2009) 87–92. H. Li, L. Zhang, Y. Yao, C. Han, Sh. Jin, Synthesis of aza-crown ether-modified silver nanoparticles as colorimetric sensors for Ba2+, Supramol. Chem. 22 (2010) 544–547. Y. Zhou, H. Zhao, Y. He, N. Ding, Q. Cao, Colorimetric detection of Cu2+ using 4mercaptobenzoic acid modified silver nanoparticles, Colloids Surf. A 391 (2011) 179–183. Y. Ma, H. Niu, X. Zhang, Y. Cai, Colorimetric detection of copper ions in tap water during the synthesis of silver/dopamine nanoparticles, Chem. Commun. 47 (2011) 12643–12645. H.K. Sung, S.Y. Oh, Ch. Park, Y. Kim, Colorimetric detection of Co2+ Ion using silver nanoparticles with spherical, plate, and rod shapes, Langmuir 29 (2013) 8978–8982. A. Ravindran, M. Elavarasi, T.C. Prathna, A.M. Raichur, N. Chandrasekaran, A. Mukherjee, Selective colorimetric detection of nanomolar Cr (VI) in aqueous solutions using unmodified silver nanoparticles, Sensoror Actuator B Chem. 166–167 (2012) 365–371. A. Alam, A. Ravindran, P. Chandran, S. Sudheer Khan, Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione, Spectrochim. Acta A 137 (2015) 503–508.

411

[25] L. Hu, Y. Zhang, L. Nie, Ch. Xie, Zh. Yan, Colorimetric detection of trace Hg2+ with near-infrared absorbing squaraine functionalized by dibenzo-18-crown6 and its mechanism, Spectrochim. Acta A 104 (2013) 87–91. [26] Y.X. Gao, J.W. Xin, Z.Y. Shen, W. Pan, X. Li, A.G. Wu, A new rapid colorimetric detection method of Mn2+ based on tripolyphosphate modified silver nanoparticles, Sensor. Actuat. B-Chem. 181 (2013) 288–293. [27] Y. Shang, F. Wu, L. Qi, Highly selective colorimetric assay for nickel ion using N-acetyl-L-cysteine-functionalized silver nanoparticles, J. Nanopart. Res. 14 (2012) 1169–1176. [28] L. Qi, Y. Shang, F. Wu, Colorimetric detection of lead (II) based on silver nanoparticles capped with iminodiacetic acid, Microchim. Acta 178 (2012) 221–227. [29] C. Liu, B. Liu, Ch. Xu, Colorimetric chiral discrimination and determination of enantiometric excess of D/L-tryptophan using silver nanoparticles, Microchim. Acta 181 (2014) 1407–1413. [30] S. Hajizadeh, Kh. Farhadi, M. Forough, R. Molaei, Silver nanoparticles in the presence of Ca2+ as a selective and sensitive probe for the colorimetric detection of cysteine, Anal. Methods 4 (2012) 1747–1752. [31] J.V. Rohit, S.K. Kailasa, Cyclen dithiocarbamate-functionalized silver nanoparticles as a probe for colorimetric sensing of thiram and paraquat pesticides via host–guest chemistry, J. Nanopart. Res. 16 (2014) 2585–2601. [32] H. Wang, D. Chen, L. Yu, M. Chang, L. Ci, One-step, room temperature, colorimetric melamine sensing using an in-situ formation of silver nanoparticles through modified Tollens process, Spectrochim. Acta A 137 (2015) 281–285. [33] E. Norkus, I. Stalnionien, D.C. Crans, Interaction of pyridine- and 4hydroxypyridine-2,6-dicarboxylic acids with heavy metal ions in aqueous solutions, Heteroat. Chem. 14 (2003) 625–632. [34] V. Stavila, R.L. Davidovich, A. Gulea, K.H. Whitmire, Bismuth(III) complexes with aminopolycarboxylate and polyaminopolycarboxylate ligands: Chemistry and structure, Coord. Chem. Rev. 250 (2006) 2782–2810. [35] S. Rastegarzadeh, M. Fatahinia, Design of an optical sensor for determination of bismuth, J. Chin. Chem. Soc. 58 (2011) 136–141. [36] E. Filippo, D. Manno, A. Buccolieri, A. Serra, Green synthesis of sucralosecapped silver nanoparticles for fast colorimetric triethylamine detection, Sensor Actuator B Chem. 178 (2013) 1–9.