A plasmonic nano-sensor for the fast detection of Ag+ based on synergistic coordination-inspired gold nanoparticle

Accepted Manuscript Title: A Plasmonic Nano-sensor for the Fast Detection of Ag+ Based on Synergistic Coordination-inspired Gold Nanoparticle Authors: Jianjun Du, Hong Du, Haoying Ge, Jiangli Fan, Xiaojun Peng PII: DOI: Reference:

S0925-4005(17)31456-9 http://dx.doi.org/doi:10.1016/j.snb.2017.08.034 SNB 22901

To appear in:

Sensors and Actuators B

Received date: Revised date: Accepted date:

5-4-2017 1-8-2017 3-8-2017

Please cite this article as: Jianjun Du, Hong Du, Haoying Ge, Jiangli Fan, Xiaojun Peng, A Plasmonic Nano-sensor for the Fast Detection of Ag+ Based on Synergistic Coordination-inspired Gold Nanoparticle, Sensors and Actuators B: Chemicalhttp://dx.doi.org/10.1016/j.snb.2017.08.034 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.

A Plasmonic Nano-sensor for the Fast Detection of Ag+ Based on Synergistic Coordination-inspired Gold Nanoparticle

Jianjun Du*, Hong Du, Haoying Ge, Jiangli Fan, and Xiaojun Peng

State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, P.R. China, [email protected]

Highlights



A fast, convenient, and colorimetric sensor for Ag+ detection in aqueous media is developed based on gold nanoparticle system.



Our sensor shows very good selectivity to Ag+ than any other interfering items, due to the synergistic coordination of adenosine and creatinine with Ag+ on AuNPs surface.



Our sensor shows high sensitivity with LOD of 7.3 nM, which could compete with even better than some of instrument-based methods.



It realizes quantitative detection of Ag+ in water samples by UV-Vis spectrometer which exhibits good recoveries with acceptable standard deviations.

1

ABSTRACT: Silver is one of most important heavy metals, which affects the environment and organism significantly along with its widespread applications. An interesting gold nanoparticles (AuNPs)-based system, in this work, was fabricated using the adenosine and creatinine for the colorimetric recognition of the Ag+ via a red-to-blue color change. A synergistic coordination of these two biomolecules with Ag+ on AuNPs’ surface supplied an excellent selectivity than examples by a single ligand-modified AuNPs in literatures.

It realized a qualitative Ag+

recognition by naked eyes in aqueous media, as well as a quantitative determination by the UVVis spectrometer over a range of 0.1–0.9 μM, covering the Ag+ standard in drinking waters (0.46 μM, US Environmental Protection Agency). This system is not only convenient but also very sensitive with a limit detection of 7.3 nM. This platform is applicable for the Ag+ recognition in mimic pollution samples with a good repeatability and relative standard deviation. KEYWORDS:

Gold nanoparticle; Ag+ detection; Environmental monitoring; Synergistic

coordination; Colorimetric sensor

1. INTRODUCTION Silver, a transition metal, is one of most important and common used metals in the past hundreds of years. Usually, it shows +1 state in almost exclusively complexes. Ag+ could interact and inactivate enzymes, DNA, cell membrane,1,

2

and excessive intake of Ag+ results in the

accumulation precipitates as well as the interaction with essential metal ions in the enzyme and bone.3, 4 Therefore, for the safety of environment and people health, various methods have been developed for the Ag+ detection, such as the inductively coupled plasma atomic emission spectrometry and flame atomic absorption spectrometry, which usually need expensive and complicated instruments. Nevertheless, Ag+ probes/sensors could be more useful for monitoring Ag+ via signals of fluorescence, absorption, and electrochemistry.5-16 In the last two decades, gold NPs (AuNPs)–based nano-sensor has attracted much attention as an excellent platform for

2

the colorimetric assay with naked eye-distinguishable signals, simpleness, and convenience, because of its unique surface Plasmon resonance (SPR) property and nano-size effect.17-27 For the Ag+ detection, Tseng et al. developed a colorimetric sensing system based on an assembly of Tween 20–stabilized AuNPs.15 Wang et al. presented a logic system for sensing heavy metal ions, such as Ag+ and Hg2+.28 Chen et al. fabricated AuNPs–DNA conjugates for heavy metal ions (e.g. Ag+, Hg2+, Zn2+, and Cr3+).29 However, the presence of interfering ions (e.g. Hg2+) could obstruct the Ag+ assay in the above examples wherein the coordination strategy and/or thiophilic specialty are the main mechanisms used in the literatures.30,

31

Therefore, the

sensitivity and especially selectivity become the key points for developing a practical Ag+ probe. In our former works, we found a synergistic coordination effect on AuNPs surface that could increase the selectivity to the target obviously. A unique complex of creatinine/uric acid/Hg2+ on gold particle surface, as a proof–of–concept, was fabricated, wherein the uric acid and creatinine worked together as a structure of tweezers at nipping the Hg2+.21 Therefore, we developed a creatinine/uric acid–AuNPs system for Hg2+ detection, as well as a uric acid/Hg2+–AuNPs system to recognize creatinine for the assessment of kidney function and the diagnosis of renal diseases, respectively.23 The results showed that the synergistic effect donated much better selectivity toward targets than any monomer ligand. In recent, through screening the biomolecule/ion library, a pair of adenosine/creatinine was found a specific synergistic response to the Ag+ on AuNPs surface.24

Herein, an

adenosine/creatinine–AuNPs system was fabricated to be a candidate of a colorimetric nano– sensor for sensing Ag+ based on the AuNPs system as shown in Scheme 1. Due to the specific synergistic effect, this adenosine/creatinine–AuNPs system exhibited an excellent selectivity and very good sensitivity to Ag+, which was applicable in both qualitative recognition and quantitative determination of Ag+ in practical aqueous samples. 2. EXPERIMENTAL SECTION

3

2.1 Chemicals: Gold(III) chloride trihydrate (>99.9%) and sodium citrate dehydrate (>99%) were purchased from Aladdin Reagent Company and Energy Chemical Reagent Company. CaCl2,

Solutions of metal ions and anions were prepared from Zn(NO 3)2·6H2O,

BaCl2,

Na2SO4,

KNO3,

MgSO4,

CoCl2,

AgNO3,

Cu(CH3COO)2·H2O,

Ni(NO3)2·6H2O, Mn(CH3COO)2·4H2O, Pb(NO3)2, HgCl2·0.5H2O, Cr(NO3)3, FeCl3·6H2O, and CH3COONa, NaNO3, NaClO4, Na3PO4, NaSCN, Na2S2O3, Na2HPO4, NaHCO3, Na2SO4, NaCl, NaF, NaBr and Na2SO3 by separately dissolving each metal ion in DI water. Solutions of amine acids and small molecules were prepared from lysine, aspartic acid, proline, arginine, histidine, phenylalanine, glycine, asparagine, glutamine, serine, methionine, tyrosine, tryptophan, cysteine, and urea, folic acid, glucose, niacin, pyrrolidone hydrotribromide, sucrose, imidazole, uric acid, sodium ascorbate, uracil, creatinine, and hydantoin by separately dissolving each amine acid or molecule in DI water. All other chemicals were supplied by Aladdin Reagent Company and Energy Chemical Reagent Company and were used as received. 2.2

Characterization: UV–Vis

spectra

were

recorded

by

using

spectrophotometer (UV–Vis 2501 PC) with the baseline correction.

a

UV–Vis

Nanoparticles

dispersion and aggregation were characterized by transmission electron microscopy (TEM, JEM2010). The zeta potentials of AuNPs before and after modification were measured with a Zetasizer Nano–ZS90 instrument. All pH measurements were made with a Model PHS-3C meter. 2.3 Synthesis of 13 nm AuNPs: AuNPs (13 nm, 5.4 nM) were prepared by sodium citrate reduction of a HAuCl4 solution as described in the literature32 and our former works.17-25 2.4 Preparation of Adenosine/creatinine–AuNPs System: After introducing adenosine (0.5 μM) to AuNPs solution (500 μL) for 5 min, the solution was centrifuged (10000 rpm,

4

10 min). The AuNPs at the bottom were re-dispersed in DI water. Quantitative creatinine (7 μM) was then added to fabricate adenosine/creatinine–AuNPs system for following use. 2.5 Ag+ Recognizing in Mineral Water Sample: The mineral water samples of varying silver ion concentrations (0.1–0.9 μM) were prepared from a concentrated stock solution of silver ion (5 mM).

In the test, 50 µL mineral water was added to 500 µL

adenosine/creatinine–AuNPs solution in optimized condition (pH = 7.0, [creatinine] = 7 µM, [AuNPs] = 5.4 nM), followed by UV–Vis spectra recording after a 10 min incubation. 3. RESULTS AND DISCUSSION AuNPs solution (13 nm) exhibited a red color with a typical localized SPR (LSPR) band at 520 nm as usual.

Based on the electrostatic effect and coordination chemistry of

adenosine/creatinine with gold, the functional AuNPs system was fabricated by adding the adenosine and creatinine successively into AuNPs solution, which was then used for the Ag+ recognition as follows. As expected, the introduction of Ag+ (2 μM) resulted in a decrease of LSPR intensity at 520 nm but an obvious increase at around 650 nm as shown in Figure 1a, along with a red–to–blue color change in a minute. The 0.5 μM adenosine was used for the decoration by nearly 1000-fold excess than AuNPs (5.4 nM), and then the excess adenosine was separated by a centrifugation process. For the creatinine, its concentration was optimized as shown in Figure S1 (supporting information), wherein the sensing capability did best in the presence of 7 μM creatinine. Besides, the testing condition, such as pH, was also optimized for the Ag+ determination as shown in Figure S2 (supporting information). At acidic condition (pH = 5.0), the adenosine/creatinine–AuNPs system was unstable before the addition of Ag+, while the Ag+ could precipitate at basic condition (pH = 9.0). In a neutral condition, this system worked well at sensing Ag+. Therefore, the optimized condition (pH = 7.0, [creatinine] = 7 µM, [AuNPs] = 5.4 nM) was applied in the following tests.

5

The titration experiment was then performed by increasing the Ag+ concentration gradually, and ratiometric changes in UV–Vis spectra were exhibited by LSPR intensity at 520 nm and 650 nm (A650 nm/520 nm) with an isoabsorptive point at 550 nm (Figure 1b), wherein a good linear relationship (R2 = 0.922) was obtained over the Ag+ concentration of 0.1–0.9 µM (Figure 1b, inset). Our system showed a very good selectivity toward Ag+ among testing metal ions (Na+, K+, Hg2+, Mn2+, Cu2+, Mg2+, Co2+, Ca2+, Ba2+, Pb2+, Ni2+, Zn2+, Fe3+, Cr3+, and Ag+) and anions (NO3-, CH3COO-, F-, Cl-, Br-, ClO4-, HCO3-, SO32-, SCN-, SO42-, S2O32-, HPO42-, and PO43-). As shown in Figure 2a and b, neither of the metal ions nor anions, except for Ag+, could induce an obvious increase of A650 nm/520 nm value. Then we examined our system with multitudinous amino acids (lysine, aspartic acid, proline, arginine, histidine, phenylalanine, glycine, asparagine, glutamine, serine, methionine, tyrosine, tryptophan, and cysteine) and variety of biomolecules (urea, folic acid, glucose, niacin, pyrrolidone, sucrose, imidazole, uric acid, sodium ascorbate, uracil, creatinine, and hydantoin). Results showed that none of those molecules, except in the presence of Ag+, led to obvious changes in the A650 nm/520 nm value as well as solution color (Figure 2c and d). The above strict selectivity experiments conformed our system can identify the Ag+ among multitudinous interferents in practice. Similar as our former work on the uric acid/creatinine/Hg2+–AuNPs system,21, 23 the roles of uric acid, creatinine and Hg2+ just seemed like three angles in a triangle, meaning three of them coordinated together on the particle’s surface.

Therefore, based on above strategy, the

adenosine/creatinine/Ag+ was screened. Because of the steric effect on AuNPs surface, some binding sites of creatinine and adenosine were covered up. Therefore, a synergistic coordination together worked in the formation of complex, which could be supported by the MS results for the adenosine/creatinine/Ag+ complex (1/1/1, m/z is 487.1587).24

And this kind of exclusive

coordination pair of adenosine/creatinine/Ag+ made sure the single selectivity of our adenosine/creatinine–AuNPs toward Ag+ as shown in the selectivity tests. TEM images in

6

Figure 3 demonstrated

the changes

in

microscopic field

that

the well-dispersed

adenosine/creatinine–AuNPs (Figure 3a) aggregated heavily after introducing the Ag+ (Figure 3b), which were consistent with the colorimetric and spectroscopic changes. Compared to methods requiring instruments, the AuNPs–based colorimetric method exhibits potentials as a new generation of fast, convenient, and portable field assay with the development of smart cell phone that can work as a portable testing device.33, 34 An accurate and colorimetric situ assay needs an excellent selectivity, fast response time, naked eye distinguishable color change and so forth. The Ag+ induced red–to–blue color change could be observed within a couple of minutes, and the A650 nm/520 nm value reached saturated within 10 min and kept stable at least for 60 mins (Figure 4a). By the titration experiment, a linear relation region of 0.1–0.9 μM was found for the Ag+ determination in aqueous media, as shown in Figure 4b, with a detection limit of 7.3 nM (calculated by 3σ/slope) which was even better that examples based on the fluorescent and electrochemical methods (Table 1), meaning that this system was sensitive enough to satisfy the Ag+ standard in the drinking waters (0.46 μM, US Environmental Protection Agency).35 For the Ag+ recognition in the practical water samples, for example, mineral water, artificial added Ag+ (0.2 and 0.6 μM respectively) was detected. The detected means with standard deviations reached 0.24  0.03 μM and 0.56  0.09 μM respectively as shown in Table 2. 4. CONCLUSION In conclusion, we developed a synergistic coordination of adenosine/creatinine with Ag+ on AuNPs surface and demonstrated its application for a fast, selective, and quantitative recognizing Ag+, which was a useful and important index for the environment monitoring and related functional study in organisms. Furthermore, we also realized a fast colorimetric determination for Ag+ in practical aqueous media with a good repeatability and accuracy. Recently, AuNPs together with synergistic effect system exhibited better performances in catalysis, plasmonic property, and sensor, than respective monomers.36-38 For instance, Li and Jiang et al. decorated

7

co-presenting non-antibiotic drugs and pyrimidinethiol on AuNPs for generating broad-spectrum antibacterial and bactericidal activities against superbugs.39 Rotello et al. presented an array of gold nanoparticle-green fluorescent protein elements to rapidly detect metastatic cancer cells.40 Therefore, the synergistic effect-based gold nanoparticles could perform various charming functionality with better properties. Supporting Information: The optimized experiments of the creatinine concentration and pH value for Ag+ detection ACKNOWLEGEMENT We thank the NSFC (21406028, 21676047, and 21421005), Doctoral Scientific Fund (20130041120014),

and

Fundamental

Research

Funds

for

the

Central

Universities

(DUT14ZD214) for financial support.

8

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Biographies

Jianjun Du is an associate professor at the State Key Laboratory of Fine Chemicals at Dalian University of Technology. He received his B.S. and Ph.D. degrees in Applied Chemistry from Dalian University of Technology in 2004 and 2010, respectively.

After his postdoctoral

fellowship work at Nanyang Technological University (Singapore) in 2010−2013, he started his independent research career at Dalian University of Technology. His research is focused on organic/inorganic nanoparticles with functional organic molecules. Hong Du obtained her Bachelor degree from Qingdao University of Science & Technology (China) in 2014. After that she became a graduate student under the supervision of Prof. Jianjun Du of the State Key Laboratory of Fine Chemicals at Dalian University of Technology (DUT). Now she is studying for a Master's degree at DUT. Her current research is the application of inorganic nanoparticles with functional molecules. Haoying Ge obtained her Bachelor degree from University of Jinan (China) in 2016. After that she became a graduate student under the supervision of Prof. Jianjun Du of the State Key Laboratory of Fine Chemicals at Dalian University of Technology (DUT). Now she is studying for a Master's degree at DUT. Her current research is the synthesis and fabrication of functional gold nanoparticles and nanorods. Jiangli Fan received her Ph.D. from Dalian University of Technology in 2005. In 2010 she attended the University of South Carolina as a visiting scholar. She is currently a professor at the State Key Laboratory of Fine Chemicals at Dalian University of Technology. Her research is focused on fluorescent-dye-based probes and their biological applications. Xiaojun Peng received his Ph.D. in 1990 at Dalian University of Technology. After completing postdoctoral research at Nankai University (China), he has worked at the Dalian University of

14

Technology since 1992. In 2001 and 2002 he was a visiting scholar at Stockholm University and Northwestern University (USA). Currently he is a professor and the director of the State Key Laboratory of Fine Chemicals at Dalian University of Technology. His research interests cover dyes for fluorescent bioimaging/labeling and digital printing/recording.

15

Scheme 1. Illustration of AuNPs-based colorimetric assay of Ag+ via a synergistic coordination with adenosine and creatinine

16

Figure 1. (a) UV–Vis spectra of adenosine/creatinine–AuNPs system in the absence (red line) and the presence (blue dash line) of Ag+ (2 μM). (b) UV–Vis spectra of adenosine/creatinine– AuNPs system in the presence of different Ag+ contents (0.1, 0.3, 0.5, 0.7, and 0.9 μM), inset: the linear region.

17

Figure 2. Selectivity experiments of adenosine/creatinine–AuNPs system in the absence and the presence of different (a) metal ions, (b) anions, (c) amino acid, and (d) small molecules respectively, wherein Ag+ was 2 μM, Hg2+, Ca2+, Pb2+, Zn2+, Fe3+, and Cr3+ were 30 μM, and others were 100 μM.

18

Figure 3. TEM images of the adenosine/creatinine–AuNPs in the (a) absence and (b) the presence of Ag+ (2 μM), scale bar: 50 nm.

19

Figure 4. (a) A650 nm/520 nm values of adenosine/creatinine–AuNPs system versus time in the absence (black square) and the presence (red point) of Ag+ (2 μM). (b) A650 nm/520 nm values versus Ag+ concentration (0.1, 0.3, 0.5, 0.7 and 0.9 μM), error bars represent the standard deviation from five parallel tests on each sample.

20

Table 1. Different Ag+ Sensors and Their LODs sensor

LOD

ref.

385.8 nM

5

100 nM

6

24.9 nM

7

fluorescent probe by Ahn et al.

129.8 nM

8

electrochemical sensor by Miao et al.

0.1 nM

9

electrochemical sensor by Amini et al.

6 nM

10

electrochemical sensor by Xie and Yao et al.

2 nM

11

electrochemical sensor by He and Wang et al.

1.3 nM

12

colorimetric sensor by Lin et al.

1690 nM

13

colorimetric sensor by Jiang et al.

53.7 nM

14

100 nM

15

luminescent

sensor

based

on

carbon

nanoparticle by Algarra et al. fluorescent

sensor

based

on

BSA-gold

nanoclusters by Li et al. fluorescent sensor based on DNAzyme by Liu et al.

colorimetric sensor based on Tween 20AuNPs by Tseng et al. AuNPs based colorimetric sensor

7.3 nM

This work

21

Table 2. Determination of Ag+ in Mineral Water Samples

sample[a]

[Ag+]

added

artificially (μM)

detected mean  [b]

SD

+

of [Ag ] by recovery (%)

RSD[c] (%)

AuNPs (μM)

[a]

1

0.2

0.24  0.03

122.4

11.6

2

0.6

0.56  0.09

93.4

15.6

The samples were prepared as described in experiment section, wherein different concentrations of

creatinine are added artificially; [b]

SD = standard deviation, the mean of 5 parallel tests on each sample;

[c]

Relative standard deviation of mean recovery RSD (%) = (SD/mean)  100

22