Colorimetric Nanosensor Based on the Aggregation of AuNP

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Novel colorimetric nanosensor based on the aggregation of AuNP triggered by carbon quantum dots for detection of Ag+ ions Feiyang Wang, Yuexiang Lu, Ying Chen, Jingwei Sun, and Yueying Liu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b04067 • Publication Date (Web): 17 Jan 2018 Downloaded from http://pubs.acs.org on January 17, 2018

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ACS Sustainable Chemistry & Engineering

Novel colorimetric nanosensor based on the aggregation of AuNP triggered by carbon quantum dots for detection of Ag+ ions Feiyang Wang,a Yuexiang Lu,b Ying Chen, a Jingwei Sun,a Yueying Liua,* a

Department of Chemistry, Capital Normal University, Xisanhuan North Rd. 105, Beijing,

100048, P. R. China b

Institute of Nuclear and New Energy Technology, Collaborative Innovation Center of

Advanced Nuclear Energy Technology, Beijing Key Lab of Radioactive Waste Treatment, Tsinghua University, Beijing, 100084, P. R. China *Corresponding authors:

Phone/Fax: +86-10-68903047 Email: [email protected]

ACS Paragon Plus Environment

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Keywords CDs-triggered AuNP aggregation; GSH; Colorimetric detection; CDs; Gold nanoparticle; Silver ions

Abstract

A novel colorimetric nanosensor based on stable aggregation of gold nanoparticle (AuNP) triggered by carbon quantum dots (CDs) has been developed for detection of Ag+ ions in the presence of glutathione (GSH). Firstly, the nanosensor is constructed by assembling carbon quantum dots (CDs) ‘shell’ on the surface of gold nanoparticle (AuNP), resulting in the generation of the stable aggregation of CDs/AuNP. The solution color changes from red to blue. In the absence of target, the addition of GSH into the aggregated CDs/AuNP exhibits the dispersion state corresponding to the color change from blue to red, because GSH can prefer to binding with AuNP comparing with CDs. On the contrary, the aggregated CDs/AuNP has been again observed with the color change from red to blue after the target analyte Ag+ ions are added. Therefore, the new sensing strategy based on ‘aggregation-dispersion-aggregation’ or ‘blue-redblue’ mode can be established for Ag+ detection. This method can selectively detect Ag+ in a linear range from 100 nM to 4000 nM with the detection limit of 50 nM. It is successfully applied to determination of Ag+ ions in tap water and lake water. Our study will expand a new sight for application of CDs in sensors, environmental monitoring and preparation of carbonbased nanomaterials.

Introduction


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The colorimetric sensors have received significant attention because of its simplicity, visualization, cost-effectiveness, and rapid analysis1-7. In particular, gold nanoparticle (AuNP) as reporting probe for the colorimetric detection of metal ions have attracted a great deal of interest due to its unique advantages of extremely high extinction coefficient, strong surface plasmon resonance (SPR), and color-tunable optical properties8, 9. The surface of AuNP is also typically modified with analyte-specific ligands, such as DNA10, peptides11, polymers12, and others13. Recently, salt induced aggregation of unmodified AuNP has attracted more attention in practical applications as the construction of sensors are more easily and cost-effectively. The analytespecific ligands are physically adsorbed on the surface of AuNP to protect them from salt induced aggregation, and the target could disturb the interaction between ligands and AuNP resulting in the change of AuNP aggregation state and solution color. Although these methods exhibit good response for target analytes, most of these ligands are still defective because of high cost, the unsteady structure, low water solubility or time-consuming analysis. In addition, the salt-induced AuNP aggregation exhibit usually unstable and irreversible state14. Because the colorimetric sensors based on salt-induced AuNP often give birth to non-recurring output signals owing to aggregation along with time. Therefore, the rational design of AuNP-based colorimetric sensor with high stability, low cost and rapid analysis is very desired and useful for promoting the analysis technique. Recently, carbon quantum dots (CDs) have drawn increasing attentions owing to their captivating properties such as excellent water-solubility, good biocompatibility, high stability, simple synthetic routes15-18. CDs with a large number of carboxyl and amino groups have provided attractive candidates as a multidentate ligand to construct novel optical sensors with AuNP. Until now, only few studies mentioned that the synthesized CDs can induce AuNP


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aggregation for various biological thiols including glutathione19-21, cysteine22, thiocyanate23, and bromelain19. Therefore, it is highly desirable to develop the new colorimetric strategy based on CDs-triggered AuNP aggregation with high stability and specificity for the detection of metal ions. Silver ions (Ag+) are one of the most toxic heavy metals, which may have adverse effects on the environment and bring about severe risks to human health21, 24, 25. The high affinity is found between GSH with Ag+ ions26. Herein, we have developed a novel colorimetric nanosensor based on the stable aggregation of CDs-triggered AuNP for the highly sensitive and selective detection of Ag+ in the presence of GSH (Scheme 1). Our base strategy of sensing system depends on the high affinity between GSH and Ag+ ions. Simultaneously, CDs can rapidly induce the stable aggregation of AuNP. Firstly, stable CDs/AuNP aggregation rapidly forms by assembling of CDs ‘shell’ on AuNP with the color change from red to blue. In the absence of targets, the aggregated CDs/AuNP restores dispersed state after the addition of GSH and the color changes from blue to red, because GSH can protect AuNP from being aggregated. On the other hand, the analyte target Ag+ shows strong affinity with GSH24, 27, 28, triggering the product of CDs/AuNP composite together along with a color change from red to blue. Finally, this colorimetric system with the color changes ‘blue-red-blue’ has been employed to detect Ag+. The successive multiple steps with ‘aggregation-dispersion-aggregation’ mode can greatly improve the specificity and selectivity of this colorimetric sensor owing to the lower possibility of false positive results. To the best of our knowledge, this is the first report that the novel colorimetric sensing strategy based on the stable CDs/AuNP composite has been developed for the sensitive detection of Ag+ ions in the presence of GSH.


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Scheme 1 Illustration of colorimetric sensing mechanism based on the stable aggregation of AuNP triggered by CDs in the presence of GSH.

Experimental section Materials and instruments Chloroauric acid (HAuCl4) and sodium chloride were purchased from Sinopharm Chemical Reagent Company (Beijing, China). Citric acid was purchased from Alfa Aesar. Sodium citrate was purchased from Xilong Chemical Co., Ltd. (Shantou, China). Silver nitrate and ethylenediaminetetraacetic acid (EDTA) were purchased from Beijing Chemical Works. Amino acids including L-glycine (Gly), L-lysine (Lys) and L-serine (Ser), L-glutathione reduced (GSH) was obtained from Beijing Biodee Biotechnology Co., Ltd (Beijing, China). Other reagents and chemicals were at least analytical reagent grade. Absorption spectra were recorded on SpectraMaxRM2e Multi-Mode Microplate Reader at room temperature (Molecular Devices, California, USA). The 96-Well micro titer plates were produced from Costar (3590, USA). The water used throughout all experiments was purified by a Milli-Q system (Millipore, Bedford,


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MA, U.S.A.). The fluorescent spectra were measured on a FLS-920 Fluorescence Spectrophotometer (Edinburgh, U.K.). The slit widths of excitation and emission were 2 nm. Preparation of CDs/AuNP composite Citrate-stabilized AuNP (13 nm) were prepared as described in previous literature29. In brief, trisodium citrate solution (38.8 mM, 20 mL) was added to a boiling and rapidly stirred solution of HAuCl4 (1.0 mM, 200 mL). The solution was kept boiling at 15 min. After being naturally cooled to room temperature, the solution was stirred in all experiment and the AuNP were filtered with 0.22 µM Millipore membrane filter. The CDs were synthesized by the hydrothermal method30. Briefly, citric acid (5.0 mM) and amino acid (including Gly, Lys, and Ser) at 10 mM were dissolved in 10 mL of deionized water. Then the mixture was transferred into PTFE (Polytetrafluoroethylene) autoclaves and heated at 180 °C for 6 h. After that, the reactors were cooled down naturally. And then the solution was purified with a dialysis bag (Mw=1000 Da) for one day. Finally, CDs were dried to solid. According to the carbon source, the resultant CDs were abbreviated as Gly-CDs (CDs1), LysCDs (CDs2) and Ser-CDs (CDs3). An amount of 5.0 mL of CDs (300 µg/mL) was added to 10.0 mL of AuNP (10 nM) carefully under suitable stirring. The color of the solution changed from wine red to dark blue within a few minutes. After stirring for 10 min, the as-prepared CDs/AuNP composite was stored at 4 °C for further use. Colorimetric sensing of Ag+ Ag+ was prepared by dissolving silver nitrate (AgNO3) in distilled water. First, 75 µL of 100 µM GSH solution was mixed with different concentration of Ag+ (50 µL). Then, 100 µL of 0.1 mM PBS (pH=7.00) were added into the mixture, which was allowed to equilibrate for 10


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minutes with mild shaking. Subsequently, 150 µL CDs/AuNP composite were incubated with vigorous shaking for 10 min to react completely. Finally, the mixture was diluted to a total of 500 µL with deionized water. For the practicality of the test, the sensing system could be diluted with appropriate proportion for detection of Ag+. For example, 25 µL of 100 µM GSH solution was mixed with different concentration of Ag+ (50 µL), following to dilute 3-fold solution. Then, 33 µL of 0.1 mM PBS (pH=7.00), 33 µL of AuNP solution and 17 µL of (300 µg/mL) CDs were added into the mixture. Selectivity of Ag+ detection To examine the detection selectivity, other ions including Cd2+, Fe3+, Ca2+, Mn2+, Cu2+, Co2+, Ni2+, Al3+, Zn2+, and Pb2+ were tested under the same experimental conditions. The concentration of Ag+ and other metal ions was 0.5 µΜ and 5 µΜ, respectively. Ag+ detection in real samples To investigate the detection performance of the sensing strategy in practical application, the tap water and lake water were collected and centrifuged at 12, 000 rpm for 10 min. And then the supernatant was obtained without physical impurities. Subsequently, the Ag+ was dissolved in the real samples for further sensing. The assay condition was same as mentioned above for Ag+ sensing.

Results and discussion Aggregation behavior of AuNP triggered by CDs CDs3 are prepared by using citric acid and amino acids as raw materials. As shown in Figure 1A and 1B, TEM image of the CDs illustrates that it dispersed well. The average diameter of AuNP and CDs3 is 13.0 nm and 2.5 nm, respectively. The fluorescence emission spectra of CDs


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exhibit a typical excitation-dependent behavior in Figure S1 (Supporting Information). The maximum emission wavelength for CDs3 is 450 nm at 380 nm excitation. These results demonstrate that CDs3 and AuNP are successfully prepared. The aggregation behavior of AuNP induced by CDs3 is investigated by TEM image, DLS and UV-vis spectroscopy as shown in Figure 1, Figure S2 and S3 (Supporting Information). Firstly, CDs3 have multiple functional groups (-NH2, -COOH, and -OH) and interact with the surface of the AuNP, through hydrogen bond, Van der Waals’ force, and electrostatic interactions. So, CDs assemble onto the surface of AuNP to form an impact ‘shell’ of CDs through the Au-N interaction31. The aggregation of AuNP rapidly occurs due to the assembly of CDs3 and AuNP, resulting in the color change from red to blue in Figure 1C. At the same time, the CDs/AuNP composite yields both a substantial shift in the plasmon band energy and a red-toblue color change. The characteristic peak of the blue curve is observed in the spectrum at 620 nm in Figure 1F. Secondly, the aggregated CDs/AuNP shows an obvious change after adding GSH. Because GSH can penetrate the impact CDs ‘shell’ and interact with the AuNP, which leads to desorb CDs from AuNP. Simultaneously, GSH can protect AuNP from being aggregated and the color became from blue to red. The corresponding TEM demonstrates that AuNP modified GSH is redispersed relatively as shown in Figure 1D. The absorption spectrum (the green curve) also exhibited a strong characteristic surface plasmon resonance (SPR) peak of AuNP at 520 nm in Figure 1F. Finally, upon addition of target analyte Ag+ to the sensing solution, GSH prefers to chelate with Ag+ ions, resulting in the reaggregation of CDs/AuNP. The color of the solution turned blue again. These results can further support by TEM image in Figure 1E and the spectrum of the green curve in Figure 1F. These results demonstrate that the


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changes ‘aggregation-dispersion-aggregation’ or ‘blue-red-blue’ based on AuNP induced by CDs3 can be employed to detect Ag+.

Figure 1 TEM of different systems: (A) AuNP; (B) CDs3; (C) CDs3/AuNP aggregation; (D) CDs3/AuNP aggregation in the presence of GSH; (E) CDs3/AuNP in the presence of GSH and Ag+; (F) UV-vis spectra of the corresponding of different systems: 1-A, 2-B, 3-C, 4-D, 5-E. Inset image is colorimetric response Screening CDs for aggregation of AuNP In order to further confirm the aggregation behavior of AuNP, the effect of different types of CDs on the sensing system is explored in Figure 2. The raw data is first normalized to eliminate the potential bias caused by the difference in the original signal intensity of sensing system. The signal change value is defined as A620/520, where A620 and A520 are UV-Vis adsorption of


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CDs/AuNP aggregation at 620 nm and AuNP at 520 nm, respectively. We also synthesize other two types of CDs1 and CDs2 by hydrothermal treatment from Gly and Lys, respectively. When the individual CDs1 and CDs2 are added to the solution of AuNP, both the characteristic absorption peak and solution color do not change in Figure 2A and 2B. Only CDs3 can be assembled ‘shell’ on the surface of AuNP and the color changes from red to blue. The characteristic peak with red shift is observed at 620 nm in Figure 2A. AuNP restores dispersion with no effect of addition order of GSH. The solution color becomes red and the absorption peak remains at 520 nm in Figure 2B. Remarkably, CDs3/AuNP aggregation can be restored to a decentralized state when GSH is added, but salt-induced AuNP aggregation does not work as shown in Figure 2C. Because GSH prefer to bind with AuNP rather than CDs32-35, suggesting that the CDs desorbed from the surface of AuNP. It has been reported that the order of the binding strength is Au-S > Au-NH2 > Au-COOH36-40. These results demonstrate CDs3 can not only induce AuNP aggregation, but also the CDs/AuNP composite shows the reversible dispersion in the presence of GSH. Moreover, when the same concentration of CDs3 and its raw material of Ser are mixed with AuNP, respectively. Only CDs itself makes AuNP aggregation rather than its original ligand as illustrated in Figure 2D. These results demonstrate that CDs with unique properties can not only be assembled ‘shell’ on the surface of AuNP, but also induce the reversible aggregation/dispersion of AuNP in the presence of GSH.


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Figure 2 (A) UV-vis spectra of the different system: (1) AuNP + CDs1, (2) AuNP + GSH + CDs1, (3) AuNP + CDs1 + GSH, (4) AuNP + CDs2, (5) AuNP + GSH + CDs2, (6) AuNP + CDs2 + GSH, (7) CDs3/AuNP, (8) Addition of GSH before CDs3/AuNP, (9) Addition of GSH after CDs3/AuNP, (10) AuNP + NaCl, (11) AuNP + NaCl + GSH, (12) AuNP + Ser, (13) AuNP. (B) Effect of different types of CDs on sensing system; only CDs3 can induce aggregation of AuNP; (C) Effect of CDs3 or NaCl on the AuNP aggregation; (D) Effect of CDs and its corresponding amino acid (Ser) on AuNP aggregation. Stability for sensing system In order to obtain the accuracy and repeatability of the sensor, the stability of CDs/AuNP composite is very important. The kinetic behaviors of CDs/AuNP aggregation is studied by monitoring ratio values A620/520 as a function of time. As seen from Figure 3A, the ratio value


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gradually increases with the elongation of time and reaches equilibrium after ∼3 min, revealing a rapid formation of CDs/AuNP at room temperature. Further, the ratio value of response signal does not change with seven hours in the absence of Ag+ or in the presence of Ag+ and GSH. CDs/AuNP composite is very stable without the observation of any precipitate as illustrated in Figure 3B. These results suggest that CDs/AuNP composite is very stable through analysis process with 20 min.

Figure 3 (A) Ratio value of CDs3/AuNP composite as a function of time; (B) stability of CDs3/AuNP composite in the absence of or presence of Ag+ and GSH. Inset: the corresponding photographs. Optimization of experimental conditions As shown in Figure 4A, the other substances do not change CDs3/AuNP from aggregation into dispersion state and the solution displays blue color. Only GSH can effectively protect AuNP from being aggregated and the solution remains red. The sensitivity of this approach is also highly dependent on the concentration of AuNP. The ratio value of A620/520 is maximal when the concentration of AuNP is set at 2.0 nM. So, the concentration of AuNP is selected at 2.0 nM for further experiments in Figure 4B and Figure S4 (Supporting Information). The absorption


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ratio of CDs3/AuNP aggregation gradually decreases until the platform appears with increasing the concentration of GSH as indicated in Figure 4C and Figure S5 (Supporting Information). GSH can induce AuNP from aggregation into dispersion. Simultaneously, the solution becomes red. Consequently, 15 µM of GSH is chosen for our experiments. Finally, 2 nM of AuNP, 30 µg/mL of CDs3, and 15 µM of GSH are served as the optimal conditions in our assay.

Figure 4 Effect of different solution on absorption ratio A620/520 of CDs3/ AuNP: (A) Different substances; (B) AuNP with different concentrations (0-8.0 nM); (C) GSH with different concentrations (0-30 µM). Inset: the corresponding photographs. Sensitivity for Determination of Ag+ Under the optimal conditions, the sensitivity of the system for Ag+ is evaluated by using CDs/AuNP composite in the presence of GSH. The change in solution color and UV-vis absorption responses of different concentrations of Ag+ is shown in Figure 5A and Figure S6 (Supporting Information). In order to detect the analyte at different concentrations in real samples, the original sensing system is adjusted to dilute 3 times and 5 times, respectively. The calibration curves are established by the ratio value at A620/520 versus the concentration of Ag+. The curves exhibit a rising trend and finally reach the platform in the three systems in Figure 5B. A linear relationship is obtained over the concentration range from 100 to 300 nM, 300 to 600 nM, and 1000 to 3000 nM, respectively. Their corresponding correlation coefficients (R2)


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are 0.992, 0.996, and 0.998, respectively (Figure 5C, 5D and 5E). And the color of the solution changes from red to purple for the detection of Ag+ in the range of 140-200 nM, following to blue for the analyte (200-300 nM) in Figure 5F. According to the gradual visible color change, the limit of detection (LOD) for assay Ag+ ions can be observed to be 140 nM by the naked eyes. LOD is estimated to be 50 nM with a signal-to-noise ratio of 3 (3σ/slope, where σ is the standard deviation) by UV-vis spectrometry. LOD from both naked-eye and UV-vis linear curve are lower than the maximum level in drinking water permitted by the United States Environmental Protection Agency (USEPA) is 50 µg/L (∼460 nM). Moreover, comparing the LOD with other sensors reported literatures in Table 1, our strategy can achieve Ag+ detection at lower or comparable concentration. Therefore, this new colorimetric sensor based on CDs3/AuNP composite ‘aggregation-dispersion-aggregation’ has favorable potential for detection of Ag+.

Figure 5 Colorimetric detection of Ag+ (A) Absorption spectra; (B) Absorption ratio values at A620/520 of colorimetric assay against different concentrations of Ag+ (0-4000 nM) in diluted 5, 3 and 0 times the original system solution; Linearity of the assay versus the Ag+ different


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concentrations: (C) 100 to 300 nM; (D) 300 to 600 nM; (E) 1000 to 3000 nM. Error bars indicate the standard deviation of three independent experiments; (F) Photographs of solution after adding the different concentrations of Ag+ (0 -300 nM). Table 1 Comparison of this work with various reported methods Probes

Read out

Analytical

LOD

Selectivity

Ref.

(nM) Tween 20-AuNP

Absorption

1-8 µM

10

Hg2+, Ag+

25

Tween 20-AuNP

Absorption

0.4-1 µM

100

Hg2+, Ag+

15

DNA-AuNP

Absorption

0.59-59 nM

0.59

Ag+

41

DNA-AgNCs

Fluorescence

5-500 nM

10

Ag+

42

DNA

Fluorescence

0.5-13 µM

80

Ag+, Cysteine

43

CDs

Fluorescence

8-200 µM

5093

Ag+

44

CDs/AuNP

Absorption

100-4000 nM

50

Ag+

This work

Selectivity for Determination of Ag+ To assess the selectivity of our sensing system based on CDs3/AuNP, many other different metal ions including Cd2+, Fe3+, Ca2+, Mn2+, Cu2+, Co2+, Ni2+, Al3+, Zn2+, Pb2+ and Ag+ ions are tested under identical conditions. As investigated in previous reports, EDTA is chose as a masking agent because it can form more stable complexes with the interfere ions. The concentration of Ag+, other metal ions, and EDTA are 0.5 µM, 5 µM, and 0.1 mM, respectively. The results are achieved in Figure 6. It could be seen that only Ag+ causes the obvious changes of absorption spectrum in Figure 6A. The absorption value of A620/520 for Ag+ ions is up to 1.2 in Figure 6C. At the same time, the solution color becomes blue only after the addition of Ag+ ions in Figure 6D. Although the concentrations of other metal ions are 10-fold to Ag+, they alone


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have no effect on the sensitivity of Ag+ assay. Nevertheless, competitive experiments are performed in the presence of Ag+ with other metal ions above-mentioned. The absorption spectra, as well as the corresponding ratio value (A620/520) from the mixtures of Ag+ with other metal ions change similarly with that from Ag+ alone in Figure 6B and 6C. The colorimetric response caused by the mixtures of Ag+ and another anion is similar to that caused by solely Ag+ ions. Only the blank color still remains red and the corresponding peak at 520 nm is observed. While the others become blue with the characteristic peak at 620 nm in Figure 6B and 6E. These results declare that tested metal ions have no interference on the determination of Ag+. Therefore, this sensing system possesses the excellent selectivity towards Ag+.

Figure 6 UV-vis absorption spectra in the presence of EDTA: (A) Individual Ag+ and other metal ions; (B) Mixtures of Ag+ and another metal ions; (C) The ratio value (A620/520) with the corresponding to (A) and (B); (D) Photo images of individual Ag+ and other metal ions; (E) Photo images of mixtures of Ag+ and another metal ions. Error bars indicate the standard


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deviation of six independent experiments. The concentrations of Ag+, other metal ions, and EDTA are 0.5 µM, 5 µM, and 0.1 mM, respectively. Practical application In certain environmental samples, such as lake water, the concentrations of some metal ions are obviously higher than that of Ag+, so potential practical assay is necessary, and it is a crucial issue to the application of most common sensors. To confirm the practical application of the proposed approach, different concentrations of Ag+ (125 nM, 200 nM, and 275 nM) are spiked in tap water and lake water. In order to detect the concentration of Ag+ ions in real samples, the linear relationship in the range of 2.0-100 nM for detection Ag+ is obtained by using ICP-MS (Figure S7). The concentration of the silver ions in tap water and lake water is less than 2.1 nM, accounting for less than 2% of the Ag+-spiked concentration. So, the effect of the original content on the recovery is negligible. These results demonstrate a good accuracy for our sensor with the recovery in the range of 98.18%-108.00% for tap water and 93.09%-109.00% for lake water samples in Table 2. The coefficients of variation for the quantification are in the range of 0.21%-1.58%. Based on the experiment results, we believe that CDs3/AuNP system can be employed as probes for Ag+, which holds great potential in practical applications. Table 2 Results of the Ag+ recovery experiments performed in tap water and lake water Ag+/nM (Added)

Ag+/nM (Detected)

Recovery (%)

RSD (%)

1

125

135

108.00

0.72

2

200

198

99.00

1.53

3

275

270

98.18

0.63

1

125

120

96.00

1.58

2

200

218

109.00

0.21

Sample

Tap water

Lake water


17


3

275

256

93.09

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0.92

Conclusion In summary, a new colorimetric nanosensor for the sensitive and selective detection of Ag+ ions have been developed based on stable aggregation of AuNP triggered by CDs. The accuracy and repeatability of this sensor can be enhanced due to stable CDs/AuNP composite through analysis process. Simultaneously, successive multiple steps with ‘aggregation-dispersionaggregation’ mode can greatly improve the specificity and selectivity of this colorimetric sensor owing to the lower possibility of false positive results. Importantly, the system has been showed to be highly sensitive and selective detection of Ag+ than other metal ions. LOD from both naked-eye and UV-vis linear curve are lower than the maximum level in drinking water permitted by USEPA is 50 µg/L (∼460 nM). We further demonstrate the analytical potential of this system for monitoring Ag+ in water samples. Our study may give a new sight for application of CDs in sensors, environmental monitoring and preparation of carbon-based nanomaterials.

AUTHOR INFORMATION Corresponding Author [*] Dr Yueying Liu. Corresponding author. E-mail: [email protected] Phone/Fax: +86-10-68903047

Author Contributions


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The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS The authors gratefully acknowledge the National Natural Science Foundation of China (Grant No. 21105066, No. 21775087), Beijing Natural Science Foundation (Grant No. 2162010), Scientific Research Project of Beijing Educational Committee (Grant No. KM201610028008), and Cross-Disciplinary Research Project of Capital Normal University.

SUPPORTING INFORMATION Six figures in Supporting Information, Fluorescence spectra at excitation wavelengths of three CDs (Figure S1); UV-vis spectra of the different system (Figure S2); DLS diagram of the system (Figure S3); UV-Vis absorption spectra and ratio value (A620/520)

of AuNP with different

concentrations (0-8.0 nM) (Figure S4); UV-Vis absorption spectra and ratio value (A620/520) of GSH with different concentrations (0-30.0 µM) (Figure S5); Absorption spectra of the diluted different sensing system against different concentrations of Ag+ ions (Figure S6); Linearity of the assay versus the Ag+ different concentrations using ICP-MS (Figure S7).

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TOC graphic

Synopsis: A colorimetric nanosensor based on the aggregation of CDs-triggered AuNP for the detection of toxic Ag+ in the presence of GSH.


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Colorimetric Nanosensor Based on the Aggregation of AuNP

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