Au nanoparticle decorated graphene oxide as a novel coating for solid-phase microextraction

Abstract

A novel solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with Au nanoparticle decorated graphene oxide was prepared using a novel protocol. Coupled with gas chromatography-flame ionization detection (GC-FID), the extraction performance of the fiber was tested with aromatic hydrophobic organic chemicals as the model analytes. The fiber showed excellent extraction efficiency, good mechanical strength, and good stability in acid, alkali and organic solutions, and under high temperature. Effects of extraction time, extraction temperature, ionic strength and desorption conditions were investigated and optimized. The relative standard deviations for the single fiber repeatability and fiber-to-fiber reproducibility were less than 6.90 and 16.87%, respectively. Compared with graphene oxide/solid-phase microextraction fibers and Au nanoparticle/solid-phase microextraction fibers, the fiber has lower detection limits (≤60 ng L⁻¹) and a better linear range for all analytes. Correlation coefficients ranged from 0.9958 to 0.9993. The as-established SPME-GC-FID method was successfully used for two real natural samples, and recovery of the analytes spiked at 10 μg L⁻¹ ranged from 82.65% to 126.06%.

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1. Introduction

As a sampling and sample preparation technique, SPME was first introduced by Belardi and Pawliszyn in 1989.¹ During the last decade, it has undergone considerable development and wide applications in food,^2,3 the environment,^4,5 biochemistry^6,7 and medicine^8,9 due to its simplicity, rapidity, high sensitivity and solvent-free protocol. It has been coupled with various instruments and analytical technologies such as GC,¹⁰ high performance liquid chromatography (HPLC),¹¹ capillary electrophoresis (CE),¹² ultraviolet spectrophotometry (UV)¹³ and mass spectrometry (MS).¹⁴ The core part of the SPME technique is the coating, a stationary phase that adsorbs the analytes from various samples. Now, numerous materials^15–17 have been used successfully as coating absorbents to improve the extraction efficiency. In addition, because the conventional fused-silica fibers are fragile in operation, metal wires have become promising support substrates for SPME.^18–22

Nanomaterials have attracted great attention lately in separation science due to their excellent physical and chemical properties. Carbon nanotubes,²³ fullerenes,²⁴ nanoporous silica²⁵ and some nano-structured metal oxides^26,27 have been successfully used as SPME fiber coatings. Graphene shares many important properties with the materials mentioned above, and has some special properties such as long term stability and a huge surface area, and thus has great potential as a sorbent material in SPME. Chen et al.²⁸ firstly prepared and evaluated the graphene-coated SPME fiber. Thereafter, Zhang et al.²⁹ prepared a plunger-in-needle SPME fiber with a graphene-based sol–gel coating for determination of polybrominated diphenyl ethers. In spite of this, graphene’s stable structure has severely restricted its potential application as a fiber coating. The presence of abundant oxygenous groups in graphene oxide (GO) makes it feasible to be assembled onto a substrate. As another nanomaterial, Au nanoparticles (Au NPs) possess many special properties such as long term stability, a high surface-to-volume ratio, an ease of chemical modification, size dependent electrical properties, compatibility with biomolecules,^30,31 and so on. In addition, organic molecules containing thiol (–SH) or amino (–NH₂) groups can be adsorbed spontaneously onto the Au surface to form a well-organized self-assembled monolayer (SAM).³² Because of the simplicity and flexibility of this approach, it has attracted great attention and has been widely used in sample preconcentration^33–35 and separation science.^36,37

Aromatic hydrophobic organic chemicals (HOCs) are important environmental contaminants in air, soil and water. Many national organizations and government departments have developed laws and regulations to set limits for them to protect public health. Based on these considerations, a new metal-supported SPME fiber was successfully developed to extract and concentrate the aromatic compounds in aqueous solutions using the physicochemical affinity between aromatic HOCs and the Au NP decorated GO coating in this study. Firstly, to overcome the fragility drawback of conventional fused-silica fibers, we adopted the technique of magnetron sputtering to introduce a Si interlayer on a stainless steel wire that had easily modified active groups, according to the procedure of our previous work.³⁸ Secondly, the nanomaterials of GO and Au NPs were used successfully as fiber coating absorbents. The novel Au NP decorated GO-coated SPME fiber was prepared through a simple layer by layer (LBL) self-assembly process of GO and a self-assembled monolayer process between the thiol (–SH) and Au NPs. Effects of the adsorption and desorption factors were investigated systematically. The single fiber repeatability and fiber-to-fiber reproducibility are both satisfactory. Moreover, the analysis of ten aromatic HOCs in two real water samples (running water and snow water) showed satisfactory results. The inherent chemical stability of Au and GO makes the novel Au NPs/GO/SPME fiber show high stability and durability towards acid, alkali and organic solutions, and high temperature.

2. Experimental

2.1 Materials and reagents

Stainless steel wire (SUS304, Φ140 μm) was purchased from the YixingShenglong Metal Wire Net Co. (Jiangsu, China). Naphthalene, fluorene, anthracene, fluoranthene, 1,4-dichlorobenzene, 1,4-dibromobenzene, 2-bromonaphthalene, bromobenzene, biphenyl and m-terphenyl were obtained from the Shanghai Chemical Reagent Corporation (Shanghai, China). Trimethoxysilylpropanethiol and 3-aminopropyltriethoxysilane (APTES) were obtained from the Chemical Industrial Corporation of Gaizhou (China). Graphene oxide was obtained from Nanoon Nanomaterials Science and Technology Co., Ltd. (Langfang, China). Chloroauric acid (HAuCl₄·4H₂O) was purchased from the Shenyang Keda Chemical Reagent Factory (Liaoning, China). All the chemicals were analytical grade and used as received.

2.2 Instruments

An Agilent 7890A series gas chromatograph (Agilent Technologies, USA) equipped with a flame ionization detector (FID) was used. Chromatographic separation was carried out on an AT.SE-54 capillary column (30 m × 0.32 mm i.d. × 0.33 μm film thickness).

Ultrapure nitrogen (>99.999%) was used as the carrier and make-up gas at 1 mL min⁻¹ and 30 mL min⁻¹, respectively. The injector and detector temperatures were both fixed at 300 °C. Separation was achieved using a temperature program as follows: the column temperature was initially held at 50 °C, and programmed to increase by 10 °C min⁻¹ to 110 °C, and then programmed to increase by 2 °C min⁻¹ to 120 °C, and finally programmed to increase by 10 °C min⁻¹ to 300 °C.

Scanning electron microscopy (SEM) images of the as-prepared Au NPs/GO/SPME fiber were obtained on an S-4800 field emission scanning electron microscope (Hitachi, Japan) equipped with an energy dispersive X-ray spectroscopy (EDX) detector.

2.3 Sample preparation

All the analytes (naphthalene, fluorene, anthracene, fluoranthene, 1,4-dichlorobenzene, 1,4-dibromobenzene, 2-bromonaphthalene, bromobenzene, biphenyl and m-terphenyl) were dissolved in ethanol, with a concentration of 1 mg mL⁻¹. HAuCl₄·4H₂O of 1% (w/w) was prepared using distilled water as the solvent and was stored at 4 °C. Two real samples (collected from running water and snow water in Lanzhou, China) were filtered through a 0.45 μm filter. All the sample solutions were stored at 4 °C in a refrigerator.

2.4 Preparation of the SPME fiber

The Au NP gel was prepared through the reduction of HAuCl₄ by trisodium citrate as described by Frens and Kolliod.³⁹ Briefly, 60 mL of HAuCl₄ aqueous solution (0.01%, w/w) was added into a round-bottom flask and then heated at 115 °C under vigorous stirring. While boiling, 1.2 mL of trisodium citrate aqueous solution (1%, w/w) was added quickly. The solution turned to wine red in 2 min. Finally, the solution was heated for 15 min continuously. Stirring did not stop until the solution cooled to room temperature. The prepared Au NP gel was stored at 4 °C in the refrigerator.

The Si interlayer was prepared using a medium frequency unbalanced magnetron sputtering method in a multifunctional deposition system, according to our previous work.³⁸ Then, the stainless steel wire with the Si interlayer was cleaned in an ultrasonic bath with ethanol and acetone for 10 min, respectively. Finally, the hydroxylation procedure of the Si interlayer was similar to that in ref. 38 and the silanization procedure was the same as that in ref. 40.

The GO/SPME fiber was prepared according to our previous work.⁴¹ Firstly, the silanized part of the fiber was put into a GO solution (0.2 mg mL⁻¹) for 12 h in an oven (80 °C). Then it was removed and heated in the oven (120 °C) for 2 h, followed by being washed with ethanol and ultrapure water, respectively. This procedure was repeated until the GO coating reached the required thickness (4 μm). Thereafter, the dried GO-coated fiber was immersed into a trimethoxysilylpropanethiol solution of toluene (1 : 1, v/v) for 12 h. After that, the fiber was put in an oven (120 °C) for 2 h to facilitate the anchoring of the trimethoxysilylpropanethiol molecules, followed by being washed with toluene, acetone, and ultrapure water in turn. Finally, the sulfhydryl propyl modified fiber was immersed in the as-prepared Au NP gel for 48 h to adsorb the Au NPs onto it. The excess Au NPs were removed by washing with deionized water. This procedure was repeated three times.

2.5 SPME procedure

The mixed standard solutions of the ten aromatic HOCs (naphthalene, fluorene, anthracene, fluoranthene, 1,4-dichlorobenzene, 1,4-dibromobenzene, bromobenzene, 2-bromonaphthalene, biphenyl and m-terphenyl) were used to evaluate the extraction capacity of the SPME fiber coatings. A modified 5 μL-syringe was used as a SPME device, as described in ref. 42. 22 mL of the prepared sample solution was put in a 25 mL glass vial with a rubber cork. The pretreated syringe was put into the glass vial and the fiber was dipped in the sample solution directly. A stirring speed of 800 rpm, using magnetic stirring apparatus, was used to accelerate the extraction process. Extraction temperature and time, ionic strength, and desorption temperature and time were all optimized in this work. The extraction was performed under all the optimized conditions.

2.6 Stability of the fiber

The tip of the as-prepared fiber was dipped in HCl (0.1 M), NaOH (0.1 M), ethanol and n-hexane solutions for 24 h under room temperature, successively. Then, the fiber was taken out for the extraction experiment to test its chemical stability. The thermal stability of the fiber was also studied through heating the fiber at 320 °C for 2 h in the GC inlet. The peak areas of the analytes (200 μg L⁻¹) were compared before and after treatment to evaluate the stability in acid, alkali and organic solutions, and under high temperature.

3. Results and discussion

3.1 Characterization of the Au NPs/GO/SPME fibers

Fig. 1 shows the preparation process of the as-prepared Au NPs/GO/SPME fiber. Firstly the Si interlayer was introduced on the stainless steel wire using the technique of magnetron sputtering. After that, the Si interlayer was hydroxylated by piranha solution (H₂SO₄ (98%) : H₂O₂ (30%) = 7 : 3) and then silanized by APTES solution. The GO/SPME fibers were formed by the reaction between the carboxyl and epoxy groups in GO and the –NH₂ groups in APTES. The GO coating reached the required thickness through a simple LBL self-assembly process of GO. Thereafter, the sulfhydryl propyl modified GO/SPME fibers were prepared by assembling trimethoxysilylpropanethiol molecules on the GO via C–O–Si bonding. Finally, due to the attraction between Au NPs and –SH, Au NPs were successfully adsorbed onto the surface of the sulfhydryl propyl modified GO/SPME fiber.

Fig. 1 Schematic illustration of the preparation process of the as-prepared Au NPs/GO/SPME fiber.

The surface properties of the as-prepared Au NPs/GO/SPME fiber were characterized using an S-4800 field emission scanning electron microscope (Hitachi, Tokyo, Japan) equipped with an energy dispersive X-ray spectroscopy (EDX) detector. The scanning electron micrographs of the GO/SPME fiber and Au NPs/GO/SPME fiber are shown in Fig. 2. Fig. 2a and b show the planar SEM images of the Au NPs/GO/SPME fiber at a magnification of 400 and 100 000, respectively. As shown in Fig. 2a, a coating can be seen compactly covered on the fiber surface. In Fig. 2b, Au NPs can be seen successfully self-assembled on the fiber. Fig. 2c shows the planar SEM image of the GO/SPME fiber at a magnification of 100 000. Compared with Fig. 2b, there were no Au NPs on the surface of the fiber. Only a multilayer-GO coating can be seen on the fiber surface. In addition, scanning electron microscopes are routinely fitted with EDX equipment, which is used as an analytical technique for elemental analysis. The as-prepared Au NPs/GO/SPME fiber was also analyzed by EDX. As shown in Fig. 3, we detected the presence of Fe, Au, silicon, sulfur etc. on the surface, which certified that the Au NPs were successfully decorated onto the sulfhydryl propyl modified GO/SPME fiber.

Fig. 2 SEM images of the as-prepared Au NPs/GO/SPME fiber at a magnification of (a) 400 and a further magnification of (b) 100 000; SEM image of the GO/SPME fiber at a magnification of (c) 100 000.

Fig. 3 EDX analysis of the as-prepared Au NPs/GO/SPME fiber.

3.2 Optimization of the SPME parameters

Ten aromatic HOCs were selected to assess the extraction performance of the SPME fiber, coupled with GC. To achieve the best extraction efficiency and highest sensitivity, the effects of extracting parameters and desorption conditions were systematically studied in this study.

Generally speaking, the extraction time is dependent on the equilibrium time of the analyte’s distribution between the fiber and sample solution. As can be seen from Fig. 4, 40 min is sufficient to establish the equilibrium extraction for most of the analytes. Therefore, 40 min was ultimately chosen as the optimized extraction time. The effect of temperature on the SPME extraction is two-fold: on one hand, an elevated temperature could elevate the mobility of the molecules and so the extraction rate; on the other hand, Henry’s constant decreases the distribution coefficient of the analytes between the extraction coating and sample solution. So it is very important to select an appropriate temperature. As can be seen from Fig. 5, with the increase of the temperature, the extraction efficiency reduced for most of the compounds and increased for some compounds containing more benzene rings. These results could be attributed to the elevated temperature enhancing the mobility of molecules, especially for the molecules with poor solubility in water. While the compounds containing more benzene rings occupied the adsorption sites, the extraction efficiency for other compounds reduced. Therefore, the optimal extraction temperatures for all the compounds are not exactly the same, and we have to choose a relatively optimal temperature. An extraction temperature of 40 °C was chosen as the optimal extraction temperature.

Fig. 4 Effect of extraction time on the peak area of the analytes. Conditions: extraction temperature, 40 °C; salt concentration, 30% NaCl; stirring rate, 800 rpm; desorption temperature, 300 °C; desorption time, 5 min; aromatic HOC concentration, 200 μg L⁻¹.

Fig. 5 Effect of extraction temperature on the peak area of the analytes. Conditions: extraction time, 40 min; salt concentration, 30% NaCl; stirring rate, 800 rpm; desorption temperature, 300 °C; desorption time, 5 min; aromatic HOC concentration, 200 μg L⁻¹.

Additionally, ionic strength also has a double influence on the extraction. Salting-out effects and procompetitive effects will influence the extraction diversely with increasing of the ionic strength. So in our work, the effect of NaCl concentration on the extraction efficiency was studied from 0 to 30 wt%. As shown in Fig. 6, the peak areas for the analytes increased as the salt concentration increased from 0 to 30%. So the salting-out effect plays the major role and the peak areas for all the analytes increase with the increase of the NaCl content. While at room temperature, a 30% NaCl content was close to the saturated concentration in water. Therefore, 30% NaCl content was selected as the optimal salt concentration.

Fig. 6 Effect of ionic strength on the peak area of the analytes. Conditions: extraction time, 40 min; extraction temperature, 40 °C; stirring rate, 800 rpm; desorption temperature, 300 °C; desorption time, 5 min; aromatic HOC concentration, 200 μg L⁻¹.

To reach the highest sensitivity, desorption conditions, including temperature and time, were evaluated to ensure the analytes were completely desorbed from the SPME fiber. Firstly, the desorption temperature was evaluated at 260, 280, 300 and 320 °C for 5 min. The results indicated that 300 °C was sufficient for complete desorption. Then, desorption time profiles ranging from 2 to 6 min were evaluated. The results showed that desorption at 300 °C for 5 min was the optimum desorption conditions. The images from the optimized desorption conditions are shown in the ESI.† Fig. 7 is the GC chromatogram of the ten aromatic compounds (200 μg L⁻¹) dissolved in ultrapure water under all the optimal extraction and desorption conditions.

Fig. 7 The chromatogram of the aromatic HOCs (200 μg L⁻¹) dissolved in ultrapure water. Conditions: extraction time, 40 min; extraction temperature, 40 °C; salt concentration, 30% NaCl; stirring rate, 800 rpm; desorption temperature, 300 °C; desorption time, 5 min.

3.3 Detection limit, precision and accuracy

The analytical evaluation parameters for the as-prepared Au NPs/GO/SPME fiber-SPME-GC were investigated under the optimized conditions. The solutions used in the study were prepared by diluting the stored solution with ultrapure water. The parameters for the extraction of the ten aromatic HOCs are listed in Table 1. Under the optimized conditions, all the compounds exhibit wide linear ranges with good linearity (R² > 0.99). The limits of detection (LODs) are in the range of 5–60 ng L⁻¹. The relative standard deviations (RSDs) for a single fiber are from 2.73% to 6.90%. The fiber-to-fiber reproducibility was also evaluated and the RSDs for all the analytes are in the range of 6.63–16.87%. Compared with a GO/SPME fiber,⁴¹ Ag-coated SPME fiber⁴³ and Au NPs/SPME fiber,³³ the as-prepared Au NPs/GO/SPME fiber has lower detection limits.

Table 1 Characteristic data of the established Au NPs/GO/SPME-GC method for determination of ten aromatic HOCs and a comparison with other methods

Compound	As-prepared Au NPs/GO/SPME fiber					GO/SPME fiber^41		LODs of Ag NPs/SPME fiber (ng L^−1)^43	LODs of Au NPs/SPME fiber (ng L^−1)^33
	Linear range (μg L^−1)	Linearity	LODs (ng L^−1)	Repeatability (n = 3, %) (single fiber)	Reproducibility (n = 3, %) (fiber-to-fiber)	Linear range (μg L^−1)	LODs (ng L^−1)
Naphthalene	1–300	0.9965	50	5.24	10.64	1–200	80	100	250
Fluorene	0.1–250	0.9973	25	3.45	8.42	0.5–200	40	50	50
Anthracene	0.1–250	0.9982	10	6.90	13.35	0.5–200	40		25
Fluoranthene	0.05–200	0.9993	10	4.19	6.63	0.05–200	5	20	25
Bromobenzene	0.5–300	0.9975	30	5.22	9.79				—
1,4-Dichlorobenzene	0.5–300	0.9968	60	5.15	7.18
1,4-Dibromobenzene	0.5–300	0.9982	30	4.46	11.46
2-Bromonaphthalene	0.5–300	0.9958	20	6.57	9.92
Biphenyl	0.1–300	0.9983	20	3.38	16.87				50
m-Terphenyl	0.05–200	0.9988	10	2.73	14.19				12.5

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3.4 Extraction selectivity studies

Compared with the other compounds, the peak areas are lower for bromobenzene, 1,4-dichlorobenzene, 1,4-dibromobenzene, and naphthalene. Compared with 1,4-dibromobenzene, the peak areas are lower for bromobenzene and 1,4-dichlorobenzene. The experimental results agreed well with the theoretical predictions. Firstly, the extraction efficiency increased in the order of the number of benzene rings, because of the π–π interactions between the inner GO layer and the aromatic HOCs. In addition, these results can be attributed to the hydrophobic characteristics of the Au surface⁴⁴ and the interactions between the π-system of the aromatic HOCs and Au, which strengthened the affinity beyond the hydrophobic effect, thus the extraction capacities were improved. Meanwhile, in theoretical and computational chemistry, gold is “anomalous” due to its very large relativistic effects.⁴⁵ The relativistic effects lead to excellent electronic mobility, which makes it easier to use its empty valence shell to form coordinate bonds with atoms having lone pair electrons, or to use its valency electrons to form feedback-coordinate bonds with atoms having an unoccupied orbital. So the Au NPs/GO/SPME fiber showed an excellent extraction efficiency for the chlorine and bromine substituted aromatic HOCs. Based on these theories and research, we ascribed the selective extraction of aromatic HOCs on the Au NPs/GO/SPME fiber to the π–π interactions between the inner GO layer and the aromatic HOCs, the hydrophobic characteristics of the Au surface, the interactions between the π-system of the aromatic HOCs and Au, and the empty valence shell of Au. To sum up, the Au NPs/SPME fiber exhibited superb selectivity to some aromatic HOCs, which is favorable for its practical utilization.

3.5 Application to real samples

Aromatic HOCs are ubiquitous carcinogenic environmental contaminants in air, soil and water, and are serious enough to threaten public health. Many national organizations and government departments have developed laws and regulations to set limits for them to protect public health. On the basis of the distribution of aromatic HOCs in the environment, two real water samples (running water and snow water) were chosen to investigate the reliability of the as-prepared Au NPs/GO/SPME fiber-SPME-GC-FID method. In our work, the ten aromatic HOCs cannot be detected in running water, while anthracene, fluoranthene and m-terphenyl can be detected but cannot be quantified in snow water. Fig. 8a illustrates the chromatogram of the standard ten aromatic HOC solution. Fig. 8b illustrates the chromatogram of the ten aromatic HOCs in a snow water sample spiked with 10 μg L⁻¹ of each aromatic HOC and extracted using the Au NPs/GO/SPME fiber. In order to demonstrate the applicability and reliability of the method, the recoveries of the target compounds were determined in the two water samples spiked at 10 μg L⁻¹. As we can see from Table 2, the recoveries are 87.73–113.82% for all the analytes in the running water sample, and 82.65–126.06% for the snow water sample.

Fig. 8 Typical chromatogram of (a) standard aromatic HOC solution, (b) ten aromatic HOCs in a snow water sample spiked with the ten aromatic HOCs (10 μg L⁻¹) and extracted using the Au NPs/GO/SPME fiber. Peaks: (1) bromobenzene, (2) 1,4-dichlorobenzene, (3) 1,4-dibromobenzene, (4) naphthalene, (5) biphenyl, (6) 2-bromonaphthalene, (7) fluorene, (8) anthracene, (9) fluoranthene, (10) m-terphenyl.

Table 2 Determination results and recoveries of ten aromatic HOCs for spiked running water and snow water samples

Compound	Recovery, RSD (%)
	Running water		Snow water
	No spiking	Spiked 10 μg L^−1	No spiking	Spiked 10 μg L^−1
Naphthalene	Not detected	89.27 ± 5.11	Not detected	94.15 ± 5.53
Fluorene	Not detected	95.18 ± 2.69	Not detected	116.34 ± 6.02
Anthracene	Not detected	104.55 ± 4.03	Detected but not quantified	96.49 ± 4.46
Fluoranthene	Not detected	95.46 ± 3.47	Detected but not quantified	107.68 ± 3.52
Bromobenzene	Not detected	108.52 ± 4.24	Not detected	85.95 ± 6.51
1,4-Dichlorobenzene	Not detected	113.82 ± 5.48	Not detected	113.36 ± 5.47
1,4-Dibromobenzene	Not detected	97.45 ± 3.66	Not detected	126.06 ± 6.64
2-Bromonaphthalene	Not detected	87.73 ± 6.40	Not detected	89.79 ± 3.84
Biphenyl	Not detected	92.89 ± 2.56	Not detected	109.86 ± 4.29
m-Terphenyl	Not detected	98.08 ± 3.94	Detected but not quantified	82.65 ± 6.58

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3.6 Stability

The lifetime of the fiber coating is a very important parameter for SPME in practical applications. The coating is usually damaged by harsh conditions like high temperature, organic solvent, strong alkaline and acidic solutions in the matrix. In this paper, its chemical stability was studied by exposing the fiber to HCl (0.1 M), NaOH (0.1 M), ethanol and n-hexane for 24 h, respectively. The thermal stability was also studied through heating the fiber at 320 °C for 2 h in the GC inlet. As shown in Fig. 9, the results showed that the peak areas had no obvious change before and after treatment. That is to say, the as-prepared Au NPs/GO/SPME fiber could function with a temperature of at least 320 °C and it demonstrated excellent stability towards acid, alkali and organic solutions.

Fig. 9 Stability of the Au NPs/GO/SPME fiber. Conditions: concentration, 200 μg L⁻¹; extraction time, 40 min; extraction temperature, 40 °C; content of NaCl, 30% (w/w); stirring rate, 800 rpm; desorption temperature, 300 °C; desorption time, 5 min.

4. Conclusions

In this study, the as-prepared Au NPs/GO/SPME fibers were prepared using a novel protocol with a stainless steel wire as the fiber substrate. A multilayer-GO coated fiber was successfully prepared based on the abundant oxygenous groups in the GO molecules and the strong van der Waals interactions present in GO. Then trimethoxysilylpropanethiol was successfully self-assembled on the GO via C–O–Si bonding. Finally, the Au NPs were self-assembled on the fiber via the attraction between the Au NPs and –SH. Coupled with GC analysis, the novel fiber was used to extract ten aromatic HOCs in aqueous solutions and was applied to two real samples, achieving satisfactory results. Based on the metal substrate and the chemical bonding design, the novel fiber exhibited good stability and durability to high temperature and acidic, alkali and organic solvents, as well as good extraction repeatability and fiber-to-fiber reproducibility. In addition, its calibration exhibited a wide linearity range and low LODs for extracting ten aromatic HOCs coupled with GC.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (no. 21105107 and no. 21175143).

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Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c4ra16740f

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