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SPECIAL ISSUE: ENVIRONMENTAL CHEMISTRY
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A highly sensitive and selective resonance Rayleigh scattering method for Hg2+ based on the nanocatalytic amplification

Key Laboratory of Ecology of Rare and Endangered Species and Environmental Conservation of Education Ministry, Guangxi Normal University, Guilin 541004, China
Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guangxi Normal University, Guilin 541004, China

⁎Corresponding authors at: Key Laboratory of Ecology of Rare and Endangered Species and Environmental Conservation of Education Ministry, Guangxi Normal University, Guilin 541004, China. Tel.: +86 0773 5846141; fax: +86 0773 5846201. ahliang2008@163.com (Aihui Liang), zljiang@mailbox.gxnu.edu.cn (Zhiliang Jiang)

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

In 0.2 mol/L HCl–0.22 mol/L HNO3 medium, trace Hg2+ catalyzed NaH2PO2 reduction of HAuCl4 to form gold nanoparticles (AuNPs), which exhibited a strong resonance Rayleigh scattering (RRS) effect at 370 nm. With increasing of [Hg2+], the RRS effect enhanced due to more AuNP generated from the catalytic reaction. Under the chosen conditions, the enhanced RRS intensity at 370 nm is linear to Hg2+ concentration in the range of 5.0–450 × 10−9 mol/L, with a detection limit of 0.1 nmol/L. This RRS method was applied for the determination of Hg in water samples, with high sensitivity and good selectivity, and its results were agreement with that of atomic fluorescence spectrometry.

Keywords

Hg(II)
Nanocatalysis
Resonance Rayleigh scattering
1

1 Introduction

As the economy development, the harm caused by toxic heavy metal pollution on the environment and human health has aroused widespread concern. Mercury has been widely recognized as one of the most hazardous pollutants and highly dangerous elements, it can cause great, long-term toxic effects on human and environment even at very low concentrations (Clarkson, 2002). Inorganic mercury can be combined with the protein sulfhydryl that would inhibit the activity of the enzyme and disruption of cell metabolism. The organic mercury such as methylmercury with strongest toxicity which can encroach the body’s central nervous system and cause speech and memory disorders (Hassan et al., 2012). Thus, simple, rapid, sensitive, and selective detection of mercury is of great significance for biochemistry, environmental science, and medicine. At present, several methods have been reported to assay Hg2+, such as atomic spectrometry (Angeli et al., 2011; Resano et al., 2009), surface-enhanced Raman scattering spectroscopy (Ren et al., 2012; Wang and Chen, 2009), colorimetry (Fan et al., 2010; Jiang et al., 2012a,b; Lee et al., 2007), and resonance Rayleigh scattering spectroscopy (RRS) (Jiang et al., 2008; Kim et al., 2012; Rodrigues et al., 2010; Wu et al., 2012; Yin et al., 2012). Atomic spectrometry, especially atomic absorption spectrometry (AAS), is commonly used to determine trace Hg. However, the instrument is expensive and analytical time is long. The colorimetry is simple and economic, but with poor sensitivity. Surface-enhanced Raman scattering spectroscopy is difficult to quantitative analysis of Hg, with disadvantage of expensive instrument and bad reproducibility (Li et al., 2012). The RRS method has been applied in inorganic and organic analysis (Chen et al., 2012; Jiang et al., 2012a,b; Li et al., 2011; Ling et al., 2009; Liu et al., 2009; Song et al., 2012; Zou et al., 2012). Recently, a RRS method has been established to determine mercury ion, based on nanogold-labeled aptamer reaction (Jiang et al., 2008). However, the labeling step is complicated and long, and precious nucleic acid reagents were used. Up to date, there is no nanocatalytic RRS method for trace Hg. In this article, a simple, low-cost, sensitive and selective RRS spectral method has been established to determine mercury ion, which is based on the trace Hg2+ catalyzing NaH2PO2 reduction of HAuCl4 to form AuNPs that exhibited a strong RRS peak at 370 nm.

2

2 Materials and methods

2.1

2.1 Apparatus and reagents

A model of F-7000 fluorescence spectrophotometer (Hitachi Company, Japan) was used to record the RRS intensity, with the excited and emission slit of 5.0 nm, emission filter = 1% T attenuator, and photoelectron multiple tube (PMT) voltage of 400 V, and a model of JLM-6380LV scan electron microscope (Electronic Co., Ltd, Japan) were used.

A 10 mmol/L Hg2+ stock standard solution was prepared as follows: a 0.2715 g HgCl2 (National Pharmaceutical Group Chemical Reagents Company, China) was dissolved in 100 mL water. A 10 μmol/L Hg2+ working solution was obtained freshly by diluting with water. A 1.1 mol/L HNO3 solution, 1 mol/L HCl solution, 4 mmol/L HAuCl4, 5 mmol/L KMnO4, 10 mg/mL polyethylene glycol (PEG) 10000, 0.14 mol/L NH2OH⋅HCl, 1% trisodium citrate and 3.75 mol/L NaH2PO2 solution were prepared. All regents were of analytical grade and the water was doubly distilled. The room temperature was 25 °C.

Preparation of AuNPs: In a 250 mL round-bottom flask equipped with 50 mL water and put on magnetic stirrer, adding 2.0 mL of 1% trisodium citrate after the water boiling. After the water boiling again, adding 500 μL of 1% HAuCl4 quickly and maintaining the water boiling. The solution turned red within 5 min and the final color changed to brilliant red. Boiling continued for 10 min, the heating source was removed, and the colloid was not stirred until cold. Last the solution was transferred to a 50 mL volumetric flask and diluted to 50.0 mL with water. The AuNP concentration is 58 μg/mL Au, and its size is 10 nm.

2.2

2.2 Procedure

A 400 μL 1.1 mol/L HNO3 solution, 40 μL 10 μmol/L HgCl2 solution, 100 μL 5 mmol/L KMnO4 solution, 40 μL 4.0 mmol/L HAuCl4 solution, 400 μL 1.0 mol/L HCl solution, 80 μL 10 mg/mL PEG10000 solution and 100 μL 0.14 mmol/L NH2OH⋅HCl solution were added to a 5 mL graduated tube successively, and mixed well. Then, a 100 μL 3.75 mol/L NaH2PO2 solution was added, and diluted to 2.0 mL to start the reaction. The mixture was placed in room temperature (25 °C) for 15 min. The RRS spectra were recorded by means of synchronous scanning excited wavelength λex and emission wavelength λem (λex − λem = Δλ = 0) on fluorescence spectrophotometer. The RRS intensity at 370 nm (I370nm) and the blank solution without Hg2+ (I0) were recorded. The value of ΔI = (I370nm − I0) was calculated.

3

3 Results and discussion

3.1

3.1 Principle

In 0.2 mol/L HCl–0.22 mol/L HNO3 media, the NaH2PO2 reduce Hg2+ to form Hg nanoparticles (HgNPs) and the HgNPs catalyzed NaH2PO2 reduce HAuCl4 to generate small AuNPs. These formed small AuNPs also have catalysis on the reaction of NaH2PO2–HAuCl4 that called as autocatalysis. The reaction of Hg2+–NaH2PO2 was considered by the RRS technique and the result showed that the Hg2+ was reduced by NaH2PO2 to form Hg nanoparticles. The linear relationship between Hg(II) concentration and ΔI value showed that the reaction order for Hg(II) catalyst is 1. According to our results and the reference (Chen, 1980; Jiang et al., 2008), the main reaction mechanism is as follows,

(1)
HgCl2+NaH2PO2Hg(fast)
(2)
nHgHgNPs(fast)
(3)
Au3++NaH2PO2Au+(fast)
(4)
Au++NaH2PO2HgNPs catalysisAu(slow)
(5)
nAuAuNP(fast)
(6)
Au++NaH2PO2AuNPs catalysisAu(slow)
(7)
nAuNPsBig AuNPs(fast)
The reduction of Hg2+ to Hg and Au3+ to Au+ is fast step in the catalytic reaction because the reducer concentration of NaH2PO2 is high (0.188 mol/L) and the value of potential different is big. There are strong inter-atomic forces between metal Hg atoms or metal Au atoms or small AuNPs, that is, metal Hg atoms, metal Au atoms and small AuNPs were rapidly aggregated to HgNPs, AuNPs and big AuNPs respectively. Eqs. (4) and (6) are slow, that is, rate control steps. When the concentration of Hg2+ increased, the formed nanocatalyst both HgNPs and AuNPs increased, the two rate control steps quicken, and the catalytic reaction rate enhanced that will result to form more AuNPs, the color of mixing solution quickly changed from blue to red. Thus, the AuNPs RRS intensity at 370 nm increased linearly with concentration of Hg2+ increasing. According to the principles of catalytic kinetic analysis and RRS (Chen, 1980; Jiang et al., 2008), we established a new catalytic RRS method to determine trace Hg2+ (Fig. 1).
Principle of nanocatalytic RRS method for Hg2+.
Figure 1
Principle of nanocatalytic RRS method for Hg2+.

3.2

3.2 Scanning electron microscopy

According to the procedure, taken 1.5 mL of reaction solution into a 2 mL centrifuge tube and centrifuged 20 min (150 × 100 r/min), discarded the supernatant and added water to 1.5 mL then dispersed 30 min with ultrasonic. After centrifuged again, added 1 mL water and dispersed 30 min. Taken 2 μL sample solution by pipette dripping on silicon slice and dried naturally. The scanning electron microscope (SEM) indicated that there are AuNPs in the system with average size of 60 nm (Fig. 2). For the blank, there are very few of AuNPs which cannot be observed by SEM.

Scanning electron microscope of the nanocatalytic system. 0.22 mol/L HNO3 + 450 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.
Figure 2
Scanning electron microscope of the nanocatalytic system. 0.22 mol/L HNO3 + 450 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.

3.3

3.3 RRS spectra

Fig. 3 is the RRS spectra of Hg2+–HAuCl4–NaH2PO2 system, there are three strong Rayleigh scattering peaks at 280 nm, 370 nm and 550 nm respectively. The peak at 280 nm caused by the lamp maximal emission at 280 nm, and other two peaks are owing to the RRS effect of AuNPs. The peak at 370 nm is the strongest and the RRS intensity increased linearly with concentrations of Hg2+, other two peaks do not have good linear response. Thus, a wavelength of 370 nm was selected to detect trace Hg2+. Because the Hg(II) catalyst concentration is very low (5.0–450 × 10−9 mol/L), the formed Hg nanoparticles do not affect the RRS spectra of the analytical systems.

RRS spectra of Hg2+–HAuCl4–NaH2PO2 system. a: 0.22 mol/L HNO3 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2, incubation time for 15 min; b: a + 20 nmol/L HgCl2; c: a + 100 nmol/L HgCl2; d: a + 200 nmol/L HgCl2.
Figure 3
RRS spectra of Hg2+–HAuCl4–NaH2PO2 system. a: 0.22 mol/L HNO3 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2, incubation time for 15 min; b: a + 20 nmol/L HgCl2; c: a + 100 nmol/L HgCl2; d: a + 200 nmol/L HgCl2.

The RRS spectra of Hg2+–NaH2PO2 system were also investigated. When Hg2+ concentration increased, the RRS signal enhanced as in Fig. 4. This result showed that there are HgNPs in the system because the NaH2PO2 reduce Hg2+ to Hg0 that were aggregate to the particles. This is very significance because metal Hg sublime easily at room temperature and its scanning electron microscope (SEM) cannot be recorded.

RRS spectra of the Hg2+–NaH2PO2 system. a: 0.22 mol/L HNO3 + 0.5 mmol/L KMnO4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2; b: a + 1000 nmol/L Hg2+; c: a + 2000 nmol/L Hg2+; d: a + 3000 nmol/L Hg2+.
Figure 4
RRS spectra of the Hg2+–NaH2PO2 system. a: 0.22 mol/L HNO3 + 0.5 mmol/L KMnO4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2; b: a + 1000 nmol/L Hg2+; c: a + 2000 nmol/L Hg2+; d: a + 3000 nmol/L Hg2+.

3.4

3.4 Catalysis of AuNPs

In the absence of Hg2+, the AuNP reaction between HAuCl4 and NaH2PO2 is slow. In the presence of 10 nm AuNPs, the particle reaction enhanced greatly, and the ΔI increased linearly with the AuNP concentration (CAuNP) in the range of 100–3000 ng/mL. The regression equation is ΔI = 1.76 CAuNP + 17.6, with a coefficient of 0.9789. That is, with increasing of CAuNP, the RRS effect enhanced linearly at 370 nm due to more big AuNPs generated from the particle reaction of HAuCl4–NaH2PO2. This result showed that the AuNPs exhibited catalysis of HAuCl4–NaH2PO2 reaction. Thus, the formed small AuNPs have catalytic effect on the catalytic reaction of Hg2+–HAuCl4–NaH2PO2.

3.5

3.5 Optimization conditions of the nanocatalytic system

HNO3 and HCl are good media of the AuNP reaction. We have studied the effect of HNO3 concentrations on the detection of 0.2 μmol/L Hg2+. The result indicated that the catalytic rate became fast when the concentration of HNO3 increased, the more AuNPs formed and caused the ΔI value increasing. When the concentration of HNO3 was 0.22 mol L−1, the value of ΔI reached its maximum. When the concentration of HNO3 exceeded 0.22 mol/L, the value of ΔI tended to decline (Fig. 5), so we chose 0.22 mol/L as the final concentration of HNO3. We also studied the effect of HCl concentration on ΔI value. When the concentration of HCl was 0.2 mol/L, the ΔI value reached the maximum, and then the ΔI value tended decreased when the HCl concentration increased further (Fig. 6). So we selected 0.2 mol/L of HCl concentration in this experiment.

Effect of HNO3 concentration on the ΔI.
Figure 5
Effect of HNO3 concentration on the ΔI.
Effect of HCl concentration on the ΔI.
Figure 6
Effect of HCl concentration on the ΔI.

In the mixed acidic medium, KMnO4 is a strong oxidization reagent that can oxidize organic mercury and low valence mercury to Hg2+ in sample. The effect of KMnO4 concentration on the ΔI was studied. Results showed that the ΔI value significantly increased as the KMnO4 concentration increased. When the concentration of KMnO4 was 0.25 mmol/L, the ΔI value reached its maximum. When the concentration of KMnO4 exceeded 0.25 mmol/L, the ΔI tended to decline (Fig. 7), so, a 0.25 mmol/L KMnO4 was chosen for use. Because NH2OH⋅HCl was the reductant of KMnO4, so we also studied the effects of NH2OH⋅HCl concentration on the ΔI. When the NH2OH⋅HCl concentration was 7 μmol/L, the ΔI value reached the maximum (Fig. 8), so a 7 μmol/L NH2OH⋅HCl was selected for use. The color of the sample solution appeared pale purple after addition of NH2OH⋅HCl, which indicated that there is no NH2OH⋅HCl existence before the next experimental process.

Effect of KMnO4 concentration on the ΔI.
Figure 7
Effect of KMnO4 concentration on the ΔI.
Effect of NH2OH⋅HCl concentration on the ΔI.
Figure 8
Effect of NH2OH⋅HCl concentration on the ΔI.

HAuCl4 is an important component because it reduced catalytically by NaH2PO2 to form AuNPs. We have studied the effect of HAuCl4 concentrations in the presence of 0.2 μmol/L Hg2+ (Fig. 9). The results indicated that the catalytic rate became fast when the concentration of HAuCl4 increased. When the HAuCl4 concentration was 0.08 mmol/L, the ΔI value reached its maximum. When the concentration of HAuCl4 was exceeded 0.08 mmol/L, the value of ΔI tended to decline, so we chose 0.08 mmol/L HAuCl4. We also studied the effect of NaH2PO2 concentration on the ΔI (Fig. 10). When the concentration of NaH2PO2 was 0.188 mol/L, the ΔI value reached the maximum. When NaH2PO2 concentration was exceed 0.188 mol/L, the value of ΔI tended to decline. Thus, we chose 0.188 mol/L NaH2PO2.

Effect of HAuCl4 concentration on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.
Figure 9
Effect of HAuCl4 concentration on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.
Effect of NaH2PO2 concentration on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl.
Figure 10
Effect of NaH2PO2 concentration on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl.

PEG10000 is a good stabilizer for the AuNPs. Results showed that When PEG10000 added concentration was 0.4 mg/mL, the value of ΔI reached its maximum. So, a 0.4 mg/mL PEG10000 was selected. Because the blank reaction rate appeared slower compared to catalytic reaction under the room temperature (25 °C), the catalytic reaction can quickly reached a stable value too, and the room temperature was chosen for use. The result indicated that the ΔI value increased when the reaction time became long in the range of 7–15 min, and it achieved the maximum in 15 min (Fig. 11). Then the value of ΔI hold constant. Thus, a reaction time of 15 min at 25 °C was chosen for use. The time zero point was defined as the moment when NaH2PO2 was added.

Effect of reaction time on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.
Figure 11
Effect of reaction time on the ΔI. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L HCl + 0.4 mg/mL PEG10000 + 7 μmol/L NH2OH⋅HCl + 0.188 mol/L NaH2PO2.

3.6

3.6 Effect of foreign substances

According to the procedure, the influence of coexistent metal ions on the detection of 0.2 μmol/L Hg2+ was tested, with a relative error of ±10%. Fig. 12 showed that the common metal ions such as 100 times of Pb(II), Co(II), Ca(II), Mg(II), Cr(III), 70 times of Ba(II) and 50 times of Fe(III), Zn(II) did not enhance the Hg2+ catalytic reaction. This indicated the RRS method has good selectivity.

Influence of metal ions on the determination. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L. Ratio = [(I370 nm)Hg–(I370 nm)Hg+MI]/(I370 nm)Hg, the MI represents metal ion.
Figure 12
Influence of metal ions on the determination. 0.22 mol/L HNO3 + 200 nmol/L HgCl2 + 0.5 mmol/L KMnO4 + 80 μmol/L HAuCl4 + 0.2 mol/L. Ratio = [(I370nm)Hg–(I370nm)Hg+MI]/(I370nm)Hg, the MI represents metal ion.

3.7

3.7 Working curve

Under the optimal conditions, Hg2+ concentration (CHg2+) and their corresponding ΔI showed a good linear relationship. The linear range was 5–450 nmol/L, with a regression equation of ΔI = 2.941C + 38.4, coefficient of 0.9801, and detection limit of 0.1 nmol/L. Compared to some reported methods for mercury (Liang et al., 2011; Chen, 1980; Wang et al., 2012; Zhou et al., 2012), this RRS method was more sensitive, and simple.

3.8

3.8 Sample analysis

We applied this catalytic RRS method to measure the concentration of Hg2+ in water samples. The water samples were pretreated by aqua regia. Then, the content of Hg2+ was determined according to the procedure. In the sample solutions, a known Hg2+ was added respectively, to measure the recovery. Table 1 showed that the recovery was in the range of 101.5–108.7%, relative standard deviation was in the range of 3–6%, and this catalytic RRS result was agreement with that of atomic fluorescence spectrometry (AFS). This indicated that this RRS assay is precision and accuracy.

Table 1 Analytical results for Hg.
Water sample Added value (nM) Found value (nM, n = 5) RSDa (%) Recovery (%) AFS (nM)
Tap-water 1 No detected No detected
200 216 5.0 108
Tap-water 2 No detected No detected
200 203 6.0 101.5
Tap-water 3 No detected No detected
300 326 3.0 108.7
Waste water 1 225 212
300 318 4.0 106
Waste water 2 308 296
250 267 5.0 106.8
RSD = relative standard deviation.

4

4 Conclusion

Based on the trace Hg2+ catalysis of the AuNP reaction between NaH2PO2 and HAuCl4, and the resonance Rayleigh scattering (RRS) effect of AuNPs at 370 nm, a simple, sensitive and selective nanocatalytic RRS method was developed for the determination of 5.0 × 10−9–450 × 10−9 mol/L Hg2+. This new nanocatalytic RRS method was applied to detect Hg2+ in water sample, with satisfactory results.

Acknowledgments

This work supported by the National Natural Science Foundation of China (Nos. 21165005, 21267004, 21365011, 21367005, 21465006, 21477025), the Research Funds of Key Laboratory of Ecology of Rare and Endangered Species and Environmental Conservation of Education Ministry, the Research Funds of Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, and the Natural Science Foundation of Guangxi (No. 2013GXNSFFA019003, 2013GXNSFAA019046).

References

  1. , , , , , , . Flow injection-chemical vapor generation atomic fluorescence spectrometry hyphenated system for organic mercury determination: a step forward. Spectrochim. Acta Part B. 2011;66:799-804.
    [Google Scholar]
  2. , . Determination of mercury with induced reaction. Chin. J. Anal. Chem.. 1980;9:160-163.
    [Google Scholar]
  3. , , , , , , . Label-free detection of target DNA sequence and single-base mismatch in hepatitis C virus corresponding to oligonucleotide by resonance light scattering technique. RSC Adv.. 2012;2:2562-2567.
    [Google Scholar]
  4. , . The three modern faces of mercury. Environ. Health Perspect.. 2002;110:11-23.
    [Google Scholar]
  5. , , , , . Direct colorimetric visualization of mercury (Hg2+) based on the formation of gold nanoparticles. Talanta. 2010;82:687-692.
    [Google Scholar]
  6. , , , . The effect of methylmercury exposure on early central nervous system development in the zebrafish (Danio rerio) embryo. J. Appl. Toxicol.. 2012;32:707-713.
    [Google Scholar]
  7. , , , , , , , , , . Catalytic effect of nanogold on Cu(II)–N2H4 reaction and its application to resonance scattering immunoassay. Anal. Chem.. 2008;80:8681-8687.
    [Google Scholar]
  8. , , , , . Environmental Nanoanalysis. Guilin: Guangxi Normal University Press; . p. :118.
  9. , , , , , , , . A sensitive colorimetric and ratiometric fluorescent probe for mercury species in aqueous solution and living cells. Chem. Commun.. 2012;48:8371-8373.
    [Google Scholar]
  10. , , , , . Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions. Chem. Soc. Rev.. 2012;41:3210-3244.
    [Google Scholar]
  11. , , , . Colorimetric detection of mercuric ion (Hg2+) in aqueous media using DNA-functionalized gold nanoparticles. Angew. Chem. Int. Ed. Eng.. 2007;46:4093-4096.
    [Google Scholar]
  12. , , , , . Studying the interaction of carbohydrate–protein on the dendrimer-modified solid support by microarray-based plasmon resonance light scattering assay. Analyst. 2011;136:4301-4307.
    [Google Scholar]
  13. , , , , , , . A stable and reproducible nanosilver-aggregation-4-mercaptopyridine surface-enhanced Raman scattering probe for rapid determination of trace Hg2+. Talanta. 2012;99:890-896.
    [Google Scholar]
  14. , , , , , , , . A highly sensitive resonance scattering spectral assay for Hg2+ based on the aptamer-modified AuRu nanoparticle-NaClO3-NaI-cationic surfactant catalytic reaction. Anal. Lett.. 2011;44:1442-1453.
    [Google Scholar]
  15. , , , , , , . Light-scattering signals from nanoparticles in biochemical assay, pharmaceutical analysis and biological imaging. TrAC Anal. Chem.. 2009;28:447-453.
    [Google Scholar]
  16. , , , , . A localized surface plasmon resonance light-scattering assay of mercury (II) on the basis of Hg2+−DNA complex induced aggregation of gold nanoparticles. Environ. Sci. Technol.. 2009;43:5022-5027.
    [Google Scholar]
  17. , , , . Enhanced sensitivity of a direct SERS technique for Hg2+ detection based on the investigation of the interaction between silver nanoparticles and mercury ions. Nanoscale. 2012;4:5902-5909.
    [Google Scholar]
  18. , , , . Direct determination of Hg in polymers by solid sampling-graphite furnace atomic absorption spectrometry: a comparison of the performance of line source and continuum source instrumentation. Spectrochim. Acta B. 2009;64:520-529.
    [Google Scholar]
  19. , , , , . Methylmercury and inorganic mercury determination in blood by using liquid chromatography with inductively coupled plasma mass spectrometry and a fast sample preparation procedure. Talanta. 2010;80:1158-1163.
    [Google Scholar]
  20. , , , . Gemini surfactant applied to the heparin assay at the nanogram level by resonance Rayleigh scattering method. Anal. Biochem.. 2012;422:1-6.
    [Google Scholar]
  21. , , . Aptameric SERS sensor for Hg2+ analysis using silver nanoparticles. Chin. Chem. Lett.. 2009;20(12):1475-1477.
    [Google Scholar]
  22. , , , . Determination of Hg2+ by resonance light scattering technique based on the interaction with HT. Acta Chim. Sin.. 2012;70:643-648.
    [Google Scholar]
  23. , , , . Oligonucleotide-functionalized silver nanoparticle extraction and laser-induced fluorescence for ultrasensitive detection of mercury(II) ion. Biosens. Bioelectron.. 2012;34:185-190.
    [Google Scholar]
  24. , , , , , , . Highly sensitive and selective fiber-optic modal interferometric sensor for detecting trace mercury ion in aqueous solution. Anal. Methods. 2012;4:1292-1297.
    [Google Scholar]
  25. , , , , . Resonance light scattering detection of mercury(II) ion using unlabelled AuNPs. Appl. Chem. Ind.. 2012;41(2):344-346.
    [Google Scholar]
  26. , , , , . Detection of avian influenza virus based on magnetic silica nanoparticles resonance light scattering system. Analyst. 2012;137:648-653.
    [Google Scholar]
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