High sensitivity fiber sensor for measurement of Cd<sup>2&#x002B;</sup> concentration in aqueous solution based on reflective Mach-Zehnder interference with temperature calibration

Zhenrong Pan; Jianxun Feng; Xiduo Hu; Chuanyu Jia; Xuguang Huang; Xuguang Huang; Xuguang Huang

doi:10.1364/OE.27.032621

1. Introduction

Atomic numbered 48, cadmium, one of the 126 priority pollutants, is not an essential element of the human body. However, as a transition metal element, cadmium is indispensable in many fields including industry [1], agriculture [2–4], and military industry, which results in a large amount of Cd²⁺ contamination being left in water or soil. Cd²⁺ can be easily absorbed by organisms or creatures and eventually reach the human body through the food chain [5,6]. Unfortunately, Cd²⁺ metabolizes very slowly in the human body and is difficult to be eliminated by excretion [2]. When Cd²⁺ accumulation in the human body reaches a certain concentration, it will induce a series of serious diseases, even leading to cancer, such as prostate [6], lung [7], and kidney cancer [8]. Therefore, accurate measurement of Cd²⁺ has great significance in various aspects, for instance, basic research [9], biochemical analysis [5,10–12], environmental protection, food and chemical industry pollution assessment. Up to now, methods for measuring Cd²⁺ have been divided into optical methods and non-optical methods, which include Atomic Absorption Spectroscopy (AAS) [13–19], Inductively Coupled Plasma-Atomic Emission Spectrometry [13,19–22], fluorescent probe method [11,23–29], solid phase extraction [13,14,30–33] and room temperature ionic liquids (RTILs) measurement [34–36]. These methods are able to measure Cd²⁺ concentration in water with high accuracy and effectiveness, but are more expensive and time-consuming. To make matters worse, measurement reagents are usually toxic and may cause secondary pollution. Therefore, it is favorable to establish a cheaper and more convenient way to measure Cd²⁺ in water.

Optical fiber sensors have characteristics such as having light weight, anti-electromagnetic interference, corrosion resistance and being flame proof. Combined with biochemical sensing, fiber can provide cheap and remote online measurement of chemicals or biochemicals. In our previous works, several concentration-measurement fiber sensors [37–39] have been proposed. Those fiber sensors, however, are not for heavy metal ions. Additionally, their fiber sensing probes are affected by ambient temperature fluctuation through the thermo-optic effect, which results in the reduction of measurement accuracy. Last year, our team proposed a differential Fresnel-intensity-modulated fiber sensor [40] with a Cd²⁺ detection limit of ∼1×10⁻⁵ mol/L and temperature self-compensation. In this paper, we present a novel and more sensitive fiber technique based on reflective Mach-Zehnder (MZ) interference for online measurement of Cd²⁺ concentration with temperature calibration. It is the first time that a phase-modulated fiber sensor is used to measure the concentration of Cd²⁺ in aqueous solution. Theoretical analysis and experimental operations are introduced and discussed in detail. The feasibility of the method is verified by measurement of different concentrations of Cd²⁺ solution at a single temperature and by measurement under different temperatures at a single Cd²⁺ concentration. The experimental results show that the method has large measurement range, low detection limit and ease of implementation. Moreover, the fiber sensor has a compact structure, which is convenient for 3D space measurement. The entire system does not require complicated optical components and optical alignment. Portable sensors can be produced with circuit design optimization and packaging.

2. Principle

In order to measure the concentration of Cd²⁺ in aqueous solution and eliminate the influence of temperature, a fiber sensor with temperature calibration based on reflective Mach-Zehnder interference is proposed. The light source used in the experiment is a broadband light source operating in the telecom C-band of wavelength range. The fibers we used are all single-mode fibers (core diameter of ∼8 µm). Firstly, light from the broadband light source transmits through a fiber Bragg grating (FBG), undergoing a Bragg reflection. Then it continually travels to port 1 of the fiber circulator, and outputs from port 2 of the circulator into the fiber sensing head, which works as a reflective Mach–Zehnder interferometer. Light splits into two optical paths in the sensing area, one passing through the optical fiber core while the other one leaking into the sensing membrane cladding. Light reflected from the fiber sensing head passes into port 2 of the circulator again, and finally outputs from port 3 to an optical spectrum analyzer (OSA), as shown in Fig. 1.

Fig. 1. The sensing system for measurement of Cd²⁺ concentration in aqueous solution.

Download Full Size | PDF

In order to measure the concentration of Cd²⁺ in aqueous solution precisely, the sensing system must contain functional groups that are sensitive to or can bind with Cd²⁺ as a specific match. In the proposed method, we utilize the characteristics of propylene thiourea [41] which can effectively adsorb Cd²⁺ in an acidic environment. The thiourea group can efficiently combine with Cd²⁺ in the polymerization system due to its high electron cloud density [42]. The fiber sensing head is formed by coating a sensing membrane, whose thiourea group in the sensing membrane has a large binding coefficient to Cd²⁺, on a fused tapering single-mode fiber shown in Fig. 1. The main components of the sensor film coated onto the fiber taper are 1-allyl-2-thiourea, acrylamide and N,N'-Methylenebisacrylamide, among which the selectivity of 1-allyl-2-thiourea refers to [42]. In the reference, 1-allyl-2-thiourea is verified to be the most sensitive Cd (II)-functional monomer among four types. Secondly, the literature reveals that the selectivity factors, defined according to the ion-binding capacity ratio (detected by graphite furnace atomic absorption spectrometry in dynamic chemical process), were Cd/Pb = 2.1, Cd/Co = 2.4 and Cd/Ni = 2.4, respectively. Therefore, it is already verified that 1-allyl-2-thiourea has a relatively high selectivity for Cd (II) ions compared to Co (II), Ni (II), and Pb (II) ions.

On the propylene thiourea membrane, a new cross-linked “-S-Cd-S-” structure is formed due to adsorption of Cd²⁺, which changes the refractive index of the membrane. At the same time, the volume of the membrane shrinks due to an increase in the crosslinking density. On the other hand, the combination of urea groups reduces the total charge in the film, causing a decline of osmotic pressure inside the film, which eventually leads to volume shrink of the membrane. Both of these two factors, shrinkage and refractive index, affect the spectral distribution of the reflective Mach-Zehnder interference fringes. In addition, the variation of ambient temperature can also change the refractive index of the sensing film coated on the fiber, and the refractive index of the fiber taper will change accordingly. Therefore, the fiber sensor has a cross-sensitivity of concentration and temperature. It is worth noting that the Cd²⁺ on the sensing membrane can be cleaned and the sensor can be used repeatedly. The cleaning method is relatively simple. Simply immerse the sensing membrane of the sensor in the eluent (0.1 mol/L Na₂EDTA-HCL) for 10 minutes, then rinse it with deionized water.

The light intensity I of the reflective MZ interference of the fiber sensing head and the minimum wavelength λ_m can be expressed respectively as follows

(1)$$I = {I_1} + {I_2} + 2\sqrt {{I_1}{I_2}\cos \varphi } ,$$

(2)$${\lambda _m}({C,T} )= \frac{{({{n_{eff2}} - {n_{eff1}}} )2L}}{{m + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}}}.$$

Where I, I₁, I₂ are the total output light intensity, the core mode intensity of the fiber taper, and the cladding mode intensity of the sensing film, respectively. φ is the phase difference between I₁ and I₂, and λ_m is the wavelength of the m-th order interference minimum. n_eff₂ and n_eff₁ are the effective refractive index values of the cladding mode and the core mode, and L is the length of the two-fiber-taper area. C is the concentration of the Cd²⁺ solution, and T is the ambient temperature.

From Eq. (2), the wavelength shift $\varDelta$λ_m can be obtained as follows:

(3)$$\Delta {\lambda _m} = {\lambda _m}({C,T} )- {\lambda _m}({0,{T_0}} ),$$

where T₀ is the reference temperature. Due to a large variation range of temperature and low concentration of Cd²⁺, after a second order approximation, the effective refractive index n_eff₂ can be expressed as

(4)$${n_{eff2}} = {n_{eff20}} + {k_c}C + {k_{T2}}({T - {T_0}} )+ k_{T2}^{\prime}{({T - {T_0}} )^2},$$

where n_eff₂₀ is the effective refractive index of the cladding mode in the case of C = 0 and T = T₀, k_c is the coefficient of concentration-expansion of the sensing membrane (related to the concentration of Cd²⁺), while k_T₂ and k^’_T₂ are thermo-optic coefficients of the sensing membrane in the first and second orders. Similarly, the effective refractive index of the core mode can be expressed as

(5)$${n_{eff1}} = {n_{eff10}} + {k_{T1}}({T - {T_0}} )+ k_{T1}^{\prime}{({T - {T_0}} )^2}.$$

By substituting n_eff₂ and n_eff₁ mentioned above into Eq. (3), it can be obtained that:

(6)$$\Delta {\lambda _m} = \frac{{2L{k_c}}}{{m + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}}}C + \frac{{2L({{k_{T2}} - {k_{T1}}} )}}{{m + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}}}({T - {T_0}} )+ \frac{{2L({k_{T2}^{\prime} - k_{T1}^{\prime}} )}}{{m + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}}}{({T - {T_0}} )^2}.$$

It can be easily derived from Eq. (6) that the movement $\varDelta$λ_m of the interference fringe is proportional to the concentration of Cd²⁺ and has a quadratic relationship with temperature. Meanwhile, it can be speculated that the higher is the order of interference(m), the higher is the resolution.

3. Materials and devices fabrication

Acrylamide (AM, 99%), 1-allyl-2-thiourea (ATU), N,N'-Methylene-bisacrylamide (BIS) and 2,2-Diethoxyacetophenone (EDAP, ≥95%) were purchased from Shanghai Macklin Biochemical Co., Ltd. All materials were of analytical grade.

To prepare a prepolymerized solution, a mixture of acrylamide (AM) (32.4 mmol), 1-allyl-2-thiourea (ATU) (15 mmol), N,N'-Methylene-bisacrylamide (BIS) (2.5 mmol) and 2,2-Diethoxyacetophenone (EDAP) (10 µL) in 1 mL H₂O was stirred for 3 hours. In order to remove oxygen and obtain a uniform prepolymerized solution, N₂ was continuously bubbled into the mixed solution for ten minutes. Figure 1 illustrates the structure of the fiber sensing head. Firstly, the single mode fiber is melt-drawn to obtain a fiber taper, and then a layer of prepolymerized solution is uniformly coated onto the tapered region. In order to make the membrane coated uniformly on the surface of the fiber taper, firstly a long and thin slot that can accommodate the optical fiber is dug out on the teflon board and the optical fiber taper is placed in the slot. Then inject a small amount of pre-polymerized solution into the fiber taper with a micro syringe, rotate the fiber slowly at a constant speed, and make sure that the fiber does not break. The coating is cured by continuous irradiation with ultraviolet light at about 270 mW/cm² for 30 minutes at room temperature. Finally, the reflective Mach-Zehnder fiber sensing head was prepared by vertically cleaving the end of the fiber. The thickness of the film measured under an optical microscope was 32 ± 1µm. In order to bond the sensing film with the tapered region strongly, the fiber taper was previously coated with a layer of γ-aminopropyltriethoxysilane (APTES) (a dilute solution with a concentration of 0.5-1%) before the coating mentioned above. This process is relatively simple, just dip APTES with medical cotton swab and evenly coat in the fiber taper, and then put it in drying oven heating at 50°C for 10 minutes.

4. Results and discussion

A sensing system as shown in Fig. 1 was set up to verify that the fiber sensor can effectively detect the concentration of Cd²⁺ in aqueous solution with temperature calibration. The broadband light source is from Lightcomm company. The programmable Temperature controller is from JieXin Testing Equipment Co., Ltd., and the Optical Spectrum Analyzer (AQ6370) is from Yokogawa.

Figure 2 shows a typical interference spectrum from the fiber sensor, in which the dip_fbg is the transmittance dip of the FBG when the light passes through it. From this, the ambient temperature during the measurement can be obtained to eliminate the influence caused by ambient temperature variation in order to improve measurement accuracy. It will be discussed later.

Fig. 2. A typical interference spectrum from the fiber sensor.

Download Full Size | PDF

Figure 3 shows interference spectra from the fiber sensing head exposed to different Cd²⁺ concentration solutions at T₀=24°C. It can be seen that the interference spectrum has a red shift as the Cd²⁺ concentration increases in the solution. Figure 4 shows the dependence of the wavelength shift of dip1 (shown in Fig. 3) on Cd²⁺ concentration in solution. The black dots are the experimental data, and the red curve is a linear fitting. It reveals that in the low concentration range of 0-1.2×10⁻⁵ mol/L, the fitting curve is very consistent with the measured data in a proportional relation of Δλ=5.126×10⁴C with r²=0.9989, as the theoretical prediction of Eq. (6). From the sensitivity of concentration S_C≡dλ/dC = 5.126×10⁴ nm/(mol/L) and the 0.02 nm-resolution of the OSA, the concentration resolution of the sensor R can be estimated to be R=□/S_C=□dC/dλ=3.9×10⁻⁷ mol/L, where □ is the spectral resolution of the OSA. Based on the resolution number, the estimated minimum detection limit can be set to be ∼4×10⁻⁷ mol/L at a spectral resolution of 0.02 nm. Additionally, from dip1 and its neighboring dips, it can be deduced that dip1 has a high order of interference (m = 15439) according to the expression:

(7)$$({m + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}} ){\lambda _m} = ({m + 1 + {1 \mathord{\left/ {\vphantom {1 2}} \right.} 2}} ){\lambda _{m + 1}}.$$

Figure 5 shows the dependence of wavelength shift of the interference spectrum on environmental temperature in the case of a 4.0×10⁻⁶ mol/L Cd²⁺ solution. The black dots are the experimental measurement data, while the curve is a polynomial fitting. It can be found that in the broad range of 0-60°C, the polynomial fitting of Δλ=1.331×10⁻²(T-24) + 2.6657×10⁻⁴(T-24)² is in good agreement with the experimental data with r²=0.9927, which is also consistent with the theoretical derivation.

Fig. 3. The interference spectra from the fiber sensing head exposed to different Cd²⁺ concentration solutions at T₀=24°C.

Download Full Size | PDF

Fig. 4. The dependence of the wavelength shift of dip1 (shown in Fig. 3) on Cd²⁺ concentration in solution.

Download Full Size | PDF

Fig. 5. The dependence of wavelength shift of the interference spectrum on environmental temperature in the case of a 4.0×10⁻⁶ mol/L Cd²⁺ solution.

Download Full Size | PDF

By combining the fitting equations from Fig. 4 and Fig. 5, the dependence of the wavelength shift of the interference spectrum on both the concentration of Cd²⁺ and the ambient temperature can be expressed as follows.

(8)$$\Delta \lambda = 5.126 \times {10^4}C + 1.331 \times {10^{ - 2}}({T - 24} )+ 2.6657 \times {10^{ - 4}}{({T - 24} )^2}$$

It is verified by Eq. (8) again that the measurement of Cd²⁺ concentration in the aqueous solution does have temperature cross-sensitivity. From Eq. (8) or Fig. 5 & Fig. 4, the wavelength shifts of the spectrum caused by temperature variations of 5°C and 10°C are respectively ∼0.07 nm and 0.16 nm, which correspond to concentration deviations of 1.4×10⁻⁶ mol/L and 3.1×10⁻⁶ mol/L, respectively. Therefore, the influence of ambient temperature on the interference spectrum must be eliminated, in order to achieve accurate measurement of Cd²⁺ concentration in the aqueous solution, especially in low concentration levels below 10⁻⁵ mol/L.

Figure 6 is a graph showing the dependence of the transmission-dip wavelength of the FBG on temperature. The black points are the experimental measurement data, and the red curve is the linear fitting. As can be seen from Fig. 6, the linear fitting expressed as λ_fbg=1559.2804 + 9.79×10⁻³T is in good agreement with the measured data in a broad range with r²=0.9994. When measuring the concentration of Cd²⁺ in aqueous solution, as long as the environmental temperature from the transmission-dip wavelength of the FBG is simultaneously obtained, one can substitute the temperature into Eq. (8) to eliminate the influence of the temperature, and thus realize the desired measurement accuracy of the concentration.

Fig. 6. The dependence of the transmission-dip wavelength of the FBG on temperature.

Download Full Size | PDF

In order to verify the long-term stability of the sensing system, a continuous measurement of a Cd²⁺ solution at a fixed concentration of 4×10⁻⁶ mol/L was carried out at 24°C for 80 minutes. The measurement results are shown in Fig. 7, from which one can check that the stability is good for a long period of time with a standard deviation of 1.2×10⁻⁷ mol/L, which is close to the estimated concentration resolution or detection limit of 4×10⁻⁷ mol/L.

Fig. 7. A continuous measurement of a Cd²⁺ solution at a fixed concentration of 4×10⁻⁶ mol/L at 24°C.

Download Full Size | PDF

5. Conclusion

In this paper, a fiber optic Cd²⁺ sensor based on reflective Mach-Zehnder interference with temperature calibration is proposed. The dependences of the wavelength shift on Cd²⁺ concentration and temperature are both theoretically analyzed and experimentally tested. It is experimentally proven that the sensor has long-term stability at a Cd²⁺ concentration of 4×10⁻⁶ mol/L with a standard deviation of 1.2×10⁻⁷ mol/L during a period of 80 minutes. The estimated minimum detection limit at the spectral resolution of 0.02 nm is around 4×10⁻⁷ mol/L. The sensor has the characteristics of high measurement accuracy with temperature calibration, compact structure, ease of manufacture, and applicability for remote online measurement. Portable sensors can be produced with appropriate circuit design and packaging.

Funding

National Natural Science Foundation of China (61804028); Dongguan core technology frontier project (2019622140003).

References

1. Lalchhingpuii, D. Tiwari, Lalhmunsiama, and S. M. Lee, “Chitosan templated synthesis of mesoporous silica and its application in the treatment of aqueous solutions contaminated with cadmium(II) and lead(II),” Chem. Eng. J. 328, 434–444 (2017). [CrossRef]

2. L. Järup and A. Åkesson, “Current status of cadmium as an environmental health problem,” Toxicol. Appl. Pharmacol. 238(3), 201–208 (2009). [CrossRef]

3. M. A. Khan, S. Khan, A. Khan, and M. Alam, “Soil contamination with cadmium, consequences and remediation using organic amendments,” Sci. Total Environ. 601-602, 1591–1605 (2017). [CrossRef]

4. B. Li, L. Peng, D. Wei, M. Lei, B. Liu, Y. Lin, Z. Li, and J. Gu, “Enhanced flocculation and sedimentation of trace cadmium from irrigation water using phosphoric fertilizer,” Sci. Total Environ. 601-602, 485–492 (2017). [CrossRef]

5. R. Borah, D. Kumari, A. Gogoi, S. Biswas, R. Goswami, J. Shim, N. A. Begum, and M. Kumar, “Efficacy and field applicability of Burmese grape leaf extract (BGLE) for cadmium removal: An implication of metal removal from natural water,” Ecotoxicol. Environ. Saf. 147, 585–593 (2018). [CrossRef]

6. E. Marettová, M. Maretta, and J. Legáth, “Toxic effects of cadmium on testis of birds and mammals: A review,” Anim. Reprod. Sci. 155, 1–10 (2015). [CrossRef]

7. G. Jiang, L. Xu, S. Song, C. Zhu, Q. Wu, L. Zhang, and L. Wu, “Effects of long-term low-dose cadmium exposure on genomic DNA methylation in human embryo lung fibroblast cells,” Toxicology 244(1), 49–55 (2008). [CrossRef]

8. M. Waisberg, P. Joseph, B. Hale, and D. Beyersmann, “Molecular and cellular mechanisms of cadmium carcinogenesis,” Toxicology 192(2-3), 95–117 (2003). [CrossRef]

9. M. I. Lelet, M. V. Charykova, V. G. Krivovichev, N. M. Efimenko, N. V. Platonova, and E. V. Suleimanov, “A calorimetric and thermodynamic investigation of zinc and cadmium hydrous selenites,” J. Chem. Thermodyn. 115, 63–73 (2017). [CrossRef]

10. M. Ghanei-Motlagh and M. A. Taher, “Novel imprinted polymeric nanoparticles prepared by sol–gel technique for electrochemical detection of toxic cadmium(II) ions,” Chem. Eng. J. 327, 135–141 (2017). [CrossRef]

11. W.-J. Gong, R. Yao, H.-X. Li, Z.-G. Ren, J.-G. Zhang, and J.-P. Lang, “Luminescent cadmium(ii) coordination polymers of 1,2,4,5-tetrakis(4-pyridylvinyl)benzene used as efficient multi-responsive sensors for toxic metal ions in water,” Dalton Trans. 46(48), 16861–16871 (2017). [CrossRef]

12. P. Pal and A. Pal, “Surfactant-modified chitosan beads for cadmium ion adsorption,” Int. J. Biol. Macromol. 104, 1548–1555 (2017). [CrossRef]

13. A. N. Anthemidis, G. A. Zachariadis, C. G. Farastelis, and J. A. Stratis, “On-line liquid–liquid extraction system using a new phase separator for flame atomic absorption spectrometric determination of ultra-trace cadmium in natural waters,” Talanta 62(3), 437–443 (2004). [CrossRef]

14. M. Behbahani, A. Esrafili, S. Bagheri, S. Radfar, M. Kalate Bojdi, and A. Bagheri, “Modified nanoporous carbon as a novel sorbent before solvent-based de-emulsification dispersive liquid–liquid microextraction for ultra-trace detection of cadmium by flame atomic absorption spectrophotometry,” Measurement 51, 174–181 (2014). [CrossRef]

15. M. Behbahani, N. A. G. Tapeh, M. Mahyari, A. R. Pourali, B. G. Amin, and A. Shaabani, “Monitoring of trace amounts of heavy metals in different food and water samples by flame atomic absorption spectrophotometer after preconcentration by amine-functionalized graphene nanosheet,” Environ. Monit. Assess. 186(11), 7245–7257 (2014). [CrossRef]

16. M. S. Cresser, L. C. Ebdon, C. W. McLeod, and J. C. Burridge, “Atomic Spectrometry Update—Environmental Analysis,” J. Anal. At. Spectrom. 1(1), 1R–17R (1986). [CrossRef]

17. S. Gunduz, S. Akman, and M. Kahraman, “Slurry analysis of cadmium and copper collected on 11-mercaptoundecanoic acid modified TiO2 core-Au shell nanoparticles by flame atomic absorption spectrometry,” J. Hazard. Mater. 186(1), 212–217 (2011). [CrossRef]

18. E. V. Oral, I. Dolak, H. Temel, and B. Ziyadanogullari, “Preconcentration and determination of copper and cadmium ions with 1,6-bis(2-carboxy aldehyde phenoxy)butane functionalized Amberlite XAD-16 by flame atomic absorption spectrometry,” J. Hazard. Mater. 186(1), 724–730 (2011). [CrossRef]

19. N. Pourreza and K. Ghanemi, “Solid phase extraction of cadmium on 2-mercaptobenzothiazole loaded on sulfur powder in the medium of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and cold vapor generation–atomic absorption spectrometric determination,” J. Hazard. Mater. 178(1-3), 566–571 (2010). [CrossRef]

20. S. Cerutti, M. F. Silva, J. A. Gásquez, R. A. Olsina, and L. D. Martinez, “On-line preconcentration/determination of cadmium in drinking water on activated carbon using 8-hydroxyquinoline in a flow injection system coupled to an inductively coupled plasma optical emission spectrometer,” Spectrochim. Acta, Part B 58(1), 43–50 (2003). [CrossRef]

21. M. S. El-Shahawi, A. S. Bashammakh, M. I. Orief, A. A. Alsibaai, and E. A. Al-Harbi, “Separation and determination of cadmium in water by foam column prior to inductively coupled plasma optical emission spectrometry,” J. Ind. Eng. Chem. 20(1), 308–314 (2014). [CrossRef]

22. N. Zhang and B. Hu, “Cadmium (II) imprinted 3-mercaptopropyltrimethoxysilane coated stir bar for selective extraction of trace cadmium from environmental water samples followed by inductively coupled plasma mass spectrometry detection,” Anal. Chim. Acta 723, 54–60 (2012). [CrossRef]

23. S. Arzhantsev, X. Li, and J. F. Kauffman, “Rapid Limit Tests for Metal Impurities in Pharmaceutical Materials by X-ray Fluorescence Spectroscopy Using Wavelet Transform Filtering,” Anal. Chem. 83(3), 1061–1068 (2011). [CrossRef]

24. Y. Dai, K. Yao, J. Fu, K. Xue, L. Yang, and K. Xu, “A novel 2-(Hydroxymethyl)quinolin-8-ol-based selective and sensitive fluorescence probe for Cd²⁺ ion in water and living cells,” Sens. Actuators, B 251, 877–884 (2017). [CrossRef]

25. Y. Ding, W. Zhu, Y. Xu, and X. Qian, “A small molecular fluorescent sensor functionalized silica microsphere for detection and removal of mercury, cadmium, and lead ions in aqueous solutions,” Sens. Actuators, B 220, 762–771 (2015). [CrossRef]

26. W.-B. Huang, W. Gu, H.-X. Huang, J.-B. Wang, W.-X. Shen, Y.-Y. Lv, and J. Shen, “A porphyrin-based fluorescent probe for optical detection of toxic Cd²⁺ ion in aqueous solution and living cells,” Dyes Pigm. 143, 427–435 (2017). [CrossRef]

27. Y. Ren, S. Zhou, Z. Wang, M. Zhang, J. Wang, and J. Cao, “A series of Cadmium(II) complexes with 2-substituted terephthalate building block and N-Donor co-ligands: Structural diversity and fluorescence properties,” J. Mol. Struct. 1147, 292–299 (2017). [CrossRef]

28. J. Sun, B. Ye, G. Xia, and H. Wang, “A multi-responsive squaraine-based “turn on” fluorescent chemosensor for highly sensitive detection of Al³⁺, Zn²⁺ and Cd²⁺ in aqueous media and its biological application,” Sens. Actuators, B 249, 386–394 (2017). [CrossRef]

29. X.-Y. Xu and B. Yan, “Eu(III) functionalized Zr-based metal-organic framework as excellent fluorescent probe for Cd²⁺ detection in aqueous environment,” Sens. Actuators, B 222, 347–353 (2016). [CrossRef]

30. M. Baghdadi and F. Shemirani, “Cold-induced aggregation microextraction: A novel sample preparation technique based on ionic liquids,” Anal. Chim. Acta 613(1), 56–63 (2008). [CrossRef]

31. J. L. Manzoori, H. Abdolmohammad-Zadeh, and M. Amjadi, “Ultratrace determination of cadmium by cold vapor atomic absorption spectrometry after preconcentration with a simplified cloud point extraction methodology,” Talanta 71(2), 582–587 (2007). [CrossRef]

32. J. E. O’Sullivan, R. J. Watson, and E. C. V. Butler, “An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration,” Talanta 115, 999–1010 (2013). [CrossRef]

33. Q. Zhou, M. Lei, Y. Liu, Y. Wu, and Y. Yuan, “Simultaneous determination of cadmium, lead and mercury ions at trace level by magnetic solid phase extraction with Fe@Ag@Dimercaptobenzene coupled to high performance liquid chromatography,” Talanta 175, 194–199 (2017). [CrossRef]

34. E. Aguilera-Herrador, R. Lucena, S. Cárdenas, and M. Valcárcel, “Ionic liquid-based single-drop microextraction/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene and xylene isomers in waters,” J. Chromatogr. A 1201(1), 106–111 (2008). [CrossRef]

35. L. Xia, X. Li, Y. Wu, B. Hu, and R. Chen, “Ionic liquids based single drop microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for determination of Co, Hg and Pb in biological and environmental samples,” Spectrochim. Acta, Part B 63(11), 1290–1296 (2008). [CrossRef]

36. F. Zhao, S. Lu, W. Du, and B. Zeng, “Ionic liquid-based headspace single-drop microextraction coupled to gas chromatography for the determination of chlorobenzene derivatives,” Microchim. Acta 165(1-2), 29–33 (2009). [CrossRef]

37. C. H. Tan, W. X. He, H. Y. Meng, and X. G. Huang, “A new method based on fiber-optic sensing for the determination of deacetylation degree of chitosans,” Carbohydr. Res. 348, 64–68 (2012). [CrossRef]

38. C. H. Tan, Z. J. Huang, and X. G. Huang, “Rapid determination of surfactant critical micelle concentration in aqueous solutions using fiber-optic refractive index sensing,” Anal. Biochem. 401(1), 144–147 (2010). [CrossRef]

39. J. R. Zhao, X. G. Huang, and J. H. Chen, “A Fresnel-reflection-based fiber sensor for simultaneous measurement of liquid concentration and temperature,” J. Appl. Phys. 106(8), 083103 (2009). [CrossRef]

40. P. Q. Zhu, J. J. Wang, F. Rao, C. Yu, G. Zhou, and X. G. Huang, “Differential Fresnel-reflection-based fiber biochemical sensor with temperature self-compensation for high-resolution measurement of Cd²⁺ concentration in solution,” Sens. Actuators, B 282, 644–649 (2019). [CrossRef]

41. G. P. Joseph, K. Rajarajan, M. Vimalan, S. Selvakumar, S. M. R. Kumar, J. Madhavan, and P. Sagayaraj, “Spectroscopic, thermal and mechanical behavior of allylthiourea cadmium chloride single crystals,” Mater. Res. Bull. 42(12), 2040–2047 (2007). [CrossRef]

42. P. Luliński, P. Kalny, J. Giebułtowicz, D. Maciejewska, and P. Wroczyński, “Synthesis and characterization of cadmium(II)-imprinted poly(1-allyl-2-thiourea-co-ethylene glycol dimethacrylate) particles for selective separation,” Polym. Bull. 71(7), 1727–1741 (2014). [CrossRef]

High sensitivity fiber sensor for measurement of Cd²⁺ concentration in aqueous solution based on reflective Mach-Zehnder interference with temperature calibration

Abstract

1. Introduction

2. Principle

3. Materials and devices fabrication

4. Results and discussion

5. Conclusion

Funding

References

Cited By

Figures (7)

Equations (8)

Optics Express