The development of real-time, highly sensitive and selective, simple technique for detection of toxic Pb 2+ in water was challenged. However, in this study a highly efficient fluorescent probe based on polythiophene imprinted CeO 2 nanocomposite for selective detection of Pb 2+ ion was developed by polymerization method. The developed fluorescent probe was characterized by using powder X-ray diffraction (XRD), Fourier- Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). Upon binding to the imprinted binding sites PT/CeO 2 the Pb 2+ interacts with the molecular orbital and their fluorescence is quenched via reverse photoinduced electron transfer which result the qualitative and quantitative detection. The factor affecting the detection system such as pH and concentration are optimized. Additionally, the PT/CeO 2 fluorescent sensor exhibits highly sensitive with stern Volmer quenching (KSV) value of 6.39 x 10 3 M -1 . The practical application of the sensor also tested by spiked with different concentration of Pb 2+ ion solutions on tab water samples. The result indicates a good linear relation between F O /F and the spiked concentrations with coefficient of regression R 2 = 0.99 (n= 3) and also confirms that the found values is agreed well with the spiked amount. The obtained amounts of lead metal ion concentrations in tap water were 15.39 μM which exceeded the allowable limit as stated by WHO .
Research Article
Polythiophene Imprinted CeO2 Fluorescent probe for Lead Detection in Water
https://doi.org/10.21203/rs.3.rs-1757124/v1
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Imprinted
Fluorescence sensor
Polythiophene
Quenching
Toxic heavy metal
Heavy metal ions pollution and its effects on human life is one of the most studied environmental issues in recent years. Today’s world faces alarming challenges in the rising demand for clean drinking water, and conditions are particularly bad in developing countries [1]. This is due to environmental pollution by heavy metals can occur by many different ways, either directly or indirectly. Soils and water are contaminated by material from the air or by direct deposition of pollutants. Heavy metals (HM), with high atomic number and much higher density than water, are present in the environment naturally. Their contamination to the environment is due to artificial industrial operations and also due to other causes such as the dissolution of metals (through metal corrosion), and heavy metals leaching [2]. Moreover, heavy metals are indestructible and have toxic effects on living organisms especially at high concentrations [3]. In general, the toxicity of metal ions to mammalians systems is due to chemical reactivity of the ions with cellular structural proteins, enzymes and membrane system. The target organs of specific metal toxicities are usually those organs that accumulate the highest concentrations of the metal in vivo.
Heavy metal ions refer metallic elements, which include such as iron, cobalt, copper, manganese, molybdenum, zinc, mercury, plutonium and lead. Heavy metals are dangerous because they tend to bioaccumulate. Among them, lead is highly toxic and can affect every organ and system in the body. The main sources of lead exposure are lead based paints, gasoline, cosmetics, toys, household dust, contaminated soil, industrial emissions [4]. Lead poisoning was considered to be a classic disease and the signs that were seen in children and adults were mainly pertaining to the central nervous system and the gastrointestinal tract [5]. These lead poisoning can also occur from drinking water. The pipes that carry the water may be made of lead and its compounds which can contaminate the water [6]. Its distribution in the body initially depends on the blood flow into various tissues and almost 95% of lead is deposited in the form of insoluble phosphate in skeletal bones. Chronic exposure of lead metal ion can result in mental retardation, birth defects, psychosis, autism, allergies, dyslexia, weight loss, hyperactivity, paralysis, muscular weakness, brain damage, kidney damage and may even cause death [7].
There exist several traditional methods characterize the presence of heavy metals in waters, qualitatively and quantitatively. Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Inductively Coupled Plasma/Atomic Emission Spectrometry (ICP-AES) are few of the methods that can be applied to detect and measure the presence of heavy metals in water samples [8]. Even though those methods have great sensitivity and selectivity, However, there exist several disadvantages such as: high cost of the instruments, long sample preparations time, requirement for calibration standards, and the requirement for well-trained personnel for the operation.
Fluorescent probes have concerned great attention due to their high accuracy, high sensitivity, fast analysis and simplicity. To date, various fluorescent probes including fluorescent metal nanoparticles, organic dyes and semiconductor quantum dots (QD) are exceptional examples among these applications. Specially in the field of environmental monitoring, the application of nanoparticles (NPs) based fluorescent probe being utilized as functional probes for analyzing toxins, metal ions, and inorganic and organic pollutants [9]. NPs, usually with a size between 1 and 100 nm, display unique properties, mainly due to the strong physical confinement of electrons or holes in the NPs at the nanoscale. From a sensing perspective, the small size of NPs gives them large surface-to-volume ratios, which lead to rapid responses and high sensitivity.
Fluorescent sensors based on decorated noble metal nanoparticles (NPs) have been also attracted great attention for their convenience of simple operation in recent years. From many metallic nanoparticles, cerium oxide with different valence state have been explored for various applications such as electrical, electronic, catalytic, adsorption, optical, functional materials, energy storage, and sensing properties [10, 11]. CeO2 has a positive prospect on luminescence properties due to its capacity of light absorption and the ability to emit through O2- Ce4+ transition. Nanoceria is optically active and can develop unique color patterns depending upon specific interactions at their surface [12]. The optical properties of cerium oxide and gold-ceria nanoparticles; and its uses for dissolved oxygen and lead metal ion detection based on fluorescence quenching also reported [13].
The improvement of fluorescent detection mechanism for pollutant became achieved when support the metallic nanomaterial by conducting polymers, because of its mechanical flexibility, large surface area and high optical properties. The semiconductive nature of these conducting polymers gives them very useful optical and optoelectronic properties. This sensitivity arises from the collective optical and conducting properties of the CP. These polymers are extremely sensitive to minor external structural perturbations or to electron density changes within the polymer, due to their ability to self-amplify their fluorescence quenching response upon perturbation of the electronic network upon binding of analytes. Depending on the system, a CP can exhibit a strong luminescence, the luminescence efficiency is related to the delocalization and polarization of the electronic structure [14]. Among from different conducting polymer, Polythiophene are one of the most valuable types of conducting polymers that may be easily modified to afford a variety of useful electrical and physical properties such as solubility, electrical conductivity, mobility and others. Polythiophene has been widely used in environmentally and thermally stable conjugated polymer materials, such as chemical and optical sensors, light emitting diodes and displays, photovoltaic devices, molecular devices, DNA detection, polymer electronic interconnects and transistors [15, 16].
This study focusses on developing of noble sensing material polythiophene imprinted CeO2 for detection of highly toxic lead metal in water. PT/CeO2 successively fabricated by polymerization method. Therefore, the material shows both remarkable enhancements in the electronic and photonic properties of the resultant materials and the creation of new functions, such as new sensory materials, critically depends on the synthesis of the polythiophene. This of course leads to the exciting prospect that the properties of polythiophenes can be selectively engineered through planarization of the backbone and assembly of the backbone in the form of π stacks lead to better materials and enhanced device performance in almost every category, ranging from optical property to stability.
2.1. Materials
Reagents were of analytical grade or the highest commercially available purity and were used as received. Cerium nitrate hexahydrate, sodium dihydrogen phosphate, disodium hydrogen phosphate, hydrochloric acid, ethanol, ammonia, copper sulphate, lead sulphate, ferric chloride, chloroform, thiophene, sodium chloride, sodium hydroxide, magnesium sulphate, calcium sulphate, nickel nitrate, cobalt nitrate, ferrous sulphate, chromium sulphate, cadmium nitrate and zinc chloride were used without purification.
2.2. Synthesis of Nanocomposites
2.2.1. Preparation of CeO2 Nanoparticle
The cerium oxide ultrafine nanoparticle was prepared by a precipitation method [17]. An aqueous solution of 0.1 M (4.334 g in 100 mL) of cerium nitrate hexahydrate Ce(NO3)3.6H2O in deionized water was prepared and stirred for 30 min. The clear solution was precipitated by dropwise addition of aqueous NH4OH solution with continuous stirring until precipitation gets completed. The stirring was continued another 2 h and the reaction condition then maintained at pH=10. The reaction mixture was then stirred for 12 h to complete the precipitation process. The mixture was aging for 12 h. The resulting yellow colored slurry was decanted, the precipitate was filtered and washed three times with deionized water and ethanol. The clean precipitate was oven dried at 140 oC for 12 h and calcined at 500 oC for 3 h to promote the crystallization.
2.2.2. Synthesis of polythiophene (PT)
The synthesis of PT is carried out with some modification described in literature. 1.0 g thiophene in 10 mL of chloroform and 8.0 g of the oxidizing agent FeCl3 in 50 mL of chloroform was prepared. The two solutions are mixed and stirred for 12 h at temperature of 5 ºC. Polymerization proceeded for 5.5 h. After the filtration and washing, the solid was re-suspended and washed using the Milli-Q water until a pH 7 was reached. The PT solid was dried under vacuum at 60 ºC for 24 h [18].
2.2.3. Synthesis of polythiophene (PT)/CeO2
A typical polymerization method was adopted for the polymerization of thiophene in the presence of CeO2 nanoparticle. Briefly, 0.2 g of CeO2 were added to 50 mL chloroform and thoroughly mixed. Later, 8.0 g of the oxidizing agent FeCl3 were added into the mixture and stirred for 30 min. 1.0 g of thiophene monomer was added to the solution and left under agitation for 12 h at 5 ºC. Polymerization proceeded for 5.5 h. Then the solution was filtered and washed with Milli-Q water. The precipitate was re-suspended in 100 mL of 1 M HCl and stirred for 2 h. After filtration, the solid was rinsed with a 1 M HCl solution until the filtrate was colourless. Following the rinsing, the composite was then washed with Milli-Q water until a pH 7 was reached. The PT/CeO2 composites were then dried under vacuum conditions at a temperature of 40 ºC for 24 h.
2.3. Characterization of the Synthesized Nanocomposites
The fluorescent emission properties were determined using a RF-5301PC spectrofluorometer equipped with a xenon discharge lamp. The surface morphology were studied by scanning electron microscopy (SEM) using a flexsem1000.The crystalline phases and the crystallite sizes were determined using powder X-ray diffraction (XRD) with X’Pert Pro PANalytical with CuKα radiation (l = 1.5405 Å). The data were registered with 2θ steps of 0.02o and accumulation times of 20 s. FT-IR (Spectrum 65, PerkinElmer) in the range 4000-400 cm-1 using KBr pellets was used to assign functional groups of as-synthesized PT/CeO2.
2.4. Preparation of Buffers
The 0.1 M phosphate buffer was prepared by weighing approximately 0.8 g of NaH2PO4.2H2O and 6.5 g of Na2HPO4 and dissolving them in water into a 500 mL volumetric flask. It was adjusted using 0.1 M HCl or 0.1 M NaOH to the desired pH. The buffer solution was stored in a fridge at 4 oC [19].
2.5. Fluorescence Detection of Lead Ions
For fluorescence detection of lead metal ions, 2 mL of PBS (0.1 M, pH 7.4) was added into 0.02 g of the PT/CeO2 nanocomposite, followed by the addition of different molar concentration of Pb2+ ion, and sonicated. After reaction of 5 min at room temperature, 100 µL of the solution was taken into a cuvette and finally, the excitation and emission spectra were recorded using fluorescence spectroscopy.
In order to quantify the Pb2+ induced quenching process, the Stern-Volmer quenching constant KSV was calculated by Stern-Volmer equation:
IO/I = 1+KSV [Q] (1)
Where IO and I are the fluorescence intensities of the fluorescent sensor in the absence and presence of lead metal ion, respectively, KSV is the Stern-Volmer constant and (Q) is the molar concentration of lead metal ion.
2.6. Optimization of Parameters
2.6.1. The Effect of pH
It is common that the pH of a solution can affects the sensitivity and selectivity of a detection. The effect of pH (2-12) of PBS on the PT/CeO2 fluorescent probe in the presence of lead ion solution was tested.
2.6.2. The Effect of Concentration
In order to investigate this effect, 2 mL of PBS (0.1 M, pH= 7) was added in to 0.02 g the PT/CeO2 nanocomposite, followed by the addition of 50, 150, 200, 250, 300, 350, 450 and 500 μM of lead solution and sonicated. After reaction of 5 min at room temperature, 100 µL of the solution was taken into a cuvette and finally, the excitation and emission spectra were recorded using fluorescence spectroscopy.
2.7. Reproducibility and Stability Tests
The reproducibility of the PT/CeO2 as the fluorescent sensor was investigated at three repetitions on three batches of the PT/CeO2. A calibration graph was plotted for mean ofFO/F, (FO and F represented the fluorescence intensity of sensor without and with lead) Vs. lead concentration, which a linear range was then determined. Limit of detection was calculated using the following formula;
Where LOD are limit of detection, SD are standard deviation from linearity of a graph and KSV is Stern-Volmer constant calculated from the graph [20].
2.8. Selectivity of the Sensor
The Zn2+, Ni2+, Co2+, Mg2+, Ca2+, Cu2+, Cd2+, Cr2+ and Fe2+ ions were used to investigate selectivity for Pb2+ ion of PT/CeO2 fluorescent probe. The concentration of each metal ion was 500 μM. The same detection conditions and approach were used as mentioned above.
2.9. Recovery Test and Real Samples Analysis
Tap water samples were collected from the Tuluawliya, Legambo Woreda. The tap water samples were spiked with different concentrations of lead (II) solutions. Typically, 300 µL of sample solutions was taken and added to PT/CeO2 nanocomposite in 2 mL PBS (pH= 6). Finally, fluorescence emission spectra were recorded after reaction of 5 min at room temperature.
The mean percentage recoveries for the lead ions were calculated using the following equation:
Where CE is the experimental concentrations determined from the calibration curve and CM is the spiked concentrations.
3.1. Characterization of the synthesized nanomaterial
3.1.1. FT-IR Analysis
The FT-IR spectrum in the mid-infrared region is the feature of a particular compound that gives the information about the functional groups. It can be seen in figure 1, pure polythiophene (PT) shows the presence of characteristic absorption bands at 3,440 cm-1 assigned for O‒H stretching, 1697.17 and 1469 cm-1 assigned for C=C asymmetric and symmetric stretching vibration of thiophene ring respectively [21]. The peaks 750 cm-1 assigned for C-S bending vibration of polythiophene which is confirms the successful polymerization of thiophene monomer and the formation of polythiophene. The bare CeO2 show characteristic’s band at 3434 cm-1 corresponds to the O-H stretching vibration, 1622.55 cm-1 assign for -OH scissor bending, which is originated from physical absorbed water molecules or surface [22]. The FT-IR spectrum contains two characteristic absorption bands at 1389 and 1050 cm-1, which are attributed to Ce–O bonds [10].
In case of polythiophene/CeO2, the peaks exhibited similar patterns of the two pure nanoparticle, however peak shifts observed that is due to upon immobilization of the nanocomposite onto the polymer support. Accordingly, such as, 3397 cm-1 assigned for O‒H stretching, 1618 cm-1 assigned for C=C stretching vibration of thiophene ring which indicate the presence of polythiophene. The band at 1080 cm-1, which are attributed to Ce–O bonds. The spectrum confirms that, the is strong covalent bond are formed between CeO2 and coplanar conformation of polythiophene.
3.1.2. XRD Analysis
The crystal structure and crystallinity of nano-material is very important characteristic because it eventually affects many physical properties. XRD gives information about the crystal structures and identifying phase of the materials, atomic spacing and unit cell dimensions of crystalline material. Therefore, the crystal structure of the as-synthesized composites was studied by powder X-ray diffraction (XRD), as shown in figure 2B. The apparent peaks for CeO2 are observed at 2q values of 28.6⁰, 33.1⁰, 47.5⁰, 56.3⁰, 59.2⁰, 69.4⁰, 76.7⁰, 79.09⁰ and 88.44⁰ corresponding to the (111), (200), (220), (311), (222), (400), (313), (402) and (422) crystal planes of cubic crystalline phases respectively [JCPDS: 96-434-3162]. The general feature of the XRD patterns of CeO2 shows the presence of strong and sharp peaks, which indicate that the produced nanoparticles are fine crystalline. For pure polythiophene (PT), figure 2A shows a significant peak at 2θ = 22.53°, which represents characteristic conducting semi-amorphous structure of polythiophene. This work is confirmed with other finding [23].
The XRD pattern of PT/CeO2 composites, as figure 2C shows the existence of both polythiophene and CeO2. The existence of CeO2 nanoparticles in the polythiophene matrix resulted in disordered stacking of the nanocomposite. Consequently, the diffraction peak of PT/CeO2 slightly shifted compared to the pure nanoparticle, which may be attributed to the crystal lattice distortion in PT owing to the relatively strong interaction between the CeO2. The diffraction peak is observed at 2q values of 23.1⁰ ascribed to PT and 30.5⁰, 35.89⁰, 47.5⁰ and 57.1⁰ assigned to the (111), (200), (220) and (311) plane is due to cubic CeO2. The crystallinity of the composite is caused by the crystalline structure of CeO2.
3.1.3. Scanning Electron Microscopy (SEM) Analysis
The scanning electron microscopy shows the surface morphology of CeO2 described in figure 3A, the result indicates nearly spherical morphology. It can be seen in figure 3B, it is apparent PT (polythiophene) nanoparticle have a film porous structure that were clump together as clusters, a type formation of PT crystals presented. Although the PT images show a granular and uniform structure, with a repetitive pattern. The surface morphologies of the as-synthesized PT/CeO2 nanocomposite, as in figure 3C described the CeO2 are nobbled on the surface of porous polythiophene polymer. Furthermore, the different structures present in the PT/CeO2 composites from bare nanoparticle, validates the formation of new materials.
3.2. Mechanism of PT/CeO2 Fluorescent probe for detection of lead ion
The emission spectra were monitored at excitation wavelengths of 320 nm and PT/CeO2 sensor was important for effective sensing of toxic Pb2+ ion. The result indicated Pb2+ can effectively quench the fluorescence intensities of PT/CeO2 fluorescent probe due to an empty p shell, hence electron is transferred. These indicate the reverse photo-induced electron transfer mechanism involving electron donation from the excited PT/CeO2 part to the Pb2+ ion resulting in no fluorescence being observed (quenching) [24]. It was also suggested that PT/CeO2 and Pb2+ form a strong bond with the interaction site in (Pb–S) and (Pb–O) illustrating static quenching from the formation of a stable non-fluorescent complex. Consequently, the fluorescence intensity is significantly quenched.
Over this, it might happen that an orbital of Pb2+ could have energy between that of the HOMO and that of the LUMO of the PT/CeO2 probe. When this “alien” orbital is full (S and O donor group), a PET from this full orbital to the HOMO of the PT/CeO2 can take place. The electron transfer from the LUMO of PT/CeO2 to the Pb2+ orbital retrieves the stable ground state. Next this sequence, fluorescence quenching occurs because the transition from the excited to the ground state takes place following a non-radiative path as described in figure 4. This process results to a decrease of the emission intensity.
3.3. Optimization of Experimental Conditions of PT/CeO2 Probe
In order to evaluate the sensitivity of the proposed material, the experimental conditions were optimized including the pH of the buffer solution and concentration of lead metal ion.
3.3.1. Influence of pH
The effect of pH on fluorescence response was carried out from pH 2- 12. The influence of pH on the quenching emission intensity of PT/CeO2 by Pb2+ is illustrated in figure 5. The relative intensity ratio values decrease on going from pH 2 to pH 6. This is due to at lower pH both the interaction sites on the sensor and the Pb2+ are fully protonated. Therefore, the complexation of Pb2+ delayed resulting in a low quenching efficiency. As the pH increased from 7, the fluorescence intensity significantly decreased due to the high quenching efficiency and maximum quenching was observed at pH 7. This is due to the deprotonation of the interaction site, which increases the covalent bond strength between the PT/CeO2 and Pb2+. The pH further increases pH greater than 8, competitive lead hydroxide is formed, it resulted in a distinct increase in fluorescence intensity resulting in a poor interaction with the PT/CeO2 probe. Hence, pH 7 is recommended as the optimal pH value for further detection.
3.3.2. Concentration of Pb2+
The sensitivity of the emission behavior of the ultrasmall particles has been exploited for the determination of Pb2+ in aqueous solution. The changes in emission spectra (quenching) of the developed probe upon addition of different concentrations of Pb2+ as designated in figure 6. As described in the mechanism above (section 3.2) this is due to the Pb2+ forming a covalent bond with the PT/CeO2, so that resulting in photoinduced electron transfers (PET). The emission is gradually quenched with an increase in the concentration of these Pb2+ in aqueous solution from 50 to 500 μM, and the fluorescence intensity therefore decreases linearly.
3.4. The Sensitivity of PT/CeO2 Probe
The fluorescence intensity of PT/CeO2 was found to be such that quenching and the Stern-Volmer fluorescence intensity ratio (FO/F) show a linear diminish with the increasing the Pb2+ concentration from 50 μM to 500 μM in a phosphate buffered solution (PBS, 0.1M, pH= 7). The result showed that the Pb2+ concentration is inversely proportional to fluorescence intensity, and gave a good linear change in Stern-Volmer fluorescence emission intensity ratio. The quenching efficiency was determined using a Stern-Volmer equation (eqn 1). From the calibration curve as described in figure 7, there is a linear dependence of the emission intensity on the concentration of Pb2+ with the coefficients of regression of R2= 0.98. The calculated KSV value for the PT/CeO2 fluorescent probe for detection of Pb2+ were found to be 6.39x10 3 M -1. The proposed PT/CeO2 fluorescent nanocomposite is more sensitive when compared with other finding.
The limit of detection was determined by performing a reproducibility test at three repetitions. Therefore, LOD of the PT/CeO2 for the Pb2+ determined from the standard deviation of the response at the intercept of the regression line and the value of the KSV (eqn 2). The limit of detection of the proposed probe for Pb2+ were found to be 9.17x10 -5 M.
3.5. Selectivity of PT/CeO2 for Pb2+
The detection of Pb2+ is usually accompanied by severe interferences of various ionic species. The fluorescence features of the developed probe were tested by other competitive metal cations rather than the target ion, including Zn2+, Ni2+, Co2+, Mg2+, Ca2+, Cu2+, Cd2+, Cr2+ and Fe2+ ions under the same conditions. The selectivity test was performed by adding of metal salts solutions to the PT/CeO2 in PBS and mixed to form metal ion-PT/CeO2 complexes. As described in figure 8, the result proposes that compared with Pb2+, the other competitive metal ions only slightly quenched the fluorescence intensity of PT/CeO2 due to the weak affinity between these metal ions and the interaction site of the developed probe. The main information in the selectivity test of the developed nanocomposite solution, the fluorescence emission of PT/CeO2 is completely quenched by adding Pb2+ in the presence of other metal ions. Generally, other metal ions have a small influence on the selective detection of Pb2+, this is due to faster chelating process with sensing site of PT/CeO2 than the other metal ions.
3.6. Recovery test
The tap water sample was spiked with different concentration of Pb2+ solutions. The unknown concentration Pb2+ in tap water is determined from the calibration curves plotted for the known standard solution (spiked) of Pb2+, the unknown (found) concentration of Pb2+ (value of X) was successfully calculated by using equation y = A + B*X obtained from the calibration curves of the standard solution. Where, the value of “A” is intercept and B (slope) and the value of y (FO/F) was obtained from the fluorescence recorded for Pb2+ from spiked tab water sample. The result indicated a good linear relation between FO/F and the spiked concentrations of Pb2+ with coefficient of regression R2 = 0.99 as designated in figure 9. The found values is agreed well with the spiked amount. The obtained recoveries in such samples varied from 97.6 to 102.8% and the relative standard deviations (RSD) were less than 1 % which indicate the developed sensor shows high validity and precision (table 1).
3.7. Detection of Pb2+ in Real Samples
In this research, under optimizing all parameters, tap water samples contain a detectable amount of Pb2+ described in figure 10. Therefore, sulfur containing polymer like polythiophene is a promising prospect for the detection of these toxic metal ions in real samples. The calculated amount of lead concentration in tap water was found to be 15.39 μM which is greater than the allowable limit of 0. 01 mM as stated by WHO. This may be due to possible reasons for high levels of lead metal ion, lead was found in gasoline and house paint, which has been extended to lead water plumbing pipes. Hence, flow into water bodies and exposure humans.
Pollution of the natural environment by heavy metals specially lead ion is a global problem because of have toxic effects on living organisms especially at high concentrations. The toxic effect of lead can result in mental retardation, birth defects, weight loss, hyperactivity, paralysis, muscular weakness, brain damage, kidney damage and may even cause death. The new sensitive fluorescent probe (polymer imprinted metal oxide nanoparticle) for detection of lead was developed in this work. Therefore, polythiophene imprinted CeO2 was synthesized by polymerization method and the structural, morphological behaviors was characterized by modern spectroscopy such as XRD, SEM and FT-IR. The results of FT-IR and XRD analysis confirmed that there is a strong interaction between PT and CeO2 nanocomposite.
The developed fluorescent probe utilized as a highly effective tool for selective detection of Pb2+ ion. Consequently, up on addition of Pb2+ to PT/CeO2, the emission intensity was decrease (quenched). Conducting polymer, particularly S- containing polythiophene shows a distinct fluorescent property for detection of lead metal ion. The operational parameter such as effect of pH is evaluated with the range of 2-12 and maximum quenching efficiency was observed at pH 7. The various concentrations of Pb2+ from 50-500 μM were tried to test the effect of concentration, linearity, and sensitivity of the method. The new developed probe exhibited a linear range, a high selectivity and sensitivity with a low detection limit of 9.17 x 10-5 M.
Acknowledgment
I thank my friend Getachew Asfaw for helping during laboratory work. I would like to express my deepest appreciation and thanks to Department of Chemistry, Wollo university for instruments and laboratory facilities. I would like also thanks Addis Ababa University for PL, XRD and FT-IR analysis and university of taiwan university of science and technology for SEM analysis.
Source of Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Competing Interests Statement
The authors declare no competing financial, professional and personal interests.
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Availability of data and material
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Table 1
Samples Added (μM) Found (μM) Mean recovery (%) a RSD (%)
Tap water
1 25 24.4 97.6 0.7
2 50 51.44 102.8 0.6
3 75 74.5 99.3 0.5
Unknown 15.39