A polymer-based fluorescent sensor for the selective detection of heavy metal IONS, in particular cadmium, and a method for its preparation

Abstract

The invention relates to a polymer-based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), and a method for its preparation. The polymer-based fluorescent sensor for selective detection of heavy metal ions according to the invention is used in the selective detection of heavy metal ions, and while the detection limit of cadmium in the sensors of the present art is 1 µM, the limit in the inventive sensor is reduced to 0.195 µM, which is approximately 10 times lower than the specified value. The inventive sensor is resistant to environmental effects and resistant to degradation. The inventive sensor can be used multiple times, and the cost of the sensor has been reduced and the damage caused by the sensor to the environment and to the health of living beings has been prevented inasmuch as it can be used repeatedly. The inventive sensor can be adapted to be wearable. The invention provides a sensor configuration for selective detection of heavy metal ions with reduced energy consumption during preparation.

Description

[0001] A POLYMER-BASED FLUORESCENT SENSOR FOR THE SELECTIVE DETECTION OF HEAVY METAL IONS, IN PARTICULAR CADMIUM, AND A METHOD FOR ITS PREPARATION

[0002] Technical Field to which the Invention Relates

[0003] The invention relates to a polymer-based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), and a method for its preparation.

[0004] The state of the art

[0005] Heavy metal is the name given to the group of elements with metallic properties for which there is no clear and complete definition. This group includes transition metals, some semimetals, lanthanides and actinides. Heavy metal poisoning can occur from a variety of sources, but most commonly from the extraction of pure metals, for example from the smelting of ores and the preparation of nuclear fuels. Electroplating is the main source of chromium and cadmium poisoning. Heavy metals accumulate in nature when their compounds are washed into soils and bay waters by rainfall or ion exchange. Unlike organic waste, heavy metals pose a threat because they do not degrade [1]. Heavy metals are elements that can be toxic even at low concentrations. The use of heavy metals in industrial processes and products has increased rapidly in recent years and their effects on humans have reached dangerous levels. A documented environmental disaster related to heavy metals is Minamata disease, caused by mercury poisoning [2], The element cadmium is one of the most dangerous heavy metal pollutants in the ecosystem and is toxic to living organisms. Due to the long-term use of phosphorus fertilizers and sewage sludge, agricultural soils in many parts of the world are exposed to low or moderate levels of cadmium accumulation. Due to its high mobility in the soil-plant system, cadmium can easily enter the food chain and thus pose a threat to plant, animal and human health. Cadmium taken up and accumulated in plants interferes with many metabolic activities such as protein synthesis, nitrogen and carbohydrate metabolism, enzyme (nitrate reductase) activation, photosynthesis and chlorophyll synthesis. As a result of cadmium accumulation in the plant body, yield and quality are reduced, resulting in significant crop losses. In addition, it seems impossible for people in modern societies to avoid cadmium toxicity in today's conditions where crops are grown under cover with intensive use of fertilizers. Cadmium and its compounds can accumulate in the kidneys and liver and cause major diseases such as high blood pressure, lung cancer, osteoporosis and anemia [3]. Therefore, given the damage that heavy metals, especially cadmium, cause to living organisms and ecosystems, the detection of heavy metals, especially the heavy metal cadmium, is of great importance.

[0006] In the state of the art, in a study presented in the literature by R. Todd Bronson, a homopolymer is used as a sensor structure by liquid polymerization for the detection of cadmium ions, but the polymerization is carried out in the liquid phase, resulting in a degradable structure. In addition, this study does not include any durability testing, investigation of reusable structures, effect of operating conditions, etc. In this study, the detection limit of cadmium ion was found to be quite high (1 microM) [5]. Liquid phase polymerization provides a degradable sensor structure. In addition, the durability and reusability of sensor configurations for cadmium ion detection are not well known in the current state of the art. The sensor structures in the state of the art are mostly produced in the liquid phase, degradable under the influence of time and temperature and disposable, limiting the application areas of sensor studies. In these sensors, the liquid sample taken from the environment is mixed with the liquid phase sensor structure, and the target substance in the environment is detected by measurements made in the liquid phase. The main problem with the mentioned sensor configurations is that the sensors are disposable and produce chemical waste that is harmful to life and the environment after each use. In addition, the overall cost of using these sensors is high due to their disposable nature. Furthermore, the detection limit in the methods where these sensors are used for detection is low due to the problems caused by the liquid phase.

[0007] In a study of the sensor for the detection of heavy metal ions in the present technique, only a homopolymer film was prepared in the liquid phase as the sensor structure and its use for the detection of cadmium ion was tested. Polymer thin films are usually prepared by polymerization reactions using solvents in the liquid phase, but solvents have very negative effects on applications. For example, these solvents damage the substrate materials (metal, polymer, ceramic, paper, etc.). In addition, these solvents cause corrosion in metals, surface abrasion and dissolution problems in ceramic and polymer-based substrates. These solvents bring the problem of the impossibility of coating on the substrate due to deterioration of surface properties in the liquid phase on substrates such as paper, etc. Since these solvents cannot be completely removed from the coatings and substrates at the end of the operations, they can cause some harmful effects such as surface abrasion, inability to obtain high purity coating, degradation of polymer structure and formation of structural defects. One of the thin film coating methods is the spin coating technique. The coating process is carried out by dropping a drop of solution into the center of a substrate and then rotating the substrate at high speeds. In this technique, the coating is achieved by removing the excess solution from the substrate surface and spreading the remaining solution as a thin film. Many parameters affect the formation of the thin film coating and these can be listed as coating speed, viscosity, drying speed, solvent type, etc. Some problems may occur due to the solvents used in the mentioned coating technique. For example, if a low boiling solvent (high evaporation rate) is used, the coating may be easier to obtain, but an amorphous (irregular) film is produced. The solvent in the solution dripped onto the surface to be coated remains on the substrate and damages the surface due to the unsuccessful drying process in the technique. In addition, after the drying process, air gaps or pores may form on the surface, which remain behind the removed solvent. These are just some of the problems associated with solvent-based coatings. In addition, the environments and conditions in which the polymer structures used in the sensor structure for detecting heavy metal ions in the state of the art are suitable for use have not been investigated, and the detection limit of these sensors for cadmium ions is quite high. In a study of cadmium sensors by Bronson et al., the detection limit of cadmium is reported to be 1 pM [4],

[0008] Especially considering that sensors are sensitive and degradable structures that are affected by all kinds of environments, the need to provide a solution for the sensitivity and degradability of sensor structures in the literature has become an increasing need day by day.

[0009] The limitations and inadequacies of the sensors used in the detection of heavy metals, in particular cadmium, in the current state of the art, the fact that the majority of these sensors are disposable, thus constantly generating additional costs due to their disposability, and the fact that they generate chemical waste harmful to human health and the environment every time they are used due to their disposability, the problems of cost and time caused by disposable sensor configurations, as well as the problems of continuous generation of environmental waste, the fact that the polymerization of the sensors used in the current technique for the detection of heavy metals takes place in the liquid phase, resulting in a degradable sensor structure, the fact that the detection limit of the sensors used in the present technique for the detection of heavy metals, in particular cadmium, are very high, that the solvents used in the sensors used in the present technique for the detection of heavy metals damage the substrate material and thus cause a burden in terms of time and costs, that high-purity coatings cannot be produced, and that the generation of problems such as the extraction of environmentally hazardous solvent waste and it is necessary to present a polymer- based fluorescent sensor and a method for its preparation for use in the detection of heavy metal ions, in particular cadmium (Cd+2), in which all these problems are eliminated.

[0010] Brief Description and Objects of the Invention

[0011] The invention clarifies a polymer-based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), and a method for its preparation. The polymer-based fluorescent sensor for the selective detection of heavy metal ions according to the invention is used for the selective detection of heavy metal ions, and while the detection limit of cadmium in the sensors of the present art is 1 pM, the limit in the inventive sensor is reduced to 0.195 pM, which is approximately 10 times lower than the specified value. The inventive sensor is resistant to environmental influences and resistant to degradation. The inventive sensor can be used multiple times, and the cost of the sensor has been reduced and the damage caused by the sensor to the environment and to the health of living beings has been prevented inasmuch as it can be used repeatedly. The inventive sensor can be adapted to be wearable. The invention provides a sensor structure for selective detection of heavy metal ions with reduced energy consumption during preparation.

[0012] The aim of the invention is to provide a sensor configuration for the selective detection of heavy metal ions in which the detection limits of heavy metals, in particular cadmium, are reduced. In the invention, a sensor structure in which the detection limits of heavy metals, in particular cadmium, are reduced in order to be used for the selective detection of heavy metal ions is provided by the nitroxide radical, which can easily interact with certain heavy metals and can form both covalent and electrostatic bonds with ions, and by combining this radical with a quantum dot (QD) nanoparticle to form a nanostructure. By using the nitroxide radical and combining it with the quantum dot (QD) nanoparticle to form a nanostructure, it is possible to realize the ion detection process using the change in fluorescence radiation. Specific ion detection is provided by the nitroxide radical in the polymer-QD-nitroxide radical structure used. A nitroxide radical has the ability to accept an electron for reduction to its diamagnetic counterpart hydroxylamine or to donate an electron for conversion to another diamagnetic counterpart oxammonium cation. During the formation of QD-nitroxide radical nanoprobe (also called fluorescent nanoprobe), the quenching mechanism of quantum dot (QD) fluorescence occurs. That is, when the nitroxide radical binds to the QD, it quenches the fluorescence radiation of the QD. If there are ions or molecules in the environment that can interact with the nitroxide radical, the nitroxide portion of the fluorescent nanoprobe will react with these ions or molecules to form a diamagnetic form and the nitroxide radical will no longer be able to quench the fluorescence of the QD and the QD will recover its fluorescence. This proves that the QD-nitroxide radical has detected the target ion or molecule. The mechanism referred to is defined in the literature as the fluorescence recovery mechanism [6-9]. The detection process of the inventive sensor structure is shown in Figure 5. Figure 5 shows the results of Cd2+ion detection with polymer-QD-nitroxide radical nanoprobe using fluorescence spectroscopy.

[0013] The fluorescence values were compared by adding Cd2+ions at different concentrations to the medium in which the polymer-QD-nitroxide radical sensor was immersed, and the detection limit was calculated from the graph obtained. The detection limit directly shows the relationship between the ion and the nanoprobe structure. In the sensors used to detect heavy metals, especially cadmium in the state of the technique, the detection limit is low due to the problems caused by the liquid phase. While the detection limit of cadmium in the sensors of the present technique is 1 pM, the limit in the inventive sensor is reduced to 0.195 pM, which is approximately 10 times lower than the specified value.

[0014] The invention provides a sensor for selective detection of heavy metal ions which is resistant to environmental effects and resistant to degradation. The invention provides a sensor for the selective detection of heavy metal ions which is resistant to environmental influences and resistant to degradation by bonding the QD-nitroxide nanoprobe structure to mechanically high-strength polymer thin films prepared by the iCVD method. Bonding of the QD-nitroxide radical nanoprobe to the polymer surface is usually achieved by amide bond formation between the carboxyl (-COOH) groups of the QDs and the primary or secondary amine groups on the polymer surface. The presence of a carbodiimide compound in the reaction medium is generally preferred to ensure activation of the QDs, as amine groups along the polymer chain can easily react with -COOH functionalized QDs through the chemistry of the carbodiimide compound. To obtain the sensor nanoprobe structure used in the inventive sensor, the initiated chemical vapor deposition (iCVD) method is used with cross-linked copolymer thin films with high mechanical and chemical resistance. The iCVD process is a solvent-free method in which polymerization takes place only in the vapor phase at low temperatures. With this method, the degradation problem of polymers produced in the liquid phase due to solvents is prevented and thus a sensor resistant to environmental effects and resistant to degradation is put forward. While obtaining the sensor subject to the invention, contribution is made to the formation of durable films by forming a cross-linked polymer structure. To bind QD-nitroxide radical nanoprobes to the surface of iCVD polymers, thin film polymers are immersed in the solution of QD-nitroxide radical nanoprobes during the nanoprobe formation process and the binding reaction is carried out.

[0015] The invention provides a reusable sensor configuration for the selective detection of heavy metal ions. A reusable sensor configuration for the selective detection of heavy metal ions has been realised in the invention. The results analysed in the literature and the experiments carried out during this study show that high pH values (pH > 8) are not suitable for ion detection. At high pH values, heavy metal ions react with hydroxyl (OH ) to form metal hydroxides (high pH values lead to high OH- concentration in solution). Considering this, a separate study based on the change in solution pH was carried out to investigate whether the polymer-QD-nitroxide radical nanoprobe introduced with the invention can be used more than once for Cd2+ion detection. The main purpose here is to provide favourable conditions (pH, etc.) under which the Cd2+ion can more easily interact with another structure in the environment for separation from the nanoprobe. During the detection of Cd2+ions, an electrostatic interaction occurs between the Cd2+ion and the nitroxide radical, so by optimising the ambient conditions, it was possible to separate the Cd2+ion from this structure. Then, the ion detection procedure was applied again and the Cd2+ion was re-detected and the reusable sensor structure was demonstrated in this way.

[0016] The invention provides a cost-reduced sensor configuration for the selective detection of heavy metal ions. Since the inventive sensor can be used repeatedly, the cost of the sensor is also reduced. In the invention, a sensor configuration that can be used repeatedly for the selective detection of heavy metal ions is provided by the change in ambient pH values.

[0017] With the invention, a sensor configuration for the selective detection of heavy metal ions is provided which prevents damage to living health and the environment. Since the sensor subject to the invention can be used repeatedly, the damage of the sensor to the environment and living health is prevented. In order to be used in the selective detection of heavy metal ions, a sensor configuration that can be used repeatedly is provided in the invention through the change in ambient pH values.

[0018] The invention presents a sensor structure in which the fields of application of sensor structures for the selective detection of heavy metal ions are expanded. In the sensor according to the invention, the problems encountered by the polymers produced in the liquid phase due to solvents are avoided and all kinds of three-dimensional porous and sensitive surfaces (paper, napkin or membrane, etc.) can be coated, thus expanding the area of use of the sensor structures, e.g. enabling the production of wearable flexible sensors. In the invention, the problems encountered with polymers produced in the liquid phase due to solvents are avoided by thin polymer films produced in the vapor phase using an iCVD system.

[0019] The invention provides a sensor configuration for selective detection of heavy metal ions with reduced energy consumption during preparation. In the process of producing polymer thin films with high mechanical strength in the iCVD system and bonding QD- nitroxide nanoprop structures to these films to produce the sensor, the polymer films are coated at room temperature in the iCVD system, thus providing high energy efficiency and also polymer-QD-nitroxide radical sensor can be used more than once (the results obtained from the experiments proved that at least 4 times ion detection was successfully performed without deterioration of the sensor structure) has reduced the energy consumption by at least 4 times. During the preparation of the sensor according to the invention, it is possible to make coatings on the surface at temperatures of 10-40°C, and the energy consumption is reduced because the coating is made without using high temperatures. In addition, compared to the sensor preparation methods in the present technique, which use very high temperatures (~2000°C, etc.), the radicals that play an important role in initiating polymerization are easily formed in the inventive sensor preparation method by using hot wires in the temperature range of 200-400°C, except for the surface where the coating is performed. This situation also contributes to energy saving.

[0020] In the polymer-based fluorescent sensor to be used for the selective detection of heavy metal ions, in particular cadmium (Cd+2), a sensor structure that has not been carried out in any previous study is revealed, both in the preparation of the cross-linked copolymer film by chemical vapor deposition method and in the binding of the nanoparticle-ligand structure to this film surface. The polymer film, to which the sensor probe is attached, is polymerized in the vapor phase and at low temperature rather than in the liquid phase, which allows it to be easily coated on three-dimensional, different types of sensitive surfaces and at room temperature, transferring the functional properties of the monomers to the polymer structures without degradation and allowing the substrates used to be coated without damage. In this way, it is possible to produce reusable sensors by functionalizing many different surfaces (metal, polymer, ceramic, paper, etc.).

[0021] Explanation of the Figures

[0022] Figure 1. Representative illustration of polymer film preparation in chemical vapor deposition system. a. Monomer b. Initiator c. Heated wire d. Reactor pressure e. Free Radical f. Polymer coating g. Substrate surface

[0023] Figure 2. Representative illustration of polymer functionalization by epoxy ring opening reaction. h. Polymer coating i. Alcohol j. Amine group

[0024] Figure 3. Schematic representation of polymer-quantum dot (QD)-nitroxide radical nanoprobe formation. k. Nitroxide radical l. Quantum dot m. Quantum dot-nitroxide radical nanoprobe n. Polymer-quantum dot-nitroxide radical nanoprobe sensor

[0025] Figure 4. Representative illustration of Cd+2ion detection by polymer-QD-nitroxide radical nanoprobe. o. Electron (ej p. Cadmium ion (Cd2+)

[0026] Figure 5. Results of Cd2+ion detection by polymer-QD-nitroxide radical nanoprobe using fluorescence spectroscopy. r. Polymer-quantum dot(QD) s. Polymer-quantum dot (QD)-Nitroxide radical t. Polymer-quantum dot(QD)-Nitroxide radical-Cd+2u. Cd+2detection v. Fluorescence quenching

[0027] Detailed Description of the Invention

[0028] The invention relates to a polymer-based fluorescent sensor for the selective detection of heavy metal ions, particularly cadmium (Cd+2), and a method for its preparation. The polymer-based fluorescent sensor for the selective detection of heavy metal ions subject to the invention is used in the selective detection of heavy metal ions, and while the detection limit of cadmium is 1 pM in the sensors in the present art, the limit in the inventive sensor is reduced to 0.195 pM, which is approximately 10 times lower than the specified value. The inventive sensor is resistant to environmental influences and resistant to degradation. The inventive sensor can be used repeatedly and the cost of the sensor has been reduced and the damage caused by the sensor to the environment and to the health of living beings has been prevented since it can be used repeatedly. The inventive sensor can be adapted to be wearable. The invention provides a sensor structure for the selective detection of heavy metal ions with reduced energy consumption during preparation.

[0029] A polymer-based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2); a cross-linked copolymer thin film obtained by using epoxy monomer and cross-linking monomer, and a nanoprobe comprising a nanoparticleligand structure containing a nitroxide radical coupled with a quantum dot (QD) solution activated in the presence of a carbodiimide compound and coupled to the cross-linked copolymer thin film by carrying out the epoxy ring opening reaction and attaching the amine functional group to the opened rings. The epoxy monomer referred to herein is (a); 1 ,2-epoxybutane (BO), 1 ,2-epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether. The relevant epoxy monomer allows the surface to be functionalized by epoxy ring opening reactions. In addition, the crosslinking monomer mentioned herein is (a); triethylene glycol di methacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5,7-tetravinyl-1 ,3,5,7- tetramethylcyclotetrasiloxane, N,N-diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-tri vi nyl- 1 ,3,5-trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate. The related cross-linking monomer (a) contributes to the formation of durable films by forming a cross-linked polymer structure. Furthermore, the amine functional group mentioned herein is aniline, triethyl amine or propylamine. The amine functional group in question is a functional group which is highly effective in epoxy ring opening and adhesion to the polymer surface. The nitroxide radical (k) mentioned herein is 2, 2,6,6- tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 -oxyl (Pyroxyl) or unsaturated pyrroxyl, 1 ,1 ,3,3-tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 ,1 ,3,3-tetramethyl-1 H-benzo[de]isoquinoline-2(3H)-oxyl (TMAO), phthalimide N-ox (PINO), 4-(N-tert-butyl-N-oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxane (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino. The quantum dot (QD) solution (I) referred to here is cadmium-selenium / zinc-sulphur (CdSe / ZnS), cadmiumtelluride (CdTe), cadmium-telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc-selenium / zinc-sulphur (ZnSe / ZnS). The inventive method of preparing a polymer-based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), comprises the following steps; i. obtaining the cross-linked copolymer thin film (f) via free radical (e) polymerization by adjusting the reaction conditions of substrate temperature (g), reactor pressure (d), heating wire temperature (c) and monomer flow rate using epoxy monomer (a), cross-linking monomer (a) and initiator (b), ii. realization of epoxy ring opening reaction by immersion of the obtained cross-linked copolymer thin films (h) in alcohol solution (i) and for the attachment of the nanoparticle-ligand structure (m) to the cross-linked copolymer thin film (h) obtained by attaching the amine functional group (j) to the opened rings, firstly the preparation of the quantum dot (QD) solution (I) using deionized water and and realization of homogeneous distribution of quantum dots (I) in water by ultrasonication at room temperature, iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. applying gentle stirring to the resulting solution at room temperature continuously, v. preparation of a solution of nitroxide radical (k) capable of interacting with the target ion and combining this nitroxide radical (k) with the activated quantum dot (I) solution and performing the quantum dot (nanoparticle)- ligand (m) formation process by applying gentle stirring continuously at room temperature, vi. immersion of the thin polymer film (h), which is produced with the iCVD system (h) and functionalized with the amine group (j), into this reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot-nitroxide radical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface. Cadmium (Cd2+) ion (p) detection study is carried out by immersing the sensor with the obtained nanoprobe structure in the medium containing Cd2+(p) and electron (o) transfer between the nitroxide radical structure (k) of the sensor (n) and Cd2+ion (p). The epoxy monomer mentioned here is; 1 ,2-epoxybutane (BO), 1 ,2- epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether. The relevant epoxy monomer (a) allows the functionalization of the polymer surface by epoxy ring opening reactions. In addition, the mentioned cross-linking monomer here is (a); triethylene glycol dimethacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5,7-tetravinyl- 1 ,3,5,7 tetramethyl cyclotetrasiloxane, N, N-diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-trivinyl-1 ,3,5-trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate. The mentioned cross-linking monomer (a) contributes to the formation of durable films by forming a cross-linked polymer structure. Furthermore, the amine functional group (j) mentioned herein is aniline, triethyl amine or propylamine. The amine functional group in question is a functional group which is highly effective in epoxy ring opening and adhesion to the polymer surface. The solvent mentioned in the method is deionized water or alcohol. Furthermore, the carbodiimide compound in question is N,N‘-dicyclohexylcarbodiimide, N,N’-diisopropylcarbodiimide, 1 -ethyl- 3-(3-dimethylaminopropyl) carbodiimide or 1 -cyclohexyl-(2-morpholinoethyl) carbodiimide meto-p-toluene sulphonate. The nitroxide radical (k) mentioned in the method is 2,2,6,6-tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 -oxyl (pyroxyl) or unsaturated pyroxyl, 1 ,1 ,3,3,3- tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 , 1 ,3,3-tetramethyl-1 H- benzo[de]isoquinoline-2(3H)-oxyl (TMAO), phthalimide N-ox (PINO), 4-(N-tert- butyl-N-oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxane (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino. The QD solution (I) referred to herein is cadmium-selenium / zinc-sulphur (CdSe / ZnS), cadmium-telluride (CdTe), cadmium-telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc-selenium / zinc-sulphur (ZnSe / ZnS). In one embodiment of the invention, a method for the preparation of a polymer- based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), comprises the following steps, i. obtaining a cross-linked copolymer thin film (f) with a thickness of 10-5000 nM via free radical (e) polymerization using epoxy monomer (a), crosslinking monomer (a) and initiator (b) by adjusting the reaction conditions such that 10-40°C substrate temperature (g), 100-1000 mTorr reactor pressure (d) 150-500°C heating wire temperature (c) and 0.1 -10.0 seem monomer flow rate, ii. performing the epoxy ring opening reaction by immersion of the obtained cross-linked copolymer thin films (h) in alcohol solution at 10-80°C (i) and after attachment of the amine functional group (j) to the opened rings, preparation of the quantum dot (QD) solution (I) using deionized water for the attachment of the nanoparticle-ligand structure (m) to the obtained crosslinked copolymer thin film (h) and homogeneous dispersion of the quantum dots (I) in water by ultrasonication for 15-30 minutes at room temperature, iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. the resulting solution is subjected to continuous gentle stirring at room temperature for 10-60 minutes, v. preparation of a nitroxide radical (k) solution capable of interacting with the target ion and combining the mentioned nitroxide radical (k) with the activated quantum dot (I) solution and performing the quantum dot (nanoparticle)-ligand (m) formation process by applying gentle stirring continuously for 2 hours at room temperature, vi. immersion of the thin polymer film (h), which is produced by the iCVD system (h) and functionalized with the amine group (j), into this reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot-nitroxide radical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface.

[0030] Cadmium (Cd2+) ion (p) detection study is carried out by immersing the sensor with the obtained nanoprobe structure in the medium containing Cd2+(p) and electron (o) transfer between the nitroxide radical structure (k) of the sensor (n) and Cd2+ion (p). The epoxy monomer mentioned here is; 1 ,2-epoxybutane (BO), 1 ,2- epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether. The epoxy monomer (a) in question allows the surface to be functionalized by epoxy ring opening reactions. In addition, the mentioned cross-linking monomer is (a); triethylene glycol dimethacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5,7-tetravinyl- 1 ,3,5,7 tetramethyl cyclotetrasiloxane, N, N-diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-trivinyl-1 ,3,5-trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate. The mentioned cross-linking monomer (a) contributes to the formation of durable films by forming a cross-linked polymer structure. Furthermore, the amine functional group mentioned herein is aniline, triethyl amine or propylamine. The amine functional group (j) in question is a functional group which is highly effective in epoxy ring opening and adhesion to the polymer surface. The solvent mentioned in the method is deionized water or alcohol. Furthermore, the carbodiimide compound in question is N,N‘-dicyclohexylcarbodiimide, N,N’- diisopropylcarbodiimide, 1 -ethyl-3-(3-dimethylaminopropyl) carbodiimide or 1 - cyclohexyl-(2-morpholinoethyl) carbodiimide meto-p-toluene sulphonate. The nitroxide radical (k) mentioned in the method is 2,2,6,6-tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 -oxyl (pyroxyl) or unsaturated pyroxyl, 1 ,1 ,3,3,3-tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 , 1 ,3,3-tetramethyl-1 H- benzo[de]isoquinoline-2(3H)-oxyl (TMAO), phthalimide N-ox (PINO), 4-(N-tert- butyl-N-oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxane (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino. The QD solution (I) referred to herein is cadmium-selenium / zinc-sulphur (CdSe / ZnS), cadmium-telluride (CdTe), cadmium-telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc-selenium / zinc-sulphur (ZnSe / ZnS).

[0031] In one embodiment of the invention, a method for the preparation of a polymer- based fluorescent sensor for the selective detection of heavy metal ions, in particular cadmium (Cd+2), comprises the following steps, i. obtaining a cross-linked copolymer thin film (f) with a thickness of 10-5000 nM via free radical (e) polymerization using epoxy monomer (a), crosslinking monomer (a) and initiator (b) by adjusting the reaction conditions such that 10-40°C substrate temperature (g), 100-1000 mTorr reactor pressure (d) 150-500°C heating wire temperature (c) and 0.1 -10.0 seem monomer flow rate, ii. performing the epoxy ring opening reaction by immersion of the obtained cross-linked copolymer thin films (h) in alcohol solution at 10-80°C (i) and after attachment of the amine functional group (j) to the opened rings, preparation of the quantum dot (QD) solution (I) using deionized water for the attachment of the nanoparticle-ligand structure (m) to the obtained crosslinked copolymer thin film (h) and homogeneous dispersion of the quantum dots (I) in water by ultrasonication for 15-30 minutes at room temperature, iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. the resulting solution is subjected to continuous gentle stirring at room temperature for 10-60 minutes, v. preparation of a nitroxide radical (k) solution capable of interacting with the target ion and combining the mentioned nitroxide radical (k) with the activated quantum dot (I) solution and performing the quantum dot (nanoparticle)-ligand (m) formation process by applying gentle stirring continuously for 2 hours at room temperature, vi. immersion of the thin polymer film (h), which is produced by the iCVD system (h) and functionalized with the amine group (j), into this reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot-nitroxide radical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface.

[0032] Cadmium (Cd2+) ion (p) detection study is carried out by immersing the sensor with the obtained nanoprobe structure in the medium containing Cd2+(p) and electron (o) transfer between the nitroxide radical structure (k) of the sensor (n) and Cd2+ion (p). The epoxy monomer mentioned here is; 1 ,2-epoxybutane (BO), 1 ,2- epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether. The epoxy monomer (a) in question allows the surface to be functionalized by epoxy ring opening reactions. In addition, the mentioned cross-linking monomer is (a); triethylene glycol dimethacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5,7-tetravinyl- 1 ,3,5,7 tetramethyl cyclotetrasiloxane, N, N-diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-trivinyl-1 ,3,5-trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate. The mentioned cross-linking monomer (a) contributes to the formation of durable films by forming a cross-linked polymer structure. Furthermore, the amine functional group mentioned herein is aniline, triethyl amine or propylamine. The amine functional group (j) in question is a functional group which is highly effective in epoxy ring opening and adhesion to the polymer surface. The solvent mentioned in the method is deionized water or alcohol. Furthermore, the carbodiimide compound in question is N,N‘-dicyclohexylcarbodiimide, N,N’- diisopropylcarbodiimide, 1 -ethyl-3-(3-dimethylaminopropyl) carbodiimide or 1 - cyclohexyl-(2-morpholinoethyl) carbodiimide meto-p-toluene sulphonate. The nitroxide radical (k) mentioned in the method is 2,2,6,6-tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 -oxyl (pyroxyl) or unsaturated pyroxyl, 1 ,1 ,3,3,3-tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 , 1 ,3,3-tetramethyl-1 H- benzo[de]isoquinoline-2(3H)-oxyl (TMAO), phthalimide N-ox (PINO), 4-(N-tert- butyl-N-oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxane (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino. The QD solution (I) referred to herein is cadmium-selenium / zinc-sulphur (CdSe / ZnS), cadmium-telluride (CdTe), cadmium-telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc-selenium / zinc-sulphur (ZnSe / ZnS).

[0033] References

[0034] [1] Wikimedia Foundation. (2024, January 7). Agir metal. Wikipedia. https: / / tr.wiki pedia.org / wiki / A%C4%9F%C4%B1 r_metal

[0035] [2] Agir metal dlqumu. Halig Qevre Laboratuvan. (2020, June 4). https: / / haliccevre.com / agir-metal-olcumu /

[0036] [3] Asri, F. 0., Sdnmez, S., & Qitak, S. (n.d.). 32 KADMlYUMUN QEVRE VE INSAN

[0037] SAGLIGI UZERlNE ETKlLERl. https: / / www.horticulturalstudies.org / uploads / pdf_242.pdf

[0038] [4] Bronson, R.T., et al., Efficient Immobilization of a Cadmium Chemosensor in a Thin Film: Generation of a Cadmium Sensor Prototype. Organic Letters, 2005. 7(6): p. 1105-1108.

[0039] [5] Bronson, R. T., Michaelis, D. J., Lamb, R. D., Husseini, G. A., Farnsworth, , P. B., Linford, M. R., Izatt, R. M., Bradshaw, J. S., & Savage, P. B. (2005, March 17). Efficient immobilization of a cadmium chemosensor in a thin film: generation of a cadmium sensor prototype, https: / / pubmed.ncbi.nlm.nih.gov / 15760150 /

[0040] [6] Chen, Wenbin, Xin Wang, Xijuan Tu, Dejun Pei, Yue Zhao, and Xiangqun Guo. 2008. "Water-Soluble Off-On Spin-Labeled Quantum-Dots Conjugate." Small 4

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[0042] [7] Lin, Feng, Dejun Pei, Weina He, Zhaoxia Huang, Yanjie Huang, and Xiangqun Guo. 2012. "Electron transfer quenching by nitroxide radicals of the fluorescence of carbon dots." Journal of Materials Chemistry 22 (23) : 11801 -11807.

[0043] [8] Maiti, Siddhartha, Ziya Aydin, Yi Zhang, and Maolin Guo. 2015. "Reaction-based turn on fluorescent probes with magnetic responses for Fe2+ detection in live cells." Dalton Transactions 44 (19):8942-8949.

[0044] [9] Maurel, Vincent, Marie Laferriere, Paul Billone, Robert Godin, and J. C. Scaiano. 2006. "Free Radical Sensor Based on CdSe Quantum Dots with Added 4-Amino- 2,2,6,6-Tetramethylpiperidine Oxide Functionality." The Journal of Physical Chemistry B 110 (33):16353-16358.

Claims

CLAIMS1 . It is a polymer-based fluorescent sensor for the detection of heavy metal ions, especially cadmium (Cd+2) and its characterization; It is a nanoprobe structure which comprising a cross-linked copolymer thin film obtained by using epoxy monomer and cross-linking monomer by attaching the nanoparticle-ligand structure containing nitroxide radical combined with quantum dot (QD) solution activated in the presence of carbodiimide compound after the amine functional group bonding to the rings opened by performing epoxy ring opening reaction to the cross-linked copolymer thin film.

2. It is a sensor according to request 1 , its feature is that mentioned epoxy monomer is 1 ,2-epoxybutane (BO), 1 ,2-epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether.

3. It is a sensor according to request 1 , its feature is that mentioned crosslinking monomer is; triethylene glycol dimethacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5, 7-tetravinyl-1 ,3,5,7 tetramethyl cyclotetrasiloxane, N, N- diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-tri vi nyl- 1 ,3,5- trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate.

4. It is a sensor according to request 1 , its feature is that the amine functional group in question is aniline, triethyl amine or propylamine.

5. It is a sensor according to request 1 , its feature is that said nitroxide radical is 2,2,6,6-tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 -oxyl (pyroxyl) or unsaturated pyrroxyl, 1 ,1 ,3,3,3- tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 ,1 ,3, 3-tetramethyl-1 H- benzo[de]isoquinoline-2(3H)-oxyl (TMAO), phthalimide N-ox (PINO), 4-(N- tert-butyl-N-oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxeye (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino.

6. It is a sensor according to request 1 , its feature is that the QD solution in question is cadmium-selenium / zinc-sulphur (CdSe / ZnS), cadmium-telluride(CdTe), cadmium-telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc-selenium / zinc-sulphur (ZnSe / ZnS).

7. It is a method of preparing polymer-based fluorescent sensor for the selective detection of heavy metal ions, especially cadmium (Cd+2), and its feature is that it includes the following process steps; i. obtaining crosslinked copolymer thin film (f) via free radical (e) polymerization using epoxy monomer (a), cross-linking monomer (a) and initiator (b) by adjusting the reaction conditions of substrate temperature (g), reactor pressure (d), heating wire temperature (c) and monomer flow rate, ii. after the realization of the epoxy ring opening reaction by immersing the obtained cross-linked copolymer thin films (h) in alcohol solution (i) and attaching the amine functional group (j) to the opened rings, for attachment of the nanoparticle-ligand structure (m) to the obtained cross-linked copolymer thin film (h) initially, the realization of the preparation of the quantum dot (QD) solution (I) using deionized water and the homogeneous distribution of quantum dots (I) in water by ultrasonication at room temperature, iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. applying gentle stirring to the resulting solution at room temperature continuously, v. preparation of a solution of nitroxide radical (k) capable of interacting with the target ion and combining said nitroxide radical (k) with the activated quantum dot (I) solution and again performing the quantum dot (nanoparticle)-ligand (m) formation process by applying gentle stirring continuously at room temperature, vi. immersion of the thin polymer film (h) produced by iCVD system (h) and functionalized with amine group (j) into the reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot-nitroxideradical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface.

8. It is a method of preparation according to request 7, its feature is that it includes the following process steps; i. obtaining a cross-linked copolymer thin film (f) with a thickness of 10-5000 nM via free radical (e) polymerization using epoxy monomer (a), cross-linking monomer (a) and initiator (b) by adjusting the reaction conditions such that 10-40°C substrate temperature (g), 100-1000 mTorr reactor pressure (d) 150-500°C heater wire temperature (c) and 0.1 -10.0 seem monomer flow rate, ii. after the realization of the epoxy ring opening reaction by immersing the obtained cross-linked copolymer thin films (h) in alcohol solution at 10-80°C (i) and attaching the amine functional group (j) to the opened rings, for attachment of the nanoparticleligand structure (m) to the obtained cross-linked copolymer thin film (h) initially, the realization of the preparation of the quantum dot (QD) solution (I) using deionized water and the homogeneous distribution of quantum dots (I) in water by ultrasonication at room temperature for 15-30 minutes. iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. the resulting solution is subjected to continuous gentle stirring at room temperature for 10-60 minutes, v. preparation of a solution of nitroxide radical (k) capable of interacting with the target ion and combining said nitroxide radical (k) with activated quantum dot (I) solution and realization of the quantum dot (nanoparticle)-ligand (m) formation process by again performing continuous gentle stirring at room temperature for 2 hours,vi. immersion of the thin polymer film (h) produced by iCVD system (h) and functionalized with amine group (j) into the reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot- nitroxide radical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface.

9. It is a method of preparation according to request 8, its feature is that it includes the following process steps; i. obtaining a cross-linked copolymer thin film (f) with a thickness of 10-5000 nM via free radical (e) polymerization using epoxy monomer (a), cross-linking monomer (a) and initiator (b) by adjusting the reaction conditions such that 10-40°C substrate temperature (g), 100-1000 mTorr reactor pressure (d) 150-500°C heater wire temperature (c) and 0.1 -10.0 seem monomer flow rate, ii. after the realization of the epoxy ring opening reaction by immersing the obtained cross-linked copolymer thin films (h) in alcohol solution at 10-80°C (i) and attaching the amine functional group (j) to the opened rings, for attachment of the nanoparticleligand structure (m) to the obtained cross-linked copolymer thin film (h) initially, the realization of the preparation of the quantum dot (QD) solution (I) using deionized water and the homogeneous distribution of quantum dots (I) in water by ultrasonication at room temperature for 15-30 minutes. iii. preparation of a solution containing carbodiimide compound with solvent and realization of quantum dot (I) surface activation, iv. the resulting solution is subjected to continuous gentle stirring at room temperature for 10-60 minutes, v. preparation of a solution of nitroxide radical (k) capable of interacting with the target ion and combining said nitroxide radical (k) with activated quantum dot (I) solution and realization of thequantum dot (nanoparticle)-ligand (m) formation process by again performing continuous gentle stirring at room temperature for 2 hours, vi. immersion of the thin polymer film (h) produced by iCVD system (h) and functionalized with amine group (j) into the reaction medium while the nanoparticle-ligand (m) formation process is in progress, and realization of the sensor with polymer-quantum dot- nitroxide radical nanoprobe (n) structure by binding the nanoparticle-ligand (m) structure to the polymer surface as a result of amide bond formation between them and the amine group (j) on the polymer surface.

10. It is a method of preparation according to any one of requests 7-9, its feature is that epoxy monomer mentioned herein is; 1 ,2-epoxybutane (BO), 1 ,2-epoxypropane (PO), tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), glycidyl acrylate, benzyl glycidyl ether (BnGE), ethoxyethyl glycidyl ether (EEGE), glycidyl methacrylate, phenyl glycidyl ether or hexyl glycidyl ether.1 1. It is a method of preparation according to any one of requests 7-9, its feature is that cross-linking monomer mentioned herein is; triethylene glycol dimethacrylate, triethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, 1 ,3,5, 7-tetravinyl-1 ,3,5,7 tetramethyl cyclotetrasiloxane, N, N-diallylacrylamide, 1 ,5-pentanediol dimethacrylate, 1 ,3,5-tri vi nyl- 1 ,3,5-trimethylcyclotrisiloxane, ethylene glycol diacrylate, 1 ,3-butanediol dimethacrylate or tetraethylene glycol dimethacrylate.

12. It is a method of preparation according to any one of requests 7-9, its feature is that amine functional group mentioned herein is; aniline, triethyl amine or propylamine.

13. It is a method of preparation according to any one of requests 7-9, its feature is that solvent mentioned herein is; deionized water or alcohol.

14. It is a method of preparation according to any one of requests 7-9, its feature is that carbodiimide compound mentioned herein is; N,N‘- dicyclohexylcarbodiimide, N,N’-diisopropylcarbodiimide, 1 -ethyl-3-(3-dimethylaminopropyl) carbodiimide or 1 -cyclohexyl-(2-morpholinoethyl) carbodiimide meto-p-toluene sulphonate.

15. It is a method of preparation according to any one of requests 7-9, its feature is that nitroxide radical mentioned herein is; 2, 2,6,6- tetramethylpiperidine-1 -oxyl (TEMPO), 2,2,5,5-tetramethyl pyrrolidine-1 - oxyl (pyroxyl) or unsaturated pyroxyl, 1 ,1 ,3,3-tetramethylisoindoline-2-oxyl (side line) (TMIO), 1 ,1 ,3, 3-tetramethyl-1 H-benzo[de]isoquinoline-2(3H)- oxyl (TMAO), phthalimide N-ox (PINO), 4-(N-tert-butyl-N- oxylamino)benzene (TBNO), 9-azabicyclo nonane N-oxeye (ABNO), nitronylnitroxide (NINO), carboxylic acid or bisamino.

16. It is a method of preparation according to any one of requests 7-9, its feature is that the QD solution mentioned herein is; cadmium- selenium / zinc-sulphur (CdSe / ZnS), cadmium-telluride (CdTe), cadmium- telluride / cadmium-sulphur (CdTe / CdS), zinc-sulphur (ZnS) or zinc- selenium / zinc-sulphur (ZnSe / ZnS).

17. A polymer-based fluorescent sensor for the detection of heavy metal ions, in particular cadmium (Cd+2), prepared by a method according to any one of requests 7-16.

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