**2. Fundamentals of synthesis of mesoporous polymers based on aromatic isocyanates**

Isocyanates are able to enter into chemical reactions leading to the formation of polymers with different structure. In most cases for the isocyanates, the reactions of nucleophilic addition of compounds containing mobile hydrogen atoms are typical. The reactions of isocyanates with diols and diamines are the most important from a practical point of view. In the presence of catalysts (tertiary amines, alkoxides and carboxylates of quaternary ammonium base, etc.) isocyanates go through dimerization and trimerization to form uretidinedions and isocyanu‐ rates [10]. The possibility of catalytic homopolymerization of isocyanates by anionic mecha‐ nism is also known. As a rule, polyisocyanates of amide nature are polyaddition products. However, in the literature [11] there is information about the formation of polyisocyanate links of acetal nature (O-polyisocyanates). The possibility of transformations in different directions is due to the ambident nature of the anion at the end of the growing chain (Figure 1). These works give the information about obtaining the polyisocyanate links of acetal structure by copolymerization of ethylene oxide and aromatic isocyanates using IR spectroscopy and chemical degradation of the polymer. Typical for these polymers, N = C bond appears in the IR spectra in the region of 1670-1680 cm-1.

In [12,13] it was established that the open chain analogs of crown ethers, which are block copolymers of ethylene oxide and propylene oxide containing terminal and potassium alcoholate groups, are effective initiators of opening the isocyanate groups along the thermo‐ dynamically more stable carbonyl group. It was assumed that the capture of the metal cation by polyester fragment acting as a linear podand promotes the preferential localization of the negative charge on the oxygen atom of the growing chain in anionic polymerization. It was also shown that such polyaddition occurs only when 2,4-tolylene diisocyanate is used involving isocyanate groups of more active para-position to the reaction process.

**Figure 1.** Ambident nature of the anionic center in the reaction of 2,4-toluene diisocyanate with alcoholates

Open chain analogs of crown ethers, which are block copolymers of ethylene oxide and propylene oxide containing terminal potassium alcoholate groups turned out to be effective initiators of isocyanate groups opening by anionic mechanism. Previously, it was found that the opening of the isocyanate groups along the N = C bond led to cyclization of polyaddition products with subsequent formation of polyisocyanurates. However, it turned out that if the macroinitiators were open-chain analogues of crown ethers there could be created favorable conditions for the opening of the isocyanate groups along the carbonyl component and the formation of the polyisocyanate structures of the acetal nature. Earlier in [14], it was shown that the polymers obtained in this way can reach the free volume up to 20% due to the formation of mesopores. Until now, there was uncertainty about the causes of the formation of transition pores in the volume of the polymer, the percentage of O-polyisocyanate blocks and how to manage the process in terms of creating the most favorable conditions for the formation of mesoporous polymers. According to the chemical structure of O-polyisocyanate links, their macroblocked structures are able to exhibit intense intermacromolecular interactions leading to their segregation.

In [15], it was shown that the involvement of the isocyanate groups in the *ortho*-position into the reaction with latent water with the following formation of urea groups contributed to

In turn, the coil of macroinitiator is quite large, larger than 50 nm. The result is that the coil of macroinitiator contains a great number of macromolecules of open-chain analogs of crown ethers and is able to engender the growth of O-polyisocyanates' units as well as to stabilize the reactive terminal

In [15], it was shown that the involvement of the isocyanate groups in the *ortho*-position into the reaction with latent water with the following formation of urea groups contributed to stabilization of

Polymerization starts from a macromolecular coil representing the block copolymers of ethylene oxide and propylene oxide. Terminal reactive O-polyisocyanate units exhibit the ability to stabilize due to their interaction with forming structural fragments of crown ethers in the coil of

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

51

In this case the initiation and stabilization acquired rigorous multi-dimensional geometry in the space,the result of which was the cell structure with voids similarto honeycombs (Figure 2).

In this case the initiation and stabilization acquired rigorous multi-dimensional geometry in the space,

where - polyether chains, - polyisocyanate block,

Figure 2. Scheme of the pores formation in the polymer based on anionic macroinitiator and 2,4-

**Figure 2.** Scheme of the pores formation in the polymer based on anionic macroinitiator and 2,4-toluene diisocyanate

Evaluation of the sorption capacity of the polymers was carried out by water absorption. The adsorption isotherm of water vapor for the polymer sample was S-shaped, which is typical for

Evaluation of the sorption capacity of the polymers was carried out by water absorption. The adsorption isotherm of water vapor for the polymer sample was S-shaped, which is typical for polymers with transition pores (Figure 3). The specific surface area of sorbents was calculated

/g. According to [16],

/g.

the result of which was the cell structure with voids similar to honeycombs (Figure 2).


by the equation proposed by Brunauer, Emmett and Teller and was 75 m2

the specific surface of transitional pores (mesopores) is in the region of 20-200 m2

stabilization of O-polyisocyanate blocks.

macroinitiators.

O-polyisocyanate blocks.

toluene diisocyanate

units.

Polymerization starts from a macromolecular coil representing the block copolymers of ethylene oxide and propylene oxide. Terminal reactive O-polyisocyanate units exhibit the ability to stabilize due to their interaction with forming structural fragments of crown ethers in the coil of macroinitiators.

In turn, the coil of macroinitiator is quite large, larger than 50 nm. The result is that the coil of macroinitiator contains a great number of macromolecules of open-chain analogs of crown ethers and is able to engender the growth of O-polyisocyanates' units as well as to stabilize the reactive terminal units.

In [15], it was shown that the involvement of the isocyanate groups in the *ortho*-position into the reaction with latent water with the following formation of urea groups contributed to stabilization of O-polyisocyanate blocks. oxide and propylene oxide. Terminal reactive O-polyisocyanate units exhibit the ability to stabilize due to their interaction with forming structural fragments of crown ethers in the coil of macroinitiators. In turn, the coil of macroinitiator is quite large, larger than 50 nm. The result is that the coil of macroinitiator contains a great number of macromolecules of open-chain analogs of crown ethers and

Polymerization starts from a macromolecular coil representing the block copolymers of ethylene

Open chain analogs of crown ethers, which are block copolymers of ethylene oxide and propylene oxide containing terminal potassium alcoholate groups turned out to be effective initiators of isocyanate groups opening by anionic mechanism. Previously, it was found that the opening of the isocyanate groups along the N = C bond led to cyclization of polyaddition products with subsequent formation of polyisocyanurates. However, it turned out that if the macroinitiators were open-chain analogues of crown ethers there could be created favorable conditions for the opening of the isocyanate groups along the carbonyl component and the formation of the polyisocyanate structures of the acetal nature. Earlier in [14], it was shown that the polymers obtained in this way can reach the free volume up to 20% due to the formation of mesopores. Until now, there was uncertainty about the causes of the formation of transition pores in the volume of the polymer, the percentage of O-polyisocyanate blocks and how to manage the process in terms of creating the most favorable conditions for the formation of mesoporous polymers. According to the chemical structure of O-polyisocyanate links, their macroblocked structures are able to exhibit intense intermacromolecular interactions leading

Polymerization starts from a macromolecular coil representing the block copolymers of ethylene oxide and propylene oxide. Terminal reactive O-polyisocyanate units exhibit the ability to stabilize due to their interaction with forming structural fragments of crown ethers

In turn, the coil of macroinitiator is quite large, larger than 50 nm. The result is that the coil of macroinitiator contains a great number of macromolecules of open-chain analogs of crown ethers and is able to engender the growth of O-polyisocyanates' units as well as to stabilize the

to their segregation.

50 Optical Sensors - New Developments and Practical Applications

in the coil of macroinitiators.

reactive terminal units.

In this case the initiation and stabilization acquired rigorous multi-dimensional geometry in the space,the result of which was the cell structure with voids similarto honeycombs (Figure 2). In this case the initiation and stabilization acquired rigorous multi-dimensional geometry in the space,

the result of which was the cell structure with voids similar to honeycombs (Figure 2).

Figure 2. Scheme of the pores formation in the polymer based on anionic macroinitiator and 2,4 toluene diisocyanate **Figure 2.** Scheme of the pores formation in the polymer based on anionic macroinitiator and 2,4-toluene diisocyanate

Evaluation of the sorption capacity of the polymers was carried out by water absorption. The adsorption isotherm of water vapor for the polymer sample was S-shaped, which is typical for Evaluation of the sorption capacity of the polymers was carried out by water absorption. The adsorption isotherm of water vapor for the polymer sample was S-shaped, which is typical for polymers with transition pores (Figure 3). The specific surface area of sorbents was calculated by the equation proposed by Brunauer, Emmett and Teller and was 75 m2 /g. According to [16], the specific surface of transitional pores (mesopores) is in the region of 20-200 m2 /g.

When slightly water-soluble reactants are immobilized on the carriers, their solutions in organic solvents are used or the reagents are applied in the form of fine powder. To increase the binding strength of the agent with the carrier the chemical bonds are formed between them (chemical immobilization). For immobilization by covalent bonding (chemical immobiliza‐ tion) cellulose, polymers sorbents and silica gels are used as carriers. However, the "physical"

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

53

The presence of voids in the mesoporous polymer was the reason to immobilize organic polymer-supported reagents. The study of sorption processes of luminophores in polymers is of interest in connection with the possibility of obtaining laser media and sensors for photo‐

The study of the sorption properties of the polymeric material with respect to organic lumi‐

**Figure 5.** Electronic spectra of the solution of rhodamine 6G (1) in ethanol and rhodamine 6G, immobilized in the

As the luminophore rhodamine 6G (R6G) was selected and used to determine gold cations. A solution of R6G of the given concentration was obtained and the maximum value of the optical density was determined. According to the Bouguer-Lambert law the molar absorption coefficient for the solution of rhodamine 6G was calculated. Rhodamine 6G was sorbed on the polymer. The value of the optical density of the polymer sample doped with R6G at λmax = 530 nm was measured. The calculation of dye concentration in the polymer was performed. It was established that electron spectra of organic agents on polymer carriers did not have substantial changes in comparison with the spectrum of their solutions. It was established that adsorption

mesoporous polymer (thickness of the cuvette for the solution and the polymer sample was 0.1 cm)

fixing is usually much simpler, so it is quite widespread.

metric and luminescent determination of metal cations.

nophores was carried out by electronic spectroscopy (Figure 5).

**Figure 3.** Water sorbtion curve for mesoporous polymer

Additional information about the processes of geometry of supramolecular structures in these polymers was obtained by using atomic force microscopy (Figure 4).

**Figure 4.** AFM image of a mesoporous polymer

#### **3. Features of the organic chromophores immobilization in mesoporous polymers**

Reactants, slightly soluble in water, are preferred, since the test-forms are more stable during storage and they are weakly leached from the test matrix during the contact with the test liquid. When slightly water-soluble reactants are immobilized on the carriers, their solutions in organic solvents are used or the reagents are applied in the form of fine powder. To increase the binding strength of the agent with the carrier the chemical bonds are formed between them (chemical immobilization). For immobilization by covalent bonding (chemical immobiliza‐ tion) cellulose, polymers sorbents and silica gels are used as carriers. However, the "physical" fixing is usually much simpler, so it is quite widespread.

The presence of voids in the mesoporous polymer was the reason to immobilize organic polymer-supported reagents. The study of sorption processes of luminophores in polymers is of interest in connection with the possibility of obtaining laser media and sensors for photo‐ metric and luminescent determination of metal cations.

The study of the sorption properties of the polymeric material with respect to organic lumi‐ nophores was carried out by electronic spectroscopy (Figure 5).

**Figure 3.** Water sorbtion curve for mesoporous polymer

52 Optical Sensors - New Developments and Practical Applications

**Figure 4.** AFM image of a mesoporous polymer

**polymers**

Additional information about the processes of geometry of supramolecular structures in these

**3. Features of the organic chromophores immobilization in mesoporous**

Reactants, slightly soluble in water, are preferred, since the test-forms are more stable during storage and they are weakly leached from the test matrix during the contact with the test liquid.

polymers was obtained by using atomic force microscopy (Figure 4).

**Figure 5.** Electronic spectra of the solution of rhodamine 6G (1) in ethanol and rhodamine 6G, immobilized in the mesoporous polymer (thickness of the cuvette for the solution and the polymer sample was 0.1 cm)

As the luminophore rhodamine 6G (R6G) was selected and used to determine gold cations. A solution of R6G of the given concentration was obtained and the maximum value of the optical density was determined. According to the Bouguer-Lambert law the molar absorption coefficient for the solution of rhodamine 6G was calculated. Rhodamine 6G was sorbed on the polymer. The value of the optical density of the polymer sample doped with R6G at λmax = 530 nm was measured. The calculation of dye concentration in the polymer was performed. It was established that electron spectra of organic agents on polymer carriers did not have substantial changes in comparison with the spectrum of their solutions. It was established that adsorption of organic phosphor 6G rhodamine is accompanied by its concentration of polymer matrix. The dye concentration in the polymer was 3 times more than in the initial solution. This fact points to the flow of intense adsorption of rhodamine 6G in the voids of the polymer.

#### **4. Mesoporous polymers as laser active media**

Dye lasers are used for spectroscopic studies to improve the sensitivity, spectral and temporal resolution by several orders of magnitude compared to traditional methods of spectroscopy. They can also be used where high energy of laser radiation is not needed. Typically, in dye lasers the solutions of dyes (solvents - water, alcohols, benzene derivatives, etc.), rarely dyes activated polymeric materials - polymethyl methacrylate, epoxy resin, polyurethane, etc. are used which are called polymeric laser-active media. However, these media have a number of drawbacks that make them difficult to use. For example, the polymer and dye undergo relatively rapid photodegradation, so the active medium often has to be changed.

Nowadays, thanks to the efforts of chemists and physicists, solid-state active media for tunable lasers are made with parameters as good as solutions' parameters. In recent years the interest in the emission of organic molecules in the thin films is growing due to the possibility of using them as the base for photoexcitating microlasers and the materials for OLEDs. Polymers have great advantages over other materials. They show high optical uniformity, good compatibility with organic dyes and at the same time they are cheap and manufacturable. The latter facilitates the miniaturization and embeddability in optical systems.

pulses, that is, about 175 times smaller than for the mesoporous polymer. PMMA demonstrates

**Figure 6.** Luminescence (dash line) and ASE (solid line) spectra of the mesoporous polymer doped with rhodamine 6G

550 575 600 625 650 675

l**, nm**

luminescence

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

55

ASE

0,4

0,6 0,8 1

**Norm. ASE energy**

0 20000 40000 60000 80000 100000

**Number of pump pulses**

**Figure 7.** Dependences of the normalized ASE energy on the number of excitation pulses of mesoporous polymer and PMMA doped with R6G (pump intensity was 25 MW/cm2). The inset shows the details of the dependences at the be‐

0 2000 4000 6000 8000

**Number of pump pulses**

**PMMA+R6G**

**mesoporous polymer+R6G**

**mesoporous polymer+R6G**

**PMMA+R6G**

exponential ASE decay (Figure 7).

0,0

0,5

**Normalized emission intensity**

1,0

0,25

**Normalized ASE energy**

ginning of the pump

0,5

0,75

1

Laser properties of mesoporous and nonporous polymers doped with rhodamine 6G dye were investigated for comparison. Because of specific samples forms it wasn't possible to measure laser efficiency directly. To estimate the laser efficiency, operating life-time amplified sponta‐ neous emission (ASE) under transverse pump by the second harmonic of Q-switched Nd:YAG laser (pulsewidth was 12 ns, pulse repetition rate was 10 Hz) was measured. The pumping region had a form of a stripe with 27 µm width and length close to the sample length. Maximum intensity at the beam waist at the sample was 25 MW/cm2 . The ASE was observed from two opposite samples cuts inside the cones with axis parallel to pump region in such setup configuration. The intensity of the ASE was measured from one side of the investigated sample with piroelectric energy sensor Ophir PE-9 (ASE was focused by spherical lens). Simultane‐ ously from the other side of the sample ASE spectra were measured with wide-range spec‐ trometer S100. At the pump intensity 25 MW/cm2 the spectral half-width of the ASE didn't exceed 5 nm for all investigated samples (Figure 6).

Photostability of Rhodamine 6G in the mesoporous polymer at low pump energies (12.5 MW/ cm2 ) amounted to 115000 pulses, at high energies (25 MW/cm2 ) - 60000 pulses. The energy of stimulated emission during irradiation reached maximum and then began to fall compared to the original value. The most widespread material for the solid-state polymer dye lasers is nonporous polymethylmethacrylate (PMMA). Therefore, the PMMA with R6G was chosen for comparison. Halving ASE energy of the PMMA doped with R6G was observed at around 200

of organic phosphor 6G rhodamine is accompanied by its concentration of polymer matrix. The dye concentration in the polymer was 3 times more than in the initial solution. This fact

Dye lasers are used for spectroscopic studies to improve the sensitivity, spectral and temporal resolution by several orders of magnitude compared to traditional methods of spectroscopy. They can also be used where high energy of laser radiation is not needed. Typically, in dye lasers the solutions of dyes (solvents - water, alcohols, benzene derivatives, etc.), rarely dyes activated polymeric materials - polymethyl methacrylate, epoxy resin, polyurethane, etc. are used which are called polymeric laser-active media. However, these media have a number of drawbacks that make them difficult to use. For example, the polymer and dye undergo

Nowadays, thanks to the efforts of chemists and physicists, solid-state active media for tunable lasers are made with parameters as good as solutions' parameters. In recent years the interest in the emission of organic molecules in the thin films is growing due to the possibility of using them as the base for photoexcitating microlasers and the materials for OLEDs. Polymers have great advantages over other materials. They show high optical uniformity, good compatibility with organic dyes and at the same time they are cheap and manufacturable. The latter facilitates

Laser properties of mesoporous and nonporous polymers doped with rhodamine 6G dye were investigated for comparison. Because of specific samples forms it wasn't possible to measure laser efficiency directly. To estimate the laser efficiency, operating life-time amplified sponta‐ neous emission (ASE) under transverse pump by the second harmonic of Q-switched Nd:YAG laser (pulsewidth was 12 ns, pulse repetition rate was 10 Hz) was measured. The pumping region had a form of a stripe with 27 µm width and length close to the sample length. Maximum

opposite samples cuts inside the cones with axis parallel to pump region in such setup configuration. The intensity of the ASE was measured from one side of the investigated sample with piroelectric energy sensor Ophir PE-9 (ASE was focused by spherical lens). Simultane‐ ously from the other side of the sample ASE spectra were measured with wide-range spec‐

Photostability of Rhodamine 6G in the mesoporous polymer at low pump energies (12.5 MW/

stimulated emission during irradiation reached maximum and then began to fall compared to the original value. The most widespread material for the solid-state polymer dye lasers is nonporous polymethylmethacrylate (PMMA). Therefore, the PMMA with R6G was chosen for comparison. Halving ASE energy of the PMMA doped with R6G was observed at around 200

. The ASE was observed from two

) - 60000 pulses. The energy of

the spectral half-width of the ASE didn't

points to the flow of intense adsorption of rhodamine 6G in the voids of the polymer.

relatively rapid photodegradation, so the active medium often has to be changed.

**4. Mesoporous polymers as laser active media**

54 Optical Sensors - New Developments and Practical Applications

the miniaturization and embeddability in optical systems.

intensity at the beam waist at the sample was 25 MW/cm2

trometer S100. At the pump intensity 25 MW/cm2

exceed 5 nm for all investigated samples (Figure 6).

) amounted to 115000 pulses, at high energies (25 MW/cm2

cm2

**Figure 6.** Luminescence (dash line) and ASE (solid line) spectra of the mesoporous polymer doped with rhodamine 6G

pulses, that is, about 175 times smaller than for the mesoporous polymer. PMMA demonstrates exponential ASE decay (Figure 7).

**Figure 7.** Dependences of the normalized ASE energy on the number of excitation pulses of mesoporous polymer and PMMA doped with R6G (pump intensity was 25 MW/cm2). The inset shows the details of the dependences at the be‐ ginning of the pump

Thus, the processes of generation of laser radiation and photochemical aging of organic luminophors in mesoporous and non-porous polymers were studied. It was shown that in the mesoporous polymers organic luminophors were able to generate laser radiation and high radiation resistance.

## **5. Mesoporous polymers as basis for optical chemical sensors**

Organic chromophores react selectively with ions of many metals forming chelate complexes which are intensely colored. The reactions of complex forming organic chromophores and the ion being identified accompanied by color change of the reaction system are the foundation of chemical test methods on metal cations.

**Figure 8.** Scheme of the organic chromophore concentration and complex formation with metal ions in mesoporous polymers

In this work, as organic chromophores were used 1-(2-pyridylazo)-2-naphthol (PAN), arsenazo III and phenazo as reactants, soluble salts of copper CuSO4 and cobalt CoCl2, manganese MnCl2, lanthanum LaCl3, calcium CaCl2, magnesium MgCl2 as analytes.

**Figure 10.** The electronic spectrum of PAN in the mesoporous polymer

tive salt for one hour.

Figure 9. The chemical structure of organic chromophores

**Figure 9.** The chemical structure of organic chromophores

To determine the sensitivity limits of complexing reactions of organic reagent with metal cations a series of solutions with salt concentrations 10-1 g/l, 10-2, 10-3 g/l, 10-4 g/l and 10-5 g/l was prepared. Polymeric carriers modified with organic reagent were kept in solutions of respec‐

Thus, the processes of generation of laser radiation and photochemical aging of organic luminophors in mesoporous and non-porous polymers were studied. It was shown that in the mesoporous polymers

Organic chromophores react selectively with ions of many metals forming chelate complexes which are intensely colored. The reactions of complex forming organic chromophores and the ion being identified accompanied by color change of the reaction system are the foundation of chemical test

Figure 8. Scheme of the organic chromophore concentration and complex formation with metal ions

In this work, as organic chromophores were used 1-(2-pyridylazo)-2-naphthol (PAN), arsenazo III and phenazo as reactants, soluble salts of copper CuSO4 and cobalt CoCl2, manganese MnCl2,

Organic chromophores arsenazo III, phenazo and 1-(2-pyridylazo)-2-naphthol (PAN) have the

Phenazo PAN

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

57

Arsenazo III

organic luminophors were able to generate laser radiation and high radiation resistance.

**5. Mesoporous polymers as basis for optical chemical sensors** 

lanthanum LaCl3, calcium CaCl2, magnesium MgCl2 as analytes.

methods on metal cations.

in mesoporous polymers

chemical structure shown in Figure 9.

Complexes of copper and PAN, PAN and manganese stained polymer in red, complex of cobalt and PAN stained in purple. The value of λmax of PAN complexes with metals when it trans‐ ferred from solution to mesoporous polymers was not changed. The analysis of the absorption spectra shown in Figures 11 and 13, revealed that 1-(2-pyridylazo)-2-naphthol in mesoporous

Organic chromophores arsenazo III, phenazo and 1-(2-pyridylazo)-2-naphthol (PAN) have the chemical structure shown in Figure 9.

Immobilization of the organic reagent PAN on mesoporous carriers was carried out by its adsorption from solution in ethanol. It was found that the electron spectrum of PAN on the polymeric carrier was not changed significantly compared with the spectrum of its solution (Figure 10).

Thus, the processes of generation of laser radiation and photochemical aging of organic luminophors in mesoporous and non-porous polymers were studied. It was shown that in the mesoporous polymers

Organic chromophores react selectively with ions of many metals forming chelate complexes which are intensely colored. The reactions of complex forming organic chromophores and the ion being identified accompanied by color change of the reaction system are the foundation of chemical test

Figure 8. Scheme of the organic chromophore concentration and complex formation with metal ions

In this work, as organic chromophores were used 1-(2-pyridylazo)-2-naphthol (PAN), arsenazo III and phenazo as reactants, soluble salts of copper CuSO4 and cobalt CoCl2, manganese MnCl2,

organic luminophors were able to generate laser radiation and high radiation resistance.

**5. Mesoporous polymers as basis for optical chemical sensors** 

methods on metal cations.

in mesoporous polymers

chemical structure shown in Figure 9.

**Figure 9.** The chemical structure of organic chromophores

Figure 9. The chemical structure of organic chromophores

Thus, the processes of generation of laser radiation and photochemical aging of organic luminophors in mesoporous and non-porous polymers were studied. It was shown that in the mesoporous polymers organic luminophors were able to generate laser radiation and high

Organic chromophores react selectively with ions of many metals forming chelate complexes which are intensely colored. The reactions of complex forming organic chromophores and the ion being identified accompanied by color change of the reaction system are the foundation of

**Figure 8.** Scheme of the organic chromophore concentration and complex formation with metal ions in mesoporous

In this work, as organic chromophores were used 1-(2-pyridylazo)-2-naphthol (PAN), arsenazo III and phenazo as reactants, soluble salts of copper CuSO4 and cobalt CoCl2,

Organic chromophores arsenazo III, phenazo and 1-(2-pyridylazo)-2-naphthol (PAN) have the

Immobilization of the organic reagent PAN on mesoporous carriers was carried out by its adsorption from solution in ethanol. It was found that the electron spectrum of PAN on the polymeric carrier was not changed significantly compared with the spectrum of its solution

manganese MnCl2, lanthanum LaCl3, calcium CaCl2, magnesium MgCl2 as analytes.

**5. Mesoporous polymers as basis for optical chemical sensors**

radiation resistance.

polymers

(Figure 10).

chemical test methods on metal cations.

56 Optical Sensors - New Developments and Practical Applications

chemical structure shown in Figure 9.

**Figure 10.** The electronic spectrum of PAN in the mesoporous polymer

To determine the sensitivity limits of complexing reactions of organic reagent with metal cations a series of solutions with salt concentrations 10-1 g/l, 10-2, 10-3 g/l, 10-4 g/l and 10-5 g/l was prepared. Polymeric carriers modified with organic reagent were kept in solutions of respec‐ tive salt for one hour.

Complexes of copper and PAN, PAN and manganese stained polymer in red, complex of cobalt and PAN stained in purple. The value of λmax of PAN complexes with metals when it trans‐ ferred from solution to mesoporous polymers was not changed. The analysis of the absorption spectra shown in Figures 11 and 13, revealed that 1-(2-pyridylazo)-2-naphthol in mesoporous polymers was able to interact with the metal cations. The height of the characteristic band of the complex PAN - metal depends on the concentration of metal in solution, which further will allow to carry out not only qualitative but also quantitative analysis of metal content.

**Figure 11.** Electronic spectra of the Cu - PAN complex, immobilized in a mesoporous polymer by adsorption from sol‐ ution,

**Figure 13.** Electronic spectra of the Co - PAN complex, immobilized in a mesoporous polymer by adsorption from sol‐

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

59

The analysis of the absorption spectra and calibration curves shown in Figures 10 - 14 for 1-(2 pyridylazo)-2-naphthol in mesoporous polymers revealed that the sensitivity of the complex‐

Phenazo chromophore forms with magnesium in alkaline medium an adsorption compound of blue-purple color, the reagent solution is painted in crimson. The absorption maxima of reagent and its complex with magnesium are observed at 490 and 560 nm, respectively. For

[CoCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 14.** The calibration curve for the Co - PAN complex in the mesoporous polymer

ation reaction of PAN and manganese cations on solid carriers was 10-5 g/l.

ution,

[CuSO4]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 12.** The calibration curve for the Cu - PAN complex in the mesoporous polymer

**Figure 13.** Electronic spectra of the Co - PAN complex, immobilized in a mesoporous polymer by adsorption from sol‐ ution,

[CoCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

polymers was able to interact with the metal cations. The height of the characteristic band of the complex PAN - metal depends on the concentration of metal in solution, which further will

**Figure 11.** Electronic spectra of the Cu - PAN complex, immobilized in a mesoporous polymer by adsorption from sol‐

[CuSO4]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 12.** The calibration curve for the Cu - PAN complex in the mesoporous polymer

ution,

allow to carry out not only qualitative but also quantitative analysis of metal content.

58 Optical Sensors - New Developments and Practical Applications

**Figure 14.** The calibration curve for the Co - PAN complex in the mesoporous polymer

The analysis of the absorption spectra and calibration curves shown in Figures 10 - 14 for 1-(2 pyridylazo)-2-naphthol in mesoporous polymers revealed that the sensitivity of the complex‐ ation reaction of PAN and manganese cations on solid carriers was 10-5 g/l.

Phenazo chromophore forms with magnesium in alkaline medium an adsorption compound of blue-purple color, the reagent solution is painted in crimson. The absorption maxima of reagent and its complex with magnesium are observed at 490 and 560 nm, respectively. For the reagent and compound with magnesium a molar absorption coefficient is 13900 and 35400, respectively [20]. The optimum concentration of NaOH is 1-2N. Colouring of magnesium compound is stable for 1 hour.

The main feature of the reagent arsenazo III is its ability to form very strong chelates with elements. The good contrast of complexes and large values of molar absorption coefficient

A maximum of the electronic spectrum of arsenazo III corresponds to a wavelength of 540 nm. From the literature [20], it is known that the absorption spectra of the complex of lanthanum with arsenazo III have the maximum at wavelength of 665 nm and a molar extinction coefficient

and arsenazo III occurs at the wavelength of 655 nm, the molar extinction coefficient of complex

Figure 17 shows the electronic spectrum of mesoporous polymer-modified arsenazo III. The spectrum does not change much compared to the spectrum of an aqueous solution of arsenazo III. Modified films were studied as an analytical sensor for detecting lanthanum and calcium. Figures 18 and 20 show the electronic spectra corresponding to the complexes of arsnazo III with calcium and lanthanum. It was found that complexes of arsenazo III with lanthanum and calcium, immobilized on a polymer, have clearly expressed characteristic bands on the electronic spectra. In case of the complex arsenazo III - calcium the bands at 600 and 655 nm are observed, for the complex arsenazo III - lanthanum the bands appear at 605 and 665 nm.

complexes provides high sensitivity of reactions - up to 0.01 µg/ml.

**Figure 17.** The electronic spectrum of arsenazo III in the mesoporous polymer

) along with the ability to reach high dilutions without dissociation of

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

61

, the maximum of the absorption spectrum of the complex of calcium

(50•103

is 104 . - 130•103

of the complex 4.5 104

Phenazo's spectra and its complexes with magnesium adsorbed in the pores of the polymer are shown in Figure 15. The limit of sensitivity of complexation reaction of chromophore with magnesium in this case was 10-5 g/l.

**Figure 15.** Electronic spectra of the Mg - Phenazo complex, immobilized in a mesoporous polymer by adsorption from solution,

[MgCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 16.** The calibration curve for the Mg - Phenazo complex in the mesoporous polymer

The main feature of the reagent arsenazo III is its ability to form very strong chelates with elements. The good contrast of complexes and large values of molar absorption coefficient (50•103 - 130•103 ) along with the ability to reach high dilutions without dissociation of complexes provides high sensitivity of reactions - up to 0.01 µg/ml.

the reagent and compound with magnesium a molar absorption coefficient is 13900 and 35400, respectively [20]. The optimum concentration of NaOH is 1-2N. Colouring of magnesium

Phenazo's spectra and its complexes with magnesium adsorbed in the pores of the polymer are shown in Figure 15. The limit of sensitivity of complexation reaction of chromophore with

**Figure 15.** Electronic spectra of the Mg - Phenazo complex, immobilized in a mesoporous polymer by adsorption from

[MgCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 16.** The calibration curve for the Mg - Phenazo complex in the mesoporous polymer

compound is stable for 1 hour.

solution,

magnesium in this case was 10-5 g/l.

60 Optical Sensors - New Developments and Practical Applications

A maximum of the electronic spectrum of arsenazo III corresponds to a wavelength of 540 nm. From the literature [20], it is known that the absorption spectra of the complex of lanthanum with arsenazo III have the maximum at wavelength of 665 nm and a molar extinction coefficient of the complex 4.5 104 , the maximum of the absorption spectrum of the complex of calcium and arsenazo III occurs at the wavelength of 655 nm, the molar extinction coefficient of complex is 104 .

Figure 17 shows the electronic spectrum of mesoporous polymer-modified arsenazo III. The spectrum does not change much compared to the spectrum of an aqueous solution of arsenazo III. Modified films were studied as an analytical sensor for detecting lanthanum and calcium. Figures 18 and 20 show the electronic spectra corresponding to the complexes of arsnazo III with calcium and lanthanum. It was found that complexes of arsenazo III with lanthanum and calcium, immobilized on a polymer, have clearly expressed characteristic bands on the electronic spectra. In case of the complex arsenazo III - calcium the bands at 600 and 655 nm are observed, for the complex arsenazo III - lanthanum the bands appear at 605 and 665 nm.

**Figure 17.** The electronic spectrum of arsenazo III in the mesoporous polymer

**Figure 18.** Electronic spectra of the Ca - Arsenazo III complex, immobilized in a mesoporous polymer by adsorption from solution,

**Figure 20.** Electronic spectra of the La - Arsenazo III complex, immobilized in a mesoporous polymer by adsorption

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

63

[LaCl3∙6H2O]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 21.** The calibration curve for the La – Arsenazo III complex in the mesoporous polymer

from solution,

[CaCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 19.** The calibration curve for the Ca – Arsenazo III complex in the mesoporous polymer

**Figure 20.** Electronic spectra of the La - Arsenazo III complex, immobilized in a mesoporous polymer by adsorption from solution,

[LaCl3∙6H2O]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

**Figure 18.** Electronic spectra of the Ca - Arsenazo III complex, immobilized in a mesoporous polymer by adsorption

[CaCl2]= 10-1 g/l (1), 10-2 g/l (2), 10-3 g/l (3), 10-4 g/l (4), 10-5 g/l (5)

62 Optical Sensors - New Developments and Practical Applications

**Figure 19.** The calibration curve for the Ca – Arsenazo III complex in the mesoporous polymer

from solution,

**Figure 21.** The calibration curve for the La – Arsenazo III complex in the mesoporous polymer

For the polymer matrix modified with arsenazo III, the limit of sensitivity to calcium and lanthanum ions was determined. The maximum concentration at which the metal ions were detected was 10-5 g/l.

**Author details**

Russia

zan, Russia

**References**

er; 2002.

11(63) 1112-1120.

2009; 9(64) 886-895.

Ruslan Davletbaev1\*, Alsu Akhmetshina2

\*Address all correspondence to: b210@bk.ru

University n.a. А.N. Tupolev, Kazan, Russia

, Askhat Gumerov3

1 Department of the Materials Science & Technology, Kazan National Research Technical

2 Department of the Synthetic Rubber, National Research Technological University, Kazan,

3 Department of the Chemical Cybernetics, National Research Technological University, Ka‐

[1] Rouquérol J., Avnir D., Fairbridge C. W., Everett D. H., Haynes J. H., Pericone N., Ramsay J. D. F., Sing K. S. W. Recommendations for the characterization of porous

[3] Baldini F.; Chester A.N.; Homola J.; Martellucci S. Proceedings of the NATO Ad‐

[4] Zolotov Y.A., Ivanov V.M., Amelin V.G. Chemical Test Methods of Analysis. Elsevi‐

[5] Amelin V.G., Abramenkova O.I. 2,3,7-Trihydrofluorones on Cellulose Matrices in Test Methods for Determining Rare Elements. Journal of Analytical Chemistry 2008;

[6] Khimchenko S.V., Eksperiandova L.P., Blank A.B. Adsorption-Spectrometric and Test Methods for Determining Perchlorate Ions with Thionine on Polyurethane

[7] Collinson M.M. Recent Trends in Analytical Applications of Organically Modified

[8] Kuznetsov V.V., Sheremet'ev S.V. Analytical Complexation Reactions of Organic Re‐ agents with Metal Ions in a Solidified Gelatin Gel. Journal of Analytical Chemistry

[9] Dimosthenis L.G., Evangelos K.P., Mamas I.P., Miltiades I.K. Development of 1-(2 pyridylazo)-2-naphthol-modified Polymeric Membranes for the Effective Batch Pre-

solids. Pure and Applied Chemistry 1994; 8(66) 1739-1758.

Foam. Journal of Analytical Chemistry 2009; 1(64) 14-17.

Silicate Materials. Trends in Analytical Chemistry 2002; 1(21) 30-38.

[2] Robert W. Cattrall. Chemical Sensors. Oxford University Press; 1997.

vanced Study Institute on Optical Chemical Sensors. Springer; 2006.

and Ilsiya Davletbaeva2

Optical Sensors Based on Mesoporous Polymers

http://dx.doi.org/10.5772/57383

65

## **6. Conclusion**

Optically transparent mesoporous block copolymers with regulated free volume were obtained by polyaddition of 2,4-toluene diisocyanate to anionic macroinitiators. It is estab‐ lished that the void formation is conditioned by the geometry of block copolymer selfassembly.

It is established that the chemical nature of a solvent influences the mechanism of polyaddition of 2,4-toluene diisocyanate to the anionic macroinitiator which is a potassium substituted block copolymer of propylene oxide with ethylene oxide.

It is shown that ethyl acetate is the most advantageous solvent for the predominant formation of O-polyisocyanate blocks during the polyaddition of 2,4-toluene diisocyanate to the anionic macroinitiator.

Polymer laser active media based on mesoporous polymers doped by organic luminophores were obtained. The possibility is shown to obtain the induced emission of Rhodamine 6G in mesoporous polymers. It is shown that photochemical stability of organic chemical agent and luminophor rhodamine 6G in polymers made up more than 70,000 pulses.

It was shown that the polymer mesoporous structure provides the possibility to immobilize organic chromatophores in mesoporous polymers. It was established that adsorption proc‐ esses of organic luminophore of rhodamine 6G were accompanied by the processes of its concentration in a polymer matrix.

The polymer laser-active media based on mesoporous polymers doped by organic chromato‐ phores were obtained. The possibility to obtain the induced emission of radiation of rhodamine 6G in mesoporous polymers was shown. It was also shown that photochemical stability of an organic reagent and luminophore of rhodamine 6G in polymers made up 70.000 pulses.

The qualitative reactions of organic chromatophores arsenazo III, PAN, and phenazo with metal cations on a mesoporous polymer carrier were carried out. It was shown that reaction sensitivity of compex formation of metals and chromatophores on mesoporous polymer substrate made up 10-5 g/l.

## **Acknowledgements**

The study was funded by the Russian Foundation for Basic Research, Project No 13-03-97022.

## **Author details**

For the polymer matrix modified with arsenazo III, the limit of sensitivity to calcium and lanthanum ions was determined. The maximum concentration at which the metal ions were

Optically transparent mesoporous block copolymers with regulated free volume were obtained by polyaddition of 2,4-toluene diisocyanate to anionic macroinitiators. It is estab‐ lished that the void formation is conditioned by the geometry of block copolymer self-

It is established that the chemical nature of a solvent influences the mechanism of polyaddition of 2,4-toluene diisocyanate to the anionic macroinitiator which is a potassium substituted block

It is shown that ethyl acetate is the most advantageous solvent for the predominant formation of O-polyisocyanate blocks during the polyaddition of 2,4-toluene diisocyanate to the anionic

Polymer laser active media based on mesoporous polymers doped by organic luminophores were obtained. The possibility is shown to obtain the induced emission of Rhodamine 6G in mesoporous polymers. It is shown that photochemical stability of organic chemical agent and

It was shown that the polymer mesoporous structure provides the possibility to immobilize organic chromatophores in mesoporous polymers. It was established that adsorption proc‐ esses of organic luminophore of rhodamine 6G were accompanied by the processes of its

The polymer laser-active media based on mesoporous polymers doped by organic chromato‐ phores were obtained. The possibility to obtain the induced emission of radiation of rhodamine 6G in mesoporous polymers was shown. It was also shown that photochemical stability of an organic reagent and luminophore of rhodamine 6G in polymers made up 70.000 pulses.

The qualitative reactions of organic chromatophores arsenazo III, PAN, and phenazo with metal cations on a mesoporous polymer carrier were carried out. It was shown that reaction sensitivity of compex formation of metals and chromatophores on mesoporous polymer

The study was funded by the Russian Foundation for Basic Research, Project No 13-03-97022.

luminophor rhodamine 6G in polymers made up more than 70,000 pulses.

copolymer of propylene oxide with ethylene oxide.

64 Optical Sensors - New Developments and Practical Applications

detected was 10-5 g/l.

**6. Conclusion**

assembly.

macroinitiator.

concentration in a polymer matrix.

substrate made up 10-5 g/l.

**Acknowledgements**

Ruslan Davletbaev1\*, Alsu Akhmetshina2 , Askhat Gumerov3 and Ilsiya Davletbaeva2

\*Address all correspondence to: b210@bk.ru

1 Department of the Materials Science & Technology, Kazan National Research Technical University n.a. А.N. Tupolev, Kazan, Russia

2 Department of the Synthetic Rubber, National Research Technological University, Kazan, Russia

3 Department of the Chemical Cybernetics, National Research Technological University, Ka‐ zan, Russia

#### **References**


concentration and Determination of Zinc Traces with Flame Atomic Absorption Spectrometry. Talanta 2002; 8(56) 491-498.

**Chapter 4**

**Photonic Crystal Laser Based Gas Sensor**

The development of new radiation source technologies has a major impact on the progression of optical trace gas detection [1]. Especially semiconductor diode lasers have proven to be extraordinarily suitable devices for spectroscopic sensors. Their small size and their low acquisition cost are here valuable properties. However, it is particularly advantageous that their emission can spectrally be tuned simply via their operating temperature and operating current. Furthermore, diode lasers can be directly modulated via their injection current. Therefore, they represent particularly suitable radiation sources for photoacoustic spectrosco‐ py because this technique is based on the absorption of modulated radiation and its transfor‐ mation into a sound wave. As an offset-free technique it enables extremely high detection

Continuous-wave (cw) single-frequency diode lasers, like distributed feedback (DFB) lasers, are particularly suitable for spectroscopy because they avoid any cross-sensitivity and enable very selective gas detection [3,4]. DFB devices were originally developed for the telecommu‐ nication industry and can conveniently be operated at room temperature. Meanwhile, available emission wavelengths cover the entire near-infrared spectral range (800 nm – 3000 nm). Most recently, DFB lasers operating in the mid-infrared were introduced (> 3000 nm) [5]. The alternative concept of interband cascade lasers (ICL) covers almost the complete midinfrared from 3 µm to 6 µm [6]. This wavelength range is extraordinarily important for trace gas detection since many molecules have their strong fundamental vibrational absorption bands in this region, enabling extremely high detection limits. These devices close the gap to quantum cascade lasers (QCL), which are currently available with single-frequency emission

> © 2014 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Marcus Wolff, Henry Bruhns, Johannes Koeth,

Additional information is available at the end of the chapter

wavelengths starting around 4 µm (multimode at 3 µm) [7].

Wolfgang Zeller and Lars Naehle

http://dx.doi.org/10.5772/57147

**1. Introduction**

sensitivity [2].

