Excellent Cooperation between Carboxyl-Substituted Porphyrins, k-Carrageenan and AuNPs for Extended Application in CO 2 Capture and Manganese Ion Detection

: Signiﬁcant tasks of the presented research are the development of multifunctional materials capable both to detect/capture carbon dioxide and to monitor toxic metal ions from waters, thus contributing to maintaining a sustainable and clean environment. The purpose of this work was to synthesize, characterize (NMR, FT-IR, UV-Vis, Fluorescence, AFM) and exploit the optical and emission properties of a carboxyl-substituted A 3 B porphyrin, 5-(4-carboxy-phenyl)-10,15,20-tris-(4-methyl-phenyl)–porphyrin, and based on it, to develop novel composite material able to adsorb carbon dioxide. This porphyrin-k-carrageenan composite material can capture CO 2 in ambient conditions with a performance of 6.97 mmol/1 g adsorbent. Another aim of our research was to extend this porphyrin- k-carrageenan material’s functionality toward Mn 2+ detection from polluted waters and from medical samples, relying on its synergistic partnership with gold nanoparticles (AuNPs). The plasmonic porphyrin-k-carrageenan-AuNPs material detected Mn 2+ in the range of concentration of 4.56 × 10 − 5 M to 9.39 × 10 − 5 M (5–11 mg/L), which can be useful for monitoring health of humans exposed to polluted water sources or those who ingested high dietary manganese.


Introduction
The capture of carbon dioxide into appropriate adsorbent materials represents an actual scientific task since the accumulation of greenhouse gas is associated with an undesired increase in temperature all around the world. For this purpose, a large variety of materials based on porphyrins was investigated, among which a series of porous hexanuclear rare-earth metal-organic frameworks (MOFs) based on Ce(III) salts and 5,10,15,20-tetrakis(4carboxy-phenyl)-porphyrin exhibited excellent CO 2 adsorption properties up to 42.4 cm 3 (83.2 mg)/g at 273 K and normal pressure [1]. A new two-dimensional covalent organic framework based on 5,10,15,20-tetra-(4-amino-phenyl)-porphyrin and 1,1 ,2,2 -tetrakis-(4formyl-(1,1 -biphenyl) ethene was used as gas storage material with a greater capacity for CO 2 adsorption of 187 mg/g, but came with the disadvantage of needing higher pressure and temperature (50 bar and 323 K) [2].
Zinc-tetraphenylporphyrin solubilized by means of a protein cage from E. coli (30 porphyrins per protein cage) was also used for CO 2 capture [3]. In addition, the protein-caged porphyrin is able to catalyze the CO 2 transformation into CaCO 3 , even at Zinc-tetraphenylporphyrin solubilized by means of a protein cage from E. coli (30 porphyrins per protein cage) was also used for CO2 capture [3]. In addition, the proteincaged porphyrin is able to catalyze the CO2 transformation into CaCO3, even at 60 °C, and no side reactions have been detected [4]. The capture and catalytic conversion of CO2 into cyclic carbonates could be also obtained on a Co(II)-porphyrin-covalent-organic framework using cobalt(II)-5,10,15,20-tetrakis(4-amino-phenyl)-porphyrin building block and 1,3,6,8-tetrakis(4-formyl-phenyl)pyrene [5]. The best CO2 adsorption capacity of these nanomaterials was 169 mg/g at 298 K and the yield in cyclic carbonates was 92% under mild conditions (at 313 K and 0.1 MPa).
Other attempts to transform CO2 were based on its electrochemical reduction performed on a graphite electrode coated via electrochemical polymerization with thiophenefunctionalized Co(II)-porphyrin, as mediator/catalyst [6].
The main purpose of this work was to develop a new kind of composite material that was able to capture carbon dioxide based on an organic nontoxic polymer, k-carrageenan [12][13][14][15], and a carboxyl-substituted porphyrin, 5-(4-carboxy-phenyl)-10,15,20-tris-(4-methyl-phenyl)-porphyrin ( The second aim was to extend this porphyrin-based material functionality toward ion metal detection based on its synergistic approach with gold nanoparticles (AuNPs). The plasmonic material, porphyrin-k-carrageenan-AuNPs, was designed with the purpose to detect Mn 2+ from polluted waters or medical samples. The second aim was to extend this porphyrin-based material functionality toward ion metal detection based on its synergistic approach with gold nanoparticles (AuNPs). The plasmonic material, porphyrin-k-carrageenan-AuNPs, was designed with the purpose to detect Mn 2+ from polluted waters or medical samples.
Monitoring manganese is a demand because chronic Mn 2+ intoxication leads to Parkinson-like neurodegenerative disorder known as manganism, inducing basal ganglia atrophy in humans [16], a disease that is usually encountered by miners, welders and steel and battery workers. Manganism, which is considered endemic in some South African manganese mines, might be associated with nerve toxicity, producing anxiety, dementia, ataxia and a 'mask-like' face [17,18]. For example, the European Commission and the United States Environmental Protection Agency have set the Mn 2+ level in drinking water at 0.05 mg/L. In China, the maximum level in surface water is 0.1 and 5.0 mg/L in wastewater [17]. The normal Mn 2+ concentrations in blood range from 4 to 15 µg/L in humans [19]. The average manganese concentration of untreated mine waters is around 17.7 mg/L at surfaces mines [20]. Therefore, Mn 2+ monitoring from wastewater is demanded to reduce the negative impacts on both the aqueous environment and human health. Although health standards limit the Mn concentration in drinking water to 0.4 mg/L this value is 20 times lower than the effluent standard of Japan (10 mg/L) [21].

Apparatus
The emission spectra were registered on a Perkin-Elmer Model LS 55 apparatus (PerkinElmer, Inc./UK Model LS 55, Waltham, MA, USA), using 1 cm path length cells, excitation slits of 10 nm and emission slits of 6 nm, at ambient temperature (22−24 • C), without cut-off filters, λ ex = 432 nm. The UV-Vis spectra were recorded on a V-650-JASCO spectrometer (Pfungstadt, Germany) using 1 cm optical path length. The pH values were measured with a pH-meter HI 98,100 Checker Plus, from Hanna Instruments (Woonsocket, RI, USA). The Rota-evaporator was from Heidolph Laborota 4010 digitally equipped with the vacuum pump PC 610 CVC2, Vacuumbrand GmbH. The atomic force microscopy (AFM) images were obtained on a Nanosurf ® EasyScan 2 Advanced Research AFM microscope (Liestal, Switzerland) equipped with a piezoelectric ceramic cantilever. Pure silica plates were used for the deposition of samples. FT-IR spectra were recorded on a JASCO 430 FT-IR (Hachioji, Tokyo, Japan) spectrometer from KBr pellets in the range 4000-400 cm −1 . The 1 H-NMR and 13 C-NMR spectra were registered on a Bruker Avance NEO Spectrometer at 400 MHz, equipped with 5 mm four nuclei ( 1 H/ 13 C/ 19 F/ 29 Si) direct detection probe (Rheinsteitten, Germany), in CDCl 3 . The chemical shifts are expressed in (ppm), using as reference tetramethylsilane (TMS).  Figure S1, and the thin layer chromatography (TLC) using as eluent CH 2 Cl 2 is represented in Figure S2. Porphyrin (5-COOCH3-3MPP) was obtained by multicomponent synthesis, presented in detail in Section 2.3 of the Supplementary Materials. The structures of the six different reaction products are illustrated in Figure S1, and the thin layer chromatography (TLC) using as eluent CH2Cl2 is represented in Figure S2.

Physical-Chemical Characterization of the Two Obtained Porphyrins
The UV-Vis ( Figure S3), FT-IR ( Figure S4

Physical-Chemical Characterization of the Two Obtained Porphyrins
The UV-Vis ( Figure S3

Method for Capturing CO 2 Gas by the (5-COOH-3MPP)-k-Carrageenan Composite Material, in DMF/Water Mixture
A volume of 3.9 mL of the gel was diluted with 62.4 mL mixture of DMF: water = 2:3. A change in color was observed from violet to violet-yellow. The adding of the DMF: water mixture led to a hypochromic effect regarding the Soret band, accompanied by bathochromic shifts for all the absorption bands ( Figure 3), as follows: for the Soret band from 418 nm to 420 nm, for QIV band from 515 nm to 520 nm, for QIII band from 550 nm to 554 nm, for QII band from 592 nm to 594 nm and for QI from 548 nm to 651 nm, respectively.
The sol thus obtained was sealed in an Erlenmeyer flask equipped with a magnetic stirrer, an elastic rubber cork and three syringe needles: one for the bubbling of CO 2 gas,

Method for Capturing CO2 Gas by the (5-COOH-3MPP)-k-Carrageenan Composite Material, in DMF/Water Mixture
A volume of 3.9 mL of the gel was diluted with 62.4 mL mixture of DMF: water = 2:3. A change in color was observed from violet to violet-yellow. The adding of the DMF: water mixture led to a hypochromic effect regarding the Soret band, accompanied by bathochromic shifts for all the absorption bands ( Figure 3), as follows: for the Soret band from 418 nm to 420 nm, for QIV band from 515 nm to 520 nm, for QIII band from 550 nm to 554 nm, for QII band from 592 nm to 594 nm and for QI from 548 nm to 651 nm, respectively.  It can be observed that the accumulation of CO2 in the sol leads to the bathochromic shift of the absorption maxima and also to a hypochromic effect. This shift to longer wavelengths can be attributed to the slight protonation of the porphyrin molecules, as carbonic acid is accumulating in the mixture due to the presence of water in the system. The acid environment produced by adding CO2, might favor the formation of J-type aggregates, also causing the enlargement of the Soret band [11]. An isosbestic point at 453 nm is observed, marking both the generation of protonated porphyrins and the link between CO2 and the -NH from internal ring of porphyrins. Figure 5 represents the linear dependence rial, in DMF/Water Mixture A volume of 3.9 mL of the gel was diluted with 62.4 mL mixture of DMF: water = 2:3. A change in color was observed from violet to violet-yellow. The adding of the DMF: water mixture led to a hypochromic effect regarding the Soret band, accompanied by bathochromic shifts for all the absorption bands (Figure 3), as follows: for the Soret band from 418 nm to 420 nm, for QIV band from 515 nm to 520 nm, for QIII band from 550 nm to 554 nm, for QII band from 592 nm to 594 nm and for QI from 548 nm to 651 nm, respectively.  It can be observed that the accumulation of CO2 in the sol leads to the bathochromic shift of the absorption maxima and also to a hypochromic effect. This shift to longer wavelengths can be attributed to the slight protonation of the porphyrin molecules, as carbonic acid is accumulating in the mixture due to the presence of water in the system. The acid environment produced by adding CO2, might favor the formation of J-type aggregates, also causing the enlargement of the Soret band [11]. An isosbestic point at 453 nm is observed, marking both the generation of protonated porphyrins and the link between CO2 and the -NH from internal ring of porphyrins. Figure 5 represents the linear dependence It can be observed that the accumulation of CO 2 in the sol leads to the bathochromic shift of the absorption maxima and also to a hypochromic effect. This shift to longer wavelengths can be attributed to the slight protonation of the porphyrin molecules, as carbonic acid is accumulating in the mixture due to the presence of water in the system. The acid environment produced by adding CO 2 , might favor the formation of J-type aggregates, also causing the enlargement of the Soret band [11]. An isosbestic point at 453 nm is observed, marking both the generation of protonated porphyrins and the link between CO 2 and the -NH from internal ring of porphyrins. Figure 5 represents the linear dependence of the intensity of absorption of (5-COOH-3MPP)-k-carrageenan composite read at 420 nm and the molar concentration of CO 2 gas in the sol.  The same samples were subjected to fluorescence measurements, where it can be observed that the accumulation of carbon dioxide in the mixture leads to the quenching of the fluorescence (Figure 6). The (5-COOH-3MPP)-k-carrageenan composite emission intensity decreases in a linear fashion with the increase in CO2 gas concentration. This linear Figure 5. Linear dependence between the intensity of absorption of (5-COOH-3MPP)-k-carrageenan composite read at 420 nm and the concentration of CO 2 in the sol, realized during 60 min of CO 2 exposure, flow rate of 10 mL/min. The same samples were subjected to fluorescence measurements, where it can be observed that the accumulation of carbon dioxide in the mixture leads to the quenching of the fluorescence ( Figure 6). The (5-COOH-3MPP)-k-carrageenan composite emission intensity decreases in a linear fashion with the increase in CO 2 gas concentration. This linear dependence is characterized by a confidence coefficient of 99.33% (Figure 7). Figure 5. Linear dependence between the intensity of absorption of (5-COOH-3MPP)-k-carrageenan composite read at 420 nm and the concentration of CO2 in the sol, realized during 60 min of CO2 exposure, flow rate of 10 mL/min. The same samples were subjected to fluorescence measurements, where it can be observed that the accumulation of carbon dioxide in the mixture leads to the quenching of the fluorescence (Figure 6). The (5-COOH-3MPP)-k-carrageenan composite emission intensity decreases in a linear fashion with the increase in CO2 gas concentration. This linear dependence is characterized by a confidence coefficient of 99.33% (Figure 7).  A quantity of 1 g composite material that contains 0.09 g porphyrin can capture 6.97 mmol CO2. This result is six times lower than the best-reported result [9], which is 42 mmol CO2/1g adsorbent material but obtained with the supplementary inconveniences of using A quantity of 1 g composite material that contains 0.09 g porphyrin can capture 6.97 mmol CO 2 . This result is six times lower than the best-reported result [9], which is 42 mmol CO 2 /1 g adsorbent material but obtained with the supplementary inconveniences of using high temperature and pressure of 373 K and 10 bar, respectively. The significant sustainability of our work is that this result has been obtained under normal conditions. Nevertheless, this result is among the best results reported in the literature in the last decade [1][2][3][4][5]. We presume that these polymer-porphyrin-based materials can be extended for the detection or monitoring of other gases requiring recovery or control [27]. triangle-shaped architectures with similar sizes and orientation, and distributed on the surface in multiple layers. This kind of morphology was found in our studies [29][30][31][32]. The composite material (5-COOH-3MPP)-k-carrageenan deposited from DMF-water mixture on silica plates (Figure 8c) reveals an uneven porous surface, having isolated aggregates with particle height distribution 6.70-13.2 nm.
After treatment with CO2 gas, the AFM images of 5-COOH-3MPP-k-carrageenan composite material (Figure 8d) presents a considerably modified height distribution of particles, from 9.4 to 14.8 nm, consistent with the hypothesis of incorporating CO2 gas in the gel. The aggregates are larger and distributed like parallel rows on the surface. It is clear that a reconfiguration of the porphyrin-polymer surface has occurred.
The complex of the porphyrin-k-carrageenan and AuNPs was obtained as follows: 1.76 mL (5-COOH-3MPP)-k-carrageenan gel was diluted with 28.24 mL DMF, acidified with HCl (c = 37%), in which a drastic change in color from pink to green took place. Then, portions of 0.2 mL concentrated gold colloid solution were added. The mixture was stirred The 4 µm × 4 µm 2D AFM image of 5-(4-carboxy-phenyl)-10,15,20-tris-(4-methylphenyl)-porphyrin deposited from THF (Figure 8b) reveals both H-and J-type aggregated triangle-shaped architectures with similar sizes and orientation, and distributed on the surface in multiple layers. This kind of morphology was found in our studies [29][30][31][32].
After treatment with CO 2 gas, the AFM images of 5-COOH-3MPP-k-carrageenan composite material (Figure 8d) presents a considerably modified height distribution of particles, from 9.4 to 14.8 nm, consistent with the hypothesis of incorporating CO 2 gas in
The complex of the porphyrin-k-carrageenan and AuNPs was obtained as follows: 1.76 mL (5-COOH-3MPP)-k-carrageenan gel was diluted with 28.24 mL DMF, acidified with HCl (c = 37%), in which a drastic change in color from pink to green took place. Then, portions of 0.2 mL concentrated gold colloid solution were added. The mixture was stirred for 90 s and the UV-Vis spectra were recorded after each adding (Figure 9). The color changed from green to dark blue, making this material suitable as colorimetric sensor for gold nanoparticles. This material can serve as optical sensitive material for AuNPs detection ( Figure S9-Supplementary Material). for 90 s and the UV-Vis spectra were recorded after each adding (Figure 9). The color changed from green to dark blue, making this material suitable as colorimetric sensor for gold nanoparticles. This material can serve as optical sensitive material for AuNPs detection ( Figure S9-Supplementary Material). It can be observed that the adding of colloidal gold significantly increases the intensity of the bands located at 520 nm. Simultaneously, a considerable enlargement of the absorption domain is obtained from 500 nm up to 680 nm, generating a plasmonic plateau. The Soret band originating from the (5-COOH-3MPP) porphyrin is red shifted toward 460 nm (due to J type aggregates generation), then blue shifted to 450 nm due to the plasmonic complex formation. The second absorption peak of the plasmonic plateau, located around 680 nm, is clearly generated by the dramatic hyperchromic transformation of the QI band of the (5-COOH-3MPP) porphyrin during the complex formation with AuNPs.
Based on the synergistic approach between porphyrin-k-carrageenan composite and AuNPs that gave a wide-band absorption material, our aim was to extend its functionality toward ion metal detection from polluted environments and in health monitoring.
As can be observed in Figure 10, adding of the manganese ion changed the aspect of the UV-Vis spectra, consisting first in the constant bathochromic shift of the absorption maximum from 617 nm to 659 nm, accompanied by a constant increase regarding the intensity. The intensity of the band located at 539 nm is constantly increasing in intensity as It can be observed that the adding of colloidal gold significantly increases the intensity of the bands located at 520 nm. Simultaneously, a considerable enlargement of the absorption domain is obtained from 500 nm up to 680 nm, generating a plasmonic plateau. The Soret band originating from the (5-COOH-3MPP) porphyrin is red shifted toward 460 nm (due to J type aggregates generation), then blue shifted to 450 nm due to the plasmonic complex formation. The second absorption peak of the plasmonic plateau, located around 680 nm, is clearly generated by the dramatic hyperchromic transformation of the QI band of the (5-COOH-3MPP) porphyrin during the complex formation with AuNPs.
Based on the synergistic approach between porphyrin-k-carrageenan composite and AuNPs that gave a wide-band absorption material, our aim was to extend its functionality toward ion metal detection from polluted environments and in health monitoring.

Spectrophotometric Detection of Mn 2+ Ions by (5-COOH-3MPP)-k-Carrageenan-AuNPs Hybrid Material
The spectroscopic detection of Mn 2+ ions was performed using the solution of porphyrin-k-carrageenan-AuNPs hybrid material in DMF. To 5 mL solution of (5-COOH-3MPP)-k-carrageenan-AuNPs hybrid material, portions of 0.01 mL MnCl 2 solution in water (c = 1 × 10 −3 M) are added. The overlapped UV-Vis spectra recorded after each addition of MnCl 2 solution, followed by 90 s stirring, are presented in Figure 10. The linear dependence between the intensity of the newly formed band at 659 nm and the Mn 2+ concentration is presented in Figure 11. It is characterized by a very good correlation coefficient of 99.62% for a narrow interval of concentrations from 4.56 × 10 −5 M to 9.39 × 10 −5 M (5-11 mg/L), which is demanded for the detection of excess manganese in humans exposed to polluted water sources or those who ingested high dietary manganese [18].
The limit of detection (LOD) for Mn 2+ is 2.80 μM. It was calculated as LOD = 3.3 σ/S, where σ is the standard deviation of the response and S is the slope of the calibration curve [35]. Figure 11. Linear dependence between the intensity of absorption of (5-COOH-3MPP)-k-carrageenan-AuNPs hybrid material measured at 659 nm and the Mn 2+ ion concentration.
As a perspective, this plasmonic material might be a suitable sensitive substrate for the design of microsensor devices to medical monitoring of patients suffering from manganism [36]. As can be observed in Figure 10, adding of the manganese ion changed the aspect of the UV-Vis spectra, consisting first in the constant bathochromic shift of the absorption maximum from 617 nm to 659 nm, accompanied by a constant increase regarding the intensity. The intensity of the band located at 539 nm is constantly increasing in intensity as the Mn 2+ ion concentration increases. An isosbestic point located at 635 nm indicates that at least one novel intermediate product is formed between Mn 2+ ions and the porphyrinbase molecule, favored by the AuNPs plasmon. This type of linking manganese ions by porphyrins is based on the multitude of oxidation states in which manganese might exist [29].
The linear dependence between the intensity of the newly formed band at 659 nm and the Mn 2+ concentration is presented in Figure 11. It is characterized by a very good correlation coefficient of 99.62% for a narrow interval of concentrations from 4.56 × 10 −5 M to 9.39 × 10 −5 M (5-11 mg/L), which is demanded for the detection of excess manganese in humans exposed to polluted water sources or those who ingested high dietary manganese [18]. The linear dependence between the intensity of the newly formed band at 659 nm and the Mn 2+ concentration is presented in Figure 11. It is characterized by a very good correlation coefficient of 99.62% for a narrow interval of concentrations from 4.56 × 10 −5 M to 9.39 × 10 −5 M (5-11 mg/L), which is demanded for the detection of excess manganese in humans exposed to polluted water sources or those who ingested high dietary manganese [18].
The limit of detection (LOD) for Mn 2+ is 2.80 μM. It was calculated as LOD = 3.3 σ/S, where σ is the standard deviation of the response and S is the slope of the calibration curve [35]. Figure 11. Linear dependence between the intensity of absorption of (5-COOH-3MPP)-k-carrageenan-AuNPs hybrid material measured at 659 nm and the Mn 2+ ion concentration.
As a perspective, this plasmonic material might be a suitable sensitive substrate for the design of microsensor devices to medical monitoring of patients suffering from manganism [36]. Figure 11. Linear dependence between the intensity of absorption of (5-COOH-3MPP)-k-carrageenan-AuNPs hybrid material measured at 659 nm and the Mn 2+ ion concentration.
The limit of detection (LOD) for Mn 2+ is 2.80 µM. It was calculated as LOD = 3.3 σ/S, where σ is the standard deviation of the response and S is the slope of the calibration curve [35].
As a perspective, this plasmonic material might be a suitable sensitive substrate for the design of microsensor devices to medical monitoring of patients suffering from manganism [36]. AFM Investigation of (5-COOH-3MPP)-k-Carrageenan-AuNPs Hybrid Material, before and after Mn 2+ Detection AFM images of (5-COOH-3MPP)-k-carrageenan-AuNPs (Figure 12a) show large aggregates grouped in zigzag course, uniformly covered with small round gold particles (<50 nm in diameter). The height distribution of aggregates is 14 to 23 nm.
After interacting with Mn 2+ , the AFM images of the hybrid material (5-COOH-3MPP)-k-carrageenan-AuNPs (Figure 12b) show small triangular particles, around 200 nm in side, evenly oriented. The J-and H-aggregation processes are amplified, leading to a very adherent, uniform and compact surface.

Interference Study
In order to verify that the detection of the manganese ion from untreated mine waters is accurate even in the presence of interfering species, the following metallic salts were tested: CuCl2, FeCl3, FeSO4, KCl, NaCl, ZnCl2, Pb(NO3)2, MgSO4 and CaCl2.
A solution of porphyrin-k-carrageenan-AuNPs hybrid material containing Mn 2+ with a concentration of 4.5 × 10 −5 M was prepared. The reference sample was composed from 2 mL of this solution in which 0.1 mL distilled water was added to replace any false results due to dilution. Portions of 0.1 mL containing each of the tested interferent, to provide a final concentration of interfering species 1000 times higher than that of Mn 2+ , have been introduced to the 2 mL samples already containing Mn 2+ . The UV-Vis spectra were recorded for each interferent and superposed in ( Figure S10-Supplementary Material).
Average percentage errors calculation is: |∆I/I| × 100, where I represents the absorption intensity of the sample containing only Mn 2+ and ∆I the difference between I and the absorption intensity of the samples containing Mn 2+ mixed with each studied interfering analyte. From Figure 13 it can be observed that only Mg 2+ and Ca 2+ ions slightly interfere in the Mn 2+ detection, introducing in the analysis an average percentage error between 3.50-3.90. After interacting with Mn 2+ , the AFM images of the hybrid material (5-COOH-3MPP)k-carrageenan-AuNPs (Figure 12b) show small triangular particles, around 200 nm in side, evenly oriented. The J-and H-aggregation processes are amplified, leading to a very adherent, uniform and compact surface.

Interference Study
In order to verify that the detection of the manganese ion from untreated mine waters is accurate even in the presence of interfering species, the following metallic salts were tested: CuCl 2 , FeCl 3 , FeSO 4 , KCl, NaCl, ZnCl 2 , Pb(NO 3 ) 2 , MgSO 4 and CaCl 2 .
A solution of porphyrin-k-carrageenan-AuNPs hybrid material containing Mn 2+ with a concentration of 4.5 × 10 −5 M was prepared. The reference sample was composed from 2 mL of this solution in which 0.1 mL distilled water was added to replace any false results due to dilution. Portions of 0.1 mL containing each of the tested interferent, to provide a final concentration of interfering species 1000 times higher than that of Mn 2+ , have been introduced to the 2 mL samples already containing Mn 2+ . The UV-Vis spectra were recorded for each interferent and superposed in ( Figure S10-Supplementary Material).
Average percentage errors calculation is: |∆I/I| × 100, where I represents the absorption intensity of the sample containing only Mn 2+ and ∆I the difference between I and the absorption intensity of the samples containing Mn 2+ mixed with each studied interfering analyte. From Figure 13 it can be observed that only Mg 2+ and Ca 2+ ions slightly interfere in the Mn 2+ detection, introducing in the analysis an average percentage error between 3.50-3.90. We can conclude that there is a good selectivity of the detection for Mn 2+ in the presence of interfering cations.
The optical properties of the porphyrin-k-carrageenan composite material were improved by complexing it with AuNPs, when the obtained wide plasmonic plateau (520-680 nm) display also a significant hyperchromic effect. As a result of this experiment, a large concentration domain of AuNPs, from 4 × 10 −6 M to 4 × 10 −4 M, can be optically detected with high confidence and might be useful for the monitoring of gold nanoparticles in fibroblasts.
The porphyrin-k-carrageenan-AuNPs complex nanomaterial was able to detect Mn 2+ ions in solution with high precision in the concentration interval of 4.56 × 10 −5 M to 9.39 × 10 −5 M (5-11 mg/L) that can be practical in the detection of excess manganese in polluted water sources or in humans that ingested toxic levels of dietary manganese. The accuracy of the Mn 2+ detection was verified by adding interfering metallic salts: CuCl2, FeCl3, FeSO4, KCl, NaCl, ZnCl2, Pb(NO3)2, MgSO4 and CaCl2 at concentrations 1000 times higher than that of Mn 2+ . The conclusion was that only Mg 2+ and Ca 2+ ions slightly interfere in the Mn 2+ detection, introducing in the analysis an average percentage error between 3.50-3.90.
In conclusion, the partnership between 5-(4-carboxyphenyl)-10,15,20-tris-(4-methylphenyl)-porphyrin, k-carrageenan and AuNPs can generate multifunctional materials acting as gas sorbents or sensitive materials for toxic metal ion detection with relevance in environmental and medical monitoring and rehabilitation.
The optical properties of the porphyrin-k-carrageenan composite material were improved by complexing it with AuNPs, when the obtained wide plasmonic plateau (520-680 nm) display also a significant hyperchromic effect. As a result of this experiment, a large concentration domain of AuNPs, from 4 × 10 −6 M to 4 × 10 −4 M, can be optically detected with high confidence and might be useful for the monitoring of gold nanoparticles in fibroblasts.
The porphyrin-k-carrageenan-AuNPs complex nanomaterial was able to detect Mn 2+ ions in solution with high precision in the concentration interval of 4.56 × 10 −5 M to 9.39 × 10 −5 M (5-11 mg/L) that can be practical in the detection of excess manganese in polluted water sources or in humans that ingested toxic levels of dietary manganese. The accuracy of the Mn 2+ detection was verified by adding interfering metallic salts: CuCl 2 , FeCl 3 , FeSO 4 , KCl, NaCl, ZnCl 2 , Pb(NO 3 ) 2 , MgSO 4 and CaCl 2 at concentrations 1000 times higher than that of Mn 2+ . The conclusion was that only Mg 2+ and Ca 2+ ions slightly interfere in the Mn 2+ detection, introducing in the analysis an average percentage error between 3.50-3.90.
In conclusion, the partnership between 5-(4-carboxyphenyl)-10,15,20-tris-(4-methylphenyl)-porphyrin, k-carrageenan and AuNPs can generate multifunctional materials acting as gas sorbents or sensitive materials for toxic metal ion detection with relevance in environmental and medical monitoring and rehabilitation.