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Ceria nanorods modified with 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin (H2TCPP) were prepared. These nanocomposites (H2TCPP-CeO2) exhibited the intrinsic peroxidase-like activity and could catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbiphenyl dihydrochloride (TMB·2HCl) in the presence of H2O2 to produce a typical color reaction from colorless to blue. Our results demonstrated that both the H2TCPP-CeO2 nanocomposites and CeO2 nanorods exhibited higher thermal durance than that of HRP. The affinity of The H2TCPP-CeO2 nanocomposites toward H2O2 and TMB is similar to that of HRP. Fluorescent results indicated that the catalytic mechanism of the H2TCPP-CeO2 nanocomposites were from the decomposition of H2O2 into hydroxyl radicals. Based on these studies, a simple, sensitive, and selective visual and colorimetric method using TMB as the substrate was designed to detect glucose when combined with glucose oxidase. The proposed colorimetric method can detect H2O2 at a low detection limit of 6.1×10(-6)M and a dynamic range of 10(-5)-10(-4)mol·L(-1). This method can also detect glucose at a low detection limit of 3.3×10(-5)mol·L(-1) and a dynamic range of 5.0×10(-5)-1.0×10(-4)mol·L(-1)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Meso-tetrakis(4-carboxyphenyl)-porphyrin-functionalized γ-Fe2O3 nanoparticles (H2TCPP-γ-Fe2O3) were successfully prepared by one-pot method under hydrothermal conditions and were found to possess intrinsic peroxidase-like activity. The H2TCPP-γ-Fe2O3 nanocomposites can catalytically oxidize peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue color reaction, which can be easily observed by the naked eye. Furthermore, kinetic studies indicate that the H2TCPP-γ-Fe2O3 nanocomposites have an even higher affinity to TMB than that of the natural enzyme, horseradish peroxidase (HRP). On the basis of the high activity, the reaction provides a simple, sensitive and selective method for colorimetric detection of H2O2 over a range of 10-100 μM with a minimum detection limit of 1.73 μM. Moreover, H2TCPP-γ-Fe2O3/glucose oxidase (GOx)/TMB system provides a novel colorimetric sensor for glucose and shows good response toward glucose detection over a range of 5-25 μM with a minimum detection limit of 2.54 μM. The results indicated that it is a simple, cheap, convenient, highly selective, sensitive and easy handling colorimetric assay. Results of a fluorescent probe suggest that the catalase-mimic activity of the H2TCPP-γ-Fe2O3 nanocomposites effectively catalyze the decomposition of H2O2 into H2O and O2., (Copyright © 2015 Elsevier B.V. All rights reserved.)

NiO nanoparticles (NPs) and 5,10,15,20-tetrakis(4-carboxyl pheyl)-porphyrin (H2TCPP) functionalized NiO nanoparticles (H2TCPP-NiO nanocomposites) have been prepared by a facile method and characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared spectra (FTIR), respectively. NiO NPs and H2TCPP-NiO nanocomposites have been proven to function as peroxidase mimetics that can catalyze the reaction of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue color reaction. Kinetic analysis indicated that the catalytic behavior was in accord with typical Michaelis-Menten kinetics. And these nanoparticles also exhibited strong affinity for the substrates of 3,3,5,5-tetramethylbiphenyl dihydrochloride (TMB). Experimental results showed that H2TCPP-NiO NPs exhibited a high sensitivity and a low detection limit towards H2O2 (8.0 × 10(-6) M). The H2TCPP-NiO NPs/glucose oxidase (GOx)/TMB system provides a novel colorimetric sensor for glucose and shows good response toward glucose detection over arrange of 0.05-0.50 mM with a limit of detection 2.0 × 10(-5)M. Fluorescence probe experiments demonstrated that the peroxidase-like activity of H2TCPP-NiO NPs originated from the generation of OH radical. Thus it may provide great potential applications in biomedicine, biotechnology and environmental chemistry., (Copyright © 2014 Elsevier B.V. All rights reserved.)

5,10,15,20-Tetrakis(4-carboxyl pheyl)-porphyrin (H2TCPP) functionalized chain-like Co3O4 nanoparticles (NPs) were prepared by a facile two-step method. The H2TCPP-Co3O4 nanocomposites were demonstrated to display enhanced peroxidase-like activity than that of pure Co3O4 nanoparticles without modification with H2TCPP molecules, catalyzing oxidation of peroxidase substrate 3,3',5,5'-tetramethyl-benzidine (TMB) in the presence of H2O2 to produce a blue color reaction. Furthermore, H2TCPP-Co3O4 nanocomposites showed typical Michaelis-Menten kinetics and higher affinity to H2O2 and TMB than that of pure Co3O4 NPs alone. Based on H2TCPP-Co3O4 nanocomposites, a simple, sensitive and selective colorimetric method with TMB as the substrate for the detection of H2O2 and glucose was successfully established. This colorimetric method can be used for the colorimetric detection of H2O2 with a low detection limit of 4×10(-7)mol·L(-1) and a dynamic range of 1×10(-6)mol·L(-1) to 75×10(-6)mol·L(-1). This method was designed to detect glucose when combined with glucose oxidase at a low detection limit of 8.6×10(-7)mol·L(-1) and a dynamic range of 1×10(-6)mol·L(-1) to 10×10(-6)mol·L(-1). Results of a fluorescent probe suggested that the peroxidase-mimic activity of the H2TCPP-Co3O4 nanocomposites effectively catalyzed the decomposition of H2O2 into [OH] radicals., (Copyright © 2014 Elsevier B.V. All rights reserved.)

5,10,15,20-Tetrakis(4-carboxyphenyl)-porphyrin-functionalized Fe3O4 nanocomposites (H2TCPP-Fe3O4) were successfully prepared by a simple two-step method. These nanocomposites exhibited ultra-high peroxidase-like activity compared with pure Fe3O4 nanoparticles. Colorless peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) was changed by H2O2 to its blue oxidized state. Kinetic studies indicated that the H2TCPP-Fe3O4 nanocomposites exhibited enhanced affinity toward H2O2 with a higher catalytic activity than Fe3O4 nanoparticles alone. Results of a fluorescent probe suggested that the catalase-mimic activity of the H2TCPP-Fe3O4 nanocomposites effectively catalyzed the decomposition of H2O2 into hydroxyl radicals. A simple, sensitive, and selective visual and colorimetric method with TMB as the substrate was designed to detect glucose when combined with glucose oxidase. This colorimetric method can be used for colorimetric detection of H2O2 with a minimum detection limit of 1.07×10(-6) M and a dynamic range of 5×10(-6) mol·L(-1) to 8×10(-5) mol·L(-1). This method can also be used to detect glucose at a minimum detection limit of 2.21×10(-6) M and a dynamic range of 25×10(-6) mol·L(-1) to 5×10(-6) mol·L(-1). Furthermore, the robustness of the nanocomposites makes them suitable for a wide range of applications in biomedicine and environmental chemistry fields., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Various nanostructures of 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin (H2TCPP) can be easily synthesized by a surfactant-assisted self-assembly (SAS) method at different temperatures. When the DMF solution of porphyrin monomer was injected into cetyltimethylammonium bromide (CTAB) aqueous solution by a syringe, diverse H2TCPP nanostructures dependent on the different temperatures, including hollow nanospheres, solid nanospheres and nanospheres with holes, were successfully obtained. As a result, the suitable concentration of the CTAB aqueous solution used to form nanostructues of porphyrin ranges from 0.15 to 0.2 mM. The various morphologies of porphyrin nanostructures were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). UV-vis adsorption spectra showed that the micro-/nano-aggregate properties of porphyrin transformed from H-aggretates to J-aggregates during the process of self-assembly of porphyrin at different temperatures. Fluorescence spectra revealed a greater fluorescence quenching of various micro-/nano-aggregatess of porphyrin formed at different temperatures in aqueous solution, compared to the DMF solution of porphyrin monomer., (© 2013.)

Hydrogen peroxide (H 2 O 2 ) is a key molecule in biology. As a byproduct of many enzymatic reactions, H 2 O 2 is also a popular biosensor target. We report the first use of uniform nanoparticles of porphyrin functionalized ceria (Por-Ceria) prepared by a one-step method, as a colorimetric probe in detection for H 2 O 2 . Por-ceria nanoparticles exhibited strong intrinsic peroxidase activity toward a classical peroxidase substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), in the presence of H 2 O 2 . Enhanced peroxidase-like activity of Por-ceria originated from synergistic effect of porphyrin and ceria, thereby explaining the high performance of Por-Ceria as an artificial enzyme mimicking peroxidase. When coupled with glucose oxidase, glucose is detected. A detection limit of 1.9 × 10 −2 mM glucose with a linear range up to 0.15 mM. [ABSTRACT FROM AUTHOR]