Search

Based on the modulated electronic properties of Fe3O4-graphene (Fe3O4/GN composite) as well as the outstanding complexation between Pb2+ and natural substances garlic extract (GE), a novel electrochemical sensor for the determination of Pb2+ in wastewater was prepared by immobilization of Fe3O4/GN composite integrated with GE onto the surface of glassy carbon electrode (GCE). Fe3O4/GN composite was employed as an electrochemical active probe for enhancing electrical response by facilitating charge transfer while GE was used to improve the selectivity and sensitivity of the proposed sensor to Pb2+ assay. The electrochemical sensing performance toward Pb2+ was appraised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave voltammetry (SWV). Under the optimized condition, the sensor exhibited two dynamic linear ranges (LDR) including 0.001 to 0.5 nM and 0.5 to 1000 nM with excellent low detection limit (LOD) of 0.0123 pM (S/N = 3) and quantification limit (LOQ) of 0.41 pM (S/N = 10). Meanwhile, it displayed remarkable stability, reproducibility (RSD of 3.61%, n = 3), and selectivity toward the assay for the 100-fold higher concentration of other heavy metal ions. Furthermore, the novel sensor has been successfully employed to detect Pb2+ from real water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 109)] NH3 was detected by the system. This prototype successfully differentiated four concentration levels of NH3 in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs. [ABSTRACT FROM AUTHOR]

With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 109)] NH3 was detected by the system. This prototype successfully differentiated four concentration levels of NH3 in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs. [ABSTRACT FROM AUTHOR]

Star-shaped porphyrin-cored poly(epsilon-caprolactone) (SPPCL) was synthesized using a tetrahydroxyethyl-terminated porphyrin as a core initiator and stannous octoate as a catalyst in bulk at 120 degrees C. The molecular weight of as-synthesized polymer could be adjusted linearly by controlling the molar ratio of epsilon-caprolactone to porphyrin core initiator, and the molecular weight distribution was reasonably narrow. Supramolecular polypseudorotaxanes were prepared by inclusion complexation of SPPCL with alpha-cyclodextrin (alpha-CD) and thoroughly characterized by means of FT-IR, 1H NMR, 13C CP/MAS NMR, DSC, TGA, and WAXD. The results demonstrated that the porphyrin-cored polypseudorotaxanes formed through alpha-CD molecules threading onto the branch chains of star-shaped SPPCL polymers, and they had a channel-type crystalline structure. Meanwhile, the original crystallization of SPPCL polymers within the polypseudorotaxanes was completely suppressed in the alpha-CD cavities. Moreover, inclusion complexation between SPPCL and alpha-CD enhanced the thermal stability of both the guest SPPCL polymers and the host alpha-CD. Furthermore, both the SPPCL polymers and the polypseudorotaxanes showed similar fluorescent and UV-vis spectra compared with porphyrin core initiator. Consequently, this will not only provide potentially porphyrin-cored poly(epsilon-caprolactone) and its polypseudorotaxanes for photodynamic therapy but also improve the compatibility between poly(epsilon-caprolactone) and peptide drugs for drug delivery.