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Novel nitrogen/iron-codoped carbon dots (N/Fe-CDs) were prepared from citric acid, ethylenediamine, and ferric chloride by a facile one-step solvothermal method and their peroxidase-like activity was evaluated. The structure and composition of the obtained carbon dots were characterized by several methods, including electron microscopy, X-ray diffraction, and spectral techniques. The presence of dopants in the particles was confirmed by X-ray photoelectron spectroscopy and inductively coupled plasma ��� mass spectrometry (ICP-MS). The obtained N/Fe-CDs displayed excellent peroxidase-like activity and efficiently catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2, leading to a rapid change in the solution color from colorless to blue. Based on this reaction, H2O2 was determined from 0 to 40 ��M under optimal conditions with a detection limit of 9.0 nM. In addition, L-cysteine was shown to cause the blue color to fade. Considering this feature, a highly sensitive, fast, and specific colorimetric method was developed for L-cysteine with a detection limit of 15.8 pM, which is lower than observed in similar studies. Further, this colorimetric method was applied for the determination of L-cysteine in real samples, and the results of recovery and relative standard deviation were satisfactory. The reported catalyst can be prepared conveniently using readily available raw materials and is inexpensive, which is advantageous for its widespread application.

Graphene oxide and cobalt oxide nanocomposites (Co3O4/GO) are fabricated in situ as heterogeneous catalysts by the decomposition of cobalt nitrate through heat and crystal growth of Co3O4 on the surface of GO sheets in 1-hexanol solvent. The Co3O4/GO catalyst is characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). Results show that the Co3O4/GO catalysts are large GO sheets decorated homogenously with well-dispersed Co3O4 nanoparticles. Although Co3O4 or GO alone exhibit little catalytic activity, their hybrid (Co3O4/GO) exhibits an unexpectedly high catalytic activity in the degradation of Orange II in water by advanced oxidation technology based on sulfate radicals, and 100% decomposition can be achieved in 6 min. These phenomena suggest a synergistic catalytic activity of Co3O4 and GO in the hybrid.

The current paper investigated the removal of the azo dye Orange II from water using advanced oxidation processes based on sulfate radicals. The cobalt oxide catalyst immobilized on graphene oxide (GO) can activate peroxymonosulfate (PMS) for the degradation of Orange II in water. The Co 3 O 4 /GO catalyst system was characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray spectroscopy. Results showed that Co 3 O 4 was distributed on GO. The Co 3 O 4 /GO catalyst system exhibited high activity in Orange II oxidation when the Co 3 O 4 /GO catalyst has an optimum Co 3 O 4 loading. In addition, 100% decomposition could be achieved within 6 min with 0.2 mM Orange II, 0.1 g L −1 catalyst, and 2 mM PMS. Meanwhile, inductively coupled plasma analysis revealed that the leach of cobalt ions was low. The catalyst also exhibited stable performance after several rounds of regeneration. Several operational parameters, such as catalyst amount, oxidant amount, pH, temperature, and oxidation rate, affected the degradation of Orange II.

Graphene oxide (GO) nanosheets as functional material have a unique planar structure and intriguing mechanical that have attracted intensive interests recently. A method was developed for the immobilization protease on GO sheets using glutaraldehyde as cross-linking reagent. The results showed that the thermostability and reusability of immobilized protease have been obviously improved compared to the free enzyme. However, there was no significant change in optimum pH value between the free and immobilized protease. The immobilized protease exhibited good operational stability. The apparent K m and V max for free and immobilized alkaline protease were determined, and the bio-catalytic activity was not impaired by immobilization.

In this paper, synthesis and characterization of poly(ethylene glycol)- grafted expanded graphite/polyaniline (PEG-grafted EG/PANi) as a novel ecofriendly composite material was reported. EG as substrate prepared from expandable graphite was firstly synthesized by in-situ polymerization at the presence of aniline (An) to obtain EG/PANi, and then graft polymerization with as-prepared PEG-grafted PANi (PEG-g-PANi) composite under no tough conditions. Structural characteristics of the products were evaluated by infrared spectrum (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The experimental results have shown that the product of PEGgrafted EG/PANi composite were synthesized by facile method.

In this paper, we developed the utilization of excess activated sludge (EAS) to extract protein. Firstly, activated sludge was hydrolyzed, using six different commercial proteolytic enzymes by the Kjeldahl method, at their optimal conditions respectively, and Alcalase was chosen as the ideal for further analysis. Secondly, important parameters on protein extraction efficiency(PEE) of EAS by hydrolysis were investigated. Experimental results have been shown that 52.5% of protein was extracted from EAS (accounting for 30.5% of initial dry sludge (DS) weight) and reducing the quality of activated sludge about 35% under optimum hydrolysis conditions. This novel technology is more environmentally friendly than the conventional sludge treatments.