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Nitrated Polycyclic aromatic hydrocarbons (NPAHs) widely exist in atmospheric aerosol particles are important constituents of brown carbon. Naphthalene and other polycyclic aromatic hydrocarbons (PAHs) are vital precursors of NPAHs. The NPAHs components of secondary organic aerosol (SOA) generated by the photooxidation of naphthalene under different concentrations of NO2 in chamber are on-line measured using synchrotron radiation vacuum ultraviolet photoionization aerosol mass spectrometer (VUV-PIMS) and verified off-line with optical spectrometry in this study. The results demonstrate that NO2 can promote the generation of NPAHs and formation of SOA. Using VUV-PIMS on-line detection, and combined with off-line UV-Vis and infrared spectroscopy verification, it is determined that carboxyls and naphthols are main components of naphthalene SOA particles without NO2, and nitro-naphthalene, dinitro-naphthalene, nitro-naphthol and dinitro-naphthol via the nitration of OH-naphthalene adduct and naphthol products of naphthalene are identified as principal constituents of SOA with NO2. The increase of strong chromophore of N = O of nitro group in NPAHs strengthens the absorbing ability of naphthalene SOA particles. The averaged mass absorption coefficient () over 200–600 nm of naphthalene SOA particles is increases gradually with the increasing concentration of NO2. The of naphthalene SOA particles with 1000 ppb NO2 is 688 cm2/g, which is close to to that of biomass burning organic aerosol particles. These results offer the reference for exploring the formation mechanism and optical properties of NPAHs under the background of high concentration of NOx in urban atmosphere.

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.