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Precious metal nanoparticles, especially Ag-based nanoparticles due to their strong surface plasma effect and excellent catalytic performance, have been widely applied in environmental remediation and detection of heavy metal ions in aqueous solution. In this study, first, bimetallic Ag/Co nanoparticles (Ag/Co NPs) modified by sodium citrate were synthesized by chemical reduction method. Second, bimetallic Ag/Co NPs were used as colorimetric probe for detecting Cr 3 + and Fe 3 + in aqueous solution simultaneously for the first time. The results showed that the probe had high specificity towards Cr 3 + and Fe 3 + among the tested metal ions. When Cr 3 + was mixed with Ag/Co NPs, the solution quickly changed from yellow to pink, meanwhile, the UV–Vis absorption intensity declined at 400 nm and a new prominent absorption band was formed at 530 nm. While Fe 3 + was mixed with Ag/Co NPs, the solution quickly changed from yellow to nearly colorless. The linear relationship between absorbance of bimetallic Ag/Co NPs at 400 nm and −log of Cr 3 + concentration is 1 nM to 10 μ M, which y = 0. 0 0 8 4 x + 1. 5 0 1 2 and R 2 = 0. 9 8 5 5. The limit of detection (LOD) for this study was 1.14 nM. Similar to Cr 3 + , the LOD for Fe 3 + was calculated 16.3 μ M. In addition, the catalytic performance of bimetallic Ag/Co NPs was evaluated by methylene blue (MB) in the presence of H2O2. The catalytic degradation efficiency of bimetallic Ag/Co NPs was about 4.8 times greater than monometallic Ag NPs, confirming Ag and Co NPs had obviously synergistic effect. Therefore, this result made bimetallic Ag/Co NPs had potential application in the field of environmental remediation. Bimetallic Ag/Co nanoparticles (NPs) modified by sodium citrate were synthesized by chemical reduction method. The prepared Ag/Co NPs were used as a colorimetric probe for detecting Cr3+ and Fe3+ in aqueous solution simultaneously for the first time. Furthermore, the catalytic performance of bimetallic Ag/Co NPs was evaluated by methylene blue in the presence of H2O2. The catalytic degradation efficency of bimetallic Ag/Co NPs was 4.8 times greater than monometallic Ag NPs, confirming that Ag and Co NPs have a synergistic effect. [ABSTRACT FROM AUTHOR]

This study was initiated to explore a method for producing higher photocatalytic performance in layered double hydroxides (LDHs) through the preparation of ultrathin nanosheets, which would generate higher surface area (SA). Herein, a method is detailed for fabricating Ni2+-Al3+-LDHs with flower-like morphology assembled from an ultrathin nanosheet (Ni2+-Al3+-LDHs-U) employing a low temperature-reflux method together with a surfactant. The resulting products' structures, morphologies, porous properties, and bandgaps were investigated using a series of characterization techniques, which confirmed the formation of Ni2+-Al3+-LDHs-U with an ultrathin nanosheet structure (4–8 nm) and large SA (151 m2/g), which were nearly three times greater than the Ni2+-Al3+-LDHs comprising a thick nanosheet structure (50 nm, Ni2+-Al3+-LDHs-T). In addition, the bandgaps of these new Ni2+-Al3+-LDHs-U materials were 5.11 electron volts lower than the Ni2+-Al3+-LDHs-T material (5.26 eV). These flower-like morphology assembled from an ultrathin nanosheet exhibited a greatly enhanced light response that utterly decomposed methyl orange and Rhodamine B in water, which represented far better photodegradation under similar conditions compared to the thicker Ni2+-Al3+-LDHs-T and thicker Ni2+-Fe3+-LDHs-T. The increased photoreaction efficiency was explained by higher SA and catalytically active sites of the experimental product. [ABSTRACT FROM AUTHOR]

La(OH)3/CaTiO3 composite photocatalyst with a heterjunction structure was synthesized by a facile method of solvothermal procedure. La(OH)3 was dispersed on the surface of CaTiO3 with butterfly-like dendrites. The photocatalytic activity of La(OH)3/CaTiO3 heterostructure was enhanced for methylene blue (MB) degradation under ultraviolet (UV) irradiation. Especially 7La(OH)3/CaTiO3 obtained a highest MB degradation of 95.9%, which is 1.33 times higher than that of pure CaTiO3. The trapping experiment suggested that •OH active radical plays the major role. The enhanced photocatalytic activity over 7La(OH)3/CaTiO3 heterostructure on the degradation of MB is attributed to the butterfly-like dendrites CaTiO3 and the effectively separation of charged carriers. [ABSTRACT FROM AUTHOR]

Fe3O4/Au nanocomopsites (Fe3O4/Au NPs) with much improved catalytic activity were successfully fabricated through a simple seed growth method in aqueous solution. The petal-like structure, high saturation magnetization, the negatively charged sodium citrate-stabilized Fe3O4/Au NPs was characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The activated-H2O2 ability of Fe3O4/Au NPs was evaluated by using methylene blue (MB) as a cationic phenothiazines dye to be degraded in near neutral solution. The results showed Fe3O4/Au NPs removed over 95% MB from an aqueous solution within 60 min under the optimum conditions. The apparent rate constant of Fe3O4/Au NPs was 1 0. 8 × 1 0 − 2 min − 1 which was 43.2 and 8.3 times higher than pure Fe3O4 (2. 5 × 1 0 − 3 min − 1) and Au (1. 3 × 1 0 − 2 min − 1) NPs. The enhanced catalytic activity and increased oxidation rate constant probably owing to the synergistic effect between Fe3O4 and Au NPs to activate H2O2 generate a large amount of strong oxidizing species, such as ⋅ OH. In addition, nanocrystalline structure of Fe3O4/Au NPs was also very important to the peroxidase-like effect, especially the interaction interface between Fe3O4 and Au NPs. Moreover, Fe3O4/Au NPs was stable and could be regenerated and reused for at least five cycles. Fe3O4/Au NPs with much improved catalytic activity were successfully fabricated through a simple seed growth method in aqueous solution. The activated-H2O2 ability of Fe3O4/Au NPs was evaluated by using methylene blue (MB) as a cationic dye to be degraded in near neutral solution. Fe3O4/Au NPs presented desirable catalytic activity after five cycling times. The possible mechanism of oxidation reaction by employing Fe3O4/Au NPs as nanocatalyst was also investigated. [ABSTRACT FROM AUTHOR]

A new type of photocatalyst, La3+-Zn2+-Al3+-MoO42− layered double hydroxide (LDH) (La:Zn:Al = 1:7:2), was prepared by a complexing agent-assisted homogeneous precipitation technique. The LDHs were used as catalysts for the desulfurization of diesel oil under UV irradiation. As revealed by the results, the catalyst showed superior desulfurization efficiency and recycling performance. Under UV irradiation, the desulfurization efficiency was 84% in 60 min. In La3+-Zn2+-Al3+-MoO42− LDHs, the introduction of MoO42− increased the interlayer space for promoting the adsorption of dibenzothiophene, and MoO42− might act as the active sites for the oxidation of dibenzothiophene, resulting in the high desulfurization efficiency. [ABSTRACT FROM AUTHOR]

High total acid number (TAN) crude oils contain large amounts of naphthenic acids that could create serious corrosion problems in the oil refining process. This paper studied the catalysts that can make the naphthenic acids in crude oil to be decomposed to decrease the TAN of the crude oil effectively. Therefore, less corrosion of the facilities would occur. The results indicated that Mg-Al hydrotalcite/γ-Al2O3 effectively removed the naphthenic acids in high TAN crude oils, and the catalyst prepared with the ball-rolling method possessed a high mechanical strength and good pore structures. The TANs of the crude oils decreased from 2.7 mg KOH/g to below 0.5 mg KOH/g at 320 °C after 60 min with a pressure of 1.013 x 105 Pa and a catalyst/oil ratio of 0.17-0.20, which meet the requirements of high TAN crude oil processing in refineries without material upgrades. FT-IR of processed crude oil and the gas product analysis certificated the occurrence of the decomposition of carboxyl group. [ABSTRACT FROM AUTHOR]