Search

Aluminum black dross (ABD) is a solid waste of aluminum smelting process that causes serious environmental and public health problems. In addition, it imposes significant disposal costs to the aluminum industry. In this study, synthesis and characterization of mesoporous alumina (MA) from the ABD using a novel recycling procedure consisting of leaching at low temperature (85 °C) and atmospheric pressure, co-precipitation, separation through selective dissolution, re-precipitation, aging and finally calcination at 600 °C for 2 h. No hard or soft template was used during the formation of the gel. The as-synthesized MA had a specific surface area, total pore volume and average pore diameter of 123–162 m2/g, 0.37 cm3/g and 10.6 nm, respectively which were obtained by nitrogen sorption analysis. The as-synthesized MA possessed more than 98% purity. Its XRD pattern exhibited the characteristic peaks of gamma, eta, theta, and delta phase alumina. FESEM and TEM analyses revealed nanoscale morphology of the as-synthesized MA; having crystal size of ∼11 nm. The TGA analysis showed that the as-synthesized MA is thermally stable and exhibits only ∼5 wt% mass loss for heating from 30 to 800 °C. The characterization of solid residue at the end of the proposed process proved that it contains mainly silica phase which can alternatively be reused as filling agent or aggregate in concrete materials applications. It is quite clear that the process of production of MA from the ABD is feasible and practical and provides a novel mitigation to the environmental problems of the ABD. • This work studies template-free synthesis of mesoporous alumina from Al black dross. • The as-synthesized mesoporous alumina had a specific surface area of 123–162 m2/g. • The specific pore volume of the as-synthesized mesoporous alumina was 0.37 cm3/g. • The as-synthesized mesoporous alumina possessed more than 98% purity. [ABSTRACT FROM AUTHOR]

A facile and one-step strategy has been developed for the preparation of highly fluorescent nitrogen and phosphor co-doped carbon quantum dots (NP-CQDs) through the thermal treatment of the mixture of citric acid and O -phosphorylethanolamine. The as-prepared NP-CQDs emit strong blue-green light under irradiation of 365 nm light and show emission maxima at 475 nm in aqueous solution. And these NP-CQDs exhibit great stability in high-salt conditions, excellent photostability and a high quantum yield of about 8.45%. Interestingly, the NP-CQDs have been successfully utilized for the sensitive and selective fluorometric detection of Fe 3+ without interference from other ions in aqueous solution. Moreover, we have found that the NP-CQDs can enhance the photocatalytic activity of TiO 2 for the degradation of dyes under simulated sunlight irradiation. [ABSTRACT FROM AUTHOR]

We report an eco-friendly strategy for fabrication of nitrogen-doped carbon nanodots (N-CDs) and demonstrate their applications for multicolor cell imaging, patterning, and biosensing. N-CDs have been synthesized using wool as raw material via pyrolysis and microwave treatment, providing a green way for the production of N-CDs without the use of toxic/expensive solvents and starting materials. The prepared N-CDs exhibit exceptional advantages including high fluorescent quantum yield (22.5%), excellent biocompatibility, low toxicity, and satisfactory chemical stability. Depending on these superior properties, the N-CDs have been applied in multicolor bioimaging, patterning, and biosensing. Imaging of living cells has been observed with high resolution using N-CDs as a probe, which validates their use in imaging applications and their multicolor property in the living cell system. Additionally, the obtained N-CDs have been used as fluorescent inks for drawing luminescent patterns, showing favorable application in anti-counterfeit and optoelectronic dimensions. Most strikingly, the as-prepared N-CDs could visualize Fe 3+ fluctuations in living cells with negligible autofluorescence based on their high sensitivity and selectivity detection for Fe 3+ ions with a linear range of 0.1–10 μM and a detection limit of 10 nM. [ABSTRACT FROM AUTHOR]

In this work, a new solid-phase microextraction fiber was prepared based on nitrogen-doped graphene (N-doped G). Moreover, a new strategy was proposed to solve problems dealt in direct coating of N-doped G. For this purpose, first, Graphene oxide (GO) was coated on Pt wire by electrophoretic deposition method. Then, chemical reduction of coated GO to N-doped G was accomplished by hydrazine and NH 3 . The prepared fiber showed good mechanical and thermal stabilities. The obtained fiber was used in two different modes (conventional headspace solid-phase microextraction and cold-fiber headspace solid-phase microextraction (CF-HS-SPME)). Both modes were optimized and applied for the extraction of benzene and xylenes from different aqueous samples. All effective parameters including extraction time, salt content, stirring rate, and desorption time were optimized. The optimized CF-HS-SPME combined with GC-FID showed good limit of detections (LODs) (0.3–2.3 μg/L), limit of quantifications (LOQs) (1.0–7.0 μg/L) and linear ranges (1.0–5000 μg/L). The developed method was applied for the analysis of benzene and xylenes in rainwater and some wastewater samples. [ABSTRACT FROM AUTHOR]

In the presence of ( R )-SEGPHOS-PdCl 2 catalyst, 5- endo -hydroaminocyclization of various 2-( tert -butyl)- N -(2-ethynylphenyl)anilines proceeds enantioselectively to afford optically active N–C axially chiral N -(2- tert -butylphenyl)indole derivatives in good yields. The enantioselectivity depends strongly on the bulkiness of ortho -substituents and the electron density on the arylethynyl group, and it is explained by the dynamic axial chirality generated by the twisting of the aryl substituent. [ABSTRACT FROM AUTHOR]

Axially chiral N -arylindoles and realated compounds were stereoselectively synthesized using the following three protocols; 1) diastereoselective nucleophilic aromatic substitution, 2) desymmetrization via a stereoselective Cr(CO) 3 migration reaction, and, 3) catalytic enantioselective synthesis via asymmetric ring-closing metathesis. Arene chromium tricarbonyls were utilized as key building blocks, and all of these methods induced extremely high stereoselectivities. Moreover, Cr(CO) 3 fragments were easily removed via air oxidation condition to afford Cr-free N -arylindoles with axially chiral N–C bonds. [ABSTRACT FROM AUTHOR]

In this report we investigated the reaction of bromo-bridged cyclopalladated complex of tri- o -tolylphosphine with aromatic and aliphatic bidentate N-donor ligands (pyrazine, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethane, 1,3-bis(4-pyridyl)propane, ethylenediamine). These reactions lead to the new P,C-palladacycles which were fully characterized by IR, NMR spectroscopies and CHN analysis. Interestingly, the linear organometallic polymer with a zig-zag manner was obtained and determined by X-ray crystallography in which the pyrazine rigid molecules act as the bridging ligands between Pd(II) centres. To understand the reason of this polymerization process, two layers ONIOM (QM:QM) calculations were performed on the organometallic polymer [Pd(P( o -tolyl) 3 )(pyrazine)] n (n = 1 to 10) in order to study the stability trend of polymer as a function of size (n). The infrared (IR) spectrum of the [Pd(P( o -tolyl) 3 )(pyrazine)] n was calculated for different values of n and its evolution with the size of polymer was observed. The shapes of HOMO, LUMO and the energy gap between them were also studied with increasing n. [ABSTRACT FROM AUTHOR]

Through a simple method, a new kind of Mn 3 O 4 nanoparticles (Mn 3 O 4 NPs) decorated nitrogen-doped graphene (N-GR) was synthesized firstly, and then a Mn 3 O 4 NPs/N-GR modified carbon paste electrode (CPE) was fabricated. Several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemistry, were performed to characterize Mn 3 O 4 NPs/N-GR. A large amount of N on the graphene surface (about 9.86% of atomic ratio) was detected by XPS. Mn 3 O 4 nanoparticles (50–80 nm) homogeneously coated on N-GR. Mn 3 O 4 NPs/N-GR/CPE was used for sensitive non-enzymatic glucose sensing, which exhibited the response current of glucose ca. 10-fold higher than that of pure CPE. Under the optimum determination conditions, Mn 3 O 4 NPs/N-GR/CPE provided glucose with a broader detection range of 2.5–529.5 μM with a low detection limit (1.0 μM, S/N = 3). This novel method was successfully used to determine glucose in human urine sample. [ABSTRACT FROM AUTHOR]

Nitrogen-enriched porous carbon nanofibers were successfully prepared by using water-soluble phenolic resin/polyvinyl alcohol blend solution as precursor via electrospinning followed by carbonization and NH 3 treatments. The NH 3 treatment time has a significant effect on the pore structure, thermal stability as well as the surface chemistry. The as-prepared carbon materials were studied as freestanding electrodes for supercapacitor without the addition of binders and conductive additives in 6 M KOH solution. The sample treated with NH 3 for 3 h exhibits a high specific surface area (763 m 2 g −1 ), rich surface functionalities (5.26 at.% nitrogen and 4.37 at.% oxygen), optimized pore structure, good thermal stability and electrical conductivity. It shows the maximum specific capacitance of up to 251.2 F g −1 at 0.1 A g −1 , about 25% higher than that of the sample treated with argon. Furthermore, the specific capacitance remains 193 F g −1 at 20 A g −1 with high rate capability of 77%, as well as excellent cycle stability (99% capacity retention after 2000 cycles). The outstanding performance of nitrogen-doped porous carbon nanofibers could be attributed to the synergistic effect of the proper pore size distribution, high effective surface area and certain amount of nitrogen- and oxygen-containing functional groups, resulting in both electrochemical double layer and faradaic capacitance contributions. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of the gold(III) isocyanide complexes [(CˆNˆC)AuCN t Bu]+X- ( 1a , X = (C 6 F 5 ) 3 BOAc F ; 1b , X = PF6) are reported [(CˆNˆC) = 2,6-bis(4-Bu t C 6 H 3 ) 2 pyridine; OAc F = trifluoroacetate]. Compound 1a slowly decomposes under C–N bond cleavage of the t BuNC ligand, to give (CˆNˆC)AuCNB(C 6 F 5 ) 3 and t BuOAc F , whereas [(CˆNˆC)AuCN t Bu]PF 6 decomposes mainly to [(CˆNˆC)AuCN. On UV irradiation the complexes show photoluminescence, with (CˆNˆC)AuCN showing the most intense emission. [ABSTRACT FROM AUTHOR]

Naturally occurring chlorophyll- a was chemically modified to methyl 3-aminomethyl-pyropheophorbides- a including primary, secondary, and tertiary amines. Reductive amination of methyl pyropheophorbide- d possessing the 3-formyl group with ammonia efficiently gave a chlorin dimer covalently linked with CH 2 NHCH 2 at the 3-position, which was transformed into a trimer through the substitution at the amino group. Conformational analyses by 1 H NMR spectroscopic observation and molecular modeling estimation indicated that the dimer and trimer were apt to form closely packed structures. Chlorin chromophores in the dimer and trimer were weakly interacted in dichloromethane to shift their Qy absorption bands to longer wavelengths by 4–6 nm than the maxima of the corresponding monomer. In the red-shifted Qy region, the trimer gave an S-shaped circular dichroism band by exciton coupling of composite chlorin units. All the semi-synthetic chlorophyll derivatives were highly fluorescent and no intramolecular quenching was observed even in the trimer. The behaviors would be ascribable to the formation of compact conformers and suppression of intramolecular motion, which are important to construct light-harvesting antenna complexes in phototrophs and their model systems. [ABSTRACT FROM AUTHOR]

The activated carbons were synthesized from hay with CO 2 as an activating agent. Furthermore hay and the chars obtained by pyrolysis were treated with urea, in order to introduce nitrogen to their structure, and then subjected to physical activation. The porous structure of activated carbons before and after impregnation was characterised by nitrogen adsorption using BET and BJH methods. The thermal properties of the samples were investigated by thermogravimetric (TG) analysis and differential thermogravimetry (DTG). The final products were activated carbons of low surface area varying from 84 to 196 m 2 /g and showing basic character of the surface. The impregnation of hay and chars with urea leads to a decrease in activated carbon surface area and pore volume. However, the materials modified by urea show a very high content of nitrogen (from 8.1 to 12.8 wt.%), which could be achieved thanks to the use of microwave heating as this method of heating permits a considerable reduction of the temperatures of pyrolysis and activation and a shortening of the time of activation. Following the character of TG and DTG curves, the nitrogen functional groups introduced into the activated carbon structure have relatively low thermal stability, as evidenced by the distinct loss of mass above the temperature of approximately 400 °C, observed both for unmodified carbon and the carbon enriched in nitrogen. [ABSTRACT FROM AUTHOR]

Herein, a facile hydrothermal treatment of lime juice to prepare biocompatible nitrogen-doped carbon quantum dots (N-CQDs) in the presence of ammonium bicarbonate as a nitrogen source has been presented. The resulting N-CQDs exhibited excitation and pH independent emission behavior; with the quantum yield (QY) up to 40%, which was several times greater than the corresponding value for CQDs with no added nitrogen source. The N-CQDs were applied as a fluorescent probe for the sensitive and selective detection of Hg 2 + ions with a detection limit of 14 nM. Moreover, the cellular uptake and cytotoxicity of N-CQDs at different concentration ranges from 0.0 to 0.8 mg/ml were investigated by using PC12 cells as a model system. Response surface methodology was used for optimization and systematic investigation of the main variables that influence the QY, including reaction time, reaction temperature, and ammonium bicarbonate weight. [ABSTRACT FROM AUTHOR]

A novel method of in-situ catalytic site (CoN x ) construction in macroporous carbon (MPC) is developed. The nitrogen-containing MPC-supported cobalt (Co/N–MPC) catalysts are synthesized via the pyrolysis of a mixture of glucose-urea resin, nano-CaCO 3 , and cobalt nitrate. The nano-CaCO 3 functions as a template to fabricate MPC that provides high electric conductivity and large specific surface area. The catalytic CoN x sites are simultaneously created during the formation of N–MPC. The use of glucose-urea resin as the carbon and nitrogen sources significantly increases the nitrogen content as high as 8.8 at% in the MPC. The synthesized Co/N–MPC demonstrates superb catalytic activity toward oxygen reduction reaction. The direct borohydride fuel cell using the Co/N–MPC shows a power density as high as 170 mW cm −2 which is much higher than the cell using 10 wt.% Pt/C but slightly lower than the cell using 20 wt.% Pt/C as the cathode catalyst at ambient conditions. [ABSTRACT FROM AUTHOR]

In this paper, we report a template-free method to fabricate hollow nitrogen-doped carbon (HNC) by pyrolysis of hollow polyaniline microspheres, which were synthesized by suspension polymerization method. The entire synthesis is simple, environmentally benign, and economic. The oxygen reduction reaction (ORR) activity of the as-prepared HNC catalyst is close to that of the commercial Pt/C catalyst in alkaline media with four electron pathway. Moreover, the HNC shows much better fuel crossover resistance and long-term durability than the commercial Pt/C in alkaline medium. All these features make HNC a potentially promising and suitable substitute for the expensive noble metal catalysts in the next generation alkaline fuel cells. [ABSTRACT FROM AUTHOR]