Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 562
Filtrar
1.
Molecules ; 26(9)2021 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-33946466

RESUMO

The species Pseudogymnoascus is known as a psychrophilic pathogenic fungus which is ubiquitously distributed in Antarctica. While the studies of its secondary metabolites are infrequent. Systematic research of the metabolites of the Antarctic fungus Pseudogymnoascus sp. HSX2#-11 led to the isolation of one new pyridine derivative, 4-(2-methoxycarbonyl-ethyl)-pyridine-2-carboxylic acid methyl ester (1), together with one pyrimidine, thymine (2), and eight diketopiperazines, cyclo-(dehydroAla-l-Val) (3), cyclo-(dehydroAla-l-Ile) (4), cyclo-(dehydroAla-l-Leu) (5), cyclo-(dehydroAla-l-Phe) (6), cyclo-(l-Val-l-Phe) (7), cyclo-(l-Leu-l-Phe) (8), cyclo-(l-Trp-l-Ile) (9) and cyclo-(l-Trp-l-Phe) (10). The structures of these compounds were established by extensive spectroscopic investigation, as well as by detailed comparison with literature data. This is the first report to discover pyridine, pyrimidine and diketopiperazines from the genus of Pseudogymnoascus.


Assuntos
Ascomicetos/química , Compostos de Nitrogênio/análise , Regiões Antárticas , Ascomicetos/metabolismo , Produtos Biológicos/química , Estrutura Molecular , Compostos de Nitrogênio/química , Metabolismo Secundário
2.
Food Chem ; 345: 128560, 2021 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-33601648

RESUMO

An efficient and convenient detection method for organophosphorus pesticide (OP) residues is needed because of their high neurotoxicity and severe threat to food safety. OPs effectively reduce the production of thiocholine in the acetylcholinesterase/acetylthiocholine reaction by inhibiting the activity of acetylcholinesterase. Therefore, we developed a feasible and convenient fluorescent and colorimetric dual-response sensor based on the competitive complexation of Cu2+ between graphitic carbon nitride nanosheets and thiocholine for the rapid detection of OPs with high sensitivity. Malathion was used as a model OP, and a linear range of 70-800 nM with a detection limit of 6.798 nM for a fluorescent signaling platform and 2.5-25 nM with a detection limit of 1.204 nM for a colorimetric probe were attained. The constructed probe was successfully applied to determine OP in actual samples of cabbages leaves and tap water. The results indicated that the dual-response probe was reliable and sensitive to actual samples.


Assuntos
Colorimetria/métodos , Cobre/química , Grafite/química , Nanoestruturas/química , Compostos de Nitrogênio/química , Compostos Organofosforados/análise , Acetilcolinesterase/química , Acetilcolinesterase/metabolismo , Água Doce/análise , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Malation/análise , Resíduos de Praguicidas/análise , Espectrometria de Fluorescência
3.
Artigo em Inglês | MEDLINE | ID: mdl-33560919

RESUMO

In this study the novel use of scoria to remove ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen from groundwater. The experiments were conducted on connect time, kinetics studies, adsorption isotherms, effect of pH and microstructure, so that the characteristics of removal were studied. The kinetics followed the pseudo-second order model. The rate of ammonia nitrogen adsorption was mainly controlled by intramolecular proliferation. The adsorption process for nitrite nitrogen and nitrate nitrogen was divided into the boundary layer diffusion and intramolecular proliferation. The isotherm data closely fitted the Langmuir isotherm models. Scoria is a mesoporous material whose cylindrical-shaped pores are dominating in microstructure. Overall, scoria was found to be an effective material for nitrogen purification of groundwater.


Assuntos
Água Subterrânea/química , Nitrogênio/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Nitrogênio/química , Compostos de Nitrogênio/química , Compostos de Nitrogênio/isolamento & purificação , Porosidade , Termodinâmica , Poluentes Químicos da Água/química
4.
Ecotoxicol Environ Saf ; 208: 111712, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396043

RESUMO

The photocatalytic process is an environmentally-friendly procedure that has been well known in the destruction of organic pollutants in water. The multiple semiconductor heterojunctions are broadly applied to enhance the photocatalytic performances in comparison to the single semiconductor. Polymeric semiconductors have received much attention as inspiring candidates owing to their adjustable optical absorption features and simply adaptable electronic structure. The shortcomings of the current photocatalytic system, which restricts their technical applications incorporate fast charge recombination, low-utilization of visible radiation, and low immigration capability of the photo-induced electron-hole. This paper indicates the novel fabrication of new CuI/g-C3N4 nanocomposite by hydrothermal and ultrasound-assisted co-precipitation methods. The structure, shape, and purity of the products were affected by different weight percentages and fabrication processes. Electron microscope unveils that CuI nanoparticles are distributed on g-C3N4. The bandgap of pure carbon nitride is estimated at 2.70 eV, and the bandgap of the nanocomposite has increased to 2.8 eV via expanding the amount of CuI. The CuI/C3N4 nanocomposite has a great potential to degrade cationic and anionic dyes in high value because of its appropriate bandgap. It can be a great catalyst for water purification. The photocatalytic efficiency is affected by multiple factors such as types of dyes, fabrication methods, the light sources, mass ratios, and scavengers. The fabricated CuI/C3N4 nanocomposite exposes higher photocatalytic performance than the pure C3N4 and CuI. The photocatalytic efficiency of nanocomposite is enhanced by enhancing the amount of CuI. Besides, the fabricated CuI/C3N4 revealed remarkable reusability without the obvious loss of photocatalytic activity. The antibacterial activity of the specimens reveals that the highest antimicrobial activities are revealed against P. aeruginosa and E. coli. These results prove that the nanocomposite possesses high potential for killing bacteria, and it can be nominated as a suitable agent against bacteria.


Assuntos
Antibacterianos/farmacologia , Cobre/química , Grafite/química , Iodetos/química , Compostos de Nitrogênio/química , Poluentes Químicos da Água/isolamento & purificação , Antibacterianos/química , Catálise , Corantes/química , Corantes/isolamento & purificação , Corantes/metabolismo , Cobre/farmacologia , Grafite/farmacologia , Iodetos/farmacologia , Luz , Nanocompostos/química , Compostos de Nitrogênio/farmacologia , Poluentes Químicos da Água/química , Purificação da Água/métodos
5.
Phys Chem Chem Phys ; 23(5): 3351-3360, 2021 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-33502403

RESUMO

The development of photocatalysts with high catalytic activity that are capable of full utilization of solar energy is a challenge in the field of photocatalysis. Accordingly, in the present study, an efficient Z-scheme cage-structured Co9S8/g-C3N4 (c-CSCN) photocatalyst was constructed for the degradation of tetracycline antibiotics under visible-light irradiation. The Z-scheme charge-transfer mechanism accelerates the separation of photogenerated charge carriers and effectively improves photocatalytic activity. Moreover, c-CSCN has a hollow structure, allowing light to be reflected multiple times inside the cavity, thereby effectively improving the utilisation efficiency of solar energy. As a result, the photocatalytic activity of c-CSCN is 1.5-, 2.5-, and 5.8-times higher than those of sheet-type Co9S8/g-C3N4 (s-CSCN), c-Co9S8, and g-C3N4, respectively, for the degradation of tetracycline. c-CSCN maintains favourable photocatalytic activity over five consecutive degradation cycles, demonstrating its excellent stability. In addition, c-CSCN performs efficient tetracycline removal in different water substrates. Moreover, c-CSCN exhibits excellent ability to remove tetracycline under direct natural sunlight. This work fully demonstrates that c-CSCN has high catalytic activity and the potential for practical application as a wastewater treatment material.


Assuntos
Antibacterianos/química , Cobalto/química , Grafite/química , Compostos de Nitrogênio/química , Sulfetos/química , Tetraciclina/química , Poluentes Químicos da Água/química , Catálise/efeitos da radiação , Cobalto/efeitos da radiação , Grafite/efeitos da radiação , Luz , Modelos Químicos , Compostos de Nitrogênio/efeitos da radiação , Sulfetos/efeitos da radiação
6.
Food Chem ; 347: 129001, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33503575

RESUMO

Conventional gold nanoparticles-based lateral flow immunoassays (AuNPs-LFIA) lack sensitivity. In this work, we developed a graphite-like carbon nitride-laden AuNPs (g-C3N4@Au) assisted LFIA to improve sensitivity for 17ß-estradiol (E2) in foods. g-C3N4 nanosheets were applied as carriers, because of their excellent chemical stability, large surface areas and low-cost, loading large numbers of AuNPs to amplify signals and improve the overall response of g-C3N4@Au-based LFIA (g-C3N4@Au-LFIA). The lowest visual limit of detection (vLOD) of E2 is 0.5 ng mL-1 for g-C3N4@Au-LFIA, which exhibit a significantly three-fold improved analytical performance compared with that of AuNPs-LFIA. Additionally, this method was successfully used to the detection of E2 in four spiked food samples, offering a great potential of the g-C3N4@Au based LFIA for its application in food products.


Assuntos
Estradiol/análise , Ouro/química , Grafite/química , Imunoensaio/métodos , Nanopartículas Metálicas/química , Compostos de Nitrogênio/química , Animais , Análise de Alimentos , Limite de Detecção , Carne/análise , Testes Imediatos
7.
Carbohydr Polym ; 256: 117413, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483008

RESUMO

This study reports the modification of cellulose acetate (CA) membrane with zinc oxide (ZnO)@graphitic carbon nitride (g-C3N4) nanocomposite to improve the antifouling and separation performance. Different combinations of the CA-based membranes such as CA/g-C3N4, CA/ZnO, and CA/ZnO@g-C3N4 were fabricated using the non-solvent induced phase separation (NIPS) method. Membranes were analyzed for their morphology (SEM), porosity, pore size, contact angle, permeability, rejection, and antifouling properties. According to the SEM images of CA/ZnO@g-C3N4, the formation of pear-shaped macro voids and finger-like canals originating from the top layer was evident. Nanocomposite blended membrane with 0.25 wt.% ZnO@g-C3N4 achieved the largest pore radius (3.05 nm) and the lowest contact angle (67.7°). With these characteristics, 0.25 wt.% ZnO@g-C3N4 membrane obtained a pure water flux of 51.3 LMH, which is 2.1 times greater than the bare CA and high BSA and dye rejections with 97.20% and 93.7% respectively. Finally, the antifouling resistance of the CA membrane was greatly improved with FRR increasing from 73.7% to 94.8%, which was accompanied by a significant decrease in the fouling resistance parameters.


Assuntos
Grafite/química , Membranas Artificiais , Nanocompostos/química , Compostos de Nitrogênio/química , Ultrafiltração , Óxido de Zinco/química , Celulose/análogos & derivados , Celulose/química , Filtração , Teste de Materiais , Microscopia Eletrônica de Varredura , Permeabilidade , Porosidade , Solventes , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
8.
Chemosphere ; 262: 127675, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32805652

RESUMO

With the increasingly serious water environment problem, the persulfate-based advanced oxidation process (PS-AOP) has attracted considerable attention in water pollution treatment. To date, graphitic carbon nitride (g-C3N4) has been greatly favored by researchers in activating PS for its capability and unique superiorities. Though g-C3N4-based PS-AOP exhibits huge development prospects in removing organic pollutants, the review about its research progress has not been reported. Herein, this paper reviews the modification of g-C3N4 on the basis of its applications and properties for PS activation systematically. The activation mechanisms of g-C3N4-based modified materials are analyzed in detail, and the main formation pathways of radicals and non-radicals and their interaction mechanism with pollutants are thoroughly summarized. Finally, the existing challenges and future development directions of the PS-AOP driven by g-C3N4-based materials are critically discussed. The key purpose is to provide a reference for promoting the further popularization of this novel and efficient cooperative AOP in water purification industries, as well as multidisciplinary inspirations for g-C3N4-involved fields.


Assuntos
Poluentes Ambientais/química , Grafite/química , Compostos de Nitrogênio/química , Catálise , Oxirredução , Água
9.
Anal Chem ; 93(3): 1702-1708, 2021 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-33369382

RESUMO

This paper introduces a novel potential-resolved paper-based biosensor for simultaneous detection of multiple microRNAs (miRNAs) (taking miRNA-155 and miRNA-126 as examples) based on the bipolar electrode (BPE) electrochemiluminescence (ECL) strategy. The proposed multiple-channel paper-based sensing microfluidic platform was prepared by wax-printing technology, screen-printing method, and in situ Au nanoparticles (AuNPs) growth to form hydrophilic areas, hydrophobic boundaries, waterproof electronic bridge, driving electrode regions, and parallel bipolar electrode regions. CdTe quantum dots (QDs)-H2 and Au@g-C3N4 nanosheets (NSs)-DNA1 were used as dual electrochemiluminescence signal probes, and carboxylated Fe3O4 magnetic nanoparticles existed as carriers. CdTe QDs-H2/S2O82- and Au@g-C3N4 NSs-DNA1/S2O82- could exhibit two strong and stable ECL emissions at a drive voltage of 9 and 12 V, respectively, which can be used as effective potential-resolved signal tags. In addition, the proposed three-dimensional (3D) DNA nanomachine model and the target miRNA cycle strategy were used to achieve double amplification of electrochemiluminescence intensity. More importantly, the combination of the bipolar electrode system and the potential-resolved multitarget electrochemiluminescence method can greatly reduce the spatial interference between substances. The prepared ECL biosensor showed a favorable linear response for the detection of miRNA-155 and miRNA-126 with relatively low detection limits of 5.7 and 4.2 fM, respectively. With excellent sensitivity, the strategy may provide an efficient method for clinical application, especially in detection of trace multiple targets.


Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , Medições Luminescentes , MicroRNAs/análise , Papel , Compostos de Cádmio/química , Eletrodos , Corantes Fluorescentes/química , Ouro/química , Grafite/química , Humanos , Compostos de Nitrogênio/química , Pontos Quânticos/química , Telúrio/química
10.
J Chromatogr A ; 1637: 461824, 2021 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-33383240

RESUMO

A fully automated online emulsification-enhanced disposable pipette extraction-gas chromatography-mass spectrometry (EE-DPX-GC-MS) method has been developed for the extraction of six polychlorinated biphenyls (PCBs) from environmental waters. An in-house prepared material, graphitic carbon nitride (g-C3N4), was used as sorbent in a home-packed DPX device. The six PCBs studied include PCB 10, 28, 52, 153, 138 and 180. g-C3N4 was characterized successfully by X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, the two-dimensional structure of g-C3N4 allows rapid analyte adsorption and desorption to take place. With a significant number of nitrogen functionalities in g-C3N4, the material dispersed well in aqueous sample, increasing the active surface area of contact between the sorbent and the sample. When coupled with a pre-emulsification step, PCBs in each portion of sample could be efficiently extracted by g-C3N4 within 20 s of gentle turbulence. Under the most favorable conditions, the automated online EE-DPX-GC-MS method achieved wide dynamic working ranges with good linearity (r2 ≥ 0.998) for all analytes. Limits of detection ranging between 4.35 and 7.82 ng L-1 were attained, with enrichment factors of between 34 and 57 and relative standard deviations (RSDs) for intra- and inter-day precision of ≤ 8.95% and ≤ 12.6%, respectively. Absolute recoveries were between 69.3% and 109%. The fully automated online EE-DPX-GC-MS approach was applied to industrial wastewaters and reservoir waters where good relative recoveries of PCBs of between 89.3% and 105% were obtained, with RSDs ≤ 11.6%.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Grafite/química , Compostos de Nitrogênio/química , Bifenilos Policlorados/análise , Poluentes Químicos da Água/análise , Adsorção , Automação
11.
Chemosphere ; 258: 127343, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32947672

RESUMO

Hydroxyl radicals (OH) have robust non-selective oxidizing properties to effectively degrade organic pollutants. However, graphitic carbon nitride (g-C3N4) is restricted to directly generate OH due to its intrinsic valence band. In this study, we report a facile environmental-friendly self-modification strategy to synthesize reduced graphitic carbon nitride (RCN), with nitrogen vacancies and CN functional groups. The incorporation of CN enabled to downshift the valence band level, which endowed RCN with the capacity to directly generate OH via h+. Experimental and instrumental analyses revealed the critical roles of nitrogen vacancies and CN groups in the modification of the RCN band structure to improve its visible light absorption and oxidizing capacity. With these superior properties, the RCN was significantly enhanced for the photocatalytic degradation of DCF under visible light irradiation. The self-modification strategy articulated in this study has strong potential for the creation of customized g-C3N4 band structures with enhanced oxidation performance.


Assuntos
Diclofenaco/química , Grafite/química , Compostos de Nitrogênio/química , Catálise , Luz , Oxirredução , Processos Fotoquímicos
12.
J Chromatogr A ; 1628: 461428, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822999

RESUMO

A covalent organic framework modified graphitic carbon nitride (g-C3N4@TpBD) was synthesized by modifying the graphitic carbon nitride (g-C3N4) with a covalent organic framework (COF-TpBD). The synthesis conditions including the mass ratio between g-C3N4 and benzidine (BD), solvent type, reaction temperature and reaction time were optimized. Under the optimal synthetic conditions, a novel spiny dendritic g-C3N4@TpBD adsorbent was obtained. The g-C3N4@TpBD was then coated on stainless-steel wire by sol-gel technique and the coated fiber was used for the solid phase microextraction of polycyclic aromatic hydrocarbons prior to gas chromatography-mass spectrometric detection. The established method was successfully applied to determine eight PAHs in six environmental water samples. Under the optimal extraction conditions, a wide linear quantification range for the analytes was obtained from 0.07 to 60.0 ng mL-1 with the coefficients of determination varying from 0.9979 to 0.9998, and the limits of detection (S/N = 3) ranged from 0.02 to 0.05 ng mL-1. The relative recoveries of the analytes for the six environmental water samples at the spiked concentrations of 0.2, 0.5, 3.0 and 30.0 ng mL-1 were between 83.6% and 118% with the relative standard deviations ranging from 2.4% to 11.3%.


Assuntos
Grafite/química , Estruturas Metalorgânicas/química , Compostos de Nitrogênio/química , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , Benzidinas/química , Limite de Detecção , Reprodutibilidade dos Testes , Temperatura
13.
PLoS One ; 15(8): e0237389, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32797116

RESUMO

In the present work, a series of magnetically separable Fe3O4/g-C3N4/MoO3 nanocomposite catalysts were prepared. The as-prepared catalysts were characterized by XRD, EDX, TEM, FT-IR, UV-Vis DRS, TGA, PL, BET and VSM. The photocatalytic activity of photocatalytic materials was evaluated by catalytic degradation of tetracycline solution under visible light irradiation. Furthermore, the influences of weight percent of MoO3 and scavengers of the reactive species on the degradation activity were investigated. The results showed that the Fe3O4/g-C3N4/MoO3 (30%) nanocomposites exhibited highest removal ability for TC, 94% TC was removed during the treatment. Photocatalytic activity of Fe3O4/g-C3N4/MoO3 (30%) was about 6.9, 5, and 19.9-fold higher than those of the MoO3, g-C3N4, and Fe3O4/g-C3N4 samples, respectively. The excellent photocatalytic performance was mainly attributed to the Z-scheme structure formed between MoO3 and g-C3N4, which enhanced the efficient separation of the electron-hole and sufficient utilization charge carriers for generating active radials. The highly improved activity was also partially beneficial from the increase in adsorption of the photocatalysts in visible range due to the combinaion of Fe3O4. Superoxide ions (·O2-) was the primary reactive species for the photocatalytic degradation of TC, as degradation rate were decreased to 6% in solution containing benzoquinone (BQ). Data indicate that the novel Fe3O4/g-C3N4/MoO3 was favorable for the degradation of high concentrations of tetracycline in water.


Assuntos
Óxido Ferroso-Férrico/química , Grafite/química , Molibdênio/química , Nanocompostos/química , Compostos de Nitrogênio/química , Óxidos/química , Processos Fotoquímicos , Tetraciclina/química , Água/química , Catálise , Luz , Imãs/química , Tetraciclina/isolamento & purificação , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
14.
J Chromatogr A ; 1625: 461337, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709361

RESUMO

Monitoring the levels of perfluorinated compounds (PFCs) in the environment is of vital importance, owing to their sustained environmental presence, extensive distribution, and associated health risks. The development of cost-effective and efficient sorbents for the establishment of sensitive analytical methods is critical for achieving trace-level detection. In this study, a graphitic carbon nitride (g-C3N4)-based sorbent is synthesized by a facile sonication-assisted method exfoliated by zeolitic imidazolate framework-67 (ZIF-67) in situ. The novel ZIF-67/g-C3N4 composites were systematically characterized by transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and N2 adsorption-desorption analysis, exhibiting good dispersity and a large surface area. Moreover, molecular dynamics simulations indicated that g-C3N4 structures can be effectively exfoliated by the introduced ZIF-67 molecules. The hybrid material was successfully utilized as a dispersive solid-phase extraction sorbent, and the extraction factors were systematically optimized by response surface methodology. Under optimal conditions, the synthesized sorbent exhibited desirable linear correlations (R2 > 0.99), a low detection limit (0.3-2 ng L-1), and good repeatability (relative standard deviation <15%, n = 6). The developed method was applied for the analysis of natural and spiked water samples. The study demonstrated that the ZIF-67/g-C3N4 composites are promising materials for pollutant adsorption from drinking water samples.


Assuntos
Água Potável/química , Fluorcarbonetos/análise , Grafite/química , Estruturas Metalorgânicas/química , Compostos de Nitrogênio/química , Extração em Fase Sólida/métodos , Sonicação , Poluentes Químicos da Água/análise , Adsorção , Simulação de Dinâmica Molecular
15.
Chemosphere ; 258: 127339, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554010

RESUMO

In this paper, a two dimensional/two dimensional (2D/2D) heterostructure of Ti3C2/g-C3N4 (T/CN) was constructed and used to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF) in water in the presence of light illumination. Compared with single photocatalytic process by T/CN (0.040/min) and with pure g-C3N4 nanosheets in PMS system (0.071/min), 5.0 and 3.0 times enhanced activities were achieved in the T/CN-PMS system at optimum Ti3C2 (1.0 wt%) loading under light illumination (0.21/min). Moreover, the decomposing processes of DCF in T/CN-PMS system were applicable in a wide initial pH range (3∼14), therefore, overcoming the limitation of pH dependence in traditional PMS system. Based on the synergistic effect of photocatalysis and PMS oxidation processes, the 1O2 was generated as primary reactive species for the removal of DCF in T/CN-PMS system. The DCF degradation mechanism was further proposed through the results of liquid chromatography-mass spectrometry (LC-MS) and density functional theory (DFT) calculations.


Assuntos
Diclofenaco/química , Grafite/química , Compostos de Nitrogênio/química , Peróxidos/química , Titânio/química , Catálise , Estrutura Molecular , Oxirredução , Peróxidos/efeitos da radiação
16.
J Vis Exp ; (159)2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32478736

RESUMO

Certain nitrogen-containing compounds can contribute to fuel instability during storage. Hence, detection and characterization of these compounds is crucial. There are significant challenges to overcome when measuring trace compounds in a complex matrix such as fuels. Background interferences and matrix effects can create limitations to routine analytical instrumentation, such as GC-MS. In order to facilitate specific and quantitative measurements of trace nitrogen compounds in fuels, a nitrogen-specific detector is ideal. In this method, a nitrogen chemiluminescence detector (NCD) is used to detect nitrogen compounds in fuels. NCD utilizes a nitrogen-specific reaction that does not involve the hydrocarbon background. Two-dimensional (GCxGC) gas chromatography is a powerful characterization technique as it provides superior separation capabilities to one-dimensional gas chromatography methods. When GCxGC is paired with a NCD, the problematic nitrogen compounds found in fuels can be extensively characterized without background interference. The method presented in this manuscript details the process for measuring different nitrogen-containing compound classes in fuels with little sample preparation. Overall, this GCxGC-NCD method has been shown to be a valuable tool to enhance the understanding of the chemical composition of nitrogen-containing compounds in fuels and their impact on fuel stability. The % RSD for this method is <5% for intraday and <10% for interday analyses; the LOD is 1.7 ppm and the LOQ is 5.5 ppm.


Assuntos
Cromatografia Gasosa/métodos , Compostos de Nitrogênio/química
17.
Chemosphere ; 256: 127100, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32460159

RESUMO

The environmental behaviors of graphitic carbon nitride (g-C3N4) have drawn increasing attention in recent. Understanding the fate and transport of g-C3N4 in porous media is necessary for evaluating its environmental risks. Column experiments were used in this study to investigate the combined effect of ionic strength (IS) and other common physicochemical factors (i.e. sand grain size, solution pH, and humic acid concentration) on g-C3N4 transport. The one-site kinetic models were applied to simulate the retention and transport of g-C3N4 in porous media, which fitted the breakthrough curves very well. Experimental and model results showed that g-C3N4 had a weak mobility with the transport mass recovery (TMR) less than 39.6% at pH 6.0 in absence of humic acid (HA). The mobility of g-C3N4 was inhibited with decreasing sand grain size, and the inhibited efficiency was enhanced with IS. However, g-C3N4 transport was significantly enhanced with increasing pH and HA concentration, and the enhanced efficiency was more obviously at high IS. The maximum TMR (78.3%) of g-C3N4 was observed with the presence of 5 mg L-1 HA. These results indicated that physicochemical factors played an important and combined role in controlling g-C3N4 transport in porous media, which would lead to the more complex evaluation on the environmental behaviors of g-C3N4.


Assuntos
Grafite/química , Modelos Químicos , Compostos de Nitrogênio/química , Substâncias Húmicas/análise , Cinética , Concentração Osmolar , Porosidade
18.
Chemosphere ; 253: 126672, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32464766

RESUMO

Mounting evidence highlights the negative impacts of neonicotinoids on non-target organisms and ecosystem, yet there are a few of methods to address the residual neonicotinoids in environment. Herein, series of sulfur and oxygen co-doped carbon nitride (SOCNx) were successfully synthesized via one-step thermal polymerization and applied in photodegradation of multi-neonicotinoids (dinotefuran, acetamiprid, clothianidin, thiacloprid, imidacloprid, nitenpyram and thiamethoxam) simultaneously for the first time. Unique tubular structure was observed at the specific doping ratio, which enhanced both mass transfer and specific surface area of graphitic carbon nitride (g-C3N4). The doping process changed the morphology of g-C3N4 materials and also affected its photocatalytic performance. The degradation rate of optimized material (SOCN8) for nitenpyram could surpass 90% just in 30 min under visible light in aqueous matrix. The degradation for target insecticide increased maximum efficiency of 57.6% compared to bulk g-C3N4. Moreover, the possible mechanism of the degradation process was proposed. The results revealed that photon-induced hole (h+) was the primary active species during the degradation of seven investigated neonicotinoids. Moreover, the SOCN8 showed excellent recyclability after four consecutive cycles, which implied promising applications for pesticide-contaminated water remedy.


Assuntos
Inseticidas/química , Neonicotinoides/química , Nitrilas/química , Fotólise , Catálise , Grafite/química , Inseticidas/efeitos da radiação , Neonicotinoides/efeitos da radiação , Compostos de Nitrogênio/química , Oxigênio/química , Enxofre/química
19.
Mikrochim Acta ; 187(5): 286, 2020 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-32328802

RESUMO

Rosette-shaped graphitic carbon nitride (rosette-GCN) is described as a promising alternative to natural peroxidase for its application to fluorescence-based glucose assays. Rosette-GCN was synthesized via a rapid reaction between melamine and cyanuric acid for 10 min at 35 °C, followed by thermal calcination for 4 h. Importantly, rosette-GCN possesses a peroxidase-like activity, producing intense fluorescence from the oxidation of Amplex UltraRed in the presence of H2O2 over a broad pH-range of, including neutral pH; the peroxidase activity of rosette-GCN was ~ 10-fold higher than that of conventional bulk-GCN. This enhancement of peroxidase activity is presumed to occur because rosette-GCN has a significantly larger surface area and higher porosity while preserving its unique graphitic structure. Based on the high peroxidase activity of rosette-GCN along with the catalytic action of glucose oxidase (GOx), glucose was reliably determined down to 1.2 µM with a dynamic linear concentration range of 5.0 to 275.0 µM under neutral pH conditions. Practical utility of this strategy was also successfully demonstrated by determining the glucose levels in serum samples. This work highlights the advantages of GCNs synthesized via rapid methods but with unique structures for the preparation of enzyme-mimicking catalysts, thus extending their applications to the diagnostics field and other biotechnological fields. Graphical abstract.


Assuntos
Fluorescência , Glucose Oxidase/química , Glucose/análise , Grafite/química , Peróxido de Hidrogênio/química , Compostos de Nitrogênio/química , Peroxidases/química , Biocatálise , Glucose/metabolismo , Glucose Oxidase/metabolismo , Grafite/metabolismo , Humanos , Peróxido de Hidrogênio/metabolismo , Concentração de Íons de Hidrogênio , Estrutura Molecular , Compostos de Nitrogênio/metabolismo , Tamanho da Partícula , Peroxidases/metabolismo , Porosidade , Propriedades de Superfície
20.
PLoS One ; 15(4): e0231286, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32275735

RESUMO

The application of photocatalyst in pavements has received comprehensive attention in recent years due to its ability to decontaminate nitrogen oxides (NOx). However, it's remarkable that NOx also accumulated extensively in parking lots. The purpose of this study is to develop a movable photocatalytic plate (remarked photocatalytic KT plates) coupled with high activity to purify NOx. Firstly, the type of photocatalytic KT plates was determined according to NO removal experiment in laboratory. Then the plates were employed in the parking lots for removing NOx. One sample T-test, normality test and paired sample T-test methods for NOx concentration variation were conducted to determine the appropriate comparative means of dates under both dark and illuminated conditions. The difference of NOX concentration between dark and illuminated conditions was obtained to evaluate the photocatalytic removal efficiency. The results indicated that NO removal efficiency in laboratory and parking lots were 51.31% and 9.2%, respectively.


Assuntos
Grafite/química , Compostos de Nitrogênio/química , Estacionamentos , Titânio/química , Catálise , Cidades , Luz , Óxido Nítrico/isolamento & purificação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...